draft-ietf-mmusic-sdp-atm-03.txt   draft-ietf-mmusic-sdp-atm-04.txt 
Internet Engineering Task Force Internet Engineering Task Force
Internet Draft Rajesh Kumar Internet Draft Rajesh Kumar
Document: draft-ietf-mmusic-sdp-atm-03.txt Mohamed Mostafa Document: draft-ietf-mmusic-sdp-atm-04.txt Mohamed Mostafa
December 18, 2000 Cisco Systems January 9, 2001 Cisco Systems
Expires: June 18, 2001 Expires: July 9, 2001
Conventions for the use of the Session Description Protocol (SDP) Conventions for the use of the Session Description Protocol (SDP)
for ATM Bearer Connections for ATM Bearer Connections
STATUS OF THIS DOCUMENT STATUS OF THIS DOCUMENT
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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addressed are Type 1, Type 2 and Type 5. This list of conventions is addressed are Type 1, Type 2 and Type 5. This list of conventions is
meant to be exhaustive. Individual applications can use subsets of meant to be exhaustive. Individual applications can use subsets of
these conventions. Further, these conventions are meant to comply these conventions. Further, these conventions are meant to comply
strictly with the SDP syntax as defined in rfc2327. strictly with the SDP syntax as defined in rfc2327.
1. Introduction...............................................................3 1. Introduction...............................................................3
2. Representation of Certain Fields within SDP description lines..............4 2. Representation of Certain Fields within SDP description lines..............4
2.1 Representation of Extension Attributes.................................4 2.1 Representation of Extension Attributes.................................4
2.2 Representation of Parameter Values.....................................5 2.2 Representation of Parameter Values.....................................5
2.3 Directionality Convention..............................................5 2.3 Directionality Convention..............................................5
2.4 Case convention.........................................................6 2.4 Case convention.........................................................7
2.5 Use of special characters in SDP parameter values.......................6 2.5 Use of special characters in SDP parameter values.......................7
3. Capabilities Provided by SDP conventions..................................7
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3. Capabilities Provided by SDP conventions..................................7 4. Format of the ATM Session Description......................................9
4. Format of the ATM Session Description......................................8 5. Structure of the Session Description Lines...............................11
5. Structure of the Session Description Lines...............................10 5.1 The Origin Line........................................................11
5.1 The Origin Line........................................................10 5.2 The Session Name Line..................................................12
5.2 The Session Name Line..................................................11 5.3 The Connection Information Line........................................12
5.3 The Connection Information Line........................................11 5.4 The Timestamp Line.....................................................14
5.4 The Timestamp Line.....................................................13 5.5 Media Information Line for ATM connections.............................15
5.5 Media Information Line for ATM connections.............................14 5.5.1 The Virtual Connection ID.........................................15
5.5.1 The Virtual Connection ID.........................................14 5.5.2 The Transport Parameter...........................................17
5.5.2 The Transport Parameter...........................................16 5.5.3 The Format List for AAL1 and AAL5 applications....................19
5.5.3 The Format List for AAL1 and AAL5 applications....................18 5.5.4 The Format List for AAL2 applications.............................19
5.5.4 The Format List for AAL2 applications.............................18 5.5.5 Media information line construction...............................19
5.5.5 Media information line construction...............................18 5.6 The Media Attribute Lines..............................................24
5.6 The Media Attribute Lines..............................................23 5.6.1 ATM bearer connection attributes..................................25
5.6.1 The 'atmmap' attribute.......................................27 5.6.1.1 The 'eecid' attribute...........................................27
5.6.2 The 'eecid' attribute............................................30 5.6.1.2 The 'aalType' attribute.........................................28
5.6.3 The 'aalType' attribute............................................32 5.6.1.3 The 'capability' attribute......................................29
5.6.4 The 'silenceSupp' attribute........................................32 5.6.1.4 The 'qosClass' attribute........................................30
5.6.5 The 'ecanf' and 'ecanb' attributes.................................34 5.6.1.5 The 'bcob' attribute............................................30
5.6.6 The 'gcf' and 'gcb' attributes.....................................35 5.6.1.6 The 'stc' attribute.............................................31
5.6.7 The 'profileDesc' attribute........................................35 5.6.1.7 The 'upcc' attribute............................................31
5.6.8 The 'vsel' attribute...............................................37 5.6.1.8 The 'atmQOSfparms' and 'atmQOSbparms' attributes................32
5.6.9 The 'dsel' attribute...............................................38 5.6.1.9 The 'atmFtrfcDesc' and 'atmBtrfcDesc' attributes................33
5.6.10 The 'fsel' attribute..............................................39 5.6.1.10 The 'abrFparms' and 'abrBparms' attributes......................35
5.6.11 The 'codecconfig' attribute......................................41 5.6.1.11 The 'abrSetup' attribute........................................36
5.6.12 The 'isup_usi' attribute.........................................41 5.6.1.12 The 'bearerType' attribute......................................37
5.6.13 The 'capability' attribute.......................................42 5.6.1.13 The 'lij' attribute.............................................38
5.6.14 The 'qosClass' attribute.........................................43 5.6.1.14 The 'anycast' attribute.........................................38
5.6.15 The 'bcob' attribute.............................................43 5.6.1.15 The 'cache' attribute...........................................39
5.6.16 The 'stc' attribute..............................................44 5.6.1.16 The 'bearerSigIE' attribute.....................................39
5.6.17 The 'upcc' attribute.............................................44 5.6.2 ATM Adaptation Layer (AAL) attributes.............................40
5.6.18 The 'atmQOSfparms' and 'atmQOSbparms' attributes..................44 5.6.2.1 The 'aalApp' attribute..........................................41
5.6.19 The 'atmFtrfcDesc' and 'atmBtrfcDesc' attributes..................46 5.6.2.2 The 'cbrRate' attribute.........................................43
5.6.20 The 'abrFparms' and 'abrBparms' attributes.......................48 5.6.2.3 The 'sbc' attribute.............................................44
5.6.21 The 'clkrec' attribute............................................49 5.6.2.4 The 'clkrec' attribute..........................................45
5.6.22 The 'fec' attribute...............................................49 5.6.2.5 The 'fec' attribute.............................................46
5.6.23 The 'prtfl' attribute.............................................50 5.6.2.6 The 'prtfl' attribute...........................................46
5.6.24 The 'bearerType' attribute........................................50 5.6.2.7 The 'structure' attribute.......................................47
5.6.25 The 'structure' attribute.........................................51 5.6.2.8 The 'fcpsSDUsize' and 'bcpsSDUsize' attributes..................47
5.6.26 The 'sbc' attribute...............................................51 5.6.2.9 The 'aal2CPS' attribute.........................................48
5.6.27 The 'fcpsSDUsize' and 'bcpsSDUsize' attributes....................52 5.6.2.10 The 'aal2CPSSDUrate' attribute..................................48
5.6.28 The 'aal2CPS' attribute...........................................53 5.6.2.11 The 'aal2sscs3661unassured' attribute...........................48
5.6.29 The 'aal2sscs3661unassured' attribute.............................54 5.6.2.12 The 'aal2sscs3661assured' attribute.............................49
5.6.30 The 'aal2sscs3661assured' attribute...............................54 5.6.2.13 The 'aal2sscs3662' attribute....................................50
5.6.31 The 'aal5sscop' attribute.........................................56 5.6.2.14 The 'aal5sscop' attribute.......................................52
5.6.32 The 'aal2sscs3662' attribute......................................56 5.6.3 Service attributes................................................52
5.6.33 The 'aalApp' attribute............................................58 5.6.3.1 The 'atmmap' attribute..........................................53
5.6.34 The 'lij' attribute...............................................60 5.6.3.2 The 'silenceSupp' attribute.....................................58
5.6.35 The 'anycast' attribute...........................................60 5.6.3.3 The 'ecanf' and 'ecanb' attributes..............................59
5.6.36 The 'cache' attribute.............................................61 5.6.3.4 The 'gcf' and 'gcb' attributes..................................60
5.6.37 Specification of Higher-layer attributes..........................61 5.6.3.5 The 'profileDesc' attribute.....................................60
5.6.38 Use of the second media-level part in H.323 Annex C applications..62 5.6.3.6 The 'vsel' attribute............................................62
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5.6.39 Chaining SDP descriptors..........................................63 5.6.3.7 The 'dsel' attribute............................................63
5.6.40 Use of the eecid media attribute in call establishment procedures.63 5.6.3.8 The 'fsel' attribute............................................64
6.0 List of Parameters with Representations...............................68 5.6.3.9 The 'codecconfig' attribute.....................................66
7.0 Examples of ATM session descriptions using SDP.........................76 5.6.3.10 The 'isup_usi' attribute........................................66
8.0 Security Considerations..................................................77 5.6.4 Miscellaneous media attributes...................................67
8.1 Bearer Security.......................................................77 5.6.4.1 The 'chain' attribute............................................67
8.2 Security of the SDP description.......................................77 5.6.5 Use of the second media-level part in H.323 Annex C applications.68
9.0 ATM SDP Grammar.........................................................78 5.6.6 Use of the eecid media attribute in call establishment procedures 68
6.0 List of Parameters with Representations...............................73
7.0 Examples of ATM session descriptions using SDP.........................82
8.0 Security Considerations..................................................83
8.1 Bearer Security.......................................................83
8.2 Security of the SDP description.......................................83
9.0 ATM SDP Grammar.........................................................84
1. Introduction 1. Introduction
SDP will be used in conjunction with a connection handling /device SDP will be used in conjunction with a connection handling /device
control protocol such as Megaco (H.248) [26], SIP [18] or MGCP [25] to control protocol such as Megaco (H.248) [26], SIP [18] or MGCP [25] to
communicate the information needed to set up ATM and AAL2 bearer communicate the information needed to set up ATM and AAL2 bearer
connections. These connections include voice connections, voiceband data connections. These connections include voice connections, voiceband data
connections, clear channel circuit emulation connections, video connections connections, clear channel circuit emulation connections, video connections
and baseband data connections (such as fax relay, modem relay, SSCOP, and baseband data connections (such as fax relay, modem relay, SSCOP,
frame relay etc.). frame relay etc.).
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1. Applications in which a new SVC is set-up for each service 1. Applications in which a new SVC is set-up for each service
connection. These SVCs could be AAL1 or AAL5 SVCs or connection. These SVCs could be AAL1 or AAL5 SVCs or
single-CID AAL2 SVCs. single-CID AAL2 SVCs.
2. Applications in which existing path resources are assigned 2. Applications in which existing path resources are assigned
to service connections. These resources could be: to service connections. These resources could be:
* AAL1/AAL5 PVCs, SPVCs or cached SVCs, * AAL1/AAL5 PVCs, SPVCs or cached SVCs,
* AAL2 single-CID PVCs, SPVCs or cached SVCs, * AAL2 single-CID PVCs, SPVCs or cached SVCs,
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* CIDs within AAL2 SVCs/PVCs/SPVCs that multiplex multiple * CIDs within AAL2 SVCs/PVCs/SPVCs that multiplex multiple
CIDs. CIDs.
Note that the difference between PVCs and SPVCs is in the way the bearer Note that the difference between PVCs and SPVCs is in the way the bearer
virtual circuit connection is set up. SPVCs are a class of PVCs that use virtual circuit connection is set up. SPVCs are a class of PVCs that use
bearer signaling, as opposed to node-by-node provisioning, for connection bearer signaling, as opposed to node-by-node provisioning, for connection
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establishment. establishment.
This document is limited to the case when the network type is ATM. This document is limited to the case when the network type is ATM.
This includes raw RTP encapsulation [45] or voice sample encapsulation This includes raw RTP encapsulation [45] or voice sample encapsulation
[46] over AAL5 with no intervening IP layer. It does not address SDP usage [46] over AAL5 with no intervening IP layer. It does not address SDP usage
for IP, with or without ATM as a lower layer. for IP, with or without ATM as a lower layer.
In some cases, IP connection set-up is independent of lower layers, which In some cases, IP connection set-up is independent of lower layers, which
are configured prior to it. For example, AAL5 PVCs that connect IP routers are configured prior to it. For example, AAL5 PVCs that connect IP routers
can be used for VoIP calls. In other cases, VoIP call set-up is closely can be used for VoIP calls. In other cases, VoIP call set-up is closely
tied to ATM-level connection set-up. This might require a chaining of IP and tied to ATM-level connection set-up. This might require a chaining of IP and
ATM descriptors, as described in section 5.6.39. ATM descriptors, as described in section 5.6.4.1.
This document makes no assumptions on who constructs the session This document makes no assumptions on who constructs the session
descriptions (media gateway, intermediate ATM/AAL2 switch, media descriptions (media gateway, intermediate ATM/AAL2 switch, media
gateway controller etc.). This will be different in different gateway controller etc.). This will be different in different
applications. Further, it allows the use of one session description applications. Further, it allows the use of one session description
for both directions of a connection (as in SIP and MGCP applications) for both directions of a connection (as in SIP and MGCP applications)
or the use of separate session descriptions for different directions. It or the use of separate session descriptions for different directions. It
also addresses the ATM multicast and anycast capabilities. also addresses the ATM multicast and anycast capabilities.
This document makes no assumptions about how the SDP description will This document makes no assumptions about how the SDP description will
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2.1 Representation of Extension Attributes 2.1 Representation of Extension Attributes
The SDP protocol [1] requires that non-standard attributes and codec The SDP protocol [1] requires that non-standard attributes and codec
names use an "X-" prefix. names use an "X-" prefix.
In this internet draft, the "X-" prefix is used consistently for In this internet draft, the "X-" prefix is used consistently for
codec names (Table 2) that have not been registered with the IANA. codec names (Table 2) that have not been registered with the IANA.
The IANA-registered codec names listed in [31] do not The IANA-registered codec names listed in [31] do not
use this prefix, regardless of whether they are statically or use this prefix, regardless of whether they are statically or
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dynamically assigned payload types. dynamically assigned payload types.
However, this prefix is not used for the extension SDP attributes However, this prefix is not used for the extension SDP attributes
defined in this document. This has been done to enhance legibility. defined in this document. This has been done to enhance legibility.
This document suggests that parsers be flexible in the use of the This document suggests that parsers be flexible in the use of the
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"X-" prefix convention. They should accept codec names and attribute "X-" prefix convention. They should accept codec names and attribute
names with or without the "X-" prefix. names with or without the "X-" prefix.
2.2 Representation of Parameter Values 2.2 Representation of Parameter Values
Depending on the format of their representation in SDP, the Depending on the format of their representation in SDP, the
parameters defined in this document fall into the following parameters defined in this document fall into the following
classes: classes:
(1) Parameters always represented in a decimal format. (1) Parameters always represented in a decimal format.
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fixed. For class 4, a "0x" prefix shall always be used to fixed. For class 4, a "0x" prefix shall always be used to
differentiate the hexadecimal from the decimal format. differentiate the hexadecimal from the decimal format.
For both decimal and hex representations, if the underlying bit field For both decimal and hex representations, if the underlying bit field
is smaller or larger than the binary equivalent of the SDP representation, is smaller or larger than the binary equivalent of the SDP representation,
then leading 0 bits should be added or removed as needed. Thus, 3 and then leading 0 bits should be added or removed as needed. Thus, 3 and
0x3 translate into the following five-bit pattern: 0 0011. The SDP 0x3 translate into the following five-bit pattern: 0 0011. The SDP
representations 0x12 and 18 translate into the following five-bit representations 0x12 and 18 translate into the following five-bit
pattern: 1 0010. pattern: 1 0010.
Generally, leading 0 digits are not used in either hexadecimal or decimal Leading 0 digits shall not be used in decimal representations.
Generally, these are also not used in hexadecimal
representations. Exceptions are when an exact number of hex digits representations. Exceptions are when an exact number of hex digits
is expected, as in the case of NSAP addresses. Parsers shall not is expected, as in the case of NSAP addresses. Parsers shall not
reject leading zeros in hex values. reject leading zeros in hex values.
Both single-character and multi-character string values are enclosed in Both single-character and multi-character string values are enclosed in
double quotes (i.e. "). By contrast, single quotes (i.e. ') are used for double quotes (i.e. "). By contrast, single quotes (i.e. ') are used for
emphasizing keywords rather than to refer to characters or strings. emphasizing keywords rather than to refer to characters or strings.
In the text representation of decimal and hex numbers, digits to the In the text representation of decimal and hex numbers, digits to the
left are more significant than digits to the right. left are more significant than digits to the right.
2.3 Directionality Convention 2.3 Directionality Convention
This section defined the meaning of the terms 'forward' and This section defined the meaning of the terms 'forward' and
'backward' as used in this document. This is specially applicable 'backward' as used in this document. This is specially applicable
to parameters that have a specific direction associated with them. to parameters that have a specific direction associated with them.
In this document, 'forward' refers to the direction away from the In this document, 'forward' refers to the direction away from the
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ATM node under consideration, while 'backward' refers to the direction ATM node under consideration, while 'backward' refers to the direction
towards the ATM node. This convention must be used in all SDP-based towards the ATM node. This convention must be used in all SDP-based
session descriptions regardless of whether underlying bearer is an SVC, a session descriptions regardless of whether underlying bearer is an SVC, a
dynamically allocated PVC/SPVC or a dynamically allocated CID. This dynamically allocated PVC/SPVC or a dynamically allocated CID. This
is regardless of which side originates the service connection. If ATM is regardless of which side originates the service connection. If ATM
SVC or AAL2 Q.2630.1 signaling is used, the directionality convention SVC or AAL2 Q.2630.1 signaling is used, the directionality convention
is independent of which side originates the SVC or AAL2 connection. is independent of which side originates the SVC or AAL2 connection.
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This provides a simple way of identifying the direction in which a This provides a simple way of identifying the direction in which a
parameter is applicable, in a manner that is independent of the parameter is applicable, in a manner that is independent of the
underlying ATM or AAL2 bearer. This simplicity comes at a price, underlying ATM or AAL2 bearer. This simplicity comes at a price,
described below. described below.
The convention used by all ATM/AAL2 signaling specifications (e.g. Q.2931 The convention used by all ATM/AAL2 signaling specifications (e.g. Q.2931
Section 1.3.3 and Q.2630.1) mandates that forward direction is from the Section 1.3.3 and Q.2630.1) mandates that forward direction is from the
end initiating setup/establishment via bearer signaling towards the end end initiating setup/establishment via bearer signaling towards the end
receiving the setup/establishment request. The backward direction is in receiving the setup/establishment request. The backward direction is in
the opposite direction. In some cases, the 'forward' and 'backward' the opposite direction. In some cases, the 'forward' and 'backward'
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gateway originating a service-level call. In the backward SVC call set-up gateway originating a service-level call. In the backward SVC call set-up
model, this gateway terminates (rather than originates) an SVC call. The model, this gateway terminates (rather than originates) an SVC call. The
media gateway refers to the traffic descriptor (and hence the PCR) in the media gateway refers to the traffic descriptor (and hence the PCR) in the
direction away from this gateway as the forward traffic descriptor and direction away from this gateway as the forward traffic descriptor and
forward PCR. Clearly, this is at odds with ATM SVC signaling which refers forward PCR. Clearly, this is at odds with ATM SVC signaling which refers
to this very PCR as the backward PCR. The gateway needs to be able to to this very PCR as the backward PCR. The gateway needs to be able to
perform the required swap of directions. In this example, the media perform the required swap of directions. In this example, the media
gateway terminating the service level call (and hence originating the SVC gateway terminating the service level call (and hence originating the SVC
call) does not need to perform this swap. call) does not need to perform this swap.
Certain attributes are defined exclusively for the forward or backward
directions. Examples are the atmQOSfparms, atmFtrfcDesc, abrFparms and
fcpsSDUsize for the forward direction, and atmQOSbparms, atmBtrfcDesc,
abrBparms and bcpsSDUsize for the backward direction. Certain parameters
within attributes are defined exclusively for the forward or backward
directions. Examples for the forward direction are the <fsssar>
subparameter within the 'aal2sscs3661unassured' media attribute line,
the <fsssar>, <fsscopsdu> and <fsscopuu> subparameters within the
'aal2sscs3661assured' media attribute line, the <fsscopsdu> and
<fsscopuu> subparameters within the 'aal5sscop' media attribute line,
and the <fmaxFrame> parameter within the 'aal2sscs3662' media attribute
line. Examples for the backward direction are the <bsssar>
subparameter within the 'aal2sscs3661unassured' media attribute line,
the <bsssar>, <bsscopsdu> and <bsscopuu> subparameters within the
'aal2sscs3661assured' media attribute line, the <bsscopsdu> and
<bsscopuu> subparameters within the 'aal5sscop' media attribute line,
and the <bmaxFrame> parameter within the 'aal2sscs3662' media attribute
line.
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For applications such as SIP, both the forward and backward attributes,
and the forward and backward subparameters within attributes can be
placed within the same SDP descriptor. In other applications
(such as Megaco-based applications), the appropriate place for the
forward attributes and subparameters within attributes is the remote
descriptor, while the appropriate place for the backward
attributes and subparameters within attributes is the local
descriptor.
2.4 Case convention 2.4 Case convention
As defined in RFC2327 [1], SDP syntax is case-sensitive. Since these ATM As defined in RFC2327 [1], SDP syntax is case-sensitive. Since these ATM
conventions conform strictly with SDP syntax, they are case-sensitive. SDP conventions conform strictly with SDP syntax, they are case-sensitive. SDP
line types (e.g. "c", "m", "o", "a") and fields in the SDP lines should be line types (e.g. "c", "m", "o", "a") and fields in the SDP lines should be
built according to the case conventions in [1] and in this document. It is built according to the case conventions in [1] and in this document. It is
suggested, but not required, that SDP parsers for ATM applications be case- suggested, but not required, that SDP parsers for ATM applications be case-
tolerant where ignoring case does not result in ambiguity. tolerant where ignoring case does not result in ambiguity.
2.5 Use of special characters in SDP parameter values 2.5 Use of special characters in SDP parameter values
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String values used in SDP descriptions of ATM connections retain this String values used in SDP descriptions of ATM connections retain this
convention, while allowing the use of the special character "/" in a manner convention, while allowing the use of the special character "/" in a manner
commensurate with [1]. In addition, the special characters "$" and "-" are commensurate with [1]. In addition, the special characters "$" and "-" are
used in the following manner. A "$" value is a wildcard that allows the used in the following manner. A "$" value is a wildcard that allows the
recipient of the SDP description to select any permitted value of the recipient of the SDP description to select any permitted value of the
parameter. A "-" value indicates that it is not necessary to specify the parameter. A "-" value indicates that it is not necessary to specify the
value of the parameter in the SDP description because this parameter is value of the parameter in the SDP description because this parameter is
irrelevant for this application, or because its value can be irrelevant for this application, or because its value can be
known from another source such as provisioning, defaults, another known from another source such as provisioning, defaults, another
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protocol, another SDP descriptor or another part of the same SDP protocol, another SDP descriptor or another part of the same SDP
descriptor. If the use of these special characters is construed as a descriptor. If the use of these special characters is construed as a
violation of rfc2327 [1] syntax, then reserved string values can be used. violation of rfc2327 [1] syntax, then reserved string values can be used.
The string "CHOOSE" can be used in lieu of "$". The string "OMIT" can be The string "CHOOSE" can be used in lieu of "$". The string "OMIT" can be
used in lieu of "-" for an omitted parameter. A decision to use special used in lieu of "-" for an omitted parameter. A decision to use special
characters or reserved keywords will be made before this internet draft characters or reserved keywords will be made before this internet draft
is upgraded to an rfc. is upgraded to an rfc.
3. Capabilities Provided by SDP conventions 3. Capabilities Provided by SDP conventions
To support the applications listed in section 1, the SDP conventions in To support the applications listed in section 1, the SDP conventions in
this document provide the following session control capabilities: this document provide the following session control capabilities:
* Identification of the underlying bearer network type as ATM. * Identification of the underlying bearer network type as ATM.
* Identification by an ATM network element of its own address, * Identification by an ATM network element of its own address,
in one of several possible formats. A connection peer can in one of several possible formats. A connection peer can
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initiate SVC set-up to this address. A call agent or connection initiate SVC set-up to this address. A call agent or connection
peer can select an pre-established bearer path to this address. peer can select an pre-established bearer path to this address.
* Identification of the ATM bearer connection that is to be * Identification of the ATM bearer connection that is to be
bound to the service-level connection. This is either bound to the service-level connection. This is either
a VCC in AAL1/AAL2/AAL5 applications or a channel (identified by a VCC in AAL1/AAL2/AAL5 applications or a channel (identified by
a CID) in AAL2 applications. a CID) in AAL2 applications.
* Identification of media type: audio, video, data. * Identification of media type: audio, video, data.
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standardization work is used for this purpose. In order to standardization work is used for this purpose. In order to
provide a common SDP base for applications based on provide a common SDP base for applications based on
Q.1901 and SIP/SIP+, the neutral term 'eecid' is used Q.1901 and SIP/SIP+, the neutral term 'eecid' is used
in lieu of 'bnc-id' in the SDP session descriptor. in lieu of 'bnc-id' in the SDP session descriptor.
* A means of mapping codec types and packetization periods into * A means of mapping codec types and packetization periods into
service types (voice, voiceband data and facsimile). This is service types (voice, voiceband data and facsimile). This is
useful in determining the encoding to use when the connection is useful in determining the encoding to use when the connection is
upspeeded in response to modem or facsimile tones. upspeeded in response to modem or facsimile tones.
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* A means of describing the adaptation type, QoS class, ATM transfer * A means of describing the adaptation type, QoS class, ATM transfer
capability/service category, broadband bearer class, traffic capability/service category, broadband bearer class, traffic
parameters, CPS parameters and SSCS parameters related the underlying parameters, CPS parameters and SSCS parameters related the underlying
bearer connection. bearer connection.
* Means for enabling or describing special functions such as leaf- * Means for enabling or describing special functions such as leaf-
initiated-join, anycast and SVC caching. initiated-join, anycast and SVC caching.
* For H.323 Annex C applications, a means of specifying the IP address * For H.323 Annex C applications, a means of specifying the IP address
and port number on which the node will receive RTCP messages. and port number on which the node will receive RTCP messages.
* A means of chaining consecutive SDP descriptors so that they refer to * A means of chaining consecutive SDP descriptors so that they refer to
different layers of the same connection. different layers of the same connection.
Rajesh Kumar, Mohamed Mostafa. 8
4. Format of the ATM Session Description 4. Format of the ATM Session Description
The sequence of lines in the session descriptions in this document The sequence of lines in the session descriptions in this document
conforms to rfc2327 [1]. In general, a session description consists of conforms to rfc2327 [1]. In general, a session description consists of
a session-level part followed by zero or more media-level parts. ATM a session-level part followed by zero or more media-level parts. ATM
session descriptions consist of a session-level part followed by one session descriptions consist of a session-level part followed by one
or two media-level parts. The only two media applicable are the ATM or two media-level parts. The only two media applicable are the ATM
bearer medium and RTCP control (where applicable). bearer medium and RTCP control (where applicable).
The session level part consists of the following lines: The session level part consists of the following lines:
skipping to change at line 425 skipping to change at line 464
k= (encryption key, zero or more lines) k= (encryption key, zero or more lines)
a= (media attribute, zero or more lines) a= (media attribute, zero or more lines)
The media level part for RTCP control consists of the following The media level part for RTCP control consists of the following
lines: lines:
m= (media information and transport address, one line) m= (media information and transport address, one line)
c= (connection information for control only, one line) c= (connection information for control only, one line)
In general, the 'v', 'o', 's', and 't' lines are mandatory. In general, the 'v', 'o', 's', and 't' lines are mandatory.
Rajesh Kumar, Mohamed Mostafa. 8
However, in the Megaco [26] context, these lines have been made optional. However, in the Megaco [26] context, these lines have been made optional.
The 'o', 's', and 't' lines are omitted in most MGCP [25] applications. The 'o', 's', and 't' lines are omitted in most MGCP [25] applications.
Note that SDP session descriptors for ATM can contain bandwidth (b=) and Note that SDP session descriptors for ATM can contain bandwidth (b=) and
encryption key (k=) lines. Like all other lines, these lines should encryption key (k=) lines. Like all other lines, these lines should
strictly conform to the SDP standard [1]. strictly conform to the SDP standard [1].
The bandwidth (b=) line is not necessarily redundant in the ATM context The bandwidth (b=) line is not necessarily redundant in the ATM context
since, in some applications, it can be used to convey application-level since, in some applications, it can be used to convey application-level
information which does not map directly into the atmFtrfcDesc and information which does not map directly into the atmFtrfcDesc and
atmBtrfcDesc media attribute lines. For instance, the 'b' line can be used atmBtrfcDesc media attribute lines. For instance, the 'b' line can be used
Rajesh Kumar, Mohamed Mostafa. 9
in SDP descriptors in RTSP commands to describe content bandwidth. in SDP descriptors in RTSP commands to describe content bandwidth.
The encryption key line (k=) can be used The encryption key line (k=) can be used
to indicate an encryption key for the bearer, and a method to to indicate an encryption key for the bearer, and a method to
obtain the key. At present, the encryption of ATM and AAL2 bearers obtain the key. At present, the encryption of ATM and AAL2 bearers
has not been conventionalized, unlike the encryption of RTP payloads. has not been conventionalized, unlike the encryption of RTP payloads.
Nor has the authentication or encryption of ATM or AAL2 bearer signaling. Nor has the authentication or encryption of ATM or AAL2 bearer signaling.
In the ATM and AAL2 contexts, the term 'bearer' can include 'bearer In the ATM and AAL2 contexts, the term 'bearer' can include 'bearer
signaling' as well as 'bearer payloads'. signaling' as well as 'bearer payloads'.
skipping to change at line 462 skipping to change at line 501
The SDP protocol version for session descriptions using these The SDP protocol version for session descriptions using these
conventions is 0. In conformance with standard SDP, it is strongly conventions is 0. In conformance with standard SDP, it is strongly
recommended that the 'v' line be included at the beginning of each recommended that the 'v' line be included at the beginning of each
SDP session description. In some contexts such as Megaco, the SDP session description. In some contexts such as Megaco, the
'v' line is optional and may be omitted unless several session 'v' line is optional and may be omitted unless several session
descriptions are provided in sequence, in which case the descriptions are provided in sequence, in which case the
'v' line serves as a delimiter. Depending on the application, 'v' line serves as a delimiter. Depending on the application,
sequences of session descriptions might refer to: sequences of session descriptions might refer to:
- Different connections or sessions. - Different connections or sessions.
- Alternate ways of realizing the same connection or session. - Alternate ways of realizing the same connection or session.
- Different layers of the same session (section 5.6.39). - Different layers of the same session (section 5.6.4.1).
The 'o', 's' and 't' lines are included for strict conformance with The 'o', 's' and 't' lines are included for strict conformance with
RFC2327. It is possible that these lines might not carry useful RFC2327. It is possible that these lines might not carry useful
information in some ATM-based applications. information in some ATM-based applications.
Therefore, some applications might omit these lines, although Therefore, some applications might omit these lines, although
it is recommended that they not do so. For maximum it is recommended that they not do so. For maximum
interoperability, it is preferable that SDP parsers not interoperability, it is preferable that SDP parsers not
reject session descriptions that do not contain these lines. reject session descriptions that do not contain these lines.
Rajesh Kumar, Mohamed Mostafa. 9 Rajesh Kumar, Mohamed Mostafa. 10
5. Structure of the Session Description Lines 5. Structure of the Session Description Lines
5.1 The Origin Line 5.1 The Origin Line
The origin line for an ATM-based session is structured as follows: The origin line for an ATM-based session is structured as follows:
o=<username> <sessionID> <version> <networkType> o=<username> <sessionID> <version> <networkType>
<addressType> <address> <addressType> <address>
skipping to change at line 527 skipping to change at line 566
is 10 digits wide. This is more restricted than [1], which allows unlimited is 10 digits wide. This is more restricted than [1], which allows unlimited
size. As in [1], the most significant digit is non-zero when an NTP size. As in [1], the most significant digit is non-zero when an NTP
timestamp is used. timestamp is used.
The <networkType> in SDP session descriptions for ATM applications The <networkType> in SDP session descriptions for ATM applications
should be assigned the string value "ATM" or wildcarded to a "$" or "-". should be assigned the string value "ATM" or wildcarded to a "$" or "-".
The <addressType> and <address> parameters are identical to The <addressType> and <address> parameters are identical to
those for the connection information ('c') line (Section 5.3). Each of those for the connection information ('c') line (Section 5.3). Each of
Rajesh Kumar, Mohamed Mostafa. 10 Rajesh Kumar, Mohamed Mostafa. 11
these parameters can be wildcarded per the conventions described these parameters can be wildcarded per the conventions described
for the 'c' line in Section 5.3. These parameters should not me omitted for the 'c' line in Section 5.3. These parameters should not me omitted
since this would violate SDP syntax [1]. since this would violate SDP syntax [1].
As with the 'c' line, SDP parsers are not expected to check the consistency As with the 'c' line, SDP parsers are not expected to check the consistency
of <networkType> with <addressType>, <address> pairs. The <addressType> of <networkType> with <addressType>, <address> pairs. The <addressType>
and <address> need to be consistent with each other. and <address> need to be consistent with each other.
5.2 The Session Name Line 5.2 The Session Name Line
In general, the session name line is structured as follows: In general, the session name line is structured as follows:
s=<sessionName> s=<sessionName>
For ATM-based sessions, the <sessionName> parameter is set to a "-". For ATM-based sessions, the <sessionName> parameter is set to a "-".
The resulting line is: The resulting line is:
s=- s=-
skipping to change at line 574 skipping to change at line 612
Further, this may be wildcarded to "$" or "-". If this is done, an Further, this may be wildcarded to "$" or "-". If this is done, an
node using ATM as the basic transport mechanism will select a node using ATM as the basic transport mechanism will select a
value of "ATM". A node that interfaces with multiple network types value of "ATM". A node that interfaces with multiple network types
("IN", "ATM" etc.) that include ATM can also choose a value of "ATM". ("IN", "ATM" etc.) that include ATM can also choose a value of "ATM".
When the SDP description is built by a node such as a media gateway, When the SDP description is built by a node such as a media gateway,
the <address> refers to the address of the node building the SDP the <address> refers to the address of the node building the SDP
description. When this description is forwarded to another node, it still description. When this description is forwarded to another node, it still
contains the original node's address. When the media gateway contains the original node's address. When the media gateway
controller builds part or all of the SDP description, the local descriptor controller builds part or all of the SDP description, the local descriptor
can contain the address of the local node, while the contains the address of the local node, while the
remote descriptor can contain the address of the remote node. remote descriptor contains the address of the remote node.
If the <address> and/or <addressType> are irrelevant or are If the <address> and/or <addressType> are irrelevant or are
known by other means, they can be wildcarded per the conventions known by other means, they can be set to a "$" or a "-", as described
described below. below.
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Additionally, in all contexts, the 'm' line can have an ATM address in the Additionally, in all contexts, the 'm' line can have an ATM address in the
Rajesh Kumar, Mohamed Mostafa. 12
<virtualConnectionId> subparameter which, if present, is the <virtualConnectionId> subparameter which, if present, is the
remote address if the 'c' line address is local, and vice versa. remote address if the 'c' line address is local, and vice versa.
For ATM networks, the <addressType> can be NSAP, E164 or GWID (ALIAS). For ATM networks, the <addressType> can be NSAP, E164 or GWID (ALIAS).
For ATM networks, the <address> syntax depends on the syntax of For ATM networks, the <address> syntax depends on the syntax of
the <addressType>. SDP parsers should check the consistency the <addressType>. SDP parsers should check the consistency
of <addressType> with <address>. of <addressType> with <address>.
NSAP: If the addressType is NSAP, the address is expressed in NSAP: If the addressType is NSAP, the address is expressed in
the standard dotted hex form. This is a string of 40 hex digits, the standard dotted hex form. This is a string of 40 hex digits,
with dots after the 2nd, 6th, 10th, 14th, 18th, 22nd, 26th, 30th, with dots after the 2nd, 6th, 10th, 14th, 18th, 22nd, 26th, 30th,
34th and 38th digits. The last octet of the NSAP address is the 34th and 38th digits. The last octet of the NSAP address is the
'selector' field that is available for non-standard use. An example 'selector' field that is available for non-standard use. An example
of a 'c' line with an NSAP address is: of a śc∆ line with an NSAP address is:
c=ATM NSAP 47.0091.8100.0000.0060.3e64.fd01.0060.3e64.fd01.00 c=ATM NSAP 47.0091.8100.0000.0060.3e64.fd01.0060.3e64.fd01.00
A "0x" prefix shall not be used in this case since this is always in A "0x" prefix shall not be used in this case since this is always in
hexadecimal format. hexadecimal format.
E164: If the addressType is E164, the address is expressed as E164: If the addressType is E164, the address is expressed as
a decimal number with up to 15 digits. For example: a decimal number with up to 15 digits. For example:
c=ATM E164 9738294382 c=ATM E164 9738294382
skipping to change at line 631 skipping to change at line 670
("A"-"Z", "a"-"z", "0" - "9",".","-","_"). For example: ("A"-"Z", "a"-"z", "0" - "9",".","-","_"). For example:
c=ATM GWID officeABCmgx101vism12 c=ATM GWID officeABCmgx101vism12
Since these SDP conventions can be used for more than gateways, the Since these SDP conventions can be used for more than gateways, the
string "ALIAS" can be used instead of "GWID" in the 'c' line. Thus, string "ALIAS" can be used instead of "GWID" in the 'c' line. Thus,
the example above is equivalent to: the example above is equivalent to:
c=ATM ALIAS officeABCmgx101vism12 c=ATM ALIAS officeABCmgx101vism12
Rajesh Kumar, Mohamed Mostafa. 12
An example of a GWID (ALIAS)is the CLLI code used for telecom An example of a GWID (ALIAS)is the CLLI code used for telecom
equipment. For all practical purposes, it should be adequate for the equipment. For all practical purposes, it should be adequate for the
Rajesh Kumar, Mohamed Mostafa. 13
GWID (ALIAS) to be a variable length string with a maximum size of 32 GWID (ALIAS) to be a variable length string with a maximum size of 32
characters. characters.
The connection information line is always present in an SDP session The connection information line is always present in an SDP session
descriptor. However, each of the parameters on this line can be wildcarded descriptor. However, each of the parameters on this line can be wildcarded
to a "$" or a "-", independently of whether other parameters on this line to a "$" or a "-", independently of whether other parameters on this line
are wildcarded or not. Not all syntactically legal wildcard combinations are wildcarded or not. Not all syntactically legal wildcard combinations
are meaningful in a particular application. are meaningful in a particular application.
Examples of meaningful wildcard combinations in the ATM context are: Examples of meaningful wildcard combinations in the ATM context are:
skipping to change at line 683 skipping to change at line 723
follows: follows:
t= <startTime> <stopTime> t= <startTime> <stopTime>
Per Ref. [49], NTP time stamps use a 32 bit unsigned Per Ref. [49], NTP time stamps use a 32 bit unsigned
representation of seconds, and a 32 bit unsigned representation of representation of seconds, and a 32 bit unsigned representation of
fractional seconds. For ATM-based sessions, the <startTime>parameter can fractional seconds. For ATM-based sessions, the <startTime>parameter can
be made equal to the NTP timestamp referring to the moment when be made equal to the NTP timestamp referring to the moment when
the SDP session descriptor was created. It can also be set to 0 the SDP session descriptor was created. It can also be set to 0
indicating its irrelevance. If it made equal to the NTP indicating its irrelevance. If it made equal to the NTP
Rajesh Kumar, Mohamed Mostafa. 13
timestamp in seconds, the fractional part of the NTP timestamp is omitted. timestamp in seconds, the fractional part of the NTP timestamp is omitted.
When equated to the integer part of an NTP timestamp, the <startTime> When equated to the integer part of an NTP timestamp, the <startTime>
field is 10 digits wide. This is more restricted than [1], which field is 10 digits wide. This is more restricted than [1], which
Rajesh Kumar, Mohamed Mostafa. 14
allows unlimited size. As in [1], the most significant digit is allows unlimited size. As in [1], the most significant digit is
non-zero when an NTP timestamp is used. non-zero when an NTP timestamp is used.
The <stopTime> parameter is set to 0 for ATM-based SDP descriptors. The <stopTime> parameter is set to 0 for ATM-based SDP descriptors.
5.5 Media Information Line for ATM connections 5.5 Media Information Line for ATM connections
The general format of the media information line adapted for AAL1 The general format of the media information line adapted for AAL1
and AAL5 applications is: and AAL5 applications is:
skipping to change at line 737 skipping to change at line 777
* <addressType>-<address>/<ex_vpci>/<ex_vci> * <addressType>-<address>/<ex_vpci>/<ex_vci>
* <address>/<ex_vpci>/<ex_vci> * <address>/<ex_vpci>/<ex_vci>
The <virtualConnectionId> in AAL2 applications can be in one of the The <virtualConnectionId> in AAL2 applications can be in one of the
following formats: following formats:
* <ex_vcci>/<ex_cid> * <ex_vcci>/<ex_cid>
* <addressType>-<address>/<ex_vcci>/<ex_cid> * <addressType>-<address>/<ex_vcci>/<ex_cid>
* <address>/<ex_vcci>/<ex_cid> * <address>/<ex_vcci>/<ex_cid>
* <ex_bcg>/<ex_vcci>/<ex_cid> * <ex_bcg>/<ex_vcci>/<ex_cid>
Rajesh Kumar, Mohamed Mostafa. 14
* <ex_portId>/<ex_vpi>/<ex_vci>/<ex_cid> * <ex_portId>/<ex_vpi>/<ex_vci>/<ex_cid>
* <ex_bcg>/<ex_vpi>/<ex_vci>/<ex_cid> * <ex_bcg>/<ex_vpi>/<ex_vci>/<ex_cid>
* <ex_vpci>/<ex_vci>/<ex_cid> * <ex_vpci>/<ex_vci>/<ex_cid>
Rajesh Kumar, Mohamed Mostafa. 15
* <addressType>-<address>/<ex_vpci>/<ex_vci>/<ex_cid> * <addressType>-<address>/<ex_vpci>/<ex_vci>/<ex_cid>
* <address>/<ex_vpci>/<ex_vci>/<ex_cid> * <address>/<ex_vpci>/<ex_vci>/<ex_cid>
Here, Here,
<ex_vcci> = VCCI-<vcci> <ex_vcci> = VCCI-<vcci>
<ex_vpci> = VPCI-<vpci> <ex_vpci> = VPCI-<vpci>
<ex_bcg> = BCG-<bcg> <ex_bcg> = BCG-<bcg>
<ex_portId> = PORT-<portId> <ex_portId> = PORT-<portId>
<ex_vpi> = VPI-<vpi> <ex_vpi> = VPI-<vpi>
<ex_vci> = VCI-<vci> <ex_vci> = VCI-<vci>
skipping to change at line 770 skipping to change at line 810
The <addressType> and <address> are identical The <addressType> and <address> are identical
to their definitions above for the connection information line with to their definitions above for the connection information line with
the difference that this address refers to the remote peer in the the difference that this address refers to the remote peer in the
media information line. Since the <virtualConnectionId>, as defined media information line. Since the <virtualConnectionId>, as defined
here, is meant for use in ATM networks, the values of <addressType> here, is meant for use in ATM networks, the values of <addressType>
and <address> in the <virtualConnectionId> are limited to ATM-specific and <address> in the <virtualConnectionId> are limited to ATM-specific
values. values.
The <vpi>, <vci> and <cid> have their usual ATM connotation. The The <vpi>, <vci> and <cid> have their usual ATM connotation. The
<vpi> is an 8 or 12 bit field. The <vci> is a 16 bit field. The <cid> <vpi> is an 8 or 12 bit field. The <vci> is a 16-bit field. The <cid>
is an 8 bit field. is an 8-bit field.
The <vpci> is a 16 bit field defined in Section 4.5.16 of ITU The <vpci> is a 16-bit field defined in Section 4.5.16 of ITU
Q.2931 [Ref. 15]. The <vpci> is similar to the <vpi>,except for its Q.2931 [Ref. 15]. The <vpci> is similar to the <vpi>,except for its
width and the fact that it retains its value across VP crossconnects. width and the fact that it retains its value across VP crossconnects.
In some applications, the size of the <vpci> is the same as the size of In some applications, the size of the <vpci> is the same as the size of
the <vpi> (8 or 12 bits). In this case, the most significant 8 or 4 bits the <vpi> (8 or 12 bits). In this case, the most significant 8 or 4 bits
are ignored. are ignored.
The <vcci> is a 16 bit field defined in ITU Recommendation Q.2941.2 [32]. The <vcci> is a 16-bit field defined in ITU Recommendation Q.2941.2 [32].
The <vcci> is similar to the <vci>, except for the fact that it retains The <vcci> is similar to the <vci>, except for the fact that it retains
its value across VC crossconnects. its value across VC crossconnects.
Since <vpci> and <vcci> values are unique between a pair of nodes, they Since <vpci> and <vcci> values are unique between a pair of nodes, they
need to be qualified, at any node, by the ATM address of the remote node. need to be qualified, at any node, by the ATM address of the remote node.
These parameters can be pre-provisioned or signaled. When signaled, the These parameters can be pre-provisioned or signaled. When signaled, the
<vpci> is encapsulated in the connection identifier information element of <vpci> is encapsulated in the connection identifier information element of
SVC signaling messages. The <vcci> is encapsulated in the Generic SVC signaling messages. The <vcci> is encapsulated in the Generic
Information Transport (GIT) information element of SVC signaling messages. Information Transport (GIT) information element of SVC signaling messages.
In an ATM node pair, either node can assign <vcci> values and signal it to In an ATM node pair, either node can assign <vcci> values and signal it to
Rajesh Kumar, Mohamed Mostafa. 15
the other end via SVC signaling. A glare avoidance scheme is defined in [32] the other end via SVC signaling. A glare avoidance scheme is defined in [32]
and [44].This mechanism works in SVC applications. A different glare and [44].This mechanism works in SVC applications. A different glare
avoidance technique is needed when a pool of existing PVCs/SPVCs is avoidance technique is needed when a pool of existing PVCs/SPVCs is
Rajesh Kumar, Mohamed Mostafa. 16
dynamically assigned to calls. One such scheme for glare reduction is the dynamically assigned to calls. One such scheme for glare reduction is the
assignment of <vcci> values from different ends of the <vcci> range, using assignment of <vcci> values from different ends of the <vcci> range, using
the lowest or highest available value as applicable. the lowest or highest available value as applicable.
When <vpci> and <vcci> values are pre-provisioned, administrations have the When <vpci> and <vcci> values are pre-provisioned, administrations have the
option of provisioning them uniquely in a network or in a subnet. In this option of provisioning them uniquely in a network or in a subnet. In this
case, the ATM address of the far end is not needed to qualify these case, the ATM address of the far end is not needed to qualify these
parameters. parameters.
In the AAL2 context, the definition of a VCC implies that there is no In the AAL2 context, the definition of a VCC implies that there is no
skipping to change at line 845 skipping to change at line 885
wildcarding the <virtualConnectionId> in the AAL2 context are: $, wildcarding the <virtualConnectionId> in the AAL2 context are: $,
VCCI-40/CID-$, BCG-100/VPI-20/VCI-120/CID-$, NSAP-$/VCCI-$/CID-$, VCCI-40/CID-$, BCG-100/VPI-20/VCI-120/CID-$, NSAP-$/VCCI-$/CID-$,
$/VCCI-$/CID-$. $/VCCI-$/CID-$.
It is also permissible to set the entire <virtualConnectionId> parameter It is also permissible to set the entire <virtualConnectionId> parameter
to a "-" indicating its irrelevance. to a "-" indicating its irrelevance.
5.5.2 The Transport Parameter 5.5.2 The Transport Parameter
The <transport> parameter indicates the method used to encapsulate the The <transport> parameter indicates the method used to encapsulate the
Rajesh Kumar, Mohamed Mostafa. 16
service payload. These methods are not defined in this document, which service payload. These methods are not defined in this document, which
refers to existing ATMF and ITU-T standards, which, in turn, might refers to existing ATMF and ITU-T standards, which, in turn, might
refer to other standards. For ATM applications, the following refer to other standards. For ATM applications, the following
Rajesh Kumar, Mohamed Mostafa. 17
<transport> values are defined: <transport> values are defined:
Table 1: List of Transport Parameter values used in SDP in the ATM context Table 1: List of Transport Parameter values used in SDP in the ATM context
+---------------------------------------------------------------------+ +---------------------------------------------------------------------+
| | Controlling Document for | | | Controlling Document for |
| Transport | Encapsulation of Service Payload | | Transport | Encapsulation of Service Payload |
+------------------------+--------------------------------------------+ +------------------------+--------------------------------------------+
| AAL1/ATMF | af-vtoa-0078.000 [7] | | AAL1/ATMF | af-vtoa-0078.000 [7] |
+------------------------+--------------------------------------------+ +------------------------+--------------------------------------------+
| AAL1/ITU | ITU-T H.222.1 [51] | | AAL1/ITU | ITU-T H.222.1 [51] |
skipping to change at line 899 skipping to change at line 939
A value of "AAL1/custom", "AAL2/custom" or "AAL5/custom" for the A value of "AAL1/custom", "AAL2/custom" or "AAL5/custom" for the
<transport> parameter can indicate non-standard or semi-standard <transport> parameter can indicate non-standard or semi-standard
encapsulation schemes defined by a corporation or a multi-vendor encapsulation schemes defined by a corporation or a multi-vendor
agreement. Since there is no standard administration of this agreement. Since there is no standard administration of this
convention, care should be taken to preclude inconsistencies convention, care should be taken to preclude inconsistencies
within the scope of a deployment. within the scope of a deployment.
The use of <transport> values "AAL1/<corporateName>", The use of <transport> values "AAL1/<corporateName>",
"AAL2/<corporateName>", "AAL5/<corporateName>", "AAL1/IEEE:<oui>", "AAL2/<corporateName>", "AAL5/<corporateName>", "AAL1/IEEE:<oui>",
Rajesh Kumar, Mohamed Mostafa. 17
"AAL2/IEEE:<oui>" and "AAL5/IEEE:<oui>" is similar. These indicate "AAL2/IEEE:<oui>" and "AAL5/IEEE:<oui>" is similar. These indicate
non-standard transport mechanisms or AAL2 profiles which should non-standard transport mechanisms or AAL2 profiles which should
be used consistently within the scope of an application or deployment. be used consistently within the scope of an application or deployment.
Rajesh Kumar, Mohamed Mostafa. 18
The parameter <corporateName> is the registered, globally unique name The parameter <corporateName> is the registered, globally unique name
of a corporation(e.g. Cisco, Telcordia etc.). The parameter <oui> of a corporation(e.g. Cisco, Telcordia etc.). The parameter <oui>
is the hex representation of a three-octet field identical to the OUI is the hex representation of a three-octet field identical to the OUI
maintained by the IEEE. Since this is always represented in hex, the "0x" maintained by the IEEE. Since this is always represented in hex, the "0x"
prefix shall not be used. For example, "IEEE:00000C" is one of the prefix shall not be used. Leading zeros can be omitted. For
<oui> values that refers to Cisco Systems, Inc. example, "IEEE:00000C" and "IEEE:C" both refer to
Cisco Systems, Inc.
5.5.3 The Format List for AAL1 and AAL5 applications 5.5.3 The Format List for AAL1 and AAL5 applications
In the AAL1 and AAL5 contexts, the <format list> is a list of payload In the AAL1 and AAL5 contexts, the <format list> is a list of payload
types: types:
<payloadType#1> <payloadType#2>...<payloadType#n> <payloadType#1> <payloadType#2>...<payloadType#n>
In most AAL1 and AAL5 applications, the ordering of payload types In most AAL1 and AAL5 applications, the ordering of payload types
implies a preference (preferred payload types before less favored implies a preference (preferred payload types before less favored
skipping to change at line 954 skipping to change at line 995
range 1-255. range 1-255.
5.5.5 Media information line construction 5.5.5 Media information line construction
Using the parameter definitions above, the 'm' for AAL1-based audio Using the parameter definitions above, the 'm' for AAL1-based audio
media can be constructed as follows: media can be constructed as follows:
m=audio <virtualConnectionId> AAL1/ATMF <payloadType#1> m=audio <virtualConnectionId> AAL1/ATMF <payloadType#1>
<payloadType#2>...<payloadType #n> <payloadType#2>...<payloadType #n>
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Note that only those payload types, whether statically mapped or Note that only those payload types, whether statically mapped or
dynamically assigned, that are consistent with af-vtoa-78 [7] can be used dynamically assigned, that are consistent with af-vtoa-78 [7] can be used
in this construction. in this construction.
Backwards compatibility note: The transport value "AAL1/AVP" used in Backwards compatibility note: The transport value "AAL1/AVP" used in
previous versions of this document should be considered equivalent to previous versions of this document should be considered equivalent to
the value "AAL1/ATMF" defined above. "AAL1/AVP" is unsuitable because the value "AAL1/ATMF" defined above. "AAL1/AVP" is unsuitable because
the AVP profile is closely tied to RTP. the AVP profile is closely tied to RTP.
An example 'm' line use for audio media over AAL1 is: An example 'm' line use for audio media over AAL1 is:
skipping to change at line 1002 skipping to change at line 1043
of the terms in the virtual connection ID are implicit in the application of the terms in the virtual connection ID are implicit in the application
context. The audio media on this VCC is encapsulated according to ITU-T context. The audio media on this VCC is encapsulated according to ITU-T
H.222.1 [51]. The encodings to be used are either ITU-T G.722 or ITU-T H.222.1 [51]. The encodings to be used are either ITU-T G.722 or ITU-T
G.728 (LD-CELP), in preferential order. G.728 (LD-CELP), in preferential order.
The 'm' for AAL5-based H.323 Annex C audio [45] can be constructed as The 'm' for AAL5-based H.323 Annex C audio [45] can be constructed as
follows: follows:
m=audio <virtualConnectionId> RTP/AVP <payloadType#1> m=audio <virtualConnectionId> RTP/AVP <payloadType#1>
<payloadType#2>...<payloadType #n> <payloadType#2>...<payloadType #n>
Rajesh Kumar, Mohamed Mostafa. 19
For example: For example:
m=audio PORT-9/VPI-3/VCI-$ RTP/AVP 2 96 m=audio PORT-9/VPI-3/VCI-$ RTP/AVP 2 96
a=rtpmap:96 X-G727-32 a=rtpmap:96 X-G727-32
a=aalType:AAL5 a=aalType:AAL5
a=aalApp:itu_h323c
Rajesh Kumar, Mohamed Mostafa. 20
a=aalApp:itu_h323c - -
implies that any VCI on VPI= 3 of trunk port #9 may be used. This VC implies that any VCI on VPI= 3 of trunk port #9 may be used. This VC
encapsulates RTP packets directly on AAL5 per [45]. The 'rtpmap' (rather encapsulates RTP packets directly on AAL5 per [45]. The 'rtpmap' (rather
than the 'atmmap') attribute is used to dynamically map the payload type than the 'atmmap') attribute is used to dynamically map the payload type
of 96 into the codec name X-G727-32 (Table 2). This name represents 32 of 96 into the codec name X-G727-32 (Table 2). This name represents 32
kbps EADPCM. kbps EADPCM.
The 'm' line for AAL5-based video media can be constructed as follows: The 'm' line for AAL5-based video media can be constructed as follows:
m=video <virtualConnectionId> AAL5/ITU <payloadType#1> m=video <virtualConnectionId> AAL5/ITU <payloadType#1>
skipping to change at line 1055 skipping to change at line 1096
AAL2 profile to be bound to a connection. AAL2 profile to be bound to a connection.
In most applications, the ordering of profiles implies a preference In most applications, the ordering of profiles implies a preference
(preferred profiles before less favored ones). Therefore, there can be (preferred profiles before less favored ones). Therefore, there can be
multiple instances of the same <transport> value in the same 'm' line. multiple instances of the same <transport> value in the same 'm' line.
An example 'm' line use for audio media over AAL2 is: An example 'm' line use for audio media over AAL2 is:
m=audio VCCI-27/CID-19 AAL2/ITU 7 AAL2/custom 100 AAL2/ITU 1 m=audio VCCI-27/CID-19 AAL2/ITU 7 AAL2/custom 100 AAL2/ITU 1
Rajesh Kumar, Mohamed Mostafa. 20
This indicates the use of CID #19 on VCCI #27 to carry audio. It provides This indicates the use of CID #19 on VCCI #27 to carry audio. It provides
a preferential list of profiles for this connection: profile AAL2/ITU 7 a preferential list of profiles for this connection: profile AAL2/ITU 7
defined in [13], AAL2/custom 100 defined in an application-specific or defined in [13], AAL2/custom 100 defined in an application-specific or
interoperability document and profile AAL2/ITU 1 defined in [13]. interoperability document and profile AAL2/ITU 1 defined in [13].
Rajesh Kumar, Mohamed Mostafa. 21
Another example of the use of the 'm' line use for audio media over AAL2 Another example of the use of the 'm' line use for audio media over AAL2
is: is:
m=audio VCCI-$/CID-$ AAL2/ATMF 6 8 m=audio VCCI-$/CID-$ AAL2/ATMF 6 8
This indicates that any AAL2 CID may be used, subject to any applicable This indicates that any AAL2 CID may be used, subject to any applicable
glare avoidance/reduction rules. The profiles that can be bound to this glare avoidance/reduction rules. The profiles that can be bound to this
connection are AAL2/ATMF 6 defined in af-vtoa-0113.000 [44] and AAL2/ATMF 8 connection are AAL2/ATMF 6 defined in af-vtoa-0113.000 [44] and AAL2/ATMF 8
defined in af-vmoa-0145.000 [52]. These sources use non-overlapping defined in af-vmoa-0145.000 [52]. These sources use non-overlapping
profile number ranges. The profiles they define fall under the <transport> profile number ranges. The profiles they define fall under the <transport>
skipping to change at line 1109 skipping to change at line 1150
m=audio VCCI-123/CID-5 - - m=audio VCCI-123/CID-5 - -
a=aalType:AAL2 a=aalType:AAL2
a=aal2sscs3662:audio off off on off on off off off - - - a=aal2sscs3662:audio off off on off on off off off - - -
Besides indicating an audio medium, a VCCI of 123 and a CID of 5, Besides indicating an audio medium, a VCCI of 123 and a CID of 5,
the 'm' line indicates an unspecified profile. The media attribute lines the 'm' line indicates an unspecified profile. The media attribute lines
indicate an adaptation layer of AAL2, and the use of the audio SAP [13] indicate an adaptation layer of AAL2, and the use of the audio SAP [13]
to carry demodulated facsimile. to carry demodulated facsimile.
Rajesh Kumar, Mohamed Mostafa. 21
The media information line for "data" media has one of the following The media information line for "data" media has one of the following
the following formats: the following formats:
m=data <virtualConnectionId> - - m=data <virtualConnectionId> - -
Rajesh Kumar, Mohamed Mostafa. 22
m=data - - - m=data - - -
The data could be circuit emulation data carried over AAL1 or AAL2, The data could be circuit emulation data carried over AAL1 or AAL2,
or packet data carried over AAL5. Media attribute lines, rather than or packet data carried over AAL5. Media attribute lines, rather than
the 'm' line, are used to indicate the adaptation type for the data the 'm' line, are used to indicate the adaptation type for the data
media. Examples of the representation of data media are listed below. media. Examples of the representation of data media are listed below.
m=data PORT-7/VPI-6/VCI-$ - - m=data PORT-7/VPI-6/VCI-$ - -
a=aalApp:AAL5_SSCOP a=aalApp:AAL5_SSCOP- -
implies that any VCI on VPI= 6 of trunk port #7 may be used. This VC implies that any VCI on VPI= 6 of trunk port #7 may be used. This VC
uses SSCOP on AAL5 to transport data. uses SSCOP on AAL5 to transport data.
m=data PORT-7/VPI-6/VCI-50 - - m=data PORT-7/VPI-6/VCI-50 - -
a=aalType:AAL1_SDT a=aalType:AAL1_SDT
a=sbc:6 a=sbc:6
implies that VCI 50 on VPI 6 on port 7 uses structured AAL1 to transfer implies that VCI 50 on VPI 6 on port 7 uses structured AAL1 to transfer
6 x 64 kbps circuit emulation data. This may be alternately represented 6 x 64 kbps circuit emulation data. This may be alternately represented
skipping to change at line 1161 skipping to change at line 1203
mapped into payload types through the 'atmmap' attribute. For example: mapped into payload types through the 'atmmap' attribute. For example:
m=audio VCCI-27 AAL1/AVP 98 m=audio VCCI-27 AAL1/AVP 98
a=atmmap:98 X-CCD a=atmmap:98 X-CCD
a=sbc:6 a=sbc:6
implies that AAL1 VCCI=27 is used for 6 x 64 transmission. implies that AAL1 VCCI=27 is used for 6 x 64 transmission.
In the AAL2 context, the X-CCD codec can be assigned a profile In the AAL2 context, the X-CCD codec can be assigned a profile
type and number. Even though it is not possible to construct type and number. Even though it is not possible to construct
Rajesh Kumar, Mohamed Mostafa. 22
a profile table as described in ITU I.366.2 for this "codec", a profile table as described in ITU I.366.2 for this "codec",
it is preferable to adopt the common AAL2 profile convention in its it is preferable to adopt the common AAL2 profile convention in its
case. An example AAL2 profile mapping for the X-CCD codec could case. An example AAL2 profile mapping for the X-CCD codec could
be as follows: be as follows:
Rajesh Kumar, Mohamed Mostafa. 23
PROFILE TYPE PROFILE NUMBER "CODEC" (ONLY ONE) PROFILE TYPE PROFILE NUMBER "CODEC" (ONLY ONE)
"custom" 200 X-CCD "custom" 200 X-CCD
The profile does not identify the number of subchannels ('n' in nx64). The profile does not identify the number of subchannels ('n' in nx64).
This is known by other means such as the 'sbc' media attribute line. This is known by other means such as the 'sbc' media attribute line.
For example, the media information line: For example, the media information line:
m=audio $ AAL2/custom 200 m=audio $ AAL2/custom 200
a=sbc:6 a=sbc:6
skipping to change at line 1214 skipping to change at line 1255
cases, a media attribute line with all parameters set to "-" carries cases, a media attribute line with all parameters set to "-" carries
no information and should be preferably omitted. In other cases, no information and should be preferably omitted. In other cases,
such as the 'lij' media attribute line, the very presence of the such as the 'lij' media attribute line, the very presence of the
media attribute line conveys meaning. media attribute line conveys meaning.
There are no restrictions placed by rfc2327 [1] regarding the order There are no restrictions placed by rfc2327 [1] regarding the order
of 'a' lines with respect to other 'a' lines. However, these lines of 'a' lines with respect to other 'a' lines. However, these lines
must not contradict each other or the other SDP lines. Inconsistencies must not contradict each other or the other SDP lines. Inconsistencies
are not to be ignored and should be flagged as errors. Repeated media are not to be ignored and should be flagged as errors. Repeated media
attribute lines can carry additional information. These should not attribute lines can carry additional information. These should not
Rajesh Kumar, Mohamed Mostafa. 23
be inconsistent with each other. be inconsistent with each other.
Applications will selectively use the optional media attribute Applications will selectively use the optional media attribute
lines listed below. This is meant to be an exhaustive list for lines listed below. This is meant to be an exhaustive list for
describing the general attributes of ATM bearer networks. describing the general attributes of ATM bearer networks.
The following is a summary list of the SDP media attributes that can Rajesh Kumar, Mohamed Mostafa. 24
be used in the ATM context. Detailed descriptions of these attributes The base specification for SDP, rfc2327 [1], allows the definition
are to be found in subsequent sections. of new attributes. In keeping with this spirit, some of the attributes
defined in this document can also be used in SDP descriptions of IP
and other non-ATM sessions. For example, the 'vsel', 'dsel' and 'fsel'
attributes defined below refer generically to codecs. These can be
used for service-specific codec negotiation and assignment in non-ATM
as well as ATM applications.
SDP media attributes defined in this document for use in the ATM
context are classified as:
* ATM bearer connection attributes (Section 5.6.1)
* AAL attributes (Section 5.6.2)
* Service attributes (Section 5.6.3).
* Miscellaneous media attributes, that cannot be classified as
ATM, AAL or service attributes (Section 5.6.4).
In addition to these, the SDP attributes defined in [1] can also
be used in the ATM context. Examples are:
* The attributes defined in RFC2327 which allow indication of * The attributes defined in RFC2327 which allow indication of
the direction in which a session is active. These are the direction in which a session is active. These are
a=sendonly, a=recvonly, a=sendrecv, a=inactive. a=sendonly, a=recvonly, a=sendrecv, a=inactive.
* The 'Ptime' attribute defined in RFC2327. It indicates the * The 'Ptime' attribute defined in RFC2327. It indicates the
packet period. It is not recommended that this attribute be used packet period. It is not recommended that this attribute be used
in ATM applications since packet period information is provided with in ATM applications since packet period information is provided with
other parameters e.g. the profile type and number in the 'm' line, other parameters e.g. the profile type and number in the 'm' line,
and the 'vsel', 'dsel' and 'fsel' attributes. Also, for AAL1 and the 'vsel', 'dsel' and 'fsel' attributes. Also, for AAL1
applications, 'ptime' is not applicable and should be flagged as an applications, 'ptime' is not applicable and should be flagged as an
error. If used in AAL2 and AAL5 applications, 'ptime' should be error. If used in AAL2 and AAL5 applications, 'ptime' should be
consistent with the rest of the SDP description. consistent with the rest of the SDP description.
* The 'atmmap' attribute. In the AAL1 and AAL5 contexts, this is
used to dynamically map payload types into codec strings. * The 'fmtp' attribute used to designate format-specific
parameters.
5.6.1 ATM bearer connection attributes
The following is a summary list of the SDP media attributes that can
be used to describe ATM bearer connections. These are detailed in
subsequent subsections.
* The 'eecid' attribute. This stands for 'end-to-end connection * The 'eecid' attribute. This stands for 'end-to-end connection
identifier'. It provides a means of correlating service-level identifier'. It provides a means of correlating service-level
connections with underlying ATM bearer connections. connections with underlying ATM bearer connections.
In the Q.1901 [36] context, the eecid is synonymous with the In the Q.1901 [36] context, the eecid is synonymous with the
bnc-id (backbone network connection identifier). bnc-id (backbone network connection identifier).
* The 'aalType' attribute. This is used to indicate the nature * The 'aalType' attribute. This is used to indicate the nature
of the ATM adaptation layer (AAL). of the ATM adaptation layer (AAL).
* The 'silenceSupp' attribute, used to indicate the use of
of voice activity detection for silence suppression, and to
optionally parameterize the silence suppression function.
* The 'ecanf' and 'ecanb' attributes, used to indicate the use of
of echo cancellation, and to parameterize the this function.
* The 'gcf' and 'gcb' attributes, used to indicate the use of
of gain control, and to parameterize the this function.
* The 'profileDesc' attribute which can be used to describe
AAL2 profiles. Although any AAL2 profile can be so described,
this attribute is useful for describing, at connection
establishment time, custom profiles that might not be known
to the far end. This attribute applies in the AAL2 context
only.
* The 'vsel' attribute which indicates a prioritized list of
3-tuples for voice service. Each 3-tuple indicates a codec,
an optional packet length and an optional packetization
period. This complements the 'm' line information and should
be consistent with it.
* The 'dsel' attribute which indicates a prioritized list of
3-tuples for voiceband data service. Each 3-tuple indicates a
codec, an optional packet length and an optional packetization
period. This complements the 'm' line information and should
Rajesh Kumar, Mohamed Mostafa. 24 Rajesh Kumar, Mohamed Mostafa. 25
be consistent with it. * The 'capability' attribute, which indicates the ATM transfer
* The 'fsel' attribute which indicates a prioritized list of
3-tuples for facsimile service. Each 3-tuple indicates a
codec, an optional packet length and an optional packetization
period. This complements the 'm' line information and should
be consistent with it.
* The 'codecconfig' attribute which is used to represent the
contents of the single codec information element (IE) defined
in ITU Q.765.5 [57].
* The 'isup_usi' attribute which is used to represent
the 'User Information Layer 1 protocol' field within the
bearer capability information element defined in Section
4.5.5 of ITU Q.931 [59].
* The 'capability' attribute which indicates the ATM transfer
capability (ITU nomenclature), synonymous with the ATM Service capability (ITU nomenclature), synonymous with the ATM Service
Category (ATMF nomenclature). Category (ATMF nomenclature).
* The 'qosClass' attribute which indicates the QoS class of the
* The 'qosClass' attribute, which indicates the QoS class of the
ATM bearer connection. ATM bearer connection.
* The 'bcob' attribute which indicates the broadband connection
oriented bearer class. * The 'bcob' attribute, which indicates the broadband connection
* The 'stc' attribute which indicates susceptibility to oriented bearer class, and whether end-to-end timing is
required.
* The 'stc' attribute, which indicates susceptibility to
clipping. clipping.
* The 'upcc' attribute which indicates the user plane connection
* The 'upcc' attribute, which indicates the user plane connection
configuration. configuration.
* The 'atmQOSfparms' and 'atmQOSbparms' attributes are
* The 'atmQOSfparms' and 'atmQOSbparms' attributes, which are
used to describe certain key ATM QoS parameters in the forward used to describe certain key ATM QoS parameters in the forward
and backward directions respectively. and backward directions respectively.
* The 'atmFtrfcDesc' and 'atmBtrfcDesc' attributes which are
* The 'atmFtrfcDesc' and 'atmBtrfcDesc' attributes, which are
used to describe ATM traffic descriptor parameters in the used to describe ATM traffic descriptor parameters in the
forward and backward directions respectively. forward and backward directions respectively.
* The 'abrFparms' and 'abrBparms' attributes which are
* The 'abrFparms' and 'abrBparms' attributes, which are
used to describe ABR-specific parameters in the used to describe ABR-specific parameters in the
forward and backward directions respectively. These parameters forward and backward directions respectively. These parameters
are per the UNI 4.0 signaling specification [5]. are per the UNI 4.0 signaling specification [5].
* The 'clkrec' attribute which indicates the clock recovery
method for AAL1 unstructured data transfer (UDT). * The 'abrSetup' attribute, which is used to indicate the
* The 'fec' attribute which indicates the use of ABR parameters needed during call/connection establishment.
forward error correction.
* The 'prtfl' attribute which indicates indicate the fill * The 'bearerType' attribute, which is used to indicate
level of partially filled cells.
* The 'bearerType' attribute is used to indicate
whether the underlying bearer is an ATM PVC/SPVC, an ATM SVC, whether the underlying bearer is an ATM PVC/SPVC, an ATM SVC,
or an AAL2 CID connection within an existing ATM SVC/PVC/SPVC. or an AAL2 CID connection within an existing ATM SVC/PVC/SPVC.
* When present, the 'structure' attribute is used to indicate
the presence or absence of AAL1 structured data transfer (SDT),
and the size of the SDT blocks.
* When present, the 'sbc' media attribute line denotes the
subchannel count in the case of n x 64 clear channel
communication.
* When present, the 'fcpsSDUsize' and 'bcpsSDUsize'
attributes are used to indicate the maximum size of the
CPCS SDU payload in the forward and backward directions.
Rajesh Kumar, Mohamed Mostafa. 25 * The 'lij' attribute, which is used to indicate the
* When present, the 'aal2CPS' attribute is used to
indicate that an AAL2 CPS sublayer as defined in
ITU I.363.2 [13] is associated with the VCC referred to in the
'm' line. Optionally, it can be used to indicate selected
CPS options and parameter values for this VCC.
* When present, the 'aal2sscs3661unassured' attribute is used
to indicate the presence of an AAL2 SSCS sublayer with
unassured transmission as defined in ITU I.366.1 [12].
Optionally, it can be used to indicate selected options and
parameter values for this SSCS.
* When present, the 'aal2sscs3661assured' attribute is used
to indicate the presence of an AAL2 SSCS sublayer with
assured transmission as defined in ITU I.366.1 [12].
Optionally, it can be used to indicate selected options and
parameter values for this SSCS.
* When present, the 'aal5sscop' attribute is used to
indicate the existence of an SSCOP protocol layer over
an AAL5 CPS layer, and the parameters which pertain to
this SSCOP layer.
* When present, the 'aal2sscs3662' attribute is used to
indicate the presence of an AAL2 SSCS sublayer as defined
in ITU I.366.2. Optionally, it can be used to indicate
selected options and parameter values for this SSCS.
* When present, the 'aalApp' attribute is used to point to the
controlling standard for an application layer above the ATM
adaptation layer.
* When present, the 'lij' attribute is used to indicate the
presence of a connection that uses the Leaf-initiated-join presence of a connection that uses the Leaf-initiated-join
capability described in UNI 4.0 [5], and to optionally capability described in UNI 4.0 [5], and to optionally
describe parameters associated with this capability. describe parameters associated with this capability.
* When present, the 'anycast' attribute line is used to
* The 'anycast' attribute, which is used to
indicate the applicability of the anycast function described indicate the applicability of the anycast function described
in UNI 4.0 [5], and to optionally qualify it with certain in UNI 4.0 [5], and to optionally qualify it with certain
parameters. parameters.
* When present, the 'cache' attribute line is used to enable
* The 'cache' attribute, which is used to enable
SVC caching and to specify an inactivity timer for SVC release. SVC caching and to specify an inactivity timer for SVC release.
* The 'fmtp' attribute line defined in the SDP standard can be
used to describe higher-layer parameters. These pertain
to layers higher than the ATM adaptation layer that are
not closely coupled with the ATM or ATM adaptation layers.
Examples are the B-HLI and B-LLI IEs specified in ITU Q.2931 [15],
and the user-to-user information element described in
ITU Q.2957 [48].
* The 'chain' attribute line is used to chain consecutive SDP
descriptions.
The base specification for SDP, rfc2327 [1], allows the definition * The 'bearerSigIE' attribute, which can be used to represent
of new attributes. In keeping with this spirit, some of the attributes ITU Q-series information elements in bit-map form. This is useful
listed above can also be used in SDP descriptions of IP
and other non-ATM sessions. For example, the 'vsel', 'dsel' and 'fsel'
attributes refer generically to codecs. These can be used for service-
specific codec negotiation and assignment in non-ATM as well as
Rajesh Kumar, Mohamed Mostafa. 26 Rajesh Kumar, Mohamed Mostafa. 26
ATM applications. in describing parameters that are not closely coupled to the
ATM and AAL layers. Examples are the B-HLI and B-LLI IEs specified
5.6.1 The 'atmmap' attribute in ITU Q.2931 [15], and the user-to-user information
element described in ITU Q.2957 [48].
The 'atmmap' attribute is defined on the basis of the 'rtpmap'
attribute used in RFC2327.
a=atmmap:<payloadType> <encodingName>
The 'atmmap' attribute is used to dynamically map encoding names
into payload types. This is necessary for those encoding names which
have not been assigned a static payload type through IANA [31]. Payload
types and encoding techniques that have been registered with IANA
for RTP are retained for AAL1 and AAL5.
The range of statically defined payload types is in the range
0-95. All static assignments of payload types to codecs are
listed in [31]. The range of payload types defined dynamically
via the 'atmmap' attribute is 96-127.
In addition to reiterating the payload types and encoding
names in [31], Table 2 defines non-standard encoding names
(with "X-" prefixes). Note that [31], rather than Table 2,
is the authoritative list of standard codec names and payload
types in the ATM context.
Rajesh Kumar, Mohamed Mostafa. 27
Table 2: Encoding Names and Payload Types
|---------------------|--------------|---------------------------|
| Encoding Technique | Encoding Name| Payload type |
|---------------------|--------------|---------------------------|
| PCM - Mu law | "PCMU" | 0 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| 32 kbps ADPCM | "G726-32" | 2 (Statically Mapped) |
|---------------------|--------------|---------------------------|
|Dual rate 5.3/6.3kbps| "G723" | 4 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| PCM- A law | "PCMA" | 8 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| 7 KHz audio coding | "G722" | 9 (Statically Mapped) |
| within 64 kbps | | |
|---------------------|--------------|---------------------------|
| LD-CELP | "G728" | 15 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| CS-ACELP | "G729" | 18 (Statically Mapped) |
|(normal/low-complexity) | |
|---------------------|--------------|---------------------------|
| Low-complexity | "X-G729a" | None, map dynamically |
| CS-ACELP | | |
|---------------------|--------------|---------------------------|
|Normal | "X-G729b" | None, map dynamically |
|CS-ACELP w/ ITU | | |
|defined silence | | |
|suppression | | |
+---------------------+--------------+---------------------------+
|Low-complexity | "X-G729ab" | None, map dynamically |
|CS-ACELP w/ ITU | | |
|defined silence | | |
|suppression | | |
|---------------------|--------------|---------------------------|
| 16 kbps ADPCM | "X-G726-16" | None, map dynamically |
|---------------------|--------------|---------------------------|
| 24 kbps ADPCM | "X-G726-24" | None, map dynamically |
|---------------------|--------------|---------------------------|
| 40 kbps ADPCM | "X-G726-40" | None, map dynamically |
|---------------------|--------------|---------------------------|
| Dual rate 5.3/6.3 |"X-G7231-H" | None, map dynamically |
| kbps - high rate | | |
|---------------------|--------------|---------------------------|
| Dual rate 5.3/6.3 |"X-G7231-L" | None, map dynamically |
| kbps - low rate | | |
|---------------------|--------------|---------------------------|
| Dual rate 5.3/6.3 |"X-G7231a-H" | None, map dynamically |
| kbps - high rate w/ | | |
| ITU-defined silence | | |
| suppression | | |
|----------------------------------------------------------------|
Rajesh Kumar, Mohamed Mostafa. 28
+---------------------+--------------+---------------------------+
| Dual rate 5.3/6.3 |"X-G7231a-L" | None, map dynamically |
| kbps - high rate w/ | | |
| ITU-defined silence | | |
| suppression | | |
|---------------------|--------------|---------------------------|
| 16 kbps EADPCM | "X-G727-16" | None, map dynamically |
|---------------------|--------------|---------------------------|
| 24 kbps EADPCM | "X-G727-24" | None, map dynamically |
|---------------------|--------------|---------------------------|
| 32 kbps EADPCM | "X-G727-32" | None, map dynamically |
|---------------------|--------------|---------------------------|
|n x 64 kbps Clear | "X-CCD" | None, map dynamically |
|Channel without CAS | | |
|per af-vtoa-78 [7] | | |
|---------------------|--------------|---------------------------|
|n x 64 kbps Clear | "X-CCD-CAS" | None, map dynamically |
|Channel with CAS | | |
|per af-vtoa-78 [7] | | |
|---------------------|--------------|---------------------------|
|GSM Full Rate | "GSM" | 3 (Statically Mapped) |
|---------------------|--------------|---------------------------|
|GSM Half Rate | "GSM-HR" | None, map dynamically |
|---------------------|--------------|---------------------------|
|GSM-Enhanced Full Rate "GSM-EFR" | None, map dynamically |
|---------------------|--------------|---------------------------|
|GSM-Enhanced Half Rate "GSM-EHR" | None, map dynamically |
|---------------------|--------------|---------------------------|
|Group 3 fax demod. "X-FXDMOD-3" | None, map dynamically |
|---------------------|--------------|---------------------------|
| Federal Standard | "1016" | 1 (Statically Mapped) |
| FED-STD 1016 CELP | | |
|---------------------|--------------|---------------------------|
| DVI4, 8 KHz [3] | "DVI4" | 5 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| DVI4, 16 KHz [3] | "DVI4" | 6 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| LPC [3], Linear | "LPC" | 7 (Statically Mapped) |
| Predictive Coding | | |
|---------------------|--------------|---------------------------|
| L16 [3], Sixteen | "L16" | 10 (Statically Mapped) |
| Bit Linear PCM, | | |
| Double channel | | |
|---------------------|--------------|---------------------------|
| L16 [3], Sixteen | "L16" | 11 (Statically Mapped) |
| Bit Linear PCM, | | |
| Single channel | | |
|---------------------|--------------|---------------------------|
| QCELP [3] | "QCELP" | 12 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| MPEG1/MPEG2 audio | "MPA" | 14 (Statically Mapped) |
|---------------------|--------------|---------------------------|
Rajesh Kumar, Mohamed Mostafa. 29
+---------------------+--------------+---------------------------+
| DVI4, 11.025 KHz[3] | "DVI4" | 16 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| DVI4, 22.05 KHz [3] | "DVI4" | 17 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| MPEG1/MPEG2 video | "MPV" | 32 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| MPEG 2 audio/video | "MP2T" | 33 (Statically Mapped) |
| transport stream | | |
|---------------------|--------------|---------------------------|
| ITU H.261 video | "H261" | 31 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| ITU H.263 video | "H263" | 33 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| ITU H.263 video |"H263-1998" | None, map dynamically |
| 1998 version | | |
|---------------------|--------------|---------------------------|
|MPEG 1 system stream | "MP1S" | None, map dynamically |
|---------------------|--------------|---------------------------|
|MPEG 2 program stream| "MP2P" | None, map dynamically |
|---------------------|--------------|---------------------------|
|Redundancy | "RED" | None, map dynamically |
|---------------------|--------------|---------------------------|
|Variable rate DVI4 | "VDVI" | None, map dynamically |
|---------------------|--------------|---------------------------|
|Cell-B | "CelB" | 25 |
|---------------------|--------------|---------------------------|
|JPEG | "JPEG" | 26 |
|---------------------|--------------|---------------------------|
|nv | "nv" | 28 |
|---------------------|--------------|---------------------------|
|L8, Eight Bit Linear | "L8" | None, map dynamically |
|PCM | | |
|---------------------|--------------|---------------------------|
| ITU-R Recommendation| "BT656" | None, map dynamically |
| BT.656-3 for | | |
| digital video | | |
|---------------------|--------------|---------------------------|
| Adaptive Multirate | "FR-AMR" | None, map dynamically |
|-Full Rate (3GPP)[58]| | |
|---------------------|--------------|---------------------------|
| Adaptive Multirate | "HR-AMR" | None, map dynamically |
|-Half Rate (3GPP)[58]| | |
|---------------------|--------------|---------------------------|
| Adaptive Multirate | "HR-UMTS" | None, map dynamically |
|- UMTS(3GPP) [58] | | |
|---------------------|--------------|---------------------------|
5.6.2 The 'eecid' attribute 5.6.1.1 The 'eecid' attribute
The 'eecid' attribute is synonymous with the 4-byte'bnc-id' The 'eecid' attribute is synonymous with the 4-byte'bnc-id'
Rajesh Kumar, Mohamed Mostafa. 30
parameter used by T1SI, the ATM forum and the ITU (Q.1901) parameter used by T1SI, the ATM forum and the ITU (Q.1901)
standardization effort. The term 'eecid' stands for 'end-to-end standardization effort. The term 'eecid' stands for 'end-to-end
connection identifier', while 'bnc-id' stands for 'backbone network connection identifier', while 'bnc-id' stands for 'backbone network
connection identifier'. The name "backbone" is slightly misleading connection identifier'. The name "backbone" is slightly misleading
since it refers to the entire ATM network including the ATM edge and since it refers to the entire ATM network including the ATM edge and
ATM core networks. In Q.1901 terminology, an ATM "backbone" ATM core networks. In Q.1901 terminology, an ATM "backbone"
connects TDM or analog edges. connects TDM or analog edges.
While the term 'bnc-id' might be used in the bearer signaling plane While the term 'bnc-id' might be used in the bearer signaling plane
and in an ISUP (Q.1901) call control plane, SDP session descriptors and in an ISUP (Q.1901) call control plane, SDP session descriptors
use the neutral term 'eecid'. This provides a common SDP baseline use the neutral term 'eecid'. This provides a common SDP baseline
for applications that use ISUP (Q.1901) and applications that use for applications that use ISUP (Q.1901) and applications that use
SIP/SIP+. SIP/SIP+.
Section 5.6.40 depicts the use of the eecid in call establishment Section 5.6.6 depicts the use of the eecid in call establishment
procedures. In these procedures, the eecid is used to correlate procedures. In these procedures, the eecid is used to correlate
service-level calls with SVC set-up requests. service-level calls with SVC set-up requests.
In the forward SVC establishment model, the call-terminating gateway In the forward SVC establishment model, the call-terminating gateway
selects an eecid and transmits it via SDP to the call-originating selects an eecid and transmits it via SDP to the call-originating
gateway. The call originating gateway transmits this eecid to the gateway. The call originating gateway transmits this eecid to the
call terminating gateway via the bearer set-up message (SVC set-up call terminating gateway via the bearer set-up message (SVC set-up
or Q.2630.1 establish request). or Q.2630.1 establish request).
In the backward SVC establishment model, the call-originating gateway In the backward SVC establishment model, the call-originating gateway
skipping to change at line 1607 skipping to change at line 1419
over using and releasing values of this parameter. The eecid over using and releasing values of this parameter. The eecid
attribute is used to correlate, one-to-one, received bearer set-up attribute is used to correlate, one-to-one, received bearer set-up
requests with service-level call control signaling. requests with service-level call control signaling.
Within an SDP session description, the eecid attribute is used as Within an SDP session description, the eecid attribute is used as
follows: follows:
a=eecid:<eecid> a=eecid:<eecid>
where <eecid> consists of up to 8 hex digits (equivalent to 4 where <eecid> consists of up to 8 hex digits (equivalent to 4
Rajesh Kumar, Mohamed Mostafa. 27
octets). Since this is always represented in hex, the "0x" octets). Since this is always represented in hex, the "0x"
prefix shall not be used. prefix shall not be used.
Within the text representation of the <eecid> parameter, hex digits Within the text representation of the <eecid> parameter, hex digits
to the left are more significant than hex digits to the right to the left are more significant than hex digits to the right
(Section 2.2). (Section 2.2).
This SDP document does not specify how the eecid (synonymous This SDP document does not specify how the eecid (synonymous
Rajesh Kumar, Mohamed Mostafa. 31
with bnc-id) is to be communicated through bearer signaling with bnc-id) is to be communicated through bearer signaling
(Q.931, UNI, PNNI, AINI, IISP, proprietary signaling equivalent, (Q.931, UNI, PNNI, AINI, IISP, proprietary signaling equivalent,
Q.2630.1). This is a task of these bearer signaling protocols. Q.2630.1). This is a task of these bearer signaling protocols.
However, the following informative statements are made to However, the following informative statements are made to
convey a sense of the interoperability that is a goal of convey a sense of the interoperability that is a goal of
current standardization efforts: current standardization efforts:
- ITU Q.2941.3 and the ATMF each recommend the use of the - ITU Q.2941.3 and the ATMF each recommend the use of the
GIT IE for carrying the eecid (synonymous with bnc-id) GIT IE for carrying the eecid (synonymous with bnc-id)
in the set-up message of ATM signaling protocols (Q.2931, in the set-up message of ATM signaling protocols (Q.2931,
skipping to change at line 1649 skipping to change at line 1461
The node assigning the eecid can release and re-use it when it The node assigning the eecid can release and re-use it when it
receives a Q.2931 [15] set-up message or a Q.2630.1 [37] receives a Q.2931 [15] set-up message or a Q.2630.1 [37]
establish request message containing the eecid. establish request message containing the eecid.
However, in both cases (backward and forward models), However, in both cases (backward and forward models),
it is recommended that this eecid be retained until the connection it is recommended that this eecid be retained until the connection
terminates. Since the eecid space is large enough, it is not terminates. Since the eecid space is large enough, it is not
necessary to release it as soon as possible. necessary to release it as soon as possible.
5.6.3 The 'aalType' attribute 5.6.1.2 The 'aalType' attribute
When present, the 'aalType' attribute is used to indicate When present, the 'aalType' attribute is used to indicate
the ATM adaptation layer. If this information is redundant the ATM adaptation layer. If this information is redundant
with the 'm' line, it can be omitted. The format of the with the 'm' line, it can be omitted. The format of the
'aalType' media attribute line is as follows: 'aalType' media attribute line is as follows:
a=aalType: <aalType> a=aalType: <aalType>
Here, <aalType> can take on the following string values: Here, <aalType> can take on the following string values:
"AAL1", "AAL1_SDT", "AAL1_UDT", "AAL2", "AAL3/4", "AAL5" "AAL1", "AAL1_SDT", "AAL1_UDT", "AAL2", "AAL3/4", "AAL5"
and "USER_DEFINED_AAL". Note that "AAL3/4" and "USER DEFINED AAL" and "USER_DEFINED_AAL". Note that "AAL3/4" and "USER DEFINED AAL"
are not addressed in this document.
5.6.4 The 'silenceSupp' attribute
When present, the 'silenceSupp' attribute is used to indicate
the use or non-use of silence suppression.
Rajesh Kumar, Mohamed Mostafa. 32
The format of the 'silenceSupp' media attribute line is
as follows:
a=silenceSupp: <silenceSuppEnable> <silenceTimer> <suppPref> <sidUse>
<fxnslevel>
If any of the parameters in the silenceSupp media attribute line
is not specified, is inapplicable or is implied, then it is set to
"-".
The <silenceSuppEnable> can take on values of "on" or "off". If it
is "on", then silence suppression is enabled.
The <silenceTimer> is a 16-bit field which can be represented in
decimal or hex. Each increment (tick) of this timer represents
a millisecond. The maximum value of this timer is between 1 and 3
minutes. This timer represents the time-lag before silence
suppression kicks in. Even though this can, theoretically, be
as low as 1 ms, most DSP algorithms take more than that to
detect silence. Setting <silenceTimer> to a large value (say
1 minute> is equivalent to disabling silence suppression
within a call. However, idle channel suppression between calls
on the basis of silence suppression is still operative in
non-switched, trunking applications if <silenceSuppEnable> = "on"
and <silenceTimer> is a large value.
The <suppPref> specifies the preferred silence suppression
method that is preferred or already selected. It can
take on the string values of "standard" and "custom". If
its value is "standard", then a standard method (e.g. ITU-defined)
is preferred to custom methods if such a standard
is defined. Otherwise, a custom method may be used. If
<suppPref> is set to "custom", then a custom method, if
available, is preferred to the standard method.
The <sidUse> indicates whether SIDs (Silence Insertion
Descriptors) are to be used, and whether they use fixed comfort
noise or sampled background noise. It can take on the
string values of "No SID", "Fixed Noise", "Sampled Noise".
If the value of <sidUse> is "Fixed Noise", then <fxnslevel>
provides its level. It can take on integer values in the range
0-127, as follows:
Rajesh Kumar, Mohamed Mostafa. 33
+-----------------------+---------------------+
| <fxnslevel> value | Meaning |
+-----------------------+---------------------+
| 0-29 | Reserved |
| 30 | -30 dBm0 |
| 31 | -31 dBm0 |
| . . . | . . . |
| 77 | -77 dBm0 |
| 78 | -78 dBm0 |
| 79-126 | reserved |
| 127 | Idle Code (no noise)|
+-----------------------+---------------------+
In addition to the decimal representation of <fxnslevel>, a
hex representation, preceded by a "0x" prefix, is also allowed.
5.6.5 The 'ecanf' and 'ecanb' attributes
When present, the 'ecanf' and 'ecanb' attributes are used to indicate
the use or non-use of echo cancellation in the forward
and backward directions respectively. See Section
2.3 for a definition of the terms 'forward' and 'backward'.
The format of the 'ecanf' and 'ecanb' media attribute lines is
as follows:
a=ecanf: <ecanEnable> <ecanType>
a=ecanb: <ecanEnable> <ecanType>
If any of the parameters in the ecanf and ecanb media attribute lines
is not specified, is inapplicable or is implied, then it is set to
"-".
If the 'ecanf' or 'ecanb' media attribute lines is not present,
then means other than the SDP descriptor must be used to determine
the applicability and nature of echo cancellation in that direction.
Examples of such means are MIB provisioning, the local connection options
structure in MGCP etc.
The <ecanEnable> parameter can take on values of "on" or "off". If it
is "on", then echo cancellation is enabled. If it is "off",
then echo cancellation is disabled.
The <ecanType> parameter can take on the string values "G165" and "G168"
respectively.
When SDP is used with some media gateway control protocols such as MGCP
and Megaco [26], there exist means outside SDP descriptions to specify
the echo cancellation properties of a connection. Nevertheless, this
media attribute line is included for completeness. As a result, the
SDP can be used for describing echo cancellation in applications
Rajesh Kumar, Mohamed Mostafa. 34
where alternate means for this are unavailable.
5.6.6 The 'gcf' and 'gcb' attributes
When present, the 'gcf' and 'gcb' attributes are used to indicate
the use or non-use of gain control in the forward and backward
directions respectively. See Section 2.3 for a definition of the
terms 'forward' and 'backward'.
The format of the 'gcf' and 'gcb' media attribute lines is as
follows:
a=gcf: <gcEnable> <gcLvl>
a=gcb: <gcEnable> <gcLvl>
If any of the parameters in the gcf and gcb media attribute lines
is not specified, is inapplicable or is implied, then it is set to
"-". If the 'gcf' or 'gcb' media attribute line is not present,
then means other than the SDP descriptor must be used to determine the
applicability and nature of gain control in that direction. Examples of such
means are MIB provisioning, the local connection options structure in MGCP
etc.
The <gcEnable> parameter can take on values of "on" or "off". If it
is "on", then gain control is enabled. If it is "off", then
gain control is disabled.
The <gcLvl> parameter is represented as the decimal or hex
equivalent of a 16-bit binary field. A value of 0xFFFF implies
automatic gain control. Otherwise, this number indicates the
number of decibels of inserted loss. The upper bound, 65,535 dB
(0xFFFE) of inserted loss, is an absurdly large number and is a
carryover from Megaco [26]. In practical applications, the inserted loss
is much lower.
When SDP is used with some media gateway control protocols such as MGCP
and Megaco [26], there exist means outside SDP descriptions to specify
the gain control properties of a connection. Nevertheless, this
media attribute line is included for completeness. As a result, the
SDP can be used for describing gain control in applications
where alternate means for this are unavailable.
5.6.7 The 'profileDesc' attribute
There is one 'profileDesc' media attribute line for each AAL2
profile that is intended to be described. The 'profileDesc' media
attribute line is structured as follows:
a=profileDesc: <aal2transport> <profile> <uuiCodeRange#1>
<encodingName#1> <packetLength#1> <packetTime#1>
<uuiCodeRange#2> <encodingName#2> <packetLength#2>
<packetTime#2>... <uuiCodeRange#N> <encodingName#N>
Rajesh Kumar, Mohamed Mostafa. 35
<packetLength#N> <packetTime#N>
Here, <aal2transport> can have those values of <transport> (Table 1) that
pertain to AAL2. These are:
AAL2/ATMF
AAL2/ITU
AAL2/custom
AAL2/<corporateName>
AAL2/IEEE:<oui>
The parameter <profile> is identical to its definition for the 'm'
line (Section 5.5.4).
The profile elements (rows in the profile tables of ITU I.366.2 or
AF-VTOA-0113) are represented as four-tuples following the <profile>
parameter in the 'profileDesc' media attribute line. If a member of
one of these four-tuples is not specified or is implied, then it is
set to "-".
The <uuiCodeRange> parameter is represented by D1-D2, where D1 and
D2 are decimal integers in the range 0 through 15.
The <encodingName> parameter can take one of the values in column 2
of Table 2. Additionally, it can take on the following descriptor
strings: "PCMG", "SIDG" and "SID729". These stand for generic PCM,
generic SID and G.729 SID respectively.
The <packetLength> is a decimal integer representation of the AAL2
packet length in octets.
The <packetTime> is a decimal integer representation of the AAL2
packetization interval in microseconds.
For instance, the 'profileDesc' media attribute line below defines
the AAL2/custom 100 profile. This profile is reproduced in the Table 3
below. For a description of the parameters in this profile such as
M and the sequence number interval, see ITU I.366.2 [13].
a=profileDesc:AAL2/custom 100 0-7 PCMG 40 5000 0-7 SIDG 1 5000 8-15
G726-32 40 10000 8-15 SIDG 1 5000
If the <packetTime> parameter is to be omitted or implied, then the
same profile can be represented as follows:
a=profileDesc:AAL2/custom 100 0-7 PCMG 40 - 0-7 SIDG 1 - 8-15
G726-32 40 - 8-15 SIDG 1 -
If a gateway has a provisioned or hard coded definition of a
profile, then any definition provided via the 'profileDesc' line
overrides it. The exception to this rule is with regard to standard
Rajesh Kumar, Mohamed Mostafa. 36
profiles such as ITU-defined profiles and ATMF-defined profiles. In
general, these should not be defined via a 'profileDesc' media
attribute line. If they are, then the definition needs to be
consistent with the standard definition else the SDP session
descriptor should be rejected with an appropriate error code.
Table 3: Example of a custom AAL2 profile
|---------------------------------------------------------------|
| UUI | Packet |Encoding | | |Packet|Seq.No. |
| Code | Length |per ITU |Description of | M |Time |Interval|
|point |(octets)|I.366.2 | Algorithm | |(ms) |(ms) |
|Range | | 2/99 | | | | |
| | | version | | | | |
|---------------------------------------------------------------|
| 0-7 | 40 | Figure | PCM, G.711-64,| 1 | 5 | 5 |
| | | B-1 | generic | | | |
|------|--------|---------|---------------|-----|------|--------|
| 0-7 | 1 | Figure | Generic SID | 1 | 5 | 5 |
| | | I-1 | | | | |
|------|--------|---------|---------------|-----|------|--------|
| 8-15 | 40 | Figure | ADPCM, | 2 | 10 | 5 |
| | | E-2 | G.726-32 | | | |
|------|--------|---------|---------------|-----|------|--------|
| 8-15 | 1 | Figure | Generic SID | 1 | 5 | 5 |
| | | I-1 | | | | |
|------|--------|---------|---------------|-----|------|--------|
5.6.8 The 'vsel' attribute
The 'vsel' attribute indicates a prioritized list of one or more
3-tuples for voice service. Each 3-tuple indicates a codec, an optional
packet length and an optional packetization period. This complements the 'm'
line information and should be consistent with it.
The 'vsel' line is structured as follows:
a=vsel:<encodingName #1> <packetLength #1><packetTime #1>
<encodingName #2> <packetLength #2><packetTime #2>
...
<encodingName #N> <packetLength #N><packetTime #N>
where the <encodingName> parameter can take one of the values in column 2 of
Table 2. The <packetLength> is a decimal integer representation of the
packet length in octets. The <packetTime> is a decimal integer
representation of the packetization interval in microseconds. The parameters
<packetLength>and <packetTime> can be set to "-" when not needed. Also, the
entire 'vsel' media attribute line can be omitted when not needed.
For example,
a=vsel:G729 10 10000 G726-32 40 10000
Rajesh Kumar, Mohamed Mostafa. 37
indicates first preference of G.729 or G.729a (both are interoperable) as
the voice encoding scheme. A packet length of 10 octets and a packetization
interval of 10 ms are associated with this codec. G726-32 is the second
preference stated in this line, with an associated packet length of 40
octets and a packetization interval of 10 ms. If the packet length and
packetization interval are intended to be omitted, then this media attribute
line becomes
a=vsel:G729 - - G726-32 - -
The media attribute line
a=vsel:G726-32 40 10000
indicates preference for or selection of 32 kbps ADPCM with a packet
length of 40 octets and a packetization interval of 10 ms.
This media attribute line can be used in ATM as well as non-ATM contexts.
Within the ATM context, it can be applied to the AAL1, AAL2 and AAL5
adaptations. The <packetLength> and <packetTime> are not meaningful
in the AAL1 case and should be set to "-". In the AAL2 case,
this line determines the use of some or all of the rows in
a given profile table. If multiple 3-tuples are present, they
can indicate a hierarchical assignment of some rows in that
profile to voice service e.g. row A preferred to row B etc.
If multiple profiles are present on the 'm' line, the profile
qualified by this attribute is the first
profile. If a single profile that has been selected for a connection
is indicated in the 'm' line, the 'vsel' attribute qualifies the
use, for voice service, of codecs within that profile.
With most of the encoding names in Figure 2, the packet length
and packetization period can be derived from each other. One of them
can be set to "-" without a loss of information. There are some
exceptions such as the IANA-registered encoding names G723, DVI4 and
L16 for which this is not true. Therefore, there is a need to
retain both the packet length and packetization period in the
definition of the 'vsel' line.
5.6.9 The 'dsel' attribute
The 'dsel' attribute indicates a prioritized list of
one or more 3-tuples for voiceband data service. The <fxIncl>
flag indicates whether this definition of voiceband data
includes fax ("on" value) or not ("off" value). If <fxIncl> is
"on", then the 'dsel' line must be consistent with any 'fsel' line
in the session description. In this case, an error event is generated
in the case of inconsistency. Each 3-tuple indicates a codec,
an optional packet length and an optional packetization
period. This complements the 'm' line information and should
be consistent with it.
Rajesh Kumar, Mohamed Mostafa. 38
The 'dsel' line is structured as follows:
a=dsel:<fxIncl> <encodingName #1> <packetLength #1><packetTime #1>
<encodingName #2> <packetLength #2><packetTime #2>
...
<encodingName #N> <packetLength #N><packetTime #N>
where the <encodingName> parameter can take one of the values in
column 2 of Table 2. The <packetLength> and <packetTime>
parameters are per their definition, above, for the 'vsel'
media attribute line. The parameters <packetLength>and <packetTime>)
can be set to "-" when not needed. The <fxIncl> flag is presumed to be
"off" if it is set to "-". Also, the entire 'dsel' media attribute line
can be omitted when not needed.
For example,
a=dsel:- G726-32 20 5000 PCMU 40 5000
indicates that this line does not address facsimile, and that the
first preference for the voiceband data codes is 32 kbps ADPCM,
while the second preference is PCMU. The packet length
and the packetization interval associated with G726-32 are 20 octets and
5 ms respectively. For PCMU, they are 40 octets and 5 ms respectively.
This media attribute line can be used in ATM as well as non-ATM contexts.
Within the ATM context, it can be applied to the AAL1, AAL2 and AAL5
adaptations. The <packetLength> and <packetTime> are not meaningful
in the AAL1 case and should be set to "-". In the AAL2 case,
this line determines the use of some or all of the rows in
a given profile table. If multiple 3-tuples are present, they
can indicate a hierarchical assignment of some rows in that
profile to voiceband data service e.g. row A preferred to row B etc.
If multiple profiles are present on the 'm' line, the profile
qualified by this attribute is the first
profile. If a single profile that has been selected for a connection
is indicated in the 'm' line, the 'dsel' attribute qualifies the
use, for voiceband data service, of codecs within that profile.
With most of the encoding names in Figure 2, the packet length
and packetization period can be derived from each other. One of them
can be set to "-" without a loss of information. There are some
exceptions such as the IANA-registered encoding names G723, DVI4 and
L16 for which this is not true. Therefore, there is a need to
retain both the packet length and packetization period in the
definition of the 'dsel' line.
5.6.10 The 'fsel' attribute
The 'fsel' attribute indicates a prioritized list of
one or more 3-tuples for facsimile service. If an 'fsel' line
Rajesh Kumar, Mohamed Mostafa. 39
is present, any 'dsel' line with <fxIncl> set to "on" in the session
description must be consistent with it. In this case,
an error event is generated in the case of inconsistency.
Each 3-tuple indicates a codec, an optional packet length and an
optional packetization period. This complements the 'm' line information
and should be consistent with it.
The 'fsel' line is structured as follows:
a=fsel:<encodingName #1> <packetLength #1><packetTime #1>
<encodingName #2> <packetLength #2><packetTime #2>
...
<encodingName #N> <packetLength #N><packetTime #N>
where the <encodingName> parameter can take one of the values in
column 2 of Table 2. The <packetLength> and <packetTime>
parameters are per their definition, above, for the 'vsel'
media attribute line. The parameters <packetLength>and <packetTime> can
be set to "-" when not needed. Also, the entire 'fsel' media attribute
line can be omitted when not needed.
For example,
a=fsel:FXDMOD-3 - -
indicates demodulation and remodulation of ITU-T group 3 fax at the
gateway.
a=fsel:PCMU 40 5000 G726-32 20 5000
indicates a first and second preference of Mu-law PCM and 32 kbps
ADPCM as the facsimile encoding scheme. The packet length
and the packetization interval associated with G726-32 are 20 octets and
5 ms respectively. For PCMU, they are 40 octets and 5 ms respectively.
This media attribute line can be used in ATM as well as non-ATM contexts.
Within the ATM context, it can be applied to the AAL1, AAL2 and AAL5
adaptations. The <packetLength> and <packetTime> are not meaningful
in the AAL1 case and should be set to "-". In the AAL2 case,
this line determines the use of some or all of the rows in
a given profile table. If multiple 3-tuples are present, they
can indicate a hierarchical assignment of some rows in that
profile to facsimile service e.g. row A preferred to row B etc.
If multiple profiles are present on the 'm' line, the profile
qualified by this attribute is the first
profile. If a single profile that has been selected for a connection
is indicated in the 'm' line, the 'fsel' attribute qualifies the
use, for facsimile service, of codecs within that profile.
With most of the encoding names in Figure 2, the packet length
and packetization period can be derived from each other. One of them
Rajesh Kumar, Mohamed Mostafa. 40
can be set to "-" without a loss of information. There are some
exceptions such as the IANA-registered encoding names G723, DVI4 and
L16 for which this is not true. Therefore, there is a need to
retain both the packet length and packetization period in the
definition of the 'fsel' line.
5.6.11 The 'codecconfig' attribute
When present, the 'codecconfig' attribute is used to represent the
contents of the single codec information element (IE) defined in [57].
The contents of this IE are: a single-octet Organizational Identifier
(OID) field, followed by a single-octet Codec Type field, followed by
zero or more octets of a codec configuration bit-map. The semantics of
the codec configuration bit-map are specific to the organization
[57, 58]. The 'codecconfig' attribute is represented as follows:
a=codecconfig:<q7655scc>
The <q7655scc> (Q.765.5 single codec IE contents) parameter is Rajesh Kumar, Mohamed Mostafa. 28
represented as a string of hex digits. The number of hex digits is are not addressed in this document.
even (range 4 -32). The "0x" prefix shall be omitted since this value
is always hexadecimal. As with other hex values [Section 2.2],
digits to the left are more significant than digits to the right.
Leading zeros shall not be omitted.
An example of the use of this media attribute is:
a=codecconfig:01080C
The first octet indicates an Organizational Identifier of 0x01
(the ITU-T). Using ITU Q.765.5 [57], the second octet (0x08) indicates
a codec type of G.726 (ADPCM). The last octet, 0x0C indicates that
16 kbps and 24 kbps rates are NOT supported, while the 32 kbps and
40 kbps rates ARE supported.
5.6.12 The 'isup_usi' attribute
When present, the 'isup_usi' attribute is used to represent the
'User Information Layer 1 protocol' field within the bearer
capability information element defined in Section 4.5.5 of [59], and
reiterated as the user service information element (IE) in Section 3.57
of [60]. The 'User Information Layer 1 protocol' field consists of
the five least significant bits of Octet 5 of this information
element. This field is represented by the USI property in Section C.9
of the Megaco/H.248 protocol [26].
Within SDP, the 'isup_usi' attribute is represented as follows:
a=isup_usi:<isupUsi>
The <isupUsi> parameter is represented as a string of two hex
Rajesh Kumar, Mohamed Mostafa. 41
digits. The "0x" prefix shall be omitted since this value
is always hexadecimal. As with other hex values [Section 2.2],
digits to the left are more significant than digits to the right.
These hex digits are constructed from an octet with three leading
'0' bits and last five bits equal to the 'User Information Layer
1 protocol' field described above. As specified in [59] and [26],
bit 5 of this field is the most significant bit. The resulting values
of the <isupUsi> parameter are as follows:
VALUE MEANING
0x01 CCITT standardized rate adaption V.110 and X.30
0x02 Recommendation G.711 Mu-law
0x03 Recommendation G.711 A-law
0x04 Recommendation G.721 32 kbps ADPCM and Recommendation I.460
0x05 Recommendations H.221 and H.242
0x06 Recommendation H.223 and H.245
0x07 Non-ITU-T standardized rate adaption
0x08 ITU-T standardized rate adaption V.120
0x09 CCITT standardized rate adaption X.31 HDLC flag stuffing
5.6.13 The 'capability' attribute 5.6.1.3 The 'capability' attribute
When present, the 'capability' attribute indicates the ATM Transfer When present, the 'capability' attribute indicates the ATM Transfer
Capability described in ITU I.371 [28], equivalent to the ATM Service Capability described in ITU I.371 [28], equivalent to the ATM Service
Category described in the UNI 4.1 Traffic Management specification [6]. Category described in the UNI 4.1 Traffic Management specification [6].
The 'capability' media attribute line is structured in one of The 'capability' media attribute line is structured in one of
the following ways: the following ways:
a=capability:<asc> <subtype> a=capability:<asc> <subtype>
skipping to change at line 2189 skipping to change at line 1507
Some applications might use non-standard <atc> and <asc> values not Some applications might use non-standard <atc> and <asc> values not
listed above. Equipment designers will need to agree on the meaning and listed above. Equipment designers will need to agree on the meaning and
implications of non-standard transfer capabilities / service capabilities. implications of non-standard transfer capabilities / service capabilities.
The <subtype> field essentially serves as a subscript to the <asc> The <subtype> field essentially serves as a subscript to the <asc>
and <atc> fields. In general, it can take on any integer value, or the and <atc> fields. In general, it can take on any integer value, or the
"-" value indicating that it does not apply or that the underlying data is "-" value indicating that it does not apply or that the underlying data is
to be known by other means, such as provisioning. to be known by other means, such as provisioning.
Rajesh Kumar, Mohamed Mostafa. 42 For an <asc> value of CBR and an <atc> value of DBR, the <subtype>
The following combinations are recognized in the ATMF and ITU field can be assigned values from Table 4-6 of ITU Q.2931 [15]. These are:
specifications:
<asc>/<atc> <subtype> Meaning <asc>/<atc> <subtype> Meaning
"CBR"/"DBR" 1 Voiceband signal transport
(ITU G.711, G.722, I.363)
"CBR"/"DBR" 2 Circuit transport (ITU I.363)
"CBR"/"DBR" 4 High-quality audio signal transport
(ITU I.363)
"CBR"/"DBR" 5 Video signal transport (ITU I.363)
Note that [15] does not define a <subtype> value of 3.
For other values of the <asc> and <atc> parameters, the following
values can be assigned to the <subtype> field, based on [6] and [28].
Rajesh Kumar, Mohamed Mostafa. 29
<asc>/<atc> <subtype> Meaning
nrt-VBR 1 nrt-VBR.1 nrt-VBR 1 nrt-VBR.1
nrt-VBR 2 nrt-VBR.2 nrt-VBR 2 nrt-VBR.2
nrt-VBR 3 nrt-VBR.3 nrt-VBR 3 nrt-VBR.3
rt-VBR 1 rt-VBR.1 rt-VBR 1 rt-VBR.1
rt-VBR 2 rt-VBR.2 rt-VBR 2 rt-VBR.2
rt-VBR 3 rt-VBR.3 rt-VBR 3 rt-VBR.3
UBR 1 UBR.1 UBR 1 UBR.1
UBR 2 UBR.2 UBR 2 UBR.2
GFR 1 GFR.1 GFR 1 GFR.1
GFR 2 GRR.2 GFR 2 GRR.2
skipping to change at line 2217 skipping to change at line 1549
SBR 3 SBR3 SBR 3 SBR3
It is beyond the scope of this specification to examine the It is beyond the scope of this specification to examine the
equivalence of some of the ATMF and ITU definitions. These need to equivalence of some of the ATMF and ITU definitions. These need to
be recognized from the ATMF and ITU source specifications and exploited, be recognized from the ATMF and ITU source specifications and exploited,
as much as possible, to simplify ATM node design. as much as possible, to simplify ATM node design.
When the bearer connection is a single AAL2 CID connection within a When the bearer connection is a single AAL2 CID connection within a
multiplexed AAL2 VC, the 'capability' attribute does not apply. multiplexed AAL2 VC, the 'capability' attribute does not apply.
5.6.14 The 'qosClass' attribute 5.6.1.4 The 'qosClass' attribute
When present, the 'qosClass' attribute indicates the QoS class When present, the 'qosClass' attribute indicates the QoS class
specified in ITU I.2965.1 [34]. specified in ITU I.2965.1 [34].
The 'qosClass' media attribute line is structured as follows: The 'qosClass' media attribute line is structured as follows:
a=qosClass:<qosClass> a=qosClass:<qosClass>
Here, <qosClass> is an integer in the range 0 - 5. Here, <qosClass> is an integer in the range 0 - 5.
<qosClass> Meaning <qosClass> Meaning
0 Default QoS 0 Default QoS
1 Stringent 1 Stringent
2 Tolerant 2 Tolerant
3 Bi-level 3 Bi-level
4 Unbounded 4 Unbounded
5 Stringent bi-level 5 Stringent bi-level
5.6.15 The 'bcob' attribute 5.6.1.5 The 'bcob' attribute
When present, the 'bcob' attribute represents the broadband When present, the 'bcob' attribute represents the broadband
connection oriented bearer class defined in ITU Q.2961.2 [33]. The connection oriented bearer class defined in [5], [15]
'bcob' media attribute line is structured as follows: and [33]. It can also be used to indicate whether end-to-end
timing is required.
Rajesh Kumar, Mohamed Mostafa. 43 Rajesh Kumar, Mohamed Mostafa. 30
a=bcob:<bcob> The 'bcob' media attribute line is structured as follows:
a=bcob:<bcob> <eetim>
Here, <bcob> is the decimal or hex representation of a 5-bit field. Here, <bcob> is the decimal or hex representation of a 5-bit field.
Currently, all values are unused and reserved with the following Currently, all values are unused and reserved with the following
exceptions: exceptions:
<bcob> Meaning <bcob> Meaning
1 BCOB-A 0x01 BCOB-A
3 BCOB-C 0x03 BCOB-C
16 BCOB-X 0x05 Frame relaying bearer service
24 BCOB-VP (transparent VP service) 0x10 BCOB-X
0x18 BCOB-VP (transparent VP service)
5.6.16 The 'stc' attribute The <eetim> parameter can be assigned a value of "on" or "off"
depending on whether end-to-end timing is required or not (Table
4-8 of [15]).
Either of these parameters can be left unspecified by setting it
to a "-". A 'bcob' media attribute line with all parameters set to
"-" carries no information and should be omitted.
5.6.1.6 The 'stc' attribute
When present, the 'stc' attribute represents susceptibility When present, the 'stc' attribute represents susceptibility
to clipping. The 'stc' media attribute line is structured as to clipping. The 'stc' media attribute line is structured as
follows: follows:
a=stc:<stc> a=stc:<stc>
Here, <stc> is the decimal equivalent of a 2-bit field. Currently, Here, <stc> is the decimal equivalent of a 2-bit field. Currently,
all values are unused and reserved with the following exceptions: all values are unused and reserved with the following exceptions:
<stc> value Binary Equivalent Meaning <stc> value Binary Equivalent Meaning
0 00 Not susceptible to clipping 0 00 Not susceptible to clipping
1 01 Susceptible to clipping 1 01 Susceptible to clipping
5.6.17 The 'upcc' attribute 5.6.1.7 The 'upcc' attribute
When present, the 'upcc' attribute represents the user plane When present, the 'upcc' attribute represents the user plane
connection configuration. The 'upcc' media attribute line is connection configuration. The 'upcc' media attribute line is
structured as follows: structured as follows:
a=upcc:<upcc> a=upcc:<upcc>
Here, <upcc> is the decimal equivalent of a 2-bit field. Currently, Here, <upcc> is the decimal equivalent of a 2-bit field. Currently,
all values are unused and reserved with the following exceptions: all values are unused and reserved with the following exceptions:
Rajesh Kumar, Mohamed Mostafa. 31
<upcc> value Binary Equivalent Meaning <upcc> value Binary Equivalent Meaning
0 00 Point to point 0 00 Point to point
1 01 Point to multipoint 1 01 Point to multipoint
5.6.18 The 'atmQOSfparms' and 'atmQOSbparms' attributes 5.6.1.8 The 'atmQOSfparms' and 'atmQOSbparms' attributes
When present, the 'atmQOSfparms' and 'atmQOSbparms' When present, the 'atmQOSfparms' and 'atmQOSbparms'
attributes are used to describe certain key ATM QoS parameters attributes are used to describe certain key ATM QoS parameters
in the forward and backward directions respectively. See Section in the forward and backward directions respectively. See Section
Rajesh Kumar, Mohamed Mostafa. 44
2.3 for a definition of the terms 'forward' and 'backward'. 2.3 for a definition of the terms 'forward' and 'backward'.
The 'atmQOSfparms' and 'atmQOSbparms' media attribute lines The 'atmQOSfparms' and 'atmQOSbparms' media attribute lines
are structured as follows: are structured as follows:
a=atmQOSfparms: <cdvType><acdv><ccdv><actd><cctd><aclr> a=atmQOSfparms: <cdvType><acdv><ccdv><eetd><cmtd><aclr>
a=atmQOSbparms: <cdvType><acdv><ccdv><actd><cctd><aclr> a=atmQOSbparms: <cdvType><acdv><ccdv><eetd><cmtd><aclr>
The <cdvType> parameter can take on the string values of The <cdvType> parameter can take on the string values of
"PP" and "2P". These refer to the peak-to-peak and two-point "PP" and "2P". These refer to the peak-to-peak and two-point
CDV as defined in UNI 4.0 [5] and ITU Q.2965.2 [35] respectively. CDV as defined in UNI 4.0 [5] and ITU Q.2965.2 [35] respectively.
The CDV parameters, <acdv> and <ccdv>, refer to the acceptable The CDV parameters, <acdv> and <ccdv>, refer to the acceptable
and cumulative CDVs respectively. These are expressed in units and cumulative CDVs respectively. These are expressed in units
of microseconds and represented as the decimal equivalent of microseconds and represented as the decimal equivalent
of a 24-bit field. These use the cell loss ratio, <aclr>, as the of a 24-bit field. These use the cell loss ratio, <aclr>, as the
"alpha" quantiles defined in the ATMF TM 4.1 specification [6] "alpha" quantiles defined in the ATMF TM 4.1 specification [6]
and in ITU I.356 [47]. and in ITU I.356 [47].
The CTD parameters, <actd> and <cctd>, refer to the acceptable and The transit delay parameters, <eetd> and <cmtd>, refer to the
cumulative CTDs respectively in milliseconds. These are represented as end-to-end and cumulative transit delays respectively in
the decimal equivalents of 16-bit fields. These parameters are milliseconds. These are represented as the decimal equivalents
equivalent to the maximum end-to-end transit delay defined in ATMF TM of 16-bit fields. These parameters are defined in Q.2965.2 [35],
4.1 specification [6] and Q.2965.2 [35]. UNI 4.0 [5] and Q.2931 [15].
The <aclr> parameter refers to forward and backward acceptable The <aclr> parameter refers to forward and backward acceptable
cell loss ratios. This is the ratio between the number of cells cell loss ratios. This is the ratio between the number of cells
lost and the number of cells transmitted. It is expressed as the decimal lost and the number of cells transmitted. It is expressed as the decimal
equivalent of an 8-bit field. This field expresses an order of equivalent of an 8-bit field. This field expresses an order of
magnitude n, where n is an integer in the range 1-15. The Cell Loss magnitude n, where n is an integer in the range 1-15. The Cell Loss
Ratio takes on the value 10 raised to the power of minus n. Ratio takes on the value 10 raised to the power of minus n.
If any of these parameters is not specified, is inapplicable or is If any of these parameters is not specified, is inapplicable or is
implied, then it is set to "-". implied, then it is set to "-".
An example use of these attributes for an rt-VBR, single-CID AAL2 An example use of these attributes for an rt-VBR, single-CID AAL2
voice VC is: voice VC is:
a=atmQOSfparms:pp 8125 3455 32000 - 11 a=atmQOSfparms:pp 8125 3455 32000 - 11
a=atmQOSbparms:pp 4675 2155 18000 - 12 a=atmQOSbparms:pp 4675 2155 18000 - 12
Rajesh Kumar, Mohamed Mostafa. 32
This implies a forward acceptable peak-to-peak CDV of 8.125 ms, a This implies a forward acceptable peak-to-peak CDV of 8.125 ms, a
backward acceptable peak-to-peak CDV of 4.675 ms, forward backward acceptable peak-to-peak CDV of 4.675 ms, forward
cumulative peak-to-peak CDV of 3.455 ms, a backward cumulative cumulative peak-to-peak CDV of 3.455 ms, a backward cumulative
peak-to-peak CDV of 2.155 ms, a forward acceptable maximum peak-to-peak CDV of 2.155 ms, a forward end-to-end
cell transfer delay of 32 ms, a backward acceptable maximum transit delay of 32 ms, a backward end-to-end
cell transfer delay of 18 ms, an unspecified forward cumulative transit delay of 18 ms, an unspecified forward cumulative
cell transfer delay, an unspecified backward cumulative cell transfer transit delay, an unspecified backward cumulative transit
delay, a forward cell loss ratio of 10 raised to minus 11 and a delay, a forward cell loss ratio of 10 raised to minus 11 and a
backward cell loss ratio of 10 to the minus 12. backward cell loss ratio of 10 to the minus 12.
In certain applications (such as SIP-based applications), an SDP 5.6.1.9 The 'atmFtrfcDesc' and 'atmBtrfcDesc' attributes
Rajesh Kumar, Mohamed Mostafa. 45
descriptor might have both the atmQOSfparms and atmQOSbparms
attributes. In other applications (such as Megaco-based applications),
the remote descriptor can have the atmQOSfparms attribute, and
the local descriptor can have the atmQOSbparms attribute.
5.6.19 The 'atmFtrfcDesc' and 'atmBtrfcDesc' attributes
When present, the 'atmFtrfcDesc' and 'atmBtrfcDesc' attributes When present, the 'atmFtrfcDesc' and 'atmBtrfcDesc' attributes
are used to indicate ATM traffic descriptor parameters in the are used to indicate ATM traffic descriptor parameters in the
forward and backward directions respectively. See Section 2.3 for a forward and backward directions respectively. See Section 2.3 for a
definition of the terms 'forward' and 'backward'. definition of the terms 'forward' and 'backward'.
The 'atmFtrfcDesc' and 'atmBtrfcDesc' media attribute lines The 'atmFtrfcDesc' and 'atmBtrfcDesc' media attribute lines
are structured as follows: are structured as follows:
a=atmFtrfcDesc:<clpLvl> <pcr><scr><mbs><cdvt><mcr><mfs><fd><te> a=atmFtrfcDesc:<clpLvl> <pcr><scr><mbs><cdvt><mcr><mfs><fd><te>
skipping to change at line 2382 skipping to change at line 1718
bursts described in these media attribute lines apply to CLP bursts described in these media attribute lines apply to CLP
values of 0 or (0+1). It can take on the following string values: values of 0 or (0+1). It can take on the following string values:
"0", "0+1" and "-". If rates and bursts for both <clpLvl> values are to "0", "0+1" and "-". If rates and bursts for both <clpLvl> values are to
be described, then it is necessary to use two separate be described, then it is necessary to use two separate
media attribute lines for each direction in the same session media attribute lines for each direction in the same session
descriptor. If the <clpLvl> parameter is set to "-", then it descriptor. If the <clpLvl> parameter is set to "-", then it
implies that the CLP parameter is known by other means such as default, implies that the CLP parameter is known by other means such as default,
MIB provisioning etc. MIB provisioning etc.
The meaning, units and applicability of the remaining parameters The meaning, units and applicability of the remaining parameters
are per the ATMF TM 4.1 specification [6] and are reiterated below: are per [6] and [28]:
Rajesh Kumar, Mohamed Mostafa. 46 Rajesh Kumar, Mohamed Mostafa. 33
PARAMETER MEANING UNITS APPLICABILITY PARAMETER MEANING UNITS APPLICABILITY
<pcr> PCR Cells/ CBR, rt-VBR, nrt-VBR, <pcr> PCR Cells/ CBR, rt-VBR, nrt-VBR,
second ABR, UBR, GFR; second ABR, UBR, GFR;
CLP=0,0+1 CLP=0,0+1
<scr> SCR Cells/ rt-VBR, nrt-VBR; <scr> SCR Cells/ rt-VBR, nrt-VBR;
second CLP=0,0+1 second CLP=0,0+1
<mbs> MBS Cells rt-VBR, nrt-VBR, <mbs> MBS Cells rt-VBR, nrt-VBR,
skipping to change at line 2432 skipping to change at line 1768
<te> (tag enable) indicates that CLP tagging is allowed. <te> (tag enable) indicates that CLP tagging is allowed.
These can take on the string values of "on" or "off". These can take on the string values of "on" or "off".
Since the <te> parameter applies only to cells with Since the <te> parameter applies only to cells with
a CLP of 0, it is meaningful in the case when <clpLvl> = "0". a CLP of 0, it is meaningful in the case when <clpLvl> = "0".
It should be set to "-" for the case when <clpLvl> = "0+1". It should be set to "-" for the case when <clpLvl> = "0+1".
An example use of these media attribute lines for an rt-VBR, An example use of these media attribute lines for an rt-VBR,
single-CID AAL2 voice VC is: single-CID AAL2 voice VC is:
Rajesh Kumar, Mohamed Mostafa. 47 Rajesh Kumar, Mohamed Mostafa. 34
a=atmFtrfcDesc:0+1 200 100 20 - - - on - a=atmFtrfcDesc:0+1 200 100 20 - - - on -
a=atmFtrfcDesc:0 200 80 15 - - - - off a=atmFtrfcDesc:0 200 80 15 - - - - off
a=atmBtrfcDesc:0+1 200 100 20 - - - on - a=atmBtrfcDesc:0+1 200 100 20 - - - on -
a=atmBtrfcDesc:0 200 80 15 - - - - off a=atmBtrfcDesc:0 200 80 15 - - - - off
This implies a forward and backward PCR of 200 cells per second This implies a forward and backward PCR of 200 cells per second
all cells regardless of CLP, forward and backward PCR of 200 cells all cells regardless of CLP, forward and backward PCR of 200 cells
per second for cells with CLP=0, a forward and backward SCR of 100 per second for cells with CLP=0, a forward and backward SCR of 100
cells per second for all cells regardless of CLP, a forward and cells per second for all cells regardless of CLP, a forward and
backward SCR of 80 cells per second for cells with CLP=0, backward SCR of 80 cells per second for cells with CLP=0,
a forward and backward MBS of 20 cells for all cells regardless a forward and backward MBS of 20 cells for all cells regardless
of CLP, a forward and backward MBS of 15 cells for cells with of CLP, a forward and backward MBS of 15 cells for cells with
CLP=0, an unspecified CDVT which can be known by other means, CLP=0, an unspecified CDVT which can be known by other means,
and an MCR and MFS which are unspecified because they are and an MCR and MFS which are unspecified because they are
inapplicable. Frame discard is enabled in both the forward and inapplicable. Frame discard is enabled in both the forward and
backward directions. Tagging is not enabled in either direction. backward directions. Tagging is not enabled in either direction.
The <pcr>, <scr>, <mbs>, <cdvt>, <mcr> and <mfs> are represented as The <pcr>, <scr>, <mbs>, <cdvt>, <mcr> and <mfs> are represented as
decimal integers, with range as defined in Section 6. decimal integers, with range as defined in Section 6. See section 2.2
regarding the omission of leading zeros in decimal representations.
In certain applications (such as SIP-based applications), an SDP
descriptor might have both the atmFtrfcDesc and atmBtrfcDesc
attributes. In other applications (such as Megaco-based applications),
the remote descriptor can have the atmFtrfcDesc attribute, and
the local descriptor can have the atmBtrfcDesc attribute.
5.6.20 The 'abrFparms' and 'abrBparms' attributes 5.6.1.10 The 'abrFparms' and 'abrBparms' attributes
When present, the 'abrFparms' and 'abrBparms' attributes When present, the 'abrFparms' and 'abrBparms' attributes
are used to indicate the 'additional' ABR parameters specified are used to indicate the 'additional' ABR parameters specified
in the UNI 4.0 signaling specification [5]. These refer to the in the UNI 4.0 signaling specification [5]. These refer to the
forward and backward directions respectively. See Section forward and backward directions respectively. See Section
2.3 for a definition of the terms 'forward' and 'backward'. 2.3 for a definition of the terms 'forward' and 'backward'.
The 'abrFparms' and 'abrBparms' media attribute lines are structured The 'abrFparms' and 'abrBparms' media attribute lines are structured
as follows: as follows:
skipping to change at line 2486 skipping to change at line 1817
for some. Details of the meaning, units and applicability of for some. Details of the meaning, units and applicability of
these parameters are in [5] and [6]. these parameters are in [5] and [6].
If any of these parameters in the 'abrFparms' or 'abrBparms' media If any of these parameters in the 'abrFparms' or 'abrBparms' media
attribute lines is not specified, is inapplicable or is implied, attribute lines is not specified, is inapplicable or is implied,
then it is set to "-". then it is set to "-".
In SDP, these parameters are represented as the decimal or hex In SDP, these parameters are represented as the decimal or hex
equivalent of the binary fields mentioned below. equivalent of the binary fields mentioned below.
Rajesh Kumar, Mohamed Mostafa. 48 Rajesh Kumar, Mohamed Mostafa. 35
+-----------+----------------------------------+-----------------------+ +-----------+----------------------------------+-----------------------+
| PARAMETER | MEANING | FIELD SIZE | | PARAMETER | MEANING | FIELD SIZE |
+-----------+----------------------------------+-----------------------+ +-----------+----------------------------------+-----------------------+
| <nrm> | Maximum number of cells per | 3 bits | | <nrm> | Maximum number of cells per | 3 bits |
| | forward Resource Management cell | | | | forward Resource Management cell | |
+-----------+----------------------------------+-----------------------+ +-----------+----------------------------------+-----------------------+
| <trm> | Maximum time between | 3 bits | | <trm> | Maximum time between | 3 bits |
| | forward Resource Management cells| | | | forward Resource Management cells| |
+-----------+----------------------------------+-----------------------+ +-----------+----------------------------------+-----------------------+
| <cdf> | Cutoff Decrease Factor | 3 bits | | <cdf> | Cutoff Decrease Factor | 3 bits |
+-----------+----------------------------------+-----------------------+ +-----------+----------------------------------+-----------------------+
| <adtf> | Allowed Cell Rate Decrease | 10 bits | | <adtf> | Allowed Cell Rate Decrease | 10 bits |
| | Time Factor | | | | Time Factor | |
+-----------+----------------------------------+-----------------------+ +-----------+----------------------------------+-----------------------+
In certain applications (such as SIP-based applications), an SDP 5.6.1.11 The 'abrSetup' attribute
descriptor might have both the abrFparms and abrBparms attributes.
In other applications (such as Megaco-based applications), the
remote descriptor can have the abrFparms attribute, and the local
descriptor can have the abrBparms attribute.
5.6.21 The 'clkrec' attribute
When present, the 'clkrec' attribute is used to indicate
the clock recovery method. This attribute is meaningful in the
case of AAL1 unstructured data transfer (UDT). The format of the
'clkrec' media attribute line is as follows:
a=clkrec:<clkrec>
The <clkrec> field can take on the following string values: "NULL",
"SRTS" or "ADAPTIVE". SRTS and adaptive clock recovery are defined in
ITU I.363.1 [10]. "NULL" indicates that the stream (e.g. T1/E1)
encapsulated in ATM is synchronous to the ATM network or is retimed,
before AAL1 encapsulation, via slip buffers.
5.6.22 The 'fec' attribute
When present, the 'fec' attribute is used to indicate the use of
forward error correction. Currently, there exists a forward error
correction method defined for AAL1 in ITU I.363.1 [10]. The format of the
'fec' media attribute line is as follows:
a=fec:<fecEnable>
The <fecEnable> flag indicates the presence of absence of Forward
Error Correction. It can take on the string values of "NULL",
"LOSS_SENSITIVE" and "DELAY_SENSITIVE". An "NULL" value implies disabling
this capability. FEC can be enabled differently for delay-sensitive
and loss-sensitive connections.
Rajesh Kumar, Mohamed Mostafa. 49
5.6.23 The 'prtfl' attribute
When present, the 'prtfl' attribute is used to indicate the fill
level of cells. When this attribute is absent, then
other means (such as provisionable defaults) are used to determine
the presence and level of partial fill.
This attribute indicates the number of non-pad payload When present, the 'abrSetup' attribute is used to indicate the
octets, not including any AAL SAR or convergence sublayer octets. For ABR parameters needed during call/connection establishment (Section
example, in some AAL1 applications that use partially filled cells with 10.1.2.2 of the UNI 4.0 signaling specification [5]). This line
padding at the end, this attribute indicates the number of leading is structured as follows:
payload octets not including any AAL overhead.
The format of the 'prtfl' media attribute line is as follows: a=abrSetup:<ficr><bicr><ftbe><btbe><crmrtt><frif><brif><frdf><brdf>
a=prtfl:<partialFill> These parameters are defined as follows:
Here, <partialFill> can be expressed as a decimal or a hex integer. Rajesh Kumar, Mohamed Mostafa. 36
In general, permitted values are integers in the range 1 - 48 +-----------+----------------------------------+-----------------------+
inclusive. However, this upper bound is different for different | PARAMETER | MEANING | REPRESENTATION |
adaptations since the AAL overhead, if any, is different. If the specified +-----------+----------------------------------+-----------------------+
partial fill is greater than or equal to the maximum fill, then complete | <ficr> | Forward Initial Cell Rate | Decimal equivalent |
fill is used. Using a 'partial' fill of 48 always disables partial fill. | | (Cells per second) | of 24-bit field |
+-----------+----------------------------------+-----------------------+
| <bicr> | Backward Initial Cell Rate | Decimal equivalent |
| | (Cells per second) | of 24-bit field |
+-----------+----------------------------------+-----------------------+
| <ftbe> | Forward transient buffer | Decimal equivalent |
| | exposure (Cells) | of 24-bit field |
+-----------+----------------------------------+-----------------------+
| <btbe> | Backward transient buffer | Decimal equivalent |
| | exposure (Cells) | of 24-bit field |
+-----------+----------------------------------+-----------------------+
| <crmrtt> | Cumulative RM round-trip time | Decimal equivalent |
| | (Microseconds) | of 24-bit field |
+-----------+----------------------------------+-----------------------+
| <frif> | Forward rate increase factor | Decimal integer |
| | (used to derive cell count) | 0 -15 |
+-----------+----------------------------------+-----------------------+
| <brif> | Backward rate increase factor | Decimal integer |
| | (used to derive cell count) | 0 -15 |
+-----------+----------------------------------+-----------------------+
| <frdf> | Forward rate decrease factor | Decimal integer |
| | (used to derive cell count) | 0 -15 |
+-----------+----------------------------------+-----------------------+
| <brdf> | Backward rate decrease factor | Decimal integer |
| | (used to derive cell count) | 0 -15 |
+-----------+----------------------------------+-----------------------+
In the AAL1 context, this media attribute line applies uniformly to See Section 2.3 for a definition of the terms 'forward' and 'backward'.
both P and non-P cells. In AAL1 applications that do not distinguish
between P and non-P cells, a value of 47 indicates complete fill (i.e. the
absence of partial fill). In AAL1 applications that distinguish between P
and non-P cells, a value of 46 indicates no padding in P-cells and a
padding of one in non-P cells.
If partial fill is enabled (i.e there is padding in at least some If any of these parameters in the 'abrSetup' media attribute line
cells), then AAL1 structures must not be split across cell boundaries. is not specified, is inapplicable or is implied, then it is set to
These shall fit in any cell. Hence, "-".
their size shall be less than or equal to the partial fill
size. Further, the partial fill size is preferably
an integer multiple of the structure size. If not, then the
partial fill size stated in the SDP description shall be
truncated to an integer multiple (e.g. a partial fill size of
40 is truncated to 36 to support six 6 x 64 channels).
5.6.24 The 'bearerType' attribute 5.6.1.12 The 'bearerType' attribute
When present, the 'bearerType' attribute is used to indicate When present, the 'bearerType' attribute is used to indicate
whether the underlying bearer is an ATM PVC/SPVC, an ATM SVC, whether the underlying bearer is an ATM PVC/SPVC, an ATM SVC,
or an AAL2 CID connection within an existing ATM PVC/SPVC. or an AAL2 CID connection within an existing ATM PVC/SPVC.
Additionally, for ATM SVCs and AAL2 CID connections, the Additionally, for ATM SVCs and AAL2 CID connections, the
'bearerType' attribute can be used to indicate whether the 'bearerType' attribute can be used to indicate whether the
media gateway initiates connection set-up via bearer signaling media gateway initiates connection set-up via bearer signaling
(Q.2931-based or Q.2630.1 based). The format of the 'bearerType' (Q.2931-based or Q.2630.1 based). The format of the 'bearerType'
media attribute line is as follows: media attribute line is as follows:
Rajesh Kumar, Mohamed Mostafa. 50 a=bearerType: <bearerType> <localInitiation>
a=bearerType: <bearerType> <localInititiation>
The <bearerType> field can take on the following string values: The <bearerType> field can take on the following string values:
Rajesh Kumar, Mohamed Mostafa. 37
"PVC", "SVC", "CID", with semantics as defined above. Here, "PVC" "PVC", "SVC", "CID", with semantics as defined above. Here, "PVC"
includes both the PVC and SPVC cases. includes both the PVC and SPVC cases.
In the case when the underlying bearer is a PVC/SPVC, or a CID In the case when the underlying bearer is a PVC/SPVC, or a CID
assigned by the MGC rather than through bearer signaling, the assigned by the MGC rather than through bearer signaling, the
<localInititiation> flag can be omitted or set to "-". In the <localInitiation> flag can be omitted or set to "-". In the
case when bearer signaling is used, this flag can be omitted case when bearer signaling is used, this flag can be omitted
when it is known by default or by other means whether the media when it is known by default or by other means whether the media
gateway initiates the connection set-up via bearer signaling. Only gateway initiates the connection set-up via bearer signaling. Only
when this is to be indicated explicitly that the <localInititiation> when this is to be indicated explicitly that the <localInitiation>
flag takes on the values of "on" or "off". An "on" value indicates flag takes on the values of "on" or "off". An "on" value indicates
that the media gateway is responsible for initiating connection set-up that the media gateway is responsible for initiating connection set-up
via bearer signaling (SVC signaling or Q.2630.1 signaling), via bearer signaling (SVC signaling or Q.2630.1 signaling),
an "off" value indicates otherwise. an "off" value indicates otherwise.
5.6.25 The 'structure' attribute 5.6.1.13 The 'lij' attribute
This attribute applies to AAL1 connections only. When present, When present, the 'lij' attribute is used to indicate
the 'structure' attribute is used to indicate the presence or the presence of a connection that uses the Leaf-initiated-join
absence of structured data transfer (SDT), and the size in octets capability described in UNI 4.0 [5], and to optionally describe
of the SDT blocks. The format of the 'structure' media attribute line parameters associated with this capability. The format of the
'lij' media attribute line is as follows:
a=lij: <sci><lsn>
The <sci> (screening indication) is a 4-bit field expressed as a
decimal or hex integer. It is defined in the UNI 4.0 signaling
specification [5]. It is possible that the values of this field will
be defined later by the ATMF and/or ITU. Currently, all values are
reserved with the exception of 0, which indicates a 'Network Join
without Root Notification'.
The <lsn> (leaf sequence number) is a 32-bit field expressed as a
decimal or hex integer. Per the UNI 4.0 signaling specification [5], it
is used by a joining leaf to associate messages and responses during
LIJ (leaf initiated join) procedures.
Each of these fields can be set to a "-" when the intention
is to not specify them in an SDP descriptor.
5.6.1.14 The 'anycast' attribute
When present, the 'anycast' attribute line is used to indicate
the applicability of the anycast function described in UNI
4.0 [5]. Optional parameters to qualify this function are
provided. The format of the 'anycast' attribute is:
a=anycast: <atmGroupAddress> <cdStd> <conScpTyp> <conScpSel>
The <atmGroupAddress> is per Annex 5 of UNI 4.0 [5]. Within
an SDP descriptor, it can be represented in one of the formats
Rajesh Kumar, Mohamed Mostafa. 38
(NSAP, E.164, GWID/ALIAS) described elsewhere in this document.
The remaining subparameters mirror the connection scope selection
information element in UNI 4.0 [5]. Their meaning and representation
is as shown below:
PARAMETER MEANING REPRESENTATION
<cdStd> Coding standard for the Decimal or hex
connection scope selection IE equivalent of
Definition: UNI 4.0 [5] 2 bits
<conScpTyp> Type of connection scope Decimal or hex
Definition: UNI 4.0 [5] equivalent of
4 bits
<conScpSel> Connection scope selection Decimal or hex
Definition: UNI 4.0 [5] equivalent of
8 bits
Currently, all values of <cdStd> and <conScpTyp> are reserved with
the exception of <cdStd> = 3 (ATMF coding standard) and <conScpTyp> = 1
(connection scope type of 'organizational').
Each of these fields can be set to a "-" when the intention
is to not specify them in an SDP descriptor.
5.6.1.15 The 'cache' attribute
This attribute is used to enable SVC caching. This attribute
has the following format:
a=cache:<cacheEnable><cacheTimer>
The <cacheEnable> flag indicates whether caching is enabled or
not, corresponding to the string values of "on" and "off"
respectively.
The <cacheTimer> indicates the period of inactivity following which
the SVC is to be released by sending an SVC release message into
the network. This is specified as the decimal or hex equivalent of
a 32-bit field, indicating the timeout in seconds. As usual, leading
zeros can be omitted. For instance,
a=cache:on 7200
implies that the cached SVC is to be deleted if it is idle for 2 hours.
The <cacheTimer> can be set to "-" if it is inapplicable or implied.
5.6.1.16 The 'bearerSigIE' attribute
ATM signaling standards provide 'escape mechanisms' to
Rajesh Kumar, Mohamed Mostafa. 39
represent, signal and negotiate higher-layer parameters. Examples
are the B-HLI and B-LLI IEs specified in ITU Q.2931 [15], and
the user-to-user information element described in ITU Q.2957 [48].
The 'bearerSigIE'(bearer signaling information element) attribute is
defined to allow a similar escape mechanism that can be used with
these ATM SDP conventions. The format of this media attribute line
is as follows: is as follows:
a=structure: <structureEnable> <blksz> a=bearerSigIE: <bearerSigIEType> <bearerSigIELng> <bearerSigIEVal>
where the <structureEnable> flag indicates the presence of absence of SDT. When an 'bearerSigIE' media attribute line is present, all its
It can take on the values of "on" or "off". An "on" value implies subparameters are mandatory. The "0x" prefix is not used since these are
AAL1 structured data transfer (SDT), while an "off" value implies always represented in hex.
AAL1 unstructured data transfer (UDT).
The block size field, <blksz>, is an optional 16-bit field (Q.2931) The <bearerSigIEType> is represented as exactly 2 hex digits. It is the
that can be represented in decimal or hex. It is set to unique IE identifier as defined in the ITU Q-series standards. Leading
a "-" when not applicable, as in the case of unstructured data transfer zeros are not omitted. Some pertinent values are 7E (User-user IE
(UDT). For SDT, it can be set to a "-" when <blksz> is known per ITU Q.2957 [48]), 5F (B-LLI IE) and 5D (B-HLI IE). B-LLI and B-HLI,
by other means. For instance, af-vtoa-78 [7] fixes the structure size for which stand for Broadband Low-layer Information and Broadband
n x 64 service, with or without CAS. The theoretical maximum value of High-layer Information respectively, are defined in ITU Q.2931 [15].
<blksz> is 65,535, although most services use much less. Both of these refer to layers above the ATM adaptation layer.
5.6.26 The 'sbc' attribute The <bearerSigIELng> consists of 1-4 hex digits. It is the length of
the information element in octets. Leading zeros may be omitted.
The <bearerSigIEVal> is the value of the information element, represented
as a hexadecimal bit map. Although the size of this bit map is network/
service dependent, setting an upper bound of 256 octets (512 hex digits)
is adequate. Since this a bit map, leading zeros should not be
omitted. The number of hex digits in this bit map is even.
5.6.2 ATM Adaptation Layer (AAL) attributes
The following is a summary list of the SDP media attributes that can
be used to describe the ATM Adaptation Layer (AAL). These are detailed in
subsequent subsections.
* The 'aalApp' attribute, which is used to point to the
controlling standard for an application layer above the ATM
adaptation layer.
* The 'cbrRate' attribute, which represents
the CBR rate octet defined in Table 4-6 of ITU Q.2931 [15].
* The 'sbc' attribute, which denotes the
subchannel count in the case of n x 64 clear channel
communication.
* The 'clkrec' attribute, which indicates the clock recovery
method for AAL1 unstructured data transfer (UDT).
Rajesh Kumar, Mohamed Mostafa. 40
* The 'fec' attribute, which indicates the use of
forward error correction.
* The 'prtfl' attribute, which indicates indicate the fill
level of partially filled cells.
* The 'structure' attribute, which is used to indicate
the presence or absence of AAL1 structured data transfer (SDT),
and the size of the SDT blocks.
* The 'fcpsSDUsize' and 'bcpsSDUsize'
attributes, which are used to indicate the maximum size of the
CPCS SDU payload in the forward and backward directions.
* The 'aal2CPS' attribute, which is used to
indicate that an AAL2 CPS sublayer as defined in
ITU I.363.2 [13] is associated with the VCC referred to in the
'm' line. Optionally, it can be used to indicate selected
CPS options and parameter values for this VCC.
* The 'aal2CPSSDUrate' attribute, which is used to place
an upper bound on the SDU bit rate for an AAL2 CID.
* The 'aal2sscs3661unassured' attribute, which is used
to indicate the presence of an AAL2 SSCS sublayer with
unassured transmission as defined in ITU I.366.1 [12].
Optionally, it can be used to indicate selected options and
parameter values for this SSCS.
* The 'aal2sscs3661assured' attribute, which is used
to indicate the presence of an AAL2 SSCS sublayer with
assured transmission as defined in ITU I.366.1 [12].
Optionally, it can be used to indicate selected options and
parameter values for this SSCS.
* The 'aal2sscs3662' attribute, which is used to
indicate the presence of an AAL2 SSCS sublayer as defined
in ITU I.366.2. Optionally, it can be used to indicate
selected options and parameter values for this SSCS.
* The 'aal5sscop' attribute, which is used to
indicate the existence of an SSCOP protocol layer over
an AAL5 CPS layer, and the parameters which pertain to
this SSCOP layer.
5.6.2.1 The 'aalApp' attribute
When present, the 'aalApp' attribute is used to point to the
controlling standard for an application layer above the ATM adaptation
layer. The format of the 'aalApp' media attribute line is as follows:
a=aalApp: <appClass> <oui> <appId>
Rajesh Kumar, Mohamed Mostafa. 41
If any of the subparameters, <appClass>, <oui> or <appId>, is meant
to be left, unspecified, it is set to "-". However, an 'aalApp' attribute
line with all subparameters set to "-" carries no information and
should be omitted.
The <appClass>, or application class, field can take on the
string values listed below.
This list is not exhaustive. An "X-" prefix should be used with
<appClass> values not listed here.
<appClass> Meaning
"itu_h323c" Annex C of H.323 which specifies direct
RTP on AAL5 [45].
"af83" af-vtoa-0083.001, which specifies
variable size AAL5 PDUs with PCM voice
and a null SSCS [46].
"AAL5_SSCOP" SSCOP as defined in ITU Q.2110 [43]
running over an AAL5 CPS [21].
No information is provided regarding
any layers above SSCOP such as Service
Specific Coordination Function (SSCF)
layers.
"itu_i3661_unassured" SSCS with unassured transmission,
per ITU I.366.1 [12].
"itu_i3661_assured" SSCS with assured transmission,
per ITU I.366.1 [12]. This uses SSCOP [43].
"itu_i3662" SSCS per ITU I.366.2 [13].
"itu_i3651" Frame relay SSCS per ITU I.365.1 [39].
"itu_i3652" Service-specific coordination function,
as defined in ITU I.365.2, for Connection
Oriented Network Service (SSCF-CONS) [40].
This uses SSCOP [43].
"itu_i3653" Service-specific coordination function,
as defined in ITU I.365.3, for Connection
Oriented Transport Service (SSCF-COTS) [41].
This uses SSCOP [43].
"itu_i3654" HDLC Service-specific coordination function,
as defined in ITU I.365.4 [42].
"FRF5" Use of the FRF.5 frame relay standard [53],
Rajesh Kumar, Mohamed Mostafa. 42
which references ITU I.365.1 [39].
"FRF8" Use of the FRF.8.1 frame relay standard [54].
This implies a null SSCS and the mapping of
the frame relay header into the ATM header.
"FRF11" Use of the FRF.11 frame relay standard [55].
"itu_h2221" Use of the ITU standard H.222.1 for audiovisual
communication over AAL5 [51].
The <oui>, or Organizationally Unique Identifier, refers to the organization
responsible for defining the <appId>, or Application Identifier. The <oui> is
maintained by the IEEE. One of its uses is in 802 MAC addresses. It is a three-
octet field represented as one to six hex digits. Since this is always
represented in hex, the "0x" prefix is not used. Leading zeros may be omitted.
The <appId> subparameter refers to the application ID, a hex number consisting
of up to 8 digits. Leading zeros may be omitted. The "0x" prefix is not used,
since the representation is always hexadecimal. Currently, the only
organization that has defined applicable application identifiers is the ATM
forum (Section 5 of [61]). These can be used with <appClass> = itu_i3662. The
<oui> value for the ATM forum is 0x00A03E.
In the following example, the aalApp media attribute line is used to
indicate 'Loop Emulation Service using CAS (POTS only) without the
Emulated Loop Control Protocol (ELCP) [52]. The Application ID is defined
by the ATM forum [61]. The SSCS used is per ITU I.366.2 [13].
a=aalApp:itu_i3662 A03E A
If leading zeros are not dropped, this can be represented as:
a=aalApp:itu_i3662 00A03E 0000000A
5.6.2.2 The 'cbrRate' attribute
When present, the 'cbrRate' attribute is used to represent the CBR
rate octet defined in Table 4-6 of ITU Q.2931 [15]. The format
of this media attribute line is:
a=cbrRate: <cbrRate>
Here, <cbrRate> is represented as exactly two hex digits. The "0x"
prefix is omitted since this parameter is always represented in
hex. Values currently defined by the ITU are:
Rajesh Kumar, Mohamed Mostafa. 43
+------------+-----------------------------------------------+
| VALUE | MEANING |
+------------+-----------------------------------------------+
| 0x01 | 64 kbps |
+------------+-----------------------------------------------+
| 0x04 | 1544 kbps |
+------------+-----------------------------------------------+
| 0x05 | 6312 kbps |
+------------+-----------------------------------------------+
| 0x06 | 32064 kbps |
+------------+-----------------------------------------------+
| 0x07 | 44736 kbps |
+------------+-----------------------------------------------+
| 0x08 | 97728 kbps |
+------------+-----------------------------------------------+
| 0x10 | 2048 kbps |
+------------+-----------------------------------------------+
| 0x11 | 8448 kbps |
+------------+-----------------------------------------------+
| 0x12 | 34368 kbps |
+------------+-----------------------------------------------+
| 0x13 | 139264 kbps |
+------------+-----------------------------------------------+
| 0x40 | n x 64 kbps |
+------------+-----------------------------------------------+
| 0x41 | n x 8 kbps |
+------------+-----------------------------------------------+
It is preferable that the cbrRate attribute be omitted rather
than set to an unspecified value of "-", since it conveys no
information in the latter case.
5.6.2.3 The 'sbc' attribute
The 'sbc' media attribute line denotes the subchannel count and The 'sbc' media attribute line denotes the subchannel count and
is meaningful only in the case of n x 64 clear channel communication. is meaningful only in the case of n x 64 clear channel communication.
A clear n x 64 channel can use AAL1 (ATM forum af-vtoa-78) or AAL2 A clear n x 64 channel can use AAL1 (ATM forum af-vtoa-78) or AAL2
adaptation (ITU I.366.2). Although no such standard definition exists, adaptation (ITU I.366.2). Although no such standard definition exists,
it is also possible to use AAL5 for this purpose. An n x 64 clear channel it is also possible to use AAL5 for this purpose. An n x 64 clear channel
is represented by the encoding names of "X-CCD" and "X-CCD-CAS" in is represented by the encoding names of "X-CCD" and "X-CCD-CAS" in
Table 2. Table 2.
Rajesh Kumar, Mohamed Mostafa. 51
The format of the 'sbc' media attribute line is as follows: The format of the 'sbc' media attribute line is as follows:
a=sbc:<sbc> a=sbc:<sbc>
Here, <sbc> can be expressed as a decimal or hex integer. This Here, <sbc> can be expressed as a decimal or hex integer. This
attribute indicates the number of DS0s in a T1 or E1 frame that are attribute indicates the number of DS0s in a T1 or E1 frame that are
aggregated for transmitting clear channel data. For T1-based aggregated for transmitting clear channel data. For T1-based
applications, it can take on integral values in the inclusive range applications, it can take on integral values in the inclusive range
[1...24]. For E1-based applications, it can take on integral values in [1...24]. For E1-based applications, it can take on integral values in
the inclusive range [1...31]. When omitted, other means are to be used the inclusive range [1...31]. When omitted, other means are to be used
Rajesh Kumar, Mohamed Mostafa. 44
to determine the subchannel count. to determine the subchannel count.
Use of the 'sbc' attribute provides a direct way to indicate the Use of the 'sbc' attribute provides a direct way to indicate the
number of 64 kbps subchannels bundled into an n x 64 clear number of 64 kbps subchannels bundled into an n x 64 clear
channel. An alternate mechanism to indicate this exists within channel. An alternate mechanism to indicate this exists within
the SDP bandwidth information, or 'b', line [1]. In this case, the SDP bandwidth information, or 'b', line [1]. In this case,
instead of specifying the number of subchannels, the aggregate instead of specifying the number of subchannels, the aggregate
bandwidth in kbps is specified. The syntax of the 'b' line, copied bandwidth in kbps is specified. The syntax of the 'b' line, copied
verbatim from [1], is as follows: verbatim from [1], is as follows:
skipping to change at line 2693 skipping to change at line 2306
b=AS:384 b=AS:384
The media attribute line The media attribute line
a=sbc:2 a=sbc:2
is equivalent to is equivalent to
b=AS:128 b=AS:128
5.6.27 The 'fcpsSDUsize' and 'bcpsSDUsize' attributes 5.6.2.4 The 'clkrec' attribute
When present, the 'clkrec' attribute is used to indicate
the clock recovery method. This attribute is meaningful in the
case of AAL1 unstructured data transfer (UDT). The format of the
'clkrec' media attribute line is as follows:
a=clkrec:<clkrec>
The <clkrec> field can take on the following string values: "NULL",
"SRTS" or "ADAPTIVE". SRTS and adaptive clock recovery are defined in
ITU I.363.1 [10]. "NULL" indicates that the stream (e.g. T1/E1)
encapsulated in ATM is synchronous to the ATM network or is retimed,
before AAL1 encapsulation, via slip buffers.
Rajesh Kumar, Mohamed Mostafa. 45
5.6.2.5 The 'fec' attribute
When present, the 'fec' attribute is used to indicate the use of
forward error correction. Currently, there exists a forward error
correction method defined for AAL1 in ITU I.363.1 [10]. The format of the
'fec' media attribute line is as follows:
a=fec:<fecEnable>
The <fecEnable> flag indicates the presence of absence of Forward
Error Correction. It can take on the string values of "NULL",
"LOSS_SENSITIVE" and "DELAY_SENSITIVE". An "NULL" value implies disabling
this capability. FEC can be enabled differently for delay-sensitive
and loss-sensitive connections.
5.6.2.6 The 'prtfl' attribute
When present, the 'prtfl' attribute is used to indicate the fill
level of cells. When this attribute is absent, then
other means (such as provisionable defaults) are used to determine
the presence and level of partial fill.
This attribute indicates the number of non-pad payload
octets, not including any AAL SAR or convergence sublayer octets. For
example, in some AAL1 applications that use partially filled cells with
padding at the end, this attribute indicates the number of leading
payload octets not including any AAL overhead.
The format of the 'prtfl' media attribute line is as follows:
a=prtfl:<partialFill>
Here, <partialFill> can be expressed as a decimal or a hex integer.
In general, permitted values are integers in the range 1 - 48
inclusive. However, this upper bound is different for different
adaptations since the AAL overhead, if any, is different. If the specified
partial fill is greater than or equal to the maximum fill, then complete
fill is used. Using a 'partial' fill of 48 always disables partial fill.
In the AAL1 context, this media attribute line applies uniformly to
both P and non-P cells. In AAL1 applications that do not distinguish
between P and non-P cells, a value of 47 indicates complete fill (i.e. the
absence of partial fill). In AAL1 applications that distinguish between P
and non-P cells, a value of 46 indicates no padding in P-cells and a
padding of one in non-P cells.
If partial fill is enabled (i.e there is padding in at least some
cells), then AAL1 structures must not be split across cell boundaries.
These shall fit in any cell. Hence,
their size shall be less than or equal to the partial fill
size. Further, the partial fill size is preferably
Rajesh Kumar, Mohamed Mostafa. 46
an integer multiple of the structure size. If not, then the
partial fill size stated in the SDP description shall be
truncated to an integer multiple (e.g. a partial fill size of
40 is truncated to 36 to support six 6 x 64 channels).
5.6.2.7 The 'structure' attribute
This attribute applies to AAL1 connections only. When present,
the 'structure' attribute is used to indicate the presence or
absence of structured data transfer (SDT), and the size in octets
of the SDT blocks. The format of the 'structure' media attribute line
is as follows:
a=structure: <structureEnable> <blksz>
where the <structureEnable> flag indicates the presence of absence of SDT.
It can take on the values of "on" or "off". An "on" value implies
AAL1 structured data transfer (SDT), while an "off" value implies
AAL1 unstructured data transfer (UDT).
The block size field, <blksz>, is an optional 16-bit field (Q.2931)
that can be represented in decimal or hex. It is set to
a "-" when not applicable, as in the case of unstructured data transfer
(UDT). For SDT, it can be set to a "-" when <blksz> is known
by other means. For instance, af-vtoa-78 [7] fixes the structure size for
n x 64 service, with or without CAS. The theoretical maximum value of
<blksz> is 65,535, although most services use much less.
5.6.2.8 The 'fcpsSDUsize' and 'bcpsSDUsize' attributes
When present, the 'fcpsSDUsize' and 'bcpsSDUsize' attributes are used to When present, the 'fcpsSDUsize' and 'bcpsSDUsize' attributes are used to
indicate the maximum size of the CPCS SDU payload in the forward and indicate the maximum size of the CPCS SDU payload in the forward and
Rajesh Kumar, Mohamed Mostafa. 52
backward directions respectively. See section 2.3 for a definition of the backward directions respectively. See section 2.3 for a definition of the
terms 'forward' and 'backward'. The format of these media attribute lines is terms 'forward' and 'backward'. The format of these media attribute lines is
as follows: as follows:
a=fcpsSDUsize: <cpcs> a=fcpsSDUsize: <cpcs>
a=bcpsSDUsize: <cpcs> a=bcpsSDUsize: <cpcs>
The <cpcs> fields is a 16-bit integer that can be represented in The <cpcs> fields is a 16-bit integer that can be represented in
decimal or in hex. decimal or in hex.
The meaning and values of these fields are as follows: The meaning and values of these fields are as follows:
Application Field Meaning Values Application Field Meaning Values
AAL5 <cpcs> Maximum CPCS-SDU size 1- 65,535 AAL5 <cpcs> Maximum CPCS-SDU size 1- 65,535
AAL2 <cpcs> Maximum CPCS-SDU size 45 or 64 AAL2 <cpcs> Maximum CPCS-SDU size 45 or 64
In certain applications (such as SIP-based applications), an SDP Rajesh Kumar, Mohamed Mostafa. 47
descriptor might have both the fcpsSDUsize and bcpsSDUsize
attributes. In other applications (such as Megaco-based applications),
the remote descriptor can have the fcpsSDUsize attribute, and
the local descriptor can have the bcpsSDUsize attribute.
5.6.28 The 'aal2CPS' attribute 5.6.2.9 The 'aal2CPS' attribute
When present, the 'aal2CPS' attribute is used to describe When present, the 'aal2CPS' attribute is used to describe
parameters associated with the AAL2 CPS layer. parameters associated with the AAL2 CPS layer.
The format of the 'aal2CPS' media attribute line is as follows: The format of the 'aal2CPS' media attribute line is as follows:
a=aal2CPS:<cidLowerLimit><cidUpperLimit><timerCU> <simplifiedCPS>
a=aal2CPS:<cidCount> <timerCU> <simplifiedCPS>
Each of these fields can be set to a "-" when the intention is to not Each of these fields can be set to a "-" when the intention is to not
specify them in an SDP descriptor. specify them in an SDP descriptor.
The <cidCount> integer can take on The <cidLowerLimit> and <cidUpperLimit> can be assigned integer
values between 1 and 255. It represents the number of channels (CIDs) values between 8 and 255 [11], with the limitation that <cidUpperLimit>
multiplexed into the AAL2 VCC. It can be represented in decimal or in hex. be greater than or equal to <cidLowerLimit>. For instance, for POTS
applications based on [52], <cidLowerLimit> and <cidUpperLimit>
Although the <cidCount> can take on values in the range 1-255, can have values of 16 and 223 respectively.
current applications do not allocate more than 248 CIDs per VC.
This is because of reserved CID values [11]. The larger range
is permitted in the SDP to allow future and proprietary applications.
The <timerCU> integer represents the "combined use" timerCU defined in The <timerCU> integer represents the "combined use" timerCU defined in
ITU I.363.2. This timer is represented as an integer number of microseconds. ITU I.363.2. This timer is represented as an integer number of microseconds.
The <simplifiedCPS> parameter can be assigned the values "on" or "off". When The <simplifiedCPS> parameter can be assigned the values "on" or "off". When
it is "on", the AAL2 CPS simplification described in [52] is adopted. Under it is "on", the AAL2 CPS simplification described in [52] is adopted. Under
this simplification, each ATM cell contains exactly on AAL2 packet. If this simplification, each ATM cell contains exactly on AAL2 packet. If
Rajesh Kumar, Mohamed Mostafa. 53
necessary, octets at the end of the cell are padded with zeros. Since the necessary, octets at the end of the cell are padded with zeros. Since the
<timerCU> value in this context is always 0, it can be omitted. <timerCU> value in this context is always 0, it can be omitted.
5.6.29 The 'aal2sscs3661unassured' attribute 5.6.2.10 The 'aal2CPSSDUrate' attribute
When present, the 'aal2CPSSDUrate' attribute is used to place an upper
bound on the SDU bit rate for an AAL2 CID. This is useful for
limiting the bandwidth used by a CID, specially if the CID is used
for frame mode data defined in [13], or with the SSSAR defined in
[12]. The format of this media attribute line is as follows:
a=aal2CPSSDUrate: <fSDUrate><bSDUrate>
The fSDUrate and bSDUrate are the maximum forward and backward SDU
rates in bits/second. These are represented as
decimal integers, with range as defined in Section 6. If any
of these parameters in these media attribute lines is not
specified, is inapplicable or is implied, then it is set to "-".
5.6.2.11 The 'aal2sscs3661unassured' attribute
When present, the 'aal2sscs3661unassured' attribute is used to indicate When present, the 'aal2sscs3661unassured' attribute is used to indicate
the options that pertain to the unassured transmission SSCS defined the options that pertain to the unassured transmission SSCS defined
in ITU I.366.1 [12]. This SSCS can be selected via the aalApp in ITU I.366.1 [12]. This SSCS can be selected via the aalApp
attribute defined below, or by virtue of the presence of the attribute defined below, or by virtue of the presence of the
'aal2sscs3661unassured' attribute. The format of this 'aal2sscs3661unassured' attribute. The format of this
media attribute line is as follows: media attribute line is as follows:
a=aal2sscs3661unassured: <ted> <fsssar> <bsssar> a=aal2sscs3661unassured: <ted> <rastimer> <fsssar> <bsssar>
Rajesh Kumar, Mohamed Mostafa. 48
Each of these fields can be set to a "-" when the intention is to not Each of these fields can be set to a "-" when the intention is to not
specify them in an SDP descriptor. specify them in an SDP descriptor.
The <ted> flag indicates the presence or absence of transmission The <ted> flag indicates the presence or absence of transmission
error detection as defined in I.366.1. It can be assigned the error detection as defined in I.366.1. It can be assigned the
values of "on" or "off". An "on" value indicates presence of values of "on" or "off". An "on" value indicates presence of
the capability. the capability.
The <rastimer> subparameter indicates the SSSAR reassembly timer
in microseconds. It is represented as the decimal equivalent of
32 bits.
The <fsssar> and <bsssar> fields are 24-bit integers that The <fsssar> and <bsssar> fields are 24-bit integers that
can be represented in decimal or in hex. The meaning and values of can be represented in decimal or in hex. The meaning and values of
the <fsssar> and <bsssar> fields are as follows: the <fsssar> and <bsssar> fields are as follows:
Field Meaning Values Field Meaning Values
<fsssar> Maximum SSSAR-SDU size 1- 65,568 <fsssar> Maximum SSSAR-SDU size 1- 65,568
forward direction forward direction
<bsssar> Maximum SSSAR-SDU size 1- 65,568 <bsssar> Maximum SSSAR-SDU size 1- 65,568
backward direction backward direction
If present, the SSTED (Service-Specific Transmission Error If present, the SSTED (Service-Specific Transmission Error
Detection) sublayer is above the SSSAR (Service-Specific Segmentation Detection) sublayer is above the SSSAR (Service-Specific Segmentation
and Reassembly) sublayer [12]. Since the maximum size of the and Reassembly) sublayer [12]. Since the maximum size of the
SSTED-SDUs can be derived from the maximum SSSAR-SDU size, it need SSTED-SDUs can be derived from the maximum SSSAR-SDU size, it need
not be specified separately. not be specified separately.
In certain applications (such as SIP-based applications), an SDP 5.6.2.12 The 'aal2sscs3661assured' attribute
descriptor might have an 'aal2sscs3661unassured' media attribute line
with the <fsssar> and <bsssar> subparameters. In other applications
(such as Megaco-based applications), the remote descriptor can have the
<fsssar> subparameter, and the local descriptor can have the
<bsssar> subparameter.
5.6.30 The 'aal2sscs3661assured' attribute
When present, the 'aal2sscs3661assured' attribute is used to indicate When present, the 'aal2sscs3661assured' attribute is used to indicate
the options that pertain to the assured transmission SSCS defined the options that pertain to the assured transmission SSCS defined
in ITU I.366.1 [12] on the basis of ITU Q.2110 [43]. This SSCS can be in ITU I.366.1 [12] on the basis of ITU Q.2110 [43]. This SSCS can be
Rajesh Kumar, Mohamed Mostafa. 54
selected via the aalApp attribute defined below, or by virtue selected via the aalApp attribute defined below, or by virtue
of the presence of the 'aal2sscs3661assured' attribute. The format of of the presence of the 'aal2sscs3661assured' attribute. The format of
this media attribute line is as follows: this media attribute line is as follows:
a=aal2sscs3661assured: <fsssar> <bsssar> <fsscopsdu> <bsscopsdu> a=aal2sscs3661assured: <rastimer> <fsssar> <bsssar> <fsscopsdu>
<fsscopuu> <bsscopuu> <bsscopsdu><fsscopuu> <bsscopuu>
Each of these fields can be set to a "-" when the intention is to not Each of these fields can be set to a "-" when the intention is to not
specify them in an SDP descriptor. specify them in an SDP descriptor.
The <rastimer> subparameter indicates the SSSAR reassembly timer
in microseconds. It is represented as the decimal equivalent of
32 bits.
The <fsssar> and <bsssar> fields are 24-bit integers that The <fsssar> and <bsssar> fields are 24-bit integers that
Rajesh Kumar, Mohamed Mostafa. 49
can be represented in decimal or in hex. The <fsscopsdu>, can be represented in decimal or in hex. The <fsscopsdu>,
<bsscopsdu>, <fsscopuu> and <bsscopuu> fields are 16-bit integers <bsscopsdu>, <fsscopuu> and <bsscopuu> fields are 16-bit integers
that can be represented in decimal or in hex. The meaning and values that can be represented in decimal or in hex. The meaning and values
of these fields is as follows: of these fields is as follows:
Field Meaning Values Field Meaning Values
<fsssar> Maximum SSSAR-SDU size 1- 65,568 <fsssar> Maximum SSSAR-SDU size 1- 65,568
forward direction forward direction
skipping to change at line 2856 skipping to change at line 2573
SSSAR-SDU size, they need not be specified separately. SSSAR-SDU size, they need not be specified separately.
The SSCOP protocol defined in [43] is used by the Assured Data The SSCOP protocol defined in [43] is used by the Assured Data
Transfer service defined in [12]. In the context of the ITU I.366.1 Transfer service defined in [12]. In the context of the ITU I.366.1
SSCS, it is possible to use the 'aal2sscs3661assured' attribute to limit SSCS, it is possible to use the 'aal2sscs3661assured' attribute to limit
the maximum sizes of the SSCOP SDUs and UU (user-to-user) fields in the maximum sizes of the SSCOP SDUs and UU (user-to-user) fields in
either direction. Note that it is necessary for the parameters on the either direction. Note that it is necessary for the parameters on the
'aal2sscs3661assured' media attribute line to be consistent with each 'aal2sscs3661assured' media attribute line to be consistent with each
other. other.
Rajesh Kumar, Mohamed Mostafa. 55 5.6.2.13 The 'aal2sscs3662' attribute
In certain applications (such as SIP-based applications), an SDP
descriptor might have an 'aal2sscs3661assured' media attribute line
with the forward and backward subparameters listed above. In other
applications (such as Megaco-based applications), the remote descriptor
can have the forward subparameters, and the local descriptor can have the
backward subparameters.
5.6.31 The 'aal5sscop' attribute
When present, the 'aal5sscop' attribute is used to indicate the
existence of an SSCOP [43] protocol layer over an AAL5 CPS
layer [21], and the parameters which pertain to this SSCOP layer.
SSCOP over AAL5 can also be selected via the aalApp attribute
defined below. The format of the 'aal5sscop' media attribute
line is as follows:
a=aal5sscop: <fsscopsdu> <bsscopsdu> <fsscopuu> <bsscopuu>
Each of these fields can be set to a "-" when the intention is to not
specify them in an SDP descriptor.
The representation, meaning and values of the <fsscopsdu>, <bsscopsdu>,
<fsscopuu> and <bsscopuu> fields are identical to those for the
'aal2sscs3661assured' media attribute line (Section 5.6.30). Note that it
is necessary for the parameters on the 'aal5sscop' media attribute
line to be consistent with each other.
In certain applications (such as SIP-based applications), an SDP
descriptor might have an 'aal5sscop' media attribute line
with the forward and backward subparameters listed above. In other
applications (such as Megaco-based applications), the remote descriptor
can have the forward subparameters, and the local descriptor can have the
backward subparameters.
5.6.32 The 'aal2sscs3662' attribute
When present, the 'aal2sscs3662' attribute is used to indicate When present, the 'aal2sscs3662' attribute is used to indicate
the options that pertain to the SSCS defined in ITU I.366.2 [13]. the options that pertain to the SSCS defined in ITU I.366.2 [13].
This SSCS can be selected via the aalApp attribute defined below This SSCS can be selected via the aalApp attribute defined below,
or through the 'aal2sscs3662' attribute. The format of this or by the presence of the 'aal2sscs3662' attribute.
media attribute line is as follows:
The format of this media attribute line is as follows:
Rajesh Kumar, Mohamed Mostafa. 50
a=aal2sscs3662: <sap> <circuitMode> <frameMode> <faxDemod> a=aal2sscs3662: <sap> <circuitMode> <frameMode> <faxDemod>
<cas> <dtmf> <mfall> <mfr1> <mfr2> <cas> <dtmf> <mfall> <mfr1> <mfr2>
<PCMencoding> <fmaxFrame> <bmaxFrame> <PCMencoding> <fmaxFrame> <bmaxFrame>
Each of these fields can be set to a "-" when the intention Each of these fields can be set to a "-" when the intention
is to not specify them in an SDP descriptor. Additionally, the values is to not specify them in an SDP descriptor. Additionally, the values
of these fields need to be consistent with each other. For instance, of these fields need to be consistent with each other. Inconsistencies
<circuitMode> = on is inconsistent with <frameMode> = on. Inconsistencies
should be flagged as errors. should be flagged as errors.
Rajesh Kumar, Mohamed Mostafa. 56
The <sap> field can take on the following string values: "AUDIO" The <sap> field can take on the following string values: "AUDIO"
and "MULTIRATE". These correspond to the audio and multirate and "MULTIRATE". These correspond to the audio and multirate
Service Access Points (SAPs) defined in ITU I.366.2. Service Access Points (SAPs) defined in ITU I.366.2.
For the multirate SAP, the following parameters on the aal2sscs3662 For the multirate SAP, the following parameters on the aal2sscs3662
attribute line do not apply: <faxDemod>,<cas>, <dtmf>, <mfall>, attribute line do not apply: <faxDemod>,<cas>, <dtmf>, <mfall>,
<mfr1>, <mfr2> and <PCMencoding>. These are set to "-" for the <mfr1>, <mfr2> and <PCMencoding>. These are set to "-" for the
multirate SAP. multirate SAP.
The <circuitMode> flag indicates whether the transport of circuit The <circuitMode> flag indicates whether the transport of circuit
skipping to change at line 2953 skipping to change at line 2635
The <mfall> flag indicates whether the transport of MF dialled The <mfall> flag indicates whether the transport of MF dialled
digits in AAL2 type 3 packets is enabled or disabled, corresponding digits in AAL2 type 3 packets is enabled or disabled, corresponding
to the string values of "on" and "off" respectively. This flag to the string values of "on" and "off" respectively. This flag
enables MF dialled digits in a generic manner, without specifying enables MF dialled digits in a generic manner, without specifying
type (e.g. R1, R2 etc.). type (e.g. R1, R2 etc.).
The <mfr1> flag indicates whether the transport, in AAL2 type 3 The <mfr1> flag indicates whether the transport, in AAL2 type 3
packets, of MF dialled digits for signaling system R1 is enabled packets, of MF dialled digits for signaling system R1 is enabled
or disabled, corresponding to the string values of "on" and "off" or disabled, corresponding to the string values of "on" and "off"
Rajesh Kumar, Mohamed Mostafa. 51
respectively. respectively.
The <mfr2> flag indicates whether the transport, in AAL2 type 3 The <mfr2> flag indicates whether the transport, in AAL2 type 3
packets, of MF dialled digits for signaling system R2 is enabled packets, of MF dialled digits for signaling system R2 is enabled
or disabled, corresponding to the string values of "on" and "off" or disabled, corresponding to the string values of "on" and "off"
respectively. respectively.
The <PCMencoding> field indicates whether PCM encoding, if used, The <PCMencoding> field indicates whether PCM encoding, if used,
is based on the A-law or the Mu-law. This can be used to qualify is based on the A-law or the Mu-law. This can be used to qualify
Rajesh Kumar, Mohamed Mostafa. 57
the 'generic PCM' codec stated in some of the AAL2 profiles. The the 'generic PCM' codec stated in some of the AAL2 profiles. The
<PCMencoding> field can take on the string values of "PCMA" <PCMencoding> field can take on the string values of "PCMA"
and "PCMU". and "PCMU".
The <fmaxFrame> and <bmaxFrame> fields are 16-bit integers that The <fmaxFrame> and <bmaxFrame> fields are 16-bit integers that
can be represented in decimal or in hex. The meaning and values of can be represented in decimal or in hex. The meaning and values of
the <fmaxFrame> and <bmaxFrame> fields are as follows: the <fmaxFrame> and <bmaxFrame> fields are as follows:
Field Meaning Values Field Meaning Values
<fmaxFrame> Maximum length of a 1- 65,535 <fmaxFrame> Maximum length of a 1- 65,535
frame mode data unit, frame mode data unit,
forward direction forward direction
<bmaxFrame> Maximum length of a 1- 65,535 <bmaxFrame> Maximum length of a 1- 65,535
frame mode data unit, frame mode data unit,
backward direction backward direction
In certain applications (such as SIP-based applications), an SDP 5.6.2.14 The 'aal5sscop' attribute
descriptor might have an 'aal2sscs3662' media attribute line
with the <fmaxFrame> and <bmaxFrame> subparameters. In other
applications (such as Megaco-based applications), the remote
descriptor can have the <fmaxFrame> subparameter, and the local
descriptor can have the <bmaxFrame> subparameter.
5.6.33 The 'aalApp' attribute When present, the 'aal5sscop' attribute is used to indicate the
existence of an SSCOP [43] protocol layer over an AAL5 CPS
layer [21], and the parameters which pertain to this SSCOP layer.
SSCOP over AAL5 can also be selected via the aalApp attribute
defined below. The format of the 'aal5sscop' media attribute
line is as follows:
When present, the 'aalApp' attribute is used to point to the a=aal5sscop: <fsscopsdu> <bsscopsdu> <fsscopuu> <bsscopuu>
controlling standard for an application layer above the ATM adaptation
layer. The format of the 'aalApp' media attribute line is as follows:
a=aalApp: <aalApp> Each of these fields can be set to a "-" when the intention is to not
specify them in an SDP descriptor.
The <aalApp> field can take on the string values listed The representation, meaning and values of the <fsscopsdu>, <bsscopsdu>,
below, along with their meaning. <fsscopuu> and <bsscopuu> fields are identical to those for the
'aal2sscs3661assured' media attribute line (Section 5.6.2.12). Note that it
is necessary for the parameters on the 'aal5sscop' media attribute
line to be consistent with each other.
This list is not exhaustive. An "X-" prefix should be used with 5.6.3 Service attributes
non-standard values, not listed here, of the <aalApp> parameter.
Rajesh Kumar, Mohamed Mostafa. 58 The following is a summary list of the SDP media attributes that can
<aalApp> Meaning be used to describe the services that use the ATM Adaptation Layer (AAL).
These attributes are detailed in subsequent subsections.
"itu_h323c" Annex C of H.323 which specifies direct Rajesh Kumar, Mohamed Mostafa. 52
RTP on AAL5 [45]. * The 'atmmap' attribute. In the AAL1 and AAL5 contexts, this is
used to dynamically map payload types into codec strings.
"af83" af-vtoa-0083.001, which specifies * The 'silenceSupp' attribute, used to indicate the use of
variable size AAL5 PDUs with PCM voice of voice activity detection for silence suppression, and to
and a null SSCS [46]. optionally parameterize the silence suppression function.
"AAL5_SSCOP" SSCOP as defined in ITU Q.2110 [43] * The 'ecanf' and 'ecanb' attributes, used to indicate the use of
running over an AAL5 CPS [21]. of echo cancellation, and to parameterize the this function.
No information is provided regarding
any layers above SSCOP such as Service
Specific Coordination Function (SSCF)
layers.
"itu_i3661_unassured" SSCS with unassured transmission, * The 'gcf' and 'gcb' attributes, used to indicate the use of
per ITU I.366.1 [12]. of gain control, and to parameterize the this function.
"itu_i3661_assured" SSCS with assured transmission, * The 'profileDesc' attribute, which can be used to describe
per ITU I.366.1 [12]. This uses SSCOP [43]. AAL2 profiles. Although any AAL2 profile can be so described,
this attribute is useful for describing, at connection
establishment time, custom profiles that might not be known
to the far end. This attribute applies in the AAL2 context
only.
"itu_i3662" SSCS per ITU I.366.2 [13]. * The 'vsel' attribute, which indicates a prioritized list of
3-tuples for voice service. Each 3-tuple indicates a codec,
an optional packet length and an optional packetization
period. This complements the 'm' line information and should
be consistent with it.
"itu_i3651" Frame relay SSCS per ITU I.365.1 [39]. * The 'dsel' attribute, which indicates a prioritized list of
3-tuples for voiceband data service. Each 3-tuple indicates a
codec, an optional packet length and an optional packetization
period. This complements the 'm' line information and should
be consistent with it.
"itu_i3652" Service-specific coordination function, * The 'fsel' attribute, which indicates a prioritized list of
as defined in ITU I.365.2, for Connection 3-tuples for facsimile service. Each 3-tuple indicates a
Oriented Network Service (SSCF-CONS) [40]. codec, an optional packet length and an optional packetization
This uses SSCOP [43]. period. This complements the 'm' line information and should
be consistent with it.
"itu_i3653" Service-specific coordination function, * The 'codecconfig' attribute, which is used to represent the
as defined in ITU I.365.3, for Connection contents of the single codec information element (IE) defined
Oriented Transport Service (SSCF-COTS) [41]. in ITU Q.765.5 [57].
This uses SSCOP [43].
"itu_i3654" HDLC Service-specific coordination function, * The 'isup_usi' attribute, which is used to represent
as defined in ITU I.365.4 [42]. the 'User Information Layer 1 protocol' field within the
bearer capability information element defined in Section
4.5.5 of ITU Q.931 [59].
"FRF5" Use of the FRF.5 frame relay standard [53], 5.6.3.1 The 'atmmap' attribute
which references ITU I.365.1 [39].
"FRF8" Use of the FRF.8.1 frame relay standard [54]. The 'atmmap' attribute is defined on the basis of the 'rtpmap'
This implies a null SSCS and the mapping of attribute used in RFC2327.
the frame relay header into the ATM header.
"FRF11" Use of the FRF.11 frame relay standard [55]. Rajesh Kumar, Mohamed Mostafa. 53
a=atmmap:<payloadType> <encodingName>
"itu_h2221" Use of the ITU standard H.222.1 for audiovisual The 'atmmap' attribute is used to dynamically map encoding names
communication over AAL5 [51]. into payload types. This is necessary for those encoding names which
have not been assigned a static payload type through IANA [31]. Payload
types and encoding techniques that have been registered with IANA
for RTP are retained for AAL1 and AAL5.
Rajesh Kumar, Mohamed Mostafa. 59 The range of statically defined payload types is in the range
0-95. All static assignments of payload types to codecs are
listed in [31]. The range of payload types defined dynamically
via the 'atmmap' attribute is 96-127.
5.6.34 The 'lij' attribute In addition to reiterating the payload types and encoding
names in [31], Table 2 defines non-standard encoding names
(with "X-" prefixes). Note that [31], rather than Table 2,
is the authoritative list of standard codec names and payload
types in the ATM context.
When present, the 'lij' attribute is used to indicate Rajesh Kumar, Mohamed Mostafa. 54
the presence of a connection that uses the Leaf-initiated-join Table 2: Encoding Names and Payload Types
capability described in UNI 4.0 [5], and to optionally describe |---------------------|--------------|---------------------------|
parameters associated with this capability. The format of the | Encoding Technique | Encoding Name| Payload type |
'lij' media attribute line is as follows: |---------------------|--------------|---------------------------|
| PCM - Mu law | "PCMU" | 0 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| 32 kbps ADPCM | "G726-32" | 2 (Statically Mapped) |
|---------------------|--------------|---------------------------|
|Dual rate 5.3/6.3kbps| "G723" | 4 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| PCM- A law | "PCMA" | 8 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| 7 KHz audio coding | "G722" | 9 (Statically Mapped) |
| within 64 kbps | | |
|---------------------|--------------|---------------------------|
| LD-CELP | "G728" | 15 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| CS-ACELP | "G729" | 18 (Statically Mapped) |
|(normal/low-complexity) | |
|---------------------|--------------|---------------------------|
| Low-complexity | "X-G729a" | None, map dynamically |
| CS-ACELP | | |
|---------------------|--------------|---------------------------|
|Normal | "X-G729b" | None, map dynamically |
|CS-ACELP w/ ITU | | |
|defined silence | | |
|suppression | | |
+---------------------+--------------+---------------------------+
|Low-complexity | "X-G729ab" | None, map dynamically |
|CS-ACELP w/ ITU | | |
|defined silence | | |
|suppression | | |
|---------------------|--------------|---------------------------|
| 16 kbps ADPCM | "X-G726-16" | None, map dynamically |
|---------------------|--------------|---------------------------|
| 24 kbps ADPCM | "X-G726-24" | None, map dynamically |
|---------------------|--------------|---------------------------|
| 40 kbps ADPCM | "X-G726-40" | None, map dynamically |
|---------------------|--------------|---------------------------|
| Dual rate 5.3/6.3 |"X-G7231-H" | None, map dynamically |
| kbps - high rate | | |
|---------------------|--------------|---------------------------|
| Dual rate 5.3/6.3 |"X-G7231-L" | None, map dynamically |
| kbps - low rate | | |
|---------------------|--------------|---------------------------|
| Dual rate 5.3/6.3 |"X-G7231a-H" | None, map dynamically |
| kbps - high rate w/ | | |
| ITU-defined silence | | |
| suppression | | |
|----------------------------------------------------------------|
a=lij: <sci><lsn> Rajesh Kumar, Mohamed Mostafa. 55
+---------------------+--------------+---------------------------+
| Dual rate 5.3/6.3 |"X-G7231a-L" | None, map dynamically |
| kbps - high rate w/ | | |
| ITU-defined silence | | |
| suppression | | |
|---------------------|--------------|---------------------------|
| 16 kbps EADPCM | "X-G727-16" | None, map dynamically |
|---------------------|--------------|---------------------------|
| 24 kbps EADPCM | "X-G727-24" | None, map dynamically |
|---------------------|--------------|---------------------------|
| 32 kbps EADPCM | "X-G727-32" | None, map dynamically |
|---------------------|--------------|---------------------------|
|n x 64 kbps Clear | "X-CCD" | None, map dynamically |
|Channel without CAS | | |
|per af-vtoa-78 [7] | | |
|---------------------|--------------|---------------------------|
|n x 64 kbps Clear | "X-CCD-CAS" | None, map dynamically |
|Channel with CAS | | |
|per af-vtoa-78 [7] | | |
|---------------------|--------------|---------------------------|
|GSM Full Rate | "GSM" | 3 (Statically Mapped) |
|---------------------|--------------|---------------------------|
|GSM Half Rate | "GSM-HR" | None, map dynamically |
|---------------------|--------------|---------------------------|
|GSM-Enhanced Full Rate "GSM-EFR" | None, map dynamically |
|---------------------|--------------|---------------------------|
|GSM-Enhanced Half Rate "GSM-EHR" | None, map dynamically |
|---------------------|--------------|---------------------------|
|Group 3 fax demod. "X-FXDMOD-3" | None, map dynamically |
|---------------------|--------------|---------------------------|
| Federal Standard | "1016" | 1 (Statically Mapped) |
| FED-STD 1016 CELP | | |
|---------------------|--------------|---------------------------|
| DVI4, 8 KHz [3] | "DVI4" | 5 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| DVI4, 16 KHz [3] | "DVI4" | 6 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| LPC [3], Linear | "LPC" | 7 (Statically Mapped) |
| Predictive Coding | | |
|---------------------|--------------|---------------------------|
| L16 [3], Sixteen | "L16" | 10 (Statically Mapped) |
| Bit Linear PCM, | | |
| Double channel | | |
|---------------------|--------------|---------------------------|
| L16 [3], Sixteen | "L16" | 11 (Statically Mapped) |
| Bit Linear PCM, | | |
| Single channel | | |
|---------------------|--------------|---------------------------|
| QCELP [3] | "QCELP" | 12 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| MPEG1/MPEG2 audio | "MPA" | 14 (Statically Mapped) |
|---------------------|--------------|---------------------------|
The <sci> (screening indication) is a 4-bit field expressed as a Rajesh Kumar, Mohamed Mostafa. 56
decimal or hex integer. It is defined in the UNI 4.0 signaling +---------------------+--------------+---------------------------+
specification [5]. It is possible that the values of this field will | DVI4, 11.025 KHz[3] | "DVI4" | 16 (Statically Mapped) |
be defined later by the ATMF and/or ITU. Currently, all values are |---------------------|--------------|---------------------------|
reserved with the exception of 0, which indicates a 'Network Join | DVI4, 22.05 KHz [3] | "DVI4" | 17 (Statically Mapped) |
without Root Notification'. |---------------------|--------------|---------------------------|
| MPEG1/MPEG2 video | "MPV" | 32 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| MPEG 2 audio/video | "MP2T" | 33 (Statically Mapped) |
| transport stream | | |
|---------------------|--------------|---------------------------|
| ITU H.261 video | "H261" | 31 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| ITU H.263 video | "H263" | 33 (Statically Mapped) |
|---------------------|--------------|---------------------------|
| ITU H.263 video |"H263-1998" | None, map dynamically |
| 1998 version | | |
|---------------------|--------------|---------------------------|
|MPEG 1 system stream | "MP1S" | None, map dynamically |
|---------------------|--------------|---------------------------|
|MPEG 2 program stream| "MP2P" | None, map dynamically |
|---------------------|--------------|---------------------------|
|Redundancy | "RED" | None, map dynamically |
|---------------------|--------------|---------------------------|
|Variable rate DVI4 | "VDVI" | None, map dynamically |
|---------------------|--------------|---------------------------|
|Cell-B | "CelB" | 25 |
|---------------------|--------------|---------------------------|
|JPEG | "JPEG" | 26 |
|---------------------|--------------|---------------------------|
|nv | "nv" | 28 |
|---------------------|--------------|---------------------------|
|L8, Eight Bit Linear | "L8" | None, map dynamically |
|PCM | | |
|---------------------|--------------|---------------------------|
| ITU-R Recommendation| "BT656" | None, map dynamically |
| BT.656-3 for | | |
| digital video | | |
|---------------------|--------------|---------------------------|
| Adaptive Multirate | "FR-AMR" | None, map dynamically |
|-Full Rate (3GPP)[58]| | |
|---------------------|--------------|---------------------------|
| Adaptive Multirate | "HR-AMR" | None, map dynamically |
|-Half Rate (3GPP)[58]| | |
|---------------------|--------------|---------------------------|
| Adaptive Multirate | "HR-UMTS" | None, map dynamically |
|- UMTS(3GPP) [58] | | |
|---------------------|--------------|---------------------------|
The <lsn> (leaf sequence number) is a 32-bit field expressed as a Rajesh Kumar, Mohamed Mostafa. 57
decimal or hex integer. Per the UNI 4.0 signaling specification [5], it
is used by a joining leaf to associate messages and responses during
LIJ (leaf initiated join) procedures.
Each of these fields can be set to a "-" when the intention 5.6.3.2 The 'silenceSupp' attribute
is to not specify them in an SDP descriptor.
5.6.35 The 'anycast' attribute When present, the 'silenceSupp' attribute is used to indicate
the use or non-use of silence suppression.
The format of the 'silenceSupp' media attribute line is
as follows:
When present, the 'anycast' attribute line is used to indicate a=silenceSupp: <silenceSuppEnable> <silenceTimer> <suppPref> <sidUse>
the applicability of the anycast function described in UNI <fxnslevel>
4.0 [5]. Optional parameters to qualify this function are
provided. The format of the 'anycast' attribute is:
a=anycast: <atmGroupAddress> <cdStd> <conScpTyp> <conScpSel> If any of the parameters in the silenceSupp media attribute line
is not specified, is inapplicable or is implied, then it is set to
"-".
The <atmGroupAddress> is per Annex 5 of UNI 4.0 [5]. Within The <silenceSuppEnable> can take on values of "on" or "off". If it
an SDP descriptor, it can be represented in one of the formats is "on", then silence suppression is enabled.
(NSAP, E.164, GWID/ALIAS) described elsewhere in this document.
The remaining subparameters mirror the connection scope selection The <silenceTimer> is a 16-bit field which can be represented in
information element in UNI 4.0 [5]. Their meaning and representation decimal or hex. Each increment (tick) of this timer represents
is as shown below: a millisecond. The maximum value of this timer is between 1 and 3
minutes. This timer represents the time-lag before silence
suppression kicks in. Even though this can, theoretically, be
as low as 1 ms, most DSP algorithms take more than that to
detect silence. Setting <silenceTimer> to a large value (say
1 minute> is equivalent to disabling silence suppression
within a call. However, idle channel suppression between calls
on the basis of silence suppression is still operative in
non-switched, trunking applications if <silenceSuppEnable> = "on"
and <silenceTimer> is a large value.
Rajesh Kumar, Mohamed Mostafa. 60 The <suppPref> specifies the preferred silence suppression
PARAMETER MEANING REPRESENTATION method that is preferred or already selected. It can
<cdStd> Coding standard for the Decimal or hex take on the string values of "standard" and "custom". If
connection scope selection IE equivalent of its value is "standard", then a standard method (e.g. ITU-defined)
Definition: UNI 4.0 [5] 2 bits is preferred to custom methods if such a standard
is defined. Otherwise, a custom method may be used. If
<suppPref> is set to "custom", then a custom method, if
available, is preferred to the standard method.
<conScpTyp> Type of connection scope Decimal or hex The <sidUse> indicates whether SIDs (Silence Insertion
Definition: UNI 4.0 [5] equivalent of Descriptors) are to be used, and whether they use fixed comfort
4 bits noise or sampled background noise. It can take on the
string values of "No SID", "Fixed Noise", "Sampled Noise".
<conScpSel> Connection scope selection Decimal or hex If the value of <sidUse> is "Fixed Noise", then <fxnslevel>
Definition: UNI 4.0 [5] equivalent of provides its level. It can take on integer values in the range
8 bits 0-127, as follows:
Currently, all values of <cdStd> and <conScpTyp> are reserved with Rajesh Kumar, Mohamed Mostafa. 58
the exception of <cdStd> = 3 (ATMF coding standard) and <conScpTyp> = 1 +-----------------------+---------------------+
(connection scope type of 'organizational'). | <fxnslevel> value | Meaning |
+-----------------------+---------------------+
| 0-29 | Reserved |
| 30 | -30 dBm0 |
| 31 | -31 dBm0 |
| . . . | . . . |
| 77 | -77 dBm0 |
| 78 | -78 dBm0 |
| 79-126 | reserved |
| 127 | Idle Code (no noise)|
+-----------------------+---------------------+
Each of these fields can be set to a "-" when the intention In addition to the decimal representation of <fxnslevel>, a
is to not specify them in an SDP descriptor. hex representation, preceded by a "0x" prefix, is also allowed.
5.6.36 The 'cache' attribute 5.6.3.3 The 'ecanf' and 'ecanb' attributes
This attribute is used to enable SVC caching. This attribute When present, the 'ecanf' and 'ecanb' attributes are used to indicate
has the following format: the use or non-use of echo cancellation in the forward
and backward directions respectively. See Section
2.3 for a definition of the terms 'forward' and 'backward'.
a=cache:<cacheEnable><cacheTimer> The format of the 'ecanf' and 'ecanb' media attribute lines is
as follows:
The <cacheEnable> flag indicates whether caching is enabled or a=ecanf: <ecanEnable> <ecanType>
not, corresponding to the string values of "on" and "off" a=ecanb: <ecanEnable> <ecanType>
If any of the parameters in the ecanf and ecanb media attribute lines
is not specified, is inapplicable or is implied, then it is set to
"-".
If the 'ecanf' or 'ecanb' media attribute lines is not present,
then means other than the SDP descriptor must be used to determine
the applicability and nature of echo cancellation in that direction.
Examples of such means are MIB provisioning, the local connection options
structure in MGCP etc.
The <ecanEnable> parameter can take on values of "on" or "off". If it
is "on", then echo cancellation is enabled. If it is "off",
then echo cancellation is disabled.
The <ecanType> parameter can take on the string values "G165" and "G168"
respectively. respectively.
The <cacheTimer> indicates the period of inactivity following which When SDP is used with some media gateway control protocols such as MGCP
the SVC is to be released by sending an SVC release message into and Megaco [26], there exist means outside SDP descriptions to specify
the network. This is specified as the decimal or hex equivalent of the echo cancellation properties of a connection. Nevertheless, this
a 32-bit field, indicating the timeout in seconds. As usual, leading media attribute line is included for completeness. As a result, the
zeros can be omitted. For instance, SDP can be used for describing echo cancellation in applications
where alternate means for this are unavailable.
a=cache:on 7200 Rajesh Kumar, Mohamed Mostafa. 59
implies that the cached SVC is to be deleted if it is idle for 2 hours. 5.6.3.4 The 'gcf' and 'gcb' attributes
The <cacheTimer> can be set to "-" if it is inapplicable or implied. When present, the 'gcf' and 'gcb' attributes are used to indicate
the use or non-use of gain control in the forward and backward
directions respectively. See Section 2.3 for a definition of the
terms 'forward' and 'backward'.
5.6.37 Specification of Higher-layer attributes The format of the 'gcf' and 'gcb' media attribute lines is as
follows:
This conventions in this ATM SDP document are limited to the ATM and adaptation a=gcf: <gcEnable> <gcLvl>
layers. Parameters associated with layers higher than the ATM adaptation a=gcb: <gcEnable> <gcLvl>
layer are addressed only if these are tightly coupled to the ATM or
adaptation layers.
Rajesh Kumar, Mohamed Mostafa. 61 If any of the parameters in the gcf and gcb media attribute lines
is not specified, is inapplicable or is implied, then it is set to
"-". If the 'gcf' or 'gcb' media attribute line is not present,
then means other than the SDP descriptor must be used to determine the
applicability and nature of gain control in that direction. Examples of such
means are MIB provisioning, the local connection options structure in MGCP
etc.
ATM signaling standards provide 'escape mechanisms' to The <gcEnable> parameter can take on values of "on" or "off". If it
represent, signal and negotiate higher-layer parameters. Examples is "on", then gain control is enabled. If it is "off", then
are the B-HLI and B-LLI IEs specified in ITU Q.2931 [15], and gain control is disabled.
the user-to-user information element described in ITU Q.2957 [48].
SDP, as described in rfc2327, has a similar mechanism to The <gcLvl> parameter is represented as the decimal or hex
describe higher-layer parameters. This is the 'fmtp' or the equivalent of a 16-bit binary field. A value of 0xFFFF implies
format-specific parameters attribute. This attribute is expressed in automatic gain control. Otherwise, this number indicates the
the following manner: number of decibels of inserted loss. The upper bound, 65,535 dB
(0xFFFE) of inserted loss, is an absurdly large number and is a
carryover from Megaco [26]. In practical applications, the inserted loss
is much lower.
a=fmtp:<format><format specific parameters> When SDP is used with some media gateway control protocols such as MGCP
and Megaco [26], there exist means outside SDP descriptions to specify
the gain control properties of a connection. Nevertheless, this
media attribute line is included for completeness. As a result, the
SDP can be used for describing gain control in applications
where alternate means for this are unavailable.
It is suggested that applications use this attribute, described in 5.6.3.5 The 'profileDesc' attribute
detail in rfc2327 [1], to express higher-layer parameters. Conventions
for the use of the 'fmtp' attribute to describe higher-layer information
are beyond the scope of the present document. However, it is recognized
that in some applications it is necessary to describe higher-layer
information within the same SDP descriptor as the ATM and AAL
information.
5.6.38 Use of the second media-level part in H.323 Annex C applications There is one 'profileDesc' media attribute line for each AAL2
profile that is intended to be described. The 'profileDesc' media
attribute line is structured as follows:
Section 4 mentions that H.323 annex C applications have a second media level a=profileDesc: <aal2transport> <profile> <uuiCodeRange#1>
part for the ATM session description. This is used to convey information about <encodingName#1> <packetLength#1> <packetTime#1>
the RTCP stream. Although the RTP stream is encapsulated in AAL5 with no <uuiCodeRange#2> <encodingName#2> <packetLength#2>
intervening IP layer, the RTCP stream is sent to an IP address and RTCP port. <packetTime#2>... <uuiCodeRange#N> <encodingName#N>
This media level part has the following format: <packetLength#N> <packetTime#N>
m= control <rtcpPortNum> H323c - Rajesh Kumar, Mohamed Mostafa. 60
c= IN IP4 <rtcpIPaddr> Here, <aal2transport> can have those values of <transport> (Table 1) that
pertain to AAL2. These are:
Consistency with rfc2327 is maintained in the location and format of these AAL2/ATMF
lines. The <fmt list> in the 'm' line is set to "-". The 'c' line in the second AAL2/ITU
media-level part pertains to RTCP only. AAL2/custom
AAL2/<corporateName>
AAL2/IEEE:<oui>
The <rtcpPortNum> and <rtcpIPaddr> subparameters indicate the port number The parameter <profile> is identical to its definition for the 'm'
and IP address on which the media gateway is prepared to receive RTCP packets. line (Section 5.5.4).
Any of the subparameters on these lines can be set to "-" if they are known by The profile elements (rows in the profile tables of ITU I.366.2 or
other means. AF-VTOA-0113) are represented as four-tuples following the <profile>
parameter in the 'profileDesc' media attribute line. If a member of
one of these four-tuples is not specified or is implied, then it is
set to "-".
The range and format of the <rtcpPortNum> and <rtcpIPaddr> subparameters is per The <uuiCodeRange> parameter is represented by D1-D2, where D1 and
[1]. The <rtcpPortNum> is a decimal number between 1024 and 65535. It is an odd D2 are decimal integers in the range 0 through 15.
number. If an even number in this range is specified, the next odd number is
used. The <rtcpIPaddr> is expressed in the usual dotted decimal IP address The <encodingName> parameter can take one of the values in column 2
representation, from 0.0.0.0 to 255.255.255.255. of Table 2. Additionally, it can take on the following descriptor
strings: "PCMG", "SIDG" and "SID729". These stand for generic PCM,
generic SID and G.729 SID respectively.
The <packetLength> is a decimal integer representation of the AAL2
packet length in octets.
The <packetTime> is a decimal integer representation of the AAL2
packetization interval in microseconds.
For instance, the 'profileDesc' media attribute line below defines
the AAL2/custom 100 profile. This profile is reproduced in the Table 3
below. For a description of the parameters in this profile such as
M and the sequence number interval, see ITU I.366.2 [13].
a=profileDesc:AAL2/custom 100 0-7 PCMG 40 5000 0-7 SIDG 1 5000 8-15
G726-32 40 10000 8-15 SIDG 1 5000
If the <packetTime> parameter is to be omitted or implied, then the
same profile can be represented as follows:
a=profileDesc:AAL2/custom 100 0-7 PCMG 40 - 0-7 SIDG 1 - 8-15
G726-32 40 - 8-15 SIDG 1 -
If a gateway has a provisioned or hard coded definition of a
profile, then any definition provided via the 'profileDesc' line
overrides it. The exception to this rule is with regard to standard
profiles such as ITU-defined profiles and ATMF-defined profiles. In
Rajesh Kumar, Mohamed Mostafa. 61
general, these should not be defined via a 'profileDesc' media
attribute line. If they are, then the definition needs to be
consistent with the standard definition else the SDP session
descriptor should be rejected with an appropriate error code.
Table 3: Example of a custom AAL2 profile
|---------------------------------------------------------------|
| UUI | Packet |Encoding | | |Packet|Seq.No. |
| Code | Length |per ITU |Description of | M |Time |Interval|
|point |(octets)|I.366.2 | Algorithm | |(ms) |(ms) |
|Range | | 2/99 | | | | |
| | | version | | | | |
|---------------------------------------------------------------|
| 0-7 | 40 | Figure | PCM, G.711-64,| 1 | 5 | 5 |
| | | B-1 | generic | | | |
|------|--------|---------|---------------|-----|------|--------|
| 0-7 | 1 | Figure | Generic SID | 1 | 5 | 5 |
| | | I-1 | | | | |
|------|--------|---------|---------------|-----|------|--------|
| 8-15 | 40 | Figure | ADPCM, | 2 | 10 | 5 |
| | | E-2 | G.726-32 | | | |
|------|--------|---------|---------------|-----|------|--------|
| 8-15 | 1 | Figure | Generic SID | 1 | 5 | 5 |
| | | I-1 | | | | |
|------|--------|---------|---------------|-----|------|--------|
5.6.3.6 The 'vsel' attribute
The 'vsel' attribute indicates a prioritized list of one or more
3-tuples for voice service. Each 3-tuple indicates a codec, an optional
packet length and an optional packetization period. This complements the 'm'
line information and should be consistent with it.
The 'vsel' line is structured as follows:
a=vsel:<encodingName #1> <packetLength #1><packetTime #1>
<encodingName #2> <packetLength #2><packetTime #2>
...
<encodingName #N> <packetLength #N><packetTime #N>
where the <encodingName> parameter can take one of the values in column 2 of
Table 2. The <packetLength> is a decimal integer representation of the
packet length in octets. The <packetTime> is a decimal integer
representation of the packetization interval in microseconds. The parameters
<packetLength>and <packetTime> can be set to "-" when not needed. Also, the
entire 'vsel' media attribute line can be omitted when not needed.
For example,
a=vsel:G729 10 10000 G726-32 40 10000
Rajesh Kumar, Mohamed Mostafa. 62 Rajesh Kumar, Mohamed Mostafa. 62
indicates first preference of G.729 or G.729a (both are interoperable) as
the voice encoding scheme. A packet length of 10 octets and a packetization
interval of 10 ms are associated with this codec. G726-32 is the second
preference stated in this line, with an associated packet length of 40
octets and a packetization interval of 10 ms. If the packet length and
packetization interval are intended to be omitted, then this media attribute
line becomes
5.6.39 Chaining SDP descriptors a=vsel:G729 - - G726-32 - -
The media attribute line
a=vsel:G726-32 40 10000
indicates preference for or selection of 32 kbps ADPCM with a packet
length of 40 octets and a packetization interval of 10 ms.
This media attribute line can be used in ATM as well as non-ATM contexts.
Within the ATM context, it can be applied to the AAL1, AAL2 and AAL5
adaptations. The <packetLength> and <packetTime> are not meaningful
in the AAL1 case and should be set to "-". In the AAL2 case,
this line determines the use of some or all of the rows in
a given profile table. If multiple 3-tuples are present, they
can indicate a hierarchical assignment of some rows in that
profile to voice service e.g. row A preferred to row B etc.
If multiple profiles are present on the 'm' line, the profile
qualified by this attribute is the first
profile. If a single profile that has been selected for a connection
is indicated in the 'm' line, the 'vsel' attribute qualifies the
use, for voice service, of codecs within that profile.
With most of the encoding names in Figure 2, the packet length
and packetization period can be derived from each other. One of them
can be set to "-" without a loss of information. There are some
exceptions such as the IANA-registered encoding names G723, DVI4 and
L16 for which this is not true. Therefore, there is a need to
retain both the packet length and packetization period in the
definition of the 'vsel' line.
5.6.3.7 The 'dsel' attribute
The 'dsel' attribute indicates a prioritized list of
one or more 3-tuples for voiceband data service. The <fxIncl>
flag indicates whether this definition of voiceband data
includes fax ("on" value) or not ("off" value). If <fxIncl> is
"on", then the 'dsel' line must be consistent with any 'fsel' line
in the session description. In this case, an error event is generated
in the case of inconsistency. Each 3-tuple indicates a codec,
an optional packet length and an optional packetization
period. This complements the 'm' line information and should
be consistent with it.
Rajesh Kumar, Mohamed Mostafa. 63
The 'dsel' line is structured as follows:
a=dsel:<fxIncl> <encodingName #1> <packetLength #1><packetTime #1>
<encodingName #2> <packetLength #2><packetTime #2>
...
<encodingName #N> <packetLength #N><packetTime #N>
where the <encodingName> parameter can take one of the values in
column 2 of Table 2. The <packetLength> and <packetTime>
parameters are per their definition, above, for the 'vsel'
media attribute line. The parameters <packetLength>and <packetTime>)
can be set to "-" when not needed. The <fxIncl> flag is presumed to be
"off" if it is set to "-". Also, the entire 'dsel' media attribute line
can be omitted when not needed.
For example,
a=dsel:- G726-32 20 5000 PCMU 40 5000
indicates that this line does not address facsimile, and that the
first preference for the voiceband data codes is 32 kbps ADPCM,
while the second preference is PCMU. The packet length
and the packetization interval associated with G726-32 are 20 octets and
5 ms respectively. For PCMU, they are 40 octets and 5 ms respectively.
This media attribute line can be used in ATM as well as non-ATM contexts.
Within the ATM context, it can be applied to the AAL1, AAL2 and AAL5
adaptations. The <packetLength> and <packetTime> are not meaningful
in the AAL1 case and should be set to "-". In the AAL2 case,
this line determines the use of some or all of the rows in
a given profile table. If multiple 3-tuples are present, they
can indicate a hierarchical assignment of some rows in that
profile to voiceband data service e.g. row A preferred to row B etc.
If multiple profiles are present on the 'm' line, the profile
qualified by this attribute is the first
profile. If a single profile that has been selected for a connection
is indicated in the 'm' line, the 'dsel' attribute qualifies the
use, for voiceband data service, of codecs within that profile.
With most of the encoding names in Figure 2, the packet length
and packetization period can be derived from each other. One of them
can be set to "-" without a loss of information. There are some
exceptions such as the IANA-registered encoding names G723, DVI4 and
L16 for which this is not true. Therefore, there is a need to
retain both the packet length and packetization period in the
definition of the 'dsel' line.
5.6.3.8 The 'fsel' attribute
The 'fsel' attribute indicates a prioritized list of
one or more 3-tuples for facsimile service. If an 'fsel' line
is present, any 'dsel' line with <fxIncl> set to "on" in the session
Rajesh Kumar, Mohamed Mostafa. 64
description must be consistent with it. In this case,
an error event is generated in the case of inconsistency.
Each 3-tuple indicates a codec, an optional packet length and an
optional packetization period. This complements the 'm' line information
and should be consistent with it.
The 'fsel' line is structured as follows:
a=fsel:<encodingName #1> <packetLength #1><packetTime #1>
<encodingName #2> <packetLength #2><packetTime #2>
...
<encodingName #N> <packetLength #N><packetTime #N>
where the <encodingName> parameter can take one of the values in
column 2 of Table 2. The <packetLength> and <packetTime>
parameters are per their definition, above, for the 'vsel'
media attribute line. The parameters <packetLength>and <packetTime> can
be set to "-" when not needed. Also, the entire 'fsel' media attribute
line can be omitted when not needed.
For example,
a=fsel:FXDMOD-3 - -
indicates demodulation and remodulation of ITU-T group 3 fax at the
gateway.
a=fsel:PCMU 40 5000 G726-32 20 5000
indicates a first and second preference of Mu-law PCM and 32 kbps
ADPCM as the facsimile encoding scheme. The packet length
and the packetization interval associated with G726-32 are 20 octets and
5 ms respectively. For PCMU, they are 40 octets and 5 ms respectively.
This media attribute line can be used in ATM as well as non-ATM contexts.
Within the ATM context, it can be applied to the AAL1, AAL2 and AAL5
adaptations. The <packetLength> and <packetTime> are not meaningful
in the AAL1 case and should be set to "-". In the AAL2 case,
this line determines the use of some or all of the rows in
a given profile table. If multiple 3-tuples are present, they
can indicate a hierarchical assignment of some rows in that
profile to facsimile service e.g. row A preferred to row B etc.
If multiple profiles are present on the 'm' line, the profile
qualified by this attribute is the first
profile. If a single profile that has been selected for a connection
is indicated in the 'm' line, the 'fsel' attribute qualifies the
use, for facsimile service, of codecs within that profile.
With most of the encoding names in Figure 2, the packet length
and packetization period can be derived from each other. One of them
can be set to "-" without a loss of information. There are some
Rajesh Kumar, Mohamed Mostafa. 65
exceptions such as the IANA-registered encoding names G723, DVI4 and
L16 for which this is not true. Therefore, there is a need to
retain both the packet length and packetization period in the
definition of the 'fsel' line.
5.6.3.9 The 'codecconfig' attribute
When present, the 'codecconfig' attribute is used to represent the
contents of the single codec information element (IE) defined in [57].
The contents of this IE are: a single-octet Organizational Identifier
(OID) field, followed by a single-octet Codec Type field, followed by
zero or more octets of a codec configuration bit-map. The semantics of
the codec configuration bit-map are specific to the organization
[57, 58]. The 'codecconfig' attribute is represented as follows:
a=codecconfig:<q7655scc>
The <q7655scc> (Q.765.5 single codec IE contents) parameter is
represented as a string of hex digits. The number of hex digits is
even (range 4 -32). The "0x" prefix shall be omitted since this value
is always hexadecimal. As with other hex values [Section 2.2],
digits to the left are more significant than digits to the right.
Leading zeros shall not be omitted.
An example of the use of this media attribute is:
a=codecconfig:01080C
The first octet indicates an Organizational Identifier of 0x01
(the ITU-T). Using ITU Q.765.5 [57], the second octet (0x08) indicates
a codec type of G.726 (ADPCM). The last octet, 0x0C indicates that
16 kbps and 24 kbps rates are NOT supported, while the 32 kbps and
40 kbps rates ARE supported.
5.6.3.10 The 'isup_usi' attribute
When present, the 'isup_usi' attribute is used to represent the
'User Information Layer 1 protocol' field within the bearer
capability information element defined in Section 4.5.5 of [59], and
reiterated as the user service information element (IE) in Section 3.57
of [60]. The 'User Information Layer 1 protocol' field consists of
the five least significant bits of Octet 5 of this information
element. This field is represented by the USI property in Section C.9
of the Megaco/H.248 protocol [26].
Within SDP, the 'isup_usi' attribute is represented as follows:
a=isup_usi:<isupUsi>
The <isupUsi> parameter is represented as a string of two hex
digits. The "0x" prefix shall be omitted since this value
is always hexadecimal. As with other hex values [Section 2.2],
Rajesh Kumar, Mohamed Mostafa. 66
digits to the left are more significant than digits to the right.
These hex digits are constructed from an octet with three leading
'0' bits and last five bits equal to the 'User Information Layer
1 protocol' field described above. As specified in [59] and [26],
bit 5 of this field is the most significant bit. The resulting values
of the <isupUsi> parameter are as follows:
VALUE MEANING
0x01 CCITT standardized rate adaption V.110 and X.30
0x02 Recommendation G.711 Mu-law
0x03 Recommendation G.711 A-law
0x04 Recommendation G.721 32 kbps ADPCM and Recommendation I.460
0x05 Recommendations H.221 and H.242
0x06 Recommendation H.223 and H.245
0x07 Non-ITU-T standardized rate adaption
0x08 ITU-T standardized rate adaption V.120
0x09 CCITT standardized rate adaption X.31 HDLC flag stuffing
5.6.4 Miscellaneous media attributes
The 'chain' media attribute line, which is used to chain consecutive
SDP descriptions, cannot be classified as an ATM, AAL or service
attribute. It is detailed in the following subsection.
5.6.4.1 The 'chain' attribute
The start of an SDP descriptor is marked by a 'v' line. In some The start of an SDP descriptor is marked by a 'v' line. In some
applications, consecutive SDP descriptions are alternative descriptions applications, consecutive SDP descriptions are alternative descriptions
of the same session. In others, these describe different layers of the of the same session. In others, these describe different layers of the
same connection (e.g. IP, ATM, frame relay). This is useful when these same connection (e.g. IP, ATM, frame relay). This is useful when these
connectivity at these layers are established at the same time e.g. an connectivity at these layers are established at the same time e.g. an
IP-based session over an ATM SVC. To distinguish between the IP-based session over an ATM SVC. To distinguish between the
alternation and concatenation of SDP descriptions, a 'chain' attribute alternation and concatenation of SDP descriptions, a 'chain' attribute
can be used in the case of concatenation. can be used in the case of concatenation.
skipping to change at line 3227 skipping to change at line 3445
Chaining averts the need to set up a single SDP description for a Chaining averts the need to set up a single SDP description for a
session that is simultaneously created at multiple layers. It allows session that is simultaneously created at multiple layers. It allows
the SDP descriptors for different layers to remain simple and clean. the SDP descriptors for different layers to remain simple and clean.
Chaining is not needed in the Megaco context, where it is possible to Chaining is not needed in the Megaco context, where it is possible to
create separate terminations for the different layers of a connection. create separate terminations for the different layers of a connection.
The 'chain' media attribute line has the following format: The 'chain' media attribute line has the following format:
a=chain:<chainPointer> a=chain:<chainPointer>
Rajesh Kumar, Mohamed Mostafa. 67
The <chainPointer> field can take on the following string values: The <chainPointer> field can take on the following string values:
"NEXT", "PREVIOUS" and "NULL". The value "NULL" is not equivalent to "NEXT", "PREVIOUS" and "NULL". The value "NULL" is not equivalent to
omitting the chain attribute from a description since it expressly omitting the chain attribute from a description since it expressly
precludes the possibility of chaining. If the 'chain' attribute is precludes the possibility of chaining. If the 'chain' attribute is
absent in an SDP description, chaining can still be realized by the absent in an SDP description, chaining can still be realized by the
presence of a chain media attribute line in the previous or next presence of a chain media attribute line in the previous or next
description. description.
5.6.40 Use of the eecid media attribute in call establishment procedures 5.6.5 Use of the second media-level part in H.323 Annex C applications
Section 4 mentions that H.323 annex C applications have a second media level
part for the ATM session description. This is used to convey information about
the RTCP stream. Although the RTP stream is encapsulated in AAL5 with no
intervening IP layer, the RTCP stream is sent to an IP address and RTCP port.
This media level part has the following format:
m= control <rtcpPortNum> H323c -
c= IN IP4 <rtcpIPaddr>
Consistency with rfc2327 is maintained in the location and format of these
lines. The <fmt list> in the 'm' line is set to "-". The 'c' line in the second
media-level part pertains to RTCP only.
The <rtcpPortNum> and <rtcpIPaddr> subparameters indicate the port number
and IP address on which the media gateway is prepared to receive RTCP packets.
Any of the subparameters on these lines can be set to "-" if they are known by
other means.
The range and format of the <rtcpPortNum> and <rtcpIPaddr> subparameters is per
[1]. The <rtcpPortNum> is a decimal number between 1024 and 65535. It is an odd
number. If an even number in this range is specified, the next odd number is
used. The <rtcpIPaddr> is expressed in the usual dotted decimal IP address
representation, from 0.0.0.0 to 255.255.255.255.
5.6.6 Use of the eecid media attribute in call establishment procedures
This informative section supplements the definition of the eecid This informative section supplements the definition of the eecid
attribute (Section 5.6.2) by describing example procedures for its use. attribute (Section 5.6.1.1) by describing example procedures for its use.
These procedures assume a bearer-signaling mechanism for connection set-up These procedures assume a bearer-signaling mechanism for connection set-up
that is independent of service-level call control. These procedures are that is independent of service-level call control. These procedures are
independent of the media gateway control protocol (MGCP, Megaco, SIP etc.), independent of the media gateway control protocol (MGCP, Megaco, SIP etc.),
the protocol used between media gateway controllers (ITU Q.1901, SIP the protocol used between media gateway controllers (ITU Q.1901, SIP
etc.) and the protocol used for bearer connection set-up (Q.2931, UNI, PNNI, etc.) and the protocol used for bearer connection set-up (Q.2931, UNI, PNNI,
AINI, IISP, Q.2630.1 etc.). AINI, IISP, Q.2630.1 etc.).
Rajesh Kumar, Mohamed Mostafa. 63 Rajesh Kumar, Mohamed Mostafa. 68
Inter-MGC Inter-MGC
+---------+ Protocol +---------+ +---------+ Protocol +---------+
| MGC |------------------| MGC | | MGC |------------------| MGC |
+---------+ +---------+ +---------+ +---------+
| | | |
|Media Gateway |Media Gateway |Media Gateway |Media Gateway
|Control Protocol |Control Protocol |Control Protocol |Control Protocol
| | | |
+------------+ (ATM Network) +------------+ +------------+ (ATM Network) +------------+
|Originating |------------------|Terminating | |Originating |------------------|Terminating |
|Media | Bearer Setup |Media | |Media | Bearer Setup |Media |
|Gateway | Protocol |Gateway | |Gateway | Protocol |Gateway |
+------------+ +------------+ +------------+ +------------+
In the diagram above, the originating media gateway originates the service- In the diagram above, the originating media gateway originates the service-
level call. The terminating media gateway terminates it. In the forward call level call. The terminating media gateway terminates it. In the forward bearer
model, the originating media gateway initiates bearer connection set-up. In the connection set-up model, the originating media gateway initiates bearer
backward call model, the terminating gateway initiates bearer connection set- connection set-up. In the backward bearer connection set-up model, the
up. terminating gateway initiates bearer connection set-up.
Example use of the Backward Call Model: Example use of the Backward Bearer Connection Set-up Model:
(1) The originating media gateway controller (OMGC) initiates service-level (1) The originating media gateway controller (OMGC) initiates service-level
call establishment by sending the appropriate control message to the call establishment by sending the appropriate control message to the
originating media gateway (OMG). originating media gateway (OMG).
(2) The originating media gateway (OMG) provides its NSAP address and an eecid (2) The originating media gateway (OMG) provides its NSAP address and an eecid
value to the OMGC, using the following SDP description: value to the OMGC, using the following SDP description:
v=0 v=0
o=- 2873397496 0 ATM NSAP o=- 2873397496 0 ATM NSAP
47.0091.8100.0000.0060.3E64.FD01.0060.3E64.FD01.00 47.0091.8100.0000.0060.3E64.FD01.0060.3E64.FD01.00
skipping to change at line 3298 skipping to change at line 3544
It provides the TMGC with the NSAP address and the eecid provided It provides the TMGC with the NSAP address and the eecid provided
by the OMG. by the OMG.
(4) The TMGC sends the appropriate control message to the TMG. This (4) The TMGC sends the appropriate control message to the TMG. This
includes the session descriptor received from the OMG. This includes the session descriptor received from the OMG. This
descriptor contains the NSAP address of the OMG and the EECID descriptor contains the NSAP address of the OMG and the EECID
assigned by the OMG. Additionally, the TMGC instructs the TMG assigned by the OMG. Additionally, the TMGC instructs the TMG
to set up an SVC to the OMG. It also requests the TMG to notify to set up an SVC to the OMG. It also requests the TMG to notify
the TMGC when SVC set-up is complete. Depending on the control the TMGC when SVC set-up is complete. Depending on the control
Rajesh Kumar, Mohamed Mostafa. 64 Rajesh Kumar, Mohamed Mostafa. 69
protocol used, this can be done through a variety of means. protocol used, this can be done through a variety of means.
In the Megaco context, the request to set-up an SVC (not the In the Megaco context, the request to set-up an SVC (not the
notification request for the SVC set-up event) can be made through notification request for the SVC set-up event) can be made through
the following local descriptor: the following local descriptor:
v=0 v=0
o=- 2873397497 0 ATM - - o=- 2873397497 0 ATM - -
s=- s=-
c=ATM - - c=ATM - -
t=0 0 t=0 0
m=audio $ - - m=audio $ - -
a=bearerType:SVC on a=bearerType:SVC on
The 'bearerType' attribute indicates that an SVC is to be used and The 'bearerType' attribute indicates that an SVC is to be used and
that the <localInititiation> flag is on i.e. the SVC is to be set up that the <localInitiation> flag is on i.e. the SVC is to be set up
by the TMG. by the TMG.
(5) The TMG acknowledges the control message from the TMGC. It returns (5) The TMG acknowledges the control message from the TMGC. It returns
the following SDP descriptor with the acknowledge: the following SDP descriptor with the acknowledge:
v=0 v=0
o=- 2873397498 0 ATM NSAP o=- 2873397498 0 ATM NSAP
47.0091.8100.0000.0040.2A74.EB03.0020.4421.2A04.00 47.0091.8100.0000.0040.2A74.EB03.0020.4421.2A04.00
s=- s=-
c=ATM NSAP c=ATM NSAP
skipping to change at line 3345 skipping to change at line 3591
(7) The OMG uses the eecid to correlate the SVC set-up request with (7) The OMG uses the eecid to correlate the SVC set-up request with
service-level control message received before from the OMGC. service-level control message received before from the OMGC.
(8) The OMG returns an SVC connect message to the TMG. On receiving (8) The OMG returns an SVC connect message to the TMG. On receiving
this message, the TMG sends an event notification to the TMGC this message, the TMG sends an event notification to the TMGC
indicating successful SVC set-up. indicating successful SVC set-up.
Note that, for this example, the "v=", "o=", "s=" and "t=" lines can be Note that, for this example, the "v=", "o=", "s=" and "t=" lines can be
omitted in the Megaco context. omitted in the Megaco context.
Example use of the Forward Call Model: Example use of the Forward Bearer Connection Set-up Model:
(1) The originating media gateway controller (OMGC) initiates service-level (1) The originating media gateway controller (OMGC) initiates service-level
call establishment by sending the appropriate control message to the call establishment by sending the appropriate control message to the
originating media gateway (OMG). originating media gateway (OMG).
(2) The originating media gateway (OMG) provides its NSAP address (2) The originating media gateway (OMG) provides its NSAP address
Rajesh Kumar, Mohamed Mostafa. 65 Rajesh Kumar, Mohamed Mostafa. 70
to the OMGC, using the following SDP description: to the OMGC, using the following SDP description:
v=0 v=0
o=- 2873397496 0 ATM NSAP o=- 2873397496 0 ATM NSAP
47.0091.8100.0000.0060.3E64.FD01.0060.3E64.FD01.00 47.0091.8100.0000.0060.3E64.FD01.0060.3E64.FD01.00
s=- s=-
c=ATM NSAP c=ATM NSAP
47.0091.8100.0000.0060.3E64.FD01.0060.3E64.FD01.00 47.0091.8100.0000.0060.3E64.FD01.0060.3E64.FD01.00
t=0 0 t=0 0
m=audio $ AAL2/ITU 8 m=audio $ AAL2/ITU 8
skipping to change at line 3405 skipping to change at line 3651
by the TMG. by the TMG.
(7) The OMGC sends the appropriate control message to the OMG. This (7) The OMGC sends the appropriate control message to the OMG. This
includes the session descriptor received from the TMG. This includes the session descriptor received from the TMG. This
descriptor contains the NSAP address of the TMG and the EECID descriptor contains the NSAP address of the TMG and the EECID
assigned by the TMG. Additionally, the OMGC instructs the OMG assigned by the TMG. Additionally, the OMGC instructs the OMG
to set up an SVC to the TMG. It also requests the OMG to notify to set up an SVC to the TMG. It also requests the OMG to notify
the OMGC when SVC set-up is complete. Depending on the control the OMGC when SVC set-up is complete. Depending on the control
protocol used, this can be done through a variety of means. protocol used, this can be done through a variety of means.
Rajesh Kumar, Mohamed Mostafa. 66 Rajesh Kumar, Mohamed Mostafa. 71
In the Megaco context, the request to set-up an SVC (not the In the Megaco context, the request to set-up an SVC (not the
notification request for the SVC set-up event) can be made through notification request for the SVC set-up event) can be made through
the following local descriptor: the following local descriptor:
v=0 v=0
o=- 2873397874 0 ATM - - o=- 2873397874 0 ATM - -
s=- s=-
c=ATM - - c=ATM - -
t=0 0 t=0 0
m=audio $ - - m=audio $ - -
a=bearerType:SVC on a=bearerType:SVC on
The 'bearerType' attribute indicates that an SVC is to be used and The 'bearerType' attribute indicates that an SVC is to be used and
that the <localInititiation> flag is on i.e. the SVC is to be set up that the <localInitiation> flag is on i.e. the SVC is to be set up
by the TMG. by the TMG.
(8) The OMG acknowledges the control message from the OMGC. (8) The OMG acknowledges the control message from the OMGC.
(9) The OMG sends an SVC set-up message to the TMG. Within the GIT (9) The OMG sends an SVC set-up message to the TMG. Within the GIT
information element, it includes eecid (B3D58E32) received from information element, it includes eecid (B3D58E32) received from
the TMG. the TMG.
(10)The TMG uses the eecid to correlate the SVC set-up request with the (10)The TMG uses the eecid to correlate the SVC set-up request with the
service-level control message received before from the TMGC. service-level control message received before from the TMGC.
(11)The TMG returns an SVC connect message to the OMG. On receiving (11)The TMG returns an SVC connect message to the OMG. On receiving
this message, the OMG sends an event notification to the OMGC this message, the OMG sends an event notification to the OMGC
indicating successful SVC set-up. indicating successful SVC set-up.
Note that, for this example, the "v=", "o=", "s=" and "t=" lines can be Note that, for this example, the "v=", "o=", "s=" and "t=" lines can be
omitted in the Megaco context. omitted in the Megaco context.
Rajesh Kumar, Mohamed Mostafa. 67 Rajesh Kumar, Mohamed Mostafa. 72
6.0 List of Parameters with Representations 6.0 List of Parameters with Representations
This section provides a list of the parameters used in this document, This section provides a list of the parameters used in this document,
and the formats used to represent them in SDP descriptions. In general, a and the formats used to represent them in SDP descriptions. In general, a
"-" value can be used for any field that is not specified, is inapplicable "-" value can be used for any field that is not specified, is inapplicable
or is implied. or is implied.
PARAMETER MEANING REPRESENTATION PARAMETER MEANING REPRESENTATION
skipping to change at line 3491 skipping to change at line 3737
representation representation
of <vcci> of <vcci>
<bcg> Bearer Connection Decimal or hex equivalent <bcg> Bearer Connection Decimal or hex equivalent
Group of 8 bits Group of 8 bits
<ex_bcg> Explicit "BCG-" prefixed to <bcg> <ex_bcg> Explicit "BCG-" prefixed to <bcg>
representation representation
of <bcg> of <bcg>
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<portId> Port ID Hex number of up to 32 digits <portId> Port ID Hex number of up to 32 digits
<ex_portId> Explicit "PORT-" prefixed to <portId> <ex_portId> Explicit "PORT-" prefixed to <portId>
representation representation
of <portId> of <portId>
<vpi> Virtual Path Decimal or hex equivalent <vpi> Virtual Path Decimal or hex equivalent
Identifier of 8 or 12 bits Identifier of 8 or 12 bits
skipping to change at line 3540 skipping to change at line 3786
<transport> Transport Values listed in <transport> Transport Values listed in
Table 1. Table 1.
<profile> Profile Decimal integer 1-255 <profile> Profile Decimal integer 1-255
<eecid> End-to-end Up to 8 hex digits <eecid> End-to-end Up to 8 hex digits
Connection Connection
Identifier Identifier
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<aalType> AAL type String values: <aalType> AAL type String values:
"AAL1","AAL1_SDT","AAL1_UDT", "AAL1","AAL1_SDT","AAL1_UDT",
"AAL2", "AAL3/4", "AAL2", "AAL3/4",
"AAL5", "USER_DEFINED_AAL" "AAL5", "USER_DEFINED_AAL"
<silenceSuppEnable> Silence suppression String values:
Enable "on", "off"
<silenceTimer> Kick-in timer Decimal or hex representation
for silence of 16-bit field
suppression
<suppPref> Preferred Silence String values:
Suppression Method "standard", "custom"
<sidUse> SID Use String values:
Method "No SID", "Fixed Noise",
"Sampled Noise"
<fxnslevel> Fixed Noise Decimal or hex representation
Level of a 7-bit field
<ecanEnable> Enable Echo String values:
Cancellation "on", "off"
<ecanType> Type of Echo String values:
Cancellation "G165", "G168"
<gcEnable> Enable Gain String values:
Control "on", "off"
<gcLvl> Level of inserted Decimal or hex equivalent
Loss of 16-bit field
<aal2transport> AAL2 transport Values listed in Table 1
that begin with the string
"AAL2"
<uuiCodeRange> UUI code range Decimal integer 0-15
<encodingName> Encoding name String values:
"PCMG", "SIDG", "SID729",
any value from column 2
of Table 2
<packetLength> Packet length Decimal integer 0-45
<packetTime> Packetization Decimal integer 1-65,536
Interval in microsec.
Rajesh Kumar, Mohamed Mostafa. 70
<fxIncl> Facsimile included String values: "on", "off"
<q7655scc> Contents of the Even number of hex
Q.765.5 Single digits (4-32)
Codec IE
<isupUsi> ISUP User Service Two hex digits
Information
<asc> ATM service String values: <asc> ATM service String values:
category defined "CBR", "nrt-VBR", "rt-VBR", category defined "CBR", "nrt-VBR", "rt-VBR",
by the ATMF "UBR", "ABR", "GFR" by the ATMF "UBR", "ABR", "GFR"
<atc> ATM transfer String values: <atc> ATM transfer String values:
capability "DBR","SBR","ABT/IT","ABT/DT", capability "DBR","SBR","ABT/IT","ABT/DT",
defined by the "ABR" defined by the "ABR"
ITU ITU
<subtype> <asc>/<atc> Decimal integer 1-10 <subtype> <asc>/<atc> Decimal integer 1-10
subtype subtype
<qosClass> QoS Class Decimal integer 0-5 <qosClass> QoS Class Decimal integer 0-5
<bcob> Broadband Bearer Decimal or hex representation <bcob> Broadband Bearer Decimal or hex representation
Class of 5-bit field Class of 5-bit field
<eetim> End-to-end timing String values: "on",
required "off".
<stc> Susceptibility Decimal equivalent of <stc> Susceptibility Decimal equivalent of
to clipping a 2-bit field to clipping a 2-bit field
<upcc> User plane Decimal equivalent of <upcc> User plane Decimal equivalent of
connection a 2-bit field connection a 2-bit field
configuration configuration
<cdvType> CDV type String values: <cdvType> CDV type String values:
"PP", "2P" "PP", "2P"
<acdv> Acceptable CDV Decimal equivalent <acdv> Acceptable CDV Decimal equivalent
of 24-bit field of 24-bit field
<ccdv> Cumulative CDV Decimal equivalent <ccdv> Cumulative CDV Decimal equivalent
of 24-bit field of 24-bit field
<actd> Acceptable CTD Decimal equivalent <eetd> End-to-end transit Decimal equivalent
of 16-bit field delay of 16-bit field
<cctd> Cumulative CTD Decimal equivalent
of 16-bit field
Rajesh Kumar, Mohamed Mostafa. 71 <cmtd> Cumulative transit Decimal equivalent
delay of 16-bit field
<aclr> Acceptable Decimal equivalent <aclr> Acceptable Decimal equivalent
Cell Loss Ratio of 8-bit field Cell Loss Ratio of 8-bit field
Rajesh Kumar, Mohamed Mostafa. 75
<clpLvl> CLP level String values: <clpLvl> CLP level String values:
"0", "0+1" "0", "0+1"
<pcr> Peak Decimal integer, 1-100,000 <pcr> Peak Decimal
Cell Rate Cell Rate equivalent of a 24-bit field.
<scr> Sustained Decimal integer, 1-100,000 <scr> Sustained Decimal
Cell Rate Cell Rate equivalent of a 24-bit field
<mbs> Maximum Decimal integer, 1-10,000 <mbs> Maximum Decimal
Burst Size Burst Size equivalent of 16-bit field
<cdvt> CDVT Decimal equivalent of 24-bit <cdvt> CDVT Decimal equivalent of 24-bit
field. field.
<mcr> Minimum Decimal integer, 1-100,000 <mcr> Minimum Decimal
Cell Rate Cell Rate equivalent of a 24-bit field
<mfs> Maximum Decimal integer, 1-10,000 <mfs> Maximum Decimal
Frame Size Frame Size equivalent of a 16-bit field
<fd> Frame Discard String Values: <fd> Frame Discard String Values:
Allowed "on", "off" Allowed "on", "off"
<te> CLP tagging String Values: <te> CLP tagging String Values:
"on", "off" "on", "off"
<nrm> NRM Decimal/hex equivalent <nrm> NRM Decimal/hex equivalent
of 3 bit field of 3 bit field
<trm> TRM - ditto- <trm> TRM - ditto-
<cdf> CDF -ditto- <cdf> CDF -ditto-
<adtf> ADTF Decimal/Hex equivalent <adtf> ADTF Decimal/Hex equivalent
of 10 bit field of 10 bit field
<ficr> Forward Initial Decimal equivalent of
Cell Rate 24-bit field
<bicr> Backward Initial Decimal equivalent of
Cell Rate 24-bit field
<ftbe> Forward Transient Decimal equivalent of
Buffer Exposure 24-bit field
<btbe> Backward Transient Decimal equivalent of
Buffer Exposure 24-bit field
<crmrtt> Cumulative RM Decimal equivalent of
round-trip time 24-bit field
(Microseconds)
Rajesh Kumar, Mohamed Mostafa. 76
<frif> Forward rate Decimal integer
increase factor 0 -15
<brif> Backward rate Decimal integer
increase factor 0 -15
<frdf> Forward rate Decimal integer
decrease factor 0 -15
<brdf> Backward rate Decimal integer
decrease factor 0 -15
<bearerType> Bearer Type String Values:
"PVC", "SVC", "CID"
<localInitiation> Local Initiation String values:
"on", "off"
<sci> Screening Indication Decimal or hex
equivalent of 4 bits.
<lsn> Leaf Sequence Number Decimal or hex
equivalent of 32 bits.
<cdStd> Coding standard for Decimal or hex
connection scope equivalent of 2 bits.
selection IE
Definition: UNI 4.0 [5]
<conScpTyp> Type of connection scope Decimal or hex
Definition: UNI 4.0 [5] equivalent of 4 bits
<conScpSel> Connection scope selection Decimal or hex equivalent
Definition: UNI 4.0 [5] of 8 bits
<cacheEnable> Enable SVC caching String values: "on", "off"
<cacheTimer> Timer for cached SVC Decimal or hex equivalent
deletion of 32-bit field
<bearerSigIEType> Bearer Signaling IE Type 2 hex digits
<bearerSigIELng> Bearer Signaling IE Length 1-4 hex digits
<bearerSigIEVal> Bearer Signaling IE Value Even number of hex digits,
2-512