draft-ietf-mmusic-sdp-bwparam-03.txt   draft-ietf-mmusic-sdp-bwparam-04.txt 
Network Working Group Magnus Westerlund Network Working Group Magnus Westerlund
INTERNET-DRAFT Ericsson INTERNET-DRAFT Ericsson
Category: Standards Track May 27, 2003 Category: Standards Track June 23, 2003
Expires: November 2003 Expires: December 2003
A Transport Independent Bandwidth Modifier for the Session A Transport Independent Bandwidth Modifier for the Session
Description Protocol (SDP). Description Protocol (SDP).
<draft-ietf-mmusic-sdp-bwparam-03.txt> <draft-ietf-mmusic-sdp-bwparam-04.txt>
Status of this memo Status of this memo
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
Task Force (IETF), its areas, and its working groups. Note that other Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts. groups may also distribute working documents as Internet-Drafts.
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3.4. RTCP problems..................................................7 3.4. RTCP problems..................................................7
3.5. Future development.............................................7 3.5. Future development.............................................7
4. Problem Scope.......................................................8 4. Problem Scope.......................................................8
5. Requirements........................................................8 5. Requirements........................................................8
6. Solution............................................................8 6. Solution............................................................8
6.1. Introduction...................................................8 6.1. Introduction...................................................8
6.2. The TIAS bandwidth modifier....................................8 6.2. The TIAS bandwidth modifier....................................8
6.2.1. Usage.....................................................9 6.2.1. Usage.....................................................9
6.2.2. Definition................................................9 6.2.2. Definition................................................9
6.2.3. Usage Rules..............................................10 6.2.3. Usage Rules..............................................10
6.3. Packet Rate parameters........................................10 6.3. Packet Rate parameter.........................................11
6.4. Converting to Transport-Dependent values......................11 6.4. Converting to Transport-Dependent values......................11
6.5. Deriving RTCP bandwidth.......................................12 6.5. Deriving RTCP bandwidth.......................................12
6.5.1. Motivation for this solution.............................12 6.5.1. Motivation for this solution.............................12
6.6. ABNF definitions..............................................12 6.6. ABNF definitions..............................................13
7. Protocol Interaction...............................................13 6.7. Example.......................................................13
7.1. RTSP..........................................................13 7. Protocol Interaction...............................................14
7.2. SIP...........................................................13 7.1. RTSP..........................................................14
7.3. SAP...........................................................13 7.2. SIP...........................................................14
8. Security Consideration.............................................13 7.3. SAP...........................................................14
9. IANA Considerations................................................14 8. Security Consideration.............................................15
10. Acknowledgments...................................................14 9. IANA Considerations................................................15
11. Author's Addresses................................................14 10. Acknowledgments...................................................15
12. References........................................................15 11. Author's Addresses................................................15
12.1. Normative references.........................................15 12. References........................................................16
12.2. Informative References.......................................15 12.1. Normative references.........................................16
13. IPR Notice........................................................16 12.2. Informative References.......................................16
14. Copyright Notice..................................................16 13. IPR Notice........................................................17
14. Copyright Notice..................................................17
1. Definitions 1. Definitions
1.1. Glossary 1.1. Glossary
ALG - Application Level Gateway.
bps - bits per second.
RTSP - Real-Time Streaming Protocol, see [8]. RTSP - Real-Time Streaming Protocol, see [8].
SDP - Session Description Protocol, see [1]. SDP - Session Description Protocol, see [1].
SAP - Session Announcement Protocol, see [5]. SAP - Session Announcement Protocol, see [5].
SIP - Session Initiation Protocol, see [6]. SIP - Session Initiation Protocol, see [6].
TIAS - Transport Independent Application Specific maximum, a TIAS - Transport Independent Application Specific maximum, a
bandwidth modifier. bandwidth modifier.
1.2. Terminology 1.2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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Figure 1, illustrates a connection scenario between a streaming Figure 1, illustrates a connection scenario between a streaming
server A and a client B over a translator here designated as a NAT- server A and a client B over a translator here designated as a NAT-
PT. When B receives the SDP from A over RTSP it will be very PT. When B receives the SDP from A over RTSP it will be very
difficult for B to know what the bandwidth values in the SDP difficult for B to know what the bandwidth values in the SDP
represent. The following possibilities exist: represent. The following possibilities exist:
1. The SDP is unchanged and "c=" null address is of type IPv4. The 1. The SDP is unchanged and "c=" null address is of type IPv4. The
bandwidth value represents the bandwidth needed in an IPv4 bandwidth value represents the bandwidth needed in an IPv4
network. network.
2. The SDP has been changed by the ALG. The "c=" address is changed 2. The SDP has been changed by an Application Level Gateway (ALG).
to IPv6 type. The bandwidth value is unchanged. The "c=" address is changed to IPv6 type. The bandwidth value is
unchanged.
3. The SDP is changed and both "c=" address type and bandwidth value 3. The SDP is changed and both "c=" address type and bandwidth value
is changed. Unfortunately, this can seldom be done, see 3.2. is converted. Unfortunately, this can seldom be done, see 3.2.
In case 1 the client can understand that the server is located in an In case 1 the client can understand that the server is located in an
IPv4 network and that it uses IPv4 overhead when calculating the IPv4 network and that it uses IPv4 overhead when calculating the
bandwidth value. The client can almost never convert the bandwidth bandwidth value. The client can almost never convert the bandwidth
value, see section 3.2. value, see section 3.2.
In case 2 the client does not know that the server is in an IPv4 In case 2 the client does not know that the server is in an IPv4
network and that the bandwidth value is not calculated with IPv6 network and that the bandwidth value is not calculated with IPv6
overhead. In cases where a client reserves bandwidth for this flow, overhead. In cases where a client reserves bandwidth for this flow,
too little will be reserved, potentially resulting in bad Quality of too little will be reserved, potentially resulting in bad Quality of
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stream, codec type, etc. In cases where more information is stream, codec type, etc. In cases where more information is
needed, then another SDP parameter will be required. needed, then another SDP parameter will be required.
- Maximum media codec rate. With the definition below of "TIAS" the - Maximum media codec rate. With the definition below of "TIAS" the
given bit-rate will mostly be from the media codec. Therefore it given bit-rate will mostly be from the media codec. Therefore it
gives a good indication on the maximum codec bit-rate required to gives a good indication on the maximum codec bit-rate required to
be supported by the decoder. be supported by the decoder.
- Communication bit-rate required for the stream. The "TIAS" value - Communication bit-rate required for the stream. The "TIAS" value
together with "maxprate" can be used to determine the maximum together with "maxprate" can be used to determine the maximum
communication bit-rate the stream will require. By adding all communication bit-rate the stream will require. Using session
maximum bit-rates from the streams in a session together, a level values or through adding all maximum bit-rates from the
receiver can determine if its communication resources are streams in a session together, a receiver can determine if its
sufficient to handle the stream. For example a modem user can communication resources are sufficient to handle the stream. For
determine if the session fits his modem's capabilities and the example a modem user can determine if the session fits his modem's
established connection. capabilities and the established connection.
- Determine the RTP session bandwidth and derive the RTCP - Determine the RTP session bandwidth and derive the RTCP
bandwidth. The derived transport dependent attribute will be the bandwidth. The derived transport dependent attribute will be the
RTP session bandwidth in case of RTP based transport. The TIAS RTP session bandwidth in case of RTP based transport. The TIAS
value can also be used to determine the RTCP bandwidth to use when value can also be used to determine the RTCP bandwidth to use when
using implicit allocation. RTP [4] specifies that if not using implicit allocation. RTP [4] specifies that if not
explicitly stated, additional bandwidth shall be used by RTCP explicitly stated, additional bandwidth shall be used by RTCP
equal to 5% of the RTP session bandwidth. The RTCP bandwidth can equal to 5% of the RTP session bandwidth. The RTCP bandwidth can
be explicitly allocated by using the RR and RS modifiers defined be explicitly allocated by using the RR and RS modifiers defined
in [9]. in [9].
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A new session and media level bandwidth modifier is defined: A new session and media level bandwidth modifier is defined:
b=TIAS:<bandwidth-value> ; see section 6.6 for ABNF definition. b=TIAS:<bandwidth-value> ; see section 6.6 for ABNF definition.
The Transport Independent Application Specific Maximum (TIAS) The Transport Independent Application Specific Maximum (TIAS)
bandwidth modifier has an integer bit-rate value in bits per second. bandwidth modifier has an integer bit-rate value in bits per second.
A fractional bandwidth value SHALL always be rounded up to the next A fractional bandwidth value SHALL always be rounded up to the next
integer. The bandwidth value is the maximum needed by the application integer. The bandwidth value is the maximum needed by the application
(SDP session level) or media stream (SDP media level) without (SDP session level) or media stream (SDP media level) without
counting IP and other transport layers like TCP or UDP. At the SDP counting IP and other transport layers like TCP or UDP.
session level, the TIAS value is simply the sum of all media streams'
TIAS values. For RTP based media streams, TIAS at the SDP media level At the SDP session level, the TIAS value is the maximal amount of
can be used to derive the RTP "session bandwidth" as defined in bandwidth need when all declared media streams are used. This MAY be
section 6.2 of [4]. However in the context of RTP transport the TIAS less than the sum of all the individual media streams values. This
value is defined as: can be due to the possibility that not all streams have their maximum
at the same point in time. This can normally only be verified for
stored media streams.
For RTP transported media streams, TIAS at the SDP media level can be
used to derive the RTP "session bandwidth", defined in section 6.2 of
[4]. In the context of RTP transport the TIAS value is defined as:
Only the RTP payload as defined in [4] SHALL be used in the Only the RTP payload as defined in [4] SHALL be used in the
calculation of the bit-rate, i.e., excluding the lower layers calculation of the bit-rate, i.e., excluding the lower layers
(IP/UDP) and RTP headers including RTP header, RTP header (IP/UDP) and RTP headers including RTP header, RTP header
extensions, CSRC list and other RTP profile specific fields. Note extensions, CSRC list and other RTP profile specific fields. Note
that the RTP payload includes both the payload format header and that the RTP payload includes both the payload format header and
the data. This may allow one to use the same value for RTP-based the data. This may allow one to use the same value for RTP-based
media transport, non-RTP transport and stored media. media transport, non-RTP transport and stored media.
Note 1: The usage of bps is not in accordance with RFC 2327 [1]. This Note 1: The usage of bps is not in accordance with RFC 2327 [1]. This
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Note 2: RTCP bandwidth is not included in the bandwidth value. In Note 2: RTCP bandwidth is not included in the bandwidth value. In
applications using RTCP, the bandwidth used by RTCP is either 5% of applications using RTCP, the bandwidth used by RTCP is either 5% of
the RTP session bandwidth including lower layers or as specified by the RTP session bandwidth including lower layers or as specified by
the RR and RS modifiers [9]. A specification of how to derive the the RR and RS modifiers [9]. A specification of how to derive the
RTCP bit-rate when using TIAS is presented in chapter 6.5. RTCP bit-rate when using TIAS is presented in chapter 6.5.
6.2.3. Usage Rules 6.2.3. Usage Rules
"TIAS" is primarily intended to be used at the SDP media level. The "TIAS" is primarily intended to be used at the SDP media level. The
TIAS bandwidth attribute MAY be present at the session level in SDP. "TIAS" bandwidth attribute MAY be present at the session level in
However, if present at the session level it SHOULD be present also at SDP, if all media streams uses the same transport. In cases when the
the media level. "TIAS" SHALL NOT be present at the session level sum of the media level values for all media streams is larger than
unless the same transport is used for all media streams. The session the actual maximum bandwidth need for all streams, it SHOULD be
level value, if present, MUST be the sum of all media level values. included at session level. However, if present at the session level
it SHOULD be present also at the media level. "TIAS" SHALL NOT be
present at the session level unless the same transport protocols is
used for all media streams. The same transport is use as long as the
same combination of protocols is used, like IPv6/UDP/RTP.
To allow for backwards compatibility with applications of SDP that do To allow for backwards compatibility with applications of SDP that do
not implement "TIAS", it is RECOMMENDED to also include the "AS" not implement "TIAS", it is RECOMMENDED to also include the "AS"
modifier when using "TIAS". The presence of a value including lower- modifier when using "TIAS". The presence of a value including lower-
layer overhead, even with its problems, is better than none. However, layer overhead, even with its problems, is better than none. However,
an SDP application implementing TIAS SHOULD ignore the "AS" value and an SDP application implementing TIAS SHOULD ignore the "AS" value and
use "TIAS" instead when both are present. use "TIAS" instead when both are present.
When using TIAS for an RTP-transported stream, the "maxprate" When using TIAS for an RTP-transported stream, the "maxprate"
attribute, defined next, SHALL be included at the corresponding SDP attribute if possible to calculate, defined next, SHALL be included
level. at the corresponding SDP level.
6.3. Packet Rate parameter 6.3. Packet Rate parameter
To be able to calculate the bandwidth value including the lower To be able to calculate the bandwidth value including the lower
layers actually used, a packet rate attribute is also defined. layers actually used, a packet rate attribute is also defined.
The SDP session and media level maximum packet rate attribute is The SDP session and media level maximum packet rate attribute is
defined as: defined as:
a=maxprate:<packet-rate> ; see section 6.6 for ABNF definition. a=maxprate:<packet-rate> ; see section 6.6 for ABNF definition.
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largest value produced when the window slides over the entire media largest value produced when the window slides over the entire media
stream. In cases that this can't be calculated, i.e. for example a stream. In cases that this can't be calculated, i.e. for example a
live stream, a estimated value of the maximum packet rate the codec live stream, a estimated value of the maximum packet rate the codec
can produce for the given configuration and content SHALL be used. can produce for the given configuration and content SHALL be used.
Note: The sliding window calculation will always yield an integer Note: The sliding window calculation will always yield an integer
number, however the attributes field is a floating-point value. The number, however the attributes field is a floating-point value. The
reason is that estimated or known maximum packet rate per second may reason is that estimated or known maximum packet rate per second may
be fractional. be fractional.
At the SDP session level, the maxprate value MUST be the sum of all At the SDP session level, the "maxprate" value is the maximum packet
media-level packet rates. The session-level value MAY only be given rate calculated over all the declared media streams. If this can't be
if all media streams use the same transport. If that is not the case, measured (stored media) or estimated (live) the sum of all media
the "maxprate" attribute MUST NOT be present at the session level. If level values provides a ceiling value. Note: the value at session
given at the session level it SHOULD also be given at the media level can be less then the sum of the individual media streams due to
level. temporal distribution of media streams maximums. The "maxprate"
attribute MUST NOT be present at session level if the media streams
use different transport. The attribute MAY be present if the media
streams use the same transport. If the attribute is present at the
session level it SHOULD also be present at the media level for all
media streams.
"maxprate" SHALL be included for all transports where a packet rate maxprate" SHALL be included for all transports where a packet rate
can be derived and TIAS is included. can be derived and TIAS is included. For example, if you use TIAS and
a transport like IP/UDP/RTP, for which the max packet rate (actual or
estimated) can be derived, then "maxprate" SHALL be included. However
if either (a) the packet rate for the transport cannot be derived, or
(b) TIAS is not included, then, "maxprate" is not required to be
included.
6.4. Converting to Transport-Dependent values 6.4. Converting to Transport-Dependent values
When converting the transport-independent bandwidth value (bw-value) When converting the transport-independent bandwidth value (bw-value)
into a transport-dependent value including the lower layers, the into a transport-dependent value including the lower layers, the
following MUST be done: following MUST be done:
1. Determine which lower layers will be used and calculate the sum of 1. Determine which lower layers will be used and calculate the sum of
the sizes of the headers in bits (h-size). In cases of variable the sizes of the headers in bits (h-size). In cases of variable
header sizes, the average size SHALL be used. For RTP-transported header sizes, the average size SHALL be used. For RTP-transported
media, the lower layers SHALL include the RTP header with header media, the lower layers SHALL include the RTP header with header
extensions, if used, the CSRC list, and any profile-specific extensions, if used, the CSRC list, and any profile-specific
extensions. extensions.
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6.6. ABNF definitions 6.6. ABNF definitions
This chapter defines in ABNF from RFC 2234 [2] the bandwidth modifier This chapter defines in ABNF from RFC 2234 [2] the bandwidth modifier
and the packet rate attribute. and the packet rate attribute.
The bandwidth modifier: The bandwidth modifier:
TIAS-bandwidth-def = "b" "=" "TIAS" ":" bandwidth-value CRLF TIAS-bandwidth-def = "b" "=" "TIAS" ":" bandwidth-value CRLF
bandwidth-value = 1*DIGIT bandwidth-value = 1*DIGIT
The maximum packet rate attribute: The maximum packet rate attribute:
max-p-rate-def = "a" "=" "maxprate" ":" packet-rate CRLF max-p-rate-def = "a" "=" "maxprate" ":" packet-rate CRLF
packet-rate = 1*DIGIT ["." 1*DIGIT] packet-rate = 1*DIGIT ["." 1*DIGIT]
6.7. Example
v=0
o=Example_SERVER 3413526809 0 IN IP4 server.example.com
s=Example of TIAS and maxprate in use
c=IN IP4 0.0.0.0
b=AS:60
b=TIAS:50780
t=0 0
a=control:rtsp://server.example.com/media.3gp
a=range:npt=0-150.0
a=maxprate:28.0
m=audio 0 RTP/AVP 97
b=AS:12
b=TIAS:8480
a=maxprate:10.0
a=rtpmap:97 AMR/8000
a=fmtp:97 octet-align;
a=control:rtsp://server.example.com/media.3gp/trackID=1
m=video 0 RTP/AVP 99
b=AS:48
b=TIAS:42300
a=maxprate:18.0
a=rtpmap:99 MP4V-ES/90000
a=fmtp:99 profile-level-id=8;
config=000001B008000001B509000001010000012000884006682C2090A21F
a=control:rtsp://server.example.com/media.3gp/trackID=3
In this SDP example of a streaming session's SDP, there are two media
streams, one audio stream encoded with AMR and one video stream
encoded with the MPEG-4 Video encoder. AMR is here used to produce a
constant rate media stream and does use a packetization resulting in
10 packets per second. This results in a TIAS bandwidth rate of 8480
bits per second, and the claimed 10 packets per second. The video
stream is more variable. However it has a measured maximum payload
rate of 42300 bits per second. The video also has variable packet
rate, despite the fact that the video is 15 frames per second there
where at least one instance when a second long window contained 18
packets.
7. Protocol Interaction 7. Protocol Interaction
7.1. RTSP 7.1. RTSP
The "TIAS" and "maxprate" parameters can be used with RTSP as The "TIAS" and "maxprate" parameters can be used with RTSP as
currently specified. To be able to calculate the transport dependent currently specified. To be able to calculate the transport dependent
bandwidth, some of the transport header parameters will be required. bandwidth, some of the transport header parameters will be required.
There should be no problem for a client to calculate the required There should be no problem for a client to calculate the required
bandwidth(s) prior to an RTSP SETUP. The reason is that a client bandwidth(s) prior to an RTSP SETUP. The reason is that a client
supports a limited number of transport setups. The one actually supports a limited number of transport setups. The one actually
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line ("m=") and its transport field. line ("m=") and its transport field.
8. Security Consideration 8. Security Consideration
The bandwidth value that is supplied by the parameters defined here The bandwidth value that is supplied by the parameters defined here
can, if not protected, be altered. By altering the bandwidth value can, if not protected, be altered. By altering the bandwidth value
one can fool a receiver to reserve either more or less bandwidth than one can fool a receiver to reserve either more or less bandwidth than
actually needed. Reserving too much may result in unwanted expenses actually needed. Reserving too much may result in unwanted expenses
on behalf of the user and also blocking of resources that other on behalf of the user and also blocking of resources that other
parties could have used. If too little bandwidth is reserved the parties could have used. If too little bandwidth is reserved the
receiving user's quality MAY be effected. Trusting a too-large TIAS receiving user's quality may be effected. Trusting a too-large TIAS
value may also result in the receiver rejecting the session due to value may also result in the receiver rejecting the session due to
insufficient communication and decoding resources. insufficient communication and decoding resources.
Due to these security risks it is strongly RECOMMENDED that the SDP Due to these security risks it is strongly RECOMMENDED that the SDP
be authenticated so no tampering can be performed. It is also be authenticated so no tampering can be performed. It is also
RECOMMENDED that any receiver of the SDP perform an analysis of the RECOMMENDED that any receiver of the SDP perform an analysis of the
received bandwidth values to verify that they are reasonable and are received bandwidth values to verify that they are reasonable and are
what can be expected for the application. For example, a single what can be expected for the application. For example, a single
channel AMR-encoded voice stream claiming to use 1000 kbps is not channel AMR-encoded voice stream claiming to use 1000 kbps is not
reasonable. reasonable.
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A new SDP [1] bandwidth modifier (bwtype) "TIAS" is also registered A new SDP [1] bandwidth modifier (bwtype) "TIAS" is also registered
in accordance with the rules requiring a standards-track RFC. The in accordance with the rules requiring a standards-track RFC. The
modifier is defined in section 6.2. modifier is defined in section 6.2.
10. Acknowledgments 10. Acknowledgments
The author would like to thank Gonzalo Camarillo and Hesham Soliman The author would like to thank Gonzalo Camarillo and Hesham Soliman
for their work reviewing this document. A very big thanks goes to for their work reviewing this document. A very big thanks goes to
Stephen Casner for reviewing and helping fixing the language and Stephen Casner for reviewing and helping fixing the language and
finding some errors in the draft. finding some errors in the draft. Further thanks for suggestion to
improvements goes to Colin Perkins, Geetha Srikantan, and Emre Aksu.
The author would also like to thank all persons on the MMUSIC working The author would also like to thank all persons on the MMUSIC working
group's mailing list that have commented on this specification. group's mailing list that have commented on this specification.
11. Author's Addresses 11. Author's Addresses
Magnus Westerlund Tel: +46 8 4048287 Magnus Westerlund Tel: +46 8 4048287
Ericsson Research Email: Magnus.Westerlund@ericsson.com Ericsson Research Email: Magnus.Westerlund@ericsson.com
Ericsson AB Ericsson AB
Torshamnsgatan 23 Torshamnsgatan 23
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draft-ietf-mmusic-sdp-bwparam-01.txt: draft-ietf-mmusic-sdp-bwparam-01.txt:
- Improved language in the whole draft - Improved language in the whole draft
- Updated the problem scope section (4) to clarify what part of the - Updated the problem scope section (4) to clarify what part of the
whole problem space that this specification provides solution to. whole problem space that this specification provides solution to.
- Clarified that the tunneling problem example may not be applicable - Clarified that the tunneling problem example may not be applicable
for the TIAS parameters (Section 2.2). for the TIAS parameters (Section 2.2).
- Included text about RFC 3006, which provides hints in RSVP that - Included text about RFC 3006, which provides hints in RSVP that
header compression is possible. header compression is possible.
- Removed an inconsistency in the normative language regarding the - Removed an inconsistency in the normative language regarding the
usage of "maxprate" attribute. It shall always be present when usage of "maxprate" attribute. It shall always be present when TIAS
TIAS is used. is used.
The following changes have been done to this version compared to The following changes have been done to this version compared to
draft-ietf-mmusic-sdp-bwparam-02.txt draft-ietf-mmusic-sdp-bwparam-02.txt
- Updated language in abstract. - Updated language in abstract.
- Replaced a reference to RFC 1889 with RFC XXXX. - Replaced a reference to RFC 1889 with RFC XXXX.
- Added a SDP-NG informative reference. - Added a SDP-NG informative reference.
- Corrected two language errors in Section 4. - Corrected two language errors in Section 4.
- Fixed reference [15]. - Fixed reference [15].
The following changes have been done to this version compared to
draft-ietf-mmusic-sdp-bwparam-03.txt
- Changed the definition of TIAS and maxprate at SDP session level.
It is now allowed to have a session rate less than the sum of the
individual rates.
- Added an example of the usage of the attributes.
- Reformulated some sentences for clarity.
RFC-Editor Considerations RFC-Editor Considerations
Please remove this and the previous section before publishing. Please remove this and the previous section before publishing.
Please update reference [4] (draft-ietf-avt-rtp-new-12.txt) with the Please update reference [4] (draft-ietf-avt-rtp-new-12.txt) with the
correct publication date and RFC number when they are available. correct publication date and RFC number when they are available.
Please remove the parenthesis pointing out the draft file. Please Please remove the parenthesis pointing out the draft file. Please
update all occurrences of XXXX with the RFC number that [4] receive. update all occurrences of XXXX with the RFC number that [4] receives.
Please replace any occurrences of YYYY with the RFC number that is Please replace any occurrences of YYYY with the RFC number that is
given to the draft in reference [9] when published. Please update given to the draft in reference [9] when published. Please update
reference [9] with the correct date of publication and remove the reference [9] with the correct date of publication and remove the
parenthesis pointing out the draft. parenthesis pointing out the draft.
This Internet-Draft expires in November 2003. This Internet-Draft expires in December 2003.
 End of changes. 

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