draft-ietf-tuba-host-clnp-multicas-01.txt   rfc1768.txt 
INTERNET-DRAFT Dave Marlow Network Working Group D. Marlow
May 13, 1994 NSWC-DD Request for Comments: 1768 NSWC-DD
Category: Experimental March 1995
Host Group Extensions for CLNP Multicasting Host Group Extensions for CLNP Multicasting
draft-ietf-tuba-host-clnp-multicas-01.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working This memo defines an Experimental Protocol for the Internet
documents of the Internet Engineering Task Force (IETF), its areas, community. This memo does not specify an Internet standard of any
and its working groups. Note that other groups may also distribute kind. Discussion and suggestions for improvement are requested.
working documents as Internet-Drafts. Distribution of this memo is unlimited.
Internet-Drafts are draft documents valid for a maximum of six
months. Internet-Drafts may be updated, replaced, or obsoleted by
other documents at any time. It is not appropriate to use Internet-
Drafts as reference material or to cite them other than as a
``working draft'' or ``work in progress.''
To learn the current status of any Internet-Draft, please check the
1id-abstracts.txt listing contained in the Internet-Drafts Shadow
Directories on ds.internic.net, nic.nordu.net, venera.isi.edu, or
munnari.oz.au.
Abstract Abstract
This draft provides a specification for multicast extensions to the This memo documents work performed in the TUBA (TCP/UDP over Bigger
Addresses) working group of IPng area prior to the July 1994 decision
to utilize SIPP-16 as the basis for IPng. The TUBA group worked on
extending the Internet Protocol suite by the use of ISO 8473 (CLNP)
and its related routing protocols. This memo describes multicast
extensions to CLNP and its related routing protocols for Internet
multicast use. Publication of this memo does not imply acceptance by
any IETF Working Group for the ideas expressed within.
This memo provides a specification for multicast extensions to the
CLNP protocol similar to those provided to IP by RFC1112. These CLNP protocol similar to those provided to IP by RFC1112. These
extensions are intended to provide the mechanisms needed by a host extensions are intended to provide the mechanisms needed by a host
for multicasting in a CLNP based Internet. This draft covers for multicasting in a CLNP based Internet. This memo covers
addressing extensions to the CLNP addressing structure, extensions to addressing extensions to the CLNP addressing structure, extensions to
the CLNP protocol and extensions to the ES-IS protocol. An appendix the CLNP protocol and extensions to the ES-IS protocol. An appendix
discusses the differences between IP multicast and the CLNP multicast discusses the differences between IP multicast and the CLNP multicast
approach provided in this draft. approach provided in this memo.
The multicast extensions to the CLNP addressing structure defines
group Network addresses which identify host groups. The multicast
extensions to CLNP provides a means for identifying a CLNP packet and
provides scope control mechanisms for CLNP multicast packets. The
multicast extensions to the ES-IS protocol provide the mechanisms
needed for a host to exchange control information with multicast
capable routers. These extensions to the ES-IS protocol provide for
a host to "announce" which multicast packets are of interest and for
a multicast capable router to dynamically "map" group Network
addresses to subnetwork addresses.
The primary change in this updated Internet Draft is the
incorporation of "direct origination of multicast packets" as
discussed at the March TUBA meeting and over the email. This change
to the behavior of hosts originating multicast packets enables hosts
announcing an interest in particular group Network addresses to
directly receive such multicast packets originated on a subnetwork to
which they are connected. This replaces the previous method which in
some cases required a multicast capable router to resend such
packets.
Contents
Status of this Memo
Abstract
1. Introduction
2. Levels of Conformance
3. Group Network Addresses
4. Model of a CLNP End System Multicast Implementation
5. Extensions to the CLNP Protocol
6. Extensions to the ES-IS Routeing Protocol
Appendix A. Differences with RFC 1112 Acknowledgments
Appendix B. Issues Under Study The specification provided here was developed by a number of
individuals in the IETF TUBA working group as well as the ANSI X3S3.3
and ISO SC6 WG2 committees. Key contributions were made by Steve
Deering, Joel Halpern, Dave Katz and Dave Oran.
References Table of Contents
Author's Address 1. Introduction .......................................... 2
2. Levels of Conformance.................................. 3
3. Group Network Addresses................................ 4
4. Model of a CLNP End System Multicast Implementation.... 8
5. Extensions to the CLNP Protocol........................ 8
6. Extensions to the ES-IS Routeing Protocol ............. 15
7. Security Considerations ............................... 39
Appendix A. Differences with RFC 1112 .................... 40
Appendix B. Issues Under Study ........................... 43
References ................................................ 44
Author's Address .......................................... 45
1. Introduction 1. Introduction
This draft provides a specification for multicast extensions for CLNP This memo provides a specification for multicast extensions for CLNP
in order to provide a CLNP based Internet the capabilities provided in order to provide a CLNP based Internet the capabilities provided
for IP by RFC 1112 (Host Extensions for IP Multicasting) [RFC1112]. for IP by RFC 1112 (Host Extensions for IP Multicasting) [RFC1112].
This draft uses an outline similar to that of RFC 1112. This memo uses an outline similar to that of RFC 1112.
Paraphrasing RFC 1112, "CLNP multicasting is the transmission of a Paraphrasing RFC 1112, "CLNP multicasting is the transmission of a
CLNP datagram to a "host group", a set of zero or more End Systems CLNP datagram to a "host group", a set of zero or more End Systems
identified by a single group Network address (GNA). A multicast identified by a single group Network address (GNA). A multicast
datagram is delivered to all members of its destination host group datagram is delivered to all members of its destination host group
with the same "best-efforts" reliability as regular unicast CLNP with the same "best-efforts" reliability as regular unicast CLNP
datagrams, i.e., the datagram is not guaranteed to arrive intact at datagrams, i.e., the datagram is not guaranteed to arrive intact at
all members of the destination group or in the same order relative to all members of the destination group or in the same order relative to
other datagrams. other datagrams.
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"A host group may be permanent or transient. A permanent group has an "A host group may be permanent or transient. A permanent group has an
administratively assigned GNA. It is the address, not the membership administratively assigned GNA. It is the address, not the membership
of the group, that is permanent; at any time a permanent group may of the group, that is permanent; at any time a permanent group may
have any number of members, even zero. have any number of members, even zero.
"Internetwork forwarding of CLNP multicast datagrams is handled by "Internetwork forwarding of CLNP multicast datagrams is handled by
"multicast capable" Intermediate Systems which may be co-resident "multicast capable" Intermediate Systems which may be co-resident
with unicast capable Intermediate Systems. with unicast capable Intermediate Systems.
This draft specifies the extensions required by an End System to make The multicast extensions to the CLNP addressing structure defines
group Network addresses which identify host groups. The multicast
extensions to CLNP provides a means for identifying a CLNP packet and
provides scope control mechanisms for CLNP multicast packets. The
multicast extensions to the ES-IS protocol provide the mechanisms
needed for a host to exchange control information with multicast
capable routers. These extensions to the ES-IS protocol provide for
a host to "announce" which multicast packets are of interest and for
a multicast capable router to dynamically "map" group Network
addresses to subnetwork addresses.
This memo specifies the extensions required by an End System to make
use of CLNP multicast. In addition the requirements placed upon use of CLNP multicast. In addition the requirements placed upon
multicast capable Intermediate Systems to exchange information with multicast capable Intermediate Systems to exchange information with
multicast capable End Systems is specified. No specifications are multicast capable End Systems is specified. No specifications are
provided related to the information exchanges between Intermediate provided related to the information exchanges between Intermediate
Systems to support multicast route selection or multicast Protocol Systems to support multicast route selection or multicast Protocol
Data Unit (PDU) forwarding. A discussion of multicast route selection Data Unit (PDU) forwarding. A discussion of multicast route selection
and PDU forwarding has been written by Steve Deering [Deering91]. and PDU forwarding has been written by Steve Deering [Deering91].
Note that for these multicast extensions to work there must exist an Note that for these multicast extensions to work there must exist an
uninterrupted path of multicast capable routers between the End uninterrupted path of multicast capable routers between the End
Systems comprising a host group (such paths may utilize tunneling Systems comprising a host group (such paths may utilize tunneling
(i.e. unicast CLNP encapsulated paths between multicast capable CLNP (i.e., unicast CLNP encapsulated paths between multicast capable CLNP
routers)). In order to support multicast route selection and routers)). In order to support multicast route selection and
forwarding for a CLNP based internet additional specifications are forwarding for a CLNP based internet additional specifications are
needed. Specifications of this type could come in the form of new needed. Specifications of this type could come in the form of new
protocols, extensions to the current CLNP based routing protocols or protocols, extensions to the current CLNP based routing protocols or
use of a technique out of the IETF`s Inter-Domain Multicast Routing use of a technique out of the IETF's Inter-Domain Multicast Routing
(IDMR) group. The IDMR group is currently investigating multicast (IDMR) group. The IDMR group is currently investigating multicast
protocols for routers which utilize a router's unicast routing protocols for routers which utilize a router's unicast routing
protocols, this approach may extend directly to CLNP routers. protocols, this approach may extend directly to CLNP routers.
While many of the techniques and assumptions of IP multicasting (as While many of the techniques and assumptions of IP multicasting (as
discussed in RFC 1112) are used in CLNP multicasting, there are discussed in RFC 1112) are used in CLNP multicasting, there are
number of differences. Appendix A describes the differences between number of differences. Appendix A describes the differences between
CLNP multicasting and IP multicasting. This draft describes CLNP multicasting and IP multicasting. This memo describes techniques
techniques brought in directly from projects within ISO to brought in directly from projects within ISO to incorporate multicast
incorporate multicast transmission capabilities into CLNP [MULT- transmission capabilities into CLNP [MULT-AMDS].
AMDS]. Coordination is being made to keep this draft consistent with
the specifications of these ISO projects. Key contributions to the
techniques described in this draft have been made by a number of
individuals within the TUBA, ANSI X3S3.3 and ISO SC6 Working Group 2
committees.
2. Levels of Conformance 2. Levels of Conformance
There are three levels of conformance for End Systems to this There are three levels of conformance for End Systems to this
specification: specification:
Level 0: no support for CLNP multicasting. Level 0: no support for CLNP multicasting.
There is no requirement for a CLNP End System (or Intermediate There is no requirement for a CLNP End System (or Intermediate
System) to support CLNP multicasting. Level 0 hosts should be System) to support CLNP multicasting. Level 0 hosts should be
unaffected by the presence of multicast activity. The destination unaffected by the presence of multicast activity. The destination
addresses used in support of multicast transfers, the GNA, should not addresses used in support of multicast transfers, the GNA, should not
be enabled by a non-multicast capable End System and the PDUs be enabled by a non-multicast capable End System and the PDUs
themselves are marked differently than unicast PDUs and thus should themselves are marked differently than unicast PDUs and thus should
be quietly discarded. be quietly discarded.
Level 1: support for sending but not receiving CLNP multicast PDUs. Level 1: support for sending but not receiving CLNP multicast PDUs.
An End System originating multicast PDUs is required to know whether An End System originating multicast PDUs is required to know whether
a multicast capable Intermediate System is attached to the a multicast capable Intermediate System is attached to the
subnetwork(s) that it originates multicast PDUs (i.e. to determine subnetwork(s) that it originates multicast PDUs (i.e., to determine
the destination SNPA (subnet) address). An End System with Level 1 the destination SNPA (subnet) address). An End System with Level 1
conformance is required to implement all parts of this specification conformance is required to implement all parts of this specification
except for those supporting only Multicast Announcement. An End except for those supporting only Multicast Announcement. An End
System is not required to know the current Multicast Address Mapping System is not required to know the current Multicast Address Mapping
to start originating multicast PDUs. to start originating multicast PDUs.
Note: It is possible for End System not implementing Multicast Note: It is possible for End System not implementing Multicast
Address Mapping to successfully originate multicast PDUs (but with Address Mapping to successfully originate multicast PDUs (but with
the End System knowing of the existence of a multicast capable the End System knowing of the existence of a multicast capable
Intermediate System). Such operation may lead to inefficient Intermediate System). Such operation may lead to inefficient
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group Network addresses. group Network addresses.
In the development of multicast address extensions to CLNP, In the development of multicast address extensions to CLNP,
requirements were identified for: (1)"easily distinguishing" group requirements were identified for: (1)"easily distinguishing" group
addresses at the Network layer from NSAP addresses; (2)leaving the addresses at the Network layer from NSAP addresses; (2)leaving the
currently allocated address families unaffected and (3)ensuring that currently allocated address families unaffected and (3)ensuring that
the approach taken would not require the establishment of new the approach taken would not require the establishment of new
addressing authorities. In addition, it was agreed that providing addressing authorities. In addition, it was agreed that providing
multicast options for all OSI Network layer users was desirable and multicast options for all OSI Network layer users was desirable and
thus the group Network addressing solution should support options for thus the group Network addressing solution should support options for
all address formats covered by ISO/IEC 8348 | Recommendation X.213. all address formats covered by ISO/IEC 8348 | CCITT Recommendation
The only viable means identified for meeting all requirements was via X.213. The only viable means identified for meeting all requirements
creating a new set of AFI values with a fixed one-to-one mapping was via creating a new set of AFI values with a fixed one-to-one
between each of the existing AFI values and a corresponding group AFI mapping between each of the existing AFI values and a corresponding
value. group AFI value.
Group Network addresses are defined by creating a new set of AFI Group Network addresses are defined by creating a new set of AFI
values, one for each existing AFI value, and a fixed one-to-one values, one for each existing AFI value, and a fixed one-to-one
mapping between each of the existing AFI values and a corresponding mapping between each of the existing AFI values and a corresponding
group AFI value. The syntax of a group Network address is identical group AFI value. The syntax of a group Network address is identical
to the syntax of an individual Network address, except that the value to the syntax of an individual Network address, except that the value
of the AFI in an individual Network address may be only one of the of the AFI in an individual Network address may be only one of the
values already allocated for individual Network addresses, whereas values already allocated for individual Network addresses, whereas
the value of the AFI in a group Network address may be only one of the value of the AFI in a group Network address may be only one of
the values allocated here for group Network addresses. The AFI values the values allocated here for group Network addresses. The AFI values
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Domain Part (IDP) and the Domain Specific Part (DSP). The first two Domain Part (IDP) and the Domain Specific Part (DSP). The first two
octets of the IDP are the Authority and Format Identifier (AFI) octets of the IDP are the Authority and Format Identifier (AFI)
field. The AFI has an abstract syntax of two hexadecimal digits with field. The AFI has an abstract syntax of two hexadecimal digits with
a value in the range of 00 to FF. In addition to identifying the a value in the range of 00 to FF. In addition to identifying the
address authority responsible for allocating a particular address and address authority responsible for allocating a particular address and
the format of the address, the AFI also identifies whether an address the format of the address, the AFI also identifies whether an address
is an individual Network address or a group Network address. There is an individual Network address or a group Network address. There
are 90 possible AFI values to support individual Network address are 90 possible AFI values to support individual Network address
allocations. In addition, when the AFI value starts with the value allocations. In addition, when the AFI value starts with the value
"0" this identifies that the field contains an incomplete individual "0" this identifies that the field contains an incomplete individual
Network address (i.e. identifies an escape code). Network address (i.e., identifies an escape code).
Table 1 allocates 90 possible AFI values to support group Network Table 1 allocates 90 possible AFI values to support group Network
address allocations. In addition if the first two digits of the IDP address allocations. In addition if the first two digits of the IDP
are hexadecimal FF, this indicates the presence of an incomplete are hexadecimal FF, this indicates the presence of an incomplete
group Network address. The allocation of group addresses is group Network address. The allocation of group addresses is
restricted to be only from the AFI values allocated for the restricted to be only from the AFI values allocated for the
assignment of group addresses in Table 1. An addressing authority in assignment of group addresses in Table 1. An addressing authority in
allocating either Network addresses or authorizing one or more allocating either Network addresses or authorizing one or more
authorities to allocate addresses, allocates both individual and the authorities to allocate addresses, allocates both individual and the
corresponding group addresses. Thus each block of addresses allocated corresponding group addresses. Thus each block of addresses allocated
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individual and group address block allocated are differentiated by individual and group address block allocated are differentiated by
the AFI values used which are related as shown in Table 1. the AFI values used which are related as shown in Table 1.
Group Network addresses are only used as the destination address Group Network addresses are only used as the destination address
parameter of a CLNP PDU. Source Address parameters are never parameter of a CLNP PDU. Source Address parameters are never
permitted to be group Network addresses. permitted to be group Network addresses.
Table 2 lists the AFI values which have not been assigned, at this Table 2 lists the AFI values which have not been assigned, at this
time, for the support of neither individual nor group address time, for the support of neither individual nor group address
allocation. Future assignment of these AFI values is possible. allocation. Future assignment of these AFI values is possible.
Additional information concerning individual Network addresses (i.e. Additional information concerning individual Network addresses (i.e.,
NSAP and NET (Network Entity Titles)) is contained in RFC 1237. NSAP and NET (Network Entity Titles)) is contained in RFC 1237.
Note: While the format of the Initial Domain Part of a group Network
address is assigned, the format for the Domain Specific Part of the
group Network address is specified by an addressing authority and is
out of the scope of this memo. While NSAP address assignments are
typically made to support hierarchical unicast routing, a similar
consideration for group Network address assignments may not exist.
TABLE 1 - Relationship of AFI Individual and Group Values TABLE 1 - Relationship of AFI Individual and Group Values
----------------------------------------------------------- -----------------------------------------------------------
|Individual Group | Individual Group | Individual Group | |Individual Group | Individual Group | Individual Group |
----------------------------------------------------------- -----------------------------------------------------------
| 0x FF | | | | 0x FF | | |
| 10 A0 | 40 BE | 70 DC | | 10 A0 | 40 BE | 70 DC |
| 11 A1 | 41 BF | 71 DD | | 11 A1 | 41 BF | 71 DD |
| 12 A2 | 42 C0 | 72 DE | | 12 A2 | 42 C0 | 72 DE |
| 13 A3 | 43 C1 | 73 DF | | 13 A3 | 43 C1 | 73 DF |
| 14 A4 | 44 C2 | 74 E0 | | 14 A4 | 44 C2 | 74 E0 |
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| 8A-8F | | 8A-8F |
| 9A-9F | | 9A-9F |
| FA-FE | | FA-FE |
-------------- --------------
4. Model of a CLNP End System Multicast Implementation 4. Model of a CLNP End System Multicast Implementation
The use of multicast transmission by a CLNP End System involves The use of multicast transmission by a CLNP End System involves
extensions to two protocols: CLNP and the ES-IS Routeing Protocol. To extensions to two protocols: CLNP and the ES-IS Routeing Protocol. To
provide level 0 service (no support for CLNP multicast), no provide level 0 service (no support for CLNP multicast), no
extensions to the two present protocols are required. To provide extensions to these two protocols are required. To provide level 1
level 1 service (support for sending but not receiving CLNP multicast service (support for sending but not receiving CLNP multicast PDUs)
PDUs) all extensions contained in the following sections are required all extensions contained in the following sections are required
except for those supporting only Multicast Announcement. In order to except for those supporting only Multicast Announcement. In order to
support level 2 service (full support for CLNP multicasting), the support level 2 service (full support for CLNP multicasting), the
extensions contained in the following sections are required. extensions contained in the following sections are required.
Extensions identified for Intermediate Systems are not required (or Extensions identified for Intermediate Systems are not required (or
appropriate) for End Systems. Multicast transmission also requires appropriate) for End Systems. Multicast transmission also requires
the use of a group Network address (as previously described) as the the use of a group Network address (as previously described) as the
destination address parameter. destination address parameter.
5. Extensions to the CLNP protocol 5. Extensions to the CLNP protocol
This section provides extensions to the CLNP Protocol [CLNP] ISO This section provides extensions to the CLNP Protocol [CLNP] ISO
8473-1, to support multicast transmission. These additions provide 8473-1, to support multicast transmission. These additions provide
procedures for the connectionless transmission of data and control procedures for the connectionless transmission of data and control
information from one network-entity to one or more peer network- information from one network-entity to one or more peer network-
entities. entities.
In developing the multicast extensions for CLNP a decision was needed In developing the multicast extensions for CLNP a decision was needed
on how to "mark" a packet as multicast (versus the current unicast on how to "mark" a packet as multicast (versus the current unicast
packets). Such marking is necessary since the forwarding behavior packets). Such marking is necessary since the forwarding behavior
for multicast packets is different (e.g. multiple copies of a packet for multicast packets is different (e.g., multiple copies of a packet
may need to be forwarded). The two alternatives considered were to may need to be forwarded). The two alternatives considered were to
mark the packet (via a particular field) or to mark the destination mark the packet (via a particular field) or to mark the destination
address, in the end both were done. The destination address for a address, in the end both were done. The destination address for a
multicast PDU identifies a host group which is of a very different multicast PDU identifies a host group which is of a very different
nature than the unicast NSAP address. Rather than changing the nature than the unicast NSAP address. Rather than changing the
nature of NSAP addresses, a new set of addresses were created named nature of NSAP addresses, a new set of addresses were created named
group Network addresses which are marked within the first octet (i.e. group Network addresses which are marked within the first octet
the AFI field) with values reserved for group Network addresses. (i.e., the AFI field) with values reserved for group Network
addresses.
Consideration was given to no further marking of the PDU; however, a Consideration was given to no further marking of the PDU; however, a
problem was identified with only using the group Network address to problem was identified with only using the group Network address to
identify multicast packets. Currently routers implementing the IS-IS identify multicast packets. Currently routers implementing the IS-IS
Intra-Domain protocol as Level 1 routers when receiving a packet with Intra-Domain protocol as Level 1 routers when receiving a packet with
an unknown destination address are permitted to either discard the an unknown destination address are permitted to either discard the
packet or send it to a Level 2 router. Such actions by non-multicast packet or send it to a Level 2 router. Such actions by non-multicast
capable routers to multicast packets can lead to non-deterministic capable routers to multicast packets can lead to non-deterministic
behavior. Level 1 routers upon receiving a packet containing a group behavior. Level 1 routers upon receiving a packet containing a group
Network address might pass the packet up to a Level 2 router (which Network address might pass the packet up to a Level 2 router (which
may or may not be multicast capable) or it might discard it. may or may not be multicast capable) or it might discard it.
Depending upon the circumstances this might lead to whole regions Depending upon the circumstances this might lead to whole regions
missing packets or packet duplication (possibly even explosion). The missing packets or packet duplication (possibly even explosion). The
result was to seek deterministic behavior by non-multicast capable result was to seek deterministic behavior by non-multicast capable
routers by creating a new PDU type (Multicast Data PDU) and inserting routers by creating a new PDU type (Multicast Data PDU) and inserting
into the CLNP reasons for discard: receiving a PDU of unknown type. into the CLNP reasons for discard: receiving a PDU of unknown type.
Note this reason for discard is mandatory on multicast capable and Note that this reason for discard is mandatory on multicast capable
non-multicast capable CLNP implementations. and non-multicast capable CLNP implementations.
5.1 Definitions 5.1 Definitions
multicast: Data transmission to one or more destinations in a multicast: Data transmission to one or more destinations in a
selected group in a single service invocation. selected group in a single service invocation.
multicast capable Intermediate System: An Intermediate System which multicast capable Intermediate System: An Intermediate System which
incorporates the multicast features of the Network layer. incorporates the multicast features of the Network layer.
5.2 Addresses 5.2 Addresses
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function shall not be invoked upon PDU discard. function shall not be invoked upon PDU discard.
5.4.3 Radius Scope Control 5.4.3 Radius Scope Control
The radius scope control function allows the originator to specify a The radius scope control function allows the originator to specify a
maximum logical distance where multicast expansion can occur. It is maximum logical distance where multicast expansion can occur. It is
closely associated with the header format analysis function. Each IS closely associated with the header format analysis function. Each IS
receiving a multicast PDU which is capable of expanding and which receiving a multicast PDU which is capable of expanding and which
contains a Radius Scope Control parameter, decrements the Radius contains a Radius Scope Control parameter, decrements the Radius
Scope Control field in the PDU by an administratively set amount Scope Control field in the PDU by an administratively set amount
between 0 and the maximum value of the field. This function between 0 and the maximum value of the field. An IS, when it
determines whether the PDU received may be forwarded or whether its decrements the Radius Scope Control field, shall place a value of 0
Radius has been reached, in which case it shall be discarded. An into this field if its current value is less than the amount it is to
Intermediate System shall not forward a multicast PDU containing a decrement by. This function determines whether the PDU received may
Radius Scope Control parameter with a value of 0. The error reporting be forwarded or whether its Radius has been reached, in which case it
function shall not be invoked upon PDU discard. shall be discarded. An Intermediate System shall not forward a
multicast PDU containing a Radius Scope Control parameter with a
value of 0. The error reporting function shall not be invoked upon
PDU discard.
5.4.3.1 Radius Scope Control Example 5.4.3.1 Radius Scope Control Example
The Radius Scope Control parameter is useful where policies have been The Radius Scope Control parameter is useful where policies have been
established across the potential forwarding path. One possible established across the potential forwarding path. One possible
policy for Internet use is for multicast capable routers to treat policy for Internet use is for multicast capable routers to treat
this field as a hop count within a domain (decrement by one unit) and this field as a hop count within a domain (decrement by one unit) and
for inter-domain routers to either decrement this field to an even for inter-domain routers to either decrement this field to an even
multiple of 256 when crossing domains where prior agreements have multiple of 256 when crossing domains where prior agreements have
been made or decrement this field to 0 (i.e. discard the packet) for been made or decrement this field to 0 (i.e., discard the packet) for
other domains. other domains.
5.5 Structure and Encoding of PDUs 5.5 Structure and Encoding of PDUs
Multicast transmission is accomplished via the transfer of Multicast Multicast transmission is accomplished via the transfer of Multicast
Data (MD) PDUs. The PDU type code for a MD PDU is "1 1 1 0 1". The Data (MD) PDUs. The PDU type code for a MD PDU is "1 1 1 0 1". The
format of the MD PDU is identical to that of the Data (DT) PDU. The format of the MD PDU is identical to that of the Data (DT) PDU. The
MD and DT PDU may contain the same optional parameters with the MD and DT PDU may contain the same optional parameters with the
following exceptions: (1)The source routing parameter is permitted following exceptions: (1)The source routing parameter is permitted
within DT PDUs but not MD PDUs; and (2)The scope control parameter is within DT PDUs but not MD PDUs; and (2)The scope control parameter is
permitted within MD PDUs but not DT PDUs. permitted within MD PDUs but not DT PDUs.
5.6 Optional parameters for multicast support 5.6 Optional parameters for multicast support
5.6.1 Prefix Based Scope Control (this section is extended beyond the 5.6.1 Prefix Based Scope Control
ISO draft)
The prefix based scope control parameter specifies one or more The prefix based scope control parameter specifies one or more
address prefixes for which Intermediate System forwarding requires a address prefixes for which Intermediate System forwarding requires a
match of one of the contained prefixes with the beginning of the match of one of the contained prefixes with the beginning of the
Intermediate System's NET. Intermediate System's NET.
Parameter Code: 1100 0100 Parameter Code: 1100 0100
Parameter Length: variable Parameter Length: variable
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The prefix shall end on a boundary that is legal in the abstract The prefix shall end on a boundary that is legal in the abstract
syntax of the address family from which it is derived. For example, syntax of the address family from which it is derived. For example,
the encoding of a prefix whose DSP is expressed in decimal syntax the encoding of a prefix whose DSP is expressed in decimal syntax
must end on a semi-octet boundary, while the encoding of a prefix must end on a semi-octet boundary, while the encoding of a prefix
whose DSP is expressed in binary syntax can end on an arbitrary bit whose DSP is expressed in binary syntax can end on an arbitrary bit
boundary. If the end of the prefix falls within the IDP, then the boundary. If the end of the prefix falls within the IDP, then the
prefix must end on a semi-octet boundary and must not contain any prefix must end on a semi-octet boundary and must not contain any
padding characters. padding characters.
NOTE - The length of the prefix based scope control Note: The length of the prefix based scope control parameter is
parameter is determined by the originator of the PDU and is not determined by the originator of the PDU and is not changed during the
changed during the lifetime of the PDU. lifetime of the PDU.
5.6.1.1 Prefix matching 5.6.1.1 Prefix matching
A prefix that extends into the DSP shall be compared directly against A prefix that extends into the DSP shall be compared directly against
the encoded NET address, including any padding characters that may be the encoded NET address, including any padding characters that may be
present. A prefix which does not extend into the DSP shall be present. A prefix which does not extend into the DSP shall be
compared against the derived quantity NET', which is obtained from compared against the derived quantity NET', which is obtained from
the NET address by removing all padding characters (as defined by the the NET address by removing all padding characters (as defined by the
binary encoding process of ISO 8348). binary encoding process of ISO 8348).
skipping to change at page 13, line 29 skipping to change at page 14, line 29
b) If the encoded NET (or NET') contains at least as many bits as b) If the encoded NET (or NET') contains at least as many bits as
the prefix, and all bits of the prefix are identical to the the prefix, and all bits of the prefix are identical to the
corresponding leading bits of the encoded NET (or NET'), there corresponding leading bits of the encoded NET (or NET'), there
is a match. Otherwise, there is no match. is a match. Otherwise, there is no match.
5.6.2 Radius Scope Control 5.6.2 Radius Scope Control
The radius scope control parameter specifies the logical distance The radius scope control parameter specifies the logical distance
that a multicast PDU can be forwarded. that a multicast PDU can be forwarded.
Parameter Code: 1100 0110 (THIS CODE MAY CHANGE) Parameter Code: 1100 0110
Parameter Length: two octets Parameter Length: two octets
Parameter Value: two octets which represents the remaining Parameter Value: two octets which represents the remaining
distance, that the PDU can be forwarded, in administratively set distance, that the PDU can be forwarded,
units. in administratively set units.
5.7 Provision of the Underlying Service 5.7 Provision of the Underlying Service
For a subnetwork that provides an inherent multicast capability, it For a subnetwork that provides an inherent multicast capability, it
is the functionality of the SNDCF to provide the mapping between is the functionality of the SNDCF to provide the mapping between
group Network addresses and the corresponding addressing capability group Network addresses and the corresponding addressing capability
of the subnetwork. of the subnetwork.
5.8 Conformance 5.8 Conformance
All of the extensions provided to the functions to support multicast All of the extensions provided to the functions to support multicast
capability are optional. For an End System or Intermediate System capability are optional. For an End System or Intermediate System
which is not multicast capable these extensions are not applicable. which is not multicast capable these extensions are not applicable.
An implementation claiming conformance as a multicast capable End An implementation claiming conformance as a multicast capable End
System shall meet all of the requirements for an End System which is System shall meet all of the requirements for an End System which is
not multicast capable and also provide all of the multicast exten- not multicast capable and also provide all of the multicast
sions provided here. An implementation claiming conformance as a mul- extensions provided here. An implementation claiming conformance as a
ticast capable Intermediate System shall meet all of the requirements multicast capable Intermediate System shall meet all of the
for an Intermediate System which is not multicast capable and also requirements for an Intermediate System which is not multicast
provide all of the multicast extensions provided here. capable and also provide all of the multicast extensions provided
here.
6. Extensions to the ES-IS Routeing Protocol 6. Extensions to the ES-IS Routeing Protocol
This section provides optional extensions to the ES-IS Routeing Pro- This section provides optional extensions to the ES-IS Routeing
tocol [ES-IS], ISO 9542 to support the transfer of multicast PDUs. It Protocol [ES-IS], ISO 9542 to support the transfer of multicast PDUs.
is an explicit goal of this specification that ESs and ISs, some of It is an explicit goal of this specification that ESs and ISs, some
which will have multicast capabilities and some without, will be able of which will have multicast capabilities and some without, will be
to fully function on the same subnetworks. This specification does able to fully function on the same subnetworks. This specification
not change any aspect of a currently defined (i.e. non-multicast) ISO does not change any aspect of a currently defined (i.e., non-
9542 implementation, it adds new optional functionality not modifying multicast) ISO 9542 implementation, it adds new optional
current functionality. Two basic functions are provided: multicast functionality not modifying current functionality. Two basic
announcement and multicast address mapping. functions are provided: multicast announcement and multicast address
mapping.
6.1 Overview of the protocol 6.1 Overview of the protocol
6.1.1 Operation of ESs receiving multicast PDUs 6.1.1 Operation of ESs receiving multicast PDUs
ESs, upon initialization and periodically thereafter, will construct ESs, upon initialization and periodically thereafter, will construct
End System Group Hello (ESGH) PDUs identifying, by particular group End System Group Hello (ESGH) PDUs identifying, by particular group
Network addresses, the multicast PDUs it wishes to receive. The ES Network addresses, the multicast PDUs it wishes to receive. The ES
will periodically originate (announce) these ESGH PDUs on the subnet- will periodically originate (announce) these ESGH PDUs on the
work it wishes to receive these on. Reporting the same group Network subnetwork it wishes to receive these on. Reporting the same group
address on multiple subnetworks may result in the reception of dupli- Network address on multiple subnetworks may result in the reception
cate PDUs. ES-IS operations related to requesting the same group Net- of duplicate PDUs. ES-IS operations related to requesting the same
work address on multiple subnetworks are handled totally indepen- group Network address on multiple subnetworks are handled totally
dently (e.g. using different logical timers,...). It is permitted for independently (e.g., using different logical timers,...). It is
an ES to report a number of group Network addresses in the same ESGH permitted for an ES to report a number of group Network addresses in
PDU. The only restrictions placed on providing multiple group Net- the same ESGH PDU. The only restrictions placed on providing
work addresses within the same ESGH PDU are that all packets multiple group Network addresses within the same ESGH PDU are that
requested are to be received on the same subnet, with the same hold- all packets requested are to be received on the same subnet, with the
ing time and that the ESGH PDU be of length equal to or less that its same holding time and that the ESGH PDU be of length equal to or less
maximum packet size constraint. Note each group Network address in that its maximum packet size constraint. Note that each group
the ESGH PDU is paired with its own SNPA (subnetwork point of attach- Network address in the ESGH PDU is paired with its own SNPA
ment) address. (subnetwork point of attachment) address.
An ES will always have an SNPA address associated with each of its An ES will always have an SNPA address associated with each of its
active group Network addresses. An SNPA address is a subnetwork active group Network addresses. An SNPA address is a subnetwork
address, in the case of a subnetwork which uses IEEE 802 addresses address, in the case of a subnetwork which uses IEEE 802 addresses
the SNPA address is a 48 bit IEEE 802 MAC (media access control) the SNPA address is a 48 bit IEEE 802 MAC (media access control)
address. Of particular interest is the address used to mark the des- address. Of particular interest is the address used to mark the
tination group. For a subnetwork using IEEE 802 addressing a group destination group. For a subnetwork using IEEE 802 addressing a
SNPA address uses a particular bit position to "mark" group SNPA group SNPA address uses a particular bit position to "mark" group
addresses. SNPA addresses.
Upon initialization the ES may have static SNPA address associations Upon initialization the ES may have static SNPA address associations
(Pre-configured SNPA addresses). For any group Network address (Pre-configured SNPA addresses). For any group Network address
without a Pre-configured SNPA address that the ES wishes to receive, without a Pre-configured SNPA address that the ES wishes to receive,
the ES will associate the "All Multicast Capable End Systems" SNPA the ES will associate the "All Multicast Capable End Systems" SNPA
address. Upon receiving a Multicast Address Mapping (MAM) PDU con- address. Upon receiving a Multicast Address Mapping (MAM) PDU
taining a group Network address that the ES is announcing, the ES containing a group Network address that the ES is announcing, the ES
will use the SNPA address pairing contained in the MAM PDU for that will use the SNPA address pairing contained in the MAM PDU for that
group Network address. Upon the expiration of the Mapping Holding group Network address. Upon the expiration of the Mapping Holding
Timer, the ES shall revert back to associating either the Pre- Timer, the ES shall revert back to associating either the Pre-
configured SNPA address if one exists or the "All Multicast Capable configured SNPA address if one exists or the "All Multicast Capable
End Systems" SNPA address for the specific group Network address. End Systems" SNPA address for the specific group Network address.
While an ES is permitted to listen in on other ESs announcements While an ES is permitted to listen in on other ESs announcements
(needed for the damping option), an ES is not permitted to change its (needed for the damping option), an ES is not permitted to change its
group Network address to SNPA address mapping based on the announce- group Network address to SNPA address mapping based on the
ment of other ESs. announcement of other ESs.
Optionally, the ES may perform damping (resetting a Multicast Optionally, the ES may perform damping (resetting a Multicast
Announcement Timer corresponding to a particular group Network Announcement Timer corresponding to a particular group Network
address) if the conditions necessary to withhold a particular address) if the conditions necessary to withhold a particular
announcement are met. In order to perform damping the following con- announcement are met. In order to perform damping the following
ditions must be met: (1)The ES must be processing other ES's conditions must be met: (1)The ES must be processing other ES's
announcements; (2)An ESGH PDU is received that identifies the exact announcements; (2)An ESGH PDU is received that identifies the exact
same group Network address and SNPA address pairing on a particular same group Network address and SNPA address pairing on a particular
subnetwork that this ES is announcing on; (3) The Multicast Holding subnetwork that this ES is announcing on; (3) The Multicast Holding
Timer parameter value in the ESGH PDU received is equal to or greater Timer parameter value in the ESGH PDU received is equal to or greater
than the Multicast Holding Timer value, for this subnetwork, that is than the Multicast Holding Timer value, for this subnetwork, that is
being used by the ES processing this ESGH PDU. being used by the ES processing this ESGH PDU.
ESs will utilize a local default value for their Multicast Announce- ESs will utilize a local default value for their Multicast
ment Timer to control the period for sending out their ESGH PDUs. The Announcement Timer to control the period for sending out their ESGH
Active Multicast IS, if one exists on a particular subnetwork, may PDUs. The Active Multicast IS, if one exists on a particular
suggest a value for ESs on the subnetwork to use for their Multicast subnetwork, may suggest a value for ESs on the subnetwork to use for
Announcement Timer for a specific group Network address. In order to their Multicast Announcement Timer for a specific group Network
support the optional damping function, ESs are required to incor- address. In order to support the optional damping function, ESs are
porate a 25% jittering to the timer values that they are using. required to incorporate a 25% jittering to the timer values that they
are using.
6.1.2 Operation of ESs originating multicast PDUs 6.1.2 Operation of ESs originating multicast PDUs
The ES originating multicast packets identified by a specific group The ES originating multicast packets identified by a specific group
Network address is not required to be a receiver of such packets (and Network address is not required to be a receiver of such packets (and
thus is not announcing that particular group Network address). The thus is not announcing that particular group Network address). The
origination of multicast PDUs involves two differences to the origi- origination of multicast PDUs involves two differences to the
nation of unicast PDUs. The two differences are: (1)The mechanism origination of unicast PDUs. The two differences are: (1)The
for selecting a destination SNPA address and (2)For End Systems mechanism for selecting a destination SNPA address and (2)For End
attached to more than one subnet, the decision on which subnet(s) to Systems attached to more than one subnet, the decision on which
originate the PDUs. subnet(s) to originate the PDUs.
The destination SNPA address used for originating each multicast The destination SNPA address used for originating each multicast
packet depends on whether there is a multicast capable IS attached to packet depends on whether there is a multicast capable IS attached to
the subnetworks. When a multicast capabale IS is attached, the deci- the subnetworks. When a multicast capable IS is attached, the
sion depends on whether there is multicast address mapping informa- decision depends on whether there is multicast address mapping
tion corresponding to the group Network address used as the destina- information available for that subnetwork corresponding to the group
tion address parameter of the multicast packet available for that Network address used as the destination address parameter of the
subnetwork. When there is a multicast capable IS attached to a sub- multicast packet. When there is a multicast capable IS attached to a
network and there is multicast address mapping information available subnetwork and there is multicast address mapping information
corresponding to the group Network address, then the SNPA address available corresponding to the group Network address, then the SNPA
obtained from the multicast address mapping information is used. Ori- address obtained from the multicast address mapping information is
ginating multicast packets using the destination SNPA address used used. Originating multicast packets using the destination SNPA
for receiving such multicast packets ensures that the multicast pack- address used for receiving such multicast packets ensures that the
ets will not require additional forwarding on the originating multicast packets will not require additional forwarding on the
subnetwork(s). When there is a multicast capable IS attached to a originating subnetwork(s). When there is a multicast capable IS
subnetwork but for which there is no multicast address mapping infor- attached to a subnetwork but for which there is no multicast address
mation available corresponding to the the group Network address, then mapping information available corresponding to the the group Network
the SNPA address used is the "All Multicast Capable Intermediate Sys- address, then the SNPA address used is the "All Multicast Capable
tems" address. Intermediate Systems" address.
When there is no multicast capable IS attached to a subnetwork then When there is no multicast capable IS attached to a subnetwork then
the ES originating a multicast PDU uses pre-configured information if the ES originating a multicast PDU uses pre-configured information if
it is available or the "All Multicast Capable End Systems" SNPA it is available or the "All Multicast Capable End Systems" SNPA
address when no pre-configured information is available. address when no pre-configured information is available.
ES's attached to more than one subnetwork forward each multicast ES's attached to more than one subnetwork forward each multicast
packet that they originate onto every attached subnetwork for which packet that they originate onto every attached subnetwork for which
the NSAP address being used as the source address of the multicast the NSAP address being used as the source address of the multicast
packet is actively being reported through the unicast ES-IS Report packet is actively being reported through the unicast ES-IS Report
Configuration function. Configuration function.
6.1.3 Operation of the Active Multicast IS 6.1.3 Operation of the Active Multicast IS
The Active Multicast IS listens in on all ESGH PDUs originated on the The Active Multicast IS listens in on all ESGH PDUs originated on the
subnetwork for which it is serving as the Active Multicast IS. All subnetwork for which it is serving as the Active Multicast IS. All
subnetworks are handled independently (even if multiple subnetworks subnetworks are handled independently (even if multiple subnetworks
have the same ESs attached and the IS is serving as the Active Multi- have the same ESs attached and the IS is serving as the Active
cast IS for these subnetworks). Multicast IS for these subnetworks).
The Active Multicast IS originates MAM PDUs, for all group Network The Active Multicast IS originates MAM PDUs, for all group Network
addresses for which it has received ESGH PDUs, on the subnetwork due addresses for which it has received ESGH PDUs, on the subnetwork due
to the following operational conditions: to the following operational conditions:
1) The IS initializes either as the Active Multicast IS after an 1) The IS initializes either as the Active Multicast IS after an
election with other multicast capable ISs or initializes believ- election with other multicast capable ISs or initializes
ing it is the only multicast capable IS; believing it is the only multicast capable IS;
Note: The determination of such conditions is outside of the scope of Note: The determination of such conditions is outside of the scope of
this specification; this specification;
2) The IS receives an ESGH PDU with a group Network address paired 2) The IS receives an ESGH PDU with a group Network address paired
to an incorrect SNPA address; to an incorrect SNPA address;
3) The expiration of the IS's Multicast Address Mapping Timer for 3) The expiration of the IS's Multicast Address Mapping Timer for
that group Network address; or that group Network address; or
Note: This is to prevent the expiration of Mapping Holding Timers in Note: This is to prevent the expiration of Mapping Holding Timers in
ESs. ESs.
4) The IS receives a multicast PDU originated on the subnetwork 4) The IS receives a multicast PDU originated on the subnetwork
skipping to change at page 16, line 49 skipping to change at page 18, line 18
that group Network address; or that group Network address; or
Note: This is to prevent the expiration of Mapping Holding Timers in Note: This is to prevent the expiration of Mapping Holding Timers in
ESs. ESs.
4) The IS receives a multicast PDU originated on the subnetwork 4) The IS receives a multicast PDU originated on the subnetwork
which used an incorrect destination SNPA address. which used an incorrect destination SNPA address.
Note: Of particular concern are those multicast packets using the Note: Of particular concern are those multicast packets using the
"All Multicast Capable Intermediate Systems" SNPA address when "All Multicast Capable Intermediate Systems" SNPA address when
another SNPA address should have been used. In addition the multi- another SNPA address should have been used. In addition the
cast capable ISs are responsible for listening in on all multicast multicast capable ISs are responsible for listening in on all
packets using destination SNPA addresses that are contained within multicast packets using destination SNPA addresses that are contained
the current multicast address mapping information. within the current multicast address mapping information.
As a result of the event driven conditions (i.e. conditions 2 or 4 As a result of the event driven conditions (i.e., conditions 2 or 4
above), the Active Multicast IS sends a MAM PDU with direct informa- above), the Active Multicast IS sends a MAM PDU with direct
tion (i.e. not needing analysis of the Mask parameters). The Active information (i.e., not needing analysis of the Mask parameters). The
Multicast IS limits the number of MAM PDUs that are sent out per unit Active Multicast IS limits the number of MAM PDUs that are sent out
of time. Particular MAM PDUs with direct information will not be per unit of time. Particular MAM PDUs with direct information will
sent more than once per second. MAM PDU will be sent in response to not be sent more than once per second. MAM PDU will be sent in
continuing event driven conditions such that events occurring greater response to continuing event driven conditions such that events
than 10 seconds after the issuance of such a MAM PDU will result in occurring greater than 10 seconds after the issuance of such a MAM
the issuance of another MAM PDU. . PDU will result in the issuance of another MAM PDU.
The Active Multicast IS is responsible for forwarding a multicast The Active Multicast IS is responsible for forwarding a multicast
packet back on the subnetwork it was originated when a multicast packet back on the subnetwork it was originated when a multicast
packet used the "All Multicast Capable Intermediate System" SNPA packet used the "All Multicast Capable Intermediate System" SNPA
address when another SNPA address should have been used. A packet address when another SNPA address should have been used. A packet
forwarded back onto the subnetwork the multicast packet was ori- forwarded back onto the subnetwork the multicast packet was
ginated on will be given a CLNP Lifetime of "1" to prevent the con- originated on will be given a CLNP Lifetime of "1" to prevent the
tinued relaying of duplicate packets by the multicast ISs. continued relaying of duplicate packets by the multicast ISs.
The further relaying of any multicast packet originated on a subnet- The further relaying of any multicast packet originated on a
work is the responsibility of the multicast routing protocol used and subnetwork is the responsibility of the multicast routing protocol
is outside the scope of this specification. used and is outside the scope of this specification.
6.2 Definitions 6.2 Definitions
Active Multicast IS: The one multicast capable IS selected (via means Active Multicast IS: The one multicast capable IS selected (via means
outside of this specification) to originate Multicast Address Mapping outside of this specification) to originate Multicast Address Mapping
information on a particular subnetwork. information on a particular subnetwork.
Paired SNPA Address: The SNPA address associated with a particular Paired SNPA Address: The SNPA address associated with a particular
group Network address on a specific subnetwork. group Network address on a specific subnetwork.
6.3 Routing information supporting multicast transmission 6.3 Routing information supporting multicast transmission
6.3.1 Multicast Announcement Information 6.3.1 Multicast Announcement Information
An IS should forward a multicast PDU containing a particular destina- An IS should forward a multicast PDU containing a particular
tion group Network address onto a subnetwork to which it is attached destination group Network address onto a subnetwork to which it is
if and only if one or more of the ESs attached to that subnetwork attached if and only if one or more of the ESs attached to that
have declared an interest in receiving multicast PDUs destined for subnetwork have declared an interest in receiving multicast PDUs
that group Network address. Multicast announcement information destined for that group Network address. Multicast announcement
enables an IS that supports CLNP multicast to dynamically discover, information enables an IS that supports CLNP multicast to dynamically
for each subnetwork to which it is attached, the group Network discover, for each subnetwork to which it is attached, the group
addresses for which ESs attached to that subnetwork have declared an Network addresses for which ESs attached to that subnetwork have
interest. declared an interest.
On a point-to-point subnetwork the multicast announcement information On a point-to-point subnetwork the multicast announcement information
informs the Network entity, in the case where it is attached to an informs the Network entity, in the case where it is attached to an
End System, of the group Network addresses for which that End System End System, of the group Network addresses for which that End System
expects to receive multicast PDUs. expects to receive multicast PDUs.
On a broadcast subnetwork the multicast announcement information On a broadcast subnetwork the multicast announcement information
informs the multicast capable Intermediate Systems, of the group Net- informs the multicast capable Intermediate Systems, of the group
work addresses for which ESs attached to that subnetwork expect to Network addresses for which ESs attached to that subnetwork expect to
receive multicast PDUs. receive multicast PDUs.
Note: Intermediate Systems with the optional OSI multicast capabili- Note: Intermediate Systems with the optional OSI multicast
ties do receive information identifying the SNPA address of ESs on capabilities do receive information identifying the SNPA address of
the broadcast network that want PDUs with particular group Network ESs on the broadcast network that want PDUs with particular group
addresses as their destination address; however, the critical Network addresses as their destination address; however, the critical
information is which multicast PDUs are needed, not which ESs need information is which multicast PDUs are needed, not which ESs need
them. them.
6.3.2 Multicast Address Mapping Information 6.3.2 Multicast Address Mapping Information
In order to receive multicast packets destined for a particular group In order to receive multicast packets destined for a particular group
Network address, an ES may need to associate with the group Network Network address, an ES may need to associate with the group Network
address a specific SNPA address. Multicast address mapping informa- address a specific SNPA address. Multicast address mapping
tion enables an IS to inform ESs that they can receive multicast information enables an IS to inform ESs that they can receive
packets destined for a particular group Network address on a multicast packets destined for a particular group Network address on
corresponding specific SNPA address. In addition, multicast address a corresponding specific SNPA address. In addition, multicast
mapping information may provide the specific destination SNPA address mapping information may provide the specific destination SNPA
addresses needed by an ES for originating multicast packets. addresses needed by an ES for originating multicast packets.
Multicast address mapping information is not employed on point-to- Multicast address mapping information is not employed on point-to-
point subnetworks. point subnetworks.
Multicast address mapping information is employed on broadcast sub- Multicast address mapping information is employed on broadcast sub-
networks to enable multicast capable Intermediate Systems to inform networks to enable multicast capable Intermediate Systems to inform
the multicast capable End Systems that they can receive, on a the multicast capable End Systems that they can receive, on a
specific broadcast subnetwork, multicast packets destined for a par- specific broadcast subnetwork, multicast packets destined for a
ticular group Network address on a corresponding specific SNPA particular group Network address on a corresponding specific SNPA
address. In addition multicast address mapping information provides address. In addition multicast address mapping information provides
the specific destination SNPA address, that corresponds to a particu- the specific destination SNPA address, that corresponds to a
lar group Network address, for each multicast packet that it ori- particular group Network address, for each multicast packet that it
ginates on a specific broadcast subnetwork. originates on a specific broadcast subnetwork.
6.4 Addresses 6.4 Addresses
All exchanges using this protocol are accomplished over a single sub- All exchanges using this protocol are accomplished over a single
network. While the control PDU's contain Network addresses (i.e. subnetwork. While the control PDU's contain Network addresses (i.e.,
group Network addresses) actual control PDU transfer is accomplished group Network addresses) actual control PDU transfer is accomplished
via Subnetwork based group addresses (i.e. group SNPA addresses). The via Subnetwork based group addresses (i.e., group SNPA addresses).
following group SNPA addresses are used: (1)All Multicast Capable End The following group SNPA addresses are used: (1)All Multicast Capable
Systems; (2)All Multicast Announcements; (3)All Multicast Capable End Systems; (2)All Multicast Announcements; (3)All Multicast Capable
Intermediate Systems and (4)a group SNPA address corresponding to a Intermediate Systems and (4)a group SNPA address corresponding to a
group Network address group Network address
6.5 Timers 6.5 Timers
Two additional timers are employed: (1)the Multicast Announcement Two additional timers are employed: (1)the Multicast Announcement
Timer (MAT) and (2)Multicast Address Mapping Timer (MAMT). Old multi- Timer (MAT) and (2)Multicast Address Mapping Timer (MAMT). Old
cast announcement or multicast address mapping information shall be multicast announcement or multicast address mapping information shall
discarded after the Holding Timer expires to ensure the correct be discarded after the Holding Timer expires to ensure the correct
operation of the protocol. operation of the protocol.
6.5.1 Multicast Announcement Timer 6.5.1 Multicast Announcement Timer
The Multicast Announcement Timer is a local timer (i.e. maintained The Multicast Announcement Timer is a local timer (i.e., maintained
independently by each End System, one timer per group Network independently by each End System, one timer per group Network
address) which assists in performing the Report Multicast Announce- address) which assists in performing the Report Multicast
ment function. The timer determines how often an End System reports Announcement function. The timer determines how often an End System
its desire to receive multicast PDUs with that group Network address reports its desire to receive multicast PDUs with that group Network
as its destination address parameter. Considerations in setting this address as its destination address parameter. Considerations in
timer are similar to those described for the Configuration timer in setting this timer are similar to those described for the
the ES-IS specification. Configuration timer in the ES-IS specification.
6.5.2 Multicast Address Mapping Timer 6.5.2 Multicast Address Mapping Timer
The Multicast Address Mapping Timer is a local timer (i.e. maintained The Multicast Address Mapping Timer is a local timer (i.e.,
independently by an Intermediate System which is actively participat- maintained independently by an Intermediate System which is actively
ing with End Systems to transfer multicast PDUs) which assists in participating with End Systems to transfer multicast PDUs) which
performing the Report Multicast Address Mapping function. The timer assists in performing the Report Multicast Address Mapping function.
determines how often an Intermediate System, actively participating The timer determines how often an Intermediate System, actively
with End Systems for the transfer of multicast PDUs, reports the Mul- participating with End Systems for the transfer of multicast PDUs,
ticast Address Mapping for a particular group Network address. The reports the Multicast Address Mapping for a particular group Network
shorter the Multicast Address Mapping Timer, the more quickly End address. The shorter the Multicast Address Mapping Timer, the more
Systems on the subnetwork will become aware of the correct address quickly End Systems on the subnetwork will become aware of the
mapping which may change due to the Intermediate System becoming correct address mapping which may change due to the Intermediate
available or unavailable. There is a trade off between increased System becoming available or unavailable. There is a trade off
responsiveness and increased use of resources in the subnetwork and between increased responsiveness and increased use of resources in
in the End Systems. the subnetwork and in the End Systems.
6.6 Extensions to the current protocol functions 6.6 Extensions to the current protocol functions
In order to support multicast transmissions the following optional In order to support multicast transmissions the following optional
ES-IS protocol functions will be implemented: ES-IS protocol functions will be implemented:
6.6.1 Report Configuration by Intermediate Systems 6.6.1 Report Configuration by Intermediate Systems
All multicast capable Intermediate Systems on a subnetwork will use All multicast capable Intermediate Systems on a subnetwork shall use
the Multicast Capable option in all ISH PDUs that they originate. the Multicast Capable option in all ISH PDUs that they originate.
This will provide multicast capable End Systems with a way to deter- This will provide multicast capable End Systems with a way to
mine that a multicast capable Intermediate System is operating on a determine that a multicast capable Intermediate System is operating
particular subnetwork. on a particular subnetwork.
6.6.2 Query Configuration 6.6.2 Query Configuration
Note: The Query Configuration function cannot be performed to find Note: The Query Configuration function cannot be performed to find
the corresponding SNPA address of a group Network address since the the corresponding SNPA address of a group Network address since the
addressing information needed is the corresponding group SNPA address addressing information needed is the corresponding group SNPA address
and not the SNPA address of a particular End System responding. On a and not the SNPA address of a particular End System responding. On a
large broadcast subnetwork, many different Configuration Responses large broadcast subnetwork, many different Configuration Responses
could result each incorporating a different End System Address. While could result each incorporating a different End System Address. While
it is possible to design a Query Configuration for use with multi- it is possible to design a Query Configuration for use with
cast, this function does not appear to be required given the use of multicast, this function does not appear to be required given the use
the "All Multicast Capable End Systems" address for supplying a SNPA of the "All Multicast Capable End Systems" address for supplying a
address when the group SNPA address is not known. SNPA address when the group SNPA address is not known.
6.7 Multicast Announcement 6.7 Multicast Announcement
6.7.1 Report Multicast Announcement Function by End Systems 6.7.1 Report Multicast Announcement Function by End Systems
An End System which needs to receive or continue to receive any mul- An End System which needs to receive or continue to receive any
ticast PDUs (i.e. PDUs with group Network addresses as their destina- multicast PDUs (i.e., PDUs with group Network addresses as their
tion address), constructs and transmits ESGH PDUs to inform multicast destination address), constructs and transmits ESGH PDUs to inform
capable Intermediate Systems of the set of group Network address des- multicast capable Intermediate Systems of the set of group Network
tinations for which it wishes to receive PDUs. This may be done by address destinations for which it wishes to receive PDUs. This may be
constructing ESGH PDUs for each group Network address. Alternatively, done by constructing ESGH PDUs for each group Network address.
ESGH PDUs may be constructed which convey information about more than Alternatively, ESGH PDUs may be constructed which convey information
one group Network address at a time, up to the limits imposed by the about more than one group Network address at a time, up to the limits
permitted SNSDU size and the maximum header size of the ESGH PDU. imposed by the permitted SNSDU size and the maximum header size of
Each ESGH PDU is transmitted by issuing an SN-UNITDATA.Request with the ESGH PDU. Each ESGH PDU is transmitted by issuing an SN-
the following parameters: UNITDATA.Request with the following parameters:
SN_Userdata (SNSDU) <- ESGH PDU SN_Userdata (SNSDU) <- ESGH PDU
SN_Destination _Address <- multi-destination address that indicates SN_Destination _Address <- multi-destination address that indicates
"All Multicast Announcements" "All Multicast Announcements"
If an End System is attached to more than one subnetwork, the infor- If an End System is attached to more than one subnetwork, the
mation about each group Network address desired for receiving on a information about each group Network address desired for receiving on
particular subnetwork serving the End System shall be transmitted via a particular subnetwork serving the End System shall be transmitted
that subnetwork. It is permissible for an End System to report group via that subnetwork. It is permissible for an End System to report
Network addresses on multiple subnetworks; however, duplicate multi- group Network addresses on multiple subnetworks; however, duplicate
cast PDUs should be anticipated. multicast PDUs should be anticipated.
The Group Address Pair parameter carries a list of Group Network The Group Address Pair parameter carries a list of Group Network
Addresses, each paired with its associated SNPA address. This infor- Addresses, each paired with its associated SNPA address. This
mation is used by the Active Multicast IS to determine whether a Mul- information is used by the Active Multicast IS to determine whether a
ticast Address Mapping PDU should be emitted to update the associa- Multicast Address Mapping PDU should be emitted to update the
tion between Group Network Addresses and SNPA addresses. association between Group Network Addresses and SNPA addresses.
The Holding Time (HT) field is set to approximately twice the ES's The Holding Time (HT) field is set to approximately twice the ES's
Multicast Announcement Timer (MAT) parameter. The value shall be Multicast Announcement Timer (MAT) parameter. The value shall be
large enough so that even if every other ESGH PDU is discarded (due large enough so that even if every other ESGH PDU is discarded (due
to lack of resources), or otherwise lost in the subnetwork, the mul- to lack of resources), or otherwise lost in the subnetwork, the
ticast announcement information will still be maintained. The value multicast announcement information will still be maintained. The
should be set small enough so that Intermediate Systems resources are value should be set small enough so that Intermediate Systems
not needlessly consumed when the ES no longer wishes to receive PDUs resources are not needlessly consumed when the ES no longer wishes to
destined to a group Network address. receive PDUs destined to a group Network address.
Note: -- When combining multiple group Network addresses in a single Note: When combining multiple group Network addresses in a single
ESGH PDU, it should be realized that there is a single Holding Time ESGH PDU, it should be realized that there is a single Holding Time
parameter associated with all of these addresses. parameter associated with all of these addresses.
6.7.1.1 Generating Jitter on Multicast Announcement Timers 6.7.1.1 Generating Jitter on Multicast Announcement Timers
The ES shall apply a 25% jitter to its Multicast Announcement Timer The ES shall apply a 25% jitter to its Multicast Announcement Timer
(MAT) parameter. When ESGH PDUs are transmitted as a result of timer (MAT) parameter. When ESGH PDUs are transmitted as a result of timer
expiration, there is a danger that the timers of individual systems expiration, there is a danger that the timers of individual systems
may become synchronised. The result of this is that the traffic dis- may become synchronised. The result of this is that the traffic
tribution will contain peaks. Where there are a large number of syn- distribution will contain peaks. Where there are a large number of
chronised systems, this can cause overloading of both the transmis- synchronised systems, this can cause overloading of both the
sion medium and the systems receiving the PDUs. In order to prevent transmission medium and the systems receiving the PDUs. In order to
this from occurring, all periodic timers, the expiration of which can prevent this from occurring, all periodic timers, the expiration of
cause the transmission of PDUs, shall have "jitter" introduced as which can cause the transmission of PDUs, shall have "jitter"
defined in the following algorithm. introduced as defined in the following algorithm.
CONSTANT CONSTANT
Jitter = 25; Jitter = 25;
Resolution = 100; Resolution = 100;
(* The timer resolution in ms *) (* The timer resolution in ms *)
PROCEDURE Random(max: Integer): Integer; PROCEDURE Random(max: Integer): Integer;
(* This procedure delivers a Uniformly distributed random (* This procedure delivers a Uniformly distributed random
integer R such that 0 < R <max *) integer R such that 0 < R <max *)
PROCEDURE WaitUntil(time: Integer) PROCEDURE WaitUntil(time: Integer)
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expirationAction; expirationAction;
WaitUntil(nextexpiration); WaitUntil(nextexpiration);
END (* of Loop *) END (* of Loop *)
END (* of DefineJitteredTimer *) END (* of DefineJitteredTimer *)
Thus the call "DefineJitteredTimer(HelloTime, SendHelloPDU);" where Thus the call "DefineJitteredTimer(HelloTime, SendHelloPDU);" where
"HelloTime" is 10 seconds, will cause the action "SendHelloPDU" to be "HelloTime" is 10 seconds, will cause the action "SendHelloPDU" to be
performed at random intervals of between 7.5 and 10 seconds. The performed at random intervals of between 7.5 and 10 seconds. The
essential point of this algorithm is that the value of "randomTimeMo- essential point of this algorithm is that the value of
difier" is randomised within the inner loop. Note that the new "randomTimeModifier" is randomised within the inner loop. Note that
expiration time is set immediately on expiration of the last inter- the new expiration time is set immediately on expiration of the last
val, rather than when the expiration action has been completed. interval, rather than when the expiration action has been completed.
The time resolution shall be less than or equal to 100 ms. It is The time resolution shall be less than or equal to 100 ms. It is
recommended to be less than or equal to 10ms. The time resolution is recommended to be less than or equal to 10ms. The time resolution is
the maximum interval than can elapse without there being any change the maximum interval than can elapse without there being any change
in the value of the timer. The periodic transmission period shall be in the value of the timer. The periodic transmission period shall be
random or pseudo-random in the specified range. with uniform distri- random or pseudo-random in the specified range. with uniform
bution across similar implementations. distribution across similar implementations.
(Note: -- Applying jitter to the MAT parameter is required in order Note: Applying jitter to the MAT parameter is required in order to
to support the optional Damping function. If no jitter is applied on support the optional Damping function. If no jitter is applied on a
a subnetwork where many ESs are requesting a particular multicast PDU subnetwork where many ESs are requesting a particular multicast PDU
it is likely that they will have the same value for their MAT and it is likely that they will have the same value for their MAT and
these timers may all become synchronised. Such synchronisation will these timers may all become synchronised. Such synchronisation will
result in peaks in the distribution of traffic as described above. result in peaks in the distribution of traffic as described above.
The resulting overloading of the transmission medium and the systems The resulting overloading of the transmission medium and the systems
receiving the PDUs will negate any beneficial use of the Damping receiving the PDUs will negate any beneficial use of the Damping
function (since systems may be attempting to transmit their own ESGH function (since systems may be attempting to transmit their own ESGH
PDUs at the time they receive ESGH PDUs originated by other ESs with PDUs at the time they receive ESGH PDUs originated by other ESs with
the same group Network address). the same group Network address.
6.7.2 Record Multicast Announcement Function 6.7.2 Record Multicast Announcement Function
The Record Multicast Announcement function receives ESGH PDUs, The Record Multicast Announcement function receives ESGH PDUs,
extracts the multicast announcement information and updates the extracts the multicast announcement information and updates the
information in its routing information base. information in its routing information base.
The receiving system is not required to process any option fields in The receiving system is not required to process any option fields in
a received ESGH PDU. a received ESGH PDU.
Note: -- When a system chooses to process these optional fields, the Note: When a system chooses to process these optional fields, the
precise actions are not specified by this International Standard. precise actions are not specified by this International Standard.
6.7.2.1 Record Multicast Announcement Function by Intermediate Systems 6.7.2.1 Record Multicast Announcement Function by Intermediate Systems
On receipt of an ESGH PDU an IS with the optional multicast capabili- On receipt of an ESGH PDU an IS with the optional multicast
ties extracts the configuration information and stores the {group capabilities extracts the configuration information and stores the
Network address, subnetwork} in its routing information base replac- {group Network address, subnetwork} in its routing information base
ing any other information for the same entry. replacing any other information for the same entry.
The Active Multicast IS upon receipt of an ESGH PDU also extracts the The Active Multicast IS upon receipt of an ESGH PDU also extracts the
Paired SNPA Address parameter corresponding to each group Network Paired SNPA Address parameter corresponding to each group Network
address in the ESGH PDU. If the Active Multicast IS has a mapping for address in the ESGH PDU. If the Active Multicast IS has a mapping for
a group Network address carried in the ESGH for which the paired SNPA a group Network address carried in the ESGH for which the paired SNPA
address does not match, the Report Multicast Address Mapping function address does not match, the Report Multicast Address Mapping function
is performed. is performed.
6.7.2.2 Optional Damping Function 6.7.2.2 Optional Damping Function
An ES with the optional capabilities to support multicast transfer An ES with the optional capabilities to support multicast transfer
may decide to process ESGH PDUs multicast by other End Systems. There may decide to process ESGH PDUs multicast by other End Systems. There
is potentially some reduction in network traffic by doing this. An ES is potentially some reduction in network traffic by doing this. An ES
requesting to receive multicast PDUs is permitted to reset its Multi- requesting to receive multicast PDUs is permitted to reset its
cast Announcement Timer corresponding to one group Network address on Multicast Announcement Timer corresponding to one group Network
one subnetwork upon receiving an ESGH PDU from another ES under the address on one subnetwork upon receiving an ESGH PDU from another ES
following circumstances: under the following circumstances:
a) The {group Network address, paired SNPA address} received on a a) The {group Network address, paired SNPA address} received on a
particular subnetwork matches that of the ES processing the ESGH particular subnetwork matches that of the ES processing the ESGH
PDU for that subnetwork. PDU for that subnetwork.
b) The Holding Timer parameter value in the ESGH PDU received is b) The Holding Timer parameter value in the ESGH PDU received is
equal to or greater than the Holding Timer value for the, group equal to or greater than the Holding Timer value for the, group
Network address, being used by the ES processing this PDU. Network address, being used by the ES processing this PDU.
6.7.3 Flush Old Multicast Announcement Function 6.7.3 Flush Old Multicast Announcement Function
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6.8.1 Report Multicast Address Mapping Function by Intermediate Systems 6.8.1 Report Multicast Address Mapping Function by Intermediate Systems
The Active Multicast Intermediate System constructs a MAM PDU, The Active Multicast Intermediate System constructs a MAM PDU,
corresponding to a group Network address for which it received via corresponding to a group Network address for which it received via
the Record Multicast Announcement function, and issues these PDUs the Record Multicast Announcement function, and issues these PDUs
under the following circumstances: under the following circumstances:
a) The IS initializes either as the Active Multicast IS after an a) The IS initializes either as the Active Multicast IS after an
election with other multicast capable ISs or initializes after election with other multicast capable ISs or initializes after
determining it is the only multicast capable IS (the determina- determining it is the only multicast capable IS (the
tion of such conditions are outside of the scope of this stan- determination of such conditions are outside of the scope of
dard), or this standard), or
b) The IS receives an ESGH PDU with a group Network address paired b) The IS receives an ESGH PDU with a group Network address paired
to an SNPA address other than the SNPA address contained in the to an SNPA address other than the SNPA address contained in the
Active Multicast IS's multicast address mapping information for Active Multicast IS's multicast address mapping information for
that group Network address, or that group Network address, or
Note: -- The Active Multicast IS determines which mappings are Note: The Active Multicast IS determines which mappings are correct.
correct. Pre-configured mappings which are used prior to the initial- Pre-configured mappings which are used prior to the initialization of
ization of the Active Multicast IS may be determined to be incorrect the Active Multicast IS may be determined to be incorrect by the
by the Active Multicast IS. Active Multicast IS.
c) The expiration of the IS's Multicast Address Mapping Timer for c) The expiration of the IS's Multicast Address Mapping Timer for
that group Network address. that group Network address.
Note: -- This is to prevent the expiration of Holding Timers in ESs. Note: This is to prevent the expiration of Holding Timers in ESs.
d) The IS receives a multicast PDU originated on the subnetwork d) The IS receives a multicast PDU originated on the subnetwork
which used an incorrect destination SNPA address. which used an incorrect destination SNPA address.
Note: Of particular concern are those multicast packets using the Note: Of particular concern are those multicast packets using the
"All Multicast Capable Intermediate Systems" SNPA address when "All Multicast Capable Intermediate Systems" SNPA address when
another SNPA address should have been used. The Originating Subnet- another SNPA address should have been used. The Originating
work Forwarding function is performed if this event occurs (see sec- Subnetwork Forwarding function is performed if this event occurs (see
tion 6.11). section 6.11).
Note: The multicast capable ISs need to receive multicast packets on Note: The multicast capable ISs need to receive multicast packets on
all SNPA addresses that are contained in the current multicast all SNPA addresses that are contained in the current multicast
address mapping information for the subnetwork. The multicast capa- address mapping information for the subnetwork. The multicast
ble ISs are not required to receive multicast packets on any SNPA capable ISs are not required to receive multicast packets on any SNPA
addresses other than those contained in the current multicast address addresses other than those contained in the current multicast address
mapping information and the "All Multicast Capable Intermediate Sys- mapping information and the "All Multicast Capable Intermediate
tems" SNPA address. Systems" SNPA address.
Circumstances b) and d) are the event driven conditions for the Circumstances b) and d) are the event driven conditions for the
Active Multicast IS to construct and issue a MAM PDU. The Active Active Multicast IS to construct and issue a MAM PDU. The Active
Multicast IS shall limit the number of MAM PDUs issued per unit of Multicast IS shall limit the number of MAM PDUs issued per unit of
time. MAM PDUs with identical information shall not be issued more time. MAM PDUs with identical information shall not be issued more
than once per second. Event conditions occurring 10 seconds after than once per second. Event conditions occurring 10 seconds after
the last issue of an appropriate MAM PDU shall result in the issuance the last issue of an appropriate MAM PDU shall result in the issuance
of another such MAM PDU. of another such MAM PDU.
The IS serving as the Active Multicast Intermediate System may con- The IS serving as the Active Multicast Intermediate System may
struct a MAM PDU for each group Network address. Alternatively, MAM construct a MAM PDU for each group Network address. Alternatively,
PDUs may be constructed which convey information about more than one MAM PDUs may be constructed which convey information about more than
group Network address at a time, up to the limits imposed by the per- one group Network address at a time, up to the limits imposed by the
mitted SNSDU size and the maximum header size of the MAM PDU. The IS permitted SNSDU size and the maximum header size of the MAM PDU. The
performs all multicast address mapping functions independently for IS performs all multicast address mapping functions independently for
each of its subnetworks even if this IS is the Active Multicast IS on each of its subnetworks even if this IS is the Active Multicast IS on
multiple subnetworks. Each MAM PDU is transmitted by issuing an SN- multiple subnetworks. Each MAM PDU is transmitted by issuing an SN-
UNITDATA.Request with the following parameters: UNITDATA.Request with the following parameters:
SN_Userdata (SNSDU) <- MAM PDU SN_Userdata (SNSDU) <- MAM PDU
SN_Destination _Address <- multi-destination address that indicates SN_Destination _Address <- multi-destination address that indicates
"All Multicast Capable End Systems" "All Multicast Capable End Systems"
The Holding Time (HT) field is set to approximately twice the The Holding Time (HT) field is set to approximately twice the
Intermediate System's Multicast Address Mapping Timer (MAMT) parame- Intermediate System's Multicast Address Mapping Timer (MAMT)
ter. This variable shall be set to a value large enough so that even parameter. This variable shall be set to a value large enough so
if every other MAM PDU, for a particular group Network address, is that even if every other MAM PDU, for a particular group Network
discarded (due to lack of resources), or otherwise lost in the sub- address, is discarded (due to lack of resources), or otherwise lost
network, the multicast address mapping information will still be in the subnetwork, the multicast address mapping information will
maintained. The value should be set small enough so that End Systems still be maintained. The value should be set small enough so that End
will quickly cease to use the multicast address mappings supplied by Systems will quickly cease to use the multicast address mappings
ISs that have failed. supplied by ISs that have failed.
Note: -- The Holding Timer parameter value applies to all group Net- Note: -- The Holding Timer parameter value applies to all group
work addresses called out in the MAM PDU. Network addresses called out in the MAM PDU.
The Group Address Pair parameter is used to convey the association The Group Address Pair parameter is used to convey the association
between Group Network Addresses and SNPA addresses. between Group Network Addresses and SNPA addresses.
Optionally, the Active Multicast IS may include information in the Optionally, the Active Multicast IS may include information in the
MAM PDU indicating a larger population of group Network addresses to MAM PDU indicating a larger population of group Network addresses to
which the same multicast address mapping information applies. There which the same multicast address mapping information applies. There
are two optional fields for this purpose: the Group Network Address are two optional fields for this purpose: the Group Network Address
Mask option and the Paired SNPA Address Mask option. Mask option and the Paired SNPA Address Mask option.
skipping to change at page 25, line 47 skipping to change at page 28, line 7
mapped to the same SNPA address. mapped to the same SNPA address.
In the third case, the MAM PDU contains both masks. As in the second In the third case, the MAM PDU contains both masks. As in the second
case, the MAM PDU conveys information about an equivalence class of case, the MAM PDU conveys information about an equivalence class of
group Network addresses. But in this case, the information reveals group Network addresses. But in this case, the information reveals
that the SNPA addresses for the equivalence class of group Network that the SNPA addresses for the equivalence class of group Network
address are embedded in the group Network address. In particular the address are embedded in the group Network address. In particular the
Paired SNPA Address Mask indicates the location of the SNPA address Paired SNPA Address Mask indicates the location of the SNPA address
in the group Network Address(es). in the group Network Address(es).
The Active Multicast IS shall construct a MAM PDU with direct infor- The Active Multicast IS shall construct a MAM PDU with direct
mation, not needing analysis of the Mask parameters, in response to information, not needing analysis of the Mask parameters, in response
the occurrence of an event driven condition. The Active Multicast IS to the occurrence of an event driven condition. The Active Multicast
may provide additional information in such a MAM PDU via the use of IS may provide additional information in such a MAM PDU via the use
Mask parameters. of Mask parameters.
An IS may suggest a value for End Systems on the local subnetwork to An IS may suggest a value for End Systems on the local subnetwork to
use as their Multicast Announcement Timers, for a specific group Net- use as their Multicast Announcement Timers, for a specific group
work address, by including the Suggested ES Multicast Announcement Network address, by including the Suggested ES Multicast Announcement
Timer (ESMAT) parameter in the transmitted MAM PDU. Setting this Timer (ESMAT) parameter in the transmitted MAM PDU. Setting this
parameter permits the Active Multicast IS to influence the frequency parameter permits the Active Multicast IS to influence the frequency
with which ESs transmit ESGH PDUs. with which ESs transmit ESGH PDUs.
Note: -- If the ESMAT parameter is used, the one value permitted in Note: If the ESMAT parameter is used, the one value permitted in the
the MAM PDU is suggested for all group Network addresses called out MAM PDU is suggested for all group Network addresses called out in
in the MAM PDU. the MAM PDU.
6.8.2 Record Multicast Address Mapping Function by End Systems 6.8.2 Record Multicast Address Mapping Function by End Systems
The Record Multicast Address Mapping function receives MAM PDUs, The Record Multicast Address Mapping function receives MAM PDUs,
extracts the multicast address mapping information and updates the extracts the multicast address mapping information and updates the
information in its routing information base. The receiving system is information in its routing information base. The receiving system is
not required to process any option fields in a received MAM PDU with not required to process any option fields in a received MAM PDU with
the exception of the Suggested ES Multicast Announcement Timer the exception of the Suggested ES Multicast Announcement Timer
(ESMAT) parameter. (ESMAT) parameter.
Note: -- When a system chooses to process these optional fields, the Note: When a system chooses to process these optional fields, the
precise actions are not specified by this International Standard. precise actions are not specified by this International Standard.
On receipt of a MAM PDU an ES with the optional multicast capabili- On receipt of a MAM PDU an ES with the optional multicast
ties extracts the multicast address mapping information and stores capabilities extracts the multicast address mapping information and
the {group Network address, paired SNPA address} for a particular stores the {group Network address, paired SNPA address} for a
subnetwork in its routing information base replacing any other infor- particular subnetwork in its routing information base replacing any
mation for the same group Network address and subnetwork. other information for the same group Network address and subnetwork.
In addition, an ES shall set its Multicast Announcement Timer, In addition, an ES shall set its Multicast Announcement Timer,
corresponding to the group Network address for which it is performing corresponding to the group Network address for which it is performing
the Record Multicast Address Mapping function, based on receipt of a the Record Multicast Address Mapping function, based on receipt of a
MAM PDU, corresponding to that group Network address, containing an MAM PDU, corresponding to that group Network address, containing an
ESMAT parameter. ESMAT parameter.
Note: -- While an ES may process ESGH PDUs multicast by other ESs to Note: While an ES may process ESGH PDUs multicast by other ESs to
support the optional Damping function, an ES is not permitted to support the optional Damping function, an ES is not permitted to
change its own mapping due to the mapping found in other ES's ESGH change its own mapping due to the mapping found in other ES's ESGH
PDUs. PDUs.
6.8.3 Flush Old Multicast Address Mapping Function by End Systems 6.8.3 Flush Old Multicast Address Mapping Function by End Systems
The Flush Old Multicast Address Mapping function is executed to The Flush Old Multicast Address Mapping function is executed to
remove multicast address mapping entries in its routing information remove multicast address mapping entries in its routing information
base whose corresponding Holding Timer has expired. When such a Hold- base whose corresponding Holding Timer has expired. When such a
ing Timer for a multicast address mapping expires, this function Holding Timer for a multicast address mapping expires, this function
removes the corresponding entry from its routing information base for removes the corresponding entry from its routing information base for
the corresponding SNPA. the corresponding SNPA.
6.9 Paired SNPA Address Selection Function by End Systems 6.9 Paired SNPA Address Selection Function by End Systems
An End System shall pair each group Network address with an associ- An End System shall pair each group Network address with an
ated SNPA address to support receiving (e.g. performing the Report associated SNPA address to support receiving (e.g., performing the
Multicast Announcement function) and originating multicast PDUs. Report Multicast Announcement function) and originating multicast
PDUs.
6.9.1 Paired SNPA Address Selection for Receiving Multicast PDUs 6.9.1 Paired SNPA Address Selection for Receiving Multicast PDUs
An End System always has a paired SNPA address for every active group An End System always has a paired SNPA address for every active group
Network address on a particular subnetwork. This mapping is obtained Network address on a particular subnetwork. This mapping is obtained
by: by:
a) recording a multicast address mapping which is maintaining an a) recording a multicast address mapping which is maintaining an
active holding timer, or if there has been no dynamic informa- active holding timer, or if there has been no dynamic
tion received, by information received, by
b) having pre-configured multicast address mapping information, or b) having pre-configured multicast address mapping information, or
if neither dynamic nor pre-configured information is available, if neither dynamic nor pre-configured information is available,
by by
c) mapping the "All Multicast Capable End Systems" multi- c) mapping the "All Multicast Capable End Systems" multi-
destination address to the group Network address. destination address to the group Network address.
6.9.2 Paired SNPA Address Selection for Originating Multicast PDUs 6.9.2 Paired SNPA Address Selection for Originating Multicast PDUs
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tems" multi-destination address, or if there is no multicast tems" multi-destination address, or if there is no multicast
capable Intermediate System on the subnetwork, by capable Intermediate System on the subnetwork, by
Note: Multicast address mapping information is valid if the Holding Note: Multicast address mapping information is valid if the Holding
Timer associated with it has not expired. Timer associated with it has not expired.
Note: An ES can determine if a multicast capable IS is reachable on Note: An ES can determine if a multicast capable IS is reachable on
the subnetwork by having for that subnetwork either (1)multicast the subnetwork by having for that subnetwork either (1)multicast
address mapping information or (2)routing information received via an address mapping information or (2)routing information received via an
ISH PDU containing a Multicast Capable optional parameter. In either ISH PDU containing a Multicast Capable optional parameter. In either
case the information must be valid (i.e. the Holding Timer for the case the information must be valid (i.e., the Holding Timer for the
information must not have expired). information must not have expired).
b) having pre-configured multicast address mapping information, or b) having pre-configured multicast address mapping information, or
if neither a multicast capable Intermediate System is present on if neither a multicast capable Intermediate System is present on
the subnetwork nor pre-configured information is available, by the subnetwork nor pre-configured information is available, by
c) mapping the "All Multicast Capable End Systems" multi- c) mapping the "All Multicast Capable End Systems" multi-
destination address to the group Network address. destination address to the group Network address.
6.10 Extensions to the ISO CLNP Route Function by End Systems 6.10 Extensions to the ISO CLNP Route Function by End Systems
An End System attached to more than one subnetwork shall determine An End System attached to more than one subnetwork shall determine
when originating a multicast PDU whether to forward this multicast when originating a multicast PDU whether to forward this multicast
PDU to more than one subnetwork or not. End Systems shall originate PDU to more than one subnetwork or not. End Systems shall originate
each multicast PDU on all subnetworks for which the ISO ES-IS Confi- each multicast PDU on all subnetworks for which the ISO ES-IS
guration function is actively reporting the NSAP address contained in Configuration function is actively reporting the NSAP address
the Source Address parameter of the multicast PDU. As a result of contained in the Source Address parameter of the multicast PDU. As a
this function multiple invocations of the ISO CLNP Forwarding func- result of this function multiple invocations of the ISO CLNP
tion may result when such an ES originates a multicast PDU. Forwarding function may result when such an ES originates a multicast
PDU.
6.11 Originating Subnetwork Forwarding Function by Intermediate Sys- 6.11 Originating Subnetwork Forwarding Function by Intermediate
tems Systems
The Active Multicast IS upon receiving a multicast PDU originated on The Active Multicast IS upon receiving a multicast PDU originated on
a subnetwork which used the "All Multicast Capable Intermediate Sys- a subnetwork which used the "All Multicast Capable Intermediate
tems" SNPA address when another SNPA address should have been used, Systems" SNPA address when another SNPA address should have been
performs the Originating Subnetwork Forwarding function. The multi- used, performs the Originating Subnetwork Forwarding function. The
cast address mapping information defines the correct SNPA address multicast address mapping information defines the correct SNPA
pairings for a given subnetwork. The Originating Subnetwork Forward- address pairings for a given subnetwork. The Originating Subnetwork
ing function forwards the multicast PDU back on subnetwork it was Forwarding function forwards the multicast PDU back on subnetwork it
originated on. In the case that the ES was attached to more than one was originated on. In the case that the ES was attached to more than
subnetwork and originated the multicast PDU on more than one subnet- one subnetwork and originated the multicast PDU on more than one
work, the Active Multicast IS for each subnetwork performs the Ori- subnetwork, the Active Multicast IS for each subnetwork performs the
ginating Subnetwork Forwarding function for the subnetwork that they Originating Subnetwork Forwarding function for the subnetwork that
are responsible for. they are responsible for.
The Active Multicast IS obtains the contents for the multicast PDU The Active Multicast IS obtains the contents for the multicast PDU
for the Originating Subnetwork Forwarding function by using the con- for the Originating Subnetwork Forwarding function by using the
tents of the multicast PDU received with the incorrect destination contents of the multicast PDU received with the incorrect destination
SNPA address and replacing the original PDU Lifetime field with the SNPA address and replacing the original PDU Lifetime field with the
value one (0000 0001). The Active Multicast IS performs the ISO 8473 value one (0000 0001). The Active Multicast IS performs the ISO 8473
PDU Composition function and forwards the PDU to the subnetwork that PDU Composition function and forwards the PDU to the subnetwork that
the PDU was originated on using the ISO 8473 Forwarding function with the PDU was originated on using the ISO 8473 Forwarding function with
the correct destination SNPA address. the correct destination SNPA address.
Note: The PDU Lifetime field is set to "one" to ensure that ISs Note: The PDU Lifetime field is set to "one" to ensure that ISs
attached to the originating subnetwork do not forward this PDU on. attached to the originating subnetwork do not forward this PDU on.
Such ISs should have received the PDU when it was originated since Such ISs should have received the PDU when it was originated since
this function is only performed in the event of receiving a multicast this function is only performed in the event of receiving a multicast
PDU incorrectly addressed to the "All Multicast Capable Intermediate PDU incorrectly addressed to the "All Multicast Capable Intermediate
Systems" SNPA address. Systems" SNPA address.
6.12 Structure and Encoding of PDUs 6.12 Structure and Encoding of PDUs
The ES-IS multicast control functions are supported via the exchange The ES-IS multicast control functions are supported via the exchange
of ESGH and MAM PDUs. The one exception to this is that a new of ESGH and MAM PDUs. The one exception to this is that a new
skipping to change at page 30, line 7 skipping to change at page 31, line 45
Network entity to retain the multicast announcement or multicast Network entity to retain the multicast announcement or multicast
address mapping information contained in the PDU. address mapping information contained in the PDU.
6.12.3 Structure of Addressing Parameters 6.12.3 Structure of Addressing Parameters
The ESGH and MAM PDUs carry one or more group Network addresses The ESGH and MAM PDUs carry one or more group Network addresses
(GNAs) each with their associated Paired SNPA Address (PSA). (GNAs) each with their associated Paired SNPA Address (PSA).
6.12.4 Group Address Pair Parameter for ESGH and MAM PDUs 6.12.4 Group Address Pair Parameter for ESGH and MAM PDUs
The Group Address Pair parameter is a list of one or more group Net- The Group Address Pair parameter is a list of one or more group
work addresses each with their associated Paired SNPA address. The Network addresses each with their associated Paired SNPA address. The
group Network address identifies specific multicast PDUs and the group Network address identifies specific multicast PDUs and the
Paired SNPA address is the SNPA address on which the ES expects to Paired SNPA address is the SNPA address on which the ES expects to
receive such multicast PDUs on that subnetwork. It is encoded in the receive such multicast PDUs on that subnetwork. It is encoded in the
ESGH and MAM PDUs as shown in Figure 1. ESGH and MAM PDUs as shown in Figure 1.
Octet Octet
,----------------------------------------------------, ,----------------------------------------------------,
| Number of Group Address Pairs | 10 | Number of Group Address Pairs | 10
|----------------------------------------------------| |----------------------------------------------------|
| Group Network Address Length Indicator (GNAL) | 11 | Group Network Address Length Indicator (GNAL) | 11
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6.12.8 Group Network Address Mask 6.12.8 Group Network Address Mask
The Group Network Address Mask option may only appear in the MAM PDU. The Group Network Address Mask option may only appear in the MAM PDU.
The Group Network Address Mask parameter indicates that the multicast The Group Network Address Mask parameter indicates that the multicast
address mapping information applies to a larger population of group address mapping information applies to a larger population of group
Network Addresses than the group Network address(es) contained in the Network Addresses than the group Network address(es) contained in the
MAM PDU indicates. When this option is provided in a MAM PDU, the MAM PDU indicates. When this option is provided in a MAM PDU, the
masking relationship contained must be valid for all group Network masking relationship contained must be valid for all group Network
addresses contained in this PDU. An End System may ignore this param- addresses contained in this PDU. An End System may ignore this
eter. parameter.
The Group Network Address Mask establishes an equivalence class of The Group Network Address Mask establishes an equivalence class of
group Network addresses to which the same multicast address mapping group Network addresses to which the same multicast address mapping
information applies. To determine whether or not a trial group Net- information applies. To determine whether or not a trial group
work address falls within the equivalence class, the ES aligns the Network address falls within the equivalence class, the ES aligns the
trial group Network address with the Group Network Address Mask pad- trial group Network address with the Group Network Address Mask
ding the latter with trailing zero octets if necessary. If in all bit padding the latter with trailing zero octets if necessary. If in all
positions where the Group Network Address Mask is "1" the trial group bit positions where the Group Network Address Mask is "1" the trial
Network address matches the Group Network Address field of the Group group Network address matches the Group Network Address field of the
Address Pair parameter of the MAM PDU, then the trial group Network Group Address Pair parameter of the MAM PDU, then the trial group
address belongs to the equivalence class described by the MAM PDU. Network address belongs to the equivalence class described by the MAM
PDU.
The Group Network Address Mask parameter has additional semantics The Group Network Address Mask parameter has additional semantics
when considered with the Paired SNPA Address Mask parameter. when considered with the Paired SNPA Address Mask parameter.
Parameter Code: 1110 0011 Parameter Code: 1110 0011
Parameter Length: variable, up to 20 octets Parameter Length: variable, up to 20 octets
Parameter Value: a comparison mask of octets to be aligned with the Parameter Value: a comparison mask of octets to be
Group Network Address field of the Group Address Pair parameter of aligned with the Group Network Address
the MAM PDU. field of the Group Address Pair
parameter of the MAM PDU.
6.12.9 Paired SNPA Address Mask 6.12.9 Paired SNPA Address Mask
The Paired SNPA Address Mask option may only appear in the MAM PDU. The Paired SNPA Address Mask option may only appear in the MAM PDU.
When the Paired SNPA Address Mask is present, the equivalence class When the Paired SNPA Address Mask is present, the equivalence class
defined by the Group Network Address Mask also has common structure defined by the Group Network Address Mask also has common structure
below the Group Network Address Mask; i.e. in the portion of the below the Group Network Address Mask; i.e., in the portion of the
group Network address where the Group Network Address Mask is logi- group Network address where the Group Network Address Mask is
cally "0". The Paired SNPA Address Mask supplies additional informa- logically "0". The Paired SNPA Address Mask supplies additional
tion about the structure, by indicating certain bit positions within information about the structure, by indicating certain bit positions
the space "below" the Group Network Address Mask. Specifically, the within the space "below" the Group Network Address Mask.
Paired SNPA Address Mask indicates the location of the Paired SNPA Specifically, the Paired SNPA Address Mask indicates the location of
address in the Group Network Address. the Paired SNPA address in the Group Network Address.
This parameter may appear in a MAM PDU only if the Group Network This parameter may appear in a MAM PDU only if the Group Network
Address Mask is also present. When this option is provided in a MAM Address Mask is also present. When this option is provided in a MAM
PDU, the masking relationship contained must be valid for all group PDU, the masking relationship contained must be valid for all group
Network addresses contained in this PDU. An ES receiving such a MAM Network addresses contained in this PDU. An ES receiving such a MAM
PDU may safely ignore both masks. However (since presence of both PDU may safely ignore both masks. However (since presence of both
masks dictates different functional behavior than the presence of the masks dictates different functional behavior than the presence of the
Group Network Address Mask alone) an ES shall not ignore one of the Group Network Address Mask alone) an ES shall not ignore one of the
masks while heeding the other. masks while heeding the other.
Parameter Code: 1110 0100 Parameter Code: 1110 0100
Parameter Length: variable Parameter Length: variable
Parameter Value: a comparison mask of octets to be aligned with the Parameter Value: a comparison mask of octets to be
Group Network Address field(s) of the Group Address Pair parameter of aligned with the Group Network Address
the MAM PDU. field(s) of the Group Address Pair
parameter of the MAM PDU.
6.12.9.1 Mask Parameters Example 6.12.9.1 Mask Parameters Example
This section provides examples of using the Group Network Address This section provides examples of using the Group Network Address
Mask and the Paired SNPA Address Mask. The examples given are for an Mask and the Paired SNPA Address Mask. The examples given are for an
Internet usage of CLNP Multicasting across subnetworks using IEEE 802 Internet usage of CLNP Multicasting across subnetworks using IEEE 802
addressing. For these examples the Group Network address format is: addressing. For these examples the group Network address format is:
+-----+----------------------------------------+ +-----+----------------------------------------+
| IDP | Upper DSP | Embedded SNPA address | SEL| | IDP | Upper DSP | Embedded SNPA address | SEL|
+-----+-----------+-----------------------+----+ +-----+-----------+-----------------------+----+
octets: | 3 | 10 | 6 | 1 | octets: | 3 | 10 | 6 | 1 |
+-----+-----------+-----------------------+----+ +-----+-----------+-----------------------+----+
Thus the group Network address used is 20 octets. For these exam- Thus the group Network address used is 20 octets. For these
ples, the only field considered is the Embedded SNPA address field examples, the only field considered is the Embedded SNPA address
and its placement within the group Network address. field and its placement within the group Network address.
In the first example it is the policy in "this part of the Internet" In the first example it is the policy in "this part of the Internet"
to map the Embedded SNPA address into the IEEE 802 address space to map the Embedded SNPA address into the IEEE 802 address space
reserved by IEEE 802 for group addressing using LOCAL assignment, reserved by IEEE 802 for group addressing using LOCAL assignment,
this corresponds to all 48 bit values with the two low order bits of this corresponds to all 48 bit values with the two low order bits of
the first octet set to "11". the first octet set to "11".
The Active Multicast Intermediate System on this subnetwork may con- The Active Multicast Intermediate System on this subnetwork may
struct a MAM PDU to map, for this example, a group Network address of construct a MAM PDU to map, for this example, a group Network address
{13 octets, 03-00-DA-DA-DA-DA, 1 octet} and a paired SNPA address of of {13 octets, 03-00-DA-DA-DA-DA, 1 octet} and a paired SNPA address
03-00-DA-DA-DA-DA. In addition the Active Multicast Intermediate of 03-00-DA-DA-DA-DA. In addition the Active Multicast Intermediate
System can include in the MAM PDU a Group Network Address Mask of System can include in the MAM PDU a Group Network Address Mask of
FF-FF-FF-FF-FF-FF-FF-FF-FF-FF-FF-FF-FF-03-00-00-00-00-00-00. FF-FF-FF-FF-FF-FF-FF-FF-FF-FF-FF-FF-FF-03-00-00-00-00-00-00.
With this parameter, all group Network addresses which share the With this parameter, all group Network addresses which share the
identical first 13 octet and with "11" in the two low order bits of identical first 13 octet and with "11" in the two low order bits of
the 14th octet are put in an equivalence class and share the same the 14th octet are put in an equivalence class and share the same
mapping information. If this were the only option present then all of mapping information. If this were the only option present then all of
these group Network addresses would all have a paired SNPA address of these group Network addresses would all have a paired SNPA address of
03-00-DA-DA-DA-DA. 03-00-DA-DA-DA-DA.
skipping to change at page 34, line 55 skipping to change at page 37, line 7
| | m-1 | | m-1
|----------------------------------------------------| |----------------------------------------------------|
| | m | | m
: Options : : Options :
| | p-1 | | p-1
'----------------------------------------------------' '----------------------------------------------------'
Figure 2 - ESGH PDU Format Figure 2 - ESGH PDU Format
6.12.11 Multicast Address Mapping (MAM) PDU 6.12.11 Multicast Address Mapping (MAM) PDU
The MAM PDU has the format shown in figure 3. The MAM PDU has the format shown in figure 3:
Octet Octet
,----------------------------------------------------, ,----------------------------------------------------,
| Network Layer Protocol Identifier | 1 | Network Layer Protocol Identifier | 1
|----------------------------------------------------| |----------------------------------------------------|
| Length Indicator | 2 | Length Indicator | 2
|----------------------------------------------------| |----------------------------------------------------|
| Version/Protocol ID Extension | 3 | Version/Protocol ID Extension | 3
|----------------------------------------------------| |----------------------------------------------------|
| reserved (must be zero) | 4 | reserved (must be zero) | 4
skipping to change at page 36, line 6 skipping to change at page 38, line 16
: Options : : Options :
| | p-1 | | p-1
'----------------------------------------------------' '----------------------------------------------------'
Figure 3 - MAM PDU Format Figure 3 - MAM PDU Format
6.13 Conformance 6.13 Conformance
All of the extensions provided to the functions to support multicast All of the extensions provided to the functions to support multicast
capability are optional. For an End System or Intermediate System capability are optional. For an End System or Intermediate System
which is not multicast capable these extensions are not applicable. A which is not multicast capable these extensions are not applicable. A
Network entity may choose to be multicast capable, a multicast capa- Network entity may choose to be multicast capable, a multicast
ble Network entity is required to support both multicast announcement capable Network entity is required to support both multicast
information and multicast address mapping information. announcement information and multicast address mapping information.
An implementation claiming conformance as a multicast capable End An implementation claiming conformance as a multicast capable End
System shall meet all of the requirements for an End System which is System shall meet all of the requirements for an End System which is
not multicast capable and shall support multicast announcement infor- not multicast capable and shall support multicast announcement
mation and shall implement the functions marked as Mandatory (M) in information and shall implement the functions marked as Mandatory (M)
column 4 of table 3. A multicast capable End System implementation in column 4 of table 3. A multicast capable End System implementation
shall also support multicast address mapping information and shall shall also support multicast address mapping information and shall
implement the functions marked as Mandatory (M) in column 5 of table implement the functions marked as Mandatory (M) in column 5 of table
3. 3.
An implementation claiming conformance as a multicast capable Inter- An implementation claiming conformance as a multicast capable
mediate System shall meet all of the requirements for an Intermediate Intermediate System shall meet all of the requirements for an
System which is not multicast capable and shall support multicast Intermediate System which is not multicast capable and shall support
announcement information and shall implement the functions marked as multicast announcement information and shall implement the functions
Mandatory (M) in column 6 of table 3. A multicast capable Intermedi- marked as Mandatory (M) in column 6 of table 3. A multicast capable
ate System implementation shall also support multicast address map- Intermediate System implementation shall also support multicast
ping information and shall implement the functions marked as Manda- address mapping information and shall implement the functions marked
tory (M) in column 7 of table 3. as Mandatory (M) in column 7 of table 3.
Table 3 - Static Conformance Requirements for Multicast Capable Table 3 - Static Conformance Requirements for Multicast Capable
Network Entities Network Entities
ES IS ES IS
Clause -------------- Clause --------------
Label Function Reference AI MI AI MI Label Function Reference AI MI AI MI
------------------------------------------------------------------ ------------------------------------------------------------------
RpMAn Report Multicast Announcement 6.7.1 M - - - RpMAn Report Multicast Announcement 6.7.1 M - - -
RcMAn Record Multicast Announcement 6.7.2.1 - - M - RcMAn Record Multicast Announcement 6.7.2.1 - - M -
RcDamp Record Damping 6.7.2.2 O - - - RcDamp Record Damping 6.7.2.2 O - - -
FlMAn Flush Old Multicast Announcement 6.7.3 O - M - FlMAn Flush Old Multicast Announcement 6.7.3 O - M -
RpMAdMa Report Multicast Address Mapping 6.8.1 - - - M RpMAdMa Report Multicast Address Mapping 6.8.1 - - - M
MATGn ESMAT Generation 6.8.1 - - - M MATGn ESMAT Generation 6.8.1 - - - M
RcMAdMa Record Multicast Address Mapping 6.8.2 - M - - RcMAdMa Record Multicast Address Mapping 6.8.2 - M - -
MATPr ESMAT Processing 6.8.2 - M - - MATPr ESMAT Processing 6.8.2 - M - -
FlMAdMa Flush Old Multicast Address Map 6.8.3 - M - - FlMAdMa Flush Old Multicast Address Map 6.8.3 - M - -
skipping to change at page 37, line 29 skipping to change at page 39, line 27
MATGn ESMAT Generation 6.8.1 - - - M MATGn ESMAT Generation 6.8.1 - - - M
RcMAdMa Record Multicast Address Mapping 6.8.2 - M - - RcMAdMa Record Multicast Address Mapping 6.8.2 - M - -
MATPr ESMAT Processing 6.8.2 - M - - MATPr ESMAT Processing 6.8.2 - M - -
FlMAdMa Flush Old Multicast Address Map 6.8.3 - M - - FlMAdMa Flush Old Multicast Address Map 6.8.3 - M - -
PSAdSel Paired SNPA Address Selection 6.9.1 - M - - PSAdSel Paired SNPA Address Selection 6.9.1 - M - -
ExtForw Extensions to CLNP Route Function 6.10 - M - - ExtForw Extensions to CLNP Route Function 6.10 - M - -
OSuForw Originating Subnetwork Forwarding 6.11 - - - M OSuForw Originating Subnetwork Forwarding 6.11 - - - M
Key: Key:
AI = Multicast Announcement information supported AI = Multicast Announcement information supported
MI = Multicast Address Mapping information supported MI = Multicast Address Mapping information supported
M = Mandatory; O = Optional; - = not applicable M = Mandatory; O = Optional; - = not applicable
7. Security Considerations
Security issues are not discussed in this memo.
Appendix A. Differences with RFC 1112 Appendix A. Differences with RFC 1112
This appendix is intended to identify differences between the mechanisms This appendix is intended to identify differences between the
defined for CLNP Multicast in this specification and those for IP multi- mechanisms defined for CLNP Multicast in this specification and those
cast defined in RFC 1112. The work on CLNP Multicast followed the work for IP multicast defined in RFC 1112. The work on CLNP Multicast
on IP multicast and was explicitly aimed at bringing the capabilities followed the work on IP multicast and was explicitly aimed at
described in RFC 1112 into a CLNP context. This appendix is intended to bringing the capabilities described in RFC 1112 into a CLNP context.
provide some background information on the difference; however, it is This appendix is intended to provide some background information on
not intended to justify the mechanisms selected for CLNP multicast use. the difference; however, it is not intended to justify the mechanisms
selected for CLNP multicast use.
Static/Dynamic Address Binding of Multicast Datagrams Static/Dynamic Address Binding of Multicast Datagrams
IP multicast utilizes a static binding of Class D IP addresses to a IP multicast utilizes a static binding of Class D IP addresses to a
specific range of IEEE 802 48 bit group addresses. The IEEE 802 address specific range of IEEE 802 48 bit group addresses. The IEEE 802
range that is used is within the address range that IEEE 802 allocates address range that is used is within the address range that IEEE 802
for "Global" administration and this block of addresses is under the allocates for "Global" administration and this block of addresses is
control of the Internet Assigned Numbers Authority (IANA) which in turn under the control of the Internet Assigned Numbers Authority (IANA)
has allocated this block of addresses for use by IP multicast. This which in turn has allocated this block of addresses for use by IP
scheme is very simple and efficient. Given the use of a 32 bit IP multicast. This scheme is very simple and efficient. Given the use
address, the lower 23 bits of the Class D address are mapped into the of a 32 bit IP address, the lower 23 bits of the Class D address are
lower 23 bits of a 48 bit IEEE 802 address where the upper 25 bits are mapped into the lower 23 bits of a 48 bit IEEE 802 address where the
fixed. Static binding of this form is global in scope (all members of a upper 25 bits are fixed. Static binding of this form is global in
group use the same IEEE 802 address on all subnets (at least all that scope (all members of a group use the same IEEE 802 address on all
use IEEE 802 addressing). subnets (at least all that use IEEE 802 addressing).
CLNP multicast uses a dynamic binding of a group Network address (up to CLNP multicast uses a dynamic binding of a group Network address (up
20 bytes) to any subnetwork address. In cases where no multicast capable to 20 bytes) to any subnetwork address. In cases where no multicast
Intermediate Systems are attached to a subnetwork then a binding using capable Intermediate Systems are attached to a subnetwork then a
preconfigured information or the "All Multicast Capable End Systems" binding using preconfigured information or the "All Multicast Capable
subnetwork addresses is used. The large GNA provides the room to contain End Systems" subnetwork addresses is used. The large GNA provides the
a full 48 bit IEEE 802 address if desired. Mask capabilities are room to contain a full 48 bit IEEE 802 address if desired. Mask
optionally provided which allow a multicast capable Intermediate System capabilities are optionally provided which allow a multicast capable
to specify a "static" binding for a particular subnetwork. One of the Intermediate System to specify a "static" binding for a particular
major purposes of providing a dynamic binding is to customize a host's subnetwork. One of the major purposes of providing a dynamic binding
subnetwork address usage to the capabilities of the attached systems. is to customize a host's subnetwork address usage to the capabilities
There is considerable differences in the numbers of group subnetwork of the attached systems. There is considerable differences in the
addresses that a system can recognize using hardware hooks built into numbers of group subnetwork addresses that a system can recognize
the integrated circuits used. For example the number of addresses that using hardware hooks built into the integrated circuits used. For
can be recognized by hardware may differ by an attached system depending example the number of addresses that can be recognized by hardware
upon the interface it uses (e.g. Ethernet interface and FDDI within the may differ by an attached system depending upon the interface it uses
same system may have quite different capabilities). Dynamic binding of (e.g., Ethernet interface and FDDI within the same system may have
this form is local in scope (members of a group may use different sub- quite different capabilities). Dynamic binding of this form is local
network addresses (e.g. IEEE 802 addresses) on different subnets). in scope (members of a group may use different subnetwork addresses
(e.g., IEEE 802 addresses) on different subnets).
Originating of Multicast Datagrams Originating of Multicast Datagrams
IP multicast originates multicast datagrams directly, where the host IP multicast originates multicast datagrams directly, where the host
originating a datagram sends it with the group Subnetwork address as its originating a datagram sends it with the group Subnetwork address as
destination. Hosts attached to the network where the datagram is ori- its destination. Hosts attached to the network where the datagram is
ginated receive the datagram directly. originated receive the datagram directly.
CLNP multicast originates multicast datagrams directly using the group's CLNP multicast originates multicast datagrams directly using the
subnetwork address as its destination when multicast address mapping group's subnetwork address as its destination when multicast address
information is available. This case occurs when a multicast capable mapping information is available. This case occurs when a multicast
Intermediate System is attached to the subnetwork and a host on the sub- capable Intermediate System is attached to the subnetwork and a host
network is announcing an interest in multicast packets identified by a on the subnetwork is announcing an interest in multicast packets
particular group Network address. The Active Multicast IS may use MAM identified by a particular group Network address. The Active
PDU mask parameters to provide multicast address mapping information for Multicast IS may use MAM PDU mask parameters to provide multicast
a large number of group Network addresses. When there is no multicast address mapping information for a large number of group Network
address mapping information for the particular group Network address on addresses. When there is no multicast address mapping information for
a subnetwork with a multicast capable IS attached to it, hosts originate the particular group Network address on a subnetwork with a multicast
packets using such addresses sends to the "All Multicast Capable Inter- capable IS attached to it, hosts originate packets using such
mediate Systems" SNPA address. This case occurs when there are no addresses sends to the "All Multicast Capable Intermediate Systems"
receivers of such multicast packets on the originating subnetwork. When SNPA address. This case occurs when there are no receivers of such
a multicast capable Intermediate System is not attached to a subnetwork, multicast packets on the originating subnetwork. When a multicast
the End System may utilize either preconfigured information (which might capable Intermediate System is not attached to a subnetwork, the End
be a direct mapping from a portion of the group Network address) or use System may utilize either preconfigured information (which might be a
the "All Multicast Capable End Systems" address. direct mapping from a portion of the group Network address) or use
the "All Multicast Capable End Systems" address.
Address Binding of Control Packets Address Binding of Control Packets
IP multicast sends the control packets related to the IGMP protocol on IP multicast sends the control packets related to the IGMP protocol
the same subnetwork address that is used by the multicast data traffic. on the same subnetwork address that is used by the multicast data
traffic.
CLNP multicast sends the control packets related to the ES-IS protocol CLNP multicast sends the control packets related to the ES-IS
extensions on specific group subnetwork addresses (i.e. "All Multicast protocol extensions on specific group subnetwork addresses (i.e.,
Capable End Systems" and "All Multicast Announcements" addresses). "All Multicast Capable End Systems" and "All Multicast Announcements"
addresses).
Router Requirements for relaying Multicast Datagrams Router Requirements for relaying Multicast Datagrams
IP multicast requires that a multicast router run in "promiscuous" mode IP multicast requires that a multicast router run in "promiscuous"
where it must receive all multicast datagrams originated on a subnetwork mode where it must receive all multicast datagrams originated on a
regardless of the destination. This is a result of the choices selected subnetwork regardless of the destination. This is a result of the
in the "Originating of Multicast Datagrams" and "Address Binding of Con- choices selected in the "Originating of Multicast Datagrams" and
trol Packets" discussed above. "Address Binding of Control Packets" discussed above.
CLNP multicast allows a multicast router to limit multicast packet CLNP multicast allows a multicast router to limit multicast packet
reception to only those datagrams sent to the SNPA addresses where there reception to only those datagrams sent to the SNPA addresses where
is current multicast address mapping information or to the "All Multi- there is current multicast address mapping information or to the "All
cast Capable Intermediate Systems" address. The intention is to allow Multicast Capable Intermediate Systems" address. The intention is to
the multicast routers to be in control of the SNPA addresses for multi- allow the multicast routers to be in control of the SNPA addresses
cast packets that they need to receive. This is a result of the for multicast packets that they need to receive. This is a result of
choices selected in the "Originating of Multicast Datagrams" and the choices selected in the "Originating of Multicast Datagrams" and
"Address Binding of Control Packets" discussed above. "Address Binding of Control Packets" discussed above.
Aggregation of Control Information Aggregation of Control Information
In IP multicast, a host is required to withhold an announcement report In IP multicast, a host is required to withhold an announcement
upon hearing another host reporting a similar interest in a particular report upon hearing another host reporting a similar interest in a
Class D address on a particular subnetwork. This is an option for CLNP particular Class D address on a particular subnetwork. This is an
multicast (upon hearing interest in a particular group Network address option for CLNP multicast (upon hearing interest in a particular
on a particular subnetwork). Such reports are not combined in IP multi- group Network address on a particular subnetwork). Such reports are
cast while CLNP multicast supports providing multiple announcements (and not combined in IP multicast while CLNP multicast supports providing
address mappings) within a single packet. A mask feature for address multiple announcements (and address mappings) within a single packet.
mappings supports identifying mappings for a range of group Network A mask feature for address mappings supports identifying mappings for
addresses within a single control packet. a range of group Network addresses within a single control packet.
Datagram Scope Control Datagram Scope Control
IP multicast supports the use of the IP Hop Count as a means to support
scope control. While not documented in RFC 1112, a technique is also
being used to use bits within the Class D address to identify whether a
datagram has single subnetwork, "campus" or global scope.
CLNP has considerable scope control functionality. While the PDU Life- IP multicast supports the use of the IP Hop Count as a means to
time field can be employed in a similar way to the IP Hop Count, two support scope control. While not documented in RFC 1112, a technique
additional options are available. The Radius scope control provides a is also being used to use bits within the Class D address to identify
mechanism for "administratively" setting distance values and de-couples whether a datagram has single subnetwork, "campus" or global scope.
the multicast scope control from the PDU lifetime function. More impor-
tantly, the Prefix based scope control appears to provide considerable
and flexible functionality that can adjust to situations where a known,
hierarchical unicast addressing structure exists.
Marking of Multicast Datagrams CLNP has considerable scope control functionality. While the PDU
Lifetime field can be employed in a similar way to the IP Hop Count,
two additional options are available. The Radius scope control
provides a mechanism for "administratively" setting distance values
and de-couples the multicast scope control from the PDU lifetime
function. More importantly, the Prefix based scope control appears to
provide considerable and flexible functionality that can adjust to
situations where a known, hierarchical unicast addressing structure
exists.
IP multicast marks a multicast PDU via the use of an IP Class D address Marking of Multicast Datagrams
as its destination address parameter. CLNP multicast marks both the PDU
(a different PDU type) and the destination address (i.e. group Network
address) parameter.
Unicast Addressing Differences IP multicast marks a multicast PDU via the use of an IP Class D
address as its destination address parameter. CLNP multicast marks
both the PDU (a different PDU type) and the destination address
(i.e., group Network address) parameter.
An IP address identifies a specific host interface while a CLNP indivi- Unicast Addressing Differences
dual Network address (i.e. NSAP address) identifies a particular Network
entity. This difference has lead to a difference with RFC 1112. IP
multicast requires a host which is attached to more than one subnetwork
to originate a multicast packet on only one subnetwork. CLNP multicast
requires a host which is attached to more than one subnetwork to ori-
ginate a multicast packet on every subnetwork that the ISO ES-IS Confi-
guration function is reporting the NSAP address contained in the source
address parameter of the multicast PDU.
Error Reports An IP address identifies a specific host interface while a CLNP
individual Network address (i.e., NSAP address) identifies a
particular Network entity. This difference has lead to a difference
with RFC 1112. IP multicast requires a host which is attached to
more than one subnetwork to originate a multicast packet on only one
subnetwork. CLNP multicast requires a host which is attached to more
than one subnetwork to originate a multicast packet on every
subnetwork that the ISO ES-IS Configuration function is reporting the
NSAP address contained in the source address parameter of the
multicast PDU.
Error reports sent in response to receiving a multicast PDU are not per- Error Reports
mitted in IP multicast while they are permitted in CLNP multicast.
Source Routing Error reports sent in response to receiving a multicast PDU are not
permitted in IP multicast while they are permitted in CLNP multicast.
Source routing of multicast PDUs are permitted in IP multicast (but at Source Routing
the present time this is discouraged) while they are not permitted in
CLNP multicast. Source routing of multicast PDUs are permitted in IP multicast (but
at the present time this is discouraged) while they are not permitted
in CLNP multicast.
Appendix B. Issues Under Study Appendix B. Issues Under Study
This appendix is intended to record the current issues (as discussed at This appendix is intended to record the current issues (as discussed
the March 1994 TUBA meeting). at the March 1994 TUBA meeting).
1. Local versus Global address bindings 1. Local versus Global address bindings
The extensions to the ES-IS protocol provide a multicast address mapping The extensions to the ES-IS protocol provide a multicast address
function which supports dynamically binding a group Network address to a mapping function which supports dynamically binding a group Network
subnetwork address. Concern has been expressed that this is an unneces- address to a subnetwork address. Concern has been expressed that
sary feature which complicates the job of network administrators without this is an unnecessary feature which complicates the job of network
suitable benefit. A static, global binding of group Network addresses administrators without suitable benefit. A static, global binding of
to IEEE 802 subnetwork addresses, as is used by IP multicast has been group Network addresses to IEEE 802 subnetwork addresses, as is used
suggested. by IP multicast has been suggested.
The two main reasons that the group Network address to subnetwork (IEEE The two main reasons that the group Network address to subnetwork
802) address was made locally configurable were to support multicast on (IEEE 802) address was made locally configurable were to support
subnets with hosts having a mixture of capabilities (as to how many mul- multicast on subnets with hosts having a mixture of capabilities (as
ticast subnetwork addresses a host could register to receive at a time) to how many multicast subnetwork addresses a host could register to
and to support multicast on subnets that do not use 48 bit IEEE 802 receive at a time) and to support multicast on subnets that do not
addresses. Thus it was felt that this should be done per subnetwork use 48 bit IEEE 802 addresses. Thus it was felt that this should be
versus globally. Even multi-homed hosts with subnets that use 802 done per subnetwork versus globally. Even multi-homed hosts with
addresses may have varying capabilities (looking at typical Ethernet, subnets that use 802 addresses may have varying capabilities (looking
FDDI and 802.5 implementations). at typical Ethernet, FDDI and 802.5 implementations).
One possible solution is to recommend a direct mapping in any Internet One possible solution is to recommend a direct mapping in any
use of CLNP multicast on subnets which use IEEE 802 addressing. This Internet use of CLNP multicast on subnets which use IEEE 802
could be a default for all Internet hosts. A policy would be needed to addressing. This could be a default for all Internet hosts. A
identify the Internet's group Network address format. Given such a map- policy would be needed to identify the Internet's group Network
ping the only operational overhead that would occur is that in the pres- address format. Given such a mapping the only operational overhead
ence of a mapping server (the Active Multicast IS), which was supporting that would occur is that in the presence of a mapping server (the
this mapping, a MAM PDU would periodically be sent with a Group Network Active Multicast IS), which was supporting this mapping, a MAM PDU
Address Mask which would identify the direct mapping. would periodically be sent with a Group Network Address Mask which
would identify the direct mapping.
2. "Real Time" Scope Control Features 2. "Real Time" Scope Control Features
The scope control features are provided via optional parameters. Use of The scope control features are provided via optional parameters. Use
multicast transfer of audio and video streams may require scope control of multicast transfer of audio and video streams may require scope
mechanisms which operate very quickly. control mechanisms which operate very quickly.
One possible solution is to embed scope control mechanisms into the One possible solution is to embed scope control mechanisms into the
group Network address itself. For example, a group Network address group Network address itself. For example, a group Network address
using the "Local" AFI is automatically limited to not cross inter-domain using the "Local" AFI is automatically limited to not cross inter-
borders. Further, more flexible, address formats may be developed. domain borders. Further, more flexible, address formats may be
developed.
References References
[Deering91] S.E. Deering. Multicast Routing in a Datagram Internetwork. [Deering91] Deering, S., "Multicast Routing in a Datagram
PhD thesis, Electrical Engineering Dept., Stanford University, December Internetwork", PhD thesis, Electrical Engineering Dept., Stanford
1991. University, December 1991.
[RFC1112] Host Extensions for IP Multicasting, Network Working Group,
RFC 1112, S. Deering, August 1989.
[RFC1237] Guidelines for OSI NSAP Allocation in the Internet, Network [RFC1112] Deering, S., "Host Extensions for IP Multicasting",
Working Group, RFC 1237, R. Colella, E. Gardner, R. Callon, July 1991. STD 5, RFC 1112, Stanford University, August 1989.
[CLNP] Protocol for providing the connectionless-mode network service, [RFC1237] Colella, R., Gardner, E., and R. Callon, "Guidelines for OSI
International Standard 8473-1, Second Edition, ISO/IEC JTC 1, Switzer- NSAP Allocation in the Internet", RFC 1237, NIST, Mitre, DEC, July
land 1994. (Available via FTP from merit.edu:pub/iso/iso8473part1.ps). 1991.
[ES-IS] End system to Intermediate system routing exchange protocol for [CLNP] Protocol for providing the connectionless-mode network service,
use in conjunction with the Protocol for providing the connectionless- International Standard 8473-1, Second Edition, ISO/IEC JTC 1,
mode network service, International Standard 9542, ISO/IEC JTC 1, Switzerland 1994. (Available via FTP from
Switzerland 1987. (Available via FTP from merit.edu:pub/iso/iso8473part1.ps).
merit.edu:pub/iso/iso9542.ps).
[MULT-AMDS]: Amendments to ISO standards to support CLNP multicast [ES-IS] End system to Intermediate system routing exchange protocol
extensions: for use in conjunction with the Protocol for providing the
connectionless-mode network service, International Standard 9542,
ISO/IEC JTC 1, Switzerland 1987. (Available via FTP from
merit.edu:pub/iso/iso9542.ps).
ISO 8348 AM5 Amendment to the Network Service to support Group Network [MULT-AMDS]: Amendments to ISO standards to support CLNP multicast
Addressing. International Standard ISO 8348 Amendment 5, ISO/IEC JTC 1, extensions:
Switzerland 1994.
ISO 8473-1 DAM1 - Draft Amendment to the Second Edition of the Protocol ISO 8348 AM5 Amendment to the Network Service to support Group Network
for providing the connectionless-mode network service [CLNP], Multicast Addressing. International Standard ISO 8348 Amendment 5, ISO/IEC JTC
Extension, 1993. 1, Switzerland 1994.
ISO 9542 DAM2 - Draft Amendment to the ES-IS [ES-IS] protocol, Addition ISO 8473-1 DAM1 - Draft Amendment to the Second Edition of the
of connectionless- mode multicast capability, 1993. Protocol for providing the connectionless-mode network service [CLNP],
Multicast Extension, 1993.
Author's Address: ISO 9542 DAM2 - Draft Amendment to the ES-IS [ES-IS] protocol,
Addition of connectionless- mode multicast capability, 1993.
Dave Marlow Author's Address
Code B35
NSWC-DD
Dahlgren, VA. 22448
Phone: (703) 663-1675 Dave Marlow
Code B35
NSWC-DD
Dahlgren, VA. 22448
Email: dmarlow@relay.nswc.navy.mil Phone: (703) 663-1675
EMail: dmarlow@relay.nswc.navy.mil
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