draft-ietf-mboned-routingarch-03.txt   draft-ietf-mboned-routingarch-04.txt 
Internet Engineering Task Force P. Savola Internet Engineering Task Force P. Savola
Internet-Draft CSC/FUNET Internet-Draft CSC/FUNET
Obsoletes: March 3, 2006 Obsoletes: June 26, 2006
3913,2189,2201,1584,1585 (if 3913,2189,2201,1584,1585 (if
approved) approved)
Intended status: Best Current Intended status: Best Current
Practice Practice
Expires: September 4, 2006 Expires: December 28, 2006
Overview of the Internet Multicast Routing Architecture Overview of the Internet Multicast Routing Architecture
draft-ietf-mboned-routingarch-03.txt draft-ietf-mboned-routingarch-04.txt
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on September 4, 2006. This Internet-Draft will expire on December 28, 2006.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2006). Copyright (C) The Internet Society (2006).
Abstract Abstract
The lack of up-to-date documentation on IP multicast routing The lack of up-to-date documentation on IP multicast routing
protocols and procedures has caused a great deal of confusion. To protocols and procedures has caused a great deal of confusion. To
clarify the situation, this memo describes the routing protocols and clarify the situation, this memo describes the routing protocols and
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2.1.1. PIM-SM . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1.1. PIM-SM . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.2. PIM-DM . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1.2. PIM-DM . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.3. Bi-directional PIM . . . . . . . . . . . . . . . . . . 5 2.1.3. Bi-directional PIM . . . . . . . . . . . . . . . . . . 5
2.1.4. DVMRP . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1.4. DVMRP . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1.5. MOSPF . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1.5. MOSPF . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.6. BGMP . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1.6. BGMP . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.7. CBT . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1.7. CBT . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.8. Interactions and Summary . . . . . . . . . . . . . . . 6 2.1.8. Interactions and Summary . . . . . . . . . . . . . . . 6
2.2. Distributing Topology Information . . . . . . . . . . . . 7 2.2. Distributing Topology Information . . . . . . . . . . . . 7
2.2.1. Multi-protocol BGP . . . . . . . . . . . . . . . . . . 7 2.2.1. Multi-protocol BGP . . . . . . . . . . . . . . . . . . 7
2.2.2. OSPF/IS-IS Multi-topology Extensions . . . . . . . . . 7 2.2.2. OSPF/IS-IS Multi-topology Extensions . . . . . . . . . 8
2.2.3. Issue: Overlapping Unicast/multicast Topology . . . . 8 2.2.3. Issue: Overlapping Unicast/multicast Topology . . . . 8
2.3. Learning (Active) Sources . . . . . . . . . . . . . . . . 8 2.3. Learning (Active) Sources . . . . . . . . . . . . . . . . 8
2.3.1. SSM . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.3.1. SSM . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.3.2. MSDP . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.3.2. MSDP . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.3.3. Embedded-RP . . . . . . . . . . . . . . . . . . . . . 9 2.3.3. Embedded-RP . . . . . . . . . . . . . . . . . . . . . 9
2.4. Configuring and Distributing PIM-SM RP Information . . . . 10 2.4. Configuring and Distributing PIM-SM RP Information . . . . 10
2.4.1. Manual Configuration with an Anycast Address . . . . . 10 2.4.1. Manual Configuration with an Anycast Address . . . . . 10
2.4.2. Embedded-RP . . . . . . . . . . . . . . . . . . . . . 10 2.4.2. Embedded-RP . . . . . . . . . . . . . . . . . . . . . 10
2.4.3. BSR and Auto-RP . . . . . . . . . . . . . . . . . . . 11 2.4.3. BSR and Auto-RP . . . . . . . . . . . . . . . . . . . 11
2.5. Mechanisms for Enhanced Redundancy . . . . . . . . . . . . 11 2.5. Mechanisms for Enhanced Redundancy . . . . . . . . . . . . 11
2.5.1. Anycast RP . . . . . . . . . . . . . . . . . . . . . . 11 2.5.1. Anycast RP . . . . . . . . . . . . . . . . . . . . . . 11
2.5.2. Stateless RP Failover . . . . . . . . . . . . . . . . 11 2.5.2. Stateless RP Failover . . . . . . . . . . . . . . . . 12
2.5.3. Bi-directional PIM . . . . . . . . . . . . . . . . . . 12 2.5.3. Bi-directional PIM . . . . . . . . . . . . . . . . . . 12
2.6. Interactions with Hosts . . . . . . . . . . . . . . . . . 12 2.6. Interactions with Hosts . . . . . . . . . . . . . . . . . 12
2.6.1. Hosts Sending Multicast . . . . . . . . . . . . . . . 12 2.6.1. Hosts Sending Multicast . . . . . . . . . . . . . . . 12
2.6.2. Hosts Receiving Multicast . . . . . . . . . . . . . . 12 2.6.2. Hosts Receiving Multicast . . . . . . . . . . . . . . 12
2.7. Restricting Multicast Flooding in the Link Layer . . . . . 12 2.7. Restricting Multicast Flooding in the Link Layer . . . . . 13
2.7.1. Router-to-Router Flooding Reduction . . . . . . . . . 13 2.7.1. Router-to-Router Flooding Reduction . . . . . . . . . 13
2.7.2. Host/Router Flooding Reduction . . . . . . . . . . . . 13 2.7.2. Host/Router Flooding Reduction . . . . . . . . . . . . 13
3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
5. Security Considerations . . . . . . . . . . . . . . . . . . . 14 5. Security Considerations . . . . . . . . . . . . . . . . . . . 14
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.1. Normative References . . . . . . . . . . . . . . . . . . . 14 6.1. Normative References . . . . . . . . . . . . . . . . . . . 14
6.2. Informative References . . . . . . . . . . . . . . . . . . 15 6.2. Informative References . . . . . . . . . . . . . . . . . . 16
Appendix A. Multicast Payload Transport Extensions . . . . . . . 18 Appendix A. Multicast Payload Transport Extensions . . . . . . . 18
A.1. Reliable Multicast . . . . . . . . . . . . . . . . . . . . 18 A.1. Reliable Multicast . . . . . . . . . . . . . . . . . . . . 18
A.2. Multicast Group Security . . . . . . . . . . . . . . . . . 18 A.2. Multicast Group Security . . . . . . . . . . . . . . . . . 19
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 18 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 19
Intellectual Property and Copyright Statements . . . . . . . . . . 20 Intellectual Property and Copyright Statements . . . . . . . . . . 20
1. Introduction 1. Introduction
Good, up-to-date documentation of IP multicast is close to non- Good, up-to-date documentation of IP multicast is close to non-
existent. This issue is severely felt with multicast routing existent. This issue is severely felt with multicast routing
protocols and techniques. The consequence is that those who wish to protocols and techniques. The consequence is that those who wish to
learn of IP multicast and how the routing works in the real world do learn of IP multicast and how the routing works in the real world do
not know where to begin. not know where to begin. Multicast addressing is described in a
companion document [I-D.ietf-mboned-addrarch].
The aim of this document is to provide a brief overview of multicast The aim of this document is to provide a brief overview of multicast
routing protocols and techniques. routing protocols and techniques.
This memo deals with: This memo deals with:
o setting up multicast forwarding state (Section 2.1), o setting up multicast forwarding state (Section 2.1),
o distributing multicast topology information (Section 2.2), o distributing multicast topology information (Section 2.2),
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(Section 2.7). (Section 2.7).
Some multicast data transport issues are also introduced in Some multicast data transport issues are also introduced in
Appendix A. Appendix A.
This memo obsoletes and re-classifies to Historic [RFC2026] Border This memo obsoletes and re-classifies to Historic [RFC2026] Border
Gateway Multicast Protocol (BGMP), Core Based Trees (CBT), Multicast Gateway Multicast Protocol (BGMP), Core Based Trees (CBT), Multicast
OSPF (MOSPF) RFCs: [RFC3913], [RFC2189], [RFC2201], [RFC1584], and OSPF (MOSPF) RFCs: [RFC3913], [RFC2189], [RFC2201], [RFC1584], and
[RFC1585]. The purpose of the re-classification is to give the [RFC1585]. The purpose of the re-classification is to give the
readers (both implementors and deployers) an idea what the status of readers (both implementors and deployers) an idea what the status of
a protocol is; there may or may not be legacy deployments of these a protocol is; there may be legacy deployments of some of these
protocols, which are not affected by this reclassification. See protocols, which are not affected by this reclassification. See
Section 2.1 for more on each protocol. Section 2.1 for more on each protocol.
1.1. Multicast-related Abbreviations 1.1. Multicast-related Abbreviations
ASM Any Source Multicast ASM Any Source Multicast
BGMP Border Gateway Multicast Protocol BGMP Border Gateway Multicast Protocol
BSR Bootstrap Router BSR Bootstrap Router
CBT Core Based Trees CBT Core Based Trees
CGMP Cisco Group Management Protocol CGMP Cisco Group Management Protocol
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GARP Group Address Resolution Protocol GARP Group Address Resolution Protocol
IGMP Internet Group Management Protocol IGMP Internet Group Management Protocol
MBGP Multi-protocol BGP (*not* "Multicast BGP") MBGP Multi-protocol BGP (*not* "Multicast BGP")
MLD Multicast Listener Discovery MLD Multicast Listener Discovery
MOSPF Multicast OSPF MOSPF Multicast OSPF
MSDP Multicast Source Discovery Protocol MSDP Multicast Source Discovery Protocol
PGM Pragmatic General Multicast PGM Pragmatic General Multicast
PIM Protocol Independent Multicast PIM Protocol Independent Multicast
PIM-DM PIM - Dense Mode PIM-DM PIM - Dense Mode
PIM-SM PIM - Sparse Mode PIM-SM PIM - Sparse Mode
PIM-SSM PIM - (Source-specific) Sparse Mode PIM-SSM PIM - Source-Specific Multicast
RGMP (Cisco's) Router Group Management Protocol RGMP (Cisco's) Router Group Management Protocol
RP Rendezvous Point RP Rendezvous Point
SSM Source-specific Multicast SSM Source-specific Multicast
2. Multicast Routing 2. Multicast Routing
2.1. Setting up Multicast Forwarding State 2.1. Setting up Multicast Forwarding State
The most important part of multicast routing is setting up the The most important part of multicast routing is setting up the
multicast forwarding state. This section describes the protocols multicast forwarding state. This section describes the protocols
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platforms support PIM-SM. platforms support PIM-SM.
2.1.2. PIM-DM 2.1.2. PIM-DM
Whereas PIM-SM is designed to avoid unnecessary flooding of multicast Whereas PIM-SM is designed to avoid unnecessary flooding of multicast
data, PIM-DM [RFC3973] operates in a "dense" mode, flooding the data, PIM-DM [RFC3973] operates in a "dense" mode, flooding the
multicast transmissions throughout the network ("flood and prune") multicast transmissions throughout the network ("flood and prune")
unless the leaf parts of the network periodically indicate that they unless the leaf parts of the network periodically indicate that they
are not interested in that particular traffic. are not interested in that particular traffic.
PIM-DM may be some fit in small and/or simple networks, where setting PIM-DM may be an acceptable fit in small and/or simple networks,
up an RP would be unnecessary, and possibly in cases where a large where setting up an RP would be unnecessary, and possibly in cases
number of users is expected to be able to wish to receive the where a large percentage of users is expected to want to receive the
transmission so that the amount of state the network has to keep is transmission so that the amount of state the network has to keep is
minimal. Therefore PIM-DM has typically only been used in special minimal. PIM-DM has been used to transition to PIM-SM but it is no
deployments, never currently in, e.g., ISPs' networks. longer in widespread use.
PIM-DM never really got popular due to its reliance of data plane and PIM-DM never became popular due to its reliance on data plane and
potential for loops, and the over-reliance of the complex Assert potential for loops, and the over-reliance of the complex Assert
mechanism. Further, it was a non-starter with high-bandwidth mechanism. Further, it was a non-starter with high-bandwidth streams
streams. due to its flooding paradigm.
Many implementations also support so-called "sparse-dense" mode, Many implementations also support so-called "sparse-dense" mode,
where Sparse mode is used by default, but Dense is used for where Sparse mode is used by default, but Dense is used for
configured multicast group ranges (such as Auto-RP in Section 2.4.3) configured multicast group ranges (such as Auto-RP in Section 2.4.3)
only. Lately, many networks have been transitioned away from sparse- only. Lately, many networks have been transitioned away from sparse-
dense to only sparse mode. dense to only sparse mode.
2.1.3. Bi-directional PIM 2.1.3. Bi-directional PIM
Bi-directional PIM [I-D.ietf-pim-bidir] aims to offer streamlined Bi-directional PIM [I-D.ietf-pim-bidir] aims to offer streamlined
PIM-SM operation, without data-driven events and data-encapsulation, PIM-SM operation, without data-driven events and data-encapsulation,
inside a PIM-SM domain. The usage of bi-dir PIM may be on the inside a PIM-SM domain. As it doesn't keep source-specific state, it
increase especially inside sites leveraging multicast. may be a lucrative approach especially in sites with a large number
of sources.
As of this writing, in IPv6 or inter-domain multicast there is no As of this writing, in IPv6 or inter-domain multicast there is no
standards based mechanism for alerting routers that a group range is standards based mechanism for alerting routers that a group range is
to be used for bi-directional PIM. to be used for bi-directional PIM.
2.1.4. DVMRP 2.1.4. DVMRP
Distance Vector Multicast Routing Protocol (DVMRP) [RFC1075] Distance Vector Multicast Routing Protocol (DVMRP) [RFC1075]
[I-D.ietf-idmr-dvmrp-v3] [I-D.ietf-idmr-dvmrp-v3-as] was the first [I-D.ietf-idmr-dvmrp-v3] [I-D.ietf-idmr-dvmrp-v3-as] was the first
protocol designed for multicasting, and to get around initial protocol designed for multicasting, and to get around initial
deployment hurdles, it also included tunneling capabilities which deployment hurdles. It also included tunneling capabilities which
were part of its multicast topology functions. were part of its multicast topology functions.
Currently, DVMRP is used only very rarely in operator networks, Currently, DVMRP is used only very rarely in operator networks,
having been replaced with PIM-SM. The most typical deployment of having been replaced with PIM-SM. The most typical deployment of
DVMRP is at a leaf network, to run from a legacy firewall only DVMRP is at a leaf network, to run from a legacy firewall only
supporting DVMRP to the internal network. However, GRE tunneling supporting DVMRP to the internal network. However, GRE tunneling
[RFC2784] seems to have overtaken DVMRP in this functionality, and [RFC2784] seems to have overtaken DVMRP in this functionality, and
there is relatively little use for DVMRP except in legacy there is relatively little use for DVMRP except in legacy
deployments. deployments.
2.1.5. MOSPF 2.1.5. MOSPF
MOSPF [RFC1584] was implemented by several vendors and has seen some MOSPF [RFC1584] was implemented by several vendors and has seen some
deployment in intra-domain networks. However, since it does not deployment in intra-domain networks. However, since it is based on
scale to the inter-domain case, operators have found it is easier to intra-domain OSPF it does not scale to the inter-domain case,
deploy a single protocol for use in both intra-domain and inter- operators have found it is easier to deploy a single protocol for use
domain networks and so it is no longer being actively deployed. in both intra-domain and inter-domain networks and so it is no longer
being actively deployed.
2.1.6. BGMP 2.1.6. BGMP
BGMP [RFC3913] did not get sufficient support within the service BGMP [RFC3913] did not get sufficient support within the service
provider community to get adopted and moved forward in the IETF provider community to get adopted and moved forward in the IETF
standards process. There were no reported production implementations standards process. There were no reported production implementations
and no production deployments. and no production deployments.
2.1.7. CBT 2.1.7. CBT
CBT [RFC2201] was an academic project that provided the basis for PIM CBT [RFC2201] was an academic project that provided the basis for PIM
sparse mode shared trees. Once the shared tree functionality was sparse mode shared trees. Once the shared tree functionality was
incorporated into PIM implementations, there was no longer a need for incorporated into PIM implementations, there was no longer a need for
a production CBT implemention. Therefore, CBT never saw production a production CBT implemention. Therefore, CBT never saw production
deployment. deployment.
2.1.8. Interactions and Summary 2.1.8. Interactions and Summary
It is worth noting that is it is possible to run different protocols It is worth noting that it is possible to run different protocols
with different groups ranges (e.g., treat some groups as dense mode with different multicast group ranges (e.g., treat some groups as
in an other-wise PIM-SM network; this typically requires manual dense mode in an otherwise PIM-SM network; this typically requires
configuration of the groups) or interact between different protocols manual configuration of the groups) or interaction between different
(e.g., use DVMRP in the leaf network, but PIM-SM upstream). The protocols (e.g., use DVMRP in the leaf network, but PIM-SM upstream).
basics for interactions among different protocols have been outlined The basics for interactions among different protocols have been
in [RFC2715]. outlined in [RFC2715].
The following figure gives a concise summary of the deployment status The following figure gives a concise summary of the deployment status
of different protocols as of this writing. of different protocols as of this writing.
+-------------+-------------+----------------+ +-------------+-------------+----------------+
| Interdomain | Intradomain | Status | | Interdomain | Intradomain | Status |
+------------+-------------+-------------+----------------+ +------------+-------------+-------------+----------------+
| PIM-SM | Yes | Yes | Active | | PIM-SM | Yes | Yes | Active |
| PIM-DM | Not feasible| Yes | Little use | | PIM-DM | Not feasible| Yes | Little use |
| Bi-dir PIM | No | Yes | Wait & see | | Bi-dir PIM | No | Yes | Wait & see |
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+------------+-------------+-------------+----------------+ +------------+-------------+-------------+----------------+
From this table, it is clear that PIM-Sparse Mode is the only From this table, it is clear that PIM-Sparse Mode is the only
multicast routing protocol that is deployed inter-domain and, multicast routing protocol that is deployed inter-domain and,
therefore, is most frequently used within multicast domains as well. therefore, is most frequently used within multicast domains as well.
2.2. Distributing Topology Information 2.2. Distributing Topology Information
When unicast and multicast topologies are the same ("congruent"), When unicast and multicast topologies are the same ("congruent"),
i.e., use the same routing tables (routing information base, RIB), it i.e., use the same routing tables (routing information base, RIB), it
has been considered sufficient just to distribute one set of has been considered sufficient just to distribute one set of
reachability information. reachability information to be used in conjunction with a protocol
that sets up multicast forwarding state (e.g., PIM-SM).
However, when PIM -- which by default built multicast topology based However, when PIM which by default built multicast topology based on
on the unicast topology -- gained popularity, it became apparent that the unicast topology gained popularity, it became apparent that it
it would be necessary to be able to distribute also non-congruent would be necessary to be able to distribute also non-congruent
multicast reachability information in the regular unicast protocols. multicast reachability information in the regular unicast protocols.
This was previously not an issue, because DVMRP built its own This was previously not an issue, because DVMRP built its own
reachability information. reachability information.
The topology information is needed to perform efficient distribution The topology information is needed to perform efficient distribution
of multicast transmissions and to prevent transmission loops by of multicast transmissions and to prevent transmission loops by
applying it to the Reverse Path Forwarding (RPF) check. applying it to the Reverse Path Forwarding (RPF) check.
This subsection introduces these protocols. This subsection introduces these protocols.
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Multiprotocol Extensions for BGP-4 [RFC2858] (often referred to as Multiprotocol Extensions for BGP-4 [RFC2858] (often referred to as
"MBGP"; however, it is worth noting that "MBGP" does *not* stand for "MBGP"; however, it is worth noting that "MBGP" does *not* stand for
"Multicast BGP") specifies a mechanism by which BGP can be used to "Multicast BGP") specifies a mechanism by which BGP can be used to
distribute different reachability information for unicast and distribute different reachability information for unicast and
multicast traffic (using SAFI=2 for multicast). Multiprotocol BGP multicast traffic (using SAFI=2 for multicast). Multiprotocol BGP
has been widely deployed for years, and is also needed to route IPv6. has been widely deployed for years, and is also needed to route IPv6.
Note that SAFI=3 was originally specified for "both unicast and Note that SAFI=3 was originally specified for "both unicast and
multicast" but has been deprecated [I-D.ietf-idr-rfc2858bis]. multicast" but has been deprecated [I-D.ietf-idr-rfc2858bis].
These extensions are in widespread use wherever BGP is used to These extensions are in widespread use wherever BGP is used to
distribute unicast topology information. Those having multicast distribute unicast topology information. Multicast-enabled networks
infrastructure and using BGP should use Multiprotocol BGP to that use BGP should use Multiprotocol BGP to distribute multicast
distribute multicast reachability information explicitly even if the reachability information explicitly even if the topologies are
topologies are congruent. A number of significant multicast transit congruent to make an explicit statement about multicast reachability.
providers even require this, by doing the RPF lookups solely based on A number of significant multicast transit providers even require
explicitly advertised multicast address family. this, by doing the RPF lookups solely based on explicitly advertised
multicast address family.
2.2.2. OSPF/IS-IS Multi-topology Extensions 2.2.2. OSPF/IS-IS Multi-topology Extensions
Similar to BGP, some IGPs also provide the capability for signalling Similar to BGP, some IGPs also provide the capability for signalling
a differing multicast topology, for example IS-IS multi-topology a differing multicast topology, for example IS-IS multi-topology
extensions [I-D.ietf-isis-wg-multi-topology]. Similar work exists extensions [I-D.ietf-isis-wg-multi-topology]. Similar work exists
for OSPF [I-D.ietf-ospf-mt]. for OSPF [I-D.ietf-ospf-mt].
It is worth noting that interdomain incongruence and intradomain It is worth noting that interdomain incongruence and intradomain
incongruence are orthogonal, so one doesn't require the other. incongruence are orthogonal, so one doesn't require the other.
Specifically, interdomain incongruence is quite common, while Specifically, interdomain incongruence is quite common, while
intradomain incongruence isn't, so you see much more deployments of intradomain incongruence isn't, so you see much more deployment of
MBGP than MT-ISIS/OSPF. Commonly deployed networks have managed well MBGP than MT-ISIS/OSPF. Commonly deployed networks have managed well
without protocols handling intradomain incongruence. However, the without protocols handling intradomain incongruence. However, the
availability of multi-topology mechanisms may in part replace the availability of multi-topology mechanisms may in part replace the
typically used workarounds such as tunnels. typically used workarounds such as tunnels.
2.2.3. Issue: Overlapping Unicast/multicast Topology 2.2.3. Issue: Overlapping Unicast/multicast Topology
An interesting case occurs when some routers do not distribute An interesting case occurs when some routers do not distribute
multicast topology information explicitly while others do. In multicast topology information explicitly while others do. In
particular, this happens when some multicast sites in the Internet particular, this happens when some multicast sites in the Internet
are using plain BGP while some use MBGP. are using plain BGP while some use MBGP.
Different implementations deal with this using different means. Different implementations deal with this in different ways.
Sometimes, multicast RPF mechanisms first look up the multicast Sometimes, multicast RPF mechanisms first look up the multicast
routing table, or RIB ("topology database") with a longest prefix routing table, or M-RIB ("topology database") with a longest prefix
match algorithm, and if they find any entry (including a default match algorithm, and if they find any entry (including a default
route), that is used; if no match is found, the unicast routing table route), that is used; if no match is found, the unicast routing table
is used instead. is used instead.
An alternative approach is to use longest prefix match on the union An alternative approach is to use longest prefix match on the union
of multicast and unicast routing tables; an implementation technique of multicast and unicast routing tables; an implementation technique
here is to copy the whole unicast routing table over to the multicast here is to copy the whole unicast routing table over to the multicast
routing table. The important point to remember here, though, is to routing table. The important point to remember here, though, is to
not override the multicast-only routes; if the longest prefix match not override the multicast-only routes; if the longest prefix match
would find both a (copied) unicast route and a multicast-only route, would find both a (copied) unicast route and a multicast-only route,
the latter should be treated as preferable. the latter should be treated as preferable.
One implemented approach is to just look up the information in the Another implemented approach is to just look up the information in
unicast routing table, and provide the user capabilities to change the unicast routing table, and provide the user capabilities to
that as appropriate, using for example copying functions discussed change that as appropriate, using for example copying functions
above. discussed above.
2.3. Learning (Active) Sources 2.3. Learning (Active) Sources
Typically, multicast routing protocols must either assume that the Typically, multicast routing protocols must either assume that the
receivers know the IP addresses of the (active) sources for a group a receivers know the IP addresses of the (active) sources for a group
priori, possibly using an out-of-band mechanism (SSM), or the sources in advance, possibly using an out-of-band mechanism (SSM), or the
must be discovered by the network protocols automatically (ASM). sources must be discovered by the network protocols automatically
(ASM).
Learning active sources is a relatively straightforward process with Learning active sources is a relatively straightforward process with
a single PIM-SM domain and with a single RP, but having a single a single PIM-SM domain and with a single RP, but having a single
PIM-SM domain for the whole Internet is a completely unscalable model PIM-SM domain for the whole Internet is a completely unscalable model
for many reasons. Therefore it is required to be able to split up for many reasons. Therefore it is required to be able to split up
the multicast routing infrastructures to smaller domains, and there the multicast routing infrastructures to smaller domains, and there
must be a way to share information about active sources using some must be a way to share information about active sources using some
mechanism if the ASM model is to be supported. mechanism if the ASM model is to be supported.
This section discusses the options. This section discusses the options.
2.3.1. SSM 2.3.1. SSM
Source-specific Multicast [I-D.ietf-ssm-arch] (sometimes also Source-specific Multicast [I-D.ietf-ssm-arch] (sometimes also
referred to as "single-source Multicast") does not count on learning referred to as "single-source Multicast") does not count on learning
active sources in the network; it is assumed that the recipients know active sources in the network. Recipients need to know the source IP
these using out of band mechanisms, and when subscribing to an (S,G) addresses using an out of band mechanism which are used to subscribe
channel indicate toward which source(s) the multicast routing to the (source, group) channel. The multicast routing uses the
protocol should send the Join messages. source address to set up the state and no further source discovery is
needed.
As of this writing, there are attempts to analyze and/or define out- As of this writing, there are attempts to analyze and/or define out-
of-band source discovery functions which would help SSM in particular of-band source discovery functions which would help SSM in particular
[I-D.lehtonen-mboned-dynssm-req]. [I-D.lehtonen-mboned-dynssm-req].
2.3.2. MSDP 2.3.2. MSDP
Multicast Source Discovery Protocol [RFC3618] was invented as a stop- Multicast Source Discovery Protocol [RFC3618] was invented as a stop-
gap mechanism, when it became apparent that multiple PIM-SM domains gap mechanism, when it became apparent that multiple PIM-SM domains
(and RPs) were needed in the network, and information about the (and RPs) were needed in the network, and information about the
active sources needed to be propagated between the PIM-SM domains active sources needed to be propagated between the PIM-SM domains
using some other protocol. using some other protocol.
MSDP is also used to share the state about sources between multiple MSDP is also used to share the state about sources between multiple
RPs in a single domain for, e.g., redundancy purposes [RFC3446]. RPs in a single domain for, e.g., redundancy purposes [RFC3446]. The
There is also work in progress to achieve the same using PIM same can be achieved using PIM extensions [I-D.ietf-pim-anycast-rp].
extensions [I-D.ietf-pim-anycast-rp]. See Section 2.5 for more. See Section 2.5 for more information.
There is no intent to define MSDP for IPv6, but instead use only SSM There is no intent to define MSDP for IPv6, but instead use only SSM
and Embedded-RP instead [I-D.ietf-mboned-ipv6-multicast-issues]. and Embedded-RP instead [I-D.ietf-mboned-ipv6-multicast-issues].
2.3.3. Embedded-RP 2.3.3. Embedded-RP
Embedded-RP [RFC3956] is an IPv6-only technique to map the address of Embedded-RP [RFC3956] is an IPv6-only technique to map the address of
the RP to the multicast group address. Using this method, it is the RP to the multicast group address. Using this method, it is
possible to avoid the use of MSDP while still allowing multiple possible to avoid the use of MSDP while still allowing multiple
multicast domains (in the traditional sense). multicast domains (in the traditional sense).
The model works by defining a single RP for a particular group for The model works by defining a single RP address for a particular
all of the Internet, so there is no need to share state about that group for all of the Internet, so there is no need to share state
with any other RPs (except, possibly, for redundancy purposes with about that with any other RPs. If necessary, RP redundancy can still
Anycast-RP using PIM). be achieved with Anycast-RP using PIM.
2.4. Configuring and Distributing PIM-SM RP Information 2.4. Configuring and Distributing PIM-SM RP Information
For PIM-SM, configuration mechanisms exist which are used to For PIM-SM, configuration mechanisms exist which are used to
configure the RP addresses and which groups are to use those RPs in configure the RP addresses and which groups are to use those RPs in
the routers. This section outlines the approaches. the routers. This section outlines the approaches.
2.4.1. Manual Configuration with an Anycast Address 2.4.1. Manual Configuration with an Anycast Address
It is often easiest just to manually configure the RP information on It is often easiest just to manually configure the RP information on
the routers when PIM-SM is used. the routers when PIM-SM is used.
Originally, static RP mapping was considered suboptimal since it Originally, static RP mapping was considered suboptimal since it
required explicit configuration changes every time the RP address required explicit configuration changes every time the RP address
changed. However, with the advent of anycast RP addressing, the RP changed. However, with the advent of anycast RP addressing, the RP
address is unlikely to ever change. Therefore, the administrative address is unlikely to ever change. Therefore, the administrative
burden is generally limited to initial configuration. Since there is burden is generally limited to initial configuration. Since there is
usually a fair amount of multicast configuration required on all usually a fair amount of multicast configuration required on all
routers anyway (eg, PIM on all interfaces), adding the RP address routers anyway (eg, PIM on all interfaces), adding the RP address
statically isn't really an issue. Further, static anycast RP mapping statically isn't really an issue. Further, static anycast RP mapping
provides the benefits of RP load balancing and redundancy (see provides the benefits of RP load sharing and redundancy (see
Section 2.5) without the complexity found in dynamic mechanisms like Section 2.5) without the complexity found in dynamic mechanisms like
Auto-RP and Bootstrap Router (BSR). Auto-RP and Bootstrap Router (BSR).
With such design, an anycast RP uses a "portable" address, which is With such design, an anycast RP uses an address that is configured on
configured on a loopback interfaces of the routers currently acting a loopback interfaces of the routers currently acting as RPs, as
as RPs, as described in [RFC3446]. described in [RFC3446].
Using this technique, each router might only need to be configured Using this technique, each router might only need to be configured
with one, portable RP address. with one, portable RP address.
2.4.2. Embedded-RP 2.4.2. Embedded-RP
Embedded-RP provides the information about the RP's address in the Embedded-RP provides the information about the RP's address in the
group addresses which are delegated to those who use the RP, so group addresses which are delegated to those who use the RP, so
unless no other ASM than Embedded-RP is used, one only needs to unless no other ASM than Embedded-RP is used, the network
configure the RP routers themselves. administrator only needs to configure the RP routers.
While Embedded-RP in many cases is sufficient for IPv6, other methods While Embedded-RP in many cases is sufficient for IPv6, other methods
of RP configuration are needed if one needs to provide ASM service of RP configuration are needed if one needs to provide ASM service
for other than Embedded-RP group addresses. In particular, service for other than Embedded-RP group addresses. In particular, service
discovery type of applications may need hard-coded addresses that are discovery type of applications may need hard-coded addresses that are
not dependent on local RP addresses. not dependent on local RP addresses.
As the RP's address is exposed to the users and applications, it is As the RP's address is exposed to the users and applications, it is
very important to ensure it does not change often, e.g., by using very important to ensure it does not change often, e.g., by using
manual configuration of an anycast address. manual configuration of an anycast address.
skipping to change at page 11, line 27 skipping to change at page 11, line 32
RPs. Further, flooding of BSR and Auto-RP messages must be prevented RPs. Further, flooding of BSR and Auto-RP messages must be prevented
at PIM borders. Additionally, routers require monitoring that they at PIM borders. Additionally, routers require monitoring that they
are actually using the RP(s) the administrators think they should be are actually using the RP(s) the administrators think they should be
using, for example if a router (maybe in customer's control) is using, for example if a router (maybe in customer's control) is
advertising itself inappropriately. All in all, while BSR and advertising itself inappropriately. All in all, while BSR and
Auto-RP provide easy configuration, they also provide very Auto-RP provide easy configuration, they also provide very
significant configuration and management complexity. significant configuration and management complexity.
It is worth noting that both Auto-RP and BSR were deployed before the It is worth noting that both Auto-RP and BSR were deployed before the
use of a manually configured anycast-RP address became relatively use of a manually configured anycast-RP address became relatively
commonplace, and there is actually relatively little use for them commonplace, and there is actually relatively little need for them
today. today.
2.5. Mechanisms for Enhanced Redundancy 2.5. Mechanisms for Enhanced Redundancy
A couple of mechanisms, already described in this document, have been A couple of mechanisms, already described in this document, have been
used as a means to enhance redundancy, resilience against failures, used as a means to enhance redundancy, resilience against failures,
and to recover from failures quickly. This section summarizes these and to recover from failures quickly. This section summarizes these
techniques explicitly. techniques explicitly.
2.5.1. Anycast RP 2.5.1. Anycast RP
As mentioned in Section 2.3.2, MSDP is also used to share the state As mentioned in Section 2.3.2, MSDP is also used to share the state
about sources between multiple RPs in a single domain for, e.g., about sources between multiple RPs in a single domain for, e.g.,
redundancy purposes [RFC3446]. The purpose of MSDP in this context redundancy purposes [RFC3446]. The purpose of MSDP in this context
is to share the same state information on multiple RPs for the same is to share the same state information on multiple RPs for the same
groups to enhance the robustness of the service. groups to enhance the robustness of the service.
There is also work in progress to achieve the same using PIM Recent PIM extensions [I-D.ietf-pim-anycast-rp] also provide this
extensions [I-D.ietf-pim-anycast-rp]. This is a required method to functionality. In contrast to MSDP, this approach works for both
be able to use Anycast RP with IPv6. IPv4 and IPv6.
2.5.2. Stateless RP Failover 2.5.2. Stateless RP Failover
It is also possible to use some mechanisms for smaller amount of It is also possible to use some mechanisms for smaller amount of
redundancy as Anycast RP, without sharing state between the RPs. A redundancy as Anycast RP, without sharing state between the RPs. A
traditional mechanism has been to use Auto-RP or BSR (see traditional mechanism has been to use Auto-RP or BSR (see
Section 2.4.3) to select another RP when the active one failed. Section 2.4.3) to select another RP when the active one failed.
However, the same functionality could be achieved using a shared- However, the same functionality could be achieved using a shared-
unicast RP address ("anycast RP without state sharing") without the unicast RP address ("anycast RP without state sharing") without the
complexity of a dynamic mechanism. Further, Anycast RP offers a complexity of a dynamic mechanism. Further, Anycast RP offers a
significantly more extensive failure mitigation strategy, so today significantly more extensive failure mitigation strategy, so today
there is actually very little need to use stateless failover there is actually very little need to use stateless failover
mechanisms, especially dynamic ones, for redundancy purposes. mechanisms, especially dynamic ones, for redundancy purposes.
2.5.3. Bi-directional PIM 2.5.3. Bi-directional PIM
Bi-directional PIM (see Section 2.1.3) uses less state than PIM-SM, Because bi-directional PIM (see Section 2.1.3) does not switch to
implying a better total convergence. On the other hand, PIM-SM or shortest path tree (SPT), the final multicast tree is built faster
SSM may be faster especially in scenarios where bi-directional needs and converges faster after failures. On the other hand, PIM-SM or
to re-do the Designated Forwarder election. SSM may converge more quickly especially in scenarios where bi-
directional needs to re-do the Designated Forwarder election.
2.6. Interactions with Hosts 2.6. Interactions with Hosts
Previous sections have dealt with the components required by routers Previous sections have dealt with the components required by routers
to be able to do multicast routing. Obviously, the real users of to be able to do multicast routing. Obviously, the real users of
multicast are the hosts: either sending or receiving multicast. This multicast are the hosts: either sending or receiving multicast. This
section describes the required interactions with hosts. section describes the required interactions with hosts.
2.6.1. Hosts Sending Multicast 2.6.1. Hosts Sending Multicast
Hosts don't need to do any signalling prior to sending multicast to a After choosing a multicast group through a variety of means, hosts
group; they just send the packets to the link-layer multicast just send the packets to the link-layer multicast address, and the
address, and the designated router will receive all the multicast designated router will receive all the multicast packets and start
packets and start forwarding them as appropriate. forwarding them as appropriate.
ASM senders may move to a new IP address without significant impact
on the delivery of their transmission. SSM senders cannot change the
IP address unless receivers join the new channel or the sender uses
an IP mobility technique that is transparent to the receivers.
2.6.2. Hosts Receiving Multicast 2.6.2. Hosts Receiving Multicast
Hosts signal their interest in receiving a multicast group or channel Hosts signal their interest in receiving a multicast group or channel
by the use of IGMP [RFC3376] and MLD [RFC3810]. IGMPv2 and MLDv1 are by the use of IGMP [RFC3376] and MLD [RFC3810]. IGMPv2 and MLDv1 are
also commonplace, but most new deployments support the latest also commonplace, but most new deployments support the latest
specifications. specifications.
2.7. Restricting Multicast Flooding in the Link Layer 2.7. Restricting Multicast Flooding in the Link Layer
skipping to change at page 13, line 14 skipping to change at page 13, line 26
These options are discussed in this section. These options are discussed in this section.
2.7.1. Router-to-Router Flooding Reduction 2.7.1. Router-to-Router Flooding Reduction
A proprietary solution, Cisco's RGMP [RFC3488] has been developed to A proprietary solution, Cisco's RGMP [RFC3488] has been developed to
reduce the amount of router-to-router flooding on a LAN. This is reduce the amount of router-to-router flooding on a LAN. This is
typically only considered a problem in some Ethernet-based Internet typically only considered a problem in some Ethernet-based Internet
Exchange points. Exchange points.
There have been proposals to snoop PIM messages There have been proposals to observe and possibly react ("snoop") PIM
[I-D.tsenevir-pim-sm-snoop][I-D.serbest-l2vpn-vpls-mcast] to achieve messages [I-D.tsenevir-pim-sm-snoop][I-D.serbest-l2vpn-vpls-mcast] to
the same effect. achieve the same effect.
2.7.2. Host/Router Flooding Reduction 2.7.2. Host/Router Flooding Reduction
There are a number of techniques to help reduce flooding both from a There are a number of techniques to help reduce flooding both from a
router to hosts, and from a host to the routers (and other hosts). router to hosts, and from a host to the routers (and other hosts).
Cisco's proprietary CGMP [CGMP] provides a solution where the routers Cisco's proprietary CGMP [CGMP] provides a solution where the routers
notify the switches, but also allows the switches to snoop IGMP notify the switches, but also allows the switches to snoop IGMP
packets to enable faster notification of hosts no longer wishing to packets to enable faster notification of hosts no longer wishing to
receive a group. IPv6 is not supported. receive a group. IPv6 is not supported.
IEEE specifications mention Group Address Resolution Protocol (GARP) IEEE specifications mention Group Address Resolution Protocol (GARP)
[GARP] as a link-layer method to perform the same functionality. The [GARP] as a link-layer method to perform the same functionality. The
implementation status is unknown. implementation status is unknown.
IGMP snooping [I-D.ietf-magma-snoop] appears to be the most widely IGMP snooping [RFC4541] appears to be the most widely implemented
implemented technique. IGMP snooping requires that the switches technique. IGMP snooping requires that the switches implement a
implement a significant amount of IP-level packet inspection; this significant amount of IP-level packet inspection; this appears to be
appears to be something that is difficult to get right, and often the something that is difficult to get right, and often the upgrades are
upgrades are also a challenge. To allow the snooping switches to also a challenge. Snooping switches also need to identify the ports
identify at which ports the routers reside (and therefore where to where routers reside (and therefore where to flood the packets) using
flood the packets) instead of requiring manual configuration, Multicast Router Discovery protocol [RFC4286], looking at certain
Multicast Router Discovery protocol is being specified [RFC4286]. IGMP queries [RFC4541], or by manual configuration. IGMP proxying
IGMP proxying [I-D.ietf-magma-igmp-proxy] is sometimes used either as [I-D.ietf-magma-igmp-proxy] is sometimes used either as a replacement
a replacement of a multicast routing protocol on a small router, or of a multicast routing protocol on a small router, or to aggregate
to aggregate IGMP/MLD reports when used with IGMP snooping. IGMP/MLD reports when used with IGMP snooping.
3. Acknowledgements 3. Acknowledgements
Tutoring a couple multicast-related papers, the latest by Kaarle Tutoring a couple multicast-related papers, the latest by Kaarle
Ritvanen [RITVANEN] convinced the author that the up-to-date Ritvanen [RITVANEN] convinced the author that up-to-date multicast
multicast routing and address assignment/allocation documentation is routing and address assignment/allocation documentation is necessary.
necessary.
Leonard Giuliano, James Lingard, Jean-Jacques Pansiot, Dave Meyer, Leonard Giuliano, James Lingard, Jean-Jacques Pansiot, Dave Meyer,
Stig Venaas, Tom Pusateri, Marshall Eubanks, Dino Farinacci, and Stig Venaas, Tom Pusateri, Marshall Eubanks, Dino Farinacci, Bharat
Bharat Joshi provided good comments, helping in improving this Joshi, Albert Manfredi, Jean-Jacques Pansiot, and Spencer Dawkins
document. provided good comments, helping in improving this document.
4. IANA Considerations 4. IANA Considerations
This memo includes no request to IANA. This memo includes no request to IANA.
5. Security Considerations 5. Security Considerations
This memo only describes different approaches to multicast routing, This memo only describes different approaches to multicast routing,
and this has no security considerations; the security analysis of the and this has no security considerations; the security analysis of the
mentioned protocols is out of scope of this memo. mentioned protocols is out of scope of this memo.
skipping to change at page 14, line 32 skipping to change at page 14, line 42
6. References 6. References
6.1. Normative References 6.1. Normative References
[I-D.ietf-idmr-dvmrp-v3] [I-D.ietf-idmr-dvmrp-v3]
Pusateri, T., "Distance Vector Multicast Routing Pusateri, T., "Distance Vector Multicast Routing
Protocol", draft-ietf-idmr-dvmrp-v3-11 (work in progress), Protocol", draft-ietf-idmr-dvmrp-v3-11 (work in progress),
December 2003. December 2003.
[I-D.ietf-idmr-dvmrp-v3-as]
Pusateri, T., "Distance Vector Multicast Routing Protocol
Applicability Statement", draft-ietf-idmr-dvmrp-v3-as-01
(work in progress), May 2004.
[I-D.ietf-isis-wg-multi-topology] [I-D.ietf-isis-wg-multi-topology]
Przygienda, T., "M-ISIS: Multi Topology (MT) Routing in Przygienda, T., "M-ISIS: Multi Topology (MT) Routing in
IS-IS", draft-ietf-isis-wg-multi-topology-11 (work in IS-IS", draft-ietf-isis-wg-multi-topology-11 (work in
progress), October 2005. progress), October 2005.
[I-D.ietf-mboned-addrarch]
Savola, P., "Overview of the Internet Multicast Addressing
Architecture", draft-ietf-mboned-addrarch-04 (work in
progress), March 2006.
[I-D.ietf-ospf-mt] [I-D.ietf-ospf-mt]
Psenak, P., "Multi-Topology (MT) Routing in OSPF", Psenak, P., "Multi-Topology (MT) Routing in OSPF",
draft-ietf-ospf-mt-06 (work in progress), February 2006. draft-ietf-ospf-mt-06 (work in progress), February 2006.
[I-D.ietf-pim-bidir] [I-D.ietf-pim-bidir]
Handley, M., "Bi-directional Protocol Independent Handley, M., "Bi-directional Protocol Independent
Multicast (BIDIR-PIM)", draft-ietf-pim-bidir-08 (work in Multicast (BIDIR-PIM)", draft-ietf-pim-bidir-08 (work in
progress), October 2005. progress), October 2005.
[I-D.ietf-pim-sm-v2-new] [I-D.ietf-pim-sm-v2-new]
Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, Fenner, B., "Protocol Independent Multicast - Sparse Mode
"Protocol Independent Multicast - Sparse Mode PIM-SM): (PIM-SM): Protocol Specification (Revised)",
Protocol Specification (Revised)", draft-ietf-pim-sm-v2-new-12 (work in progress),
draft-ietf-pim-sm-v2-new-11 (work in progress), March 2006.
October 2004.
[I-D.ietf-ssm-arch] [I-D.ietf-ssm-arch]
Holbrook, H. and B. Cain, "Source-Specific Multicast for Holbrook, H. and B. Cain, "Source-Specific Multicast for
IP", draft-ietf-ssm-arch-07 (work in progress), IP", draft-ietf-ssm-arch-07 (work in progress),
October 2005. October 2005.
[RFC2026] Bradner, S., "The Internet Standards Process -- Revision [RFC2026] Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026, October 1996. 3", BCP 9, RFC 2026, October 1996.
[RFC2858] Bates, T., Rekhter, Y., Chandra, R., and D. Katz, [RFC2858] Bates, T., Rekhter, Y., Chandra, R., and D. Katz,
skipping to change at page 16, line 8 skipping to change at page 16, line 19
[GARP] Tobagi, F., Molinero-Fernandez, P., and M. Karam, "Study [GARP] Tobagi, F., Molinero-Fernandez, P., and M. Karam, "Study
of IEEE 802.1p GARP/GMRP Timer Values", 1997. of IEEE 802.1p GARP/GMRP Timer Values", 1997.
[I-D.daley-magma-smld-prob] [I-D.daley-magma-smld-prob]
Daley, G. and G. Kurup, "Trust Models and Security in Daley, G. and G. Kurup, "Trust Models and Security in
Multicast Listener Discovery", Multicast Listener Discovery",
draft-daley-magma-smld-prob-00 (work in progress), draft-daley-magma-smld-prob-00 (work in progress),
July 2004. July 2004.
[I-D.ietf-idmr-dvmrp-v3-as]
Pusateri, T., "Distance Vector Multicast Routing Protocol
Applicability Statement", draft-ietf-idmr-dvmrp-v3-as-01
(work in progress), May 2004.
[I-D.ietf-idr-rfc2858bis] [I-D.ietf-idr-rfc2858bis]
Bates, T., "Multiprotocol Extensions for BGP-4", Bates, T., "Multiprotocol Extensions for BGP-4",
draft-ietf-idr-rfc2858bis-08 (work in progress), draft-ietf-idr-rfc2858bis-10 (work in progress),
January 2006. March 2006.
[I-D.ietf-magma-igmp-proxy] [I-D.ietf-magma-igmp-proxy]
Fenner, B., He, H., Haberman, B., and H. Sandick, "IGMP/ Fenner, B., He, H., Haberman, B., and H. Sandick, "IGMP/
MLD-based Multicast Forwarding ('IGMP/MLD Proxying')", MLD-based Multicast Forwarding ('IGMP/MLD Proxying')",
draft-ietf-magma-igmp-proxy-06 (work in progress), draft-ietf-magma-igmp-proxy-06 (work in progress),
April 2004. April 2004.
[I-D.ietf-magma-snoop]
Christensen, M., Kimball, K., and F. Solensky,
"Considerations for IGMP and MLD Snooping Switches",
draft-ietf-magma-snoop-12 (work in progress),
February 2005.
[I-D.ietf-mboned-ipv6-multicast-issues] [I-D.ietf-mboned-ipv6-multicast-issues]
Savola, P., "IPv6 Multicast Deployment Issues", Savola, P., "IPv6 Multicast Deployment Issues",
draft-ietf-mboned-ipv6-multicast-issues-02 (work in draft-ietf-mboned-ipv6-multicast-issues-02 (work in
progress), February 2005. progress), February 2005.
[I-D.ietf-mboned-mroutesec] [I-D.ietf-mboned-mroutesec]
Savola, P., Lehtonen, R., and D. Meyer, "PIM-SM Multicast Savola, P., Lehtonen, R., and D. Meyer, "PIM-SM Multicast
Routing Security Issues and Enhancements", Routing Security Issues and Enhancements",
draft-ietf-mboned-mroutesec-04 (work in progress), draft-ietf-mboned-mroutesec-04 (work in progress),
October 2004. October 2004.
[I-D.ietf-pim-anycast-rp] [I-D.ietf-pim-anycast-rp]
Farinacci, D. and Y. Cai, "Anycast-RP using PIM", Farinacci, D. and Y. Cai, "Anycast-RP using PIM",
draft-ietf-pim-anycast-rp-07 (work in progress), draft-ietf-pim-anycast-rp-07 (work in progress),
February 2006. February 2006.
[I-D.ietf-pim-sm-bsr] [I-D.ietf-pim-sm-bsr]
Bhaskar, N., "Bootstrap Router (BSR) Mechanism for PIM", Bhaskar, N., "Bootstrap Router (BSR) Mechanism for PIM",
draft-ietf-pim-sm-bsr-06 (work in progress), October 2005. draft-ietf-pim-sm-bsr-09 (work in progress), June 2006.
[I-D.lehtonen-mboned-dynssm-req] [I-D.lehtonen-mboned-dynssm-req]
Lehtonen, R., "Requirements for discovery of dynamic SSM Lehtonen, R., "Requirements for discovery of dynamic SSM
sources", draft-lehtonen-mboned-dynssm-req-00 (work in sources", draft-lehtonen-mboned-dynssm-req-00 (work in
progress), February 2005. progress), February 2005.
[I-D.savola-pim-lasthop-threats] [I-D.savola-pim-lasthop-threats]
Savola, P., "Last-hop Threats to Protocol Independent Lingard, J. and P. Savola, "Last-hop Threats to Protocol
Multicast (PIM)", draft-savola-pim-lasthop-threats-01 Independent Multicast (PIM)",
(work in progress), January 2005. draft-savola-pim-lasthop-threats-02 (work in progress),
June 2006.
[I-D.serbest-l2vpn-vpls-mcast] [I-D.serbest-l2vpn-vpls-mcast]
Serbest, Y., "Supporting IP Multicast over VPLS", Serbest, Y., "Supporting IP Multicast over VPLS",
draft-serbest-l2vpn-vpls-mcast-03 (work in progress), draft-serbest-l2vpn-vpls-mcast-03 (work in progress),
July 2005. July 2005.
[I-D.tsenevir-pim-sm-snoop] [I-D.tsenevir-pim-sm-snoop]
Senevirathne, T. and S. Vallepali, "Protocol Independent Senevirathne, T. and S. Vallepali, "Protocol Independent
Multicast-Sparse Mode (PIM-SM) Snooping", Multicast-Sparse Mode (PIM-SM) Snooping",
draft-tsenevir-pim-sm-snoop-00 (work in progress), draft-tsenevir-pim-sm-snoop-00 (work in progress),
skipping to change at page 18, line 17 skipping to change at page 18, line 28
[RFC3740] Hardjono, T. and B. Weis, "The Multicast Group Security [RFC3740] Hardjono, T. and B. Weis, "The Multicast Group Security
Architecture", RFC 3740, March 2004. Architecture", RFC 3740, March 2004.
[RFC3913] Thaler, D., "Border Gateway Multicast Protocol (BGMP): [RFC3913] Thaler, D., "Border Gateway Multicast Protocol (BGMP):
Protocol Specification", RFC 3913, September 2004. Protocol Specification", RFC 3913, September 2004.
[RFC4286] Haberman, B. and J. Martin, "Multicast Router Discovery", [RFC4286] Haberman, B. and J. Martin, "Multicast Router Discovery",
RFC 4286, December 2005. RFC 4286, December 2005.
[RFC4541] Christensen, M., Kimball, K., and F. Solensky,
"Considerations for Internet Group Management Protocol
(IGMP) and Multicast Listener Discovery (MLD) Snooping
Switches", RFC 4541, May 2006.
[RITVANEN] [RITVANEN]
Ritvanen, K., "Multicast Routing and Addressing", HUT Ritvanen, K., "Multicast Routing and Addressing", HUT
Report, Seminar on Internetworking, May 2004, Report, Seminar on Internetworking, May 2004,
<http://www.tml.hut.fi/Studies/T-110.551/2004/papers/>. <http://www.tml.hut.fi/Studies/T-110.551/2004/papers/>.
Appendix A. Multicast Payload Transport Extensions Appendix A. Multicast Payload Transport Extensions
A couple of mechanisms have been, and are being specified, to improve A couple of mechanisms have been, and are being specified, to improve
the characteristics of the data that can be transported over the characteristics of the data that can be transported over
multicast. multicast.
skipping to change at page 18, line 40 skipping to change at page 19, line 8
A.1. Reliable Multicast A.1. Reliable Multicast
Reliable Multicast Working Group has been working on experimental Reliable Multicast Working Group has been working on experimental
specifications so that applications requiring reliable delivery specifications so that applications requiring reliable delivery
characteristics, instead of simple unreliable UDP, could use characteristics, instead of simple unreliable UDP, could use
multicast as a distribution mechanism. multicast as a distribution mechanism.
One such mechanism is Pragmatic Generic Multicast (PGM) [RFC3208]. One such mechanism is Pragmatic Generic Multicast (PGM) [RFC3208].
This does not require support from the routers, bur PGM-aware routers This does not require support from the routers, bur PGM-aware routers
may act as helpers delivering missing data. may act in router assistance role in the initial delivery and
potential retransmission of missing data.
A.2. Multicast Group Security A.2. Multicast Group Security
Multicast Security Working Group has been working on methods how the Multicast Security Working Group has been working on methods how the
integrity, confidentiality, and authentication of data sent to integrity, confidentiality, and authentication of data sent to
multicast groups can be ensured using cryptographic techniques multicast groups can be ensured using cryptographic techniques
[RFC3740]. [RFC3740].
Author's Address Author's Address
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