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Versions: (draft-savola-mboned-routingarch)
00 01 02 03 04 05 06 07 08 09 10 11
12 RFC 5110
Internet Engineering Task Force P. Savola
Internet-Draft CSC/FUNET
Obsoletes: June 26, 2006
3913,2189,2201,1584,1585 (if
approved)
Intended status: Best Current
Practice
Expires: December 28, 2006
Overview of the Internet Multicast Routing Architecture
draft-ietf-mboned-routingarch-04.txt
Status of this Memo
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This Internet-Draft will expire on December 28, 2006.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
The lack of up-to-date documentation on IP multicast routing
protocols and procedures has caused a great deal of confusion. To
clarify the situation, this memo describes the routing protocols and
techniques currently (as of this writing) in use.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Multicast-related Abbreviations . . . . . . . . . . . . . 4
2. Multicast Routing . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Setting up Multicast Forwarding State . . . . . . . . . . 4
2.1.1. PIM-SM . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.2. PIM-DM . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.3. Bi-directional PIM . . . . . . . . . . . . . . . . . . 5
2.1.4. DVMRP . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1.5. MOSPF . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.6. BGMP . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.7. CBT . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.8. Interactions and Summary . . . . . . . . . . . . . . . 6
2.2. Distributing Topology Information . . . . . . . . . . . . 7
2.2.1. Multi-protocol BGP . . . . . . . . . . . . . . . . . . 7
2.2.2. OSPF/IS-IS Multi-topology Extensions . . . . . . . . . 8
2.2.3. Issue: Overlapping Unicast/multicast Topology . . . . 8
2.3. Learning (Active) Sources . . . . . . . . . . . . . . . . 8
2.3.1. SSM . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.3.2. MSDP . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.3.3. Embedded-RP . . . . . . . . . . . . . . . . . . . . . 9
2.4. Configuring and Distributing PIM-SM RP Information . . . . 10
2.4.1. Manual Configuration with an Anycast Address . . . . . 10
2.4.2. Embedded-RP . . . . . . . . . . . . . . . . . . . . . 10
2.4.3. BSR and Auto-RP . . . . . . . . . . . . . . . . . . . 11
2.5. Mechanisms for Enhanced Redundancy . . . . . . . . . . . . 11
2.5.1. Anycast RP . . . . . . . . . . . . . . . . . . . . . . 11
2.5.2. Stateless RP Failover . . . . . . . . . . . . . . . . 12
2.5.3. Bi-directional PIM . . . . . . . . . . . . . . . . . . 12
2.6. Interactions with Hosts . . . . . . . . . . . . . . . . . 12
2.6.1. Hosts Sending Multicast . . . . . . . . . . . . . . . 12
2.6.2. Hosts Receiving Multicast . . . . . . . . . . . . . . 12
2.7. Restricting Multicast Flooding in the Link Layer . . . . . 13
2.7.1. Router-to-Router Flooding Reduction . . . . . . . . . 13
2.7.2. Host/Router Flooding Reduction . . . . . . . . . . . . 13
3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
5. Security Considerations . . . . . . . . . . . . . . . . . . . 14
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.1. Normative References . . . . . . . . . . . . . . . . . . . 14
6.2. Informative References . . . . . . . . . . . . . . . . . . 16
Appendix A. Multicast Payload Transport Extensions . . . . . . . 18
A.1. Reliable Multicast . . . . . . . . . . . . . . . . . . . . 18
A.2. Multicast Group Security . . . . . . . . . . . . . . . . . 19
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 19
Intellectual Property and Copyright Statements . . . . . . . . . . 20
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1. Introduction
Good, up-to-date documentation of IP multicast is close to non-
existent. This issue is severely felt with multicast routing
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
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
routing protocols and techniques.
This memo deals with:
o setting up multicast forwarding state (Section 2.1),
o distributing multicast topology information (Section 2.2),
o learning active sources (Section 2.3),
o configuring and distributing the PIM-SM RP information
(Section 2.4),
o mechanisms for enhanced redundancy (Section 2.5),
o interacting with hosts (Section 2.6), and
o restricting the multicast flooding in the link layer
(Section 2.7).
Some multicast data transport issues are also introduced in
Appendix A.
This memo obsoletes and re-classifies to Historic [RFC2026] Border
Gateway Multicast Protocol (BGMP), Core Based Trees (CBT), Multicast
OSPF (MOSPF) RFCs: [RFC3913], [RFC2189], [RFC2201], [RFC1584], and
[RFC1585]. The purpose of the re-classification is to give the
readers (both implementors and deployers) an idea what the status of
a protocol is; there may be legacy deployments of some of these
protocols, which are not affected by this reclassification. See
Section 2.1 for more on each protocol.
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1.1. Multicast-related Abbreviations
ASM Any Source Multicast
BGMP Border Gateway Multicast Protocol
BSR Bootstrap Router
CBT Core Based Trees
CGMP Cisco Group Management Protocol
DR Designated Router
DVMRP Distance Vector Multicast Routing Protocol
GARP Group Address Resolution Protocol
IGMP Internet Group Management Protocol
MBGP Multi-protocol BGP (*not* "Multicast BGP")
MLD Multicast Listener Discovery
MOSPF Multicast OSPF
MSDP Multicast Source Discovery Protocol
PGM Pragmatic General Multicast
PIM Protocol Independent Multicast
PIM-DM PIM - Dense Mode
PIM-SM PIM - Sparse Mode
PIM-SSM PIM - Source-Specific Multicast
RGMP (Cisco's) Router Group Management Protocol
RP Rendezvous Point
SSM Source-specific Multicast
2. Multicast Routing
2.1. Setting up Multicast Forwarding State
The most important part of multicast routing is setting up the
multicast forwarding state. This section describes the protocols
commonly used for this purpose.
2.1.1. PIM-SM
By far, the most common multicast routing protocol is PIM-SM
[I-D.ietf-pim-sm-v2-new]. The PIM-SM protocol includes both Any
Source Multicast (ASM) and Source-Specific Multicast (SSM)
functionality; PIM-SSM is a subset of PIM-SM. Most current routing
platforms support PIM-SM.
2.1.2. PIM-DM
Whereas PIM-SM is designed to avoid unnecessary flooding of multicast
data, PIM-DM [RFC3973] operates in a "dense" mode, flooding the
multicast transmissions throughout the network ("flood and prune")
unless the leaf parts of the network periodically indicate that they
are not interested in that particular traffic.
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PIM-DM may be an acceptable fit in small and/or simple networks,
where setting up an RP would be unnecessary, and possibly in cases
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
minimal. PIM-DM has been used to transition to PIM-SM but it is no
longer in widespread use.
PIM-DM never became popular due to its reliance on data plane and
potential for loops, and the over-reliance of the complex Assert
mechanism. Further, it was a non-starter with high-bandwidth streams
due to its flooding paradigm.
Many implementations also support so-called "sparse-dense" mode,
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)
only. Lately, many networks have been transitioned away from sparse-
dense to only sparse mode.
2.1.3. Bi-directional PIM
Bi-directional PIM [I-D.ietf-pim-bidir] aims to offer streamlined
PIM-SM operation, without data-driven events and data-encapsulation,
inside a PIM-SM domain. As it doesn't keep source-specific state, it
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
standards based mechanism for alerting routers that a group range is
to be used for bi-directional PIM.
2.1.4. DVMRP
Distance Vector Multicast Routing Protocol (DVMRP) [RFC1075]
[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
deployment hurdles. It also included tunneling capabilities which
were part of its multicast topology functions.
Currently, DVMRP is used only very rarely in operator networks,
having been replaced with PIM-SM. The most typical deployment of
DVMRP is at a leaf network, to run from a legacy firewall only
supporting DVMRP to the internal network. However, GRE tunneling
[RFC2784] seems to have overtaken DVMRP in this functionality, and
there is relatively little use for DVMRP except in legacy
deployments.
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2.1.5. MOSPF
MOSPF [RFC1584] was implemented by several vendors and has seen some
deployment in intra-domain networks. However, since it is based on
intra-domain OSPF it does not scale to the inter-domain case,
operators have found it is easier to deploy a single protocol for use
in both intra-domain and inter-domain networks and so it is no longer
being actively deployed.
2.1.6. BGMP
BGMP [RFC3913] did not get sufficient support within the service
provider community to get adopted and moved forward in the IETF
standards process. There were no reported production implementations
and no production deployments.
2.1.7. CBT
CBT [RFC2201] was an academic project that provided the basis for PIM
sparse mode shared trees. Once the shared tree functionality was
incorporated into PIM implementations, there was no longer a need for
a production CBT implemention. Therefore, CBT never saw production
deployment.
2.1.8. Interactions and Summary
It is worth noting that it is possible to run different protocols
with different multicast group ranges (e.g., treat some groups as
dense mode in an otherwise PIM-SM network; this typically requires
manual configuration of the groups) or interaction between different
protocols (e.g., use DVMRP in the leaf network, but PIM-SM upstream).
The basics for interactions among different protocols have been
outlined in [RFC2715].
The following figure gives a concise summary of the deployment status
of different protocols as of this writing.
+-------------+-------------+----------------+
| Interdomain | Intradomain | Status |
+------------+-------------+-------------+----------------+
| PIM-SM | Yes | Yes | Active |
| PIM-DM | Not feasible| Yes | Little use |
| Bi-dir PIM | No | Yes | Wait & see |
| DVMRP | Not anymore | Stub only | Going out |
| MOSF | No | Not anymore | Inactive |
| CBT | No | No | Never deployed |
| BGMP | No | No | Never deployed |
+------------+-------------+-------------+----------------+
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From this table, it is clear that PIM-Sparse Mode is the only
multicast routing protocol that is deployed inter-domain and,
therefore, is most frequently used within multicast domains as well.
2.2. Distributing Topology Information
When unicast and multicast topologies are the same ("congruent"),
i.e., use the same routing tables (routing information base, RIB), it
has been considered sufficient just to distribute one set of
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 on
the unicast topology gained popularity, it became apparent that it
would be necessary to be able to distribute also non-congruent
multicast reachability information in the regular unicast protocols.
This was previously not an issue, because DVMRP built its own
reachability information.
The topology information is needed to perform efficient distribution
of multicast transmissions and to prevent transmission loops by
applying it to the Reverse Path Forwarding (RPF) check.
This subsection introduces these protocols.
2.2.1. Multi-protocol BGP
Multiprotocol Extensions for BGP-4 [RFC2858] (often referred to as
"MBGP"; however, it is worth noting that "MBGP" does *not* stand for
"Multicast BGP") specifies a mechanism by which BGP can be used to
distribute different reachability information for unicast and
multicast traffic (using SAFI=2 for multicast). Multiprotocol BGP
has been widely deployed for years, and is also needed to route IPv6.
Note that SAFI=3 was originally specified for "both unicast and
multicast" but has been deprecated [I-D.ietf-idr-rfc2858bis].
These extensions are in widespread use wherever BGP is used to
distribute unicast topology information. Multicast-enabled networks
that use BGP should use Multiprotocol BGP to distribute multicast
reachability information explicitly even if the topologies are
congruent to make an explicit statement about multicast reachability.
A number of significant multicast transit providers even require
this, by doing the RPF lookups solely based on explicitly advertised
multicast address family.
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2.2.2. OSPF/IS-IS Multi-topology Extensions
Similar to BGP, some IGPs also provide the capability for signalling
a differing multicast topology, for example IS-IS multi-topology
extensions [I-D.ietf-isis-wg-multi-topology]. Similar work exists
for OSPF [I-D.ietf-ospf-mt].
It is worth noting that interdomain incongruence and intradomain
incongruence are orthogonal, so one doesn't require the other.
Specifically, interdomain incongruence is quite common, while
intradomain incongruence isn't, so you see much more deployment of
MBGP than MT-ISIS/OSPF. Commonly deployed networks have managed well
without protocols handling intradomain incongruence. However, the
availability of multi-topology mechanisms may in part replace the
typically used workarounds such as tunnels.
2.2.3. Issue: Overlapping Unicast/multicast Topology
An interesting case occurs when some routers do not distribute
multicast topology information explicitly while others do. In
particular, this happens when some multicast sites in the Internet
are using plain BGP while some use MBGP.
Different implementations deal with this in different ways.
Sometimes, multicast RPF mechanisms first look up the multicast
routing table, or M-RIB ("topology database") with a longest prefix
match algorithm, and if they find any entry (including a default
route), that is used; if no match is found, the unicast routing table
is used instead.
An alternative approach is to use longest prefix match on the union
of multicast and unicast routing tables; an implementation technique
here is to copy the whole unicast routing table over to the multicast
routing table. The important point to remember here, though, is to
not override the multicast-only routes; if the longest prefix match
would find both a (copied) unicast route and a multicast-only route,
the latter should be treated as preferable.
Another implemented approach is to just look up the information in
the unicast routing table, and provide the user capabilities to
change that as appropriate, using for example copying functions
discussed above.
2.3. Learning (Active) Sources
Typically, multicast routing protocols must either assume that the
receivers know the IP addresses of the (active) sources for a group
in advance, possibly using an out-of-band mechanism (SSM), or the
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sources must be discovered by the network protocols automatically
(ASM).
Learning active sources is a relatively straightforward process with
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
for many reasons. Therefore it is required to be able to split up
the multicast routing infrastructures to smaller domains, and there
must be a way to share information about active sources using some
mechanism if the ASM model is to be supported.
This section discusses the options.
2.3.1. SSM
Source-specific Multicast [I-D.ietf-ssm-arch] (sometimes also
referred to as "single-source Multicast") does not count on learning
active sources in the network. Recipients need to know the source IP
addresses using an out of band mechanism which are used to subscribe
to the (source, group) channel. The multicast routing uses the
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-
of-band source discovery functions which would help SSM in particular
[I-D.lehtonen-mboned-dynssm-req].
2.3.2. MSDP
Multicast Source Discovery Protocol [RFC3618] was invented as a stop-
gap mechanism, when it became apparent that multiple PIM-SM domains
(and RPs) were needed in the network, and information about the
active sources needed to be propagated between the PIM-SM domains
using some other protocol.
MSDP is also used to share the state about sources between multiple
RPs in a single domain for, e.g., redundancy purposes [RFC3446]. The
same can be achieved using PIM extensions [I-D.ietf-pim-anycast-rp].
See Section 2.5 for more information.
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].
2.3.3. Embedded-RP
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
possible to avoid the use of MSDP while still allowing multiple
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multicast domains (in the traditional sense).
The model works by defining a single RP address for a particular
group for all of the Internet, so there is no need to share state
about that with any other RPs. If necessary, RP redundancy can still
be achieved with Anycast-RP using PIM.
2.4. Configuring and Distributing PIM-SM RP Information
For PIM-SM, configuration mechanisms exist which are used to
configure the RP addresses and which groups are to use those RPs in
the routers. This section outlines the approaches.
2.4.1. Manual Configuration with an Anycast Address
It is often easiest just to manually configure the RP information on
the routers when PIM-SM is used.
Originally, static RP mapping was considered suboptimal since it
required explicit configuration changes every time the RP address
changed. However, with the advent of anycast RP addressing, the RP
address is unlikely to ever change. Therefore, the administrative
burden is generally limited to initial configuration. Since there is
usually a fair amount of multicast configuration required on all
routers anyway (eg, PIM on all interfaces), adding the RP address
statically isn't really an issue. Further, static anycast RP mapping
provides the benefits of RP load sharing and redundancy (see
Section 2.5) without the complexity found in dynamic mechanisms like
Auto-RP and Bootstrap Router (BSR).
With such design, an anycast RP uses an address that is configured on
a loopback interfaces of the routers currently acting as RPs, as
described in [RFC3446].
Using this technique, each router might only need to be configured
with one, portable RP address.
2.4.2. Embedded-RP
Embedded-RP provides the information about the RP's address in the
group addresses which are delegated to those who use the RP, so
unless no other ASM than Embedded-RP is used, the network
administrator only needs to configure the RP routers.
While Embedded-RP in many cases is sufficient for IPv6, other methods
of RP configuration are needed if one needs to provide ASM service
for other than Embedded-RP group addresses. In particular, service
discovery type of applications may need hard-coded addresses that are
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not dependent on local RP addresses.
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
manual configuration of an anycast address.
2.4.3. BSR and Auto-RP
BSR [I-D.ietf-pim-sm-bsr] is a mechanism for configuring the RP
address for groups. It may no longer be in as wide use with IPv4 as
it was ealier, and for IPv6, Embedded-RP will in many cases be
sufficient.
Cisco's Auto-RP is an older, proprietary method for distributing
group to RP mappings, similar to BSR. Auto-RP has little use today.
Both Auto-RP and BSR require some form of control at the routers to
ensure that only valid routers are able to advertise themselves as
RPs. Further, flooding of BSR and Auto-RP messages must be prevented
at PIM borders. Additionally, routers require monitoring that they
are actually using the RP(s) the administrators think they should be
using, for example if a router (maybe in customer's control) is
advertising itself inappropriately. All in all, while BSR and
Auto-RP provide easy configuration, they also provide very
significant configuration and management complexity.
It is worth noting that both Auto-RP and BSR were deployed before the
use of a manually configured anycast-RP address became relatively
commonplace, and there is actually relatively little need for them
today.
2.5. Mechanisms for Enhanced Redundancy
A couple of mechanisms, already described in this document, have been
used as a means to enhance redundancy, resilience against failures,
and to recover from failures quickly. This section summarizes these
techniques explicitly.
2.5.1. Anycast RP
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.,
redundancy purposes [RFC3446]. The purpose of MSDP in this context
is to share the same state information on multiple RPs for the same
groups to enhance the robustness of the service.
Recent PIM extensions [I-D.ietf-pim-anycast-rp] also provide this
functionality. In contrast to MSDP, this approach works for both
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IPv4 and IPv6.
2.5.2. Stateless RP Failover
It is also possible to use some mechanisms for smaller amount of
redundancy as Anycast RP, without sharing state between the RPs. A
traditional mechanism has been to use Auto-RP or BSR (see
Section 2.4.3) to select another RP when the active one failed.
However, the same functionality could be achieved using a shared-
unicast RP address ("anycast RP without state sharing") without the
complexity of a dynamic mechanism. Further, Anycast RP offers a
significantly more extensive failure mitigation strategy, so today
there is actually very little need to use stateless failover
mechanisms, especially dynamic ones, for redundancy purposes.
2.5.3. Bi-directional PIM
Because bi-directional PIM (see Section 2.1.3) does not switch to
shortest path tree (SPT), the final multicast tree is built faster
and converges faster after failures. On the other hand, PIM-SM or
SSM may converge more quickly especially in scenarios where bi-
directional needs to re-do the Designated Forwarder election.
2.6. Interactions with Hosts
Previous sections have dealt with the components required by routers
to be able to do multicast routing. Obviously, the real users of
multicast are the hosts: either sending or receiving multicast. This
section describes the required interactions with hosts.
2.6.1. Hosts Sending Multicast
After choosing a multicast group through a variety of means, hosts
just send the packets to the link-layer multicast address, and the
designated router will receive all the multicast packets and start
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
Hosts signal their interest in receiving a multicast group or channel
by the use of IGMP [RFC3376] and MLD [RFC3810]. IGMPv2 and MLDv1 are
also commonplace, but most new deployments support the latest
specifications.
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2.7. Restricting Multicast Flooding in the Link Layer
Multicast transmission in the link layer, for example Ethernet,
typically includes some form of flooding the packets through a LAN.
This causes unnecessary bandwidth usage and discarding unwanted
frames on those nodes which did not want to receive the multicast
transmission.
Therefore a number of techniques have been developed, to be used in
Ethernet switches between routers, or between routers and hosts, to
limit the flooding.
These options are discussed in this section.
2.7.1. Router-to-Router Flooding Reduction
A proprietary solution, Cisco's RGMP [RFC3488] has been developed to
reduce the amount of router-to-router flooding on a LAN. This is
typically only considered a problem in some Ethernet-based Internet
Exchange points.
There have been proposals to observe and possibly react ("snoop") PIM
messages [I-D.tsenevir-pim-sm-snoop][I-D.serbest-l2vpn-vpls-mcast] to
achieve the same effect.
2.7.2. Host/Router Flooding Reduction
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).
Cisco's proprietary CGMP [CGMP] provides a solution where the routers
notify the switches, but also allows the switches to snoop IGMP
packets to enable faster notification of hosts no longer wishing to
receive a group. IPv6 is not supported.
IEEE specifications mention Group Address Resolution Protocol (GARP)
[GARP] as a link-layer method to perform the same functionality. The
implementation status is unknown.
IGMP snooping [RFC4541] appears to be the most widely implemented
technique. IGMP snooping requires that the switches implement a
significant amount of IP-level packet inspection; this appears to be
something that is difficult to get right, and often the upgrades are
also a challenge. Snooping switches also need to identify the ports
where routers reside (and therefore where to flood the packets) using
Multicast Router Discovery protocol [RFC4286], looking at certain
IGMP queries [RFC4541], or by manual configuration. IGMP proxying
[I-D.ietf-magma-igmp-proxy] is sometimes used either as a replacement
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of a multicast routing protocol on a small router, or to aggregate
IGMP/MLD reports when used with IGMP snooping.
3. Acknowledgements
Tutoring a couple multicast-related papers, the latest by Kaarle
Ritvanen [RITVANEN] convinced the author that up-to-date multicast
routing and address assignment/allocation documentation is necessary.
Leonard Giuliano, James Lingard, Jean-Jacques Pansiot, Dave Meyer,
Stig Venaas, Tom Pusateri, Marshall Eubanks, Dino Farinacci, Bharat
Joshi, Albert Manfredi, Jean-Jacques Pansiot, and Spencer Dawkins
provided good comments, helping in improving this document.
4. IANA Considerations
This memo includes no request to IANA.
5. Security Considerations
This memo only describes different approaches to multicast routing,
and this has no security considerations; the security analysis of the
mentioned protocols is out of scope of this memo.
However, there has been analysis of the security of multicast routing
infrastructures [I-D.ietf-mboned-mroutesec], IGMP/MLD
[I-D.daley-magma-smld-prob], and PIM last-hop issues
[I-D.savola-pim-lasthop-threats].
6. References
6.1. Normative References
[I-D.ietf-idmr-dvmrp-v3]
Pusateri, T., "Distance Vector Multicast Routing
Protocol", draft-ietf-idmr-dvmrp-v3-11 (work in progress),
December 2003.
[I-D.ietf-isis-wg-multi-topology]
Przygienda, T., "M-ISIS: Multi Topology (MT) Routing in
IS-IS", draft-ietf-isis-wg-multi-topology-11 (work in
progress), October 2005.
[I-D.ietf-mboned-addrarch]
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Savola, P., "Overview of the Internet Multicast Addressing
Architecture", draft-ietf-mboned-addrarch-04 (work in
progress), March 2006.
[I-D.ietf-ospf-mt]
Psenak, P., "Multi-Topology (MT) Routing in OSPF",
draft-ietf-ospf-mt-06 (work in progress), February 2006.
[I-D.ietf-pim-bidir]
Handley, M., "Bi-directional Protocol Independent
Multicast (BIDIR-PIM)", draft-ietf-pim-bidir-08 (work in
progress), October 2005.
[I-D.ietf-pim-sm-v2-new]
Fenner, B., "Protocol Independent Multicast - Sparse Mode
(PIM-SM): Protocol Specification (Revised)",
draft-ietf-pim-sm-v2-new-12 (work in progress),
March 2006.
[I-D.ietf-ssm-arch]
Holbrook, H. and B. Cain, "Source-Specific Multicast for
IP", draft-ietf-ssm-arch-07 (work in progress),
October 2005.
[RFC2026] Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026, October 1996.
[RFC2858] Bates, T., Rekhter, Y., Chandra, R., and D. Katz,
"Multiprotocol Extensions for BGP-4", RFC 2858, June 2000.
[RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
Thyagarajan, "Internet Group Management Protocol, Version
3", RFC 3376, October 2002.
[RFC3618] Fenner, B. and D. Meyer, "Multicast Source Discovery
Protocol (MSDP)", RFC 3618, October 2003.
[RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery
Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.
[RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous
Point (RP) Address in an IPv6 Multicast Address",
RFC 3956, November 2004.
[RFC3973] Adams, A., Nicholas, J., and W. Siadak, "Protocol
Independent Multicast - Dense Mode (PIM-DM): Protocol
Specification (Revised)", RFC 3973, January 2005.
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6.2. Informative References
[CGMP] "Cisco Group Management Protocol",
<http://www.javvin.com/protocolCGMP.html>.
[GARP] Tobagi, F., Molinero-Fernandez, P., and M. Karam, "Study
of IEEE 802.1p GARP/GMRP Timer Values", 1997.
[I-D.daley-magma-smld-prob]
Daley, G. and G. Kurup, "Trust Models and Security in
Multicast Listener Discovery",
draft-daley-magma-smld-prob-00 (work in progress),
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]
Bates, T., "Multiprotocol Extensions for BGP-4",
draft-ietf-idr-rfc2858bis-10 (work in progress),
March 2006.
[I-D.ietf-magma-igmp-proxy]
Fenner, B., He, H., Haberman, B., and H. Sandick, "IGMP/
MLD-based Multicast Forwarding ('IGMP/MLD Proxying')",
draft-ietf-magma-igmp-proxy-06 (work in progress),
April 2004.
[I-D.ietf-mboned-ipv6-multicast-issues]
Savola, P., "IPv6 Multicast Deployment Issues",
draft-ietf-mboned-ipv6-multicast-issues-02 (work in
progress), February 2005.
[I-D.ietf-mboned-mroutesec]
Savola, P., Lehtonen, R., and D. Meyer, "PIM-SM Multicast
Routing Security Issues and Enhancements",
draft-ietf-mboned-mroutesec-04 (work in progress),
October 2004.
[I-D.ietf-pim-anycast-rp]
Farinacci, D. and Y. Cai, "Anycast-RP using PIM",
draft-ietf-pim-anycast-rp-07 (work in progress),
February 2006.
[I-D.ietf-pim-sm-bsr]
Bhaskar, N., "Bootstrap Router (BSR) Mechanism for PIM",
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draft-ietf-pim-sm-bsr-09 (work in progress), June 2006.
[I-D.lehtonen-mboned-dynssm-req]
Lehtonen, R., "Requirements for discovery of dynamic SSM
sources", draft-lehtonen-mboned-dynssm-req-00 (work in
progress), February 2005.
[I-D.savola-pim-lasthop-threats]
Lingard, J. and P. Savola, "Last-hop Threats to Protocol
Independent Multicast (PIM)",
draft-savola-pim-lasthop-threats-02 (work in progress),
June 2006.
[I-D.serbest-l2vpn-vpls-mcast]
Serbest, Y., "Supporting IP Multicast over VPLS",
draft-serbest-l2vpn-vpls-mcast-03 (work in progress),
July 2005.
[I-D.tsenevir-pim-sm-snoop]
Senevirathne, T. and S. Vallepali, "Protocol Independent
Multicast-Sparse Mode (PIM-SM) Snooping",
draft-tsenevir-pim-sm-snoop-00 (work in progress),
April 2002.
[RFC1075] Waitzman, D., Partridge, C., and S. Deering, "Distance
Vector Multicast Routing Protocol", RFC 1075,
November 1988.
[RFC1584] Moy, J., "Multicast Extensions to OSPF", RFC 1584,
March 1994.
[RFC1585] Moy, J., "MOSPF: Analysis and Experience", RFC 1585,
March 1994.
[RFC2189] Ballardie, T., "Core Based Trees (CBT version 2) Multicast
Routing -- Protocol Specification --", RFC 2189,
September 1997.
[RFC2201] Ballardie, T., "Core Based Trees (CBT) Multicast Routing
Architecture", RFC 2201, September 1997.
[RFC2715] Thaler, D., "Interoperability Rules for Multicast Routing
Protocols", RFC 2715, October 1999.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
March 2000.
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[RFC3208] Speakman, T., Crowcroft, J., Gemmell, J., Farinacci, D.,
Lin, S., Leshchiner, D., Luby, M., Montgomery, T., Rizzo,
L., Tweedly, A., Bhaskar, N., Edmonstone, R.,
Sumanasekera, R., and L. Vicisano, "PGM Reliable Transport
Protocol Specification", RFC 3208, December 2001.
[RFC3446] Kim, D., Meyer, D., Kilmer, H., and D. Farinacci, "Anycast
Rendevous Point (RP) mechanism using Protocol Independent
Multicast (PIM) and Multicast Source Discovery Protocol
(MSDP)", RFC 3446, January 2003.
[RFC3488] Wu, I. and T. Eckert, "Cisco Systems Router-port Group
Management Protocol (RGMP)", RFC 3488, February 2003.
[RFC3740] Hardjono, T. and B. Weis, "The Multicast Group Security
Architecture", RFC 3740, March 2004.
[RFC3913] Thaler, D., "Border Gateway Multicast Protocol (BGMP):
Protocol Specification", RFC 3913, September 2004.
[RFC4286] Haberman, B. and J. Martin, "Multicast Router Discovery",
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, K., "Multicast Routing and Addressing", HUT
Report, Seminar on Internetworking, May 2004,
<http://www.tml.hut.fi/Studies/T-110.551/2004/papers/>.
Appendix A. Multicast Payload Transport Extensions
A couple of mechanisms have been, and are being specified, to improve
the characteristics of the data that can be transported over
multicast.
These go beyond the scope of multicast routing, but as reliable
multicast has some relevance, these are briefly mentioned.
A.1. Reliable Multicast
Reliable Multicast Working Group has been working on experimental
specifications so that applications requiring reliable delivery
characteristics, instead of simple unreliable UDP, could use
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multicast as a distribution mechanism.
One such mechanism is Pragmatic Generic Multicast (PGM) [RFC3208].
This does not require support from the routers, bur PGM-aware routers
may act in router assistance role in the initial delivery and
potential retransmission of missing data.
A.2. Multicast Group Security
Multicast Security Working Group has been working on methods how the
integrity, confidentiality, and authentication of data sent to
multicast groups can be ensured using cryptographic techniques
[RFC3740].
Author's Address
Pekka Savola
CSC - Scientific Computing Ltd.
Espoo
Finland
Email: psavola@funet.fi
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