Internet DRAFT - draft-ietf-msdp-deploy
draft-ietf-msdp-deploy
INTERNET-DRAFT M. McBride
draft-ietf-msdp-deploy-06.txt J. Meylor
D. Meyer
Category Best Current Practice
Expires: September 2004 March 2004
Multicast Source Discovery Protocol (MSDP) Deployment Scenarios
<draft-ietf-mboned-msdp-deploy-06.txt>
Status of this Document
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This document is a product of the MBONED Working Group. Comments
should be addressed to the authors, or the mailing list at
mboned@lists.uoregon.edu.
Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
McBride, Meylor, and Meyer [Page 1]
INTERNET-DRAFT Expires: September 2004 March 2004
Abstract
This document describes best current practices for intra-domain and
inter-domain deployment of the Multicast Source Discovery Protocol
(MSDP) in conjunction with Protocol Independent Multicast Sparse Mode
(PIM-SM).
McBride, Meylor, and Meyer [Page 2]
INTERNET-DRAFT Expires: September 2004 March 2004
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. BCP, Experimental Protocols and Normative References. . . . 5
2. Inter-domain MSDP Peering Scenarios. . . . . . . . . . . . . . 6
2.1. Peering between PIM Border Routers. . . . . . . . . . . . . 7
2.2. Peering between Non-Border Routers. . . . . . . . . . . . . 8
2.3. MSDP Peering without BGP. . . . . . . . . . . . . . . . . . 9
2.4. MSDP Peering at a Multicast Exchange. . . . . . . . . . . . 10
3. Intra-domain MSDP Peering Scenarios. . . . . . . . . . . . . . 10
3.1. Peering between MSDP and MBGP Configured Routers. . . . . . 10
3.2. MSDP Peer is not BGP Peer (or no BGP Peer). . . . . . . . . 11
3.3. Hierarchical Mesh Groups. . . . . . . . . . . . . . . . . . 12
3.4. MSDP and Route Reflectors . . . . . . . . . . . . . . . . . 13
3.5. MSDP and Anycast RPs. . . . . . . . . . . . . . . . . . . . 14
4. Security Considerations. . . . . . . . . . . . . . . . . . . . 14
4.1. Filtering SA messages . . . . . . . . . . . . . . . . . . . 15
4.2. SA message state limits . . . . . . . . . . . . . . . . . . 15
5. IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 15
6. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . 16
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7.1. Normative References. . . . . . . . . . . . . . . . . . . . 17
7.2. Informative References. . . . . . . . . . . . . . . . . . . 18
8. Author's Addresses . . . . . . . . . . . . . . . . . . . . . . 18
9. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 18
10. Intellectual Property . . . . . . . . . . . . . . . . . . . . 19
11. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 19
McBride, Meylor, and Meyer [Page 3]
INTERNET-DRAFT Expires: September 2004 March 2004
1. Introduction
MSDP [RFC3618] is used primarily in two deployment scenarios:
o Between PIM Domains
MSDP can be used between Protocol Independent Multicast Sparse
Mode (PIM-SM) [PIM-SM] domains to convey information
about active sources available in other domains. MSDP peering
used in such cases is generally one to one peering, and
utilizes the deterministic peer-RPF (Reverse Path Forwarding)
rules described in the MSDP specification (i.e., does not use
mesh-groups). Peerings can be aggregated on a single MSDP
peer. Such a peer can typically have from one to hundreds of
peerings, which is similar in scale to BGP peerings.
o Within a PIM Domain
MSDP is often used between Anycast Rendezvous Points
(Anycast-RPs) [RFC3446] within a PIM domain to synchronize
information about the active sources being served by each
Anycast-RP peer (by virtue of IGP reachability). MSDP peering
used in this scenario is typically based on MSDP mesh groups,
where anywhere from two to tens of peers can comprise a given
mesh group, although more than ten is not typical. One or more
of these mesh-group peers may then also have additional
one-to-one peering with MSDP peers outside that PIM domain for
discovery of external sources. MSDP for anycast-RP without
external MSDP peering is a valid deployment option and common.
Current best practice for MSDP deployment utilizes PIM-SM and the
Border Gateway Protocol with multi-protocol extensions (MBGP)
[RFC1771, RFC2858]. This document outlines how these protocols work
together to provide an intra-domain and inter-domain Any Source
Multicast (ASM) service.
The PIM-SM specification assumes that SM operates only in one PIM
domain. MSDP is used to enable the use of multiple PIM domains by
distributing the required information about active multicast sources
to other PIM domains. Due to breaking the Internet multicast
infrastructure down to multiple PIM domains, MSDP also enables the
possibility to set policy on the visibility of the groups and
sources.
Transit IP providers typically deploy MSDP to be part of the global
multicast infrastructure by connecting to their upstream and peer
McBride, Meylor, and Meyer Section 1. [Page 4]
INTERNET-DRAFT Expires: September 2004 March 2004
multicast networks using MSDP.
Edge multicast networks typically have two choices: to use their
Internet providers RP, or to have their own RP and connect it to
their ISP using MSDP. By deploying their own RP and MSDP, one can
use internal multicast groups which are not visible to the provider's
RP. This helps with internal multicast being able to continue to work
in the event there is a problem with connectivity to the provider or
the provider's RP/MSDP is experiencing difficulties. In the simplest
cases where no internal multicast groups are necessary, there is
often no need to deploy MSDP.
1.1. BCP, Experimental Protocols and Normative References
This document describes the best current practice for a widely
deployed Experimental protocol, MSDP. There is no plan to advance the
MSDP's status (for example, to Proposed Standard). The reasons for
this include:
o MSDP was originally envisioned as a temporary protocol to be
supplanted by whatever the IDMR working group produced as an
inter-domain protocol. However, the IDMR WG (or subsequently,
the BGMP WG) never produced a protocol that could be deployed
to replace MSDP.
o One of the primary reasons given for MSDP to be classified as
Experimental was that the MSDP Working Group came up with
modifications to the protocol that the WG thought made it
better but that implementors didn't see any reasons to
deploy. Without these modifications (e.g., UDP or GRE
encapsulation), MSDP can have negative consequences to initial
packets in datagram streams.
o Scalability: Although we don't know what the hard limits might
be, readvertising everything you know every 60 seconds clearly
limits the amount of state you can advertise.
o MSDP reached near ubiquitous deployment as the de-facto
standard inter-domain multicast protocol in the IPv4 Internet.
o No consensus could be reached regarding the reworking of MSDP
to address the many concerns of various constituencies within
the IETF. As a result, a decision was taken to document what is
(ubiquitously) deployed and move that document to Experimental.
While advancement of MSDP to Proposed Standard was considered,
McBride, Meylor, and Meyer Section 1.1. [Page 5]
INTERNET-DRAFT Expires: September 2004 March 2004
for the reasons mentioned above, it was immediately discarded.
o The advent of protocols such as source specific multicast and
bi-directional PIM, as well as embedded RP techniques for
IPv6, have further reduced consensus that a replacement
protocol for MSDP for the IPv4 Internet is required.
The RFC Editor's policy regarding references is that they be split
into two categories known as "normative" and "informative". Normative
references specify those documents which must be read to understand
or implement the technology in an RFC (or whose technology must be
present for the technology in the new RFC to work) [RFCED]. In order
to understand this document, one must also understand both the PIM
and MSDP documents. As a result, references to these documents are
normative.
The IETF has adopted the policy that BCPs must not have normative
references to Experimental protocols. However, this document is a
special case in that the underlying Experimental document (MSDP) is
not planned to be advanced to Proposed Standard.
The MBONED Working Group requests approval under the Variance
Procedure as documented in RFC 2026 [RFC2026].
Note to RFC-Editor: If IETF/IESG approves this, please change the
above sentence into: The MBONED Working Group has requested approval
under the Variance Procedure as documented in RFC 2026 [RFC2026].
The IESG followed the Variance Procedure, and after an additional 4
week IETF Last Call evaluated the comments and status and has
approved this document.
The key words "MUST"", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC 2119].
2. Inter-domain MSDP Peering Scenarios
The following sections describe the most common inter-domain MSDP
peering possibilities and their deployment options.
McBride, Meylor, and Meyer Section 2. [Page 6]
INTERNET-DRAFT Expires: September 2004 March 2004
2.1. Peering between PIM Border Routers
In this case, the MSDP peers within the domain have their own RP
located within a bounded PIM domain. In addition, the domain will
typically have its own Autonomous System (AS) number and one or more
MBGP speakers. The domain may also have multiple MSDP speakers. Each
border router has an MSDP and MBGP peering with its peer routers.
These external MSDP peering deployments typically configure the MBGP
peering and MSDP peering using the same directly connected next hop
peer IP address or other IP address from the same router. Typical
deployments of this type are providers who have a direct peering with
other providers, providers peering at an exchange, or providers who
use their edge router to MSDP/MBGP peer with customers.
For a direct peering inter-domain environment to be successful, the
first AS in the MBGP best path to the originating RP should be the
same as the AS of the MSDP peer. As an example, consider the
following topology:
AS1----AS2----AS4
| /
| /
| /
AS3
In this case, AS4 receives a Source Active (SA) message, originated
by AS1, from AS2. AS2 also has an MBGP peering with AS4. The MBGP
first hop AS from AS4, in the best path to the originating RP, is
AS2. The AS of the sending MSDP peer is also AS2. In this case, the
peer-Reverse Path Forwarding check (peer-RPF check) passes and the SA
message is forwarded.
A peer-RPF failure would occur in this topology when the MBGP first
hop AS, in the best path to the originating RP, is AS2 while the
origin AS of the sending MSDP peer is AS3. This reliance upon BGP AS
PATH information prevents endless looping of SA packets.
Router code, which has adopted the latest rules in the MSDP draft,
will relax the rules Between AS's a bit. In the following topology we
have an MSDP peering between AS1<->AS3 and AS3<->AS4:
RP
AS1----AS2----AS3----AS4
McBride, Meylor, and Meyer Section 2.1. [Page 7]
INTERNET-DRAFT Expires: September 2004 March 2004
If the first AS in best path to the RP does not equal the MSDP peer,
MSDP peer-RPF fails. So AS1 cannot MSDP peer with AS3 since AS2 is
the first AS in the MBGP best path to AS4 RP. With the latest MSDP
draft compliant code, AS 1 will choose the peer in the closest AS
along best AS path to the RP. AS1 will then accept SA's coming from
AS3. If there are multiple MSDP peers to routers within the same AS,
the peer with the highest IP address is chosen as the RPF peer.
2.2. Peering between Non-Border Routers
When MSDP peering between border routers, intra-domain MSDP
scalability is restricted because it is necessary to also maintain
MBGP and MSDP peerings internally towards their border routers.
Within the intra-domain, the border router becomes the announcer of
the next hop towards the originating RP. This requires that all
intra-domain MSDP peerings must mirror the MBGP path back towards the
border router. External MSDP (eMSDP) peerings rely upon AS path for
peer RPF checking, while internal MSDP (iMSDP) peerings rely upon the
announcer of the next hop.
While the eMBGP peer is typically directly connected between border
routers, it is common for the eMSDP peer to be located deeper into
the transit providers AS. Providers, which desire more flexibility in
MSDP peering placement, commonly choose a few dedicated routers
within their core network for the inter-domain MSDP peerings to their
customers. These core MSDP routers will also typically be in the
providers intra-domain MSDP mesh group and configured for Anycast RP.
All multicast routers in the providers AS should statically point to
the Anycast RP address. Static RP assignment is the most commonly
used method for group to RP mapping due to its deterministic nature.
Auto-RP [AUTORP] and/or the Bootstrap Router (BSR) [BSR] dynamic RP
mapping mechanisms could be also used to disseminate RP information
within the provider's network
For an SA message to be accepted in this (multi-hop peering)
environment, we rely upon the next (or closest, with latest MSDP
spec) AS in the best path towards originating RP for the RPF check.
The MSDP peer address should be in the same AS as the AS of the
border router's MBGP peer. The MSDP peer address should be advertised
via MBGP.
For example, using the diagram below, if customer R1 router is MBGP
peering with R2 router and if R1 is MSDP peering with R3 router, then
R2 and R3 must be in the same AS (or appear, to AS1, to be from the
same AS in the event private AS numbers are deployed). The MSDP peer
McBride, Meylor, and Meyer Section 2.2. [Page 8]
INTERNET-DRAFT Expires: September 2004 March 2004
with the highest IP address will be chosen as the MSDP RPF peer. R1
must also have the MSDP peer address of R3 in its MBGP table.
+--+ +--+ +--+
|R1|----|R2|----|R3|
+--+ +--+ +--+
AS1 AS2 AS2
From R3's perspective, AS1 (R1) is the MBGP next AS in the best path
towards the originating RP. As long as AS1 is the next AS (or
closest) in the best path towards the originating RP, RPF will
succeed on SAs arriving from R1.
In contrast, with the single hop scenario, with R2 (instead of R3)
border MSDP peering with R1 border, R2's MBGP address becomes the
announcer of the next hop for R3, towards the originating RP, and R3
must peer with that R2 address. And all AS2 intra-domain MSDP peers
need to follow iMBGP (or other IGP) peerings towards R2 since iMSDP
has a dependence upon peering with the address of the MBGP (or other
IGP) announcer of the next hop.
2.3. MSDP Peering without BGP
In this case, an enterprise maintains its own RP and has an MSDP
peering with their service provider, but does not BGP peer with them.
MSDP relies upon BGP path information to learn the MSDP topology for
the SA peer-RPF check. MSDP can be deployed without BGP, however, and
as a result there are some special cases where the requirement to
perform an peer-RPF check on the BGP path information is suspended.
These cases are:
o There is only a single MSDP peer connection
o A default peer (default MSDP route) is configured
o The originating RP is directly connected
o A mesh group is used
o An implementation is used which allows for an MSDP peer-RPF
check using an IGP
These cases are when there is only a single MSDP peer connection, a
default peer (default MSDP route) is configured, the originating RP
McBride, Meylor, and Meyer Section 2.3. [Page 9]
INTERNET-DRAFT Expires: September 2004 March 2004
is directly connected, a mesh group is used, or an implementation is
used which allows for an MSDP peer-RPF check using an IGP.
An enterprise will typically configure a unicast default route from
their border router to the provider's border router and then MSDP
peer with the provider's MSDP router. If internal MSDP peerings are
also used within the enterprise, then an MSDP default peer will need
to be configured on the border router pointing to the provider. In
this way, all external multicast sources will be learned and internal
sources can be advertised. If only a single MSDP peering was used (no
internal MSDP peerings) towards the provider, then this stub site
will MSDP default peer towards the provider and skip the peer-RPF
check.
2.4. MSDP Peering at a Multicast Exchange
Multicast exchanges allow multicast providers to peer at a common IP
subnet (or by using point to point virtual LANs) and share MSDP SA
updates. Each provider will MSDP and MBGP peer with each others
directly connected exchange IP address. Each exchange router will
send/receive SAs to/from their MSDP peers. They will then be able to
forward SAs throughout their domain to their customers and any direct
provider peerings.
3. Intra-domain MSDP Peering Scenarios
The following sections describe the different intra-domain MSDP
peering possibilities and their deployment options.
3.1. Peering between MSDP and MBGP Configured Routers
The next hop IP address of the iBGP peer is typically used for the
MSDP peer-RPF check (IGP can also be used). This is different from
the inter-domain BGP/MSDP case, where AS path information is used for
the peer-RPF check. For this reason, it is necessary for the IP
address of the MSDP peer connection be the same as the internal MBGP
peer connection whether or not the MSDP/MBGP peers are directly
connected. A successful deployment would be similar to the following:
McBride, Meylor, and Meyer Section 3.1. [Page 10]
INTERNET-DRAFT Expires: September 2004 March 2004
+----+
| Rb | 3.3.3.3
/ +----+
AS1 AS2 / |
+---+ +--+ / |
|RP1|---------|Ra| |
+---+ +--+ |
1.1.1.1 2.2.2.2 |
\ |
\ |
\ +-----+
| RP2 |
+-----+
Where RP2 MSDP and MBGP peers with Ra (using 2.2.2.2) and with Rb
(using 3.3.3.3). When the MSDP SA update arrives on RP2 from Ra, the
MSDP RPF check for 1.1.1.1 passes because RP2 receives the SA update
from MSDP peer 2.2.2.2 which is also the correct MBGP next hop for
1.1.1.1.
When RP2 receives the same SA update from MSDP peer 3.3.3.3, the MBGP
lookup for 1.1.1.1 shows a next hop of 2.2.2.2 so RPF correctly
fails, preventing a loop.
This deployment could also fail on an update from Ra to RP2 if RP2
was MBGP peering to an address other than 2.2.2.2 on Ra. Intra-domain
deployments must have MSDP and MBGP (or other IGP) peering addresses
which match, unless a method to skip the peer-RPF check is deployed.
3.2. MSDP Peer is not BGP Peer (or no BGP Peer)
This is a common MSDP intra-domain deployment in environments where
few routers are running MBGP or where the domain is not running MBGP.
The problem here is that the MSDP peer address needs to be the same
as the MBGP peer address. To get around this requirement, the intra-
domain MSDP RPF rules have been relaxed in the following topologies:
o By configuring the MSDP peer as a mesh group peer
o By having the MSDP peer be the only MSDP peer
o By configuring a default MSDP peer
McBride, Meylor, and Meyer Section 3.2. [Page 11]
INTERNET-DRAFT Expires: September 2004 March 2004
o By peering with the originating RP.
o By relying upon an IGP for MSDP peer-RPF
The common choice around the intra-domain BGP peering requirement,
when more than one MSDP peer is configured, is to deploy MSDP mesh
groups. When a MSDP mesh group is deployed, there is no RPF check on
arriving SA messages when received from a mesh group peer.
Subsequently, SA messages are always accepted from mesh group peers.
MSDP mesh groups were developed to reduce the amount of SA traffic in
the network since SAs, which arrive from a mesh group peer, are not
flooded to peers within that same mesh group. Mesh groups must be
fully meshed.
If recent (but not currently widely deployed) router code is running
which is fully complaint with the latest MSDP draft, another option,
to work around not having BGP to MSDP RPF peer, is to RPF using an
IGP like OSPF, IS-IS, RIP, etc. This new capability will allow for
enterprise customers, who are not running BGP and who don't want to
run mesh groups, to use their existing IGP to satisfy the MSDP peer-
RPF rules.
3.3. Hierarchical Mesh Groups
Hierarchal Mesh Groups are occasionally deployed in intra-domain
environments where there are a large number of MSDP peers. Allowing
multiple mesh groups to forward to one another can reduce the number
of MSDP peerings per router (due to the full mesh requirement) and
hence reduce router load. A good hierarchical mesh group
implementation (one which prevents looping) contains a core mesh
group in the backbone and these core routers serve as mesh group
aggregation routers:
[R2]{A,2}
/ \
/ \
/ \
/ \
/ \
/ \
/ \
{A,1}[R1]-------------[R3]{A,3}
McBride, Meylor, and Meyer Section 3.3. [Page 12]
INTERNET-DRAFT Expires: September 2004 March 2004
In this example, R1, R2, R3 are in MSDP mesh group A (the core mesh
group) and each serves as MSDP aggregation routers for their leaf (or
second tier) mesh groups 1, 2, and 3. Since SA messages received from
a mesh group peer are not forwarded to peers within that same mesh
group, SA messages will not loop. Do not create topologies which
connect mesh-groups in a loop. In the above example for instance,
second tier mesh-groups 1, 2, and 3 must not directly exchange SA
messages with each other or an endless SA loop will occur.
Redundancy, between mesh groups, will also cause a loop and is
subsequently not available with Hierarchical mesh groups. For
instance, assume R3 had two routers connecting its leaf mesh group 3
with the core mesh group A. A loop would be created between mesh
group 3 and mesh group A because each mesh group must be fully meshed
between peers.
3.4. MSDP and Route Reflectors
BGP requires all iBGP speakers, that are not route-reflector clients
or confederation members, be fully meshed to prevent loops. In the
route reflector environment, MSDP requires that the route reflector
clients peer with the route reflector since the router reflector (RR)
is the BGP announcer of the next hop towards the originating RP. The
RR is not the BGP next hop, but is the announcer of the BGP next hop.
The announcer of the next hop is the address typically used for MSDP
peer-RPF checks. For example, consider the following case:
Ra--------RR
/|\
/ | \
A B C
Ra is forwarding MSDP SAs to the route reflector RR. Routers A, B,
and C also MSDP peer with RR. When RR forwards the SA to A, B, and C,
these RR clients will accept the SA because RR is the announcer of
the next hop to the originating RP address.
An SA will peer-RPF fail, if Ra MSDP peers directly with Routers A,
B, or C, because the announcer of the next hop is RR, but the SA
update came from Ra. Proper deployment is to have RR clients MSDP
peer with the RR. MSDP mesh groups may be used to work around this
requirement. External MSDP peerings will also prevent this
requirement since the next AS is compared between MBGP and MSDP
McBride, Meylor, and Meyer Section 3.4. [Page 13]
INTERNET-DRAFT Expires: September 2004 March 2004
peerings, rather than the IP address of the announcer of the next
hop.
Some recent MSDP implementations conform to the latest MSDP draft
which relaxes the requirement of peering with the Advertiser of the
Next Hop (the Route Reflector). This new rule allows for peering with
the Next-Hop, in addition to the Advertiser of the next hop. In the
example above, for instance, if Ra is the Next-Hop (perhaps due to
using BGP's Next hop self attribute) and if routers A,B,C are peering
with Ra, the SA's received from Ra will now succeed.
3.5. MSDP and Anycast RPs
A network, with multiple RPs, can achieve RP load sharing and
redundancy by using the Anycast RP mechanism in conjunction with MSDP
mesh groups [RFC3446]. This mechanism is a common deployment
technique used within a domain by service providers and enterprises
which deploy several RPs within their domain. These RPs will each
have the same IP address configured on a Loopback interface (making
this the Anycast address). These RPs will MSDP peer with each other
using a separate loopback interface and are part of the same fully
meshed MSDP mesh group. This loopback interface, used for MSDP
peering, will typically also be used for the MBGP peering. All
routers within the provider's domain will learn of the Anycast RP
address either through Auto-RP, BSR, or a static RP assignment. Each
designated router in the domain will send source registers and group
joins to the Anycast RP address. Unicast routing will direct those
registers and joins to the nearest Anycast RP. If a particular
Anycast RP router fails, unicast routing will direct subsequent
registers and joins to the nearest Anycast RP. That RP will then
forward an MSDP update to all peers within the Anycast MSDP mesh
group. Each RP will then forward (or receive) the SAs to (from)
external customers and providers.
4. Security Considerations
An MSDP service should be secured by explicitly controlling the state
which is created by, and passed within, the MSDP service. As with
unicast routing state, MSDP state should be controlled locally, at
the edge origination points. Selective filtering at the multicast
service edge helps ensure that only intended sources result in SA
McBride, Meylor, and Meyer Section 4. [Page 14]
INTERNET-DRAFT Expires: September 2004 March 2004
message creation, and this control helps to reduce the likelihood of
state-aggregation related problems in the core. There are a variety
of points where local policy should be applied to the MSDP service.
4.1. Filtering SA messages
The process of originating SA messages should be filtered to ensure
only intended local sources are resulting in SA message origination.
In addition, MSDP speakers should filter on which SA messages get
received and forwarded.
Typically there is a fair amount of (S,G) state in a PIM-SM domain
that is local to the domain. However, without proper filtering, sa-
messages containing these local (S,G) announcements may be advertised
to the global MSDP infrastructure. Examples of this includes domain
local applications that use global IP multicast addresses and sources
that use RFC 1918 addresses [RFC1918]. To improve on the scalability
of MSDP and to avoid global visibility of domain local (S,G)
information, an external SA filter list is recommended to help
prevent unnecessary creation, forwarding, and caching of well-known
domain local sources.
4.2. SA message state limits
Proper filtering on SA message origination, receipt, and forwarding
will significantly reduce the likelihood of unintended and unexpected
spikes in MSDP state However, a sa-cache state limit SHOULD be
configured as a final safeguard to state spikes. When an MSDP peering
has reached a stable state (i.e., when the peering has been
established and the initial SA state has been transferred), it may
also be desirable to configure a rate limiter for the creation of new
SA state entries.
5. IANA Considerations
This document creates no new requirements on IANA namespaces
[RFC2434].
McBride, Meylor, and Meyer Section 5. [Page 15]
INTERNET-DRAFT Expires: September 2004 March 2004
6. Acknowledgments
The authors would like to thank Pekka Savola, John Zwiebel, Swapna
Yelamanchi, Greg Shepherd, and Jay Ford for their feedback on earlier
versions of this document.
McBride, Meylor, and Meyer Section 6. [Page 16]
INTERNET-DRAFT Expires: September 2004 March 2004
7. References
7.1. Normative References
[PIM-SM] Fenner, B., et. al, "Protocol Independent Multicast -
Sparse Mode (PIM-SM): Protocol Specification
(Revised)", draft-ietf-pim-sm-v2-new-09.txt. Work
in progress.
[RFC1771] Rekhter, Y., and T. Li, "A Border Gateway
Protocol 4 (BGP-4)", RFC 1771, March 1995.
[RFC1918] Y. Rekhter, R. Moskowitz, D. Karrenberg, G. de
Groot, E. Lear, "Address Allocation for Private
Internets", RFC 1918, Feburary, 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to
Indicate Requirement Levels" RFC 2119/BCP 14,
March 1997.
[RFC2365] Meyer, D. "Administratively Scoped IP Multicast",
RFC 2365, July, 1998.
[RFC2434] Narten, T., and H. Alvestrand, "Guidelines for
Writing an IANA Considerations Section in
RFCs", RFC 2434/BCP 0026, October, 1998.
[RFC2858] Bates T., Y. Rekhter, R. Chandra, D. Katz,
"Multiprotocol Extensions for BGP-4", RFC 2858,
June 2000.
[RFC3330] IANA, "Special-User IPv4 Addresses", RFC 3330,
September 2002.
[RFC3446] Kim, D., et. al., "Anycast Rendezvous Point (RP)
Mechanism using Protocol Independent Multicast
(PIM) and Multicast Source Discovery Protocol
(MSDP)", RFC 3446, January, 2003.
[RFC3618] Meyer, D. and W. Fenner (Editors), "The Multicast
Source Discovery Protocol (MSDP)", RFC 3618,
October, 2003.
McBride, Meylor, and Meyer Section 7.1. [Page 17]
INTERNET-DRAFT Expires: September 2004 March 2004
7.2. Informative References
[AUTORP] Fenner, W., et. al., " Protocol Independent
Multicast - Sparse Mode (PIM-SM): Protocol
Specification (Revised)", draft-ietf-pim-sm-v2-new-08.txt,
April, 2004. Work in progress.
[BSR] Fenner, W., et. al., "Bootstrap Router (BSR)
Mechanism for PIM Sparse Mode", draft-ietf-pim-sm-bsr-03.txt,
February, 2003. Work in progress.
[IANA] http://www.iana.org
[RFCED] http://www.rfc-editor.org/policy.html#policy.refs
8. Author's Addresses
Mike McBride
Cisco Systems
Email: mcbride@cisco.com
John Meylor
Cisco Systems
Email: jmeylor@cisco.com
David Meyer
Email: dmm@1-4-5.net
9. Full Copyright Statement
Copyright (C) The Internet Society (2004). This document is subject
to the rights, licenses and restrictions contained in BCP 78 and
except as set forth therein, the authors retain all their rights.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
McBride, Meylor, and Meyer Section 9. [Page 18]
INTERNET-DRAFT Expires: September 2004 March 2004
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
10. Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at ietf-
ipr@ietf.org.
11. Acknowledgement
Funding for the RFC Editor function is currently provided by the
McBride, Meylor, and Meyer Section 11. [Page 19]
INTERNET-DRAFT Expires: September 2004 March 2004
Internet Society.
McBride, Meylor, and Meyer Section 11. [Page 20]
