Network Working Group T. Pusateri
Request for Comments: 4602 Juniper Networks
Category: Informational August 2006
Protocol Independent Multicast - Sparse Mode (PIM-SM)
IETF Proposed Standard Requirements Analysis
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This document provides supporting documentation to advance the
Protocol Independent Multicast - Sparse Mode (PIM-SM) routing
protocol from IETF Experimental status to Proposed Standard.
Table of Contents
1. Introduction ....................................................2
2. RFC 1264 Requirements ...........................................2
2.1. Documents Specifying the Protocol and Its Usage ............2
2.2. Management Information Base ................................2
2.3. Explicit Security Architecture .............................2
2.4. Implementation Existence ...................................3
2.4.1. XORP ................................................3
2.4.2. Cisco IOS/IOX .......................................3
2.4.3. Infosys Technologies, Ltd. ..........................3
2.4.4. Procket Networks ....................................3
2.5. Evidence of Testing ........................................4
2.5.1. Cisco ...............................................4
2.5.2. XORP ................................................4
2.5.3. Procket Networks ....................................5
2.6. Suitability ................................................5
2.7. Authentication Mechanisms ..................................5
3. Security Considerations .........................................5
4. Acknowledgements ................................................5
5. References ......................................................6
5.1. Normative References .......................................6
5.2. Informative References .....................................6
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1. Introduction
This analysis provides supporting documentation to advance the
Protocol Independent Multicast - Sparse Mode (PIM-SM) routing
protocol from the IETF Experimental status to Proposed Standard.
PIM-SM was first published as RFC 2117 [RFC2117] in 1997 and then
again as RFC 2362 [RFC2362] in 1998. The protocol was classified as
Experimental in both of these documents. The PIM-SM protocol
specification was then rewritten in whole in order to more fully
specify the protocol. It is this new specification that is to be
advanced to Proposed Standard.
2. RFC 1264 Requirements
Section 4.0 of RFC 1264 [RFC1264] describes the requirements for
routing protocols to advance to Proposed Standard. Each requirement
is listed below along with an explanation of how the requirement has
been satisfied.
2.1. Documents Specifying the Protocol and Its Usage
The authors of the new PIM-SM specification [RFC4601] have taken
considerable care to fully specify the protocol operation. It
removes all known ambiguities and tries to normalize corner cases
that existed in the previous specification. It has been used to
provide several interoperable implementations by developers that were
not authors of the specification. These implementations will be
described below.
2.2. Management Information Base
A Management Information Base for PIM is currently specified in RFC
2934 [RFC2934]. This MIB has many implementations and has been used
by network management applications for several years. Updates to
this MIB to support IPv6 and other improvements based on operation
experience are in progress in the PIM Working Group of the IETF.
2.3. Explicit Security Architecture
The new PIM Sparse-Mode protocol specification contains an extensive
security section explaining its security features and limitations.
Data integrity protection and groupwise data origin authentication is
provided for PIM protocol messages.
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2.4. Implementation Existence
There are at least 4 known independent implementations of the new
protocol specification, and there are over 6 independent
implementations of a previous version (RFC 2362) of the
specification. The new specification was carefully written to be
backward compatible with the old specification allowing
implementations compliant with RFC 2362 to also be compliant with the
new specification.
The 4 implementations of the new version are described below.
2.4.1. XORP
The XORP project [XORP] has an open-source implementation of PIM-SM
v2 as specified in RFC 4601. It was written by Pavlin Radoslavov
<pavlin@icir.org> and has been available to the public since December
2002. Pavlin is not an author of the protocol specification. It
does not use any other existing code as a base.
2.4.2. Cisco IOS/IOX
Cisco Systems, Inc., has written an implementation of the new
protocol specification that has been deployed in production routers.
There exists an IOS implementation for IPv6 only. There exists an
IOX implementation for both IPv4 and IPv6. This code was initially
written by Isidor Kouvelas <kouvelas@cisco.com>. It does not depend
on any existing code base. Isidor is a co-author of the protocol
specification.
2.4.3. Infosys Technologies, Ltd.
Infosys Technologies, Ltd. (www.infosys.com), has developed a limited
shared-tree implementation of the new Sparse-Mode specification
including PIM Hello messages, DR election, PIM join/prune messages,
join suppression, and prune override. It was written by Bharat Joshi
<bharat_joshi@infosys.com> and is used in commercial products.
Bharat is not an author of the protocol specification.
2.4.4. Procket Networks
An implementation was written from scratch at Procket Networks by
Dino Farinacci <dino@cisco.com>. This implementation is now owned by
Cisco Systems, Inc. Dino is not an author of the new protocol
specification.
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2.5. Evidence of Testing
2.5.1. Cisco
The Cisco implementation has undergone extensive laboratory testing
as well as testing in production deployments. It is found to
interoperate with implementations of earlier versions of the PIM
Sparse-Mode protocol specification.
2.5.2. XORP
The XORP PIM-SM implementation has been thoughtfully tested
internally by the XORP project. The emphasis during testing has been
on correctness. In a typical setup, a PIM-SM router's behavior is
tested by connecting it to external packet generators and observers.
The packet generators are used to generate messages such as IGMP and
PIM-SM control packets, and multicast data packets. The packet
observers are used to observe the PIM-SM control packets generated by
the PIM-SM router under test, and to observe the data packets that
may be forwarded by that router. In addition, the router's command-
line interface has been used to observe its internal state during
some of the tests.
The test scenarios have been designed to follow the protocol
specification closely (e.g., a separate test has been created for
each event in the various protocol state machines, etc). All test
scenarios are described in detail in the XORP PIM-SM Test Suite
[XORP-TEST].
The major tested features are:
1. Multicast data forwarding.
2. PIM Hello messages exchange, PIM router neighbor discovery,
option exchange, and DR election.
3. PIM Register messages transmission and reception, PIM Register
state machine, and multicast data packets encapsulation and
decapsulation.
4. Transmission and reception of PIM Join/Prune messages and
upstream and downstream protocol state machines. The tests
consider the following state: (*,*,RP), (*,G), (S,G), and
(S,G,rpt).
5. Transmission and reception of PIM Assert messages and the per-
interface (*,G) and (S,G) Assert state machines.
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6. PIM Bootstrap mechanism: transmission, reception, and forwarding
of PIM Bootstrap messages (BSMs), transmission and reception of
PIM Cand-RP-Adv messages, candidate and non-candidate Bootstrap
Router (BSR) state machines, creating the RP-Set at the BSR,
receiving and using the RP-Set, and semantic fragmentation of
BSMs.
In the final tests, the tested router behaved as specified in the
PIM-SM protocol specification. All issues found in the protocol
specification itself have been corrected in earlier versions of the
document.
2.5.3. Procket Networks
The Procket Networks implementation was deployed in many research and
service provider networks and showed interoperability with new and
old Cisco Systems implementations as well as Juniper Networks
implementations.
2.6. Suitability
PIM Sparse-Mode is a protocol for efficiently routing multicast
groups that may span wide-area (and inter-domain) Internets. PIM
uses the underlying unicast routing to provide reverse-path
information for multicast tree building, but it is not dependent on
any particular unicast routing protocol.
2.7. Authentication Mechanisms
PIM specifies the use of the IP security (IPsec) authentication
header (AH) to provide data integrity protection and groupwise data
origin authentication of protocol messages. The specific AH
authentication algorithm and parameters, including the choice of
authentication algorithm and the choice of key, are configured by the
network administrator. The threats associated with receiving forged
PIM messages are outlined in the security considerations section of
the protocol specification.
3. Security Considerations
No considerations apply to a requirements analysis about a routing
protocol, only to a specification for that routing protocol.
4. Acknowledgements
Pavlin Radoslavov provided text for the section on XORP testing.
Dino Farinacci provided text for the Procket Networks testing.
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5. References
5.1. Normative References
[RFC2934] McCloghrie, K., Farinacci, D., Thaler, D., and B. Fenner,
"Protocol Independent Multicast MIB for IPv4", RFC 2934,
October 2000.
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, August 2006.
5.2. Informative References
[RFC1264] Hinden, R., "Internet Engineering Task Force Internet
Routing Protocol Standardization Criteria", RFC 1264,
October 1991.
[RFC2117] Estrin, D., Farinacci, D., Helmy, A., Thaler, D.,
Deering, S., Handley, M., Jacobson, V., Liu, C., Sharma,
P., and L. Wei, "Protocol Independent Multicast-Sparse
Mode (PIM-SM): Protocol Specification", RFC 2117, June
1997.
[RFC2362] Estrin, D., Farinacci, D., Helmy, A., Thaler, D.,
Deering, S., Handley, M., Jacobson, V., Liu, C., Sharma,
P., and L. Wei, "Protocol Independent Multicast-Sparse
Mode (PIM-SM): Protocol Specification", RFC 2362, June
1998.
[XORP] "XORP Project", <http://www.xorp.org>.
[XORP-TEST] "XORP PIM-SM Test Suite", <http://www.xorp.org/releases/
current/docs/pim_testsuite/pim_testsuite.pdf>.
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Author's Address
Tom Pusateri
Juniper Networks
1194 North Mathilda Avenue
Sunnyvale, CA 94089
USA
Phone: +1 408 745 2000
EMail: pusateri@juniper.net
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