draft-ietf-pim-sm-v2-new-11.txt

xorp源码hg

Internet Engineering Task Force                                   PIM WG
INTERNET-DRAFT                                          Bill Fenner/AT&T
draft-ietf-pim-sm-v2-new-11.txt                         Mark Handley/UCL
                                                     Hugh Holbrook/Cisco
                                                   Isidor Kouvelas/Cisco
                                                         25 October 2004
                                                     Expires: April 2005


         Protocol Independent Multicast - Sparse Mode (PIM-SM):
                    Protocol Specification (Revised)


Status of this Document

By submitting this Internet-Draft, I certify that any applicable patent
or other IPR claims of which I am aware have been disclosed, or will be
disclosed, and any of which I become aware will be disclosed, in
accordance with RFC 3668.

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 IETF PIM WG.  Comments should be
addressed to the authors, or the mailing list at [e-mail].






Fenner/Handley/Holbrook/Kouvelas                                [Page 1]

INTERNET-DRAFT             Expires: April 2005              October 2004


                                Abstract


     This document specifies Protocol Independent Multicast -
     Sparse Mode (PIM-SM).  PIM-SM is a multicast routing protocol
     that can use the underlying unicast routing information base
     or a separate multicast-capable routing information base.  It
     builds unidirectional shared trees rooted at a Rendezvous
     Point (RP) per group, and optionally creates shortest-path
     trees per source.









































Fenner/Handley/Holbrook/Kouvelas                                [Page 2]

INTERNET-DRAFT             Expires: April 2005              October 2004


                           Table of Contents


     1. Introduction. . . . . . . . . . . . . . . . . . . . . .   6
     2. Terminology . . . . . . . . . . . . . . . . . . . . . .   6
      2.1. Definitions. . . . . . . . . . . . . . . . . . . . .   6
      2.2. Pseudocode Notation. . . . . . . . . . . . . . . . .   7
     3. PIM-SM Protocol Overview. . . . . . . . . . . . . . . .   8
     4. Protocol Specification. . . . . . . . . . . . . . . . .  13
      4.1. PIM Protocol State . . . . . . . . . . . . . . . . .  13
       4.1.1. General Purpose State . . . . . . . . . . . . . .  14
       4.1.2. (*,*,RP) State. . . . . . . . . . . . . . . . . .  15
       4.1.3. (*,G) State . . . . . . . . . . . . . . . . . . .  16
       4.1.4. (S,G) State . . . . . . . . . . . . . . . . . . .  18
       4.1.5. (S,G,rpt) State . . . . . . . . . . . . . . . . .  20
       4.1.6. State Summarization Macros. . . . . . . . . . . .  21
      4.2. Data Packet Forwarding Rules . . . . . . . . . . . .  26
       4.2.1. Last-hop Switchover to the SPT. . . . . . . . . .  28
       4.2.2. Setting and Clearing the (S,G) SPTbit . . . . . .  29
      4.3. Designated Routers (DR) and Hello Messages . . . . .  30
       4.3.1. Sending Hello Messages. . . . . . . . . . . . . .  30
       4.3.2. DR Election . . . . . . . . . . . . . . . . . . .  32
       4.3.3. Reducing Prune Propagation Delay on LANs. . . . .  34
       4.3.4. Maintaining Secondary Address Lists . . . . . . .  37
      4.4. PIM Register Messages. . . . . . . . . . . . . . . .  38
       4.4.1. Sending Register Messages from the DR . . . . . .  38
       4.4.2. Receiving Register Messages at the RP . . . . . .  42
      4.5. PIM Join/Prune Messages. . . . . . . . . . . . . . .  44
       4.5.1. Receiving (*,*,RP) Join/Prune Messages. . . . . .  45
       4.5.2. Receiving (*,G) Join/Prune Messages . . . . . . .  49
       4.5.3. Receiving (S,G) Join/Prune Messages . . . . . . .  52
       4.5.4. Receiving (S,G,rpt) Join/Prune Messages . . . . .  55
       4.5.5. Sending (*,*,RP) Join/Prune Messages. . . . . . .  61
       4.5.6. Sending (*,G) Join/Prune Messages . . . . . . . .  65
       4.5.7. Sending (S,G) Join/Prune Messages . . . . . . . .  70
       4.5.8. (S,G,rpt) Periodic Messages . . . . . . . . . . .  75
       4.5.9. State Machine for (S,G,rpt) Triggered
              Messages. . . . . . . . . . . . . . . . . . . . .  76
       4.5.10. Background: (*,*,RP) and (S,G,rpt)
               Interaction. . . . . . . . . . . . . . . . . . .  80
      4.6. PIM Assert Messages. . . . . . . . . . . . . . . . .  82
       4.6.1. (S,G) Assert Message State Machine. . . . . . . .  82
       4.6.2. (*,G) Assert Message State Machine. . . . . . . .  90
       4.6.3. Assert Metrics. . . . . . . . . . . . . . . . . .  97
       4.6.4. AssertCancel Messages . . . . . . . . . . . . . .  98
       4.6.5. Assert State Macros . . . . . . . . . . . . . . .  99
      4.7. PIM Bootstrap and RP Discovery . . . . . . . . . . . 102
       4.7.1. Group-to-RP Mapping . . . . . . . . . . . . . . . 103



Fenner/Handley/Holbrook/Kouvelas                                [Page 3]

INTERNET-DRAFT             Expires: April 2005              October 2004


       4.7.2. Hash Function . . . . . . . . . . . . . . . . . . 104
      4.8. Source-Specific Multicast. . . . . . . . . . . . . . 105
       4.8.1. Protocol Modifications for SSM destination
              addresses . . . . . . . . . . . . . . . . . . . . 105
       4.8.2. PIM-SSM-only Routers. . . . . . . . . . . . . . . 106
      4.9. PIM Packet Formats . . . . . . . . . . . . . . . . . 107
       4.9.1. Encoded Source and Group Address Formats. . . . . 109
       4.9.2. Hello Message Format. . . . . . . . . . . . . . . 112
       4.9.3. Register Message Format . . . . . . . . . . . . . 115
       4.9.4. Register-Stop Message Format. . . . . . . . . . . 117
       4.9.5. Join/Prune Message Format . . . . . . . . . . . . 118
        4.9.5.1. Group Set Source List Rules. . . . . . . . . . 121
        4.9.5.2. Group Set Fragmentation. . . . . . . . . . . . 125
       4.9.6. Assert Message Format . . . . . . . . . . . . . . 125
      4.10. PIM Timers. . . . . . . . . . . . . . . . . . . . . 127
      4.11. Timer Values. . . . . . . . . . . . . . . . . . . . 128
     5. IANA Considerations . . . . . . . . . . . . . . . . . . 134
      5.1. PIM Address Family . . . . . . . . . . . . . . . . . 134
      5.2. PIM Hello Options. . . . . . . . . . . . . . . . . . 135
     6. Security Considerations . . . . . . . . . . . . . . . . 135
      6.1. Attacks based on forged messages . . . . . . . . . . 135
       6.1.1. Forged link-local messages. . . . . . . . . . . . 135
       6.1.2. Forged unicast messages . . . . . . . . . . . . . 136
      6.2. Non-cryptographic Authentication Mechanisms. . . . . 136
      6.3. Authentication using IPsec . . . . . . . . . . . . . 137
       6.3.1. Protecting link-local multicast messages. . . . . 137
       6.3.2. Protecting unicast messages . . . . . . . . . . . 138
        6.3.2.1. Register messages. . . . . . . . . . . . . . . 138
        6.3.2.2. Register-Stop messages . . . . . . . . . . . . 138
      6.4. Denial of Service Attacks. . . . . . . . . . . . . . 139
     7. Authors' Addresses. . . . . . . . . . . . . . . . . . . 139
     8. Acknowledgments . . . . . . . . . . . . . . . . . . . . 140
     9. Normative References. . . . . . . . . . . . . . . . . . 140
     10. Informative References . . . . . . . . . . . . . . . . 141
     11. Appendix A: PIM Multicast Border Router
         Behavior . . . . . . . . . . . . . . . . . . . . . . . 142
      11.1. Sources External to the PIM-SM Domain . . . . . . . 142
      11.2. Sources Internal to the PIM-SM Domain . . . . . . . 143
     12. Index. . . . . . . . . . . . . . . . . . . . . . . . . 145
     13. Full Copyright Statement . . . . . . . . . . . . . . . 148











Fenner/Handley/Holbrook/Kouvelas                                [Page 4]

INTERNET-DRAFT             Expires: April 2005              October 2004


                            List of Figures


     Figure 1. Per-(S,G) register state machine at a DR . . . .  38
     Figure 2. Downstream per-interface (*,*,RP) state
               machine. . . . . . . . . . . . . . . . . . . . .  46
     Figure 3. Downstream per-interface (*,G) state
               machine. . . . . . . . . . . . . . . . . . . . .  49
     Figure 4. Downstream per-interface (S,G) state
               machine. . . . . . . . . . . . . . . . . . . . .  53
     Figure 5. Downstream per-interface (S,G,rpt) state
               machine. . . . . . . . . . . . . . . . . . . . .  56
     Figure 6. Upstream (*,*,RP) state machine. . . . . . . . .  61
     Figure 7. Upstream (*,G) state machine . . . . . . . . . .  66
     Figure 8. Upstream (S,G) state machine . . . . . . . . . .  71
     Figure 9. Upstream (S,G,rpt) state machine for
               triggered messages . . . . . . . . . . . . . . .  76
     Figure 10. Per-interface (S,G) Assert State
                machine . . . . . . . . . . . . . . . . . . . .  83
     Figure 11. Per-interface (*,G) Assert State
                machine . . . . . . . . . . . . . . . . . . . .  91






























Fenner/Handley/Holbrook/Kouvelas                                [Page 5]

INTERNET-DRAFT             Expires: April 2005              October 2004


1.  Introduction

This document specifies a protocol for efficiently routing multicast
groups that may span wide-area (and inter-domain) internets.  This
protocol is called Protocol Independent Multicast - Sparse Mode (PIM-SM)
because, although it may use the underlying unicast routing to provide
reverse-path information for multicast tree building, it is not
dependent on any particular unicast routing protocol.

PIM-SM version 2 was originally specified in RFC 2117, and revised in
RFC 2362.  This document is intended to obsolete RFC 2362, and to
correct a number of deficiencies that have been identified with the way
PIM-SM was previously specified.  As far as possible, this document
specifies the same protocol as RFC 2362, and only diverges from the
behavior intended by RFC 2362 when the previously specified behavior was
clearly incorrect.  Routers implemented according to the specification
in this document will be able to successfully interoperate with routers
implemented according to RFC 2362.

2.  Terminology

In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
"SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
"OPTIONAL" are to be interpreted as described in RFC 2119 and indicate
requirement levels for compliant PIM-SM implementations.

2.1.  Definitions

This specification uses a number of terms to refer to the roles of
routers participating in PIM-SM.  The following terms have special
significance for PIM-SM:

Rendezvous Point (RP):
      An RP is a router that has been configured to be used as the root
      of the non-source-specific distribution tree for a multicast
      group.  Join messages from receivers for a group are sent towards
      the RP, and data from senders is sent to the RP so that receivers
      can discover who the senders are, and start to receive traffic
      destined for the group.

Designated Router (DR):
      A shared-media LAN like Ethernet may have multiple PIM-SM routers
      connected to it. A single one of these routers, the DR, will act
      on behalf of directly connected hosts with respect to the PIM-SM
      protocol.  A single DR is elected per interface (LAN or otherwise)
      using a simple election process.





Fenner/Handley/Holbrook/Kouvelas                  Section 2.1.  [Page 6]

INTERNET-DRAFT             Expires: April 2005              October 2004


MRIB  Multicast Routing Information Base.  This is the multicast
      topology table, which is typically derived from the unicast
      routing table, or routing protocols such as MBGP that carry
      multicast-specific topology information.  In PIM-SM, the MRIB is
      used to decide where to send Join/Prune messages.  A secondary
      function of the MRIB is to provide routing metrics for destination
      addresses, these metrics are used when sending and processing
      Assert messages.

RPF Neighbor
      RPF stands for "Reverse Path Forwarding".  The RPF Neighbor of a
      router with respect to an address is the neighbor that the MRIB
      indicates should be used to forward packets to that address.  In
      the case of a PIM-SM multicast group, the RPF neighbor is the