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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group Greg Shepherd 2 INTERNET DRAFT Juniper Networks 3 Rob Rockell 4 David Meyer 5 Sprint 6 Category Best Current Practices 7 Feburary, 2002 9 Source-Specific Protocol Independent Multicast in 232/8 11 13 1. Status of this Memo 15 This document specifies an Internet Best Current Practices for the 16 Internet Community, and requests discussion and suggestions for 17 improvements. Distribution of this memo is unlimited. 19 This document is an Internet-Draft and is in full conformance with 20 all provisions of Section 10 of RFC 2026. 22 Internet Drafts are working documents of the Internet Engineering 23 Task Force (IETF), its areas, and its working groups. Note that other 24 groups may also distribute working documents as Internet-Drafts. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 The list of current Internet-Drafts can be accessed at 32 http://www.ietf.org/ietf/1id-abstracts.txt. 34 The list of Internet-Draft Shadow Directories can be accessed at 35 http://www.ietf.org/shadow.html. 37 2. Copyright Notice 39 Copyright (C) The Internet Society (2002). All Rights Reserved. 41 3. Abstract 43 IP Multicast group addresses in the 232/8 (232.0.0.0 to 44 232.255.255.255) range are designated as source-specific multicast 45 [SSM] destination addresses and are reserved for use by source- 46 specific applications and protocols [IANA]. This document defines 47 operational recommendations to ensure source-specific behavior within 48 the 232/8 range. 50 The keywords MUST, MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED, 51 SHALL, SHALL NOT, SHOULD, SHOULD NOT are to be interpreted as defined 52 in RFC 2119 [RFC2119]. 54 4. Introduction 56 Current PIM Sparse Mode [RFC2362] relies on the shared Rendezvous 57 Point (RP) tree to learn about active sources for a group and to 58 support group-generic (not source specific) data distribution. The IP 59 Multicast group address range 232/8 has been designated for source- 60 specific [SSM] applications and protocols [IANA] and SHOULD support 61 source-only trees only, precluding the requirement of an RP and a 62 shared tree; active sources in the 232/8 range will be discovered out 63 of band. PIM Sparse Mode Designated Routers (DR), with local 64 membership, are capable of joining the shortest path tree for the 65 source directly using Source-Specific PIM [SSM]. 67 Operational best common practices in the 232/8 group address range 68 are necessary to ensure shortest path source-only trees across 69 multiple domains in the Internet [SSM], and to prevent data from 70 sources sending to groups in the 232/8 range from arriving via shared 71 trees. This avoids unwanted data arrival, and allows several sources 72 to use the same group address without conflict at the receivers. 74 The operational practices SHOULD 76 o Prevent local sources from sending to shared tree 78 o Prevent remote sources from being learned/joined via MSDP [MSDP] 80 o Prevent receivers from joining the shared tree 81 o Prevent RP's as candidates for 232/8 83 5. Operational practices in 232/8 85 5.1. Preventing local sources from sending to shared tree 87 Eliminating the use of shared trees for groups in 232/8, while 88 maintaining coexistence with PIM-SM, behavior of the RP and/or the DR 89 needs to be modified. This can be accomplished by 91 - preventing data for 232/8 groups from being sent encapsulated to 92 the RP by the DR 94 - preventing the RP from accepting registers for 232/8 groups from 95 the DR 97 - preventing the RP from forwarding accepted data down (*,G) tree 99 5.2. Preventing remote sources from being learned/joined via MSDP 101 PIM-SS does not require active source announcements via MSDP. All 102 source announcements are received out of band, the the last hop 103 router is responsible for sending (S,G) joins directly to the source. 104 To prevent propagation of SAs in the 232/8 range, an RP SHOULD 106 - never originate an SA for any 232/8 groups 108 - never accept or forward an SA for any 232/8 groups. 110 5.3. Preventing receivers from joining the shared tree 112 Local PIM domain practices need to be enforced to prevent local 113 receivers from joining the shared tree for 232/8 groups. This can be 114 accomplished by 116 - preventing DR from sending (*,G) joins 118 - preventing RP from accepting (*,G) join 120 Within a local PIM domain, any last-hop router NOT preventing (*,G) 121 joins MAY trigger (*,G) state toward the RP which intersects an 122 existing (S,G) tree, allowing the receiver on the shared tree to 123 receive the data. So if the last-hop routers are not preventing (*,G) 124 joins, then all routers in the domain must also prevent (*,G) joins. 126 5.4. Preventing RP's as candidates for 232/8 128 Because PIM-SS does not require an RP, all RPs SHOULD NOT offer them� 129 selves as candidates in the 232/8 range. This can be accomplished by 131 - preventing RP/BSR from announcing in the 232/8 range 133 - preventing DRs from accepting delegations in this range 135 - precluding RP functionality on RP for the 232/8 range 137 6. References 139 [IANA] http://www.iana.org 141 [SSM] Holbrook, H., Cain, B., "Source-Specific Multicast", 142 draft-ietf-ssm-arch-00.txt, November, 2001. 144 [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate 145 Requirement Levels", RFC 2119, March, 1997. 147 [RFC2362] D. Estrin, et. al., "Protocol Independent Multicast-Sparse 148 Mode (PIM-SM): Protocol Specification", RFC 2362, June, 149 1998. 151 [MSDP] D. Meyer and Bill Fenner (Editors), "The Multicast 152 Source Discovery Protocol (MSDP)", draft-ietf-msdp-spec-13.txt, 153 November 2001. 155 7. Author's Addresses 157 Greg Shepherd 158 Juniper Networks 159 Email: shep@juniper.net 161 Robert Rockell 162 Sprint 163 Email: rrockell@sprint.net 165 David Meyer 166 Sprint 167 Email: dmm@sprint.net 169 8. Full Copyright Statement 171 Copyright (C) The Internet Society (2002). All Rights Reserved. 173 This document and translations of it may be copied and furnished to 174 others, and derivative works that comment on or otherwise explain it 175 or assist in its implementation may be prepared, copied, published 176 and distributed, in whole or in part, without restriction of any 177 kind, provided that the above copyright notice and this paragraph are 178 included on all such copies and derivative works. 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