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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group David Meyer 2 INTERNET DRAFT Sprint 3 Rob Rockell 4 Sprint 5 Greg Shepherd 6 Procket 7 Category Best Current Practices 8 January, 2003 10 Source-Specific Protocol Independent Multicast in 232/8 12 14 1. Status of this Memo 16 This document specifies an Internet Best Current Practices for the 17 Internet Community, and requests discussion and suggestions for 18 improvements. Distribution of this memo is unlimited. 20 This document is an Internet-Draft and is in full conformance with 21 all provisions of Section 10 of RFC 2026. 23 Internet Drafts are working documents of the Internet Engineering 24 Task Force (IETF), its areas, and its working groups. Note that other 25 groups may also distribute working documents as Internet-Drafts. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 The list of current Internet-Drafts can be accessed at 33 http://www.ietf.org/ietf/1id-abstracts.txt. 35 The list of Internet-Draft Shadow Directories can be accessed at 36 http://www.ietf.org/shadow.html. 38 2. Copyright Notice 40 Copyright (C) The Internet Society (2003). All Rights Reserved. 42 3. Abstract 44 IP Multicast group addresses in the 232/8 (232.0.0.0 to 45 232.255.255.255) range are designated as source-specific multicast 46 [SSM] destination addresses and are reserved for use by source- 47 specific applications and protocols [IANA]. This document defines 48 operational recommendations to ensure source-specific behavior within 49 the 232/8 range. 51 The keywords MUST, MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED, 52 SHALL, SHALL NOT, SHOULD, SHOULD NOT are to be interpreted as defined 53 in RFC 2119 [RFC2119]. 55 4. Introduction 57 Current PIM Sparse Mode [RFC2362] relies on the shared Rendezvous 58 Point (RP) tree to learn about active sources for a group and to 59 support group-generic (not source specific) data distribution. The IP 60 Multicast group address range 232/8 has been designated for source- 61 specific [SSM] applications and protocols [IANA] and SHOULD support 62 source-only trees only, precluding the requirement of an RP and a 63 shared tree; active sources in the 232/8 range will be discovered out 64 of band. PIM Sparse Mode Designated Routers (DR), with local 65 membership, are capable of joining the shortest path tree for the 66 source directly using Source-Specific PIM [SSM]. 68 Operational best common practices in the 232/8 group address range 69 are necessary to ensure shortest path source-only trees across 70 multiple domains in the Internet [SSM], and to prevent data from 71 sources sending to groups in the 232/8 range from arriving via shared 72 trees. This avoids unwanted data arrival, and allows several sources 73 to use the same group address without conflict at the receivers. 75 The operational practices SHOULD 77 o Prevent local sources from sending to shared tree 79 o Prevent remote sources from being learned/joined via MSDP [MSDP] 81 o Prevent receivers from joining the shared tree 82 o Prevent RP's as candidates for 232/8 84 5. Operational practices in 232/8 86 5.1. Preventing local sources from sending to shared tree 88 Eliminating the use of shared trees for groups in 232/8, while 89 maintaining coexistence with PIM-SM, behavior of the RP and/or the DR 90 needs to be modified. This can be accomplished by 92 - preventing data for 232/8 groups from being sent encapsulated to 93 the RP by the DR 95 - preventing the RP from accepting registers for 232/8 groups from 96 the DR 98 - preventing the RP from forwarding accepted data down (*,G) 99 tree for 232/8 groups 101 5.2. Preventing remote sources from being learned/joined via MSDP 103 PIM-SS does not require active source announcements via MSDP. All 104 source announcements are received out of band, the the last hop 105 router is responsible for sending (S,G) joins directly to the source. 106 To prevent propagation of SAs in the 232/8 range, an RP SHOULD 108 - never originate an SA for any 232/8 groups 110 - never accept or forward an SA for any 232/8 groups. 112 5.3. Preventing receivers from joining the shared tree 114 Local PIM domain practices need to be enforced to prevent local 115 receivers from joining the shared tree for 232/8 groups. This can be 116 accomplished by 118 - preventing DR from sending (*,G) joins for 232/8 groups 120 - preventing RP from accepting (*,G) join for 232/8 groups 122 However, within a local PIM domain, any last-hop router NOT 123 preventing (*,G) joins may trigger unwanted (*,G) state toward 124 the RP which intersects an existing (S,G) tree, allowing the 125 receiver on the shared tree to receive the data, breaking the 126 source-specific [SSM] service model. It is therefore recommended 127 that ALL routers in the domain MUST reject AND never originate 128 (*,G) joins for 232/8 groups. 130 5.4. Preventing RP's as candidates for 232/8 132 Because PIM-SS does not require an RP, all RPs SHOULD NOT offer them� 133 selves as candidates in the 232/8 range. This can be accomplished by 135 - preventing RP/BSR from announcing in the 232/8 range 137 - preventing ALL routers from accepting RP delegations in the 138 232/8 range 140 - precluding RP functionality on RP for the 232/8 range 142 6. Informative References 144 [IANA] http://www.iana.org 146 [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate 147 Requirement Levels", RFC 2119, March, 1997. 149 7. Normative References 151 [MSDP] D. Meyer and Bill Fenner (Editors), "The Multicast 152 Source Discovery Protocol (MSDP)", 153 draft-ietf-msdp-spec-14.txt, November 2002. 155 [SSM] Holbrook, H., Cain, B., "Source-Specific Multicast", 156 draft-ietf-ssm-arch-01.txt, November, 2002. 158 [RFC2362] D. Estrin, et. al., "Protocol Independent Multicast-Sparse 159 Mode (PIM-SM): Protocol Specification", RFC 2362, June, 160 1998. 162 8. Author's Addresses 164 David Meyer 165 Sprint 166 Email: dmm@sprint.net 168 Robert Rockell 169 Sprint 170 Email: rrockell@sprint.net 172 Greg Shepherd 173 Procket 174 Email: shep@procket.com 176 9. Full Copyright Statement 178 Copyright (C) The Internet Society (2003). All Rights Reserved. 180 This document and translations of it may be copied and furnished to 181 others, and derivative works that comment on or otherwise explain it 182 or assist in its implementation may be prepared, copied, published 183 and distributed, in whole or in part, without restriction of any 184 kind, provided that the above copyright notice and this paragraph are 185 included on all such copies and derivative works. However, this doc� 186 ument itself may not be modified in any way, such as by removing the 187 copyright notice or references to the Internet Society or other 188 Internet organizations, except as needed for the purpose of develop� 189 ing Internet standards in which case the procedures for copyrights 190 defined in the Internet Standards process must be followed, or as 191 required to translate it into languages other than English. 193 The limited permissions granted above are perpetual and will not be 194 revoked by the Internet Society or its successors or assigns. 196 This document and the information contained herein is provided on an 197 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 198 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 199 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 200 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MER� 201 CHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.