INTERNET-DRAFT David Meyer
draft-ietf-mboned-ssm232-06.txtdraft-ietf-mboned-ssm232-07.txt Rob Rockell Greg Shepherd Category Best Current Practice Expires: MarchJuly 2004 January 2004 September 2003Source-Specific Protocol Independent Multicast in 232/8 <draft-ietf-mboned-ssm232-06.txt><draft-ietf-mboned-ssm232-07.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. 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]. This document is a product of the MBONED WG. Comments should be addressed to the authors, or the mailing list at firstname.lastname@example.org. Copyright Notice Copyright (C) The Internet Society (2003).(2004). All Rights Reserved. Abstract IP Multicast group addresses in the 232/8 (18.104.22.168 to 22.214.171.124) range are designated as source-specific multicast [SSM]destination addresses and are reserved for use by source- specificsource-specific multicast applications and protocols. This document defines operational recommendations to ensure source-specific behavior within the 232/8 range. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Operational practices in 232/8 . . . . . . . . . . . . . . . . 4 2.1. Preventing local sources from sending to shared tree. . . . 4 2.2. Preventing remote sources from being learned/joined via MSDP. 4 2.3. Preventing receivers from joining the shared tree . . . . . 5 2.4. Preventing RP's as candidates for 232/8 . . . . . . . . . . 5 3. Intellectual Property. . . . . . . . . . . . . . . . . . . . . 6 4. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . 6 5. Security Considerations. . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 7 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 7.1. Normative References. . . . . . . . . . . . . . . . . . . . 8 7.2. Informative References. . . . . . . . . . . . . . . . . . . 8 8. Author's Addresses . . . . . . . . . . . . . . . . . . . . . . 9 9. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 9 1. Introduction Current PIM Sparse Mode (PIM-SM) [RFC2362] relies on the shared Rendezvous Point (RP) tree to learn about active sources for a group and to support group-generic (not source specific) data distribution. The IP Multicast group address range 232/8 has been designated for Source-Specific PIM [SSM][RFC3569] applications and protocols [IANA] and SHOULD support source-only trees only, precluding the requirement of an RP and a shared tree; active sources in the 232/8 range will be discovered out of band. PIM Sparse Mode Designated Routers (DR), with local membership, are capable of joining the shortest path tree for the source directly using Source-Specific PIM (also knowknown as PIM-SSM or simply SSM). Operational best common practices in the 232/8 group address range are necessary to ensure shortest path source-only trees across multiple domains in the Internet [SSM],[RFC3569], and to prevent data from sources sending to groups in the 232/8 range from arriving via shared trees. This avoids unwanted data arrival, and allows several sources to use the same group address without conflict at the receivers. The operational practices SHOULD: o Prevent local sources from sending to shared tree o Prevent receivers from joining the shared tree o Prevent RP's as candidates for 232/8 o Prevent remote sources from being learned/joined via MSDP [MSDP][RFC3618] 2. Operational practices in 232/8 2.1. Preventing local sources from sending to shared tree Eliminating the use of shared trees for groups in 232/8, while maintaining coexistence with PIM-SM, behavior of the RP and/or the DR needs to be modified. This can be accomplished by - preventing data for 232/8 groups from being sent encapsulated to the RP by the DR - preventing the RP from accepting registers for 232/8 groups from the DR - preventing the RP from forwarding accepted data down (*,G) tree for 232/8 groups 2.2. Preventing remote sources from being learned/joined via MSDP PIM-SSM does not require active source announcements via MSDP. All source announcements are received out of band, the the last hop router being responsible for sending (S,G) joins directly to the source. To prevent propagation of SAs in the 232/8 range, an RP SHOULD - never originate an SA for any 232/8 groups - never accept or forward an SA for any 232/8 groups. 2.3. Preventing receivers from joining the shared tree Local PIM domain practices need to be enforced to prevent local receivers from joining the shared tree for 232/8 groups. This can be accomplished by - preventing DR from sending (*,G) joins for 232/8 groups - preventing RP from accepting (*,G) join for 232/8 groups However, within a local PIM domain, any last-hop router NOT preventing (*,G) joins may trigger unwanted (*,G) state toward the RP which intersects an existing (S,G) tree, allowing the receiver on the shared tree to receive the data, breaking the source-specific [SSM][RFC3569] service model. It is therefore recommended that ALL routers in the domain MUST reject AND never originate (*,G) joins for 232/8 groups. In those cases in which an ISP is offering its customers (or others) the use of the ISP's RP, the ISP SHOULD NOT allow (*,G) joins in the 232/8 range. 2.4. Preventing RP's as candidates for 232/8 Because PIM-SSM does not require an RP, all RPs SHOULD NOT offer themselves as candidates in the 232/8 range. This can be accomplished by - preventing RP/BSR from announcing in the 232/8 range - preventing ALL routers from accepting RP delegations in the 232/8 range - precluding RP functionality on RP for the 232/8 range Note that in typical practice, RP's announce themselves as candidates for the 224/4 (which obviously includes 232/8). It is still acceptable to allow the advertisement of 224/4 (or any other superset of 232/8); however, this approach relies on the second point, above, namely, that routers silently just ignore the RP delegation in the 232/8 range, and prevent sending or receiving using the shared tree, as described previously. Finally, an RP SHOULD NOT be configured as a candidate RP for 232/8 (or more specific range). 3. Intellectual Property The IETF takes no position regarding the validity or scope of any intellectual property 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; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11 [RFC2028]. Copies of claims of rights made available for publication 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 implementors or users of this specification can be obtained from the IETF Secretariat. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. 4. Acknowledgments This document is the work of many people in the multicast community, including (but not limited to) Dino Farinacci, John Meylor, John Zwiebel, Tom Pusateri, Dave Thaler, Toerless Eckert, Leonard Giuliano, Mike McBride, and Pekka Savola. 5. Security Considerations This document describes operational practices that introduce no new security issues to either PIM-SM or PIM-SSM. However, in the event that the operational practices described in this document are not adhered to, some problems may surface. In particular, section 2.3 describes the effects of non-compliance of last-hop routers (or to some degree, rogue hosts sending PIM messages themselves) on the source-specific service model; creating the (*,G) state for source-specific (S,G) could enable a receiver to receive data it should not get. This can be mitigated by host-side multicast source filtering. 6. IANA Considerations This document creates no new requirements on IANA namespaces [RFC2434]. 7. References 7.1. Normative References [MSDP] Meyer, D. and B. Fenner (Editors), "The Multicast Source Discovery Protocol (MSDP)", draft-ietf-msdp-spec-20.txt. Work in Progress. [SSM] Holbrook, H., and B. Cain,, "Source-Specific Multicast", draft-ietf-ssm-arch-03.txt. Work in Progress.[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, March, 1997. [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 3", RFC 2026/BCP 9, October, 1996. [RFC2028] Hovey, R. and S. Bradner, "The Organizations Involved in the IETF Standards Process", RFC 2028/BCP 11, October, 1996. [RFC2362] Estrin, D., et. al., "Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification", RFC 2362, June, 1998. [RFC2434] Narten, T., and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", RFC 2434/BCP 26, October 1998. [RFC3569] Bhattacharyya, S. Editor, "An Overview of Source-Specific Multicast (SSM)" RFC 3569, July, 2003. [RFC3618] Meyer, D. and B. Fenner (Editors), "The Multicast Source Discovery Protocol (MSDP)", RFC 3618, October, 2003. 7.2. Informative References [IANA] http://www.iana.org 8. Author's Addresses David Meyer Email: email@example.com Robert Rockell Sprint Email: firstname.lastname@example.org Greg Shepherd Procket Email: email@example.com 9. Full Copyright Statement Copyright (C) The Internet Society (2003).(2004). All Rights Reserved. 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