INTERNET-DRAFT David Meyer
draft-ietf-mboned-ssm232-07.txtdraft-ietf-mboned-ssm232-08.txt Rob Rockell Greg Shepherd Category Best Current Practice Expires: JulySeptember 2004 JanuaryMarch 2004 Source-Specific Protocol Independent Multicast in 232/8 <draft-ietf-mboned-ssm232-07.txt><draft-ietf-mboned-ssm232-08.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 email@example.com. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract IP Multicast group addresses in the 232/8 (126.96.36.199 to 188.8.131.52) range are designated as source-specific multicast destination addresses and are reserved for use by source-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 1.1. BCP, Experimental Protocols and Normative References. . . . 4 2. Operational practices in 232/8 . . . . . . . . . . . . . . . . 45 2.1. Preventing local sources from sending to shared tree. . . . 45 2.2. Preventing remote sources from being learned/joined via MSDP. 46 2.3. Preventing receivers from joining the shared tree . . . . . 56 2.4. Preventing RP's as candidates for 232/8 . . . . . . . . . . 57 3. Intellectual Property. .Acknowledgments. . . . . . . . . . . . . . . . . . . . 6 4. Acknowledgments.. . . . 7 4. Security Considerations. . . . . . . . . . . . . . . . . . . . 67 5. SecurityIANA Considerations. . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations.. . 8 6. References . . . . . . . . . . . . . . . . . . . 7 7. References. . . . . . . 9 6.1. Normative References. . . . . . . . . . . . . . . . . . . . 8 7.1. Normative9 6.2. Informative References. . . . . . . . . . . . . . . . . . . 9 7. Author's Addresses . 8 7.2. Informative References.. . . . . . . . . . . . . . . . . . 8 8. Author's Addresses. . . 10 8. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 910 9. Full Copyright StatementIntellectual Property. . . . . . . . . . . . . . . . . . . . 9. 11 10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 11 1. Introduction Current PIM Sparse Mode (PIM-SM) [RFC2362][PIM-SM] 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 [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 known 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 [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 [RFC3618] 2. Operational practices in 232/8 2.1. Preventing local sources from sending to shared tree Eliminating1.1. BCP, Experimental Protocols and Normative References This document describes the use of shared treesbest current practice for groups in 232/8, while maintaining coexistence with PIM-SM, behavior of the RP and/ora widely deployed Experimental protocol, MSDP. There is no plan to advance the DR needsMSDP's status (for example, to be modified. This can be accomplished by - preventing dataProposed Standard). The reasons for 232/8 groups from being sent encapsulatedthis include: o MSDP was originally envisioned as a temporary protocol to the RPbe supplanted by whatever the DR - preventingIDMR working group produced as an inter-domain protocol. However, the RP from accepting registers for 232/8 groups fromIDMR WG (or subsequently, the DR - preventingBGMP WG) never produced a protocol that could be deployed to replace MSDP. o One of the RP from forwarding accepted data down (*,G) treeprimary reasons given for 232/8 groups 2.2. Preventing remote sources from being learned/joined viaMSDP PIM-SSM does not require active source announcements viato be classified as Experimental was that the MSDP Working Group came up with modifications to the protocol that the WG thought made it better but that implementors didn't see any reasons to deploy. Without these modifications (e.g., UDP or GRE encapsulation), MSDP can have negative consequences to initial packets in datagram streams. o Scalability: Although we don't know what the hard limits might be, readvertising everything you know every 60 seconds clearly limits the amount of state you can advertise. o MSDP reached near ubiquitous deployment as the de-facto standard inter-domain multicast protocol in the IPv4 Internet. o No consensus could be reached regarding the reworking of MSDP to address the many concerns of various constituencies within the IETF. As a result, a decision was taken to document what is (ubiquitously) deployed and move that document to Experimental. While advancement of MSDP to Proposed Standard was considered, for the reasons mentioned above, it was immediately discarded. o The advent of protocols such as source specific multicast and bi-directional PIM, as well as embedded RP techniques for IPv6, have further reduced consensus that a replacement protocol for MSDP for the IPv4 Internet is required. The RFC Editor's policy regarding references is that they be split into two categories known as "normative" and "informative". Normative references specify those documents which must be read to understand or implement the technology in an RFC (or whose technology must be present for the technology in the new RFC to work) [RFCED]. In order to understand this document, one must also understand both the PIM and MSDP documents. As a result, references to these documents are normative. The IETF has adopted the policy that BCPs must not have normative references to Experimental protocols. However, this document is a special case in that the underlying Experimental document (MSDP) is not planned to be advanced to Proposed Standard. The MBONED Working Group requests approval under the Variance Procedure as documented in RFC 2026 [RFC2026]. Note to RFC-Editor: If IETF/IESG approves this, please change the above sentence into: The MBONED Working Group has requested approval under the Variance Procedure as documented in RFC 2026 [RFC2026]. The IESG followed the Variance Procedure, and after an additional 4 week IETF Last Call evaluated the comments and status and has approved this document. 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]. 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 [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 toor receiving using the IETF Executive Director. 4.shared tree, as described previously. Finally, an RP SHOULD NOT be configured as a candidate RP for 232/8 (or more specific range). 3. 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. 5.4. 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. 6.5. IANA Considerations This document creates no new requirements on IANA namespaces [RFC2434]. 7.6. References 184.108.40.206. Normative References [PIM-SM] Fenner, B., et. al, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", draft-ietf-pim-sm-v2-new-09.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. 220.127.116.11. Informative References [IANA] http://www.iana.org 8.7. Author's Addresses David Meyer Email: firstname.lastname@example.org Robert Rockell Sprint Email: email@example.com Greg Shepherd Procket Email: firstname.lastname@example.org 9.8. Full Copyright Statement Copyright (C) The Internet Society (2004). All Rights Reserved.This document is subject to the rights, licenses and restrictions contained in BCP 78 and except as set forth therein, the authors retain all their rights. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. 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Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat 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 implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf- email@example.com. 10. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society.