Network Working Group R. Chokkanathapuram Sundaram Internet-Draft S. Venaas Intended status: Standards Track Cisco Systems, Inc. Expires: January 9, 2020 July 8, 2019 Source specific multicast range distribution for L2 multicast networks draft-ramki-igmp-ssm-ranges-00 Abstract In an IGMP snooping multicast network with version 3 (v3) enabled on the routers, when a v2 join/leave is received for a multicast group the router operates on V2 compatible mode. For SSM ranges a (*,G)v2 or v3 report should be ignored by the router/switch. The IGMP snooping switches may not have knowledge about the user configured SSM range in the network to correctly discard/ignore the v2 join/ leave. Accepting (*,G) v2 or v3 will cause SSM operations to fail. This draft discusses distribution of SSM ranges in the L2 multicast network so that L2 snooping switches can learn about the configured SSM ranges and discard any (*,G) v2/v3 reports for the said ranges. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on January 9, 2020. Copyright Notice Copyright (c) 2019 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents Chokkanathapuram SundaramExpiresaJanuary 9, 2020 [Page 1]
Internet-DraSSM range distribution for L2 multicast networks. July 2019 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Conventions Used in This Document . . . . . . . . . . . . 2 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2 2. L2 network with a PIM router . . . . . . . . . . . . . . . . 3 3. L2 multicast network with no PIM router . . . . . . . . . . . 3 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 4 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 6.1. Normative References . . . . . . . . . . . . . . . . . . 4 6.2. Informative References . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction IGMP v2 join and leaves and IGMP v3 (*,G) group records should be discarded for Source specific multicast group ranges. The default SSM range is 232/8 but changing the range is possible. In a L2 multicast network the Snooping switches are unaware of the user configured SSM ranges in the network. Methods are needed to distribute user configured SSM ranges so that all snooping switches in the L2 domain knows about the same. Thus the snooping switches can discard the Version 2 joins/leaves falling in the SSM range. If the v2 joins/leaves for the SSM ranges are not discarded then the router/ querier start operating in v2 mode. This will result in outages. The same problem is applicable for MLD as well. 1.1. Conventions Used in 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 [RFC2119]. 1.2. Terminology DR: Designated Router SSM: Source Specific Multicast Chokkanathapuram SundaramExpiresaJanuary 9, 2020 [Page 2]
Internet-DraSSM range distribution for L2 multicast networks. July 2019 2. L2 network with a PIM router In a LAN if a PIM router is detected the LAN segment should use the PIM SSM range configured on the PIM router which is the DR on the LAN. Snooping switches typically process PIM Hello packets already to detect routers. A new PIM Hello Option will carry the current (default or configured) SSM group ranges. The PIM Hello Option can be used by the snooping switches to learn the SSM ranges used in the network. Thus an IGMP message for a group in the SSM range in a v3 enabled network can correctly be discarded/ignored. Preventing hosts (whether by accident or a DoS attack) from disrupting the SSM service. Routers could be statically configured with the SSM group range. In case there are multiple routers on the LAN it is possible that routers are configured with different ranges. In that case, switches should use the range announced by the DR. The option allows for detecting configuration mistakes. A PIM router can log a message if it sees a neighbor announcing a different SSM range. Also, switches can log a message if they are statically configured with ranges that differ from what what is announced by the DR. There is no hold time for the config. The config is removed if the router sends a hello without the option, or the DR expires. If a new DR is elected, the config will be replaced by what the new DR is announcing. Figure 1: PIM SSM range hello option. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = TBD | Length = Variable. | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Group Address 1 (Encoded-Group format) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Group Address N (Encoded-Group format) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3. L2 multicast network with no PIM router In a pure L2 only network a new IGMP message is sent from querier to learn the SSM ranges. The SSM range used should be configured on the querier and the querier will distribute it with a new message type so that all L2 switches can learn about the SSM range. Chokkanathapuram SundaramExpiresaJanuary 9, 2020 [Page 3]
Internet-DraSSM range distribution for L2 multicast networks. July 2019 Figure 2: IGMP SSM range message. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = TBD | Reserved | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Num SSM ranges | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSM range 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | .... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSM range N | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ SSM range is an IP address plus a length octet. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSM Prefix address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Prefix length | +-+-+-+-+-+-+-+-+ 4. IANA Considerations This document requires the assignment of a PIM hello option and an IGMP message type. 5. Acknowledgments 6. References 6.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>. [RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. Thyagarajan, "Internet Group Management Protocol, Version 3", RFC 3376, DOI 10.17487/RFC3376, October 2002, <https://www.rfc-editor.org/info/rfc3376>. [RFC4604] Holbrook, H., Cain, B., and B. Haberman, "Using Internet Group Management Protocol Version 3 (IGMPv3) and Multicast Listener Discovery Protocol Version 2 (MLDv2) for Source- Specific Multicast", RFC 4604, DOI 10.17487/RFC4604, August 2006, <https://www.rfc-editor.org/info/rfc4604>. Chokkanathapuram SundaramExpiresaJanuary 9, 2020 [Page 4]
Internet-DraSSM range distribution for L2 multicast networks. July 2019 [RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for IP", RFC 4607, DOI 10.17487/RFC4607, August 2006, <https://www.rfc-editor.org/info/rfc4607>. 6.2. Informative References [RFC3973] Adams, A., Nicholas, J., and W. Siadak, "Protocol Independent Multicast - Dense Mode (PIM-DM): Protocol Specification (Revised)", RFC 3973, DOI 10.17487/RFC3973, January 2005, <https://www.rfc-editor.org/info/rfc3973>. Authors' Addresses Ramakrishnan Chokkanathapuram Sundaram Cisco Systems, Inc. Tasman Drive San Jose CA 95134 USA Email: ramaksun@cisco.com Stig Venaas Cisco Systems, Inc. Tasman Drive San Jose CA 95134 USA Email: stig@cisco.com Chokkanathapuram SundaramExpiresaJanuary 9, 2020 [Page 5]