Network Working Group V. Kamath Internet-Draft VMware Intended status: Standards Track R. Chokkanathapuram Sundaram Expires: 12 August 2023 Cisco Systems, Inc. R. Banthia Apstra A. Gopal Cisco Systems, Inc. 8 February 2023 PIM Null-Register packing draft-ietf-pim-null-register-packing-13 Abstract In PIM-SM networks PIM Null-Register messages are sent by the Designated Router (DR) to the Rendezvous Point (RP) to signal the presence of Multicast sources in the network. There are periodic PIM Null-Registers sent from the DR to the RP to keep the state alive at the RP as long as the source is active. The PIM Null-Register message carries information about a single Multicast source and group. This document defines a standard to send multiple Multicast source and group information in a single PIM message. This document refers to the new messages as the PIM Packed Null-Register message and PIM Packed Register-Stop message. 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 12 August 2023. Kamath, et al. Expires 12 August 2023 [Page 1] Internet-Draft PIM Null-Register packing February 2023 Copyright Notice Copyright (c) 2023 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 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Conventions used in this document . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. Packed Null-Register Capability . . . . . . . . . . . . . . . 3 3. PIM Packed Null-Register message format . . . . . . . . . . . 3 4. PIM Packed Register-Stop message format . . . . . . . . . . . 4 5. Protocol operation . . . . . . . . . . . . . . . . . . . . . 4 6. Operational Considerations . . . . . . . . . . . . . . . . . 5 6.1. PIM Anycast RP Considerations . . . . . . . . . . . . . . 5 6.2. Interoperability between different versions . . . . . . . 5 6.3. PIM RP router version downgrade . . . . . . . . . . . . . 6 7. Fragmentation Considerations . . . . . . . . . . . . . . . . 6 8. Security Considerations . . . . . . . . . . . . . . . . . . . 6 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 11. Normative References . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 1. Introduction The DR periodically sends PIM Null-Registers to keep the state of existing multicast sources active on the RP. As the number of multicast sources increases, the number of PIM Null-Register messages that are sent also increases. This results in more PIM packet processing at the RP and the DR. This draft proposes a method to efficiently pack multiple PIM Null- Registers [RFC7761] and Register-Stops [RFC7761] into a single message as these packets do not contain encapsulated data. Kamath, et al. Expires 12 August 2023 [Page 2] Internet-Draft PIM Null-Register packing February 2023 The draft also discusses interoperability between PIM routers that support PIM Packed Null-Registers and PIM Packed Register-Stops and PIM routers that do not. 1.1. Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 1.2. Terminology RP: Rendezvous Point DR: Designated Router 2. Packed Null-Register Capability This section allocates a bit in the PIM Register-Stop message Flag Bits field for the RP to indicate its ability to receive PIM Packed Null-Register messages (Section 3), and send PIM Packed Register-Stop messages (Section 4). 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |PIM Ver| Type |P|6 5 4 3 2 1 0| Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Group Address (Encoded-Group format) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Address (Encoded-Unicast format) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: PIM Register-Stop message with capability option The fields in the PIM Register-Stop message are defined in Section 4.9.4 of [RFC7761], and the common header in [RFC8736]. Capability bit (Flag Bit TBD1): When set, it indicates the ability of the RP to receive PIM Packed Null-Register messages, and send PIM Packed Register-Stop messages. 3. PIM Packed Null-Register message format Kamath, et al. Expires 12 August 2023 [Page 3] Internet-Draft PIM Null-Register packing February 2023 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |PIM Ver| Type | Flag Bits | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Group Address[1] (Encoded-Group format) | | Source Address[1] (Encoded-Unicast format) | . . . . . . . . . Group Address[N] . | Source Address[N] | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: PIM Packed Null-Register message format The fields in the PIM Packed Null-Register message are defined in Section 4.9.4 of [RFC7761], and the common header in [RFC8736] Type: The new PIM Packed Null-Register Type value TBD2. [RFC8736] 4. PIM Packed Register-Stop message format 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |PIM Ver| Type | Flag Bits | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Group Address[1] (Encoded-Group format) | | Source Address[1] (Encoded-Unicast format) | . . . . . . . . . Group Address[N] . | Source Address[N] | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: PIM Packed Register-Stop message format The fields in the PIM Packed Register-Stop message are defined in Section 4.9.4 of [RFC7761], and the common header in [RFC8736] Type: The PIM Packed Register-Stop Type TBD3 5. Protocol operation Kamath, et al. Expires 12 August 2023 [Page 4] Internet-Draft PIM Null-Register packing February 2023 * As specified in [RFC7761], the DR sends PIM Register messages towards the RP when a new source is detected. * When this feature is enabled/configured, an RP supporting this specification MUST set the P-bit (Flag bit TBD1) in all Register- Stop messages. * When a Register-Stop message with the P-bit set is received, the DR MAY send PIM Packed Null-Register messages (Section 3) to the RP instead of multiple Register messages with the N-bit set [RFC7761]. The DR may use a mixture of PIM Packed Null-Register messages and Register messages. The decision is up to the implementation and out of the scope of this document. However, it is RECOMMENDED to stick to the packed format as long as the RP and DR have the feature enabled. * The RP, after receiving a PIM Packed Null-Register message, MAY start sending PIM Packed Register-Stop messages (Section 4) to the corresponding DR instead of individual Register-Stop messages. The RP may use a mixture of PIM Packed Register-Stop messages and individual Register-Stop messages. The decision is up to the implementation and out of the scope of this document. However, it is RECOMMENDED to stick to the packed format as long as the RP and DR have the feature enabled. 6. Operational Considerations 6.1. PIM Anycast RP Considerations The PIM Packed Null-Register packet format should be enabled only if it is supported by all the routers in the Anycast-RP set [RFC4610]. This consideration applies to PIM Anycast RP with MSDP [RFC3446] as well. 6.2. Interoperability between different versions A router (DR) can decide to pack multiple Null-Register messages based on the capability received from the RP as part of the PIM Register-Stop. This ensures compatibility with routers that do not support processing of the new packet format. The capability information can be indicated by the RP via the PIM Register-Stop message sent to the DR. Thus a DR will switch to the new packet format only when it learns that the RP is capable of handling the PIM Packed Null-Register messages. Conversely, a DR that does not support the packed format can continue generating the PIM Null-Register as defined in [RFC7761] (Section 4.4). Kamath, et al. Expires 12 August 2023 [Page 5] Internet-Draft PIM Null-Register packing February 2023 6.3. PIM RP router version downgrade Consider a PIM RP router that supports PIM Packed Null-Registers and PIM Packed Register-Stops. When this router downgrades to a software version which does not support PIM Packed Null-Registers and PIM Packed Register-Stops, the DR that sends the PIM Packed Null-Register message will not get a PIM Register-Stop message back from the RP. When the DR switches to Data Registers from Null-Registers, it should start a Packed_Register_Probe_Time timer. If no PIM Packed Register- Stop or Register-Stop with capability is received within Packed_Register_Probe_Time seconds, the DR can decide that the RP no longer supports PIM Packed Null-Registers. It is RECOMMENDED that the Packed_Register_Probe_Time is configurable, with its default value being 60 seconds. When Packed_Register_Probe_Time expires, The DR MAY also send an unpacked PIM Null-Register and check the PIM Register-Stop to see if the capability bit (P-bit) for PIM Packed Null-Register is set or not. If it is not set then the DR will continue sending unpacked PIM Null-Register messages. In case the network manager disables the packed capability at the RP, or in other words, disables the feature from the RP, the router SHOULD NOT advertise the capability. However, an implementation MAY choose to still parse any packed registers if they are received. This may be particularly useful in the transitional period after the network manager disables it. 7. Fragmentation Considerations For IPv4 PIM Packed Null-Register messages or PIM Packed Register- Stop messages, the DR may perform Path MTU Discovery, but for IPv6 this is mandatory. This allows the DR to fragment packets as needed. However, in order to avoid fragmentation altogether, a DR sending packed registers SHOULD limit the number of records such that the message can fit within the Path MTU. A record consists of a Group Address and Source Address pair. 8. Security Considerations The Security Considerations from [RFC7761] apply to this document. In particular, the effect of forging a PIM Packed Null-Register or Register-Stop message would be amplified to all the records included and not a single source/group pair. Kamath, et al. Expires 12 August 2023 [Page 6] Internet-Draft PIM Null-Register packing February 2023 By forging a PIM Register-Stop message and setting the P-bit, an attacker can trigger the use of PIM Packed Null-Register messages by a DR thus creating unnecessary churn in the network. 9. IANA Considerations When this document is published, IANA is asked to assign a Capability bit (TBD1) in the PIM Register-Stop Common Header from the PIM Message Types registry. When this document is published, IANA is asked to assign a PIM message type (TBD2) for the PIM Packed Null-Register from the PIM Message Types registry. When this document is published, IANA is asked to assign a PIM message type (TBD3) for the PIM Packed Register-Stop from the PIM Message Types registry. 10. Acknowledgments The authors would like to thank Stig Venaas, Alvaro Retana, Anish Peter, Zheng Zhang and Umesh Dudani for their helpful comments on the draft. 11. 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, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I., Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March 2016, . [RFC4610] Farinacci, D. and Y. Cai, "Anycast-RP Using Protocol Independent Multicast (PIM)", RFC 4610, DOI 10.17487/RFC4610, August 2006, . Kamath, et al. Expires 12 August 2023 [Page 7] Internet-Draft PIM Null-Register packing February 2023 [RFC8736] Venaas, S. and A. Retana, "PIM Message Type Space Extension and Reserved Bits", RFC 8736, DOI 10.17487/RFC8736, February 2020, . [RFC3446] Kim, D., Meyer, D., Kilmer, H., and D. Farinacci, "Anycast Rendevous Point (RP) mechanism using Protocol Independent Multicast (PIM) and Multicast Source Discovery Protocol (MSDP)", RFC 3446, DOI 10.17487/RFC3446, January 2003, . Authors' Addresses Vikas Ramesh Kamath VMware 3401 Hillview Ave Palo Alto, CA 94304 United States of America Email: vkamath@vmware.com Ramakrishnan Chokkanathapuram Sundaram Cisco Systems, Inc. Tasman Drive San Jose, CA 95134 United States of America Email: ramaksun@cisco.com Raunak Banthia Apstra 333 Middlefield Rd STE 200 Menlo Park, CA 94025 United States of America Email: rbanthia@apstra.com Ananya Gopal Cisco Systems, Inc. Tasman Drive San Jose, CA 95134 United States of America Email: ananygop@cisco.com Kamath, et al. Expires 12 August 2023 [Page 8]