PIM Null-Register packing
draft-ietf-pim-null-register-packing-16

Network Working Group                                          V. Kamath
Internet-Draft                                                    VMware
Intended status: Standards Track            R. Chokkanathapuram Sundaram
Expires: 14 September 2023                           Cisco Systems, Inc.
                                                              R. Banthia
                                                                  Apstra
                                                                A. Gopal
                                                     Cisco Systems, Inc.
                                                           13 March 2023

                       PIM Null-Register packing
                draft-ietf-pim-null-register-packing-16

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 14 September 2023.

Kamath, et al.          Expires 14 September 2023               [Page 1]
Internet-Draft          PIM Null-Register packing             March 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 Packing Capability . . . . . . . . . . .   3
   3.  PIM Packed Null-Register message format . . . . . . . . . . .   3
   4.  PIM Packed Register-Stop message format . . . . . . . . . . .   4
   5.  Protocol operation  . . . . . . . . . . . . . . . . . . . . .   5
   6.  Operational Considerations  . . . . . . . . . . . . . . . . .   6
     6.1.  PIM Anycast RP Considerations . . . . . . . . . . . . . .   6
     6.2.  Interoperability between different versions . . . . . . .   6
     6.3.  Disabling PIM Packed Message Support at RP and/or DR  . .   6
   7.  Fragmentation Considerations  . . . . . . . . . . . . . . . .   7
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   8
   11. Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

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 document specifies a method to efficiently pack the content of
   multiple PIM Null-Register and Register-Stop messages [RFC7761] into
   a single message.

Kamath, et al.          Expires 14 September 2023               [Page 2]
Internet-Draft          PIM Null-Register packing             March 2023

   The document 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 Packing Capability

   The RP indicates its ability to receive PIM Packed Null-Register
   messages (Section 3) and send PIM Packed Register-Stop messages
   (Section 4) with a Packing Capability bit (P-bit) in the PIM
   Register-Stop message.  The P-bit is allocated in Section 9.

   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 Packing Capability option

   The fields in the PIM Register-Stop message are defined in
   Section 4.9.4 of [RFC7761], and the common header in
   [I-D.venaas-pim-rfc8736bis].

   Packing Capability bit (P-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 14 September 2023               [Page 3]
Internet-Draft          PIM Null-Register packing             March 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  |Subtype|  FB   |           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
   [I-D.venaas-pim-rfc8736bis]

   Type, Subtype: The PIM Packed Null-Register Type value TBD2.
   [I-D.venaas-pim-rfc8736bis]

   N: The total number of records; A record consists of a Group Address
   and Source Address pair.

   After parsing the PIM common header, individual records are then
   parsed one by one until the length of the PIM Packed Null-Register
   message.  This length is inferred from the IP layer.

   Sending or receiving a PIM Packed Null-Register message is the
   equivalent, for all purposes, of sending or receiving an individual
   Null-Register message for each record represented in the PIM Packed
   Null-Register message.

4.  PIM Packed Register-Stop message format

Kamath, et al.          Expires 14 September 2023               [Page 4]
Internet-Draft          PIM Null-Register packing             March 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  |Subtype|  FB   |           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
   [I-D.venaas-pim-rfc8736bis]

   Type, Subtype: The PIM Packed Register-Stop Type TBD3

   N: The total number of records; A record consists of a Group Address
   and Source Address pair.

   After parsing the PIM common header, individual records are then
   parsed one by one until the length of the PIM Packed Register-Stop
   message.  This length is inferred from the IP layer.

   Sending or receiving a PIM Packed Register-Stop message is the
   equivalent, for all purposes, of sending or receiving an individual
   Null-Register message for each record represented in the PIM Packed
   Register-Stop.

5.  Protocol operation

   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
   SHOULD 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

Kamath, et al.          Expires 14 September 2023               [Page 5]
Internet-Draft          PIM Null-Register packing             March 2023

   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 PIM Packed Null-Register and PIM Packed Register-Stop formats
   as long as the RP and DR have the feature enabled.

   The RP, after receiving a PIM Packed Null-Register message, SHOULD
   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 PIM Packed Null-Register and PIM Packed
   Register-Stop formats 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 use the PIM Packed Null-Register message
   format based on the Packing 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 Packing
   Capability information MUST 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).

6.3.  Disabling PIM Packed Message Support at RP and/or DR

   Consider a PIM RP router that supports PIM Packed Null-Registers and
   PIM Packed Register-Stops.  In scenarios where this router now no
   longer supports this feature, for example, in case of a software
   downgrade, it will not send a PIM Register-Stop message to the DR in
   response to a PIM Packed Null-Register message.

Kamath, et al.          Expires 14 September 2023               [Page 6]
Internet-Draft          PIM Null-Register packing             March 2023

   When the DR switches to Data Registers from Null-Registers, it MUST
   start a Packed_Register_Probe_Time timer.  If no PIM Packed Register-
   Stop or Register-Stop with the P-bit set is received within
   Packed_Register_Probe_Time seconds, the DR can decide that the RP no
   longer supports PIM Packed Null-Registers.  The
   Packed_Register_Probe_Time timer is configurable; its default value
   is 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 P-bit 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 Packing Capability at the
   RP, or in other words, disables the feature from the RP, the router
   MUST NOT advertise the Packing 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

   As explained in Section 4.4.1 of [RFC7761], the DR may perform Path
   MTU Discovery to the RP before sending PIM Packed Null-Register
   messages.  Similarly, the RP may perform Path MTU Discovery to the DR
   before sending PIM Packed Register-Stop messages.  In both cases, the
   number of records in a message should be limited such that it can fit
   within the Path MTU.

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
   instead of just one.

   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 Packing
   Capability bit (TBD1) in the PIM Register-Stop Common Header from the
   PIM Message Types registry.

Kamath, et al.          Expires 14 September 2023               [Page 7]
Internet-Draft          PIM Null-Register packing             March 2023

   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.  The Flag Bits (0-3) for PIM message type
   (TBD2) are requested to be "Unassigned".

   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.  The Flag Bits (0-3) for PIM message type
   (TBD3) are requested to be "Unassigned".

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
   document.

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,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [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, <https://www.rfc-editor.org/info/rfc7761>.

   [RFC4610]  Farinacci, D. and Y. Cai, "Anycast-RP Using Protocol
              Independent Multicast (PIM)", RFC 4610,
              DOI 10.17487/RFC4610, August 2006,
              <https://www.rfc-editor.org/info/rfc4610>.

   [I-D.venaas-pim-rfc8736bis]
              Venaas, S. and A. Retana, "PIM Message Type Space
              Extension and Reserved Bits", Work in Progress, Internet-
              Draft, draft-venaas-pim-rfc8736bis-00, 1 March 2023,
              <https://datatracker.ietf.org/doc/html/draft-venaas-pim-
              rfc8736bis-00>.

Kamath, et al.          Expires 14 September 2023               [Page 8]
Internet-Draft          PIM Null-Register packing             March 2023

   [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,
              <https://www.rfc-editor.org/info/rfc3446>.

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 14 September 2023               [Page 9]