Internet DRAFT - draft-ietf-pim-rfc8736bis

draft-ietf-pim-rfc8736bis







PIM                                                            S. Venaas
Internet-Draft                                       Cisco Systems, Inc.
Obsoletes: 8736 (if approved)                                  A. Retana
Updates: 3973, 5015, 5059, 6754, 7761,      Futurewei Technologies, Inc.
         8364 (if approved)                                  24 May 2023
Intended status: Standards Track                                        
Expires: 25 November 2023


           PIM Message Type Space Extension and Reserved Bits
                      draft-ietf-pim-rfc8736bis-04

Abstract

   The PIM version 2 messages share a common message header format.  The
   common header definition contains eight reserved bits.  This document
   specifies how these bits may be used by individual message types and
   extends the PIM type space.

   This document updates RFC7761 and RFC3973 by defining the use of the
   currently Reserved field in the PIM common header.  This document
   further updates RFC7761 and RFC3973, along with RFC5015, RFC5059,
   RFC6754, and RFC8364, by specifying the use of the currently reserved
   bits for each PIM message.

   This document obsoletes RFC8736.

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
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   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 25 November 2023.

Copyright Notice

   Copyright (c) 2023 IETF Trust and the persons identified as the
   document authors.  All rights reserved.



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   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
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   3
   3.  PIM Header Common Format  . . . . . . . . . . . . . . . . . .   3
   4.  Flag Bit Definitions  . . . . . . . . . . . . . . . . . . . .   3
     4.1.  Flag Bits for Type 4 (Bootstrap)  . . . . . . . . . . . .   4
     4.2.  Flag Bits for Type 10 (DF Election) . . . . . . . . . . .   4
     4.3.  Flag Bits for Type 12 (PFM) . . . . . . . . . . . . . . .   4
     4.4.  Flag Bits for Types 13, 14, and 15 (Type Space
           Extension)  . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  PIM Type Space Extension  . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   The PIM version 2 messages share a common message header format
   defined in the PIM Sparse Mode specification [RFC7761].  The common
   header definition contains eight reserved bits.  While all message
   types use this common header, there is no document formally
   specifying that these bits are to be used per message type.

   This document refers to the bits in the Reserved field of the common
   PIM header [RFC7761] as "PIM message type Flag Bits" or, simply,
   "Flag Bits", and it specifies that they are to be separately used on
   a per-message-type basis.  It updates the "PIM Message Types"
   registry to indicate the per-message-type usage.

   This document updates [RFC7761] and [RFC3973] by defining the use of
   the currently Reserved field in the PIM common header.  This document
   further updates [RFC7761] and [RFC3973], along with [RFC5015],
   [RFC5059], [RFC6754], and [RFC8364], by specifying the use of the
   currently reserved bits for each PIM message.




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   The originally defined PIM message types were in the range from 0 to
   15.  Message type 15 had been reserved by [RFC6166] for type space
   extension.  In Section 5, this document specifies the use of the Flag
   Bits for message types 13, 14, and 15 in order to extend the PIM type
   space.  The type space extension in [RFC6166] was made obsolete by
   [RFC8736].  This document obsoletes [RFC8736].

2.  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.

3.  PIM Header Common Format

   The common PIM header is defined in Section 4.9 of [RFC7761].  This
   document updates the definition of the Reserved field and refers to
   that field as "PIM message type Flag Bits" or, simply, "Flag Bits".
   The updated common header format is as below.

       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            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 1: Updated Common Header

   The Flag Bits field is defined in Section 4.  All other fields remain
   unchanged.

4.  Flag Bit Definitions

   Unless otherwise specified, all the flag bits for each PIM type are
   Unassigned [RFC8126].  They MUST be set to zero on transmission, and
   they MUST be ignored upon receipt.  The specification of a new PIM
   type MUST indicate whether the bits should be treated differently.

   When defining flag bits, it is helpful to have a well-defined way of
   referring to a particular bit.  The most significant of the flag
   bits, the bit immediately following the Type field, is referred to as
   bit 7.  The least significant, the bit right in front of the Checksum
   field, is referred to as bit 0.  This is shown in the diagram below.






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       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  |7 6 5 4 3 2 1 0|           Checksum            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                            Figure 2: Flag Bits

4.1.  Flag Bits for Type 4 (Bootstrap)

   PIM message type 4 (Bootstrap) [RFC5059] defines flag bit 7 as No-
   Forward.  The usage of the bit is defined in that document.  The
   remaining flag bits are unassigned.

4.2.  Flag Bits for Type 10 (DF Election)

   PIM message type 10 (DF Election) [RFC5015] specifies that the four
   most significant flag bits (bits 4-7) are to be used as a subtype.
   The usage of those bits is defined in that document.  The remaining
   flag bits are unassigned.

4.3.  Flag Bits for Type 12 (PFM)

   PIM message type 12 (PIM Flooding Mechanism) [RFC8364] defines flag
   bit 7 as No-Forward.  The usage of the bit is defined in that
   document.  The remaining flag bits are unsassigned.

4.4.  Flag Bits for Types 13, 14, and 15 (Type Space Extension)

   These types and the corresponding flag bits are defined in Section 5.

5.  PIM Type Space Extension

   This document extends types 13, 14, and 15 such that each becomes 16
   new types, resulting in 48 types available for future PIM extensions.
   This extension is achieved by defining a Subtype field (see Figure 3)
   using the four most significant flag bits (bits 4-7).  The notation
   type.subtype is used to reference the new extended types.  The
   remaining four flag bits (bits 0-3, abbreviated as FB below) are to
   be defined by each extended type.

   Each of the extended types is represented by the eight bits resulting
   from the concatenation of the Type and Subtype fields.  No
   relationship is expected or implied between extended type messages
   with a common Type field.






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       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            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                             Figure 3: Subtypes

6.  Security Considerations

   This document clarifies the use of the flag bits in the common PIM
   header, and it extends the PIM type space.  As such, there is no
   impact on security or changes to the considerations in [RFC7761] and
   [RFC3973].

7.  IANA Considerations

   This document updates the "PIM Message Types" registry to indicate
   which flag bits are defined for use by each of the PIM message types,
   and changes their registration status to Unassigned, as shown in
   Table 1.  The registration policy remains IETF Review [RFC8126].
   Assignments to this registry MUST define any non-default usage (see
   Section 4) of the flag bits in addition to the type.

   Extended type 15.15 is Reserved [RFC8126] for future extensions.

   Because this document obsoletes RFC 8736, IANA is asked to change all
   registration information that references [RFC8736] to instead
   reference [this document].

   The updated "PIM Message Types" registry is shown below.

   +============+===============+=================+====================+
   | Type       | Name          | Flag Bits       | Reference          |
   +============+===============+=================+====================+
   | 0          | Hello         | 0-7:            | [RFC3973][RFC7761] |
   |            |               | Unassigned      |                    |
   +------------+---------------+-----------------+--------------------+
   | 1          | Register      | 0-7:            | [RFC7761]          |
   |            |               | Unassigned      |                    |
   +------------+---------------+-----------------+--------------------+
   | 2          | Register Stop | 0-7:            | [RFC7761]          |
   |            |               | Unassigned      |                    |
   +------------+---------------+-----------------+--------------------+
   | 3          | Join/Prune    | 0-7:            | [RFC3973][RFC7761] |
   |            |               | Unassigned      |                    |
   +------------+---------------+-----------------+--------------------+
   | 4          | Bootstrap     | 0-6:            | [RFC5059][RFC7761] |



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   |            |               | Unassigned      |                    |
   |            |               +-----------------+--------------------+
   |            |               | 7: No-          | [RFC5059]          |
   |            |               | Forward         |                    |
   +------------+---------------+-----------------+--------------------+
   | 5          | Assert        | 0-7:            | [RFC3973][RFC7761] |
   |            |               | Unassigned      |                    |
   +------------+---------------+-----------------+--------------------+
   | 6          | Graft         | 0-7:            | [RFC3973]          |
   |            |               | Unassigned      |                    |
   +------------+---------------+-----------------+--------------------+
   | 7          | Graft-Ack     | 0-7:            | [RFC3973]          |
   |            |               | Unassigned      |                    |
   +------------+---------------+-----------------+--------------------+
   | 8          | Candidate RP  | 0-7:            | [RFC7761]          |
   |            | Advertisement | Unassigned      |                    |
   +------------+---------------+-----------------+--------------------+
   | 9          | State Refresh | 0-7:            | [RFC3973]          |
   |            |               | Unassigned      |                    |
   +------------+---------------+-----------------+--------------------+
   | 10         | DF Election   | 0-3:            | [RFC5015]          |
   |            |               | Unassigned      |                    |
   |            |               +-----------------+--------------------+
   |            |               | 4-7:            | [RFC5015]          |
   |            |               | Subtype         |                    |
   +------------+---------------+-----------------+--------------------+
   | 11         | ECMP Redirect | 0-7:            | [RFC6754]          |
   |            |               | Unassigned      |                    |
   +------------+---------------+-----------------+--------------------+
   | 12         | PIM Flooding  | 0-6:            | [RFC8364]          |
   |            | Mechanism     | Unassigned      |                    |
   |            |               +-----------------+--------------------+
   |            |               | 7: No-          | [RFC8364]          |
   |            |               | Forward         |                    |
   +------------+---------------+-----------------+--------------------+
   | 13.0-15.14 | Unassigned    | 0-3:            | [This document]    |
   |            |               | Unassigned      |                    |
   +------------+---------------+-----------------+--------------------+
   | 15.15      | Reserved      | 0-3:            | [This document]    |
   |            |               | Reserved        |                    |
   +------------+---------------+-----------------+--------------------+

                Table 1: Updated PIM Message Types Registry

   The unassigned types above, as explained in Section 5, use the
   extended type notation of type.subtype.  Each extended type only has
   4 flag bits available.  New extended message types should be assigned
   consecutively, starting with 13.0, then 13.1, etc.



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8.  References

8.1.  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>.

   [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>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [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>.

8.2.  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>.

   [RFC5015]  Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano,
              "Bidirectional Protocol Independent Multicast (BIDIR-
              PIM)", RFC 5015, DOI 10.17487/RFC5015, October 2007,
              <https://www.rfc-editor.org/info/rfc5015>.

   [RFC5059]  Bhaskar, N., Gall, A., Lingard, J., and S. Venaas,
              "Bootstrap Router (BSR) Mechanism for Protocol Independent
              Multicast (PIM)", RFC 5059, DOI 10.17487/RFC5059, January
              2008, <https://www.rfc-editor.org/info/rfc5059>.

   [RFC6166]  Venaas, S., "A Registry for PIM Message Types", RFC 6166,
              DOI 10.17487/RFC6166, April 2011,
              <https://www.rfc-editor.org/info/rfc6166>.







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   [RFC6754]  Cai, Y., Wei, L., Ou, H., Arya, V., and S. Jethwani,
              "Protocol Independent Multicast Equal-Cost Multipath
              (ECMP) Redirect", RFC 6754, DOI 10.17487/RFC6754, October
              2012, <https://www.rfc-editor.org/info/rfc6754>.

   [RFC8364]  Wijnands, IJ., Venaas, S., Brig, M., and A. Jonasson, "PIM
              Flooding Mechanism (PFM) and Source Discovery (SD)",
              RFC 8364, DOI 10.17487/RFC8364, March 2018,
              <https://www.rfc-editor.org/info/rfc8364>.

   [RFC8736]  Venaas, S. and A. Retana, "PIM Message Type Space
              Extension and Reserved Bits", RFC 8736,
              DOI 10.17487/RFC8736, February 2020,
              <https://www.rfc-editor.org/info/rfc8736>.

Authors' Addresses

   Stig Venaas
   Cisco Systems, Inc.
   Tasman Drive
   San Jose, CA 95134
   United States of America
   Email: stig@cisco.com


   Alvaro Retana
   Futurewei Technologies, Inc.
   2330 Central Expressway
   Santa Clara, CA 95050
   United States of America
   Email: alvaro.retana@futurewei.com




















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