rfc9436.original		rfc9436.txt
	PIM S. Venaas		Internet Engineering Task Force (IETF) S. Venaas
	Internet-Draft Cisco Systems, Inc.		Request for Comments: 9436 Cisco Systems, Inc.
	Obsoletes: 8736 (if approved) A. Retana		Obsoletes: 8736 A. Retana
	Updates: 3973, 5015, 5059, 6754, 7761, Futurewei Technologies, Inc.		Updates: 3973, 5015, 5059, 6754, 7761, Futurewei Technologies, Inc.
	8364 (if approved) 24 May 2023		8364 August 2023
	Intended status: Standards Track		Category: Standards Track
	Expires: 25 November 2023		ISSN: 2070-1721
	PIM Message Type Space Extension and Reserved Bits		PIM Message Type Space Extension and Reserved Bits
	draft-ietf-pim-rfc8736bis-04
	Abstract		Abstract
	The PIM version 2 messages share a common message header format. The		The PIM version 2 messages share a common message header format. The
	common header definition contains eight reserved bits. This document		common header definition contains eight reserved bits. This document
	specifies how these bits may be used by individual message types and		specifies how these bits may be used by individual message types and
	extends the PIM type space.		extends the PIM type space.
	This document updates RFC7761 and RFC3973 by defining the use of the		This document updates RFCs 7761 and 3973 by defining the use of the
	currently Reserved field in the PIM common header. This document		Reserved field in the PIM common header. This document further
	further updates RFC7761 and RFC3973, along with RFC5015, RFC5059,		updates RFCs 7761 and 3973, along with RFCs 5015, 5059, 6754, and
	RFC6754, and RFC8364, by specifying the use of the currently reserved		8364, by specifying the use of the bits for each PIM message.
	bits for each PIM message.
	This document obsoletes RFC8736.		This document obsoletes RFC 8736.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This is an Internet Standards Track document.
	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		This document is a product of the Internet Engineering Task Force
	and may be updated, replaced, or obsoleted by other documents at any		(IETF). It represents the consensus of the IETF community. It has
	time. It is inappropriate to use Internet-Drafts as reference		received public review and has been approved for publication by the
	material or to cite them other than as "work in progress."		Internet Engineering Steering Group (IESG). Further information on
			Internet Standards is available in Section 2 of RFC 7841.
	This Internet-Draft will expire on 25 November 2023.		Information about the current status of this document, any errata,
			and how to provide feedback on it may be obtained at
			https://www.rfc-editor.org/info/rfc9436.
	Copyright Notice		Copyright Notice
	Copyright (c) 2023 IETF Trust and the persons identified as the		Copyright (c) 2023 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents (https://trustee.ietf.org/		Provisions Relating to IETF Documents
	license-info) in effect on the date of publication of this document.		(https://trustee.ietf.org/license-info) in effect on the date of
	Please review these documents carefully, as they describe your rights		publication of this document. Please review these documents
	and restrictions with respect to this document. Code Components		carefully, as they describe your rights and restrictions with respect
	extracted from this document must include Revised BSD License text as		to this document. Code Components extracted from this document must
	described in Section 4.e of the Trust Legal Provisions and are		include Revised BSD License text as described in Section 4.e of the
	provided without warranty as described in the Revised BSD License.		Trust Legal Provisions and are provided without warranty as described
			in the Revised BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction
	2. Conventions Used in This Document . . . . . . . . . . . . . . 3		2. Conventions Used in This Document
	3. PIM Header Common Format . . . . . . . . . . . . . . . . . . 3		3. PIM Header Common Format
	4. Flag Bit Definitions . . . . . . . . . . . . . . . . . . . . 3		4. Flag Bit Definitions
	4.1. Flag Bits for Type 4 (Bootstrap) . . . . . . . . . . . . 4		4.1. Flag Bits for Type 4 (Bootstrap)
	4.2. Flag Bits for Type 10 (DF Election) . . . . . . . . . . . 4		4.2. Flag Bits for Type 10 (DF Election)
	4.3. Flag Bits for Type 12 (PFM) . . . . . . . . . . . . . . . 4		4.3. Flag Bits for Type 12 (PIM Flooding Mechanism)
	4.4. Flag Bits for Types 13, 14, and 15 (Type Space		4.4. Flag Bits for Types 13, 14, and 15 (Type Space Extension)
	Extension) . . . . . . . . . . . . . . . . . . . . . . . 4		5. PIM Type Space Extension
	5. PIM Type Space Extension . . . . . . . . . . . . . . . . . . 4		6. Security Considerations
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 5		7. IANA Considerations
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5		8. References
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7		8.1. Normative References
	8.1. Normative References . . . . . . . . . . . . . . . . . . 7		8.2. Informative References
	8.2. Informative References . . . . . . . . . . . . . . . . . 7		Authors' Addresses
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
	1. Introduction		1. Introduction
	The PIM version 2 messages share a common message header format		The PIM version 2 messages share a common message header format
	defined in the PIM Sparse Mode specification [RFC7761]. The common		defined in the PIM Sparse Mode specification [RFC7761]. The common
	header definition contains eight reserved bits. While all message		header definition contains eight reserved bits. While all message
	types use this common header, there is no document formally		types use this common header, there is no document formally
	specifying that these bits are to be used per message type.		specifying that these bits are to be used per message type.
	This document refers to the bits in the Reserved field of the common		This document updates the definition of the Reserved field and refers
	PIM header [RFC7761] as "PIM message type Flag Bits" or, simply,		to it as the "Flag Bits field". It specifies that the flag bits are
	"Flag Bits", and it specifies that they are to be separately used on		to be separately used on a per-message-type basis. It updates the
	a per-message-type basis. It updates the "PIM Message Types"		"PIM Message Types" registry to indicate the per-message-type usage.
	registry to indicate the per-message-type usage.
	This document updates [RFC7761] and [RFC3973] by defining the use of		This document updates [RFC7761] and [RFC3973] by defining the use of
	the currently Reserved field in the PIM common header. This document		the Reserved field in the PIM common header. This document further
	further updates [RFC7761] and [RFC3973], along with [RFC5015],		updates [RFC7761] and [RFC3973], along with [RFC5015], [RFC5059],
	[RFC5059], [RFC6754], and [RFC8364], by specifying the use of the		[RFC6754], and [RFC8364], by specifying the use of the bits for each
	currently reserved bits for each PIM message.		PIM message.
	The originally defined PIM message types were in the range from 0 to		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		15. Message type 15 had been reserved by [RFC6166] for type space
	extension. In Section 5, this document specifies the use of the Flag		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		Bits field for message types 13, 14, and 15 in order to extend the
	space. The type space extension in [RFC6166] was made obsolete by		PIM type space. The type space extension in [RFC6166] was made
	[RFC8736]. This document obsoletes [RFC8736].		obsolete by [RFC8736]. This document obsoletes [RFC8736].
	2. Conventions Used in This Document		2. Conventions Used in This Document
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in		"OPTIONAL" in this document are to be interpreted as described in
	BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all		BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
	capitals, as shown here.		capitals, as shown here.
	3. PIM Header Common Format		3. PIM Header Common Format
	The common PIM header is defined in Section 4.9 of [RFC7761]. This		The common PIM header is defined in Section 4.9 of [RFC7761]. This
	document updates the definition of the Reserved field and refers to		document updates the definition of the Reserved field and refers to
	that field as "PIM message type Flag Bits" or, simply, "Flag Bits".		it as the "Flag Bits field". The updated common header format is as
	The updated common header format is as below.		below.
	0 1 2 3		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		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 |		|PIM Ver| Type | Flag Bits | Checksum |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 1: Updated Common Header		Figure 1: Updated Common Header
	The Flag Bits field is defined in Section 4. All other fields remain		The Flag Bits field is defined in Section 4. All other fields remain
	unchanged.		unchanged.
	4. Flag Bit Definitions		4. Flag Bit Definitions
	Unless otherwise specified, all the flag bits for each PIM type are		Unless otherwise specified, all the flag bits for each PIM type are
	Unassigned [RFC8126]. They MUST be set to zero on transmission, and		Unassigned [RFC8126]. They MUST be set to zero on transmission, and
	they MUST be ignored upon receipt. The specification of a new PIM		they MUST be ignored upon receipt. The specification of a new PIM
	type MUST indicate whether the bits should be treated differently.		type MUST indicate whether the bits should be treated differently.
	When defining flag bits, it is helpful to have a well-defined way of		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		referring to a particular bit. The most significant of the flag
	bits, the bit immediately following the Type field, is referred to as		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		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.		field, is referred to as bit 0. This is shown in the diagram below.
	0 1 2 3		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		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 |		|PIM Ver| Type |7 6 5 4 3 2 1 0| Checksum |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 2: Flag Bits		Figure 2: Flag Bits
	4.1. Flag Bits for Type 4 (Bootstrap)		4.1. Flag Bits for Type 4 (Bootstrap)
	PIM message type 4 (Bootstrap) [RFC5059] defines flag bit 7 as No-		PIM message type 4 (Bootstrap) [RFC5059] defines flag bit 7 as No-
	Forward. The usage of the bit is defined in that document. The		Forward. The usage of the bit is defined in that document. The
	remaining flag bits are unassigned.		remaining flag bits are unassigned.
	4.2. Flag Bits for Type 10 (DF Election)		4.2. Flag Bits for Type 10 (DF Election)
	PIM message type 10 (DF Election) [RFC5015] specifies that the four		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.		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		The usage of those bits is defined in that document. The remaining
	flag bits are unassigned.		flag bits are unassigned.
	4.3. Flag Bits for Type 12 (PFM)		4.3. Flag Bits for Type 12 (PIM Flooding Mechanism)
	PIM message type 12 (PIM Flooding Mechanism) [RFC8364] defines flag		PIM message type 12 (PIM Flooding Mechanism) [RFC8364] defines flag
	bit 7 as No-Forward. The usage of the bit is defined in that		bit 7 as No-Forward. The usage of the bit is defined in that
	document. The remaining flag bits are unsassigned.		document. The remaining flag bits are unassigned.
	4.4. Flag Bits for Types 13, 14, and 15 (Type Space Extension)		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.		These types and the corresponding flag bits are defined in Section 5.
	5. PIM Type Space Extension		5. PIM Type Space Extension
	This document extends types 13, 14, and 15 such that each becomes 16		This document extends types 13, 14, and 15 such that each becomes 16
	new types, resulting in 48 types available for future PIM extensions.		new types, resulting in 48 types available for future PIM extensions.
	This extension is achieved by defining a Subtype field (see Figure 3)		This extension is achieved by defining a Subtype field (see Figure 3)
	using the four most significant flag bits (bits 4-7). The notation		using the four most significant flag bits (bits 4-7). The notation
	type.subtype is used to reference the new extended types. The		type.subtype is used to reference the new extended types. The
	remaining four flag bits (bits 0-3, abbreviated as FB below) are to		remaining four flag bits (bits 0-3, abbreviated as FB below) are to
	be defined by each extended type.		be defined by each extended type.
	Each of the extended types is represented by the eight bits resulting		Each of the extended types is represented by the eight bits resulting
	from the concatenation of the Type and Subtype fields. No		from the concatenation of the Type and Subtype fields. No
	relationship is expected or implied between extended type messages		relationship is expected or implied between extended type messages
	with a common Type field.		with a common Type field.
	0 1 2 3		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		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 |		|PIM Ver| Type |Subtype| FB | Checksum |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 3: Subtypes		Figure 3: Subtypes
	6. Security Considerations		6. Security Considerations
	This document clarifies the use of the flag bits in the common PIM		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		header, and it extends the PIM type space. As such, there is no
	impact on security or changes to the considerations in [RFC7761] and		impact on security or changes to the considerations in [RFC7761] and
	[RFC3973].		[RFC3973].
	7. IANA Considerations		7. IANA Considerations
	This document updates the "PIM Message Types" registry to indicate		This document updates the "PIM Message Types" registry to indicate
	which flag bits are defined for use by each of the PIM message types,		which flag bits are defined for use by each of the PIM message types
	and changes their registration status to Unassigned, as shown in		and changes their registration status to Unassigned except where the
	Table 1. The registration policy remains IETF Review [RFC8126].		bits have already been specified, as shown in Table 1. The
	Assignments to this registry MUST define any non-default usage (see		registration policy remains IETF Review [RFC8126]. Assignments to
	Section 4) of the flag bits in addition to the type.		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.		Extended type 15.15 is Reserved [RFC8126] for future extensions.
	Because this document obsoletes RFC 8736, IANA is asked to change all		Because this document obsoletes [RFC8736], IANA has changed the
	registration information that references [RFC8736] to instead		references to [RFC8736] in the registry to point to this document
	reference [this document].		instead.
	The updated "PIM Message Types" registry is shown below.		The updated "PIM Message Types" registry is shown below.
	+============+===============+=================+====================+		+============+===============+=================+===========+
	| Type | Name | Flag Bits | Reference |		| Type | Name | Flag Bits | Reference |
	+============+===============+=================+====================+		+============+===============+=================+===========+
	| 0 | Hello | 0-7: | [RFC3973][RFC7761] |		| 0 | Hello | 0-7: Unassigned | [RFC3973] |
	| | | Unassigned | |		| | | | [RFC7761] |
	+------------+---------------+-----------------+--------------------+		+------------+---------------+-----------------+-----------+
	| 1 | Register | 0-7: | [RFC7761] |		| 1 | Register | 0-7: Unassigned | [RFC7761] |
	| | | Unassigned | |		+------------+---------------+-----------------+-----------+
	+------------+---------------+-----------------+--------------------+		| 2 | Register Stop | 0-7: Unassigned | [RFC7761] |
	| 2 | Register Stop | 0-7: | [RFC7761] |		+------------+---------------+-----------------+-----------+
	| | | Unassigned | |		| 3 | Join/Prune | 0-7: Unassigned | [RFC3973] |
	+------------+---------------+-----------------+--------------------+		| | | | [RFC7761] |
	| 3 | Join/Prune | 0-7: | [RFC3973][RFC7761] |		+------------+---------------+-----------------+-----------+
	| | | Unassigned | |		| 4 | Bootstrap | 0-6: Unassigned | [RFC5059] |
	+------------+---------------+-----------------+--------------------+		| | | | [RFC7761] |
	| 4 | Bootstrap | 0-6: | [RFC5059][RFC7761] |		| | +-----------------+-----------+
	| | | Unassigned | |		| | | 7: No-Forward | [RFC5059] |
	| | +-----------------+--------------------+		+------------+---------------+-----------------+-----------+
	| | | 7: No- | [RFC5059] |		| 5 | Assert | 0-7: Unassigned | [RFC3973] |
	| | | Forward | |		| | | | [RFC7761] |
	+------------+---------------+-----------------+--------------------+		+------------+---------------+-----------------+-----------+
	| 5 | Assert | 0-7: | [RFC3973][RFC7761] |		| 6 | Graft | 0-7: Unassigned | [RFC3973] |
	| | | Unassigned | |		+------------+---------------+-----------------+-----------+
	+------------+---------------+-----------------+--------------------+		| 7 | Graft-Ack | 0-7: Unassigned | [RFC3973] |
	| 6 | Graft | 0-7: | [RFC3973] |		+------------+---------------+-----------------+-----------+
	| | | Unassigned | |		| 8 | Candidate RP | 0-7: Unassigned | [RFC7761] |
	+------------+---------------+-----------------+--------------------+		| | Advertisement | | |
	| 7 | Graft-Ack | 0-7: | [RFC3973] |		+------------+---------------+-----------------+-----------+
	| | | Unassigned | |		| 9 | State Refresh | 0-7: Unassigned | [RFC3973] |
	+------------+---------------+-----------------+--------------------+		+------------+---------------+-----------------+-----------+
	| 8 | Candidate RP | 0-7: | [RFC7761] |		| 10 | DF Election | 0-3: Unassigned | [RFC5015] |
	| | Advertisement | Unassigned | |		| | +-----------------+-----------+
	+------------+---------------+-----------------+--------------------+		| | | 4-7: Subtype | [RFC5015] |
	| 9 | State Refresh | 0-7: | [RFC3973] |		+------------+---------------+-----------------+-----------+
	| | | Unassigned | |		| 11 | ECMP Redirect | 0-7: Unassigned | [RFC6754] |
	+------------+---------------+-----------------+--------------------+		+------------+---------------+-----------------+-----------+
	| 10 | DF Election | 0-3: | [RFC5015] |		| 12 | PIM Flooding | 0-6: Unassigned | [RFC8364] |
	| | | Unassigned | |		| | Mechanism +-----------------+-----------+
	| | +-----------------+--------------------+		| | | 7: No-Forward | [RFC8364] |
	| | | 4-7: | [RFC5015] |		+------------+---------------+-----------------+-----------+
	| | | Subtype | |		| 13.0-15.14 | Unassigned | 0-3: Unassigned | |
	+------------+---------------+-----------------+--------------------+		+------------+---------------+-----------------+-----------+
	| 11 | ECMP Redirect | 0-7: | [RFC6754] |		| 15.15 | Reserved | 0-3: Reserved | RFC 9436 |
	| | | 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		Table 1: Updated PIM Message Types Registry
	The unassigned types above, as explained in Section 5, use the		The unassigned types above, as explained in Section 5, use the
	extended type notation of type.subtype. Each extended type only has		extended type notation of type.subtype. Each extended type only has
	4 flag bits available. New extended message types should be assigned		4 flag bits available. New extended message types should be assigned
	consecutively, starting with 13.0, then 13.1, etc.		consecutively, starting with 13.0, then 13.1, etc.
	8. References		8. References
	8.1. Normative References		8.1. Normative References
End of changes. 23 change blocks.
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