< draft-song-mpls-eh-indicator-00.txt		draft-song-mpls-eh-indicator-01.txt >
	MPLS H. Song, Ed.		MPLS H. Song, Ed.
	Internet-Draft Z. Li		Internet-Draft Futurewei Technologies
	Intended status: Informational T. Zhou		Intended status: Informational Z. Li
	Expires: August 19, 2019 Huawei		Expires: September 11, 2021 T. Zhou
			Huawei
	L. Andersson		L. Andersson
	Bronze Dragon Consulting		Bronze Dragon Consulting
	February 15, 2019		March 10, 2021
	Options for MPLS Extension Header Indicator		Options for MPLS Extension Header Indicator
	draft-song-mpls-eh-indicator-00		draft-song-mpls-eh-indicator-01
	Abstract		Abstract
	This document describes the schemes that indicates the presence of		This document describes the schemes that indicates the presence of
	the MPLS extension header(s) following the MPLS label stack. After a		the MPLS extension header(s) following the MPLS label stack. After a
	thorough evaluation of these options by comparing their pros and		thorough evaluation of these options by comparing their pros and
	cons, one should be chosen as the final scheme for MPLS extension		cons, one should be chosen as the final scheme for MPLS extension
	header indicator.		header indicator.
	Requirements Language		Requirements Language
	skipping to change at page 1, line 45 ¶		skipping to change at page 1, line 46 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on August 19, 2019.		This Internet-Draft will expire on September 11, 2021.
	Copyright Notice		Copyright Notice
	Copyright (c) 2019 IETF Trust and the persons identified as the		Copyright (c) 2021 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		Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	skipping to change at page 5, line 10 ¶		skipping to change at page 5, line 10 ¶
	be used. ACH starts with a nibble value "0001". A different nibble		be used. ACH starts with a nibble value "0001". A different nibble
	value may be used to redefine the remaining part of the word. The		value may be used to redefine the remaining part of the word. The
	idea has been exploited by [I-D.guichard-sfc-mpls-metadata] to define		idea has been exploited by [I-D.guichard-sfc-mpls-metadata] to define
	a Metadata Channel Header (MCH) with the leading nibble value "0000".		a Metadata Channel Header (MCH) with the leading nibble value "0000".
	Similarly, we can use another nibble value (e.g., "0010") to define a		Similarly, we can use another nibble value (e.g., "0010") to define a
	new header, namely the MPLS Extension Header Indicator (EHI).		new header, namely the MPLS Extension Header Indicator (EHI).
	The format of the GAL and EHI is depicted in Figure 2.		The format of the GAL and EHI is depicted in Figure 2.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| GAL (13) | EXP |1| TTL |		| GAL (13) | EXP |1| TTL |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|0 0 1 0|Version| Reserved | Extension Header Class |<-EHI		|0 0 1 0|Version| Reserved | Extension Header Class |<-EHI
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |		| |
	| HEH and EH(s) |		| HEH and EH(s) |
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 2: Extension Header Indicator Format		Figure 2: Extension Header Indicator Format
	The Extension Header Class field in EHI is used to differentiate the		The Extension Header Class field in EHI is used to differentiate the
	extension headers. Potentially there are three classes: Hop-by-Hop		extension headers. Potentially there are three classes: Hop-by-Hop
	(HbH), End-to-End (E2E), or both. If finally we decide to not		(HbH), End-to-End (E2E), or both. If finally we decide to not
	differentiate the extension headers, we have the opportunity to merge		differentiate the extension headers, we have the opportunity to merge
	the HEH (see [I-D.song-mpls-extension-header] for details) into EHI,		the HEH (see [I-D.song-mpls-extension-header] for details) into EHI,
	so we can reduce the header overhead by four bytes. The header		so we can reduce the header overhead by four bytes. The header
	format is depicted in Figure 3.		format is depicted in Figure 3.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| GAL (13) | EXP |1| TTL |		| GAL (13) | EXP |1| TTL |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|0 0 1 0| EHCNT | EHTLEN | NH |<-HEH		|0 0 1 0| EHCNT | EHTLEN | NH |<-HEH
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |		| |
	| EH(s) |		| EH(s) |
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 3: Merge HEH to EHI		Figure 3: Merge HEH to EHI
	4. Configured FEC Labels		4. Configured FEC Labels
	It is also possible to use FEC labels to indicate the presence of		It is also possible to use FEC labels to indicate the presence of
	extension headers. An FEC label has the same forwarding semantics as		extension headers. An FEC label has the same forwarding semantics as
	the original label, but it also means that one or more extension		the original label, but it also means that one or more extension
	headers exist below the label stack.		headers exist below the label stack.
	skipping to change at page 9, line 24 ¶		skipping to change at page 9, line 24 ¶
	mpls-metadata-00 (work in progress), September 2013.		mpls-metadata-00 (work in progress), September 2013.
	[I-D.song-mpls-extension-header]		[I-D.song-mpls-extension-header]
	Song, H., Li, Z., Zhou, T., and L. Andersson, "MPLS		Song, H., Li, Z., Zhou, T., and L. Andersson, "MPLS
	Extension Header", draft-song-mpls-extension-header-02		Extension Header", draft-song-mpls-extension-header-02
	(work in progress), February 2019.		(work in progress), February 2019.
	Authors' Addresses		Authors' Addresses
	Haoyu Song (editor)		Haoyu Song (editor)
	Huawei		Futurewei Technologies
	2330 Central Expressway		2330 Central Expressway
	Santa Clara		Santa Clara
	USA		USA
	Email: haoyu.song@huawei.com		Email: haoyu.song@huawei.com
	Zhenbin Li		Zhenbin Li
	Huawei		Huawei
	156 Beiqing Road		156 Beiqing Road
	Beijing, 100095		Beijing, 100095
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