draft-ietf-mpls-explicit-null-00.txt		draft-ietf-mpls-explicit-null-01.txt
	Network Working Group Eric C. Rosen		Network Working Group Eric C. Rosen
	Internet Draft Cisco Systems, Inc.		Internet Draft Cisco Systems, Inc.
	Expiration Date: September 2004		Expiration Date: October 2004
	Updates RFC 3032		Updates RFC 3032
	March 2004		April 2004
	Removing a Restriction on the use of MPLS Explicit NULL		Removing a Restriction on the use of MPLS Explicit NULL
	draft-ietf-mpls-explicit-null-00.txt		draft-ietf-mpls-explicit-null-01.txt
	Status of this Memo		Status of this Memo
	This document is an Internet-Draft and is in full conformance with		This document is an Internet-Draft and is in full conformance with
	all provisions of Section 10 of RFC2026.		all provisions of Section 10 of RFC2026.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF), its areas, and its working groups. Note that other		Task Force (IETF), its areas, and its working groups. Note that other
	groups may also distribute working documents as Internet-Drafts.		groups may also distribute working documents as Internet-Drafts.
	skipping to change at page 2, line 10		skipping to change at page 2, line 10
	reserved label value known as "IPv6 Explicit NULL". Previously,		reserved label value known as "IPv6 Explicit NULL". Previously,
	these labels were only legal when they occurred at the bottom of the		these labels were only legal when they occurred at the bottom of the
	MPLS label stack. This restriction is now removed, so that these		MPLS label stack. This restriction is now removed, so that these
	label values may legally occur anywhere in the stack.		label values may legally occur anywhere in the stack.
	Contents		Contents
	1 Introduction ......................................... 2		1 Introduction ......................................... 2
	2 Detail of Change ..................................... 2		2 Detail of Change ..................................... 2
	3 Reasons for Change ................................... 4		3 Reasons for Change ................................... 4
	4 Acknowledgments ...................................... 5		4 Security Considerations .............................. 5
	5 Normative References ................................. 5		5 Acknowledgments ...................................... 5
	6 Informative References ............................... 5		6 Normative References ................................. 6
	7 Author's Address ..................................... 6		7 Informative References ............................... 6
	8 Intellectual Property Notice ......................... 6		8 Author's Address ..................................... 6
	9 Copyright Notice ..................................... 6		9 Intellectual Property Notice ......................... 6
			10 Copyright Notice ..................................... 7
	1. Introduction		1. Introduction
	RFC 3032 defines a reserved label value known as "IPv4 Explicit NULL"		RFC 3032 defines a reserved label value known as "IPv4 Explicit NULL"
	and a reserved label value known as "IPv6 Explicit NULL". It states		and a reserved label value known as "IPv6 Explicit NULL". It states
	that these label values are only legal at the bottom of the MPLS		that these label values are only legal at the bottom of the MPLS
	label stack. However, no reason is given for this restriction.		label stack. However, no reason is given for this restriction.
	It has turned out that in practice there are some situations in which		It has turned out that in practice there are some situations in which
	it is useful to send MPLS packets which have Explicit NULL occur		it is useful to send MPLS packets which have Explicit NULL occur
	skipping to change at page 5, line 30		skipping to change at page 5, line 30
	using Explicit NULL enables the egress to determine immediately		using Explicit NULL enables the egress to determine immediately
	(i.e., without need for lookup in the Label Information Base) that		(i.e., without need for lookup in the Label Information Base) that
	the further forwarding of the packet is to be determined by whatever		the further forwarding of the packet is to be determined by whatever
	is below the label. Avoiding this lookup can have favorable		is below the label. Avoiding this lookup can have favorable
	implications on forwarding performance.		implications on forwarding performance.
	Removing the restriction that Explicit Null only occur at the bottom		Removing the restriction that Explicit Null only occur at the bottom
	of the stack is the simplest way to facilitate the proper operation		of the stack is the simplest way to facilitate the proper operation
	of the Pipe Model.		of the Pipe Model.
	4. Acknowledgments		4. Security Considerations
			This document updates RFC 3032 by allowing Explicit NULL to occur at
			any position in the label stack. This modification does not impose
			any new security considerations beyond those discussed in RFC 3032.
			5. Acknowledgments
	Thanks to Rahul Aggarwal, Francois LeFaucheur, Yakov Rekhter, and Dan		Thanks to Rahul Aggarwal, Francois LeFaucheur, Yakov Rekhter, and Dan
	Tappan for their helpful comments.		Tappan for their helpful comments.
	5. Normative References		6. Normative References
	[RFC3032] "MPLS Label Stack Encoding", Rosen, et. al., January 2001		[RFC3032] "MPLS Label Stack Encoding", Rosen, et. al., January 2001
	6. Informative References		7. Informative References
	[RFC3270] "Multi-Protocol Label Switching (MPLS) Support of		[RFC3270] "Multi-Protocol Label Switching (MPLS) Support of
	Differentiated Services", Le Faucheur, et. al., May 2002		Differentiated Services", Le Faucheur, et. al., May 2002
	7. Author's Address		8. Author's Address
	Eric C. Rosen		Eric C. Rosen
	Cisco Systems, Inc.		Cisco Systems, Inc.
	1414 Massachusetts Avenue		1414 Massachusetts Avenue
	Boxborough, MA 01719		Boxborough, MA 01719
	Email: erosen@cisco.com		Email: erosen@cisco.com
	8. Intellectual Property Notice		9. Intellectual Property Notice
	The IETF takes no position regarding the validity or scope of any		The IETF takes no position regarding the validity or scope of any
	intellectual property or other rights that might be claimed to		intellectual property or other rights that might be claimed to
	pertain to the implementation or use of the technology described in		pertain to the implementation or use of the technology described in
	this document or the extent to which any license under such rights		this document or the extent to which any license under such rights
	might or might not be available; neither does it represent that it		might or might not be available; neither does it represent that it
	has made any effort to identify any such rights. Information on the		has made any effort to identify any such rights. Information on the
	IETF's procedures with respect to rights in standards-track and		IETF's procedures with respect to rights in standards-track and
	standards-related documentation can be found in BCP-11. Copies of		standards-related documentation can be found in BCP-11. Copies of
	claims of rights made available for publication and any assurances of		claims of rights made available for publication and any assurances of
	skipping to change at page 6, line 35		skipping to change at page 7, line 5
	obtain a general license or permission for the use of such		obtain a general license or permission for the use of such
	proprietary rights by implementors or users of this specification can		proprietary rights by implementors or users of this specification can
	be obtained from the IETF Secretariat.		be obtained from the IETF Secretariat.
	The IETF invites any interested party to bring to its attention any		The IETF invites any interested party to bring to its attention any
	copyrights, patents or patent applications, or other proprietary		copyrights, patents or patent applications, or other proprietary
	rights which may cover technology that may be required to practice		rights which may cover technology that may be required to practice
	this standard. Please address the information to the IETF Executive		this standard. Please address the information to the IETF Executive
	Director.		Director.
	9. Copyright Notice		10. Copyright Notice
	"Copyright (C) The Internet Society (2004). All Rights Reserved.		"Copyright (C) The Internet Society (2004). All Rights Reserved.
	This document and translations of it may be copied and furnished to		This document and translations of it may be copied and furnished to
	others, and derivative works that comment on or otherwise explain it		others, and derivative works that comment on or otherwise explain it
	or assist in its implementation may be prepared, copied, published		or assist in its implementation may be prepared, copied, published
	and distributed, in whole or in part, without restriction of any		and distributed, in whole or in part, without restriction of any
	kind, provided that the above copyright notice and this paragraph are		kind, provided that the above copyright notice and this paragraph are
	included on all such copies and derivative works. However, this		included on all such copies and derivative works. However, this
	document itself may not be modified in any way, such as by removing		document itself may not be modified in any way, such as by removing
End of changes.
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