draft-ietf-bfd-multihop-01.txt		draft-ietf-bfd-multihop-02.txt
	Network Working Group D. Katz		Network Working Group D. Katz
	Internet Draft Juniper Networks		Internet Draft Juniper Networks
	D. Ward		D. Ward
	Cisco Systems		Cisco Systems
	Expires: August, 2005 February, 2005		Expires: September, 2005 March, 2005
	BFD for Multihop Paths		BFD for Multihop Paths
	draft-ietf-bfd-multihop-01.txt		draft-ietf-bfd-multihop-02.txt
	Status of this Memo		Status of this Memo
	By submitting this Internet-Draft, I certify that any applicable		By submitting this Internet-Draft, I certify that any applicable
	patent or other IPR claims of which I am aware have been disclosed,		patent or other IPR claims of which I am aware have been disclosed,
	or will be disclosed, and any of which I become aware will be		or will be disclosed, and any of which I become aware will be
	disclosed, in accordance with RFC 3668.		disclosed, in accordance with RFC 3668.
	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		Task Force (IETF), its areas, and its working groups. Note that
	skipping to change at page 1, line 37		skipping to change at page 1, line 37
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	The list of current Internet-Drafts can be accessed at		The list of current Internet-Drafts can be accessed at
	http://www.ietf.org/1id-abstracts.html		http://www.ietf.org/1id-abstracts.html
	The list of Internet-Draft Shadow Directories can be accessed at		The list of Internet-Draft Shadow Directories can be accessed at
	http://www.ietf.org/shadow.html		http://www.ietf.org/shadow.html
	Copyright Notice		Copyright Notice
	Copyright (C) The Internet Society (2004). All Rights Reserved.		Copyright (C) The Internet Society (2005). All Rights Reserved.
	Abstract		Abstract
	This document describes the use of the Bidirectional Forwarding		This document describes the use of the Bidirectional Forwarding
	Detection protocol (BFD) over multihop paths, including		Detection protocol (BFD) over multihop paths, including
	unidirectional links.		unidirectional links.
	Conventions used in this document		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",
	skipping to change at page 2, line 33		skipping to change at page 2, line 33
	BFD can also be useful on arbitrary paths between systems, which may		BFD can also be useful on arbitrary paths between systems, which may
	span multiple network hops and follow unpredictable paths.		span multiple network hops and follow unpredictable paths.
	Furthermore, a pair of systems may have multiple paths between them		Furthermore, a pair of systems may have multiple paths between them
	that may overlap. This document describes methods for using BFD in		that may overlap. This document describes methods for using BFD in
	such scenarios.		such scenarios.
	2. Issues		2. Issues
	There are two primary issues in the use of BFD for multihop paths.		There are two primary issues in the use of BFD for multihop paths.
	The first is security and spoofing; the one-hop spec describes a		The first is security and spoofing; [BFD-1HOP] describes a
	lightweight method of avoiding spoofing by requiring a TTL/hop limit		lightweight method of avoiding spoofing by requiring a TTL/hop limit
	of 255 on both transmit and receive, but this obviously does not work		of 255 on both transmit and receive, but this obviously does not work
	across multiple hops. The utilization of BFD authentication		across multiple hops. The utilization of BFD authentication
	addresses this issue.		addresses this issue.
	The more subtle issue is that of demultiplexing multiple BFD sessions		The more subtle issue is that of demultiplexing multiple BFD sessions
	between the same pair of systems to the proper BFD session. In		between the same pair of systems to the proper BFD session. In
	particular, the first BFD packet received for a session may carry a		particular, the first BFD packet received for a session may carry a
	Your Discriminator value of zero, resulting in ambiguity as to which		Your Discriminator value of zero, resulting in ambiguity as to which
	session the packet should be associated. Once the discriminator		session the packet should be associated. Once the discriminator
	values have been exchanged, all further packets are demultiplexed to		values have been exchanged, all further packets are demultiplexed to
	the proper BFD session solely by the contents of the Your		the proper BFD session solely by the contents of the Your
	Discriminator field.		Discriminator field.
	The one-hop specification addresses this by requiring that multiple		[BFD-1HOP] addresses this by requiring that multiple sessions
	sessions traverse independent physical or logical links--the first		traverse independent physical or logical links--the first packet is
	packet is demultiplexed based on the link over which it was received.		demultiplexed based on the link over which it was received. In the
	In the more general case, this scheme cannot work, as two paths over		more general case, this scheme cannot work, as two paths over which
	which BFD is running may overlap to an arbitrary degree (including		BFD is running may overlap to an arbitrary degree (including the
	the first and/or last hop.)		first and/or last hop.)
	3. Demultiplexing Packets		3. Demultiplexing Packets
	There are a number of possibilities for addressing the demultiplexing		There are a number of possibilities for addressing the demultiplexing
	issue which may be used, depending on the application.		issue which may be used, depending on the application.
	3.1. Totally Arbitrary Paths		3.1. Totally Arbitrary Paths
	It may be desired to use BFD for liveness detection over paths for		It may be desired to use BFD for liveness detection over paths for
	which no part of the route is known (or if known, may not be stable.)		which no part of the route is known (or if known, may not be stable.)
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	4. Authentication		4. Authentication
	By their nature, multihop paths expose BFD to spoofing.		By their nature, multihop paths expose BFD to spoofing.
	Implementations of BFD SHOULD utilize authentication over multihop		Implementations of BFD SHOULD utilize authentication over multihop
	paths to help mitigate denial-of-service attacks.		paths to help mitigate denial-of-service attacks.
	Normative References		Normative References
	[BFD] Katz, D., and Ward, D., "Bidirectional Forwarding Detection",		[BFD] Katz, D., and Ward, D., "Bidirectional Forwarding Detection",
	draft-ietf-bfd-base-01.txt, February, 2005.		draft-ietf-bfd-base-02.txt, March, 2005.
	[BFD-1HOP] Katz, D., and Ward, D., "BFD for IPv4 and IPv6 (Single		[BFD-1HOP] Katz, D., and Ward, D., "BFD for IPv4 and IPv6 (Single
	Hop)", draft-ietf-bfd-v4v6-1hop-01.txt, February, 2005.		Hop)", draft-ietf-bfd-v4v6-1hop-02.txt, March, 2005.
	[BFD-MPLS] Aggarwal, R., and Kompella, K., "BFD for MPLS LSPs",		[BFD-MPLS] Aggarwal, R., and Kompella, K., "BFD for MPLS LSPs",
	draft-ietf-bfd-mpls-01.txt, February, 2005.		draft-ietf-bfd-mpls-01.txt, February, 2005.
	[GTSM] Gill, V., et al, "The Generalized TTL Security Mechanism
	(GTSM)", RFC 3682, February 2004.
	[KEYWORD] Bradner, S., "Key words for use in RFCs to Indicate		[KEYWORD] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", RFC 2119, March 1997.		Requirement Levels", RFC 2119, March 1997.
	[OSPFv2] Moy, J., "OSPF Version 2", RFC 2328, April 1998.		[OSPFv2] Moy, J., "OSPF Version 2", RFC 2328, April 1998.
	[OSPFv3] Coltun, R., et al, "OSPF for IPv6", RFC 2740, December 1999.		[OSPFv3] Coltun, R., et al, "OSPF for IPv6", RFC 2740, December 1999.
	Security Considerations		Security Considerations
	No additional security issues are raised in this document beyond		No additional security issues are raised in this document beyond
	skipping to change at page 6, line 7		skipping to change at page 6, line 7
	Dave Ward		Dave Ward
	Cisco Systems		Cisco Systems
	170 W. Tasman Dr.		170 W. Tasman Dr.
	San Jose, CA 95134 USA		San Jose, CA 95134 USA
	Phone: +1-408-526-4000		Phone: +1-408-526-4000
	Email: dward@cisco.com		Email: dward@cisco.com
	Changes from the previous draft		Changes from the previous draft
	No changes were made other than updating references and boilerplate		No changes were made other than updating references.
	language.
	Full Copyright Notice		Full Copyright Notice
	Copyright (C) The Internet Society (2004). This document is subject		Copyright (C) The Internet Society (2005). This document is subject
	to the rights, licenses and restrictions contained in BCP 78, and		to the rights, licenses and restrictions contained in BCP 78, and
	except as set forth therein, the authors retain all their rights.		except as set forth therein, the authors retain all their rights.
	This document and the information contained herein are provided on an		This document and the information contained herein are provided on an
	"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS		"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
	OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET		OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
	ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,		ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
	INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE		INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
	INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED		INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
	WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.		WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
	Acknowledgement		Acknowledgement
	Funding for the RFC Editor function is currently provided by the		Funding for the RFC Editor function is currently provided by the
	Internet Society.		Internet Society.
	This document expires in August, 2005.		This document expires in September, 2005.
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