draft-ietf-tcpm-tcp-uto-07.txt		draft-ietf-tcpm-tcp-uto-08.txt
	TCP Maintenance and Minor L. Eggert		TCP Maintenance and Minor L. Eggert
	Extensions (tcpm) Nokia		Extensions (tcpm) Nokia
	Internet-Draft F. Gont		Internet-Draft F. Gont
	Intended status: Standards Track UTN/FRH		Intended status: Standards Track UTN/FRH
	Expires: May 16, 2008 November 13, 2007		Expires: May 22, 2008 November 19, 2007
	TCP User Timeout Option		TCP User Timeout Option
	draft-ietf-tcpm-tcp-uto-07		draft-ietf-tcpm-tcp-uto-08
	Status of this Memo		Status of this Memo
	By submitting this Internet-Draft, each author represents that any		By submitting this Internet-Draft, each author represents that any
	applicable patent or other IPR claims of which he or she is aware		applicable patent or other IPR claims of which he or she is aware
	have been or will be disclosed, and any of which he or she becomes		have been or will be disclosed, and any of which he or she becomes
	aware will be disclosed, in accordance with Section 6 of BCP 79.		aware will be disclosed, in accordance with Section 6 of BCP 79.
	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 35		skipping to change at page 1, line 35
	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."
	The list of current Internet-Drafts can be accessed at		The list of current Internet-Drafts can be accessed at
	http://www.ietf.org/ietf/1id-abstracts.txt.		http://www.ietf.org/ietf/1id-abstracts.txt.
	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.
	This Internet-Draft will expire on May 16, 2008.		This Internet-Draft will expire on May 22, 2008.
	Copyright Notice		Copyright Notice
	Copyright (C) The IETF Trust (2007).		Copyright (C) The IETF Trust (2007).
	Abstract		Abstract
	The TCP user timeout controls how long transmitted data may remain		The TCP user timeout controls how long transmitted data may remain
	unacknowledged before a connection is forcefully closed. It is a		unacknowledged before a connection is forcefully closed. It is a
	local, per-connection parameter. This document specifies a new TCP		local, per-connection parameter. This document specifies a new TCP
	skipping to change at page 2, line 30		skipping to change at page 2, line 30
	4.1. Middleboxes . . . . . . . . . . . . . . . . . . . . . . . 10		4.1. Middleboxes . . . . . . . . . . . . . . . . . . . . . . . 10
	4.2. TCP Keep-Alives . . . . . . . . . . . . . . . . . . . . . 10		4.2. TCP Keep-Alives . . . . . . . . . . . . . . . . . . . . . 10
	5. Security Considerations . . . . . . . . . . . . . . . . . . . 11		5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
	6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12		6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
	7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12		7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12		8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
	8.1. Normative References . . . . . . . . . . . . . . . . . . . 12		8.1. Normative References . . . . . . . . . . . . . . . . . . . 12
	8.2. Informative References . . . . . . . . . . . . . . . . . . 13		8.2. Informative References . . . . . . . . . . . . . . . . . . 13
	Appendix A. Document Revision History . . . . . . . . . . . . . . 14		Appendix A. Document Revision History . . . . . . . . . . . . . . 14
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
	Intellectual Property and Copyright Statements . . . . . . . . . . 16		Intellectual Property and Copyright Statements . . . . . . . . . . 17
	1. Introduction		1. Introduction
	The Transmission Control Protocol (TCP) specification [RFC0793]		The Transmission Control Protocol (TCP) specification [RFC0793]
	defines a local, per-connection "user timeout" parameter that		defines a local, per-connection "user timeout" parameter that
	specifies the maximum amount of time that transmitted data may remain		specifies the maximum amount of time that transmitted data may remain
	unacknowledged before TCP will forcefully close the corresponding		unacknowledged before TCP will forcefully close the corresponding
	connection. Applications can set and change this parameter with OPEN		connection. Applications can set and change this parameter with OPEN
	and SEND calls. If an end-to-end connectivity disruption lasts		and SEND calls. If an end-to-end connectivity disruption lasts
	longer than the user timeout, no acknowledgments will be received for		longer than the user timeout, no acknowledgments will be received for
	skipping to change at page 4, line 4		skipping to change at page 4, line 4
	Although some TCP implementations allow applications to set their		Although some TCP implementations allow applications to set their
	local user timeout, TCP has no in-protocol mechanism to signal		local user timeout, TCP has no in-protocol mechanism to signal
	changes to the local user timeout to the other end of a connection.		changes to the local user timeout to the other end of a connection.
	This causes local changes to be ineffective in allowing a connection		This causes local changes to be ineffective in allowing a connection
	to survive extended periods without connectivity, because the other		to survive extended periods without connectivity, because the other
	end will still close the connection after its user timeout expires.		end will still close the connection after its user timeout expires.
	The ability to inform the other end of a connection about the local		The ability to inform the other end of a connection about the local
	user timeout can improve TCP operation in scenarios that are		user timeout can improve TCP operation in scenarios that are
	currently not well supported. One example of such scenarios are		currently not well supported. One example of such a scenario is
	mobile hosts that change network attachment points based on current		mobile hosts that change network attachment points based on current
	location. Such hosts, maybe using Mobile IP [RFC3344], HIP [RFC4423]		location. Such hosts, maybe using Mobile IP [RFC3344], HIP [RFC4423]
	or transport-layer mobility mechanisms [I-D.eddy-tcp-mobility], are		or transport-layer mobility mechanisms [I-D.eddy-tcp-mobility], are
	only intermittently connected to the Internet. In between connected		only intermittently connected to the Internet. In between connected
	periods, mobile hosts may experience periods without end-to-end		periods, mobile hosts may experience periods without end-to-end
	connectivity. Other factors that can cause transient connectivity		connectivity. Other factors that can cause transient connectivity
	disruptions are high levels of congestion or link or routing failures		disruptions are high levels of congestion or link or routing failures
	inside the network. In these scenarios, a host may not know exactly		inside the network. In these scenarios, a host may not know exactly
	when or for how long connectivity disruptions will occur, but it		when or for how long connectivity disruptions will occur, but it
	might be able to determine an increased likelihood for such events		might be able to determine an increased likelihood for such events
	skipping to change at page 5, line 6		skipping to change at page 5, line 6
	UTO option advertised to the remote TCP peer. This is an		UTO option advertised to the remote TCP peer. This is an
	application-specified value, and may be specified on a system-wide		application-specified value, and may be specified on a system-wide
	basis. If unspecified, it defaults to the default system-wide		basis. If unspecified, it defaults to the default system-wide
	USER TIMEOUT.		USER TIMEOUT.
	ENABLED (Boolean)		ENABLED (Boolean)
	Flag that controls whether the UTO option is enabled for a		Flag that controls whether the UTO option is enabled for a
	connection. Defaults to false.		connection. Defaults to false.
	CHANGEABLE (Boolean)		CHANGEABLE (Boolean)
	Flag that controls whether USER_TIMEOUT (TCP's USER_TIMEOUT		Flag that controls whether USER_TIMEOUT (TCP's USER TIMEOUT
	parameter) may be changed based on an UTO option received from the		parameter) may be changed based on an UTO option received from the
	other end of the connection. Defaults to true and becomes false		other end of the connection. Defaults to true and becomes false
	when an application explicitly sets USER_TIMEOUT.		when an application explicitly sets USER_TIMEOUT.
	Note that an exchange of UTO options between both ends of a		Note that an exchange of UTO options between both ends of a
	connection is not a binding negotiation. Transmission of a UTO		connection is not a binding negotiation. Transmission of a UTO
	option is a suggestion that the other end consider adapting its user		option is a suggestion that the other end consider adapting its user
	timeout. This adaptation only happens if the the other end of the		timeout. This adaptation only happens if the the other end of the
	connection has explicitly allowed it (both ENABLED and CHANGEABLE are		connection has explicitly allowed it (both ENABLED and CHANGEABLE are
	true).		true).
	Before opening a connection, an application that wishes to use the		Before opening a connection, an application that wishes to use the
	UTO option enables its use by setting ENABLED to true. It may choose		UTO option enables its use by setting ENABLED to true. It may choose
	an appropriate local UTO by explicitly setting ADV_UTO; otherwise,		an appropriate local UTO by explicitly setting ADV_UTO; otherwise,
	UTO is set to the default USER TIMEOUT value. Finally, the		UTO is set to the default USER TIMEOUT value. Finally, the
	application should determine whether it will allow the local USER		application should determine whether it will allow the local USER
	TIMEOUT to change based on received UTO options from the other end of		TIMEOUT to change based on received UTO options from the other end of
	a connection. The default is to allow this for connections that do		a connection. The default is to allow this for connections that do
	not have specific user timeout concerns. If an application		not have specific user timeout concerns. If an application
	explicitly sets the USER TIMEOUT, CHANGEABLE MUST become false, to		explicitly sets the USER_TIMEOUT, CHANGEABLE MUST become false, to
	prevent UTO options from the other end to override local application		prevent UTO options from the other end to override local application
	requests. Alternatively, applications can set or clear CHANGEABLE		requests. Alternatively, applications can set or clear CHANGEABLE
	directly through socket API calls.		directly through socket API calls.
	Performing these steps before an active or passive open causes UTO		Performing these steps before an active or passive open causes UTO
	options to be exchanged in the SYN and SYN-ACK packets and is a		options to be exchanged in the SYN and SYN-ACK packets and is a
	reliable way to initially exchange, and potentially adapt to, UTO		reliable way to initially exchange, and potentially adapt to, UTO
	values. TCP implementations MAY provide system-wide default settings		values. TCP implementations MAY provide system-wide default settings
	for the ENABLED, ADV_UTO and CHANGEABLE connection parameters.		for the ENABLED, ADV_UTO and CHANGEABLE connection parameters.
	skipping to change at page 7, line 39		skipping to change at page 7, line 39
	REMOTE_UTO		REMOTE_UTO
	Last user timeout value received from the other end in a TCP User		Last user timeout value received from the other end in a TCP User
	Timeout Option.		Timeout Option.
	L_LIMIT		L_LIMIT
	Current lower limit imposed on the user timeout of a connection by		Current lower limit imposed on the user timeout of a connection by
	the local host.		the local host.
	The RECOMMENDED formula results in the maximum of the two advertised		The RECOMMENDED formula results in the maximum of the two advertised
	values to be adopted for the user timeout of the connection on both		values, adjusted for the configured upper and lower limits, to be
	ends, provided they are within the upper and lower limits. The		adopted for the user timeout of the connection on both ends. The
	rationale is that choosing the maximum of the two values will let the		rationale is that choosing the maximum of the two values will let the
	connection survive longer periods without end-to-end connectivity.		connection survive longer periods without end-to-end connectivity.
	If the end that announced the lower of the two user timeout values		If the end that announced the lower of the two user timeout values
	did so in order to reduce the amount of TCP state information that		did so in order to reduce the amount of TCP state information that
	must be kept on the host, it can close or abort the connection		must be kept on the host, it can close or abort the connection
	whenever it wants.		whenever it wants.
	It must be noted that the two endpoints of the connection will not		It must be noted that the two endpoints of the connection will not
	necessarily adopt the same user timeout.		necessarily adopt the same user timeout.
	skipping to change at page 12, line 39		skipping to change at page 12, line 39
	The following people have improved this document through thoughtful		The following people have improved this document through thoughtful
	suggestions: Mark Allman, Caitlin Bestler, David Borman, Bob Braden,		suggestions: Mark Allman, Caitlin Bestler, David Borman, Bob Braden,
	Marcus Brunner, Wesley Eddy, Gorry Fairhurst, Abolade Gbadegesin, Ted		Marcus Brunner, Wesley Eddy, Gorry Fairhurst, Abolade Gbadegesin, Ted
	Faber, Guillermo Gont, Tom Henderson, Joseph Ishac, Jeremy Harris,		Faber, Guillermo Gont, Tom Henderson, Joseph Ishac, Jeremy Harris,
	Alfred Hoenes, Phil Karn, Michael Kerrisk, Dan Krejsa, Jamshid		Alfred Hoenes, Phil Karn, Michael Kerrisk, Dan Krejsa, Jamshid
	Mahdavi, Kostas Pentikousis, Juergen Quittek, Anantha Ramaiah, Joe		Mahdavi, Kostas Pentikousis, Juergen Quittek, Anantha Ramaiah, Joe
	Touch, Stefan Schmid, Simon Schuetz, Tim Shepard and Martin		Touch, Stefan Schmid, Simon Schuetz, Tim Shepard and Martin
	Stiemerling.		Stiemerling.
	Lars Eggert has been partly funded by Ambient Networks, a research
	project supported by the European Commission under its Sixth
	Framework Program.
	8. References		8. References
	8.1. Normative References		8.1. Normative References
	[I-D.narten-iana-considerations-rfc2434bis]		[I-D.narten-iana-considerations-rfc2434bis]
	Narten, T. and H. Alvestrand, "Guidelines for Writing an		Narten, T. and H. Alvestrand, "Guidelines for Writing an
	IANA Considerations Section in RFCs",		IANA Considerations Section in RFCs",
	draft-narten-iana-considerations-rfc2434bis-08 (work in		draft-narten-iana-considerations-rfc2434bis-08 (work in
	progress), October 2007.		progress), October 2007.
	skipping to change at page 14, line 12		skipping to change at page 14, line 12
	Sun Microsystems, "Solaris Tunable Parameters Reference		Sun Microsystems, "Solaris Tunable Parameters Reference
	Manual", Part No. 806-7009-10, 2002.		Manual", Part No. 806-7009-10, 2002.
	Appendix A. Document Revision History		Appendix A. Document Revision History
	[[Note to the RFC Editor: Section to be removed upon publication.]]		[[Note to the RFC Editor: Section to be removed upon publication.]]
	+----------+--------------------------------------------------------+		+----------+--------------------------------------------------------+
	| Revision | Comments |		| Revision | Comments |
	+----------+--------------------------------------------------------+		+----------+--------------------------------------------------------+
	| 07 | Addressed working group last call comments. |		| -08 | Addressed additional, minor working group last call |
	| 06 | Includes a note on the limited space for TCP options |		| | comments. |
	| | and miscelaneous editorial changes(suggested by |		| | |
			| -07 | Addressed working group last call comments. |
			| | |
			| -06 | Includes a note on the limited space for TCP options |
			| | and miscellaneous editorial changes (suggested by |
	| | Anantha Ramaiah). Includes possible enforcement of |		| | Anantha Ramaiah). Includes possible enforcement of |
	| | per-outgoing-interface limits for the UTO, and |		| | per-outgoing-interface limits for the UTO, and |
	| | miscellaneous editorial changes (suggested by Alfred |		| | miscellaneous editorial changes (suggested by Alfred |
	| | Hoenes). Includes relevant changes to reflect WG |		| | Hoenes). Includes relevant changes to reflect WG |
	| | consesus how the local user timeout should be selected |		| | consensus how the local user timeout should be |
	| | (i.e., record both the current user timeout, and the |		| | selected (i.e., record both the current user timeout, |
	| | advertised UTO). |		| | and the advertised UTO). |
	| 05 | Made behavior on when to change/not change the local |		| | |
			| -05 | Made behavior on when to change/not change the local |
	| | UTO in response to incoming options consistent through |		| | UTO in response to incoming options consistent through |
	| | the document. This required some reshuffling of text |		| | the document. This required some reshuffling of text |
	| | and also removed the need for the special "don't care" |		| | and also removed the need for the special "don't care" |
	| | option value. |		| | option value. |
	| 04 | Clarified the results obtained by Medina et al. Added |		| | |
			| -04 | Clarified the results obtained by Medina et al. Added |
	| | text to suggest inclusion of the UTO in the first |		| | text to suggest inclusion of the UTO in the first |
	| | non-SYN segment by the TCP that sent a SYN in response |		| | non-SYN segment by the TCP that sent a SYN in response |
	| | to an active OPEN. |		| | to an active OPEN. |
	| 03 | Corrected use of RFC2119 terminology. Clarified how |		| | |
			| -03 | Corrected use of RFC2119 terminology. Clarified how |
	| | use of the TCP UTO is triggered. Clarified reason for |		| | use of the TCP UTO is triggered. Clarified reason for |
	| | sending a UTO in the SYN and SYN/ACK segments. |		| | sending a UTO in the SYN and SYN/ACK segments. |
	| | Removed discussion of the SO_SNDTIMEO and SO_RCVTIMEO |		| | Removed discussion of the SO_SNDTIMEO and SO_RCVTIMEO |
	| | socket options. Removed text that suggested that a |		| | socket options. Removed text that suggested that a |
	| | UTO should be sent upon receipt of an UTO from the |		| | UTO should be sent upon receipt of an UTO from the |
	| | other end. Required minimum value for the lower limit |		| | other end. Required minimum value for the lower limit |
	| | of the user timeout. Moved alternative solutions to |		| | of the user timeout. Moved alternative solutions to |
	| | appendix. Miscellaneous editorial changes. |		| | appendix. Miscellaneous editorial changes. |
	| 02 | Corrected terminology by replacing terms like |		| | |
			| -02 | Corrected terminology by replacing terms like |
	| | "negotiate", "coordinate", etc. that were left from |		| | "negotiate", "coordinate", etc. that were left from |
	| | pre-WG-document times when the UTO was a more |		| | pre-WG-document times when the UTO was a more |
	| | formalized exchange instead of the advisory one it is |		| | formalized exchange instead of the advisory one it is |
	| | now. Application-requested UTOs take precedence over |		| | now. Application-requested UTOs take precedence over |
	| | ones received from the peer (pointed out by Ted |		| | ones received from the peer (pointed out by Ted |
	| | Faber). Added a brief mention of SO_SNDTIMEO and a |		| | Faber). Added a brief mention of SO_SNDTIMEO and a |
	| | slightly longer discussion of SO_RCVTIMEO. |		| | slightly longer discussion of SO_RCVTIMEO. |
	| 01 | Clarified and corrected the description of the |		| | |
			| -01 | Clarified and corrected the description of the |
	| | existing user timeout in RFC793 and RFC1122. Removed |		| | existing user timeout in RFC793 and RFC1122. Removed |
	| | distinction between operating during the 3WHS and the |		| | distinction between operating during the 3WHS and the |
	| | established states and introduced zero-second "don't |		| | established states and introduced zero-second "don't |
	| | care" UTOs in response to mailing list feedback. |		| | care" UTOs in response to mailing list feedback. |
	| | Updated references and addressed many other comments |		| | Updated references and addressed many other comments |
	| | from the mailing list. |		| | from the mailing list. |
	| 00 | Resubmission of |		| | |
			| -00 | Resubmission of |
	| | draft-eggert-gont-tcpm-tcp-uto-option-01.txt to the |		| | draft-eggert-gont-tcpm-tcp-uto-option-01.txt to the |
	| | secretariat after WG adoption. Thus, permit |		| | secretariat after WG adoption. Thus, permit |
	| | derivative works. Updated Lars Eggert's funding |		| | derivative works. Updated Lars Eggert's funding |
	| | attribution. Updated several references. No |		| | attribution. Updated several references. No |
	| | technical changes. |		| | technical changes. |
	+----------+--------------------------------------------------------+		+----------+--------------------------------------------------------+
	Authors' Addresses		Authors' Addresses
	Lars Eggert		Lars Eggert
End of changes. 16 change blocks.
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