< draft-ietf-sip-acr-code-04.txt		draft-ietf-sip-acr-code-05.txt >
	SIP J. Rosenberg		SIP J. Rosenberg
	Internet-Draft Cisco Systems		Internet-Draft Cisco
	Expires: September 1, 2007 February 28, 2007		Intended status: Standards Track July 5, 2007
			Expires: January 6, 2008
	Rejecting Anonymous Requests in the Session Initiation Protocol (SIP)		Rejecting Anonymous Requests in the Session Initiation Protocol (SIP)
	draft-ietf-sip-acr-code-04		draft-ietf-sip-acr-code-05
	Status of this Memo		Status of this Memo
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	skipping to change at page 1, line 33 ¶		skipping to change at page 1, line 34 ¶
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	Copyright Notice		Copyright Notice
	Copyright (C) The IETF Trust (2007).		Copyright (C) The IETF Trust (2007).
	Abstract		Abstract
	The Session Initiation Protocol (SIP) allows for users to make		The Session Initiation Protocol (SIP) allows for users to make
	anonymous calls. However, users receiving such calls have the right		anonymous calls. However, users receiving such calls have the right
	to reject them because they are anonymous. SIP has no way to		to reject them because they are anonymous. SIP has no way to
	skipping to change at page 3, line 14 ¶		skipping to change at page 3, line 14 ¶
	1. Introduction		1. Introduction
	The Session Initiation Protocol (SIP) [1] allows for users to make		The Session Initiation Protocol (SIP) [1] allows for users to make
	anonymous calls. In RFC 3261, this is done by including a From		anonymous calls. In RFC 3261, this is done by including a From
	header field whose display name has the value of "Anonymous".		header field whose display name has the value of "Anonymous".
	Greater levels of anonymity were subsequently defined in RFC 3323		Greater levels of anonymity were subsequently defined in RFC 3323
	[2], which introduces the Privacy header field. The Privacy header		[2], which introduces the Privacy header field. The Privacy header
	field allows a requesting UA to ask for various levels of anonymity,		field allows a requesting UA to ask for various levels of anonymity,
	including user level anonymity, header level anonymity, and session		including user level anonymity, header level anonymity, and session
	level anonymity. RFC 3325 [3] additionally defined the P-Asserted-		level anonymity. RFC 3325 [5] additionally defined the P-Asserted-
	Identity header field, used to contain an asserted identity. RFC		Identity header field, used to contain an asserted identity. RFC
	3325 also defined the 'id' value for the Privacy header field, which		3325 also defined the 'id' value for the Privacy header field, which
	is used to request the network to remove the P-Asserted-Identity		is used to request the network to remove the P-Asserted-Identity
	header field.		header field.
	Though users need to be able to make anonymous calls, users that		Though users need to be able to make anonymous calls, users that
	receive such calls retain the right to reject the call because it is		receive such calls retain the right to reject the call because it is
	anonymous. SIP does not provide a response code that allows the UAS,		anonymous. SIP does not provide a response code that allows the UAS,
	or a proxy acting on its behalf, to explicitly indicate that the		or a proxy acting on its behalf, to explicitly indicate that the
	request was rejected because it was anonymous. The closest response		request was rejected because it was anonymous. The closest response
	skipping to change at page 3, line 42 ¶		skipping to change at page 3, line 42 ¶
	retries, or conversion to equivalent error codes in the Public		retries, or conversion to equivalent error codes in the Public
	Switched Telephone Network (PSTN) when the client is a gateway.		Switched Telephone Network (PSTN) when the client is a gateway.
	To remedy this, this specification defines the 433 (Anonymity		To remedy this, this specification defines the 433 (Anonymity
	Disallowed) response code.		Disallowed) response code.
	2. Terminology		2. Terminology
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in RFC 2119 [4].		document are to be interpreted as described in RFC 2119 [3].
	3. Server Behavior		3. Server Behavior
	A server (generally acting on behalf of the called party, though this		A server (generally acting on behalf of the called party, though this
	need not be the case) MAY generate a 433 (Anonymity Disallowed)		need not be the case) MAY generate a 433 (Anonymity Disallowed)
	response when it receives an anonymous request, and the server		response when it receives an anonymous request, and the server
	refuses to fulfill the request because the requestor is anonymous. A		refuses to fulfill the request because the requestor is anonymous. A
	request SHOULD be considered anonymous when the identity of the		request SHOULD be considered anonymous when the identity of the
	originator of the request has been explicitly withheld by the		originator of the request has been explicitly withheld by the
	originator. This occurs in any one of the following cases:		originator. This occurs in any one of the following cases:
	skipping to change at page 4, line 19 ¶		skipping to change at page 4, line 19 ¶
	o The From header field contains a display name whose value is		o The From header field contains a display name whose value is
	either 'Anonymous' or 'anonymous'. Note that display names make a		either 'Anonymous' or 'anonymous'. Note that display names make a
	poor choice for indicating anonymity, since they are meant to be		poor choice for indicating anonymity, since they are meant to be
	consumed by humans, not automata. Thus, language variations and		consumed by humans, not automata. Thus, language variations and
	even misspelling can cause an automaton to miss a hint in the		even misspelling can cause an automaton to miss a hint in the
	display name. Despite these problems, a check on the display name		display name. Despite these problems, a check on the display name
	is included here because RFC 3261 explicitly calls out the usage		is included here because RFC 3261 explicitly calls out the usage
	of the display name as a way to declare anonymity.		of the display name as a way to declare anonymity.
	o The request contained a Privacy header field whose value was 'id'		o The request contained a Privacy header field whose value indicates
	[3] or 'user'.		that the user wishes their identity withheld. Values meeting this
			criteria are 'id' [5] or 'user'.
	o The From or P-Asserted-Identity header field contains a URI which		o The From header field contains a URI which has an explicit
	has an explicit indication that it is anonymous. One such example		indication that it is anonymous. One such example of a mechanism
	of a mechanism that would meet this criteria is [7]. This		that would meet this criteria is [7]. This criteria is true even
	criteria is true even if the request has a validated Identity		if the request has a validated Identity header field [4], which
	header field [5], which can be used in concert with anonymized		can be used in concert with anonymized From header fields.
	From header fields.
	Lack of a P-Asserted-Identity header field, in and of itself, SHOULD		Lack of a network asserted identity (such as the P-Asserted-Identity
	NOT be considered an indication of anonymity. Even though a Privacy		header field), in and of itself, SHOULD NOT be considered an
	header field value of 'id' will cause the removal of the P-Asserted-		indication of anonymity. Even though a Privacy header field value of
	Identity header field, there is no way to differentiate this case		'id' will cause the removal of a network asserted identity, there is
	from one in which P-Asserted-Identity was not supported by the		no way to differentiate this case from one in which a network
	originating domain. As a consequence, a request without a		asserted identity was not supported by the originating domain. As a
	P-Asserted-Identity is considered anonymous only when there is some		consequence, a request without a network asserted identity is
	other indication of this, such as a From header field with a display		considered anonymous only when there is some other indication of
	name of 'Anonymous'.		this, such as a From header field with a display name of 'Anonymous'.
	In addition, requests where the identity of the requestor cannot be		In addition, requests where the identity of the requestor cannot be
	determined or validated, but it is not a consequence of an explicit		determined or validated, but it is not a consequence of an explicit
	action on the part of the requestor, are not consider anonymous. For		action on the part of the requestor, are not consider anonymous. For
	example, if a request contains a non-anonymous From header field,		example, if a request contains a non-anonymous From header field,
	along with the Identity and Identity-Info header fields [5], but the		along with the Identity and Identity-Info header fields [4], but the
	certificate could not be obtained from the reference in the Identity-		certificate could not be obtained from the reference in the Identity-
	Info header field, it is not considered an anonymous request, and the		Info header field, it is not considered an anonymous request, and the
	433 response code SHOULD NOT be used.		433 response code SHOULD NOT be used.
	4. UAC Behavior		4. UAC Behavior
	A UAC receiving a 433 (Anonymity Disallowed) MUST NOT retry the		A UAC receiving a 433 (Anonymity Disallowed) MUST NOT retry the
	request without anonymity unless it obtains confirmation from the		request without anonymity unless it obtains confirmation from the
	user that this is desirable. Such confirmation could be obtained		user that this is desirable. Such confirmation could be obtained
	through the user interface, or by accessing user defined policy. If		through the user interface, or by accessing user defined policy. If
	skipping to change at page 6, line 42 ¶		skipping to change at page 6, line 42 ¶
	9.1. Normative References		9.1. Normative References
	[1] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,		[1] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
	Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:		Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
	Session Initiation Protocol", RFC 3261, June 2002.		Session Initiation Protocol", RFC 3261, June 2002.
	[2] Peterson, J., "A Privacy Mechanism for the Session Initiation		[2] Peterson, J., "A Privacy Mechanism for the Session Initiation
	Protocol (SIP)", RFC 3323, November 2002.		Protocol (SIP)", RFC 3323, November 2002.
	[3] Jennings, C., Peterson, J., and M. Watson, "Private Extensions		[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
	to the Session Initiation Protocol (SIP) for Asserted Identity
	within Trusted Networks", RFC 3325, November 2002.
	[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
	Levels", BCP 14, RFC 2119, March 1997.		Levels", BCP 14, RFC 2119, March 1997.
	[5] Peterson, J. and C. Jennings, "Enhancements for Authenticated		[4] Peterson, J. and C. Jennings, "Enhancements for Authenticated
	Identity Management in the Session Initiation Protocol (SIP)",		Identity Management in the Session Initiation Protocol (SIP)",
	RFC 4474, August 2006.		RFC 4474, August 2006.
	9.2. Informative References		9.2. Informative References
			[5] Jennings, C., Peterson, J., and M. Watson, "Private Extensions
			to the Session Initiation Protocol (SIP) for Asserted Identity
			within Trusted Networks", RFC 3325, November 2002.
	[6] Sparks, R., "Multiple Dialog Usages in the Session Initiation		[6] Sparks, R., "Multiple Dialog Usages in the Session Initiation
	Protocol", draft-ietf-sipping-dialogusage-06 (work in		Protocol", draft-ietf-sipping-dialogusage-06 (work in
	progress), February 2007.		progress), February 2007.
	[7] Rosenberg, J., "Coexistence of P-Asserted-ID and SIP Identity",		[7] Rosenberg, J., "Coexistence of P-Asserted-ID and SIP Identity",
	draft-rosenberg-sip-identity-coexistence-00 (work in progress),		draft-rosenberg-sip-identity-coexistence-00 (work in progress),
	June 2006.		June 2006.
	[8] Hautakorpi, J. and G. Camarillo, "Extending the Session		[8] Hautakorpi, J. and G. Camarillo, "Extending the Session
	Initiation Protocol Reason Header with Warning Codes",		Initiation Protocol Reason Header with Warning Codes",
	draft-hautakorpi-reason-header-for-warnings-00 (work in		draft-hautakorpi-reason-header-for-warnings-00 (work in
	progress), October 2005.		progress), October 2005.
	[9] Jesske, R., "Input Requirements for the Session Initiation		[9] Jesske, R., "Input Requirements for the Session Initiation
	Protocol (SIP) in support for the European Telecommunications		Protocol (SIP) in support for the European Telecommunications
	Standards Institute",		Standards Institute",
	draft-jesske-sipping-tispan-requirements-03 (work in progress),		draft-jesske-sipping-tispan-requirements-03 (work in progress),
	June 2006.		June 2006.
	[10] Jennings, C. and J. Rosenberg, "The Session Initiation Protocol		[10] Jennings, C. and J. Rosenberg, "The Session Initiation Protocol
	(SIP) and Spam", draft-ietf-sipping-spam-03 (work in progress),		(SIP) and Spam", draft-ietf-sipping-spam-04 (work in progress),
	October 2006.		February 2007.
	Author's Address		Author's Address
	Jonathan Rosenberg		Jonathan Rosenberg
	Cisco Systems		Cisco
	Edison, NJ		Edison, NJ
	US		US
	Phone: +1 973 952-5000
	Email: jdrosen@cisco.com		Email: jdrosen@cisco.com
	URI: http://www.jdrosen.net		URI: http://www.jdrosen.net
	Full Copyright Statement		Full Copyright Statement
	Copyright (C) The IETF Trust (2007).		Copyright (C) The IETF Trust (2007).
	This document is subject to the rights, licenses and restrictions		This document is subject to the rights, licenses and restrictions
	contained in BCP 78, and except as set forth therein, the authors		contained in BCP 78, and except as set forth therein, the authors
	retain all their rights.		retain all their rights.
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