draft-ietf-sipcore-refer-clarifications-04.txt   rfc7647.txt 
Network Working Group R. Sparks Internet Engineering Task Force (IETF) R. Sparks
Internet-Draft Oracle Request for Comments: 7647 Oracle
Updates: 3515 (if approved) A. Roach Updates: 3515 A.B. Roach
Intended status: Standards Track Mozilla Category: Standards Track Mozilla
Expires: October 24, 2015 April 22, 2015 ISSN: 2070-1721 September 2015
Clarifications for the use of REFER with RFC6665 Clarifications for the Use of REFER with RFC 6665
draft-ietf-sipcore-refer-clarifications-04
Abstract Abstract
The SIP REFER method relies on the SIP-Specific Event Notification The SIP REFER method relies on the SIP-Specific Event Notification
Framework. That framework was revised by RFC6665. This document framework. That framework was revised by RFC 6665. This document
highlights the implications of the requirement changes in RFC6665, highlights the implications of the requirement changes in RFC 6665,
and updates the definition of the REFER method, RFC3515, to clarify and updates the definition of the REFER method described in RFC 3515
and disambiguate the impact of those changes. to clarify and disambiguate the impact of those changes.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on October 24, 2015. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7647.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Conventions and Definitions . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions Used in This Document . . . . . . . . . . . . . . 2
3. Use of GRUU is mandatory . . . . . . . . . . . . . . . . . . 3 3. Use of GRUU Is Mandatory . . . . . . . . . . . . . . . . . . 3
4. Dialog reuse is prohibited . . . . . . . . . . . . . . . . . 3 4. Dialog Reuse Is Prohibited . . . . . . . . . . . . . . . . . 3
5. The 202 response code is deprecated . . . . . . . . . . . . . 4 5. The 202 Response Code Is Deprecated . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 7.1. Normative References . . . . . . . . . . . . . . . . . . 4
9. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 5 7.2. Informative References . . . . . . . . . . . . . . . . . 5
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6
10.1. Normative References . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
10.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Conventions and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Introduction 1. Introduction
The SIP REFER method relies on the SIP-Specific Event Notification The SIP REFER method relies on the SIP-Specific Event Notification
Framework. That framework was revised by [RFC6665]. This document framework. That framework was revised by [RFC6665]. This document
highlights the implications of the requirement changes in RFC6665, highlights the implications of the requirement changes in RFC 6665,
and updates [RFC3515] to clarify and disambiguate the impact of those and updates [RFC3515] to clarify and disambiguate the impact of those
changes. changes.
Accepting a REFER request (without invoking extensions) results in an Accepting a REFER request (without invoking extensions) results in an
implicit SIP-Events subscription. If that REFER was part of an implicit SIP-Events subscription. If that REFER was part of an
existing dialog, the implicit subscription creates a new, problematic existing dialog, the implicit subscription creates a new, problematic
dialog-usage within that dialog [RFC5057]. The "norefersub" dialog usage within that dialog [RFC5057]. The "norefersub"
extension defined in [RFC4488] asks to suppress this implicit extension defined in [RFC4488] asks to suppress this implicit
subscription, but cannot prevent its creation. subscription, but cannot prevent its creation.
There are implementations in some known specialized environments There are implementations in some known specialized environments
(such as 3gpp) that use out-of-signalling agreements to ensure that (such as 3GPP) that use out-of-signaling agreements to ensure that
in-dialog REFER requests using the RFC4488 extension do not create a in-dialog REFER requests using the RFC 4488 extension do not create a
new subscription inside that dialog. In the 3gpp environment, the new subscription inside that dialog. In the 3GPP environment, the
behavior is based on capabilities advertised using media feature behavior is based on capabilities advertised using media feature
tags. That mechanism does not, however, prevent additional dialog tags. That mechanism does not, however, prevent additional dialog
usages when interoperating with implementations that do not support usages when interoperating with implementations that do not support
the mechanism. The extensions in the mechanism. The extensions in [RFC7614] provide a standardized
[I-D.ietf-sipcore-refer-explicit-subscription] provide a standardized
mechanism that allows avoiding any additional dialog usage. mechanism that allows avoiding any additional dialog usage.
3. Use of GRUU is mandatory 2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Use of GRUU Is Mandatory
Section 4.5.1 of [RFC6665] makes GRUU [RFC5627] mandatory for Section 4.5.1 of [RFC6665] makes GRUU [RFC5627] mandatory for
notifiers to implement and use as the local target in the notifiers to implement and use as the local target in the
subscription created by the REFER request. subscription created by the REFER request.
A user agent accepting a REFER that creates a subscription MUST A user agent (UA) accepting a REFER that creates a subscription MUST
populate its Contact header field with a GRUU. populate its Contact header field with a GRUU.
A UA that might possibly become a notifier (e.g. by accepting a REFER A UA that might possibly become a notifier (e.g., by accepting a
request that creates a subscription) needs to include a GRUU in the REFER request that creates a subscription) needs to include a GRUU in
Contact header field of dialog-forming and target-refresh methods the Contact header field of dialog-forming and target-refresh methods
(such as INVITE) [I-D.roach-sipcore-6665-clarification]. This (such as INVITE) [RFC7621]. This ensures that out-of-dialog REFER
ensures that out-of-dialog REFER requests corresponding to any requests corresponding to any resulting INVITE dialogs arrive at this
resulting INVITE dialogs arrive at this UA. Future extensions (such UA. Extensions can relax this requirement by defining a REFER
as [I-D.ietf-sipcore-refer-explicit-subscription]) might relax this request that cannot create an implicit subscription, thus not causing
requirement by defining a REFER request that cannot create an the accepting UA to become an RFC 6665 notifier in the context of
implicit subscription, thus not causing the accepting UA to become an this dialog. [RFC7614] is an example of such an extension.
RFC6665 notifier in the context of this dialog.
4. Dialog reuse is prohibited 4. Dialog Reuse Is Prohibited
If a peer in an existing dialog has provided a GRUU as its Contact, If a peer in an existing dialog has provided a GRUU as its Contact,
sending a REFER that might result in an additional dialog usage sending a REFER that might result in an additional dialog usage
within that dialog is prohibited. This is a direct consequence of within that dialog is prohibited. This is a direct consequence of
[RFC6665] requiring the use of GRUU, and the requirements in section [RFC6665] requiring the use of GRUU and the requirements in
4.5.2 of that document. Section 4.5.2 of that document.
A user agent constructing a REFER request that could result in an A user agent constructing a REFER request that could result in an
implicit subscription in a dialog MUST build it as an out-of-dialog implicit subscription in a dialog MUST build it as an out-of-dialog
message as defined in [RFC3261], unless the remote endpoint is an message as defined in [RFC3261], unless the remote endpoint is an
older, pre-RFC6665 implementation (as determined by the absence of a older implementation of RFC 3515 that has not been updated to conform
GRUU in the remote target). Thus, the REFER request will have no tag to RFC 6665 (as determined by the absence of a GRUU in the remote
parameter in its To: header field. target). Thus, the REFER request will have no tag parameter in its
To: header field.
Using the "norefersub" option tag [RFC4488] does not change this Using the "norefersub" option tag [RFC4488] does not change this
requirement, even if used in a "Require" header field. Even if the requirement, even if used in a "Require" header field. Even if the
recipient supports the "norefersub" mechanism, and accepts the recipient supports the "norefersub" mechanism, and accepts the
request with the option tag in the "Require" header field, it is request with the option tag in the "Require" header field, it is
allowed to return a "Refer-Sub" header field with a value of "true" allowed to return a "Refer-Sub" header field with a value of "true"
in the response, and create an implicit subscription. in the response, and create an implicit subscription.
A user agent wishing to identify an existing dialog (such as for call A user agent wishing to identify an existing dialog (such as for call
transfer as defined in [RFC5589]) MUST use the "Target-Dialog" transfer as defined in [RFC5589]) MUST use the "Target-Dialog"
extension defined in [RFC4538] to do so, and user agents accepting extension defined in [RFC4538] to do so, and user agents accepting
REFER MUST be able to process that extension in requests they REFER MUST be able to process that extension in requests they
receive. receive.
If a user agent can be certain that no implicit subscription will be If a user agent can be certain that no implicit subscription will be
created as a result of sending a REFER request (such as by requiring created as a result of sending a REFER request (such as by requiring
an extension that disallows any such subscription an extension that disallows any such subscription [RFC7614]), the
[I-D.ietf-sipcore-refer-explicit-subscription]), the REFER request REFER request MAY be sent within an existing dialog (whether or not
MAY be sent within an existing dialog (whether or not the remote the remote target is a GRUU). Such a REFER will be constructed with
target is a GRUU). Such a REFER will be constructed with its Contact its Contact header field populated with the dialog's local URI as
header field populated with the dialog's Local URI as specified in specified in Section 12 of [RFC3261].
section 12 of [RFC3261].
As described in section 4.5.2 of [RFC6665], there are cases where a As described in Section 4.5.2 of [RFC6665], there are cases where a
user agent may fall back to sharing existing dialogs for backwards- user agent may fall back to sharing existing dialogs for backwards-
compatibility purposes. This applies to REFER only when the peer has compatibility purposes. This applies to a REFER only when the peer
not provided a GRUU as its Contact in the existing dialog (i.e. when has not provided a GRUU as its Contact in the existing dialog (i.e.,
the peer is a pre-RFC6665 implementation). when the peer is an implementation of RFC 3515 that has not been
updated to conform with RFC 6665).
5. The 202 response code is deprecated 5. The 202 Response Code Is Deprecated
Section 8.3.1 of [RFC6665] requires that elements do not send a 202 Section 8.3.1 of [RFC6665] requires that elements not send a 202
response code to a subscribe request, but use the 200 response code response code to a subscribe request, but use the 200 response code
instead. Any 202 response codes received to a subscribe request are instead. Any 202 response codes received to a subscribe request are
treated as 200s. These changes also apply to REFER. Specifically, treated as 200s. These changes also apply to REFER. Specifically,
an element accepting a REFER request MUST NOT reply with a 202 an element accepting a REFER request MUST NOT reply with a 202
response code and MUST treat any 202 responses received as identical response code and MUST treat any 202 responses received as identical
to a 200 response. Wherever [RFC3515] requires sending a 202 to a 200 response. Wherever [RFC3515] requires sending a 202
response code, a 200 response code MUST be sent instead. response code, a 200 response code MUST be sent instead.
6. Security Considerations 6. Security Considerations
This document introduces no new security considerations directly. This document introduces no new security considerations directly.
The updated considerations in [RFC6665] apply to the implicit The updated considerations in [RFC6665] apply to the implicit
subscription created by an accepted REFER request. subscription created by an accepted REFER request.
7. IANA Considerations 7. References
This document has no actions for IANA.
8. Acknowledgements
Christer Holmberg provided the formulation for the final paragraph of
the introduction. Christer Holmberg and Ivo Sedlacek provided
detailed comments during working group discussion of the document.
9. Changelog
RFC Editor - please remove this section when formatting this document
as an RFC
-03 to -04
Added section on deprecating 202.
-02 to -03
Reinforced that the MAY send in-dialog applied no matter what
the remote target URI contained.
-01 to -02
Tweaked the third paragraph of section 3 per list discussion.
(Note the subject line of that discussion said -explicit-
subscription)
-00 to -01
Added the 3rd paragraph to the introduction per extensive list
discussion
draft-sparks-sipcore-refer-clarifications-05 to draft-ietf-
sipcore-refer-clarifications-00
Attempted to improve the accuracy of the Abstract and
Introduction without diluting the essential point of the
document.
Added an informative reference to RFC5057.
Adjusted text to more reflect what RFC6665 (as clarified by
draft-roach-sipcore-6665-clarification) actually requires, and
added a normative reference to that clarification draft.
Specifically, the requirement for the _sender_ of a REFER to
use a GRUU as its local target was removed.
Clarified why the explicit-subscription extensions relieve an
in-dialog REFERer from the 6665 requirements for using GRUU as
its contact in the INVITE dialog.
10. References
10.1. Normative References
[I-D.roach-sipcore-6665-clarification] 7.1. Normative References
Roach, A., "A clarification on the use of Globally
Routable User Agent URIs (GRUUs) in the Session Initiation
Protocol (SIP) Event Notification Framework", draft-roach-
sipcore-6665-clarification-00 (work in progress), October
2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E. A., Peterson, J., Sparks, R., Handley, M., and
Schooler, "SIP: Session Initiation Protocol", RFC 3261, E. Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002. DOI 10.17487/RFC3261, June 2002,
<http://www.rfc-editor.org/info/rfc3261>.
[RFC3515] Sparks, R., "The Session Initiation Protocol (SIP) Refer [RFC3515] Sparks, R., "The Session Initiation Protocol (SIP) Refer
Method", RFC 3515, April 2003. Method", RFC 3515, DOI 10.17487/RFC3515, April 2003,
<http://www.rfc-editor.org/info/rfc3515>.
[RFC4538] Rosenberg, J., "Request Authorization through Dialog [RFC4538] Rosenberg, J., "Request Authorization through Dialog
Identification in the Session Initiation Protocol (SIP)", Identification in the Session Initiation Protocol (SIP)",
RFC 4538, June 2006. RFC 4538, DOI 10.17487/RFC4538, June 2006,
<http://www.rfc-editor.org/info/rfc4538>.
[RFC5627] Rosenberg, J., "Obtaining and Using Globally Routable User [RFC5627] Rosenberg, J., "Obtaining and Using Globally Routable User
Agent URIs (GRUUs) in the Session Initiation Protocol Agent URIs (GRUUs) in the Session Initiation Protocol
(SIP)", RFC 5627, October 2009. (SIP)", RFC 5627, DOI 10.17487/RFC5627, October 2009,
<http://www.rfc-editor.org/info/rfc5627>.
[RFC6665] Roach, A., "SIP-Specific Event Notification", RFC 6665, [RFC6665] Roach, A.B., "SIP-Specific Event Notification", RFC 6665,
July 2012. DOI 10.17487/RFC6665, July 2012,
<http://www.rfc-editor.org/info/rfc6665>.
10.2. Informative References [RFC7621] Roach, A.B., "A Clarification on the Use of Globally
Routable User Agent URIs (GRUUs) in the SIP Event
Notification Framework", RFC 7621, DOI 10.17487/RFC7621,
August 2015, <http://www.rfc-editor.org/info/rfc7621>.
[I-D.ietf-sipcore-refer-explicit-subscription] 7.2. Informative References
Sparks, R., "Explicit Subscriptions for the REFER Method",
draft-ietf-sipcore-refer-explicit-subscription-00 (work in
progress), November 2014.
[RFC4488] Levin, O., "Suppression of Session Initiation Protocol [RFC4488] Levin, O., "Suppression of Session Initiation Protocol
(SIP) REFER Method Implicit Subscription", RFC 4488, May (SIP) REFER Method Implicit Subscription", RFC 4488,
2006. DOI 10.17487/RFC4488, May 2006,
<http://www.rfc-editor.org/info/rfc4488>.
[RFC5057] Sparks, R., "Multiple Dialog Usages in the Session [RFC5057] Sparks, R., "Multiple Dialog Usages in the Session
Initiation Protocol", RFC 5057, November 2007. Initiation Protocol", RFC 5057, DOI 10.17487/RFC5057,
November 2007, <http://www.rfc-editor.org/info/rfc5057>.
[RFC5589] Sparks, R., Johnston, A., and D. Petrie, "Session [RFC5589] Sparks, R., Johnston, A., Ed., and D. Petrie, "Session
Initiation Protocol (SIP) Call Control - Transfer", BCP Initiation Protocol (SIP) Call Control - Transfer",
149, RFC 5589, June 2009. BCP 149, RFC 5589, DOI 10.17487/RFC5589, June 2009,
<http://www.rfc-editor.org/info/rfc5589>.
[RFC7614] Sparks, R., "Explicit Subscriptions for the REFER Method",
RFC 7614, DOI 10.17487/RFC7614, August 2015,
<http://www.rfc-editor.org/info/rfc7614>.
Acknowledgements
Christer Holmberg provided the formulation for the final paragraph of
the introduction. Christer Holmberg and Ivo Sedlacek provided
detailed comments during working group discussion of the document.
Authors' Addresses Authors' Addresses
Robert Sparks Robert Sparks
Oracle Oracle
7460 Warren Parkway 7460 Warren Parkway
Suite 300 Suite 300
Frisco, Texas 75034 Frisco, Texas 75034
US United States
Email: rjsparks@nostrum.com Email: rjsparks@nostrum.com
Adam Roach Adam Roach
Mozilla Mozilla
Dallas, TX Dallas, TX
US United States
Phone: +1 650 903 0800 x863 Phone: +1 650 903 0800 x863
Email: adam@nostrum.com Email: adam@nostrum.com
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