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rfc:rfc7621

Internet Engineering Task Force (IETF) A.B. Roach Request for Comments: 7621 Mozilla Updates: 6665 August 2015 Category: Standards Track ISSN: 2070-1721

A Clarification on the Use of Globally Routable User Agent URIs (GRUUs)

              in the SIP Event Notification Framework

Abstract

 Experience since the publication of the most recent SIP Events
 framework (in July 2012) has shown that there is room for
 interpretation around the use of Globally Routable User Agent URIs in
 that specification.  This document clarifies the intended behavior.
 This document updates RFC 6665.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 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/rfc7621.

Copyright Notice

 Copyright (c) 2015 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Roach Standards Track [Page 1] RFC 7621 SIP Events GRUU Clarification August 2015

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
 2.  Clarification of GRUU Handling  . . . . . . . . . . . . . . .   2
 3.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
 4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
 5.  Normative References  . . . . . . . . . . . . . . . . . . . .   3
 Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   4

1. Introduction

 This document is intended to clarify a point of implementor confusion
 arising from lack of clarity in [RFC6665].

2. Clarification of GRUU Handling

 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].
 Section 4.5.1 of [RFC6665] contains the following normative
 requirement on implementations:
    Notifiers MUST implement the Globally Routable User Agent URI
    (GRUU) extension defined in [RFC5627], and MUST use a GRUU as
    their local target.  This allows subscribers to explicitly target
    desired devices.
 The second sentence of this paragraph attempted to set context for
 the normative statement: the reason GRUUs are required in this
 context is to allow you to send SUBSCRIBE or REFER requests to a
 specific user agent, with the target of the subscription request
 being something like an INVITE dialog on that device.  Consequently,
 the requirement to include a GRUU as a local target was intended to
 apply not just to the local target for SUBSCRIBE-created dialogs, but
 to *all* dialogs, even those created by INVITE.  This requirement has
 been interpreted in a variety of ways by implementors, so a
 clarification is in order.
 Discussion subsequent to the publication of [RFC6665] has highlighted
 obscure cases in which implementations might be notifiers in some
 contexts, but may not wish to act as notifiers in others.  Under
 these narrow circumstances, the restriction described above is not
 necessary for dialogs about which the notifier will never accept
 subscriptions (although the use of GRUUs in such a context causes no
 harm, either).

Roach Standards Track [Page 2] RFC 7621 SIP Events GRUU Clarification August 2015

 This document updates [RFC6665] to clarify the actual requirements.
 The replacement text is as follows:
    Notifiers MUST implement the Globally Routable User Agent URI
    (GRUU) extension defined in [RFC5627].  Notifiers MUST use a GRUU
    as their local target for all dialog-forming methods and all
    target-refresh methods, except for those dialogs for which they
    will reject all subscription requests (implicit or explicit).  For
    clarity: an implementation that uses a non-GRUU local contact
    under the exception described above MUST reject a request that
    might create a subscription to the associated dialog, regardless
    of whether such subscription would be created by a SUBSCRIBE or a
    REFER message.  The rejection code under such conditions SHOULD be
    403 (Forbidden) unless some other code is more appropriate to the
    circumstances.  The foregoing requirements to implement and use
    GRUUs specifically include dialogs created by the INVITE method.

3. Security Considerations

 This mechanism does not introduce any security issues beyond those
 discussed in [RFC6665].

4. IANA Considerations

 This document requests no actions of IANA.

5. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119,
            DOI 10.17487/RFC2119, March 1997,
            <http://www.rfc-editor.org/info/rfc2119>.
 [RFC5627]  Rosenberg, J., "Obtaining and Using Globally Routable User
            Agent URIs (GRUUs) in the Session Initiation Protocol
            (SIP)", RFC 5627, DOI 10.17487/RFC5627, October 2009,
            <http://www.rfc-editor.org/info/rfc5627>.
 [RFC6665]  Roach, A.B., "SIP-Specific Event Notification", RFC 6665,
            DOI 10.17487/RFC6665, July 2012,
            <http://www.rfc-editor.org/info/rfc6665>.

Roach Standards Track [Page 3] RFC 7621 SIP Events GRUU Clarification August 2015

Author's Address

 Adam Roach
 Mozilla
 Dallas, TX
 United States
 Phone: +1 650 903 0800 x863
 Email: adam@nostrum.com

Roach Standards Track [Page 4]

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