Network Working Group                                        A. B. Roach
Internet-Draft                                                   Mozilla
Updates: 6665 (if approved)                            February 27, 2015
Intended status: Standards Track
Expires: August 31, 2015

A clarification on the use of Globally Routable User Agent URIs (GRUUs)
 in the Session Initiation Protocol (SIP) Event Notification Framework


   Experience since the publication of the most recent SIP Events
   framework 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

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on August 31, 2015.

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   include Simplified BSD License text as described in Section 4.e of
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   described in the Simplified BSD License.

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  . . . . . . . . . . . . . . . . . . . . . . . .   3

1.  Introduction

   This document is intended to clarify a point of implementor confusion
   arising from lack of clarity in [RFC2119].

2.  Clarification of GRUU Handling

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

   [RFC6665] section 4.5.1 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
   for *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

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   subscriptions (although the use of GRUUs in such a context causes no
   harm, either).

   This document updates [RFC6665] to clarify the actual requirements:
   "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, March 1997.

   [RFC5627]  Rosenberg, J., "Obtaining and Using Globally Routable User
              Agent URIs (GRUUs) in the Session Initiation Protocol
              (SIP)", RFC 5627, October 2009.

   [RFC6665]  Roach, A.B., "SIP-Specific Event Notification", RFC 6665,
              July 2012.

Author's Address

   Adam Roach
   Dallas, TX

   Phone: +1 650 903 0800 x863

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