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
draft-ietf-sipcore-6665-clarification-00
Abstract
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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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",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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
Mozilla
Dallas, TX
US
Phone: +1 650 903 0800 x863
Email: adam@nostrum.com
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