One document matched: draft-ietf-sipping-gruu-reg-event-06.txt
Differences from draft-ietf-sipping-gruu-reg-event-05.txt
Sipping P. Kyzivat
Internet-Draft Cisco Systems, Inc.
Expires: November 18, 2006 May 17, 2006
Registration Event Package Extension for Session Initiation Protocol
(SIP) Globally Routable User Agent URIs (GRUU)
draft-ietf-sipping-gruu-reg-event-06
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
RFC 3680 defines a Session Initiation Protocol (SIP) event package
for registration state. This package allows a watcher to learn about
information stored by a SIP registrar, including its registered
contact.
However, the registered contact is frequently unreachable and thus
not useful for watchers. The Globally Routable User Agent URI (GRUU)
has been defined for SIP as a URI that is capable of reaching a
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particular contact, however this URI is not present in the format
defined in RFC 3680. This specification defines an extension to the
registration event package to include a GRUU.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Description . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Notifier Processing of SUBSCRIBE Requests . . . . . . . . . . 4
5. Notifier Generation of NOTIFY Requests . . . . . . . . . . . . 4
6. Subscriber Processing of NOTIFY Requests . . . . . . . . . . . 4
7. Sample reginfo Document . . . . . . . . . . . . . . . . . . . 5
8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Example: Welcome Notice . . . . . . . . . . . . . . . . . 5
8.2. Example: Implicit Registration . . . . . . . . . . . . . . 6
9. XML Schema Definition . . . . . . . . . . . . . . . . . . . . 8
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
10.1. URN Sub-Namespace Registration . . . . . . . . . . . . . . 9
10.2. XML Schema Registration . . . . . . . . . . . . . . . . . 10
11. Security Considerations . . . . . . . . . . . . . . . . . . . 10
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
13.1. Normative References . . . . . . . . . . . . . . . . . . . 10
13.2. Informative References . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . . . . 13
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1. Introduction
RFC 3680 [2] defines a Session Initiation Protocol (SIP) event
package for registration state. This package allows a watcher to
learn about information stored by a SIP registrar, including the
registered contacts.
However, a registered contact is frequently unreachable from hosts
outside of the domain of the user agent. It is commonly a private
address, or even when public, direct access to it may be blocked by
firewalls.
The Globally Routable User Agent URI (GRUU) [3] has been defined as a
URI that reaches a particular UA instance, but is reachable by any
host on the Internet. The GRUU represents another piece of
registration state. However, the GRUU is not included in the
notifications provided by RFC 3860. For many applications of the
registration event package, the GRUU is needed, and not the
registered contact.
For example, the Welcome Notices example in [2] will only operate
correctly if the contact address in the reg event notification is
reachable by the sender of the welcome notice. When the registering
device is using the GRUU extension, it is likely that the registered
contact address will not be globally addressable, and the GRUU should
be used as the target address for the MESSAGE.
Another case where this feature may be helpful is within the 3GPP IP
Multimedia Subsystem (IMS). IMS employs a technique where a REGISTER
of a contact address to one Address of Record (AOR) causes the
implicit registration of the same contact to other associated AORs.
If a GRUU is requested and obtained as part of the registration
request, then additional GRUU will also be needed for the implicit
registrations. While assigning the additional GRUU is
straightforward, informing the registering UA of them is not. In
IMS, UAs typically subscribe to the "reg" event, and subscriptions to
the "reg" event for an AOR result in notifications containing
registration state for all the associated AORs. The proposed
extension provides a way to easily deliver the GRUU for the
associated AORs.
The reg event package has provision for including extension elements
within the <contact> element. This document defines a new element
that may be used in that context to deliver the GRUU corresponding to
the contact.
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2. Terminology
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 RFC 2119. [1]
3. Description
A new element (<gruu>) is defined which contains a GRUU.
This optional element is included within the body of a NOTIFY for the
"reg" event package when a GRUU is associated with the contact. The
contact URI and the GRUU are then both available to the watcher.
4. Notifier Processing of SUBSCRIBE Requests
Unchanged from RFC 3680 [2].
5. Notifier Generation of NOTIFY Requests
A notifier for the "reg" event package [2] SHOULD include the <gruu>
element when a contact has an Instance ID and a GRUU is associated
with the combination of the AOR and the Instance ID. When present,
the <gruu> element MUST be be positioned as a child of the <contact>
element.
Note that it is possible for multiple registered contacts to share
the same instance ID. In such a case, each <contact> element will
have a child <gruu> element, and the URI contained within those
<gruu> elements will be identical. Since a particular contact can
not be associated with more than one instance ID, a <contact> element
will never have more than one <gruu> child element.
The content of the <gruu> element is the GRUU that is associated with
the instance ID and AOR of the registered contact.
6. Subscriber Processing of NOTIFY Requests
When a subscriber receives a "reg" event notification [2] with a
<contact> containing a <gruu>, it SHOULD use the GRUU in preference
to the corresponding <uri> when sending SIP requests to the contact.
Subscribers that are unaware of this extension will, as required by
[2], ignore the <gruu> element.
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7. Sample reginfo Document
Note: This example and others in the following section are
indented for readability by the addition of a fixed amount of
whitespace to the beginning of each line. This whitespace is not
part of the example. The conventions of [8] are used to describe
representation of long message lines.
The following is an example registration information document
including the new element:
<?xml version="1.0"?>
<reginfo xmlns="urn:ietf:params:xml:ns:reginfo"
xmlns:gr="urn:ietf:params:xml:ns:gruuinfo"
version="0" state="full">
<registration aor="sip:user@example.com" id="as9"
state="active">
<contact id="76" state="active" event="registered"
duration-registered="7322"
q="0.8">
<uri>sip:user@192.0.2.1</uri>
<allOneLine>
<unknown-param name="+sip.instance">
"<urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>"
</unknown-param>
</allOneLine>
<allOneLine>
<gr:gruu>sip:user@example.com
;gruu;opaque=hha9s8d-999a</gr:gruu>
</allOneLine>
</contact>
</registration>
</reginfo>
8. Examples
Note: In the following examples the SIP messages have been
simplified, removing headers that are not pertinent to the example.
When the value of the Content-Length header field is "..." this means
that the value should be whatever the computed length of the body is.
8.1. Example: Welcome Notice
Consider the Welcome Notices example in [2]. When the application
server receives a notification of a new registration containing the
reginfo shown in Section 7 it should address messages using the
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contained GRUU as follows:
MESSAGE sip:user@example.com;gruu;opaque=hha9s8d-999a SIP/2.0
To: <sip:user@example.com>
From: "SIPland Notifier" <sip:notifier@example.com>;tag=7xy8
Content-Type: text/plain
Content-Length: ...
Welcome to SIPland!
Blah, blah, blah.
8.2. Example: Implicit Registration
In an 3GPP IMS setting, a UA may send a single register message,
requesting assignment of a GRUU, as follows:
REGISTER sip:example.net SIP/2.0
From: <sip:user_aor_1@example.net>;tag=5ab4
To: <sip:user_aor_1@example.net>
Contact: <sip:ua.example.com>
;expires=3600
;+sip.instance="<urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>"
Supported: path, gruu
Content-Length: 0
The response reports success of the registration and returns the GRUU
assigned for the combination of AOR, Instance ID, and Contact. It
also indicates (via the P-Associated-URI header [6]) that there are
two other associated AORs that may have been implicitly registered
using the same contact. Each of those implicitly registered AORs
will have a unique GRUU assigned. The REGISTER response will not
include those GRUU; it will only include the GRUU for the AOR and
instance ID explicitly included in the registration.
SIP/2.0 200 OK
From: <sip:user_aor_1@example.net>;tag=5ab4
To: <sip:user_aor_1@example.net>;tag=373392
Path: <sip:proxy.example.net;lr>
Service-Route: <sip:proxy.example.net;lr>
Contact: <sip:ua.example.com>
;expires=3600
;+sip.instance="<urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>"
;gruu="sip:user_aor_1@example.net;gruu;opaque=hha9s8d-999a"
P-Associated-URI: <sip:user_aor_2@example.net>,
<sip:+358504821437@example.net;user=phone>
Content-Length: 0
The UA then subscribes to the "reg" event package as follows:
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SUBSCRIBE sip:user_aor_1@example.net SIP/2.0
From: <sip:user_aor_1@example.net>;tag=27182
To: <sip:user_aor_1@example.net>
Route: <sip:proxy.example.net;lr>
Event: reg
Expires: 3600
Accept: application/reginfo+xml
Contact: <sip:user_aor_1@example.net;gruu;opaque=hha9s8d-999a>
Content-Length: 0
(The successful response to the subscription is not shown.) Once the
subscription is established an initial notification is sent giving
registration status. In IMS deployments the response includes, in
addition to the status for the requested URI, the status for the
other associated URIs.
NOTIFY sip:user_aor_1@example.net;gruu;opaque=hha9s8d-999a SIP/2.0
From: <sip:user_aor_1@example.net>;tag=27182
To: <sip:user_aor_1@example.net>;tag=262281
Subscription-State: active;expires=3600
Event: reg
Content-Type: application/reginfo+xml
Contact: <sip:registrar.example.net>
Content-Length: ...
<?xml version="1.0"?>
<reginfo xmlns="urn:ietf:params:xml:ns:reginfo"
xmlns:gr="urn:ietf:params:xml:ns:gruuinfo"
version="1" state="full">
<registration aor="sip:user_aor_1@example.net" id="a7"
state="active">
<contact id="92" state="active" event="registered"
duration-registered="1" expires="3599">
<uri>
sip:ua.example.com
</uri>
<allOneLine>
<unknown-param name="+sip.instance">
"<urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>"
</unknown-param>
</allOneLine>
<allOneLine>
<gr:gruu>sip:user_aor_1@example.net
;gruu;opaque=hha9s8d-999a</gr:gruu>
</allOneLine>
</contact>
</registration>
<registration aor="sip:user_aor_2@example.net" id="a8"
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state="active">
<contact id="93" state="active" event="created"
duration-registered="1" expires="3599">
<uri>
sip:ua.example.com
</uri>
<allOneLine>
<unknown-param name="+sip.instance">
"<urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>"
</unknown-param>
</allOneLine>
<allOneLine>
<gr:gruu>sip:user_aor_2@example.net
;gruu;opaque=hha9s8d-999b</gr:gruu>
</allOneLine>
</contact>
</registration>
<registration
aor="sip:+358504821437@example.net;user=phone"
id="a9"
state="active">
<contact id="94" state="active" event="created"
duration-registered="1" expires="3599">
<uri>
sip:ua.example.com
</uri>
<allOneLine>
<unknown-param name="+sip.instance">
"<urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>"
</unknown-param>
</allOneLine>
<allOneLine>
<gr:gruu>sip:+358504821437@example.net;user=phone
;gruu;opaque=hha9s8d-999c</gr:gruu>
</allOneLine>
</contact>
</registration>
</reginfo>
The status indicates that the associated URIs all have the same
contact registered. It also includes the unique GRUU that has been
assigned to each. The UA may then retain those GRUU for use when
establishing dialogs using the corresponding AORs.
9. XML Schema Definition
The <gruu> element is defined within a new XML namespace URI. This
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namespace is "urn:ietf:params:xml:ns:gruuinfo". The schema for the
<gruu> element is:
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema targetNamespace="urn:ietf:params:xml:ns:gruuinfo"
elementFormDefault="qualified"
attributeFormDefault="unqualified"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:tns="urn:ietf:params:xml:ns:gruuinfo">
<xs:element name="gruu" type="xs:anyURI"/>
</xs:schema>
10. IANA Considerations
There are two IANA considerations associated with this specification.
10.1. URN Sub-Namespace Registration
This section registers a new XML namespace, per the guidelines in
[4].
URI: The URI for this namespace is urn:ietf:params:xml:ns:gruuinfo
Registrant Contact: IETF, SIPPING working group, <sipping@ietf.org>,
Paul Kyzivat <pkyzivat@cisco.com>
XML:
BEGIN
<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
"http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type"
content="text/html;charset=iso-8859-1"/>
<title>Reg Information GRUU Extension Namespace</title>
</head>
<body>
<h1>Namespace for Reg Information GRUU Extension</h1>
<h2>urn:ietf:params:xml:ns:gruuinfo</h2>
<p>See <a href="[URL of published RFC]">RFCXXXX [[NOTE
TO RFC-EDITOR/IANA: Please replace XXXX with the RFC Number of
this specification]]</a>.</p>
</body>
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</html>
END
10.2. XML Schema Registration
This section registers an XML schema per the procedures in [4].
URI: urn:ietf:params:xml:schema:gruuinfo.
Registrant Contact: IETF, SIPPING working group, <sipping@ietf.org>,
Paul Kyzivat <pkyzivat@cisco.com>
The XML for this schema can be found in Section 9.
11. Security Considerations
Security considerations for the registration event package is
discussed in RFC 3680 [2], and those considerations apply here.
If the contact address is not reachable by the subscriber to the
registration event package, then its disclosure may arguably be
considered of minimal security risk. In that case the inclusion of
the GRUU may be considered to increase the risk by providing a
reachable address. On the other hand, requests addressed to the GRUU
are always first processed by the servicing proxy before they reach
the intended user agent. The proxy may control access as desired,
just as it may for the AOR. In this respect disclosing the GRUU
presents no more risk than disclosing the AOR.
12. Acknowledgements
The author would like to thank Jonathan Rosenberg for encouraging
this draft, and Jari Urpalainen for assistance with the XML.
13. References
13.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Rosenberg, J., "A Session Initiation Protocol (SIP) Event
Package for Registrations", RFC 3680, March 2004.
[3] Rosenberg, J., "Obtaining and Using Globally Routable User Agent
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(UA) URIs (GRUU) in the Session Initiation Protocol (SIP)",
draft-ietf-sip-gruu-07 (work in progress), May 2006.
[4] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004.
13.2. Informative References
[5] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002.
[6] Garcia-Martin, M., Henrikson, E., and D. Mills, "Private Header
(P-Header) Extensions to the Session Initiation Protocol (SIP)
for the 3rd-Generation Partnership Project (3GPP)", RFC 3455,
January 2003.
[7] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, "Indicating User
Agent Capabilities in the Session Initiation Protocol (SIP)",
RFC 3840, August 2004.
[8] Sparks, R., "Session Initiation Protocol Torture Test Messages",
draft-ietf-sipping-torture-tests-09 (work in progress),
November 2005.
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Author's Address
Paul H. Kyzivat
Cisco Systems, Inc.
1414 Massachusetts Avenue
Boxborough, MA 01719
USA
Email: pkyzivat@cisco.com
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