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Versions: (draft-kyzivat-sipping-gruu-reg-event)
00 01 02 03 04 05 06 07 08 09 RFC 5628
Sipping P. Kyzivat
Internet-Draft Cisco Systems, Inc.
Intended status: Standards Track July 6, 2007
Expires: January 7, 2008
Registration Event Package Extension for Session Initiation Protocol
(SIP) Globally Routable User Agent URIs (GRUUs)
draft-ietf-sipping-gruu-reg-event-09
Status of this Memo
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This Internet-Draft will expire on January 7, 2008.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
RFC 3680 defines a Session Initiation Protocol (SIP)[5] 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
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(GRUU), defined in RFC YYYY [3], is a URI that is capable of reaching
a particular contact. However this URI is not included in the
document format defined in RFC 3680. This specification defines an
extension to the registration event package to include GRUUs assigned
by the registrar.
[[NOTE TO RFC-EDITOR/IANA: Please replace YYYY throughout this
document with the RFC number assigned to the referenced draft [3]
when it is published.]]
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 . . . . . . . . . . . 5
6.1. Managing Temporary GRUU Lifetime . . . . . . . . . . . . . 5
7. Sample reginfo Document . . . . . . . . . . . . . . . . . . . 6
8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Example: Welcome Notice . . . . . . . . . . . . . . . . . 7
8.2. Example: Implicit Registration . . . . . . . . . . . . . . 8
9. XML Schema Definition . . . . . . . . . . . . . . . . . . . . 11
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
10.1. URN Sub-Namespace Registration . . . . . . . . . . . . . . 12
10.2. XML Schema Registration . . . . . . . . . . . . . . . . . 12
11. Security Considerations . . . . . . . . . . . . . . . . . . . 13
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
13.1. Normative References . . . . . . . . . . . . . . . . . . . 14
13.2. Informative References . . . . . . . . . . . . . . . . . . 14
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14
Intellectual Property and Copyright Statements . . . . . . . . . . 16
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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), defined in RFC YYYY [3],
is a URI that reaches a particular UA instance, but is reachable by
any host on the Internet. GRUUs assigned by the registrar represent
additional registration state. However, GRUUs assigned by the
registrar are not included in the notifications provided by RFC 3680.
For many applications of the registration event package, a 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 a 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 GRUUs are requested and obtained as part of the registration
request, then additional GRUUs will also be needed for the implicit
registrations. While assigning the additional GRUUs 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 GRUUs for the
associated AORs.
As specified in RFC YYYY [3], temporary GRUUs are invalidated when
contact address bindings for the corresponding AOR and instance id
are not refreshed, or when a registration to the AOR and instance id
is performed with a new Call-Id. A UA cannot always determine with
certainty which temporary GRUUs are valid based solely on the
response to the REGISTER requests it has issued, or from
notifications according to RFC 3680 [2]. The herein defined
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extension provides sufficient information for a UA to determine which
temporary GRUUs are valid.
The "reg" event package has provision for including extension
elements within the <contact> element. This document defines new
elements that may be used in that context to deliver the public and
temporary GRUUs corresponding to the contact.
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
Two new elements (<pub-gruu> and <temp-gruu>) are defined, each of
which contains a GRUU. The <temp-gruu> element also identifies the
oldest temporary gruu that is currently valid.
These optional elements may be included within the body of a NOTIFY
for the "reg" event package when GRUUs are associated with the
contact. The contact URI and the GRUUs are then all 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 <pub-
gruu> element when a contact has an Instance ID and a public GRUU is
associated with the combination of the AOR and the Instance ID. When
present, the <pub-gruu> element MUST be be positioned as a child of
the <contact> element.
A notifier for the "reg" event package [2] MAY include the <temp-
gruu> element when a contact has an Instance ID and a temporary GRUU
is associated with the combination of the AOR and the Instance ID.
This element SHOULD be included if the subscriber is also authorized
to register to the AOR. This element SHOULD NOT be included if the
subscriber is not authorized to register to the AOR, unless there is
an explicitly configured policy directing that it be included. When
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present, the <temp-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 child <pub-gruu> and <temp-gruu> elements, and those child
elements of each <contact> element 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 <pub-gruu> and
one <temp-gruu> child element.
If the notifier includes the <pub-gruu> element it MUST populate the
element with the public GRUU that is associated with the instance ID
and AOR of the registered contact.
If the notifier includes the <temp-gruu> element it MUST populate the
element with the most recently assigned temporary GRUU that is
associated with the instance ID and AOR of the registered contact.
It MUST also populate the element with the CSeq value of the first
currently active temporary GRUU that is associated with the instance
ID and AOR of the registered contact. The CSeq value is the CSeq of
the REGISTER request that caused that temporary GRUU to be assigned.
6. Subscriber Processing of NOTIFY Requests
When a subscriber receives a "reg" event notification with a
<contact> containing a <pub-gruu> it MAY associate the public GRUU
with corresponding AOR and Instance ID. Any previously received
public GRUU for the same AOR and Instance ID MUST be discarded. (It
will no longer function.)
When a subscriber receives a "reg" event notification with a
<contact> containing a <temp-gruu> it MAY associate the temp GRUU,
together with the "callid" and "cseq" attributes, with the
corresponding AOR and Instance ID.
Subscribers that are unaware of this extension will, as required by
[2], ignore the <pub-gruu> and <temp-gruu> elements.
6.1. Managing Temporary GRUU Lifetime
Section 4.2 of RFC YYYY [3] gives guidance for developers of UAs on
how to ensure that only valid temporary GRUUs are retained and used
by the UA. A UA cannot always determine with certainty which
temporary GRUUs are valid based solely on the response to the
REGISTER requests it has issued, or from notifications according to
RFC 3680 [2]. The herein defined extensions to RFC 3680 provide
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added information to help with that process. The following are steps
that the UA MAY take to ensure it only retains valid GRUUs:
o The UA should subscribe to the "reg" event package for the AOR it
is registering.
o When a UA receives a 2xx response to a REGISTER request, it may
extract and retain temporary GRUUs from the response for future
use as long as they remain valid. Appropriate GRUUs to retain are
those corresponding to the Contact address and instance ID it has
registered. (Typically the UA will register only one Contact
address, and so receive at most one temporary GRUU.)
o The UA may add the temporary GRUU to the set of valid temporary
GRUUs associated with the AOR. (The To-address of the REGISTER
request.) To aid in tracking validity the UA should also remember
the Call-ID and CSeq values of the REGISTER response containing
the temporary GRUU.
o If the UA receives a "reg" event notification with an AOR that it
supports and a <contact>, for a contact address and instance ID it
has registered, that contains a <temp-gruu> it may update its set
of valid temporary GRUUs associated with the AOR, as follows:
* It may add the temporary GRUU to the set. To aid in tracking
validity the UA should also remember the "callid" and "cseq"
attributes of the <contact>.
* It should remove any temporary GRUUs with a callid value
different from that in the value of the "callid" attribute of
the <contact>, or with a cseq value less than the value of the
"first-cseq" attribute of the <temp-gruu>.
o If the UA receives a "reg" event notification with an AOR that it
supports, and there are no <contact> entries for its instance ID,
then it should discard all the temporary GRUUs it has saved for
that AOR.
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 [7] are used to describe
representation of long message lines.
The following is an example registration information document
including the new element:
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<?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="36001" expires="3599"
callid="1j9FpLxk3uxtm8tn@192.0.2.1" cseq="54321"
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:pub-gruu uri="sip:user@example.com
;gr=hha9s8d-999a"/>
</allOneLine>
<allOneLine>
<gr:temp-gruu uri="sip:8ffkas08af7fasklzi9@example.com
;gr" first-cseq="54301"/>
</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
contained public GRUU as follows:
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MESSAGE sip:user@example.com;gr=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 GRUUs, 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>
Call-Id: faif9a@ua.example.com
CSeq: 23001 REGISTER
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
GRUUs 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 unique GRUUs assigned. The REGISTER
response will not include those GRUUs; it will only include the GRUUs
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
Call-Id: faif9a@ua.example.com
CSeq: 23001 REGISTER
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>"
;pub-gruu="sip:user_aor_1@example.net;gr=hha9s8d-999a"
;temp-gruu="sip:8ffkas08af7fasklzi9@example.net;gr"
P-Associated-URI: <sip:user_aor_2@example.net>,
<sip:+358504821437@example.net;user=phone>
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Content-Length: 0
The UA then subscribes to the "reg" event package as follows:
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>
Call-Id: gbjg0b@ua.example.com
CSeq: 45001 SUBSCRIBE
Route: <sip:proxy.example.net;lr>
Event: reg
Expires: 3600
Accept: application/reginfo+xml
Contact: <sip:user_aor_1@example.net;gr=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;gr=hha9s8d-999a SIP/2.0
From: <sip:user_aor_1@example.net>;tag=27182
To: <sip:user_aor_1@example.net>;tag=262281
Call-Id: gbjg0b@ua.example.com
CSeq: 633 NOTIFY
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"
callid="faif9a@ua.example.com" cseq="23001">
<uri>
sip:ua.example.com
</uri>
<allOneLine>
<unknown-param name="+sip.instance">
"<urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>"
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</unknown-param>
</allOneLine>
<allOneLine>
<gr:pub-gruu uri="sip:user_aor_1@example.net
;gr=hha9s8d-999a"/>
</allOneLine>
<allOneLine>
<gr:temp-gruu uri="sip:8ffkas08af7fasklzi9@example.net
;gr" first-cseq="54301"/>
</allOneLine>
</contact>
</registration>
<registration aor="sip:user_aor_2@example.net" id="a8"
state="active">
<contact id="93" state="active" event="created"
duration-registered="1" expires="3599"
callid="faif9a@ua.example.com" cseq="23001">
<uri>
sip:ua.example.com
</uri>
<allOneLine>
<unknown-param name="+sip.instance">
"<urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>"
</unknown-param>
</allOneLine>
<allOneLine>
<gr:pub-gruu uri="sip:user_aor_2@example.net
;gr=hha9s8d-999b"/>
</allOneLine>
<allOneLine>
<gr:temp-gruu uri="sip:07hcovy36vp6vngvbia@example.net
;gr" first-cseq="54301"/>
</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"
callid="faif9a@ua.example.com" cseq="23001">
<uri>
sip:ua.example.com
</uri>
<allOneLine>
<unknown-param name="+sip.instance">
"<urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>"
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</unknown-param>
</allOneLine>
<allOneLine>
<gr:pub-gruu uri="sip:+358504821437@example.net
;user=phone;gr=hha9s8d-999c"/>
</allOneLine>
<allOneLine>
<gr:temp-gruu uri="sip:h99egjbv17fe8ibvlka@example.net
;gr" first-cseq="54301"/>
</allOneLine>
</contact>
</registration>
</reginfo>
The status indicates that the associated URIs all have the same
contact registered. It also includes the unique GRUUs that have been
assigned to each. The UA may then retain those GRUUs for use when
establishing dialogs using the corresponding AORs.
9. XML Schema Definition
The <pub-gruu> and <temp-gruu> elements are defined within a new XML
namespace URI. This namespace is "urn:ietf:params:xml:ns:gruuinfo".
The schema for these elements 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:complexType name="pubGruu">
<xs:attribute name="uri" type="xs:anyURI"
use="required"/>
</xs:complexType>
<xs:complexType name="tempGruu">
<xs:complexContent>
<xs:extension base="tns:pubGruu">
<xs:attribute name="first-cseq"
type="xs:unsignedLong"
use="required"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
<xs:element name="pub-gruu" type="tns:pubGruu"/>
<xs:element name="temp-gruu" type="tns:tempGruu"/>
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</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>
</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>
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The XML for this schema can be found in Section 9.
11. Security Considerations
Security considerations for the registration event package are
discussed in RFC 3680 [2], and those considerations apply here.
If a contact address obtained via subscription to the registration
event package is not reachable by the subscriber then its disclosure
may arguably be considered a minimal security risk. In that case the
inclusion of a GRUU may be considered to increase the risk by
providing a reachable address. On the other hand requests addressed
to a 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. For instance, the proxy
servicing a GRUU may accept requests from senders whose identity
appears on a white list, and reject other requests. In this respect
disclosing a GRUU presents no more risk than disclosing the AOR.
Temporary GRUUs have an additional security consideration. The
intent of the temporary GRUU is to provide a contact address that
cannot be correlated to the identity of the calling party. The
recipient of a call using a temporary GRUU may guess the identity of
the calling party and then attempt to obtain the temporary GRUUs
assigned to that caller to confirm the conjecture. Two possible
approaches to obtaining the temporary GRUUs are:
o Send a REGISTER request to a conjectured caller.
o Send a SUBSCRIBE request for the "reg" event package to the
conjectured caller.
Typically REGISTER is restricted to devices or users that are
authorized to originate and received calls with the AOR. Anonymity
among users of the same AOR is hard to achieve and typically
unnecessary. It is recommended (see Section 5) that the
authorization policy for the "reg" event package permit only those
subscribers authorized to register to the AOR to receive temporary
GRUUs. With this policy, the confidentiality of the temporary GRUU
will be the same with and without the "reg" event package. User
agents that use a temporary GRUU should note that confidentiality
does not extend to parties that are permitted to register to the AOR
or obtain the temporary GRUU when subscribing the "reg" event
package.
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12. Acknowledgements
The author would like to thank Jonathan Rosenberg for help with 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
(UA) URIs (GRUU) in the Session Initiation Protocol (SIP)",
draft-ietf-sip-gruu-14 (work in progress), June 2007.
[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] Sparks, R., Hawrylyshen, A., Johnston, A., Rosenberg, J., and H.
Schulzrinne, "Session Initiation Protocol (SIP) Torture Test
Messages", RFC 4475, May 2006.
Kyzivat Expires January 7, 2008 [Page 14]
Internet-Draft Reg Event GRUU Extension July 2007
Author's Address
Paul H. Kyzivat
Cisco Systems, Inc.
1414 Massachusetts Avenue
Boxborough, MA 01719
USA
Email: pkyzivat@cisco.com
Kyzivat Expires January 7, 2008 [Page 15]
Internet-Draft Reg Event GRUU Extension July 2007
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