draft-ietf-sipping-dialog-package-00.txt   draft-ietf-sipping-dialog-package-01.txt 
Internet Engineering Task Force SIPPING WG Internet Engineering Task Force SIPPING WG
Internet Draft J. Rosenberg Internet Draft J. Rosenberg
dynamicsoft dynamicsoft
H. Schulzrinne H. Schulzrinne
Columbia U. Columbia U.
draft-ietf-sipping-dialog-package-00.txt draft-ietf-sipping-dialog-package-01.txt
June 24, 2002 March 1, 2003
Expires: December 2002 Expires: September 1, 2003
A Session Initiation Protocol (SIP) Event Package for Dialog State An INVITE Inititiated Dialog Event Package
for the Session Initiation Protocol (SIP)
STATUS OF THIS MEMO STATUS OF THIS MEMO
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
skipping to change at page 2, line 7 skipping to change at page 2, line 7
Abstract Abstract
This document defines a dialog event package for the SIP Events This document defines a dialog event package for the SIP Events
architecture, along with a data format used in notifications for this architecture, along with a data format used in notifications for this
package. The dialog package allows users to subscribe to another package. The dialog package allows users to subscribe to another
user, an receive notifications about the changes in state of INVITE user, an receive notifications about the changes in state of INVITE
initiated dialogs that the user is involved in. initiated dialogs that the user is involved in.
Table of Contents Table of Contents
1 Introduction ........................................ 4 1 Introduction ........................................ 3
2 Dialog Event Package ................................ 5 2 Dialog Event Package ................................ 4
2.1 Event Package Name .................................. 5 2.1 Event Package Name .................................. 4
2.2 Event Package Parameters ............................ 5 2.2 Event Package Parameters ............................ 4
2.3 SUBSCRIBE Bodies .................................... 5 2.3 SUBSCRIBE Bodies .................................... 4
2.4 Subscription Duration ............................... 5 2.4 Subscription Duration ............................... 5
2.5 NOTIFY Bodies ....................................... 6 2.5 NOTIFY Bodies ....................................... 6
2.6 Notifier Processing of SUBSCRIBE Requests ........... 6 2.6 Notifier Processing of SUBSCRIBE Requests ........... 6
2.7 Notifier Generation of NOTIFY Requests .............. 7 2.7 Notifier Generation of NOTIFY Requests .............. 6
2.7.1 The Dialog State Machine ............................ 7 2.7.1 The Dialog State Machine ............................ 7
2.7.2 Applying the state machine .......................... 9 2.7.2 Applying the state machine .......................... 8
2.8 Subscriber Processing of NOTIFY Requests ............ 10 2.8 Subscriber Processing of NOTIFY Requests ............ 10
2.9 Handling of Forked Requests ......................... 11 2.9 Handling of Forked Requests ......................... 11
2.10 Rate of Notifications ............................... 11 2.10 Rate of Notifications ............................... 11
2.11 State Agents ........................................ 11 2.11 State Agents ........................................ 11
3 Dialog Information Format ........................... 11 3 Dialog Information Format ........................... 11
3.1 Structure of Dialog Information ..................... 12 3.1 Structure of Dialog Information ..................... 12
3.1.1 Dialog Element ...................................... 12 3.1.1 Dialog Element ...................................... 12
3.1.2 State ............................................... 13 3.1.2 State ............................................... 13
3.1.3 Local URI ........................................... 13 3.1.3 Local URI ........................................... 13
3.1.4 Remote URI .......................................... 13 3.1.4 Remote URI .......................................... 13
3.1.5 Local Session Description ........................... 13 3.1.5 Local Session Description ........................... 13
3.1.6 Remote Session Description .......................... 13 3.1.6 Remote Session Description .......................... 14
3.1.7 Remote Target ....................................... 13 3.1.7 Remote Target ....................................... 14
3.1.8 Local CSeq .......................................... 14 3.1.8 Local CSeq .......................................... 14
3.1.9 Remote CSeq ......................................... 14 3.1.9 Remote CSeq ......................................... 14
3.1.10 Duration ............................................ 14 3.1.10 Duration ............................................ 14
3.2 Constructing Coherent State ......................... 14 3.2 Constructing Coherent State ......................... 14
3.3 Schema .............................................. 15 3.3 Schema .............................................. 15
3.4 Example ............................................. 18 3.4 Example ............................................. 18
4 Security Considerations ............................. 20 4 Security Considerations ............................. 21
5 IANA Considerations ................................. 20 5 IANA Considerations ................................. 21
5.1 application/dialog-info+xml MIME Registration ....... 20 5.1 application/dialog-info+xml MIME Registration ....... 21
5.2 URN Sub-Namespace Registration for 5.2 URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:dialog-info ............................. 21 urn:ietf:params:xml:ns:dialog-info ............................. 22
6 Acknowledgements .................................... 22 6 Acknowledgements .................................... 23
7 Authors Addresses ................................... 22 7 Authors Addresses ................................... 23
8 Normative References ................................ 22 8 Normative References ................................ 23
9 Informative References .............................. 23 9 Informative References .............................. 24
1 Introduction 1 Introduction
The SIP Events framework [1] defines general mechanisms for The SIP Events framework [1] defines general mechanisms for
subscription to, and notification of, events within SIP networks. It subscription to, and notification of, events within SIP networks. It
introduces the notion of a package, which is a specific introduces the notion of a package, which is a specific
"instantiation" of the events mechanism for a well-defined set of "instantiation" of the events mechanism for a well-defined set of
events. Packages have been defined for user presence [8], watcher events. Packages have been defined for user presence [9], watcher
information [9], and message waiting indicators [10], amongst others. information [10], and message waiting indicators [11], amongst
Here, we define an event package for INVITE initiated dialogs. others. Here, we define an event package for INVITE initiated
Dialogs refer to the SIP relationship established between two SIP dialogs. Dialogs refer to the SIP relationship established between
peers [2]. two SIP peers [2]. Dialogs can be created by many methods, although
RFC 3261 defines only one - the INVITE method. RFC 3265 defines the
SUBSCRIBE and NOTIFY methods, which also create dialogs. However, the
usage of this package to model transitions in the state of those
dialogs is out of the scope of this specification.
There are a variety of applications enabled through the knowledge of There are a variety of applications enabled through the knowledge of
dialog state. Some examples include: INVITE dialog state. Some examples include:
Automatic Callback: In this basic PSTN application, user A calls Automatic Callback: In this basic Public Switched Telephone
user B. User B is busy. User A would like to get a callback Network (PSTN) application, user A calls user B. User B is
when user B hangs up. When B hangs up, user A's phone busy. User A would like to get a callback when user B hangs
rings. When A picks it up, they here ringing, and are being up. When B hangs up, user A's phone rings. When A picks it
connected to B. In VoIP, this requires A to receive a up, they here ringing, and are being connected to B. To
notification when the dialogs at A are complete. implement this with SIP, a mechanism is required for B to
receive a notification when the dialogs at A are complete.
Presence-Enabled Conferencing: In this application, a user A Presence-Enabled Conferencing: In this application, a user A
wishes to set up a conference call with users B and C. wishes to set up a conference call with users B and C.
Rather than scheduling it, it is to be created Rather than scheduling it, it is to be created
automatically when A, B and C are all available. To do automatically when A, B and C are all available. To do
this, the server providing the application would like to this, the server providing the application would like to
know whether A, B and C are "online", not idle, and not in know whether A, B and C are "online", not idle, and not in
a phone call. Determining whether or not A, B and C are in a phone call. Determining whether or not A, B and C are in
calls can be done in two ways. In the first, the server calls can be done in two ways. In the first, the server
acts as a call stateful proxy for users A, B and C, and acts as a call stateful proxy for users A, B and C, and
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This section provides the details for defining a SIP Events package, This section provides the details for defining a SIP Events package,
as specified by [1]. as specified by [1].
2.1 Event Package Name 2.1 Event Package Name
The name of this event package is "dialog". This package name is The name of this event package is "dialog". This package name is
carried in the Event and Allow-Events header, as defined in [1]. carried in the Event and Allow-Events header, as defined in [1].
2.2 Event Package Parameters 2.2 Event Package Parameters
This package does not define any event package parameters. This package defines three Event Package parameters. They are call-
id, to-tag and from-tag. If a subscription to a specific dialog is
requested, all three of these parameters MUST be present. They
identify the dialog or that is being subscribed to. The to-tag is
matched against the local tag, the from-tag is matched against the
remote tag, and the call-id is matched against the Call-ID.
It is also possible to subscribe to the set of dialogs created as a
result of a single INVITE sent by a UAC. In that case, the call-id
and to-tag MUST be present. The to-tag is matched against the local
tag, and the call-id is matched against the Call-ID.
The BNF for these parameters is:
call-id = "call-id" EQUAL SWS DQUOTE callid DQUOTE
;;callid, EQUAL, SWS, DQUOTE from rfc3261
from-tag = "from-tag" EQUAL token
to-tag = "to-tag" EQUAL token
Note that the call-id parameter is a quoted string. This is because
the BNF for word (which is used by callid) allows for characters not
allowed within token.
2.3 SUBSCRIBE Bodies 2.3 SUBSCRIBE Bodies
A SUBSCRIBE for a dialog package MAY contain a body. This body A SUBSCRIBE for a dialog package MAY contain a body. This body
defines a filter to apply to the subscription. defines a filter to apply to the subscription. Filter documents are
not specified in this document, and at the time of writing, are
expected to be the subject of future standardization activity.
A SUBSCRIBE for a dialog package MAY be sent without a body. This A SUBSCRIBE for a dialog package MAY be sent without a body. This
implies the default subscription filtering policy. The default policy implies the default subscription filtering policy. The default policy
is: is:
o Notifications are generated every time there is any change in o If the Event header field contained dialog identifiers,
notifications are generated every time there is a change in
the state of any matching dialogs for the user identified in
the request URI of the SUBSCRIBE.
o If there were no dialog identifiers in the Event header field,
notifications are generated every time there is any change in
the state of any dialogs for the user identified in the the state of any dialogs for the user identified in the
request URI of the SUBSCRIBE. request URI of the SUBSCRIBE.
o Notifications do not normally contain full state; rather, they o Notifications do not normally contain full state; rather, they
only indicate the state of the dialog whose state has changed. only indicate the state of the dialog whose state has changed.
The exception is a NOTIFY sent in response to a SUBSCRIBE. The exception is a NOTIFY sent in response to a SUBSCRIBE.
These NOTIFYs contain the complete view of dialog state. These NOTIFYs contain the complete view of dialog state.
o The notifications contain the identities of the participants o The notifications contain the identities of the participants
in the dialog, and the dialog identifiers. Additional in the dialog, and the dialog identifiers. Additional
information, such as the route set, remote target URI, CSeq information, such as the route set, remote target URI, CSeq
numbers, SDP information, and so on, are not included normally numbers, SDP information, and so on, are not included normally
unless explicitly requested and/or explicitly authorized. unless explicitly requested and/or explicitly authorized.
OPEN ISSUE: It might be useful to define a filter within
this document that would allow a subscriber to ask about a
specific dialog.
2.4 Subscription Duration 2.4 Subscription Duration
Dialog state changes fairly quickly; once established, a typical Dialog state changes fairly quickly; once established, a typical
phone call lasts a few minutes (this is different for other session phone call lasts a few minutes (this is different for other session
types, of course). However, the interval between new calls is types, of course). However, the interval between new calls is
typically infrequent. As such, we arbitrarily choose a default typically infrequent. As such, we arbitrarily choose a default
duration of one hour, and RECOMMEND that clients specify an explicit duration of one hour, and RECOMMEND that clients specify an explicit
duration. duration.
There are two distinct use cases for dialog state. The first is when There are two distinct use cases for dialog state. The first is when
a subscriber is interested in the state of a specific dialog (and a subscriber is interested in the state of a specific dialog or
they are authorized to find out about just the state of that dialog). dialogs (and they are authorized to find out about just the state of
In that case, when the dialog terminates, so too does the those dialogs). In that case, when the dialogs terminate, so too does
subscription. In these cases, the value of the subscription duration the subscription. In these cases, the value of the subscription
is largely irrelevant, and SHOULD be longer than the typical duration duration is largely irrelevant, and SHOULD be longer than the typical
of a dialog, about two hours would cover most dialogs. duration of a dialog, about two hours would cover most dialogs.
In another case, a subscriber is interested in the state of all call In another case, a subscriber is interested in the state of all
legs for a specific user. In these cases, a shorter interval makes dialogs for a specific user. In these cases, a shorter interval makes
more sense. The default is one hour for these subscriptions. more sense. The default is one hour for these subscriptions.
2.5 NOTIFY Bodies 2.5 NOTIFY Bodies
The body of the notification contains a dialog information document. As described in RFC 3265 [1], the NOTIFY message will contain bodies
The format of this document is described in Section 3. Its MIME type that describe the state of the subscribed resource. This body is in a
is "application/dialog-info+xml". All subscribers MUST support this format listed in the Accept header field of the SUBSCRIBE, or a
format, and MUST list its type in any Accept header in the SUBSCRIBE. package-specific default if the Accept header field was omitted from
When no Accept header is present in the SUBSCRIBE, its default value the SUBSCRIBE.
is "application/dialog-info+xml".
Other dialog information formats might be defined in the future. In In this event package, the body of the notification contains a dialog
that case, the subscriptions MAY indicate support for other formats. information document. This document describes the state of one or
However, they MUST always support and list "application/dialog- more dialogs associated with the subscribed resource. All subscribers
info+xml" as an allowed format. and notifiers MUST support the "application/dialog-info+xml" data
format described in 3. The subscribe request MAY contain an Accept
header field. If no such header field is present, it has a default
value of "application/dialog-info+xml". If the header field is
present, it MUST include "application/dialog-info+xml", and MAY
include any other types capable of representing dialog state.
Of course, the notifications generated by the server MUST be in one Of course, the notifications generated by the server MUST be in one
of the formats specified in the Accept header in the SUBSCRIBE of the formats specified in the Accept header field in the SUBSCRIBE
request. request.
2.6 Notifier Processing of SUBSCRIBE Requests 2.6 Notifier Processing of SUBSCRIBE Requests
The dialog information for a user contains very sensitive The dialog information for a user contains sensitive information.
information. Therefore, all subscriptions SHOULD be authenticated and Therefore, all subscriptions SHOULD be authenticated and then
then authorized before approval. Authorization policy is at the authorized before approval. All implementors of this package MUST
discretion of the administrator, as always. However, a few support the digest authentication mechanism as a baseline.
recommendations can be made. Authorization policy is at the discretion of the administrator, as
always. However, a few recommendations can be made.
It is RECOMMENDED that if the policy of a user is that A is allowed It is RECOMMENDED that, if the policy of user B is that user A is
to call them, dialog subscriptions from user A be allowed. However, allowed to call them, dialog subscriptions from user A be allowed.
the information provided in the notifications does not contain any However, the information provided in the notifications does not
dialog identification information; merely an indication of whether contain any dialog identification information; merely an indication
the user is in one or more calls, or not. Specifically, they should of whether the user is in one or more calls, or not. Specifically,
not be able to find out any more information than if they sent an they should not be able to find out any more information than if they
INVITE. sent an INVITE.
It is RECOMMENDED that if a user agent registers with the address- It is RECOMMENDED that if a user agent registers with the address-
of-record X, that this user agent authorize subscriptions that come of-record X, that this user agent authorize subscriptions that come
from any entity that can authenticate itself as X. Complete from any entity that can authenticate itself as X. Complete
information on the dialog state SHOULD be sent in this case. This information on the dialog state SHOULD be sent in this case. This
authorization behavior allows a group of devices representing a authorization behavior allows a group of devices representing a
single user to all become aware of each other's state. This is useful single user to all become aware of each other's state. This is useful
for applications such as single-line-extension. for applications such as single-line-extension.
2.7 Notifier Generation of NOTIFY Requests 2.7 Notifier Generation of NOTIFY Requests
Notifications are generated for the dialog package when an INVITE
Notifications are generated for the dialog package when a new dialog request is sent, when a new dialog comes into existence at a UA, or
comes into existence at a UA, or when the state or characteristics of when the state or characteristics of an existing dialog changes.
an existing dialog changes. Therefore, a model of dialog state is Therefore, a model of dialog state is needed in order to determine
needed in order to determine precisely when to send notifications, precisely when to send notifications, and what their content should
and what their content should be. The SIP specification has a be. The SIP specification has a reasonably well defined lifecycle for
reasonably well defined lifecycle for dialogs. However, it is not dialogs. However, it is not explicitly modelled. This specification
explicitly modelled. This specification provides an explicit model of provides an explicit model of dialog state through a finite state
dialog state through a finite state machine. machine.
It is RECOMMENDED that NOTIFY requests only contain information on It is RECOMMENDED that NOTIFY requests only contain information on
the dialogs whose state has changed. However, if a notifier receives the dialogs whose state has changed. However, if a notifier receives
a SUBSCRIBE request, the triggered NOTIFY SHOULD contain the state of a SUBSCRIBE request, the triggered NOTIFY SHOULD contain the state of
all dialogs that the subscriber is authorized to see. all dialogs that the subscriber is authorized to see.
2.7.1 The Dialog State Machine 2.7.1 The Dialog State Machine
Modelling of dialog state is complicated by two factors. The first is Modelling of dialog state is complicated by two factors. The first is
forking, which can cause a single INVITE to generate many dialogs at forking, which can cause a single INVITE to generate many dialogs at
a UAC. The second is the differing views of state at the UAC and UAS. a UAC. The second is the differing views of state at the UAC and UAS.
We have chosen to handle the first issue by extending the dialog FSM We have chosen to handle the first issue by extending the dialog FSM
to include the states between transmission of the INVITE and the to include the states between transmission of the INVITE and the
creation of actual dialogs through receipt of 1xx and 2xx responses. creation of actual dialogs through receipt of 1xx and 2xx responses.
As a result, this specification supports the notion of dialog state
for dialogs before they are fully instantiated.
We have also chosen to use a single FSM for both UAC and UAS. We have also chosen to use a single FSM for both UAC and UAS.
The FSM for dialog state is shown in Figure 1. The FSM is best The FSM for dialog state is shown in Figure 1. The FSM is best
understood by considering the UAC and UAS cases separately. understood by considering the UAC and UAS cases separately.
The FSM is created in the "trying" state when the UAC sends an INVITE The FSM is created in the "trying" state when the UAC sends an INVITE
request. Upon receipt of a 1xx without a tag (the "1xx-notag" event), request. Upon receipt of a 1xx without a tag (the "1xx-notag" event),
the FSM transitions to the "proceeding" state. Note that there is no the FSM transitions to the "proceeding" state. Note that there is no
actual dialog yet, as defined by the SIP specification. However, actual dialog yet, as defined by the SIP specification. However,
there is a "half-dialog", in the sense that two of the three there is a "half-dialog", in the sense that two of the three
components of the dialog ID are known (the call identifier and local components of the dialog ID are known (the call identifier and local
tag). If a 1xx with a tag is received, the FSM transitions to the tag). If a 1xx with a tag is received, the FSM transitions to the
early state. The full dialog identifier is now defined. Had a 2xx early state. The full dialog identifier is now defined. Had a 2xx
+----------+ +----------+
| | 1xx-notag | |
| |----------->| |
| Trying | |Proceeding|-----+
| |---+ +-----| | |
| | | | | | |
+----------+ | | +----------+ |
| | | | | |
| | | | | |
+<--C-----C--+ |1xx-tag |
| | | | |
cancelled| | | V |
rejected| | |1xx-tag +----------+ |
| | +------->| | |2xx
| | | | |
+<--C--------------| Early | |
| | | | |
| | | | |
| | +----------+ |
| | 2xx | |
| +----------------+ | |
| | |2xx |
| | | |
V V V |
+----------+ +----------+ |
| | | | |
| | | | |
|Terminated|<-----------| Confirmed|<----+
| | hungup | |
| | error | |
+----------+ timeout +----------+
Figure 1: Dialog finite state machine
been received, the FSM would have transitioned to the "confirmed" been received, the FSM would have transitioned to the "confirmed"
state. state.
If, after transitioning to the "early" or "confirmed" states, the UAC If, after transitioning to the "early" or "confirmed" states, the UAC
receives another 1xx or 2xx with a different tag, another instance of receives another 1xx or 2xx respectively with a different tag,
the FSM is created, initialized into the "early" or "confirmed" state another instance of the FSM is created, initialized into the "early"
depending on the response code. The benefit of this approach is that or "confirmed" state respectively. The benefit of this approach is
there will be a single FSM representing the entire state of the that there will be a single FSM representing the entire state of the
invitation and resulting dialog when dealing with the common case of invitation and resulting dialog when dealing with the common case of
no forking. no forking.
If the UAC should send a CANCEL, and then subsequently receive a 487 If the UAC should send a CANCEL, and then subsequently receive a 487
to its INVITE transaction, all FSMs spawned from that INVITE to its INVITE transaction, all FSMs spawned from that INVITE
transition to the "terminated" state with the event "canceled". If transition to the "terminated" state with the event "cancelled". If
the INVITE transaction terminates with a non-2xx response for any the INVITE transaction terminates with a non-2xx response for any
other reason, all FSMs spawned from that INVITE transition to the other reason, all FSMs spawned from that INVITE transition to the
terminated state with the event "rejected". terminated state with the event "rejected".
Once in the confirmed state, the call is active. It can transition to Once in the confirmed state, the call is active. It can transition to
the terminated state if the UAC sends a BYE or receives a BYE the terminated state if the UAC sends a BYE or receives a BYE
(corresponding to the "hungup" event), if a mid-dialog request (corresponding to the "hungup" event), if a mid-dialog request
generates a 481 or 408 response (corresponding to the "error" event), generates a 481 or 408 response (corresponding to the "error" event),
or a mid-dialog request generates no response (corresponding to the or a mid-dialog request generates no response (corresponding to the
"timeout" event). "timeout" event).
skipping to change at page 10, line 9 skipping to change at page 9, line 4
terminated state. terminated state.
2.7.2 Applying the state machine 2.7.2 Applying the state machine
The notifier MAY generate a NOTIFY request on any event transition of The notifier MAY generate a NOTIFY request on any event transition of
the FSM. Whether it does or not is policy dependent. However, some the FSM. Whether it does or not is policy dependent. However, some
general guidelines are provided. general guidelines are provided.
When the subscriber is unauthenticated, or is authenticated, but When the subscriber is unauthenticated, or is authenticated, but
represents a third party with no specific authorization policies, it represents a third party with no specific authorization policies, it
is RECOMMENDED that actual dialog states across all dialogs not be +----------+ +----------+
reported. Rather, a single "virtual" dialog FSM be used, and event | | 1xx-notag | |
transitions on that FSM be reported. If there is any dialog at the UA | |----------->| |
whose state is "confirmed", the virtual FSM is in the "confirmed" | Trying | |Proceeding|-----+
state. If there are no dialogs at the UA in the confirmed state, but | |---+ +-----| | |
there is at least one in the "early" state, the virtual FSM is in the | | | | | | |
"early" state. If there are no dialogs in the confirmed or early +----------+ | | +----------+ |
states, but there is at least one in the "proceeding" state, the | | | | | |
virtual FSM is in the "proceeding" state. If there are no dialogs in | | | | | |
the confirmed, early, or proceeding states, but there is at least one +<--C-----C--+ |1xx-tag |
in the "trying" state, the virtual FSM is in the "trying" state. | | | | |
Furthermore, it is RECOMMENDED that the notifications of changes in cancelled| | | V |
the virtual FSM machine not convey any information except the state rejected| | |1xx-tag +----------+ |
of the FSM and its event transitions - no dialog identifiers (which | | +------->| | |2xx
are ill-defined in this model in any case). The use of this virtual | | | | |
FSM allows for minimal information to be conveyed. A subscriber +<--C--------------| Early |-----C----+1xx-tag
cannot know how many calls are in progress, or with whom, just that | | | | | | w. new tag
there exists a call. | | | |<----C----+ (new
| | +----------+ | FSM
| | 2xx | | instance
| +----------------+ | | created)
| | |2xx |
| | | |
V V V |
+----------+ +----------+ |
| | | | |
| | | | |
|Terminated|<-----------| Confirmed|<----+
| | hungup | |
| | error | |
+----------+ timeout +----------+
| ^
| |
| |
+------+
2xx w. new tag
(new FSM instance
created)
Figure 1: Dialog finite state machine
dialogs (i.e., there are no dialog identifiers in the Event header
field) are permitted. In that case, actual dialog states across all
dialogs not be reported. Rather, a single "virtual" dialog FSM be
used, and event transitions on that FSM be reported. If there is any
dialog at the UA whose state is "confirmed", the virtual FSM is in
the "confirmed" state. If there are no dialogs at the UA in the
confirmed state, but there is at least one in the "early" state, the
virtual FSM is in the "early" or "confirmed" state. If there are no
dialogs in the confirmed or early states, but there is at least one
in the "proceeding" state, the virtual FSM is in the "proceeding",
"early" or "confirmed" state. If there are no dialogs in the
confirmed, early, or proceeding states, but there is at least one in
the "trying" state, the virtual FSM is in the "trying", "proceeding",
"early" or "confirmed" state. The choice about which state to use
depends on whether the UA wishes to let unknown users that their
phone is ringing, as opposed to in an active call. It is RECOMMENDED
that, in the absence of any preference, "confirmed" is used in all
cases. Furthermore, it is RECOMMENDED that the notifications of
changes in the virtual FSM machine not convey any information except
the state of the FSM and its event transitions - no dialog
identifiers (which are ill-defined in this model in any case). The
use of this virtual FSM allows for minimal information to be
conveyed. A subscriber cannot know how many calls are in progress, or
with whom, just that there exists a call. This is the same
information they would receive if they simply sent an INVITE to the
user instead; a 486 response would indicate that they are on a call.
When the subscriber is authenticated, and has authenticated itself When the subscriber is authenticated, and has authenticated itself
with the same address-of-record that the UA itself uses, if no with the same address-of-record that the UA itself uses, if no
explicit authorization policy is defined, it is RECOMMENDED that all explicit authorization policy is defined, it is RECOMMENDED that all
state transitions on all dialogs be reported, along with complete state transitions on dialogs that have been subscribed to (which is
dialog IDs. either all of them, if no dialog identifiers were present in the
Event header field, or a specific set of them identified by the Event
header field parameters) be reported, along with complete dialog IDs.
The notifier MAY generate a NOTIFY request on any change in the The notifier MAY generate a NOTIFY request on any change in the
characteristics associated with the dialog. Since these include CSeq characteristics associated with the dialog. Since these include CSeq
numbers and SDP, receipt of re-INVITEs and UPDATE requests [11] which numbers and SDP, receipt of re-INVITEs and UPDATE requests [3] which
modify this information MAY trigger notifications. modify this information MAY trigger notifications.
2.8 Subscriber Processing of NOTIFY Requests 2.8 Subscriber Processing of NOTIFY Requests
The SIP Events framework expects packages to specify how a subscriber The SIP Events framework expects packages to specify how a subscriber
processes NOTIFY requests in any package specific ways, and in processes NOTIFY requests in any package specific ways, and in
particular, how it uses the NOTIFY requests to contruct a coherent particular, how it uses the NOTIFY requests to contruct a coherent
view of the state of the subscribed resource. view of the state of the subscribed resource.
Typically, the NOTIFY for the dialog package will only contain Typically, the NOTIFY for the dialog package will only contain
skipping to change at page 11, line 39 skipping to change at page 11, line 44
2.11 State Agents 2.11 State Agents
Dialog state is ideally maintained in the user agents in which the Dialog state is ideally maintained in the user agents in which the
dialog resides. Therefore, the elements that maintain the dialog are dialog resides. Therefore, the elements that maintain the dialog are
the ones best suited to handle subscriptions to it. Therefore, the the ones best suited to handle subscriptions to it. Therefore, the
usage of state agents is NOT RECOMMENDED for this package. usage of state agents is NOT RECOMMENDED for this package.
3 Dialog Information Format 3 Dialog Information Format
Dialog information is an XML document [3] that MUST be well-formed Dialog information is an XML document [4] that MUST be well-formed
and SHOULD be valid. Dialog information documents MUST be based on and SHOULD be valid. Dialog information documents MUST be based on
XML 1.0 and MUST be encoded using UTF-8. This specification makes use XML 1.0 and MUST be encoded using UTF-8. This specification makes use
of XML namespaces for identifying dialog information documents and of XML namespaces for identifying dialog information documents and
document fragments. The namespace URI for elements defined by this document fragments. The namespace URI for elements defined by this
specification is a URN [4], using the namespace identifier 'ietf' specification is a URN [5], using the namespace identifier 'ietf'
defined by [5] and extended by [6]. This URN is: defined by [6] and extended by [7]. This URN is:
urn:ietf:params:xml:ns:dialog-info urn:ietf:params:xml:ns:dialog-info
A dialog information document begins with the root element tag A dialog information document begins with the root element tag
"dialog-info". "dialog-info".
3.1 Structure of Dialog Information 3.1 Structure of Dialog Information
A dialog information document starts with a dialog-info element. This A dialog information document starts with a dialog-info element. This
element has three mandatory attributes: element has three mandatory attributes:
version: This attribute allows the recipient of dialog version: This attribute allows the recipient of dialog
information documents to properly order them. Versions information documents to properly order them. Versions
skipping to change at page 12, line 32 skipping to change at page 12, line 35
entity: This attribute contains a URI that identifies the user entity: This attribute contains a URI that identifies the user
whose dialog information is reported in the remainder of whose dialog information is reported in the remainder of
the document. the document.
The dialog-info element has a series of dialog sub-elements. Each of The dialog-info element has a series of dialog sub-elements. Each of
those represents a specific dialog. those represents a specific dialog.
3.1.1 Dialog Element 3.1.1 Dialog Element
The dialog element reports information on a specific dialog. It has a The dialog element reports information on a specific dialog or
single mandatory attribute, id. The id attribute provides a single "half-dialog". It has a single mandatory attribute, id. The id
string that can be used as an identifier for this dialog. This is a attribute provides a single string that can be used as an identifier
different identifier than the formal dialog ID defined in SIP [2]. for this dialog or "half-dialog". This is a different identifier than
This identifier exists before the dialog exists, and remains the dialog ID defined in RFC 3261 [2], but related to it.
unchanged when the actual dialog is established.
For a caller, the id is created when an INVITE request is sent. When
a 1xx with a tag, or a 2xx is received, the dialog is formally
created. The id remains unchanged. However, if an additional 1xx or
2xx is received, resulting in the creation of another dialog (and
resulting FSM), that dialog is allocated a new id.
For a callee, the id is created when an INVITE outside of an existing
dialog is received. When a 2xx or a 1xx with a tag is sent, creating
the dialog, the id remains unchanged.
The id MUST be unique amongst all dialogs at a UA.
There are a number of optional attributes which provide There are a number of optional attributes which provide
identification information about the dialog: identification information about the dialog:
call-id: This attribute is a string which represents the call-id call-id: This attribute is a string which represents the call-id
component of the dialog identifier. component of the dialog identifier.
local-tag: This attribute is a string which represents the local-tag: This attribute is a string which represents the
local-tag component of the dialog identifier. local-tag component of the dialog identifier.
remote-tag: This attribute is a string which represents the remote-tag: This attribute is a string which represents the
remote-tag component of the dialog identifier. The remote remote-tag component of the dialog identifier. The remote
tag attribute won't be present if there is only a "half- tag attribute won't be present if there is only a "half-
dialog", resulting from generation of a request that can dialog", resulting from the generation of an INVITE for
create a dialog. which no final responses or provisional responses with tags
has been received.
direction: This attribute is either initiator or recipient, and direction: This attribute is either initiator or recipient, and
indicates whether the notifier was the initiator of the indicates whether the notifier was the initiator of the
dialog, or the recipient of the INVITE that created it. dialog, or the recipient of the INVITE that created it.
The sub-elements of the dialog element provide additional information The sub-elements of the dialog element provide additional information
about the dialog. The only mandatory one is status. about the dialog. The only mandatory one is state.
3.1.2 State 3.1.2 State
The state element indicates the state of the dialog. Its value is an The state element indicates the state of the dialog. Its value is an
enumerated type describing one of the states in the FSM above. It has enumerated type describing one of the states in the FSM above. It has
an optional event attribute that can be used to indicate the event an optional event attribute that can be used to indicate the event
which caused the transition into the current state, and an optional which caused the transition into the current state, and an optional
code attribute that indicates the response code associated with the code attribute that indicates the response code associated with the
transition, assuming the event was 1xx-tag, 1xx-notag, or 2xx. transition, assuming the event was 1xx-tag, 1xx-notag, or 2xx.
skipping to change at page 14, line 4 skipping to change at page 14, line 20
3.1.6 Remote Session Description 3.1.6 Remote Session Description
The remote-session-description element contains the session The remote-session-description element contains the session
description used by the peer of the notifier for its end of the description used by the peer of the notifier for its end of the
dialog. This element should generally NOT be included in the dialog. This element should generally NOT be included in the
notifications, unless explicitly requested by the subscriber. It has notifications, unless explicitly requested by the subscriber. It has
a single attribute, type, which indicates the MIME media type of the a single attribute, type, which indicates the MIME media type of the
session description. session description.
3.1.7 Remote Target 3.1.7 Remote Target
The remote-target contains the remote-target URI as constructed by The remote-target contains the remote-target URI as constructed by
the user agent for this dialog, as defined in RFC BBBB [2]. This the user agent for this dialog, as defined in RFC 3261 [2]. This
element should generally not be included in notifications, unless element should generally not be included in notifications, unless
explicitly requested by the subscriber. explicitly requested by the subscriber.
3.1.8 Local CSeq 3.1.8 Local CSeq
The local-cseq element contains the most recent value of the CSeq The local-cseq element contains the most recent value of the CSeq
header used by the UA in an outgoing request on the dialog. This header used by the UA in an outgoing request on the dialog. This
element should generally NOT be included in the notifications, unless element should generally NOT be included in the notifications, unless
explicitly requested by the subscriber. If no CSeq has yet been explicitly requested by the subscriber. If no CSeq has yet been
defined, the value of the element is -1. defined, the value of the element is -1.
skipping to change at page 14, line 45 skipping to change at page 15, line 14
element. The contents of each row contain the state of that dialog as element. The contents of each row contain the state of that dialog as
conveyed in the document. The table is also associated with a version conveyed in the document. The table is also associated with a version
number. The version number MUST be initialized with the value of the number. The version number MUST be initialized with the value of the
"version" attribute from the "dialog-info" element in the first "version" attribute from the "dialog-info" element in the first
document received. Each time a new document is received, the value of document received. Each time a new document is received, the value of
the local version number, and the "version" attribute in the new the local version number, and the "version" attribute in the new
document, are compared. If the value in the new document is one document, are compared. If the value in the new document is one
higher than the local version number, the local version number is higher than the local version number, the local version number is
increased by one, and the document is processed. If the value in the increased by one, and the document is processed. If the value in the
document is more than one higher than the local version number, the document is more than one higher than the local version number, the
local version number is set to the value in the new document, the local version number is set to the value in the new document, and the
document is processed, and the subscriber SHOULD generate a refresh document is processed. If the document did not contain full state,
request to trigger a full state notification. If the value in the the subscriber SHOULD generate a refresh request to trigger a full
document is less than the local version, the document is discarded state notification. If the value in the document is less than the
without processing. local version, the document is discarded without processing.
The processing of the dialog information document depends on whether The processing of the dialog information document depends on whether
it contains full or partial state. If it contains full state, it contains full or partial state. If it contains full state,
indicated by the value of the "state" attribute in the "dialog-info" indicated by the value of the "state" attribute in the "dialog-info"
element, the contents of the table are flushed. They are repopulated element, the contents of the table are flushed. They are repopulated
from the document. A new row in the table is created for each from the document. A new row in the table is created for each
"dialog" element. If the document contains partial state, as "dialog" element. If the document contains partial state, as
indicated by the value of the "state" attribute in the "dialog-info" indicated by the value of the "state" attribute in the "dialog-info"
element, the document is used to update the table. For each "dialog" element, the document is used to update the table. For each "dialog"
element in the document, the subscriber checks to see whether a row element in the document, the subscriber checks to see whether a row
skipping to change at page 18, line 10 skipping to change at page 18, line 27
<xs:minInclusive value="-1"/> <xs:minInclusive value="-1"/>
</xs:restriction> </xs:restriction>
</xs:simpleContent> </xs:simpleContent>
</xs:complexType> </xs:complexType>
</xs:schema> </xs:schema>
3.4 Example 3.4 Example
For example, if a UAC sends an INVITE that looks like, in part: For example, if a UAC sends an INVITE that looks like, in part:
INVITE sip:callee@foo.com SIP/2.0 INVITE sip:bob@example.com SIP/2.0
From: sip:caller@bar.com;tag=123 Via: SIP/2.0/UDP pc33.example.com;branch=z9hG4bKnashds8
To: sip:callee@foo.com Max-Forwards: 70
Call-ID: 987@1.2.3.4 To: Bob <sip:bob@example.com>
From: Alice <sip:alice@example.com>;tag=1928301774
Call-ID: a84b4c76e66710
CSeq: 314159 INVITE
Contact: <sip:alice@pc33.example.com>
Content-Type: application/sdp
Content-Length: 142
The XML document in a notification might look like: [SDP not shown]
The XML document in a notification from Alice might look like:
<?xml version="1.0"?> <?xml version="1.0"?>
<dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info" <dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info"
version="0" version="0"
state="full" state="full"
entity="sip:caller@bar.com"> entity="sip:alice@example.com">
<dialog id="as7d900as8" call-id="987@1.2.3.4" <dialog id="as7d900as8" call-id="a84b4c76e66710"
local-tag="123" direction="initiator"> local-tag="1928301774" direction="initiator">
<state>trying</state> <state>trying</state>
</dialog> </dialog>
</dialog-info> </dialog-info>
If a 1xx with a tag is received, the XML document in a notification If the following 180 response is received:
might look like:
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP pc33.example.com;branch=z9hG4bKnashds8
To: Bob <sip:bob@example.com>;tag=456887766
From: Alice <sip:alice@example.com>;tag=1928301774
Call-ID: a84b4c76e66710
CSeq: 314159 INVITE
Contact: <sip:bob@host.example.com>
The XML document in a notification might look like:
<?xml version="1.0"?> <?xml version="1.0"?>
<dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info" <dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info"
version="1" version="1"
state="full" state="full"
entity="sip:caller@bar.com"> entity="sip:alice@example.com">
<dialog id="as7d900as8" call-id="987@1.2.3.4" <dialog id="as7d900as8" call-id="a84b4c76e66710"
local-tag="123" remote-tag="456" direction="initiator"> local-tag="1928301774" remote-tag="456887766"
direction="initiator">
<state>early</state> <state>early</state>
</dialog> </dialog>
</dialog-info> </dialog-info>
If it receives a second 1xx, with a different tag, this results in If it receives a second 180 with a different tag:
the creation of a second dialog:
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP pc33.example.com;branch=z9hG4bKnashds8
To: Bob <sip:bob@example.com>;tag=hh76a
From: Alice <sip:alice@example.com>;tag=1928301774
Call-ID: a84b4c76e66710
CSeq: 314159 INVITE
Contact: <sip:jack@host.example.com>
This results in the creation of a second dialog:
<?xml version="1.0"?> <?xml version="1.0"?>
<dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info" <dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info"
version="2" version="2"
state="full" state="full"
entity="sip:caller@bar.com"> entity="sip:alice@example.com">
<dialog id="as7d900as8" call-id="987@1.2.3.4" <dialog id="as7d900as8" call-id="a84b4c76e66710"
local-tag="123" remote-tag="456" direction="initiator"> local-tag="1928301774" remote-tag="456887766"
direction="initiator">
<state>early</state> <state>early</state>
</dialog> </dialog>
<dialog id="as7d900as8" call-id="987@1.2.3.4" <dialog id="as7d900as8" call-id="a84b4c76e66710"
local-tag="123" remote-tag="789" direction="initiator"> local-tag="1928301774" remote-tag="hh76a"
direction="initiator">
<state>early</state> <state>early</state>
</dialog> </dialog>
</dialog-info> </dialog-info>
If a 200 OK is received on the second dialog, it moves to confirmed: If a 200 OK is received on the second dialog, it moves to confirmed:
<?xml version="1.0"?> <?xml version="1.0"?>
<dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info" <dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info"
version="3" version="3"
state="partial" state="partial"
entity="sip:caller@bar.com"> entity="sip:alice@example.com">
<dialog id="as7d900as8" call-id="987@1.2.3.4" <dialog id="as7d900as8" call-id="a84b4c76e66710"
local-tag="123" remote-tag="789" direction="initiator"> local-tag="1928301774" remote-tag="hh76a"
<state event="2xx">confirmed</state> direction="initiator">
<state>confirmed</state>
</dialog> </dialog>
</dialog-info> </dialog-info>
32 seconds later, the other early dialog terminates because no 2xx is 32 seconds later, the other early dialog terminates because no 2xx is
received for it. This implies that it was successfully cancelled, and received for it. This implies that it was successfully cancelled, and
therefore the following notification is sent: therefore the following notification is sent:
<?xml version="1.0"?> <?xml version="1.0"?>
<dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info" <dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info"
version="4" version="4"
state="partial" state="partial"
entity="sip:caller@bar.com"> entity="sip:alice@example.com">
<dialog id="as7d900as8" call-id="987@1.2.3.4" <dialog id="as7d900as8" call-id="a84b4c76e66710"
local-tag="123" remote-tag="456" direction="initiator"> local-tag="1928301774" remote-tag="hh76a"
direction="initiator">
<state event="cancelled">terminated</state> <state event="cancelled">terminated</state>
</dialog> </dialog>
</dialog-info> </dialog-info>
4 Security Considerations 4 Security Considerations
Subscriptions to dialog state can reveal very sensitive information. Subscriptions to dialog state can reveal sensitive information. For
For this reason, this specification recommends authentication and this reason, Section 2.6 discusses authentication and authorization
authorization of subscriptions, and provides guidelines on sensible of subscriptions, and provides guidelines on sensible authorization
authorization policies. policies. All implementations of this package MUST support the digest
authentication mechanism.
Since the data in notifications is sensitive as well, end-to-end SIP Since the data in notifications is sensitive as well, end-to-end SIP
encryption mechanisms using S/MIME MAY be used to protect it. encryption mechanisms using S/MIME MAY be used to protect it.
5 IANA Considerations 5 IANA Considerations
This document registers a new MIME type, application/dialog-info+xml This document registers a new MIME type, application/dialog-info+xml
and registers a new XML namespace. and registers a new XML namespace.
5.1 application/dialog-info+xml MIME Registration 5.1 application/dialog-info+xml MIME Registration
MIME media type name: application MIME media type name: application
MIME subtype name: dialog-info+xml MIME subtype name: dialog-info+xml
Mandatory parameters: none Mandatory parameters: none
Optional parameters: Same as charset parameter application/xml Optional parameters: Same as charset parameter application/xml
as specified in RFC 3023 [7]. as specified in RFC 3023 [8].
Encoding considerations: Same as encoding considerations of Encoding considerations: Same as encoding considerations of
application/xml as specified in RFC 3023 [7]. application/xml as specified in RFC 3023 [8].
Security considerations: See Section 10 of RFC 3023 [7] and Security considerations: See Section 10 of RFC 3023 [8] and
Section 4 of this specification. Section 4 of this specification.
Interoperability considerations: none. Interoperability considerations: none.
Published specification: This document. Published specification: This document.
Applications which use this media type: This document type has Applications which use this media type: This document type has
been used to support SIP applications such as call return been used to support SIP applications such as call return
and auto-conference. and auto-conference.
skipping to change at page 21, line 28 skipping to change at page 22, line 36
Rosenberg, <jdrosen@jdrosen.net> Rosenberg, <jdrosen@jdrosen.net>
Intended usage: COMMON Intended usage: COMMON
Author/Change controller: The IETF. Author/Change controller: The IETF.
5.2 URN Sub-Namespace Registration for urn:ietf:params:xml:ns:dialog- 5.2 URN Sub-Namespace Registration for urn:ietf:params:xml:ns:dialog-
info info
This section registers a new XML namespace, as per the guidelines in This section registers a new XML namespace, as per the guidelines in
[6]. [7].
URI: The URI for this namespace is URI: The URI for this namespace is
urn:ietf:params:xml:ns:dialog-info. urn:ietf:params:xml:ns:dialog-info.
Registrant Contact: IETF, SIMPLE working group, Registrant Contact: IETF, SIMPLE working group,
<simple@mailman.dynamicsoft.com>, Jonathan Rosenberg <simple@ietf.org>, Jonathan Rosenberg
<jdrosen@jdrosen.net>. <jdrosen@jdrosen.net>.
XML: XML:
BEGIN BEGIN
<?xml version="1.0"?> <?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN" <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
"http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd"> "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"> <html xmlns="http://www.w3.org/1999/xhtml">
<head> <head>
skipping to change at page 22, line 31 skipping to change at page 23, line 40
Henning Schulzrinne Henning Schulzrinne
Columbia University Columbia University
M/S 0401 M/S 0401
1214 Amsterdam Ave. 1214 Amsterdam Ave.
New York, NY 10027-7003 New York, NY 10027-7003
email: schulzrinne@cs.columbia.edu email: schulzrinne@cs.columbia.edu
8 Normative References 8 Normative References
[1] A. Roach, "SIP-specific event notification," Internet Draft, [1] A. Roach, "Session initiation protocol SIP specific event
Internet Engineering Task Force, Mar. 2002. Work in progress. notification," RFC 3265, Internet Engineering Task Force, June 2002.
[2] J. Rosenberg, H. Schulzrinne, et al. , "SIP: Session initiation [2] J. Rosenberg, H. Schulzrinne, G. Camarillo, A. Johnston, J.
protocol," Internet Draft, Internet Engineering Task Force, Feb. Peterson, R. Sparks, M. Handley, and E. Schooler, "SIP: Session
2002. Work in progress. initiation protocol," RFC 3261, Internet Engineering Task Force, June
2002.
[3] W. W. W. C. (W3C), "Extensible markup language (xml) 1.0." The [3] J. Rosenberg, "The session initiation protocol SIP update
XML 1.0 spec can be found at http://www.w3.org/TR/1998/REC-xml- method," RFC 3311, Internet Engineering Task Force, Sept. 2002.
19980210.
[4] R. Moats, "URN syntax," RFC 2141, Internet Engineering Task [4] T. Bray, J. Paoli, and C. M. Sperberg-McQueen, "Extensible markup
Force, May 1997. language (XML) 1.0 (second edition)," W3C Recommendation REC-xml-
20001006, World Wide Web Consortium (W3C), Oct. 2000. Available at
http://www.w3.org/XML/.
[5] R. Moats, "A URN namespace for IETF documents," RFC 2648, [5] R. Moats, "URN syntax," Request for Comments 2141, Internet
Internet Engineering Task Force, Aug. 1999. Engineering Task Force, May 1997.
[6] M. Mealling, "The IANA XML registry," Internet Draft, Internet [6] R. Moats, "A URN namespace for IETF documents," Request for
Engineering Task Force, Nov. 2001. Work in progress. Comments 2648, Internet Engineering Task Force, Aug. 1999.
[7] M. Murata, S. S. Laurent, and D. Kohn, "XML media types," RFC [7] M. Mealling, "The IETF XML registry," internet draft, Internet
3023, Internet Engineering Task Force, Jan. 2001. Engineering Task Force, July 2002. Work in progress.
[8] M. Murata, S. S. Laurent, and D. Kohn, "XML media types," Request
for Comments 3023, Internet Engineering Task Force, Jan. 2001.
9 Informative References 9 Informative References
[8] J. Rosenberg, "Session initiation protocol (SIP) extensions for [9] J. Rosenberg, "A presence event package for the session
presence," Internet Draft, Internet Engineering Task Force, May 2002. initiation protocol (SIP)," internet draft, Internet Engineering Task
Work in progress. Force, Jan. 2003. Work in progress.
[9] J. Rosenberg, "A session initiation protocol (SIP)event [10] J. Rosenberg, "A watcher information event template-package for
template-package for watcher information," Internet Draft, Internet the session initiation protocol (SIP)," internet draft, Internet
Engineering Task Force, May 2002. Work in progress. Engineering Task Force, Jan. 2003. Work in progress.
[10] R. Mahy, "A message summary and message waiting indication event [11] R. Mahy, "A message summary and message waiting indication event
package for the session initiation protocol (SIP)," Internet Draft, package for the session initiation protocol (SIP)," internet draft,
Internet Engineering Task Force, June 2002. Work in progress. Internet Engineering Task Force, Nov. 2002. Work in progress.
[11] J. Rosenberg, "The session initiation protocol UPDATE method," Intellectual Property Statement
Internet Draft, Internet Engineering Task Force, May 2002. Work in
progress. The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
Full Copyright Statement Full Copyright Statement
Copyright (c) The Internet Society (2002). All Rights Reserved. Copyright (c) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of Internet organizations, except as needed for the purpose of
 End of changes. 

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