Internet DRAFT - draft-ietf-stox-7248bis
draft-ietf-stox-7248bis
Network Working Group P. Saint-Andre
Internet-Draft Filament
Obsoletes: 7248 (if approved) April 28, 2016
Intended status: Standards Track
Expires: October 30, 2016
Interworking between the Session Initiation Protocol (SIP) and the
Extensible Messaging and Presence Protocol (XMPP): Presence
draft-ietf-stox-7248bis-08
Abstract
This document defines a bidirectional protocol mapping for the
exchange of presence information between the Session Initiation
Protocol (SIP) and the Extensible Messaging and Presence Protocol
(XMPP). This document obsoletes RFC 7248.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 30, 2016.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
Saint-Andre Expires October 30, 2016 [Page 1]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Intended Audience . . . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Architectural Assumptions . . . . . . . . . . . . . . . . . . 5
5. Presence Authorizations . . . . . . . . . . . . . . . . . . . 5
5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2. XMPP to SIP . . . . . . . . . . . . . . . . . . . . . . . 6
5.2.1. Requesting a Presence Authorization . . . . . . . . . 6
5.2.2. Refreshing a Notification Dialog . . . . . . . . . . 10
5.2.3. Cancelling a Presence Authorization . . . . . . . . . 10
5.3. SIP to XMPP . . . . . . . . . . . . . . . . . . . . . . . 13
5.3.1. Requesting a Presence Authorization . . . . . . . . . 13
5.3.2. Refreshing a Notification Dialog . . . . . . . . . . 17
5.3.3. Cancelling a Presence Authorization . . . . . . . . . 17
6. Notifications of Presence Information . . . . . . . . . . . . 18
6.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 18
6.2. XMPP to SIP . . . . . . . . . . . . . . . . . . . . . . . 19
6.3. SIP to XMPP . . . . . . . . . . . . . . . . . . . . . . . 23
7. Polling for Presence Information . . . . . . . . . . . . . . 25
7.1. XMPP to SIP . . . . . . . . . . . . . . . . . . . . . . . 25
7.2. SIP to XMPP . . . . . . . . . . . . . . . . . . . . . . . 26
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
9. Privacy and Security Considerations . . . . . . . . . . . . . 26
9.1. Amplification Attacks . . . . . . . . . . . . . . . . . . 27
9.2. Presence Leaks . . . . . . . . . . . . . . . . . . . . . 27
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 28
10.1. Normative References . . . . . . . . . . . . . . . . . . 28
10.2. Informative References . . . . . . . . . . . . . . . . . 29
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 29
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 29
1. Introduction
Presence is information about the availability of an entity (such as
network availability or availability for communication). Presence
features in both SIP and XMPP involve several aspects:
o A presence authorization request from a user, which is then
approved (or not) by the contact; the authorization is long-lived
and is often associated with an address list or "buddy list".
Saint-Andre Expires October 30, 2016 [Page 2]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
o A relatively ephemeral presence session, during which the contact
is online (i.e., available for interaction) and after which the
contact is offline again.
o Presence notifications that are sent from the contact to the user
during the contact's presence session.
Although specifications for both SIP and XMPP use the term
"subscription", that term is employed in different ways. In SIP, a
"subscription" is the specfic mechanism whereby a subscriber (or an
entity acting on the subscriber's behalf, such as a server) requests
presence notifications from the contact over a relatively short
period of time, renewed as necessary to keep receiving presence
notifications. By contrast, in XMPP a "subscription" is essentially
shorthand for a long-lived presence authorization. To prevent
confusion, this document uses the term "notification dialog" for SIP
subscriptions and the term "presence authorization" for XMPP
subscriptions.
In order to help ensure interworking between presence systems that
conform to the instant message / presence requirements [RFC2779], it
is important to clearly define protocol mappings between such
systems. Within the IETF, work has proceeded on two presence
technologies:
o Various extensions to the Session Initiation Protocol ([RFC3261])
for presence, in particular [RFC3856]
o The Extensible Messaging and Presence Protocol (XMPP), which
consists of a formalization of the core XML streaming protocols
developed originally by the Jabber open-source community; the
relevant specifications are [RFC6120] for the XML streaming layer
and [RFC6121] for basic presence and instant-messaging extensions
One approach to helping ensure interworking between these protocols
is to map each protocol to the abstract semantics described in
[RFC3860]; however, apparently that approach has never been
implemented. The approach taken in this document is to directly map
semantics from one protocol to another (i.e., from SIP/SIMPLE (SIP
for Instant Messaging and Presence Leveraging Extensions) to XMPP and
vice versa), because that is how existing systems solve the
interworking problem.
The architectural assumptions underlying such direct mappings are
provided in [RFC7247], including mapping of addresses and error
conditions. The mappings specified in this document cover basic
Saint-Andre Expires October 30, 2016 [Page 3]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
presence functionality. Mapping of more advanced functionality
(e.g., so-called "rich presence") is out of scope for this document.
This document obsoletes RFC 7248.
2. Intended Audience
The documents in this series are intended for use by software
developers who have an existing system based on one of these
technologies (e.g., SIP) and would like to enable communication from
that existing system to systems based on the other technology (e.g.,
XMPP). We assume that readers are familiar with the core
specifications for both SIP [RFC3261] and XMPP [RFC6120], with the
base document for this series [RFC7247], and with the following
presence-related specifications:
o "A Presence Event Package for the Session Initiation Protocol"
[RFC3856]
o "Presence Information Data Format (PIDF)" [RFC3863]
o "Extensible Messaging and Presence Protocol (XMPP): Instant
Messaging and Presence" [RFC6121]
o "SIP-Specific Event Notification" [RFC6665]
3. Terminology
A number of terms used here (user, contact, notification, etc.) are
explained in [RFC3261], [RFC3856], [RFC3857], [RFC6120], and
[RFC6121]. This document uses some, but not all, of the presence-
related terms defined in the Model for Presence and Instant Messaging
[RFC2778]. In particular, the term "presence session" is used as
described in [RFC6121] to mean a delimited time period in which an
endpoint is online and available for communications.
In flow diagrams, SIP traffic is shown using arrows such as "***>",
whereas XMPP traffic is shown using arrows such as "...>". As in
[RFC7247], the terms "SIP to XMPP Gateway" and "XMPP to SIP Gateway"
are abbreviated as "S2X GW" and "X2S GW", respectively.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
Saint-Andre Expires October 30, 2016 [Page 4]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
4. Architectural Assumptions
The fundamental architectural assumptions underlying SIP-XMPP
interworking are described in [RFC7247].
Note that, in SIP, there are two ways that presence services can be
deployed on the server side:
1. Under this model, described most fully in [RFC3857], a dedicated
SIP Presence Server handles events related to the presence event
package. Instead of forwarding a SUBSCRIBE message to the SIP
user, the Presence Server would act on the basis of a policy set
by the SIP User Agent using the 'presence.winfo' event package,
for which the SIP user would receive events. The SIP User Agent
would then authorize the subscribing contact through some
interaction with the Presence Server (for instance using XCAP
[RFC4825]). Therefore, presence updates from the SIP User Agent
would not be sent as NOTIFY messages to the XMPP user but as
PUBLISH messages to the Presence Server, which would then
generate NOTIFY messages to all active subscribers.
2. Under this model, a SIP Presence Server acts in proxy mode and
merely passes through the SUBSCRIBE and NOTIFY messages to the
SIP User Agent.
Because the behavior of the XMPP-to-SIP gateway is not changed by the
SIP architectural model that is used, the diagrams and protocol flows
in this document cover both options by labeling the end entity a "SIP
User Agent or Presence Server".
5. Presence Authorizations
5.1. Overview
Both XMPP and presence-aware SIP systems enable entities (often, but
not necessarily, human users) to subscribe to the presence of other
entities. XMPP presence is specified in [RFC6121]. Presence using a
SIP event package is specified in [RFC3856].
As described in [RFC6121], XMPP presence authorizations are managed
using XMPP <presence/> stanzas of type "subscribe", "subscribed",
"unsubscribe", and "unsubscribed". The main states are:
o "none" (neither the user nor the contact is subscribed to the
other's presence information)
o "from" (the contact will receive presence notifications from the
user)
Saint-Andre Expires October 30, 2016 [Page 5]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
o "to" (the contact will send presence notifications to the user)
o "both" (both user and contact will receive each other's presence
notifications)
As described in [RFC3856], SIP notification dialogs and presence
authorizations are managed through the use of SIP SUBSCRIBE events
sent from a SIP User Agent or Presence Server to an intended
recipient who is most generally referenced by a Presence URI of the
form <pres:user@domain> but who might be referenced by a SIP or SIPS
(Session Initiation Protocol Secure) URI of the form
<sip:user@domain> or <sips:user@domain>. In practice, 'pres' URIs
are rarely used, which is why the examples in this document use 'sip'
URIs.
In both SIP and XMPP, presence authorizations are long-lived (indeed
permanent if not explicitly cancelled). In SIP, notification dialogs
are short-lived (the default time-to-live of a SIP notification
dialog is 3600 seconds, as specified in Section 6.4 of [RFC3856], so
that a notification dialog needs to be explicitly refreshed if it
will have the appearance of being permanent or even of lasting as
long as the duration of a presence session). In XMPP, the equivalent
of notification dialogs are automatically generated and handled by
servers.
5.2. XMPP to SIP
5.2.1. Requesting a Presence Authorization
The following diagram illustrates the protocol flow for establishing
a presence authorization from an XMPP user to a SIP contact, as
further explained in the text and examples after the diagram.
XMPP XMPP SIP SIP UA or
Client Server Proxy Presence Server
| + X2S GW | |
| | | |
| (F1) XMPP | | |
| subscribe | | |
|...........>| | |
| | (F2) SIP | |
| | SUBSCRIBE | |
| |***********>| |
| | | (F3) SIP |
| | | SUBSCRIBE |
| | |***********>|
| | | (F4) SIP |
| | | 200 OK |
Saint-Andre Expires October 30, 2016 [Page 6]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
| | |<***********|
| | (F5) SIP | |
| | 200 OK | |
| |<***********| |
| | | (F6) SIP |
| | | NOTIFY |
| | | (pending) |
| | |<***********|
| | (F7) SIP | |
| | NOTIFY | |
| |<***********| |
| | (F8) SIP | |
| | 200 OK | |
| |***********>| |
| | | (F9) SIP |
| | | 200 OK |
| | |***********>|
| | | (F10) SIP |
| | | NOTIFY |
| | | (active) |
| | |<***********|
| | (F11) SIP | |
| | NOTIFY | |
| |<***********| |
| | (F12) SIP | |
| | 200 OK | |
| |***********>| |
| | | (F13) SIP |
| | | 200 OK |
| | |***********>|
| (F14) XMPP | | |
| subscribed | | |
|<...........| | |
| (F15) XMPP | | |
| presence | | |
|<...........| | |
| | | |
An XMPP user (e.g., juliet@example.com) asks for a presence
authorization by sending a request to a SIP contact (e.g.,
romeo@example.net), and the contact either accepts or declines the
request. If the SIP contact accepts the request, the XMPP user will
have a long-lived authorization to receive the SIP contact's presence
information until (1) the XMPP user unsubscribes or (2) the SIP
contact cancels the authorization. The request is encapsulated in a
<presence/> stanza of type "subscribe":
Saint-Andre Expires October 30, 2016 [Page 7]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
Example 1: XMPP User Subscribes to SIP Contact (F1)
| <presence from='juliet@example.com'
| to='romeo@example.net'
| type='subscribe'/>
Upon receiving such a <presence/> stanza, the XMPP server to which
Juliet has connected needs to determine the identity of the
domainpart in the 'to' address, which it does by following the
procedures explained in Section 5 of [RFC7247]. If the domain is a
SIP domain, the XMPP server will hand off the <presence/> stanza to
an associated XMPP-to-SIP gateway or connection manager that natively
communicates with presence-aware SIP proxies.
The XMPP-to-SIP gateway is then responsible for translating the XMPP
request into a SIP SUBSCRIBE request addressed from the XMPP user to
the SIP contact:
Example 2: SIP Transformation of XMPP Presence Authorization Request
(F2)
| SUBSCRIBE sip:romeo@example.net SIP/2.0
| Via: SIP/2.0/TCP x2s.example.com;branch=z9hG4bKna998sk
| From: <sip:juliet@example.com>;tag=j89d
| Call-ID: 5BCF940D-793D-43F8-8972-218F7F4EAA8C
| Event: presence
| Max-Forwards: 70
| CSeq: 1 SUBSCRIBE
| Contact: <sip:juliet@example.com>;gr=yn0cl4bnw0yr3vym
| Accept: application/pidf+xml
| Expires: 3600
| Content-Length: 0
Once the SIP proxy has delivered the SIP SUBSCRIBE to the SIP User
Agent or Presence Server (F3, no example shown), the SIP User Agent
then would send a response indicating acceptance of the request:
Example 3: SIP User Accepts Presence Authorization Request (F4)
| SIP/2.0 200 OK
| Via: SIP/2.0/TCP s2x.example.net;branch=z9hG4bKna998sk
| From: <sip:juliet@example.com>;tag=j89d
| To: <sip:romeo@example.net>;tag=ffd2
| Call-ID: 5BCF940D-793D-43F8-8972-218F7F4EAA8C
| CSeq: 1 SUBSCRIBE
| Contact: <sip:romeo@example.net>;gr=dr4hcr0st3lup4c
| Expires: 3600
| Content-Length: 0
Saint-Andre Expires October 30, 2016 [Page 8]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
In accordance with Section 6.7 of [RFC3856], the XMPP-to-SIP gateway
needs to consider the state to be "neutral" until it receives a
NOTIFY message with a Subscription-State header [RFC6665] whose value
is "active". Therefore, the SIP User Agent or Presence Server SHOULD
immediately send such a NOTIFY message (see Section 6 below). In
case the XMPP-to-SIP gateway initially receives one or more NOTIFY
messages with Subscription-State header whose value is "pending"
(F6), it MUST respond to them on the SIP side but not generate any
presence stanzas towards the XMPP User.
Example 4: SIP User Agent or Presence Server Sends Presence
Notification (F10)
| NOTIFY sip:juliet@example.com SIP/2.0
| Via: SIP/2.0/TCP simple.example.net;branch=z9hG4bKna998sk
| From: <sip:juliet@example.com>;tag=j89d
| To: <sip:romeo@example.net>;tag=ffd2
| Call-ID: 5BCF940D-793D-43F8-8972-218F7F4EAA8C
| Event: presence
| Subscription-State: active;expires=499
| Max-Forwards: 70
| CSeq: 2 NOTIFY
| Content-Type: application/pidf+xml
| Content-Length: 193
|
| <?xml version='1.0' encoding='UTF-8'?>
| <presence xmlns='urn:ietf:params:xml:ns:pidf'
| entity='pres:romeo@example.net'>
| <tuple id='ID-dr4hcr0st3lup4c'>
| <status>
| <basic>open</basic>
| <show xmlns='jabber:client'>away</show>
| </status>
| </tuple>
| </presence>
Upon receiving the first NOTIFY with a state of active, the XMPP-to-
SIP gateway returns a 200 OK to the SIP User Agent or Presence Server
(F12, no example shown).
The XMPP-to-SIP gateway also generates a <presence/> stanza of type
"subscribed":
Example 5: XMPP User Receives Acknowledgement from SIP Contact (F14)
| <presence from='romeo@example.net'
| to='juliet@example.com'
| type='subscribed'/>
Saint-Andre Expires October 30, 2016 [Page 9]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
As described in Section 6, the XMPP-to-SIP gateway also generates a
presence notification addressed to the XMPP user:
Example 6: XMPP User Receives Presence Notification from SIP Contact
(F15)
| <presence from='romeo@example.net/dr4hcr0st3lup4c'
| to='juliet@example.com'/>
5.2.2. Refreshing a Notification Dialog
It is the responsibility of the XMPP-to-SIP gateway to set the value
of the Expires header and to periodically renew the notification
dialog on the SIMPLE side of the gateway. For example, the XMPP-to-
SIP gateway SHOULD send a new SUBSCRIBE request to the SIP contact
whenever the XMPP user initiates a presence session with the XMPP
server by sending initial presence to its XMPP server (this is
functionally equivalent to sending an XMPP presence probe). The
XMPP-to-SIP gateway also SHOULD send a new SUBSCRIBE request to the
SIP contact whenever the SIP notification dialog is scheduled to
expire during the XMPP user's active presence session.
The rules regarding SIP SUBSCRIBE requests for the purpose of
establishing and refreshing a notification dialog are provided in
[RFC6665]. Those rules also apply to XMPP-to-SIP gateways.
Furthermore, an XMPP-to-SIP gateway MUST consider the XMPP presence
authorization to be permanently cancelled (and so inform the XMPP
user) if it receives a SIP response of 403, 489, or 603. By
contrast, it is appropriate to consider a SIP response of 423 or 481
to be a transient error and to honor the long-lived XMPP presence
authorization. [RFC6665] explains more detailed considerations about
the handling of SIP responses in relation to notification dialogs and
refreshes.
Finally, see the security considerations section (Section 9) of this
document for important information and requirements regarding the
security implications of notification refreshes.
5.2.3. Cancelling a Presence Authorization
The following diagram illustrates the protocol flow for cancelling an
XMPP user's presence authorization to a SIP contact, as further
explained in the text and examples after the diagram.
Saint-Andre Expires October 30, 2016 [Page 10]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
XMPP XMPP SIP SIP UA or
Client Server Proxy Presence Server
| + X2S GW | |
| | | |
| (F16) XMPP | | |
|unsubscribe | | |
|...........>| | |
| | (F17) SIP | |
| | SUBSCRIBE | |
| | Expires: 0 | |
| |***********>| |
| | | (F18) SIP |
| | | SUBSCRIBE |
| | | Expires: 0 |
| | |***********>|
| | | (F19) SIP |
| | | 200 OK |
| | |<***********|
| | (F20) SIP | |
| | 200 OK | |
| |<***********| |
| (F21) XMPP | | |
|unsubscribed| | |
|<...........| | |
| | (F22) SIP | |
| | NOTIFY | |
| | terminated | |
| |***********>| |
| | | (F23) SIP |
| | | NOTIFY |
| | | terminated |
| | |***********>|
| | | (F24) SIP |
| | | 200 OK |
| | |<***********|
| | (F25) SIP | |
| | 200 OK | |
| |<***********| |
| | | |
At any time after subscribing, the XMPP user can unsubscribe from the
contact's presence. This is done by sending a <presence/> stanza of
type "unsubscribe":
Saint-Andre Expires October 30, 2016 [Page 11]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
Example 7: XMPP User Unsubscribes from SIP Contact (F16)
| <presence from='juliet@example.com'
| to='romeo@example.net'
| type='unsubscribe'/>
The XMPP-to-SIP gateway is responsible for translating the
unsubscribe command into a SIP SUBSCRIBE request with the Expires
header set to a value of zero:
Example 8: SIP Transformation of XMPP Unsubscribe (F17)
| SUBSCRIBE sip:romeo@example.net SIP/2.0
| Via: SIP/2.0/TCP s2x.example.net;branch=z9hG4bKna998sk
| From: <sip:juliet@example.com>;tag=j89d
| To: <sip:romeo@example.com>;tag=ffd2
| Call-ID: 5BCF940D-793D-43F8-8972-218F7F4EAA8C
| Event: presence
| Max-Forwards: 70
| CSeq: 42 SUBSCRIBE
| Contact: <sip:juliet@example.com>;gr=yn0cl4bnw0yr3vym
| Accept: application/pidf+xml
| Expires: 0
| Content-Length: 0
Upon receiving the SIP 200 OK acknowleding the unsubscribe, the XMPP-
to-SIP gateway SHOULD send a <presence/> stanza of type
"unsubscribed" addressed to the XMPP user:
Example 9: XMPP User Receives Unsubscribed Notification (F21)
| <presence from='romeo@example.net'
| to='juliet@example.com'
| type='unsubscribed'/>
In accordance with Section 4.4.1 of [RFC6665], the XMPP-to-SIP
gateway is then responsible for sending a NOTIFY with a
"Subscription-State" of "terminated" in order to formally end the
presence authorization and the associated SIP dialog.
Saint-Andre Expires October 30, 2016 [Page 12]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
Example 10: XMPP-to-SIP Gateway Sends Presence Notification to
Terminate Authorization (F25)
| NOTIFY sip:juliet@example.com SIP/2.0
| Via: SIP/2.0/TCP simple.example.net;branch=z9hG4bKna998sk
| From: <sip:juliet@example.com>;tag=j89d
| To: <sip:romeo@example.net>;tag=ffd2
| Call-ID: 5BCF940D-793D-43F8-8972-218F7F4EAA8C
| Event: presence
| Subscription-State: terminated
| Max-Forwards: 70
| CSeq: 43 NOTIFY
| Content-Type: application/pidf+xml
| Content-Length: 0
5.3. SIP to XMPP
5.3.1. Requesting a Presence Authorization
The following diagram illustrates the protocol flow for establishing
a presence authorization from a SIP user to an XMPP contact, as
further explained in the text and examples after the diagram.
Saint-Andre Expires October 30, 2016 [Page 13]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
SIP SIP XMPP XMPP
UA Proxy Server Client
| + S2X GW | |
| | | |
| (F26) SIP | | |
| SUBSCRIBE | | |
|**********>| | |
| (F27) SIP | | |
| 200 OK | | |
|<**********| | |
| | (F28) XMPP | |
| | subscribe | |
| |...........>| |
| | | (F29) XMPP|
| | | subscribe |
| | |..........>|
| | | (F30) XMPP|
| | | subscribed|
| | |<..........|
| | (F31) XMPP | |
| | subscribed | |
| |<...........| |
| (F32) SIP | | |
| NOTIFY | | |
| (active) | | |
|<**********| | |
| (F33) SIP | | |
| 200 OK | | |
|**********>| | |
| | | |
A SIP User Agent initiates a presence authorization to a contact's
presence information by sending a SIP SUBSCRIBE request to the
contact. The following is an example of such a request:
Saint-Andre Expires October 30, 2016 [Page 14]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
Example 11: SIP User Subscribes to XMPP Contact (F26)
| SUBSCRIBE sip:juliet@example.com SIP/2.0
| Via: SIP/2.0/TCP s2x.example.net;branch=z9hG4bKna998sk
| From: <sip:romeo@example.net>;tag=xfg9
| To: <sip:juliet@example.net>
| Call-ID: AA5A8BE5-CBB7-42B9-8181-6230012B1E11
| Event: presence
| Max-Forwards: 70
| CSeq: 1 SUBSCRIBE
| Contact: <sip:romeo@example.net>;gr=dr4hcr0st3lup4c
| Accept: application/pidf+xml
| Content-Length: 0
Notice that the Expires header was not included in the SUBSCRIBE
request; this means that the default value of 3600 (i.e., 3600
seconds = 1 hour) applies.
Upon receiving the SUBSCRIBE, the SIP proxy needs to determine the
identity of the domain portion of the Request-URI, which it does by
following the procedures explained in Section 5 of [RFC7247]. If the
domain is an XMPP domain, the SIP proxy will hand off the SUBSCRIBE
to an associated SIP-to-XMPP gateway or connection manager that
natively communicates with XMPP servers.
The SIP-to-XMPP gateway is then responsible for translating the
SUBSCRIBE into an XMPP authorization request addressed from the SIP
user to the XMPP contact:
Example 12: XMPP Transformation of SIP SUBSCRIBE (F28)
| <presence from='romeo@example.net'
| to='juliet@example.com'
| type='subscribe'/>
In accordance with [RFC6121], the XMPP user's server delivers the
presence authorization request to the XMPP user (or, if an
authorization already exists in the XMPP user's roster, the XMPP
server SHOULD auto-reply with a <presence/> stanza of type
'subscribed').
The "happy path" is for the XMPP user to approve the presence
authorization request by generating a <presence/> stanza of type
"subscribed" (F30). The XMPP server then stamps that presence stanza
with the 'from' address of the XMPP contact and sends it to the SIP
user (F31). Upon receiving the stanza, the SIP-to-XMPP gateway
generates an empty SIP NOTIFY message with a Subscription-State
Saint-Andre Expires October 30, 2016 [Page 15]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
header [RFC6665] of "active", which serves to inform the SIP user
that the presence authorization request has been approved (F32).
Example 13: XMPP User Approves Presence Authorization Request (F31)
| <presence from='juliet@example.com'
| to='romeo@example.net'
| type='subscribed'/>
Example 14: Presence Authorization Request Approved (F32)
| NOTIFY sip:romeo@example.net SIP/2.0
| Via: SIP/2.0/TCP s2x.example.net;branch=z9hG4bKna998sk
| From: <sip:romeo@example.net>;tag=xfg9
| To: <sip:juliet@example.com>;tag=ur93
| Call-ID: AA5A8BE5-CBB7-42B9-8181-6230012B1E11
| Event: presence
| Subscription-State: active
| Max-Forwards: 70
| CSeq: 2 NOTIFY
| Content-Length: 0
As an alternative to the "happy path", the XMPP user could decline
the presence authorization request by generating a <presence/> stanza
of type "unsubscribed". The XMPP server would stamp that presence
stanza with the 'from' address of the XMPP contact and would send it
to the SIP user. The SIP-to-XMPP gateway then transforms that stanza
into an empty SIP NOTIFY message with a Subscription-State header
[RFC6665] of "terminated" and a reason of "rejected":
Example 15: XMPP User Rejects Presence Authorization Request
| <presence from='juliet@example.com'
| to='romeo@example.net'
| type='unsubscribed'/>
Example 16: Presence Authorization Request Rejected
| NOTIFY sip:romeo@example.net SIP/2.0
| Via: SIP/2.0/TCP s2x.example.net;branch=z9hG4bKna998sk
| From: <sip:romeo@example.net>;tag=xfg9
| To: <sip:juliet@example.com>;tag=ur93
| Call-ID: AA5A8BE5-CBB7-42B9-8181-6230012B1E11
| Event: presence
| Subscription-State: terminated;reason=rejected
| Max-Forwards: 70
| CSeq: 2 NOTIFY
| Content-Length: 0
Saint-Andre Expires October 30, 2016 [Page 16]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
5.3.2. Refreshing a Notification Dialog
For as long as a SIP user is online and interested in receiving
presence notifications from the XMPP contact, the user's SIP User
Agent is responsible for periodically refreshing the notification
dialog by sending an updated SUBSCRIBE request with an appropriate
value for the Expires header. In response, the presence-aware SIP-
to-XMPP gateway sends a SIP NOTIFY to the user agent (per [RFC6665]);
if the SIP-to-XMPP gateway has meaningful information about the
availability state of the XMPP user (e.g., obtained from the core
presence session in the XMPP server or learned by sending a presence
probe as described under Section 7) then the NOTIFY communicates that
information (e.g., by including a PIDF body [RFC3863] with the
relevant data), whereas if the SIP-to-XMPP gateway does not have
meaningful information about the availability state of the XMPP user
then the NOTIFY MUST be empty as allowed by [RFC6665].
5.3.3. Cancelling a Presence Authorization
At any time, the SIP User Agent can cancel the presence authorization
by sending a SUBSCRIBE message whose Expires header is set to a value
of zero ("0"):
Example 17: SIP User Cancels Presence Authorization
| SUBSCRIBE sip:juliet@example.com SIP/2.0
| Via: SIP/2.0/TCP simple.example.net;branch=z9hG4bKna998sk
| From: <sip:romeo@example.net>;tag=xfg9
| To: <sip:juliet@example.com>;tag=ur93
| Call-ID: AA5A8BE5-CBB7-42B9-8181-6230012B1E11
| Event: presence
| Max-Forwards: 70
| CSeq: 66 SUBSCRIBE
| Contact: <sip:romeo@example.net>;gr=dr4hcr0st3lup4c
| Expires: 0
| Content-Length: 0
A presence-aware SIP-to-XMPP gateway is then responsible for sending
a SIP NOTIFY request to the SIP User Agent containing a PIDF document
specifying that the XMPP contact now has a basic status of "closed",
including a Subscription-State header [RFC6665] of "terminated" with
a reason of "timeout"; and sending an XMPP <presence/> stanza of type
"unavailable" to the XMPP contact
Saint-Andre Expires October 30, 2016 [Page 17]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
6. Notifications of Presence Information
6.1. Overview
Both XMPP and presence-aware SIP systems enable entities (often, but
not necessarily, human users) to send presence notifications to other
entities. At its most basic, the term "presence" refers to
information about an entity's "on/off" availability for communication
on a network. Often, this basic concept is supplemented by
information that further specifies the entity's context or status
while available for communication; these availability states commonly
include "away" and "do not disturb". Some systems and protocols
extend the concepts of presence and availability even further and
refer to any relatively ephemeral information about an entity as a
kind of presence; categories of such "extended presence" include
geographical location (e.g., GPS coordinates), user mood (e.g.,
grumpy), user activity (e.g., walking), and ambient environment
(e.g., noisy). This document focuses on the "least common
denominator" of network availability only, although future documents
might address broader notions of presence, including availability
states and extended presence.
[RFC6121] defines how XMPP <presence/> stanzas can indicate
availability (via absence of a 'type' attribute) or lack of
availability (via a 'type' attribute with a value of "unavailable").
SIP presence using a SIP event package for presence is specified in
[RFC3856].
As described in [RFC6121], XMPP presence information about an entity
is communicated by means of an XML <presence/> stanza sent over an
XML stream. This document assumes that such a <presence/> stanza is
sent from an XMPP client to an XMPP server over an XML stream
negotiated between the client and the server, and that the client is
controlled by a human user. In general, XMPP presence is sent by the
user to the user's server and then broadcast to all entities who are
subscribed to the user's presence information.
As described in [RFC3856], presence information about an entity is
communicated by means of a SIP NOTIFY event sent from a SIP User
Agent to an intended recipient who is most generally referenced by a
Presence URI of the form <pres:user@domain> but who might be
referenced by a SIP or SIPS URI of the form <sip:user@domain> or
<sips:user@domain>.
This document addresses basic presence or network availability only,
not the various extensions to SIP and XMPP for "rich presence" such
as [RFC4480], [XEP-0107], and [XEP-0108].
Saint-Andre Expires October 30, 2016 [Page 18]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
6.2. XMPP to SIP
When Juliet interacts with her XMPP client to modify her presence
information (or when her client automatically updates her presence
information, e.g., via an "auto-away" feature), her client generates
an XMPP <presence/> stanza. The syntax of the <presence/> stanza,
including required and optional elements and attributes, is defined
in [RFC6121]. The following is an example of such a stanza:
Example 18: XMPP User Sends Presence Notification
| <presence from='juliet@example.com/yn0cl4bnw0yr3vym'/>
Upon receiving such a stanza, the XMPP server to which Juliet has
connected broadcasts it to all subscribers who are authorized to
receive presence notifications from Juliet (this is similar to the
SIP NOTIFY method). For each subscriber, broadcasting the presence
notification involves adding the 'to' address of the subscriber and
then either delivering the notification to a local recipient (if the
hostname in the subscriber's address matches one of the hostnames
serviced by the XMPP server) or attempting to route it to the foreign
domain that services the hostname in the subscriber's address. If
the notification is bound for an address at a foreign domain, the
XMPP server needs to determine the identity of the domainpart in the
'to' address, which it does by following the procedures discussed in
[RFC7247]. If the domain is a SIP domain, the XMPP server will hand
off the <presence/> stanza to an associated XMPP-to-SIP gateway or
connection manager that natively communicates with presence-aware SIP
proxy (no example shown).
The XMPP-to-SIP gateway is then responsible for translating the XMPP
<presence/> stanza into a SIP NOTIFY request and included PIDF
document from the XMPP user to the SIP contact.
Saint-Andre Expires October 30, 2016 [Page 19]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
Example 19: SIP Transformation of XMPP Presence Notification
| NOTIFY sip:juliet@example.com SIP/2.0
| Via: SIP/2.0/TCP x2s.example.com;branch=z9hG4bKna998sk
| From: <sip:juliet@example.com>;tag=gh19
| To: <sip:romeo@example.net>
| Contact: <sip:juliet@example.com>;gr=yn0cl4bnw0yr3vym
| Call-ID: 2B44E147-3B53-45E4-9D48-C051F3216D14
| Event: presence
| Subscription-State: active;expires=599
| Max-Forwards: 70
| CSeq: 2 NOTIFY
| Content-Type: application/pidf+xml
| Content-Length: 192
|
| <?xml version='1.0' encoding='UTF-8'?>
| <presence xmlns='urn:ietf:params:xml:ns:pidf'
| entity='pres:juliet@example.com'>
| <tuple id='ID-yn0cl4bnw0yr3vym'>
| <status>
| <basic>open</basic>
| <show xmlns='jabber:client'>away</show>
| </status>
| </tuple>
| </presence>
The mapping of XMPP syntax elements to SIP syntax elements MUST be as
shown in the following table. (Mappings for elements not mentioned
are undefined.)
Saint-Andre Expires October 30, 2016 [Page 20]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
+-----------------------------+---------------------------+
| XMPP Element or Attribute | SIP Header or PIDF Data |
+-----------------------------+---------------------------+
| <presence/> stanza | "Event: presence" (1) |
+-----------------------------+---------------------------+
| XMPP resource identifier | tuple 'id' attribute (2) |
+-----------------------------+---------------------------+
| from | From |
+-----------------------------+---------------------------+
| id | no mapping (3) |
+-----------------------------+---------------------------+
| to | To |
+-----------------------------+---------------------------+
| type | basic status (4) (5) |
+-----------------------------+---------------------------+
| xml:lang | Content-Language |
+-----------------------------+---------------------------+
| <priority/> | priority for tuple (6) |
+-----------------------------+---------------------------+
| <show/> | no mapping (7) |
+-----------------------------+---------------------------+
| <status/> | <note/> |
+-----------------------------+---------------------------+
Table 1: Presence Syntax Mapping from XMPP to SIP
Note the following regarding these mappings:
1. Only an XMPP <presence/> stanza that lacks a 'type' attribute or
whose 'type' attribute has a value of "unavailable" MUST be
mapped by an XMPP-to-SIP gateway to a SIP NOTIFY request, because
those are the only <presence/> stanzas that represent
notifications.
2. The PIDF schema defines the tuple 'id' attribute as having a
datatype of "xs:ID"; because this datatype is more restrictive
than the "xs:string" datatype for XMPP resourceparts (in
particular, a number is not allowed as the first character of an
ID), it is RECOMMENDED to prepend the resourcepart with "ID-" or
some other alphabetic string when mapping from XMPP to SIP.
3. In practice, XMPP <presence/> stanzas often do not include the
'id' attribute.
4. Because the lack of a 'type' attribute indicates that an XMPP
entity is available for communications, the XMPP-to-SIP gateway
MUST map that information to a PIDF basic status of "open".
Because a 'type' attribute with a value of "unavailable"
Saint-Andre Expires October 30, 2016 [Page 21]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
indicates that an XMPP entity is not available communications,
the XMPP-to-SIP gateway MUST map that information to a PIDF
<basic/> status of "closed".
5. When the XMPP-to-SIP gateway receives XMPP presence of type
"unavailable" from the XMPP contact, it sends a SIP NOTIFY
request from the XMPP contact to the SIP User Agent containing a
PIDF document specifying that the XMPP contact now has a basic
status of "closed".
6. The value of the XMPP <priority/> element is an integer between
-128 and +127, whereas the value of the PIDF <contact/> element's
'priority' attribute is a decimal number from zero to one
inclusive, with a maximum of three decimal places. If the value
of the XMPP <priority/> element is negative, an XMPP-to-SIP
gateway MUST NOT map the value. If an XMPP-to-SIP gateway maps
positive values, it SHOULD treat XMPP priority 0 as PIDF priority
0 and XMPP priority 127 as PIDF priority 1, mapping intermediate
values appropriately so that they are unique (e.g., XMPP priority
1 to PIDF priority 0.007, XMPP priority 2 to PIDF priority 0.015,
and so on up through mapping XMPP priority 126 to PIDF priority
0.992; note that this is an example only and that the exact
mapping is up to the implementation).
7. Some implementations support custom extensions to encapsulate
detailed information about availability; however, there is no
need to standardize a PIDF extension for this purpose, because
PIDF is already extensible and thus the <show/> element
(qualified by the 'jabber:client' namespace) can be included
directly in the PIDF XML. The examples in this document
illustrate this usage, which is RECOMMENDED. The most useful
values are likely "away" and "dnd", although note that the latter
value merely means "busy" and does not imply that a server or
client ought to block incoming traffic while the user is in that
state. Naturally, an XMPP-to-SIP gateway can choose to translate
a custom extension into an established value of the <show/>
element [RFC6121] or translate a <show/> element into a custom
extension that the XMPP-to-SIP gateway knows is supported by the
user agent of the intended recipient. Unfortunately, this
behavior does not guarantee that information will not be lost; to
help prevent information loss, an XMPP-to-SIP gateway ought to
include both the <show/> element and the custom extension if it
cannot suitably translate the custom value into a <show/> value.
However, there is no guarantee that the SIP receiver will render
a standard XMPP <show/> value or custom extension.
In XMPP, a user can connect with multiple devices at the same time
[RFC6120]; for presence notification purposes [RFC6121], each device
Saint-Andre Expires October 30, 2016 [Page 22]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
is associated with a distinct resourcepart [RFC7622] and a contact's
user agent will receive a separate presence notification from each of
the user's devices. Although the interpretation of multiple presence
notifications from a single user is a matter of implementation by the
contact's user agent, typically the user agent will show the "most
available" status for the contact (e.g., if the user is online with
three devices, one of which is away, one of which is in do not
disturb mode, and one of which is available with no qualifications,
then the status shown will simply be available. In SIP, it is
reasonable for a user agent to model multiple presence notifications
from an XMPP user in the same way that it would handle multiple
tuples from a SIP user.
6.3. SIP to XMPP
When Romeo changes his presence, his SIP User Agent generates a SIP
NOTIFY request for any active subscription authorizations. The
syntax of the NOTIFY request is defined in [RFC3856]. The following
is an example of such a request:
Example 20: SIP User Sends Presence Notification
| NOTIFY sip:romeo@example.net SIP/2.0
| Via: SIP/2.0/TCP simple.example.net;branch=z9hG4bKna998sk
| From: <sip:romeo@example.net>;tag=yt66
| To: <sip:juliet@example.com>;tag=bi54
| Contact: <sip:romeo@example.net>;gr=dr4hcr0st3lup4c
| Call-ID: C33C6C9D-0F4A-42F9-B95C-7CE86B526B5B
| Event: presence
| Subscription-State: active;expires=499
| Max-Forwards: 70
| CSeq: 8 NOTIFY
| Content-Type: application/pidf+xml
| Content-Length: 193
|
| <?xml version='1.0' encoding='UTF-8'?>
| <presence xmlns='urn:ietf:params:xml:ns:pidf'
| entity='pres:romeo@example.net'>
| <tuple id='ID-dr4hcr0st3lup4c'>
| <status>
| <basic>closed</basic>
| </status>
| </tuple>
| </presence>
Upon receiving the NOTIFY, the SIP proxy needs to determine the
identity of the domain portion of the Request-URI, which it does by
following the procedures discussed in [RFC7247]. If the domain is an
Saint-Andre Expires October 30, 2016 [Page 23]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
XMPP domain, the SIP proxy will hand off the NOTIFY to an associated
SIP-to-XMPP gateway or connection manager that natively communicates
with XMPP servers.
The SIP-to-XMPP gateway is then responsible for translating the
NOTIFY into an XMPP <presence/> stanza addressed from the SIP user to
the XMPP contact:
Example 21: XMPP Transformation of SIP Presence Notification
| <presence from='romeo@example.net'
| to='juliet@example.com/yn0cl4bnw0yr3vym'
| type='unavailable'/>
The mapping of SIP syntax elements to XMPP syntax elements MUST be as
shown in the following table. (Mappings for elements not mentioned
are undefined.)
+---------------------------+-----------------------------+
| SIP Header or PIDF Data | XMPP Element or Attribute |
+---------------------------+-----------------------------+
| basic status | type (1) |
+---------------------------+-----------------------------+
| Content-Language | xml:lang |
+---------------------------+-----------------------------+
| From | from |
+---------------------------+-----------------------------+
| priority for tuple | <priority/> (2) |
+---------------------------+-----------------------------+
| To | to |
+---------------------------+-----------------------------+
| <note/> | <status/> |
+---------------------------+-----------------------------+
| <show/> | <show/> (3) |
+---------------------------+-----------------------------+
Table 2: Presence Syntax Mapping from SIP to XMPP
Note the following regarding these mappings:
1. A PIDF basic status of "open" MUST be mapped to no 'type'
attribute, and a PIDF basic status of "closed" MUST be mapped to
a 'type' attribute whose value is "unavailable".
2. See the notes following Table 1 of this document regarding
mapping of presence priority.
Saint-Andre Expires October 30, 2016 [Page 24]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
3. If a SIP implementation supports the <show/> element (qualified
by the 'jabber:client' namespace) as a PIDF extension for
availability status as described in the notes following Table 1
of this document, the SIP-to-XMPP gateway is responsible for
including that element in the XMPP presence notification.
7. Polling for Presence Information
Both SIP and XMPP provide methods for explicitly requesting one-time
information about the current presence status of another entity.
These are "polling" methods as opposed to the subscribing methods
described in the rest of this document.
7.1. XMPP to SIP
In XMPP, an explicit request for information about current presence
status is completed by sending a <presence/> stanza of type "probe":
Example 22: XMPP Server Sends Presence Probe on Behalf of XMPP User
| <presence from='juliet@example.com/chamber'
| to='romeo@example.net'
| type='probe'/>
Note: As described in [RFC6121], presence probes are used by XMPP
servers to request presence on behalf of XMPP users; XMPP clients are
discouraged from sending presence probes, because retrieving presence
is a service that servers provide.
A SIP-to-XMPP gateway would transform the presence probe into its SIP
equivalent, which is a SUBSCRIBE request with an Expires header value
of zero:
Example 23: SIP Transformation of XMPP Presence Probe
| SUBSCRIBE sip:romeo@example.net SIP/2.0
| Via: SIP/2.0/TCP x2s.example.com;branch=z9hG4bKna998sk
| From: <sip:juliet@example.com>;tag=j89d
| Call-ID: 5BCF940D-793D-43F8-8972-218F7F4EAA8C
| Event: presence
| Max-Forwards: 70
| CSeq: 1 SUBSCRIBE
| Contact: <sip:juliet@example.com>;gr=yn0cl4bnw0yr3vym
| Accept: application/pidf+xml
| Expires: 0
| Content-Length: 0
Saint-Andre Expires October 30, 2016 [Page 25]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
As described in [RFC3856], this cancels any notification dialog but
causes a NOTIFY to be sent to the subscriber, just as a presence
probe does (the transformation rules for presence notifications have
been previously described in Section 6.2 of this document).
7.2. SIP to XMPP
In SIP, an explicit request for information about current presence
status is effectively completed by sending a SUBSCRIBE with an
Expires header value of zero:
Example 24: SIP User Sends Presence Request
| SUBSCRIBE sip:juliet@example.com SIP/2.0
| Via: SIP/2.0/TCP simple.example.net;branch=z9hG4bKna998sk
| From: <sip:romeo@example.net>;tag=yt66
| Call-ID: 717B1B84-F080-4F12-9F44-0EC1ADE767B9
| Event: presence
| Max-Forwards: 70
| CSeq: 1 SUBSCRIBE
| Contact: <sip:romeo@example.net>;gr=dr4hcr0st3lup4c
| Expires: 0
| Content-Length: 0
A presence-aware SIP-to-XMPP gateway translates such a SIP request
into a <presence/> stanza of type "probe" if it does not already have
presence information about the contact:
Example 25: XMPP Transformation of SIP Presence Request
| <presence from='romeo@example.net'
| to='juliet@example.com'
| type='probe'/>
8. IANA Considerations
This document makes no requests of IANA.
9. Privacy and Security Considerations
Detailed privacy and security considerations for presence protocols
are given in [RFC2779], for SIP-based presence in [RFC3856] (see also
[RFC3261]), and for XMPP-based presence in [RFC6121] (see also
[RFC6120]).
Saint-Andre Expires October 30, 2016 [Page 26]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
9.1. Amplification Attacks
There exists the possibility of an amplification attack launched from
the XMPP network against a SIP presence server, because each long-
lived XMPP presence authorization would typically result in multiple
notification dialog refreshes on the SIP side of an XMPP-to-SIP
gateway. Therefore, access to an XMPP-to-SIP gateway SHOULD be
restricted in various ways; for example:
o Only an XMPP service that carefully controls account provisioning
and provides effective methods for the administrators to control
the behavior of registered users ought to host an XMPP-to-SIP
gateway (e.g., not a service that offers open account
registration).
o An XMPP-to-SIP gateway ought to be associated only with a single
domain or trust realm. For example, an XMPP-to-SIP gateway hosted
at simple.example.com ought to allow only users within the
example.com domain to access the XMPP-to-SIP gateway, not users
within example.org, example.net, or any other domain (unless they
are part of the same multi-tenanted environment as example.com).
This helps to prevent the gateway equivalent of open relays that
are shared across XMPP domains from different trust realms.
If a SIP presence server receives communications through an XMPP-to-
SIP gateway from users who are not associated with a domain that is
so related to the hostname of the XMPP-to-SIP gateway, it SHOULD
(based on local service provisioning) refuse to service such users or
refuse to receive traffic from the XMPP-to-SIP gateway. As a further
check, whenever an XMPP-to-SIP gateway seeks to refresh an XMPP
user's long-lived authorization to a SIP user's presence, it first
sends an XMPP <presence/> stanza of type "probe" from the address of
the XMPP-to-SIP gateway to the "bare JID" (user@domain.tld) of the
XMPP user, to which the user's XMPP server responds in accordance
with [RFC6121]; this puts an equal burden on the XMPP server and the
SIP proxy.
9.2. Presence Leaks
Presence notifications can contain sensitive information (e.g., about
network availability). In addition, it is possible in both SIP and
XMPP for an entity to send different presence notifications to
different subscribers. Therefore, a gateway MUST honor data about
the intended recipient of a presence notification (as represented by
the 'to' address for XMPP and by the Request-URI for SIP) and it MUST
NOT route or deliver a presence notification to any other entities,
because it does not possess information about authorization to
Saint-Andre Expires October 30, 2016 [Page 27]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
receive presence notifications for such entities - that information
resides at the user's home service, not at the receiving gateway).
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3261] 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.
[RFC3856] Rosenberg, J., "A Presence Event Package for the Session
Initiation Protocol (SIP)", RFC 3856, August 2004.
[RFC3857] Rosenberg, J., "A Watcher Information Event Template-
Package for the Session Initiation Protocol (SIP)", RFC
3857, August 2004.
[RFC3863] Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr,
W., and J. Peterson, "Presence Information Data Format
(PIDF)", RFC 3863, August 2004.
[RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 6120, March 2011.
[RFC6121] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Instant Messaging and Presence", RFC
6121, March 2011.
[RFC6665] Roach, A., "SIP-Specific Event Notification", RFC 6665,
July 2012.
[RFC7247] Saint-Andre, P., Houri, A., and J. Hildebrand,
"Interworking between the Session Initiation Protocol
(SIP) and the Extensible Messaging and Presence Protocol
(XMPP): Architecture, Addresses, and Error Handling", RFC
7247, May 2014.
[RFC7622] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Address Format", RFC 7622, DOI 10.17487/
RFC7622, September 2015,
<http://www.rfc-editor.org/info/rfc7622>.
Saint-Andre Expires October 30, 2016 [Page 28]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
10.2. Informative References
[RFC2778] Day, M., Rosenberg, J., and H. Sugano, "A Model for
Presence and Instant Messaging", RFC 2778, February 2000.
[RFC2779] Day, M., Aggarwal, S., and J. Vincent, "Instant Messaging
/ Presence Protocol Requirements", RFC 2779, February
2000.
[RFC3860] Peterson, J., "Common Profile for Instant Messaging
(CPIM)", RFC 3860, August 2004.
[RFC4480] Schulzrinne, H., Gurbani, V., Kyzivat, P., and J.
Rosenberg, "RPID: Rich Presence Extensions to the Presence
Information Data Format (PIDF)", RFC 4480, July 2006.
[RFC4825] Rosenberg, J., "The Extensible Markup Language (XML)
Configuration Access Protocol (XCAP)", RFC 4825, May 2007.
[XEP-0107]
Saint-Andre, P. and R. Meijer, "User Mood", XSF XEP 0107,
October 2008, <http://xmpp.org/extensions/xep-0107.html>.
[XEP-0108]
Meijer, R. and P. Saint-Andre, "User Activity", XSF XEP
0108, October 2008,
<http://xmpp.org/extensions/xep-0108.html>.
Appendix A. Acknowledgements
Thanks to the authors, contributors, and other individuals
acknowledged in RFC 7248.
Thanks to Saul Ibarra Corretge and Markus Isomaki for their reviews
during working group consideration.
Special thanks to Ben Campbell for identifying the underlying
discrepancy that resulted in the need to obsolete RFC 7248.
Thanks also to Markus Isomaki and Yana Stamcheva as the working group
chairs and Alissa Cooper as the sponsoring Area Director.
Author's Address
Saint-Andre Expires October 30, 2016 [Page 29]
Internet-Draft SIP-XMPP Interworking: Presence April 2016
Peter Saint-Andre
Filament
Email: peter@filament.com
URI: https://filament.com/
Saint-Andre Expires October 30, 2016 [Page 30]
