Internet DRAFT - draft-cridland-xmpp-session
draft-cridland-xmpp-session
Network Working Group D. Cridland
Internet-Draft Surevine Limited
Intended status: Standards Track June 10, 2014
Expires: December 12, 2014
Here Lies Extensible Messaging and Presence Protocol (XMPP) Session
Establishment
draft-cridland-xmpp-session-01
Abstract
The Extensible Messaging and Presence Protocol (XMPP) historically
had a Session Establishment request defined in RFC 3921 which clients
were required to perform at the beginning of a session. RFC 6121
dropped this entirely. This specification reinstates it as an
optional no-op to aid backwards compability, matching commonly
deployed workarounds.
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 December 12, 2014.
Copyright Notice
Copyright (c) 2014 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
Cridland Expires December 12, 2014 [Page 1]
Internet-Draft XMPP Session June 2014
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. The Session Establishment Tombstone . . . . . . . . . . . . . 3
2.1. Feature Advertisement . . . . . . . . . . . . . . . . . . 3
2.2. Session Establishment Request . . . . . . . . . . . . . . 4
3. Security Considerations . . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4.1. XML Namespace Name for Session Data . . . . . . . . . . . 4
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
6.1. Normative References . . . . . . . . . . . . . . . . . . 5
6.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
Within this specification, we refer to "Old" clients and servers
meaning those conforming to the [RFC3921] particularly with respect
to its Section 3 (Session Establishment). We refer to "New" clients
and servers meaning those conforming to the newer definition of
Session Establishment within this document.
While [RFC6121] removed Session Establishment entirely from XMPP,
there exist deployed clients which expect the feature to be
advertised, and will refuse to proceed if it is not. Similarly,
where the feature is advertised, clients were advised to use it, as
deployed Old servers may require it.
This has led to a situation where although deprecated by RFC 6121,
the status quo is unchanged.
A number of servers advertise it with a discussed (but not
standardized) <optional/> subelement to the feature, which clients
can use as a hint that they may elide Session Establishment without
penalty.
This document formalizes this and acts as the tombstone for Session
Establishment, deprecating it in a manner where one can see where it
used to be.
Cridland Expires December 12, 2014 [Page 2]
Internet-Draft XMPP Session June 2014
2. The Session Establishment Tombstone
This specification formalizes the <optional/> marker and explicitly
defines the Session Establishment request itself as a no-op.
2.1. Feature Advertisement
Session Establishment SHALL be advertised within the Stream Features
element as an element of local name "session", qualified by the
"urn:ietf:params:xml:ns:xmpp-session" XML namespace. This element
MUST contain a child element within the same namespace with local
name "optional", known as the "<optional/> marker". Clients MAY
ignore such advertisements, and are encouraged to do so.
Advertisement 1: New server
<stream:features>
<session xmlns='urn:ietf:params:xml:ns:xmpp-session'>
<optional/>
</session>
</stream:features>
If a client sees an advertisement which does not contain the
<optional/> marker, however, this indicates an Old server, and it
MUST perform Session Establishment as detailed in the next section.
Also, note that Old Clients will also perform the protocol despite
the existence of the <optional/> marker.
Advertisement 2: Old server
<stream:features>
<session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
</stream:features>
Note the lack of >optional/> marker, meaning the feature is mandatory
to negotiate.
Note that the <optional/> element defined by this specification only
applies to the Session Establishment feature, and only exists within
this namespace. It does not form part of a general mechanism.
Cridland Expires December 12, 2014 [Page 3]
Internet-Draft XMPP Session June 2014
2.2. Session Establishment Request
A Old client connecting to a New server, or a New client against a
Old server, issues a Session Establishment request. This consists of
an IQ stanza of type "set" containing an empty <session/> child
element qualified by the "urn:ietf:params:xml:ns:xmpp-session"
namespace:
Step 1: Client requests session with server:
<iq to='example.com' type='set' id=sess_1'>
<session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
</iq>
A New server MUST treat this as a no-op; that is, it MUST NOT perform
any special processing which has any effect on the session. The only
behaviour allowed and required by this specification is the empty
result:
Step 2: Server informs client of success:
<iq from='example.com' type='result' id='sess_1'/>
Note that this specification does not allow any error to be generated
at this point in response to a syntactically valid request.
It is important to note that there is no value in performing this
request, and New clients are expected to elide the request when the
<optional/> marker is present.
3. Security Considerations
This document defines, in effect, a no-op, and therefore it is
thought not to have any security impact.
4. IANA Considerations
This document supercedes the original definition of the XML namespace
defined in RFC 3921, therefore the IANA is requested to update the
registry as follows:
4.1. XML Namespace Name for Session Data
A URN sub-namespace for session-related data in the Extensible
Messaging and Presence Protocol (XMPP) is defined as follows. (This
Cridland Expires December 12, 2014 [Page 4]
Internet-Draft XMPP Session June 2014
namespace name aheres to the format defined in The IETF XML Registry
[RFC3688].)
URI: urn:ietf:params:xml:ns:xmpp-session
Specification: This document
Description: Here lies the XML namespace name for session-related
data in the Extensible Messaging and Presence Protocol (XMPP),
as defined in "this document".
Registrant Contact: IETF, XMPP Working Group, <xmpp@ietf.org>
5. Acknowledgements
The impetus for documenting this came from Christian Schudt's
proposal to remove XMPP Session support from Openfire, which spawned
a discussion within the XSF about the status quo.
The examples and some of the text were lifted from RFC 3921 by Peter
Saint-Andre. The optional marker itself was proposed during the
revision of RFC 3921 some time ago, and was implemented by Curtis
King and Waqas Hussein amongst others.
Waqas Hussein, Curtis King, Ralph Meijer, Florian Schmaus, Kevin
Smith, and Lance Stout all gave valuable comments both for and
against, helping to shape this document.
6. References
6.1. Normative References
[RFC6121] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Instant Messaging and Presence", RFC
6121, March 2011.
6.2. Informative References
[RFC3921] Saint-Andre, P., Ed., "Extensible Messaging and Presence
Protocol (XMPP): Instant Messaging and Presence", RFC
3921, October 2004.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004.
Author's Address
Cridland Expires December 12, 2014 [Page 5]
Internet-Draft XMPP Session June 2014
Dave Cridland
Surevine Limited
PO Box 1136
Guildford, Surrey GU1 9ND
UK
Email: dave.cridland@surevine.com
Cridland Expires December 12, 2014 [Page 6]
