This JEP defines protocol for publishing the availability of a particular Stream Initiation request, such as a file.
NOTICE: This JEP is currently within Last Call or under consideration by the Jabber Council for advancement to the next stage in the JSF standards process. For further details, visit <http://www.jabber.org/council/queue.shtml>.
Status: Proposed
Type: Standards Track
Number: 0137
Version: 0.3
Last Updated: 2005-07-21
JIG: Standards JIG
Approving Body: Jabber Council
Dependencies: XMPP Core, JEP-0030, JEP-0095
Supersedes: None
Superseded By: None
Short Name: sipub
Email: linuxwolf@outer-planes.net
JID: linuxwolf@outer-planes.net
Email: temas@jabber.org
JID: temas@jabber.org
This Jabber Enhancement Proposal is copyright 1999 - 2005 by the Jabber Software Foundation (JSF) and is in full conformance with the JSF's Intellectual Property Rights Policy <http://www.jabber.org/jsf/ipr-policy.shtml>. This material may be distributed only subject to the terms and conditions set forth in the Open Publication License, v1.0 or later (the latest version is presently available at <http://www.opencontent.org/openpub/>).
The preferred venue for discussion of this document is the Standards-JIG discussion list: <http://mail.jabber.org/mailman/listinfo/standards-jig>.
The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 3920) and XMPP IM (RFC 3921) specifications contributed by the Jabber Software Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this JEP has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.
The keywords "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 RFC 2119.
Stream Initiation [1] defines a protocol to initiate a data stream between two Jabber/XMPP entities (e.g., for the purpose of File Transfer [2]). However, the sender is still responsible for informing potential receivers about the existence of a given stream. This JEP provides an automated way for a sender to announce the availability of a stream without initiating the data transfer. The purpose is to provide a "pull" protocol that enables a receiver to then request initiation of the stream from the sender.
This proposal addresses the following requirements:
A stream owner uses the <sipub/> element to announce that it can perform a specific SI request. This element can be sent to a publish-subscribe (JEP-0060) node, or sent directly to potential recipients within a <message/> stanza.
The format of the <sipub/> element is as follows:
Example 1. Sample <sipub/>
<sipub xmlns='http://jabber.org/protocol/sipub'
from='sender-jid'
id='publish-0123'
profile='si-profile'
mime-type='mime/type'>
<profile xmlns='si-profile' ...>...</profile>
</sipub>
This format is nearly identical to that for the stream initiation <si/> element (see JEP-0095). The major difference is the lack of the feature negotiation for the stream methods, and the addition of a 'from' attribute.
The 'from' attribute SHOULD be present, and MUST be present if the stanza containing the <sipub/> is not from the stream owner (e.g., if the stream is advertised at a publish-subscribe node). If present, this attribute MUST be the valid JID for the stream owner.
The 'id' attribute is an opaque identifier. This attribute MUST be present, and MUST be a valid non-empty string. It uniquely identifies the published request at the potential sender.
As with stream initiation, the 'profile' attribute MUST be present, and MUST be the namespace URI governing the profile information. It identifies the format for the SI profile.
As with stream initiation, the 'mime-type' attribute SHOULD be present, and MUST be an IANA-registered content type. [5] It provides the receiver with additional information about what the data stream will be.
The <sipub/> element MUST contain an element qualified by the namespace specified by the 'profile' attribute (e.g., <file xmlns='http://jabber.org/protocol/si/profile/file-transfer'/> for file transfer). This is the additional information about the data stream.
The <sipub/> information is typically provided via pubsub:
Example 2. Sender advertises stream via publish-subscribe
<iq from='bard@shakespeare.lit/globe'
to='pubsub.shakespeare.lit'
id='ps1'>
<pubsub xmlns='http://jabber.org/protocol/pubsub'>
<publish node='characters'>
<sipub xmlns='http://jabber.org/protocol/si-pub'
from='bard@shakespeare.lit'
id='publish-0123'
mime-type='text/plain'
profile='http://jabber.org/protocol/si/profile/file-transfer'>
<file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
name='NDA.pdf'
size='138819'
date='2004-01-28T10:07Z'>
<desc>All Shakespearean characters must sign and return this NDA ASAP</desc>
</file>
</sipub>
</publish>
</pubsub>
</iq>
Example 3. Pubsub service pushes announcement to all subscribers
<message from='pubsub.shakespeare.lit' to='juliet@capulet.com/balcony'>
<event xmlns='http://jabber.org/protocol/pubsub#event'>
<items node='characters'>
<item id='current'>
<sipub xmlns='http://jabber.org/protocol/si-pub'
from='bard@shakespeare.lit'
id='publish-0123'
mime-type='text/plain'
profile='http://jabber.org/protocol/si/profile/file-transfer'>
<file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
name='NDA'
size='1024'
date='2004-01-28T10:07Z'>
<desc>All Shakespearean characters must sign and return this NDA ASAP</desc>
</file>
</sipub>
</item>
</items>
</event>
</message>
The <sipub/> element MAY also be included directly within a <message/> stanza sent to another entity (or multiple entities, e.g., in Multi-User Chat [6] or via Extended Stanza Addressing [7]). This can be especially useful for informing an offline entity about an available stream.
Example 4. Advertising a stream in a message stanza
<message from='romeo@montague.net/pda' to='juliet@capulet.com'>
<sipub xmlns='http://jabber.org/protocol/si-pub'
id='publish-0123'
mime-type='text/plain'
profile='http://jabber.org/protocol/si/profile/file-transfer'>
<file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
name='missive.html'
size='1024'
date='2005-07-21T11:21Z'>
<desc>All Shakespearean characters must sign and return this NDA ASAP</desc>
</file>
</sipub>
</message>
One of the goals of sipub is to integrate Stream Initiation with Data Forms to provide a "file upload" capability. This is accomplished via the datatypes specified in Data Forms Validation [8]. Each datatype is specific to the profile desired.
For example the datatype "sipub:file-transfer" is used to identify the file upload field(s) corresponding to JEP-0096:
Example 5. "Upload File" Data Forms Field
<field var='file' type='text-single' label='File to Upload'>
<validate xmlns='http://jabber.org/protocol/xdata-validate'
datatype='sipub:file-transfer'/>
</field>
When submitting such a form, a field's value(s) MUST be the <sipub/> identifier(s). Also, the submitter MUST provide an <sipub/> element within the data form for each file to be uploaded:
Example 6. Submitting an "Upload File" form
<x xmlns='jabber:x:data' type='submit'>
<field var='file'>
<value>publish-0123</value>
</field>
<sipub xmlns='http://jabber.org/protocol/sipub'
id='publish-0123'
mime-type='text/plain'
profile='http://jabber.org/protocol/si/profile/file-transfer'>
<file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
name='missive.html'
size='1024'
date='2005-07-21T11:21Z'/>
</sipub>
</x>
The form processor will use this to retrieve the file(s) to be uploaded.
A potential receiver starts the stream initiation session by sending an IQ-get to the sender, using the <start xmlns='http://jabber.org/protocol/sipub'/> element. This element contains the 'id' attribute to specify which published stream to retrieve:
Example 7. Receiver requests start of stream
<iq type='get'
id='sipub-request-0'
from='juliet@capulet.com/balcony'
to='romeo@montague.net/pda'>
<start xmlns='http://jabber.org/protocol/sipub'
id='publish-0123'/>
</iq>
If the sender accepts the request, it responds with an IQ-result containing a <starting/> element. This element indicates the stream initiation identifier to be used:
Example 8. Sender accepts request to start stream
<iq type='result'
id='sipub-request-0'
from='romeo@montague.net/pda'
to='juliet@capulet.com/balcony'>
<starting xmlns='http://jabber.org/protocol/sipub'
sid='session-87651234'/>
</iq>
Then the sender begins the stream initiation negotiation:
Example 9. Sender starts negotiation
<iq type='set'
id='sipub-set-1'
from='romeo@montague.net/pda'
to='juliet@capulet.com/balcony'>
<si xmlns='http://jabber.org/protocol/si'
id='session-87651234'
mime-type='text/plain'
profile='http://jabber.org/protocol/si/profile/file-transfer'>
<file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
name='missive.html'
size='1024'
date='2005-07-21T11:21Z'>
<desc>A love letter</desc>
</file>
</si>
</iq>
If the requested identifier is not valid, the sender SHOULD respond with a <not-acceptable/> error:
Example 10. Sender denies because of invalid id
<iq type='error'
id='sipub-set-1'
from='romeo@montague.net/pda'
to='juliet@capulet.com/balcony'>
<start xmlns='http://jabber.org/protocol/sipub'>publish-0123</start>
<error code='405' type='modify'>
<not-acceptable xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
If the receiver does not have permission to request the data stream, the sender SHOULD respond with a <forbidden/> error:
Example 11. Sender denies because receiver is forbidden
<iq type='error'
id='sipub-set-1'
from='romeo@montague.net/pda'
to='juliet@capulet.com/balcony'>
<start xmlns='http://jabber.org/protocol/sipub'>publish-0123</start>
<error code='403' type='auth'>
<forbidden xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
When publishing a stream via the <sipub/> element, the identifier SHOULD NOT be used as-is for the <si/> element, since a single publication will likely result in multiple <si/> requests, possibly from the same receiver.
This JEP introduces no security concerns beyond those specified in JEP-0060 and the relevant Stream Initiation profile in use.
This JEP requires no interaction with the Internet Assigned Numbers Authority (IANA) [9].
The Jabber Registrar [10] shall include 'http://jabber.org/protocol/sipub' in its registry of protocol namespaces.
The Jabber Registrar shall include 'sipub:' in its registry of Data Forms Validation Datatype Prefixes.
Normally, each SI profile that wishes to be considered for use with Data Forms MUST register its own datatype qualified by the "sipub:" prefix. However, this JEP provides an initial seed, based on the currently accepted SI profiles. The following datatypes shall be registered for use with Data Forms Validation:
Data Forms Validation Datatypes Registry Submission
<datatype>
<name>sipub:file-transfer</name>
<desc>Datatype for publishing an SI using the File Transfer Profile</desc>
<doc>JEP-0096</doc>
</datatype>
<?xml version='1.0' encoding='UTF-8'?>
<xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='http://jabber.org/protocol/sipub'
xmlns='http://jabber.org/protocol/sipub'
elementFormDefault='qualified'>
<xs:element name='sipub'>
<xs:annotation>
<xs:documentation>This is the root content element for advertising a stream.</xs:documentation>
</xs:annotation>
<xs:complexType>
<xs:choice>
<xs:any namespace='##other' minOccurs='1'/>
</xs:choice>
<xs:attribute name='id' type='xs:string' use='required'/>
<xs:attribute name='from' type='xs:string' use='optional'/>
<xs:attribute name='mime-type' type='xs:string' use='optional'/>
<xs:attribute name='profile' type='xs:string' use='optional'/>
</xs:complexType>
</xs:element>
<xs:element name='start'>
<xs:annotation>
<xs:documentation>This is the element for requesting retrieval of a stream.</xs:documentation>
</xs:annotation>
<xs:complexType>
<xs:attribute name='id' type='xs:string' use='required'/>
</xs:complexType>
</xs:element>
<xs:element name='starting'>
<xs:annotation>
<xs:documentation>This is the element for specifying the stream to be retrieved.</xs:documentation>
</xs:annotation>
<xs:complexType>
<xs:attribute name='sid' type='xs:string' use='required'/>
</xs:complexType>
</xs:element>
</xs:schema>
1. JEP-0095: Stream Initiation <http://www.jabber.org/jeps/jep-0095.html>.
2. JEP-0096: File Transfer <http://www.jabber.org/jeps/jep-0096.html>.
3. JEP-0060: Publish-Subscribe <http://www.jabber.org/jeps/jep-0060.html>.
4. JEP-0004: Data Forms <http://www.jabber.org/jeps/jep-0004.html>.
5. The IANA registry of content types is located at <http://www.iana.org/assignments/media-types/>.
6. JEP-0045: Multi-User Chat <http://www.jabber.org/jeps/jep-0045.html>.
7. JEP-0033: Extended Stanza Addressing <http://www.jabber.org/jeps/jep-0033.html>.
8. JEP-0122: Data Forms Validation <http://www.jabber.org/jeps/jep-0122.html>.
9. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.
10. The Jabber Registrar maintains a list of reserved Jabber protocol namespaces as well as registries of parameters used in the context of protocols approved by the Jabber Software Foundation. For further information, see <http://www.jabber.org/registrar/>.
END