WebSphere brand IBM WebSphere XML Document Management Server, Version 7.0

Subscribe and notify

The XCAP component provides a SIP SUBSCRIBE and NOTIFY interface into IBM® WebSphere® XML Document Management Server Component. The interface is used to provide subscribers notification when a group definition is modified in an XCAP document which they own, or have sufficient rights to view or modify.

Overview

The SIP SUBSCRIBE and NOTIFY interface is described in the draft RFC 3265 Session Initiation Protocol (SIP)-Specific Event Notification. The IBM XDMS implementation of subscription and notification is based on the specifications described in the XML Document Manager Specification OMA-TS-XDM_Core-V1_0_1 and OMA-TS-XDM_Core-V2_0 for the new xcap-diff event type.

Subscription types

The IBM XDMS supports two type of subscription events:
UA-profile events
UA-profile events allow for subscription to XDMS documents. Notification patch operations may include a <changelog> element describing changes made to the subscribed document.
xcap-diff events
xcap-diff events allow for subscriptions to documents as well as elements and attributes within those elements. These documents, elements, or attributes may already exist, or if not, subscriptions can be made in pending state. xcap-diff events also allow for batch subscriptions, where more than one resource is subscribed to in one session. Notifications may include patch operations for document level subscriptions, and complete element or attribute content for node level subscriptions.

Subscription notifications

The SIP NOTIFY method is used to notify a SIP client (also known as an end point) about an event change or changes to a document that the SIP application had earlier requested notification about through an earlier SIP SUBSCRIBE request. In the case of IBM XDMS, the SIP NOTIFY is sent when a change is made to an XCAP document that has been subscribed to. The SIP NOTIFY generated contains an xcap-diff document when the initial SIP SUBSCRIBE has the header accept: application/xcap-diff+xml.

The following conditions will cause a SIP NOTIFY request to be sent:
  • If SIP SUBSCRIBE request results in a successful 200 response code then a SIP NOTIFY request is sent to the requester with the state of the subscription. If the response to the SIP SUBSCRIBE is not a 200 response code then no SIP NOTIFY is sent
  • If the subscribed document has been modified or deleted a SIP NOTIFY is sent to the SIP client.
Subscription-State headers provided in the SIP NOTIFY requests include the following:
  • ACTIVE: indicates that the subscription has been accepted.
  • TERMINATED: the subscription is not active. A reason tag will be included with the following information:
    • Timeout: The subscription expired or was canceled.
    • Noresource: The document which was subscribed to has been deleted.

Restrictions

  1. In IBM XDMS when using UA-profile events XCAP SUBSCRIBE is only performed against an XCAP XML document. It is important to understand that the interface does not allow a subscribe request against a resource element or attribute.
  2. Because the xcap-caps is a generated document, the SUBSCRIBE interface does not accept subscriptions to it.
  3. The directory.xml file can only be subscribed to in Access Control List (ACLS) AUIDs. This file does not exist in standard AUIDs and is not available for subscriptions.

Security

The XCAP interface supports authentication to ensure that a requester has the appropriate privilege to perform the requested operation.

In order to issue a SIP SUBSCRIBE request, the requester must have read permission on the target document being subscribed to. If no read permission has been granted then a 403 Forbidden response will be returned.

The p-asserted-identity header field is used to contain the identity of the user sending a SIP message that will be used for verify by authentication. The asserted identity header is parsed by the WebSphere IMS™ Connector Trust Association Interceptor (TAI). Refer to the TAI topics in this information center for more information about how to configure the TAI for handling asserted identities.




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