Chapter 18 - Service Configuration in the IMS pot

Chapter 18

Service Configuration in the IMS

Chapter 17 provided a description of the protocols at the user’s disposal for configuring

services on the Internet. We saw that the service configuration architecture assumes an XML

document stored on a server. The client retrieves a copy of the XML document, makes

changes to it, and sends the delta back to the server.

In IMS, the architecture for service configuration architecture is developed around the

XML Document Management (XDM) architecture created by the Open Mobile Alliance

(OMA) in the XDM [244] set of specifications. XDM allows a user to modify XML

documents stored in remote network servers. It also allows the local copy of those XML

documents in the IMS terminal to be synchronized with the copy stored in network servers,

so that if the user makes changes to one XML document from a given IMS terminal, other

terminals are updated with the latest changes. Last, the XDM architecture also provides

limited support for searches of information stored in these XML documents.

18.1 XDM architecture

Let us describe the XDM architecture with the help of Figure 18.1. The XDM architecture

assumes a terminal that implements the role of an XCAP client, and one or more servers,

called XDM servers, that implement the role of XCAP servers. XML documents are stored

in any of the servers and kept synchronized with the copy in the client. When a user wants to

change a configuration setting in a service, such as adding a friend to a presence list, the user

changes the local copy of the XML document in the client and sends the change to the server,

which applies it, and stores an updated version of the XML configuration document.

The XDM architecture introduces the following concepts.

XDM client (XDMC). This is an XCAP client running in the IMS terminal. The XDMC

implements the core XDM features and some application-specific features.

Aggregation proxy. This is an HTTP proxy that is configured as an HTTP reverse proxy.

The Aggregation Proxy authenticates the XDMC towards an XDMS. It may also route

XCAP requests towards an XDMS or towards an Aggregation Proxy located in remote

network. It also routes search requests towards the Search proxy. When receiving

responses, it can compress the body of the response.

ıa- ´ Martın´

The 3G IP Multimedia Subsystem (IMS): Merging the Internet and the Cellular Worlds Third Edition

Gonzalo Camarillo and Miguel A. Garc

© 2008 John Wiley & Sons, Ltd. ISBN: 978- 0- 470- 51662- 1