Browse Prior Art Database

IMS Priority and Pre-Emptive Service Architecture

IP.com Disclosure Number: IPCOM000167961D
Published in the IP.com Journal: Volume 8 Issue 3A (2008-03-11)
Included in the Prior Art Database: 2008-Mar-11
Document File: 3 page(s) / 66K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

In an IMS (IP Multimedia Subsystem) network the SIP (Session Initiation Protocol) can be used for real-time communication applications which includes also pre-emptive services such as disaster warning systems. In order to indicate the priority of a communication, the SIP header contains two fields, namely "Resource-Priority" and "Accept-Resource-Priority". The SIP UAC (User Agent Client) has to be able to generate the "Resource-Priority" header field for requests that require elevated resource access priority. The "Resource-Priority" indication may be used by the SIP proxy in its routing decisions. At present, the UE (User Equipment) may insert the RPH (Resource Priority Header) into the SIP, which ensures appropriate protocol usage and architecture. The other possibility is that the P-CSCF (Proxy-Call Service Control Function) inserts the RPH on behalf of the UE, which has the advantage of having no impact on the IMS terminal (e.g. UE) due to the priority feature. However, the UE based solution has the disadvantage that the priority allocation to the user is not authenticated by the network, i.e. the network can not avoid the abuse of such priority headers. The P-CSCF solution has the disadvantage that the P-CSCF cannot know when a session should be prioritized because no service information or user subscription information is available for reference at the P-CSCF. A static configuration in the P-CSCF for the RPH determination would restrict both the service flexibility of priority services in the IMS network and the accuracy.

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IMS Priority and Pre-Emptive Service Architecture

Idea: Li Zhu, CN-Beijing

In an IMS (IP Multimedia Subsystem) network the SIP (Session Initiation Protocol) can be used for real-time communication applications which includes also pre-emptive services such as disaster warning systems. In order to indicate the priority of a communication, the SIP header contains two fields, namely "Resource-Priority" and "Accept-Resource-Priority". The SIP UAC (User Agent Client) has to be able to generate the "Resource-Priority" header field for requests that require elevated resource access priority. The "Resource-Priority" indication may be used by the SIP proxy in its routing decisions.

At present, the UE (User Equipment) may insert the RPH (Resource Priority Header) into the SIP, which ensures appropriate protocol usage and architecture. The other possibility is that the P-CSCF (Proxy-Call Service Control Function) inserts the RPH on behalf of the UE, which has the advantage of having no impact on the IMS terminal (e.g. UE) due to the priority feature. However, the UE based solution has the disadvantage that the priority allocation to the user is not authenticated by the network, i.e. the network can not avoid the abuse of such priority headers. The P-CSCF solution has the disadvantage that the P-CSCF cannot know when a session should be prioritized because no service information or user subscription information is available for reference at the P-CSCF. A static configuration in the P-CSCF for the RPH determination would restrict both the service flexibility of priority services in the IMS network and the accuracy.

A novel solution to the problem mentioned above is presented in the following. The UE indicated priority indication and network controlled model can be combined, i.e. both is to be applied the UE SIP priority indication and the IMS AS (Application Server) priority determination in the IMS domain.

In a specific embodiment, special requirements in terms of network resources are indicated by the UE in the session initiation. To this end, the IMS UE has to support the RPH. Moreover, operators can pre-configure criteria for the resource request level. When the P-CSCF receives the resource request, it passes the request to the S-CSCF (Serving-CSCF) instead of handling it as a B2BUA (Back-to-Back User Agent). The S-CSCF can contain criteria to dispatch different priority messages. The iFC (initial Filter Criteria) in the S-CSCF (originating side) can be enhanced such that it includes filters which trigger at the SIP header "Resource-Priority". The iFC invoking sequence can be arranged appropriately in order to ensure that the priority request is routed to the predefined service AS. SIP requests with "Resource-Priority" are forwarded to a dedicated SIP AS for authentication and authorization.

This means in detail that a se...