| This thesis investigates existing Next Generation Network (NGN) architectures and protocols, and proposes modifications and extensions to enable the creation of NGN services that are dependable and extensible. Extensibility is addressed at the application layer by building on the SIP protocol: first decoupling its underlying session establishment capability from its upper layer call setup functionality, then defining a new application protocol for extensible services on top of the decoupled base SIP. Dependability is addressed at the transport layer, by trading off strict sequencing for improved performance. This is achieved by extending the domain of a new partially ordered transport protocol, SCTP, into the services domain where it is used to carry service-related messaging between Communication and Application Servers. A simulation model is used to compare this SCTP approach with previous TCP schemes. The results achieved are promising, showing a 30% performance improvement in response times under typical traffic conditions. |
