Dynamically Adaptable Multi-service Switch (DAMS)

Abstract

Currently, most voice and data services are provided by separate networks which use either circuit or packet switched techniques. The DAMS project is aimed to establish an integrated solution for the business environment. A distributed system architecture on the basis of a LAN/MAN was selected. It consists of a standardized optical backbone ring system connecting several subsystems which provide terminal and network access (figure 1). The system, where possible, is based on standardized protocols. The subsystems are specified to operate as stand-alone systems. They are subdivided into the following modular blocks:

• Port Unit (to adapt to various terminals and external networks)

• Local Switch Unit (to provide internal switching functions)

• Backbone Unit (to connect the subsystem to the backbone ring)

• Control Unit (for local system control)

In order to determine the best solution for the backbone ring standard, a performance analysis was carried out to investigate the two alternative proposed standards: FDDI-II and IEEE 802.6 (MST). The results showed that:

• FDDI-II has a similar performance as IEEE 802.6 (MST)

• certain management strategies improve the overall efficiency of bandwidth usage

• no general problems arise by using ATM as a transmission technique, however further investigations are necessary

Investigations into the available technology and the support of these standards by semi­conductor manufacturers showed that there was more commitment to FDDI-II. For this reason it is expected that, for the first solution, the transmission scheme will be based on the emerging FDDI-II standard. It supports circuit switched (CS) and packet switched (PS) traffic types, with dynamic bandwidth allocation. Since asynchronous transfer mode (ATM) is expected to be a final integration mechanism, a strategy towards a long term solution based on ATM was elaborated. This includes an overall ATM system design and a migration strategy from a first hybrid solution (CS + PS) to ATM. Three possible signalling standards (CCITT No7, DPNSS & ISDN LAPD) have been considered suitable to be adapted to the DAMS requirements. A subset of CCITT No7 is preferred to be implemented on the FDDI-II backbone network.