A simple adaptive SVC caching scheme for voice trunking over ATM (VTOA) applications

In voice trunking over ATM (VTOA) technology, the tandem is replaced by three components: trunk inter-working function (T-IWF), control and signaling inter-working function (CS-IWF), and ATM network. This new architecture calls for re-examination of the signaling channel delay issues, which are well-studied and well-specified for TDM networks. In VTOA, the ATM network together with the inter-working functions act as a virtual tandem switching system, which is called "ATM-based distributed virtual tandem switching system". The aim is that the performance of the ATM-based trunking network should be at least as good as the TDM-based network. The cross-office delay budget must be shared among the inter-working functions and the ATM network. Hence, the time for the ATM network to establish a switched virtual connection (SVC) is stringent. In this paper, we propose a simple adaptive SVC caching scheme to offload the high processing capacity burden on ATM switches. After a SVC is established in the usual way for a call, it is not torn down after the conversation is over. Instead, it is kept alive for variable duration (i.e., delayed release) with the expectation that there would be another call request for the same terminating end office during that time. The caching duration is adaptively changed with call arrival rate and call setup delay in the ATM network in order to stay within the delay budget specified by the requirements. The adaptability and the convergence of the algorithm are also shown by extensive simulations related to practical scenarios.