Theoretical Analysis of Difference Between Edge-Based and Core-Node-Supported TACCS

Internet protocol (IP) networks need admission control mechanism to provide full-fledged multimedia services. Therefore we previously proposed an admission control scheme called the "tentative accommodating and congestion confirming strategy (TACCS)". The basic idea of TACCS is to tentatively accommodate incoming flows and then, after a certain period, determine whether accommodating them has created congestion. In this scheme, the ingress nodes of a domain make flow- accommodation decisions based on packet-loss event information. The information is assumed to be advertised from congestion detection agents (CDAs) located in the domain. However, adding CDA functionality to core nodes is a barrier to deploy TACCS and limits its scalability. Thus, we furthermore developed an enhanced version called "edge-based TACCS" that performs admission control on the basis of only cooperation between edge nodes- it does not depend on CDAs in the core network. In this paper, we compared the operation of the edge-based version with that of the core-node-supported TACCS and investigated a problem: some flows, which should be rejected in the core- node-supported version, could be wrongly accommodated in the edge-based TACCS. Theoretical analysis of this "rejection failure" problem showed that it does not significantly degrade flow quality, meaning that edge-based TACCS is feasible.