AbstractsComputer Science

This study investigates routing in a MPLS-based IP network with heterogeneous holding time traffic (for example, an IP call versus an IP conference). Our basic idea is to exploit the large differences existing in the holding time of different types of traffic to make more efficient resource allocation decision in the admission and routing processes. In particular, this study investigates the concept of vacating, in which requests with short holding times vacate the bandwidth on direct links in favor of requests with long holding times under some traffic conditions. Based on an analytical framework we developed, we propose several state-dependent routing schemes, namely preventive-vacating routing (PVV), preemptive-vacating routing (PEV) and restricted-access routing (RAR). Additionally, we deduce an approximated expression to compute the cost of accepting a long or short request. This leads to an approximated least cost routing (A-LCR) scheme directly. Furthermore, along with the simulation study, some of the significant results we obtained are: (1) The effective range in traffic mix is [0.60, 0.99], within which our vacating schemes outperform the traditional LLR+TR (least loaded routing + Trunk Reservation) in terms of network throughput. (2) Besides its particular flow control mechanism, the A-LCR scheme shows a constant outperformance compared to LLR+TR. (3) The routing schemes we proposed perform better than the differentiated shortest distance routing (Diff-SDR) scheme, which is the only currently published dynamic routing scheme addressing the question of heterogeneous holding times. We also study the inter-network routing issue, which focuses on how to select the best among several gateway nodes to a foreign network. Simulation results show that the intra-network links play a much more important role than inter-network links when making gateway selection decision.