Reducing the Size of Routing Tables for Large-scale Network Simulation Akihito Hiromori, Hirozumi Yamaguchi†, Keiichi Yasumoto‡, Teruo Higashino† and Kenichi Taniguchi† Graduate School of Engineering Science, Osaka University 1-3 Machikaneyamacho, Toyonaka, Osaka 560-8531, JAPAN hiromori@ics.es.osaka-u.ac.jp TEL: +81-6-6850-6607 FAX: +81-6-6850-6609 † Graduate School of Information Science and Technology, Osaka University 1-3 Machikaneyamacho, Toyonaka, Osaka 560-8531, JAPAN {h-yamagu,higashino,taniguchi}@ist.osaka-u.ac.jp TEL: +81-6-6850-6607 FAX: +81-6-6850-6609 ‡ Graduate School of Information Science, Nara Institute of Science and Technology 8916-5 Takayamacho, Ikoma, Nara 630-0192, JAPAN yasumoto@is.aist-nara.ac.jp TEL: +81-743-72-5251 FAX: +81-743-72-5259 December 16, 2002 Abstract In simulating large-scale networks, due to the limitation of available resources on computers, the size of the networks and the scale of simulation scenarios are often restricted. Especially, routing tables, which indicate the directions to forward packets, are considered to consume memory space. A simple routing table requires O(N 2 ) space where N is the number of nodes. An algorithmic routing recently proposed by Heung et al. only requires O(N ) space for representing routing tables, however this can be applied in the case that all the routes between two nodes are contained in a spanning tree (i.e. very limited routing strategies are allowed). In this paper, we propose a new method to reduce a capacity of routing tables under any routing strategy. In our method, given a simple routing table, we can find a (near-optimal) algorithmic routing based table that can represent a part of the given routing table in a smaller size. Our experimental results have shown that our method could reduce about 90 % of the routing table size compared with a simple routing table in hierarchical networks. 1