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Abstract-The forwarding paths in an IP network may change due to a link failure, network equipment maintenance, or reconfiguration of link weights. The forwarding tables in the routers need then to be updated. These updates may cause transient loops and link overflow, if they are not performed in an appropriate order. While existing proposals achieve loopfree updates, transient link overflow is still a problem during the updating process. In this paper, we present a method that compares the initial and final forwarding paths, and obtains the updatable nodes that do not cause any transient loop or link overflow. However, this goal is not always achievable, therefore, we propose an algorithm to update the forwarding tables that will refrain the link overflows to a minimal level. The performance study on a real topology with two setups confirms that our approach achieves smaller link overflow than by using a previously proposed approach.

IP-address lookup is a key processing function of Internet routers. The lookup is challenging because it needs to perform a longest prefix match. In this paper, we present our modifications to an efficient lookup algorithm, the LC-trie, based on a technique called prefix transformation. Thereafter, the LC-trie’s performance is analyzed for both the original and our modified algorithm using real and synthetically generated traces. The performance study includes trie search depth, prefix vector access behavior, cache behavior and packet lookup time. The study is based both on experiments and a model for packet lookup time. The results show that the modified algorithm requires only 30% of the lookup time of the original algorithm. In particular, the modified algorithm is capable of performing 60 million packet lookups per second on a Pentium 4, 2.8 GHz, computer for a real traffic trace. Further, the results show that the performance is about five times better on the real trace compared to a synthetically generated network trace. This illustrates that the choice of traces may have a large influence on the results when evaluating lookup algorithms.

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Network processor systems provide the performance of ASICs combined with the programmability of general-purpose processors. One of the main challenges in designing these systems is the memory subsystem used when forwarding and queueing packets. In this work, we study the queueing behavior and packet delays in a network processor system which works as a router. We introduce a system model and a simulation tool based on the model. Using the simulation tool, both best-effort and diffserv IPv4 forwarding were modeled and tested using real-world and synthetically generated packet traces. The results on queueing behavior have been used to dimension various queues, and can be used as guidelines for designing memory subsystems and queueing disciplines. In particular, a system with small queue sizes has been proposed. The results on packet delays also show that our diffserv setup provides good service differentiation for best-effort and priority packets. Finally, the study reveals that the choice of traces has a large impact on the results when evaluating router and switch architectures.