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Tracing IP packets to their sources, known as IP traceback, is an important task in defending against IP spoofing and DoS attacks. Log-based IP traceback technique is to log packets at routers in the network and then determine the network paths which packets traversed using data extraction techniques. The biggest advantage of log-based IP traceback is the potential to trace a single packet. Tracing a single packet in the Internet using log-based IP traceback involves cooperation among all Autonomous Systems (AS) traversed by the packet. The single packet traceback process may not reach the packet origin if some AS on the forwarding path does not support IP traceback. IP traceback mechanisms are deployed within each AS independently. It is not reasonable to assume all ASes begin to support the same IP traceback mechanism in a short period of time. In this paper, we study the effectiveness of log-based IP traceback in tracing a single packet under the environment where not every AS supports log-based IP traceback. We propose a scheme to conduct the single packet traceback process in AS-level partial deployment scenario. We evaluate the performance of single packet IP traceback in AS-level partial deployment scenario based on our scheme through simulation.

Cooperating proxy caches are groups of HTTP proxy servers that organize to share cached objects. This paper develops analytical models for proxy cooperation based on speedup in user response time. Speedup expressions are derived for the cooperation upper bound, a proxy mesh, and a three-level proxy hierarchy. The equations allow comparisons of fundamental design choices by separating the delivery organization from the discovery mechanism. For the mesh and hierarchy models, the discovery mechanisms include ideal discovery, ICP query, and distributed metadata directories. Equations are evaluated using parameter estimates from experiments and cache trace analysis. Results indicate that proxy cooperation is marginally viable from the standpoint of average user response time, and that the miss penalty for the hierarchy renders it less viable than the mesh. Proxy cooperation can, however, reduce the variability in user response time and the number of long delays. A trace-driven simulation shows that caching constraints have little effect on cooperation performance due to request filtering by lower level caches.