Lightweight Resource Reservation Signaling: Design, Performance and Implementation

Recent studies take two different approaches to admission control. Some argue that due scalability limitations, using a signaling protocol to set up reservations is too costly and CPU-intensive for routers. Instead, end users should apply various end-to-end measurement-based mechanisms to run admission control. Several other proposals have recommended to reduce the number of reservations in the network by using aggregation algorithms, and, thus, reduce the number of signaling messages and states. We study the signaling cost factors, propose several solutions that achieve good performance with reduced processing cost, and evaluate an implementation of a lightweight signaling protocol that incorporates these solutions. First, we identify some the protocol design issues that determine protocol complexity and efficiency, namely the choice of a two-pass vs. one-pass reservation model, partial reservation, and the effect of reservation fragmentation. We also explore several design options that can speed up reservation setup and quickly recover from reservation fragmentation. Based on the conclusion of these studies, we developed a lightweight signaling protocol that can achieve good performance with low processing cost. We also show that with careful implementation and by using some of basic hashing techniques to manage flow states, we can support up to 10,000 flow setups per second (or about 300,000 active flows) on a commodity 700 MHz Pentium PC.