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 setup reservations is too costly and CPU-intensive for routers. Instead, endusers should apply various end-to-end measurement-based mechanisms to runadmission control. Several other proposals have recommended to reduce thenumber 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 achievegood performance with reduced processing cost, and evaluate an implementationof a lightweight signaling protocol that incorporates these solutions. First,we identify some the protocol design issues that determine protocol complexityand efficiency, namely the choice of a two-pass vs. one-pass reservationmodel, partial reservation, and the effect of reservation fragmentation. Wealso explore several design options that can speed up reservation setup andquickly recover from reservation fragmentation. Based on the conclusion ofthese studies, we developed a lightweight signaling protocol that can achievegood performance with low processing cost. We also show that with carefulimplementation and by using some of basic hashing techniques to manage flowstates, we can support up to 10,000 flow setups per second (or about 300,000active flows) on a commodity 700 MHz Pentium PC.