Incremental deployment strategies for router-assisted reliable multicast

Incremental deployment of a new network service or protocol is typically a hard problem, especially when it has to be deployed at the routers. First, an incrementally deployable version of the protocol may be needed. Second, a systematic study of the performance impact of incremental deployment is needed to evaluate potential deployment strategies. Choosing the wrong strategy can be disastrous, as it may inhibit reaping the benefits of an otherwise robust service and prevent widespread adoption. We focus on two router-assisted reliable multicast protocols, namely PGM and LMS. Our evaluation consists of three parts: 1)selection and classification of deployment strategies; 2) definition of performance metrics; and 3) systematic evaluation of deployment strategies. Our study yields several interesting results: 1)the performance of different deployment strategies varies widely, for example, with some strategies, both PGM and LMS approach full deployment performance with as little as 5% of the routers deployed; other strategies require up to 80% deployment to approach the same level; 2) our sensitivity analysis reveals relatively small variation in the results in most cases; and 3) the impact associated with partial deployment is different for each of these protocols; PGM tends to impact the network, whereas LMS the endpoints. Our study clearly demonstrates that the choice of a strategy has a substantial impact on performance.