Incremental Deployment Strategies for

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 eval- uate potential deployment strategies. Choosing the wrong strategy can be disastrous, as it may inhibit reaping the benefits of an oth- erwise 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) defi- nition 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.