In this paper, we consider the design of a reliable multicast facility over an unreliable multicast network. Our multicast facility has several interesting properties: it has different numbers of clients interested in each data packet, allowing us to tune our strategy for each data transmission; it has recurring data items, so that missed data items can be rescheduled for later transmission; and it allows the server to adjust the scheduler according to loss information. We exploit the properties of our system to extend traditional reliability techniques for our case, and use performance evaluation to highlight the resulting differences. We find that our reliability techniques can reduce the average client wait time by over thirty percent.
This paper considers a number of ways to guarantee reliable delivery, including some methods particular to our type of multicast data server. These methods, including a variable forward error correction scheme, selective retransmission of lost data, and rescheduling data items in lieu of correcting partially lost transmissions, are compared for a variety of client data-loss rates, including near-uniform and two-tiered loss-rate distributions. We also consider the effect of using error-correcting data packets versus unencoded data packets for transmission; the potential benefit of a server with better knowledge of its clients' loss rates; and the effect of notifying just-connected clients when there is a relevant transmission already in progress.
@inproceedings{lg-srds03,
author = {Wang Lam and Hector Garcia-Molina},
title = {Reliably Networking a Multicast Repository},
booktitle = {Proceedings of the 22nd International Symposium on Reliable Distributed Systems (SRDS 2003)},
month = {October},
year = {2003},
publisher = {IEEE Computer Society},
isbn = {0-7695-1955-5},
pages = {5--14},
note = {Available at http://dbpubs.stanford.edu/pub/2003-49}
}
@techreport{lg-reliability-extended,
author = {Wang Lam and Hector Garcia-Molina},
title = {Reliably Networking a Multicast Repository (extended version)},
institution = {Stanford University},
year = {2002},
note = {Available at http://dbpubs.stanford.edu/pub/2002-37}
}