Paper Review : IP Multicast Channels: EXPRESS Support for Large-Scale Single-source Applications

Reviewer : Seh Leng Lim

This paper discusses the EXPlicitly Requested Single-Source (EXPRESS) multicast channels which are an extension to the conventional IP multicast model to support the channel mode of multicast.

The main contribution of the paper is its detailed description of the implementation of EXPRESS. With EXPRESS, issues relating to charging, restricting of access, limitation of address space and scaling of IP multicast routing in conventional IP multicast are overcome. Therefore, large-scale multicast applications such as Internet TV can be realized.

The key main ideas expounded are :

(a) The idea of channel as opposed to group addressing where the subscriber is assured of only receiving traffic from the source it designates, and does not need to explicitly exclude other sources

(b) The idea of the single-source “ownership” where the source can be billed

© The idea of the source using CountQuery mechanism to efficiently determine the number of subscribers or to take a subscriber vote

I think that the paper has a significant contribution (rating of 4) to the study of IP multicast . The authors have proposed an interesting concept that can be realized in the Internet. They have also performed realistic cost benefit analysis to support their claims that EXPRESS can be implemented at a cost which is very much lower than the value of the large scale applications that it can support. As acknowledged by the authors, there is still work to be done to make EXPRESS a standard Internet service.

System and application builders may have a better appreciation from this paper of the difficulties involved in implementing IP multicast.