Using network coding over p-cycles for survivable network operation

Using network coding to provide protection against link failures has been introduced by the author. This paper presents an overview of the progress which has been done so far in employing network coding for protection. The paper introduces the basics of network coding-based protection against single link failures. In these strategies, in addition to transmitting signals on link disjoint paths, a single set of protection circuits, which are also link disjoint from working circuits, is used to carry linear combinations of signals from several sessions. The protection circuit is implemented using a p-cycle. By using simple modulo 2 addition operations, receivers in each session can recover a backup copy of the signal. In the case of a failure in the working circuits, the receivers can use the backup copy recovered from the protection circuit. It is also shown how this technique can be extended to protect against multiple failures. Necessary and sufficient conditions for this protection against multiple failures are presented. The paper also shows how 1:N protection, which is provided by p-cycles, can be combined with the proposed network coding protection, to also provide protection on on-cycle links.