Protecting against link failures in communication networks is essential to increase robustness, accessibility, and reliability of data transmission. Recently, network coding has been proposed as a solution to provide agile and cost efficient network protection against link failures, which does not require data rerouting, or packet retransmission. To achieve this, separate paths have to be provisioned to carry encoded packets, hence requiring either the addition of extra links, or reserving some of the resources for this purpose. In this paper, we propose network protection codes against a single link failure using network coding, where a separate path using reserved links is not needed. In this case portions of the link capacities are used to carry the encoded packets. The scheme is extended to protect against multiple link failures and can be implemented at an overlay layer. Although this leads to reducing the network capacity, the network capacity reduction is asymptotically small in most cases of practical interest. We demonstrate that such network protection codes are equivalent to error correcting codes for erasure channels. Finally, we study the encoding and decoding operations of such codes over the binary field.
@cite_18: In [1], the author introduced a strategy to use network coding on p-Cycles in order to provide 1+N protection for straddling connections and links against single link failures in mesh optical networks. In this paper we extend the work in [1] and introduce a GMPLS-based implementation of this strategy for link protection, that is also used to protect on-cycle links. We refer to this scheme as hybrid 1+N protection, since some data units are transmitted without being combined with other data units. The strategy uses a combination of GMPLS standard label switched paths (LSP) for protecting on-cycle links, and modified LSPs, which we refer to as label switched cycles (LSC), for protecting straddling links. The strategy does not have to explicitly detect failures, but rather detects the absence of data units. Destinations receive backup copies of packets within no more than the p-Cycle propagation delay for on-cycle link failures, and no more than the sum of the propagation delays of the p-Cycle and the longest straddling link for straddling link failures. The implementation details of this strategy are presented, and the cost of implementation, in terms of link usage is evaluated and is shown to be modest. This scheme can therefore provide protection at higher layers, at a speed that is comparable to that achieved at the physical layer, but at a much reduced cost, while being flexible, and requiring less involvement from the management and control planes.
@cite_11: p-Cycles have been proposed for pre-provisioned 1:N protection in optical mesh networks. Although the protection circuits are preconfigured, the detection of failures and the rerouting of traffic can be a time consuming operation. Another survivable mode of operation is the 1+1 protection mode, in which a signal is transmitted on two link disjoint circuits, and the destination chooses the strongest of the two signals, hence recovery from failures is instantaneous. The disadvantage is the large number of protection circuits. In this paper we introduce a new concept in protection: 1+N protection, in which a p-Cycle can be used to protect a number of bidirectional connections. Data from different circuits are combined using network coding, which can be implemented in a number of technologies. The maximum outage time under this protection scheme is limited to no more than twice the p-Cycle propagation delay.
@cite_18 , the author extended the protection model in @cite_11 and provided a GMPLS-based implementation of a link protection strategy that is a hybrid of 1+N and 1:N. It is claimed that the hybrid 1+N link protection provides protection at higher layers and with a speed that is comparable to the speed achieved by the physical layer implementations. In addition, it has less cost and much flexibility.