Toward an optimal 1+N protection strategy

This paper introduces an implementation of the network coding-based generalized 1+N protection technique presented earlier by the author in [1] to protect against single link failures. Instead of using two protection circuits for a group of connections which are to be protected together as in [1], only one protection circuit is used, which takes the form of a tree. The protection circuit carries linear combinations of the data units originally transmitted on the working circuits, and these linear combinations can be used to recover lost data due to link failures. This recovery is carried out with the assistance of one node on the protection tree, which is chosen to reduce the recovery time. Moreover, unlike the scheme in [1] which protects unidirectional connections, this scheme is used to protect bidirectional connections. This protection technique requires exactly the same amount of protection resources used by 1:N protection, and can therefore be considered as a step towards achieving optimal 1+N protection. The paper also makes a number of other contributions. It introduces an integer linear program (ILP) formulation to evaluate the cost of protection using this technique, and compares it to the cost of 1+1 protection. The comparison shows that a significant saving in cost can be achieved, while still recovering from failures within a short time.