Critical Span Protection with Pre-configured (P) Cycles

Some spans b are always very critical in any network. These spans may be; i) Most heavily loaded spans in the network, ii) Spans with small MTTF (mean time to failure), iii) Spans with high MTTR (mean time to repair), iv) Spans having large amount of premium traffic etc. In this paper a new scheme is proposed to provide protection to these critical spans using p-cycles. Fully distributed method DCPC (Distributed cycle PreConfiguration) protocol for formation of p-cycle is developed. Using this method of formation of p-cycles several p-cycles may be required (at least half of the total unit of traffic on the critical span) to cover entire traffic on the span. Hence management among p-cycles becomes very much difficult. Therefore, in the present work, a new concept of capacity of p-cycles is introduced and an effort has been made to protect entire traffic of critical span with minimum number of p-cycles. The p-cycles are formed with as much capacity as possible and it is ensured that critical span will appear as straddling span on the formed p-cycle, so that selected p-cycle will protect double amount of traffic as compare to its capacity. For the test network taken the results are very much encouraging. For the same amount of protection capacity the number of p-cycles required is reduced to 49% on an average. For some critical links the reduction in number is up to 25%.