Multi-tiers route design coordinating QoS-specific K shortest paths over optical network

In the Wavelength Division Multiplexing (WDM) based optical circuit switching network, it takes longer time to set up the intermediate optical cross-connecting devices on the route. Thus, pre-computed routing approaches are desirable to instantly set up the connection. Most of their research works are based on the K Shortest Path (KSP) algorithm or it's variants considering route disjointness, because of load balancing effect in network, its simplicity, and quick response caused by heuristic approach. However, it essentially remains some issues to be solved, especially on the capability for various QoS support and fairer load balancing. In particular, the set of K shortest paths independently selected between any two nodes is insufficient for entire network load balancing. Specifically, sequential selection of the K routes for each source-destination (S-D) pair causes the unfairness and unbalance in network load among all S-D pairs. In the paper, to tackle the above problems, we propose multi-tiers route design method, which provides more enhanced load balancing by selecting QoS specific multiple routes for each node pair, coordinating with the routes for other node pairs. The proposed method is not the improvement of the KSP algorithm and it's variants themselves, but the framework to find a limited number (K') of adequate paths from the K (K' ≤ K) routes pre-computed by KSP based algorithms for each S-D pair and each QoS level, taking spatial relationship between routes into account. Thus, the proposed method has complementary relationship with the KSP based algorithms themselves.