Synchronous Digital Hierarchy (SDH) and Synchronous Optical Network (SONET) are time-division multiplexing technologies widely used in transport networks to provide bandwidth services. Dynamic service provisioning requires the use of online algorithms that automatically compute the path to be taken to satisfy the given service request. SDH/SONET multiplexing structure imposes restrictions on the allocation of bandwidth. Bandwidth services mostly require protection so that they are resilient to failures in the network. Two types of protection techniques—namely, dedicated protection and shared protection—are commonly used to protect bandwidth. Also, SDH/SONET provides standard protection mechanisms like linear MSP/APS, MS-SPRing/BLSR and SNCP/UPSR. In shared protection, complete path information for all the existing connections has to be maintained to maximize sharing for future service requests. This information will be typically very large. To overcome this problem, a minimum information scenario is proposed as a tradeoff between maintaining less information and maximizing sharing. In this work, heuristic algorithms are proposed for dedicated and shared protection that take into account the above-mentioned factors. These algorithms use the path computation algorithms for SDH networks proposed in a previous work of the authors, which compute paths for service requests without considering protection. The performance is evaluated for different values for the relative weight of sharing for the complete and minimum information scenarios. An extension to these algorithms for satisfying bandwidth requests that use various inverse multiplexing techniques is also proposed.

Synchronous digital hierarchy (SDH) is a time division multiplexing technology widely used in transport networks to provide bandwidth services. Dynamic service provisioning refers to the arrival of service requests one-by-one randomly with no prior information on future requests. This requires the use of on-line algorithms which automatically compute the path to be taken to satisfy the given service request. This problem involves a tradeoff between minimizing the number of requests that are rejected and minimizing the total bandwidth that is utilized. Many earlier works have addressed path computation algorithms, but they treat each link as having some integer units of bandwidth. They do not take into account the multiplexing structure defined by SDH which imposes restrictions on the allocation of bandwidth and the fact that higher order trails (logical connections) have to be established to support any bandwidth requirement. In this work, these factors are considered in the path computation algorithms. The network is treated as a graph containing physical links and logical trails and weights are assigned to them before computing a path with the least cost. Weights are assigned such that the trails are given higher preference to physical links so that existing trails are used wherever possible. This avoids unnecessary creation of new trails. The performance is evaluated for different values of weights. An improvement in the form of dynamically adjusting the weights of links and trails is done and its performance is shown to be better than having constant weights.