Path Computation for Dynamic Provisioning in Multi-Technology Multi-Layer Transport Networks

Abstract

Service providers employ different transport technologies such as PDH, SDH/SONET, OTN, DWDM, Ethernet, MPLS-TP to support different types of traffic and service requirements. A typical transport network element supports adaptation of multiple technologies and multiple layers of those technologies to carry the input traffic. Further, transport networks are deployed such that they follow different topologies like linear, ring, mesh, protected linear, dual homing etc. in different layers. Dynamic service provisioning requires the use of on-line algorithms that automatically compute the path to be taken to satisfy the given service request. Path computation algorithms can be implemented in Path Computation Element (PCE) which can be invoked from Transport SDN controller to automate service provisioning. This paper studies automated path computation for service requests considering the above factors where, a new mechanism for building an auxiliary graph that models each layer as a node within each network element and creates adaptation edges between them and also supports creation of special edges to represent different types of topologies, is proposed. Logical links that represent multiplexing or adaptation are also created in the auxiliary graph. An initial weight assignment scheme for non-adaptation edges that consider both link distance and link capacity is introduced along with three dynamic weight assignment functions that consider the current link utilization. Path computation algorithms considering adaptation and topologies are proposed over the auxiliary graph structure. The performance of the algorithms is evaluated and it is found that the weighted number of requests accepted is higher and the weighted capacity provisioned is lesser for one of the dynamic weight function and certain combination of values proposed as part of the weight assignment. It is found that the proposed approach results in better overall network utilization (improvement of up to 30 Gbps for a scenario with 50,000 service requests) and fragmentation compared to the traditional layered path computation approach for a representative large-scale service provider transport network (Network 1) with 2955 network elements, 5753 physical links and 480 hub nodes. It is also found that the proposed approach results in better overall network utilization (3–4 times lesser utilization for a scenario up to 50,000 service requests) and fragmentation compared to the traditional layered path computation approach for another representative large-scale service provider transport network (Network 2) generated randomly with 2040 network elements and more than 7000 physical links.