The Transit Network Configuration (TNC) tool supports the user in placing a set of specifications corresponding to customers' requirements on the bandwidth available across a transit network. The transit network can be viewed as a collection of large circuits each with cost and quality and each capable of supporting a number of customer requirements. The user and the tool configure the network by placing the customer requirements on those circuits.
The specification for a customer's requirements for the transit network will describe the required bandwidth. It also describes the required Quality of Service (QoS) that may include factors such as security, reliability and availability and usage information, describing how much network traffic the service is expected to produce. The aim of the Transit Network Configuration (TNC) tool is to meet those requirements to a level acceptable to the customer while meeting the business objectives of the Service Provider.
An Operations Research technique, a Linear Programming Solver (LP-Solver), is adopted in the TNC. It packs channels (i.e. transit requirements) into pipes (i.e. available transit connections) while optimising cost. This part of the TNC is termed the pipe filler. The pipe filler requires support functionality which pre-processes the input data into a format suitable for the LP-Solver, and interprets the output suitable for use by the rest of the TNC. Further detail of the Pipe Filler and LP-Solver can be found in [D21]. The performance of the LP-Solver is proportional to the number of Quality of Service (QoS) criteria and the number of possible values of those criteria. A small change can lead to a large change in the time needed for a solution. The pipe filler estimates how long a solution will take. If it is above a threshold value it will approximate the problem to reduce the computation time. For example, if five levels of security are available initially this could be reduced to two levels with subsequent reduction in solution time.
The user is permitted to set channel exclusion constraints in cases where customers requirements need to be routed through separate pipes. This is handled by treating such requirements separately before running the LP-Solver (see top window Figure 1).
Figure 1: First window of the TNC tool.
Figure 2: Evaluation of the TNC result.
The TNC tool provides an evaluation of the result produced by the pipe filler. Factors considered include utilisation, fragmentation, spare capacity, cost per unit of bandwidth and quality of service provided (see bottom window, Figure 2).
