Segment Routing Optimization for VNF Chaining

Segment Routing (SR) is an emerging source routing based tunneling technique, which allows source router to steer traffic by encoding segment list in the packet header. Due to its fine-grained control of routing path, SR can be leveraged to facilitate the deployment of Service Function Chains (SFCs). Using SR, multiple segments compose a specific path delivering traffic along a set of ordered Virtual Network Function (VNF) instances. However, when introducing SR into VNF chaining, the segment list depth of SR may face the scalability problem since traffic flows must be steered to traverse a serial of ordered VNFs. To address this problem, we study on segment routing optimization for VNF chaining. Our objective is to minimize the packet overhead of SR for all SFC demands, which indicates the scalability performance of SR. We first formulate the problem as an Integer Linear Programming (ILP) model. Since the ILP model is NP-hard, we then propose a heuristic algorithm named Segment Routing for SFC Steering (SR-SFCS), which is based on the method of backtracking and dynamic programming. Extensive simulation results show that compared with the benchmark algorithms, SR-SFCS can reduce the packet overhead by 23.77% in average.