Cost Effective Control Plane Design for Service Assurance in Software Defined Service Function Chaining

Service Function Chain (SFC) is an ordered list of dynamically deployed virtual service/network functions (SFs). In a software defined SFC, Network Function Virtualization (NFV) framework manages the lifecycle of SFs, and Software Defined Networking (SDN) control plane steers the traffic through the SFs in a given order to deliver a service. SFCs provide several benefits over conventional approaches through their agility and control, but also present new challenges. One of these challenges is service assurance that requires prompt resumption of a service in case of a SF unavailability due to traffic load, failure, maintenance or any other reasons. To ensure service availability, traffic from unavailable SF is migrated to a backup SF. Most of the studies deploy dedicated backup server for each SF in every SFC, which leads to needless consumption of resources. This paper exploits the fact that many instances of a SF are usually deployed in the network as part of different SFCs, and uses one of these instances as a backup SF in case of the primary SF unavailability. Selection of backup SF is done based on shortest detouring path to minimize the added delay due to altered path and the service disruption time. Emulation results from fat tree topology confirm that proposed mechanism reduces resource wastage by more than 20% comparing to conventional approaches while only adding 0.006 ms and 4 ms approximately in switching delay and transmission delay, respectively.