An Effective Use of SDN for Virtual-Link Provisioning in ISP Networks

抄録

The ability of Software Defined Networking (SDN) to dynamically adjust the network behaviour and to support fine-grained routing policies becomes increasingly attractive beyond the boundaries of Data Centre domains, where SDN has already gained enormous momentum. However, the wider adoption of SDN in ISP (Internet Service Provider) networks is still uncertain due to concerns about the scalability of a centralized traffic management in large-scale environments. This is particularly problematic when ISP offers virtual-link services, which imply a performance guaranteed data transfer between two network points. Our solution is a new approach to virtual-link mapping in SDN-based ISP networks. Within the problem's scope, we address traffic engineering (TE), QoS provisioning and failure recovery issues. In order to decrease the controller load, computational effort, and processing delay, we introduce a function split between online routing and TE. The TE functions are performed periodically, with configurable periodicity. In order to reduce the control overhead, we restrict the traffic optimization problem to load balancing over multiple static tunnels. This allows retention of the traditional MPLS routers in the network core and to achieve fast virtual-link restoration in case of physical-link failures. The online routing and admission control algorithms have been designed with the goal of low complexity, and to minimize Flow-table updates. In our simulation study, we compare the proposed virtual-link mapping solution with the solutions that exploit routing flexibility in fully SDN-enabled networks. We find that the throughput loss due to the use of static traffic tunnels is relatively small, while the control overhead is reduced significantly. A prototype of the proposed SDN control-plane is developed and validated in the Mininet emulator.