A multi-domain SDN for dynamic layer-2 path service

This paper describes our experience in deploying a multidomain Software-Defined Network (SDN) that supports dynamic Layer-2 (L2) path service, and offers insights gained from this experience. SDN controllers, capable of handling requests for advance-reservation and provisioning of rate-guaranteed L2 paths, were deployed in each domain. The experience demonstrated that this architecture can support global-scale multi-domain dynamic L2 path service. However, to reach this scale, better tools are required for diagnostics of end-to-end L2 connectivity, and better error-reporting functionality is needed from the SDN controllers. As a use case for rate-guaranteed L2 path service, we experimented with high-speed large dataset transfers. We found that a combination of Circuit TCP (CTCP), in which the sending rate is held fixed, and a token bucket filter based rate shaper at the sending host, is best to achieve almost 0-loss, high-throughput transfers across L2 paths. Detailed studies were conducted to understand the impact of the rate-shaper and CTCP parameters to find the best settings.