For Peer Review TCP FLOW AWARE ADAPTIVE PATH SWITCHING

We propose an adaptive flow-level multipath routing-based traffic engineering solution for an IP backbone network carrying TCP/IP traffic. Incoming TCP flows are switched between two explicitly routed paths, namely the primary and secondary paths, for resilience and potential goodput improvement at the TCP layer. In the proposed architecture, primary paths receive a preferential treatment over secondary paths with respect to packet forwarding using differentiated services mechanisms. The reason for this choice is not for service differentiation but for coping with the detrimental knock-on effect stemming from the use of longer secondary paths that is well known for conventional network load balancing algorithms. Moreover, both paths are congestion-controlled using ECN marking at the core and AIMD rate adjustment at the ingress nodes. The delay difference between primary and secondary paths is estimated using two per-egress rate-controlling buffers maintained at the ingress nodes for each path, and this delay difference is used for determining the path over which a new TCP flow will be routed. We perform extensive simulations using ns-2 in order to demonstrate the viability of the proposed distributed adaptive multipath routing method in terms of per-flow TCP goodput. The proposed solution consistently outperforms the single-path routing policy and provides substantial per-flow goodput gains under poor primary path conditions. Moreover, highest goodput improvements under the proposed scheme are achieved by flows that receive the lowest goodputs with single-path routing, while the performances of the flows with high goodputs do not deteriorate with the proposed path switching technique.