Congestion-Aware Load Balancing on P4 Switch

Abstract

In current data center networks, huge amount of paths are provided with multi-rooted Clos topologies. Equal Cost Multi-Path (ECMP), which is a routing strategy , is used for load balancing. However, ECMP is due to ECMP congestion agnostic nature, severe performance requirements in data center are not easily be fulfilled, Expeditus is designed for solving this problem. If expeditus performs better, it may be considered for replacing ECMP in the future.

Expeditus is a congestion-aware load balancing protocol designed for Clos data center network. It had been implemented in Click but Click is already not being supported. As Programming Protocol-Independent Packet Processors -- P4(a new programming language) becomes the trend for network protocol development("Five 2017 trends in data forwarding acceleration Netcope can help you with," 2016), it provide quick building property that Click does not provided. Moreover, Expeditus has never been developed in P4. Therefore, P4 implementation is required and the P4 implementation will be analyzed and compared with ECMP for showing its performance.

In the experiments, throughput and flow completion time(FCT) are evaluated. Expeditus performs similar in the throughput with ECMP. However, for FCT which is an important metric for congestion control, Expeditus shows obvious advantage on ECMP.

In this project, P4 is the main programming language for developing. Therefore, P4 language is studied and evaluated throughout the whole project for reference. P4 is found only suitable for developing specific kind of network protocol currently as it does not provide much features for building some kinds of protocols. By reading the p4 limitations studied in this report, readers can know what kind of protocols are not so very suitable to be developed with P4 before start developing.