Lightweight, Packet-Centric Monitoring of Network Traffic and Congestion Implemented in P4

Communication cost is an important factor for distributed applications running in data centers. To improve communication performance, developers need tools that enable them to measure and to understand how their application's communication patterns interact with the network, especially when those interactions result in congestion. This paper describes a lightweight sampling-based technique for monitoring communication that has a switch help a packet collect information about the path it takes from source to destination and congestion it encounters along the way. This scheme has essentially no bandwidth overhead, as it stores only a few bits of information in the header of a monitored IP packet, making it practical to monitor every packet. In our prior work, network simulations of large-scale tightly-coupled HPC applications showed this approach can provide detailed information about traffic and congestion that is useful for diagnosing the problem's root cause. Here, we describe an implementation of this scheme in P4 for data center networks and demonstrate its functionality with a basic experiment.