An Overview of RDMA over IP

Abstract

This paper gives an overview of Remote Direct Memory Access (RDMA) over IP. The first part of the paper is taken from an internet draft [RMTB02] that describes the problem of high system costs due to network I/O copying in end-hosts at high speeds. A review of experience and research over the last ten or so years shows that the problem is due to limits on available memory bandwidth, and the prohibitive cost of additional memory bandwidth, and that it can be substantially improved using copy avoidance. The second part of the paper considers an RDMA over IP solution, giving background and current status. An architecture is described that is that currently being adopted by the RDMA Consortium and the RDDP WG in the IETF. Outstanding issues, some of a research nature, are considered.