An Overview of RDMA over IP Allyn Romanow Cisco Systems San Jose, CA 95134 USA
[email protected] Stephen Bailey Sandburst Corporation Andover, MA 01810 USA
[email protected] 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. 1 Introduction This paper considers RDMA over IP. Much of the paper is taken from the internet draft, draft-rddp- problem-statement-00.txt [RMTB02], by the authors, and Jeff Mogul and Tom Talpey. While the internet draft describes the problem and reviews the literature, it also motivates why the topic should be in the IETF, and the draft is constrained as a document or an IETF working group. This workshop paper covers the same ground with respect to describing the problem and reviewing relevant literature- in fact we have changed the IETF draft text very little.