Effort To Greatly Enhance Ethernet Hits Milestone

The RDMA Consortium is completing the host interface for remote direct memory access over Internet Protocol networks, a technique it expects will find widespread use in computer and network gear.

RDMA is a technology originally developed for the Infiniband interconnect. It helps reduce latency in data transfers between systems by directly placing data from one system's main memory to another's without the need for extensive buffering or CPU intervention.

Many RDMA Consortium members believe the technology when applied to TCP/IP will make Ethernet the most compelling of multiple emerging interconnects to link servers, switches and storage devices in future data centers. Consortium members include Adaptec, Broadcom, Cisco, EMC, HP, IBM, Intel, Microsoft and Network Appliance.

Backers expect products using the technique will emerge early in 2004. The completion of the host interface is one of the last major gating items enabling chip and system makers to support RDMA over Ethernet.

Microsoft ultimately is expected to support RDMA over TCP/IP in all versions of Windows, because RDMA's boosts in I/O performance are felt most strongly when the capability is widely supported. The company is expected to detail its plans for RDMA as part of a new Windows scalable networking architecture at the Windows Hardware Engineering Conference in May.

However, servers are the first target for RDMA as a means for handling storage networking over Ethernet. A Microsoft engineer recently wrote a paper detailing the performance advantages of the approach over Infiniband for storage traffic.

Consortium members expect RDMA will be implemented in TCP offload engine chips, called TOEs, now being developed by multiple chip makers. One backer estimated an RDMA block would require only 1 mm2 of silicon using a 130-nm process.

Adaptec and other companies have already launched Ethernet TOE cards without RDMA costing as much as $660. Proponents expect the technology ultimately will fall in price to a much smaller premium over Ethernet network interface cards as the so-called R-NICs become mainstream commodities.

"The R-NIC will be a mainstream product, but when that will happen--who knows," said Hari Ghadia, a technology strategy officer in Adaptec's storage networking group.

Some work remains on the RDMA spec. The consortium is finishing work on bringing RDMA to high level protocols such as iSCSI for storage and the Sockets Direct Protocol which may take until the fall. Beyond that, the consortium is transferring its results to a working group at the Internet Engineering Task Force (IETF).

Consortium members expect to build products based on the group's specification and let the IETF effectively develop a next-generation spec that may emerge in two or three years. One IETF group is already said to be drafting requirements to bring RDMA to version 4 of the Network File System.

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