A year ago, I wrote about an emerging chip called the TCP offload engine (TOE). Since then, some startups have announced products or plans in this area, demonstrating the interest in Transmission Control Protocol devices.

Much of the initial work has focused on smart network interface cards (NIC) that offload TCP termination from the server's host CPU. For a Gigabit Ethernet (GbE) connection, terminating TCP in software can reduce a host CPU's performance by up to 65 percent.

Alacritech Inc. was the first to deploy custom silicon to solve that problem. The company markets both chips and complete GbE NICs that offload much of the TCP processing from the host CPU. In 2001, Adaptec Inc. acquired startup Platys for its TCP technology but is still struggling to deploy fully functional products.

Intel, the leading NIC vendor, is shipping a smart NIC that uses a standard XScale CPU for TCP processing. The XScale chip, however, cannot keep up with a fully loaded GbE port. This highlights a key issue: general-purpose processors can't match the efficiency of TCP hardware.

Though the NIC market has an immediate need for TOE devices, in the longer term, the Internet Protocol storage market is potentially a larger and more lucrative target. IP storage relies on iSCSI, a protocol that sits atop TCP. Without TOE, it is difficult to implement iSCSI at 1 Gbit/s and above.

Trebia Networks Inc. was the first to announce a processor aimed at the IP storage market. Besides a TOE, Trebia's storage network processor includes programmable engines that can execute iSCSI or other upper-layer protocols.

Trebia has yet to sample this device, however, and other startups are catching up. Silverback Systems Inc. expects to sample a similar product soon, and Astute Networks will disclose its storage processor at NPC West next month.

Also at NPC West, iReady Corp. will announce a chip that combines that company's TCP technology with a GbE MAC and PHY from partner National Semiconductor.

Those vendors, and ones to come, are racing to fill a new market need. The startups are taking various approaches, combining TOE with different sets of functions aimed at different applications. It will take a few years for things to settle out, but it looks like TOE is here to stay.

Linley Gwennap is founder and principal analyst of the Linley Group, which recently announced "a guide to storage and tcp processors" (www.linleygroup.com/npu).