A second Gigabit Ethernet port may require another expensive processor just to keep up with the I/O. Clearly, this approach does not scale to 10-Gbit Ethernet, which is beginning to be deployed in high-end data centers. The solution is to offload some of the protocol processing from the host processor. This offload is typically handled on the network interface card, turning a standard dumb NIC into a smart one.

Some vendors are marketing smart Gigabit Ethernet NICs that offload only a portion of the TCP processing. To support these NICs, Broadcom offers a Gigabit Ethernet MAC with an integrated MIPS processor that can be used for TCP offload. Alacritech has developed a TCP offload engine ASIC for its own smart NIC.

Whereas protocol offload is a nice feature in a Gigabit Ethernet NIC, it is highly desired in multiport Gigabit Ethernet NICs and a requirement in 10-Gbit Ethernet NICs. Several startups — including Siliquent and Chelsio — are developing protocol processors that support speeds of up to 10 Gbits/second. NetEffect, another startup in this space, will reveal its first protocol processor at Network Systems Design Conference in October.

One barrier to protocol offload has been a lack of software standards. The recent iWarp or remote-DMA standard establishes standard interfaces to offload devices. Microsoft's "Chimney" technology is another means of bypassing the protocol stack to enable hardware offload.

The demand for protocol processors is small today but will grow with network bandwidth. The number of vendors developing these products supports the idea that, someday soon, NICs will have to get smart.

Linley Gwennap is founder and principal analyst of The Linley Group and coauthor of "A Guide to Storage Networking Silicon" (www.linleygroup.com/npu).