Web Performance Tuning

Network Interface Card

The Network Interface Card (NIC) provides the connection between the network cable and the server’s bus. NICs fill a conceptually simple niche, but their variety reflects the many permutations possible between network cable, cable signalling protocol, and host computer bus. NICs take an incoming serial stream of bits and output a parallel stream onto the bus, and vice versa. Until recently, it could be assumed that the network connection would be far slower than the CPU and bus, but LAN network speeds have been increasing faster than CPU and bus speeds, so it is no longer a safe bet that your network card can be handled by your machine. Still, at the interface to the Internet, you can be fairly sure that your server will be more constrained by Internet access than by any other component, save perhaps disk.

NICs have on-board buffers, and a bigger buffer always gives you more flexibility. The buffer has historically been important for holding outgoing data until the network can deal with it all, but as mentioned, that situation is reversing, so the buffers will in the future tend to hold incoming data, waiting for the computer. In either case, a larger buffer makes a buffer overflow and consequent data loss less likely. Lost TCP/IP data is simply retransmitted, adding to overhead. Typically, 8-bit Ethernet cards have 8K buffers, while 16-bit cards have 16K buffers.

When a NIC has a complete unit of data from the network and is ready to forward it on to the computer’s ...