How much memory does a common NIC have?

Question

What's a common amount of memory for a Network Interface Card to have? In a scenario where a fast network connection is available and there is a slow (or busy) disk, will the NIC be smart enough to slow network transactions?

Answer 1

This NIC has a memory of 32MB with ECC protection. Here is another useful link for more information about NICs. That NIC seems pretty standard to me in terms of speed.

Answer 2

It's up to the protocol, not the NIC.

TCP will adapt. If you run a download over a gigabit lan on a 7200RPM hard drive (these typically have about a gigabit (120MB/s) of read speed and about 500Mbit (60MB/s) of write speed), the network connection will (by virtue of being unable to buffer TCP packets for long enough) drop a few packets, which will not be counted as received. They will not be ACK'd, and the sender will have to resend them. The TCP implementation on the sender's side will typically slow down to compensate for what it sees as a network bottleneck.

UDP offers no rate limiting and will send packets as fast as it can (if this is too fast, they just get dropped).

Different network cards have different amounts of memory.

• High end ethernet cards will almost certainly have their own memory and microprocessors to offload work from the rest of the computer.
• Low end ethernet cards may not have their own onboard memory or microprocessors, and will use the host system's resources to handle network traffic.
• Infiniband cards on the other hand will tend to have their own onboard processors but no onboard memory, and will use direct memory access for all IO.