Excessively large buffers confuses TCP windowing. On network devices like switches and routers buffers are only actually needed for two things: internal switchi

Excessively large buffers confuses TCP windowing. On network devices like switches and routers buffers are only actually needed for two things: internal switching/routing latency (which is usually constant and very small) and serialization onto output interfaces (which varies by input/output port speed mismatch and/or number of inputs multiplexed to one output). Handling network "burstiness" should be left up to the endpoint TCP stack or applications in the case of UDP. Ethernet flow control should be disabled unless you find it actually helps (unlikely). On servers buffers have more work to do since the CPU may be busy with many other tasks. It is rare that I have had to adjust the default buffer sizes but keep in mind server buffers too large can increase jitter as well as confuse TCP windowing (depending on when ACK's are sent). Some applications may prefer that packets be dropped instead of queued for excessively long times. The most important thing is to ensure that selective ACK's and window scaling TCP options are enabled. They are enabled by default in modern operating systems but you might be surprised how often they are disabled by clueless sysadmins. A common cause of this is/was buggy TCP offloading drivers where the apparent "solution" was to disable ALL tcp options instead of just TCP offload. Window scaling in particular is essential with modern port speeds.