The are a number of issues at play here — RTT (Round Trip Time, i.e. ping/latency), window sizes, packet loss and initcwnd (TCP's initial window). Initial wind

The are a number of issues at play here — RTT (Round Trip Time, i.e. ping/latency), window sizes, packet loss and initcwnd (TCP's initial window). Initial window size: not relevant AFAICS, I'm not talking about connection startup behavior. RTT, Window size: if the bandwidth-delay product is large, obviously you need a large window size (>>65K). Thankfully, recent TCP stacks support TCP window scaling. Packet loss: you need relatively large buffers (by the standards of traditional TCP) and a sane scheme for recovering from packet loss (e.g., SACK), but I don't see why this is a show stopper on modern TCP stacks. I'm not super familiar with the SPDY work, but from what I recall, it primarily addresses connection startup behavior, rather than steady-state behavior.