On Sat, Jul 03, 2010 at 11:54:17AM +0100, Stuart Henderson wrote: > Does anyone know offhand the reason why network connections fail > if socket buffers are set above 256k? >
There is this magical define in uipc_socket2.c called SB_MAX that limits the socket buffers to 256k going over that line makes the initial scaling fail and you end up with no buffer at all. > # sysctl net.inet.tcp.sendspace=262145 > # telnet naiad 80 > Trying 2a01:348:108:108:a00:20ff:feda:88b6... > Trying 195.95.187.35... > # > > I was thinking of looking into it, but before going down that rabbit > hole I thought I'd ask in case there's a quick answer that somebody > already knows... > > (yes, people do use buffers much bigger than this, I looked at some > of the academic ftp mirror sites - looks like mirrorservice.org wil > negotiate 3MB buffers, aarnet 35MB, if you let them - presumably > they try to avoid buffers being a bottleneck for clients reaching > them over a national network of at least 1Gb/s end-to-end). > 35M, that is insane. Either they have machines with infinite memory or you can kill the boxes easily. -- :wq Claudio
