source quelch



i'm sorry in advance for not having all the information that may be needed to answer this post.

at my company we are trying to transfer a large amount of data from an nt server to a hp-ux server using ftp. the problem is that when transferring data we are getting extremely slow speeds of 240kb/sec and we are going to be transferring ~100gb!

we had the network group put a sniffer on to trace what is going on and they said on the network level everything is ok, but they said the destination server is sending "source quelch" messages back to the source server, which is causing the source server to slow down the transfer. can anyone explain this in more detail and does this sound like a likely scenario or are the network guys telling me a story?

http://en.wikipedia.org/wiki/icmp_source_quench

afaik, a lot of oses ignore them and they are often filtered by firewalls. most tcps have their own congestion control mechanisms so icmp source quench is not used a lot.

if your hp-ux sends them and your winnt uses them.. i would try to filter them on the nt box; cause nt might be overreacting.

that might not solve the problem but at least you would know the slowness is not caused by icmp alone. hp-ux could be sending them as part of a more general slowdown mechanism (ex, it could be reducing the tcp window and dropping some packets too).