Why is my ftp transfer between two 100Mb machines so slow on SCO Unix?

Updated September 2009

Or any other slow ftp issue.

Usually this sort of thing is from bad (cheap) Nic cards and/or mis-negotiation with the switch or just lousy drivers. Ftp does a lot of work; junk affects it more than simple http, telnet or ssh connections. The amount of data transferred is larger; larger packets mean more chance of losses from window sizes, misnegotiation and so on.

It is just slow CONNECTING and not slow after that, it's probably DNS (see Telnet/FTP is very slow to connect).

If performance is bad during the actual transfer, it is a packet issue somewhere - look for losses and errors (netstat, llistat) and check negotiation, retransmission and so on.

At FTP slow xfer SCO OpenServer 5.06? it was noted that 3c905A and B cards had NWAY negotiation difficulties. That same post suggested using traceroute to make sure that packets aren't going half way around the world to get next door.

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