UNIX for Advanced & Expert Users

[solaris 5.9]

hi all,

i am looking for ways to make ftp efficient by tuning the parameters

currently,
tcp_max_buf is 1 MB
tcp_xmit_hiwat is 48 KB

say to transmit multiple 2 gb files from unix server to mainframe sys,
will increasing the window size or the send buffer size of the current TCP/IP configuration have an effect on the time taken to tranmit the file from unix server to mainframe sys ?

upon setting new values to conf, is a reboot required ?

is there any maximum file size limit that can be transmitted via ftp?

else or there any other ways to effectively transmit larger files from unix server to mainframe sys.

1) one thing could be compression, but i am not sure of an uncompress binary constructed on the same adaptive Lempel-Ziv coding and available there in the mainframe system.

2) setting the same buffer size for send and receive would avoid unnecessary fragmentation across network prior sending it. But no control can be exercised over the receive buffer size of the mainframe system.

Thanks,
Mad.

What speed are you getting now?

If the link is slow, no amount of tuning will make it faster. If the link is fast, tuning won't make much difference either. So, yeah. Make the link faster.

currently,

766 Kbytes/s (approx)

Over what kind of link? 10baseT?

If it's 10baseT, you're getting pretty close to the practical maximum, the theoretical one is one megabyte per second. 100baseT would be ten times faster.

Its a t1 fiber link.

even with that wont i able to tune the parameters and maximize the throughput?

T1 maxes out at 150 kilobytes per second, so 766KBytes/s is actually... pretty good. Or maybye you have something else. Not to mention, the point of fiber is often distance and noise-immunity rather than bandwidth. So you still haven't really given much info on what your connection's rated for, sadly.

I'm guessing compression wouldn't help much unless the file is very repetetive, or the transmitting system very fast CPU-wise. However I have found compression useful under some situations(generally in combination with the udpcast multicast tool, with which I've been able to achieve 99% of rated speed on a TCP/IP link -- at the expense of all other traffic on the link however ). lzop in particular is designed to be realtime compression.

this thread on google groups shows a few tips. Window size is apparently important.