François, You say throughput is bad for a PUT from the mainframe to the Linux server. Check the throughput when, from the mainframe, you do a GET from the Linux server. If the throughput is good in only one direction then this, in my experience, is the classic symptom of a full duplex/half duplex mismatch. Check the lights on the m/f and linux switch ports - they should both be FDX/100. If not, you may have to get your network people to lock the switch ports at FDX/100 instead of letting them auto-negotiate.
BTW, 900 KB/sec is pretty good for a 10 Mbps ethernet link, but not for a 100 Mpbs link. I would expect about 11 MB/sec for a 100 Mbps end-to-end (i.e. with no 10 Mbps hops in between). If all else fails, you can do a packet trace. If you see lots of packet re-transmissions then it's probably network-related. Cheers, A. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html