I believe that these sizes are actually negotiated with each appliance in the path. All it would take is one device configured such and all along that path would follow suit.
I'd try a trace route on each path and compare the results. Then have the network folks check the routers/firewalls in the z/os path but not in the PC path. -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@bama.ua.edu] On Behalf Of Mauri Kanter Sent: Wednesday, June 06, 2012 9:05 AM To: IBM-MAIN@bama.ua.edu Subject: Question on TCP window size for FTP Good morning list: I'm FTPing files from one z/OS mainframe at my site to another mainframe. On a packet trace I can clearly see that the FTP window is small (about 20K) while if I FTP from my PC to my mainframe I see that the window is scaled and it is 256K. My side uses TCPSENDBFRSIZE 256K TCPRCVBUFRSIZE 256K and I understood the target side uses the same values. What are the knobs that control the window size? Is there any parameter in the z/OS FTP client or z/OS FTP server side to control this? Thanks in advance for your help. Mauri. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: INFO IBM-MAIN NOTICE: This electronic mail message and any files transmitted with it are intended exclusively for the individual or entity to which it is addressed. The message, together with any attachment, may contain confidential and/or privileged information. Any unauthorized review, use, printing, saving, copying, disclosure or distribution is strictly prohibited. If you have received this message in error, please immediately advise the sender by reply email and delete all copies. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: INFO IBM-MAIN
