Hal, > I believe that these sizes are actually negotiated with each appliance > in the path.
You're confusing path MTU size with TCP window size. The receiver's window size is a reflection of his available buffer space. Mauri, what is the value of TCPMAXRCVBUFRSIZE on the receiving stack? This will limit what is available for FTP. See "Configuring PROFILE.TCPIP for FTP" at http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/f1a1b3a0/2.3.1. Steven St.Jean http://sdsusa.com > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:IBM-MAIN@bama.ua.edu] On > Behalf Of Hal Merritt > Sent: Wednesday, June 06, 2012 11:19 AM > To: IBM-MAIN@bama.ua.edu > Subject: Re: Question on TCP window size for FTP > > 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 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: INFO IBM-MAIN
