Path: utzoo!attcan!uunet!clyde.concordia.ca!news-server.csri.toronto.edu!cs.utexas.edu!usc!ucsd!ucbvax!FTP.COM!jbvb
From: jbvb@FTP.COM ("James B. Van Bokkelen")
Newsgroups: comp.protocols.tcp-ip.ibmpc
Subject: Re: Low Power AT adapter
Message-ID: <9011061412.AA04825@ftp.com>
Date: 6 Nov 90 14:12:11 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Reply-To: jbvb@ftp.com
Organization: The Internet
Lines: 33


    .....  I have been trying for three months to get the XIRCOM adapter to
    work with FTP software's Generic ethernet packet interface. It has not
    worked since the day it was purchase.  FTP tells me that they are aware
    of the problem and that is has to do with Xircom's packet driver being
    faulty.  Xircom has given me the latest driver and it still locks up
    during any FTP transfers.  When I asked Xircom to send me one of the old
    drivers while they worked out the problems with the new ones, they told
    me that the never had one that worked!  How can they market these things
    to the FTP users if the software has never worked?

It actually does work reasonably well when talking to canonical 4bsd Unix
host systems (I know, we have several Xircom widgets in-house).  The problem
is that early versions of the Xircom Packet Driver cannot handle full-size
Ethernet packets (1500 bytes of data and 14 of header).  There have been a
number of other drivers which have hit the streets with this problem, because
neither 4bsd Unix nor most of the freeware TCP/IP packages ever use packets
bigger than about 1100 bytes.  PC/TCP will cheerfully request 1460-byte
TCP segments, and if the foreign host is willing (other copies of PC/TCP,
VMS systems and IBM mainframes are), away we go.

There is also a partial work-around:  PC/TCP allows the TCP window to be
configured (with IPCONFIG).  If you set the window to 1024 bytes on all
the Xircom-equipped PCs you have, this will limit the size of packets
sent to the PC, and all will be well on FTP 'get' commands, and 'put'
commands between pairs of PCs.  If your problem is 'put' commands to
other hosts which ask for large segments, you'll have to get Xircom to
fix the driver (I don't know if the non-Clarkson driver, which first appeared
in early October, has the problem or not).  At any rate, our support people
ought to have told you this.  If they didn't, my apologies...

James B. VanBokkelen		26 Princess St., Wakefield, MA  01880
FTP Software Inc.		voice: (617) 246-0900  fax: (617) 246-0901