Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!ucbvax!VAX.FTP.COM!jbvb
From: jbvb@VAX.FTP.COM (James Van Bokkelen)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: sendmail hanging followup
Message-ID: <8905241347.AA19716@vax.ftp.com>
Date: 24 May 89 13:47:12 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 15

One consideration that hasn't been discussed is what TCP MSS options are
sent when the connection is opened, and how the two hosts are supposed to
deal with them.  I have some recent experience with IBM VM systems which
request 1460 byte MSS regardless of whether the connection is on the local
subnet, or routed via a gateway.  If your host's TCP/IP is just accepting
and using the requested MSS (or min(1024, FRN_MSS), as Unices tend to), this
could be the problem.

FTP's TCP requests a 512-byte MSS when the connection is routed via a
gateway, and uses min(512, FRN_MSS) on the transmit side (a relatively
recent change; I used to just do what they told me, but 'they' were all
too frequently broken).

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