Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!ucbcad!ucbvax!RADC-MULTICS.ARPA!Ata
From: Ata@RADC-MULTICS.ARPA ("John G. Ata")
Newsgroups: comp.protocols.tcp-ip
Subject: Re: TCP/SMTP ULTRIX <-> MULTICS PROBLEM
Message-ID: <871231171431.988445@RADC-MULTICS.ARPA>
Date: 31 Dec 87 17:14:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 42


    Delivery-Date:  30 December 1987 12:36 est
    Delivery-By:  Network_Server.Daemon (tcp-ip-RELAY@SRI-NIC.ARPA)
    Date:  Wednesday, 30 December 1987 12:24 est
    From:  scottr at CSC-LONS.CSV001.TV (Scott W. Rogers)
    Subject:  TCP/SMTP ULTRIX <-> MULTICS PROBLEM
    To:  tcp-ip at SRI-NIC
    cc:  cscmaint at RADC-LONS
    
     I'm having a problem receiving some (SMTP) mail from a MULTICS host on
     my ULTRIX 1.2 and 2.0 (binary, sigh) VAX 8600 and 8650 systems.
    
     I can send mail to MULTICS without any problem, and most mail is
     received.  The problem is as follows:
    
        After the SMTP initialization, MULTICS sends a 51 character 'MAIL
        From: <username.mailbox.qualification.etc>' string which is never
        acknowledged by ULTRIX.  The MULTICS engineer says that his system
        is not receiving the TCP ACK even after several retrys and changing
        his timeout from 1 to 2 minutes.

The connection seems to go comotose.  We send the 51 character packet
out, and retransmit a number of times, but the ACK never arrives.  Our
logs show no checksum errors or any other kind of error.  We have tried
it with different size packets, but strangly enough 51 seems to be the
magic number causing this problem.
    
          .
          .
          .
    
        The problem is completely reproducable through MAIL.  Using TELNET,
        the Multics engineer was able to produce it only sometimes.

This problem is also completely reproducable by opening a TELNET
connection to CSC-LONS mail server and simulating a message.

This problem appears to affect certain ULTRIX sites, but not all of
them.  We chose some ULTRIX sites at random and they seemed to work ok.
Suspect that they are running a different version of TCP/SMTP.

                    John G. Ata
          Site Technical Specialist at RADC-MULTICS