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From: glass@anableps.berkeley.edu (Brett Glass)
Newsgroups: comp.protocols.tcp-ip.ibmpc
Subject: Re: NetBIOS Datagrams: Potential Incompatibility
Message-ID: <21782@agate.BERKELEY.EDU>
Date: 17 Mar 89 16:20:40 GMT
References: <8903161245.aa20821@Obelix.TWG.COM>
Sender: usenet@agate.BERKELEY.EDU
Organization: University of California, Berkeley
Lines: 55

In article <8903161245.aa20821@Obelix.TWG.COM> kuan@TWG.COM (Chia-Chee Kuan) wri
tes:

>According to the pseudo code listed in appendix C page C-47 in "Technical
>Reference: IBM PC Network", it does seems to me a received datagram completes
>all pending RECEIVE DATAGRAM commands which have matching source and
>destination specification.  This brings the two most authoritative
>documents, "Technical Reference: IBM PC Network" and RFC1001/1002, together
>without conflicting each other.

I've examined Appendix C, page C-47 of "Technical Reference: IBM PC
Network," and I see the section you're referring to; indeed,
there isn't a clear indication that the checking process
terminates after the first match is found. [I originally thought
I DID see such an indication, and posted two articles to that
effect to this newsgroup. But I cancelled them after taking
another look at the IBM manual.]

The one thing I can say for certain -- because I've checked it --
is that NO IBM implementation of NetBIOS has actually satisfied
more than one Receive Datagram command with a single datagram.
IBMer Dave Schwaderer's book and third-party NetBIOS
implementations also support this modus operandi. It's possible
that the description in IBM's manual was never checked for
accuracy, or even that it was INTENTIONALLY vague to make
correct implementation more difficult. But the de facto standard
is that only one command is satisfied.

As it turns out, the "Receive Datagram" pseudocode in RFC1002
could be made consistent with "reality" by moving a single line and
deleting one comment:

X Delete               /*
X                       * Replicate received NetBIOS datagram for
X                       * each recipient
X                       */
                       FOR EACH pending NetBIOS user's receive
                            datagram operation
                       BEGIN
                            IF source name of operation
                               matches destination name
                               of packet THEN
                            BEGIN
                               deliver USER_DATA from UDP
                                 packet(s);
                  +--------->
           Move   |         END
                  |    END /* for each */
                  --<< return;
                  END /* good */

I think it might be a good idea to make this change, and to
correct the other parts of the documents accordingly.

--Brett