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From: xjeldc@GEMINI.LDC.LU.SE (Jan Engvald LDC)
Newsgroups: comp.protocols.tcp-ip.ibmpc
Subject: Bootp and 3C501
Message-ID: <8910092133.AAsunic17654@sunic.sunet.se>
Date: 9 Oct 89 19:28:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 47

>I have a BOOTP problem with the Clarkson 3C501 packet driver and
>NCSA TN3270 software. We are using a Gould NP1 to run the BootP
>program and all works well with an IBM with a 3C523 card. But when
>using an IBM Model 30 w/3c501 card, I get a scambled packet with
>the BootP request. The same machine works fine without BootP, that is,
>when I include "myip=a_real_number" instead of "myip=BOOTP"

David,

If your bootp server is fast, you can't use bootp from a 3C501 card. This is
because the 3C501 is a stoneage old Ethernet card, and it is even designed in
violition with the recomendations in the Ethernet specifications. Quoting from
DIX The Ethernet, A Local Area Network, Data Link Layer and Physical Layer
Specification, appendix E: Interframe Recovery, last paragraph: 

  Reception of an incoming frame immediately after transmission of an outgoing
  frame is a very important capability, even for stations which do not tend to
  communicate with several other stations concurrently. All stations, low
  performance to high performance, should allow reception of an incoming
  frame immediately after transmission of an outgoing frame.

Well, the 3C501 can't do that, and it will miss the answer unless you have
a slow server or some communication delay.

I noticed this when installing packet drivers and NCSA Telnet with bootp.
We mostly use WD8003 Ethernet cards, but had a few 3C501. Installation and
first test went well, then I returned to one of the PCs with a 3C501 and
it didn't work any longer. Checked the other PC with 3C501, and that one
was also not working.

The reason for this behaviour was that I updated the bootptab file after
each installation. For the first test bootp didn't have the ethernet address
in RAM memory, so it had to read the updated file (takes a short while).
From then on, all answers for that address was from RAM memory, and thus
were fast and got lost in the 3C501.

In summury: Use a modern Ethernet card (3C503, WD8003, NI5210, or the like).
                                             
Jan Engvald, Lund University Computing Center
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