Excelan tcp-ip on VMS


Terry Slattery (tcs@USNA.ARPA)
Sun, 19 Jan 86 23:58:14 EST


> We're thinking about getting a few of the Excelan TCP/IP boards/software
> for our 11/780's running VMS. I remember a few problems mentioned about
> their products before, but don't have that mail to refer back to now.
> What are peoples experiences with Excelan, and mostly with the current
> revision of their software EXOS 8043 3.2? Also, are there any archives
> of tcp-ip mail around?

I have installed Excelan's TCP/IP front-end-protocol hardware/software
on several 2.9BSD Unix PDP11's at the Naval Academy. I can't comment
on the VMS installation, but will try to shed some light on the
implementation.

Excelan makes several boards for Unibus, Q-bus, Multibus, and VME-bus.
In terms of operation and capabilities, they are all identical. An on
board 80186 CPU, ethernet chip, and SEEQ xcvr chip do most of the
work. (The Unibus board is quite nice, Quad height, 5.5 amps total
current.) When operated in link level mode, an on board PROM based
kernel communicates with the host to transfer packets between the host
and the wire. The driver is somewhat similar to the DEC DEUNA driver in
that the host and interface communicate via a set of message buffers
(organized in circular queues). In this mode, the measured throughput is
60Kbytes per second of user data from memory to memory between two Vax
780 processors with a cpu load of about 50% (BRL Vax Unix; based on
4.2BSD).

When operated in front-end mode, the on board PROM module implements
a skeleton operating system in which the TCP/IP network code module
can execute. The net code is RAM resident and is generally downloaded
to the board at boot time. (Avoid the 128Kb RAM configuration board
for front-end operation; the additional memory is used for buffering
to increase performance.) The host communicates with the net code via
four device drivers and a set of library routines. The library
implements the 4.1a network semantics which are sufficient for most
applications.

At the application level, they supply Telnet, FTP, rlogin, rcp, rsh,
and rwho. The rlogin and telnet daemons run in the card for performance
reasons. This implies that their rlogin daemon doesn't handle automatic
authentication. They currently don't have an SMTP server, but I'm told
that they are seriously considering one so that they have a full
implementation. ARP, ICMP echo, and ICMP redirect are also supported.
Gateways are supported and routes are determined by incoming ICMP
packets or can be built manually with a maintenance program that they
supply. (The older version 3.1 couldn't handle gateways. In fact,
version 3.1 would crash if it received a packet from a host with a
different net address. The 3.1a network module fixes this serious
flaw. Anyone running Excelan software which says that the net module is
version 3.1 should contact their supplier for the 3.1a version. ) The
board status (things like ethernet collisions, etc) can be polled using
another program. Sub-nets are not supported but I have mailed them some
of the recent discussion and suggested that they work on it. I have
measured the data rate of the PDP11 to Vax at 60Kbytes/sec for memory to
memory transfers.

Having ported their old 3.1 version and then beta tested the 3.2 version
before its release, I found that they significantly cleaned up the code
in their port to RSX and VMS. (I did find some additional bugs, but
they have been reported and presumably fixed. Most of the ones I found
would have appeared only on a machine like the PDP11 with its restricted
addressing.)

I'm quite pleased with my decision to use the Excelan cards. I've had
no problems with the hardware and their software and documentation has
improved significantly. Excelan has been quite helpful. Why didn't I
chose CMC cards? They didn't have a shippable product at the time I
needed the cards. Excelan's presence in the market seems to have been
hurt a bit by the time they spent in getting the VMS/RSX ports done, but
it has probably helped their code significantly. The next release is
supposed to increase the performance. Now, if they just had an SMTP
server for VMS, I'd buy it for our VMS machine.

        -tcs
        Terry Slattery U.S. Naval Academy 301-267-4413
        ARPA: tcs@usna.arpa
        UUCP: decvax!brl-bmd!usna!tcs



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