Re: Interesting Ethernet/UNIX 4.2 observation.


David C. Plummer (DCP@SCRC-QUABBIN.ARPA)
Mon, 24 Feb 86 10:22 EST


    Date: Sun, 23 Feb 86 23:22:24 EST
    From: Chris Torek <chris@gyre.umd.edu>

[Sigh, our domain code isn't quite in yet... I'm assuming this gets to
you through the mailing list...]

[Disclaimer: I don't use Unix. For that matter, I seriously dislike
Unix.]

    Unix does not broadcast rwho requests; rwho runs entirely locally.
    Rwhod *must* send updates in order to allow downtime determination
    at remote sites (though if all you are interested in is load average
    and users, sending updates makes little sense). In addition, there
    is no easy way to determine who really *is* interested in the
    information; the problem is quite similar to that of determining
    to whom to send routing information. The obvious easy answer is
    to use broadcasts (on networks that support the concept).

Maybe I'm confused then. Somebody is sending out broadcast packets to
UDP port 513 (decimal). Is that RWHO or RWHOD? Our Lisp machine system
thinks that the protocol is called :UNIX-RWHO. Maybe that is wrong.

    In 4.3, rwhod sends broadcasts only once every two minutes. If
    this is still too much for your network, why are you running it at
    all?
I wish we weren't. Tell me the flag to set, and I'll tell our unix
people to set it. If you tell me, 'Well, you have to go in a modify
code...' I'll ask why there isn't a flag.
    And if you are running it because it is more useful than it
    is expensive, why are you complaining?
I don't know if anybody uses the information. I would guess not. We
aren't a unix house.
    If you know how to make it work better, change it!
I've fixed my machine to ignore these, but that doesn't affect the other
100+ workstations that are still wasting time responding to our 3 unix
machines.

    This is not intended as flamage. I am entirely serious: if it is
    broken, fix it; if it is useless, do not use it; but please do not
    simply complain that Unix is flawed because rwho uses broadcasts.
    It comes configured that way only because those who make the tapes
    find it more useful than costly. It is quite simple to turn off.

Tell me how.



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