Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!mips!ultra!wayne
From: wayne@ultra.com (Wayne Hathaway)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Question on forwarding broadcasts
Message-ID: <1990Oct1.151910.10282@ultra.com>
Date: 1 Oct 90 15:19:10 GMT
References: <1990Sep28.143945.7440@ultra.com> <36540012@hpindwa.HP.COM>
Reply-To: wayne@ultra.com (Wayne Hathaway)
Distribution: comp
Organization: Ultra Network Technologies
Lines: 32

Thanks to all who responded to my "Question on forwarding broadcasts"
posting.  Two quickies.

One, I apologize for over-simplifying the picture.  In the real life
situation both hosts do in fact have other network connections, so
they really SHOULD be forwarding packets.  If I had drawn a couple
more lines it would have been clearer.

But mostly, I should have read RFC 1009 more carefully, 'cause sure
enough, there it is right on page 36:

      In general, a gateway must not forward a datagram which
      arrives via local network broadcast, and must not send
      an ICMP error message when dropping the datagram.  A
      discussion of the rules will be found in Appendix A;
      see also [50].

(Interesting that this specific situation does NOT seem to be
mentioned anywhere in Appendix A, however!)

Now the only question is when the support for the above requirement
(that is, Data Link telling IP whether a packet arrived via broadcast
or multicast) will get out in the various host implementations.  And
THAT is what I should/would have asked, if I had read RFC 1009 better!

Anyway, apologies for the wasted net bandwidth on red herrings.  Now,
about the REAL question ... ?

    Wayne Hathaway               domain: wayne@Ultra.COM
    Ultra Network Technologies     uucp: ...!ames!ultra!wayne
    101 Daggett Drive             phone: 408-922-0100 x132
    San Jose, CA 95134           direct: Hey, you!