Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!decwrl!ucbvax!HOGG.CC.UOREGON.EDU!jqj From: jqj@HOGG.CC.UOREGON.EDU Newsgroups: comp.protocols.tcp-ip Subject: Re: ICMP's & IP src addrs Message-ID: <8809171424.AA01138@hogg.cc.uoregon.edu> Date: 17 Sep 88 14:24:29 GMT Sender: daemon@ucbvax.BERKELEY.EDU Organization: The Internet Lines: 20 >Flame: An ICMP echo to a broadcast address should get no response! >What an incredibly obnoxious thing to do! What do you mean it should get no response? It is a legal broadcast that all machines should reply to. Recall that broadcast was not originally part of the IP design, and indeed that many media that support IP do not support hardware broadcast. As such, it is to be expected that the "proper" behavior of various protocols in response to broadcasts is not well defined in the specs. IP broadcast was added mostly to support the functionality provided by Ethernet broadcast. In any CSMA environment (though not on a TR!) a broadcast ICMP echo request is a VERY BAD idea since it is guaranteed to generate a massive collision as everyone tries to answer at once. Designers of broadcast request-response Ethernet protocols almost always go to great effort to insure that the number of legitimate respondents is bounded, and preferably 1 (cf proxy ARP). If the spec doesn't forbid it, it should.