Re: Broadcast RPC question


Doug Nelson (08071TCP%MSU.BITNET@CUNYVM.CUNY.EDU)
Tue, 18 Oct 88 17:13:21 EDT


Your detailed trace allows me to confirm my suspicions. The hosts which
reply with a "port unreachable" are definitely in error. They are
making the following mistakes (I'm using the Host Requirements draft
RFC as my point of reference):

1. A host should not send an ICMP error reply in response to a
    link layer broadcast (section 3.2.2).

2. The Dec host either a) thinks that 3.0.0.0 is a valid IP broadcast
    address, in which case it should not send an ICMP error reply (section
    3.2.2), or b) doesn't think 3.0.0.0 is an IP broadcast address,
    in which case it should have discarded the datagram immediately upon
    receipt as not being destined for itself (section 3.2.1.9).

3. The host is responding with an IP source address of 3.0.0.0, rather
    than its own IP address (sections 3.3.5 and 3.3.6).

To be fair, there are quite a number of TCP/IP implementations which make
one or more of these mistakes. It will be nice to have the Host Requirements
RFC in hand to use as a definitive reference for such errant software.

Even now while this document is still in draft form, I'd recommend pointing
vendors in this direction if they aren't already aware of its existence, and
if they are, I'd suggest that they read it.

Doug Nelson
Michigan State University



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