Re: Question on ICMP Parm Problem Messages


CLYNN@G.BBN.COM
17 Nov 1987 10:06-EST


Chris,
        If the IP header length is bad, I would send a parameter problem
message with a pointer of 0 and include a worst-case IP header (60 octets)
+ 64 bits of data; if something is that bad, give as much help as possible.
        For a bad IP length the pointer should be 2 or 3, and include the
IP header as specified in the IP Header Length field. Note that there is
more than one possible IP length error: a) too small to include the IP
header [I do not think I have ever seen a specification that the layer
above IP HAS to have a non-zero length, although it seems rather unlikely],
or b) that the length is too large for the datagram passed to the IP from
below. (Maybe a convention could be [informally?] established that a
pointer of 2 means the IP Length was too large and 3 that it was too small;
all in the spirit of adding as much diagnostic information as possible.)
PS: "columbia-pdn" is an interesting domain-style name.



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