Re: workstation != gateway -- CLANG CLANG CLANG

Jeff Mogul (
25 Feb 1986 1736-PST (Tuesday)

Although I entirely agree with Geof that the 4.2 networking architecture
got this part wrong, in fairness to the current crew at Berkeley it should
be noted that 4.3 remembers which interface a packet arrived on. This
should make it possible, finally, to implement ICMPs such as Address Mask
and Information Request, perhaps even Host Redirect, and reverse-path
forwarding of broadcasts (if anyone wants it.)

Maybe the lesson that should be learned from Geof's message is that
the incoming interface is not the only piece of information that should
stay stuck onto a packet for its entire lifetime in a gateway. Whether
it is reasonable given the current 4.2/4.3 networking architecture to
track things such as
        packet source (data link layer address)
        was it sent as a broadcast?
        how long is it? [so that higher levels don't have to count it again]
        when it arrived [for accurate metering]
etc. may depend on how committed people are to the current model, where
only the "data" gets passed between layers. I think this stems from a
basic confusion between networking and IPC in 4.2; there seems to me to
be an attempt to shoehorn both kinds of communication into a single model.

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