Re: 4.2/4.3 TCP and long RTTs

Bob Walsh (
Mon, 8 Dec 86 13:32:44 EST

        How can the TCP "just" inform the application about the problem?
        Unless there's a control channel to the application that allows
        the passage of status data, a send call must return an error.
        After that error, the application can't tell how much of the data,
        if any, was transmitted. "Reliable byte stream with possible gaps
        in case of error" isn't very satisfying.

Informing the application that the networking system is having trouble
getting acknowledgements does not mean that the networking system has
given up on sending that data. My intent was to point out that such a
decision should be left up to the application, which may in turn defer
the decision to the user. This was one of the qualities of the BBN
TCP/IP software, as you know. It is one of the reasons Bob Gilligan used
the BBN software for his demos.

Whether it is 30, 45 or 108 seconds doesn't matter. What does matter is
that Craig is preserving the RDP connection for a longer time under such
circumstances and therefore is less likely to see the connection fail.

There is also the point of extended acknowledgements.

Bob Walsh

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