RFC 142 (rfc142) - Page 2 of 2

Time-Out Mechanism in the Host-Host Protocol

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ne 5
a.  On sending out a STR or RTS and if you do not get back a match-
    ing RTS or STR, or a CLS in T time units a CLS will be sent.
    After sending the time-out CLS race condition can be avoided
    by ignoring the matching RTS or STR that arrives before the
    matching CLS.

b.  On sending out a CLS (any kind, including the time-out CLS),
    and if you do not get back a matching CLS in T time units, the
    matching CLS is assumed to have returned.  However, if a RTS or
    STR is sent on the same pair of sockets anytime after the time
    out and before a CLS is returned, and then we receive the CLS,
    there is no way to determine whether this returning CLS is for
    matching the previous CLS or for refusing the RTS or STR.  (See
    the figure for detail).  So far we could not solve this race
    condition except by assigning sequence number to connection
    throughout the Network which we don't think is a good solution
    at all.  Hence, we would like to bring the attention of the
    Host-Host Protocol Glitch Cleaning Committe to this problem.
    The time limit T should be a Network Standard and its value should
    be decided also.

       Reason                                Our NCP
       ------                                -------

    1. User requests connection              1. RTS ->

    2. User gets tired requests CLS
       (or NCP timeout)                      2. CLS ->

    3. No matching CLS returned in
       T time units                          3. CLS assumed returned
                                                free socket and other
                                                resources

    4. User requests another connection
       over same socket pair                 4. RTS ->

    5. CLS received                          ?? does it belong to
                                             2 or 4?

                                   Figure

         [ This RFC was put into machine readable form for entry ]
            [ into the online RFC archives by Gert Doering 4/97]
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