Re: TCP/IP header question


David C. Plummer (DCP@QUABBIN.SCRC.Symbolics.COM)
Mon, 16 Mar 87 10:09 EST


    Date: Tue, 10 Mar 87 23:09:57 est
    From: jbvb@BORAX.LCS.MIT.EDU (James B. VanBokkelen)

    I don't see any reason to send obsolete information; our
    implementation updates both ACKs and Window to the values current at
    the instant the packet is sent. Of course, this does mean we have to
    re-checksum the packet, but we have to do this anyway if a packet gets
    partially ack'ed (which you'd better be prepared for...)
Nit: Indeed, you'd better be prepared for it, but you don't have to
rechecksum if you don't reshuffle the data around. Not reshuffling is
paramount to sending old+new data, which the spec allows.
                                                              Note that it
    *does* seem like a good idea (not mine) to retain the IP
    'identification' so that fragments can be assembled from any instance
    of (re)transmission of a given packet.



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