[e2e] TCP improved closing strategies?

Joe Touch touch at ISI.EDU
Mon Aug 17 07:16:23 PDT 2009

Hash: SHA1

William Allen Simpson wrote:
>> As I recall Andy Tanenbaum used to point out that TP4 had an abrupt close
>> and it worked.  It does require somewhat more application coordination
>> but
>> perhaps we can fake that by, say, retransmitting the last segment and
>> the FIN
>> a few times to seek to ensure that all data is received by the client???
> Cannot depend on the DNS client's OS to be that smart.  Has to be a server
> only solution.  Or based on a new TCP option, that tells us both ends are
> smart.  (I've an option in mind.)

There are two different problems here:

1) server maintaining state clogging the server

2) server TIME-WAIT slowing connections to a single address

Both go away if the client closes the connection. If you are going to
modify both ends, then that's a much simpler place to start than a TCP
option (which will need to be negotiated during the SYN, and might be
removed/dropped by firewalls or NATs, etc.).

FWIW, persistent connections helps only #2. If it's the number of
different clients connecting a server that is locking up too much server
memory, then persistent connections will make the problem worse, not better.

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