[e2e] TCP improved closing strategies?

John Day day at std.com
Thu Aug 13 12:51:40 PDT 2009

Correct me if I am wrong, but in terms of recycling port-ids so that 
no late packets are accepted and having to wait 2MSL, I believe that 
Dick Watson proved in 1981 that waiting 2MSL was both necessary and 
sufficient. Actually it is 2MSL on one side and 3MSL on the other.

Watson, Richard. "Timer-Based Mechanisms in Reliable Transport 
Protocol Connection Management, Computer Networks 5 (1981) 47 - 56.

As far as TP4 is concerned, it has the same constraint.  There is no 
avoiding it.

Earlier Belnes showed that the 5 way exchange was required to deliver 
one message reliably as long as there were no failures, but to be 
absolutely sure timers were required and you were back to Watson's 

Belnes, Dag  "Single Message Communiction," IEEE Transactions on 
Communications, Vol. COM-24, No. 2 February, 1976, pp 190 - 194.

Watson shows that bounding 3 timers are necessary and sufficient to 
ensure reliable transfer.  Matta and his students did a paper 
recently that looked at the single message case under harsh 
conditions and found that even though TCP bounds the same 3 timers it 
isn't as effective as Watson's approach,.

Take care,
John Day

At 8:53 -0700 2009/08/13, rick jones wrote:
>On Aug 13, 2009, at 5:58 AM, William Allen Simpson wrote:
>>AFAIK, the last survey (6-7 years ago) was 100 million queries per day, so
>>that's roughly 694,444 during each 2MSL period.  Of course, that's average,
>>not peak (likely much more)....
>>We're talking about Linux, Solaris, HP-UX, AIX, maybe some others. Do all
>>these servers have the capability to handle that many TCP connections,
>>rather than UDP connections?
>>Do *any* of them?
>Modulo the variations in how persistent the connections were 
>relative to the transaction rate, and the differences in the 
>metrics, you can probably look at the archives of SPECweb96 (HTTP 
>1.0) SPECweb99 (1.1), SPECweb99_SSL (new SSL session for each new 
>TCP connection, IIRC, but it has been a while) or even 
>SPECweb2005/SPECweb2009 if you can decide which among "Banking," 
>"Ecommerce," and "Support" workload is closest, to get an idea of 
>how many TCP connections servers can handle.  During the heyday of 
>web server benchmarking, there was a lot of work done in minimizing 
>the overhead of TIME_WAIT tracking etc.
>>>That said, the problem is fun.
>>>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.)
>Isn't a new TCP option by definition depending on the client's OS to be smart?
>rick jones
>Wisdom teeth are impacted, people are affected by the effects of events
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