[e2e] TCP improved closing strategies?

rick jones perfgeek at mac.com
Thu Aug 13 08:41:26 PDT 2009

On Aug 12, 2009, at 2:51 PM, William Allen Simpson wrote:

> With the advent of more widespread DNSsec deployment, more UDP  
> sessions
> are likely to fallover into TCP sessions.
> I've been informed that even today, with a more limited TCP activity,
> busy servers cannot wait 2MSL to finish closing.

One wonders how a web server survives...

> Also, busy caching servers run out of port numbers, and cycle quickly.
> So there's ample opportunity for seemingly duplicate transmissions.

Presuming a single source and destination IP address and a single well- 
known server port number, the caching server could run through ~60000/ 
MSL connections per second before attempting to reuse a four-tuple  
still in TIME_WAIT.  If one were holding strictly to a four minute MSL  
that is ~250 connections per second.  60 seconds seems to be a rather  
more common MSL (well, length of TIME_WAIT) so that would be ~1000  
connections per second.

> I've been searching my personal copy of the e2e-interest archives  
> back to
> '98 (the previous years are only on backup somewhere), and haven't  
> found
> anything on improved closing strategies.  Ideas?

Don't close after the first transaction.  There is a reason HTTP added  
persistent/pipelined connections.

> Of course, there's T/TCP, but wasn't closing one of its Achilles  
> heels?

T/TCP was an engineering excercise - it was interesting, I enjoyed  
trying it out and even had a netperf test for it, but it didn't go  

rick jones
Wisdom teeth are impacted, people are affected by the effects of events

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