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Re: productivity?

2011-08-22 18:52:49

Hector Santos wrote:
One issue not raised here: ephemeral port exhaustion. It's a rather specialized problem, more of an issue for Windows folks than Linux, and mostly an issue for routers, proxies, and similar devices that tend to funnel a large volume of mail to smaller number of destinations. But it's a real problem, one where reusing existing client connections can provide a complete and permanent resolution.

The ephemeral port exhaustion exploit began with Microsoft DNS server DoS attacks....

I'm talking about the normal operational condition where an SMTP sender connects repeatedly to the same receiver. On platforms where the default ephemeral port space is small (e.g., Windows Server 2003 and older BSD kernels), the sender can exhaust the ephemeral ports. For those of us in the filtering business, this is a constant nuisance.

The problem can be mitigated by increasing the number of ephemeral ports (Vista defaults to the IANA recommend range), reducing TIME_WAIT, or (tada!) reusing connections.

None of which has any relevance to any existing RFCs. But tuning connection reuse might make for an interesting Informational doc or BCP.


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