[mailto:owner-ietf-smtp(_at_)mail(_dot_)imc(_dot_)org] On Behalf Of Hector
Sent: Thursday, August 18, 2011 12:32 PM
Subject: Re: Mail Data termination
First, a server may have Receiver Loading Limits and a client with a
tenacity to take up more CPU time than it needs can get it flagged. To
use CS for the purpose to reduce its redundancy without considering
the load it places on receivers is a very selfish engineering
consideration. Chewing up a channel unnecessarily for 5 minutes
disallowing other clients connection access increases system available
and scalability problems.
Second, it uses a dangerous presumption that a server is FIXED on
using 5 minutes for idle times. 5 minutes is a SHOULD, not a MUST and
for a client to DEPEND on a SERVER using 5 minutes is short-sighted
The five-minute timeout is a SHOULD. If you're resource constrained, I would
argue that issuing a 221 to the most idle open connection and closing it down
so the resources can be re-used is just fine.
I don't think the practice of connection caching is particularly selfish when
compared to the cost of having the connection torn down and then re-established
with some frequency, when it's generally much cheaper for both the sender and
the receiver to just leave it open.
This should be done using an SMTP extension where a server can expose
server timeouts perhaps and willingness to allow a client to sit idle
redundantly and repeatedly.
Or it can simply impose an idle time that's more strict than what 184.108.40.206.7 of
RFC5321 says, understanding that one needs to be pretty careful about doing so.