Neither Keith nor I are talking about the mailer. If the remote MACHINE
cannot handle the load, it should be set up to reject the excess
connections. This is true no matter WHAT MTA is running on the remote
system.
What is a valid limit? Only the administrator of that particular machine
knows since it depends on what the hardware is, what other software is
running, etc... The sending qmail only knows one thing, you accepted the
connection so you can handle the load.
On Mon, 12 Apr 1999, Marc Slemko wrote:
> On Mon, 12 Apr 1999, Keith Burdis wrote:
>
> > > qmail is great that way at inflicting remote DoS attacks against other
> > > mailers.
> >
> > Well, the obvious question is why do mailers accept connections that they
> > cannot handle? If the remote host accepts the mail it should be prepared to
> > deal with it.
>
> blah blah blah.
>
> I don't know? Why does "qmail" accept connections that it cannot handle?
>
> It is a pretty simple concept: even if a mailer can "handle" it, if you
> send 1 simultaneous bit of mail to 1 machine, while using all your other
> slots for sending to other machines, you will get x% of each machine's
> resources. If you send 120 simultaneous messages, then you only get y% of
> the machine's resources, where y is between a little (eg. if the machine
> normally has 10000 incoming connections) to a huge amount (eg. if the
> machine normally has 2 incoming connections) less than x.
>
> Because of somewhat nonsensical hard coded limits, when sending a lot of
> outbound mail with qmail, the number of simultaneous connections open
> total often is a big limitation. Because of that, the fastest way to send
> mail is to ensure you aren't overloading any remote machine more than
> necessary at any given time, so that each connection to that machine takes
> the least time possible, even if that involves more seialization.
>
> Trying to blame the remote mailer for qmail's less than great behaviour in
> this area is silly.
>
>
---------------------------------
Timothy L. Mayo mailto:[EMAIL PROTECTED]
Senior Systems Administrator
localconnect(sm)
http://www.localconnect.net/
The National Business Network Inc. http://www.nb.net/
One Monroeville Center, Suite 850
Monroeville, PA 15146
(412) 810-8888 Phone
(412) 810-8886 Fax
