linux-kernel - Re: more than 65535 outbound connections

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Message-ID: <85e0e3140703090243n36fd467dwc83aff0d7b6fb004@mail.gmail.com>
Date:	Fri, 9 Mar 2007 16:13:00 +0530
From:	Niklaus <niklaus@...il.com>
To:	unlisted-recipients:; (no To-header on input)
Cc:	linux-kernel@...r.kernel.org
Subject: Re: more than 65535 outbound connections

On 3/9/07, David Lang <david.lang@...italinsight.com> wrote:
> On Fri, 9 Mar 2007, Florian Weimer wrote:
>
> >> i read on the web that terry lambert has got 1.6 million simultaneous
> >> connection ? how is the way it is done.
> >
> > Multiple IP addresses, I guess.
>
> what must be unique is the four-parts of a connection
> source IP, source port, destination IP, destination port
>
> as long as the set is unique any element can be re-used (a big webserver has one
> IP and port on the server side, but many IPs and ports on the client side)
>
> when you make a connection you have the option of not specifying the source IP
> and port (letting the OS/library pick ones for you). some libraries will not
> re-use the same source port for multiple connections, others will (with the
> appropriate options)
>
> if you want to have your program assign the source IPs and port itself you can
> do so (you may have to also give the library/os a flag that tells it you know
> what you're doing, and it's ok to let you re-use ports)
>

yes now lets take 2 dest machines , source ip is fixed , source port (2^16 - 1)
destip is fixed (a.a.a.a and b.b.b.b) ,dest port(2^16 -1) each ,

for a connection we have one port used , say connection 1 is

source ip,port 1 , a.a.a.a port 1
source ip,port 2 , a.a.a.a port 2
.
.
.
source ip,port 65535 , a.a.a.a port 65535

so total of 65535 connections (assume traffic is still going on, a
movie on a slow line dialup or 1kbps )

now if i try to open another connection (assume lots of file
descriptors are present) to a.a.a.a what happens

to b.b.b.b what happens

i think both will not get established as the OS doesn't have any free
source ports or am i wrong

> David Lang
>
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