erlyaws-list

[Erlyaws-list] 64K tcp/ip port constrain

[Pat e <pat...@gm...>]

Can anyone tell me how can Yaws have almost 80,000 concurrent
connections, and some "home-made" erlang servers over 110K concurrent
connections if there are only 64,000 tcp/ip ports?

BR
Patrick

Re: [Erlyaws-list] 64K tcp/ip port constrain

[<ju...@pr...>]

Hello Patrick,

I don't know anything about the 80,000 claim,
but,

A) a single webserver can certainly serve requests on multiple IP addresses
at once, thus isn't limited to 64K listening ports in total.

B) as a server it only needs one IP address and 1 port anyway.. no matter
how many requests!

Each client isn't assigned a unique port at the server end - and nor does it
even need to be unique at the client end
4 pieces of information identify each tcp/ip flow.  SourceIP, SourcePort,
DestIP, DestPort.

It's only that combined flow identifier that needs to be unique.

Julian

----- Original Message ----- 
From: "Pat e" <pat...@gm...>
To: <erl...@li...>
Sent: Tuesday, February 13, 2007 10:24 AM
Subject: [Erlyaws-list] 64K tcp/ip port constrain


> Can anyone tell me how can Yaws have almost 80,000 concurrent
> connections, and some "home-made" erlang servers over 110K concurrent
> connections if there are only 64,000 tcp/ip ports?
>
> BR
> Patrick
>
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Re: [Erlyaws-list] 64K tcp/ip port constrain

[David H. <dav...@bl...>]

Pat e wrote:
> Can anyone tell me how can Yaws have almost 80,000 concurrent
> connections, and some "home-made" erlang servers over 110K concurrent
> connections if there are only 64,000 tcp/ip ports?

A TCP/IP connection is identified on each host by a
(local port, local IP, remote port, remote IP) tuple.

Therefore, there can be more than 2^16 connections to a server (even if
the server is listening on a fixed port) provided that they are from more
than one client.

In theory it's also possible to have more than 2^16 connections between a
specific pair of hosts provided that they use all of the available port
combinations. However, TCP/IP stacks generally do not support reusing
local port numbers (when the port is not specified by the client software)
by default, so the practical restriction in this case may still be 2^16.

-- 
David Hopwood <dav...@bl...>