RE: limit to number of consoles?

On Mon, 2007-10-22 at 15:00 -0700, Harris, David (IT Solutions US)
wrote:
>    Each one of those
>    connections is using a port# on the conservere end too.  For
>    example:
> 
> delos: {1} netstat -an | grep 7001
> tcp        0      0  172.17.2.254.59046     172.17.2.14.7001 ESTABLISHED
> tcp        0      0  172.17.2.254.59081     172.17.2.11.7001 ESTABLISHED
> tcp        0      0  172.17.2.254.59106     172.17.2.13.7001 ESTABLISHED
> tcp        0      0  172.17.2.254.59195     172.17.2.12.7001 ESTABLISHED
> tcp        0      0  172.17.2.254.50994     172.17.2.3.7001 ESTABLISHED
> tcp        0      0  172.17.2.254.51007     172.17.2.2.7001 ESTABLISHED
> tcp        0      0  172.17.2.254.51021     172.17.2.1.7001 ESTABLISHED

There's no actual requirement in the TCP protocol that the local port be
unique for an outgoing connection; it's the 4-tuple (local address,
local port, remote address, remote port) which uniquely identifies the
connection.

The system I'm most familiar with -- Solaris -- was fixed about two
years ago to do controlled reuse of local ports to permit more
connections than the available anonymous port range permits.

The easiest way to demonstrate this feature is to artificially constrain
the available anonymous port space:

# ndd -set /dev/tcp tcp_smallest_anon_port 32768
# ndd -set /dev/tcp tcp_largest_anon_port 32770

and then make a few outgoing connections to web servers:

% netstat -n -finet | grep 10.8.57 | grep 80
129.148.174.66.32768 10.8.57.1.80         32811      0 502094      0 ESTABLISHED
129.148.174.66.32768 10.8.57.2.80         32811      0 502094      0 ESTABLISHED
129.148.174.66.32768 10.8.57.3.80         49232      0 501008      0 ESTABLISHED

The default 2^15 anonymous ports available can make many more than 2^15
outgoing connections.

(this was bug 4461538; the fix is in the current development builds aka
sunos 5.11 or solaris "nevada").

					- Bill