Squid running out of free ports.

Symptons from a busy squid with high traffic:

commBind: Cannot bind socket FD 98 to *:0: (98) Address already in use

Solution:

You have run out of free ports, all available ports occupied by
TIME_WAIT sockets.

Things to look into

1. Make sure you internally use persistent connections between Squid and
the web servers. This cuts down on the number of initiated connections/s
considerably.

2. Configure the unassigned port range as big as possible in your OS. On
Linux this is set in /proc/sys/net/ipv4/ip_local_port_range. The biggest
possible range is 1024-65535 and can sustain up to at least 500
connections/s continuous load squid->webservers.