TCP / IP无法建立传出连接

We're seeing TCP/IP warning and quite a few connection failures on our web and SQL server (Win 2008 SP1 with IPv6 enabled) and it happens more often when the worker process/SQL server process has been running for a couple of days continuously. I am wondering what causes these warnings? What is the default number of TCP connections allowed and how can we bump this up?We're seeing TCP/IP warning and quite a few con