With the newer versions of the Windows operating system and SQL Server 2005,
the software layer of the networking stack autoconfigures itself
for a majority of the cases requiring little or no user intervention.
However, there may be times when you may experience connectivity problems.
If you experience problems connecting a SQL Server client to a SQL Server 2005 server,
you may want to the check the following:
* Make sure that the SQL Server service is enabled and running.
* Make sure that the SQL Server 2005 instance has been enabled
to accept remote connections.
* Make sure that the correct protocols have been configured
on the client and SQL Server systems.
* Try connecting the client to the server system in some other manner,
for example by using Windows Explorer.
If you cannot connect via Windows Explorer,
your problem probably relates to some hardware issue or network adapter configuration.
* If connecting to a named SQL Server instance,
make sure that the SQL Server Browser service is running.
In addition, if using a firewall, make sure that the UDP port 1434 is not blocked.
While SQL Server 2005 network stack exposes many user configurable settings,
these hardly ever need to be changed to enhance performance.
In experience,
the network performance is good with just the default settings as long as
the hardware layer is configured and operating correctly.
Source: Microsoft SQL 2005 Administrator's Companion, Page 234