SQL Server and Protocols

TCP/IP and Named Pipes
By default, clients have TCP and Named Pipes as available protocols on most of client computer. You can manipulate the protocol ordering by using the SQL Server Client utility. The client application uses the protocols in the order specified on the client computer. If you are using SQL Server 2005, the protocol order is stored in the ProtocolOrder registry entry under the following registry subkey:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSSQLServer\Client\SNI9.0

IPX/SPX
SQL Server 2005 does not support IPX/SPX. The newer versions of NetWare, such as NetWare 6.5, support TCP/IP which makes it the common protocol for all clients.

VIA
The Virtual Interface Adapter (VIA) can be used only by VIA hardware.

Shared Memory
Shared Memory can only be used on the local computer and cannot be used as a network protocol.

Reference: Microsoft SQL Server 2005 Books Online (2006), Index: client connections [SQL Server], about client network connections, choosing a network protocol