Multiprotocol Clients

The Multiprotocol selection has two key features:

• Automatic selection of an available network protocol to communicate with Microsoft® SQL Server™.

  This is convenient when you want to connect to multiple servers running different network protocols, but do not want to reconfigure the client connection for each server. If the client and server Net-Libraries for TCP/IP Sockets, NWLink IPX/SPX, or Named Pipes are installed on the client and server, the Multiprotocol Net-Library will automatically choose the first available network protocol to establish a connection.

• Client encryption.

  You can enforce encryption over the Multiprotocol Net-Library on clients running Microsoft Windows NT® or Microsoft Windows® 95/98 to prevent others from intercepting and viewing sensitive data.

The Multiprotocol Net-Library takes advantage of the remote procedure call (RPC) facility of Windows NT, which provides Windows NT Authentication and ease of use. For the Multiprotocol Net-Library, clients determine the server address using the server name.

The Multiprotocol Net-Library does not support server enumeration. From applications that can list servers by calling dbserverenum, you cannot identify servers running SQL Server and listening on the Multiprotocol Net-Library.

Multiprotocol Name Resolution

Using the RPC run time, which is called by the Multiprotocol Net-Library, clients can connect to servers using a variety of other protocols. When establishing a connection, the Multiprotocol Net-Library passes the computer name to the RPC run time, which determines the network protocols available and attempts to use each one until a connection is established. (Only NWLink IPX/SPX, TCP/IP Sockets, and Named Pipes are considered tested and supported.)

To accomplish the computer name to node connection, the RPC run time uses a naming service compatible with the network protocol used (WINS for TCP/IP, SAP for NWLink IPX/SPX, and Net BIOS broadcasts for Named Pipes). Only the computer name should be specified, because a local RPC database is used to resolve the names over the supported protocols.

Client Encryption

You can enforce encryption over the Multiprotocol Net-Library on a per-client basis. On each client where you want encryption to take place, you must create the RPCNetlib registry key and add the following registry value:

HKEY_LOCAL_MACHINE
    \SOFTWARE
        \Microsoft
            \MSSQLServer
                \Client
                    \RPCNetlib

Value Name: Security
Data Type: REG_SZ
String: Encrypt

This causes all communication over the Multiprotocol Net-Library between this client and the server to be encrypted. (Only this client’s communications are encrypted. Other clients using the Multiprotocol Net-Library that do not have this parameter set do not use encryption.)

To configure a client to use the Multiprotocol Net-Library