SQL Server: What is the browser service?

This service is newly added to SQL Server 2005. Every time I give a lecture, I have to ask questions and explain them in detail.

To put it simply,If a physical server has multiple SQL Server instances, SQL Server 2005 provides a new browser service to ensure that the client can access the correct instances.

If you are interested, take a good look at the introduction below. This is part of online help.

The SQL Server Browser program runs as a Windows service. The SQL Server Browser listens for incoming requests to Microsoft SQL Server resources and provides information about the SQL server instance installed on the computer. The SQL Server Browser can be used to perform the following operations:

• View the list of available servers
• Connect to the correct server instance
• Connect to the dedicated administrator connection (DAC) Endpoint

The SQL Server Browser Service (sqlbrowser) provides the Instance name and version number for each instance of the database engine and SSAs. The SQL Server Browser is installed with SQL Server to provide this service for earlier versions of SQL server running on the computer (starting from SQL Server 7.0.

The SQL Server Browser can be configured during installation or by using the SQL Server Configuration Manager. By default, the SQL Server Browser Service is automatically started:

• During upgrade and installation.
• In parallel with SQL Server 2000 instances.
• When installed on the cluster.
• When you install a named instance of SQL Server Enterprise, standard, or workgroup.
• When you install Analysis Services named instances.

Background

Before SQL Server 2000, only one SQL server instance can be installed on one computer. SQL server listens for incoming requests from port 1433. This port is allocated to SQL Server by the official Internet number distribution organization (IANA. Only one SQL server instance can use a port. Therefore, when SQL Server 2000 introduces support for multiple SQL Server instances, SQL Server Parsing protocol (ssrp) is developed ), listen on UDP port 1434. The Listener service uses the name of the installed instance and the port or name pipeline used by the instance to respond to client requests. To address ssrp System Restrictions, SQL Server 2005 introduces the SQL Server Browser service to replace ssrp.

How SQL Server Explorer works

After an SQL server instance is started, if TCP/IP or via is enabled for SQL server, the server will be allocated a TCP/IP Port. If the Named Pipes protocol is enabled, SQL server listens to a specific named pipeline. This particular instance will use this port (or "pipe") to exchange data with the client application. During installation, TCP port 1433 and MPs queue\sql\queryThe instance is assigned to the default instance, but the server administrator can then use the SQL Server Configuration Manager to change the instance. Since only one SQL server instance can use a port or MPs queue, different port numbers and MPs queue names are allocated to the named instance, including SQL Server Express. By default, the named instance and SQL Server express are configured to use dynamic ports when enabled, that is, the available ports are allocated when SQL Server is started. If necessary, you can assign specific ports to the SQL server instance. During connection, the client can specify a specific port. However, if the port is dynamically allocated, the port number may be changed when SQL Server is restarted. Therefore, the correct port number is unknown to the client.

After it is started, the SQL Server Browser starts and uses UDP port 1434. The SQL Server Browser reads the registry, recognizes all SQL Server instances on the computer, and specifies the ports and named pipes they use. When a server has two or more NICs, the SQL Server Browser returns the first enabled port for SQL Server. The SQL Server Browser supports IPv6 and IPv4.

When the SQL Server Client Requests SQL Server resources, the client network library uses port 1434 to send a UDP message to the server. The SQL Server Browser responds with the requested instance's TCP/IP Port or named pipe. Then, the network library in the client application will use the port or named pipe of the desired instance to send a request to the server to complete the connection.

For information about starting and stopping the SQL Server Browser Service, see how to start and stop the SQL Server Browser Service.

By the author: Chen xizhang in 2009/6/30 18:14:45 published in: http://www.cnblogs.com/chenxizhang/
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