1.2 Compare a file-and-print server with an application server.

File-and-print Server: A computer provides storage space and print service for the other computers in a network. In most cases, we don't say file-and-print server such as in Microsoft's Networking Essentials exam outline. We mention file server and print server separately.

  

Figure 1.8 File server

Suppose we have several computers in a network. Computer A has a directory c:\ww that is network shared. Because other computers such as computer B and computer F in the network can also access this shared directory, computer A is called file server. In a Microsoft's operating system such as Windows 95 or Windows NT, you can use Windows Explorer to share a directory or map a shared directory to a local driver.

  

Figure 1.9 Printer server

Now a printer is connected to computer A. Computer A shares this printer and provides printing service to other computers in the network. If any of the computer in the network such as computer B or computer F can print documents in this printer via computer A's printing service, computer A is called a printer server.

Application Server: An application server is a computer provides back-end data processing for other computers in the network. SQL Server and Exchange Server are examples of an application server. Compared to a file server, which saves the file directly, an application server executes data processing. Sometimes it is difficult to distinguish a file server with an application especially in the database area. Most database applications such as Oracle, Sybase, Informix, Ingress and Microsoft's SQL Server for Windows NT Server meet the requirement of application server because they provide back-end data processing.

  

Figure 1.10 Application server

Now we install SQL server for Windows NT in computer A and install the client tools of SQL Server in computer B and computer F. We create an employee table (Table 1.1) in computer A via the SQL server.

Table 1.1 Employee information

Name

Age

Sex

Wang Wei

30

Male

Li Bo

27

Female

Bill Gates

44

Male

 

Now computer B wants to list all the employees whose age is bigger than 28, it sends the following SQL statement to computer A.

Select Name from employee where age > 28.

After computer A receives this request, it executes the data processing and returns the result -- "Wang Wei" and "Bill Gates" to the computer B.

Some databases such as FoxPro and Access also can be shared and accessed by other computers in the network, however, it is still a file server solution. For example, if you share an Access database file employee.db in computer A, when computer B needs to access the database, it just treats this database file as a local file. Computer A doesn't perform any back-end processing. Imagine we have the same employee database structure shown in table 1.1 but we have 1000 rows data now. In computer B, we perform the same query to list all the employees whose age is bigger than 28.

In an application server solution, the application server processes this query and sends the result. For example, of the 1000 names, only 200 names have corresponding ages which are greater than 28. So, only 200 names are sent to computer B. However, in a file server solution, the file server doesn't perform any execution, computer B needs to map the whole database locally and retrieve the data after that. For an application server solution, you just need to transmit 200 names over the network, however for a file server solution, 1000 records include name, age and sex information are transmitted over the network. Therefore, an application server solution reduces networking traffic significantly, compared to a file server solution.