| Lesson 6 | Servers |
| Objective | Describe the different types of servers and their functions. |
Different Types of Servers
Server features and functions
A server is a computer that stores content and then delivers that content when it's requested by a client. The term "server" can refer both to a program that performs these operations and to the machine that runs server programs.
The primary function of the server is to coordinate the exchange of data between the users (called nodes) or other networks.
Because all data must pass through the server, the more data that is passed, the slower the server becomes. To off-load some of the more demanding tasks, general purpose servers pass these tasks to specialized servers for processing.
These 'specialized' servers are optimized to perform one particular task, thereby improving the throughput of the general server.
As an example, when calling for information through your local telephone, you dial 411 for local information, or (Area Code) 555-1212 for information outside your area. This system is more efficient than requiring the local operator
to handle all information calls. The same is true for servers. Whenever the general purpose server receives a special request, it routes that request to a specialized server to handle.
Let's see what some of these special servers do.
- Application: An application server typically handles database queries.
- Certificate:A certificate server stores and retrieves a user's digital ID to verify authenticiy.
- E-commerce: An e-commerce server supports a full range of Internet commerce activities such as order entry, credit card processing, shopping cart applications, and customer catalog searching.
- DNS: Each time a user types an Internet address, such as Amazon.com, that domain name must be translated to a numeric IP address. The IP address is nothing more than a series of numbers that represents Amazon's Web site. The DNS (domain name server) performs these translations quickly.
Directory
A directory server is similar to a DNS server, but instead of translating Internet domain names to a number, it is used to translate user names to a LAN address. The protocal used is LDAP (Lightweight Directory Access Protocol).
An LDAP is essentially a two-column list:
- user names on one side and
- network card addresses for each PC on the LAN, on the other.
Like DNS, a directory server permits users to send files to a LAN destination by name, rather than using numbers.
File
A file server simply stores thousands of files and is especially designed to locate and transmit those files as rapidly as possible.
FTP
Like a file server, an FTP server is dedicated to transferring files also, but to transfer those files via the Internet. The primary difference between these servers is that special security and transport capabilities are required on the FTP server.
In the next lesson, the additional types of servers and their features and functions will be discussed.