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Lesson 7 Additional servers and their functions
Objective Describe the additional types of servers and their functions.

Additional Servers and Their Functions

There are many other types of servers used to perform specific client activities. Some servers work as search engines, while others are used for mailing lists, security, or even handling the amount of traffic coming to a specific site.
  1. Index or Catalog: An index or catalog server indexes documents in multiple Web sites in an organization, in effect becoming a search engine. The results are viewed in a format similar to a catalog, hence the name.
  2. List Server: A list server is an email server that manages a special type of email list called a listserv. It allows listserv subscribers to add or remove themselves from the mailing list without human intervention.
  3. Mail Server: A mail server provides electronic mail messaging services. Mail servers store and forward email using the POP3 and SMTP protocols. In other words, the mail server is responsible for handling your email, much the way the post office is responsible for handling your snail mail.
  4. Mirror Server: A mirror server is a replica of an original server. It contains an exact copy of an existing Internet site. The purpose is to reduce the load on the individual servers for heavily trafficked sites, such as the Amazon Web site, and to accommodate the volume of daily hits. Mirror servers are often connected to ISPs in other parts of the world.

The table below continues the list of servers with their functions.

News, Proxy, Telnet and Web Servers

1. News ServerA news server is a set of software used to handle Usenet articles. It may also refer to a computer itself which is primarily or solely used for handling Usenet. A reader server provides an interface to read and post articles, generally with the assistance of a news client. A transit server exchanges articles with other servers. Most servers can provide both functions.
2. Proxy ServerIn computer networks, a proxy server is a server (a computer system or an application) that acts as an intermediary for requests from clients seeking resources from other servers.A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource available from a different server and the proxy server evaluates the request as a way to simplify and control its complexity. Proxies were invented to add structure and encapsulation to distributed systems. Today, most proxies are web proxies, facilitating access to content on the World Wide Web and providing anonymity.
3. Telnet ServerTelnet Server hosts the remote sessions for Telnet clients. When Telnet Server is running on a computer, users can connect to the server with a Telnet client from a remote computer. Telnet Server is implemented in Windows as a service that can be configured to always run, even when no one is logged on to the server.When a Telnet client connects to a computer running Telnet Server, the remote user is asked to enter a user name and password. The user name and password combination must be one that is valid on the Telnet Server. Telnet Server on Windows supports two types of authentication: NTLM and Password (or plaintext).
4. Web HTTP ServerA web server is a computer system that processes requests via HTTP, the basic network protocol used to distribute information on the World Wide Web. The term can refer to the entire system, or specifically to the software that accepts and supervises the HTTP requests.

Review Hardware Devices and Servers

  1. Application server: Processes and hosts data applications used by groups of users.
  2. Router: Filters traffic based on protocol-specific software address, source and destination port numbers.
  3. Switch: Connects network segments with high-usage percentages and are used to create virtual LANs.
  4. DNS server: Translates host names to IP addresses.
  5. List server: Centralizes the organization of mailing lists and allows users to add/remove themselves automatically.

File and Network Servers

One or more network servers is a part of nearly every local area network and these are very fast computers with a large amount of RAM and storage space, along with one or more fast network interface cards. The network operating system provides tools to share server resources and information with network users. A sophisticated permissions-handling system is included, so that access to sensitive information can be carefully tailored to the needs of the users. For small networks, a singe network server may provide
  1. access control,
  2. file sharing,
  3. printer sharing,
  4. database, and
  5. other services.

The network server may be responding to requests from many network users simultaneously. For example, it may be asked to
  1. load a word processor program to one workstation,
  2. receive a database file from another workstation, and
  3. store an e-mail message during the same time period.
This requires a computer that can store and quickly share large amounts of information. When configuring such a server, the following guidelines should be followed:
  1. Fastest processor(s)
  2. Large amount of RAM
  3. multiple large, fast hard drives
  4. Extra expansion slots
  5. Fast network interface card(s)
Optionally (if no other such devices are available on the network):
  1. A RAID (Redundant Array of Inexpensive Disks) to preserve large amounts of data(even after a disk failure)
  2. A back-up unit (i.e. DAT tape drive, removable hard drives, or CD/DVD/BluRay burner)

In the next lesson, Internet bandwidth technologies will be discussed.

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