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Server Types

When planning for server installation, it is essential to identify the

type of servers that is the best suited for the network requirements

of an organization.

To identify the appropriate server, you need to be acquainted with

the features of various server types.

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Client/Server Model

In a network, a client/server model enables the efficient

interconnectivity of program makes a service request to a server

program, which fulfils the request.

Multiple client programs share the services of a common server

program.

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Name of Servers

Access Servers

Security Servers

Network Infrastructure Servers

File Distribution Servers

Communication Servers

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Access Servers

Access Servers provide interconnectivity between computers and

devices with in a LAN, connect WAN sites, and provide internet

access.

Types of access servers are:

Gateway Server

Router Server

Bridge Server

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Gateway Server

A gateway server connects diverse networks by using a

combination of hardware and software.

A gateway server must be configured with multiple network cards,

which are linked internally and connected to different networks. This

feature is known as multihoming.

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Router Server

A router server consist of routing table, which specified the optimum

path for transmitting network information to a particular destination.

Like a gateway server, a router must be multihomed and can be

substituted by a dedicated network device.

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Bridge Server

A bridge server transmits network packets between two diverse

networks. For example, a bridge server enables an Ethernet

network to communicate with a Token Ring network.

Bridge servers are protocol independent but they can not perform

special routing functions.

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Security Servers

Security Server Provide security by allowing or blocking specified

applications, protocols or network traffic. They are also capable of

redirecting network traffic to its specified destination.

Example-

Firewall Servers

Proxy Servers

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Firewall Servers

A firewall server functions as a security filter for segregating private

and public networks to preserve confidential data.

The traffic is directed through the firewall server and is allowed or

blocked on the basis of rules and filters configured by the server

administrator.

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Implementation of a Firewall Server

Generally, firewall security is implemented in three zones:

An internal network

An external network

A demilitarized Zone

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DMZ

A DMZ grants external users access to certain services, such as e-

mail services, on the internal network while preventing unauthorized

access to sensitive internal services, such as file and print services.

However, a separate NIC should be installed on the firewall server

when a DMZ network is implemented.

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Proxy Server

A proxy server forwards requests from a client or another server. It is used to redirect webpage requests from a client to a web server.

A proxy server caches web pages so that a web page downloads faster the next time it is requested.

If a web page is not available on the cache, the server retrieves it from the internet.

Proxy server can also use for restricting access to unauthorized websites.

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Network Infrastructure Servers

Network Infrastructure Servers provide network services, such as IP services and domain name resolving that are critical to the functioning of the LAN or WAN.

EXAMPLES- DHCP DNS WINS SNA

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DHCP server

A DHCP server dynamically assigns network IP addresses to

network clients at start-up. Therefore, each client computer does not

require a static IP address.

When the client computer starts, the DHCP server assigns an IP

address to the client computer in response to its request

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DNS Server

A DNS server uses a database of tables to resolve FQDN to their

respective IP address.

A user can therefore access an Internet server by referring to its

name.

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WINS Server

A WINS server is a special Microsoft Windows server that enables clients to resolve windows NETBIOS name to IP addresses.

Therefore, clients must communicate with the WINS server using NETBIOS over TCP/IP(NBT). Clients send information to the WINS Server instead of broadcasting it over the network.

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SNA Server

An SNA Server functions as a gateway between a client computer

and a mainframe computer.

This server uses the SNA set of protocols developed by IBM for

main mainframe computers.

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File Distribution Servers

File distribution servers enable authenticated users to access files

and printers. These servers enable users to share a common

network printer, share files across LANs, WANs or the INTERNET

and host web sites.

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File Distribution Server

FTP Server

File and Print Server

Web Server

Database Server

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FTP Server

An FTP server transfers files efficiently and securely and ensures

that the integrity of the files is maintained.

After authenticating the logon credentials of a user, the FTP server

enables the user to access files on the server.

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File and Print Server

File and print servers enable client computers to store files and access printers. A file server provides a centralized location for client files. This enables them to be backed up easily.

A print server facilitates client computers to send print requests to a network printer. It queues the requests for printing and directs them to the destination printer.

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Web Server

A web server enables the client computers to access Web Pages. A

client computer uses a web browser to request the server for a web

page.

The server processes the request and downloads the required web

page on the client’s web browser, where it is displayed.

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Database Server

A database server stores structured data in filing system that can be

accessed by several users concurrently.

To ensure efficient storage and processing of data, the database

server must be equipped with a large amount of disk space and

RAM.

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Communication Servers

Communication Servers provide access to methods of

communication, such as fax and e-mails. These servers can be

configured to operate locally on a LAN or through the internet.

Example:

FAX SERVER

MAIL SERVER

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FAX server

A fax server is configured by using special faxing software and a

modem and telephone line.

This server facilitates users to fax documents directly from their

computer.

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Mail Server

A Mail server enables users to send and receive e-mail. Users

connect to the mail server by supplying their mail account

information.

A mail server is accessible from the internal network. However,

external users can also send and receive e-mail messages over the

internet.

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Server Hardware Types

Blade Servers

Tower Servers

Rack-Mount Servers

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Blade Servers

Blade servers are self-contained servers embedded in computer boards. A

blade server consists of a single circuit board that may have one or more

processors, chipsets memory and storage units.

The blades are housed in a chassis known a razor. Each blade server can

be hot plugged into a common chassis so that power supplies, network

connections, and cooling are all shared.

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Blade Server- advantages

The main advantage of a blade server is that it requires less space that a

conventional server. Also, in blade servers many processors are utilized on

a single system.

This is useful for organizations that use high density cluster of servers. In

addition, if one of the blade server fails, it can easily and quickly be replaced

without affecting the whole system.

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Blade Servers- disadvantages

Disadvantage of a blade server is the amount of power consumed to cool the dense cluster of servers.

Blade servers have low performance and storage capacities. A blade servers do not include floppy drives, issues related to updating or

resolving is difficult. Moreover, blade servers are generally proprietary and do not work with

blade servers from other manufacturers.

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Tower Servers

Tower Servers are typically servers that resemble traditional

personal computer cases.

They are independent units that have dedicated storage and

network capabilities. The tower server can range from single

processor systems to multiple processor systems.

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Tower Servers- Advantages and disadvantages

The main advantages of tower servers is that they provide the flexibility of having different adapter cards, dedicated storage and peripheral connections.

The design of the tower server is robust to ensure power reliability. The disadvantage of tower servers is that it requires more space. Wiring of these servers is a tedious job.

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Rack- Mount Servers

A Rack mount server is designed to fit in a standardized rack

enclosure and stacked vertically. As the servers are mounted on

racks, floor space is better utilized in a data center.

A rack-mount server can be an independent unit, similar to tower

servers, or can be blade server based.

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Rack-Mount Servers: advantages and disadvantages

As rack-mount servers are mounted in racks, they can be easily

managed using centralized management systems, such as a

keyboard/video/mouse (KVM) system.

The KVM system can be plugged into any server for configuration

purposes. In addition, the rack-mount server allows easier

scalability.

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Application Server model

Application Server models are used for designing computing

environments.

Types-

Dedicated Application Server Model

Distributed Application Server Model

Peer to Peer Application Server Model

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Dedicated Application Server Model

A dedicated application server model uses servers for hosting

special single-purpose application services, such as Web services

and e-mail services.

This servers are specifically configured to host applications such as

web hosting and middleware applications.

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Distributed Application Server Modle

A distributed application server model is also referred to as

client/server model or an n-tier model.

This model allows a client to access more than one server on a

network simultaniously.

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Distributed Application Server Model- an example

Examples of networks that implement a distributed application

server model are Web and Internet.

They are very large distributed networks.

The web browsers allow clients to access applications and

resources on local as well as remote servers.

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Peer to Peer Application Server Model

In peer to peer application server model, applications can perform

as both clients and servers. This model is usually used in

decentralized networks where servers and clients are equal

contributors.

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