Chapter 1, Server Technology

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Server Types

When planning for server installation, it isessential to identify the type of servers thatis the best suited for the network

requirements of an organization.

To identify the appropriate server, youneed to be acquainted with the features of

various server types.


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Client/Server Model

In a network, a client/server modelenables the efficient interconnectivity ofprogram makes a service request to a

server program, which fulfils the request.

Multiple client programs share theservices 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 interconnectivitybetween computers and devices with in aLAN, 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 diversenetworks by using a combination ofhardware and software.

A gateway server must be configured withmultiple network cards, which are linkedinternally and connected to different

networks. This feature is known asmultihoming.


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Router Server

A router server consist of routing table,which specified the optimum path fortransmitting network information to a

particular destination.

Like a gateway server, a router must bemultihomed and can be substituted by a

dedicated network device.


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Bridge Server

A bridge server transmits network packetsbetween two diverse networks. Forexample, a bridge server enables an

Ethernet network to communicate with aToken Ring network.

Bridge servers are protocol independent

but they can not perform special routingfunctions.


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Security Servers

Security Server Provide security byallowing or blocking specified applications,protocols or network traffic. They are also

capable of redirecting network traffic to itsspecified destination.

Example-

Firewall Servers

Proxy Servers


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Firewall Servers

A firewall server functions as a securityfilter for segregating private and publicnetworks to preserve confidential data.

The traffic is directed through the firewallserver and is allowed or blocked on thebasis of rules and filters configured by the

server administrator.


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Implementation of a Firewall Server

Generally, firewall security is implementedin three zones:

An internal network

An external network

A demilitarized Zone


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DMZ

A DMZ grants external users access tocertain services, such as e-mail services,on the internal network while preventing

unauthorized access to sensitive internalservices, such as file and print services.

However, a separate NIC should be

installed on the firewall server when aDMZ network is implemented.


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Proxy Server

A proxy server forwards requests from a client oranother server. It is used to redirect webpagerequests from a client to a web server.

A proxy server caches web pages so that a webpage downloads faster the next time it isrequested.

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 providenetwork services, such as IP services anddomain 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 assignsnetwork IP addresses to network clients atstart-up. Therefore, each client computer

does not require a static IP address.

When the client computer starts, theDHCP 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 toresolve FQDN to their respective IPaddress.

A user can therefore access an Internetserver by referring to its name.


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WINS Server

A WINS server is a special MicrosoftWindows server that enables clients toresolve windows NETBIOS name to IP

addresses. Therefore, clients must communicate with

the WINS server using NETBIOS overTCP/IP(NBT). Clients send information tothe WINS Server instead of broadcasting itover the network.


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SNA Server

An SNA Server functions as a gatewaybetween a client computer and amainframe computer.

This server uses the SNA set of protocolsdeveloped by IBM for main mainframecomputers.


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File Distribution Servers

File distribution servers enableauthenticated users to access files andprinters. These servers enable users to

share a common network printer, sharefiles across LANs, WANs or theINTERNET 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 efficientlyand securely and ensures that the integrityof the files is maintained.

After authenticating the logon credentialsof a user, the FTP server enables the userto access files on the server.


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File and Print Server

File and print servers enable clientcomputers to store files and accessprinters. A file server provides a

centralized location for client files. Thisenables them to be backed up easily.

A print server facilitates client computersto send print requests to a network printer.It queues the requests for printing anddirects them to the destination printer.


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Web Server

A web server enables the client computersto access Web Pages. A client computeruses a web browser to request the server

for a web page.

The server processes the request anddownloads the required web page on the

clients web browser, where it is displayed.


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Database Server

A database server stores structured datain filing system that can be accessed byseveral users concurrently.

To ensure efficient storage and processingof data, the database server must beequipped with a large amount of disk

space and RAM.


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Communication Servers

Communication Servers provide access tomethods of communication, such as faxand e-mails. These servers can be

configured to operate locally on a LAN orthrough the internet.

Example:

FAX SERVER

MAIL SERVER


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FAX server

A fax server is configured by using specialfaxing software and a modem andtelephone line.

This server facilitates users to faxdocuments directly from their computer.


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Mail Server

A Mail server enables users to send andreceive e-mail. Users connect to the mailserver by supplying their mail account

information.

A mail server is accessible from theinternal network. However, external users

can also send and receive e-mailmessages 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 serversembedded in computer boards. A blade serverconsists of a single circuit board that may have

one or more processors, chipsets memory andstorage units.

The blades are housed in a chassis known arazor. 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 itrequires 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 ofthe 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 ofpower consumed to cool the dense cluster ofservers.

Blade servers have low performance andstorage capacities.

A blade servers do not include floppy drives,issues related to updating or resolving is difficult.

Moreover, blade servers are generallyproprietary and do not work with blade serversfrom other manufacturers.


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Tower Servers

Tower Servers are typically servers thatresemble traditional personal computercases.

They are independent units that havededicated storage and networkcapabilities. The tower server can range

from single processor systems to multipleprocessor systems.


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Tower Servers- Advantages and

disadvantages

The main advantages of tower servers isthat they provide the flexibility of havingdifferent 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 thatit 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 astandardized rack enclosure and stackedvertically. As the servers are mounted on

racks, floor space is better utilized in adata 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 inracks, they can be easily managed usingcentralized management systems, such as

a keyboard/video/mouse (KVM) system.

The KVM system can be plugged into anyserver for configuration purposes. In

addition, the rack-mount server allowseasier scalability.


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Application Server model

Application Server models are used fordesigning computing environments.

Types-

Dedicated Application Server Model

Distributed Application Server Model

Peer to Peer Application Server Model

S


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Dedicated Application Server

Model

A dedicated application server model usesservers for hosting special single-purposeapplication services, such as Web

services and e-mail services.

This servers are specifically configured tohost applications such as web hosting and

middleware applications.


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Di ib d A li i S


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Distributed Application Server

Modle

A distributed application server model isalso referred to as client/server model oran n-tier model.

This model allows a client to access morethan one server on a networksimultaniously.


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Di t ib t d A li ti S


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Distributed Application Server

Model- an example

Examples of networks that implement adistributed application server model areWeb and Internet.

They are very large distributed networks.

The web browsers allow clients to accessapplications and resources on local as well

as remote servers.


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Chapter 1, Server Technology