Lab 3 Computer Networks

8/12/2019 Lab 3 Computer Networks

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Application Architectures

Client-server

Peer-to-peer (P2P)

Hybrid of client-server and P2P


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Client Server Architecture

server: always-on host

permanent IP address

server farms for scaling

clients: communicate with

server

may be intermittentlyconnected

may have dynamic IPaddresses

do not communicatedirectly with each other


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Pure P2P Architecture

no always-on server

arbitrary end systems

directly communicate

peers are intermittentlyconnected and change

IP addresses

example: Gnutella

Highly scalable

But difficult to manage


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Hybrid of Client Server and P2P

Napster

File transfer P2P

File search centralized:

Peers register content at central server

Peers query same central server to locate content

Instant messaging

Chatting between two users is P2P

Presence detection/location centralized:

User registers its IP address with central server when itcomes online

User contacts central server to find IP addresses of

buddies


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Network Operating System (NOS)

Network require special software to control the

flow of information between users.

A NOS, is installed onto each PC that requires

network access.

The NOS is like a traffic controller that monitors

the exchange and flow of files, electronic mail,

and other network information.


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Peer to Peer Vs Client Server

Network Operating Systems are classified

according to whether they are peer-to-peer or

client- server NOSs.

Peer-to-peer NOSslike Windows 95, Windows98and Windows for Workgroups are best for home &

small office use.

Client-server NOSslike Windows NT, Linux and

NetWare are ideal for large-scale organizations


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Peer to Peer Network


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Peer to Peer Network


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Peer-to-Peer Model


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Peer to Peer Network (contd.)

A peer-to-peer network allows two or more

PCs to pool their resources together.

Individual resources like disk drives, CD-

ROM drives, and even printers are

transformed into shared, collective resources

that are accessible from every PC.


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Peer to Peer Network (contd.)

Unlike client-server networks, where networkinformation is stored on a centralized file server

PC and made available to tens, hundreds, or

thousands client PCs, the information storedacross peer-to-peer networks is uniquely

decentralized.

Because peer-to-peer PCs have their own hard

disk drives that are accessible by all computers,

each PC acts as both a client (information

requestor) and a server (information provider).


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Advantages of Peer to Peer Network

Less initial expense

No need for a dedicated server

Setup An operating system (such as

Widows 95) already in place may only need

to be reconfigured for peer-to-peer

operations.


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Disadvantages of Peer to Peer Network

DecentralizedNo central repository for files

and applications.

Security Does not provide the security

available on a client/server network.


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Client Server Network


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Client Server Network


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Client/Server Model with Dedicated Servers


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Client/Server Model with a General Server


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Advantages of Client Server Network

Centralized Resources and data security

are controlled through the server.

ScalabilityAny or all elements can be

replaced individually as needs increase.

FlexibilityNew technology can be easily

integrated into system.

Accessibility

Server can be accessedremotely and across multiple platforms.


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Disadvantages of Client Server Network

Expense Requires initial investment in

dedicated server

MaintenanceLarge networks will require a

staff to ensure efficient operation.

DependenceWhen server goes down,

operations will cease across the network.

Lab 3 Computer Networks

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Transcript of Lab 3 Computer Networks