CLIENT/ SERVER ARCHITECTURE

INCLUDING BASIC NETWORKING

Architecture• 3 primary logical architectures

1. Host-based • Traditional mainframe / central computer model

2. Client-based / Peer-to-Peer• Historically most home-based and many small

office networks3. Client-server

• Microsoft model – or what we commonly see today

• Fairly powerful clients interacting with some number of servers

• Model used on campus WE WILL ONLY FOCUS ON CLIENT/ SERVER

ARCHITECTURE.

CLIENT/ SERVER ARCHITECTURE

CLIENT/ SERVER ARCHITECTURE

A network architecture in which each computer or process on the network is either a client or a server.

A simple definition

A simple definition of CS is “ server software accepts requests for data

from client software and returns the results to the client.”

COMPONENTS• Clients• Servers• Communication Networks

Server

Server Client

Client / Server (CS) Architecture

• CS model distinguishes between client / server devices and applications.

• Clients request specific services.• Servers respond to individual client

requests for services.– Functionality implemented in software

• Depending on services the server provides, physical server computers can be different than other servers and client computers (i.e. more processing power, more memory, etc.)

Client/Server Architecture

Client/Server Architecture

• Structured architecture with specific roles for specific devices using specific applications.– File server, printer server.

• A “managed” network .– Unlike P2P will have a network admin.

• CS is the most commonly observed architecture.– Most applications are designed to be

used on CS architecture.

Client/Server architecture

• Balance processing between clients and server(s) by dividing functions.– Client – presentation and application

logic.– Server – Data access logic, data storage,

application logic.

Clients• Applications that run on computers.• Rely on servers for

– Files.– Devices. Clients are

Applications– Processing power.

• Example: E-mail client– An application that enables you to send

and receive e-mail.

Servers• Computers or processes that

manage network resources– Disk drives (file servers) Servers

Manage – Printers (print servers) Resources– Network traffic (network servers)

• Example: Database Server– A computer system that processes

database queries.

Categories of Servers

• Data Server• Communication Server• Internet Server

Data Server• Data-oriented; used only for data storage

and management.• Since a data server can serve more than

one compute server, compute-intensive applications can be spread among multiple severs.

• Does not prefer any application logic processing.

• Performs processes such as data validation, required as part of the data management function.

• Requires fast processor, large amount of memory and substantial Hard disk capacity..

Data Server

ComputerServer

Communication Server

Provides gateway to other LANs, networks & Computers.

E-mail Server & internet server. Modest system requirements .

multiple slots. fast processor to translate

networking protocols.

Internet Server

Internet ServerPC client

UNIX workstations

Local AreaNetwork

Communication Networks

Networks Connect Clients and

Servers.

Multi-Tier Client/Server architecture

Distinct characteristics of Client/ Server Architecture o Client-server is a computing architecture which

separates a client from a server.o It is almost always implemented over a

computer network.o The most basic type of client-server architecture

employs only two types of nodes: clients and servers. This type of architecture is sometimes

referred to as two-tier. It allows devices to share files and resources.

o Server provides the service. o Client is considered as the customer requesting

the service. o The server service can be shared among a

number of clients.o Clients must request or initiate the service. o The location of the server in the network is

transparent to clients.

Systems with C/S Architecture

• File servers – File sharing and file processing.

• Data base servers– Passing file results – Example: Query in DBMS server – Typically one single request/reply

• Transaction servers– Transaction server includes DBMS and transaction

monitoring.– Server has remote procedures run online by the client.

• web servers– Super-fat servers and thin clients. – Uses HTTP protocol.– Java was first to introduce interactive C/S forms.

Client

Client

Server

ServerInternetClient

JAVA

ClientHTML

Application

Client/Server Models

• Where to push the application to • Fat clients

– The bulk of the application is running on the client .– The client knows how the data is organized and where it is .– Different clients access the same applications different ways .

• Fat servers– The server more complicated. – The clients are less complex .– More of the code runs on the server .– The network interaction is minimized.

ServerClient

Application

Middleware Software

It is the (/) between client and server which glues them together. – Allowing the client request for a service and the

server providing it. • Middleware can also be between server/server.• Two broad classes

– General • LAN servers, TCP/IP, Communication stacks,

Queuing services, etc. – Application specific

• Used to accomplish a specific task • Groupware specific: SMTP • Internet specific: HTTP• Database specific: SQL.

Client/Server Building Blocks

• Purpose – To divide the application

between the client and server

– Different functionalities of client and server

• Basic client server model– Fits various applications

• Small office • Small business • Enterprise • Global Client

Server

Server

Client ServerMiddleware

Single Machine

Client Server

Middleware

Client Middleware

C/S Middleware

C/S

C/S

C/S

Servers and Client Building Blocks

Web Browser GUI DSM OS

Service-Specific; DSM NOS (security, peer-to-peer, directory, distributed files);

Transport stack (TCP/IP)

Web serverGroupware

DMBSEtc.

ClientMiddleware

Server

Server Scalability

PC Server

Asymmetric Multi-processing Superserver

symmetric Multi-processing Superserver

Multiservers

Server Scalability

• Superserver – A very powerful server.– Single-server or multiserver.– Each server can have a single processor or

multiprocessor.– Multiprocessing can be Asymmetric or Symmetric.

• Multiprocessing • Asymmetric: each processor is dedicated to

a specific task • Fully symmetric (SMP): applications are

divided into threads and threads are sent to available processors

– Examples: 32-bit NT, Unix, NetWare – Requires 3 basic functionalities:

» Global scheduling » I/O sharing structure » OS access sharing

Server scalability• Multi servers

– Pool of servers, providing more processing power (also called a cluster).

– They divide the task between different servers.

• Server lite– As opposed to full blown servers. – Provides a background process on the

client machine that can accept unsolicited networks request (refreshing database, synchronizing time, etc.)

Network Services• Network services (in general) are

the specific functions/tasks/jobs provided by the network– File sharing– Printing– Communication– Mail– Internet– Management.

Common Network Services

• File and print services– Allow sharing of data files and printers

• Communications services– Such as mail services

• Coordination and storage of email• Internet services

– WWW, FTP, some security• Access services

– Allow remote users to connect to network• Login (authorization / authentication)

• Network Management Services– Traffic monitoring, load balancing, diagnostics

Client/Server Networking Model

• Networking in Linux follows the client/server model– Server provides the resource (web server).– Client talks to the server (browser, e-mail

program).• Server has a corresponding program that

communicates with the client (runs in the background)– In Windows the server program called

service .– In Linux the server program called daemon.

NETWORKINGBASIC NETWORKING

3 General Categories of Networks

• 1) Local Area Network (LAN)

• 2) Wide Area Network (WAN)

• 3) Metropolitan Area Network (MAN)

Local Area Network{LAN}

• A LAN is a group of computers located in a relatively small geographical area (like a building or group of buildings).– Typically owned by a single organization

• A local area network (LAN) is a computer network that interconnects computers within a limited area such as a home, school, computer laboratory, or office building, using network media.[1] The defining characteristics of LANs, in contrast to wide area networks (WANs), include their smaller geographic area, and non-inclusion of leased telecommunication lines.

• A group of computers connected within a confined geographic area.

• Commonly used for intra office communication.

Local Area Network• Various configurations, called topologies,

have been used to administer LANs.– Ring topology A configuration that connects

all nodes in a closed loop on which messages travel in one direction.

– Star topology A configuration that centers around one node to which all others are connected and through which all messages are sent.

– Bus topology All nodes are connected to a single communication line that carries messages in both directions.

Local Area Network

Switch

PC PC PC

PrinterPC

?

Wide Area Network{WAN}

• A wide area network (WAN) is a network that covers a broad area (i.e., any telecommunications network that links across metropolitan, regional, national or international boundaries) using leased telecommunication lines. Business and government entities utilize WANs to relay data among employees, clients, buyers, and suppliers from various geographical locations. In essence, this mode of telecommunication allows a business to effectively carry out its daily function regardless of location. The Internet can be considered a WAN as well, and is used by businesses, governments, organizations, and individuals for almost any purpose imaginable.[1]

Wide Area Networks

Leased lines from a larger provider form part of the WAN

LAN versus WANLAN

• High speed (≥1000 mbps)• Tend to primarily use Ethernet

and Wi Fi, but also use Token Passing.

• Generally consist of layer 2 devices like switches, bridges. To a lesser extent layer1 devices like hubs & repeaters.

• Typically owned, controlled, and managed by a single organization.

• Cost is Low as compared to WAN.

WAN• Low speed (≤ 155 mbps)• WANs tend to use technology like

MPLS and ATM, and to a lesser extent (Frame Relay & X.25) for connectivity over the longer distances.

• Layer 3 (+) devices such as routers, multi-layer switches and technology specific devices like ATM or Frame-relay Switches etc.

• WANs are typically not owned by any one organization but exist under collective or distributed ownership and management over long distances.

• Cost is high as compared to LAN.

Metropolitan Area Network {MAN}

• A metropolitan area network (MAN) is a computer network in which two or more computers or communicating devices or networks which are geographically separated but in same metropolitan city and are connected to each other are said to be connected on MAN. Metropolitan limits are determined by local municipal corporations; the larger city, bigger then MAN, the smaller a metro city, smaller the MAN. [1]

Metropolitan Area Network

Difference between LAN, WAN and MAN

A presentation by:- Abhinav

singh Class:- 9th ‘B’Roll no:- 01