Networks

Engr. M Jamil Khan, PhD Student, UETTAXILAmuhammad.jamil@uettaxila.edu.pk

OUTLINE

• Basic concepts in communications

• Understanding Networking.

• Understanding Transmission Medium (Network Cables)

• Understanding Network Hardware

• WAN and LAN

• Understanding Network Protocols

BASIC CONCEPTS IN COMMUNICATION

BASIC CONCEPTS Communications – activity associated with

distributing or exchanging information Telecommunications – technology of

communications at a distance that permits information to be created any where and used everywhere with little delay

Today it, involves

Data: digital and analog

Voice: spoken word

Video: telecommunication imaging

ESSENTIALS FOR COMMUNICATIONS

Must have a messageMessage must have a transmitterMessage must have a mediumMessage must be understoodMessage must have some level of

security

Source Transmitter Transmission Receiver Destination

Source System Destination System

Workstation/PC Workstation/PC

Medium

1 2 3 4 5 6

ESSENTIALS FOR COMMUNICATIONS

Source Transmitter Transmission Receiver Destination

Source System Destination System

Workstation/PC Workstation/PC

Medium

1 2 3 4 5 6

1. Text input information2. Input data digital bit stream3. Transmitted analog signal4. Received analog signal5. Output data digital bit

stream6. Text output information

UNDERSTANDING NETWORKING

NETWORK

“A network is a group of computers and other devices (such as printers) that are connected by some type of transmission

media”.

NETWORK Networks can be as small as two computers

connected by a cable in a home office or as

large as several thousand computers

connected across the world via a

combination of cable, phone lines, and

satellite links. Networks might link mainframe computers,

printers, plotters, fax machines, and phone

systems. Networks might communicate through

copper wires, fiber-optic cable, radio waves,

infrared, or satellite links.

WHY USE NETWORK?

Using networks offers advantages relative to

using a stand-alone computer—that is, a

computer that is not connected to other

computers and that uses software applications

and data stored on its local disks. Most

importantly, networks enable multiple users to

share devices (for example, printers) and data

(such as spreadsheet files), which are

collectively known as the network’s resources.

WHY USE NETWORK? Sharing devices saves money.

For example, rather than buying 20 printers

for 20 staff members, a company can buy

one printer and have those 20 staff members

share it over a network. Sharing devices also saves time.

For example, it’s faster for coworkers to

share data over a network than to copy data

to a removable storage device and physically

transport the storage device from one

computer to another e.g. sneakernet.

WHY USE NETWORK? Helps to Manage.

Imagine you work in the Information

Technology (IT) department of a

multinational company and must verify that

each of 5000 employees around the globe

uses the same version of a database

program. Without a network, you would have

to visit every employee’s machine to check

and install the proper software. With a

network, however, you could check the

software installed on computers around the

world from the computer on your desk.

TYPES OF NETWORKS

Computers can be positioned on a

network in different ways relative to each

other. They can have different levels of

control over shared resources. They can

also be made to communicate and share

resources according to different

schemes.

CLASSIFICATION OF NETWORKS

Classification by component roles.

Peer to Peer

Client/Server

Classification by network geography.

Local Area Network(LAN)

Metropolitan Area Network (MAN)

Wide Area Network (WAN)

Classification by component roles

PEER TO PEER NETWORKS

The simplest form of a network is a peer-to-peer

network. In a peer-to-peer network, every

computer can communicate directly with every

other computer. By default, no computer on a

peer-to-peer network has more authority than

another. However, each computer can be

configured to share only some of its resources

and prevent access to other resources.

PEER TO PEER NETWORKS

PEER TO PEER NETWORKS ADVANTAGESThe following are advantages of using traditional peer-to-peer networks:

P2P networks are simple to configure. For

this reason, they may be used in

environments in which time or technical

expertise is insufficient.

P2P networks are often less expensive to set

up and maintain than other types of

networks. This fact makes them suitable for

environments in which saving money is

critical.

PEER TO PEER NETWORKS DISADVANTAGESThe following are disadvantages of using traditional peer-to-peer networks: They are not very flexible. As a peer-to-peer

network grows larger, adding or changing significant elements of the network may be difficult.

They are also not necessarily secure—meaning that in simple installations, data and other resources shared by network users can be easily discovered and used by unauthorized people.

They are not practical for connecting more than a handful of computers, because they do not always centralize resources.

CLIENT/SERVER NETWORK

In this way of designing a network is to use a

central computer, known as a server, to

facilitate communication and resource sharing

between other computers on the network,

which are known as clients. Clients usually take

the form of personal computers, also known as

workstations. A network that uses a server to

enable clients to share data, data storage

space, and devices is known as a client/server

network.

CLIENT/SERVER NETWORK

CLIENT/SERVER NETWORKS ADVANTAGESThe following are advantages of using traditional client server networks: User logon accounts and passwords for anyone

on a server-based network can be assigned in one place. Access to multiple shared resources (such as data files or printers) can be centrally granted to a single user or groups of users.

Problems on the network can be monitored, diagnosed, and often fixed from one location.

Servers are optimized to handle heavy processing loads and dedicated to handling requests from clients, enabling faster response time.

Because of their efficient processing and larger disk storage, servers can connect more than a handful of computers on a network.

Classification by network

geography

CLASSIFICATION BY NETWORKGEOGRAPHY

Networks are frequently classified according to the geographical boundaries spanned by the network itself.

LAN, WAN, and MAN are the basic types of classification, of which LAN and WAN are frequently used.

Local area network (LAN):

A LAN covers a relatively small area such as a

classroom, school, or a single building.

LANs are inexpensive to install and also provide

higher speeds.

CLASSIFICATION BY NETWORKGEOGRAPHY

Local area network

CLASSIFICATION BY NETWORKGEOGRAPHY

Metropolitan area network (MAN):

A MAN spans the distance of a typical

metropolitan city.

The cost of installation and operation is higher.

MANs use high-speed connections such as fiber

optics to achieve higher speeds.

CLASSIFICATION BY NETWORKGEOGRAPHY

Metropolitan area network

CLASSIFICATION BY NETWORKGEOGRAPHY

Wide area network (WAN):

WANs span a larger area than a single city.

These use long distance telecommunication

networks for connection, thereby increasing the

cost.

The Internet is a good example of a WAN.

CLASSIFICATION BY NETWORKGEOGRAPHY

Wide area network

CLASSIFICATION BY NETWORKGEOGRAPHY

NETWORK TOPOLOGIES

NETWORK TOPOLOGY

The network topology defines the way in which computers, printers, and other devices are connected. A network topology describes the layout of the wire and devices as well as the paths used by data transmissions.

BUS TOPOLOGY

Commonly referred to

as a linear bus, all the

devices on a bus

topology are

connected by one

single cable.

Introduction to Computer Networks

STAR & TREE TOPOLOGYThe star topology is the most commonly used architecture in Ethernet LANs.

When installed, the star topology resembles spokes in a bicycle wheel.

Larger networks use the extended star topology also called tree topology. When used with network devices that filter frames or packets, like bridges, switches, and routers, this topology significantly reduces the traffic on the wires by sending packets only to the wires of the destination host.

RING TOPOLOGYA frame travels around the ring, stopping at each node. If a node wants to transmit data, it adds the data as well as the destination address to the frame.

The frame then continues around the ring until it finds the destination node, which takes the data out of the frame.

Single ring – All the devices on the network share a single cable

Dual ring – The dual ring topology allows data to be sent in both directions.

MESH TOPOLOGY

The mesh topology connects all devices (nodes) to each other for redundancy and fault tolerance.

It is used in WANs to interconnect LANs and for mission critical networks like those used by banks and financial institutions.

Implementing the mesh topology is expensive and difficult.

Introduction to Computer Networks

BASIC ELEMENTS IN CLIENT/SERVER

Client—A computer on the network that requests

resources or services from another computer on a network;

in some cases, a client could also act as a server. The term

client may also refer to the human user of a client

workstation or to client software installed on the

workstation.

Server—A computer on the network that manages shared

resources; servers usually have more processing power,

memory, and hard disk space than clients. They run

network operating software that can manage not only data,

but also users, groups, security, and applications on the

network.

• A Simple WAN

BASIC ELEMENTS IN CLIENT/SERVER

Workstation—A personal computer (such as a desktop or

laptop), which may or may not be connected to a network;

most clients are workstation computers.

NIC (network interface card)—The device (pronounced nick)

inside a computer that connects a computer to the network

media, thus allowing it to communicate with other

computers;

BASIC ELEMENTS IN CLIENT/SERVER

NOS (network operating system)—The software that runs

on a server and enables the server to manage data, users,

groups, security, applications, and other networking

functions. Examples include various types of UNIX and

Linux operating systems, Microsoft Windows Server 2003 or

Windows Server 2008, and Mac OS X Server.

Host—A computer that enables resource sharing by other

computers on the same Network.

Node—A client, server, or other device that can

communicate over a network and that is identified by a

unique number, known as its network address.

BASIC ELEMENTS IN CLIENT/SERVERSegment—A part of a network. Usually, a segment is composed of a group of nodes that use the same communications channel for all their traffic.Backbone—The part of a network to which segments and significant shared devices (such as routers, switches, and servers) connect. A backbone is sometimes referred to as “a network of networks,” because of its role in interconnecting smaller parts of a LAN or WAN. Topology—The physical layout of a computer network. Topologies vary according to the needs of the organization and available hardware and expertise. Networks can be arranged in a ring, bus, or star formation, and the star formation is the most common. Hybrid combinations of these patterns are also possible.

BASIC ELEMENTS IN CLIENT/SERVERProtocol—A standard method or format for communication between networked devices. Protocols ensure that data are transferred whole, in sequence, and without error from one node on the network to another.Data packets—The distinct units of data that are exchanged between nodes on a network. Breaking a large stream of data into many packets allows a network to deliver that data more efficiently and reliably.Addressing—The scheme for assigning a unique identifying number to every node on the network. The type of addressing used depends on the network’s protocols and network operating system. Each network device must have a unique address so that data can be transmitted reliably to and from that device.Transmission media—The means through which data is transmitted and received. Transmission media may be physical, such as wire or cable, or atmospheric (wireless), such as radio waves.

HOW NETWORKS ARE USED

The functions provided by a network are usually referred to as network services. e.g.

Email Services

Printer sharing

File sharing

Internet access and Web site delivery

Remote access capabilities

The provision of voice (telephone) and video services

Network management Services.

Assignment(a)

HOW NETWORKS ARE USED (VOIP)

UNDERSTANDING TRANSMISSION MEDIUM

NETWORK MEDIA

Links that connect nodes Choice impacts

Speed Security Size

WIRE BASED MEDIA Twisted-pair cabling

Most common LAN cable

Called Cat5 or 100BaseT

Four pairs of copper cable twisted

May be shielded from interference

Speeds range from 1 Mbps to 1,000 Mbps

WIRE BASED MEDIA

Coaxial cable Similar to cable TV wire One wire runs through cable Shielded from interference Speeds up to 10 Mbps Nearly obsolete

9A-49

WIRE BASED MEDIA

Fiber-optic cable Data is transmitted with light pulses Glass strand instead of cable Immune to interference Very secure Hard to work with Speeds up to

100 Gbps

9A-50

NETWORK HARDWARE

Network interface cards Network adapter Connects node to the media Unique Machine Access Code (MAC)

NETWORK HARDWARE

Network linking devices Connect nodes in the network Cable runs from node to device Crossover cable connects two computers

NETWORK HARDWARE

Hubs Center of a star network All nodes receive transmitted packets Slow and insecure

NETWORK HARDWARE

Switches Replacement for hubs Only intended node receives transmission Fast and secure

NETWORK HARDWARE

Bridge Connects two or more LANs together Packets sent to remote LAN cross

Other packets do not cross Segments the network on MAC addresses

NETWORK HARDWARE

Router Connects two or more LANs together Packets sent to remote LAN cross Network is segmented by IP address Connect internal networks to the Internet Need configured before installation

9A-56

NETWORK HARDWARE

Gateway Connects two dissimilar networks Connects coax to twisted pair Most gateways contained in other devices

NETWORK CABLING

Cabling specifications Bandwidth measures cable speed

Typically measured in Mbps Maximum cable length Connector describes the type of plug

NETWORK CABLING

Ethernet Very popular cabling technology 10 Base T, 10Base2, 10Base5 Maximum bandwidth 10 Mbps Maximum distances100 to 500 meters

NETWORK CABLING

Fast Ethernet Newer version of Ethernet Bandwidth is 100 Mbps Uses Cat5 or greater cable

Sometimes called 100Base T Requires a switch

9A-60

NETWORK CABLING

Gigabit Ethernet High bandwidth version of Ethernet 1 to 10 Gbps Cat 5 or fiber optic cable Video applications

WIRELESS MEDIA

•Wireless LAN or WLAN Wireless local area network that uses radio waves as its carrier

•Wi-Fi ("Wireless Fidelity“)A set of standards for WLANs based on IEEE 802.11

•Wi-Max Emerging technology that can cover ranges up to 10 miles or more

•Satellite/MicrowaveHigh speed media used for longer distances and remote locations

UNDERSTANDING NETWORK PROTOCOLS

PROTOCOLS OF COMPUTER COMMUNICATIONS AND NETWORKS Protocol are used for communication between

computers in different computer networks. Protocol achieves: What is communicated between computers? How it is communicated? When it is communicated? What conformance (bit sequence) between computers?

Key elements of a protocol are: SYNTAX: Data format and signal levels SEMANTICS: Control information for coordination and error

handling TIMING: Synchronization, speed matching, and sequencing

Examples of protocols: WAN Protocol: TCP/IP LAN Protocol: Media Access Control; Contention; Token

Passing

PROTOCOL ARCHITECTURE

Architecture provides high degree of cooperation between two computers.

Example:

ISO/OSI REFERENCE MODEL

Open Systems Interconnection No one really uses this in the real world. A reference model so others can develop

detailed interfaces. Value: The reference model defines 7 layers

of functions that take place at each end of communication and with each layer adding its own set of special related functions.

Flow of data through each layer at one

ISO/OSI REFERENCE MODEL

How to transmit signal; codingHardware means of sending and receiving data on a carrier

Two party communication: Ethernet

Routing and Forwarding Address: IP

End-to-end control & error checking (ensure complete data transfer): TCP

Establish/manage connection

ASCII Text, Sound (syntax layer)

File Transfer, Email, Remote Login

NETWORK PROTOCOLS

TCP/IP Transmission Control Protocol/Internet Protocol Most popular protocol Machines assigned a name of 4 numbers

IP address 209.8.166.179 is the White House’s web site

Dynamic Host Configuration Protocol Simplifies assignment of IP addresses

Required for Internet access

NETWORK PROTOCOLS

IPX/SPX Internet Packet Exchange/Sequenced Packet

Exchange Older protocol Associated with Novell Netware Replaced by TCP/IP

NETWORK PROTOCOLS

NetBEUI Network BIOS Extended User Interface Used by Windows to name computers Transmission details handled by TCP/IP

NETWORK PROTOCOLS

Token ring Popular in manufacturing and finance Nodes communicate when they have the token