LAN,

WAN,

INTERNET

&

INTRANET

INTRODUCTION TO COMPUTER NETWORK

A collection of computers and devices connected by communications channels that facilitates communications among users and allows users to share resources with other users.

PURPOSE OF A NETWORKI. Facilitate communication

(a) E-mail

(b) Instant Messaging

(c) Chat rooms

(d) Video conference

II. Share hardware's

(a) Printer sharing

(b) Camera

III. Share files data and information's

(a) File sharing

(b) FTP Server's

IV. Share software's

(a) Operating System

(b) Games

NETWORK CLASSIFICATIONS

One way to categorize the different types of computer network designs is by their scope or scale.

LAN and WAN were the original categories of area networks, while the

others have gradually emerged over many years of technology evolution.

Note that these network types are a separate concept from network

topologies such as bus, ring and star.

NETWORK CLASSIFICATIONSCommon examples of area network types are:

LAN : Local Area Network

WLAN: Wireless Local Area Network

WAN : Wide Area Network

MAN : Metropolitan Area Network

SAN : Storage Area Network, System Area Network, Server Area

Network, or sometimes Small Area Network

CAN : Campus Area Network, Controller Area Network, or sometimes

Cluster Area Network

PAN : Personal Area Network

DAN : Desk Area Network

NETWORK HARDWARES

All networks are made up of basic hardware building blocks to interconnect network nodes, such as:

Network Interface Cards (NICs)

Bridges

Hubs

Switches

Routers

NETWORK INTERFACE CARD

A network card, network adapter, or NIC (network interface card) is a piece of computer hardware designed to allow computers to communicate over a computer network which provides physical access to a networking medium and often provides a low-level addressing system through the use of MAC (Media Access Control) addresses.

REPEATERS

A repeater is an electronic device that receives a signal, cleans it from the unnecessary noise, regenerates it and retransmits it at a higher power level, or to the other side of an obstruction, so that the signal can cover longer distances without degradation. In most twisted pair Ethernet configurations, repeaters are required for cable which runs longer than 100 meters.

HUB

A network hub contains multiple ports. When a packet arrives at one port, it is copied unmodified to all ports of the hub for transmission. The destination address in the frame is not changed to a broadcast address.

BRIDGES

A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model. Bridges do send broadcasts to all ports except the one on which the broadcast was received. However, bridges do not promiscuously copy traffic to all ports, as hubs do, but learn which MAC addresses are reachable through specific ports. Once the bridge

associates a port and an address, it will send traffic for that address to that port only.

SWITCH

A network switch is a device that forwards and filters OSI layer 2 datagrams (chunk of data communication) between ports (connected cables) based on the MAC addresses in the packets. This is distinct from a hub in that it only forwards the frames to the ports involved in the communication rather than all ports connected.

Switches make forwarding decisions of frames on the basis of MAC

addresses. A switch normally has numerous ports, facilitating a star

topology for devices, and cascading additional switches.

The term switch is used loosely in marketing to encompass devices

including routers and bridges

SWITCH

ROUTER

A router is a networking device that forwards packets between networks using information in protocol headers and forwarding tables to determine the best next router for each packet.

NETWORK HARDWARES

LOCAL AREA NETWORK

A local area network (LAN) supplies networking capability to a group of computers in close proximity to each other such as in an office building, a school, or a home. A LAN is useful for sharing resources like files, printers, games or other applications. A LAN in turn often connects to other LANs, and to the Internet or other WAN.

The defining characteristics of LANs, in contrast to wide-area networks

(WANs), include their usually higher data-transfer rates, smaller

geographic area, and lack of a need for leased telecommunication lines.A

LAN can be either wired or wireless.

LOCAL AREA NETWORK

Most LANs connect workstations and personal computers. Each node (individual computer ) in a LAN has its own CPU with which it executes programs, but it also is able to access data and devices anywhere on the LAN. This means that many users can share expensive devices, such as laser printers, as well as data. Users can also use the LAN to communicate with each other, by sending e-mail or engaging in chat sessions.

The following characteristics differentiate one LAN from another :

Topology

The geometric arrangement of devices on the network. For example,

devices can be arranged in a ring or in a straight line.\

Protocols

The rules and encoding specifications for sending data. The protocols also

determine whether the network uses a peer-to-peer or client/server

architecture.

Media

Devices can be connected by twisted-pair wire, coaxial cables, or fiber

optic cables. Some networks do without connecting media

altogether, communicating instead via radio waves.

LOCAL AREA NETWORK

WIDE AREA NETWORK

A Wide Area Network is a computer network that spans a relatively large geographical area. Typically, a WAN consists of two or more local-area networks (LANs).

Computers connected to a wide-area network are often connected through

public networks, such as the telephone system. They can also be

connected through leased lines or satellites.

WIDE AREA NETWORKWANs cover cities, countries, continents and the whole world.

A WAN is formed by linking LANs together. For example, several major

LANs in a city can connect together forming a WAN.

When networks connect to form a bigger network (a bigger WAN), the

resulting network is called an internetwork, which is generically

abbreviated to ‘an internet’. Now when all WANs in the world connect

forming a global internet, we call it The Internet, which everyone knows!

That’s why the Internet is always written with a capital I. It is the biggest

WAN we have.

INTERNET

The Internet is a global network connecting millions of computers. More than 100 countries are linked into exchanges of data, news and opinions. Unlike online services, which are centrally controlled, the Internet is decentralized by design. Each Internet computer, called a host, is independent. Its operators can choose which Internet services to use and which local services to make available to the global Internet community. Remarkably, this anarchy by design works exceedingly well.

There are a variety of ways to access the Internet. Most online services,

such as America Online, offer access to some Internet services. It is also

possible to gain access through a commercial Internet Service Provider

(ISP) such as TM, Celcom, Digi, Jaring, P1 and many more.

INTERNET

The Internet has no centralized governance in either technological implementation or policies for access and usage; each constituent network sets its own standards. Only the overreaching definitions of the two principal name spaces in the Internet, the Internet Protocol address space and the Domain Name System, are directed by a maintainer organization, the Internet Corporation for Assigned Names and Numbers (ICANN). The technical underpinning and standardization of the core protocols (IPv4 and IPv6) is an activity of the Internet Engineering Task Force (IETF), a non-profit organization of loosely-affiliated international participants that anyone may associate with by contributing technical expertise.

INTRANET

An intranet is a private network that is contained within an enterprise. It may consist of many interlinked local area networks and also use leased lines in the wide area network. Typically, an intranet includes connections through one or more gateway computers to the outside Internet. The main purpose of an intranet is to share company information and computing resources among employees. An intranet can also be used to facilitate working in groups and for teleconferences.

An intranet uses TCP/IP, HTTP, and other Internet protocols and in general

looks like a private version of the Internet. With tunneling, companies can

send private messages through the public network, using the public network

with special encryption/decryption and other security safeguards to

connect one part of their intranet to another.

INTRANETIt is accessible only by the organization's members, employees, or others with authorization. An intranet's Web sites look and act just like any other Web sites, but the firewall surrounding an intranet fends off unauthorized access.

Typically, larger enterprises allow users within their intranet to access the

public Internet through firewall servers that have the ability to screen

messages in both directions so that company security is

maintained. When part of an intranet is

made accessible to customers, partners,

suppliers, or others outside the company,

that part becomes part of an extranet.

Network Topology

Type of Network Topology

• Bus Network Topology

• Ring Network Topology

• Star Network Topology

• Mesh Network Topology

• Tree Network Topology

Bus Network Topology• use a common backbone to

connect all devices. • A single cable, the backbone

functions as a shared communication medium that devices attach or tap into with an interface connector.

• A device wanting to communicate with another device on the network sends a broadcast message onto the wire that all other devices see, but only the intended recipient actually accepts and processes the message.

Advantages

• If one computer fails in the network the others are still not affected and they continue to work

• Very simple and easy to set up • Use the least amount of cable • Well-suited for temporary or small

networks not requiring high speeds (quick setup)

• Easy identification of cable faults • Cost effective.

Disadvantages

• Limited cable length and number of stations. • If there is a problem with the cable, the entire

network breaks down. • Maintenance costs may be higher in the long

run. • Performance degrades as additional computers

are added or on heavy traffic (shared bandwidth) • Slower data transfer rate than other topologies

Ring Network Topology

• every device has exactly two neighbors for communication purposes.

• All messages travel through a ring in the same direction (either "clockwise" or "counterclockwise").

• A failure in any cable or device breaks the loop and can take down the entire network.

Advantages• Very orderly network where every device

has access to the token and the opportunity to transmit

• Performs better than a star topology under heavy network load

• Can create much larger network using Token Ring

• Does not require network server to manage the connectivity between the computers

Disadvantages

• One malfunctioning workstation

• Moves, adds and changes of devices can affect the network

• Network adapter cards and MAU's are much more expensive than Ethernet cards and hubs

• Much slower than an Ethernet network under normal load

Star Network Topology• Many home networks

use the star topology.

• A star network features a central connection point called a "hub" that may be a hub, switch or router.

• Devices typically connect to the hub with Unshielded Twisted Pair (UTP) Ethernet.

Advantages

• Better performance: The star topology prevents the passing of data packets through an excessive number of nodes

• Isolation of devices: Each device is inherently isolated by the link that connects it to the hub.

• Benefits from centralization: As the central hub is the bottleneck, increasing its capacity, or connecting additional devices to it, increases the size of the network very easily.

Advantages (cont)

• Simplicity: This topology is easy to understand, establish, and navigate.

• Easy to install and wire.

• Easy to detect faults and to remove parts

• No disruptions to the network when connecting or removing devices.

Disadvantages

• High dependence of the system on the functioning of the central hub

• The failure of the central hub renders the network inoperable, immediately isolating all nodes.

• The performance and scalability of the network also depend on the capabilities of the hub

• Wiring up of the system can be very complex and high costing.

Mesh Network Topology

• Mesh topologies involve the concept of routes.

• Messages sent on a mesh network can take any of several possible paths from source to destination.

• Some WANs, most notably the Internet, employ mesh routing.

Advantages• The arrangement of the network nodes is

such that it is possible to transmit data from one node to many other nodes at the same time

Disadvantages• The arrangement wherein every network

node is connected to every other node of the network, many of the connections serve no major purpose. This leads to the redundancy of many of the network connections

Tree Network Topology

• Integrate multiple star topologies together onto a bus.

• In its simplest form, only hub devices connect directly to the tree bus, and each hub functions as the "root" of a tree of devices.

• This bus/star hybrid approach supports future expandability of the network much better than a bus or a star alone.

Advantages

• Tree Topology is supported by many network vendors ad even hardware vendors.

• A point to point connection is possible with Tree Networks.

• All the computers have access to the larger and their immediate networks.

• Best topology for branched out networks.

Disadvantages

• In a Network Topology the length of the network depends on the type of cable that is being used.

• The Tree Topology network is entirely dependant on the trunk which is the main backbone of the network. If that has to fail then the entire network would fail.

• Since the Tree Topology network is big it is difficult to configure and can get complicated after a certain point.

Network Hardware

Cable type & functionTwisted-Pair Cable

• One of the more widely used transmission media for network cabling and telephone system.

• Consists of one or more twisted-pair wires bundled together.

Twisted-Pair Cable

• Each twisted-pair wire consists of two separate insulated copper wires that are twisted together

• The wire are twisted together to reduc noise.

• Noise is an electrical disturbance that can degrade communications.

Coaxial Cable

• Often referred to as coax, consists of a single copper wire surrounded by at least three layer: (1) an insulating material, (2) a woven or braided metal, (3) a plastic outer coating.

Coaxial Cable

• Cable television network wiring often uses coaxial cable because it can be cabled over longer distances than twisted-pair cable.

• Most of today’s computer networks, do not use coaxial cable because other transmission media such as fiber-optic cable transmit signals at faster rates.

Fiber-Optic Cable

• The core of a fiber-optic cable consists of dozens or hundreds of thin strands of glass or plastic that use light to transmit signals.

• Inside the fiber-optic cable, an insulating glass cladding and a protective coating surround each optical fiber.

Fiber-Optic Cable - Advantages

• Capability of carrying significantly more signals than wire cable

• Faster data transmission

• Less susceptible to noise

• Better security for signal

• Smaller size

Fiber-Optic Cable - Disadvantages

• Expensive

• Difficult to install and modify

Socket Type & FunctionRJ-45

• RJ45 is name of connector types used for Ethernet connections on computers and other Ethernet networking devices like routers and switches and also modems and other devices which support Ethernet interface.

• RJ45 is the standard for the plug that you use for connecting cat5 cable to a network. It's an 8 connector plug that looks like a larger version of a phone plug.

BNC

• The BNC (Bayonet Neill-Concelman) connector is a very common type of RF connector used for terminating coaxial cable.

• used for RF signal connections, for analog and serial digital interface video signals, amateur radio antenna connections, aviation electronics (avionics) and many other types of electronic test equipment.

ST Connector

• The ST (Straight Tip) connector is a fiber optic connector which uses a plug and socket which is locked in place with a half-twist bayonet lock.

• They are amongst the most frequently used fiber optic connectors in networking applications

• They are used both for short distance applications and long distance coordination.

• They can effortlessly be attached and detached because of their flexible design.

SC Connector

• The SC connector is a fiber optic connector with a push-pull latching mechanism which provides quick insertion and removal while also ensuring a positive connection.

• SC connector has a benefit in keyed duplex capability to support send/receive channels

• These connectors are commonly used for most modern network applications. The SC is a snap-in connector that is extensively used in single-mode systems for its remarkable efficiency.

• They are inexpensive, trouble-free, and robust. SC connectors give precise positioning via their ceramic ferrules

• The SC connector has been standardized as FOCIS 3 (Fiber Optic Connector Intermateability Standards) in EIA/TIA-604-03.

Network Devices

• Computer network devices including routers, switches, hubs, LAN cards, gateway, modems, hardware firewall, CSU/DSU, ISDN terminals and transceivers.

Router• Used to connect two logically

and physically different networks, two LANs, two WANs and a LAN with WAN

• The main function of the router is to sorting and the distribution of the data packets to their destinations based on their IP addresses.

• Cisco routers are widely used in the world.

Switches • A switch is an intelligent device that

maps the IP address with the MAC address of the LAN card

• Unlike the hubs, a switch does not broadcast the data to all the computers, it sends the data packets only to the destined computer.

• In an Ethernet network, computers are directly connected with the switch via twisted pair cables.

• In a network, switches use the three methods to transmit the data i.e. store and forward, cut through and fragment free.

Hubs• The central connecting device in

a computer network • There are two types of a hub i.e.

active hub and passive hub. • Every computer is directly

connected with the hub. • When data packets arrives at

hub, it broadcast them to all the LAN cards in a network and the destined recipient picks them and all other computers discard the data packets.

• Hub has five, eight, sixteen and more ports and one port is known as uplink port, which is used to connect with the next hub.

Modem

• A modem is a communication device that is used to provide the connectivity with the internet. 

• Modem works in two ways i.e. modulation and demodulation.

• It coverts the digital data into the analog and analog to digital

LAN Cards• LAN cards or network

adapters are the building blocks of a computer network

• No computer can communicate without a properly installed and configured LAN card

• Every LAN card is provided with a unique IP address, subnet mask, gateway and DNS (if applicable).

LAN Cards

• An UTP/STP cable connects a computer with the hub or switch.  Both ends of the cable have the RJ-45 connectors one is inserted into the LAN card and one in the hub/switch.

• LAN cards are inserted into the expansion slots inside the computer. 

• Different LAN cards support different speed from 10/100 to 10/1000.