Presentation on

Introduction to Networking &

Network Devices

What is a Network?What is a Network?

A network consists of 2 or more computers connected together, and they can communicate and share resources (e.g. information)

Why Networking?Why Networking?

Sharing information — i.e. data communication

Do you prefer these?

• Or this?

HowHow many kinds of Networks?many kinds of Networks?

• Depending on one’s perspective, we can classify networks in different ways

• Based on transmission media: Wired (UTP, coaxial cables, fiber-optic cables) and Wireless

• Based on network size: LAN and WAN (and MAN)

• Based on management method: Peer-to-peer and Client/Server

• Based on topology (connectivity): Bus, Star, Ring …

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Network DeviceNetwork Device

HubsRepeatersBridgesSwitchesRoutersGatewaysMODEM

OSI ModelOSI Model

HUBHUBActs on the physical layerOperate on bits rather than framesMultiple Hubs can be used to extend the network

lengthRegenerate the network’s signal and resend them to

other segments

Features & Limitations Features & Limitations

Features• Can connect different types of media• The most economic way of expanding networks

Limitations• Cannot join segments with

different access methods (e.g. CSMA/CD and token passing)

• cannot filter network traffic• cannot determine best path

RepeatersRepeaters

• Used to boost the signal between two cable segments or wireless access points.

Repeaters clean, amplify, and resend signals that are weakened by long cable length.

• Resides on Layer 1 of the OSI model.

BridgesBridges

• Connects two LANs and forwards or filters data packets between them.• Forward data depending on the Hardware (MAC)

address, not the Network address (IP).• The purpose is to filter traffic on a LAN, to keep

local traffic local, yet allow connectivity to other segments of the network.• Resides on Layer 2 of the OSI model.

Differences Between Bridges and Differences Between Bridges and RepeatersRepeaters

Repeaters Bridges

OSI layer Physical layer Data link layer

Dataregeneration

Regenerate data atthe signal level

Regenerate dataat the packetlevel

Reduce networktraffic

No Yes

SwitchesSwitchesSwitches operate at the Data Link layer (layer 2) of the OSI

model• Split large networks into small segments, decreasing the

number of users sharing the same network resources and bandwidth.

Each channel has its own capacity and need not be shared with other channels

10Mbps

10Mbps10Mbps

Switch

Hub 3.3Mbps

3.3Mbps

3.3Mbps

RouterRouter• Connects any number of LANs.• Uses standardized protocols to move packets

efficiently to their destination.• More sophisticated than bridges, connecting

networks of different types (for example, star and token ring)• Forwards data depending on the Network address

(IP), not the Hardware (MAC) address.• Used routing tables to determine the best path for

data delivery

RouterRouter

GatewaysGateways

Joining together two networks that use different base protocols.

Implemented completely in software, completely in hardware, or as a combination of both.

Gateways operate at the any layer of the OSI model.Also called protocol converters.

GatewaysGateways

MODEMMODEM

Devices and the layers at which Devices and the layers at which They operateThey operate

Layer Name of Layer Device

3 Network Routers, layer 3 switches

2 Data Link Switches, bridges, NIC’s

1 Physical Hubs

SummarySummary

• Repeaters are the least expensive way to expand a network, but they are limited to connecting two segments

• Bridges function similar to repeaters, but can understand the node addresses

• Switches can be considered as multiport bridges, can divide a network into some logical channels

• Routers interconnect networks and provide filtering functions. They can determine the best route