Network Devices

Types of Network Devices

Modulator Demodulator (MODEM)

• A device that modulates an

analog carrier signal to encode

digital information, and also

demodulates such a carrier

signal to decode the transmitted information

• The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data

Modulation Techniques

• We basically have three modulation techniques-

• Amplitude Modulation• Frequency Modulation• Phase Modulation

Working of a MODEM

MODEM

DATA COMMUNICATI

ONEQUIPMENT

MODEM

DATA COMMUNICATI

ONEQUIPMENT

DATATERMINAL

EQUIPMENT

DATATERMINAL

EQUIPMENT

TRANSMIT

REQUEST TO SENDRECIEVE

DATA TERMINAL READY

CARRIER DETECT

DATA SET READY

CLEAR TO SEND

Registered Jack 45 (RJ-45)

• An 8-wire connecter, used to connect various Computer systems to LANs

• RJ45 is used almost exclusively to refer to Ethernet (type of LAN system that uses bus or star topology for data sharing) -type computer connectors.

• The RJ-45 connector is commonly used for network cabling and for telephony applications.

Ethernet• Most widely used LAN technology

• Developed by Xerox Corp

• Typically uses coaxial cables and special grades of twisted pair cables

• Ethernet was named by Robert Metcalfe, one of its developers, for the passive substance called "luminiferous (light-transmitting) ether" that was once thought to pervade the universe, carrying light throughout. Ethernet was so- named to describe the way that cabling, also a passive medium, could similarly carry data everywhere throughout the network.

Hub• A device used to connect several computers

together• Is a fairly unsophisticated device as it doesn’t

manage the traffic through it• There are two types of hubs

1) Active Hub2) Passive Hub

Functioning of a Hub• Receives a data packet

• Forwards it to all the remaining ports

Switch• A device used to segment networks into sub-

networks, which prevents traffic overloading in network

• It is a sophisticated device, is responsible for filtering and forwarding data

• In environments where there is a need for a great deal of analysis of network performance and security, there is a provision of a firewall, network intrusion detection and performance analysis modules that can plug into switch ports.

What does it do?• It establishes a temporary connection b/w the source and the destination and then

terminates the connection when conversation is done

Repeater• A device used to expand the boundaries of a

wired or wireless LAN.• Amplify the data signals before sending them on

to the uplinked segment, thereby countering signal decay that occurs over extended lengths of wire.

• Receives a signal and retransmits it at a higher level and/or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances.

• Over distance, cables connecting a network lose the signal transmitted. If it degrades too much, it fails to reach its destination.

• These are of 2 types:AmplifierSignal repeater

• Connects multiple network segments.

• Similar to repeaters or network hubs, however, can manage data from one network rather than simply rebroadcast to adjacent network segments.

• Analyze incoming data packets to determine if the bridge is able to send the given packet to another segment of the network.

Bridge

Advantages and Disadvantages ADVANTAGES OF

BRIDGESDISADVANTAGES OF

BRIDGESSimple bridges are

inexpensiveDoes not scale to extremely large

networksLANs interconnected

are separateBuffering and

processing introduces delays

Helps minimize bandwidth usage

Bridges are more expensive than

repeaters or hubs

Router• Device that interconnects two or more computer

networks, and selectively interchanges packets of data between them

• It works like a bridge but can handle diff. protocols• Each data packet contains address information that a

router can use to determine if the source and destination are on the same network, or if the data packet must be transferred from one network to another

• In case of an unknown destination, a router sends the traffic to another router

Gateway• Has the ability to connect dissimilar networks

• Acts as an entrance to a network • Generally, a gateway node is often also acting

as a proxy server and a firewall server, blocking an unauthorized access to or from a private network.