NETWORKING DEVICES

BY ADEEBA KHANCOMPUTER TECHNOLOGY

All but the most basic of networks

require devices to provide connectivity and functionality

Some networking devices

✓ Hubs ✓ Switches ✓ Bridges ✓ Routers ✓ Gateways ✓ CSU/DSU (Channel Service Unit/Data Service Unit) ✓ NICs (Network Interface Card) ✓ ISDN (Integrated Services Digital Network) adapters ✓ Modems ✓ Firewalls

HUB

CHEAP SIMPLE BUT WASTES BANDWIDTH

H

Network with a Hub

SENDER

RECEIVER

H

Network with a Hub

SENDER

RECEIVER

H

Network with a Hub

How a hub behavesEach incoming bit is replicated on all other interfacesSimplest and cheapest way to create a networkLots of unnecessary trafficSecurity problem

A hub may be passive or active :-

Those which operate below the physical layer is a passive hub.

Those which operate at the physical layer is an active hub

Uses of hub Hubs are used to create small Home

Networks. Hubs are used for monitoring the networks. Hubs are used in Organizations and

Computer Labs for connectivity. It Makes one device or peripheral available

throughout the whole network.

Repeater A repeater is a

device that operates only at the physical layer

Repeater

Repeater connecting two segments of a LAN Function of a repeater

BridgeBridge is a more

intelligent form of Hub.

Packets are processed based on MAC address inside the incoming packet.

Bridge is not very useful for end – computing devices

Switch

Switch is bridge with more than 2 ports.

More scalable and practical

If a hub capture a list where every host can be reached than it would be able to send every packet straight to it destination without expanding the entire network.

Two layer switch operate at physical and data link layer.

Three layer switch operates at network, data link and physical layer.

The Switch Table

1 2 3 4 5 6

A B

Interface MAC address

1 AA-AA-AA-AA-AA

2 BB-BB-BB-BB-BB

The Switch Table1 2 3 4 5 6

Interface MAC address

1 AA-AA-AA-AA-AA

3 CC-CC-CC-CC-CC4 DD-DD-DD-DD-DD6 BB-BB-BB-BB-BB

B

D

A

C

Ways in which Switch work..Flooding Forwarding Filtering Broadcasting 

Flooding :-Flooding is performed when the switch has no entry for the frame's destination MAC address. When a frame is flooded, it is sent out every single port on the switch except the one it came in one.

Forwarding :-Forwarding is performed when the switch does have an entry for the frame's destination MAC address. Forwarding a frame means the frame is being sent out only one port on the switch. 

Filtering :-Filtering is performed when the switch has an entry for both the source and destination MAC address, and the MAC table indicates that both addresses are found off the same port.

Broadcasting :- There is one other frame type that is sent out every port on the switch except the one that received it, and that's a broadcast frame, Broadcast frames are intended for all hosts, and the MAC broadcast address is ff-ff-ff-ff-ff-ff .

Router

Routes packets based on their logical addresses (host-to-host addressing)

A router normally connects LANs and WANs in the Internet and has a routing table that is used for making decision about the route.

The routing tables are normally dynamic and are updated using routing protocols.

Need of Routers

packet

LAPTOP INTERNET SEARCH ENGINE

GatewayAny device that translates one data format to another is called a gateway.

Gateways, also called protocol converters, can operate at any network layer.

A gateway takes an application message ,reads it and interpret it .

Gateway can provide security.It filter unwanted application layer messages. The activities of a gateway are more complex

than that of the router or switch as it communicates using more than one protocol.

Each device work on different layer

OTHER NETWORK DEVICES

NIC (network interface card)NIC are devices that enablecomputers to connect to the network.

It is both a physical layer and data link layer device

It allows users to connect to each other either by using cables or wirelessly.

How NIC works ?A computer or device on a network can be

reached by its MAC(media access control) address through the NIC card.

Every Ethernet network card has a unique 48-bit serial number called a MAC address which is stored in ROM carried on the card.

The MACs on the network are used to direct traffic between the computers

The Ethernet address is 6 bytes (48bits),normally written in Hexadecimal notation with a colon between the bytes.

Example06:01:02:01:2C:4B

Source address is unicast address –the frame comes from only one station .

Destination address ,however can be unicast , multicast, or broadcast.

LSB of first byte defines the type of address. If the bit is 0 ,the address is unicast otherwise multicast .

Broadcast is a special case of multicast where all bits are 1.

Modem

A modem, short for modulator/demodulator, is a device that converts the digital signals generated by a computer into analog signals that can travel overconventional phone lines.

The modem at the receiving end converts the signal back into a format the computer can understand.

Modems can be used as a means to connect

to an ISP or as a mechanism for dialing up to a LAN.

FEATURES OF MODEMModulated SignalsData CompressionError CorrectionFlow Control

Modulated signal The essential function of a modem is to create an easily

transmitted and decoded signal that allows digital data to be sent from place to place without the loss of information.

Data Compression

To reduce the amount of time it takes to send data and to cut down on the amount of error in the signal, modems need to employ data compression. Data compression techniques reduce the size of the signal needed to send the required data.

Error Correction When information is transmitted between modems, it can

sometimes be damaged -- meaning that parts of the data are altered or lost. To get around this, modems use error correction.

Flow Control

Individual modems send information at different speeds. It's necessary for faster modems to slow down so that slower modems can catch up, otherwise the slower modem will receive more data than it can process.

ISDNIntegrated Services Digital Network (ISDN) is a remote access and WAN technology .

ISDN offers greater speeds than a modem .

Integrated services refers to ISDN's ability to deliver at minimum two simultaneous connections, in any combination of data, voice, video, and fax, over a single line. Multiple devices can be attached to the line, and used as needed.

CSU/DSUA Channel Service

Unit/Digital Service Unit (CSU/DSU), is a device that converts the digital signal format used on LANs into one used on WANs.

The CSU/DSU sits between the LAN and the access point provided by the telecommunications company.

FirewallsA firewall controls access to

your organization’s network.

Firewalls can be implemented through software or through a

dedicated hardware device

Sources http://www.pearsonhighered.com/

samplechapter/0789732548.pdf Data Communications and networking by Behrouz A Forouzan (Tata

McGrawHill) http://www.wikiforu.com/2013/04/hub-types-

applications-in-network.html https://www.youtube.com/watch?

v=Xmwmezk75Tk

THANKYOU