Computer Networks
Hub, Switch, Router, Bridge
Jan 2021 Prepared By Dr. Sujata Pal, IIT Ropar 1 / 34
Previous Class
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Network
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Computer Network
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Medium of Communications
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Data Flow
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Topology
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LAN, MAN, WAN
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Jan 2021
Network Components
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Jan 2021
Host
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Network
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Repeater
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A repeater operates at the physical layer.
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Its job is to regenerate the signal over the same network before the signal becomes too weak
or corrupted so as to extend the length to which the signal can be transmitted over the same
network.
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It is a 2 port device.
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Jan 2021
Hub
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Jan 2021
Hub
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Hub
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A hub is basically a multiport repeater.
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A hub connects multiple wires coming from
different branches, for example, the
connector in star topology which connects
different stations.
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Hubs cannot filter data, so data packets are
sent to all connected devices.
Demerits:
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No security
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Creates unnecessary traffic
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Waste bandwidth
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Jan 2021
Bridge
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A bridge operates at data link layer.
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A bridge is a repeater, with add on the
functionality of filtering content by reading
the MAC addresses of source and destination.
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It is also used for interconnecting two LANs
working on the same protocol.
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It has a single input and single output port,
thus making it a 2 port device.
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Jan 2021
Bridge
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Switch
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A switch is a layer-2 network connecting device, i.e., it works on the physical and
data-link layer of the OSI model.
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A switch maintains a Switch table which has the MAC addresses of all the devices
connected to it.
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Jan 2021
Switch
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It is preferred more over the hub, as it reduces any kind of unnecessary traffic in the
transmission channel.
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A switch can connect the devices only in the same network.
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It uses the full-duplex mode of communication and saves bandwidth. The switch
table keeps on updating every few seconds for better processing.
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A Switch is an intelligent device with filtering capabilities.
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When a data frame arrives at the Switch, it first checks for any kind of
error in the data frame. If the frame is error-free, it will search the MAC
address of the destination in the Switch table. If the address is
available in the switch table, it will forward the data frame to that
specific node, else switch will register the MAC address in the switch
table.
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Jan 2021
Switch
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If the destination address is not specified, it will broadcast the data
frame to each node in the network.
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A Switch can have 8/6/24/48 ports. The data transmission speed is
slow in a switch(around 10-100 Mbps). Also, it has only one
broadcasting domain.
Disadvantages of using a Switch:
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It can connect devices of the same network only.
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There is a delay in forwarding the frames due to error checking.
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There is a need to maintain a Switch table.
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Two networks with two switches
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Router
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Jan 2021
Router
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Jan 2021
Router
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The Router is the Gateway of a network.
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Hubs and switches are used to create networks.
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Router are used to connect networks.
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Jan 2021
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Jan 2021
Router
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A Router is a layer-3 network connecting device, i.e., it works on
the physical, data-link and network layer of the OSI model.
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It is mainly an internetworking device, which can connect
devices of different networks
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A Router is used to connect the networks or it routes traffic
between the networks.
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In other words, a Router is the Gateway of a network.
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It can have 2/4/8 ports for connecting the devices.
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A router maintains a routing table using the routing algorithms.
When a data packet is received at the router, it first checks the
IP address. If the IP address is the same as the network's IP
address, it receives the data packet, else it forwards the data
packet to the destination IP address using the routing table.
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Jan 2021
Router
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MODEM (modulator-demodulator)
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A modem is what brings the Internet into your home or
business.
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As analog data comes from the Internet the modem
demodulates incoming analog signals into a digital signal, so
that computer can understand it.
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Modem also outgoing digital signal into an analog signal.
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Some router have builtin switch within it.
Those router can pass Internet connections to
all of your devices.
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You do not need a router if you want only one
of your device needs Internet access.
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Jan 2021
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A lot of time the modem is a combination of
modem and router.
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A modem router device would have a modem
with a built-in wireless router in one device.
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A modem is part of the data link layer (layer
2) and connects an internal network to the
external Internet.
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A digital subscriber line (DSL) modem is a
device used to connect a computer or router
to a telephone line.
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Cable modem connected by co-axial cable.
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Jan 2021
Common network cable types
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Unshielded
twisted pair
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Coaxial
cable
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Fiber optic
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Ethernet Cable
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It is composed of 4-
pair twist wirings.
– Orange
– Green
– Blue
– Brown
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Unshielded twisted pair: because they are not wrapped
inside a metallic film.
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Solid colours are -ve polarity, whereas stripped colours
represent +ve polarity.
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Orange pair sends data. Used for sending photos, videos.
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Green pair receives data. Used for downloading
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Blue and brown pairs can be used to increase bandwidth.
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Rj45 plug
Color Pin (T568B)
White/Orange 1
Orange 2
White/Green 3
Blue 4
White/Blue 5
Green 6
White/Brown 7
Brown 8
You can use the order of rainbow colors to memorize
the order of this wiring. “red, orange, yellow, green,
blue, indigo and violet”
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Connection of 8 cables
T568A and T568B
T568B Color Code
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RJ45 Pin---Pair Color
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1-------------White/Orange
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2-------------Orange
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3-------------White/Green
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4-------------Blue
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5-------------White/Blue
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6-------------Green
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7-------------White/Brown
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8-------------Brown
We can use either of them. Generally, we use T568B. Both the end
T568A Color Code Same standard at both ends ---> straight cable/patch cable
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RJ45 Pin---Pair Color
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1-------------White/Green Opposite standard at both the ends ---> crossover cable
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2-------------Green
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3-------------White/Orange
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4-------------Blue
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5-------------White/Blue
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6-------------Orange
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7-------------White/Brown
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8-------------Brown
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LAN cable or CAT - 5 Cable
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RJ45
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Pin Usage
1 Transmission (Tx+)
2 Transmission (Tx-)
3 Receive (Rx+)
4 --
5 --
6 Receive (Rx-)
7 --
8 --
• We can use the concept to justify the order of the wiring
colors of straight through and crossover.
33
Prepared by Dr. S. Pal
Prepared By Dr. Sujata Pal, IIT Ropar 34 / 34
Jan 2021
