Contents
• Network Devices
• NIC
• Repeater
• HUB
• Switches
• Bridge
• Gateway
• Routers
• CSU/ DSU
• Modem
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Network Devices
NIC – Repeater – HUB – Switch – Bridge – Router – Gateway
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1. NIC
• Network Interface Card.
• A hardware component that connects your computer to a
local data network or the Internet.
• A device that takes a signal from a network and converts it
to a signal that a computer can understand and
• Translates computer data into electrical signals it sends
through the network.
• Provides an interface onto a network (usually a LAN) for a
computer system.
• A NIC is also known as a network interface controller (NIC),
network interface controller card, expansion card, computer
circuit board, network card, LAN card, network adapter or
network adapter card (NAC).
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NIC
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• It’s a plastic circuit board about the size of a playing
card.
• It has several computer chips that process signals from
the network and the PC.
• The card slides into the PC’s framework with a
connector on the motherboard.
• A steel bracket holds the card in place.
• The bracket may have a network cable jack or an
antenna.
• The bracket also has light-emitting diodes that indicate
network status and activity.
• Need drivers (software code that helps to run NIC).

NIC Functioning
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• Middleman/ Interface between your computer and
the data network.
• For example,
• when you log in to a website, the PC passes the site
information to the network card, which converts the
address into electrical impulses.
• Network cables carry these impulses to a Web server
somewhere on the Internet, which responds by sending
a Web page back to you, once again in the form of
electronic signals.
• The card receives these signals and turns them into data
that your PC displays.

NIC Types
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• Work with Wi-Fi wireless networks: these cards
have an antenna to send data signals via radio
waves.
• Wired Ethernet connections: these cables have a
rectangular plug which mates with a jack on the
network card's bracket.

How to install NIC
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• https://www.youtube.com/watch?v=xjOWxpvo7uw

2. Repeater
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• A repeater operates at the physical layer.
• Its job is to regenerate the signal over the same
network before the signal becomes too weak or
corrupted.
• It extend the length to which the signal can be
transmitted over the same network.
• An important point to be noted about repeaters is that
they do not amplify the signal.
• When the signal becomes weak, they copy the signal
bit by bit and regenerate it at the original strength.

3. BRIDGE
• Hardware device, works at data link layer.
• It provides interconnection with other bridge networks
that use the same protocol.
• Connecting two different networks together and
providing communication between them.
• Bridges are similar to repeaters and hubs in that they
broadcast data to every node.
• Bridges maintain the media access control (MAC)
address table as soon as they discover new segments,
so subsequent transmissions are sent to only to the
desired recipient.
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How BRIDGEs Work
• A bridge uses a database to discover where to pass,
transmit or discard the data frame.
• If the frame received by the bridge is meant for a
segment that resides on the same host network, it
will pass the frame to that node and the receiving
bridge will then discard it.
• If the bridge receives a frame whose node MAC
address is of the connected network, it will forward
the frame toward it.
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4. HUB
• A Hardware device, physical layer device.
• A common connection point for devices in a
network – connects multiple computers or other
network devices together.
• Hubs connect segments of a LAN.
• Work as repeaters.
• It has no routing tables or intelligence on where to
send information – broadcasts all network data
across each connection.
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HUB
• In the past, network hubs were popular because
they were cheaper than a switch or router.
• Today, switches do not cost much more than a hub
and are a much better solution for any network.
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Types of HUB
LAN HUB USB HUB
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How Network HUB Works
• A hub is an inexpensive way to connect devices on
a network.
• Data travels around a network in 'packets' and a
hub forwards these data packets out to all the
devices connected to its ports.
• As a hub distributes packets to every device on the
network, when a packet is destined for only one
device, every other device connected to the hub
receives that packet.
• Sometimes slow down the network because of
traffic collision.
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5. SWICTH
• Hardware device.
• A high-speed device that receives incoming data
packets and redirects them to their destination on
a local area network (LAN).
• A LAN switch operates at the data link layer or the
network layer of the OSI Model.
• A switch, however, keeps a record of the MAC
addresses of all the devices connected to it.
• Switches also run in full duplex mode.
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How SWICTH Work
• Reads incoming TCP/IP data packets/frames
containing destination information as they pass
into one or more input ports.
• The destination information in the packets is used
to determine which output ports will be used to
send the data on to its intended destination.
• Node-to-node communication in the same
network.
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Similarities between Switches and HUBs
• Switches are similar to hubs, but smarter than
hubs.
• A hub simply connects all the nodes on the
network – communication in broadcast – resulting
in many collisions.
• A switch, on the other hand, creates an electronic
tunnel between source and destination ports – no
other traffic can enter.
• This results in communication without collisions.
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6. Routers
• Network Layer device
• A router is a device like a switch that routes data
packets based on their IP addresses.
• Routers normally connect LANs and WANs together
or a LAN and its ISP's network –for example, your
PC and your service provider.
• Have a dynamically updating routing table based
on which they make decisions on routing the data
packets.
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Routers
• Routers are located at gateways, the places where
two or more networks connect.
• Routers use packet headers and forwarding tables
to determine the best path for forwarding the
packets.
• And they use protocols to communicate with each
other and configure the best route between any
two hosts.
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7. Gateway
• A gateway, as the name suggests, is a passage to
connect two networks together that may work
upon different networking models.
• They basically works as the messenger agents that
take data from one system, interpret it, and
transfer it to another system.
• Gateways are also called protocol converters and
can operate at any network layer.
• Gateways are generally more complex than switch
or router.
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Gateway
• Gateways serve as the entry and exit point of a
network; all data routed inward or outward must first
pass through and communicate with the gateway in
order to use routing paths.
• Generally, a router is configured to work as a gateway
device in computer networks.
• The gateway (or default gateway) is implemented at the
boundary of a network to manage all the data
communication that is routed internally or externally
from that network.
• Besides routing packets, gateways also possess
information about the host network's internal paths.
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8. CSU/ DSU
• Channel Service Unit/Data Service Unit.
• Is a hardware device about the size of an
external modem.
• It converts a digital data frame from the
communications technology used on a local area
network (LAN) into a frame appropriate to a wide-
area network (WAN) and vice versa.
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CSU / DSU
• For Example: If have leased a digital line to a phone
company or a gateway at an Internet service
provider, you have a CSU/DSU at your end and the
phone company or gateway host has a CSU/DSU at
its end.
• The Channel Service Unit (CSU) receives and
transmits signals from and to the WAN line and
provides a barrier for electrical interference from
either side of the unit.
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9. MODEM
• Modem is short for Modulator / Demodulator.
• It is a hardware component that allows
a computer or other device, such as
a router or switch, to connect to the Internet.
• It converts or modulates an analog signal from a
telephone or cable wire to a digital signal that a
computer can recognize.
• Similarly, it converts outgoing digital data from a
computer or other device to an analog signal.
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MODEM
• The first modems were dial-up meaning they had to
dial a phone number to connect to an ISP.
• These modems operated over standard analog
phone lines and used the same frequencies as
telephone calls, which limited their maximum data
transfer rate to 56 Kbps.
• Dial-up modems also required full use of the local
telephone line, meaning voice calls would interrupt
the Internet connection.
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MODEM
• Modern modems are typically DSL or cable
modems, which are considered broadband devices.
• DSL modems operate over standard telephone
lines, but use a wider frequency range.
• This allows for higher data transfer rates than dial-
up modems and enables them to not interfere with
phone calls.
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Basics of Computer Network Device