NetworkDevices 2
Network Device
Contents
 Introduction
 Network card
1. ARC Net card
2. Ethernet card
3. Token Ring
 Network Cables
1. Coaxial cable
2. Twisted pair cable
3. Fiber optic cable
 Network Topology
1. Bus Topology
2. Star Topology
3. Ring Topology
4. Mesh Topology
 Network Connectivity Devices
1. Hub
2. Repeaters
3. Switches
4. Gateways
5. Bridges
 Conclusion

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Introduction
Networking hardware may also be known as network equipment, computer networking devices.
Units which are the last receiver or generate data are called hosts or data terminal equipment. All
these terms refer to devices facilitating the use of a computer network. Network devices are
components used to connect computers or other electronic devices together so that they can share
files or resources like printers or fax machines. Devices used to setup a Local Area Network
(LAN) are the most common type of network devices used by the public. A LAN requires a hub,
router, cabling or radio technology, network cards, and if online access is desired, a high-speed
modem. Happily this is much less complicated than it might sound to someone new to
networking.
Network card
What is a network card?
A network card (also called a Network Adapter or Network Interface Card, or NIC for short)
acts as the interface between a computer and a network cable. The purpose of the network card is
to prepare, send, and control data on the network.
A network card usually has two indicator lights (LEDs):
 The green LED shows that the card is receiving electricity;
 The orange (10 Mb/s) or red (100 Mb/s) LED indicates network activity (sending or
receiving data). To prepare data to be sent the network card uses a transceiver, which
transforms parallel data into serial data. Each cart has a unique address, called a MAC
address, assigned by the card's manufacturer, which lets it be uniquely identified among
all the network cards in the world.

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ARC Net card
ARCNET is a widely-installed local area network (LAN) technology that uses a token-bus
scheme for managing line sharing among the workstations and other devices connected on the
LAN. The LAN server continuously circulates empty message frames on a bus (a line in which
every message goes through every device on the line and a device uses only those with its
address). When a device wants to send a message, it inserts a "token" (this can be as simple as
setting a token bit to 1) in an empty frame in which it also inserts the message. When the
destination device or LAN server reads the message, it resets the token to 0 so that the frame can
be reused by any other device. The scheme is very efficient when traffic increases since all
devices are afforded the same opportunity to use the shared network.
Ethernet card
An Ethernet card is one kind of network adapter. These adapters support the Ethernet standard
for high-speed network connections via cables. Ethernet cards are sometimes known as network
interface cards (NICs).
Ethernet cards are available in several different standard packages called form factors:

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Ethernet cards may operate at different network speeds depending on the protocol standard they
support. Old Ethernet cards were capable only of the 10 Mbps maximum speed offered by
Ethernet originally. Modern Ethernet adapters all support the 100 Mbps Fast Ethernet standard
and an increasing number now also offer Gigabit Ethernet support at 1 Gbps (1000 Mbps).
An Ethernet card does not directly support Wi-Fi wireless networking, but home network
broadband routers contain the necessary technology to allow Ethernet devices to connect via
cables and communicate with Wi-Fi devices via the router.
Token Ring
A Token Ring network is a local area network (LAN) in which all computers are connected in a
ring or star topology and a bit- or token-passing scheme is used in order to prevent the collision
of data between two computers that want to send messages at the same time. The Token Ring
protocol is the second most widely-used protocol on local area networks after Ethernet. The IBM

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Token Ring protocol led to a standard version, specified as IEEE 802.5. Both protocols are used
and are very similar. The IEEE 802.5 Token Ring technology provides for data transfer rates of
either 4 or 16 megabits per second. Very briefly, here is how it works.
Network Cables
Networking cables are used to connect one network device to other network devices or to
connect two or more computers to share printer, scanner etc. Different types of network cables
like Coaxial cable, Optical fiber cable, Twisted Pair cables are used depending on the network's
topology, protocol and size. The devices can be separated by a few meters (e.g. via Ethernet) or
nearly unlimited distances (e.g. via the interconnections of the Internet).

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Coaxialcable:Coaxial lines confine the electromagnetic wave to area inside the cable,
between the centre conductor and the shield. The transmission of energy in the line occurs totally
through the dielectric inside the cable between the conductors. Coaxial lines can therefore be
bent and twisted (subject to limits) without negative effects, and they can be strapped to
conductive supports without inducing unwanted currents in them and though.
Twistedpair cable: Twisted pair cabling is a form of wiring in which pairs of wires (the
forward and return conductors of a single circuit) are twisted together for the purposes of
cancelling out electromagnetic interference (EMI) from other wire pairs and from external
sources. This type of cable is used for home and corporate Ethernet newt.
orks.

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Fiber Optic cable:An optical fiber cable consists of a center glass core surrounded by
several layers of protective material. The outer insulating jacket is made of Teflon or PVC to
prevent interference. It is expensive but has higher bandwidth and can transmit data over longer
distances
Different Kinds of Network Topology in
Computer Networks
The way in which the connections are made is called the topology of the computer network.
Now I am discussing about network topology, Network topology specifically refers to the
physical layout of the network, especially the locations of the computers and how the cable is run
between them. Four most common topologies are:
 Bus
 Star
 Ring
 Mesh
Bus Topology: All the devices on a bus topology are connected by one single cable. When one
computer sends a signal up the wire, all the computers on the network receive the information,

NetworkDevices 9
but only one accepts the information. The rest regrets the message. One computer can send a
message at a time. A computer must wait until the bus is free before it can transmit .
When the signal reaches the end of the wire, it bounces back and travels back up the wire. When
a signal echoes back and forth along an undermanaged bus, it is called ringing. To stop the
signals from ringing, attach terminators at either end of the segment. The terminators absorb the
electrical energy and stop the reflection.
Star Topology: the cables run from the computers to a central location, where they are all
connected by a device called a hub. Each computer on a star network communicates with a
central hub that resends the message either to all the computers or only to the destination
Computers
Hub can be active or passive in the star network Active hub regenerates the electrical signal and
sends it to all the computers connected to it. Passive hub does not amplify or regenerate signal
and does not require electrical power to run. We can expand a star network by placing another
star hub.

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Ring Topology: Each computer is connected to the next computer ,with the last one connected
to the first. Every computer is connected to the next computer in the ring, and each retransmits
what it receives from the previous computer. The message flow around the ring in one direction.
Some ring networks do token passing. It passes around the ring until a computer wishes to send
information
.
to another computer. The computer adds an electronic address and data and sends it around the
ring. Each computer in sequence receives the token and the information and passes them to the
next until either the electronic address matches the address of the computer or the token returns
to the origin. The receiving computer returns a message to the originator indicating that the
message has been received. The sending computer then creates another token and place it on the
network, allowing another station to capture the token and being transmitted.
MeshTopology: The mesh topology connects all devices (nodes) to each other for redundancy
and fault tolerance. It is used in WANs to interconnect LANs and for mission critical networks
like those used by banks and financial institutions. Implementing the mesh topology is expensive
and difficult.

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Common Network Connectivity Devices
It’s easy to forget about all the small pieces of hardware that sit and hum along 24-7 just so that
we can check our email or catch the latest stats for our fantasy team. Just what are those little
boxes and why do they have so many little blinking lights?
Network connections are made possible by two main types of hardware: network media and
network connectivity devices. This article is going to cover the later in enough detail to have you
picking up the network-speak in no time. Network connection devices include:
 Hubs
 Repeaters
 Bridges
 Switches
 Gateways
A hub is a small Network Device. A hub joins multiple computers (or
other network devices) together to form a single network segment. On this network segment, all

NetworkDevices 12
computers can communicate directly with each other. Ethernet hubs are by far the most common
type, but hubs for other types of networks such as USB also exist.
A hub includes a series of ports that each accept a network cable, one port is reserved for
"uplink" connections to another hub or similar device.
Main Features
■ Operate at Layer 1 devices ( Physical layer ) in the OSI model .
■ Hubs do not read any of the data passing through them and are not aware of their source or
destination.
■ Hub simply receives incoming packets, possibly amplifies the electrical signal, and broadcasts
these packets out to all devices on the network - including the one that originally sent the packet!
Network Router:
A Network Router is a network device with interfaces in multiple networks whose task is to
copy packets from one network to another. Router gives path to data packet to destination.
Routers provide connectivity inside enterprises, between enterprises and the Internet, and within
an Internet Service Provider (ISP).
Main Features
■ Operates at Layer 3 (Network Layer) of the OSI Model.
■ Router works with Static Routing manfully configure by Network Administrator.
■ Router works with Dynamic Routing which routers calculate automatically by different
methods.
■ Router stores calculate path in his Routing Table.

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■ The network router will then use its routing table to make intelligent decisions about which
packets to copy to which of its interfaces .
■ The router will use this information to create a routing table.
■ This process is known as routing.
Bridge:
A bridge reads the outermost section of data on the data packet, to tell where the message is
going. It reduces the traffic on other network segments, since it does not send all packets.
Bridges can be programmed to reject packets from particular networks. Bridging occurs at the
data link layer of the OSI model, whcih means the bridge cannot read IP address, but only the
outermost hardware address of the packet. In our case the bridge can read the ethernet data whcih
gives the hardware address of the destination address, not the IP address. Bridges forward all
broadcast messages. Only a special bridge called a translation bridge will allow two networks of
different architectures to be connected. Bridges do not normally allow connection of networks
with different architectures. The hardware address is also called the MAC (media access control)
address. To determine the network segment a MAC address belongs to, bridges use one of the
following

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Switches:A switch is like a hub in that every device on the network is connected to it.
However, a switch does not rebroadcast signals to all other devices. A switch makes a direct link
between the device that is transmitting and the device that is receiving. All other devices are
totally unaware of the communication taking place. For this reason, switches realize greater
performance because bandwidth is not being wasted on needless rebroadcasting.
Gateways:A gateway can translate information between different network data formats or
network architectures.

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It can translate TCP/IP to AppleTalk so computers supporting TCP/IP can communicate with
Apple brand computers. Most gateways operate at the application layer, but can operate at the
network or session layer o the OSI model. Gateways will start at the lower level and strip
information until it gets to the required level and repackage the information and work its way
back toward the hardware layer of the OSI model. To confuse issues, when talking about a router
that is used to interface to another network, the word gateway is often used. This does not mean
the routing machine is a gateway as defined here, although it could be.
Conclusion
While the age-old concept of the network is foundational in virtually all areas of society,
Computer Networks and Protocols have forever changed the way humans will work, play, and
communicate. Forging powerfully into areas of our lives that no one had expected, digital
networking is further empowering us for the future. New protocols and standards will emerge,
new applications will be conceived, and our lives will be further changed and enhanced. While
the new will only be better, the majority of digital networking's current technologies are not
cutting-edge, but rather are protocols and standards conceived at the dawn of the digital
networking age that have stood solid for over thirty years.

Network Devices

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