Hardware devices that are used to
connect computers, printers, fax machines and other electronic devices to a
network are called network devices. These devices transfer data in
a fast, secure and correct way over same or different networks. Network devices
may be inter-network or intra-network. Some devices are installed on the
device, like NIC card or RJ45 connector, whereas some are part of the network,
like router, switch, etc. Let us explore some of these devices in greater detail.
Modem: Modem is a device that enables a computer to send or
receive data over telephone or cable lines. The data stored on the computer is
digital whereas a telephone line or cable wire can transmit only analog data.
The main function of the modem is to
convert digital signal into analog and vice versa. Modem is a combination of
two devices − modulator and demodulator. The modulator converts
digital data into analog data when the data is being sent by the computer.
The demodulator converts analog data signals into digital data
when it is being received by the computer.
Types of Modem
Modem can be categorized in several
ways like direction in which it can transmit data, type of connection to the
transmission line, transmission mode, etc.
Depending on direction of data
transmission, modem can be of these types −
- Simplex − A simplex modem can transfer
data in only one direction, from digital device to network (modulator) or
network to digital device (demodulator).
- Half duplex − A half-duplex modem has the
capacity to transfer data in both the directions but only one at a time.
- Full duplex − A full duplex modem can
transmit data in both the directions simultaneously.
RJ45 Connector: RJ45 is the acronym for Registered Jack 45.
RJ45 connector is an 8-pin jack used by devices to physically connect
to Ethernet based local area networks (LANs). Ethernet is
a technology that defines protocols for establishing a LAN. The cable used for
Ethernet LANs are twisted pair ones and have RJ45 connector pins at
both ends. These pins go into the corresponding socket on devices and connect
the device to the network.
Ethernet Card: Ethernet card, also known as network interface card (NIC),
is a hardware component used by computers to connect to Ethernet LAN and
communicate with other devices on the LAN. The earliest Ethernet cards were
external to the system and needed to be installed manually. In modern computer
systems, it is an internal hardware component. The NIC has RJ45 socket where
network cable is physically plugged in.
Ethernet card speeds may vary depending upon the protocols it
supports. Old Ethernet cards had maximum speed of 10 Mbps. However,
modern cards support fast Ethernets up to a speed of 100 Mbps. Some
cards even have capacity of 1 Gbps.
Router: A router is a network layer hardware
device that transmits data from one LAN to another if both networks support the
same set of protocols. So a router is typically connected to
at least two LANs and the internet service provider (ISP). It
receives its data in the form of packets, which are data
frames with their destination address added. Router
also strengthens the signals before transmitting them. That is why it is also
called repeater.
Routing Table
A router reads its routing table to
decide the best available route the packet can take to reach its destination
quickly and accurately. The routing table may be of these two types −
- Static − In a static routing table the
routes are fed manually. So it is suitable only for very small networks
that have maximum two to three routers.
- Dynamic − In a dynamic routing table,
the router communicates with other routers through protocols to determine which
routes are free. This is suited for larger networks where manual feeding
may not be feasible due to large number of routers.
Switch: Switch is a network device that connects other devices
to Ethernet networks through twisted pair cables.
It uses packet switching technique to receive, store and forward
data packets on the network. The switch maintains a list of network
addresses of all the devices connected to it.
On receiving a packet, it checks the
destination address and transmits the packet to the correct port. Before
forwarding, the packets are checked for collision and other network errors. The
data is transmitted in full duplex mode
Data transmission speed in switches
can be double that of other network devices like hubs used for networking. This
is because switch shares its maximum speed with all the devices connected to
it. This helps in maintaining network speed even during high traffic. In fact,
higher data speeds are achieved on networks through use of multiple switches.
Gateway: Gateway is a network device used to connect two or more
dissimilar networks. In networking parlance, networks that use different
protocols are dissimilar networks. A gateway usually is a computer
with multiple NICs connected to different networks. A gateway
can also be configured completely using software. As networks connect to a
different network through gateways, these gateways are usually hosts or end
points of the network.
Gateway uses packet switching technique
to transmit data from one network to another. In this way it is similar to
a router, the only difference being router can transmit data only
over networks that use same protocols.
Hub: A Hub is a hardware device that divides the network
connection among multiple devices. When computer requests for some information
from a network, it first sends the request to the Hub through cable. Hub will
broadcast this request to the entire network. All the devices will check
whether the request belongs to them or not. If not, the request will be dropped.
The process used by the Hub consumes
more bandwidth and limits the amount of communication. Nowadays, the use of hub
is obsolete, and it is replaced by more advanced computer network components
such as Switches, Routers.
Wi-Fi Card: Wi-Fi is the acronym for wireless fidelity.
Wi-Fi technology is used to achieve wireless connection to
any network. Wi-Fi card is a card used to
connect any device to the local network wirelessly. The physical area of the
network which provides internet access through Wi-Fi is called Wi-Fi
hotspot. Hotspots can be set up at home, office or any public space.
Hotspots themselves are connected to the network through wires.
A Wi-Fi card is used
to add capabilities like teleconferencing, downloading digital
camera images, video chat, etc. to old devices. Modern devices come
with their in-built wireless network adapter.
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