2. Transmission Modes in Computer
Networks
Data Transmission mode defines the direction of the flow of
information between two communication devices. It is also called
Data Communication or Directional Mode. It specifies the direction of
the flow of information from one place to another in a computer
network.
The data transmission modes can be characterized in the following
three types based on the direction of exchange of information:
3. Simplex
In Simplex mode, the communication is unidirectional, as on a one-way street. Only
one of the two devices on a link can transmit, the other can only receive.The simplex
mode can use the entire capacity of the channel to send data in one direction.
Example:Keyboard and traditional monitors.The keyboard can only introduce input,
the monitor can only give the output.
4. Half-Duplex
Half-Duplex is the data transmission mode in which the data can flow
in both directions but in one direction at a time. It is also referred to
as Semi-Duplex. In other words, each station can both transmit and
receive the data but not at the same time. When one device is sending
the other can only receive and vice-versa.
5. Full-Duplex
In full-duplex mode, both stations can transmit and receive
simultaneously. In full_duplex mode, signals going in one direction
share the capacity of the link with signals going in another direction,
this sharing can occur in two ways:
Either the link must contain two physically separate transmission
paths, one for sending and the other for receiving.
Or the capacity is divided between signals travelling in both
directions.
6. Analog & Digital Signal
Analog Signal: An analog signal is any continuous signal for which the time
varying feature of the signal is a representation of some other time-varying quantity
i.e.,analogous to another time-varying signal.For example,in an analog audio signal,
the instantaneous voltage of the signal varies continuously with the pressure of the
sound waves.
Digital Signal: A digital signal is a signal that is being used to represent data as a
sequence of discrete values; at any given time it can only take on, at most, one of a
finite number of values. This contrasts with an analog signal, which represent cont-
inous values; at any given time it represents a real number within a continuous
range of values.
7. MAC & NIC
MAC: A media access control is a network data transfer policy that determines how
data is transmitted between two computer terminals through a network cable.The
media access control policy involves sub-layers of the data link layer 2 in the OSI
reference model.
The essence of the MAC protocol is to ensure non-collision and eases the transfer of
data packets between two computer terminals . A collision takes place when two or
more terminals transmit data/information simultaneously. This leads to a breakdown
of communication, which can prove costly for organizations that lean heavily on data
transmission.
NIC: A network interface card (NIC) is a hardware component without which a
computer cannot be connected over a network . It is a circuit board installed in a
computer that provides a dedicated network connection to the computer. It is also
called network interface controller, network adapter or LAN adapter.
8. WAN
WAN: A wide area network (also known as WAN), is a large network
of information that is not tied to a single location. WANs can facilitate
communication, the sharing of information and much more between
devices from around the world through a WAN provider.
9. MAN
MAN: A metropolitan area network (MAN) is a computer network
that connects computers within a metropolitan area, which could be
a single large city, multiple cities and towns, or any given large area
with multiple buildings.A MAN is larger than a local area network(LAN)
but smaller than a wide area network (WAN).
10. LAN
LAN:A local area network (LAN) is a collection of devices connected
together in one physical location, such as a building, office, or home
etc. .In contrast,a wide area network (WAN) or metropolitan area
network (MAN) covers larger geographic areas.Some WANs and
MANs connect many LANs together.
11. Keys HUB Switch Router
Layer Physical layer Data link layer Network layer
Function
To connect a network of
personal computers
together, they can be
joined through a central
hub
Allow connections to
multiple devices,
manage ports, manage
VLAN security settings
Direct data in a
network
Data
Transmissio
n form
electrical signal or bits frame & packet packet
Port 4/12 ports
multi-port, usually
between 4 and 48
2/4/5/8 ports
Transmissio
n type
Frame flooding, unicast,
multicast or broadcast
First broadcast, then
unicast and/or
multicast depends on
the need
At Initial Level
Broadcast then Uni-
cast and multicast
Transmissio
n mode
Half duplex Half/Full duplex Full duplex
