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DATA COMMUNICATIONS
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MCS-I
TELECOMMUNICATION
• The term telecommunication means communication at a
distance.
DATA
• The word data refers to information presented in whatever
form is agreed upon by the parties creating and using the
data.
DATA COMMUNICATIONS
• Data communications are the exchange of data between
two devices via some form of transmission medium such
as a wire cable.
Five components of Data Communication System
The five components are :
1. Message:
It is the information to be communicated. Popular forms
of information include text, pictures, audio, video etc.
2. Sender:
It is the device which sends the data messages. It can
be a computer, workstation, telephone handset etc.
3. Receiver:
It is the device which receives the data messages. It can
be a computer, workstation, telephone handset etc.
4. Transmission
Medium:
It is the physical path by which a message travels from
sender to receiver. Some examples include twisted-pair
wire, coaxial cable, radio waves etc.
5. Protocol:
It is a set of rules that governs the data communications.
It represents an agreement between the communicating
devices. Without a protocol, two devices may be
connected but not communicating.
Data flow (simplex, half-duplex, and full-duplex)
1. DATA FLOW:
In communications, the path taken by a message from
origination to destination that includes all nodes through
which the data travels.
2. SIMPLEX:
Simplex transmission allows data to travel only in a
single, pre specified direction.
An example from everyday life is doorbell the signal can go
only from the button to the chime. Two other examples are
television and radio broadcasting.
3. HALF DUPLEX: In half duplex transmission messages can move in
either direction , but only one way at a time.
A walkie-talkie is an example.
4. FULL DUPLEX: In full duplex mode the communication is from both the
sides simultaneously.
Example is cellular Phone (mobile phone).
Types of connections: point-to-point and multipoint
Point to Point:
A point-to-point link is a dedicated link that connects
exactly two communication facilities (e.g., two nodes of
a network, an intercom station at an entryway with a
single internal intercom station, a radio path between
two points, etc.). Point-to-point interfaces are used in
serial communication. These types of connections are
assumed to transmit solely to the station at the opposite
end.
The examples of Point-to-point are EIA/TIA 232, EIA/TIA 449,
X.25, Frame Relay, T-carrier, and OC3 - OC192.
Multipoint:
A multipoint link is a link that connects two or more
nodes It connects one station to several other stations.
Point-to-multipoint are of two types • Point-to-multipoint
Non-Broadcast • Point-to-multipoint Broadcast In Pointto-multipoint Non-broadcast, the communication is
replicated to all the remote stations. Only specific,
selected stations hear the replicated communication.
Categories of topology
TOPOLOGY :
Topology refers to the layout of connected devices. Network
topology is defined as the physical interconnection of the
various elements (links, nodes, etc.) of a computer network.
Network Topologies can be physical or logical.
Physical Topology means the physical design of a network including the devices,
location and cable installation. Logical topology refers to the fact that how data
actually transfers in a network as opposed to its design.
i. STAR:
In local area networks with a star topology, each network host
is connected to a central hub.
ii.RING:
In Ring topology each computer is connected to the network in
a closed loop or ring.
iii.BUS:
A type of network setup where each of the computers and
network devices are connected to a single cable or backbone.
iv.MESH:
A type of network setup where each of the computers and
network devices are interconnected with one another, allowing
for most transmissions to be distributed, even if one of the
connections go down.
v. HYBRID:
A network topology that uses two or more network topologies.
Categories of topology