Data communication basics

NTIPRIT

National Telecommunication Institute for Policy Research, Innovation and TrainingGhaziabad – 201002. www.ntiprit.gov.in

Data Communication

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An IntroductionBy Naveen Jakhar, ITS

NTIPRIT

Discussion Points

05/01/2023 Introduction Data Com 2

Basic Data Communication Concepts

• Message, Packets, Nodes, link, Backbone Communication Channel, Protocol

Network Elements

• Hub, Switch, Bridge, Router, gateway

Packet Switching Concepts

Various Types of Data Communication

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Why Data Communication?

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Over the past few years, it has become clear that the world has changed forever.

We are now in the Information Age—the second Industrial Revolution,

The first Industrial Revolution revolutionized the way people worked by introducing machines and new organizational forms.

Information is power, information is tool! (information is processed Data)

One of the challenges in studying data communications and networking is that there are many perspectives that can be used

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Is the process of using computing and communication technologies to transfer data from one place to another, and vice versa. It enables the movement of electronic or digital data between two or more nodes, regardless of geographical location, technological medium or data contents.

DC incorporates several techniques and technologies with the primary objective of enabling any form of electronic communication. These technologies include telecommunications, computer networking and radio/satellite communication.

Data communications (DC)

05/01/2023 5Introduction Data Com

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Electronic transmission of information that has been encoded digitally

(as for storage and processing by computers)

sending digital messages using communication technology

Data Communication


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Basic Elements of Data Communication

Five Basic Elements

Message

Sender

Receiver

Transmission Medium –Channel

Protocol - Rule

Basic Data Communication Model

Cooperating Applications at Each Node

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5 Basic Components


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MESSAGE

Examples of Message : Data, Program, File, Snippet of Personal Conversation, Stream of Audio, Video, Voice, etc

The Message is the primary purpose of communication. It can take many forms

Limitations of use of Message as Communication Tool: Varying Message Length & Inefficient Utilization of Bandwidth

Message as Byte Stream

The meaning of message is established by the protocols recognized by the cooperating applications at each node

Messages are converted into Analog/Digital Signals for transmission over the communication Medium

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DSLModem

DSLAM Internet

Ethernet packets Analog Signal Digital ATM, MPLS,SONET Ethernet packets

Converter Various converters

WebserverHome PC Links Links

JOURNEY OF MESSAGE FROM SOURCE TO DESTINATION

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Packets

Basic Unit of Data Communication

Broken, delimited part of Message, a formatted unit of data.

Payload Vs. Header

Makes Possible sharing of Communication channel for messages

Consists of data in bits/bytes encapsulated by information about the packet :

Specific Data Packets : Segment, Datagram, Frame, Control Message Packet

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Why Packet is the Basic Unit?

Represents a reasonable unit for routing of data

The use of packets simplifies operations and increases communication efficiency

Enables processing of a block of data all at once, instead of a character or byte at a time

Packets offer an alternative to dedicated channel for entire message length

It increases the productivity of the communication channel

It simplifies synchronisation of the sending and receiving systems

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Payload v.s Header

Payload : User data Header: Control information,

which is required for delivery of User Data or Payload, e.g. Source address, Destination address, error detection codes like checksum & sequencing information (FCS).

Usually the payload information is found between Header and Trailer.

Packet

Header Payload


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NODE

Can be any communication Device – PC, Smart Phone, Router, gateway

Can be either source, Destination, or Intermediary

Each node on a network is identified by unique logical address – IP address on TCP/IP

Node connect to the network through its Interface

Node


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INTERFACE

Connects Node to the network

Each Interface is identified by unique Physical Address – MAC address in NIC

A node may have multiple Interfaces

Multi Homing


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LINK

A Segment of the transmission Channel

A LAN or Subnet is a Link

Devices on same Link uses Physical Address to identify each other

Devices connected on same Link communicate at Layer 2, Data Link Layer

Hub and switch works on the Link

Link


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BACKBONE A Backbone is a network

Infrastructure that interconnect diverse LANs or Sub networks

A backbone can tie together diverse networks in the same building, in different buildings in a campus environment, or over wide areas

Network backbones are designed to maximize the reliability and performance of large-scale, long-distance data communications.

WAN Backbones typically consist of routers and switches connected by fibre optic


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HUB A common connection point

for devices in a network. Also known as concentrator.

A hub is the place where data converges from one or more directions and is forwarded out in one or more directions.

Hubs are commonly used to connect segments of a LAN.

Hub basically acts as signal splitter. When a data frame arrives at one port, it is redistributed to all the other ports so that all devices of the LAN can see all frames.

Types of Hub• Active, Passive, Intelligent

Hub


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SWITCH A network switch joins multiple

Devices together within one LAN. Allow different nodes of a network to

communicate directly with each other.

It receives a message (Ethernet frame) from any device connected to its input ports and then transmits the message only to that output port to which the destination device is connected.

One to one connection Ensures optimum utilization of

Bandwidth or N/W resources.

LAN SWITCH


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SWITCH

Switch Types• Managed Vs. Unmanaged

• Layer 2 Vs. layer 3 switch

• Multi layer Switch


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Unmanaged Switch

• In scenarios where the network traffic is light, all that is required is a way for the data to pass from one device to another.

• There is no need for prioritizing the packets as all the traffic will flow unimpeded.

• An unmanaged switch will fill this need without issues.


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Managed Switch

• As the number of devices increases, the ability to ensure that the time-sensitive packets are prioritized becomes increasingly difficult as more concurrent streams of data hit the network.

• Another issue that may need to be dealt with is which devices have access to what portion of the network.


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Multilayer Switch

• A multilayer switch is a network device that has the ability to operate at higher layers of the OSI reference model.

• A multilayer switch can perform the functions of a switch as well as that of a router at incredibly fast speeds.

• Multilayer switches became devices that examine Layer 2 through Layer 7.


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Hub vs. Switch

HUB Broadcast Data Frame to all

nodes connected to it

Inefficient use of LAN Bandwidth

Half Duplex Communication

Unmanaged

SWITCH Frame from source node is

sent only to destination node

Efficient use of Bandwidth – Micro segmenting

Full Duplex Communication

Can be managed

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HUB

Hub vs. Switch

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BRIDGE A bridge connects a LAN to

another LAN that uses the same protocol (for example, Ethernet or token ring).

Has ports connected to two or more separate LANs. Packets received on one port may be re-transmitted on another port.

Bridges learn which addresses are on which network and develop a learning table so that subsequent messages can be forwarded to the right network.

Operates at Data Link Layer.

Bridge

LAN1 LAN2


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ROUTER A router is a device or a software in a

computer that determines the next network point to which a packet should be forwarded to its destination.

Allows different networks to communicate with each other

A router creates and maintain a table of the available routes and their conditions and uses this information along with distance and cost algorithms to determine the best route for a given packet.

A packet will travel through a number of network points with routers before arriving at its destination.


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SWITCH

Processor

MemoryNIC

NIC

NIC

NIC

NIC

NIC

OUTPUTPORT

INPUT PORT

INSIDE THE ROUTER

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ROUTERS Edge Router

• Routes data packets between a Backbone Network and LAN

Core Router

• Routes data packets Within a Backbone Network Gateway Router B-router

• Router Combined with Bridge Functionality Firewall Router

• Router having Packet Filtering capabilities


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GATEWAY

A gateway is a network point , similar to router that acts as an entrance to another network;

Gateway Connects Networks on Different Protocols/dissimilar networks

Gateway nodes are computers that control traffic within a company’s network or at local internet service provider (ISP)

Gateway


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Dynamic vs. Static Routing

STATIC ROUTING :

Routers forward the arriving Data packets to predefined output port. The routing table is manually configured.

DYANMIC ROUTING :

The Router learns the state of the Network and continuously update its routing table. For this, it uses routing protocols.


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What is the difference between….?

Bridge: device to interconnect two LANs that use the SAME logical link control protocol but may use different medium access control protocols.

Router: device to interconnect SIMILAR networks, e.g. similar protocols and workstations and servers

Gateway: device to interconnect DISSIMILAR protocols and servers.


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SWITCHING

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• Switching is basically transfer of information from one point to another point with some intelligence or control

or

• Establishing a temporary path or connection between two points or writing at one point of time and reading at another point of time.

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SWITCH A switch is a device that channels incoming data from any of multiple

input ports to the specific output port that will take the data toward its intended destination

In the traditional circuit-switched telephone network, one or more switches are used to set up a dedicated though temporary connection or circuit for an exchange between two or more parties

On local area network (LAN), a switch determines, from the physical device (Media Access Control or MAC) address in each incoming message frame, which output port to forward it

In a wide area packet-switched network such as the Internet, a switch determines from the IP address in each packet which output port to use for the next part of its trip to the intended destination


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Packet Switching A digital network technology that breaks up a message (Bit Stream)

into fixed size packets for transmission

Each packet is then transmitted individually and can even follow different routes to its destination.

Once all the packets forming a message arrive at the destination, they are recompiled into the original message.

Packets of different messages share the communication channel

When traversing network switches, routers and other network nodes, packets are buffered and queued, resulting in variable delay and throughput depending on the traffic load in the network.


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AN END TO END CHANNEL WITH MULTIPLE PATHS THROUGH THE INTERMEDIATE NODES

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Packet Switching : Illustration


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3

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3 41

1 131

4

4 3 2 1

2 1

1432

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Data traffic is divided into packets.

• Packets travel separately through network• Packet forwarding based on the header• Network nodes may store packets temporarily

Destination reconstructs the message

• Best-effort delivery• Packets may be lost• Packets may be corrupted• Packets may be delivered out of order

Each packet contains a header with Source and destination address

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Packet Switching : features

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The effectiveness of a data communication system depends on four fundamental characteristicsDelivery

The system must deliver data to the correct destination. Accuracy

Accurately- without errors/ alteration/ duplication/ missing Timeliness

Data delivered late are useless. •in the same order that they are produced, •without significant delay. •This kind of delivery is called Real-time transmission.

Jitter Variation in the arrival time of packets. Uneven delay in delivery of

packets may cause data disruption .

.

Fundamental Characteristics


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Routing vs. Switching

ROUTING

Routing is the process of selecting paths in a network along which to send network traffic

Based on Logical (IP) Address Forwarding Decision by

Microprocessor At Layer 3 (Network layer) of

OSI

SWITCHING

Switching is one to one data frame transmission in a LAN Segment

Based on Physical (MAC) address

Generally Hardwired (ASIC)* At Layer 2 (Data Link layer) of

OSI

(* Application Specific Integrated Circuit.: Customized for particular use rather than general purpose.)

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Advantages:o Bandwidth used to full

potential.

o Diverse Devices & Networks can communicate

o Not affected by line failure (re-diverts signal)

o Availability – do not have to wait for a direct connection to become available

o More Robust : Shared resources & Redundancies

Disadvantageso Low Throughput

o Under heavy use there can be a delay

o Data packets can get lost or become corrupted

o Variable delay : Jitter

o Each packet need header : Overload

Packet Switching

NTIPRITTYPES OF DATA COMMUNICATION

GUIDED

BASED UPON THE KIND OF COMMUNICATION CHANNEL

UNGUIDED

:waves are guided along a solid medium path (twisted pair, coaxial cable, and optical fiber).

:waves are propagated through the atmosphere and inner/outerspace (satellite, laser, and wireless transmissions). 42


SIMPLEX

BASED UPON THE DIRECTIONALITY OF DATA

TRANSMISSION

HALF DUPLEX

FULL DUPLEX

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NTIPRITTYPES OF DATA COMMUNICATION: Routing of Packet

ANYCASTBASED UPON DIRECTION OF DATA

TRANSMISSION

UNICAST

Anycast is a network addressing and routing methodology in which datagrams from a single sender are routed to the topologically nearest node in a group of potential receivers all identified by the same destination address.

Addressing uses a one-to-one association between destination address and network endpoint: each destination address uniquely identifies a single receiver endpoint.

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MULTICAST

Multicast is the delivery of a message or information to a group of destinations, simultaneously in a single transmission from the source.

Copies are automatically created in other network elements, such as routers.

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BROADCAST

broadcasting refers to transmitting a packet that will be received by every device on the network

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Geocast refers to the delivery of information to a group of destinations in a network identified by their geographical locations.

It is a specialized form of multicast addressing used by some routing protocols for mobile ad hoc networks.

GEOCAST

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CONNECTION ORIENTED

BASED UPON END TO END CONNECTION

CONNECTIONLESS

UDP

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Connection Vs. Connectionless Connection Oriented

• Requires a session connection (analogous to a phone call) be established before any data can be sent

• data is delivered in correct order, and signalling overhead is required during a connection establishment phase

• This Provides Reliable Service

• Implemented at Transport and Data Link layer

• Examples Frame Relay and ATM networks- Data Link

– TCP – Transport layer

– MPLS – Network layer

– Example is IP (Internet Protocol) – Network layer ; UDP – Transport layer


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Connection oriented vs. Connectionless

Connectionless

• Does not require a session connection between sender and receiver. The sender simply starts sending packets (called Datagrams) to the destination. (Like sending a Post Card).

• Packets of same message may reach to the end node via different intermediate node and may reach out of order

• Un-reliable but fast service

– Example is IP (Internet Protocol) – Network layer ; UDP – Transport layer


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Types Of Data Communication

SERIAL

PARALLEL

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Serial Transmission

Data is transmitted, on a single channel, one bit at a time one after another

Receiver received Sender transmitted

101 0 0 1 1 0


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R

ecei

ver r

ecei

ved

- each bit has it’s own piece of wire along which it travels

- often used to send data to a printer

Parallel Transmission

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All bits are sent simultaneously

Sender transm

itted

1

0

0

1

1

0

0

1

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What is MAC Address?!

Media Access Control (MAC) Address – are the physical

address of any device, e.g. a NIC in a computer on the

network.

The MAC address has two parts of 3 bytes long.

The first 3 bytes specify the company that made the NIC

and the second 3 bytes are the serial number of the NIC.


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Protocol are used for communication between computers

in different computer networks. Protocol achieves:

What is communicated between computers?

How it is communicated?

When it is communicated?

What conformance (bit sequence) between computers?

Protocols


Data Communication Tasks/functions

•Switching •Addressing •Sequencing

•Interfacing •Routing •Flow Control

•Signal Generation •Recovery •Error Feedback

•Synchronization •Formatting •Network MGT

•Exchange Management •Security/safety •QoS

•Error Detection & Correction

•Monitoring System Utilization

•N/W Administration

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V. SobhanaDDG, NTIPRIT

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Circuit Switching

SAS

Direction of transmission

Time Slots as Physical Channels

BCDAD

D

A

B

C

D

BCSC

B

A

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Circuit Switching

SAS


Inefficient Utilization of media

___A_

D

A

__SC

B

A

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A


BDAD

D

A

B

C

D

BCB

A

Virtual ChannelsNo Physical channel like a Time Slot

Statistical or Asynchronous Multiplexing

Packet Switching

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Data communication basics

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