REVIEW OF COMPUTER NETWORKS

REVIEW OF COMPUTER NETWORKS
K. PALANIVEL
Systems Analyst, Computer Centre
Pondicherry University, Puducherry – 605014.
COMS 525: TCPIPLECTURE 1
TOPIC
COURSE

Internet in a Minute
Department of Computer Science, Pondicherry University, Puducherry - 605014

Internet in a Minute
This is what happens in an internet minute in 2018
Internet connectivity:
• unique ICANN-overseen IP number for duration of
connection;
• ability to exchange general Internet traffic (POP, http) with
other ICANN-overseen IP addresses

Network in India (BSNL)
BSNL Core Router

Network in India (BSNL)
BSNL Core Network

Computer Networking
• Computer Network - A collection of computing devices
that are connected in various ways in order to
communicate and share resources
• Usually, the connections between computers in a network
are made using physical wires or cables
• However, some connections are wireless, using radio
waves or infrared signals
• The generic term node or host refers to any device on a
network
• Data transfer rate The speed with which data is moved
from one place on a network to another
• Data transfer rate is a key issue in computer networks

Networking (Contd.)
• Computer networks have opened up an entire frontier
in the world of computing called the client/server
model

Networking (Contd.)
• File server A computer that stores and manages files
for multiple users on a network
• Web server A computer dedicated to responding to
requests (from the browser client) for web pages
15-12

Types of Networks
• Local-area network (LAN) A network that connects a
relatively small number of machines in a relatively close
geographical area
• A LAN connects network devices over a relatively short
distance.
• A networked office building, school, or home usually
contains a single LAN, though sometimes one building
will contain a few small LANs (perhaps one per room),
and occasionally a LAN will span a group of nearby
buildings.
• In addition to operating in a limited space, LANs are also
typically owned, controlled, and managed by a single
person or organization.

Local Area Networks (LAN)
• LANs are confined to a relatively small area such as a
school or a building
• LANs usually have one computer designated as the
file server
• Other computers are connected to the network by
cables connecting network interface cards in each
computer

Wireless LANS
• Wireless networks use high frequency radio signals to
communicate between the workstations and the fileserver or
hubs.
• Disadvantages of wireless networks are:
– they are expensive (relatively),
– provide poor security,
– are susceptible to interference and
– are slower than cabled networks

Metropolitan-Area Network (MAN)
• MAN - The communication infrastructures that
have been developed in and around large cities
• A MAN is a large computer network that usually
spans a city or a large campus.
• A MAN usually interconnects a number of local
area networks (LANs) using a high-capacity
backbone technology, such as fiber-optical links,
and provides up-link services to wide area
networks (or WAN) and the Internet.
15-17

Wide-Area Network (WAN)
• Wide-area network (WAN) A network that connects
two or more local-area networks over a potentially
large geographic distance
Often one particular node on a LAN is set up to
serve as a gateway to handle all communication
going between that LAN and other networks
Communication between networks is called
internetworking
The Internet, as we know it today, is essentially
the ultimate wide-area network, spanning the
entire globe

Wide-Area Network (WAN)
• WANs connect larger areas, such as whole states, or
even the world.
• Transoceanic cables and satellites are used to
connect WANs

LAN vs. WAN
LAN WAN
1.Diameter of not more than a
few kilometers.
1.Span entire countries.
2.A total data rate of at least
several mbps.
2.Data rate less than 1 mbps.
3.Complete ownership by a
single organization.
3.Owned by multiple
organization.
4.Very low error rates. 4.Comparitively higher error
rates.

Protocol
• A protocol is a set of
rules that governs the
communications
between computers on a
network
• These rules include
guidelines that regulate
the method of access,
types of cabling and
speed of data transfer
PROTOCOL =
SET OF RULES
ABOUT
COMMUNICATIO
NS BETWEEN
NETWORKS!

The most common protocols are:
• Ethernet
• Local Talk
• Token Ring
• FDDI
• ATM
Protocol = a
formal
description of a
set of rules and
conventions
that govern how
devices on a
network
exchange
information

Sample LAN Implementation

Topology
• The physical topology of a network refers to the
configuration of cables, computers and other
peripherals.
• The main types of network topologies are:
– Linear Bus
– Star
– Ring
– Tree or Hybrid

Types of Networks Topology
• Various configurations, called topologies, have been
used to administer LANs
– Ring topology A configuration that connects all
nodes in a closed loop on which messages travel in
one direction
– Star topology A configuration that centers
around one node to which all others are connected
and through which all messages are sent
– Bus topology All nodes are connected to a
single communication line that carries messages in
both directions

Types of Topology
• A bus technology called Ethernet has become the industry
standard for local-area networks

Linear Bus
• A linear bus topology consists of a main run of cable
with a terminator at each end. All servers
workstations and peripherals are connected to the
linear cable

Star
• A star network is designed
with each node (file server,
workstation, peripheral)
connected directly to a
central network hub or
server

Ring
• A ring network is one where all workstations and
other devices are connected in a continuous loop.
There is no central server

Tree or hybrid
• A tree or hybrid
topology combines
characteristics of
linear bus and star
and/or ring
topologies.
• It consists of groups
of star-configured
workstations
connected to a linear
bus backbone cable

Mesh Topology
• In a mesh network topology, each of the network node,
computer and other devices are interconnected with one
another.
• Every node not only sends its own signals but also relays data
from other nodes. in fact a true mesh topology is the one
where every node is connected to every other node in the
network.
• This type of topology is very expensive as there are many
redundant connections, thus it is not mostly used in computer
networks.

Sending a packet from One Location to Another

Sending a packet from Argon to Neon
34
neon.tcpip-lab.edu
"Neon"
128.143.71.21
argon.tcpip-lab.edu
"Argon"
128.143.137.144
router137.tcpip-lab.edu
"Router137"
128.143.137.1
"Router71"
128.143.71.1
Ethernet NetworkEthernet Network
Router

Explanation
35
DNS: The IP address of
“neon.tcpip-lab.edu” is
128.143.71.21
ARP: What is the MAC
address of 128.143.137.1?
neon.tcpip-lab.edu
"Neon"
128.143.71.21
argon.tcpip-lab.edu
"Argon"
128.143.137.144
"Router137"
128.143.137.1
"Router71"
128.143.71.1
Ethernet NetworkEthernet Network
Router
DNS: What is the IP address
of “neon.tcpip-lab.edu”?ARP: The MAC address of
128.143.137.1 is 00:e0:f9:23:a8:20
128.143.71.21 is not on my local network.
Therefore, I need to send the packet to my
default gateway with address 128.143.137.1
frame
128.143.71.21 is on my local network.
Therefore, I can send the packet directly.
ARP: The MAC address of
128.143.137.1 is 00:20:af:03:98:28
ARP: What is the MAC
address of 128.143.71.21?
frame

Communications Architecture
• The complexity of the communication task is reduced
by using multiple protocol layers:
• Each protocol is implemented independently
• Each protocol is responsible for a specific
subtask
• Protocols are grouped in a hierarchy
• A structured set of protocols is called a
communications architecture or protocol suite
37

OSI Reference Model
The OSI model is now considered the primary
Architectural model for inter-computer communications.
The OSI model describes how information or data makes
its way from application programmes (such as
spreadsheets) through a network medium (such as wire)
to another application programme located on another
network.
The OSI reference model divides the problem of moving
information between computers over a network medium
into SEVEN smaller and more manageable problems .
This separation into smaller more manageable functions
is known as layering.

OSI Reference Model: 7 Layers

OSI Reference Model: Packet Movement

OSI Reference Model: Protocols

OSI Reference Model: LAN to WAN

OSI: A Layered Network Model
The process of breaking up the functions or tasks of
networking into layers reduces complexity.
Each layer provides a service to the layer above it in the
protocol specification.
Each layer communicates with the same layer’s software or
hardware on other computers.
The lower 4 layers (transport, network, data link and physical
—Layers 4, 3, 2, and 1) are concerned with the flow of data
from end to end through the network.
The upper four layers of the OSI model (application,
presentation and session—Layers 7, 6 and 5) are orientated
more toward services to the applications.
Data is Encapsulated with the necessary protocol information
as it moves down the layers before network transit.

Physical Layer
Provides physical interface for transmission of
information.
Defines rules by which bits are passed from one
system to another on a physical communication
medium.
Covers all - mechanical, electrical, functional and
procedural - aspects for physical communication.
Such characteristics as voltage levels, timing of
voltage changes, physical data rates, maximum
transmission distances, physical connectors, and
other similar attributes are defined by physical
layer specifications.

Data Link Layer
Data link layer attempts to provide reliable communication
over the physical layer interface.
Breaks the outgoing data into frames and reassemble the
received frames.
Create and detect frame boundaries.
Handle errors by implementing an acknowledgement and
retransmission scheme.
Implement flow control.
Supports points-to-point as well as broadcast communication.
Supports simplex, half-duplex or full-duplex communication.

Network Layer
Implements routing of frames (packets) through the network.
Defines the most optimum path the packet should take from
the source to the destination
Defines logical addressing so that any endpoint can be
identified.
Handles congestion in the network.
Facilitates interconnection between heterogeneous networks
(Internetworking).
The network layer also defines how to fragment a packet into
smaller packets to accommodate different media.

Transport Layer
Purpose of this layer is to provide a reliable
mechanism for the exchange of data between two
processes in different computers.
Ensures that the data units are delivered error free.
Ensures that data units are delivered in sequence.
Ensures that there is no loss or duplication of data
units.
Provides connectionless or connection oriented
service.
Provides for the connection management.
Multiplex multiple connection over a single channel.

Session Layer
Session layer provides mechanism for controlling the dialogue
between the two end systems. It defines how to start, control
and end conversations (called sessions) between applications.
This layer requests for a logical connection to be established
on an end-user’s request.
Any necessary log-on or password validation is also handled
by this layer.
Session layer is also responsible for terminating the
connection.
This layer provides services like dialogue discipline which can
be full duplex or half duplex.
Session layer can also provide check-pointing mechanism such
that if a failure of some sort occurs between checkpoints, all
data can be retransmitted from the last checkpoint.

Presentation Layer
Presentation layer defines the format in which the
data is to be exchanged between the two
communicating entities.
Also handles data compression and data encryption
(cryptography).

Application Layer
1. Application layer interacts with application programs and is
the highest level of OSI model.
2. Application layer contains management functions to support
distributed applications.
3. Examples of application layer are applications such as file
transfer, electronic mail, remote login etc.

OSI in Action
A message begins at the top
application layer and moves
down the OSI layers to the
bottom physical layer.
As the message descends, each
successive OSI model layer adds
a header to it.
A header is layer-specific
information that basically
explains what functions the layer
carried out.
Conversely, at the receiving end,
headers are striped from the
message as it travels up the
corresponding layers.

Data Encapsulation

OSI Vs TCP/IP

Data Transmission Via UTP

Data Transmission Via Devices

Data Transmission Via UTP Cables

Data Transmission Via Wirless Devices

Data Transmission Via Wireless Devices

Network Devices: Hub

Network Devices: Switch

Network Devices: Router

Communication : Satellite

Communication : Mobile

Questions?
77

Review

REVIEW OF COMPUTER NETWORKS

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to REVIEW OF COMPUTER NETWORKS

Similar to REVIEW OF COMPUTER NETWORKS (20)

More from Palanivel Kuppusamy

More from Palanivel Kuppusamy (17)

Recently uploaded

Recently uploaded (20)

REVIEW OF COMPUTER NETWORKS