ICT role in 21st century education and it's challenges.
Computer Networks basics
1. Distributed Computing
Class assignment - I
A Presentation on
Computer Network
Basics
BIPLABA SAMANTARAY
MCA ,University of
Hyderabadd
A computer network is a set of
computers connected together for the
purpose of communicating data
electronically. In this presentation we are
going to focus on the basics of Computer
networking which will further relevant
for understanding the topic Distributed
computing.
3. What is Network Protocol ?
Network protocol is established set of rules that are predefined to determine how data is transmitted
between different nodes in the same network. Protocols must be formally defined and precisely
implemented.
For each protocol there must be rules that specify
following :-
• How is the data exchange encoded
• How the events (sending and receiving) synchronised
(ordered) so that the participants can send and receive
in a coordinated manner
Note
The specification of a protocol
does not dictate how the rules to
be implemented.
For example HTTP specifies
the rules that must be observed
between a web server and
browser process and is
independent of the language and
syntax.
4. Network Architecture
What is Open System Interconnect?
• The classical network architecture called the
Open System Interconnect(OSI) divides the
complex functionalities of network in to seven
layers.
• The OSI model of network architecture is
promoted by an organisation named
International organisation for
standardisation(ISO).
Application Layer
Presentation Layer
Network Layer
Data Link Layer
Session Layer
Transport Layer
Physical Layer
Allnetworked
devices
Hosts
The OSI model
5. Network Architecture
What is TCP / IP model?
The TCP/IP architecture is very similar to the OSI model but
instead of seven it uses five layers and we can called it as a
generalised version of OSI model.
Why Layering?
With layering, each layer is responsible for a different facet
of the communications.
Layers are beneficial because a layered design allows
developers to evolve different portions of the system
separately, often by different people with somewhat different
areas of expertise.
Application Layer
Allnetworked
devices
Hosts
Transport Layer
Internet
Network Interface
Physical Layer
TCP/IP architecture
6. Network Architecture
Functionalities of Layers :-
Layer Functionalities
Physical
• Protocols in the Physical layer specify details about the underlying transmission
medium and the associated hardware.
• All specifications related to electrical properties, radio frequencies, and signals belong
to this layer.
Network interface
• Protocols in the Network Interface layer specify details about communication between
higher layers of protocols, which are usually implemented in software, and the
underlying network, which is implemented in hardware.
• Specifications about network addresses and the maximum packet size that a network
can support, protocols Layers used to access the underlying medium, and hardware
addressing belong to this layer.
7. Network Architecture
Layers Functionalities
Internet • Protocols of this layer specify communication between two computers across the Internet (i.e., across
multiple interconnected networks).
• The Internet addressing structure, the format of Internet packets, the method for dividing a large Internet
packet into smaller packets for transmission, and mechanisms for reporting errors belong to this.
Transport • Protocols in the Transport layer provide for communication from an application program on one computer
to an application program on another.
• Specifications that control the maximum rate a receiver can accept data, mechanisms to avoid network
congestion, and techniques to insure that all data is received in the correct order belong to this layer.
Application • Protocols of this layer specify how a pair of applications interact when they communicate.
• Application layer protocols specify details about the format and meaning of messages that applications
can exchange as well as procedures to be followed during communication.
• Specifications for email exchange, file transfer, web browsing, telephone services, and video
teleconferencing all belong to this layer.
8. How data passes through the layers:-
Net. Interface
Internet
Transport
Application
Net. Interface
Internet
Transport
Application
NETWORK
Layers vs Headers:-
Actual message
Physical
Header(optional)
Net. Interface
header
Internet Header
Transport Header
Device1 Device2
Layers vs Protocols:-
9. Connection less vs Connection Oriented Communicat
Connection Oriented
Communication
In connection oriented service we have to establish
a connection before starting the communication.
When connection is established, we send the
message or the information and then we release the
connection.
Connectionless Communication
Each message is routed independently from source
to destination. The order of message sent can be
different from the order received
Connection oriented
Connection less
10. Connection less vs Connection Oriented Communicati
Connection-Oriented Connection-less
Addressing Specified at connection time, there is no need
to re-specify with each subsequent
operation(send or receive).
Addressing is specified with each operation
Connection overhead There is overhead for establishing a
connection.
Not applicable.
Addressing overhead There is no addressing overhead with each
individual operation.
Overhead incurred with each operation.
Data delivery order The connection abstraction allows the IPC
mechanism to maintain the order of delivering
data packets.
The lack of connection makes it difficult for
IPC facility to maintain delivery order.
Protocols This mode of communication is appropriate
for protocols that require exchange of large
stream of data and a large number of rounds
of exchange.
This mode of communication is appropriate
for protocols that exchange a small amount of
data in a limited number of rounds of
exchange.
11. Network Resources
“Network Resources” in terms of distributed computing refers to the resources that are available to the
participants of a distributed computing community.
Examples :-
Hardware[Printers, routers, cameras etc ]
Software[Process, Files, mailbox, web document]
The key challenge in distributed computing is the unique identification of resources that available in the
network.
To achieve this goal the naming schemes are there such as :-
• Domain Name System(DNS)
• The Extensive Name System(XNS)
• Protocol Port Numbers
• Uniform Resource Identifier(URI) and Uniform Resource Locator(URL)
• Email ID
12. Host Identification and IP address
“Hosts” are the computers with TCP/Ip supports and are connected to a network. “Host identification” is the crucial
part of Internet protocol. Two versions of IP : IPv4 ,IPv6.
IPv4 addressing
IP address : An Internet address (IP address) is a unique 32-bit binary string assigned to a host and used for all
communication with the host.
Each 32-bit IP address is divided into two parts: a prefix and a suffix.
IP prefix identifies the physical network to which the host is attached.
IP suffix identifies a specific computer on the network.
The important point is that the IP address scheme guarantees two properties:
• Each computer is assigned a unique address (i.e., a single address is never assigned to more than one
computer).
• Although network number assignments must be coordinated globally, suffixes can be assigned locally without
global coordination.
13. Host Identification and IP address
Class -A
Class -B
Class -C
Class -D
Class -E
Classes of IP address-
Suffixprefix1
01 prefix Suffix
11 Multicast
1 prefix Suffix1 0
1 0
11 Reserved1 1
Note : Class D addresses are still used for multicasting, but multicastingdoes not work
globally.
14. Host Identification and IP address
Subnet and supernet addressing :
One of the earliest difficulties encountered when the Internet began to grow was the inconvenience of
having to allocate a new network number for any new network segment that was to be attached to the
Internet. To over come this problem subnet and supernet addressing are included to the classes of IP.
Subnetting Supernetting
Subnetting is the procedure to divide the
network into sub-networks.
While supernetting is the procedure of combine the
small networks.
In subnetting, Network addresses’s bits are
increased.
While in subnetting, Host addresses’s bits are
increased.
In subnetting, The mask bits are moved
towards right.
While In supernetting, The mask bits are moved
towards left.
15. Host Identification and IP address
Domain Name System(DNS)
• Memorising a 32 bit string or a dot separated decimal
values to identify each host in a network is quite
difficult task for the users. Therefore DNS is adopted
which is used for identifying the host through a domain
name. These domain names are not case sensitive.
• The mapping of a domain name to its corresponding
ip-address and vice versa can be performed using a
network service known as DNS naming resolution
Examples:
Some top level DNS are .com, .edu, .uk , .gov etc
16. Identifying process with protocol ports
• Specifying the correct domain name or its corresponding IP address allows us to locate
the computer or the host or the internet.
• But in network application data needs to be delivered to a specific process running on a
computer.
• One simple solution for this problem is to make a use of unique process identifier(PID)
assigned to the process by operating system.
• On the internet the protocol process identification involves the use of a logical entity
known as a protocol port or a port for short.
• The transport layer protocols such as TCP and UDP are responsible for dispatching the
data to the process with some reserved port numbers.
17. Email
• Structure: username@domainname
• On delivering a email a mailer program on the IP host with specified domain name deliver the email to the
mailbox of the specified user on that system.
URI and URLs
• URL(Uniform resource locator) is a naming scheme under the more general scheme known as Uniform resource
Identifier(URI)
• URIs are short strings that identify resource on the web including docs and images.
• Example : https://www.biplabas.com
XNS
• Extensible Name Service (XNS) is an open Extensible Markup Language (XML)-based protocol that specifies a
way to establish and manage a universal addressing system.
• XNS can be considered to be an enhanced version of the domain name system (DNS) because it resolves a
universal address into any other kind of address, just as DNS resolves a domain name into an IP address.
18. References :
Distributed Computing: Principles and Applications 1st Edition by M.L. Liu
Computer Networks and Internets by DOUGLAS E. COMER
Praise for the First Edition of TCP/IP Illustrated, Volume 1: The Protocols
Thank You
