AIT Assignment 1(2)

8/3/2019 AIT Assignment 1(2)

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AIT

ASSIGNMENT NO. 1

Submitted To: Submitted From:

Er. Mandeep Kumar Group 5

I.T.

81307113041 - 400


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1)Explain the concept of layeringLayering is a common technique to simplify networking designs by dividing them intofunctional layers, and assigning protocols to perform each layer's task. Each layer of the

model communicates with an adjacent level (above or below it). Each layer therefore

uses the services of the lower layers and supplies them to that of the upper layer.

For example: It is common to separate the functions of data delivery and connection

management into separate layers, and therefore separate protocols. Thus, one protocol

is designed to perform data delivery, and another protocol, layered above the first,

performs connection management. The data delivery protocol is fairly simple and knows

nothing of connection management. The connection management protocol is also fairly

simple, since it doesn't need to concern itself with data delivery.

It gives the ability to independently design, modify and build the functions and services

of each layer without affecting the other layers.

Benefits of layering:

y Reduces Complexity - The aim of TCP/IP in layers is to separate the problem intodifferent parts (the layers) depending on their level of abstraction. This reduces thecomplexity of network operations by dividing them into simpler components.

y Enables multi-vendor integration - It enables multi-vendor integration by definingstandard interfaces.

y Increased Life Expectancy - Increased product working life expectancies as backwardscompatibility is made considerably easier. Devices from different technology

generations can co-exist thus the older units do not get discarded immediately newer

technologies are adopted.

y Better Flexibility Layering and the greater compatibility that it delivers goes a longway to improving the flexibility; particularly in terms of options and choices, thatnetwork engineers and administrators alike crave so much.

y Interoperability Layering promotes greater interoperability between devices fromdifferent manufacturers and even between different generations of the same type of

device from the same manufacturer.


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y Greater Compatibility One of the greatest of all of the benefits of using a hierarchal orlayered approach to networking and communications protocols is the greater

compatibility between devices, systems and networks that this delivers.

y Cost Effective Quality The layered approach has proven time and time again to be themost economical way of developing and implementing any system(s) be they small,simple, large or complex makes no difference.

2)What is protocol suite? Why we need it?A protocol suite is a collection of communications procedures, broken down into small data

packets. Each contains its own set of rules and message formats, which work together to

transmit information electronically across computer networks, via a common communications

language.

Protocol suit means a collection of PROTOCOLS that are associated with

particular network architecture. It is also known by protocol stack. For

example, TCP-IP is associated with a number of individual protocols which carry

out functions such as network management and DOMAIN NAME lookup. It is

often referred to by the term PROTOCOL STACK to stress the hierarchic

relationship between protocols.

Need of protocol suite:

y A Protocol Suite defines rules and conventions for communication between networkdevices.

y Protocol Suite include mechanisms for devices to identify and make connections witheach other, as well as formatting rules that specify how data is packaged into messages

sent and received.

y Computer networks consist of devices and software made by many different vendors.The only way to ensure compatibility among them all is to have common document (i.e.

the protocol specifications) that describe the mechanics and formats of all the data

exchanged over the network.


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y It provides reliable data delivery. Reliable means that it can guarantee that the data isdelivered to its intended destination (e.g., through the use of error checking and the

retransmission of corrupted or missing packets).

y Data is passed down the stack from one layer to next, until it is transmitted over thenetwork by network access layer protocols. The four layers in this reference model arecrafted to distinguish between the different ways that the data is hanled as it passed

down the protocol stack from the one layer to another.

y At the remote end, the data is passed up the stack to the receiving application. Theindividual layers do not need to know how the layers above or below them function;

they only need to know how to pass data to them

3)Define DNS.Domain Name System is an Internet service that translates domain names into IP addresses.

Because domain names are alphabetic, they're easier to remember. The Internet however, is

really based on IP addresses. Every time you use a domain name, therefore, a DNS service must

translate the name into the corresponding IP address.

For example: the domain name www.example.com might translate to 198.105.232.4.

The Domain Name System (DNS) is a hierarchical naming system built on a distributed database

for computers, services, or any resource connected to the Internet or a private network. It

translates domain names meaningful to humans into the numerical identifiers associated with

networking equipment for the purpose of locating and addressing these devices worldwide.

The Domain Name System makes it possible to assign domain names to groups of Internet

resources and users in a meaningful way, independent of each entity's physical location.

Because of this, World Wide Web (WWW) hyperlinks and Internet contact information can

remain consistent and constant even if the current Internet routing arrangements change or

the participant uses a mobile device


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Advantages of DNS:

y It's more reliable- DNS's Directory Services Platform currently spans 15 locations andfive continents around the world. This allows us to offer you the most reliable fully

redundant DNS service anywhere. Each node has multiple servers, and is connected by

several Tier 1 carriers to the Internet.

y It's Faster- Our strategically placed nodes are located at the most optimal intersectionsof the Internet. Unlike most DNS providers, DNS's Directory Services Platform uses any

cast routing technology - which means that no matter where you are located in the

world, your DNS requests are answered by the closest available DNS Advantage servers.

Combine this with our huge cache and we can get the answers you seek faster and more

reliably than anyone else.


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y It's Smarter- Our technology allows us to automatically correct many typing errors youmay make. We don't think you should be penalized for inadvertently typing an invalid

top level domain address into your browser, so we will correct many typos and take

you where you intended to go automatically - saving you valuable time and improving

your Internet experience. Our DNS Advantage Directory guides you with relevant

alternatives when your browser's Address Bar can't resolve your search words or

destination.

y Its Efficient- DNS as a distributed name resolution service proved to be very efficient,even though the amount of people using it has increased tremendously with the growth

of the Internet.

y It's

Safer- As the leading authoritative DNS provider, we are keenly aware of the

dangers that plague the Internet today. That's why we've created unique security

solutions that don't require you to install any hardware or download any software. Our

DNS Real-Time Directory signals the DNS Advantage recursive servers anytime one of

the DNS authoritative customers or DNS-RTD partners updates a DNS record. This

fundamentally eliminates the concept of a TTL by invalidating the recursive server's

cache for updated Domains, providing you the most accurate and up to date view of

these sites.

y Easy Maintainability. The last advantage of DNS-based redirection is its goodmaintainability. Deployment of the complete redirection mechanism boils down to

launching a single modified DNS server, and subsequently delegating a service domain

to this server.

y Speed: The Domain Name System is optimized for speed. Because it is DNS-based, a .tellookup takes just a fraction of a second, and is much quicker than loading a typical web

page.

y Real-Time: Whenever you update your data in the DNS, the change goes liveimmediately.

y Encryptable: Data stored in the DNS may be encrypted so that only authorized usersmay access it, ensuring total privacy.


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y Global: The DNS is ubiquitous. Everything on the Internet uses the DNS all the time andall information stored within the DNS is globally accessible from any device connected

to the internet.

4)Define Client-Server Model.Client/server describes the relationship between two computer programs in which one

program, the client, makes a service request from another program, the server, which fulfills

the request. Although programs within a single computer can use the client/server idea, it is a

more important idea in a network.

In a network, the client/server model provides a convenient way to interconnect programs that

are distributed efficiently across different locations. Computer transactions using the

client/server model are very common.


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Example: Database Server A computer system that processes database queries

Classes of servers:

1. Iterative: steps of iterative server Wait for a client request to arrive Process the client request. Send the response back to the client that sent the request. Go to step 1.

2.

Concurrent: Stepsy Wait for a client request to arrive.y Start a new server to handle this clients request. This may involve

creating a new task, thread or a process depending upon what the

underlying operating system supports. This new server handles the

clients entire request. When complete, this new server terminates.

y Go back to step 1.Advantage of concurrent over iterative:

yEach client has its own server. In this multiple clients are servicedconcurrently that allows multiprogramming.

y In general, TCP servers are con current and UDP are iterative.

5)Explain TCP/IP layering.The TCP/IP reference model consists of protocol suite that allows computers of all sizes, from

many different computer vendors, running totally different operating systems, to communicate


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with each other.

y Link layer/ Data Link Layer:It includes the device driver in the operating system and the corresponding networking

interface card in the computer. They handle all the hardware details of physically

interfacing with the cable.

At this layer TCP/IP the protocols used are:

1. Address Resolution Protocol (ARP): It is used to find the physical address frominternet address. On a network, each device on a link is identified by a physical

address imprinted on a NIC (Network Interface Card).


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2. Reverse Address Resolution Protocol (RARP): It allows a host to find its Internetaddress when it knows its Physical address.

y Network/

I

nternet Layer:This layer handles the movement of packets around the networks. Routing of packets

takes place here. It divides the data into packets. IP, ICMP and IGMP provide the

Network layer.

The various protocols used are:

1. Internet Protocol (IP): It is an unreliable and connectionless protocol. IP doesnot keep track of the routes on which packets are sent, due to which it is

unreliable. It has no facility for recording datagrams once they arrive at their

destination. Each packet is sent individually of each other, due to which it is

connectionless.

It provides maximum efficiency. It allows the user to add only those facilities that

are necessary for a given application.

2. Internet Control Message Protocol (ICMP): It is a mechanism used by hosts tosend notifications of datagram problems back to the sender. ICMP sends error

reporting messages.

3. InternetGroup Message Protocol (IGMP): It is used to facilitate simultaneoustransmission of a message to a group of recipients.

y Transport Layer:It provides a flow of data between two hosts. The Transport Layer establishes host-to-

host connectivity, meaning it handles the details of data transmission that are

independent of the structure of user data. The layer simply establishes a basic data

channel that an application uses in its task-specific data exchange. For this purpose the

layer establishes the concept of theport, a numbered logical construct allocated

specifically for each of the communication channels an application needs.

The main protocols defined in this layer are:

1. Transmission Control Protocol (TCP): It is a transport level protocol responsiblefor delivery of a message from a process to another process. It is reliable as it

keeps track of datagrams sent. It acknowledges the received packets. It sets

timeouts, and if a packet is not sent successfully within the timeout. The packet

is sent again.


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2. User Datagram Protocol (UDP): It is a connectionless protocol. It has noprocedure for making sure that packet is sent successfully at the other end. After

UDP has placed a packet on the network (via the IP protocol), it forgets about it.

UDP doesn't guarantee that the packet actually arrives at its destination. Thebest-known Application layer protocol that uses UDP is DNS

y Application Layer:The Application Layer refers to the higher-level protocols used by most applications for

network communication. This layer handles the details of a particular application. Many

protocols are defined in this layer

Some of them are:1. FTP File Transfer Protocol copies arbitrary files (e.g. binary, data, and source)

from

one machine to another.

2. DNS Domain Name Service.3. HTTP Hyper Text Transport Protocol4. Remote Login5. SMTP - The Simple Mail Transfer Protocol is used to send mail from one machine

to

another.6. Telnet - Provides remote login service. It allows a user on one machine to log

into another machine on the network. Etc.

AIT Assignment 1(2)

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