Unit 6: Overview of Application Layer

DOMAIN NAME SPACE

DOMAIN NAME SPACE

An application layer protocol defines how the application processes running on different systems, pass the messages to each other.

• DNS stands for Domain Name Space.
• DNS is a service that translates the domain name into IP addresses. This allows the users of networks to utilize user-friendly names when looking for other hosts instead of remembering the IP addresses.
• For example, suppose the FTP site at EduSoft had an IP address of 132.147.165.50, most people would reach this site by specifying ftp.EduSoft.com. Therefore, the domain name is more reliable than IP address.

WORKING

• DNS is a client/server network communication protocol. DNS clients send requests to the server while DNS servers send responses to the client.
• Client requests contain a name which is converted into an IP address known as a forward DNS lookups while requests containing an IP address which is converted into a name known as reverse DNS lookups.

DYNAMIC DOMAIN NAME SPACE (DDNS)

DYNAMIC DNS

Dynamic Domain Name System (DDNS): It is a method of automatically updating a name server in the Domain Name Server (DNS), often in real-time, with the active DDNS configuration of its configured hostnames, addresses, or other information.

By using DDNS, users can create a hostname (e.g. “myhome.dyndns.org”) that will always point to their router’s current IP address, making it easy to connect to devices on their home network from anywhere in the world.

Advantages :

• Accessibility: DDNS allows users to connect to devices on their home network from anywhere in the world, using a hostname instead of a constantly changing IP address. This makes it easy to remotely access files, control IoT devices, and perform other tasks.
• Convenience: DDNS eliminates the need to manually update IP addresses, which can be a tedious and time-consuming task.
• Compatibility: DDNS is compatible with a wide range of devices and services, including Remote Desktops, FTP, and VPN, making it easy to connect to a variety of devices on a home network.
• Ease of use: DDNS services are often easy to set up and use, with user-friendly interfaces and clear instructions.

TELNET(Teletype network)

• Telnet is a network protocol used to virtually access a computer and to provide a two-way, collaborative and text-based communication channel between two machines.
• The computer which starts the connection is known as the local computer. The computer which is being connected to i.e. which accepts the connection known as the remote computer.
• It follows a user command Transmission Control Protocol/Internet Protocol (TCP/IP) networking protocol for creating remote sessions.
• On the web, Hypertext Transfer Protocol (HTTP) and File Transfer Protocol (FTP) simply enable users to request specific files from remote computers, while, through Telnet, users can log on as a regular user with the privileges they are granted to the specific applications and data on that computer.

for eg-telnet the.libraryat.whatis.ed

The result of this request would be an invitation to log on with a user ID, and then the program would prompt the user for a password. If accepted, the user is granted access to the remote host.

TELNET

EMAIL(Electronic mail)

EMAIL

Electronic mail (e-mail) is a computer-based program that allows users to send and receive messages. E-mail is the electronic version of a letter, but with time and flexibility advantages. While a letter can take anywhere from a week to a couple of months to reach its intended destination, an e-mail is sent virtually almost instantly.

Messages in the mail contain not just text but also photos, audio, and video data. A person sending an e-mail is a sender, and the person receiving it is the recipient.

Services offered by Electronic Mail

Composition: Creating messages and responses is referred to as composition.

Transfer: Sending mail from the sender to the receiver is known as a transfer.

Reporting: Mail delivery confirmation is known as reporting. It allows users to see if

their mail has been delivered, misplaced, or rejected.

Displaying: It refers to presenting messages so that the user can understand them.

Disposition: This stage concerns the recipient's actions after receiving mail, such as saving it, deleting it before reading it, or after reading it.

BLUETOOTH

Bluetooth is universal for short-range wireless voice and data communication. It is a Wireless Personal Area Network (WPAN) technology and is used for exchanging data over smaller distances.

• Maximum devices that can be connected at the same time are 7.
• Bluetooth ranges up to 10 meters.
• It provides data rates up to 1 Mbps or 3 Mbps depending upon the version.
• The spreading technique that it uses is FHSS (Frequency-hopping spread spectrum).
• A Bluetooth network is called a piconet and a collection of interconnected piconets is called scatternet.

Advantage:

• It is a low-cost and easy-to-use device.
• It can also penetrate through walls.
• It creates an Ad-hoc connection immediately without any wires.
• It is used for voice and data transfer.

Disadvantages:

• It can be hacked and hence, less secure.
• It has a slow data transfer rate: of 3 Mbps.
• It has a small range: 10 meters.
• Bluetooth communication does not support routing.
• The issues of handoffs have not been addressed.

File Transfer Protocol (FTP)

and

Hyper Text Transfer protocol (HTTP)

FTP AND HTTP

HyperText Transfer Protocol (HTTP) and File Transfer Protocol(FTP) are the protocols used for file transfer between client and server. There is a lot of difference between FTP and HTTP. In this article, we will learn what are the differences between HTTP and FTP.

File Transfer Protocol (FTP) :

It stands for File Transfer Protocol. It is an internet standard that allows the process of file downloading and uploading on different computers from the internet. FTP site consists of different types of files(text, graphics, videos, images, etc). It was developed when security was not a big issue. It is older and is being replaced with new protocols. FTP supports two separate Transmission Control Protocols the first one is a control connection or command port (port 21 ) to authenticate the user and the second one is a data connection or data port(port 20) to transfer the files. It requires a specific username and password for access.

HyperText Transfer Protocol (HTTP) :

It stands for HyperText Transfer Protocol. It is the backbone of WWW. It is an internet standard that allows the process of transfer of web pages over the internet. It also defines how the web browser will respond to any web request. The web address of all the web pages contains a protocol, domain name, and path to the web page. Most of the web address contains http:// in their URL to show the HTTP protocol. HTTP works similar to the combined functions of FTP and SMTP. It also uses Transmission Control Protocol.

FIREWALLS

A Firewall is a network security device that monitors and filters incoming and outgoing network traffic based on an organization’s previously established security policies.

• At its most basic, a firewall is essentially the barrier that sits between a private internal network and the public Internet.
• A firewall’s main purpose is to allow non-threatening traffic in and to keep dangerous traffic out.
• It accepts, rejects or drops that specific traffic. Accept : allow the traffic Reject : block the traffic but reply with an “unreachable error” Drop : block the traffic with no reply.
• There are two types of firewalls, Host-based firewalls and network based firewalls.

Advantages of firewalls

• Protection from unauthorized access
• Prevention of malware and other threats
• Control of network access
• Monitoring of network activity
• Regulation compliance
• Network segmentation

BASICS OF CRYPTOGRAPHY

Basics of cryptography

Cryptography is technique of securing information and communications through use of codes so that only those person for whom the information is intended can understand it and process it. Thus preventing unauthorized access to information. The prefix “crypt” means “hidden” and suffix graphy means “writing”. In Cryptography the techniques which are use to protect information are obtained from mathematical concepts and a set of rule based calculations known as algorithms to convert messages in ways that make it hard to decode it. These algorithms are used for cryptographic key generation, digital signing, verification to protect data privacy, web browsing on internet and to protect confidential transactions such as credit card and debit card transactions.

Techniques used For Cryptography: In today’s age of computers cryptography is often associated with the process where an ordinary plain text is converted to cipher text which is the text made such that intended receiver of the text can only decode it and hence this process is known as encryption. The process of conversion of cipher text to plain text this is known as decryption.

Features Of Cryptography are as follows:

• Confidentiality: Information can only be accessed by the person for whom it is intended and no other person except him can access it.
• Integrity: Information cannot be modified in storage or transition between sender and intended receiver without any addition to information being detected.
• Non-repudiation: The creator/sender of information cannot deny his intention to send information at later stage.
• Authentication: The identities of sender and receiver are confirmed. As well as destination/origin of information is confirmed.