Domain Name System (DNS)
To identify an entity, TCP/IP protocol uses the IP address which uniquely identifies the connection of a host to the Internet. However, people refer to use names instead of address. Therefore, we need a system that can rn(P a name to an address and conversely an address to name. In TCP/IP, this is the domain name system.
DNS in the Internet
DNS is protocol that can be used in different platforms. Dorrnan name space is divided into three categories.
- Generic Domain The generic domain defines registered hosts es °,, according, to their generic behavior. Each node in the tree defin domain which is an index to the domain name space. database.
- Country Domain The country domain section follows the same format as the generic domain but uses 2 characters country abbreviations(e.g., US for United States) in place of 3 characters.
- Inverse Domain The inverse domain is used to map an address to a name.
Application Layer Protocols
There are various application layer protocols as given below
SMTP (Simple Mail Transfer Protocol)
One of the most popular network service is electronic mail (e-mail). The TCP/IP protocol that supports electronic mail on the Internet is called Simple Mail Transfer Protocol (SMTP).
SMTP is system for sending messages to other computer. Users based on e-mail addresses. SMTP provides services for mail exchange between users on the same or different computers.
TELNET (Terminal Network)
TELNET is client-server application that allows a user to log onto remote machine and lets the user to access any application program on a remote computer.
TELNET uses the NVT (Network Virtual Terminal) system to encode characters on the local system. On the server (remote) machine, NVT decodes the characters to a form acceptable to the remote machine.
FTP (File Transfer Protocol)
FTP is the standard mechanism provided by TCP/IP for copying a file from One host to another.
FTPdiffers form other client-server applications because establishes 2 connections between hosts. One connection is used for data transfer, the Other for control information (commands and responses).
Multipurpose Internet Mail Extensions (NINE)
It is an extension of SMTP that allows the transfer of multimedia rues
POP (Post Office Protocol)
This is a protocol used by a mail server in conjuction with SMTP to receive and holds mail for hosts.
HTTP (Hypertext Transfer Protocol) This is a protocol used mains.
access data on the World Wide Web (www) , a respository of information to spread all over the world and linked together.
The HTTP protocol transfer data in the form of plain text, hyper text video and so on.
Important Terms Related to Computer Security
- Computer Security It is a generic name of the collection of tools designed to protect data and thwart hackers.
- Network Security It measures to protect data during their transmission.
- Internet Security It measures to protect data during their transmission over a collection of interconnected networks.
- Information Security We consider 3 aspects of information security (a) Security attack (b) Security mechanism (c) Security service