Communication Protocols
A communication protocol is a formal description of digital message formats and the rules for exchanging those messages in between computer systems. Protocols define a set of formal rules describing how to transmit data especially across a network. Low level protocols define the electrical and physical standards to be observed, bit- and byte-ordering and the transmission of the bit stream. High level protocols deal with the data formatting, including the syntax of messages, character sets, sequencing of messages etc. Many protocols are defined by RFCs or by OSI.
Protocols may include signaling. Authentication and error detection and correction capabilities. A protocol describes the syntax, semantics and synchronization of communication and may be implemented in hardware or software, or both. The communication protocols in use on the internet are designed to function in very complex and diverse settings. To case design, communications protocols are structured using a layering scheme as a basis. Instead of using a single universal protocol to handle all transmission tasks a set of cooperating protocols used for the layering scheme. Some protocols are described as below:
TCP/IP: The Transmission Control Protocol(TCP) and Internet Protocol (IP) are commonly referred Layer 4 and Layer 3 Protocols respectively. But, TCP/IP represents a protocol suit. It is a collection of different protocols and work as an implemented version of protocols. It consists more than 50 individual protocols with in it. Hence, TCP/IP commonly referrer as protocol suit. TCP represents transport layer protocol that provides end to end reliable transmission. For the same purpose, TCP includes such functions such as flow control, error control and status exchange information. IP represents unreliable source of transmission between networks. TCP delivers message in reliable manner i.e. message will not discarded or dropped but the delivery time is high. IP deliver in unreliable manner i.e. some message can be discarded or dropped within networks but the delivery time is short. The network uses both types of protocol, if you want to send email message then dropping the portion of emails generate meaningless message but delay can tolerate for certain period of time. Similarly, if you can be tolerated instead of delay during conversation. For reliable message transfer TCP is used and for time critical message transmit IP is used. TCP/IP is not a single protocol but a set of more than a dozen. Protocols. Each protocol within the TCP/IP family is dedicated to a different task.
SMTP: Simple Mail Transfer Protocol (SMTP) is an Application Layer protocol used for email transmission across the Internet. The mail applications use SMTP for sending messages to a mail server on the internet. SMTP is a delivery protocol only. It cannot pull messages from a remote server on demand. Other protocols, such as the Post Office Protocol (POP) and the Internet Message Access Protocol (IMAP) are specifically designed for retrieving messages and managing mail boxes. However, SMTP has a feature to initiate mail queue processing on a remote server so that the requesting system may receive any messages destined for it. Still, SMTP broadly used to forward email messages over the Internet.
POP3: The Post Office Protocol version 3 (POP3) is an Application Layer protocol used by local email clients to retrieve email from a remote server over internet connection. POP and IMAP (Internet Message Access Protocol) are the most common internet standard protocols for email retrieval. Virtually all modern email clients and servers support both. The POP3 potocol has been developed. Like IMAP and POP3 is supported by most webmail services such as Hotmail, Gmail and Yahoo! Mail.
FTP: The File Transfer Protocol (FTP) is an Application Layer protocol for transferring files between computer systems. FTP is not hardware dependent, hence it can work anywhere in the network. FTP is built on client-server architecture and utilizes separate control and data connections between the client and server, FTP client and server exist in the network, where client sends commands to the FTP server and the server responds.
HTTP: It is the underlying protocol used by the World Wide WEB. HTTP defines how messages are formatted and transmitted over the internet. It decides what action should be taken on web-server and web-browsers for the various commands. HTTP has been in use by the World Wide Web since 1990. HTTP is called a stateless protocol because each command is executed independently. The HTTP is a networking protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundations of data communication for the World Wide Web.
Hypertext Transfer Protocol Secure (HTTPs) is a combination of the HTTP with some security protocols to provide encrypted communication and security. HTTPs connections are often used for password, payment and other sensitive transactions in the Internet. The main idea of HTTPs is to create a secure channel over an insecure network. This ensures reasonable protection from hackers and data tappers.
Telnet: Telnet is a remote login protocol for executing commands on remote host. The Telnet protocol runs in a client server mode and uses the TCP for data transmission. The Telnet client generates username and password for the Telnet server. The transmitted data will encode before transmission by Telnet client. Recently, the use of Telnet in public network has been discouraged since telnet does not offer good protection against third parties.
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