In computing, a protocol is a convention or standard that controls or enables the connection, communication, and data transfer between two computing endpoints.
In its simplest form, a protocol can be defined as the rules governing the syntax, semantics, and synchronization of communication.
Protocols may be implemented by hardware, software, or a combination of the two.
At the lowest level, a protocol defines the behavior of a hardware connection.
Typical Properties of Protocol
• It is difficult to generalize about protocols because they vary so greatly in purpose and sophistication.
• Most protocols specify one or more of the following properties:
• Detection of the underlying physical connection (wired or wireless), or the existence of the other endpoint or node -Handshaking :
• Negotiation of various connection characteristics
• How to start and end a message
• How to format a message
• What to do with corrupted or improperly formatted messages (error correction)
• How to detect unexpected loss of the connection, and what to do next
• Termination of the session and or connection.
Importance of Network Protocol
• The widespread use and expansion of communications protocols is both a prerequisite for the Internet, and a major contributor to its power and success.
• The pair of Internet Protocol (or IP) and Transmission Control Protocol (or TCP) are the most important of these, and the term TCP/IP refers to a collection (or protocol suite) of its most used protocols.
• Most of the Internet's communication protocols are described in the RFC documents of the Internet Engineering Task Force (or IETF).
• The need for protocols also applies to network devices. Computers have no way of learning protocols, so network engineers have written rules for communication that must be strictly followed for successful host-to-host communication.
• These rules apply to different layers of sophistication such as which physical connections to use, how hosts listen, how to interrupt, how to say good-bye, and in short how to communicate, what language to use and many others.
• These rules, or protocols, that work together to ensure successful communication are grouped into what is known as a protocol suite.
Types of Network Protocols
• IP (Internet Protocol)
• UDP (User Datagram Protocol)
• TCP (Transmission Control Protocol)
• DHCP (Dynamic Host Configuration Protocol)
• HTTP (Hypertext Transfer Protocol)
• FTP (File Transfer Protocol)
• Telnet (Telnet Remote Protocol)
• SSH (Secure Shell Remote Protocol)
• POP3 (Post Office Protocol 3)
• SMTP (Simple Mail Transfer Protocol)
• IMAP (Internet Message Access Protocol)
Advantages TCP/IP for Internet Connectivity
• The Internet Protocol Suite (commonly TCP/IP) is the set of communications protocols used for the Internet and other similar networks.
• It is named from two of the most important protocols in it: the Transmission Control Protocol (TCP) and the Internet Protocol (IP), which were the first two networking protocols defined in this standard.
• The Internet Protocol Suite, like many protocol suites, may be viewed as a set of layers.
• Each layer solves a set of problems involving the transmission of data, and provides a welldefined service to the upper layer protocols based on using services from some lower layers. Upper layers are logically closer to the user and deal with more abstract data, relying on lower layer protocols to translate data into forms that can eventually be physically transmitted.
• The Internet Protocol (IP) is the method or protocol by which data is sent from one computer to another on the Internet. Each computer (known as a host) on the Internet has at least one IP address that uniquely identifies it from all other computers on the Internet.
• When you send or receive data (for example, an e-mail note or a Web page), the message gets divided into little chunks called packets.
• Each of these packets contains both the sender's Internet address and the receiver's address.
• Any packet is sent first to a gateway computer that understands a small part of the Internet.
• The gateway computer reads the destination address and forwards the packet to an adjacent gateway that in turn reads the destination address and so forth across the Internet until one gateway recognizes the packet as belonging to a computer within its immediate neighborhood or domain.
• That gateway then forwards the packet directly to the computer whose address is specified.
• Because a message is divided into a number of packets, each packet can, if necessary, be sent by a different route across the Internet.
• Packets can arrive in a different order than the order they were sent in. The Internet Protocol just delivers them. It's up to another protocol, the Transmission Control Protocol (TCP) to put them back in the right order.
• IP is a connectionless protocol, which means that there is no continuing connection between the end points that are communicating.
• Each packet that travels through the Internet is treated as an independent unit of data without any relation to any other unit of data. (The reason the packets do get put in the right order is because of TCP, the connection-oriented protocol that keeps track of the packet sequence in a message.)
• In the Open Systems Interconnection (OSI) communication model, IP is in layer 3, the Networking Layer.
• The most widely used version of IP today is Internet Protocol Version 4 (IPv4). However, IP Version 6 (IPv6) is also beginning to be supported. IPv6 provides for much longer addresses and therefore for the possibility of many more Internet users. IPv6 includes the capabilities of
IPv4 and any server that can support IPv6 packets can also support IPv4 packets
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