What Is Protocol Overhead?

In computer networks, the protocols are classified according to the reliability of protocol transmission, and protocols can be divided into reliable protocols and unreliable protocols. Reliable protocols guarantee reliable attributes. Unreliable protocol refers to an unreliable connectionless datagram protocol ^[1] . Unreliable protocols do not guarantee that data is transmitted losslessly, or even whether it is transmitted or not, providing "best effort" delivery services.

An unreliable protocol is an unreliable connectionless datagram protocol. In computer networks, there are many unreliable protocols, such as

Also called procedure. Refers to a set of procedural rules for communication between computers, communication equipment, terminals and networks. The protocol ensures and defines the format, timing, and other procedures for communication, namely syntax, semantics, timing. In information technology, a protocol is a special set of rules. A set of conventions for the format and transmission order of information for the correct exchange of information between communication terminals or in a communication network. It is recognized by the receiver and sender of the communication, and the information received and sent is interpreted according to this rule. In a computer system or network, a set of rules for the operation of functional units in order to achieve communication functions. There are many protocols in each layer of the network, and the agreement between the receiver and the sender must be the same, otherwise one party will not be able to identify the information sent by the other party ^[2]

Unreliable Protocol Frame Relay

Frame relay (frame relay) is a new public data network communication protocol that emerged in 1992, and has rapidly developed since 1994. Frame relay is an effective data transmission technology. It can quickly and inexpensively transmit digital information in one-to-one or one-to-many applications. It can be used for voice and data communication. It can be used for both local area network (LAN) and wide area network (WAN) communication. Each Frame Relay user will get a dedicated line to the Frame Relay node. For the end user, the frame relay network handles data transmission with other users through a channel that is often changed and invisible to the user.

Main features: User information is transmitted in frames. The network checks the frame structure and transmission errors during the transmission process, and discards the errored frames. At the same time, by identifying the DLCI in the address segment of the frame, Achieve statistical multiplexing of user information.

Frame Relay is a data packet switching communication network, which is generally used in the Data Link Layer in the Open System Interconnection Reference Model (Open System Interconnection). Permanent virtual circuit PVC is used to form end-to-end logical links on physical network switched virtual circuits (SVCs). It is similar to circuit switching in public telephone switching networks and is part of the Frame Relay description. Less used in practice. In addition, Frame Relay was originally designed for the compact format version of the X.25 protocol.

The data link connection identifier DLCI is a numerical value with local significance used to identify each endpoint. Multiple PVCs can be connected to the same physical terminal. Generally, PVCs specify CIR and EIR.

Frame Relay is designed to make more effective use of existing physical resources. Since most customers cannot use data services 100%, it allows telecommunications operators to provide customers with data services that exceed the supply. It is because telecom operators have over-subscribed bandwidth that has led to Frame Relay gaining a bad reputation in some markets. Telecommunications companies have been selling Frame Relay services to customers who are looking for cheaper than leased lines. According to government and telecommunications company policies, it is used in a variety of different applications. Frame Relay is gradually being replaced by protocols such as ATM and IP (including IP virtual private networks).

Unreliable protocol network protocol

Internet Protocol (abbreviated as IP) is a data-oriented protocol used in packet-switched networks. IP is the main protocol of the network layer in the TCP / IP protocol, and the task is to transfer data based only on the addresses of the source and destination hosts. To this end, IP defines addressing methods and the encapsulation structure of datagrams. The major version of the first architecture, now called IPv4, is still the most important Internet protocol, although IPv6 is being actively deployed around the world. The design principles of the Internet Protocol assume that the network infrastructure itself is an unreliable single network element or transmission medium, and that it uses dynamic nodes and connections. There is no central monitoring and performance measurement mechanism to track and maintain the status of the network. In order to reduce the complexity of the network, most network intelligence is deliberately distributed at the end nodes of each data transmission. The router in the transmission path simply sends the data packet to the next local gateway that matches the routing prefix of the destination address.

As a result of this design, Internet protocols only provide best-effort delivery and their services are considered unreliable. It is a connectionless protocol in the network professional language, as opposed to the so-called connection-oriented model. Allow any of the following faults to occur in the absence of reliability:

• Data corruption

• Lost packet

• Repeat

• The data packet is delivered out of order; meaning that if packet 'A' was sent before packet 'B', but B may arrive before A arrives.

UDP Unreliable protocol UDP

UDP is the abbreviation of User Datagram Protocol. The Chinese name is User Datagram Protocol. It is a connectionless transport layer protocol in the OSI (Open System Interconnection) reference model, which provides simple and unreliable information transfer services for transactions , IETF RFC 768 is the official specification of UDP. The protocol number of UDP in IP packets is 17.

The full name of the UDP protocol is the user datagram protocol. In the network, it is used to process data packets in the same way as the TCP protocol. It is a connectionless protocol. In the OSI model, the fourth layer, the transport layer, is on top of the IP protocol. UDP has the disadvantages of not providing packet grouping, assembling, and inability to sort the data packets, that is, after the message is sent, it is impossible to know whether it arrived safely and completely. UDP is used to support network applications that need to transfer data between computers. Many client / server network applications, including network video conferencing systems, need to use the UDP protocol. The UDP protocol has been used for many years since its introduction. Although its original glory has been covered by some similar protocols, UDP is still a very practical and feasible network transport layer protocol even today. Often in computer games or other places where speed is important and a small amount of data is allowed to be lost.

Unreliable protocol asynchronous transfer mode

Asynchronous Transfer Mode (ATM), also known as cell relay. ATM adopts the circuit switching method, which uses the cell as a unit. Each cell is 53 bytes long. The header occupies 5 bytes. Asynchronous transmission is a way of data transmission. Because the data is generally transmitted serially one by one, for example, when transmitting a string of character information, each character code consists of 7 binary bits. But in a series of binary bits, which 7-bit count does each 7-bit count from? When transmitting asynchronously, before transmitting each data character, first send a binary bit called the start bit. When the receiving end receives this signal, it knows that the 7 binary bits sent in succession is a character data. After this, one or two binary bits are given, which is called the end bit. After the receiver receives the end bit, it indicates the end of a data character transmission. In this way, in asynchronous transmission, each character is synchronized separately, that is, each binary bit in the character is synchronized, but the length of the gap between characters is not fixed.

ATM can ideally implement various QoS, which can support both connected services and connectionless services. Is a model of broadband ISDN (B-ISDN) technology. ATM is a switching technology. When sending data, the digital data is first cut into multiple fixed-length data packets, and then sent using optical fiber or DS1 / DS3. When you reach your destination, regroup. ATM networks can integrate sound, video, and data simultaneously. Provide the best transmission environment for various types of information.