Packet switching ( Eng. Packet switching ) - a way to dynamically allocate resources of a communication network [1] by transmitting and switching digitized information in the form of small parts - the so-called packets that are transmitted over the network in the general case independently of each other (datagrams) or sequentially one after another over virtual connections . The receiving node from the packets collects the message. In such networks, many nodes can exchange data on one physical communication line.
Content
Basic Principles
When switching packets, all digital data transmitted by the user is divided by the transmitting node into small (up to several kilobytes) parts — packets ( English packet ). Each packet is equipped with a header, which indicates at least the destination host address and the packet number. Packets are transmitted over the network either independently of each other, then the packets are called datagrams , and the individual packet switching mode is called the datagram mode, or via virtual connections, that is, in connection -oriented mode ( Connection-oriented communication) ) The switches of such a network have an internal buffer memory for temporary storage of packets, which makes it possible to smooth out traffic ripples on the communication lines between the switches.
- Advantages of packet switching
- Bandwidth efficiency.
- When the network is overloaded, it does not “throw out” anyone with the message “the network is busy,” the network simply reduces the transmission speed for all or several subscribers.
- A subscriber who does not fully use his channel actually gives up the network bandwidth to the others [2] .
- Lower costs.
- The disadvantages of packet switching
- Complex device; without microprocessor technology, it is almost impossible to establish a packet network.
- Bandwidth is spent on the transfer of technical data (service information).
- Delivery delays, including variables, due to the fact that when an outbound channel is busy, a packet can wait for its turn in the switch.
A packet-switched network differs from a circuit-switched network in that with a certain probability it can slow down the interaction process of each particular pair of nodes, since their packets can wait in the switches until other packets are transmitted. This is especially critical for real-time services (audio, video). However, the overall efficiency (the amount of data transmitted per unit time) during packet switching will be higher than when switching channels. This is due to the fact that the traffic of each individual subscriber is pulsating in nature, and the pulsations of different subscribers, in accordance with the law of large numbers, are distributed over time, increasing the uniformity of the load.
See also
- Circuit switched connection
- Fast packet switching
- Channel level
Notes
- ↑ LG Roberts, 1978 , p. 1307.
- ↑ For example, during pauses in conversation.
Bibliography
- LG Roberts Packet Switch Network Development = The evolution of packet switching // Proceedings of the IEEE / RE Kahn, KW Uncapher, HL Van Trees. - 1978. - Vol. 66 , iss. on packet communication networks , no. 11 (November) . - P. 1307-1313 .
- D. Davis, D. Barber, W. Price, S. Solomonides. Computing Networks and Network Protocols = Computer Networks and their Protocols / Per. from English under the editorship of Doctor of Technical Sciences, prof. S. I. Samoilenko. - M .: "World", 1982. - 562 p. - 10,000 copies.
- I.A. Mizin, V.A. Bogatyrev, A.P. Kuleshov. Packet Switching Networks / Acad. V. S. Semenikhin . - M .: "Radio and Communications", 1986. - 408 p. - 5,500 copies.
Links
- V.G. Olifer, N.A. Olifer. Fundamentals of data transmission networks . INTUIT.ru::Internet- University of Information Technologies (05.21.2003). - distance education. Date of treatment March 10, 2012. Archived May 26, 2012.
- Networks computer networks, a directory of computer networks . Date of treatment March 10, 2012. Archived May 26, 2012.