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High-Level Data Link Control (HDLC) is a bit-oriented synchronous data link layer protocol developed by the International Organization for Standardization (ISO). Image File history File links Please see the file description page for further information. ...
// Throughput measurement People are often concerned about measuring the maximum data throughput rate of a communications link. ...
// Throughput measurement People are often concerned about measuring the maximum data throughput rate of a communications link. ...
The data link layer is layer two of the seven-layer OSI model. ...
This article concerns communication between pairs of electronic devices. ...
Logo of the International Organization for Standardization The International Organization for Standardization (ISO) is an international standard-setting body composed of representatives from national standards bodies. ...
HDLC was imported by the ITU into the X.25 protocol stack as LAPB. It was modified by IBM to become the SDLC protocol that became the layer 2 protocol for IBM's Systems Network Architecture (SNA). HDLC is now the basis for synchronous PPP (point to point protocol) used by many servers to connect to a wide area network, most commonly the Internet. Monument in Bern, Switzerland. ...
X.25 is an ITU-T standard protocol suite for WAN networks using the phone or ISDN system as the networking hardware. ...
LAPB (Link Access Procedure, Balanced) is a data link layer protocol in the X.25 protocol stack. ...
International Business Machines Corporation (IBM, or colloquially, Big Blue) NYSE: IBM (incorporated June 15, 1911, in operation since 1888) is headquartered in Armonk, NY, USA. The company manufactures and sells computer hardware, software, infrastructure services and consulting services. ...
Synchronous Data Link Control (SDLC) is a computer communications protocol. ...
Systems Network Architecture (SNA) is IBMs proprietary networking architecture created in 1974. ...
In computing, the Point-to-Point Protocol, or PPP, is commonly used to establish a direct connection between two nodes. ...
A wide area network or WAN is a computer network covering a wide geographical area, involving a vast array of computers. ...
The frame begins and ends with the bit pattern 01111110 or hex 7E, called the frame delimiter (or flag). In mathematics and computer science, hexadecimal, or simply hex, is a numeral system with a radix or base of 16 usually written using the symbols 0–9 and A–F or a–f. ...
Then there is an address and a control field followed by a data field that may be 0 to 5000 octets long. Then a frame check sequence (FCS) is added, followed by a frame delimiter. The frame delimiter continues to be sent until another frame is sent. This generates a continuous bit pattern: An octet is a group consisting of eight (8) elements, but it has several more specific meanings (usually given by a specific field or application): Music In music, an octet is a musical ensemble consisting of eight instruments or a musical composition written for it. ...
A frame check sequence (FCS) refers to the extra checksum characters added to a Frame in a communication protocol for error detection and correction. ...
01111110011111100111111001111110 ______ ______ ______ ______ _ __ __ __ _
This is used by modems to train and synchronize their clocks via phase-locked loops. A modem (a portmanteau word constructed from modulator and demodulator) is a device that modulates a carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. ...
In electronics, a phase-locked loop (PLL) is a closed-loop feedback control system that maintains a generated signal in a fixed phase relationship to a reference signal. ...
To avoid transmission failures special care must be taken if this special bit pattern (h7E) occurs in data. Therefore bit stuffing is performed on the transmitting side; a 0-bit is introduced after 5 1-bits, to avoid the frame delimiter pattern. The receiver deletes 1 0-bit after 5 1-bits to restore the original data. In data transmission and telecommunication, bit stuffing (also known -- uncommonly -- as positive justification) is the insertion of noninformation bits into data. ...
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