Communication protocol

1. Chapter 2 (Standard and Protocol) Communication protocol Sifat-sifat protokol Direct or indirect – system berkongsi dari satu hubungan ke satu hubungan (direct), rangkaian yang menggunakan konsep switched networks.(indirect) Monolithic or structured – dari sesuatu yang kompleks kepada unit-unit yang lebih kecil, struktur berlapis. Symmetric or asymmetric – komunikasi antara peer (symmetric), konsep client server (asymmetric). Standard or Nonstandard – untuk komputer yang spesifik dan untuk tugasan kompleks ( nonstandard), komputer biasa dan tidak kompleks (standard)

2. Communication protocol BAUD In telecommunications and electronics, baud (pronounced /bɔːd/) is a measure of the "signaling rate" which is the number of changes to the transmission media per second in a modulated signal. It is named after Émile Baudot, the inventor of the Baudot code for telegraphy. • The term baud is sometimes misused to refer to "bits per second" which is the "data rate". In some systems the signaling rate and the data rate are the same since it is possible for one signalling event to carry one bit, but in general it is more common to make more efficient use of bandwidth by encoding multiple bits—as many as sixteen—in one event. Thus, a 2400-bit/s modem actually transmits at 600 baud, where each quadrature amplitude modulation event carries two bits (four values) of information.

3. Communication protocol BPS bit rate (sometimes written bitrate) is the frequency at which bits are passing a given (physical or metaphorical) "point". It is quantified using the bit per second (bit/s) unit. • While often referred to as "speed", bit rate does not measure distance/time but number of bits/time, and thus should be distinguished from the "propagation speed" (which depends on the transmission medium and has the usual physical meaning). • The formal abbreviation for "bit per second" is "bit/s" (not bits/s). In less formal contexts the abbreviations b/s or bps are often used, though this risks confusion with "bytes per second" (B/s). Even less formally, it is common to drop the "per second", and simply refer to "a 128 kilobit audio stream" or "a 100 megabit network". • "Bit rate" is sometimes used interchangeably with "baud rate", which is only the same if each bit occurs in a unit interval.

4. Communication protocol • For large bit rates, SI prefixes are used, not binary prefixes: • 1,000 bit/s=1 Kbit/s (one kilobit or one thousand bits per second)1,000,000 bit/s=1 Mbit/s (one megabit or one million bits per second)1,000,000,000 bit/s=1 Gbit/s (one gigabit or one billion bits per second)There are typically eight bits in a byte (octet), but communications data rates are almost never expressed in bytes per second, with the notable exceptions of disk and memory I/O transfer rates. To convert from byte/s to bit/s, simply multiply by 8. Divide by 8 to go the other way. • Using binary prefixes, these rates take on different conversions (note that kibi-, mebi-, etc. are not typos): • 1,024 bit/s=1 Kibit/s (one kibibit per second)1,048,576 bit/s=1 Mibit/s (one mebibit per second)1,073,741,824 bit/s=1 Gibit/s (one gibibit per second)

5. Communication protocol • SynchronousTwo different time sequences may be synchronized in one sense without being synchronized in another, or synchronized at one time scale whilst being asynchronous in another. • Systems operating with all their parts in synchrony are said to be synchronous. Some systems may be only approximately synchronized, or plesiochronous. • For some applications relative offsets between events need to be determined, for others only the order of the event is important. The idea of simultaneity has many difficulties, both in practice and theory.  • In general, synchronous (pronounced SIHN-kro-nuhs, from Greek syn-, meaning "with," and chronos, meaning "time") is an adjective describing objects or events that are coordinated in time. In information technology, the term has several different usages.

6. Communication protocol • 1) In telecommunication signaling within a network or between networks, synchronous signals are those that occur at the same clock rate when all clocks are based on a single reference clock. (plesiochronous signals are almost but not quite in synchronization and asynchronous signals are those that run from different clocks or at a different transition rate.) • 2) In program-to-program communication, synchronous communication requires that each end of an exchange of communication respond in turn without initiating a new communication. A typical activity that might use a synchronous protocol would be a transmission of files from one point to another. As each transmission is received, a response is returned indicating success or the need to resend. Each successive transmission of data requires a response to the previous transmission before a new one can be initiated. • Synchronous program communication is contrasted with asynchronous program communication.

7. Communication protocol

8. Communication protocol • AsynchronousIn general, asynchronous (pronounced ay-SIHN-kro-nuhs, from Greek asyn-, meaning "not with," and chronos, meaning "time") is an adjective describing objects or events that are not coordinated in time. In information technology, the term has several different usages. • 1) In telecommunication signaling within a network or between networks, an asynchronous signal is one that is transmitted at a different clock rate than another signal. (plesiochronous signals are almost but not quite in synchronization - and a method is used to adjust them - and synchronous signals are those that run at the same clock rate.

9. Communication protocol • 2) In computer programs, asynchronous operation means that a process operates independently of other processes, whereas synchronous operation means that the process runs only as a result of some other process being completed or handing off operation. A typical activity that might use a synchronous protocol would be a transmission of files from one point to another. As each transmission is received, a response is returned indicating success or the need to resend. Each successive transmission of data requires a response to the previous transmission before a new one can be initiated. • Synchronous program communication is contrasted with asynchronous program communication.

10. Communication protocol Half Duplex • Refers to the transmission of data in just one direction at a time. For example, a walkie-talkie is a half-duplex device because only one party can talk at a time. In contrast, a telephone is a full-duplex device because both parties can talk simultaneously. Duplex modes often are used in reference to network data transmissions. • Some modems contain a switch that lets you select between half-duplex and full-duplex modes. The correct choice depends on which program you are using to transmit data through the modem. In half-duplex mode, each character transmitted is immediately displayed on your screen. (For this reason, it is sometimes called local echo -- characters are echoed by the local device).

11. Communication protocol Full-Duplex • Refers to the transmission of data in two directions simultaneously. For example, a telephone is a full-duplex device because both parties can talk at once. In contrast, a walkie-talkie is a half-duplex device because only one party can transmit at a time. • Most modems have a switch that lets you choose between full-duplex and half-duplex modes. The choice depends on which communications program you are running. • In full-duplex mode, data you transmit does not appear on your screen until it has been received and sent back by the other party. This enables you to validate that the data has been accurately transmitted. If your display screen shows two of each character, it probably means that your modem is set to half-duplex mode when it should be in full-duplex mode.