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Information about In Band Signalling

Main article: Signalling (telecommunications)
In telecommunications, in-band signaling is the sending of metadata and control information in the same band, on the same channel, as used for data.

For example, when dialing a modern telephone, the telephone number is encoded and transmitted across the telephone line as Dual-Tone Multi-Frequency (DTMF) tones. The tones "control" the telephone system by instructing the telephone company's equipment where to route the call to. These control tones are sent over the same channel and in the same band (300Hz to 3.4kHz) as the voice and other sounds of the telephone call. In-band signalling is also used on older telephone carrier systems to provide inter-exchange information on how to route calls. Examples of this kind of in-band signalling system are SS5 and R2.

Separating the control signals, also referred to as the control plane, from the data (if a bit-transparent connection is desired) is usually done by escaping the control instructions. Occasionally, however, networks are designed so that data is (to a varying degree) garbled by the signaling. Allowing data to become garbled is usually acceptable when transmitting sounds between humans, since the users rarely notice the slight degradation, but this leads to problems when sending data that has very low error tolerance, such as information transmitted using a modem.

In-band signaling is insecure because it exposes control signals, protocols and management systems to the user(s), which may result in falsing. In the case of the blue boxes that were popular in the 1960s and 1970s, such falsing was deliberate. By using blue boxes to generate the appropriate tones, a caller could abuse functions intended for testing and administrative use to make free long-distance calls.

Modems may also interfere with in-band signaling, so in some countries, a guard tone is employed to prevent this.

In-band signalling applies only to Channel Associated Signalling (CAS). In Common Channel Signaling (CCS) separate channels are used for control and data, as opposed to the shared channel in CAS, so all control is out-of-band by definition.

In computer programming, magic numbers are used for in-band signaling of file formats.

When out-of-band communication is unavailable, one of two techniques may be used to preserve network transparency.
  • Encapsulation: The bundling of the control data in the a packet's header and then removing the header (and/or footer) of the packet at the far end, restoring the data to be the same as the original.
  • Bit Stuffing: The insertion of noninformation or escape characters to modify, synchronize and justify the data so it never looks like signaling information (and remove the stuffed bits and escape codes at the far end, restoring the data to be the same as the original).

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In telecommunication, signalling (UK spelling) or signaling (US spelling) has the following meanings:
  • The use of signals for controlling communications.

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Telecommunication is the transmission of signals over a distance for the purpose of communication. In modern times, this process typically involves the sending of electromagnetic waves by electronic transmitters, but in earlier times telecommunication may have involved the use of
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Metadata is data about data. An item of metadata may describe an individual datum, or content item, or a collection of data including multiple content items.

Metadata (sometimes written 'meta data') is used to facilitate the understanding, use and management of data.
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In telecommunication, signalling (UK spelling) or signaling (US spelling) has the following meanings:
  • The use of signals for controlling communications.

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The telephone is a telecommunications device which is used to transmit and receive sound (most commonly speech). Most telephones operate through transmission of electric signals over a complex telephone network which allows almost any phone user to communicate with almost anyone.
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worldwide view of the subject.
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In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls.
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Channel, in communications (sometimes called communications channel), refers to the used to convey information from a sender (or transmitter) to a receiver.

Overview

A Channel can take many forms.
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Please help recruit one or [ improve this article] yourself. See the talk page for details.
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R2 is a 1960s- and 1970s-era channel-associated-signalling signalling protocol used outside of the former Bell System to convey information along a telephone trunk between two telephone switches in order to establish a single telephone call along that trunk.
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transparency can refer to:
  1. The property of an entity that allows another entity to pass thorough it without altering either of the entities.
  2. The property that allows a transmission system or channel to accept, at its input, unmodified user information, and

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This article refers to codes used as commands for computing devices. Escape sequence can also refer to a sequence of escape characters used in parsing source code.

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Modem (from modulate and demodulate) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information.
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In telecommunications, falsing describes a decoder detecting a valid input when one is not present. This is also known as a false decode. To make the concepts simpler, this article will discuss analog circuits used before digital signal processing.
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blue box is an electronic device that simulates a telephone operator's dialing console. It functions by replicating the tones used to switch long-distance calls and using them to route the user's own call, bypassing the normal switching mechanism.
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Guard tone is a feature of wireline modems.

The guard tone is sent by the answering modem after it has sent the answer tone. It is a single continuous tone with a frequency of either 1800 Hz or 550 Hz, sent at a level of -6dB or -3dB, respectively, below the level of the
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Channel Associated Signaling (CAS), also known as Per-Trunk Signaling (PTS), is a form of digital communication signaling. As with most telecommunication signaling methods, it uses routing information to direct the payload of voice or data to its destination.
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Common Channel Signalling (CCS) or in the US Common Channel Interoffice Signalling (CCIS) is the transmission of signaling information (control information) on a separate channel to the data, and, more specifically, where that signalling channel controls multiple data
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In computer programming, the term magic number has multiple meanings. It could refer to:
  • a constant used to identify a file format or protocol;
  • an unnamed and/or ill-documented numerical constant; or
  • distinctive debug values or GUIDs, et cetera.

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Out-of-band is a technical term with different uses in communications and telecommunication. It refers to communications which occur outside of a previously established communications method or channel.
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transparency can refer to:
  1. The property of an entity that allows another entity to pass thorough it without altering either of the entities.
  2. The property that allows a transmission system or channel to accept, at its input, unmodified user information, and

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Encapsulation may refer to:
  • molecular encapsulation, in chemistry, the confinement of an individual molecule within a larger molecule
  • encapsulation (networking), in computer networking, to include data from an upper layer protocol in a lower layer protocol

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In information technology, Header refers to supplemental data placed at the beginning of a block of data being stored or transmitted, which contain information for the handling of the data block.
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In data transmission and telecommunication, bit stuffing (also known -- uncommonly -- as positive justification) is the insertion of noninformation bits into data. Stuffed bits should not be confused with overhead bits.
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In computing and telecommunication, an escape character is a single character which in a sequence of characters signifies that what is to follow takes an alternative interpretation.
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Out-of-band is a technical term with different uses in communications and telecommunication. It refers to communications which occur outside of a previously established communications method or channel.
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Line signaling is a class of telecommunications signaling protocols. Line signaling is responsible for off-hook, ringing signal, answer, ground start, on-hook unidirectional supervision messaging in each direction from calling party to called party and vice versa.
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XON/XOFF is software data flow communications protocol for controlling the flow of data between computers and other devices. X stands for transmitter. This is frequently referred to as "software flow control".
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The Portland Pattern Repository (PPR) is a repository for computer programming design patterns. It was accompanied by a companion website, WikiWikiWeb, which was the world's first wiki.

The repository has an emphasis on extreme programming.
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