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Appendix A
Glossary
- ACU See Automatic Call Unit.
- ACU stack mode An AG ISDN protocol stack mode in which the stack implements all ISDN layer 2 and layer 3 functionality, but no channelizer is present. The application communicates directly with the ACU using the AG ISDN Messaging API.
- AG board See Alliance Generation board.
- AG configuration file A text file containing configuration information for the AG boards in a system. When agmon runs, it configures the AG boards as described in this file.
- AG ISDN Messaging API
An API supplied with the AG ISDN software which allows an application direct access to Q.931 (layer 3) call control. Switch- and country-invariant D channel messages are exchanged with the application at this interface.
- AG ISDN protocol stack
Software running on the AG board which implements ISDN layer functionality. The stack can run in NCC stack mode, ACU stack mode, or LAPD stack mode, depending upon how the application is to access the AG ISDN protocol stack.
- agmon Utility program which reads a configuration file and uses it to load and monitor AG hardware.
- Alliance Generation board (AG board)
A member of Natural MicroSystems' Alliance Generation family of telephony and voice processing hardware products.
- ANI See Automatic Number Identification.
- asynchronous programming
Enables concurrent processing between telephony boards and the host CPU. The application initiates telephony functions on the AG board and continues its own processing instead of waiting for events from the AG board to arrive. CT Access supports this programming model.
- Automatic Call Unit (ACU)
An entity within layer 3, directly above the network layer. When the ISDN protocol stack is in ACU configuration, the application uses the AG ISDN Messaging API to communicate with the ACU, sending message sequences and handling network responses. When the ISDN protocol stack is in NCC stack mode, the TCP instances communicate with the ACU.
- Automatic Number Identification (ANI)
A network service that provides a called party with the phone number of the calling party. ANI information is typically available to the called party in R1, R2, and ISDN signaling systems. The implementation of ANI can vary between different telephone companies and even different Central Office switches.
- B channel See bearer channel.
- bearer channel (B channel)
One of the timeslots on an E1 trunk or T1 trunk over which voice data and in-band signaling is passed.
- blocking Call control action taken by an application to refuse incoming calls. Depending on the protocol, blocking tells the Central Office or switch either not to offer any calls, or to reject every call that is being offered (not answer, or to play busy, or to play ring, or to play a voice prompt). Blocking is not supported by AG ISDN Natural Call Control.
- call control The act of setting up, monitoring, and dismantling a telephone call.
- call progress analysis Functions that allow the application to control call placement. Call progress monitors in-band energy to detect network tones, voice, and other tones such as modems.
- CAS See Channel Associated Signaling.
- CCITT Comite Consultatif Internationale de Telegraphique et Telephonique; an international organization, based in Geneva, that recommends standard practices for communications. Now publishing under the name of its parent organization - ITU.
- CCS See Common Channel Signaling.
- chained layers In the OSI protocol layering model, the chained layers are the lowest three layers: the physical layer, the data link layer, and the network layer.
- channel An electronic communications path. In digital telephony, a channel usually refers to a separate connection carried on a digital trunk. Channel information is carried in timeslots, time-division-multiplexed into a single continuous stream of information.
- channelizer An entity on the ISDN protocol stack between the ACU and the TCP. It routes D channel information between the lower ISDN layers through the state machine implemented by the AG ISDN TCP to the CTA contexts.
- Channel Associated Signaling (CAS)
A signaling system in which signaling information is sent for all channels at regular intervals, regardless of each channel's state changes. The information for each channel consists of a set of bits (called the ABCD bits). Whenever a channel's state changes, the ABCD bit pattern for that channel changes. On T1 trunks, this information is "buried" in the voice information using robbed-bit signaling. On E1 trunks, this signaling is carried in a separate channel.
- Common Channel Signaling (CCS)
A signaling method where signaling information is provided for a number of channels in data-packet form sent over a separate link.
- CT Access One of the NMS telephony application programming interface products.
- D channel The timeslot on an E1 trunk or on a T1 trunk in which common channel signaling information is passed.
- data link layer In the OSI protocol layering model, the data link layer (layer 2) is the layer above the physical layer. Protocols for this layer describe methods for error-free communication between devices across the physical link. One protocol used at this layer is CCITT recommendation Q.921, also known as Link Access Procedures on the D Channel (LAPD).
- default channel The B channel assigned to a TCP instance when it is launched. The TCP will always request use of this channel when attempting to place an outbound call.
- Digital Signal Processor (DSP)
A microprocessor that is designed to perform the calculations required for voice processing.
- downloadable object module
A module of basic low-level software which an AG board requires to operate. The module for a board is specified in the AG configuration file. When agmon runs, it transfers the module file from the host into on-board memory.
- DSP See Digital Signal Processor.
- DSP files Software modules that program an AG board's DSPs to perform certain functions. The DSP files that an AG board will use are specified in the AG configuration file, and are loaded to on-board memory by agmon.
- E1 A standard used in Europe for digital telephone carriers. E1 is similar to T1 but operates at 2.048 Mbit/s and has 32 channels instead of T1's 24 channels.
- e1stat A utility that lets you monitor the status of an E1 trunk, including alarm states, errored and failed seconds, bit error rate violations, framing slips, and framer synchronization state.
- end-to-end layers In the OSI protocol layering model, layers above layer 3 (the network layer). These layers describe how information is exchanged and delivered end-to-end. They also define process-to-process communication, and describe application-independent user services, user interfaces and applications, etc.
- Exclusive Mode One of two modes which determine what the TCP does if the network denies the TCP use of its default channel. In Exclusive Mode, the TCP aborts the call.
- glare The simultaneous occurrence of an attempt to place a call and the appearance of an incoming call on the same channel. In general, the incoming call is given precedence.
- H.100 bus A PCM digital bus standard for integrating various board vendors. Allows boards to share data, signaling, and switching information.
- inbound application An application designed to receive inbound calls.
- inbound call A call received by an inbound application, placed by a remote party.
- Integrated Services Digital Network (ISDN)
A standard for providing voice and data telephone service with all digital transmission and message-based signaling.
- International Standards Organization (ISO)
The standards organization that developed the OSI protocol layering model.
- ISO See International Standards Organization.
- ITU See CCITT.
- LAPD See Link Access Procedures on the D Channel.
- LAPD stack mode An AG ISDN protocol stack mode in which the stack implements layer 2 functionality only. No channelizer or ACU is present. The application communicates directly with the data link layer.
- layer In the OSI protocol layering model, a level of digital communication. Each layer generally has one or more protocols associated with it.
- LE An ISDN equipment category. LE is Local Exchange equipment.
- line A logical telephone connection on which a call can take place.
- Link Access Procedures on the D Channel (LAPD)
CCITT recommendation Q.921: a protocol for communication at the data link layer.
- MVIP Multi-Vendor Integration Protocol; a PCM digital bus standard for integrating various board vendors. An interoperable subset of the H.100 bus standard.
- NAI See network access identifier.
- NCC stack mode A protocol stack mode in which the stack implements all ISDN layer 2 and layer 3 functionality. A channelizer is also present. ISDN TCP instances communicate with the application and with the channelizer entity in the stack.
- network access identifier (NAI)
A handle used to refer to a trunk.
- network layer In the OSI protocol layering model, the network layer (layer 3) is the layer above the data link layer. Protocols for this layer describe methods for transferring information between computers. They also describe how data is routed within and between networks. One protocol used at this layer is CCITT recommendation Q.931.
- Non-Exclusive Mode (Also called Preferred Mode) One of two modes which determine what the TCP does if the network denies the TCP use of its default channel. In Non-Exclusive Mode, the TCP will accept any B channel that the network assigns.
- Non-Facility Associated Signaling (NFAS)
An ISDN configuration where a single D channel on a T1 trunk carries the signaling for all B channels on more than one trunk. This leaves the 24th channels on the trunks free for use as B channels. NFAS is not supported on E1 trunks.
- NT1 An ISDN equipment category. Equipment in this category physically terminates the local loop.
- NT2 An ISDN equipment category. Equipment in this category is network terminating equipment, class 2.
- Open System Interconnect (OSI)
A model for digital communication, developed by the International Organization for Standardization (ISO). In OSI, seven separate layers of communication are defined.
- OSI See Open Systems Interconnect (OSI).
- outbound application An application designed to place outbound calls.
- outbound call A call placed by an application to a remote party.
- physical layer In the OSI protocol layering model, the physical layer (layer 1) is the electrical and mechanical layer. Protocols for this layer describe, on an electrical and mechanical basis, the methods used to transfer bits from one device to another. One protocol used at this layer is CCITT recommendation I.430/I.
- PRI See primary rate.
- primary rate In ISDN parlance, a term used to describe a trunk configuration consisting of 23 B channels and one D channel running at 1.544 Mbit/s (or 30 B channels and 1 D channel at 2.048 Mbit/s in Europe).
- Preferred Mode See Non-Exclusive Mode.
- protocol A scheme for communication. Many different protocols for digital telephony, and variations of these standards, are in use around the world.
- Q.921 See Link Access Procedures on the D Channel.
- Q.931 CCITT recommendation Q.931 describes a protocol for the network layer (layer 3 in the OSI protocol layering model).
- SAP See service access point.
- SAPI See service access point identifier.
- service access point (SAP)
In the OSI protocol layering model, the point at which a layer provides services to the layer directly above it. Each SAP is associated with a unique Service Access Point Identifier (SAPI).
- service access point identifier (SAPI)
In the OSI protocol layering model, a unique identifier for a service access point (SAP).
- showsig A utility which monitors the signals on all lines on a trunk simultaneously.
- solicited event An event that occurs as a direct consequence of a function call.
- Special Information Tone (SIT)
A sequence of three tones which indicate to a calling party that a network-provided recorded announcement will follow.
- stream A group of timeslots. Typically, this term refers to the entire set of timeslots on a trunk, or the mapping of those timeslots onto the MVIP bus.
- swish A utility program shipped with CT Access for configuring and controlling MVIP boards. MVIP-95 compliant.
- synchronous function A function that does not return until its operation is complete.
- T1 A standard for telephone transmission that multiplexes up to 24 channels on a single 1.544 Mbit/s carrier.
- t1stat A utility shipped that lets you monitor the status of a T1 trunk, including alarm states, errored and failed seconds, bit error rate violations, framing slips, and framer synchronization state.
- TCP See Trunk Control Program.
- TE1 An ISDN equipment category. Equipment in this category is ISDN end-user terminating equipment, class 1, which terminates a single ISDN trunk.
- timeslot On a digital trunk and on the MVIP bus, information in each channel is time-division multiplexed into a single continuous stream of data. The interval in which each channel broadcasts is called a timeslot.
- trunk A transmission channel connecting two switching machines.
- Trunk Control Program (TCP)
A software module designed to run in an AG board's on-board memory, which interfaces a host application with an analog or digital trunk running a certain protocol. The TCP to use is specified in the AG configuration file, and is transferred to the AG board by agmon.
- unsolicited events Events that can occur at any time, regardless of the application's current activities.
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