Введение
Часть пользователя ISDN (Integrated Services Digital Network) или ISUP является частью системы сигнализации № 7 (SS7), используемой для установления телефонных соединений в общедоступной телефонной сети (PSTN). Она специфицирована ITU-T как часть серии Q.76x. При установлении телефонного соединения между двумя абонентами может быть задействовано несколько телефонных станций, возможно, через международные границы. Для обеспечения правильного установления соединения, при поддержке ISUP, коммутатор передает информацию, связанную с вызовом, такую как номер вызываемого абонента, следующему коммутатору в сети, используя сообщения ISUP. Телефонные станции могут быть соединены через магистральные линии T1 или E1, которые передают речевой трафик. Эти магистрали разделены на временные интервалы по 64 кбит/с, и каждый интервал может нести только одно соединение. Независимо от используемых средств для соединения коммутаторов, каждая цепь между двумя коммутаторами однозначно идентифицируется кодом идентификации цепи (CIC), который содержится в сообщениях ISUP. Коммутатор использует эту информацию вместе с полученной сигнальной информацией (особенно номер вызываемого абонента) для определения того, какие входящие и исходящие цепи следует соединить, чтобы обеспечить сквозной речевой канал. Помимо информации, связанной с вызовом, ISUP также используется для обмена информацией о состоянии и управления доступными цепями. В случае отсутствия свободной исходящей цепи на конкретном коммутаторе, сообщение об освобождении отправляется обратно на предыдущие коммутаторы в цепочке.
The ISDN (Integrated Services Digital Network) User Part or ISUP is part of Signaling System No. 7 (SS7), which is used to set up telephone calls in the public switched telephone network (PSTN). It is specified by the ITU T as part of the Q.76x series. When a telephone call is set up from one subscriber to another, several telephone exchanges could be involved, possibly across international boundaries. To allow a call to be set up correctly, where ISUP is supported, a switch will signal call related information like called party number to the next switch in the network using ISUP messages. The telephone exchanges may be connected via T1 or E1 trunks which transport the speech from the calls. These trunks are divided into 64 kbit/s timeslots, and one timeslot can carry exactly one call. Regardless of what facilities are used to interconnect switches, each circuit between two switches is uniquely identified by a circuit identification code (CIC) that is included in the ISUP messages. The exchange uses this information along with the received signaling information (especially the called party number) to determine which inbound and outbound circuits should be connected together to provide an end to end speech path. In addition to call related information, ISUP is also used to exchange status information for, and permit management of, the available circuits. In the case of no outbound circuit being available on a particular exchange, a release message is sent back to the preceding switches in the chain.
Варианты ISUP
Существуют различные варианты ISUP. ITU-T определяет вариант, используемый в международной сети. В Европе ETSI выпускает собственную спецификацию ISUP, которая близка к спецификации ITU-T. ISUP ITU-T используется для международных соединений и является основой для некоторых национальных вариантов ISUP. Большинство стран имеют свои вариации ISUP для удовлетворения национальных требований. ANSI определяет вариации ISUP, используемые в рамках Североамериканского плана нумерации; однако некоторые страны, входящие в NANP, отличаются в поддержке определенных процедур (например, LATA не имеет значения для Канады. Кроме того, RBOC поддерживают процедуры Telcordia, которые не полностью специфицированы ANSI). Некоторые страны за пределами NANP поддерживают варианты на основе ANSI (например, Мексика). Несмотря на то, что эти вариации ISUP отличаются незначительными деталями, подавляющее большинство типов сообщений ISUP, типов параметров, кодовых точек полей параметров и связанных с ними основных процедур обработки вызовов согласуются во всех вариантах.
Different ISUP variants exist. ITU T specifies the variant used in the international network. In Europe ETSI releases its own ISUP specification which is close that of the ITU T. ITU T ISUP is used for international connections and is the base for some national ISUP variants. Most countries have their own variation of ISUP to cover national requirements. ANSI specifies variations of ISUP utilized under the North American Numbering Plan; however, some countries under the NANP differ in their support of some procedures (for example, LATA is meaningless within Canada. Also, RBOCs support Telcordia procedures not fully specified by ANSI.) Some countries outside the NANP support ANSI based variants (e. g. Mexico). While these variations of ISUP differ in subtle ways, the vast majority of ISUP message type, parameter type, and parameter field code points, and related fundamental call processing procedures, agree across all variants.
Типы сообщений
Сообщение ISUP содержит фиксированный заголовок, включающий идентификационный код схемы и тип сообщения ISUP, за которым следуют обязательная часть параметров фиксированной длины, обязательная часть параметров переменной длины и необязательная часть параметров, зависящие от типа отправляемого сообщения. Сообщения ISUP могут передаваться с использованием услуг части передачи сообщений или, реже, части управления соединением сигнализации. Эти сообщения передаются на различных этапах установления и завершения вызова. Наиболее распространенными сообщениями являются:
An ISUP message contains a fixed header containing the circuit identification code and the ISUP message type, followed by a mandatory fixed length parameter part, a mandatory variable length parameter part, and an optional parameter part that are dependent on the type of message being sent. ISUP messages can be sent using the services of the Message Transfer Part, or, less often, the Signalling Connection Control Part. These messages are transmitted in various stages of call setup and release. The most common messages are:
Initial address message (IAM) — First message sent to inform the partner switch that a call has to be established on the CIC contained in the message. Contains the called number, type of service (speech or data) and optional parameters. Subsequent address message (SAM) — For networks that support overlap dialing procedures, and then in the case that the IAM did not contain the full called number, one or more SAMs follow containing additional digits. This message is not supported by networks that only support en bloc dialing procedures. Address complete message (ACM) — Message returned from the terminating switch when the subscriber is reached and the phone starts ringing, or when the call traverses an interworking point and the intermediate trunk is seized. Call progress (CPG) — Contains additional information about the progress of a call. Normally sent after the ACM when the status of the call changes from that reported in the ACM. Answer message (ANM) — Sent when the subscriber picks up the phone, a resource is connected or answer supervision is returned by an interworking point. Normally charging starts at this moment. It is required that the call be cut through in both directions by this point. Connect (CON) — Sent when the call is answered by an automatic terminal. This message replaces the ACM, CPG and ANM for calls that are answered by automatic terminals. Release (REL) — Sent to clear the call when a subscriber goes on hook. This is also sent (in direct response to an IAM) if the terminating switch determines that the call cannot be completed. In either case, the terminating switch provides a cause value in the message to explain the reason for the release, e. g., "User busy". Release complete (RLC) — Acknowledgment of the release – the circuit is idle afterward and can be used again.
Initial address message (IAM) — First message sent to inform the partner switch that a call has to be established on the CIC contained in the message. Contains the called number, type of service (speech or data) and optional parameters. Subsequent address message (SAM) — For networks that support overlap dialing procedures, and then in the case that the IAM did not contain the full called number, one or more SAMs follow containing additional digits. This message is not supported by networks that only support en bloc dialing procedures. Address complete message (ACM) — Message returned from the terminating switch when the subscriber is reached and the phone starts ringing, or when the call traverses an interworking point and the intermediate trunk is seized. Call progress (CPG) — Contains additional information about the progress of a call. Normally sent after the ACM when the status of the call changes from that reported in the ACM. Answer message (ANM) — Sent when the subscriber picks up the phone, a resource is connected or answer supervision is returned by an interworking point. Normally charging starts at this moment. It is required that the call be cut through in both directions by this point. Connect (CON) — Sent when the call is answered by an automatic terminal. This message replaces the ACM, CPG and ANM for calls that are answered by automatic terminals. Release (REL) — Sent to clear the call when a subscriber goes on hook. This is also sent (in direct response to an IAM) if the terminating switch determines that the call cannot be completed. In either case, the terminating switch provides a cause value in the message to explain the reason for the release, e. g., "User busy". Release complete (RLC) — Acknowledgment of the release – the circuit is idle afterward and can be used again.
Сообщение о первоначальном адресе (IAM) — Первое сообщение, отправляемое для информирования оконечного коммутатора о необходимости установления вызова на схеме, идентифицированной в сообщении. Содержит номер вызываемого абонента, тип услуги (речь или данные) и необязательные параметры.
An ISUP message contains a fixed header containing the circuit identification code and the ISUP message type, followed by a mandatory fixed length parameter part, a mandatory variable length parameter part, and an optional parameter part that are dependent on the type of message being sent. ISUP messages can be sent using the services of the Message Transfer Part, or, less often, the Signalling Connection Control Part. These messages are transmitted in various stages of call setup and release. The most common messages are:
Initial address message (IAM) — First message sent to inform the partner switch that a call has to be established on the CIC contained in the message. Contains the called number, type of service (speech or data) and optional parameters. Subsequent address message (SAM) — For networks that support overlap dialing procedures, and then in the case that the IAM did not contain the full called number, one or more SAMs follow containing additional digits. This message is not supported by networks that only support en bloc dialing procedures. Address complete message (ACM) — Message returned from the terminating switch when the subscriber is reached and the phone starts ringing, or when the call traverses an interworking point and the intermediate trunk is seized. Call progress (CPG) — Contains additional information about the progress of a call. Normally sent after the ACM when the status of the call changes from that reported in the ACM. Answer message (ANM) — Sent when the subscriber picks up the phone, a resource is connected or answer supervision is returned by an interworking point. Normally charging starts at this moment. It is required that the call be cut through in both directions by this point. Connect (CON) — Sent when the call is answered by an automatic terminal. This message replaces the ACM, CPG and ANM for calls that are answered by automatic terminals. Release (REL) — Sent to clear the call when a subscriber goes on hook. This is also sent (in direct response to an IAM) if the terminating switch determines that the call cannot be completed. In either case, the terminating switch provides a cause value in the message to explain the reason for the release, e. g., "User busy". Release complete (RLC) — Acknowledgment of the release – the circuit is idle afterward and can be used again.
Initial address message (IAM) — First message sent to inform the partner switch that a call has to be established on the CIC contained in the message. Contains the called number, type of service (speech or data) and optional parameters. Subsequent address message (SAM) — For networks that support overlap dialing procedures, and then in the case that the IAM did not contain the full called number, one or more SAMs follow containing additional digits. This message is not supported by networks that only support en bloc dialing procedures. Address complete message (ACM) — Message returned from the terminating switch when the subscriber is reached and the phone starts ringing, or when the call traverses an interworking point and the intermediate trunk is seized. Call progress (CPG) — Contains additional information about the progress of a call. Normally sent after the ACM when the status of the call changes from that reported in the ACM. Answer message (ANM) — Sent when the subscriber picks up the phone, a resource is connected or answer supervision is returned by an interworking point. Normally charging starts at this moment. It is required that the call be cut through in both directions by this point. Connect (CON) — Sent when the call is answered by an automatic terminal. This message replaces the ACM, CPG and ANM for calls that are answered by automatic terminals. Release (REL) — Sent to clear the call when a subscriber goes on hook. This is also sent (in direct response to an IAM) if the terminating switch determines that the call cannot be completed. In either case, the terminating switch provides a cause value in the message to explain the reason for the release, e. g., "User busy". Release complete (RLC) — Acknowledgment of the release – the circuit is idle afterward and can be used again.
Последующее адресное сообщение (SAM) — Для сетей, поддерживающих процедуры упреждающего набора, и в случае, если IAM не содержал полный номер вызываемого абонента, за IAM следуют одно или несколько SAM, содержащих дополнительные цифры. Это сообщение не поддерживается сетями, поддерживающими только процедуру набора номера полным блоком.
An ISUP message contains a fixed header containing the circuit identification code and the ISUP message type, followed by a mandatory fixed length parameter part, a mandatory variable length parameter part, and an optional parameter part that are dependent on the type of message being sent. ISUP messages can be sent using the services of the Message Transfer Part, or, less often, the Signalling Connection Control Part. These messages are transmitted in various stages of call setup and release. The most common messages are:
Initial address message (IAM) — First message sent to inform the partner switch that a call has to be established on the CIC contained in the message. Contains the called number, type of service (speech or data) and optional parameters. Subsequent address message (SAM) — For networks that support overlap dialing procedures, and then in the case that the IAM did not contain the full called number, one or more SAMs follow containing additional digits. This message is not supported by networks that only support en bloc dialing procedures. Address complete message (ACM) — Message returned from the terminating switch when the subscriber is reached and the phone starts ringing, or when the call traverses an interworking point and the intermediate trunk is seized. Call progress (CPG) — Contains additional information about the progress of a call. Normally sent after the ACM when the status of the call changes from that reported in the ACM. Answer message (ANM) — Sent when the subscriber picks up the phone, a resource is connected or answer supervision is returned by an interworking point. Normally charging starts at this moment. It is required that the call be cut through in both directions by this point. Connect (CON) — Sent when the call is answered by an automatic terminal. This message replaces the ACM, CPG and ANM for calls that are answered by automatic terminals. Release (REL) — Sent to clear the call when a subscriber goes on hook. This is also sent (in direct response to an IAM) if the terminating switch determines that the call cannot be completed. In either case, the terminating switch provides a cause value in the message to explain the reason for the release, e. g., "User busy". Release complete (RLC) — Acknowledgment of the release – the circuit is idle afterward and can be used again.
Initial address message (IAM) — First message sent to inform the partner switch that a call has to be established on the CIC contained in the message. Contains the called number, type of service (speech or data) and optional parameters. Subsequent address message (SAM) — For networks that support overlap dialing procedures, and then in the case that the IAM did not contain the full called number, one or more SAMs follow containing additional digits. This message is not supported by networks that only support en bloc dialing procedures. Address complete message (ACM) — Message returned from the terminating switch when the subscriber is reached and the phone starts ringing, or when the call traverses an interworking point and the intermediate trunk is seized. Call progress (CPG) — Contains additional information about the progress of a call. Normally sent after the ACM when the status of the call changes from that reported in the ACM. Answer message (ANM) — Sent when the subscriber picks up the phone, a resource is connected or answer supervision is returned by an interworking point. Normally charging starts at this moment. It is required that the call be cut through in both directions by this point. Connect (CON) — Sent when the call is answered by an automatic terminal. This message replaces the ACM, CPG and ANM for calls that are answered by automatic terminals. Release (REL) — Sent to clear the call when a subscriber goes on hook. This is also sent (in direct response to an IAM) if the terminating switch determines that the call cannot be completed. In either case, the terminating switch provides a cause value in the message to explain the reason for the release, e. g., "User busy". Release complete (RLC) — Acknowledgment of the release – the circuit is idle afterward and can be used again.
Сообщение о завершении адреса (ACM) — Сообщение, возвращаемое оконечным коммутатором, когда вызываемый абонент достигнут и телефон начинает звонить, или когда вызов проходит через точку межсетевого взаимодействия и промежуточный канал занят.
An ISUP message contains a fixed header containing the circuit identification code and the ISUP message type, followed by a mandatory fixed length parameter part, a mandatory variable length parameter part, and an optional parameter part that are dependent on the type of message being sent. ISUP messages can be sent using the services of the Message Transfer Part, or, less often, the Signalling Connection Control Part. These messages are transmitted in various stages of call setup and release. The most common messages are:
Initial address message (IAM) — First message sent to inform the partner switch that a call has to be established on the CIC contained in the message. Contains the called number, type of service (speech or data) and optional parameters. Subsequent address message (SAM) — For networks that support overlap dialing procedures, and then in the case that the IAM did not contain the full called number, one or more SAMs follow containing additional digits. This message is not supported by networks that only support en bloc dialing procedures. Address complete message (ACM) — Message returned from the terminating switch when the subscriber is reached and the phone starts ringing, or when the call traverses an interworking point and the intermediate trunk is seized. Call progress (CPG) — Contains additional information about the progress of a call. Normally sent after the ACM when the status of the call changes from that reported in the ACM. Answer message (ANM) — Sent when the subscriber picks up the phone, a resource is connected or answer supervision is returned by an interworking point. Normally charging starts at this moment. It is required that the call be cut through in both directions by this point. Connect (CON) — Sent when the call is answered by an automatic terminal. This message replaces the ACM, CPG and ANM for calls that are answered by automatic terminals. Release (REL) — Sent to clear the call when a subscriber goes on hook. This is also sent (in direct response to an IAM) if the terminating switch determines that the call cannot be completed. In either case, the terminating switch provides a cause value in the message to explain the reason for the release, e. g., "User busy". Release complete (RLC) — Acknowledgment of the release – the circuit is idle afterward and can be used again.
Initial address message (IAM) — First message sent to inform the partner switch that a call has to be established on the CIC contained in the message. Contains the called number, type of service (speech or data) and optional parameters. Subsequent address message (SAM) — For networks that support overlap dialing procedures, and then in the case that the IAM did not contain the full called number, one or more SAMs follow containing additional digits. This message is not supported by networks that only support en bloc dialing procedures. Address complete message (ACM) — Message returned from the terminating switch when the subscriber is reached and the phone starts ringing, or when the call traverses an interworking point and the intermediate trunk is seized. Call progress (CPG) — Contains additional information about the progress of a call. Normally sent after the ACM when the status of the call changes from that reported in the ACM. Answer message (ANM) — Sent when the subscriber picks up the phone, a resource is connected or answer supervision is returned by an interworking point. Normally charging starts at this moment. It is required that the call be cut through in both directions by this point. Connect (CON) — Sent when the call is answered by an automatic terminal. This message replaces the ACM, CPG and ANM for calls that are answered by automatic terminals. Release (REL) — Sent to clear the call when a subscriber goes on hook. This is also sent (in direct response to an IAM) if the terminating switch determines that the call cannot be completed. In either case, the terminating switch provides a cause value in the message to explain the reason for the release, e. g., "User busy". Release complete (RLC) — Acknowledgment of the release – the circuit is idle afterward and can be used again.
Прогресс вызова (CPG) — Содержит дополнительную информацию о ходе вызова. Обычно отправляется после ACM, когда статус вызова изменяется по сравнению со статусом, указанным в ACM.
An ISUP message contains a fixed header containing the circuit identification code and the ISUP message type, followed by a mandatory fixed length parameter part, a mandatory variable length parameter part, and an optional parameter part that are dependent on the type of message being sent. ISUP messages can be sent using the services of the Message Transfer Part, or, less often, the Signalling Connection Control Part. These messages are transmitted in various stages of call setup and release. The most common messages are:
Initial address message (IAM) — First message sent to inform the partner switch that a call has to be established on the CIC contained in the message. Contains the called number, type of service (speech or data) and optional parameters. Subsequent address message (SAM) — For networks that support overlap dialing procedures, and then in the case that the IAM did not contain the full called number, one or more SAMs follow containing additional digits. This message is not supported by networks that only support en bloc dialing procedures. Address complete message (ACM) — Message returned from the terminating switch when the subscriber is reached and the phone starts ringing, or when the call traverses an interworking point and the intermediate trunk is seized. Call progress (CPG) — Contains additional information about the progress of a call. Normally sent after the ACM when the status of the call changes from that reported in the ACM. Answer message (ANM) — Sent when the subscriber picks up the phone, a resource is connected or answer supervision is returned by an interworking point. Normally charging starts at this moment. It is required that the call be cut through in both directions by this point. Connect (CON) — Sent when the call is answered by an automatic terminal. This message replaces the ACM, CPG and ANM for calls that are answered by automatic terminals. Release (REL) — Sent to clear the call when a subscriber goes on hook. This is also sent (in direct response to an IAM) if the terminating switch determines that the call cannot be completed. In either case, the terminating switch provides a cause value in the message to explain the reason for the release, e. g., "User busy". Release complete (RLC) — Acknowledgment of the release – the circuit is idle afterward and can be used again.
Initial address message (IAM) — First message sent to inform the partner switch that a call has to be established on the CIC contained in the message. Contains the called number, type of service (speech or data) and optional parameters. Subsequent address message (SAM) — For networks that support overlap dialing procedures, and then in the case that the IAM did not contain the full called number, one or more SAMs follow containing additional digits. This message is not supported by networks that only support en bloc dialing procedures. Address complete message (ACM) — Message returned from the terminating switch when the subscriber is reached and the phone starts ringing, or when the call traverses an interworking point and the intermediate trunk is seized. Call progress (CPG) — Contains additional information about the progress of a call. Normally sent after the ACM when the status of the call changes from that reported in the ACM. Answer message (ANM) — Sent when the subscriber picks up the phone, a resource is connected or answer supervision is returned by an interworking point. Normally charging starts at this moment. It is required that the call be cut through in both directions by this point. Connect (CON) — Sent when the call is answered by an automatic terminal. This message replaces the ACM, CPG and ANM for calls that are answered by automatic terminals. Release (REL) — Sent to clear the call when a subscriber goes on hook. This is also sent (in direct response to an IAM) if the terminating switch determines that the call cannot be completed. In either case, the terminating switch provides a cause value in the message to explain the reason for the release, e. g., "User busy". Release complete (RLC) — Acknowledgment of the release – the circuit is idle afterward and can be used again.
Сообщение об ответе (ANM) — Отправляется, когда вызываемый абонент снимает трубку, ресурс подключен или оконечная точка взаимодействия возвращает подтверждение ответа. Обычно в этот момент начинается тарификация. К этому моменту вызов должен быть соединен в обоих направлениях.
An ISUP message contains a fixed header containing the circuit identification code and the ISUP message type, followed by a mandatory fixed length parameter part, a mandatory variable length parameter part, and an optional parameter part that are dependent on the type of message being sent. ISUP messages can be sent using the services of the Message Transfer Part, or, less often, the Signalling Connection Control Part. These messages are transmitted in various stages of call setup and release. The most common messages are:
Initial address message (IAM) — First message sent to inform the partner switch that a call has to be established on the CIC contained in the message. Contains the called number, type of service (speech or data) and optional parameters. Subsequent address message (SAM) — For networks that support overlap dialing procedures, and then in the case that the IAM did not contain the full called number, one or more SAMs follow containing additional digits. This message is not supported by networks that only support en bloc dialing procedures. Address complete message (ACM) — Message returned from the terminating switch when the subscriber is reached and the phone starts ringing, or when the call traverses an interworking point and the intermediate trunk is seized. Call progress (CPG) — Contains additional information about the progress of a call. Normally sent after the ACM when the status of the call changes from that reported in the ACM. Answer message (ANM) — Sent when the subscriber picks up the phone, a resource is connected or answer supervision is returned by an interworking point. Normally charging starts at this moment. It is required that the call be cut through in both directions by this point. Connect (CON) — Sent when the call is answered by an automatic terminal. This message replaces the ACM, CPG and ANM for calls that are answered by automatic terminals. Release (REL) — Sent to clear the call when a subscriber goes on hook. This is also sent (in direct response to an IAM) if the terminating switch determines that the call cannot be completed. In either case, the terminating switch provides a cause value in the message to explain the reason for the release, e. g., "User busy". Release complete (RLC) — Acknowledgment of the release – the circuit is idle afterward and can be used again.
Initial address message (IAM) — First message sent to inform the partner switch that a call has to be established on the CIC contained in the message. Contains the called number, type of service (speech or data) and optional parameters. Subsequent address message (SAM) — For networks that support overlap dialing procedures, and then in the case that the IAM did not contain the full called number, one or more SAMs follow containing additional digits. This message is not supported by networks that only support en bloc dialing procedures. Address complete message (ACM) — Message returned from the terminating switch when the subscriber is reached and the phone starts ringing, or when the call traverses an interworking point and the intermediate trunk is seized. Call progress (CPG) — Contains additional information about the progress of a call. Normally sent after the ACM when the status of the call changes from that reported in the ACM. Answer message (ANM) — Sent when the subscriber picks up the phone, a resource is connected or answer supervision is returned by an interworking point. Normally charging starts at this moment. It is required that the call be cut through in both directions by this point. Connect (CON) — Sent when the call is answered by an automatic terminal. This message replaces the ACM, CPG and ANM for calls that are answered by automatic terminals. Release (REL) — Sent to clear the call when a subscriber goes on hook. This is also sent (in direct response to an IAM) if the terminating switch determines that the call cannot be completed. In either case, the terminating switch provides a cause value in the message to explain the reason for the release, e. g., "User busy". Release complete (RLC) — Acknowledgment of the release – the circuit is idle afterward and can be used again.
Соединение (CON) — Отправляется, когда на вызов отвечает автоматическое устройство. Это сообщение заменяет ACM, CPG и ANM для вызовов, на которые отвечают автоматические устройства.
An ISUP message contains a fixed header containing the circuit identification code and the ISUP message type, followed by a mandatory fixed length parameter part, a mandatory variable length parameter part, and an optional parameter part that are dependent on the type of message being sent. ISUP messages can be sent using the services of the Message Transfer Part, or, less often, the Signalling Connection Control Part. These messages are transmitted in various stages of call setup and release. The most common messages are:
Initial address message (IAM) — First message sent to inform the partner switch that a call has to be established on the CIC contained in the message. Contains the called number, type of service (speech or data) and optional parameters. Subsequent address message (SAM) — For networks that support overlap dialing procedures, and then in the case that the IAM did not contain the full called number, one or more SAMs follow containing additional digits. This message is not supported by networks that only support en bloc dialing procedures. Address complete message (ACM) — Message returned from the terminating switch when the subscriber is reached and the phone starts ringing, or when the call traverses an interworking point and the intermediate trunk is seized. Call progress (CPG) — Contains additional information about the progress of a call. Normally sent after the ACM when the status of the call changes from that reported in the ACM. Answer message (ANM) — Sent when the subscriber picks up the phone, a resource is connected or answer supervision is returned by an interworking point. Normally charging starts at this moment. It is required that the call be cut through in both directions by this point. Connect (CON) — Sent when the call is answered by an automatic terminal. This message replaces the ACM, CPG and ANM for calls that are answered by automatic terminals. Release (REL) — Sent to clear the call when a subscriber goes on hook. This is also sent (in direct response to an IAM) if the terminating switch determines that the call cannot be completed. In either case, the terminating switch provides a cause value in the message to explain the reason for the release, e. g., "User busy". Release complete (RLC) — Acknowledgment of the release – the circuit is idle afterward and can be used again.
Initial address message (IAM) — First message sent to inform the partner switch that a call has to be established on the CIC contained in the message. Contains the called number, type of service (speech or data) and optional parameters. Subsequent address message (SAM) — For networks that support overlap dialing procedures, and then in the case that the IAM did not contain the full called number, one or more SAMs follow containing additional digits. This message is not supported by networks that only support en bloc dialing procedures. Address complete message (ACM) — Message returned from the terminating switch when the subscriber is reached and the phone starts ringing, or when the call traverses an interworking point and the intermediate trunk is seized. Call progress (CPG) — Contains additional information about the progress of a call. Normally sent after the ACM when the status of the call changes from that reported in the ACM. Answer message (ANM) — Sent when the subscriber picks up the phone, a resource is connected or answer supervision is returned by an interworking point. Normally charging starts at this moment. It is required that the call be cut through in both directions by this point. Connect (CON) — Sent when the call is answered by an automatic terminal. This message replaces the ACM, CPG and ANM for calls that are answered by automatic terminals. Release (REL) — Sent to clear the call when a subscriber goes on hook. This is also sent (in direct response to an IAM) if the terminating switch determines that the call cannot be completed. In either case, the terminating switch provides a cause value in the message to explain the reason for the release, e. g., "User busy". Release complete (RLC) — Acknowledgment of the release – the circuit is idle afterward and can be used again.
Разъединение (REL) — Отправляется для завершения вызова, когда абонент вешает трубку. Также отправляется (в ответ на IAM), если оконечный коммутатор определяет, что вызов не может быть завершен. В любом случае, оконечный коммутатор предоставляет причину разъединения в сообщении, например, "Абонент занят".
An ISUP message contains a fixed header containing the circuit identification code and the ISUP message type, followed by a mandatory fixed length parameter part, a mandatory variable length parameter part, and an optional parameter part that are dependent on the type of message being sent. ISUP messages can be sent using the services of the Message Transfer Part, or, less often, the Signalling Connection Control Part. These messages are transmitted in various stages of call setup and release. The most common messages are:
Initial address message (IAM) — First message sent to inform the partner switch that a call has to be established on the CIC contained in the message. Contains the called number, type of service (speech or data) and optional parameters. Subsequent address message (SAM) — For networks that support overlap dialing procedures, and then in the case that the IAM did not contain the full called number, one or more SAMs follow containing additional digits. This message is not supported by networks that only support en bloc dialing procedures. Address complete message (ACM) — Message returned from the terminating switch when the subscriber is reached and the phone starts ringing, or when the call traverses an interworking point and the intermediate trunk is seized. Call progress (CPG) — Contains additional information about the progress of a call. Normally sent after the ACM when the status of the call changes from that reported in the ACM. Answer message (ANM) — Sent when the subscriber picks up the phone, a resource is connected or answer supervision is returned by an interworking point. Normally charging starts at this moment. It is required that the call be cut through in both directions by this point. Connect (CON) — Sent when the call is answered by an automatic terminal. This message replaces the ACM, CPG and ANM for calls that are answered by automatic terminals. Release (REL) — Sent to clear the call when a subscriber goes on hook. This is also sent (in direct response to an IAM) if the terminating switch determines that the call cannot be completed. In either case, the terminating switch provides a cause value in the message to explain the reason for the release, e. g., "User busy". Release complete (RLC) — Acknowledgment of the release – the circuit is idle afterward and can be used again.
Initial address message (IAM) — First message sent to inform the partner switch that a call has to be established on the CIC contained in the message. Contains the called number, type of service (speech or data) and optional parameters. Subsequent address message (SAM) — For networks that support overlap dialing procedures, and then in the case that the IAM did not contain the full called number, one or more SAMs follow containing additional digits. This message is not supported by networks that only support en bloc dialing procedures. Address complete message (ACM) — Message returned from the terminating switch when the subscriber is reached and the phone starts ringing, or when the call traverses an interworking point and the intermediate trunk is seized. Call progress (CPG) — Contains additional information about the progress of a call. Normally sent after the ACM when the status of the call changes from that reported in the ACM. Answer message (ANM) — Sent when the subscriber picks up the phone, a resource is connected or answer supervision is returned by an interworking point. Normally charging starts at this moment. It is required that the call be cut through in both directions by this point. Connect (CON) — Sent when the call is answered by an automatic terminal. This message replaces the ACM, CPG and ANM for calls that are answered by automatic terminals. Release (REL) — Sent to clear the call when a subscriber goes on hook. This is also sent (in direct response to an IAM) if the terminating switch determines that the call cannot be completed. In either case, the terminating switch provides a cause value in the message to explain the reason for the release, e. g., "User busy". Release complete (RLC) — Acknowledgment of the release – the circuit is idle afterward and can be used again.
Завершение разъединения (RLC) — Подтверждение разъединения – схема освобождается и может быть использована повторно.
An ISUP message contains a fixed header containing the circuit identification code and the ISUP message type, followed by a mandatory fixed length parameter part, a mandatory variable length parameter part, and an optional parameter part that are dependent on the type of message being sent. ISUP messages can be sent using the services of the Message Transfer Part, or, less often, the Signalling Connection Control Part. These messages are transmitted in various stages of call setup and release. The most common messages are:
Initial address message (IAM) — First message sent to inform the partner switch that a call has to be established on the CIC contained in the message. Contains the called number, type of service (speech or data) and optional parameters. Subsequent address message (SAM) — For networks that support overlap dialing procedures, and then in the case that the IAM did not contain the full called number, one or more SAMs follow containing additional digits. This message is not supported by networks that only support en bloc dialing procedures. Address complete message (ACM) — Message returned from the terminating switch when the subscriber is reached and the phone starts ringing, or when the call traverses an interworking point and the intermediate trunk is seized. Call progress (CPG) — Contains additional information about the progress of a call. Normally sent after the ACM when the status of the call changes from that reported in the ACM. Answer message (ANM) — Sent when the subscriber picks up the phone, a resource is connected or answer supervision is returned by an interworking point. Normally charging starts at this moment. It is required that the call be cut through in both directions by this point. Connect (CON) — Sent when the call is answered by an automatic terminal. This message replaces the ACM, CPG and ANM for calls that are answered by automatic terminals. Release (REL) — Sent to clear the call when a subscriber goes on hook. This is also sent (in direct response to an IAM) if the terminating switch determines that the call cannot be completed. In either case, the terminating switch provides a cause value in the message to explain the reason for the release, e. g., "User busy". Release complete (RLC) — Acknowledgment of the release – the circuit is idle afterward and can be used again.
Initial address message (IAM) — First message sent to inform the partner switch that a call has to be established on the CIC contained in the message. Contains the called number, type of service (speech or data) and optional parameters. Subsequent address message (SAM) — For networks that support overlap dialing procedures, and then in the case that the IAM did not contain the full called number, one or more SAMs follow containing additional digits. This message is not supported by networks that only support en bloc dialing procedures. Address complete message (ACM) — Message returned from the terminating switch when the subscriber is reached and the phone starts ringing, or when the call traverses an interworking point and the intermediate trunk is seized. Call progress (CPG) — Contains additional information about the progress of a call. Normally sent after the ACM when the status of the call changes from that reported in the ACM. Answer message (ANM) — Sent when the subscriber picks up the phone, a resource is connected or answer supervision is returned by an interworking point. Normally charging starts at this moment. It is required that the call be cut through in both directions by this point. Connect (CON) — Sent when the call is answered by an automatic terminal. This message replaces the ACM, CPG and ANM for calls that are answered by automatic terminals. Release (REL) — Sent to clear the call when a subscriber goes on hook. This is also sent (in direct response to an IAM) if the terminating switch determines that the call cannot be completed. In either case, the terminating switch provides a cause value in the message to explain the reason for the release, e. g., "User busy". Release complete (RLC) — Acknowledgment of the release – the circuit is idle afterward and can be used again.