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MCP/PCP (ITU)

Overview

MCP and PCP messages provide support for unrecognized signaling as defined by ISUP 1992 (ITU-T White Book). This support becomes necessary, for example, if the exchange receives unrecognized signaling information from a later version of ISUP. With MCP/PCP, the exchange can take the appropriate action and ensure its compatibility with new signaling messages, no matter what version they may be.

MCP

Message Compatibility Procedure (MCP, Section 2.9.5, Q.764)

It may happen that an exchange receives an unrecognized message. The message compatibility procedures are invoked in this case to ensure predictable network behavior. Message compatibility information is received in the unrecognized message and following actions can be taken based on the compatibility information contained in the message.

Procedures include:

• Send Notification to the exchange sending unrecognized message (Confusion).

• Do not send notification.

• Initiate release procedure.

• Discard message.

• Pass on unrecognized message transparently.

PCP

Parameter Compatibility Procedure

PCP defines a set of procedures executed when a message containing unrecognized optional parameters is received by the exchange. Parameter compatibility information is contained in the received message. Receipt of unrecognized parameters only refers to optional parameters and unexpected parameters for that particular message. Based on the instruction indicator contained in the parameter compatibility information for the unrecognized parameter, the following actions can be taken.

• Send Notification to the exchange sending unrecognized parameter (Confusion).

• Do not send notification.

• Initiate release procedure.

• Discard message.

• Discard unrecognized parameter.

• Pass on unrecognized parameters transparently.

Unrecognized Message Handling—for Message without MCP

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Unrecognized Message Handling---for Message with MCP Discard Indicator

Unrecognized Message—with MCP Containing Release Indicator

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Unrecognized Message—with MCP Containing Discard and Send Notification Indicator

Unrecognized Message--with MCP Containing Pass On Indicator

Message with Unrecognized Optional Parameters and no PCP

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Message with Unrecognized Parameter—with PCP Containing Discard Message and Send Notification Indicator for that Parameter

Message with Unrecognized Parameter—with PCP Containing Release Call Indicator

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Message with Unrecognized Optional Parameter—with PCP Containing Discard Parameter and Send Notification Indicator

Release with Unrecognized Parameter with PCP

Message with Unrecognized Parameter and PCP Having Pass On Indicator

See Integrated Services Digital Network User Part.
International Telecommunications Union (UN)
ITU-TSS Publication on Signaling Procedures (ISUP)