[转]SS7(四)-ISUP (ISDN User Part)

[转]SS7(4)-ISUP (ISDN User Part)

图1-ISUP功能层次图

图2-ISUP信令在Call建立与拆除中的用法

图3-ISUP信令在trunk管理的使用(闭塞与解闭)

图4-ISUP消息Overview

ISUP information is carried in the service information field (SIF) of an MSU. The SIF contains the routing label followed by a 14-bit (ANSI) or 12-bit (ITU) circuit identification code (CIC). The CIC indicates the trunk circuit reserved by the originating switch to carry the call.

The CIC is followed by the message type field - IAM, ACM, ANM, REL, RLC - which defines the contents of the remainder of the message.

Each ISUP message contains a mandatory part that includes fixed-length parameters. Sometimes the mandatory fixed part is comprised only of the message type field.

The mandatory fixed part may be followed by a mandatory variable part and/or an optional part. The optional part contains parameters which are identified by a one-octet parameter code followed by a length indicator ("octets to follow") field.

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图5-ISUP消息格式(ANSI和ITU两种)

图6-ISUP Call建立与释放过程

1. 图7-ISUP IAM格式

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      图8-ISUP ACM 消息格式

      1. 图9-ISUP REL消息格式

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            图10-ISUP RLC消息格式

            1. STP X转发RLC消息给交换机A.
            2. 交换机A收到RLC消息后，置CIC=10的trunk为Idle状态.