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Circuit Status Query

Overview

The Circuit Query feature allows the host to query the status of a single circuit or a range of circuits using the PPL Event Request message. A Circuit Query Message (CQM) is sent to the remote CSP, which returns a Circuit Query Response (CQR) message containing the status of all the circuits. The local and remote circuit status for each circuit is sent to the host in a PPL Event Indication message.

Recovery Action for ANSI Only

For ANSI only, if the circuit is found in the invalid state by the CQM, a recovery action is taken by CQS. The host can configure the recovery action taken by the CSP using the PPL Configuration Bytes of the CQS component. Recovery actions taken by the CSP are as defined by the ANSI-ISUP T1.113 specification.

Implementation

When a CQM request is received from the host, the CSP sends a CQM message to the network. When a CQR is received from the network, the CSP sends a PPL Event Indication message to the host with an SS7 Data Parameters ICB (0x22) containing the status of the local and remote circuits. If the CQR indicates a maintenance state, the CSP takes appropriate action based on Table 2 in ANSI T1.113.4.

If a CQR is not received before the expiration of T28 (default =10 seconds), a PPL Event Indication of 0x01 is sent to the host indicating the error.

Call Flows

This call flow shows a CQM request from the host and a CQR response from the network.

Status Values

Local and Remote Status

The local and remote status are reported to the host in an SS7 Data Parameters ICB (0x22) in a PPL Event Indication message, where:

Data[0] | Local Status
Data[1] | Remote Status

One of the following values is reported for both Data[0] and Data[1].

0x00 | Transient

Maintenance States

0x01 | Spare (no interpretation)
0x02 | Spare (no interpretation)
0x03 | Unequipped
0x04 | Incoming Circuit Busy, Active
0x05 | Incoming Circuit Busy, Locally Blocked
0x06 | Incoming Circuit Busy, Remotely Blocked
0x07 | Incoming Circuit Busy, Locally and Remotely Blocked
0x08 | Outgoing Circuit Busy, Active

Call Processing States

0x09 | Outgoing Circuit Busy, Locally Blocked
0x0A | Outgoing Circuit Busy, Remotely Blocked
0x0B | Outgoing Circuit Busy, Locally and Remotely Blocked
0x0C | Idle
0x0D | Idle, Locally Blocked
0x0E | Idle, Remotely Blocked
0x0F | Idle, Locally and Remotely Blocked
0x10 to 0xFF | Spare

See Programmable Protocol Language.
A condition that, when met, drives a state machine from one state to another. A condition that drives a Component out of its current state by invoking an associated primitive.
American National Standards Institute. ANSI administers and coordinates the U.S. voluntary standardization and conformity assessment system for the
telecommunications industry. More details on these standards may be
viewed at www.ansi.org.
See Integrated Services Digital Network User Part.
Digital communications link - voice, data, and video at a 1.544 Mbps rate (24 64 Kbps channels)
See Signaling System Number Seven.
See Information Control Block.
ISDN User Part (ISUP)