Understanding TDM Port Alarms

The alarm events from the TDM port that are detected and the alarm response transmitted on the TDM port are listed in the following section.

The alarm response on the TDM port/time-slot(s) depends on the port or time-slot(s) configuration state. The port or time-slot is said to be in disconnected or in idle configuration state when they are not added to a TDM service. The port or time-slot(s) are said to be connected if they are part of a TDM service. In idle state, depending on the framing configuration on the port, the alarm response would vary. The alarms generated and the alarm events detected are logged.

TDM Port Alarms in Unframed mode

AIS Alarm Generation

The TDM ports generate an Alarm Indication Signal (AIS) alarm by default on the ports that are not connected to a service. On ports that are connected to a service, the AIS alarm is generated to indicate pseudowire faults.

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AIS Alarm
../Graphics/EX_ports_AIS_Alarm.svg

E4G switches do not detect AIS alarm events in unframed mode of operation.

LOS Alarm Generation

The TDM ports generate Loss of Signal (LOS) alarm on the ports that are administratively disabled. The alarm is cleared when the port is enabled.

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LOS Alarm Generation
../Graphics/EX_ports_LOS_Alarm_Generation.svg

LOS Alarm Response

The TDM ports detect a Loss of Signal alarm event. No specific data is played out as a response for this alarm event. However, when the port is not a part of TDM service, the preset idle pattern of all ones (or AIS) is played out. If the port is connected to a TDM service bound to a CES pseudowire, the TDM data from the remote end of the CES pseudo-wire, is played out, facilitating the tunneling of alarm event response from the remote TDM CE node.

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LOS Alarm Response
../Graphics/EX_ports_LOS_Alarm_Response.svg

TDM Port Alarms in Framed Mode

Default Line State

The TDM ports send out a preset idle pattern of 0xFF on all timeslot(s) that carry TDM data. If signaling multiframe is configured on the TDM port (mf in E1 hierarchy and d4 or esf in T1 hierarchy), a configurable idle code is played out on the signaling channel/bits.

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Default Line State
../Graphics/EX_ports_Default_Line_State.svg

However, the idle pattern is not played out on certain special timeslots, as listed in the following table below.

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Idle Pattern on Timeslots

E1 Hierarchy
Timeslot - 1 Carries frame alignment signal, CRC and remote alarm information.
Timeslot - 16 (in frame 1/16) Carries signaling multiframe alignment signal, spare bits and multiframe alarms. Applicable only if port handles signaling multiframe.
T1 Hierarchy
F-bits Carries framing alignment signal information. In case of Extended Super Frame formats, carries data link and CRC-6 information.

Note that the idle pattern playout does not indicate the presence or generation of alarms and is presented here for information purposes.

LOS/LOF/AIS Alarm Response

The Loss of Signal, Loss of Frame and Alarm Indication Signal events are detected and a Remote Alarm Indication is played out as alarm response. The Framed modes in E1 and T1 hierarchy have specific bits in the frame formats for indicating the remote TDM CE interface about the faults.
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LOS/LOF/AIS Alarm Response
../Graphics/EX_ports_LOS_LOF_AIS_Alarm_Response.svg
The following framing types configured on the CE node and on the E4G node are considered as incompatible in the E4G node. This would result in detection of Loss of Frame alarm. The Loss of Signaling Multiframe and the Loss of CRC Multiframe are detected as Loss of Frame alarm events.
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Framing Types

Hierarchy Framing in E4G node Framing in Remote CE node

E1

Basic

Unframed

Signaling multiframe

Unframed

Basic

CRC4 enabled

CRC4 disabled

T1

Super frame (D4)

Unframed

Extended super frame (ESF)

Extended super frame (ESF)

Unframed

Super frame (D4)

LOS Alarm Generation

The TDM ports generate Loss of Signal alarm on the ports that are administratively disabled. The alarm is cleared when the port is enabled.

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LOS Alarm Generation
../Graphics/EX_ports_LOS_Alarm_Generation.svg