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Locate T3 Alarms and Errors

 

This section includes the following information to assist you when troubleshooting T3 interfaces:

Checklist of Common T3 Alarms and Errors

Purpose

To check T3 alarms and errors,

Action

Table 1 provides the links and commands for checking T3 alarms and errors.

Table 1: Checklist of Common T3 Alarms and Errors

Tasks

Command or Action

Display T3 Alarms and Errors

show interfaces t3-fpc/pic/port extensive

Locate Most Common T3 Alarms and Errors 
  1. Locate Loss of Signal and Loss of Frame Alarms

Check the connection between the router port and the first T3 network element.

  1. Locate Alarm Indication Signal Alarms

Check the T3 network element connected to the T3 interface.

  1. Locate an Incoming Yellow Alarm

Check the cable between the T3 interface and the directly connected T3 network element.

  1. Locate IDLE on a T3 Interface

Check that the line is provisioned for service.

Note

T3 is a general term used to refer to the transmission of 44.736-Mbps digital circuits over any media. T3 can be transported over copper, fiber, or radio. DS3 is the term for the electrical signal found at the metallic interface for this circuit where most of the testing is performed.

Display T3 Alarms and Errors

Purpose

To display T3 alarms and errors, use the following Junos OS command-line interface (CLI) operational mode command:

Action

Sample Output

user@host> show interfaces t3-1/0/0 extensive

Meaning

The sample output shows active alarms and active defects. When a major error (such as an alarm indication signal [AIS]) is seen for a few consecutive frames, a defect is declared within 1 second from detection. At the defect level, the interface is taken down and routing protocols are immediately notified (this is the default). In most cases, when a defect persists for 2.5 second plus or minus 0.5 seconds, an alarm is declared.

Notification messages are logged at the alarm level. Depending on the type of T3 alarm, you can configure the craft panel to display the red or yellow alarm LED and simultaneously have the alarm relay activate a physically connected device (such as a bell).

Table 2 lists the T3 media-specific alarms or errors that can render the interface unable to pass packets.

Table 2: T3 Interface Error Counter Definitions

T3 Alarm or Error

Definition

AIS

Alarm indication signal

EXZ

Excessive zeros

FERF

Far-end failures

IDLE

Idle code detected

LCV

Line code violation

LOS

Loss of signal

LOF

Loss of frame

YLW

Remote defect indication (yellow alarm)

PLL

Phase locked loop

Locate Most Common T3 Alarms and Errors

The following alarms and errors are described in this chapter:

  1. Locate Loss of Signal and Loss of Frame Alarms

  2. Locate Alarm Indication Signal Alarms

  3. Locate an Incoming Yellow Alarm

  4. Locate IDLE on a T3 Interface



Locate Loss of Signal and Loss of Frame Alarms

Problem

Description: A loss of signal (LOS) or loss of frame (LOF) alarm indicates that a signal could not be detected at the T3 interface.

Solution

To locate the LOS or LOF alarm, check the connection between the router port and the first T3 network element. In the example network in Figure 1, the X indicates that there is a connection problem between Router 2 and the nearest T3 network element.

Figure 1: Location of an LOS or LOF Alarm in a T3 Network
Location of an LOS or LOF Alarm in
a T3 Network
Note

Tx represents the transmit port and Rx represents the receive port.

Sample Output

user@router2> show interfaces t3-1/1/1 extensive

Meaning

The sample output shows that Router 2 (Rx) detected a cumulative LOS and LOF for 273 seconds. The defect was declared twice during that time.



Locate Alarm Indication Signal Alarms

Problem

Description: An alarm indication signal (AIS) is a valid framed signal with payload containing a repeating 1010 pattern. An AIS alarm indicates a problem with the line upstream from the T3 network element connected to the T3 interface.

Solution

To locate the AIS alarm, have the carrier check the T3 network element connected to the T3 interface and trace the problem.

All diagnostics are from the perspective of Router 2 (the Juniper Networks router). Figure 2 illustrates the location of an AIS alarm in a T3 network.

Figure 2: Location of an AIS Alarm in a T3 Network
Location of an AIS Alarm in a T3 Network

Meaning

In Figure 2, the X indicates that there is an LOS or LOF alarm between the repeater and the Tx T3 multiplexer. An AIS alarm is sent from the repeater to Router 2.



Locate an Incoming Yellow Alarm

Problem

Description: An incoming yellow alarm indicates that the T3 network element connected to the T3 interface has a problem with the signal it is receiving from the T3 interface.

Solution

To locate the yellow alarm, check the cable between the T3 interface and the directly connected T3 network element.

All diagnostics are from the perspective of Router 2. Figure 3 illustrates the location of a yellow alarm in a T3 network.

Figure 3: Location of a Yellow Alarm in a T3 Network
Location of a Yellow Alarm in a T3
Network

Meaning

The T3 multiplexer detects an LOS or LOF on its connection from Router 2 and sends a yellow (YLW) alarm to Router 2.



Locate IDLE on a T3 Interface

Problem

Description: The T3 (DS3) IDLE signal is a validly framed DS3 signal with a payload consisting of a repeated 1100 signal. IDLE indicates that the line has not been provisioned for service.

Solution

Have the carrier make sure that the line is provisioned for service.

Sample Output

user@router2> show interfaces t3-1/1/0

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