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Locate T1 Alarms and Errors

 

This section includes the following information to assist you when troubleshooting T1 interfaces:

Checklist for T1 Alarms and Errors

Purpose

To check T1 alarms and errors.

Action

Table 1 provides the links and commands for checking T1 alarms and errors.

Table 1: Checklist for T1 Alarms and Errors

Tasks

Command or Action

Display T1 Alarms and Errors

show interfaces t1-fpc/pic/port extensive

Locate Most Common T1 Alarms and Errors 
  1. Locate Loss of Signal and Loss of Frame Alarms

Check the connection between the router port and the first T1 network element.

  1. Locate Alarm Indication Signal Alarms

Check the T1 network element connected to the T1 interface.

  1. Locate an Incoming Yellow Alarm

Check the cable between the T1 interface and the directly connected T1 network element.

Display T1 Alarms and Errors

Purpose

To display T1 alarms and errors, use the following Junos OS command-line interface (CLI) operational mode command:

Action

Sample Output

user@host> show interfaces t1-1/1/0 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 seconds plus or minus 0.5 seconds, an alarm is declared.

Notification messages are logged at the alarm level. Depending on the type of T1 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 T1 media-specific alarms or defects that can render the interface unable to pass packets.

Table 2: T1 Interface Alarms and Error Definitions

T1 Alarm or Error

Definitions

SEF

Severely errored frame

BEE

Block error event

AIS

Alarm indication signal (blue alarm)

LOF

Loss of frame

LOS

Loss of signal

YLW

Yellow alarm

BPV

Bipolar violation

EXZ

Excessive zeros

LCV

Line code violation

PCV

Path code violation

CS

Controlled slip

LES

Line errored seconds

ES

Errored seconds

SES

Severely errored seconds

SEFS

Severely errored frame seconds

BES

Bursty errored seconds

UAS

Unavailable seconds

Locate Most Common T1 Alarms and Errors

To locate common alarms and errors, follow these steps:

  1. Locate Loss of Signal and Loss of Frame Alarms

  2. Locate Alarm Indication Signal Alarms

  3. Locate an Incoming Yellow Alarm



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 T1 interface.

Solution

To locate the LOS or LOF alarm, check the connection between the router port and the first T1 network element. In the example network in Figure 1, the X indicates that there is a connection problem between Router2 and the nearest T1 network element.

Figure 1: Location of an LOS or LOF Alarm in a T1 Network
Location of an LOS or LOF Alarm in
a T1 Network
Note

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

Sample Output

user@router2> show interfaces t1-1/1/1 extensive

Meaning

The sample output shows that Router 2 (Rx) detected a cumulative LOS and LOF alarm for 32 seconds.



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 T1 network element connected to the T1 interface.

Solution

To locate the AIS alarm, have the carrier check the T1 network element connected to the T1 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 T1 network.

Figure 2: Location of an AIS Alarm in a T1 Network
Location of an AIS Alarm in a T1 Network

Meaning

In Figure 2, the X indicates that there is an LOS or LOF alarm between the repeater and the Tx T1 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 T1 network element connected to the T1 interface has a problem with the signal it is receiving from the T1 interface.

Solution

To locate the yellow alarm, check the cable between the T1 interface and the directly connected T1 network element.

All diagnostics are from the perspective of Router 2. Figure 3 illustrates the location of a yellow alarm in a T1 network.

Figure 3: Location of a Yellow Alarm in a T1 Network
Location of a Yellow Alarm in a T1
Network

Meaning

In Figure 3, the T1 multiplexer detects an LOS or LOF alarm on its connection from Router 2 and sends a yellow (YLW) alarm to Router 2.

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