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

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 6, the X indicates that there is a connection problem between Router 2 and the nearest T3 network element.

Figure 6: 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

[... Output truncated...]
 Active alarms  : LOF, LOS
  Active defects : LOF, LOS
   DS3 Media:            Seconds        Count  State
    PLL Lock                  0            0  OK
    Reframing               273            2  Defect Active
    AIS                       0            0  OK
    LOF                     273            2  Defect Active
    LOS                     273            2  Defect Active
[...Output truncated...]

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

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 7 illustrates the location of an AIS alarm in a T3 network.

Figure 7: Location of an AIS Alarm in a T3 Network

Meaning

In Figure 7, 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

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 8 illustrates the location of a yellow alarm in a T3 network.

Figure 8: 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

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

Physical interface: t3-1/1/0, Enabled, Physical link is Down
   Interface index: 13, SNMP ifIndex: 21
   Link-level type: PPP, MTU: 4474, Clocking: Internal
   Speed: T3, Loopback: None, CRC: 16, Mode: C/Bit parity
   Device flags   : Present Running Down
   Interface flags: Hardware-Down Point-To-Point SNMP-Traps
   Link flags     : Keepalives
   Input rate     : 0 bps (0 pps), Output rate: 0 bps (0 pps)
   Active alarms  : IDLE
   Active defects : IDLE