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Locating SONET Alarms and Errors

 

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

List of Common SONET Alarms and Errors

Purpose

To check for the most common SONET alarms and errors you can encounter when investigating line problems on a Juniper Networks router.

Action

Table 1 provides links and commands for checking SONET alarms and errors.

Table 1: List of Common SONET Alarms and Errors

Tasks

Command or Action

Displaying SONET Alarms and Errors

show interfaces so-fpc/pic/port extensive

Locating Most Common SONET Alarms and Errors 
  1. Locating Loss of Signal Alarms

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

  1. Locating Alarm Indication Signal Alarms

Downstream from the router, check the path-terminating equipment, section-terminating equipment, and line-terminating equipment for a loss of signal or loss of frame.

  1. Locating Remote Defect Indication Alarms

Upstream from the router, check the path-terminating equipment, section-terminating equipment, and line-terminating equipment for a loss of signal or loss of frame.

  1. Locating Remote Error Indication Line Errors

Upstream from the router, check the line-terminating equipment and path-terminating equipment for an error in the B2 or B3 byte.

  1. Locating Bit Error Rate Alarms

Check the following:

  • Optical fiber

  • Optical transmitter and receiver

  • Clocking

  • Attenuation in the optical signal

  1. Locating Payload Label Mismatch Path Alarms

Check the received and transmitted C2 byte.

  1. Locating Loss of Pointer Path Alarms

Check that both sides of the connection are configured for concatenate mode or nonconcatenate mode.

  1. Locating Unequipped Payload Alarms

Check provisioning with the SONET provider, and if possible, check the configuration of the add/drop multiplexer (ADM).

  1. Locating Phase Lock Loop Alarms

Investigate the timing source, and configure the clocking to external or internal depending on the situation.

Displaying SONET Alarms and Errors

Action

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

Sample Output

user@host> show interfaces so-1/1/1 extensive

Meaning

The sample output shows where you find SONET alarms and errors. SONET alarms and errors fall into three different areas of the output: section, line, and path.

Section, line, and path errors occur over different spans of the SONET network and between different pieces of equipment. Figure 1 shows an example of a SONET network with the section, line, and path areas delimited. Figure 1 also shows the different pieces of equipment that comprise a SONET network:

  • A router, usually a path-terminating equipment (PTE)

  • An add/drop multiplexer (ADM), usually a line-terminating equipment (LTE)

  • A repeater, usually a section-terminating equipment (STE)

Figure 1: Example of a SONET Network
Example of a SONET Network

SONET Section

The SONET section is the connection between two STEs. The STE performs the simple regeneration of the SONET signal to the next SONET equipment span between itself, the PTE, and the ADM. For example, Repeater 1 (STE) regenerates the SONET signal between itself and ADM1, and the section between itself andRouter 1 (PTE). The STE checks to make sure that the incoming SONET frame, arriving from a directly connected neighbor, is good. An STE does not have any knowledge of the rest of the span.

An STE looks at the section overhead bytes of the SONET frame even though it can rewrite the other overhead bytes if an alarm is generated.

SONET Line

The SONET line is the span between two LTEs. The LTE pays particular attention to the line overhead bytes of the SONET frame, can add and remove payload, and has more knowledge of the SONET network than the STEs. The LTE does not do the final processing of the SONET payload as does the PTE. The ADM is an LTE.

SONET Path

The SONET path is the span between two PTEs. The PTE is the final destination where the SONET frame is terminated and the payload it carries is processed. A PTE pays particular attention to the path overhead bytes of the SONET frame.

SONET System Hierarchy

The SONET system hierarchy is comprised of PTEs, LTEs, and STEs. The characteristics of each are as follows:

  • The main role of a PTE is to read the path overhead bytes. However, it also reads the line overhead bytes and the section overhead bytes. Therefore the PTE also plays the role of an LTE and an STE.

  • The main role of an LTE is to read the line overhead bytes. However, it also reads the section overhead bytes. Therefore the LTE also plays the role of an STE.

  • An STE reads only the section overhead bytes of the SONET frame. (See Figure 2.)

Upstream and Downstream

The terms upstream and downstream are used in defining SONET alarms and errors. The terms are meaningful when viewed from the point of view of the failure in the circuit.

For example, in Figure 2 the failure occurs in the section between ADM 1 and ADM 2. The signal is transmitted from Router 2 in the direction of Router 1(from right to left). In this example, Router 1, Repeater 1, and ADM 1 are downstream from the failure. ADM 2, Repeater 2, and Router 2 are upstream from the failure.

Figure 2: Example of an Upstream or Downstream Failure
Example of an Upstream or Downstream
Failure

The failure sends an alarm from ADM 1 to Router 1 in the direction of the signal transmission (downstream). Alarms are also sent from ADM1 to ADM2 and from Router1 to Router2 in the opposite direction of the signal transmission (upstream).

In Figure 3, the failure is also between ADM 1 and ADM 2. However, the signal is transmitted from Router 1 in the direction of Router 2 (from left to right). Router 2, Repeater 2, and ADM 2 are downstream from the failure. ADM 1, Repeater 1, and Router 1 are upstream from the failure.

Figure 3: Another Example of an Upstream or Downstream Failure
Another Example of an Upstream or
Downstream Failure

This failure sends an alarm from ADM 2 to Router 2 in the direction of the signal transmission (downstream). Alarms are also sent from ADM 2 to ADM 1 and from Router 2 to Router 1 in the opposite direction of the signal transmission (upstream).

All diagnostics are from the perspective of the PTE (the Juniper Networks router). Although the exact source of the problem can be difficult to find without having access to the LTE or the STE, you can at least determine from the PTE output whether the problem is remote or local.

Locating Most Common SONET Alarms and Errors

Problem

Description: This information describes the most common SONET alarms and errors you can encounter when investigating line problems on a Juniper Networks router.

Solution

The following alarms and errors are described in this section:

Locating Loss of Signal Alarms

Problem

Description: A loss of signal (LOS) alarm indicates that there is a physical link problem with the connection to the router receive port from the neighboring SONET equipment transmit port.

Solution

To locate the LOS alarm, check the connection between the router port and the first SONET network element. In the example network in Figure 4, the X indicates that there is a connection problem between Repeater 2 and Router 2.

Figure 4: Location of an LOS Alarm in a SONET Network
Location of an LOS Alarm in a SONET
Network

To display SONET alarms and errors, use the following Junos OS CLI operational mode command:

Sample Output

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

Meaning

The sample output shows at the time the command was run, Router 2 continued to be in a LOS alarm state for around 51 seconds.

Locating Alarm Indication Signal Alarms

An alarm indication signal (AIS) is sent downstream to signal an error condition. There are two types of AIS alarms:

  • Alarm indication signal path (AIS-P) is sent by an LTE to a downstream PTE when an LOS or LOF is detected on a upstream SONET section.

  • Alarm indication signal line (AIS-L) is sent by an STE to a downstream LTE when an LOS or LOF is detected on an incoming SONET section.

  1. Example of a Router Receiving Only an AIS-P Alarm

  2. Example of a Router Receiving Both an AIS-L and AIS-P Alarm



Example of a Router Receiving Only an AIS-P Alarm

Problem

Description: Figure 5 shows a router receiving only an AIS-P alarm. The X indicates that the LOS or LOF occurs in the section between Router 1 and Repeater 1.

Solution

All diagnostics are from the perspective of Router 2 (the Juniper Networks router).

Figure 5: Example of a Router Receiving Only an AIS-P Alarm
Example of a Router Receiving Only
an AIS-P Alarm

Meaning

In Figure 5, the progression of events occurring after the failure is as follows:

  1. Repeater 1 detects an LOS or LOF on an incoming SONET section.

  2. Repeater 1 sends an AIS-L downstream to ADM1 (LTE).

  3. ADM 1 sends an AIS-P to Router 2 (PTE).

  4. The only alarm that Router 2 receives is the AIS-P alarm from ADM 1.



Example of a Router Receiving Both an AIS-L and AIS-P Alarm

Problem

Description: Figure 6 shows a router receiving both an IS-L and AIS-P Alarm. The X indicates that the LOS or LOF occurs in the section between ADM 2 and Repeater 2.

Solution

All diagnostics are from the perspective of Router 2 (the Juniper Networks router).

Figure 6: Example of a Router Receiving Both an AIS-L and an AIS-P Alarm
Example of a Router Receiving Both
an AIS-L and an AIS-P Alarm

What It Means

In Figure 6, the progression of events occurring after the failure is as follows:

  1. Repeater 2 detects an LOS or LOF on the incoming section.

  2. Repeater 2 sends an AIS-L and AIS-P downstream to Router 2.

  3. Router 2 receives both an AIS-L and an AIS-P from Repeater 2.

Locating Remote Defect Indication Alarms

A remote defect indication (RDI) is sent upstream to signal an error condition. There are two types of RDI alarms:

  • Remote defect indication line (RDI-L) is sent upstream to a peer LTE when an alarm indication signal line (AIS-L) or low-level defects are detected.

  • Remote defect indication path (RDI-P) is sent upstream to a peer PTE when a defect in the signal, typically an AIS-P, is detected.

  1. Example of a Router Receiving Only an RDI-P Alarm

  2. Example of a Router Receiving Both an RDI-L and RDI-P Alarm



Example of a Router Receiving Only an RDI-P Alarm

Problem

Description: Figure 7 shows a router receiving only an RDI-P Alarm. The X indicates that the LOS or LOF occurs in the section between ADM 1 and ADM 2.

Solution

All diagnostics are from the perspective of Router 2 (the Juniper Networks router).

Figure 7: Example of a Router Receiving Only an RDI-P Alarm
Example of a Router Receiving Only
an RDI-P Alarm

What It Means

In Figure 7, the progression of events occurring after the failure is as follows:

  1. ADM 1 detects an LOS or LOF on an incoming SONET section.

  2. ADM 1 sends an RDI-L to ADM 2.

  3. ADM 1 sends an AIS-P downstream to Router 1.

  4. Router 1 sends an RDI-P upstream to Router 2.

  5. Router 2 only receives an RDI-P alarm.



Example of a Router Receiving Both an RDI-L and RDI-P Alarm

Problem

Description: Figure 8 shows router receiving both an RDI-L and RDI-P Alarm. The X indicates that the LOS occurs in the section between Repeater 2 and Router 2.

Solution

All diagnostics are from the perspective of Router 2 (the Juniper Networks router).

Figure 8: Example of a Router Receiving Both an RDI-L and RDI-P Alarm
Example of a Router Receiving Both
an RDI-L and RDI-P Alarm

Meaning

In Figure 8, the progression of events occurring after the failure is as follows:

  1. Repeater 2 detects an LOS on an incoming section.

  2. Repeater 2 sends an AIS-L downstream to ADM 2.

  3. ADM 2 sends an RDI-L upstream to Router 2.

  4. ADM 2 sends an AIS-P downstream to Router 1.

  5. Router 1 sends an RDI-P upstream to Router 2.

  6. Router 2 receives both RDI-P and RDI-L alarms.

Locating Remote Error Indication Line Errors

A remote error indication (REI) is sent upstream to signal an error condition. There are two types of REI alarms:

  • Remote error indication line (REI-L) is sent to the upstream LTE when errors are detected in the B2 byte.

  • Remote error indication path (REI-P) is sent to the upstream PTE when errors are detected in the B3 byte.

  1. Example of Only an REI-P Counter Incrementing

  2. Example of Both REI-L and REI-P Counters Incrementing



Example of Only an REI-P Counter Incrementing

Problem

Description: Figure 9 shows an REI-P Counter Incrementing. The wavy line indicates that there is a line error in the section between ADM 1 and ADM 2.

Solution

All diagnostics are from the perspective of Router 2 (the Juniper Networks router).

Figure 9: Example of a Router Receiving Only an REI-P Counter Incrementing
Example of a Router Receiving Only
an REI-P Counter Incrementing

Meaning

In Figure 9, the progression of events occurring after the failure is as follows:

  1. ADM 1 detects parity errors in the B1 byte.

  2. ADM 1 sends an REI-L upstream to ADM 2.

  3. Router 1 detects parity errors in the B3 byte.

  4. Router 1 sends an REI-P upstream to Router 2.

  5. Router 2 only sees an REI-P incrementing counter.





Example of Both REI-L and REI-P Counters Incrementing

Problem

Description: Figure 10 shows both REI-L and REI-P Counters Incrementing. The wavy line indicates that there is a line error in the section between Repeater 2 and Router 2.

Solution

All diagnostics are from the perspective of Router 2 (the Juniper Networks router).

Figure 10: Example of a Router Receiving Both An REI-L and REI-P Counter Incrementing
Example of a Router Receiving Both
An REI-L and REI-P Counter Incrementing

Meaning

In Figure 10, the progression of events occurring after the failure is as follows:

  1. Repeater 2 detects some parity errors in the B1 byte from a corrupted SONET frame.

  2. ADM 2 detects parity errors in the B2 byte.

  3. ADM 2 sends an REI-L upstream to Router 2.

  4. Router 1 detects parity errors in the B3 byte.

  5. Router 1 sends back an REI-P upstream to Router 2.

  6. Router 2 sees incrementing REI-L and REI-P errors.

Locating Bit Error Rate Alarms

Problem

Description: Bit error rate (BER) alarms are declared when the number of BIP-B2 errors hits a certain threshold. Depending on the threshold, there are two types of BER alarms. In both cases the interface is taken down.

  • Bit error rate-signal degrade (BERR-SD) is declared when a bit error rate of 10^-6 is reached.

  • Bit error rate-signal failure (BERR-SF) is declared when a bit error rate of 10^-3 is reached.

Solution

To display SONET alarms and errors, use the following Junos OS CLI operational mode command:

Sample Output

The following sample output displays a BERR-SD error:

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

Meaning

Bit error rates can be caused by any of the following situations:

  • Degrading optical fiber

  • Optical transmitter or receiver problems

  • Dirty fiber-optic connector

  • Clocking issues

  • Too much attenuation in the optical signal

  • BIP-B1 and BIP-B3 are not used in the BER alarm calculations

Locating Payload Label Mismatch Path Alarms

Problem

Description: Payload mismatch path (PLM-P; also called signal label mismatch) alarms are reported by PTEs because the SONET byte used to determine the PLM-P alarm is located in the path overhead (the C2 byte). PLM-P alarms occur when the C2 byte received does not match the C2 byte transmitted by the PTE; for example, when the received C2 value is Oxcf, the transmitted C2 value must also be Oxcf.

Note

When the received C2 byte has a value of 0x01—indicating equipped-nonspecific payload—the PTE accepts this value (regardless of the PTE setting) since 0x01 is considered a wildcard value.

Solution

To display SONET alarms and errors, use the following Junos OS CLI operational mode command:

Sample Output

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

Meaning

In the SONET path section of the sample output, the PLM-P counter is incrementing and defective. In the Received SONET overhead and Transmitted SONET overhead sections, the received C2 value is 0x13 and the transmitted C2 value is 0xcf. The C2 byte mismatch has caused a PLM-P alarm.

The C2 byte tells the PTE what kind of information is in the synchronous payload envelope (SPE). For example, when the SPE contains Asynchronous Transfer Mode (ATM) cells, the C2 byte has a value of 0x13. If a Packet over SONET (POS) card is used on the Juniper Networks router, the link does not come up and a PLM-P alarm is raised (since the Juniper Networks router sends 0xcf and receives 0x13). However, if the C2 byte has a value of 0x01, the PTE accepts this value (regardless of what the PTE is set to) since 0x01 is considered a wildcard value.

The SONET specifications have assigned a small handful of values (of the 256 possible binary values), but Juniper Networks routers only use a few of these (Oxcf or Ox16 for POS, Ox13 for ATM, and so on). Table 2 shows the synchronous transport signal (STS) path signal label assignments as described in Issue 3 (Sept. 2000) of the GR-253 CORE.

Table 2: STS Path Signal Label Assignments

Code (Hex)

Content of the STS SPE

00

Unequipped

01

Equipped - Nonspecific Payload

02

VT-Structured STS1 SPE a

03

Locked VT Mode a

04

Asynchronous Mapping for DS3

12

Asynchronous Mapping for DS4NA

13

Mapping for ATM

14

Mapping for DQDB

15

Asynchronous Mapping for FDDI

16

HDLC-over-SONET Mapping

FE

O.181 Test Signal (TSS1 to TSS3) Mapping b

On POS interfaces, Juniper Networks routers by default accept a C2 value of either 0xcf or 0x16. Any other values raise a PLM-P alarm. An important thing to remember is that the C2 byte value of 0x16 is a standardized value (per RFC 2615, G.707, and GR-253) used for POS interfaces. 0xcf is used by default since much SONET equipment still uses this value. If you need to change this byte, use the rfc-2615 option as follows:

This option changes the following values:

Locating Loss of Pointer Path Alarms

Problem

Description: A loss of pointer path (LOP-P) alarm indicates a possible provisioning problem and occurs when the Juniper Networks router cannot determine a valid payload pointer. The Juniper Networks router monitors the H1/H2 bytes, located in the line overhead area. This alarm is usually discovered upon initial provisioning of SONET circuits, and is not generally seen after the router has been deployed in the network for some time.

Solution

To display SONET alarms and errors, use the following Junos OS CLI operational mode command:

Sample Output

user@host> show interfaces so-1/1/1 extensive

Meaning

The sample output shows that an LOP-P alarm occurred for 174 seconds. An LOP-P alarm can occur when the ADM on the other end is configured for nonconcatenate mode, while the Juniper Networks router is configured for concatenate mode (the default setting). In this instance, the pointer word in the required STS frame does not have the concatenation indicator set.

The condition of 8, 9, or 10 consecutive frames without valid pointer values can raise an LOP-P alarm.

Note

Although Juniper Networks routers do not report pointer adjustments, an LOP-P alarm will not occur as long as the pointer adjustments stay within tolerance levels.

Locating Unequipped Payload Alarms

Problem

Description: An unequipped payload (UNEQ-P) alarm indicates a possible provisioning problem and occurs when the Juniper Networks router detects a value of 0x00 in the C2 byte.

Solution

To display SONET alarms and errors, use the following Junos OS CLI operational mode command:

Sample Output

user@host> show interfaces so-1/1/1 extensive

Meaning

The sample output shows that an UNEQ-P alarm occurred within 10 seconds and was declared twice. An UNEQ-P alarm can occur when the ADM on the other end has not provisioned the SPE. An UNEQ-P alarm sets the STS SPE to all zeros when it is provisioned. If the alarm occurs, the problem is probably with the configuration of the ADM. Since the UNEQ-P is not a common alarm reported by Juniper Networks routers, it is a good idea to first check with the SONET provider.

Locating Phase Lock Loop Alarms

Problem

Description: The phase lock loop (PLL) alarm occurs when the PLL cannot lock on to a timing device, and indicates a possible hardware or network timing problem.

Solution

To display SONET alarms and errors, use the following Junos OS CLI operational mode command:

Sample Output

user@host> show interfaces so-1/1/1 extensive

Meaning

The sample output shows a PLL alarm lasting for 26 seconds. You must investigate the timing source to diagnose the problem. The timing source is derived from an incoming SONET circuit (when clock external is configured), or from the onboard Stratum 3 clock (when clock internal is configured). Internal clocking is the default for Juniper Networks routers.

The cause of the problem differs depending on the type of system board on the router. (See Table 3.) For example:

  • On the M20 and M40 Internet router OC48-SM-IR PIC and the M160 Internet router OC192 board, the problem might be caused by the following:

    • An out-of-tolerance clock coming from the far end, if clocking external is configured.

    • An out-of-tolerance clock coming from the far end or a problem with the board being unable to lock on to its internal clock to derive the transmit clock, if clocking internal is configured.

    • On OC3 and OC12 PICs, the PIC not establishing a lock to the onboard clock to derive the outgoing clock.

  • To further diagnose the problem, try the following:

    • Configure clocking to external. If the alarm disappears, the board might not have locked to the internal clock used to derive the outgoing clock.

    • Configure clocking to internal and make sure that a loopback fiber is plugged in. If the PLL alarm persists, it is most likely a hardware problem. However, you may not be able to determine if the direction is on the inbound or outbound side of the board.

Table 3 shows the location of the onboard clock on the various system boards of Juniper Networks routers.

Table 3: Location of the Onboard Clock

Router

System Board

M5, M10, M20, and M40 routers

System Control Board (SCB), System and Switch Board (SSB), Switching and Forwarding Module (SFM), and Single Board Router (SBR)

OC48-SM-IR PIC used on the M20 and M40 routers

Flexible PIC Concentrator (FPC)

M40e and M160 routers

Miscellaneous Control Subsystem (MCS)

T-series routing platforms

SONET Clock Generator (SCG)