Locate Payload Label Mismatch Path Alarms

Purpose

Payload mismatch path (PLM-P) 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, the PTE accepts this value (regardless of the PTE setting) since 0x01 is considered a wildcard value.

Action

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

user@host> show interfaces so-fpc/pic/port extensive

Sample Output

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

[...Output truncated...]

SONET alarms   : PLM-P

SONET defects  : PLM-P

  [...Output truncated...]

SONET path:

    BIP-B3                    0            0

    REI-P                     0            0

    LOP-P                     0            0  OK

    AIS-P                     0            0  OK

    RDI-P                     2            1  OK

    UNEQ-P                    0            0  OK

    PLM-P                    96            1  Defect Active

    ES-P                      0

    SES-P                     0

    UAS-P                     0

    ES-PFE                    2

    SES-PFE                   2

    UAS-PFE                   0

  Received SONET overhead:

    F1      : 0x00, J0      : 0x00, K1      : 0x00, K2      : 0x00

    S1      : 0x00, C2      : 0x13, C2(cmp) : 0xcf, F2      : 0x00

    Z3      : 0x00, Z4      : 0x00, S1(cmp) : 0x00, V5      : 0x00

    V5(cmp) : 0x00

  Transmitted SONET overhead:

    F1      : 0x00, J0      : 0x01, K1      : 0x00, K2      : 0x00

    S1      : 0x00, C2      : 0xcf, F2      : 0x00, Z3      : 0x00

    Z4      : 0x00, V5      : 0x00

What It Means

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 32 shows the synchronous transport signal (STS) path signal label assignments as described in Issue 3 (Sept. 2000) of the GR-253 CORE.

Table 32: STS Path Signal Label Assignments

Code (Hex)	Content of the STS SPE
00	Unequipped
01	Equipped - Nonspecific Payload
02	VT-Structured STS-1 SPE a
03	Locked VT Mode a
04	Asynchronous Mapping for DS-3
12	Asynchronous Mapping for DS-4NA
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:

user@host# set interface so-fpc/pic/port sonet-options rfc-2615

This option changes the following values:

    C2 byte 22 (0x16)

    FCS 32

    payload-scrambling (this was already the default)