Juniper JUNOS 10.1 - CONFIGURATION GUIDE 1-2010 Configuration Manual page 981

For the STM1 PIC, you can configure virtual tributary mapping by including the
vtmapping
level:
Table 42 on page 481 lists the KLM mappings used by the Channelized STM1-to-E1
PIC interfaces.
Configuring APS and MSP
Automatic Protection Switching (APS) is used by SONET add/drop multiplexers (ADMs)
to protect against circuit failures. The JUNOS implementation of APS allows you to
protect against circuit failures between an ADM and one or more routers, and between
multiple interfaces in the same router. When a circuit or router fails, a backup
immediately takes over.
NOTE: For SDH interfaces, the JUNOS Software supports multiplex section protection
(MSP). You configure MSP with the same CLI statements you use to configure APS.
The JUNOS Software supports APS 1+1 switching, either revertive or nonrevertive
mode, and bidirectional mode only (although you can configure interoperation with
line-terminating equipment [LTE] provisioned for unidirectional mode). The JUNOS
Software does not transmit identical data on the working and protect circuits, as the
APS specification requires for 1+1 switching, but this causes no operational impact.
For DS3 channels on a channelized OC12 interface, you can configure APS on channel
0 only. If you configure APS on channels 1 through 11, it is ignored.
With APS and MSP, you configure two circuits, a working circuit and a protect circuit.
Normally, traffic is carried on the working circuit (that is, the working circuit is the
active circuit), and the protect circuit is disabled. If the working circuit fails or
degrades, or if the working router fails, the ADM and the protect router switch the
traffic to the protect circuit, and the protect circuit becomes the active circuit.
To configure APS or MSP, you configure a working and a protect circuit, as shown
in Figure 76 on page 912. To protect against a router failure, you connect two routers
to the ADM, configuring one of them as the working router and the second as the
protect router. To protect against a PIC or FPC failure, you connect one router to the
ADM through both the working and protect circuits, configuring one of the PICs or
FPCs as the working circuit and the second as the protect circuit.
[edit interfaces cau4-fpc/pic/port sonet-options]
vtmapping (klm | itu-t);
statement at the
[edit chassis fpc slot-number pic pic-number]
vtmapping (klm | itu-t);
Chapter 61: Configuring SONET/SDH Interfaces
[edit chassis fpc slot-number pic pic-number]
Configuring SONET/SDH Physical Interface Properties
hierarchy
911