APS and MSP

E-series routers support Automatic Protection Switching (APS) and Multiplex Section Protection (MSP) on selected I/O modules that provide SONET/SDH connections. This feature provides a redundant connection if a primary SONET/SDH connection fails.

For a list of I/O modules that support APS/MSP, see ERX Module Guide, Appendix A, Module Protocol Support.

Note: The E120 router and the E320 router do not support APS/MSP.

I/O modules that support APS/MSP have some ports designated for primary operation and other ports designated for redundant operation. For APS/MSP to work correctly, you must provide connections from a primary port and a corresponding redundant port to the remote device. The remote device must also support APS/MSP.

You configure a working interface on the primary port and a corresponding protect interface on the redundant port of the I/O module. The working interface provides the primary connection, and the protect interface provides the redundant connection.

The router sends and receives data through both interfaces; however, in normal operation, only the signal on the working interface is used. If the signal on the primary interface fails, the router can use the signal on the protect interface. The process by which the router switches to the protect interface is called switchover.

When you configure APS/MSP, you must assign a working interface and a corresponding protect interface to a unique group. This group establishes the relationship between the interfaces. Within the group, each interface is identified by an APS/MSP channel number. For information about identifying the channel number, see Numbering Scheme.

You must pair a working interface and its corresponding protect interface on an I/O module to form a valid linear APS 1+1 group. For example, on an I/O module that provides four working (primary) ports and four protect (redundant) ports, the working interface ports are numbered 0–3, and the protect interface ports are numbered 4–7. Table 7 lists the pairings required to form four valid APS 1+1 groups on this I/O module. Each working/protect port pair (for example, port 0 and port 4) forms a valid APS 1+1 group.

Table 7: Sample Pairings for Valid APS/MSP Groups

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