7705 SAR Interfaces
130
Interface Configuration Guide
3HE 11011 AAAC TQZZA Edition: 01
MC-APS with TDM access is supported on DS3, DS1, E1, and DS0 (64 kb/s)
channels. TDM SAP-to-SAP with MC-APS is not supported.
With MC-APS, the working circuit of an APS group can be configured on one
7705 SAR node while the protection circuit of the same APS group is configured on
a different 7705 SAR node. The working and protection nodes are connected by an
IP link that establishes an MC-APS signaling path between the nodes.
The working and protection circuit must have compatible configurations, such as the
same speed, framing, and port type. The circuits in APS group in both the working
and protection nodes must also have the same group ID, but they can have different
port descriptions. In order for MC-APS to function correctly, pseudowire redundancy
must be configured on both the working and protection circuits. For more information,
refer to 7705 SAR Services Guide. MC-APS with pseudowire redundancy also
supports Inter-Chassis Backup (ICB); see MC-APS and Inter-Chassis Backup for
more information.
The working and protection nodes can be different platforms, such as a 7705 SAR-8
and a 7705 SAR-18. However, to prevent possible switchover performance issues,
it is recommended to avoid mixing different platform types in the same MC-APS
group. The 7705 SAR does not enforce configuration consistency between the
working circuit and the protection circuit. Additionally, no service or network-specific
configuration data is signaled or synchronized between the two routers.
An MC-APS signaling path is established using the IP link between the two routers
by matching APS group IDs. A heartbeat protocol can also be used to add
robustness. The signaling path verifies that one router is configured as the working
circuit and the other is configured as the protection circuit. In case of a mismatch, an
incompatible neighbor trap is generated. The protection router uses K1/K2 byte data,
member circuit status, and APS Tools Commands to select the working circuit.
Changes in working circuit status are sent across the MC-APS signaling link from the
working router to keep the protection router synchronized. External requests such as
lockout, force, and manual switches are allowed only on the APS group with the
protection circuit.
Figure 13 shows an MC-APS group with physical port, adapter card, and node
protection. Figure 14 shows a packet network using MC-APS.
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