Alcatel-Lucent 7750 SR OS - Figure 11: APS Working and Protection Circuit Example

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Page 76 7750 SR OS Interface Configuration Guide
Protection of Upper Layer Protocols and Services
APS prevents upper layer protocols and services from being affected by the failure of the active
circuit.
The following example with figures and description illustrate how services are protected during a
single-chassis APS swithover.
Figure 11: APS Working and Protection Circuit Example
Figure 11 is an example in which the APS working circuit is connected to IOM-1 / MDA-1 and the
protection circuit is connected to IOM-2 / MDA-1. In this example, assume that the working
circuit is currently used to transmit and receive data.
Switchover Process for Transmitted Data
For packets arriving on all interfaces that need to be transmitted over APS protected interfaces, the
next hop associated with all these interfaces are programmed in all Flexible Fast-Path complexes
in each MDA with a logical next-hop index. This next hop-index identifies the actual next-hop
information used to direct traffic to the APS working circuit on IOM-1 / MDA-1.
All Flexible Fast-Path complexes in each MDA are also programmed with next hop information
used to direct traffic to the APS protect circuit on IOM-2 / MDA-1. When the transmitted data
needs to be switched from the working to the protect circuit, only the relevant next hop indexes
IOM-CPU
MDA-1
Flexible FastPath
Complex
MDA-2
Flexible FastPath
Complex
IOM-CPU
APS-CTL
Services
IOM-CPU
APS Working
MDA-1
Flexible FastPath
Complex
MDA-2
Flexible FastPath
Complex
MDA-1
Flexible FastPath
Complex
MDA-2
Flexible FastPath
Complex
APS Protect
IOM-1
IOM-2
IOM-3
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