Extreme Networks PoS Installation And User Manual page 29

Automatic Protection Switching
Automatic Protection Switching, or APS, is a physical-layer resiliency feature specified
in the SONET standards. Multiplex Section Protection, or MSP, is the APS equivalent in
the SDH standard, which is also supported by the PoS module. Throughout this guide,
the terms APS and Automatic Protection Switching are used to refer to the protection
switching features of both standards.
Of the various protection switching modes specified in the SONET/SDH standards, the
BlackDiamond 6800 series switches use the linear 1+1 architecture to protect tributary
SONET lines. In the linear 1+1 architecture, there is one protection line for each working
line. If the working line fails, traffic is automatically switched to the protection line. You
can also control whether traffic switched to the protection line is automatically switched
back to the working line when it is restored to service.
The Extreme Networks implementation supports network configurations where:
• Working and protection lines are terminated in the same PoS module.
• Working and protection lines are terminated in different PoS modules residing in the
same BlackDiamond 6800 series switch.
• Working and protection lines are terminated in different PoS modules residing in
different BlackDiamond 6800 series switches.
Packet Over SONET Module Installation and User Guide
About the PoS Modules
1-13