User:Dweissnj/Protection Switch

Protection Switch or Automatic Protection Switch (APS) is designed to help build fault tolerant communications circuits by allowing two diverse routes to act redundantly of each other. The switch detects failures in the active communication circuit and automatically re-routes traffic to the alternate path.

Protection switches are often described by the communications circuit they are designed to protect as in T1 Protection Switch, SONET Protection Switch, Serial Protection Switch, etc.

1:1 Protection
1:1 protection switching switches both the transmit and receive paths of a circuit between redundant facilities. Failure detection is determined by the receive channel, based on pre-programmed parameters. By auto switching at one end, the failure is detected at the other end, causing switching at that end as well. < >

1+1 Protection
1+1 protection switching uses both active and standby channels to broadcast data to the other end of the circuit. The receive end selects which of the two broadcasts to use as the active data, based on pre-programmed quality conditions. With 1+1 switching, bidirectional traffic can be send on different paths, if switch setup allows for this.

1:n Protection
In 1:n switching, one standby facility is available to replace some number (n) of normal paths. 1:n switching the standby facility is allocated to the first failed normal path, or based on some priority scheme.