ABSTRACT
For fault tolerance, an emerging APON specification will enable redundancy in the network. The APON will work similar to SONET's dual-ring configuration: Each ONT will connect to two OLTs. Two protection scenarios are then possible. One-to-one protection lets the transmitter choose which line to use, leaving the other untouched. Providers could use this configuration to put Unspecified Bit Rate (UBR) traffic on the backup line, with the understanding that a failure could cause the traffic to be bumped from the network.
