System for redundancy in ethernet passive optical networks (epons)

Abstract

A system for redundancy in Ethernet passive optical networks (EPONs) facilitates fast recovery from failure (less than 50 msec), path redundancy of the fiber optic network, and location redundancy of the OLTs. An optical networking unit (ONU) in a normal state monitors input communications, and when the input communications are quiet for a predetermined minimum length of time, the ONU transitions to a lenient state in which: the ONU accepts old and new security keys; upon receiving a packet: the ONU updates an ONU timestamp based on the packet's timestamp; and the ONU transitions to the normal state of operation. While the ONU is in the lenient state if a packet is not received for a predetermined given length of time the ONU transitions to a deregistered state. In this system, main and standby OLTs do not require synchronization of security parameters or synchronization for differences in fiber lengths.

What is claimed is: 
     
         1 . A system for redundancy in Ethernet passive optical networks (EPONs) comprising:
 (a) at least two optical line transmission equipment (OLT) wherein a first OLT is deployed at a first location and a second OLT is deployed at a second location;   (b) at least one optical networking unit (ONU); and   (c) a passive optical splitter for exchanging packets between the OLTs and said at least one ONU,   wherein the OLTs are configured to transmit a switchover signal and the OLTs are configured to receive said switchover signal from other OLTs.   
     
     
         2 . The system of  claim 1  wherein when an OLT receives said switchover signal, said OLT executes a switchover process. 
     
     
         3 . The system of  claim 2  wherein said. OLT is configured such that after said switchover process IGMP and MAC address table information is determined. 
     
     
         4 . The system of  claim 1  further comprising one or more hosts configured to transmit a switchover signal, and wherein the OLTs are configured to receive a switchover signal from said one or more hosts. 
     
     
         5 . The system of  claim 4  wherein when an OLT receives said switchover signal, said OLT executes a switchover process. 
     
     
         6 . The system of  claim 1  further comprising one or more network switches operationally connected to the OLTs, said one or more network switches configured to interface between the OLTs and a network. 
     
     
         7 . The system of  claim 1  wherein the OLTs are configured to maintain independently statistic counters for monitoring and troubleshooting. 
     
     
         8 . The system of  claim 1  wherein said system is configured to switch from using said first OLT to using said second OLT in less than 50 msec (milliseconds). 
     
     
         9 . A system for redundancy in Ethernet passive optical networks (EPONs) comprising:
 (a) at least two optical line transmission equipment (OLT) wherein a first OLT is deployed at a first location and a second OLT is deployed at a second location;   (b) at least one optical networking unit (ONU); and   (c) a passive optical splitter for exchanging packets between the OLTs and the at least one ONU.   wherein said system is configured to recalculate the round trip time (RTT) after OLT switchover while said at least one ONU is still registered.   
     
     
         10 . The system of  claim 9  wherein the OLTs are configured to transmit a switchover signal and the OLTs are configured to receive a switchover signal from other OLTs. 
     
     
         11 . The system of  claim 10  wherein when an OLT receives said switchover signal, said OLT executes a switchover process. 
     
     
         12 . The system of  claim 11  wherein said OLT is configured such that after said switchover process IGMP and MAC address table information is determined. 
     
     
         13 . The system of  claim 9  further comprising one or more hosts configured to transmit a switchover signal, and wherein the OLTs are configured to receive a switchover signal from said one or more hosts. 
     
     
         14 . The system of  claim 13  wherein when an OLT receives said switchover signal, said OLT executes a switchover process. 
     
     
         15 . The system of  claim 9  further comprising one or more network switches operationally connected to the OLTs, said one or more network switches configured to interface between the OLTs and a network. 
     
     
         16 . The system of  claim 9  wherein the OLTs are configured to maintain independently statistic counters for monitoring and troubleshooting.