PDF user manual for CopperEdge 150

2$0)DXOW0DQDJHPHQWIRU$70:$1/LQNVThe OAM fault management function on the CE150 allows systemadministrators to monitor basic conditions for transmittingand receiving on end-to-end ATM WAN links, made up of manysegments. It also allows them to locate a break on one of thesegments.7UDQVPLWWLQJ5HFHLYLQJ)DXOW0HVVDJHVWhen a fault occurs on upstream or downstream segments,OAM fault management software installed on switching or routingdevices on the segments sends out Alarm Indication Signal(AIS) messages. The messages travel to devices (such asDSLAMs and routers) at opposite ends of the link. In response,the DSLAM and routers send out Remote Defect Indication(RDI) messages.The diagrams below show two possible scenarios: first, a faulton both the upstream and downstream parts of a connection;second, a fault on the upstream part of a connection.Node ANode B Node C Node DRDIAISAISRDIATM ConnectionEnd PointA Break on the Upstream and Downstream ConnectionsATM ConnectionEnd PointIn the diagram above, the devices at Node B and Node C sensethe fault between them. The device at Node B sends an AIS messageto the device at the endpoint on Node A. Similarly, the deviceat node C sends an AIS message to the device on theendpoint at Node D. Each device on the endpoint sends an RDImessage to the device at the other endpoint, notifying it of thefault.But, neither message gets through the fault between Node Band Node C. Neither message needs to. The devices at bothends of the link know the connection is broken because of theAIS messages they have already received. Manual loopbacktesting can begin from the devices at either end to determinethe exact location of the fault.&RSSHU(GJH,QVWDOODWLRQDQG2SHUDWLQJ*XLGH