An ATM interface reports detected C-bit parity errors back to the source via a far-end block error (FEBE). The M-subframe uses C bits in a format called C-bit parity, which copies the result of the P bits at the source and checks the result at the destination.
The DS-3 M-frame uses P bits to check the line parity. Any other value is interpreted as zero errors. The legal range for the 4-bit field is between 00, representing zero to eight errors. This specific setup of error reporting is what causes the confusion between many technicians trying to perform repairs.Īn error detected by extracting the 4-bit FEBE field from the path status byte (G1). So, errors are generated on the incoming side of the loop, the device terminating that end picks up the errors, and transmits a 'FEBE errors' message on the outgoing side. The terminating device then sends the 'FEBE' error signal outbound to alert further devices there were problems. The errors are being generated by a device in the central office, and being detected by the terminating device (a NID, M13 Mux or router). If you have a DS3 running from New York to Atlanta, and there's a problem within one of the central offices in Virginia. Network monitoring equipment located anywhere along the path then measures these FEBEs in each direction to gauge the quality of the circuit while in service. If an error is detected on the incoming DS3, the terminating elements transmit a FEBE bit on the outgoing direction of the DS3. REI or FEBE errors are mostly seen on DS3 circuits, however they are known to be present on other types (SONET/T1s etc.).Įach terminating device ( router or otherwise) monitors the incoming signal for CP-bit path errors. It indicates to the transmitting node that the receiver has detected a block error. Remote error indication ( REI) or formerly far end block error (FEBE) is an alarm signal used in synchronous optical networking (SONET). ( Learn how and when to remove this template message) WikiProject Telecommunications may be able to help recruit an expert. Please add a reason or a talk parameter to this template to explain the issue with the article. This article needs attention from an expert in Telecommunications.
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