Each OC3 performance monitoring statistic is retained for the current 15-minute interval, a history of the last 32 15-minute intervals (8 hours), the current 24-hour period (starting and ending at midnight GMT), and the previous 24-hour period. Along with statistics, it is also possible to verify the elapsed time in the current 15-minute interval and the amount of 15-minute intervals currently stored (this is relevant only during the first 8 hours of operation). The following statistics are retained:
Note Line Errored Seconds, Line Severely Errored Seconds, and Line Coding Violations are not
supported directly on the MGX 8240 because the MGX 8240 does not terminate the DS1
line. This means that no performance monitoring statistics can be supported when the DS1
is not set for ESF or SF framing. Since the only means of monitoring far end performance
statistics is through the ESF Facilities Data Link, far end statistics can only be supported
when ESF framing is selected.
The following statistics are retained:
Errored Seconds (applies only to ESF and SF framing types)
Severely Errored Seconds (applies only to ESF and SF framing types)
Severely Errored Framing (applies only to ESF and SF framing types)
Unavailable Seconds (applies only to ESF and SF framing types)
Path Coding Violations (applies only to ESF and SF framing types)
Alarm Indication Signal Seconds (applies only to ESF and SF framing types)
Far End Errored Seconds (applies only to ESF framing type)
Far End Severely Errored Seconds (applies only to ESF framing type)
Far End Severely Errored Framing Seconds (applies only to ESF framing type)
Far End Path Coding (applies only to ESF framing type)
Far End Line Errored Seconds (applies only to ESF framing type)
Far End Unavailable Seconds (applies only to ESF framing type)
Each DS3 performance monitoring statistic is retained for the current 15-minute interval, a history of the last 32 15-minute intervals (8 hours), and the current 24-hour period (starting and ending at midnight GMT). Along with the statistics, it is also possible to verify the elapsed time in the current 15-minute interval and the amount of 15-minute intervals currently stored (this is relevant only during the first 8 hours of operation). The following statistics are retained:
P-bit Errored Seconds
P-bit Severely Errored Seconds
P-bit Coding Violations
Severely Errored Framing Seconds
Line Errored
Line Severely Errored Seconds
Line Coding Violations
Unavailable Seconds
Alarm Indication Signal Seconds
C-bit Errored Seconds (applies only to C-bit Parity line type)
C-bit Severely Errored Seconds (applies only to C-bit Parity line type)
C-bit Coding Violations (applies only to C-bit Parity line type)
Far End C-bit Errored Seconds (applies only to C-bit Parity line type)
Far End C-bit Severely Errored (applies only to C-bit Parity line type)
Far End C-bit Coding Violations (applies only to C-bit Parity line type)
Far End Unavailable Seconds (applies only to C-bit Parity line type)
Each ATM logical port statistic is kept for the current 15-minute interval, a history of the last two 15-minute intervals (30 minutes), and the current 24-hour period (starting and ending at midnight GMT). The ATM statistics are as follows:
Circuit Emulation Service (CES) connection statistics are kept for the current 15-minute interval, a history of the last 96 15-minute intervals (24 hours), the current and previous 24-hour period (starting and ending at midnight GMT).
Cells Reassembled—Number of incoming cells that were played out to the CES Service interface. It excludes cells that were discarded for any reason, such as cells that were not used due to being declared misinserted, or discarded while the reassembler was waiting to achieve synchronization.
Cells with Header Errors—cells received with AAL1 header errors detected, including those corrected. This includes cells with both correctable and uncorrectable CRC, as well as bad parity in the Sequence Number Protection field of the AAL1 header.
Pointer Reframes—Number of events in which the AAL1 reassembler found that an SDT pointer is not where it is expected, and the pointer must be reacquired. This count is only meaningful for structured CES modules, as Unstructured CES modules do not use pointers. For Unstructured CES connections, this count is zero. If this occurs, any received cells are dropped until the reassembly underflows. Sequence number synchronization and valid pointer is then searched for. When sync is reached, cells are buffered until the configured Cell Delay Variation Tolerance buffer is filled. Once filled, the buffered data is played out the CES service interface.
Pointer Parity Errors—Number of events in which the AAL1 reassembler detects a parity check failure at the point where a structured data pointer is expected. This count is only meaningful for structured CES modules, as Unstructured CES modules do not use pointers. For Unstructured CES connections, this count is zero.
Sequence Errors—Number of times that the sequence number of an incoming cell causes a transition from the "Sync" state to the "Out of Sequence" state, as defined in ITU-T I.363.1
Lost Cells—Number of cells lost in the ATM network, as detected by the AAL1 sequence number processing.
Misinserted Cells—Number of AAL1 sequence violations interpreted as a misinserted cell, as defined by ITU-T I.363.1
Buffer Underflows - the number of times the CES reassembly buffer underflows. In the case of a continuous underflow caused by a loss of ATM cell flow, a single buffer underflow is counted. After an underflow occurs, data is again buffered until the configured Cell Delay Variation Tolerance buffer is filled. Once filled, the buffered data is played out the CES service interface.
Buffer Overflows—Number of times the CES reassembly buffer overflows. When this occurs, any received cells are dropped until the reassembly underflows. Sequence number synchronization is then searched for again (and structure pointers if in structured mode). When sync is reached, cells are buffered until the configured Cell Delay Variation Tolerance buffer is filled. Once filled, the buffered data is played out the CES service interface.
Dropped Cells—Number of incoming cells dropped due to one of the following:
Alarms are generated when the following conditions are detected, and cleared when the conditions clear. LOS and LOF alarms require 2 seconds to declare and 16 seconds to clear. AIS alarms require 1.6 seconds to declare and 10 seconds to clear. All of the following are "critical" alarms.
Receiving AIS
Receiving Yellow Alarm
Not Receiving Valid Signal (LOS) (only for DS3 I/O)
Alarms are generated when the following conditions are detected, and cleared when the conditions clear. Line and Path AIS, RDI, FERF, LOS, LOF, and LOP alarms require 2 seconds to declare and 16 seconds to clear. The severity of these alarms depends on whether the line is protected using SONET APS. If one of the APS lines is still active, these are "minor" alarms. If both lines alarm, or APS protection has been disabled, these are "critical" alarms.
The OC3 alarms are as follows:
Receiving Path AIS
Receiving Path Yellow Signal (RDI)
Not Receiving Valid Signal (LOS)
Loss of Frame Pointer (LOF)
Receiving Line AIS
Receiving Line Failure from Far End (FERF)
Loss of Payload Pointer
Signal Degrade
The APS specific alarms require 2 seconds to declare and 16 seconds to clear. The APS specific alarms are as follows:
Alarms are generated when the following conditions are detected, and cleared when the conditions clear. LOF alarms require 2 seconds to declare and 16 seconds to clear. AIS alarms require 1.6 seconds to declare and 10 seconds to clear. All of the following are "critical" alarms.
This section covers how CES Service Interface alarms and loss of cells (persistent reassembly buffer underflow) alarms are handled. Structured and Unstructured CES are handled differently.
In Unstructured mode, any alarms received at the input of the service interface are carried through without modification. These alarms can be optionally monitored by the MGX 8240.
Some conditions exist when the frame is not passed through. The ATM Forum CES specification states that the CES IWF sends cells containing all ones (an unframed AIS signal) when Loss of Signal (LOS) is detected for the DS1. Since the MGX 8240 does not physically terminate the DS1s, LOS cannot be detected. If an auxiliary M13 multiplexer is used to terminate the DS1, it detects the LOS and generates an AIS signal within the DS1 toward the MGX 8240, which passes it through in cells towards the far end.
Although the MGX 8240 cannot detect DS1 LOS, it can detect the following problems:
Containing DS3 Loss of Signal (LOS) (only for DS3 I/O)
Containing DS3 Loss of Frame
Containing DS3 Receiving AIS
DS1 Out-of-Frame (only applies when set to monitor the DS1 frame)
When the MGX 8240 detects one of these problems, it sends cells containing all ones toward the far end.
When providing structured DS1 CES service, the DS1 frame is terminated on the local CES service interface. The ATM Forum CES specification states that when DS1 Loss of Signal, AIS, or Out-of-Frame is detected, the CES IWF sends cells containing Trunk Conditioning. Since the MGX 8240 does not physically terminate the DS1s, LOS cannot be detected. If an auxiliary M13 multiplexer is used to terminate the DS1, it detects the LOS and generates an AIS signal within the DS1, towards the MGX 8240, which detects the AIS and reacts appropriately. Although the MGX 8240 cannot detect DS1 LOS, it can detect the following problems:
DS1 Out-of-Frame
DS1 Receiving AIS
Containing DS3 Loss of Signal
Containing DS3 Loss of Frame
Containing DS3 Receiving AIS
When the MGX 8240 detects one of these problems, it sends cells containing Trunk Conditioning towards the far end.
Each of the ATM connection statistics below is kept for the current 15-minute interval, a history of the last two 15-minute intervals (30 minutes), and the current 24-hour period (starting and ending at midnight GMT).
Several statistics and status values are available to aid in troubleshooting and repairing a failed in-band connection. Several commands may be used to test some parts of the in-band connection, including OAM loopback tests on the PVC circuit.
