Line Stats from Voyager router	Linestats from Speedtouch router

BER - Bit Error Rate

The ratio of Errored bits to Transmitted bits.
BERT = Bit Error Rate Test. Most modem/routers have a tool to check the Bit Error Rate.

CRC Errors - Cyclic Redundancy Check

Count of CRC errors. CRC is an error detection code used to verify packet transmission between the sender and receiving end. A CRC error indicates that part of the data packet is corrupt and requires retransmission. - see Cyclic Redundancy Check (CRC) for a more in depth explanation.

Many CRC errors in a short period of time will show a noticeable reduction in throughput speed. This can be an early indication that there is too much noise on the line and in extreme situations can lead to loss of sync (disconnection with the exchange).

D Value - Depth of Interleaving

The Depth of Interleaving applied to the line. Various depths of interleaving may be applied by the DSLAM by both BTw and the LLU Operators. See Interleaving for more information.
A depth of 1 indicates the line is on Fast Path and no interleaving applied.

Delay

The delay due to interleaving being applied on the line - recorded in microseconds.

ES - Errored Seconds

A one second period of time in which either one or more coding violations occurred OR at least one Loss of Signal events occurred.

Its not unusual to see occasional ES and its best looking at the broader picture. Some routers will display the ES over 15 min periods (900 seconds), therefore a couple of errored seconds will probably go un-noticed.

ESF - Extended Super Frames

In DS1 systems an ESF extends the 12 frames per superframe, to 24 frames contiguously transmitted together.

Clarification is needed for the exact amount of frames used in an adsl ESF and reference is given to adsl SuperFrames.

FEC Errors - Forward Error Correction

Count of errors that have been corrected due to error correction being applied to the line. Error correction is turned on at the same time as Interleaving. Its normal to see FEC errors on an Interleaved line and rather than anything to be too concerned about its more an indication that the Interleaving & Error Correction process is working and doing what it should. - See Error Correction for more information.

HEC Errors - Header Error Check/Correction

Count of HEC Errors. HEC is a type of CRC error check which has been performed on the header of an ATM cell, but 1 bit errors can be corrected. This count is usually where HECs have been uncorrected and have been discarded.

If these errors are too high within a short period of time it will slow throughput... and could even lead to connection instability - See Out Of Cell Delineation.

K Value - Bytes in the DMT Frame

Number of Bytes in the Frame. Each Byte is said to give 32 kbps of sync speed.
I don't know why the 1st Byte isn't counted on some occasions
eg (255 x 32 = 8160) - 32 = 8128 down sync and (27 x 32 = 864) - 32 = 832 up sync
If anyone has an explanation please let me know and I will update.

LCD Errors - Lost Cell Delineation

Count of the number of Lost Cell Delineation errors - See LOCD

LOCD - Loss of Cell Delineation.

An alarm state process, different routers may have different alarm periods. A typical alarm integration period may be 2.5 seconds with a 10 second deactivation period.

A Loss of Cell Delineation defect is initially triggered when an Out of Cell Delineation (see OOCD) condition occurs and doesn't clear for more than 4ms. This starts then starts the integration period.
If the defect doesn't clear during the integration period, then an LOCD event is recorded.
The LOCD alarm event will clear when an LOCD defect is not detected within the deactivation period.

LOF - Loss of Frame

An alarm state process, different routers may have different alarm periods. A typical alarm integration period may be 2.5 seconds with a 10 second deactivation period.

A Loss of Frame defect is initially triggered when an Out of Frame (see OOF) condition occurs and doesn't clear for more than 3ms. This then starts the integration period.
If the defect doesn't clear during the integration period, then a LOF event is recorded.
The LOF alarm will clear when an LOF defect is not detected within the deactivation period.

LOS - Loss of Signal

An alarm state process, different routers may have different alarm periods. A typical alarm integration period may be 2.5 seconds with a 10 second deactivation period.

A LOS defect may initially be triggered when all zeros are received for 20 microseconds which starts the integration period. During the integration period, 2 consecutive frames with 20 microseconds of signal loss will record a LOS event.
The LOS alarm will clear when no LOS defects are detected within the deactivation period.

A couple or so LOS events may go totally un-noticed during bursty activity such as web-browsing etc. The connection should be able to cope with this momentary loss of signal with the exchange, however a high level indicates a noise problem.

Some users have observed that 4 LOF events can trigger a LOS.

Loss Of Link

Physical failure of the link.

Loss Of Power

Failed re-initialisation of the DSL link due to power loss.

NCD - No Cell Delineation

See LOCD - Loss of Cell Delineation

OCD Errors - Out-of Cell Delineation

Count of out-of-cell delineation errors - see OOCD.

OOCD - Out Of Cell Delineation

Out of Cell Delineation event occurs when seven consecutive cells fail to contain a valid HEC (Header Error Check). An OOCD clears when six consecutive HEC valid cells are detected.

OOF - Out Of Frame

An Out of Frame event occurs when four consecutive frames do not contain a valid frame word. OOF clears when two valid consecutive frames are detected.

R Value - RS check Bytes

Number of (redundant) Bytes occupied by the Error Correction process (overhead).
Often used to describe the level of error correction and can range from 0 to 20. The more check bytes that are used then the more errors can be corrected.

RS Correctable Errors

The number of Reed-Solomon code words with correctable errors. Reed-Soloman is a method of Forward Error Correction and therefore a count of data successfully recovered. See FEC.

RS Uncorrectable Errors

The number of Reed-Solomon code words that had uncorrectable errors. Reed-Soloman is a method of Forward Error Correction. Uncorrectable Errors are those that are too severe to be corrected by FEC.

RS Words

Count of the total number of Reed-Solomon code words transmitted/received.

SES - Severely Errored Seconds

As the name indicates this is more worse than an Errored Second (which only needs one event to trigger an ES).
A Severely Errored Second is a one second period which contains 30% or more errored blocks OR several other events such as one or more OOF.

SF - Super Frames

Traditionally, a (Digital Signal 1) superfame consists of 24 frames contiguously transmitted together.

In adsl, a superframe consists of 68 adsl frames plus a synchronisation frame.
The adsl modem generates 4000 frames per second. The global duration of an adsl superframe is 17ms.

Super Frame Errors

Count of the Super Frames received which had an error.

Total ES / ESF

The total Extended Super Frame errors - See ESF

UAS - Unavailable seconds

Ten consecutive SES's will trigger a UAS event, and will remove the path from use. The path will become usable again after 10 consecutive seconds with no SES.