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    Detailed stats - explanation of them ?

    This is a discussion on Detailed stats - explanation of them ? within the Speed tests and how to get better results forums, part of the Sky Broadband help and support category; I've just had a play with my extension wiring, removed all cores except 2 & 5 - discovered I had ...

    1. #1
      phoe's Avatar
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      Detailed stats - explanation of them ?

      I've just had a play with my extension wiring, removed all cores except 2 & 5 - discovered I had a second master looped through as an extension socket (connected on the front plate, but whether the electronics behind it - now removed - might have affected the signal once the front plate went into the test socket of it I don't know), and my connection speed has now shot up from ~3500kbps to 7136kbps, and at first glance my noise levels have improved slightly.

      Now to my problem - my connection speed has rocketed, but my actual throughput has plummeted to <100k/sec.

      I think the counters section of the detailed stats now shows a large amount of errors, but i'm looking for some clarification :-}

      SF: 151144 151142
      SFErr: 965 18
      RS: 10277850 1284707
      RSCorr: 367086 170
      RSUnCorr: 1470 0

      Just as an aside, I wonder if it might be worth a sticky somewhere explaining what each section of the detailed stats mean ?!?

      TIA :-}


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    3. #2
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      Re: Detailed stats - explanation of them ?

      Small update - my speeds now seem to have leapt up again, but they're very intermittent, and range from about 700k/sec to _zero_ (completely stalled).

      A fresh set of counters (still connecting at 7136kbps after several reboots) are as follows:

      SF: 358043 358041
      SFErr: 967 18
      RS: 24346994 3043348
      RSCorr: 371379 394
      RSUnCorr: 1524 0

      Last edited by phoe; 18-04-07 at 02:47 PM.

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      Re: Detailed stats - explanation of them ?

      Quote Originally Posted by phoe View Post
      Just as an aside, I wonder if it might be worth a sticky somewhere explaining what each section of the detailed stats mean ?!?
      What - like this (from router stats sticky)?


      CRC (Cyclic Redundancy Check).

      Data is transmitted as streams of packets through a network. A TCP module at the far end sends back an acknowledgement for packets which have been successfully received. It checks for damaged bytes by using a checksum. In simple terms, if any packets fail the check they will be recorded as CRC errors.

      The number of CRC errors recorded must be looked at in relation to the total number of packets transmitted and the superframe figure (SF) can be used in the absence of a packet count.

      There is no standard formula which would indicate whether a given level of CRC is acceptable or unacceptable. A useful "rule of thumb" is that the number of CRCs should be less than 0.1% of the superframe count. A bit more than this (2x or 5x) is probably going to be fine, a lot higher (10x or 100x) probably won't be.

      In any event CRC must not be looked at in isolation; it is quite possible for instance to have a "low" level of CRC but a high level of errored seconds/loss of signal and vice versa.

      LOS (Loss of signal)

      This sounds bad but a handfull of these in any 15 minute period will probably go unnoticed in normal surfing/downloading. It's showing that connection to the exchange was lost momentarily but the connection will cope with this. A high level however, say more than 5% of the CRCs, indicates a fairly severe line problem, possibly noise spiking.

      ES (Errored Seconds)

      An Errored Second is a second in which one or more coding violations occurred OR one or more loss of signal defects occurred.

      Again, as with CRC there is no standard formula which would indicate whether a given level of ES is acceptable or unacceptable. Anything other than a near perfect line will give some level of ES error. Look at the 15 minute periods. There are 900 seconds in 15 minutes. An errored second figure of up to 5 or 10 is probably manageable. On really bad lines the ES number can actually equal the total seconds i.e. every second of connection experienced a coding violation or loss of signal.

      In many ways, errored seconds are a better indicator of a line that is struggling than CRC. Severely errored seconds give an additional quantification.

      SES (Severely Errored Seconds)

      As the name suggests, a severely errored second is worse than an errored second. To be counted as errored only one event needs to occur. A severely errored second quantifies this. Typically a severely errored second is one where a threshold number of events is passed. Each router manufacturer will set their own threshold for what constitutes a severely errored second.



      One last thing. A caveat on the above:

      Interpretation is down to subjective evaluation - you can't simply say "this is good - that's bad". The whole picture must be looked at.

      When looking at the stats, particular attention must be paid to the noise margin levels during the stat measurement period. For example, if the noise margin had dropped down to less than 6db then even the best quality line would record errors. Similarly, if the noise margin had been boosted up so it was always above say 9db and the line showed errors, then the "real" error level will have been under reported.

      Different consideration must be given to capped lines e.g. if comparing two lines both reporting similar error levels, where one is capped and one not, the capped line has a much bigger problem.

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      Re: Detailed stats - explanation of them ?

      That's pretty much what I was looking for thanks :-)

      Is there a way to reset the counters (other than a full reset of the firmware), or do the counters re-zero themselves over the space of 24hrs ?

      (just thinking in terms of a clean start having had a play with the wiring, to see how it fares, rather than having to compare old and new copies of the stats to work it out)

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      Re: Detailed stats - explanation of them ?

      Rebooting (power or from admin pages) will reset the counters.

      The stats roll over each 24 hours but detailed stats only cover the most recent periods. How often they roll over before new replaces old I've not noticed.

     

     

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