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    Interleave value 64? (stat report)

    This is a discussion on Interleave value 64? (stat report) within the Sky Broadband help forums, part of the Sky Broadband help and support category; Dear saturday I left a post on the other thread directing you back here, just to keep it in one ...

    1. #21
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      Re: Interleave value 64? (stat report)

      Dear saturday
      I left a post on the other thread directing you back here, just to keep it in one place.
      You say I'm chasing the wrong problem, my first post on this thread was questioning the interleave value.
      Today I was informed by T3 that sky's default interleave value was 32/32 not 64/8.
      I also queried the fact that the "sky box", netgear reported fast yet dmt with the netgear, the dynamode router I have and dmt via it report interleave and all three agree on the DEPTH as 64/8.
      There is a further anomaly that on the detailed sync report from the dynamode the date seems to be at default both routers and all systems show the correct date time.
      In my conversation with the gentleman from T3 earlier today we cordially went though the symptoms displayed , he informed myself re sky default settings( a question you ignored in the other post) he then informed me that he had altered the interleave to 8/8, from the figure he must have concluded the line could tale that even with the higher frequencies of adsl2+. He then confirmed the date time of the dslam (unsure whether that was altered or not) he admitted being unsure why the netgear should report fast, but an open mind is better than closed. We then carried out a series of pings to a site for which I had records these proved to be 20+ms faster ie around the 24ms average , we carried out at his suggestion the download of of a 15Meg file from btopen world where good download speeds were received and finally a speed test where the speed had improved to an acceptable level (80% ish). At that point we agreed I should test the connection further and he would call back in a couple of days to confirm all was ok. The call for all the issues was cordial and time spent kept to a minimum, in other word I did not ask him to wait and check all the permutations as the call back was placed for that purpose. I then had a couple of errands but upon my return ran the mognuts to get line stats etc The stats still report fast, the line sync speed has risen to near the 20 mark (was 15323) when checked with dmt the interleave was reported as 64/8, i then decided to check with the dynamode this also stated 64/8 and confirmed by dmt, and still reported is this strange "default" date.
      The snr has dropped now from 13-14 to around 7.5-8 , speed still up, something which is really a feeling ie average download speeds sre in my opinion lower than the previous isp,s 8128 connection.
      Now believing what the T3 gentleman told me he adjusted the interleave to 8/8 (sky's default, possibly set to 32/32, he assured me they were normally kept the same) and the dslam date was ok. this now leads to the original questions is the dslam not holding its settings and reverting to the manufactures default ie 64/64, date not even sure where that originates but the stats are getting some of the negotiation from the dslam, and why despite having seen lots of mognuts stats post on this and other forums all show interleaved this one shows Fast.
      You also keep almost chanting the mantra of its the depth, let me put that in perspective . You to me are an unknown quantity I know neither your age ,sex or background and really have no desire to. However for my part I started in electronics training in 1964 spent the last 40years at all levels in a variety of companies from one man bands 3rd party maintenance freelanced with the likes of unsys and reuters and if i don't understand something I read and listen to rational explanation.From what I have read it is an excepted fact that interleave increases ping, latency and results in reduced download speed.
      I will not post all the quotes unless you insist and want the links they weren't hard to find, time consuming to read yes. If you cast your sights beyond here you will find a heathly discussion with regard to BE the members there are on different interleave factors(or depth) which BE see to have introduced on long and marginal lines. for someone who I believe works or at least is known to T3 something of a blinkered attitude. And could you inform me what exactly is sky's fault resolution process? I'm talking to T3 what do I do if they don't call back?


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    3. #22
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      Re: Interleave value 64? (stat report)

      I'm sorry you don't agree with my views which in some instances appear to be 180 degrees from your own. As far as I am aware an "excepted fact" as you put it is that interleaving does not materially impact throughput except in very specific circumstances such as unusually long noise bursts as I referred to before and even then the impact would not match the speed degradation you report.

      I have no "mantra" on interleave depth but if you read the posts again you'll see that I was simply correcting statements made which appeared to confuse depth with delay.

      I don't work for Sky so can't comment on what their default interleave settings are. However, I can say that to the best of my knowledge a depth of 64/8 is standard for many ISPs.

      I've offered you my opinion and have tried to offer you advice. This is a public forum so of course you are free to disregard it.

    4. #23
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      Re: Interleave value 64? (stat report)

      Saturday you are quite right this is a public forum and all are entitled to their opinion and I will always respect that right as much as I defend my own rights.
      I have actually been out of the "trade" for a number of years which is why I can only form opinions from what I glean from books,www etc. and of course the current bun. Another posted (who incidentally admits working for Sky stated "what difference does 200k make" the 200k refered to was in term of download throughput and as I stated elsewhere download speed is subjective, but when you can "normally" download from a particular regularly used site in the order 400-600k change isp to a higher speed and find the same downloads run at a max of 200-300 and should these be distro's then the time doubles ie not 20min but 40min. Things then become emotive.
      Strange you don't work for sky as your "handle" actually came up in conversation.
      As a footnote I have read over the last few days a number of articles and discussions re interleave and from what I have garnered it is almost a prerequisite for iptv, and whether the public want it or not, whether the UK infrastructure can even support it ( Tiscali tv brrrr their normal service was bad enough) but interleave will soon be a fact of life however it seems some provider are actively adjusting the depth dependant of the customers line to lessen the effect.
      This is a passage from one of the numerous articles I have read.
      "With ADSL, there is a choice of “fast” or “interleaved” paths for packet transmission. The fast path provides immediate serial transmission of waiting packets, and the packet transmission times given in Table A-2.3 apply. The interleaved path buffers a substantial amount of data, and performs interleaving of this data over a specified interleave depth in order to improve immunity to burst noise on the DSL link. The interleave depth is specified in milliseconds, and the effect of interleaving is to add delay to the voice path equal to the magnitude of the interleave depth.

      The interleaved path of ADSL has value primarily for the transport of highly compressed video streams, where relatively low bit error rates can cause substantial impairments to the received picture. The fast path is preferred for both data transmissions and voice over DSL.

      The line coding for both fast and interleave paths use Forward Error Correction algorithms that require block processing, and therefore incur fixed delays. G.992.1 defines the ATM payload transfer delay to be (4 + (S-1)/4 +SxD/4) ms, where S is 1 for the fast path and 1, 2, 4, 8, or 16 for the interleave path, and D is 1, 2, 4, 8, 16, 32, 64 for the interleave path (not applicable for the fast path).

      Thus the lower bound of delay for ADSL line encoding is 4 ms. The upper bound, using the interleave path, is as much as 263.75 ms (S = 16 and D = 64). Note that G.lite (G.992.2) uses only the interleave path and thus has a lower bound of 4.25 ms.

      The ADSL line encoding time is additive to the packet transmission time."

      Although in this article it specifies voice path delay it does stated depth is measured in ms and ecoding time is additive other articles are more specific re the effects on data paths as this one states the fast path is preferred for data and voice. Its also interesting to note the maximum depth for adsl2+ is in fact 511, imaging should that become standard people living > 3km from the exchange could find pigs measured in sec.
      I actually think something added to my line Modem inc is not holding its settings as the path was supposedly set to 8/8 and according to info should have initially been set to 32/32. At this point I am at a loss and not really sure whether to wait to find out.
      respecfully yours

    5. #24
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      Re: Interleave value 64? (stat report)

      Quote Originally Posted by geo48 View Post
      Strange you don't work for sky as your "handle" actually came up in conversation.
      LOL. Famous at last!

      Quote Originally Posted by geo48 View Post
      This is a passage from one of the numerous articles I have read.
      "With ADSL, there is a choice of “fast” or “interleaved” paths for packet transmission. The fast path provides immediate serial transmission of waiting packets, and the packet transmission times given in Table A-2.3 apply. The interleaved path buffers a substantial amount of data, and performs interleaving of this data over a specified interleave depth in order to improve immunity to burst noise on the DSL link. The interleave depth is specified in milliseconds, and the effect of interleaving is to add delay to the voice path equal to the magnitude of the interleave depth.

      The interleaved path of ADSL has value primarily for the transport of highly compressed video streams, where relatively low bit error rates can cause substantial impairments to the received picture. The fast path is preferred for both data transmissions and voice over DSL.
      Yes that's absolutely correct - interleave has to in effect disassemble chunks of data and transmit them in rearranged form. This is of no consequence to the throughput of data in a given time period greater than a few hundred milliseconds. The data is disassembled, transmitted and reassembled, the disassembly and reassembly adding typically around 20 to 40 milliseconds of latency not throughput reduction. Remember, this isn't adding a cumulative lot of 20 to 40 milliseconds. This is the total for that "chunk" of data, however big or small.

      I don't agree with the statement that fast path is preferred for data transmissions unless it has the proviso "for very low noise lines". Interleave is implemented to overcome the effects of line noise. If the line has any significant noise level then interleave will give an improved throughput at the expense of a small amount of latency. Without reading the paper I'm not sure about the voice path comment. If it means applications such as voip then latency becomes an issue and a non interleaved line is to be preferred if possible.


      Quote Originally Posted by geo48 View Post
      The line coding for both fast and interleave paths use Forward Error Correction algorithms that require block processing, and therefore incur fixed delays. G.992.1 defines the ATM payload transfer delay to be (4 + (S-1)/4 +SxD/4) ms, where S is 1 for the fast path and 1, 2, 4, 8, or 16 for the interleave path, and D is 1, 2, 4, 8, 16, 32, 64 for the interleave path (not applicable for the fast path).

      Thus the lower bound of delay for ADSL line encoding is 4 ms. The upper bound, using the interleave path, is as much as 263.75 ms (S = 16 and D = 64). Note that G.lite (G.992.2) uses only the interleave path and thus has a lower bound of 4.25 ms.

      The ADSL line encoding time is additive to the packet transmission time."

      Although in this article it specifies voice path delay it does stated depth is measured in ms and ecoding time is additive
      Yes but it is not cumulative.

      Quote Originally Posted by geo48 View Post
      I actually think something added to my line Modem inc is not holding its settings as the path was supposedly set to 8/8 and according to info should have initially been set to 32/32.
      I'm sure that's possible. As I said before, I wouldn't be surprised if Sky's default was 64/8 and it reverts back to this at an exchange level. Of course it could also be that the T3 guy didn't know how to change it, didn't want to, or wasn't allowed to.

      In any event, changing the level of interleave will make no material difference to your throughput issue.

     

     
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