Fibre v ADSL

Discussion in 'Broadband' started by ash burton, Jan 1, 2015.

  1. ash burton

    Graham. Guest

    The fibre cable is (for our purposes) loss-less.
    That's the whole point of it.
    Graham., Apr 3, 2015
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  2. I wonder if it's possible that the speed estimates for ADSL and VDSL
    have somehow become based on different assumptions about which cabinet
    a particular house is connected to? All other things being equal, the
    cable from cabinet to home would be the same as before, but I wonder
    if they have to reallocate them sometimes because of cabinet limits?

    What I mean by this is that there will be a limit to the number of
    connections a cabinet can handle, and I would expect that number to be
    bigger for ADSL where the cabinet is really just a big junction box,
    than for VDSL, where the cabinet must house a piece of electronic
    equipment for each subscriber. If a standard cabinet has more phone
    connections than its replacement fibre cabinet will be able to handle,
    then one way of dealing with this would be to re-route some of them to
    a different cabinet.

    I've never worked for BT so this is guesswork and might be rubbish.

    Roderick Stewart, Apr 4, 2015
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  3. Go on. You know you want to. :)

    Roderick Stewart, Apr 4, 2015
  4. ash burton

    Kraftee Guest

    Differing services uses differing frequencies and very possibly your line
    (from the PCP to your property) attenuates the frequencies which FTTC
    prefers far more than those used by DSL.

    The other idea is that all the speed estimates are just guesses as they have
    been from the advent of any online data services.
    Kraftee, Apr 4, 2015
  5. ash burton

    Kraftee Guest

    They've supposedly improved the RF filtering....
    Kraftee, Apr 4, 2015
  6. ash burton

    Phil W Lee Guest

    If that were the case, the cabinet would be showing as congested, and
    you wouldn't be able to get connected at all.

    The distance between the exchange and the cabinet being bypassed by
    fibre while allowing the existing pair to be used from cabinet to
    premises, is the whole point of FTTC/VDSL - if they had to lay a cable
    from a different cabinet to your premises, they might as well lay a
    fibre instead, and just roll out FTTH everywhere.
    Phil W Lee, Apr 4, 2015
  7. ash burton

    Phil W Lee Guest

    Having examined some of the firewalling options, they appear to be
    pretty good.
    As I already have a standalone hardware firewall, I can't speak from
    experience of having used them, but firewalling appears to be possible
    based on not just IP addresses but filtered on keywords as well, with
    rules able to be scheduled (so you can tighten it when the kids are up
    during the day, for example). So it might make my hardware firewall
    redundant with a bit of experimentation (although I'm hesitant to move
    from a proven system I know reasonably well to a new one which is
    unproven and uses a totally different control mechanism and operating
    Oh, and it does IPv4 to 6 conversions as well. in either direction.
    So if you only have 4, and need to reach a site which only has 6, you
    Oh, and it supports vectoring out of the box, so once that arrives
    you'll probably get a bandwidth improvement.

    Regarding power, simply reducing the number of cables and sockets
    required can be a significant benefit.
    You can never have too many spare sockets :)
    Phil W Lee, Apr 4, 2015
  8. ash burton

    Woody Guest

    I don't know about the Mk2 but the Mk3 supposedly has some line
    powered electronic line balancing gubbins in it so it should also
    benefit telephone used by reducing the noise level.
    Woody, Apr 4, 2015
  9. ash burton

    Kraftee Guest

    Closely connected to the older PCP, where else???
    Kraftee, Apr 4, 2015
  10. ash burton

    Roger Mills Guest

    PCP? Presumably a roadside cabinet - but what do the letters stand for?
    Please reply to Newsgroup. Whilst email address is valid, it is seldom
    Roger Mills, Apr 4, 2015
  11. ash burton

    Graham. Guest

    Primary Cross-connection Point.
    Graham., Apr 4, 2015
  12. ash burton

    Roger Mills Guest

    Ta! Obvious, really, isn't it?!
    Please reply to Newsgroup. Whilst email address is valid, it is seldom
    Roger Mills, Apr 4, 2015
  13. [...]
    There are two distances involved, the distance from the exchange to
    the cabinet, and the distance from the cabinet to the premises. I've
    noted some semi-rural locations near the edge of town where the latter
    distance is quite large in comparison with the former. Those tend to
    be the ones where the predictions show a worse performance for VDSL.
    This suggests to me that in these cases it is the cable from cabinet
    to premises that is having the major effect on performance.

    This could be improved if these communities could be given their own
    fibre cabinets closer to the premises, but installing a new cabinet is
    a much bigger task than simply upgrading an existing one, which is
    probably why the estimates appear to be based on the assumption of a
    simple upgrade.

    Roderick Stewart, Apr 4, 2015
  14. ash burton

    Rodney Pont Guest

    I'm not sure that you understand how this is all set up from your
    comments. The voice signal goes from the exchange to the old cabinet as
    before FTTC. The fibre goes from the exchange to the new fibre cabinet.
    Distances involved are negligible for fibre and the signal won't
    degrade so this distance is no longer relevent to what the the uses can

    The voice is then sent from the old cabinet to the new fibre cabinet
    where it's merged with the VDSL signal and then sent back to the old
    cabinet where it's connected to the line that goes to the premises.
    This distance, from the old cabinet to the premises, is the only one
    that can have any effect on performance.

    To connect the premises to a nearer cabinet the cabling to the old
    cabinet would need to be moved to a new wiring cabinet and then new
    cable would have to be run from the new wiring cabinet to the premises,
    that's not going to happen. The fibre cabinet has to be close to the
    old cabinet since the line to the premises comes from the older
    cabinet. Putting a new fibre cabinet nearer to the premises will simply
    lengthen the distance for the VDSL signal since it has to go back to
    the old cabinet first, the fibre cabinet is not connected to the user
    except via the old cabinet and wiring.
    Rodney Pont, Apr 5, 2015
  15. ash burton

    Graham J Guest

    I live in a village where the ADSL service averages about 1.5 Mbits/sec
    - we are about 6km line length from the exchange.

    Our nearest green cabinet is about 2km from the centre of the village,
    at a road junction where the BT cables split, some to us, some to
    another community along the main road.

    So there isn't a green cabinet in the village. There are underground
    chambers (generally full of water) with cable joints in them; and funny
    pods on some of the poles carying overhead cables.

    Our County Council (Norfolk) is funding FTTC and the promise is that we
    will get it - but it is "not scheduled for an upgrade as part of the
    current rollout" - so no date yet. Some contractors working for
    Openreach dug a trench along the roadside approximately between two
    premsises and laid in a duct. When asked, they explained it was
    preparation for FTTC.

    Is this likely to be bullshit? It seems to me that without a nearby
    green cabinet much more work is needed to create a PCP in the village
    and re-route all the existing subscriber cables through it.

    There is actually fibre in the village, and has been since before the
    days of ADSL. There is a business with fibre which is actually used to
    deliver ISDN30. Sometime soon after 1997 when I used ISDN2e (in the
    form of BT Home Highway) it all stopped working. Checking with
    neighbours revealed that many had lost telephone service. Walking along
    the road out of the village revealed the local council drainage
    contractor had re-cut the "grips" which allow water to run off the road
    into the ditch alongside - and in doing so had cut through the phone
    cable in three places - and the broken duct revealed the shredded ends
    of optical fibres as well as copper. Later that day there were BT
    engineers camped at the roadside and about 4 days later it was all
    working again.
    Graham J, Apr 5, 2015
  16. ash burton

    Ash Burton Guest

    Yes, i am with you on all that but how can it explain why i am being
    given a lower speed estimate for fibre bb (4.6 Mbps) than i am getting
    on my ADSL (8 Mbps) Ash

    --- news:// - complaints: ---
    Ash Burton, Apr 5, 2015
  17. ash burton

    Rodney Pont Guest

    It can't but people are human and make mistakes.
    Rodney Pont, Apr 5, 2015
  18. ash burton

    Rodney Pont Guest

    They could put a wiring cabinet in somewhere that the bundle of wires
    to the village pass by chopping into the bundle and extending the cut
    ends into a new wiring cabinet then place a fibre cabinet next to it.

    They have done something similar at our exchange where two new cabinets
    have appeared on the verge outside of the exchange. The problem with
    dropping a cabinet onto a bundle of wires is that they need to get
    power to the fibre cabinet from somewhere so it won't be practical
    Rodney Pont, Apr 5, 2015
  19. I do understand this. What I was trying to point out is that in some
    cases the distance from cabinet to premises is larger than others.
    Inevitably a 12MHz signal is going to fare worse than a 2MHz one along
    the same length of telephone cable, and the longer the cable the worse
    the discrepancy will become. At some distance from the cabinet, the
    degradation of the higher frequency signal could be so great as to
    give a worse performance than the more rugged lower frequency one.

    This could of course be helped by installing new cabinets closer to
    the premises, so that the cable runs are shorter, but in most
    instances near where I live they just seem to have replaced the old
    cabinets with new ones in the same locations. Villages and remote
    suburbs will probably have to wait.

    Roderick Stewart, Apr 5, 2015
  20. ash burton

    Graham J Guest

    There are street lights so nearby power should not be a problem ...

    There was once a phone box so there may be ducting and power at that
    location - I will look next time I go that way.
    Graham J, Apr 5, 2015
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