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    How will 21CN affect Sky Broadband?

    This is a discussion on How will 21CN affect Sky Broadband? within the Sky Broadband feedback forums, part of the Sky Broadband help and support category; Originally Posted by dq1 Sounds a bit pointless really. Thats the planning dept at BT for you, cant see the ...

    1. #11
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      Re: How will 21CN affect Sky Broadband?

      Quote Originally Posted by dq1 View Post
      Sounds a bit pointless really.
      Thats the planning dept at BT for you, cant see the wood for the trees
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    3. #12
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      Re: How will 21CN affect Sky Broadband?

      Quote Originally Posted by dq1 View Post
      Dunno if anyone can interpret this diagram:
      BT's 21st Century network - 21CN key technologies
      These diagrams here should shed more light..

      [edit]

      MSAN

      A multiservice access node (MSAN) is a device typically installed in a telephone exchange (although sometimes in a roadside cabinet) which connects customers' telephone lines to the core network and is able to provide telephony, ISDN, and broadband such as DSL all from a single platform.

      Prior to the deployment of MSANs, telecom providers typically had a multitude of separate equipment to provide the various types of services to customers. Integrating everything on a single node, which typically backhauls everything over IP or Asynchronous Transfer Mode can be more cost effective and may enable customers to have new service enabled far more quickly.

      Interesting...
      Last edited by TRIaXOR™; 21-05-07 at 06:30 PM. Reason: adding new info
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    4. #13
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      Re: How will 21CN affect Sky Broadband?

      Sky Easynet already are already setup for 21CN as they have a full IP core network. The problem (which is the same problem for BT) is the last mile / local loop. Currently this uses the copper pair of the telephone line which is, as previously mentioned, limited to 24Mbps max. What is needed is IP from the exchange to the house instead of ATM (in the form of ADSL).

      This could be done with street cabs containing DSLAM or with something else. The arguement is that if you are going to dig up the road to install the infrastructure for street cabs why not put fibres all the way to peoples homes or install VDSL. Who knows maybe a new technique will arrive on the scene for getting even more out of the copper pair telephone line.

    5. #14
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      Re: How will 21CN affect Sky Broadband?

      Quote Originally Posted by dq1 View Post
      Dunno if anyone can interpret this diagram:
      BT's 21st Century network - 21CN key technologies

      OK:

      Core Links (links between Metro Networks)
      Lets start at the top. The DWDM Dense Wave Division Multiplexing. What this is is using different wavelengths to send light down a fibre. Basically you have a big box full of prisms which allow you to send multiple lights down a fibre at the same time. BT use ciena kit (same as we have at work :-) ) sky use marconi. This gives nice fast backbone links around the country and (for 21CN) is IP most likely TenGig Ethernet (10G BASE-ZR and ER).

      Also running over the core links is MPLS (Multi Protocol Label Switching) which allows the traffic to be treated as if it were circuit switched (like a traditional telephone network) rather than packet switched. MPLS helps in shipping old style communications through packet switched networks (IP networks) which don't offer many guarantees on how packets move through the network.


      Metro Links (links which form the Metro Network)
      These are large networks which serve large areas e.g. Manchester, London, Birmingham, etc.. Under 21CN these are IP based networks which again use technologies like Ten Gigabit Ethernet and Gigabit Ethernet. BT's equipment is mostly Cisco where as Sky have gone for a mix of Cisco and Juniper. The links at this stage are still mostly fibre and use a mix of Coarse and Dense WDM. Telephone exchanges connect to the MANs and this is where your data enters the core network.

      Access Domain
      The access domain is where consumer links meet the network. Currently these are DSLAMs (Digital Subscriber Line Access Multiplexer). Your copper telephone line terminates at an MDF (Main Distribution Frame). From there the line goes into the DSLAM and the data is split off and put onto the the relevant providers network. For this Sky use Lucent Stinger DSLAMs (not sure what BT). The last part of the 21CN masterplan is to replace the DSLAMs with MSANs. These are all singing all dancing bits of kit which maybe placed in street cabs. The idea is these act as layer 2 devices bridging your home connection onto the IP network.
      Last edited by armitasp; 21-05-07 at 11:38 PM.

    6. #15
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      Re: How will 21CN affect Sky Broadband?

      Thanks for the explanation. As a physics student I understand many of the principles but the 'big industry' jargon eludes me.

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      Re: How will 21CN affect Sky Broadband?

      Quote Originally Posted by armitasp View Post
      The arguement is that if you are going to dig up the road to install the infrastructure for street cabs why not put fibres all the way to peoples homes......
      No need to dig up the road - much cheaper to replace the copper with fibre using available technologies such as this Cabel-X. BT may be making lots of public noises about FTTH not being part of their current plans but it will come much quicker than they are saying. They also have huge quantities of redundant copper cables in the network that are worth millions in the commodity market for the raw material.

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      Re: How will 21CN affect Sky Broadband?

      redundant copper cables in the network that are worth millions in the commodity market for the raw material
      ahhh, that old one. I once heard that back in the 90's AT&T nearly went bankrupt and the liquidators put the copper cables down as their biggest asset.

      I'm no expert in layer 1 particularly telco layer 1 but I suppose there is nothing to stop BT stringing fibre between their telegraph poles instead of the wet string they use at the moment. (perhaps someone can tell me why they don't do that)

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      Re: How will 21CN affect Sky Broadband?

      The fibre cable would snap in the wind because it is an unsupported cable without suspension wires.

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      Re: How will 21CN affect Sky Broadband?

      Is it an urban myth that BT wanted to replace all the copper cabling to peoples homes with fibre optic cable, back in the 1980s, but the Thatcher government didn't want to help with the cost. If this is true then thats why UK languishes so far behind in broadband penetration and speed. Of course they didn't foresee the internet.

     

     
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