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Author Topic: SKY BRAS / architecture (DSL Broadband)  (Read 1152 times)


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SKY BRAS / architecture (DSL Broadband)
« on: August 15, 2017, 10:13:18 AM »

Hi, anyone know if Sky have their own BRAS or is it a BT hand-off thing? I'm interested in the backhaul network from the DSLAM i guess into the ISP core. Any clues as to the general architecture involved? Which part would BT deal with, if any?


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Re: SKY BRAS / architecture (DSL Broadband)
« Reply #1 on: August 16, 2017, 09:05:46 AM »

Sky have no BRAS for regular customers - you aren't using PPPoE on a Sky ADSL or VDSL connection, you use MER. They have no handover of anything interesting from BT as they don't use BT's DSLAMs on ADSL and get delivered straight Ethernet on VDSL.

BT's involvement ends either at the end of the copper line on ADSL, or the end of the Cablelink connecting BT and Sky for GEA/FTTC. BT don't aggregate any connections together for Sky in any way other than to deliver a bunch of them on each Ethernet link so no BRAS needed.

Use of MER means the network until the Sky edge router is all layer 2. From there it's into their MPLS cloud so they can show you as many or as few of the hops they desire.

The closest thing to a BRAS is the edge routers where the switched MER connections terminate and the network becomes a layeer 3 network, but that's just a router with a layer 2 interface.

Basically if you aren't reselling your xDSL network a BRAS is optional, if you are reselling but also have your own retail customers a BRAS isn't required for your own customers but is likely required for the wholesale ones.


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Re: SKY BRAS / architecture (DSL Broadband)
« Reply #2 on: August 17, 2017, 08:23:47 AM »

Hi thanks that's great, appreciate it. So someone like SKY will have no DSLAM or use a DSLAM? From the end of the copper phone line it just goes back via Ethernet into their pop/core? No MSAN? No BRAS? What about an authentication server (radius?)

Are they predominantly sending data and voice down as Ethernet?

Sorry to ramble I'm looking at traditional DSL setups and from what you say they have bypassed some of the equipment t I mentioned? How do they terminate PPP/PPPoE or IPoE sessions?

Thanks again


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Re: SKY BRAS / architecture (DSL Broadband)
« Reply #3 on: August 17, 2017, 11:24:41 AM »

So someone like SKY will have no DSLAM or use a DSLAM?

Depends upon the product.   
For ADSL, being MPF LLU they have their own MSANs in the local exchange.  Everything goes over Openreach copper to the MDF in the exchange.
A Handover Frame passes voice and data over to the LLU MSAN and traffic then goes via their backhaul - See LLU Handover Frames.  There's photos on that page of the Handover Frames & the Optical Fibre Distribution Frame Cabinet.

For VDSL the DSLAM is in the FTTC cab so belongs to Openreach and all the DMT stuff such as sync etc is done there.
Data from the cab goes back to the headend exchange (which may not be the local one) to the Openreach OLT.  From here the SP can purchase GEA cablelink connectivity to hook up to their backhaul.
Any voice telephony is as normal from the PCP to the MDF at the local exchange. - See How FTTC works
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