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Standard User mrnelster
(regular) Wed 23-Feb-11 11:11:14
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FTTC-Contention ratio on "double cab"?


[link to this post]
 
Hi guys.

Our FTTC cabinet has gone in! The thing is there are two existing cabinets next to each other. I believe that the fibre feeding FTTC cabinets is apparently 1Gbps?

Does anybody know if openreach would have still only installed 1Gig for a "double cab"?

Also, when reading BT's unlimited FTTC package offers they claim 50:1 contention for home use. But it also goes on to state that one of the factors affecting FTTC speeds is the number of lines connected to the cabinet. Surely that's what the stated contention ratio determines anyway?

Anybody think they would contemplate oversubscribing our cabinet/s?? ;o)

Thanks.

Knowing how it works is completely different to understanding how it works.
Standard User Spasch
(experienced) Wed 23-Feb-11 11:15:34
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Re: FTTC-Contention ratio on "double cab"?


[re: mrnelster] [link to this post]
 
There are a maximum of 288 connections in a FTTC cab. There was a post sometime back (IIRC in this sub-forum) that explained the bandwidth available and the thinking behind extending capacity from individual cabinets. Keep in mind that not all connections will have the full 40Mbps capability.
Administrator MrSaffron
(staff) Wed 23-Feb-11 11:52:20
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Re: FTTC-Contention ratio on "double cab"?


[re: mrnelster] [link to this post]
 
One cable carrying fibre will carry multiple fibres, maybe 30 individual fibres. So multiple GigE is likely

Openreach delivers the FTTC connections in an uncontended manner to the handover node (exchange). How BT Infinity claim 50:1 when this is nigh on impossible since 2004 given how the wholesale network works is another matter.

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.


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Standard User yarwell
(sensei) Wed 23-Feb-11 12:37:43
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Re: FTTC-Contention ratio on "double cab"?


[re: mrnelster] [link to this post]
 
I think six fibres are the standard capacity of the chinese cabs. The committed rate per user is 20M or line speed if lower. 288 * 20M = 5.76G = 6 x 1G fibre. Seems to fit.

The overall contention of BT Infinity will be much higher than that from the cab to the exchange. Less than 100k provisioned per user so a 30M connection is probably 300:1

This might sound daft, but not if you look at the GB/month allowances and turn them into kbits/s. 40 GB over 5 hours per night = 74 kbytes/s = less than 1Mbit/s per Option 1 user if all on at the same time.

Phil

MaxDSL - goes as fast as it can and doesn't read the line checker first.

MaxDSL diagnostics
Are your kids pirates ? Limewire, Bearshare, Kazaa, BitTorrent, eMule are all tools of the trade.
Anonymous
(Unregistered)Wed 23-Feb-11 13:28:49
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Re: FTTC-Contention ratio on "double cab"?


[re: mrnelster] [link to this post]
 
The fact that there are 2 cab is irrelevent, It is the number of people on FTTC that defines how much backhaul will be provided.
This is 1G up to 66 customers then 2G to 132 etc. This get you the Openreach guaranteed 15Mb download from Cab to Exchange. Anything above 15Mb is contended.

The 50;1 refers to the end-end contention including exchange to core POP and Core to Internet.

BTRetail have no say in the Openreach capacity between Cab and Exchange so over contention is not possible here for individual ISPs..
Standard User mrnelster
(regular) Wed 23-Feb-11 18:35:40
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Re: FTTC-Contention ratio on "double cab"?


[re: Anonymous] [link to this post]
 
So assuming that the copper between the end user and the cabinet is short and in good condition, does that make the minimum throughput 15Mbps taking contention into account? And is traffic management likely to affect this minimum?

I'm not a heavy downloader. It's mainly gaming and forum browsing, so I shouldn't be throttled on that basis.

I'd like to use AAISP or Aquiss etc., because I have been led to believe that BT don't manage their traffic shaping consistently from a users point of view. Is that a misguided belief? ;o)

Knowing how it works is completely different to understanding how it works.
Administrator MrSaffron
(staff) Wed 23-Feb-11 20:10:08
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Re: FTTC-Contention ratio on "double cab"?


[re: mrnelster] [link to this post]
 
If connected at 40Meg you would expect to get 40Meg to the local handover node, but as no websites are hosted at this node it does not help.

What it means is that you are then down to the contention from the exchange, so if an ISP budgets on 100Kbps per user at peak times it might be slow, but an ISP budgetting on 200Kbps may be faster.

Openreach carries out no traffic management or throttling, anything you've read will be confused people believing that BT Infinity is the same product that ALL FTTC providers are selling.

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User Zarjaz
(knowledge is power) Wed 23-Feb-11 20:43:00
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Re: FTTC-Contention ratio on "double cab"?


[re: mrnelster] [link to this post]
 
How can you be be sure that the DSLAM cab is supplying both copper cabs ? Are you even sure that they are two Openreach cabs ?
Maybe one is a PCP, (primary connection point,) and the second an SCP (secondary connection point) ?

Standard User mrnelster
(regular) Wed 23-Feb-11 22:49:04
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Re: FTTC-Contention ratio on "double cab"?


[re: Zarjaz] [link to this post]
 
In reply to a post by Zarjaz:
How can you be be sure that the DSLAM cab is supplying both copper cabs ? Are you even sure that they are two Openreach cabs ?
Maybe one is a PCP, (primary connection point,) and the second an SCP (secondary connection point) ?




Both identical cabs. One appeared next to the other when a new development of around 100 houses was built around 10 years ago. They are on the edge of the development by the main road, with nothing but fields opposite. I know which cab I am connected to (P33). Couldn't see a code on the one stood next to it.

As for the scp/pcp bit?

Stares blankly into space! smile

Knowing how it works is completely different to understanding how it works.

Edited by mrnelster (Wed 23-Feb-11 23:17:49)

Standard User chris6273
(member) Wed 23-Feb-11 23:31:15
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Re: FTTC-Contention ratio on "double cab"?


[re: mrnelster] [link to this post]
 
In reply to a post by mrnelster:
Hi guys.

Our FTTC cabinet has gone in! The thing is there are two existing cabinets next to each other. I believe that the fibre feeding FTTC cabinets is apparently 1Gbps?

Does anybody know if openreach would have still only installed 1Gig for a "double cab"?

Also, when reading BT's unlimited FTTC package offers they claim 50:1 contention for home use. But it also goes on to state that one of the factors affecting FTTC speeds is the number of lines connected to the cabinet. Surely that's what the stated contention ratio determines anyway?

Anybody think they would contemplate oversubscribing our cabinet/s?? ;o)

Thanks.


FTTC cabinets can only serve 288 lines so they won't be oversubscribed.

Also, each and every cabinet will house a DSLAM with its own 1Gbps (Or multiples thereof) fibre connection to the exchange.

Nothing to worry about wink

-------------------------------------------------------------------
6851kbps Throughput:
My Broadband Speed Test

Downstream Upstream
Connection Speed 8128 kbps 448 kbps
Line Attenuation 13.0 db 10.0 db
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