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[phi2008]

I'm due to move to Talk Talk Fibre Large and was wondering what people thought of their network? Do they skimp on exchange backhaul for instance? This document is from a presentation by Talk Talk and shows a typical backhaul of 1Gb/s(I'm in a small town - Exmouth - so assume this might be applicable). To me this doesn't sound like a lot of bandwidth to service significant numbers of FTTC customers but since I've nothing to compare it with I could be completely wrong. Any opinions?

[kitz]

hmmm  it doesnt seem a lot - especially if FTTC is involved.  BTw has quite a lot more bandwidth than that on their backhauls and use (multiple) 2.5Gb or 10Gb links.  iirc Be/O2 used to have Gb links for their adsl2+ backhauls.  It will depend on how many MSANs they own in the exchange.

Having looked at it again, that diagram could imply just copper adsl2+ and its possible that they may have multiple Gb links.  At my own exchange years ago TT used to have 2 x possible 1Gb links, but at the time they both fed to the same Gb (opal) backhaul , and they will also have inherited the Tiscali one which they use for TalkTalk Business.




I wouldnt be too surprised if at the larger exchanges at least they will install another link for the FTTC customers, but that could become a point of contention depending upon how many users there are.  1Gb backhaul is insufficient to cope with fttc   

   

[phi2008]

Yes, looking at the diagram again it shows copper all the way from the customer to the exchange so perhaps it's representing ADSL? Also if you had a fibre optic backhaul why run it at a speed as low as 1Gb/s?

[kitz]

Also if you had a fibre optic backhaul why run it at a speed as low as 1Gb/s?

Some of the links are just 1Gb links - used to be that way for BT's 20CN backhaul.   

You cant just use any type of fibre optic for backhaul - unlike fibre cable used in the field for fttc (the blue jacketed stuff) multi-mode cable is absolutely no good for backhaul. Modal dispersion reduces bandwidth on multi-mode fibre, kind of in a similar way to how copper attenuates over distance... so they have to use the more expensive single mode fibre.  To go >10 Gbps they then use Wave Division Multiplexing to get sufficient bandwidth for the core.   WDM is not multi-mode, they are two separate beasts.  WDM is very expensive - especially D-WDM.  BT has 86 DWDMs and 1000 CWDM locations. 

The fact that TT's Collector nodes to core are 10Gb links, and they say 2 DWDM for the core,  then the satellite exchanges possibly are going to be 1Gb links (or multiples of). 

[Chrysalis]

whether its enough or not depends on the utilisation, from an accountant point of view it be bit silly to deploy 10gbit/sec capacity for say a couple of hundred adsl customers.  Now days isp's dont deploy using fixed contention levels but instead deploy as needed.  So whether its enough or not would depend on the usage levels of customers, spec of line's been served and the number of customers.

BE also used to only deploy 100mbit/sec to some of their exchanges on adsl2+, hence their congestion problems.

When i was on ukonline many years ago my exchange had a single gigabit backhaul and the service was perfect in terms of performance.

[guest]

When i was on ukonline many years ago my exchange had a single gigabit backhaul and the service was perfect in terms of performance.

It didn't.

It had 2 x 1 Gbps backhaul links as that was the minimum provisioning Easynet did once BT managed to get themselves out of the Mbps backhaul mindset.