On 14/05/13 23:47, Brandon Butterworth wrote:
I see a lot of operators are already selling FTTC
as "uncontended"
I've only noticed unlimited.
Googling FTTC and uncontended definitely yields results!
Can FTTC really be claimed as uncontended when
People stopped implementing a specific cotnention long
ago and at BTs backhaul rates why would they contend you,
there's money to be made on letting it flow and each of
you pay.
I was referring specifically to GEA where the FTTC circuits are handed
over to the LLU operator in the local exchange rather than the use of a
wholesaler to deliver the circuit back to you centrally.
In my mind, in the case of using a wholesaler, you have even less
visibility over how contention is provisioned on the wholesalers network
(e.g. you have no monitoring of internal circuit usage or ability to
force circuit bandwidth upgrades on the wholesaler where required -
you're relying on them to do that for you).
operators have zero control or monitoring of the fibre circuit from the
exchange to the cabinet (which is only going to become more congested
over time)?
I don't see why that would congst while they are charging
a profitable rate, many times global transit rates which others
seem able to sustain. Seems like they'll just build a bigger
network.
In the vast majority of cases there will only be a single 1G circuit
(PON on the back end - congestion on that is another story!) feeding a
cabinet. When that becomes congested, all bets are off. In fact, the NGA
FTTC product description describes just that case:
----SNIP---
Openreach has implemented a downstream Prioritisation Rate (PR) for each
of our downstream product bandwidth variants. The PR is a speed to help
us manage network capacity during peak times and acts like a variable
speed limit where we will momentarily reduce any line that is working
above the PR to ensure that everyone gets a share of bandwidth during
that peak period. If an end user’s actual access line sync speed (the
Peak Information Rate), is already below the prioritisation rate, their
line will be unaffected by any momentary speed reduction that we apply.
The two prioritisation rates that we have applied in the network:
Product Bandwidth | Variant Prioritisation Rate
Up to 40Mbit/s | 15Mbit/s
Up to 80Mbit/s | 30Mbit/s
If the network experiences congestion and needs to implement the
prioritisation rate, we will discard any packets of traffic above the
prioritisation rate. You can, if you wish, mark traffic coming into our
network to help us determine the priority of traffic to drop in this
scenario. There are two levels of priority, can drop, and should not
drop. These are 802.1p markings and are described in SIN498.
FROM:
http://www.openreach.co.uk/orpg/customerzone/products/super-fastfibreaccess/fibretothecabinet/description/downloads/FTTC%20Product%20Description%20Issue%209.pdf
---/ SNIP----
At least with an LLU install, I can put in EFM equipment into a BT
exchange and backhaul it directly over my own network and know that I
control all circuits end-to-end (and can thus monitor contention etc). I
can't say that about FTTC and nor can anyone else as the backhaul to the
cabinet is shared by design with no visibility to the network operators.
Cheers,
Robin.
