In reply to a post by MrSaffron:

Backhaul is usually 1Gbps but can be multiples of this

Is that from exchange to fibre cabinet using 1Gbps speed down & up but capped at 80Mbps / 20Mbps or 40Mbps / 10Mbps whichever the customers choose product?

No. That is like saying your PC has a 1Gb link to your router but capped to 100Mb by the Open reach modem and 80Mb by the VDSL line.

There is no capping. The speed of your VDSL link and the speed of the cabinet backhaul are nothing to do with each other they are completely separate links so no capping of one to the other.

Actually 1Gbps doesn't sound enough to me for anything but a lightly-loaded cabinet. A fully-connected one would need a lot more than that.

Bearing in mind (for those who don't know) that if the user modem is on then the number of bps passing is as per the connection speed independent of how much data that user is consuming at any given time.

Edit - final paragraph struck out as per Ignitionnet's points. I was thinking ADSLx not FTTC . 1Gbps still doesn't sound enough for a well-used cabinet.

Edited by RobertoS (Sun 29-Jun-14 20:30:59)

If you look at the specs for the ECI M41 MSAN it supports link speeds up to 2Gbit per card so I guess it is possible to have a link up to that speed.

And the DSLAM in the cabinet will not be passing on the handshakes etc, only the useful data from the PPPoE tunnel

NOTE: Multiple Gig fibre links is possible and as many FTTH advocates keep pointing out once you have a fibre link in place you can run what ever speed you like across it.

Taking the extreme figure, a 1Gb connection on a 288 user cabinet would provide on average 3.47Mbps per user. So 10Gbps would be necessary.

Edit - typo of 3.74.

Edited by RobertoS (Sun 29-Jun-14 19:43:32)

In reply to a post by RobertoS:

Bearing in mind (for those who don't know) that if the user modem is on then the number of bps passing is as per the connection speed independent of how much data that user is consuming at any given time.

Yes the cabinet is sending up to 80Mb of 0s to the end user if the line is entirely idle. Relevance to the backhaul question though Bob?

The relevance is probably related to the lines being in use.

In reply to a post by RobertoS:

Taking the extreme figure, a 1Gb connection on a 288 user cabinet would provide on average 3.47Mbps per user. So 10Gbps would be necessary.

Edit - typo of 3.74.

Taking the extreme. However with the average uptake and the use of 40Mb products by some I can easily imagine most cabinets being okay with a single backhaul or at most 2.

There are at least 5 hanging off here. Hmm. That 5 would've been ample to backhaul 320 premises via GPON. They could even have used the minimally 40mm ducting network specified for copper or CATV that's already in the ground serving each and every house.

You just reminded me of something actually Bob, thank you!

Isn't it sending empty packets, as does ADSLx?

Anyway, we are talking about the link from the cabinet to the exchange, not to the end user.

Thinks ....

How is the PPP session between the user and ISP get maintained if there is no traffic? The norm appears to be to keep FTTC routers switched on as well as the modem. Plus BT and Sky at least are now both supplying modem/routers.