BT Infinity

I thought I would throw my three penneth into the discussion about BT infinity.

I switched to BT on 18 May. I am 3900 ft from the cabinet. Thats measured by line reflection by the BT engineer and is pretty close to the OS map and Sat Nav ( I know the cable route). On day 1 I got 52Mbs down and 8 up. It settled down to about 36 Dn 8 Up by the end of the day. However, the modem was dropping PPP 4-6 times an hour, but the speeds didn't drop. A week later Openreach brought me a new modem which didn't drop PPP.

When BT took over my phone I started getting noisy phone calls which I had never had in the past.

After a few weeks I bought a Draytek 2750n which worked straight away. I could see from the line stats lots of UAS errors on the upstream. The margins were about 6 db Dn and 3 db Up. Over the following weeks the Up margin climbed to 12db Dn remained at 6db but the dn speed dropped to 23Mbs and Up to 2Mbs. The electrical line length was climbing too.

After weeks of complaining and several engineer visits to give me new modems I didn't need, BT finally sent someone look at the line. He replaced the drop cable, modem and the hub. It didn't work at all then. He then got me moved onto a new pair and port in the fiber cabinet and got my line "flexed". Everything worked then. The speed came back in both directions.

He told me I wasn't allowed to use any other modem, which was the first I had heard of the condition.

Speed tests with spedtest.net and BTSpeedtester gave consistent results about 34 Dn 8 Up.

After a week I switched back to the Draytek. The down speeds are the same but the up speeds are about 3-4 Mbs on Speedtest.net and 5-6 Mbs on BtSpeedtest. I then found TBB speedtest. It gives about the same down but about 8Mbs up. Putting the Openreach modem back gets 8Mbs up with all testers.

Dsl reports tweak test shows my MTU up and down is 1442, it was 1492.

My margins are 13db Up, 6Db Dn. Sync is 9998 Kbs Up, 36350 Dn. My electrical line length has dropped and is now 19db.

BT have not been able to solve the noisy calls problem.

Draytek have sent me new firmware and are trying to figure out why their box wont achieve the same speed on the up side as the BT modem.

Bt support has been useless through out. If they hacve anybody who understands VDSL I cant get to speak to them.

You are aware that only the Openreach modem is supported, so that would explain why no real help with VDSL2 modems.

In short the only support you will get is Draytek, I presume the UK supplier has tested the hardware on a VDSL2 line to see if it works reasonably.

If the upstream sync is at the 10Meg point on the draytek then the issue may NOT be the VDSL modem, but routing performance of the device. The speedtest test is using HTTP profocol, and our tester is not and this may be the difference, hint look at upstream QoS settings.

Whilst I would not expect BT or Openreach to provide support for 3rd party modems/routers, I would also not expect it to be a contractual condition that only the Openreach modem can be used. Any VDSL2 compliant modem should be able to work.

The new firmware Draytek sent me made a big difference. I no longer get streams of error messages in the Draytek's log complaining about missing PADO packets.

I don't believe there is anything wrong with the modem at VDSL level, but there is obviously something different in the way the two modems handle the traffic.

My observation on speed tests was that the only differences I see are in upstream rates. Downstream is similar no matter whose speed tester I try. Upstream rates using your tester are about the same as the BT tester with the Draytek and the Openreach modem. With the Draytek, Speedtest.net and BT give consistently lower results. I will take a look at Qos.

My home network is hard wired and usually has 6 or more PCs sharing the bandwidth through a switch. If the PCs are not all using the same MTU is that likely to have an effect on throughput? The differences may be something to do with the way the Draytek integrates the routing and modem functions in the same hardware.

I think ypu have discovered exactly why you are "expected" to use the Openreach modem.

I was reading a believable article a few weeks ago, saying that the VDSL2 standards, (re firmware capabilities), are a minefield still, compared to ADSLx. Don't forget there are several different VDSL2 setups possible at the DSLAM end - Openreach currently using 8c? Which as I understand it will change when they increase the top speed. To 17something?

So anyone's chosen VDSL2 router may fail to get on well with the DSLAM.

All a very woolly explanation sorry - just what I remember of something sensible.

" would also not expect it to be a contractual condition that only the Openreach modem can be used"

Sorry to say, but as VDSL2 is new then this is what they expect at this time, until inter operability testing has been done, then anyone with their own hardware is on their own.

Was the same with ADSL in the early days (2000/2001).