LLU *technical* question

Trying to help an LLU victim - can someone tell us what ADSL mode (G.dmt, ADSL2+ etc) their LLU connection uses and what SNR margin/downstream speed/attenuation figures they get. Thanks.

Operation mode: G.DMT
Encapsulation: PPPoA VC Mux

My SNR is 6.0dB, Attenuation is 41dB and speeds are 5184/512Kbps (down/upstream respectively).

thanks, so it can work

the other guy gets ADSL2+

The default LLU minimum SNR for both up and downstream is currently 12dB. I suspect Chris may not be on LLU.


The PUG Tiscali FAQ explains what you need as well as a lot more info, available here.

Definitely on LLU, Peter (and suffering because of it!), but I suspect my router doesn't accurately report the SNR. It used to say 3dB when I was on IPStream for example, which seems a little unlikely!

Your router is way off then as LLU won't allow an SNR below 12dB, I know as I have been in discussions with PN about it being so high and hope to do some testing with with a lower SNR 'soon'.

his upstream looked LLU-like. Heard of anyone else with an ADSL2+ capable router having problems with it using the "wrong" standard ?

how come my SNR is 16.5 (up and down) and I'm on the dreaded LUU?

Not all routers report correct line stats. While my SNR appears to be shown correctly, the line attenuation I know is still 4dB out on a DG834v2 f/w 3.01.25.

What router are you using? Have you looked to see if a firmware update exists?

Chris could have been on a business product (Max pro) which has an upstream speed of up to 832Kbs. The SNR of 6dB is the normal default for Max, hence my initial thought that that was what he was on.

Anyway, I'm not aware of tiscali having any exchanges currently set for ADSL2+ so using that setting on the router should, in the absence of a true ADSL2+ protocol on the exchange, switch back to ADSL1 functionality, but what that would default to on the router I dont know.

The actual protocol selected may not matter much anyway, it the MUX setting that is the important one for LLU - i.e. VC MUX.

Peter,
Its a Belkin F5d7630UK4a with firmware 1.08.03 (latest I think). If the SNR was lower would my connection be higher? On BTmax I was 8000/256, now I'm 6176/512, but I think it's the interleaving (spit) that is throttling the upload limit.

Due to the conservative SNR that Tiscali are using, it does mean your speeds, both up and down will be slower than they were under Max if you could only achieve the higher speeds with a SNR at or near 6dB. I'm not yet sure what impact interleaving is having on LLU with regards to sync speeds as I have not yet asked for interleaving to be disabled on LLU (which is also a sticking point with Tiscali!). It certainly is not affecting my ping times which have returned to pre Max levels - I had interleaving on when on max with a ping time around 50->60ms, now with LLU & interleaving it is back to 16 -> 20ms.

I know I could achieve 2500Kbs downstream speeds as that was what I was getting under Max initially with a 6dB SNR before BT decided to up my SNR to 15dB for no reason. Under LLU I currently cannot go above 1600Kbs on my Vigor 2600G or around 1900Kbs on my DG834v2 with the SNR limited to 12dB.

As I mentioned earlier, I am in discussions with PN via PUG to get my SNR limit lowered (which I know my line will take) but Tiscali are being difficult on this subject. PN are trying to convince them that they should be allowd to set the SNR on a line and it looks like they may be making some inroads with this with the aim of me being able to test a lower SNR profile 'soon, but soon has been stated for several weeks now so I still don't know when it will be.

I'm on MAX, my router can report SNR anywhere between -1db and 12db depending on the time of day. I don't believe it is unusual to start at a particular noise margin (in my case 12db) and then depending on the line conditions for this to vary during the day. I used to use a belkin 7633uk4a router where you could force the initial noise margin negotiation to a lower value than 12db but sadly for my connection I had to change router to achieve stability.

Hi

On LLU connecting via ADSL1

Sync around 7500 down, 640 up, SNR around 12-13db.

Via ADSL2+

Sync 8157 down, 600-630 up, SNR around 18-21db

Downloads speeds around 6500 whether peak or off peak.

Currently suffering from the disconnect issue where PPP is dropping a couple of times a time day, everyone seems to be affected at exactly the same time and Tiscali still looking into it. PlusNet have asked for all LLU users to raise a fault report via the fault checker on the portal but I am very reluctant to do this as it will be completely mis-understood by support staff who don't/can't read and I will end up with SNR being upped or something!

The LLU SNR cannot currently be changed by PN so there is no danger of that. With BT, it was the equipment that was automatically increasing the min SNR when it thought there was a problem, with Tiscali, that does not happen as the SNR is fixed at 12dB.

I'm also affected by the LLU disconnections but so far no signs of a fix from Tiscali/NTL yet.

As for raising a fault, as Tiscali have seen the problem happen, and the fact that quite a few would have already raised a fault due to the SS report, I don't see any benefit in adding to the ticket queues for a problem Tiscali have already admitted exists.

I'm also puzzeled by your SNR being significantly higher when using ADSL2+? My understanding is SNR is a physical condition of the line and it should not be affected by the ADSL protocol being used.

Also it does appear to be that some Tiscali echanges do allow ADSL2+ connections - assuming that is what was finally used during the ADSL negotiation phase.

Edited by deleted (Tue 05-Sep-06 11:24:18)

It will change on ADSL2+, more bins to average out.

Hi Peter

I didnt know NTL were providing anything in the Tiscali Wholesale network is it just the backhaul from some exchanges ?

Regards

bs0d.

It was news to me and a lot of others in PUG that NTL were involved. I'm not sure but I suspect some backhaul connections may be going via NTL where Tiscali don't have the connectivity to the exchanges or areas of the country then onto Tiscali before getting to PlusNet. How much NTL are involved I don't know. At the moment the finger is pointing in their direction but nothing conclusive has been communicated yet.

Thanks Peter.

Strange they only mention a 3rd party when they're looking to shift some blame

bs0d.

The disconnect issue appears to be fixed for me and possibly others - see the latest service status. I've been connected for 45 hours without a drop which is the longest I can recall when on LLU.

Tiscali are also using C&W backhaul. The backhaul provider has no affect on the ability to issue LLU Macs though. Sounds like a useful bit of buck passing to me.