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Author Topic: BT nationwide rolling out G.INP/PhyR and changes to DLM.  (Read 63156 times)

kitz

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BT nationwide rolling out G.INP/PhyR and changes to DLM.
« on: January 07, 2015, 11:12:09 PM »

It would appear that from 12th of Jan, BT Openreach is rolling out G.INP technology nationwide on VDSL lines. G.INP -alternatively known as PhyR, gives effective protection against noise bursts.

Traditionally the way the DLM handled lines that were subject to frequent noise bursts was to increase the Target SNR Margin to give the line a larger buffer zone.   G.INP works slightly differently by lowering the BER rate and is designed to work alongside Vertoring (which improves sync speeds by effective protection of crosstalk).

Quote
G.inp coding now provides an improved retransmission-based error-handling mechanism for VDSL2 & VDSL2 Vectoring which results in significantly lower overheads. By replacing the traditional Forward Error Correction (FEC) mechanism, G.inp avoids the FEC-associated fixed overhead of about 12 percent in typical cases, and G.inp only kicks in when there’s actually an error to correct.

- See more at: http://www2.alcatel-lucent.com/techzine/vdsl2-vectoring-delivers-on-its-promise/#sthash.Gibov2ll.dpuf

Some of the more observant amongst us on this forum have already suspected that BT had possibly been dabbling with G.INP/phyR & DLM for a while and its certainly not gone unnoticed the introduction of FEC without interleaving.

What is unclear at the moment is any definite statement that BT 'may' start to use g.inp as one of the parameters for the DLM, but from information available, it would appear that they may well be doing so - Again some of us have noticed differing levels of INP applied.   

What is new is the nationwide roll out and the possibility that some modems with older firmware may have problems obtaining internet access (sync but no PPP) if it has a G.INP profile applied by the DLM.

An example could be replacement of an ECI modem (which natively does not support PhyR) on a line that already has an INP profile applied by the DLM,  may not be able to obtain PPP until its firmware has been updated.
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guest

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Re: BT nationwide rolling out G.INP/PhyR and changes to DLM.
« Reply #1 on: January 08, 2015, 09:42:35 AM »

Finally!

Not joking but I'm pretty sure that BT are the last teleco in any developed country to implement g.INP - its verging on farcical how far behind they are.
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broadstairs

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Re: BT nationwide rolling out G.INP/PhyR and changes to DLM.
« Reply #2 on: January 08, 2015, 10:12:30 AM »

Sorry if this is a naive question but how - if at all - might this affect customers who do not have BT as their ISP?

Stuart
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Chrysalis

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Re: BT nationwide rolling out G.INP/PhyR and changes to DLM.
« Reply #3 on: January 08, 2015, 10:32:17 AM »

Sorry if this is a naive question but how - if at all - might this affect customers who do not have BT as their ISP?

Stuart

Openreach handle all the VDSL connections so I think it will affect everyone, the only reason there may be "any" doubt to this is the recent discussions about the "custom" field in the DLM parameters.

I had FEC enabled on fast path on my downstream during my last fault, although I have no idea if it was due to this phyr or not because interleaving has never been a requirement for FEC.  But one thing was clear, I believe when that happened it was the first time I had heard of DLM implementing such a configuration and it was on my own line.
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kitz

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Re: BT nationwide rolling out G.INP/PhyR and changes to DLM.
« Reply #4 on: January 08, 2015, 09:15:11 PM »

Reading the info again it certainly seems to imply that it is now used as one of the DLM parameters for FTTC and they have named this profile parameter "ReTX".


What does it mean for the EU's..  well basically g.inp/PhyR Error correction is far more efficient with overheads that the traditional RS FECs.  Less overheads = more actual throughput speed.  So the theory is that lines using G.INP FEC algorithm should be able to sync at a slightly higher rate than a comparable line using traditional RS FEC.

The warning is that because its now used as a DLM parameter, it could cause problems on modems that aren't compatible with g.inp - such as the native ECI modems. These should be automatically updated via the BT Agent thingy so if you've had one a while then it should be fine....  but no doubt there are some ECI modems which havent been upgraded yet (such as the one thats been in my cupboard for a well over a year and some on BT vans etc)  and those are the modems that may not be able to attain PPP session.

This is worth bearing in mind for users that swap between modems, because if the line has already been categorised and profiled by the DLM with a ReTX profile, then it wont be able to get access to the internet despite being in sync.  One way round that would be a DLM profile reset.. but on that latter point BT are also monitoring for "misuse of DLM resets".
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guest

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Re: BT nationwide rolling out G.INP/PhyR and changes to DLM.
« Reply #5 on: January 09, 2015, 08:36:56 AM »

When Sky implemented g.INP on ADSL nearly 3 years ago they found that it increased sync rates by between 10-20%.

My own line went from being rock-solid (handful of CRC errors/day) @ 17.5Mbps to being just as rock-solid at 20.5Mbps. This of course depended on the modem/router being capable of g.INP, which most of the Be/O2 routers weren't & hence as they (mainly) all wanted to use their own (ancient) Technicolor junk they had lower speeds when they were switched to Sky exchange kit.
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kitz

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Re: BT nationwide rolling out G.INP/PhyR and changes to DLM.
« Reply #6 on: January 09, 2015, 11:19:01 AM »

I just found this which states that Sky have been using it since Easter 2013, but what I note in there is that it confirms that as we suspected that BT has indeed been trialling it on VDSL since 2013. - link


Re the TG582n - the DSLchipset in those routers is actually very good.  I dont deny that its been around a while now and the wifi isnt brilliant, but when it comes to the DSLside its damn good.  It has a BCM6328 chipset (same as the HG612 & most of the Billions). 

Despite having several routers available I stuck with the TG582n when on adsl2+ because it gave me the best sync speeds and was rock steady. This is why so many BE users liked it.  Any moans about that particular router are all to do with wifi not the DSL chipset. Its because of its chipset and DSL stability why ISPs such as AAISP and Zen also recommend it. 
Due to its BCM6368 it should natively be compatible with g.INP so no idea why it shouldnt work when on Sky. Be* were talking about implementing g.inp on their MSANs several years ago before they got bought out. afaik they trialled it, but never got around to rolling it out to all their MSANs.

It's the modems such as the ECI's which use a Lantiq VRX-268 chipset which may have problems and need updated f/w.  This includes the HomeHubs, but BT will automatically do that via the BTAgent.  All the BCM6368 and BCM63168 based routers should be fine. 
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Chrysalis

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Re: BT nationwide rolling out G.INP/PhyR and changes to DLM.
« Reply #7 on: January 09, 2015, 11:21:03 AM »

BT trials really are excessive, a 2 year period for testing is just insane. DSL can be so much better than it is in this country, think of all their wasted cash on engineer visits etc. because they like a limping duck on technology rollouts.
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HPsauce

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Re: BT nationwide rolling out G.INP/PhyR and changes to DLM.
« Reply #8 on: January 09, 2015, 11:27:49 AM »

Interesting that BT are only doing this on VDSL whereas Sky were able to do it on ADSL2+.
I wonder if that's because BT have little control over what consumer-end equipment is connected except for FTTC installs?
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broadstairs

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Re: BT nationwide rolling out G.INP/PhyR and changes to DLM.
« Reply #9 on: January 09, 2015, 11:48:04 AM »

Another naive question  ;)  Is there any easy way to see this is active when looking at the router/modem?

Stuart
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kitz

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Re: BT nationwide rolling out G.INP/PhyR and changes to DLM.
« Reply #10 on: January 09, 2015, 11:56:06 AM »

Interesting that BT are only doing this on VDSL whereas Sky were able to do it on ADSL2+.
I wonder if that's because BT have little control over what consumer-end equipment is connected except for FTTC installs?

I have absolutely no doubt about that being the most likely explanation. 

I seem to recall in the hardware section someone purchasing a new vdsl modem/router and being unable to obtain a PPP session.  They ended up twiddling with all the settings including g.inp and SRA.. and only then being able to get a valid connection. We couldnt at the time understand why this would be. I cant recall the exact details now - I think it may have been in one of the ASUS threads, but dont quote me on that.
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les-70

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Re: BT nationwide rolling out G.INP/PhyR and changes to DLM.
« Reply #11 on: January 09, 2015, 12:01:56 PM »

   I wonder if the 63168 modems are designed to expect g-INP to be working.  At the time of the 63168 release most of the worlds service providers were probably already implementing g-INP. 

  That might help explain why I, and some others with CRC and ES spikes present on their line, get bigger CRC and ES and often SES spikes with the 63168 modems.  The HG612 with the 6368  currently seems better on these lines but only with regard to these spikes.
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kitz

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Re: BT nationwide rolling out G.INP/PhyR and changes to DLM.
« Reply #12 on: January 09, 2015, 12:19:02 PM »

   I wonder if the 63168 modems are designed to expect g-INP to be working.  At the time of the 63168 release most of the worlds service providers were probably already implementing g-INP. 

  That might help explain why I, and some others with CRC and ES spikes present on their line, get bigger CRC and ES and often SES spikes with the 63168 modems.  The HG612 with the 6368  currently seems better on these lines but only with regard to these spikes.

I did wonder that myself when I saw your post last night in another thread about it. 
 
I (and several others) didnt see the same issue with the 63168 as it works better on my own line, but then again I dont get many large burst noise events...  which is where g.inp is supposed to be the most effective. I dont know Im afraid but yep it could be a contributing factor that cant be ruled out.     
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guest

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Re: BT nationwide rolling out G.INP/PhyR and changes to DLM.
« Reply #13 on: January 09, 2015, 01:12:39 PM »

Interesting that BT are only doing this on VDSL whereas Sky were able to do it on ADSL2+.
I wonder if that's because BT have little control over what consumer-end equipment is connected except for FTTC installs?

I have absolutely no doubt about that being the most likely explanation.

Amusingly that's not the case as Sky permit you (they changed T&Cs a couple of years ago - just after the g.INP trial) to use whatever equipment you like on ADSL services. The DLM works fine on a 6dB margin regardless of whether the router supports g.INP but obviously ex-Be people were used to 3dB margins with no DLM & things are a bit iffy at 3dB IMHO.

You are however obliged to use Sky-provided equipment on VDSL2 services. Sky changed their T&Cs last year to specify that & blamed BT (quelle surprise!) so its not the way you think.....

Edit - and regarding the Technicolor Be/O2 kit, just how much of that do you think had modem firmware released in the last 5 years ;) Sky updated the 2504n kit remotely after the trial so g.INP was enabled - pretty sure that most BCM reference kit shipped with modem f/w that disabled g.INP prior to 2012 or so. People did try to tell the ex-Be people but most had made their minds up that Sky was junk long before they came onto forums :)
« Last Edit: January 09, 2015, 01:22:41 PM by rizla »
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kitz

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Re: BT nationwide rolling out G.INP/PhyR and changes to DLM.
« Reply #14 on: January 09, 2015, 04:20:55 PM »

lol...   still mates and a lot of respect for each other..  but the time old argument between you and me.  :lol:

I liked BE.. it was great, as was the support.   3dB worked fine for me with my TG582n rock steady 24/2.6 until x-talk even then lots of BE users were stable on 3dB.  BT also does 3dB and theres quite a few BT users on a 3dB profile. BE went down the pan due to lack of investment in technology and we all know why that was.

My experiences with Sky havent been good, I put several pple on Sky years ago thinking it was cheap and they wouldnt notice the difference.  One of them was dad, another my daughter and its me that has to sort out any problems they have.   My experience with dads line wasnt good.  Support are awful and with my daughter they repeatedly promised things that never materialised - including the MAC key when she'd had enough and wanted to move after a physical line fault and how Sky handled it. She's very happy with her current ISP.   

Dads problem was the DLM restricting him to <2Mb and no matter how hard we tried over many months that never much improved so he moved away last year.  Yet it happily syncs at 7Mb on a BTw based line with just a small amount of interleaving (22ms v skys at one time 96ms to the BBC).  I know you say things are different with their DLM now... but up until last April, things certainly weren't.

Would I go with Sky..  nope I wouldnt, but I respect that you have a different opinion and experiences.

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