How to get Chorus to look into problems that might cause low ADSL2+ sync rate?

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Ragnor

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#647323 28-Jun-2012 01:10

IcI:
... Chorus has tried port reset, re-termination of the line at the exchange/cabinet, tried moving your line to a different port/line card... then it's probably down to dodgy phone cable between you and the exchange/cabinet.

I believe that is exactly what is being asked. How to get Chorus to do the 'port reset, re-termination, moving port/line' etc without simply closing the ticket as done previously?

Yes, it's the ISP's job to log requests for these with Chorus. Nothing @dteirney can do personally other than check with the ISP really.

@dteirney, you sure these have been tried?

Anyway...
- Noise margin is a buffer, the amount of the normal dsl frequency range that is not used for stability (more buffer = lower line rate but more stable connection)
- Signal to noise ratio is not the same thing as noise margin
- Lots of modems label these badly/wrong/mix them up

Unfortunately...

Chorus do not offer profiles with lower than 12dB due to historical issues with poor wiring/lines. Yes it's the dumbest decision ever and should be reviewed, can't see it happening.

6dB is common overseas. Telstraclear offer 9dB on their own equipment, Orcon/Slingshot/Vodafone/Compass offer down to 6dB on their own equipment.

Yes 6dB noise margin vs 12 noise margin accounts for the ~2Mbit difference in line rate but I still think your line rate for 32dB @ 12dB Noise margin should be around ~10Mbit rather than ~5-6Mbit.

@dteirney you definitely want to confirm with Fyx that a port rest, different line card etc have been tried imo.

Ragnor

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#647324 28-Jun-2012 01:21

ChorusVan:

Your Internet Service Provider decides what service profile is configured on your ADSL2+ line - not Chorus.

Chorus does not offer lower than 12dB noise margin profiles though! ISP can't request what Chorus isn't offering!

dteirney

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#647371 28-Jun-2012 07:49

I got an email last night stating that the change to turn interleaving off has been made. Not entirely sure if I can confirm that from the modem somehow. If it has indeed happened it doesn't appear to have made any significant difference to throughput.

Both of these were just done with the noise margin set back to 12dB.

I tried to get a measure of international throughput last night but stats with speedtest.net to San Francisco were all over the place last night.

I contacted FYX via email this morning to ask if port reset, re-termination etc. has been looked into.

dteirney

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#647378 28-Jun-2012 07:57

The interleaving change must have been made because now the line connection stats are quite different.

Before, with interleaving ON:
Connection rate: 5.5Mbit
Line attenuation: 32db
Noise margin: 12.0db

After, with interleaving OFF:
Connection rate: 5.0Mbit
Line attenuation: 29db
Noise margin: 12.3db

The lower connection rate probably accounts for the lower throughput test just done to the geekzone speedtest server.

Regs

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Snowflake

#647532 28-Jun-2012 11:39

dteirney: I got an email last night stating that the change to turn interleaving off has been made. Not entirely sure if I can confirm that from the modem somehow.

your ping latency often drops with interleaving off. mine went from 30ms on the seond hop, to 7 or 8ms:

1 1ms 1 ms 1 ms RTA1320.home [192.168.0.1]
2 8 ms 7 ms 7 ms cpiak-internet.tranzpeer.net [202.180.x.x]

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webwat

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#649141 1-Jul-2012 16:52

ubergeeknz: As you've probably realised already, this is just the result of a "safe" DSL profile being used by Chorus whereas Vodafone may have been using a more "aggressive" profile.

Aside from any wiring faults in your house, which are largely negated by your master filter anyway, there's not much you can do unfortunately, unless you can convince them to use a more aggressive profile. Sometimes non-interleaving profiles have a tendency for lower SNR margin targets, if that helps.

Interleaving off means that latency improves but data errors on the ADSL link aren't corrected, so if your SNR reduces then you will have lost data packets until the modem negotiates a slower line speed. ADSL2 does this automatically so the problems aren't as bad as they used to be, but it shouldn't affect the ADSL data rate (only the effective throughput).

Some telecom lines have lots of branches going to multiple streets, so they have more noise issues despite reasonable attenuation. The line speed is nothing special but ok for the attenuation, so I would focus on whether the ISP can find any issues that might cause your video to buffer. 5Mbps should be enough for video.

Time to find a new industry!

dteirney

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#652319 7-Jul-2012 18:46

I've found some more tools that have shed some light on why the sync rate is so low but unfortunately not why.

I installed the ADSL DMT tools package onto an old netbook (the only Windows computuer I have in the house) and connected it to the modem. As can be seen from the picture below a reasonable chunk of the ADSL spectrum is not being used, presumably due to interference of some description. Perhaps from either external noise or internal noise caused by echos if there are indeed any bridge taps between us and the exchange.

The SNR monitor didn't appear to show any extreme variation.

If anyone knows how to read these ADSL spectrum usage graphs and could provide more information that would be grand.

Quic Broadband

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webwat

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#652600 8-Jul-2012 19:15

Might have a play with that software and see if it runs with my test modem. I don't think chorus block different frequencies as part of spectrum management at the moment (but they should be if the cables are shared by both cabinetised and unbundled users in the same area). Long reach profiles certainly would focus more on the lower frequencies in the spectrum but thats even slower than yours.

Keep in mind that some frequencies you can see there are used for upstream data.

Time to find a new industry!

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