Now on 21CN, Next Step?

Last night my line was migrated to the 21CN platform. Looking at my line stats in RouterStats this morning, there has been an improvement with a lower attenuation, higher sync speed and higher profile.

Downstream:
Noise Margin: 6.7 dB
Connection Rate: 5184 Kbps
Line Attenuation: 51.0 dB
Power: 19.1 dBm
Max Rate: 5216 Kbps

SF: 1968062
SF Errors: 556
Reed Solomon: 0
RS Corrected: 0
RS Un-Corrected: 0
HEC: 313
Errored Seconds: 1187
Severe ES: 8
Interleave Depth: 1

Upstream:
Noise Margin: 19.0 dB
Connection Rate: 448 Kbps
Line Attenuation: 28.0 dB
Power: 12.6 dBm
Max Rate: 964 Kbps

SF: 1970383
SF Errors: 25
Reed Solomon: 0
RS Corrected: 0
RS Un-Corrected: 0
HEC: 14
Errored Seconds: 0
Severe ES: 0
Interleave Depth: 1

Total Up Times (From SF counts):
WAN: 0 day, 09:18:17
LAN: 0 day, 09:18:17

CRC: 556
LOS: 5
LOF: 12
ES : 1187

I was previously syncing at around 4800 with a 4Mbps profile. My attenuation had been 53dB and I had long suspected a problem with my line's connection at the exchange (Dudley, West Midlands), as until about 2 years ago, my stats looked much like they do now. I have previously had a fault raised with Zen and BT where BT claimed they couldn't find any problems.

My Zen Portal Line Line Rate Data:

Upstream Downstream Sync Rate BRAS Profile Interleave Sync Date Date
0 4500 5120 adsl4500 Opt out 12-May-2010 02:47 12-May-2010 02:47
448 4000 4544 adsl4000 Auto 05-May-2010 18:43 05-May-2010 18:43

I notice that it's also switched interleaving off whereas it was previously on automatically. Is that a difference on the 21CN platform? It's certainly had the effect of reducing my ping times to websites and gaming servers (even while checking via a remote connection to my home PC that's connected to the router over a homeplug network).

On my Zen Portal I have an order showing (order no. 587199):

Order Item ID Product Price Billed to Status
687510 ZenADSL 21CN Migration New Product: Don't change product Care Level: Don't change care level zen******@zen 01384****** £0

Is this relating to the migration to the new platform and do I still need to raise a separate regrade request to move to the ADSL2+ service? I know I'm not going to see a massive improvement over my current speeds due to my distance from the exchange and my stats above, but what are my realistic expectations for speed and quality of service? I'd be happy with anything around 6Mbps (at least until BT add Dudley to their FTTC rollout).

Yes you need to place a separate regrade to get onto the ADSL2+ product.
Log onto the customer portal, and go to my services -> upgrade a service.

When you are selecting the new product choose the version without an 8000 in the description
(ie Zen 8000 Lite -> Zen Lite etc)

Edited by deleted (Wed 12-May-10 12:53:08)

How quickly after regrade can I expect to see an uplift in downstream speeds? I was regraded a couple of days ago, I can see I'm connecting using ADSL2+ and the upstream speed has increased to over 1Mbps, but my downstream speed has dropped to 5.5Mbps. I was expecting between 14 and 20Mbps with ADSL2+. Is there a retraining period or is this something Zen can fix?

TT

Hi,

I believe there is a training period for regrades to ADSL2+.
If you're still experiencing slower than expected speeds then please post your line stats, so we can compare sync speed/margin to your actual observed speed. (Usually you can find this on your router's admin section somewhere)

If the sync speed is as low as your observed line speed then its probably time to start investigating possible causes... Do the usual checks at your own premises (ie test at the BT master socket with nothing else connected - including at extensions, etc) If there is no improvement I'd contact support next!

I should point out of course that ADSL2+, does not always bring an improvement to your line speed. A small percentage of lines are more stable, and faster on the standard ADSL profiles. If it turns out this is the case we can of course swap you back.

Hope that helps....

Edited by deleted (Fri 14-May-10 14:55:43)

Hi,

I've got no issues with stability or random disconnections. Line length is around a mile.

gw1#show dsl int
ATM0/0/0
Alcatel 20190 chipset information
ATU-R (DS) ATU-C (US)
Modem Status: Showtime (DMTDSL_SHOWTIME)
DSL Mode: ITU G.992.5 (ADSL2+) Annex A
ITU STD NUM: 0x03 0x2
Chip Vendor ID: 'STMI' 'IFTN'
[...]
Capacity Used: 44% 100%
Noise Margin: 18.0 dB 6.0 dB
Output Power: 19.5 dBm 12.5 dBm
Attenuation: 28.5 dB 13.0 dB
[...]
DS Channel1 DS Channel0 US Channel1 US Channel0
Speed (kbps): 0 6656 0 1013

TT

Edited by deleted (Sat 15-May-10 17:44:16)

In reply to a post by _TT_:

DS Channel1 DS Channel0 US Channel1 US Channel0
Speed (kbps): 0 6656 0 1013

One thing I have noticed with the new connection is that the downstream channel doesn't change. It stays at 6656. The upstream is extremely variable, anywhere from 800 to 1222kbps. Is this indicative of misconfiguration or a fault?

TT

A variable sync speed should be ok on ADSL 2+, its supposed to support this without dropping the connection...

One thing that does look odd though is the huge (18db) Margin. Its normally around the 6db mark. Some SNR margin is required in order to maintain a stable connection, but with a margin that big there is a large chunk of your line's capacity going unused.

If everything looks ok at your end in terms of filters, internal wiring etc then I think a quick call or e-mail to support would be a good bet. Hopefully they can help get that sorted!

Looks like a banded profile? If so, support should be able to help.

In reply to a post by Gorskar:

A variable sync speed should be ok on ADSL 2+, its supposed to support this without dropping the connection...

As I read that statement I think SRA - is that the case as I thought BTWS had no plans to use it at this time, and the likes of BE are only just testing it with mixed results.

Could you clarify please ?

Hi IamQ,

You are correct with your thoughts on SRA. BTW were flirting with the idea but has put it onto the back burner for the moment and is continuing with DLM albeit with some enhancements in the pipeline. We've been offering our assistance with this.

The trade off between DLM and SRA is an interesting one. We've been quite keen to see DLM play a less intrusive part in the service with SRA doing its own thing however upon seeing some of the analysis, there are cases seen where it appears to offer a less solid experience or the return isn't as great as originally expected. Of course there are also circumstances where it offers a better experience, depending on the dB margins applied.

Work in Progress shall we say!

Regards,
Brian