A long line question

Our office has two bonded lines, both 54db attenuation. Earlier this year they were upgraded to ADSL2+ by BT. Since then we've been having more stability issues than we ever used to. I've been pursuing this with our ISP but not making much progress. They had us change the filters and cables because they were seeing a lot of upstream errors and they claimed the lines looked better. Now this puzzles me because the lines were installed specifically for broadband. The router is connected to the master socket and there's nothing else plugged in so I'd have thought we only need filters for the plug adaptor. Since replacing the filters the lines have synced at 2Mb/s and 12db and 9db noise which the ISP thinks is normal and quite fine. I don't - I think it ought to be at least 3Mb/s on both.

Anyway yesterday we had several outages including one that lasted several hours (no-one was in the office to reset the router).

My question is - I know that ADSL2+ has a bad reputation on long lines. Should it be okay at 54db or is that where things start to get wobbly? Looking at graphs that's about where the difference stops being relevant anyway. Presumably it's possible to ask an ISP to disable ADSL2+ on 21cn?

Edited by Andrue (Sun 13-Mar-11 08:52:58)

Can you force a change of mudulation type in the router as ADSL2 or even standard G.DMT may perform better than ADSL2+ on longer/unstable lines.

How are the lines brought to the routers? Via the same dropwire and terminated close to each other or do they take completely different routes?
Can you trace these routes to see if they run near internal switching etc equipment or perhaps near "noisy" external industrial/commercial premises?

An attenuation figure of 54dB might give trouble free operation in some cases but not in other whilst half that might fall over elsewhere. It all depends on electrical, environmental and a host of other factors - In other words, noise. Don't forget that as ADSL2+ uses higher frequencies, noise plays a much bigger part.
Incidentally, 63dB is the supposed cutoff point for ADSL so you should be fine where simple attn is concerned.

If a recce of the physical conditions such as cable runs etc turns up nothing, try monitoring each with Routerstats or similar to see if any clues are yielded there.

In reply to a post by Ribble:

Can you force a change of mudulation type in the router as ADSL2 or even standard G.DMT may perform better than ADSL2+ on longer/unstable lines.

Unfortunately not. It's a Cisco 1800 and I have no idea how to do that. The ISP ought to be able to.

In reply to a post by Deadbeat:

How are the lines brought to the routers? Via the same dropwire and terminated close to each other or do they take completely different routes?

There are no drop wires near our office. The lines appear to come to our office park underground. There's a BT access cover in the car park not far from our office.

Previously I think one line syncd at 3Mb/s and the other at 2Mb/s. More importantly they were quite stable. We'd have the occasional bad day when the weather was turning and there'd be a couple of drops in the afternoon but that was about it. On average we noticed perhaps one drop a month. Since February we've been getting four or five drops a week. We're also getting lengthy outages that takes hours to fix by themselves eg yesterday:

http://www.thinkbroadband.com/ping/share/9de6005f92b...

Edit:Although looking at that graph it appears the long outage wasn't a total outage. Judging by an email sent from our US IT department it looks more like a sustained period of 'high noise'.

Edited by Andrue (Sun 13-Mar-11 09:34:44)

Were they bonded before you went to adsl2+? What sort of bonding is it - g.bond?

As you know adsl2+ uses much higher frequencies which are more prone to noise, so that's always a problem.

It may be a problem with the router, I'm not sure Cicso routers are as good as broadcom-based ones.

In reply to a post by BatBoy:

Were they bonded before you went to adsl2+? What sort of bonding is it - g.bond?

Yes, they've been bonded since we moved in nearly five years ago. No idea what kind of bonding though

It may be a problem with the router, I'm not sure Cicso routers are as good as broadcom-based ones.

That wouldn't surprise me. Unfortunately I don't have a practical way to investigate the router. Even if I connect a PC to it the CLI is beyond me.

In that case I would move back to 20cn, the long lines just aren't benefiting enough.

In reply to a post by Andrue:

..... looking at that graph it appears the long outage wasn't a total outage. Judging by an email sent from our US IT department it looks more like a sustained period of 'high noise'.....

Did any nearby events such as a factory/workshop starting production, internal electrical equipment switching in and out, road or construction works etc fit into that nasty looking 6AM-8PM slot? The preceding spikes also look to be fairly regular events occurring at about half past the hour.
Look at your graphs and see if you can spot any patterns. If there are patterns, it might be a lot easier to pinpoint the source.
it's a lot of work though for what I would conceive as perhaps little gain because as Batboy has said above, with your attenuation, ADSL2 isn't really doing much for you and if a (Temporary via the router?) switch back to ADSL stabilises things, that might be your best option.

Edited by Deadbeat (Sun 13-Mar-11 10:58:41)

In reply to a post by Deadbeat:

In reply to a post by Andrue:

..... looking at that graph it appears the long outage wasn't a total outage. Judging by an email sent from our US IT department it looks more like a sustained period of 'high noise'.....

Did any nearby events such as a factory/workshop starting production, internal electrical equipment switching in and out, road or construction works etc fit into that nasty looking 6AM-8PM slot? The preceding spikes also look to be fairly regular events occurring at about half past the hour.
Look at your graphs and see if you can spot any patterns. If there are patterns, it might be a lot easier to pinpoint the source.
it's a lot of work though for what I would conceive as perhaps little gain because as Batboy has said above, with your attenuation, ADSL2 isn't really doing much for you and if a (Temporary via the router?) switch back to ADSL stabilises things, that might be your best option.

Well there's a pig farm across the road

Come Monday I'm going to try and suggest a switch back to ADSL. Unfortunately the whole thing seems designed to be a PITA. Although we are a UK office it's the US IT department that deals with it. Added to the usual obfuscation resulting from Ofcom's ministrations it doesn't bode well

Edited by Andrue (Sun 13-Mar-11 12:13:26)

You really need to study the Cisco's CLI guide as I would imagine that it supports user modulation mode selection. From there you should be able to force ADSL1 through ADSL2+ Mode and back etc at whim. Look out for Modulation or ITU G.992.x etc innside the web interface or the CLI guide.

I'm sure that I saw a post somewhere on ADSLG regarding a Cisco router and using an IS to properly upgrade the WAN interface for use over ADSL2+. Have a search for it. Also, this might help.

Edited by Deadbeat (Sun 13-Mar-11 12:44:38)

Andrue, have you tried different makes of router ? I used to think that matching the manufacturer at both ends of the line was twaddle until I went over to ADSL2+, and now I find that my Draytek router syncs at 5Mbps, whereas using a Zyxel router it will reliably sync at 7Mbps.