DLM Reset / Line Capped?

[#1]

Hello,

I've recently moved to using a Draytek 167 router. Speeds are the same as I've had for a while, but I noticed that my downstream is 'interleaved' and achieving a speed that is significantly below the attainable rate. I was wondering if there is any benefit in attempting a DLM reset, or anything else, to try and achieve something closer to the attainable rate.

Many thanks!

[#2]

Usually interleaving is applied to attempt to maintain best speed in the presence of line errors - the fact that interleaving is applied and the downstream rate is well below the max attainable rate suggests that there are (or has been) a significant number of errors seen.

Does your router report error statistics?

Usually interleaving will eventually (after some weeks...) be removed automatically. A DLM may reset things sooner - if the noise which triggered it is no longer present.

[#3]

Thanks for this. It's been sitting at this speed for many months unfortunately. I've attached an image with the error stats, which I don't think are excessive.

I'd really appreciate it if a DLM reset could be attempted to see if that improves things.

Many thanks indeed!

[#4 · Accepted solution]

Because I like to break rules, I'm not going to follow through the troubleshooting side of things and just do the DLM reset for you, Popped it through now for you. 

I feel like a rebel now.

[#5]

Really appreciate this - thanks so much!

[#6]

You're very welcome. Let us know if it doesn't resolve it.

[#7]

Hello again!

So since I last posted here, my line speed is up which is good. Interleaving is still on thought and I'm not sure why.

I've attached screenshots of my line stats.

Thank you!

[#8]

I usually use a Vigor 130 modem, that runs a close to 80/20Mbps and non-interleaved fastpath on my SoGEA line.

Recently I have been experimenting with a Vigor 166, and have the same issues as you, with unexpected interleaving and 'actual' sync rate much lower than 'attainable'.

Swapping between Vigor 130 and 166,  the 130 is always fastpath and full sync speed, the 166 is much slower and interleaved.

I raised a support ticket with DrayTek, who sent me a 'beta' firmware to experiment with, that I installed last night.  So far the interleaving is still occurring but the 'actual' sync rate is 5Mbps faster than the official latest firmware, but still well short of 'attainable'.  I'm going to leave it alone for a few days to see what DLM does with the 'beta' firmware, in the hope 'actual' sync increases - I don't anticipate any improvement but I might as well try it anyway.

I'm getting the feeling that the Vigor 166 and 167 are incomplete products, and that the ten year old 130 is much better.

I will continue raising support tickets with DrayTek, and providing screenshots and feedback, showing that the 166 is worse than the 130, and demand that they do something about it and kick up a fuss until they do.

I'm just glad that I only spent £20 on the almost new 166,  I would have been gutted if I'd paid the current £124 shop price !

For what it's worth, my line isn't DLM stuck or doing anything unexpected, and going back to the Vigor 130 fixes the issues the 166 has.

[#9]

Hi,

This is really helpful - thank you. Would be really good to get an update from you on how things go with the beta firmware. 

I might have to get looking on eBay for an old 130...

Thanks!

[#10]

Yes I'll report back here if DrayTek fix our issues with a new firmware.

eBay Vigor 130 modems in pristine condition often go for less than £30 these days.

If you do get one, make sure you install the latest firmware, as that contains a lot of performance and console command improvements that resulted from months of me sending DrayTek support tickets, to get that model working properly - it looks like I'm going to have to do the same regarding the Vigor 166 - sigh !.  I have a list of other problems with the 166 that also need fixing, but currently they would be pointless raising tickets for if the basic sync speeds and interleaving aren't fixed first.

From my own research my experience with the 166 seems to be common,  but have read other forum posts where users have owned both a 166 and 167,  with the 167 performing much better on an FTTC connection than the 166.  From that observation I was going to see if I can get a cheap 167,  but now having read your experience I doubt whether the 167 will ever be any better than my 130.

What router are you running your 167 in to ? - I'm wondering if you've got PPP link jumbo frames working, allowing your internet MTU to be 1500 (rather than the typical 1492 for PPPoE with an external modem).

[#11]

Thanks again. The speeds I'm getting with the 167 are better than I had before. I'm using the TP-Link ER605 as my router. My main motivation for switching from the Plusnet router in bridge mode was to try and make some energy savings. If I manage to get a better connection then that's a bonus.

I'll order a 130 off eBay and give it a shot. Not much to lose at that price.

For whatever reason the ER605 doesn't seem to support an MTU of greater than 1492 😕

All the best.

[#12]

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@sdhuk wrote:

For whatever reason the ER605 doesn't seem to support an MTU of greater than 1492 😕

You would have to set the MTU of the Vigor 167 to at least 1508, to have any chance of the ER605 MTU working at 1500 (if the TP-Link does support jumbo frames).

Having the Vigor 167 set too high (say 1508 or 1520) won't cause any harm as the PPP link MTU is auto-negotiated between the router, modem, and Openreach line, down to whichever device has the lowest spec, and then minus another eight for the PPP link overhead (hence the typical 1492 MTU).