Extremely high interleave values

[Zwiebi]

Hello everyone!

I noticed that my ping is pretty high (31 ms on the first hop to my ISP's datacenter, which is located around 20 km away from me), so I checked out my modem's settings and I found some pretty interesting values:

Less well formatted for mobile users:

Modulation Type VDSL2
Actual Rate (Up/Down) 6015/33022 kbps
Attainable Rate (Up/Down) 7175/49440 kbps
Noise Margin (Up/Down) 6.4/10.1 dB
Output Power (Up/Down) 6.4/13.3 dBm
Data Path (Up/Down) Interleaved/Interleaved
Interleave Depth (Up/Down) 255/1531
Interleave Delay (Up/Down) 8/16 ms
INP (Up/Down) 4/7.5 symbols
Profile 17a
LinkEncap G.993.2_Annex_K_PTM
CRC Errors (Up/Down) 0/0

Connection time: 44 hours


The interleave depth / delay and INP values all look freakishly weird. Unfortunately, I can't set these values in my modem, so I will have to call my provider and yell at them to change the values. Based on the values, what settings I should ask for? The easy one would be fastpath, but I'm not sure if my line is good enough for it. Also the delay / INP values are a bit blurry in relation to latency (should I ask to set the delay to 0 or go with a more standard 4/4 ms).
I have to add, that apart from the high latency, my connection is very stable. No disconnects, latency or speed fluctuation. I pay for 30/5 mbit and I get a constant 31/5.5 mbit at any give time.

 

[Gryz]

After a quick googling, it seems G.993.2_Annex_K_PTM is mainly used in Greece and the Netherland. I happen to live in NL.

I know that KPN (who owns all the copper, and leases DSL-service to other providers) will not change anything that you ask for. They have generic "profiles" on their DSLAM. They change profiles maybe once every few months. Those changes are based on the performance of your line during the previous months. As a customer of another ISP, I can not directly ask anything to KPN. And my ISP says they have no influence at all about how KPN runs their DSL network. (Even though my ISP is a full daughter company of KPN).

Your DSL-provider might have set you on those interleave values because your line has had problems in the past. It will probably be impossible to convince them to change settings for you. The ones who own the copper tend to be the old PTTs from the previous century. Those old PTTs tend to value reliability over speed. If they can give you a 2 Mbps with no bit errors, they rather do that than give you 100 Mbps with 0.01% bit-errors. They suck.

As a reference, I am on ADSL2 myself. I use a Fritzbox. It's connected to a Ikanos DSLAM. Speed is 6.2 Mbps down, 776 Kbps up. My line has ran on 7.5 Mbps for a few months. It worked fine. But KPN has downgraded my profile to 6.2 Mbps. For whatever reason. They probably saw some bit-errors, and thought it would be better to lower my speed. They suck.

My interleaving is set to 8ms downstream and 2ms upstream. So your downstream (16ms) is not much worse than mine (8ms).

You can always ask your ISP to change values. But what values depends on the quality (and distance) of your copper line. And what your provider thinks is acceptable.

Even 15 years after the introduction of DSL, I find it hard to find information and facts about DSL. How to measure, how to troubleshoot, how to improve. We end-users have to accept what we get. Not fun. I wish I could get fiber here. Good luck.

 

[Zwiebi]

I actually live in Hungary and here my ISP is the old PTT (it was a 100% state owned company, with full monopoly) and such they own the whole network from top to bottom, so they should be able to change it if they are willing.
The delay is annoying on it's own, but the Depth values are extremely high which is a cause of concern. I just don't know what changes should I ask for, given that I will probably only be able to get them change it once, and then they will tell me to get lost.
Also, I read something about VDSL being different from the older ADSL standard in that they are not changing the above mentioned values, but rather DLM profiles.

 

[Gryz]

My ISP told me that their DSL-provider has a bunch of standard profiles. Each user gets one of those standard profiles for their line. They keep measuring performance of the line over the weeks. And once every 2-3 months they adjust profiles, if they think it's necessary.

I had problems with lots of errors on my upstream. My ISP could ask their DSL-provider to change the profile to something lower. But only to standard values. E.g. I could chose between 8Mbps/1Mbps or 6Mbps/1Mbps or 6Mbps/776Kbps. But I could not get 8Mbps/776Kbps.

I don't know if your ISP does the same thing. I'm just saying that they could. And if they would, you might be out of luck.

Anandtech.com is mostly visited by Americans. Almost all questions I see here on the networking sub-forum is from Americans. They seem to do DSL very differently from the way its done in Europe. E.g. all Americans seem to be using a separate modem and router, and do PPPoE. While in Europe most providers give us, or let us use a router with a built-in DSL interface. And we use PPPoA. Therefor you will probably get more useful information from other Hungarians. If you can find a Hungarian forum where you can ask these questions. Sorry.

6.5dB SNM isn't very high. I believe 6 is the minimum ISPs want their customers on. (I've been on 5 myself for years now. I think it's only possible because of the heavy interleaving they do on my line). So your line might start giving troubles if you lower the interleaving. If I were you, I'd keep a close eye on the CRC-errors and other errors on your line.

I guess lowering your interleaving values to half of what they are now would be a good start. 4/8ms. Do you really need to lower it further than that ? For bandwidth (downloading files) it really doesn't matter how much latency you have. For MMOs and other games, it doesn't really matter much either. Only when you play online multi-player FPS games, it makes a difference. Or maybe pvp in MMOs. Otherwise, I wouldn't worry too much if I were you.

Again, I am sorry that I don't know more about DSL. It seems it is still hard to find detailed information about DSL-technology.

 

[Harrod]

Interleaving is really just for error correction on your DSL line, as opposed to fast path, which has no error correction on it. Basically if your line is taking errors, interleaving will keep your speeds at close to the rate that you are paying for at the sacrifice of latency on the first hop towards the ISP's internet drain.

If you have a way of seeing if both your upstream and downstream lines are not taking errors you could have the ISP set your line to fast path. In my experience(6 years of working on DSL) the delay settings are set on the pin, and the customers can't really change them on the CPE side of things.

Here is an example of the difference on a test line for a DSL pin that is not taking errors with fast path and interleaving enabled. This is with the same settings that you listed in your original post. Just look at the first two numbers on the list.

---- PING Statistics----
10000 packets transmitted, 10000 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 7.868/9.827/74.055/2.009 ms


---- PING Statistics----
10000 packets transmitted, 10000 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 24.928/27.712/4184.210/41.654 ms

With interleaving off, you could see a significant drop in speeds if your line is actively taking errors.