So comparing both of these tests, I see that the ridiculous high idle bufferbloat occurs at time point 13 seconds, with the download test nominally ending just short of 13, so this pretty much looks like "back-spill" or packets that where collected in the buffers of the upstream end of the bottleneck link. I heard rumors that DSLAMs/MSANs are not really designed with such a load in mind, and your tests seem to support that.
In your shoes, I would try the following first:
configure the fritzbox for pppoe-passthrough and empty the fritzboxes own pppoe credentials, so that the fb will not actually interfere with your traffic anymore than it needs to. Unfortunatelly AVM jettisoned the Modem-mode they once offered, but pppoe-passthrough might be good enough for your problem.
set up an openwrt router with properly configured sqm-scripts with ingress shaping to avoid back-spill traffic collecting in the over-sized and under-managed upstream buffers that I predict to exist from the speed tests.
I will happily guide you through configuring sqm-scripts for your link/ISP.
As far as I can tell that dsl spectrum looks okay, it is just a loooong line. The notches below bin 512 are from both DPBO and the fact that below bin 512 vectoring is not enabled, so you typically also see more cross-talk issues, a tell-tale sign for working vectoring is a noticeable jump from bin 512 on. But the overall level just above say 45 dB is just really low... in the second downstream band there are also two small notches that indicates some RF ingress, but fixing these (if possible at all) will only give minor improvements...
Sometimes low quality in house wiring can make a bad situation worse, so it might be an interesting idea to move the modem to the APL in the basement and connect it directly (while at the same time disconnecting the wires going up to the TAE for the duration of the test), but I doubt that will solve the issue you opened the thread for.
Good thought. I tend to try to run something like mtr -zeb4 8.8.8.8 and the look at the development of the RTT along the path, if from one hop on all RTTs are noticeably increased when you load you link with a speedtest, that is a decent first indicator for an overloaded link (exactly pinpointing the overloaded link is a bit trickier and requires traceroute/mtr also in the reverse direction, but to just detect "overloaded uplink" conditions having only the forward mtr/traceroute is quite helpful).
Maybe you could post all of this again after accumulating a bit more uptime? And for the spectrum, I believe there is an option to also show maximum and/or minimum, which would be interesting.
I do not know if that is true. I always used to think differently, but I have never tried it myself. This is how I think it should be able to be used as modem.
Choose in the menu Internet / Zugangsdaten (in english should be something like "access data", or "credentials"). In the first tab "Internetzugang" ("Internet access" or similar) there is a dropdown labeled "Internetanbieter" ("Internet provider"). Choose "Vorhandener Zugang via LAN" ("Existing connection via LAN"). Then, a little further down, click "Verbindungseinstellungen ändern" ("Change connection settings"). In the area showing up you activate PPPoE-Passthrough: "Angeschlossene Netzwerkgeräte dürfen zusätzlich ihre eigene Internetverbindung aufbauen" ("Connected devices are allowed to build their own internet connection"). After accepting the settings the Fritzbox should behave like a modem. Don't forget to deactivate other Fritzbox services like DHCP if you want only a modem.
Caveats:
1.) I did not try this out myself. I intent to at some point in the future though, as I'm on a similar quest: An APU.2 will be my new router, and I will test it with the existing DSL line and the Fritzbox as a modem, before I switch over to cable (cheaper, more bandwidth).
2.) The description is for Fritz!OS 7.01. Other versions may look a little different.
3.) I did not bother to change my Fritzbox to english to read the labels. So beware of some inaccurate translations of the labels that I found in my box' web interface.
It certainly is unusual. However, the modem would not use these frequency, that is the whole idea of DSL. I would add that this looks like a fairly long line to DSLAM, for all the damping visible. The SNR is down to 30dB at 5MHz, on my line that is reached at 15MHz.
Edit: Seems I'm a little late with my comments. I'll leave them here anyway.
Sorry for the late response. I got vodafone to send me a technician to check the connection. I really hope he understands the problem if I show it to him. Unfortunately the woman on the Vodafone hotline never heard of "latency"
In the first place I did not exactly understood how your solution could fix my problem, but I found a german article who explained it (bufferbloat) a bit easier for me to understand. So the SQM would decrease the window size or improve what data is send with what packages, right?
So do I understand that correctly, If I use a Fritz!Box 7490 in PPPoE mode connected with an OpenWRT Router and SQM activated, the OpenWRT Router "handles" the connection, not the Fritz!Box, right?
We'll see what the technician can / will do about my problem. As the connection aswell as the router is from Vodafone it is theirs to provide a fully functional connection. (I hope).
EDIT: If he can't fix it, is there any router you could recommend to me? Easy to flash to OpenWRT with good WiFi?
Yes, in pppoe passthrough mode, FBs will pass additional pppoe packets on unmolested (the trick is to make sure the FB itself does not get a valid pppoe session up and running, as most ISPs only allow a single pppoe connection with the same credentials). Once openwrt handles the termination of the PPPoE link, it will for all intents and purposes have control over your "internet connection".
Jein, SQM is just a convenience package to set-up a rather generic traffic/shaping plus advanced queue management (AQM) set-up. Typically the variable delay your packets encounter on their psth through the internet comes when they are stuck/buffered in a queue instead of being transferred over a link. Some buffering is a good idea and helps to maintain reasonable throughput, but too much just introduces too much latency/delay and makes the TCP feed-back control loop too "floppy". Maintaining just the right amount of buffering is the trick here and is what SQM offers (for most internet users the smallest or bottleneck-link is the internet access link, and most queueing along a network path happens roughly at the slowest link, so improving the queue management at that link can do wonders to keep latency-under-load from growing to ridiculous values). Maintenance of "windows" like TCP's receive and congestion window, and deciding which data to send when still is left to the endpoints, but with SQM they get better feedback from the network about the congestion state. And SQM will also isolate different traffic flows from each other, so that a single large download will not starve concurrent smaller data transfers. (I could go on, but unless you are interested, I will stop wasting your time).
I had to read it twice, but I think I undertand what you're talking about.
Just in case that the technician tomorrow will not or can not change anything about the connection, what router could you recommend? I would prefer something easy to flash OpenWRT to and with good WiFi? What do you think about the TP-Link Archer C7? Is that one sufficient? Or should it preferably be something like the Netgear R7800?
I would then buy one and would appreciate your help to configure it
That really depends on what you want your router to do for you. Now, your current link with its 25/5 Mbps routing, firewalling, and even traffic shaping your internet traffic is not going to be too hard for anything not completely ancient... But if you want to use OpenVpn/Wireguard at link speed or you want to be "future-proof" for a potential upgrade of your link, you might want to look at something slightly more recent or even something like a pcengines APU2 or if you are a Bastler, a raspberry pi4B (with additional USB3 ethernet dongle and a separate AP for wifi)... Or if you want least hassle, but are willing to spend a few EUR more, maybe an evenrouter iqrouter or a turris omnia might be to your liking (the last two are commercial offerings based on OpenWrt, that offer things like automatic updates).
In short without knowing your use-case it is hard to make a reasonable recommendation (there are quite some threads in this forum about "best"/"cheapest" router hardware for OpenWrt).
I would guess, that for your link speed a C7 should work well, I have no personal experience with that device but the reports here in the forum make me believe this to be a solid little device. I would recommend to install a master snapshot though or build your own firmware from master, as for its atheros ath10K wifi radios a really nice new feature just landed this year that offers better air time usage.
No personal experience with that device, again there are quite a community here in the forum specialized on that router. And again at 25/5 this should work well out of the box.
Oh, I a willing to help, but my schedule can be choppy, so no promises about timeliness.
Guys, a friend of mine has a TP-Link TL-WR1043ND v1.8 with OpenWRT already flashed. As far as I can see the device is capable of running the release 19.07.2. Unfortunately it has low specs (400 MHz CPU, 8 MB Flash, 32 MB RAM).
Do I have to install SQM on the device or is it included in the version 19.07.2 by default?
Would you say I could give this device a try or isn't it worth it?
SQM is not included by default. The 32 M RAM should still be enough for a basic router with SQM. Two applications that are in the standard build but aren't strictly necessary are uhttpd, the LuCI web server and odhcpd, ipv6 dhcp. You don't have to build these out of the ROM, but use init.d to disable them from loading into RAM.
Unless money, really is tight or I had the device already sitting on my desk, I would not start with a 8/32 device, IMHO time is too valuable to constantly fight against too tight constraints... (unless, you enjoy the "fight" for itself, in that case, go for it )
Good Point! I ordered an Archer C7 and flashed OpenWRT already. Now I'm stuck on configuring the WAN PPPoE Connection. I have the 7490 configured to allow PPPoE Passthrough. But not sure if it will work with my ISP.
I tried the UI configuration. Unfortunately I'm not sure where to add the VLAN Tag. I have Vodafone as my ISP but they're just a reseller. So it is Hardware from the Telekom. I know I have to configure a vlan tag 7 or 132. I have to try.
Attached is what the network configuration looks like. Now I have some questions. 1. Do I need the wan6 configuration? 2. What is that "device" with the name wan_eth0_2_dev for? 3. What is the port "0t"? 4. Why are there two vlans on the switch? 5. How can I set the vlan tag on the WAN?
Usually it is not necessary to apply VLAN tags to the WAN. In the most common configuration your router sends untagged packets to the DSL modem and the modem's configuration will apply tags if necessary before sending out on the wire.
As for your questions:
wan6 is not used for PPPoE since if the ISP supports IPv6 the pppoe can handle it.
the config device is used to associate a MAC to the device (during setup, the factory "sticker" MAC is read from the flash and set for the default) to a device it doesn't do anything else.
port 0t means send tagged packets into the CPU
At least two VLANs are defined inside the switch so that the WAN and LAN networks are kept separate. The switch would switch every port to every other port if VLANs are not used.
To set a VLAN on an external port (here WAN) change its definition in the ports line from 1 to 1t. The VLAN number and/or vid number needs to be set to the number the tag should contain. This will also cause a different tag on the CPU port, so change in the wan section from eth0.2 to eth0.X as well.
But if I understood @moeller0 correctly, I need an own PPPoE connection to the ISP from the OpenWRT device in order to use SQM later on. In order to establish a working connection I guess I need to add the vlan tag as the Fritz!Box 7490 hopefully just passes the packets through. So you think I still don't need to configure the VLAN tag?
Okay, I think I slowly understand how the configuration is structured. Aswell I found the network stack on the wiki here basic networking.
So I change the option vlan '2' to option vlan '7', change the all the eth0.2 names to eth0.7 and with the option ports '1t 0t' I enable sending the vlan tag 7 included in the packages, correct?
I then have just one other question. I still haven't figured out / understood what the "0" is for the port 0t? Why port 0t? What do I miss?
Config looks like this now. Unfortunately I still have no connection. I should recheck with the ISP if the username and password is still the same.
I'll leave them here anyway.
) and I will try them if the technician on friday won't be able to fix it.
)