Asus RT-AC68U QOS issue

[GranDad]

G'Day from down under

I am new to Merlin and am using an Asus RT-AC68U router and 3.0.0.4_376.48_1 firmware.

I like the added features of Merlin and the ease of a Graphic interface.

I was disappointed to find in the stock Asus firmware (and Merlin) that the QOS does not work to control the download bandwidth.

I use a Gigaset IP phone behind this router which works beautifully until I saturate the download bandwidth by using IDM Download Manager.
My line specs are 25/5 Mb/s, it is almost impossible to throttle IDM with its in built controls effectively.

With all past routers I have just used the limit download bandwidth field in the QOS section, and not using any other rules, this is testable by running a speed test and seeing the results of the reduced bandwidth (eg Ookla)

On other routers by using a figure of 23 Mbs in the QOS download box usually results in my VOIP phone working perfectly While IDM still downloads about 2.9 -3 MB/s

I don't mind taking the small drop in performance with this simple set up, I know rules can be set up but they invariably don't work as well as the above.

I am sure Asus thinks that all you have to do is control the upload bandwidth which works fine in the stock firmware. But saturated download and VOIP don't mix due to UDP packets not error correcting

Oddly enough if you create a QOS rule of any client on any port then you can limit the download bandwidth, however it is uncontrollable by the advanced options in any way and only works on wired Ethernet and not WiFi. this results in the download band width being limited to around 4.5 Mb/s (only on Ethernet).

I have also tried DD-WRT firmware with the RT-AC68U and the QOS works perfectly, all I have to do is put 45000 in the limit download box and my VOIP is fine while IDM is running at full blast

Is Merlin limited by the stock Asus firmware? or can it be made to work. I would like to keep using Merlin as I do Like the GUI and all its features.


Cheers Grandad.

 

[MDA]

I too have been noticing this issue with my TM-AC1900 (T-Mobile RT-AC68U variant) on the stock 3.0.0.4.376_2827 firmware for that device and are using Merlin's 3.0.0.4.376_48_1 after using modified RT-AC68U CFE.

This is important though as a lot of cable and DSL connections more apparent source of bufferbloat is related to download speed being saturated (since upload speed isn't as utilized as download and also works on the AC68U like you mentioned).
Without throttling below my max download bandwidth, i get an extra 57ms of latency if I saturate the downlink since my damn ISP is too stubborn to implement multiple CMTS fifo queues.


DD-wrt is a good example of solid QoS functionality (download throttling works well enough even at 50mbps+), but i'm avoiding flashing that until they get IPv6 squared away without having to download iptables module and configure radvd (got a comcast IPv6 connection to keep for the future).

 

[GranDad]

CFE

When I first got the Router I upgraded the stock Asus firmware to Ver 3.0.0.4.376.3626 I believe that did a partition upgrade (currently 1.0.2.0) I tried that firmware and found that download throttling did not work.

I then moved to 3.0.0.4_376.48_1 firmware and had the same result. I just cant understand how Asus can release a product and it just doesn't do what they say it is capable of.

It seems like this function doesn't work across the whole range of AC routers. I know the router can do it because it works correctly with DD-WRT firmware.

 

[RMerlin]

Throttling and QoS are two different topics.

QoS (Quality of Service) is about ensuring that high priority traffic goes in and out before lower priority traffic. A properly working QoS setup should still allow low priority traffic to run at full speed, provided there's no higher priority traffic requesting to access the same pipe.

Throttling, however, is about traffic shaping.

Asuswrt supports QoS, not traffic shaping/throttling/download capping.

 

[GranDad]

QOS

QoS (Quality of Service) is about ensuring that high priority traffic goes in and out before lower priority traffic. A properly working QoS setup should still allow low priority traffic to run at full speed, provided there's no higher priority traffic requesting to access the same pipe.

For this to work correctly it is important that the upstream and downstream bandwidth values pertaining to the service be entered in the first page in their respective input boxes.

What's the point of having a downstream entry box if it does nothing and does not work. How then can the QOS work.

How come on other modems and this modem (with different firmware) this function works?

 

[Nullity]

G'Day from down under

I am new to Merlin and am using an Asus RT-AC68U router and 3.0.0.4_376.48_1 firmware.

I like the added features of Merlin and the ease of a Graphic interface.

I was disappointed to find in the stock Asus firmware (and Merlin) that the QOS does not work to control the download bandwidth.

I use a Gigaset IP phone behind this router which works beautifully until I saturate the download bandwidth by using IDM Download Manager.
My line specs are 25/5 Mb/s, it is almost impossible to throttle IDM with its in built controls effectively.

With all past routers I have just used the limit download bandwidth field in the QOS section, and not using any other rules, this is testable by running a speed test and seeing the results of the reduced bandwidth (eg Ookla)

On other routers by using a figure of 23 Mbs in the QOS download box usually results in my VOIP phone working perfectly While IDM still downloads about 2.9 -3 MB/s

I don't mind taking the small drop in performance with this simple set up, I know rules can be set up but they invariably don't work as well as the above.

I am sure Asus thinks that all you have to do is control the upload bandwidth which works fine in the stock firmware. But saturated download and VOIP don't mix due to UDP packets not error correcting

Oddly enough if you create a QOS rule of any client on any port then you can limit the download bandwidth, however it is uncontrollable by the advanced options in any way and only works on wired Ethernet and not WiFi. this results in the download band width being limited to around 4.5 Mb/s (only on Ethernet).

I have also tried DD-WRT firmware with the RT-AC68U and the QOS works perfectly, all I have to do is put 45000 in the limit download box and my VOIP is fine while IDM is running at full blast

Is Merlin limited by the stock Asus firmware? or can it be made to work. I would like to keep using Merlin as I do Like the GUI and all its features.


Cheers Grandad.

Could you find out what commands/features dd-wrt employs to limit your connection then see if Asuswrt is capable of the same? I presume dd-wrt is using some iptables command that could be ran on Asuswrt too.

I think Asuswrt uses HFSC (I know it supports it) for QoS, and I know that HFSC supports an "upper limit" that does exactly what it sounds like.

For a good tutorial about understanding and configuring HFSC check out http://linux-tc-notes.sourceforge.net/tc/doc/sch_hfsc.txt


Edit: It seems like Asuswrt uses SFQ by default, not HFSC.

 

[GranDad]

Could you find out what commands/features dd-wrt employs to limit your connection then see if Asuswrt is capable of the same? I presume dd-wrt is using some iptables command that could be ran on Asuswrt too.

Here is a snip from the dd-wrt map. All I have to do is turn QOS on and put 23000 in the box, My speedtest download is always around 24 MBs hence I sacrifice about 1 Meg but my ip phone works all the time and I can use the browser

 

[L&LD]

Throttling and QoS are two different topics.

QoS (Quality of Service) is about ensuring that high priority traffic goes in and out before lower priority traffic. A properly working QoS setup should still allow low priority traffic to run at full speed, provided there's no higher priority traffic requesting to access the same pipe.

Throttling, however, is about traffic shaping.

Asuswrt supports QoS, not traffic shaping/throttling/download capping.

How come on other modems and this modem (with different firmware) this function works?

Seems like you already have your answer?

And it was understood too.

Simply, different products offer different options.

 

[GranDad]

L&LD
Seems like you already have your answer?

And it was understood too.

Simply, different products offer different options.

Thank you for your most helpful answer.

The point I am trying to make is that I have set up QOS rules (not by trying to throttle) and they don't work.
If you look at the rules they are based on the up and down bandwidth.

If the downstream bandwidth does not work in its most simple way (throttling) without rules being applied.
Then how can it be expected to work when rules are applied.

If you look at the rules they have values that are determined by the bandwidth specified on the first page.

These rules do not help my sip phone from staying registered when downloading a large file. The downloading file takes all the bandwidth.

On other modems just using the downstream bandwidth box is a workaround for the problem (without rules). But on the Asus RT-AC68U QOS does not seem to work whatever you do.

Here are the rules based on 5Mb up and 25Mb down

And

 

[Nullity]

Thank you for your most helpful answer.

The point I am trying to make is that I have set up QOS rules (not by trying to throttle) and they don't work.
If you look at the rules they are based on the up and down bandwidth.

If the downstream bandwidth does not work in its most simple way (throttling) without rules being applied.
Then how can it be expected to work when rules are applied.

If you look at the rules they have values that are determined by the bandwidth specified on the first page.

These rules do not help my sip phone from staying registered when downloading a large file. The downloading file takes all the bandwidth.

On other modems just using the downstream bandwidth box is a workaround for the problem (without rules). But on the Asus RT-AC68U QOS does not seem to work whatever you do.

Here are the rules based on 5Mb up and 25Mb down

And

I thought you said you were using "23mbit" as your download setting, though it looks like you are using "25mbit" in the screenshots.

Using the setting "25mbit" for a 25mbit line will not work. You need to use a setting that is 3-20% lower than your real-world throughput. This applies to both upload and download settings.

 

[GranDad]

Yes you are correct in what you have spotted and 23Mb is correct.

I have tried 23Mb and 24Mb and 25Mb None work
It just happens that I already had the screen shot of the 25Mb setting.

In dd-wrt the setting of 23Mb works

 

[Nullity]

Yes you are correct in what you have spotted and 23Mb is correct.

I have tried 23Mb and 24Mb and 25Mb None work
It just happens that I already had the screen shot of the 25Mb setting.

In dd-wrt the setting of 23Mb works

If you are still having trouble, one workaround for limiting TCP downloads is to limit the upload bitrate of the ACK packets. TCP ACK packets are transferred from receiver to sender ACKnowledge successful receipt of packets. If you artificially limit the bitrate of your responding ACK packets, then the download will be throttled back. My ACK bitrate was ~18Kbyte to saturate my ~750Kbyte download, so I limited the ACK bitrate to 12Kbyte and it slowed my downloads to ~500Kbyte. You will need to experiment.

This method is imprecise so I ultimately switched to artificially limiting bulk downloads directly, like you are trying to achieve in your OP. This and a few other reasons are why I switched to pfSense as my router over AsusWRT. Linux download/ingress limiting is less intuitive than on pfSense.

I got tired of trying to get QoS to work by trial and error and decided to learn about QoS. Sadly, this journey immediately showed me that linux's documention for traffic control ("tc" command) is awful and outdated. That is another reason I switched to pfSense.