Why isn't WMM Support default?

hendry · Fri Sep 01, 2017 4:13 am

Since Apple recommends WMM support as the default: https://support.apple.com/en-sg/HT202068

I am curious as to why it doesn't appear Mikrotik have followed their decision for the default Home AP Dual quickset?

The documentation that results from a "wmm mikrotik" search is https://wiki.mikrotik.com/wiki/Manual:WMM
Which is Kafka-esque bad. It's a boolean on other network routers yet that page makes it look like a 20 step process.

(remember, that both require setting up correct rule(s)!)

Awful.

AlainCasault · Fri Sep 01, 2017 5:42 am

For a good reference on WMM, grab a copy of CWNA. You'll get good information. For WMM to work per 802.11 specs, everything in the loop has to be WMM aware.

I've read the MT page (quickly) and what I've seen is more of a work around to classify traffic. WMM aware apps will have proper values in the required fields. There's not a whole lot to do with it. I've read Apple's page and it doesn't say a whole lot about WMM either and suggests a few Wi-Fi settings I would never use, such as auto channel or using older protocols (b and g) which will turn on protected mode Wi-Fi and slow the network down.

Sent from Tapatalk

Jotne · Fri Sep 01, 2017 8:39 am

The Apple way is not always the best way.
I am working for a large company and we have a guest network setup.
Since Apple device pr default connects to all network it can see, it eats up our DHCP pools so I have to set the leas time to a low number.
If a buss with people passes within a range of a wifi access point, all Apple uses connect to it and tries to call home.
You can turn this of if you like, but no one does it. Also Apple devices appears more than double in our support calls. (there are more android units in total)
If you have more than one SSID on the same Wifi access point and an Apple device has connected to one of them, it will not connect to second SSID without delete the first one.
Android has no problem with this.

iOS 8 and later uses a randomized MAC address when running Wi-Fi scans
Why this? It makes it harder to see if a device has been on several of our SSID.

Fri Sep 01, 2017 11:05 am

iOS 8 and later uses a randomized MAC address when running Wi-Fi scans
Why this? It makes it harder to see if a device has been on several of our SSID.

Randomisation is good for the end user, it protects them from being tracked. Why would you want to track somebody that just scans, but doesn't connect?

pe1chl · Fri Sep 01, 2017 12:03 pm

The documentation that results from a "wmm mikrotik" search is https://wiki.mikrotik.com/wiki/Manual:WMM
Which is Kafka-esque bad. It's a boolean on other network routers yet that page makes it look like a 20 step process.

(remember, that both require setting up correct rule(s)!)
Awful.

Well, although that document is titleed "Manual:WMM" it really isn't a manual. It merely is a white paper on WMM.
It does however touch on the subject that WMM, and QoS in general, is not as straightforward as some make you think.
You really need to decide on the strategy you are going to use and what effect you want and can expect.

Of course, this does not preclude a better manual and maybe some wizard button to implement a default form of WMM
similar to what you find in other equipment. Fine-tuning could be done by those who really care.

For MikroTik, it would likely consist of:

/interface wireless
set [ find default-name=wlan1 ] wmm-support=enabled
/ip firewall mangle
add action=set-priority chain=postrouting new-priority=from-dscp-high-3-bits passthrough=yes

One could argue these should be in the default settings these days.
Additional mangle rules to set the DSCP for traffic passing by are possible, but with reasonably designed equipment
on a local network they often are not required. When traffic is coming in from internet, it can be a different story.
(some ISP just clear out the DSCP field... and the sending party may not have set it correctly)
Some equipment from other manufacturers has a config page where you can enable some rules e.g. to prioritize
VoIP traffic, this normally works by matching certain protocol/port combinations and can be done in mangle rules.
However, this is less straightforward and will often have to be adapted to local situation.

hendry · Sun Sep 03, 2017 5:58 pm

Of course, this does not preclude a better manual and maybe some wizard button to implement a default form of WMM
similar to what you find in other equipment. Fine-tuning could be done by those who really care.

For MikroTik, it would likely consist of:
Code: Select all
/interface wireless
set [ find default-name=wlan1 ] wmm-support=enabled
/ip firewall mangle
add action=set-priority chain=postrouting new-priority=from-dscp-high-3-bits passthrough=yes

Thanks for this interesting information. Didn't quite understand what you were suggesting... am I fine tuning here?

Since I like to use Caps manager for my sanity, is it possible to set this within CAPSMAN?

[hendry@MikroTik] /caps-man configuration> print
 0 name="sunny" ssid="sunny" country=singapore datapath=datapath1
[hendry@MikroTik] /caps-man configuration> set
Change properties of one or several items.

<numbers> -- List of item numbers
channel --
channel.band --
channel.control-channel-width --
channel.extension-channel --
channel.frequency --
channel.reselect-interval --
channel.save-selected --
channel.skip-dfs-channels --
channel.tx-power --
comment -- Short description of the item
country --
datapath --
datapath.arp --
datapath.bridge --
datapath.bridge-cost --
datapath.bridge-horizon --
datapath.client-to-client-forwarding --
datapath.l2mtu --
datapath.local-forwarding --
datapath.mtu --
datapath.openflow-switch --
datapath.vlan-id --
datapath.vlan-mode --
disconnect-timeout --
distance --
frame-lifetime --
guard-interval --
hide-ssid --
hw-protection-mode --
hw-retries --
keepalive-frames --
load-balancing-group --
max-sta-count --
mode --
multicast-helper --
name --
rates --
rates.basic --
rates.ht-basic-mcs --
rates.ht-supported-mcs --
rates.supported --
rates.vht-basic-mcs --
rates.vht-supported-mcs --
rx-chains --
security --
security.authentication-types --
security.eap-methods --
security.eap-radius-accounting --
security.encryption --
security.group-encryption --
security.group-key-update --
security.passphrase --
security.tls-certificate --
security.tls-mode --
ssid --
tx-chains --

Couldn't see the wmm-support option...

Tue Sep 05, 2017 1:50 pm

In CAPsMAN WMM is enabled by default and you can't disable it.

pe1chl · Tue Sep 05, 2017 2:51 pm

In CAPsMAN WMM is enabled by default and you can't disable it.

Does that include making the required mangle rule? And how is it constructed? ("from DSCP 3 bits" or other?)

squeeze · Wed Mar 28, 2018 2:29 pm

Just being going through my Wireless settings:

Why is WMM disabled by default in 802.11n/ac devices?

This is already perverse because those standards are stated to require tools in WMM for HT (High Throughput) link rates, i.e. greater than 54Mbps (*) and is enabled by default for Wi-Fi Certified devices.

It is even stranger because to quote uldis of Mikrotik Support: "In CAPsMAN WMM is enabled by default and you can't disable it." (which may be the worst of both worlds).

Note. I am genuinely and generally asking. I have no specific interest in WMM/QoS at this time. I just want to make sure I have understood the basics.

(*) https://www.smallnetbuilder.com/wireles ... s-with-wmm

pe1chl · Wed Mar 28, 2018 3:00 pm

Well, what uldis answered is probably only the wmm-support=enabled that is somehow enforced by CapsMAN,
but of course that is absolutely useless without the associated mangle rule that does some set-priority and there
was no answer on the question if and how this is arranged. I expect it isn't.

In addition to the above: when your wlan interface is part of a bridge, and you want the mangle rule to be applied
to the bridged traffic (traffic from ethernet to wifi), you need to enable the "use IP firewall" in Bridge Settings as
well, of course only after checking for possible consequences of existing firewall filter rules (you could lock yourself
out of the router!!!).

Wed Mar 28, 2018 3:04 pm

... And you will delay the packet processing above that.

pe1chl · Wed Mar 28, 2018 3:57 pm

So, MikroTik: PLEASE implement some option at the wlan level to allow WMM to operate from DSCP, as the other manufacturers have done years ago.
It is nice when there can be some override via mangle but it should not be the only option as it incurs manual configuration and CPU loading.

Remember that such operation was implemented for "clamp MSS to PMTU" at PPP level as well. For the same reasons.

UpRunTech · Fri Sep 21, 2018 10:47 pm

So, MikroTik: PLEASE implement some option at the wlan level to allow WMM to operate from DSCP, as the other manufacturers have done years ago.
It is nice when there can be some override via mangle but it should not be the only option as it incurs manual configuration and CPU loading.

Remember that such operation was implemented for "clamp MSS to PMTU" at PPP level as well. For the same reasons.

The nice thing about Mikrotik is that they give you everything you need to do just what you want. Shame though their documentation is terrible. Here is how to do QOS for WMM. Put this rule in every AP.

/ip firewall mangle add action=set-priority chain=postrouting comment="Set priority for WMM" new-priority=from-dscp-high-3-bits passthrough=yes

[edit] reading back through the thread I see you mention this rule already. It's the only way and it makes sense to do it this way. Making an tick box in the wireless interface is a kind of dumbification and it's doubtful it'd save much on CPU.

aa74 · Thu Aug 05, 2021 7:46 pm

Here is how to do QOS for WMM. Put this rule in every AP.

/ip firewall mangle add action=set-priority chain=postrouting comment="Set priority for WMM" new-priority=from-dscp-high-3-bits passthrough=yes

[edit] reading back through the thread I see you mention this rule already. It's the only way and it makes sense to do it this way. Making an tick box in the wireless interface is a kind of dumbification and it's doubtful it'd save much on CPU.

How does it work with queues? Does it override the priority set by the queue? Or the queue still overrides the priority set in mangle rule since packets flow through queues after being mangled? And how to tell those apart if I want that voip must have the highest priority (derived by the queue from voip gateway's IP) no matter dscp-high-3-bits is set to?

pe1chl · Thu Aug 05, 2021 9:18 pm

Queues don't set a priority. Queue tree items *have* a priority, but they are only selected via packet marks.
You can use mangle to derive the packet marks from the priority, e.g. after setting that via the "new-priority=from-dscp-high-3-bits" method.
It is all a bit convoluted and it is not required in plain Linux, but RouterOS omits the possibility to directly select a queue item using the priority field.

rolelael · Wed Nov 23, 2022 9:49 am

Can I up this post please?

I had/have the same issues on my Microtik outdoor AP ..

Wlan1 & Wlan2 active and ios devices can't connect . Sometimes they do, mostly they don't

Also throughput is very slow ( max 50Mbps , where my providers router is going to 280Mbps )

I deleted every firewall rule to test and did enter the Mangle options ( priority etc ) above

Now it seems under mangle I have 4 rules?

0 passtrough prerouting
1 passtrough forward
2 passtrough postrouting
3 set priority postrouting

WMM I have enabled in the advanced options o,n both wlans

ANy other options from getting ios devices to connect correctly + good troughput? thanks

bpwl · Wed Nov 23, 2022 12:48 pm

See viewtopic.php?t=165698r#p912792 and posts above this on "WMM, priority and A-MPDU".
All 3 are needed for performance!
CAPsMAN might be a different story if local forwarding is not used. Where do you set these things then? On the CAP interface in CAPsMAN?
WLAN settings for CAPsMAN controlled WLAN interfaces can be set but seem not used at all (except antenna gain, which is hidden in the GUI by now)
Does that (CAPWAP protocol based) tunnel between CAPsMAN and CAP transfer the priority set on packets or not? viewtopic.php?t=190274&hilit=CAPWAP#p964021
(Normally according the wiki "priority" setting is only local to the router, e.g. not transferred with the packet via ethernet L2. DSCP is transferred.)

pe1chl · Wed Nov 23, 2022 4:03 pm

Well, priority can also be transferred via a VLAN tag. When traffic is VLAN-tagged, there are 3 bits defining the priority, and a "priority from ingress" mangle rule can copy that to the packet priority field, where it will be used for the WMM priority when that is enabled.
The issue is that those mangle actions require traffic to pass through the IP firewall, which it normally doesn't do when the AP is operating in bridge mode.
For efficient operation, there should be a "set WMM priority from" field at the Wireless interface level, which should have the option "none", "ingress" and "dscp". It should default to "dscp". And this action would be performed inside the Wireless driver, so it does not require firewall processing.
Of course it is a "dirty hack". But such is the "change TCP MSS" option in PPP profiles, that can also be done in a mangle rule but still it was added "for efficiency".
And all other Wireless AP manufacturers do this "set WMM priority from DSCP" by default, usually you cannot even configure it.

bpwl · Wed Nov 23, 2022 5:49 pm

And all other Wireless AP manufacturers do this "set WMM priority from DSCP" by default, usually you cannot even configure it.

That is also what I expected from other manufactures. We should be able to see the WMM priority logic in OpenWRT code. It is difficult to detect otherwise in MT.
- The WMM CWmin and CWmax are in the wifi header by MT (CAPsMAN or not) as expected for the different WMM priorities.
- But at what WMM priority (what CWmin and CWmax) is a packet sent? It's not visible to me in the packet when sent, is it only in the timing used?

So a MT AP in a crowded environment gets pushed back in performance by others (all AP and all clients) in the same channel
- With CAPsMAN where do you set priority? In CAPsMAN device or CAP device? Will it be handled in the CAP device or ignored, and will it ever reach the driver if done in CAPsMAN device?
- Without WMM priority one counts to long before trying to access the channel for free airtime and fails, if others react faster because of WMM. I suspect some devices to cheat in WMM priority.
- MT AP is limited to the "non-TPC" level EIRP TX Power, where I see others using TPC level EIRP (3 dB stronger). Wifiwave2 or OpenWRT on MT router bring TPC level limits for that device.

pe1chl · Wed Nov 23, 2022 6:33 pm

I have only tested relative priorities for traffic on point-to-point links. E.g. saturate a link with a large download at DSCP 0, 8 or 16, then run a VoIP call at DSCP 46 over the same link.
MikroTik equipment with default config: garbled voice call.
UBNT equipment with default config: works fine.
MikroTik after enabling WMM, AMPDU priorities 0/1/2, adding "set priority from dscp high 3 bits" mangle rule, "use IP firewall" on bridge: works fine as well.
But of course the casual user will never do that.

Why isn't WMM Support default?

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