WMM vs. QOS, Advantage and Disadvantages


#1

Hey everyone, I have searched for a few days, finding some things that are relevant and some that aren’t. I feel I am tech savvy, although I haven’t delved into these configurations before. I understand what these are basically, but please correct me if any of my assumptions or statements are incorrect.

-QOS: Manually configured to allow voice data to have a set priority. Seems to be pretty technical and every router calls for different settings. The Defy required this because it had no WMM support.

-WMM: A type of “auto” QOS that allows voice data to have priority over all wifi enabled devices.

The WMM works flawlessly on my home router. I’m assuming this is because there is nothing BUT wireless connected to that, so by default it will have priority. In my office however, I am not getting as good results. My next step is to ask our IT guys if WMM is enabled on these routers (and even what type or router it is, maybe I can sweet talk them for the password to delve into the settings.) But to make sure my understanding is correct, I wanted to ask this here first.

What, if any, advantages does WMM have over QOS, or vice versa? In my limited knowledge of this, it seems that WMM works best for any router that has no wired internet sources. For a workplace that has computers with wired connections, WMM isn’t as effective because voice will NOT have priority over the wired connections…correct? I have seen someone write though, that if you want to enable QOS on a router, you will need to disable WMM, which many say isn’t good because WMM is an overall good feature for everyone.

I am guessing my best bet for home is to leave WMM enabled, and not worry about QOS, please correct me if I am wrong in this. Work is a different story. We get 50 mbps internet, yet it still switches to cell, even on low sensitivity. I chose to manually switch the network only at work, but I had some terrible quality calls doing this (I had a few good ones too, and on some I had good ones for 5 minutes, then it got horrible and I had to manually make the switch.) Is it possible these routers do NOT have WMM enabled? I walked around and this office has one big server, but there is only 2 computers hard wired in, and they are rarely used, so I feel as if WMM was enabled it should work. Obviously there may be other factors. I’m a coach in college, so our internet is shared throughout campus. Even if our router in our building isn’t being taxed very hard, if other buildings on campus are would that effect my phone call on our router?

I know this is a lot, and I am more interested in the differences in WMM and QOS, but I wanted to give a little of my situation for context.


#2

benjaminm.xg3cp3 wrote:

Is it possible these routers do NOT have WMM enabled?

Absolutely it is possible. They might have it disabled, or it might not be supported at all.

I haven’t seen anyone write that QOS and WMM can’t be used at the same time. You’ll need to show a source URL for that one to get my comment on that theory.

BTW there’s QOS and then there’s QOS. What most routers call QOS is the attempt to throttle low-priority traffic (or all traffic to lower-priority devices) so that Internet bandwidth is available for high priority traffic or devices. My advice is, if the router allows it, set up QOS to give priority to the phone’s MAC address.

Also follow the #1 rule - if it’s not broken, don’t fix it. Don’t worry about QOS If you’re not having problems. If you are having problems, give it a try.


#3

WMM is a subset implementation of QoS (sorta) that only applies to the wireless aspect of the access point. QoS on the other hand is an end to end mechanism to assure delivery.

Just because WMM works doesn’t mean you get the benefits past the access point. The LAN and WAN can both affect your throughput/latency negatively if there is congestion and no other QoS implemented.

Generally a network will be setup with WMM profiles that map traffic types into already established QoS queues on the Ethernet portion of the AP/network. If ONLY WMM is enabled, you’ll see no benefit past the AP itself.

QoS also can’t do much for you on the download metrics. Lets say for example you have a usable bandwidth of 30Mbx5Mb coming into your office, just because you have QoS doesn’t mean the provider modem can’t be inundated with data that actually drops your voice packets at the modem. In these situations you’d experience drops in the voice from the other participant. That’s on the 30Mb side of that, QoS DOES help on the upload side, the 5Mb portion. Proper QoS will prioritize the voice traffic as first to be delivered OUT of the modem/router to the real world. This prevents breakup of your voice to the other participant. You really only have control over the upload side of most networks.

Edit: The reason it works at home is because it’s an integrated AP/router so the WMM is probably already mapped to QoS within the device. At most work locations (maybe not mom-pop shops), only AP’s are used for wireless access, those go to Ethernet switches then to the company’s router. That’s where QoS really comes into play.


#4

Thanks for the replies. Obviously I am going to follow rule #1 for my home. I had to manually uncheck my router so that it forces wifi, but I have never had any issues with call quality so it’s not a big deal.

@michaelahess So what do you suggest I do for my work? It’s a brand new Cisco router, literally installed two weeks ago. I’m pretty good friends with the IT department. Should I ask if WMM is enabled or should I go straight to ask if I can get a QoS setup?

Also, if I went to a different building, it automatically connects because the routers are the same name, but obviously it’s a different physical name. By doing this it only would change the settings in the specific router in my building, not across the whole campus correct?


#5

Depends on their topology. If building 2 is simply extended from main network / separate VLAN, then it’s possible.

I’d start with asking if there’s any QoS in place already on the routers/switches. Depending on their wireless system, it may also be configured to provide priority to voice. The trick with QoS is that it really should be set up across everything in order to be most effective.


#6

Is it an all in one cisco? AP and router? If so, have them verify WMM is enabled and ask if they have outbound QoS running. That’s about all you can do. If it’s a separate AP/router, then we are well past simple fixes.

Your last comment, if the SSID your phone displays is the same between both buildings, your phone will roam across them. If they are not connected physically to one another, your phone will get a new IP and pretty much redo it’s entire connection, this is usually bad as you’ll loose any active calls or data sessions. If the buildings are connected to a common backbone and the AP’s are connected to that with the same SSID, they will roam properly, no new IP, connection shouldn’t drop, etc. Assuming it’s all configured correctly on the back end of course.

If the SSID’s are different, it’s like a whole new office and you loose connection regardless as it needs to reestablish to the “new” network.


#7

Sounds great, thank you for that. If they do not have QoS outbound running, I will need to give them my phone’s MAC address to do that right?


#8

That or they can enable it based on traffic type so SIP traffic is prioritized in general. Depends on how they have, or will, implement it. They can also do it via IP and give your phone a static DHCP mapping if they want, that still needs the mac.


#9

I just turned QOS off on my ASUS router as it was throttling the DSL connection severely. I may have not used it properly but it was thought to be the solution few months ago when I was dropping Moto X calls. That issue was fixed and I just determined the QOS was to blame for the slow internet speed. I will watch the calls carefully but things are better with my internet.


#10

Some router QOS setups require you to input the speed of your Internet service, and if you don’t set that, will assume a very low number which would slow the connection more than necessary.


#11

Certainly you are not the only one trying to figure ‘how does it really work’?

  • All the current (as of 1/6/2015) Moto models carried by Republic has WMM by default (checked against Wi-Fi Alliance)
  • To be effective the router or AP must have properly implemented WMM (to display the WMM™ it must be certified by Wi-Fi Alliance who provides the certification and testing (via independent labs).
  • Additional information
  • My understanding
    • WMM, if enabled on the AP or Router should prioritize the WiFi data it receives over the air and if collisions occur the phone with WMM will have the shortest back off time, thus it will beat the other devices and get to transmit. As the data is flagged as VO (Voice) it will have the highest priority and will be placed in the Transmit queue of the AP/Router ahead of others on the Lan/WLan. This queue priority will only be maintained on the Lan/Wan and once the Router transmit to the ISP the priority bits are reset.
      • Essentially it will get it out of your router at the highest priority, and other outbound traffic will wait
  • My Recommendation (for now : )
    • Use WMM whenever available, if you have problems, disable it at the Router level to see if that makes a difference

Excerted from Don’t Mess With WMM! - SmallNetBuilder

Basically, the 802.11n spec requires devices to support 802.11e (Quality of Service [QoS] enhancements for wireless LAN) in order to use HT (High Throughput) link rates, i.e. higher than 54 Mbps. (WMM is a subset of 802.11e that was created by the Wi-Fi Alliance as a stop-gap measure while 802.11e made its way slowly through the IEEE review process.) WMM’s Traffic Identifier (TID) field is key to aggregation mechanisms, including block acknowledgement (block ACK), that enable 802.11n’s high throughput rates.

Since WMM support is required for products to be certified for 802.11n, WMM comes enabled by defaultin all Wi-Fi Certified n APs and wireless routers. So even if you don’t have any WMM-aware devices on your network, leave WMM enabled or you may find your clients connecting only at 54 Mbps rates.

Ben ~ user since 2012 ~ not a Republic employee


#12

I’m pretty sure I came across that when setting up my Netgear R7000…had to do a speed test, and reset something, because my internet slowed to a crawl, and then it was all fast and good again.


#13

I’ve been looking at this for sometime and testing options etc. - I’m wondering, if you’re getting better access with QoS/WMM disable if it is because many Service Providers are running the same thus adding this function locally on top of an, already implemented version upstream? I know in my area Cox, LUS, Charter… says that these functions are on your “tap” coming in. I have seen substantial increases on all home networks I assist with as well as small office networks by disabling this function. Two small offices also use SIP phone systems and we’ve seen no signal degradation or stutter issues thus far.


Notable Newbies: Welcome!
#14

My guess: The chance of ISP’s providing end-to-end QoS over the networks that the majority of Republic user traffic flows is somewhere between slim and none.
Many manufactures do not test/certify their products with Wi-Fi Alliance making it difficult to determine any given product truly adheres to the 802.11xx specifications

  • My advice to the Republic user community is still as follows: (I am assuming that the WMM is enabled on all of your phones, but I can not verify this to be a fact)
    • At your home router, always enable WMM (it provides the WiFi level detection and recovery and insertion of the phones data stream into the routers TX queues)
    • Disable WMM APSD, as there appears to be problems with this power save function and Googles Doze function