topic Re: Improve airtime / recommended users per WiNG AP in ExtremeWireless (WiNG)

Improve airtime / recommended users per WiNG AP

Richard_Augusto — Wed, 24 Apr 2019 09:33:54 GMT

Hello,

Is there any way to prioritize the air time on the Guest network and the corporate network in a same AP?

I have used the airtime fairness feature (enable by default), but I would like to know if I can customize something to improve response time (we use SAP).

Other question as to the number of concurrent users, is there any realistic number to distribute the APs?

Does AP7632 and 7532, per example? How many concurrent users does AP recommend? The total bandwidth (unicast traffic) that should pass is 30 Mbps.

Re: Improve airtime / recommended users per WiNG AP

ckelly — Wed, 24 Apr 2019 20:13:41 GMT

Richard,

It sounds like you might be wanting to introduce prioritization for SAP traffic (QoS).
On the wired side though, is the SAP traffic given any priority? If not, then prioritizing the SAP traffic on the wireless would likely not be much help.

Regarding the number of concurrent users, there are several variables to consider. This topic can get a little lengthy to describe. It might be better if you could just supply some information and I could give you a final number.
The only number you've given so far is total unicast traffic being 30Mbps "that should pass". I'm not sure how to interpret what you are saying here though regarding what this 30Mbps is.

What sort of devices associate with these APs?

What percentage are one spatial stream, two spatial stream?

At a minimum, how much bandwidth do you *need* to allocate to each device?
What PHY rate does these devices tend to connect at?
What channel width are you using?
What does the environment look like around these APs? Dense wireless environment? Moderate office type environment?

Re: Improve airtime / recommended users per WiNG AP

Richard_Augusto — Wed, 24 Apr 2019 21:13:10 GMT

Hi Chris,

-Two spatial streams (Many devices uses 1 spatial stream)
-10 or 15 APs per site (300 client concurrent users / 50 Enterprise users per site/store)
-My target in most site is -50/-55. Agressive because high density.
-We have 4 SSIDs per AP
-20 Mhz in 5Ghz
-Band per device is 1 Mbps (limit for 30 Mbps / we use QoS)
-18 Mbps (minimum rate)
-Latency is very decisive for sucess!

In Wired side we have specific VLAN, applyed QoS for priorize SAP server traffic (Layer 3 QoS in this case).

Re: Improve airtime / recommended users per WiNG AP

ckelly — Wed, 24 Apr 2019 21:41:33 GMT

-Two spatial streams (Many devices uses 1 spatial stream)
Safe estimate is that it's a 50/50 mix?

-10 or 15 APs per site (300 client concurrent users / 50 Enterprise users per site/store)
300 total users for all sites? 50 users/store? So 6 stores? And then 10-15 APs/site? (10-15 APs for a site with only 50 users seems pretty light. How big are these sites?

-My target in most site is -50/-55. Agressive because high density.
What are the -50/-55 numbers referencing?

-Band per device is 1 Mbps (limit for 30 Mbps / we use QoS)
Not sure what you are explaining here. Band per device is 1Mbps?

-18 Mbps (minimum rate)
Is this the minimum PHY rate you are wanting to achieve per user? If so, that effectively equates to a TCP throughput of roughly 7-9 Mpbs. Or are you simply stating that 18Mbps is your configured Basic rate for the WLAN config?

-Latency is very decisive for sucess!
Certain things are out of your control on the wireless side. If medium contention is an issue due to high domain contention, you can only really fix that by finding a cleaner channel. About all you can do is try to find a low contention channel and then prioritize the traffic on the wireless/wired side.

In Wired side we have specific VLAN, applyed QoS for priorize SAP server traffic (Layer 3 QoS in this case).
Ok good. In that case, are the WLANs for the SAP traffic mapped to this VLAN on the AP?

Re: Improve airtime / recommended users per WiNG AP

Richard_Augusto — Wed, 24 Apr 2019 22:26:54 GMT

@Chris Kelly ,

Safe estimate is that it's a 50/50 mix?

70/30

300 total users for all sites? 50 users/store? So 6 stores? And then 10-15 APs/site? (10-15 APs for a site with only 50 users seems pretty light. How big are these sites?

In all sites we have 3500+ concurrent users in all stores. 14.000 unique users in a day.

For this example, we talk for one specific store.

We have 300 concurrent GUEST users total in this specific store + 50 enterprise users. 26909 square feet.

What are the -50/-55 numbers referencing?

RSSI, -55 dBm

Not sure what you are explaining here. Band per device is 1Mbps?

Yes. Average band per device. SAP uses low BW but require low latency. QoS is primordial in enterprise WLAN.

Is this the minimum PHY rate you are wanting to achieve per user?

Minimum PHY in WiNG in some stores is 48.7 Mbps

If so, that effectively equates to a TCP throughput of roughly 7-9 Mpbs. Or are you simply stating that 18Mbps is your configured Basic rate for the WLAN config?

18 Mbps is my basic rate

Certain things are out of your control on the wireless side. If medium contention is an issue due to high domain contention, you can only really fix that by finding a cleaner channel. About all you can do is try to find a low contention channel and then prioritize the traffic on the wireless/wired side.

Ok. We have Chanalyzer for this and check best channel. I will turn off smart-rf because some events...

Layer 2 traffic priorization (DSCP) on the my router side help for WMM/Priorize latency?

Ok good. In that case, are the WLANs for the SAP traffic mapped to this VLAN on the AP?

Yes. Layer 3 priorization, SAP VLAN (/26 network) are mapped to all APs.

Re: Improve airtime / recommended users per WiNG AP

ckelly — Thu, 25 Apr 2019 00:02:40 GMT

Okay...so here's what I think you're looking at.
Good SNR. Users should be able to connect at VHT MCS-7/8
20MHz channel
Moderate/High density situation (350 potential associations*/store with 10-15 APs). Best case, that's about 23 users per radio (per AP if we're ONLY talking about 5GHz connections). Worst case, 35 users per radio.

Those user/radio figures are WELL within norms from a very simple high-level view, but what matters far more is the amount of bandwidth that each user requires and at what PHY rate they are getting with the association. It appears that the PHY rate *should* be good based on the SNR.
The last important variable is the amount of bandwidth being used by the clients. You seem to be indicating that YOUR employees only need about 1Mbps of TCP bandwidth for SAP. Confirm?

*What I don't know though is how much of the radio's bandwidth is also being consumed by all of the store customers. Are they allowed to connect to the 5GHz radio as well or are customers only allowed on the 2.4GHz radio maybe?

What I also cannot account for is the actual amount of medium contention in that environment. What I mean by that is that you could have a PERFECTLY setup system that provides everything needed for wireless users....but if the wireless medium is suffering from an OBSS situation or some other interfering source, it could/would slow everything down. It would be like trying to hold a conversation on a talkie-talkie when there are a 100 people all wanting to talk. Everyone has to wait their turn before transmitting.
For the sake of this conversation though, we'll just assume that the medium is 'healthy'.

So what I need to lastly know then is an answer regarding the customer's ability to also connect to this 5GHz network.
Also, for the sake of the calculations, I'm going to consider that only about 80% of your employees will be actively transmitting/receiving to SAP at the same time. If you think that this figure should be different, tell me.

(What I have so far though, if I assume that ONLY 80% of employees are transmitting/receiving on the 5GHz network at the same time, you should should be able to maintain about 60 connections @1Mbps before airtime saturation occurs. That's 1 single 5GHz radio.
Even if we bump that up to ALL connections are active at the same time, 100%, you should still be able to maintain about 50 users @1Mbps.

Re: Improve airtime / recommended users per WiNG AP

Richard_Augusto — Thu, 25 Apr 2019 00:54:20 GMT

@Chris Kelly ,

Thanks for numbers!

We have problems in 2.4 Ghz with 50+ Guest users... The problem: latency.

We not have ANY PROBLEMS WITH LATENCY in low density network, in this case, in our Warehouse (we have +90 APs and Zebra mobile computers). I can not remember the last time I went to see user complaints.

You seem to be indicating that YOUR employees only need about 1Mbps of TCP bandwidth for SAP. Confirm?

Yes! We use SAP Netweaver and Custom our Android App for consumer retail. Works great, but is very sensible with response time! I need help for tips for improve performance in use of airtime in mixed network (guest+enterprise).

Our employers use your Smartphone (BYOD) 60% is 1ss 2.4 Ghz only. The easy way for optimze retries and airme saturation for get low latency and solve this is "in fact" separate one channel for 2.4 Ghz for Guest Network and add more aps and create small cells for enterprise SSID (with channel 6 and 11)? We not have limits for buy more and more APs for create small cells .

I can use DSCP, Radio QoS, change priority for improve latency performance? WiNG know change priority? My router have capabilities to mark packets for DSCP values.

See below, my traffic in WLAN for retail APP is minimum (in Guest network we have 3x or more traffic w/ high density).

Re: Improve airtime / recommended users per WiNG AP

ckelly — Thu, 25 Apr 2019 01:52:13 GMT

Ideally, the best way to deal with this is as you mentioned.....only allow employees using the SAP system to use the 5GHz network. At that point, the question is....would these employees also be using devices on the 5GHz for OTHER things that do not use SAP?

Question: Have you confirmed that the devices using SAP support WMM?

Re: Improve airtime / recommended users per WiNG AP

Richard_Augusto — Thu, 25 Apr 2019 20:00:02 GMT

@Chris Kelly

would these employees also be using devices on the 5GHz for OTHER things that do not use SAP?

Yes. We use Motorola/Zebra collectors in all stores. Newer collectors from Zebra (MC67/MC33) have 5 Ghz.

Question: Have you confirmed that the devices using SAP support WMM?

Yes. All devices have WMM Support (i get from 'wi cli det').

Question:

How to enable WMM for priorize traffic on SSIDs? I can use router side to mark packets? I can use WiNG for this? How?

Re: Improve airtime / recommended users per WiNG AP

Richard_Augusto — Thu, 25 Apr 2019 20:19:56 GMT

At now, i apply this for specific SSID for Guest.

Work? We wait... Collecting reponse times from iPad Kiosks....

Re: Improve airtime / recommended users per WiNG AP

Richard_Augusto — Thu, 25 Apr 2019 22:57:47 GMT

@Chris Kelly ,

Good News! WMM is part of process, rework/good reuse of physical channels is premisse... but..

The problem of high latency of my enterprise/BYOD is in my application...

We use iPad Kioks with our application and Android app for BYOD.

In particular case of iPad, we have experienced 30~100ms with always-on screen. Rare cases, have 200ms.

iOS have Power Management and priorize wifi traffic only necessary. If app not have any optimizations for "always on traffic", the latency increase 10x. SAP is very sensitive.

I explained to our devloper to take action to improve this. I wished him good luck.

Re: Improve airtime / recommended users per WiNG AP

ckelly — Fri, 26 Apr 2019 01:14:51 GMT

Richard,

In addition to the "Low" classification on the Guest Network WLAN QoS Policy that you setup (from the screenshot), I would also modify the WLAN that is used for SAP and change the "Configure Non WMM Client Traffic Type" to "Low". This will ensure that any non-WMM devices that *also use* that same WLAN are also de-prioritized. This way, only WMM devices on that WLAN are prioritized.

If you wanted to go even further and make sure that ONLY the iPad devices had priority, you could create an IP firewall rule rule that re-marks traffic priority of non-iPAD WMM devices. 

Re: Improve airtime / recommended users per WiNG AP

Richard_Augusto — Wed, 01 May 2019 06:03:19 GMT

What happened to the AP7632? After the last update (5.9.4.0) this AP model gets better with each version.

We put 90 users in a single AP7632 running well. Unfortunately this version has a small detail: with SMART-RF enabled, set maximum power 23 dBm (being that we configured 12 or 14 dBm). We have already opened an open case in GTAC.

Only the fact that it has 90+ clients connected and with quality, has shown that Engineering is investing heavily in improvements/bugs corrections. I'm really happy about this AP now!