Upcoming Maintenance Alert:

The UBNT Community will be upgraded at 5pm MDT on April 25th. During this time the community forums will be set to read-only status.

Learn more

×
Reply
Highlighted
Established Member
Posts: 2,464
Registered: ‎07-28-2009
Kudos: 667
Solutions: 33

Fixed-Frame, Voip, bandwidth, and Airmax Priorities

[ Edited ]

This is a followup from a previous thread.

https://community.ubnt.com/t5/airMAX-AC/Negative-impact-of-Airmax-Priority-on-VOIP/m-p/1959754#M2224...

 

I have an Isostation5AC on the roof of our building and I connected to it via a Mikrotik router with my laptop to run tests to see how Airmax Priorities affect the Voip and bandwidth performance on FF.

CPE Performance when idleCPE Performance when idle

 

AP has 41 clients.  Mix of XW and AC.  Running 20mhz channel at 75/25 8ms split.  AP was under an average of 18-25Mbps load from other clients.  Clients are set to manual priorities based on signal/capacity from Low to Medium.  I do not ever use High priority.

 

I ran a TCP bandwidth test from the router behind the CPE to our main core router in our offices.  The tower AP is connected to our offices via fiber.

 

I also ran an online VOIP test 3 times at each priority to make sure the results were consistent.

 

Here are the results.

 

Airmax Priority Medium

Bandwidth TestBandwidth TestVoip TestVoip Test

 

Airmax Priority Base

Bandwidth testBandwidth testVoip testVoip test

 

Airmax Priority Low

Bandwidth TestBandwidth TestVoip TestVoip Test

  1. Airmax Priority has a large impact on Medium vs Base or Low.  Difference between Base and Low is there but not as large.
  2. To get the best VOIP results, even on fixed-frame, Medium priority or higher appears to be the best.

 

 

SuperUser
Posts: 10,389
Registered: ‎10-28-2009
Kudos: 3449
Solutions: 268

Re: Fixed-Frame, Voip, bandwidth, and Airmax Priorities

@UBNT-sriram
@UBNT-SNK

Worth taking a look at this.
Tony Pierro
CTO - Wireless Internet Services, Inc.
Ubiquiti Employee
Posts: 764
Registered: ‎08-12-2009
Kudos: 371
Solutions: 26

Re: Fixed-Frame, Voip, bandwidth, and Airmax Priorities

Thanx @sbyrd

 

The FF scheduler is indeed airMAX priority first and within the same airMAX priority, packet priority is then used.

We could possibly add an advanced option to make it packet priority first and within it use airMAX priority for precedence. 

 

May I ask what is the VOIP quality measurement tool you have used here ?

It could be useful for us to check it out.

 

Established Member
Posts: 2,464
Registered: ‎07-28-2009
Kudos: 667
Solutions: 33

Re: Fixed-Frame, Voip, bandwidth, and Airmax Priorities


UBNT-sriram wrote:

Thanx @sbyrd

 

The FF scheduler is indeed airMAX priority first and within the same airMAX priority, packet priority is then used.

We could possibly add an advanced option to make it packet priority first and within it use airMAX priority for precedence. 

 

May I ask what is the VOIP quality measurement tool you have used here ?

It could be useful for us to check it out.

 


@UBNT-sriram I use the tool on this website. https://www.whichvoip.com/voip/speed_test/ppspeed.html

Since I do not offer VOIP service to my clients I looked online for a way to simulate VOIP to troubleshoot customer VOIP issues.  I use the Java based test tool as I had problems running the HTML5 one.

Established Member
Posts: 2,464
Registered: ‎07-28-2009
Kudos: 667
Solutions: 33

Re: Fixed-Frame, Voip, bandwidth, and Airmax Priorities

Since just by changing Airmax Priority can have a dramatic affect of device throughput, I wonder if that is why I see lower peak/avg usage on some of the APs I have moved to FF?   

 

I use Airmax Priorities extensively with my default type being Medium and then clients getting manually bumped to Base or Low based on signal, TX/RX rates, and capacity.  Being in flat farm land we have a decent number of clients who suffer heavy thermal inversion so for part of the year they get bumped to a lower priority.  Also long term clients who now have less than clear shots due to tree growth or interference get bumped down as well.

 

On any given AP I will have a healthy mix of Low, Base, and Medium clients.

 

In my tests above with a perfect client I got the following.

  • Medium - 45Mbps avg
  • Base - 29Mbps
  • Low - 20Mbps

My guess is that on Flex the DL/UL frames are able to expand large enough where more lower priority clients are able to make it into the current frame.  Also the lower clients can take advantage of Automatic Retries and hold onto the AP's time for longer to get their data.

 

On Fixed since the frames are obviously a fixed size there is a higher chance that lower priority clients will be bumped to the next frame at the expense of the AP filling the current frame with higher priority clients. The smaller fixed frame holds less clients so less lower clients get in.

 

This is not a complaint; just an observation.

Established Member
Posts: 2,464
Registered: ‎07-28-2009
Kudos: 667
Solutions: 33

Re: Fixed-Frame, Voip, bandwidth, and Airmax Priorities

[ Edited ]

Would a more efficient solution be to put all the CPEs at Base Priority and then have the AP dynamically adjust the CPE priority based on Capacity? 

 

I see that pretty much since AC was released the Station list in the AP has the fields 'Priority' and 'Desired Priority'.  I assume that was to indicate the difference between the CPE configured Priority and the Priority currently assigned by the AP (dynamic Airmax Priority?).  However I have never seen any difference between those two fields, no matter what the signal, modulation rates, or capacity of a CPE was.

 

Was there a plan for Dynamic Airmax Priority and it just never got implemented?  Was it replaced by the TDMA filter?

 

I understood the TDMA filter as a way to further prioritize based on capacity within Airmax Priority groups only.  Airmax Priority always comes first.

 

 

Senior Member
Posts: 3,774
Registered: ‎07-03-2008
Kudos: 1019
Solutions: 86

Re: Fixed-Frame, Voip, bandwidth, and Airmax Priorities

Is there a way we can create a low latency path for a specified amount of bandwidth (typically ~ 100 kbits for a VoIP channel but it could vary per client) while leaving the rest of the traffic for that STA at its normal level?  This would also help for gamer clients.

Ubiquiti Employee
Posts: 764
Registered: ‎08-12-2009
Kudos: 371
Solutions: 26

Re: Fixed-Frame, Voip, bandwidth, and Airmax Priorities

@MimCom one issue with kbits based rules is that at the scheduler level, airtime is what matters and on links that are below average, this may cause issues.

 

We will circle back on this topic after XM sync release.

 

Senior Member
Posts: 3,774
Registered: ‎07-03-2008
Kudos: 1019
Solutions: 86

Re: Fixed-Frame, Voip, bandwidth, and Airmax Priorities

[ Edited ]

Understood, thank you.

 

This relates to the dynamic queuing scheme discussed here (pasting from my last comment):


I'd like to make sure we have a way of creating 'first priority' (with a CIR) links along with the 'best effort fair queuing' scheme being discussed here.  That highest priority traffic could be in a VPLS, a VLAN, DSCP-based or IP-based, but we would need some way to handle it.  The simplest probably being to constrain token buckets to the three lowest tiers, though other optimizations are certainly possible.

 

Perhaps display what a single timeslot will yield in the current environment and offer that?

 


On the latency testing, there's a handy bit of open source here that I believe should run on EdgeMAX or airOS.

Reply