topic Re: Wireless High Latency in Wireless

Wireless High Latency

ciscoscott2012 — Sun, 04 Jul 2021 05:48:21 GMT

Hi All,

I have just setup a new WLAN using 5508 controllers (located in our HQ) and 3602I APs located in the branches configured in Flexconnect mode.

I created a basic WLAN with WPA2/AES/802.1X and wireless clients are seeing high latecny of 200ms and packet loss, this happens on both 2.4 and 5 with and without wireless N enabled. No significant interferance being reported on the APs or by cleanair. This happens on a range of wireless client devices and wireless adapters.

After lots of testing I noticed that disabling WMM on the WLAN dramatically reduces latency down to 2-3ms. Has anyone seen this behaviour before with 3602I clean air aps?

Re: Wireless High Latency

Scott Fella — Thu, 11 Oct 2012 02:36:26 GMT

I ran into issues with Intel 6200 adapters which had high latency on the 5ghz only. Disabling 40mhz channel width fixed the issue. Upgrading the client adapter to 15.x also fixed the problem. Using 20mhz was the fix for my client since many of the devices having these issues were consultants.

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Re: Wireless High Latency

andrie prabudhi — Fri, 18 Jan 2013 04:11:48 GMT

Hi ciscoscott,

so, its working if you disabling WMM?, cause I have same problem like this,

I have cisco WLC 5508 and 3602 AP configured local and flexconnect mode.

please tell me the update..

for the info I limiting the user for radio b/g and a/n is max 24 user, so the AP will accept 48 user right?

but if the AP have more than 24 client, the client having bad performance.

thanks in advance...

Andrie

Re: Wireless High Latency

Scott Fella — Fri, 18 Jan 2013 04:18:41 GMT

You don't have client load balancing enabled do you? That causes a lot of issues. Can you be specific with what you have seen?

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Re: Wireless High Latency

andrie prabudhi — Fri, 18 Jan 2013 04:52:47 GMT

hi Scott,

do you mean this :

i didnt enable yet, is this must enable ?

is this affect the parameter shown below :

thank in advance,,

Andrie

Re: Wireless High Latency

Scott Fella — Fri, 18 Jan 2013 09:53:45 GMT

It shouldn't be enabled. What you need to do is define what devices are being affected and what radio bands the users are on. Most of the time a device driver that just needs to be upgraded. Limiting 24 connections per AP might help but I have seen more connection on a given AP with no issues. When users complain, I usually ask questions but almost always go out on site to see the issue for myself.

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Re: Wireless High Latency

andrie prabudhi — Sat, 19 Jan 2013 20:58:38 GMT

Hi Scott,

thanks for your reply,

I followed what you said yesterday, go out and testing.

the most users get impact when using 2,4 ghz, but good performance on 5 ghz,

after I check the area with software, theres so many interference specially for channel 1,6,11 (cause theres another AP that cannot be shut)

so I try to change the channel with channel 2 or 3, and the result is really good

the question is? its okay when I used the channel (2,3) ?

Thanks in Advance

Andrie

Re: Wireless High Latency

Scott Fella — Sat, 19 Jan 2013 21:22:04 GMT

I would not use channel 2. If your doing high density, 1,6,11 are the channels that you need to use. What you can try in the 2.4 is to disable everything below 24mbps or 36mbps and also reduce the power level 3-5 and see if that helps. Can you post your show run-config when your wireless is being heavily utilized.

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Re: Wireless High Latency

andrie prabudhi — Sat, 19 Jan 2013 21:56:10 GMT

hi Scott,

802.11g still work when disable below 24mbps? wlc automatic setting the power level,

can you tell me detail what the affect when use channel 2/3?

sorry for too much asking

attached show running-config and report too,

thanks in advance

Re: Wireless High Latency

Scott Fella — Sat, 19 Jan 2013 22:47:57 GMT

Well the non overlapping channels are 1,6,11. So channel each channel bleed to the adjacent 2 channels. So an AP on channel 6 will bleed into 4,5,7,8. AP in channel 1 bleeds into 2 and 3 and channel 11 bleeds into 9 and 10. So if you use channel 2, that will also affect 1,3,4 and that overlaps with channel 6 which bleed also into 4,5

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Re: Wireless High Latency

Scott Fella — Sat, 19 Jan 2013 22:51:39 GMT

Disabling data rates below 24 or 36 or 48 just reduces the cell size. So you would set one of these to mandatory and disable everything below that data rate. So set 24mbps as mandatory and disable all lower data rates. Setting the power or let RRM adjust the power is fine too. What TX power level do you see your APs on in the 2.4ghz. On my phone so can't really look at what you posted.

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Re: Wireless High Latency

Scott Fella — Sun, 20 Jan 2013 00:38:30 GMT

Here are some of my suggestions... your environment doesn't seem that high density, but you only provided me with only one of the WLC's in the mobility group, so I'm going off of this.

Configure this:

Data Rates 2.4 Band:

1 Mbps: Disabled

2 Mbps: Disabled

5 Mbps: Disabled

6 Mbps: Disabled

9 Mbps: Disabled

11 Mbps: Disabled

12 Mbps: Disabled

18 Mbps: Supported

24 Mbps: Mandatory

36 Mbps: Supported

48 Mbps: Supported

54 Mbps: Mandatory

Max TX power 2.4 Band: 17

Min TX power 2.4 Band: 11

Data Rates 5.0 Band:

6 Mbps: Disabled

9 Mbps: Disabled

12 Mbps: Disabled

18 Mbps: Supported

24 Mbps: Mandatory

36 Mbps: Supported

48 Mbps: Supported

54 Mbps: Mandatory

Max TX power 5.0 Band: 17

Min TX power 5.0 Band: 11

After your wireless settles down a bit change the DCS to 24 hours

Thanks,

Scott

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Re: Wireless High Latency

xiahuiyi123 — Fri, 25 Jan 2013 11:29:18 GMT

Dear Scott,

We got the same problem in our office recently after we purchased new 3602I APs. Problem is on 2.4Ghz band. Your solution to disable low speed data rate works very well. Do you know why this happen - hardware design issue or software bugs? And is there any other solution? Thanks.

Re: Wireless High Latency

Scott Fella — Fri, 25 Jan 2013 13:28:00 GMT

Well this helps because you are limiting clients to connect to the lowest mandatory or supported data rate. This is not a bug and is done on any vendors wireless. So if you prevent clients from staying connected at 1mbps, well how do you thing their throughput would be. Somewhat you are doing is decreasing the coverage cell size by eliminating the lower data rates thus forcing uses to roam when they go below the lowest supported data rate. Also removing data rates below 11mbps also stops 802.11b only device from associating this also helping since the WLAN doesn't have to perform any back offs to support these slower devices.

Hope this clears things up.

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Re: Wireless High Latency

andrie prabudhi — Tue, 26 Feb 2013 05:31:21 GMT

hi Scott,

thanks for your advice,

I already setting what you said, but the connection still slow,

I have upgrade IOS too (from 7.3 to 7.4)

I have cisco PRIME NCS that reporting Channel utilization every AP on :

1. RF 2,4Ghz (channel 1,6,11) is high (>60%),

2. but on RF 5 Ghz the CU is low (<50%),

when the CU on AP low, we have good performance

my Tshoot :

1. I change and using channel 3,8,13.. suddenly the CU AP is low (<50%), and we have good performance.

2. there is no issue on this RF

my question is :

1. why we get high CU on AP on radio 2,4Ghz?

2. is there any setting on WLC that make CU still low without using non-standart channel ?

Thanks in Advance Scott,

Andrie

Re: Wireless High Latency

Scott Fella — Tue, 26 Feb 2013 12:54:27 GMT

Well you really should stick with the standard channels since maybe some clients aren't connecting:)

The reason for high CU is interference and other RF using the 2.4ghz frequency. If you are around other companies or home, you might see high CU because of that. This is one reason the 5ghz is there. There is not 3 channels like the 2.4ghz but you have 12 available in the US. Now it seems like the CU that high might not be caused by other 2.4ghz wireless AP but might also be caused by interference on those channels. If you have high density of users, then that can also cause high CU because everyone want to send traffic on this half duplex network.

So as long as you make sure it's not the client drivers, etc maybe it's time to tweak your configuration on the WLC.

Do you have high density of APs and it clients, do you have to support 802.11b devices, do you have 802.11a compatible APs, are the APs connected to 10/100 or gigabit. What applications do these WLC use in the wireless? Things like these help decide how to setup your WLC.

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Wireless High Latency

Richard Marot — Wed, 13 Mar 2013 18:41:13 GMT

I set WMM to required and upgrading to 7.4.100 and afterwards all of my IOS devices started working perfectly. very little latency and proper speedtests and download speeds were acheived.

-R

Wireless High Latency

Saravanan Lakshmanan — Thu, 14 Mar 2013 05:27:19 GMT

N rates are not achieved if wmm is disabled, are you getting good throughput on non N 2.4 & 5ghz bands.

If N AP is performing poor try this:

WLC>config ap tcp-adjust-mss enable all 1363 --- All AP

WLC>config ap tcp-adjust-mss enable ap-name 1363 -- Specific AP

Wireless High Latency

Richard Marot — Mon, 18 Mar 2013 15:25:34 GMT

Saravanan, We are achieving very good thoughput. See attached screen grab.

Thank,

Wireless High Latency

Saravanan Lakshmanan — Mon, 18 Mar 2013 15:55:31 GMT

Thanks for Sharing it.