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RTS/CTS best practice

Hi,

 

I am looking at fine tuning the RTS/CTS settings at a site as there seems to be performance issues related to the wireless.

 

I see this parameter is in the ssid-profile, but was wondering if this should be change on all ssids at the site, or just the one in question?

 

Thanks


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ACCP, ACMP, ACMX #294
mclarke@arubanetworks.com
Guru Elite

Re: RTS/CTS best practice

I would tell you that is probably the last thing you would ever change to solve a performance problem.  I personally would not touch it.

 

I would try every last suggestion in the thread here:  http://community.arubanetworks.com/t5/Community-Knowledge-Base/802-11-RF-Troubleshooting-Best-Practices/ta-p/20410 before editing the rts/cts settings.

 

 



Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Re: RTS/CTS best practice

Appreciate that, but the issue is bad enough to start considering all options.

 

A very high level of retries, 10-30%.  The clients are showing 1-15 % ping loss.  Interference index on APs is fine though.

 

It is happening with particular clients on a-HT. I've tweak a few parameters here and there and will have to wait on the testing tomorrow.  Latest driver for the clients actually makes things worse.

 

Next step is packet capture from an AM, and maybe from the controller at the same time, but any other suggestions appreciated.

 

Client:  HP thin client t5740e (Atheros AR5009  driver ver: 9.2.0.225)

 

 

 

 


If my post is helpful please give kudos, or mark as solved if it answers your post.

ACCP, ACMP, ACMX #294
mclarke@arubanetworks.com
Guru Elite

Re: RTS/CTS best practice

Is Airwave in the environment?

How many Clients on one AP?

Are there other interferers?

Did you do a "show ap arm rf-summary ap-name" to see all the parameters on that AP?

          show ap arm rf-summary ap-name "AP125"

Channel Summary
---------------
channel  retry  phy-err  mac-err  noise  cov-idx  intf_idx
-------  -----  -------  -------  -----  -------  --------
161      0      0        0        0      0/0      0/0//0/0
1        0      0        0        91     5/0      29/6//0/0
48       0      0        0        0      0/0      0/0//0/0
165      0      0        0        0      0/0      0/0//0/0
5        0      0        0        89     0/0      11/19//0/0
6        0      0        0        85     0/0      11/19//0/0
7        0      0        0        84     0/0      0/24//0/0
11       0      0        20       93     7/0      26/2//0/0
149      0      0        0        0      0/0      0/0//0/0
36       0      0        0        0      0/0      0/0//0/0
153      0      0        0        0      0/0      0/0//0/0
40       3      0        2        89     11/0     21/0//0/0
157      0      0        0        0      0/0      0/0//0/0
44       0      0        0        0      0/0      0/0//0/0
HT Channel Summary
------------------
channel_pair  Pairwise_intf_index
------------  -------------------
1-5           65
7-11          52
149-153       0
36-40         21
157-161       0
44-48         0

Interface Name           :wifi0
Current ARM Assignment   :40/21
Covered channels a/g     :0/0
Free channels a/g        :9/0
ARM Edge State           :enable
Last check channel/pwr   :2d:23h:7m:38s/2m:22s
Last change channel/pwr  :2d:23h:7m:38s/2d:23h:7m:38s
Next Check channel/pwr   :0s/8m:4s

Interface Name           :wifi1
Current ARM Assignment   :11/21
Covered channels a/g     :0/2
Free channels a/g        :0/1
ARM Edge State           :enable
Last check channel/pwr   :1d:8h:50m:59s/6m:9s
Last change channel/pwr  :2d:18h:31m:7s/1d:15h:50m:11s
Next Check channel/pwr   :0s/24s

 

On a single client, what is the output of "show ap association client-mac" to see the client retries vs. the channel retries and error rates, as well as the noise?

         show ap association client-mac 00:90:4c:02:00:da

Flags: W: WMM client, A: Active, K: 802.11K client, B: Band Steerable

PHY Details: HT: High throughput; 20: 20MHz; 40: 40MHz
             ss:  spatial streams

Association Table
-----------------
Name   bssid              mac                auth  assoc  aid  l-int  essid    vlan-id  tunnel-id  phy          assoc. time  num assoc  Flags
----   -----              ---                ----  -----  ---  -----  -----    -------  ---------  ---          -----------  ---------  -----
AP125  00:1a:1e:20:82:e0  00:90:4c:02:00:da  y     y      2    10     CatchMe  1        0x108a     g-HT-20-1ss  32m:29s      1          WAB

00:90:4c:02:00:da-00:1a:1e:20:82:e0 Stats
------------------------------------------
Parameter                            Value
---------                            -----
Channel                              11
Channel Frame Retry Rate(%)          0
Channel Frame Low Speed Rate(%)      0
Channel Frame Non Unicast Rate(%)    0
Channel Frame Fragmentation Rate(%)  0
Channel Frame Error Rate(%)          2
Channel Bandwidth Rate(kbps)         0
Channel Noise                        92
Client Frame Retry Rate(%)           0
Client Frame Low Speed Rate(%)       0
Client Frame Non Unicast Rate(%)     0
Client Frame Fragmentation Rate(%)   0
Client Frame Receive Error Rate(%)   0
Client Bandwidth Rate(kbps)          0
Client Tx Packets                    1965
Client Rx Packets                    764
Client Tx Bytes                      210807
Client Rx Bytes                      462463
Client SNR                           34

 

 

 



Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Re: RTS/CTS best practice

yep, doing all that.  Many clients showing things not so good.

 

About to do some captures from the AP and session mirroring on the clients.

 

So back to my original question, if all options exhausted, then what would you suggest for RTS/CTS?

 

The options in the clients driver are basically nil.

 

:smileyhappy:


If my post is helpful please give kudos, or mark as solved if it answers your post.

ACCP, ACMP, ACMX #294
mclarke@arubanetworks.com
Guru Elite

Re: RTS/CTS best practice

I wouldn't change that.  I would do a packet capture first, to find out what is really going on.

 

 



Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

MVP

Re: RTS/CTS best practice

How are we sure it is a wireless/RF issue and not a networking or processing issue at the controller. We have seen incidents where high packet loss was experienced but it was the datapath at fault. I'm only mentioning this in your quest to explore all options.
==========
Ryan Holland, ACDX #1 ACMX #1
The Ohio State University
Guru Elite

Re: RTS/CTS best practice

RF issues can definitively spotted with a packet capture.

 

If a regular packet capture does not reveal anything, a controller performance issue would accomplished with TAC in conjunction with a packet capture.

 

What is common to both scenarios?  Yes, a packet capture.

 



Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Re: RTS/CTS best practice

Thanks guys.  I don't think it is RF, but I know this site to be a challenging rf environment, so was looking at that side first.

 

Have done the AP capture, but it didn't work at first.  The stream was in the datapath with 'D' and denied.  The TAC guy couldn't see why and we tried a few things with no luck.  Eventually got the customer to plug directly into controller and on same subnet as APs, which then worked.  The support guys will hopefully find out why that was the case.

 

Was doing some session mirroring on some clients to another laptop, but I couldn't see those streams in the the datapath either, but could see it hitting the acl.  Am I correct  in assuming that I should see something in the datapath for that session-mirror-destination ip ?

 

I'll get a capture from the controller port.  Unfortunately, that is on a port channel so have to pull one leg out to get all the traffic.  Would be great to be able to capture from a virtual interface like vlan or port channel instead of just a physical.  Sounds like a feature request to me though. :smileywink:


If my post is helpful please give kudos, or mark as solved if it answers your post.

ACCP, ACMP, ACMX #294
mclarke@arubanetworks.com
MVP

Re: RTS/CTS best practice

If you/they are seeing D flags in session table but don't know why, I would update all the acls/policies so that the deny statements (as well as the implicit deny statement) are set to log. This way "show log security" would uncover which policy these denies are hitting.
==========
Ryan Holland, ACDX #1 ACMX #1
The Ohio State University
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