Controller Based WLANs

How much bandwidth will be used by RTLS?

Environment : This applies to all AOS versions above 3.4.x

 

Before we try to understand how much bandwidth will be consumed by RTLS packets we need to understand what is "Update Interval" and how it works.

Update Interval:
*****************
(Aruba3400) #show ap monitor debug status ap-name 125

RTLS Configuration and State
-----------------------------
Type       Server IP  Port  Freq  Active  Rpt-Tags  Tag-Mcast-Addr     Tags-Sent  Rpt-Sta  Incl-Unassoc-Sta  Sta-Sent  Cmpd-Msgs-Sent  CM
----       ---------  ----  ----  ------  --------  --------------     ---------  -------  ----------------  --------  --------------  --
MMS        N/A        N/A   30            disable   01:0c:cc:00:00:00  N/A        disable  N/A               N/A       N/A             N/A
Aeroscout  N/A        N/A   N/A           disable   00:00:00:00:00:00  N/A        disable  N/A               N/A       N/A             N/A
RTLS       1.1.1.1    1234  30            disable   01:18:8e:00:00:00  N/A        disable  N/A               N/A       N/A             enable

The update interval sets how often updated information for a single device will be sent in the RTLS data stream.  If it is set to 30 seconds, rtls data for a specific client will be sent every 30 seconds. So if there 30 clients, there will be an update roughly every second that includes a single clients data.   Now if there are 90 clients heard, there will still be an update every second but it will include data for 3 clients.  If there are only 10 clients, there will be some seconds where no updates are sent.  There will be 10 updates in that 30 seconds.

Now we know how update interval works, we have the below formulae to calculate the approximate bandwidth requirement per second:

  •  (header size)+(signature size)+(1/update interval)*(num of clients)*(client data size).

header size: 16 bytes
signature size: 20 bytes
client data size: 28 bytes

The requirement changes based on the "update interval" set and the "number of clients" connected to the AP.
If we assume there are 90 clients being heard, then the average Bps will be (16)+(20)+(1/30)(90)(28) = 120 Bytes per second for a single AP.

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‎04-09-2015 04:01 AM
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