Controller Based WLANs

Requirement:

How to find the number of mDNS packet hitting the controller per second and mDNS packet per second exceeds the hardware limit?

Each Controller model has limit of handling the number of mDNS packet per second and other airgroup limits

Below are the listed limits:

Controller Model mDNS Packets Per Second (PPS) No of AirGroup Servers No of AirGroup Users mDNS Memory consumption
-------------------------------------------------------------------------------------------------------------------------------
7240                 100                         10000                   20000                 49 MB
7220                 60                         7000                 15000                 31 MB
7210                 60                         5000                 10000                 26 MB
6000-M3                 20                         2500                 5500                 17 MB
3600                 20                         2000                 6000                 15 MB
3400                 20                         2000                 2000                 11 MB
3200XM                 20                         600                 1500                 5 MB
7005                 30                         300                 700                 5MB
7010                 40                         500                 1500                 8MB
7030                 50                         1000                 3000                 14MB
7024                 50                         600                 1400                 9MB
7205                 40                         2000                 6000                 15MB

So it is important to understand the load of mDNS on a controller. If the mDNS exceeds the hardware limit, it may end up in high CPU utilization and the controller may go unresponsive. To find the number of mDNS packet hitting the controller we could use the following command

(Aruba) #show airgroup internal-state statistics

To find the nunber of packets hitting the controller per second we need to take a difference of the internal state statistics in a 5 minute interval window. In 5 mins window find out the number of packets received in “Recv Since Last Read column” for Rx Request, Then calculate the packet per second based on the output.

(Aruba) #show clock

Wed May 25 21:05:28 PST 2016

(Aruba #show airgroup internal-state statistics

Time: Wed May 25 21:05:33 2016

Sibyte MDNS Messages
--------------------
Opcode  Name                         Sent Since Last Read  Sent Total  Recv Since Last Read  Recv Total
------  ----                         --------------------  ----------  --------------------  ----------

7       app                          2                     2           0                     0

193     N/A                          29051                 29051       5734                  5734

Rx      Request                      N/A                   N/A         141                   141

Rx      Response                     N/A                   N/A         5125                  5125

Tx      Request-Refresh              1182                  1182        N/A                   N/A

Tx      Request-discovery            25584                 25584       N/A                   N/A

Tx      Request-wildcard             0                     0           N/A                   N/A

Tx      Response-Solicited           19                    19          N/A                   N/A

Tx      Response-Solicited-Fragment  0                     0           N/A                   N/A

Tx      Response-Unsolicited         0                     0           N/A                   N/A

Tx/Rx   Total                        32051                 0           N/A                   N/A

After 5 minutes interval:

(Aruba) #show clock

Wed May 25 21:10:53 PST 2016

(Aruba) #show airgroup internal-state statistics

Time: Wed May 25 21:11:04 2016

Sibyte MDNS Messages
--------------------
Opcode  Name                         Sent Since Last Read  Sent Total  Recv Since Last Read  Recv Total
------  ----                         --------------------  ----------  --------------------  ----------

7       app                          0                     2           0                     0

193     N/A                          0                     29051       0                     5734

Rx      Request                      N/A                   N/A         300                     441

Rx      Response                     N/A                   N/A         0                     5125

Tx      Request-Refresh              0                     1182        N/A                   N/A

Tx      Request-discovery            0                     25584       N/A                   N/A

Tx      Request-wildcard             0                     0           N/A                   N/A

Tx      Response-Solicited           0                     19          N/A                   N/A

Tx      Response-Solicited-Fragment  0                     0           N/A                   N/A

Tx      Response-Unsolicited         0                     0           N/A                   N/A

Tx/Rx   Total                        0                     0           N/A                   N/A

Here in the above output the "Recv Since Last Read" is 300 in 5 minutes interval. So it got to be 300 packets divided by 5 minutes which is 300 packets /300 sec which is 1 packet per second. This command help us to understand if the mDNS packets exceeds the hardware limit.