Access Points

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Aruba Employee
Posts: 19
Registered: ‎04-03-2007

Calculating bandwidth needs for Campus APs deployments on slow links

If you want to calculate the bandwidth a campus AP need to operate in tunneled mode, you need to count the following

Fixed:

    A 102-byte heartbeat for every GRE tunnel (i.e. per tunneled SSID) per second AND per radio type (between AP and local)
  • A 178-byte PAPI heartbeat every 5 seconds (between AP and master)


In short, fixed traffic accounts for about 2 kbits per SSID broadcast in 2.4 and 5Ghz. Half if it' s only broadcast on a single channel

Variable:


  • Wifi management frames (Association Request, Auth Request, Deauth, etc). This number will depend on

    • the number of clients attached to the AP
    • How often they roam from one AP to one another- EAP negociation if you are using .1x
  • IP+GRE+802.11 header to all the data packets (20+4+24=48 bytes)
  • IP+GRE header to all the Wifi management packets (20+4=24 bytes)
  • Alerts and radio events sent by the AP through the switch by PAPI
  • Statistics update (can be turned off)


Considering an average frame size of 400 bytes, overhead accounts roughly for 10%.


S.
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