[STDS-802-11-TGBH] 46 or 44 bit IRMs

[G Smith <gsmith@xxxxxxxxxxxxxxxxxxx>]

Hi TGbh’s,

At the Interim last week we discussed CID 3085  which proposed to define IRM as follows :

" A MAC address selected randomly from among the Administratively Assigned local identifiers specified in IEEE Std 802 and used by a non-access point (non-AP) station (STA) to identify itself to a network."

 

Using the AA designation means that the IRM would comprise 44 random bits as against 46 bits if we kept to the present “constructed from the locally administered address space”.

 

I had previously uploaded, but never presented, 23/2148r0 which looked at the theoretical probabilities of IRM duplicates for ESSs up to 80,000 stations using IRMs of 46 random bits.  I have now posted  r1 where I have added the results for IRMs of 44 random bits.

https://mentor.ieee.org/802.11/dcn/23/11-23-2148-01-00bh-probability-of-irm-duplicates.pptx

 

The results are:

For a busy ESS (network), with each STA associating 3 x per day, storing a high number of IRMs (80,000)

For 46 random bits:

• Each AP (40) in ESS has a duplicate every 2.54 days
• Each STA only experiences a duplicate every 14 years.

(i.e., Action frame exchange to get new IRM is a small overhead)

Notes: Assumed 2000 STAs per AP

For S1G (8000 STAs per AP), each AP has 1.57 duplicates per day.

 

For 44 random bits:

• Each AP in ESS has a duplicate 1.57 times per day (i.e., 4 times more frequently)
• Each STA experiences a duplicate every 3.5 years.

Note: For S1G (8000 STAs per AP), each AP has 6.3 duplicates per day

 

I do not intend to ask Mark for time to present this as it would probably take up a lot of valuable time.  I have included all the formulas and derivations I used, so those interested can check my analysis and results, and of course, I welcome comments.  The results are what matters as I have provided above.  Of course if anyone feels that my assumptions of the maximum size (80,000) ESS should be different, or each STA should on average associate more (or less) than 3x a day,  please let me know and I will run the numbers accordingly.

 

I leave it to the group to decide if the effect of reducing the random bits from 46 to 44 is significant enough that we could use it as a reason to stick with the “locally administered address space”, and not change to “selected randomly from among the Administratively Assigned local identifiers specified in IEEE Std 802.”?

 

Thanks

Graham

 

 

 

 

 

 

 

---

To unsubscribe from the STDS-802-11-TGBH list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-11-TGBH&A=1