What is the purpose of both 802.11 re-authentication and re-association while roaming?

1

I mean this. Firstly I've connected to my iPhone to my D-Link router :

iphone to D-link authentication, association, eapol handshake

And then I've moved to another floor and was reasonably connected to my another ZyXEL router that was closer:

iphone to ZyXEL authentication, association, eapol handshake

Authentication frames are always type 0 (open auth) nowadays and Association ones consist of information about NIC of the STA, but while roaming process in all of the types of security (Open, WEP, WPA2) there is exchange with authentication frames and reassociation frames between STA and AP.

So my questions are:

  1. Why have not IEEE included information, that is contained in Association frame, into the Authentication frame? There wouldn't have been a necessity in Association frame exchange and thus roaming would have been faster a little.
  2. The disassociation frames exist. Okay, I understand: the STA must notify the AP with message "good bye, I'm moving to another girl". But what is the purpose of RE-authentication frames then?

heyjohnnyfunt

Posted 2016-06-20T07:00:14.263

Reputation: 13

Note, AFAIK, WPA actually uses the "Open" authentication type and speaks EAPOL separately from that. The only other type, "Shared-key", seems to be a relic from WEP days. – user1686 – 2016-06-20T08:38:44.610

@grawity Thank's for the comment. I decided to rename the question. Yes, I know, that historically there were authentication frames for there direct purpose, but they have not manage that. But I can not understand what is the purpose now of both authentication and association frames, especially while roaming? – heyjohnnyfunt – 2016-06-20T22:13:46.217

Why are you asking about "RE-authentication" frames? No such frame type exists. Did you mean to write "reassociation"? – Spiff – 2016-06-22T07:02:39.417

@Spiff I know. I've meant not the type of frames exactly, but the processes, that occur while roaming. And in case of reassociation the designations have coincided. – heyjohnnyfunt – 2016-06-22T08:39:56.247

Answers

1

From IEEE Std 802.11-2012, 4.5.3.4 Reassociation

Association is sufficient for no-transition message delivery between IEEE 802.11 STAs. Additional functionality is needed to support BSS-transition mobility and is provided by the reassociation service.

The reassociation service is invoked to “move” a current association from one AP to another. This keeps the Distribution System informed of the current mapping between AP and STA as the STA moves from BSS to BSS within an ESS. Reassociation also enables changing association attributes of an established association while the STA remains associated with the same AP. Reassociation is always initiated by the mobile STA.

AP = Access point

STA = Station

BSS = Basic Service Set (basically the WiFi network constituted by one AP)

ESS = Extended Service Set (a WiFi network made of several APs)

The abbreviations are given for long-term answer purposes.

Doezer

Posted 2016-06-20T07:00:14.263

Reputation: 431

Thank's! Not the full answer as I've expected, but pretty enough. But I can not understand why STAs and APs still waste their time for re-authentication packets exchange as it's not necessary. I can only suppose that's only for the legacy purposes. – heyjohnnyfunt – 2016-09-11T20:33:18.440

Asked: 2016-06-20T07:00:14.263

Viewed: 761 times

Active: 2016-09-02T09:05:30.370