Subject: Re: [Ecrit] Review of IEEE 802.11k: Urgent!

From: [email-masked]
Date: Fri, 4 May 2007 11:35:18 -0400

Hannes, Bernard, all, 

I have finally had a chance to go through the 802.11k document in some 
detail and have some comments.  (Very sorry for the delay!  All the usual 
excuses apply.)  I have also included the other reviewers and interested 
parties here directly.  My apologies in advance if (when) I mess up 
terminology and details -- I am certainly far from deep on 802.11. 

THE BIG COMMENT:

My main comment is that I am very concerned that 802.11k does not  reuse 
IEEE 802.1AB Link Layer Discovery Protocol (LLDP) as the mechanism to 
return device-specific location.  More specifically, I believe LLDP-MED 
(ANSI/TIA-1057, a VoIP-specific extension of 802.1AB) is the appropriate 
means to return location or other device-specific parameters of similar 
nature in WLAN environments.  In 802.11k, this appears to be happening 
through a lower level mechanisms (Measurement Request Frames), different 
from LLDP.  My fear is this will result in multiple different ways to 
return the very same location information at L2, dependent on the specific 
802 network technology.  Such differences and proliferation of methods 
would, I believe, be very problematic for Emergency Call Service and other 
location-based applications, so should be avoided at all costs.  Also note 
that LLDP-MED is the *one* method for location determination at L2 
currently specified in IETF ECRIT (of 3 methods total, at various layers). 

In addition, reuse of LLDP / LLDP-MED for location and similar purposes 
(not related to the measurement itself) would have several other benefits: 

o LLDP and extensions to it can support any 802 link layer, or could be 
readily extended to do so (more on this below), so could be common to all; 

o Since LLDP is above the MAC layer, it can be implemented without 
driver-level changes, making it much easier to deploy; 

o LLDP/LLDP-MED is already deployed in VoIP endpoints, and that deployment 
is growing, so forms a base for moving the same types of information in 
WLAN environments as well (noting also that LLDP-MED can already support 
AP-specific location today); 

o LLDP/LLDP-MED, with appropriate extension, could also be used to carry 
other device-specific information in WLAN environments, such as 
device-specific LAN policy or others (LLDP-MED is already used for this 
today in wired environments, and can already carry AP-specific information 
along these lines). 

As further background, 802.1AB is currently in revision process ("ABrev"), 
so it would a very opportune time to define appropriate extensions to 
allow for device-specific information exchange in WLAN environments.  One 
proposal is to allow 802.1AB frames to be addressed to the endpoint device 
MAC (rather than a broadcast seen by all endpoints on the same SSID), 
which would allow 802.11i to be used to address individual devices through 
the corresponding virtual port.  If I understand correctly (which may or 
may not be the case) this would allow LLDP to be used for device-specific 
exchanges, as well as provide security for those exchanges.  Comments 
related to this are about to be submitted to the ABrev group as well. 

ADDITIONAL COMMENTS: 

o Section 7.3.2.21.9 & ..22.9, adding to Brian Rosen's comment, yes it 
does appear that the location information carried would not be secured, 
since encryption does not apply to 802.11 action frames.  Additionally, 
these frames can be exchanged before 802.1X completes (not the case with 
LLDP).  I believe this is a serious issues as well, and could potentially 
preclude its use in Geopriv. 

o Section 7.3.2.21.9 & ..22.9, only geolocation LCI format is supported. 
For compatibility with IETF ECRIT and Geopriv, this should also be capable 
of carrying Civic Location format (RFC 4776, or LLDP-MED).  Additional 
formats may be desirable in future, which may be difficult to deploy after 
the fact. 

---------------------------------------------------

I hope this helps clarify the situation and acts as useful input to 
802.11k and others. 

Regards,
Peter Blatherwick
(Editor, LLDP-MED, ANSI/TIA-1057)

Hannes Tschofenig <[email-masked]>
03.04.07 15:49
 
        To:     ECRIT <[email-masked]>, GEOPRIV <[email-masked]>
        cc:     Bernard Aboba <[email-masked]>
        Subject:        [Ecrit] Review of IEEE 802.11k: Urgent!

Hi all,

based on the IETF ECRIT / IEEE information sharing event at IETF#68 it 
was indicated that a review of IEEE documents would be useful. Bernard 
Aboba has provided me with information about the documents that should 
be reviewed. Thank you, Bernard.

We should start with IEEE 802.11k (with a focus on the location 
information format specific sections). Unfortunately, the document is 
already in sponsor ballot and a review needs to be provided very soon. 
Who would be willing to review the document? I will send the 
username/passwd to fetch the latest document version to the reviewers.

Ciao
Hannes

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