[Emu] Revised liaison response for IEEE 802.11u EAP method for emergency calls

I modified the liaison response below based on the comments received.
Please respond indicating if this looks OK or indicate what needs to be
modified or added.

Thanks,

Joe

==============================================================

802.11u Liaison response for EAP Methods for Emergency Communications 

We have had discussion of EAP method for Emergency services at the last
IETF meeting in Chicago.  The following is a summary of working group
discussion on this topic.  

Currently there are no standards track EAP methods that exactly meet the
requirements as understood by the EMU working group.  There are several
possible candidates of existing EAP methods that may meet or be slightly
modified to meet some of the 802.11u requirements for emergency
services.  TTLS (draft-funk-eap-ttls-v0-01.txt) and EAP-FAST (RFC4851)
are TLS based methods that can support server only authentication.  It
was also pointed out that EAP-TLS (draft-simon-emu-rfc2716bis-11.txt)
could be modified to create a new EAP method that only requires server
side authentication.  If the peer can validate the server then it is
possible to mitigate many man-in-the-middle attacks against the
authentication, however if the peer cannot validate the server then this
would leave the protocol open to man-in-the-middle attacks.   These TLS
based methods require a significant number of round trips, however this
may not be an issue especially if the emergency authentication is
terminated locally instead of in a home server.  

There were also several questions raised in the working group during the
discussion that might help in further determining the best approach.
These are summarized below:

1) It is not clear what security properties are desirable.  Is it
important for the emergency services network to be authenticated?  Is it
possible for the peer to have a trust root for emergency services
network? Is there expected to be an existing profile with a specific
SSID that needs to be authorized?   Is there another use for the
authenticated identity?

2) What regulatory requirements are driving the need for encryption?
This creates some conflicts because encryption without authentication
does not satisfy most useful security requirements. 

3) Will the authentication for emergency services be terminated locally
or in a remote network?  What is the tolerance for delay before network
connectivity is established?

4) PSK was described as having worse DOS resistance properties that EAP.
It seems that in many cases EAP would have worse DOS resistance that
PSK, which cases is EAP better?

5) It seems that most public access networks already provide an open
access network, why couldn't this network be used for emergency
communication? 

As the 802.11u group is certainly aware, there are other groups within
the IETF that are looking at unauthenticated emergency services.  In
particular, the ECRIT group within the IETF has ongoing work in this
area:

http://tools.ietf.org/html/draft-schulzrinne-ecrit-unauthenticated-acces
s-00  

We encourage IEEE working group members to continue the discussion with
the IETF in the EMU and the ECRIT working groups.

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