Heavily revised call flow example

["Charles E. Perkins" <charles.perkins@xxxxxxxxxxxxx>]

Hello folks,

Here is a replacement for the first signaling diagram in
existing Annex N.  Please review it for understandability
and accuracy.  I have changed a lot of things.  Foremost,
I clarified the algorithm for distributing MNmsrk.  What
the diagram shows is that MNmsrk is computed from MNmirk.

More specifically:

T_pos extracts MNmirk in message received from S_pos.

T_pos computes MNmsrk from MNmirk

T_pos distributes MNmsrk to T_poa

T_pos returns MNnetworkaccessID to S_pos

S_pos sends MNnetworkaccessID and MNmirk to MN

MN computes MNmsrk from MNmirk using same well-known
	algorithm used by T_pos.

I know this is a possible way to make the preauthentication.
I reckon it is compatible with the intention of the rest
of the document in the way that functionality and naming
are designed for S_pos, T_pos, T_pos, etc. -- but I'd really
appreciate separate verification of that.

I also redrew the signaling diagram to better display what
I think was intended, and supplying parameters according
to the above algorithm for distributing MNmsrk etc.

I hope the example is:
- accurate
- clear
- consistent with previous 802.21(c) design

The algorithm for computing MNmsrk from MNmirk *could* be
media-specific.  I can design a media-independent
algorithm to be used in other cases when no media-specific
algorithm has been mandated, but somehow it seems likely
that a media-specific key such as MNmsrk would be
computed by a media-specific algorithm.  Notably, if
it is required to compute MNmsrk without regard to the
value of MNmirk, then the above method is incomplete or
maybe even broken.

Your comments will be very much appreciated.  If I have
this correctly, I will try to complete the document
revision tomorrow.  Visio does work.  I am not going to
spend much time on the long Annex containing the use
cases for handovers between WiFi and WiMAX, etc., at
least not before getting this revision to a consistent
state worthy of consideration by the 802.21 task group.


Regards,
Charlie P.

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