Re: Proposed Resolution to Issue 377 (NetSel NITs) (Section 4)

I am enclosing a proposed cleanup of Section 4 to address
grammar and 
readability issues.

Recommended rewrite:

4.  Conclusions

   This document describes the network selection and
discovery problem.
   In the opinion of the authors, the major findings are as
follows:

   o  There is a need for additional work on access network
discovery, 
identifier
      selection, AAA routing, and payload routing.

   o  Credential selection and AAA routing are aspects of
the same problem,
      namely identity selection.

   o When considering selection among a large number of
potential
     access networks and points of attachment, the issues
described in
     the document become much harder to solve, in an
automated way,
     particularly if there are constraints on handoff
latency.

   o  The proliferation of network discovery technologies
within
      IEEE 802, IETF, and 3GPP has the potential to become
a
      significant problem going forward.  Without a unified
approach,
      multiple non-interoperable solutions may be deployed,
resulting in
      fragmentation.

   o  New link layer designs should include the efficient
distribution
       of network and realm information as a design
requirement.

   o  It may not be possible to solve all aspects of the
problem for
      legacy NAS devices on existing link layers.  Therefore
a phased
      approach may be more realistic.  For example, a
partial solution
      could be made available for existing link layers, with
a more
      complete solution requiring support for extensions.

   With respec to specific mechanisms for access
   network discovery and selection:

   o  Studies such as [MACScale] and [Velayos], demonstrate
that the IEEE
      802.11 Beacon/Probe Response mechanism has substantial
scaling
      issues, and as a result a single physical access point
is in
      practice limited to less than a dozen virtual APs on
each channel
      with IEEE 802.11b.

      The situation is improved substantially with
successors such as
      IEEE 802.11a which enable additional channels, thus
potentially
      increasing the number of potential virtual APs.

      However, even with these enhancements it is not
feasible to advertise
      more than 50 different networks, and probably less in
most 
circumstances.

      As a result, there appears to be a need to enhance the
scalability of
     IEEE 802.11 network advertisements.

   o  Work is underway in IEEE 802.1, IEEE 802.21 and the
IEEE
      802.11u to provide enhanced discovery functionality. 
Similarly,
      IEEE 802.1af has discussed addition of network
functionality to
      IEEE 802.1X.  However, neither IEEE 802.1ab nor IEEE
802.1af is
      likely to support fragmentation of advertisement
frames, so that
      the amount of data that can be transported will be
limited.

   o While IEEE 802.11k provides support for the Neighbor
Report,
      this only provides for gathering of information on
neighboring
     802.11 APs, not points of attachment supporting other
link layers.
     Solution to this problem would appear to require
coordination
     across IEEE 802 as well as between standards bodies.

   o  Given that EAP does not support fragmentation of
EAP-Request/
      Identity packets, the volume of "realm
hints" that can be fit with
      these packets is limited.  In addition, within IEEE
802.11,
      EAP packets can only be exchanged within State 3
(associated
      and authenticated).  As a result, use of EAP for realm
discovery
      may result in significant delays.   In addition, the
ability of EAP to
      carry Quality of Service information 
[I-D.groeting-eap-netselection-results]
      appears limited.  As a result, we believe that use of
EAP as described 
in
     [RFC4284] is not a sound long-term approach for
solution of
     the realm discovery problem.  Instead, we believe it is
more 
appropriate
     for this functionality to be handled within the link
layer,  so that 
the
     information can be available early in the handoff
process.

   o  Where link layer approaches are not available, higher
layer approaches
      can be considered.  A limitation of higher layer
solutions is that 
they
      can only optimize the movement of already connected
hosts, but
      cannot address scenarios where network discovery is
required for
      successful attachment.

      Higher layer alternatives worth considering include
the SEAMOBY CARD
      protocol [RFC4066], which enables advertisement of
network device
      capabilities over IP and Device Discovery Protocol
(DDP)
     [I-D.marques-ddp], which provides functionality
equivalent to
     IEEE 802.1ab using ASN.1 encoded advertisements sent to
a
     link-local scope multicast address.

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Re: Proposed Resolution to Issue 377 (NetSel NITs) (Section 4)

Thread: Re: Proposed Resolution to Issue 377 (NetSel NITs) (Section 4)