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

[Bernard Aboba (bernard_aboba]

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.