Subject: Re: [eap] Proposed Resolution to Issue 377 (NetSel NITs) (Section 4)

From: "Bernard Aboba" <[email-masked]>
Date: Thu, 01 Mar 2007 21:38:09 -0800

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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---

From: "Bari, Farooq" <[email-masked]>
Date: Fri, 2 Mar 2007 11:27:24 -0800

Hi Bernard,

One clarification - the scope of network discovery is not just for
mobile users but also for nomadic users where network discovery happens
just for initial attachment and not for handoffs. Latency in those cases
of initial attach will not be an issue.

Suggest chnaging proposed text 

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.

to 

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 for mobile users where the information is needed for handoff
purposes.  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.

BR,

Farooq Bari
[email-masked]
+1 425 580 5526
 
> -----Original Message-----
> From: Bernard Aboba [mailto:[email-masked]]
> Sent: Thursday, March 01, 2007 9:38 PM
> To: [email-masked]
> Subject: Re: [eap] Proposed Resolution to Issue 377 (NetSel NITs)
(Section 4)

---

From: "Bernard Aboba" <[email-masked]>
Date: Fri, 02 Mar 2007 12:00:37 -0800

Sounds good.

>From: "Bari, Farooq" <[email-masked]>
>To: "Bernard Aboba" <[email-masked]>,<[email-masked]>
>Subject: RE: [eap] Proposed Resolution to Issue 377 (NetSel NITs) (Section 
>4)
>Date: Fri, 2 Mar 2007 11:27:24 -0800
>
>Hi Bernard,
>