Re: [DNA-BOF] Re: link "hints"

[Alper Yegin <alper@docomolabs-usa.com>]

There has been various discussions on possible uses of L2 hints. Using them
for fast Mobile IP handovers, transport layers, and now DNA... I think we
limit the scope of L2 hints to the ones that are relevant to network
attachment in this group.

I think the information below is very useful, it can go under the IEEE
802.11 section of the L2 hints catalog (draft).

These are about what the L2 mac provides. It's presentation to upper layers
depends on the OS/architecture/etc. Here is an example, that I was pointed
by Jean Tourrilhes recently:

http://gd.tuwien.ac.at/linuxcommand.org/man_pages/iwevent8.html

This is a Linux API that allows upper layers to be notified about wireless
link events. 

Alper

> My understanding was that the relevance of L2 "hints" to DNA was for
> determining whether a change is made in the point of attachment, and
> if so, whether a change of subnet has also taken place.
> 
> This is in contrast to other discussions such as in ALIAS, where L2
> information could potentially be used for a much wider range of purposes.
> 
> If this perception is correct, then it allows us to focus the conversation
> somewhat.  For example, in IEEE 802.11 we have:
> 
> a. Information in the Beacon and Probe Responses.  This can provide the
> host with the capabilities of potential future points of attachment.
> However, it doesn't reliably provide information on the subnets.  Since
> VLAN assignment can be dynamic it might even be argued that such
> information might not be appropriate in the Beacon/Probe Response (unless
> the SSID to VLAN mapping is static).
> 
> In some Virtual AP implementations the same BSSID is used with multiple
> SSIDs, so a host attempting to determine whether it is reattaching to the
> same "point of attachment" probably needs to use the combination of the
> BSSID and SSID, rather than just the BSSID alone.
> 
> In future (IEEE 802.11k), the Beacon/Probe Response might provide
> information on neighbor capabilities as well as capabilities of the
> advertising AP.
> 
> Note that in some implementations the BSSID (WM MAC Address) is the same
> as the DS MAC address; in others the DS MAC address is distinct.
> 
> b. Association/Reassociation.  IEEE 802.11i has two association
> exchanges (an insecure one using 802.11 management frames, and a secure
> one using the 4-way handshake).  In general, where both are available, the
> completion of "secure association" is used as the "hint" that kicks off
> DNA.  Today the "secure association" provides the SSID, but in future
> it might provide prefix/subnet information as well.
> 
> c. Radio measurements.  This can include a wide spectrum of things under
> consideration in IEEE 802.11k, including measurements of signal strength,
> S/N ratio, packet loss, jitter, etc.  While many of these things might be
> relevant to roaming or load balancing decisions, they don't appear
> relevant to DNA in that they don't provide "hints" relating to the network
> topology of a potential point of attachment.
> 
> 
>