Subject: [seamoby] Duplication of eff with IEEE

From: [email-masked]
Date: Thu, 22 Feb 2001 14:41:31 -0600

Is anybody that follows SeaMoby involved with IEEE P802.11 Task Group F,
"Recommended Practice for Inter-Access Point Protocol"?  I would be
interested in knowing where TG F is heading.

Thanks,

Phil

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From: "Zwemmer, Arnoud" <[email-masked]>
Date: Tue, 27 Feb 2001 04:17:51 -0500

Phil,

First, let me say that I'm far behind on the seamoby work. Yet I attended most
of the TGf sessions at the last IEEE 802.11 meeting in January and I think I can
say something about that. 

TGf is concerned with providing multi-vendor Access Point interoperability
across a Distribution System (which as you may know is the opaque network cloud
interconnecting APs), in particular where the distribution system is an IP
network. Workings of such a Distribution System is currently outside the scope
of the 802.11 standard. Hence a recommended practice is being developed for IP.

A specific problem exists with the frame delivery service when an 802.11 ESS
spans multiple IP subnets. The frame delivery service must deliver frames that
are addressed to a particular station to the AP with which that station is
associated, within the entire ESS (deliver it to the correct BSS, that is). If
the ESS spans multiple IP subnets, appropriate mechanisms should be in place to
correctly forward frames across L3 devices separating portions of the ESS.

Instead of devising tunneling or other forwarding mechanisms at L2, TGf has now
adopted the approach to leave it to the mobile node to ascertain it has a valid
L3 address wherever it is in the network, so that traffic will be appropriately
delivered to it by normal L3 routing protocols. Examples are DHCP renew and
Mobile-IP. TGf decided L3 has appropriate mechanisms in place to do this, and
this should not be duplicated at L2.

This simplifies the work of TGf considerably. All that the IAPP needs to do now
is keep track of the set of APs that comprise the ESS and enable multi-vendor
interoperability of handoff. The first item becomes an issue of registration of
APs. Current thinking is this could be done using the Service Location Protocol
or some other registration database. Only APs that successfully register with
the registration service will be considered part of the ESS (authentication will
probably be involved here). The second item is handoff. For this, a (recommended
practice) handoff message will be sent from the new AP to the old AP, indicating
the station has roamed to the new AP, and possibly requesting any state the old
AP holds for the station to be transferred. The new AP can obtain the IP address
of the old AP using the registration service. Another packet (with the station
as source) must probably be sent to flip switch tables.

Last meeting was used to draft some text reflecting all this. Next meeting in
March will be used to work further and comment on this text. After that, a first
draft will be produced.

Regards,

Arnoud.

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]]
> Sent: Thursday, February 22, 2001 9:42 PM
> To: [email-masked]
> Subject: [seamoby] Duplication of eff with IEEE
> 
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> 
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