Subject: [mobile-ip] FW: [Seamoby] Summary on CARD Discussion

From: Singh Ajoy-ASINGH1 <[email-masked]>
Date: Mon, 18 Nov 2002 17:03:33 -0600

Hello James,
Please find my inline reply. My earlier
post did not show up in the seamoby
list, hence copying mobile/ip list.
Regards,
Ajoy

-----Original Message-----
From: James Kempf [mailto:[email-masked]]
Sent: Friday, November 15, 2002 7:29 AM
To: [email-masked]
Subject: [Seamoby] Summary on CARD Discussion

Folks,

This email is a summary of the CARD Seamoby list traffic for discussion in
ATL.

The optimized handover work in MIP has identified a need for address
translation, a function that takes a wireless access point Layer 2
identifier
and maps that to an access router Layer 2 address and IP address, along with
subnet prefixes, and other information that a MN could get from a Router
Advertisement. 

AJOY-> I agree. 

In addition, the CARD problem statement
(draft-ietf-seamoby-cardiscovery-issues-xx.txt) identifies the link
technology
associated with an access point as an important capability that should be
included in CARD, since it could possibly lead to more efficient power
management for intertechnology handover.

A suggestion has been made on the MIP list that the FMIP signaling be used
to
accomplish simple CARD between the mobile node and the access router,
focussing
on the address translation function. An additional suggestion was made to
include a link technology indicator to facilitate intertechnology handover.

AJOY->

The process of identifying the appropriate AR for an IP-layer handoff is 
performed in two steps: first identifying the neighboring candidate AR(s) 
along with their capabilities and then selecting the appropriate AR from 
the CAR list as TAR. The AR or MN invokes the CARD process when it receives 
an indication about the discovery of a new AP ID by the MN during L2 scan 
process. In case of the network assisted CARD, this information is 
communicated to the AR from the MN either using some L3 signaling 
message or though some link layer trigger events generated by the serving 
AP of the mobile node. Upon receiving this indication, current AR uses L2 ID
of 
the new AP to obtain the IP address of AR connected with it along with its 
capabilities. Typically, this process is independent of 
handoff timing and can take place long before any L3 handoff event. Whereas
the 
TAR selection process is invoked when an MN or AR receives indication of
imminent L3 
handoff via some L2 triggers. The L2 triggers can be received either at MN
or an 
Access Router. Given that the TAR selection process is performed prior to
IP-layer handoff, 
it is possible to piggyback the TAR signaling with IP-layer handoff
signaling.
But the CARD (step 1) signaling may not be possible to 
piggyback upon IP-layer handoff signaling without changing the FMIP
protocol.  In the current version of the draft, we have 
allowed the options of piggybacking CARD signaling upon any ICMP message 
including FMIP signaling.  Please let me know if you have something else in
mind.

Reaction on the Seamoby list was split between those who supported CARD
utilizing the FMIP signaling, and those who opposed it as an unnecessary
linking
of CARD to FMIP, and a premature simplification. 

A suggestion was made to
discuss what capabilities would be appropriate to support, but that is out
of
scope for CARD as defined in the issues and requirements documents..

AJOY-> I agree. The focus of the present work is to define CARD
protocol not the capabilitities itself. 

Objection was also raised on the Seamoby list to the inclusion of "TAR
selection" on the router. Additional discussion on the Seamoby list
established
that "TAR selection" didn't necessarily mean that the router was in
possession
of any more information about what the mobile node wanted than what was sent
in
the CARD signaling which triggered the requrest.

A possible compromise solution is the following. Since FMIP needs this
signaling
now, let the mobile to router signaling for simple CARD to perform
quasi-reverse
address translation and maybe link technology be done now, and have CARD
rather
focus on interrouter exchange of capability information, which may become
more
important in the future. CARD would thus provide dynamic router
configuration
capability and AP address to AR address mapping information between routers
rather than between the router and the mobile node. Later, if mobile to
router
exchange of additional capability information becomes necessary, the simple
CARD
could be modified to addresss it, or the interrouter protocol could be
extended
to mobile to router.

AJOY-> As I mentioned earlier, TAR selection signaling can be 
piggybacked upon FMIPv6 signaling. But I am not sure if we can piggyback 
step 1 signaling (i.e., notifying AR about the identity of 
the newly discovered AP ID) on IP-layer handoff signaling.
BTW, in some access technology, such signaling may be available 
at L2, hence in those case it may be possible to eliminate such 
signaling at L3.

                        jak

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