Re: [Mipshop] LLA in FBUs

Emil Ivov wrote:
> Hello all,
> 
> Section 6.2.1 - HI msg fmt (page 23)
> draft-ietf-mipshop-fast-mipv6-03.txt says
> 
>     The link-layer address of the MN that is
>         undergoing handover to the destination (i.e., NAR).
>         This option MUST be included so that the destination
>         can recognize the MN.
> 
> The thing is that when sending a HI the PAR is not necessarily aware of
> MN's address.
> 
> Ideally (at least according to us here ) a PAR would learn an MN's L2
> addr from the FBU. Yet Section 6.3.1. does not mention anything about
> including an MH LLA Option. Without such an option we could try and
> extract the L2 addr from FBUs L2 packet (which is a bit dirty -
> implementation wise) but this would only work for predictive handovers
> and there will be no way to do it with an FBU coming from the NAR.
> 
> Another way to get MN's L2 addr would be to use the one that arrived
> with the RtSolPr and was recorded in the neighbor cache. Yet there is no
> guarantee that it will still be there, not to mention the fact that it
> might have not been in the RtSolPr in the first place.

a neighbor cache for the MN's PCoA does not depend on the
the MN sending a RtSolPr. the PAR most probably will have
one for just forwarding traffic meant for the MN's PCoA.
the PAR can just lookup the neighbor cache to get the L2
address that corresponds to the MN's PCoA.

but, I do agree that it is not certain that the L2 address
is available when the PAR needs it. the PAR might need to
extract the information from the neighbor cache, whenever
available and store it somewhere else.

> So in other words - wouldn't it be better if we had a MUST MH LLA option
> for FBUs?

thats sounds okay to me.

Vijay

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