Re: [netlmm] Timestamp Option for Message Ordering

["Vijay Devarapalli" <[e-mail]>]

Sandesh,

> I am proposing a solution for the problem which
> section '5.5 Timestamp Option for Message Ordering'
> of draft-ietf-netlmm-proxymip6-18.txt intends to solve.
> Please ignore this mail if this approach has been discussed earlier.
> 
> IMO problem can be defined as following -
> ------------------------------------------
> When LMA has received two or more PBU message for binding
> lifetime extension
> from two or more MAGs (and has not received PBUs from with
> lifetime = 0
> indicating MN detachment from all except one) then (in the
> absence of sequence
> number and timestamp) how can it be find out which MAG the MN is
> actually connected to. 

One of the approaches, the timestamp or the sequence number is always
used. So we don't have a scenario where neither are present. 

Vijay

> 
> SOLUTION
> ------------------------------------------
> In this solution a new trigger type in BRI (from LMA to MAG)
> is added which
> indicate 'PBU Registration Confusion'.
> 
> MAG Procedures -
> MAG PROCEDURE 1. MAG retransmits PBU if matching PBA is not
> received before
>   retransmission timeout. If MN is attached to MAG it keeps on
>   retransmitting PBU until it receives matching PBA. If MN detaches
>   from MAG it retransmits PBU with lifetime = 0 a number of times (N).
> MAG PROCEDURE 2. MAG sends PBU again if it receives BRI (Trigger =
>   PBU Registration Confusion). And after that it does PBU
> retransmissions as per MAG PROCEDURE 1. 
> 
> LMA procedures -
> LMA CASE 1: LMA received two or more PBUs (with lifetime !=0)
> and it has not
> sent PBA to any of the MAGs.
> It does not send PBA to any MAG. Soon it will receive the PBUs
> with lifetime = 0 from MAGs from which MN has detached and
> PBU(lifetime !=0) retransmission from MAG to which MN is actually
> attached. 
> MN is considered to be attached to a MAG if and only all MAGs
> except one sends
> PBUs(lifetime = 0) and that one MAG sends PBU (lifetime !=0).
> A max timer can be defined to declare that MN is not attached
> to the MAG if no
> PBUs are received from a MAG (which first sent PBU with
> lifetime !=0) for
> that max timer duration.
> After the decision has been taken about which MAG an MN is
> attached to PBAs
> (status =0) are sent to all the MAGs.
> 
> 
> LMA CASE 2: LMA received two or more PBUs (with lifetime !=0)
> and it has
> sent PBA (Status = 0) to one of the MAGs.
> LMA send BRI(Trigger = PBU Registration Confusion) to the MAG to
> which it has sent PBA (Status = 0). After that LMA follows the
> procedure defined in Case 
> 
> Sequence number in PBU can be considered per MAG and can be
> used to drop
> old/duplicate PBUs from the same MAG.
> 
> Disadvantage of this approach is that it will take little
> longer to declare
> which MAG a MN is attached to.
> 
> Advantages of this solution are -
> - MAG need not send timestamp to LMA in PBUs
> - MAG need not sync sequence number with other MAGs.
> 
> Thanks and Regards,
> Sandesh
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