Re: [nemo] multiple CoAs registration

Hi Ryuji,

I carry on my remarks... hope it helps !

Ryuji Wakikawa wrote:

>Hello Nicolas
>
>thanks for comments.
>
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>
>>Hi Ryuji,
>>
>>I read your draft on multiple CoAs registration and I also think that we 
>>really need to define a solution to use MIPv6 with a multiple interfaces 
>>MN.
>>
>>Here are some comments on your draft:
>>
>>   - Why do you introduce the interface identification (IFID) ? It could 
>>be sufficient to only register a CoA with the associated priority. 
>>Therefore, when the MN has to choose the destination address for a HoA, 
>>it can take the most preferred CoA, which is bound to the most preferred 
>>interface of the MN.
>>    
>>
>
>Priority can be changed by some reason during communication, but IFID
>can not be changed until MN want to change it.
>
Ok, I understand that. But what I mean is that I don't see the 
requirement to have the IFID... In the Binding Cache, an entry could be 
identified by both the Home address and the CoA. It is sufficient to 
distinguish tow different entries. The priority field is then used to 
choose the CoA, i.e. the interface. No need to have the IFID I guess.

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>>Anyway you use a one-to-one mapping between a CoA and a IFID, therefore 
>>you don't need both, or I missed a point ?
>>
>>IMO, this is easier than all the mechanism to manage the IFID 
>>(generation, maintenance...)
>>    
>>
>
>could be,  but I don't know why the maintenance and generation are so
>difficult.
>
I don't say they are so much difficult, but they are not useful, since 
the IFID is not necessary (from my point of view). Maybe you can explain 
me when the IFID is useful ?

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>>   - If I well understand your draft, when the MN registers a CoA with a 
>>CN, the MN has to first register the primary CoA. Then it can send a 
>>Binding Update (after the RR procedure) to regsiter other CoA(s), with 
>>the associated priority. However, you say that the lowest priority is 
>>the preferred CoA/IF, and that the primary CoA has the priority 0. 
>>Therefore, each CN will use the primary CoA with the MN. Then, you are 
>>not able to perform load balancing, aren't you ?
>>    
>>
>
>Well, the draft does not mention about how to utilize multiple care-of
>addresses. I don't think MIP is only way to manage policy sets to divide
>flows to each CoAs. If you really want load-balancing, you need some
>mechanism to maintain policy sets between MN and CNs.
>
>Load-balancing, for example, can be supported by upper
>layers.
>The point is that CN must be able to accept packets sent from multiple
>.CoAs of MN. 
>
Ok I agree with you. But is it necessary to impose that a MN MUST 
register the pCoA with the highest priority with CN ? I thnik it is 
important that the MN does it with the HA, but I don't think it is 
necessary with CN.

If you have the choice to register the pCoA with a different priority 
with different CNs, you let an open door for upper layers to decide some 
load balancing policies.

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>>   - Last point: If you return home with your primary interface (you 
>>connect to your home network with P-IF), do you have to de-register all 
>>CoA (P-CoA and NP-CoA) with both your HA and CNs (see section 7.8) ?
>>    
>>
>
>You are right. I personally got the same comment. 
>I just keep protocol simple. 
>I will update the draft before the next meeting.
>
>thanks again!
>
>regards,
>ryuji
>
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