Re: Terminology and scenario (wasRe: [Monami6] about draft-montavont-mobileip-multihoming-pb-statement-05current)

[marcelo bagnulo braun <[e-mail]>]

El 27/07/2005, a las 12:03, Ryuji Wakikawa escribió:

> Hi Marcelo
>
> On 2005/07/27, at 0:29, marcelo bagnulo braun wrote:
>
>>
>> El 26/07/2005, a las 16:19, Ryuji Wakikawa escribió:
>>
>>>>>> I will only consider CoAs, now.
>>>>>> Suppose that you have a given visited network, which is 
>>>>>> multihomed to
>>>>>> ISPA and ISPB, and each one of the ISPs has delegated a prefix 
>>>>>> i.e.
>>>>>> PrefA and PrefB
>>>>>>
>>>>>> The MN arrives to the visited network and configures one CoA from 
>>>>>> each
>>>>>> prefix, let's say PrefA:MN and PrefB:MN
>>>>>>
>>>>>> The situation then is:
>>>>>>
>>>>>>
>>>>>>         +---------------------+
>>>>>>         | Rest of the Internet|---------|
>>>>>>         +---------------------+         |
>>>>>>           |                 |          +----+
>>>>>>        +-----+          +-------+      | CN2|
>>>>>>        |ISPA |          | ISPB  |--|   +----+
>>>>>>        +-----+          +-------+  |
>>>>>>           |                 |     +----+
>>>>>>         +---------------------+   | CN1| PrefB:CN1
>>>>>>         | Visited Network     |   +----+
>>>>>>         |    PrefA    PrefB   |
>>>>>>         +---------------------+
>>>>>>                 |
>>>>>>              +-----+
>>>>>>              |  MN | CoA1: PrefA:MN
>>>>>>              +-----+ CoA2: PrefB:MN
>>>>>>
>>>>>> Now consider the case where the link between ISPB and the rest of 
>>>>>> the
>>>>>> internet fails
>>>>>> Which addresses does MN has to use in order to maintain a
>>>>>> communication
>>>>>> with CN1? and with CN2?
>>>>>>
>>>>>> With CN1, the only path available between CN1 and the MN is 
>>>>>> through
>>>>>> ISPB, so the MN must use PrefB:MN as CoA for this communication
>>>>>>

....
>
>> I mean, it is not good to say, "ok, i will use this CoA because it it 
>> reachable", but what would be more appropriate would be to say "this 
>> CoA is reachable from this particular CN address" and maybe for a 
>> different CN, a different CoA is needed.
>
> This shouldn't be happened in the Internet.
>

well, i guess failures shouldn't occur, but they do :-)

I mean, i think that outages may affect connectivty and because of 
using PA addresses in multihomed environments, the result is the 
situation expressed above, where certain locations are reachable using 
a given source address but when using others...

> If we consider such scenarios., there are more complicated case.
> Ex. CoA-x is reachable for the traffic using port-xxx, but CoA-y is 
> not due to port filtering.
>

right, we are currently disucssing this specific issue in shim

moreover, in the shim design, we are considering also the possibility 
of one way failure, resulting in one way connectivity (in other words, 
we are not assumning bidirectional connectivity) (the cause for this 
may be for instance ingress filtering)

bottom line is: we are desingning a fault tolerance mechanism, so we 
should support most failure modes

>> The idea is to talk about working address pairs, rather than a 
>> reachable address
>>
>> Is this good?

> You want to use  reachability to the destination as a selection 
> parameter?
>

well, my point is that different source addresses may need to be used 
to reach different destinations

> IMO, from end nodes, the reachability to a destination should be 
> assumed
> if the end node has connectivity to the Internet.

not if you are designing a fault tolerance mechanism imho

i mean the point of fault tolerance should be to provide a protection 
domain as big as possible

regards, marcelo


>
> ryuji
>
>
>> regards, marcelo
>>
>>
>>
>>> ryuji
>>>
>>>
>>>> Regards, marcelo
>>>>
>>>>
>>>>> regards,
>>>>> ryuji
>>>>>
>>>>>
>>>>>
>>>>>> (this is site multihoming example adapted to mobile host 
>>>>>> multihoming,
>>>>>> sorry for that, but there maybe better examples that express this
>>>>>> situation in a more relevant fashion for this case)
>>>>>>
>>>>>> Regards, marcelo
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>> Nicolas
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> Monami6 mailing list
>>>>>>> [e-mail]
>>>>>>> https://www1.ietf.org/mailman/listinfo/monami6
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> Monami6 mailing list
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>>>>>> https://www1.ietf.org/mailman/listinfo/monami6
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>


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