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RE: [DNA] Considerations for DNA Schemes with multiple Interface andLayer 2 Technologies
In the same respect,
the sentence "Today, a link change necessitates an IP configuration change." in the dna goals document introduction let the reader believe that a node would not be having interfaces attached to other links. Because if it is so, then the a configuration that might have been built on the non used link could start being used without requiring new IP configuration.
Is it possible to recall the definition of the word link in that dna goal document? Copy-paste from RFC 2461....
Eric
regards
-----Message d'origine-----
De : owner-dna@ecselists.eng.monash.edu.au [mailto:owner-dna@ecselists.eng.monash.edu.au] De la part de Pekka Nikander
Envoyé : lundi 25 octobre 2004 08:59
À : Dna
Cc : Erik Nordmark; YGHONG; ???; Greg Daley; JinHyeock Choi; ???
Objet : Re: [DNA] Considerations for DNA Schemes with multiple Interface and Layer 2 Technologies
>> I think that the case 3.2, 'Single interface with Make before Break'
>> will affect DNA solution design. I agree that we are not familiar
>> with this case, so it would be of much help, if you elaborate the
>> below with more detail.
>>
>> ... But in CDMA[7], a
>> mobile station can access two or more different base stations
>> simultaneously. In this case, a host can make a new link-layer
>> connection before an old link-layer connection is torn down.
>
> I hope that L2 can actually tell the packets apart.
> If this is possible, then the implementation could present the packets
> from the different links are arriving on different interfaces to IP.
I agree with Erik and others that the apparently cleanest way is to model the situation with distinct (virtual) interfaces, each corresponding to a wireless connection.
However, I am also wondering how often we need that in practise.
As far as I've understood (which may be completely wrong), in the typical case the CDMA network models the whole base station network as a single link, with a single excess router. OTOH, I have no idea whether soft handovers between operators is defined or not.
If they are, then we probably need some care there.
Taking a slightly wider angle, we can imagine various anomalies like someone inadvertedly connecting two (wireline) LAN segments together. That would (temporarily) create a similar situation.
Hence, I'm afraid that we need to make the DNA scheme(s) robust against these kinds of situations. However, my current opinion (subject to change) is that we should not worry too much about these kinds of situations, and it would be perfectly OK if it takes some more time to system to recover in such a situation. In other words, if some hosts unnecessarily run DNA and autoconfiguration, that wouldn't be too bad.
Network operators have to live with the limits of technology anyway. If our DNA effort results in a piece of technology that has a number of well documented limitations, that is OK, as long as the WG agrees on the limitations.
--Pekka