Re: [Autoconf] aspects of multi-hop wireless communication

Hello again Alex,

Alexandru Petrescu wrote:
>
>>
>> Actually, all that is needed is for IP to have a useful interface to the
>> device driver.
>
> I agree.  Device driver interfaces are known for several wireless link 
> layers.  I think there isn't one special for the A-B-C hidden terminal 
> problem.  I may be wrong, but I think.

That's because IP doesn't need to know whether the link
has problems with hidden terminals.

>
>>>> If you would like to suggest limiting the applicability of IP to 
>>>> _only_ be allowed to work for links with specific characteristics, 
>>>> then I think you should be explicit about it.
>>>
>>> YEs, I'm explicit: it's wifi.
>>
>> That restriction is not in the charter.  Do you want to campaign
>> for a charter revision?
>
> Right... No, no, I don't want to restrict to wifi.  I think the A-B-C 
> hidden terminal problem was mentioned in the wifi context.  I haven't 
> seen it elsewhere.
>
> I agree for a solution IP to run over several link layers, for example 
> wifi and 802.16.
>
> When a router needs to route between a wifi and a 802.16 link it never 
> has the hidden terminal problem.

The main thing a router needs, is to know the next hop.

>
>
>
> Yes, I'd like to help with a protocol for wireless links, like wifi 
> and 802.16.  But routing between these two doesn't expose the hidden 
> terminal problem.  I'm pretty sure about it, I can say that because I 
> have experience with IP over wifi and over 802.16 (emulated) links.

Again, routing doesn't need to know about that.  And, in fact,
I believe that IP doesn't have to know about asymmetry, nontransitivity,
or the time of day.  It just has to know about the next hop.

But the routing protocols have to be engineered to provide that
information.  And, as this overly long and time-consuming discussion
has shown, there is a bit of confusion about how to engineer
routing protocols that work over the links under discussion.

You seem to claim that we shouldn't worry about them because
the link layer has to solve problems like asymmetry and hidden
terminal problems.  I'm of the opinion that routing protocols have
to be engineered in some circumstances to avoid making
unwarranted inferences about symmetry and transitivity.

I think it would be nice to identify exactly what your concern is.
Once it was WiFi only, now it's not.  Do you think that routing
protocol work should only be chartered for links that conform to
certain regularity assumptions like symmetry and transitivity?

Regards,
Charlie P.

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