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

["Emmanuel Baccelli" <[e-mail]>]

On Mon, Dec 22, 2008 at 4:35 AM, Charles E. Perkins <
[e-mail]> wrote:
>
>
>
>  - If multi-hopping is done at layer 2, isn't that a good thing? I
>> mean, you can deal with problems specific to the link layer (including
>> the aforementioned hidden node problem, or whatever
>> next-popular-link-layer for multi-hop become available in the future)
>> and make IP more neutral. I think that would conserve the initial aim
>> of IP, which is simply to glue heterogeneous networks, not fixing a
>> particular link-layer problem as it is being done with 802.11 b/g.
>>
>>
>
> There is no free lunch.  You are going to solve those problems at layer 3,
> or you are going to solve them at layer 2.  And, even if the latter, you
> may
> still have to worry about it at layer 3 unless you impose some very strong
> regularity conditions (I'm still puzzling over truckloads of repeaters).



First, this is not just about 802.11 b/g. The same behavior was observed
with other radio MAC, such as simple proprietary sensor "MAC" layers for
example, and there are many other examples. One can also anticipate some
future L2 standards that will have the same properties.

We are dealing with a specific _category_ of networks here. And thus, this
would not be the first time that something special is done at L3 to cope
with a specific category of L2 networks. Lets recall different OSPF
interface types, for instance.

Emmanuel

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