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

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

Hi Teco,yes I agree, the term "non-transitive" was not very
straightforwardly used. Saying as you propose would be better, more
precisely (correct me if I'm mistaken about what you meant), that if:
C and A can hear each other through A's interface, and,
A and D can hear each other through A's interface, then
it does not mean that C can hear D or that D can hear C

Emmanuel


On Mon, Dec 22, 2008 at 9:48 AM, Teco Boot <[e-mail]> wrote:

> I tried to get rid of B->A and C->A and [NOT B->A].
>
> Somewhat adjusted proposal, and using C and D and not the newly
> introduced R1 and R2:
>
>  Second, there is no guarantee that two given routers within S can
>  directly communicate with one another.  In other words, even though
>  two routers C and D have symmetric communication with router A, there is
>  no guarantee that C can hear packets from D, and there is likewise
>  no guarantee that D can hear packets from C.  Thus, multi-hop ad
>  hoc wireless communications may be "non-transitive".  Such non-
>  transitivity is often observed on multi-hop ad hoc wireless networks,
>  due to well-known properties of wireless communication.
>
> Now C->A and A->D, but [NOT C->D] and also D->A and A->D, but [NOT D->C].
> This characteristic is "non-transitive" and it is orthogonal with
> "asymmetry".
>
> Your terms "hidden terminal problem" and "non-broadcast" could be used
> as alternative terminology, but could have different meanings in
> different context.
>  o  "hidden terminal problem" could have to do with collisions.
>  o  "non-broadcast" does not apply here, because set S contains at
>     least 3 routers (B, C, D).
>     Term "Semi-Broadcast" (I-D.ietf-autoconf-manetarch) was introduced,
>     where S is subset of N. (N is all nodes in network N). I suggested
>     not introducing new terms if they not needed.
>
> Teco.
>
> |-----Oorspronkelijk bericht-----
> |Van: [e-mail] [mailto:[e-mail]] Namens Seung Yi
> |Verzonden: maandag 22 december 2008 0:00
> |Aan: Teco Boot
> |CC: Charles E. Perkins; [e-mail]
> |Onderwerp: Re: [Autoconf] aspects of multi-hop wireless communication
> |
> |I'm sorry but it sounds even more confusing to me.
> |
> |I'm not sure what to call it but it seems to describe the hidden
> |terminal problem to me. Or, it's simply saying that the link (or
> |whatever you want to call the "S") is of non-broadcast flavor because
> |R1 and R2 can expect to hear each other only when the medium itself
> |provides broadcast capability as in the Ethernet.
> |
> |- Seung
> |
> |On Sun, Dec 21, 2008 at 3:59 AM, Teco Boot <[e-mail]> wrote:
> |> What about a small adjustment:
> |>
> |>   Second, there is no guarantee that two given routers within S can
> |>   directly communicate with one another.  In other words, even though
> |>   two routers R1 and R2 have symmetric communication with router A,
> |there
> |> is
> |>   no guarantee that R1 can hear packets from R2, and there is likewise
> |>   no guarantee that R2 can hear packets from R1.  Thus, multi-hop ad
> |>   hoc wireless communications may be "non-transitive".  Such non-
> |>   transitivity is often observed on multi-hop ad hoc wireless
> |networks,
> |>   due to well-known properties of wireless communication.
> |>
> |>
> |> Now it says: "If R1->A and A->R2, there is no guarantee for R1->R2".
> |> And the second behavior is not mixed up with the first one.
> |>
> |> Teco.
> |>
> |> |-----Oorspronkelijk bericht-----
> |> |Van: [e-mail] [mailto:[e-mail]]
> |Namens
> |> |Charles E. Perkins
> |> |Verzonden: zondag 21 december 2008 2:10
> |> |Aan: Seung Yi
> |> |CC: [e-mail]
> |> |Onderwerp: Re: [Autoconf] aspects of multi-hop wireless communication
> |> |
> |> |
> |> |Hello Seung,
> |> |
> |> |Yes, of course you are right (embarrassment).
> |> |
> |> |What is a good name for the property under discussion?
> |> |
> |> |Regards,
> |> |Charlie P.
> |> |
> |> |
> |> |Seung Yi wrote:
> |> |> Just one simple comment unrelated to the ongoing interesting
> |> |discussion threads.
> |> |>
> |> |> Isn't the definition of transitivity "If A->B and B->C, then A->C"?
> |> |> This document seems to use the term to mean "if A->B and A->C, then
> |> |> B->C" in Section 2, second point.
> |> |>
> |> |> - Seung
> |> |>
> |> |> 2008/12/19 Emmanuel Baccelli <[e-mail]>:
> |> |>
> |> |>> Hi all,
> |> |>> here's a draft that aims at describing important aspects of multi-
> |hop
> |> |>> wireless communication, as observed over the past decade of
> |> |experience with
> |> |>> such networks.
> |> |>> The goal of this document is to identify a consensus about this
> |> |topic, and
> |> |>> then use this to move on quicker with the working group documents.
> |> |>>
> |> |>> Please review it, and provide feedback as soon as possible.
> |> |>> http://tools.ietf.org/html/draft-baccelli-multi-hop-wireless-
> |> |communication-00
> |> |>>
> |> |>> cheers
> |> |>> Emmanuel
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