Re: [Autoconf] practical addressing

"Teco Boot" <teco@inf-net.nl> Fri, 27 February 2009 19:45 UTC

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From: "Teco Boot" <teco@inf-net.nl>
To: "'Alexandru Petrescu'" <alexandru.petrescu@gmail.com>
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Subject: Re: [Autoconf] practical addressing
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Inline.

|-----Oorspronkelijk bericht-----
|Van: Alexandru Petrescu [mailto:alexandru.petrescu@gmail.com]
|Verzonden: vrijdag 27 februari 2009 19:25
|Aan: Teco Boot
|CC: autoconf@ietf.org
|Onderwerp: Re: practical addressing
|
|Teco Boot a écrit :
|> Inline.
|>
|> |-----Oorspronkelijk bericht-----
|> |Van: Alexandru Petrescu [mailto:alexandru.petrescu@gmail.com]
|> |Verzonden: vrijdag 27 februari 2009 18:45
|> |Aan: Teco Boot
|> |CC: autoconf@ietf.org
|> |Onderwerp: Re: practical addressing (was: [Autoconf] new charter)
|> |
|> |[Thanks for the details Linux/Vista/IOS routing tables!  I didn't
|know
|> |  all that, only for linux]
|> |
|> |Teco Boot a écrit :
|> |>>> Routers may generate a /128 prefix-address, and advertize this in
|> |>>>  the routing domain.
|> |>
|> |>> A host-based route propagated and deleted throughout a domain? I
|> |>> don't see the necessity of doing so. Assuming the routers are
|> |>> mobile within 25m ranges then they wouldn't need to change their
|> |>> addresses, thus no need to propagate host-based routes.
|> |>
|> |> If the /128 is not propagated, there will be no multi-hop network.
|> |
|> |Well I disagree.  In the multi-hop network below only /64 prefixes
|are
|> |present in Routers' routing tables, no /128 (host-based) routes:
|> |
|> |
|> |   -----  wifi "adhoc1"  ------  wifi "adhoc2"  ------- "adhoc3"-----
|> |  |Host1|---------------|Router|---------------|Router2|-------
||Host2|
|> |   ----- LL1    P1   LL2 ------ LL3   P2   LL4  -------LL5 P3  LL6---
|> |         G1                                                    G4
|> |
|> |           P1, P2, P3: /64 prefixes, such as:
|> |                       2001:db8:1::/64
|> |                       2001:db8:2::/64 and
|> |                       2001:db8:3::/64
|> |
|> |Would this kind of use of /64 prefixes alleviate the need to
|> |propagate/delete /128 prefixes throughout the network?
|>
|> Your routers need two wifi interfaces.
|
|Yes.
|
|> Often, there is only one wifi interface.
|
|If the charter text said we only look at routers with one physical
|interface then I'd go away.
|
|And if it said we only look at routers with at least two physical
|interfaces then my figures would be right.

MANET Routers have one MANET Interface at a minimum. Two interfaces is OK. 
No one said your figures were "wrong". But there are cases that need other
topologies, like the two nearby hosts.



|> The MANET Routing protocol provides connectivity between nodes that
|> are out of range from each other, via relay nodes that are in range.
|
|Well that can be achieved with simple plain routing, not necessarily a
|dynamic routing protocol.

No. 
One of the goals is providing connectivity in a dynamic topology. Static
routing cannot provide this.



|> Using many distinct SSIDs can introduce problems, e.g. Host-1 and
|> Host-2 are near each other, but on a different SSID:
|
|Using a single SSID can introduce other problems, such as the now
|documented hidden terminal problem.

The hidden terminal problem MAY introduce somewhat reduced performance. In
802.11, we have collision avoidance for unicast using RTS - CTS and
automatic retransmit using ACK. Other MANET radios may use other mechanisms.
By the way, 802.11 tests have shown that the carrier sense range is larger
than Tx-Rx range and hidden terminal problem does not occur.
(http://info.iet.unipi.it/~anastasi/papers/book_ch03.pdf).

And keep in mind the hidden terminal problem applies to infrastructure mode
as well!


On the multiple SSID solution, this is not acceptable in many cases, as my
life or dead example (2 hosts in range, connected to different SSISs).


Teco.



|We should make choices.
|
|Alex