Please help this person...

[Dan Williams]

On Wed, 2007-04-11 at 19:47 -0300, Hilton Garcia Fernandes wrote:
> Hi! 
> 
> Could you please be as kind as to elaborate on the reasons why the 
> peer-to-peer, serverless mode was abandoned in the current build ?

Too many issues that still need to be worked out.  There are three
non-interfering channels in 802.11b/g, 1, 6, and 11.  It's unclear how
to automatically pick which channel to mesh on.  It probably can't be
random, otherwise your laptop might pick 1 and your friends (who is
sitting next to you) might pick 11.  Then you wouldn't be able to see
each other anyway.  Having a straight-up UI to pick a channel is just
bad design and simply won't work; besides the fact that it requires
explicit interaction.

Furthermore, when we move to IPv6, we'll have automatic link-local IP
addresses and won't need an IPv4 solution like avahi-autoipd.  That
removes a lot of complexity in the peer-to-peer case.  We tried that,
but the problem with autoip is that it's locked to 169.254.x.x/16, and
_cannot_ be routed between channels by the mesh portals in a school
situation.  A bridging solution between mesh channels won't work for
various reasons, not the least of which is that multicast traffic would
get bridged.

One major benefit of the school server is that it can knit together the
mesh channels and provide a way for you to see other laptops on other
channels, because you are grabbing presence information from the server
_as well as_ from the local link with mDNS.

Link-local mDNS is also flakey because 802.11b/g in infrastructure mode
explicitly does not ACK multicast frames, and since wireless
environments are quite interference prone, frames get lost quite a bit.
Therefore, avahi just has to work that much harder to discover peers on
the local link.  I'm currently unsure how the mesh treats multicast
frames in RX or TX error situations or collisions.

> A serverless configuration was an ad-hoc dream come true. :) 

Oh, serverless peer-to-peer meshing will _definitely_ be in later
builds.  Make no mistake, it's quite crucial.  There are simply some
outstanding issues from both a technical standpoint and an interaction
standpoint that need to get worked out.

Dan

> Thanks, 
> hilton
> 
> Em Quarta 11 Abril 2007 18:51, Dan Williams escreveu:
> > On Wed, 2007-04-11 at 18:09 -0300, Leandro Biazon wrote:
> > > We're having the same mesh problem with ours machines, which were
> > > update with the last autoreinstallation image (build 385 and firmware
> > > q2b87)
> > >
> > > We were using build 368 with firmware q2b85, and the mesh was
> > > working.
> > >
> > > Now, the mesh icon flashes for a long time, and when it stops
> > > flashing, there's no IP address assigned to the machine.
> > >
> > > It works, however, if the interface is configured manually (iwconfig,
> > > ifconfig).
> > >
> > > Should the UI be working? Is anyone having the same problem?
> >
> > The mesh networking currently relies on DHCP and a mesh portal.  There
> > is no serverless peer-to-peer networking in this build.  If you want to
> > see laptops, you can still use normal 802.11 mode with an access point,
> > just hit F1 to jump to Mesh View and click on your access point to
> > connect.
> >
> > Dan
> >
> > > Leandro
> > >
> > > On 4/11/07, Richard Smith <smithbone at gmail.com> wrote:
> > >         I got this request for help but I'm really busy preping for my
> > >         trip to
> > >         QSMC and really I'm not the best guy to help with this anyway.
> > >         Somebody please help them get setup.
> > >
> > >         Thanks.
> > >
> > >         ===============================
> > >         *"Sam Taufao" <SamT at spc.int>*
> > >
> > >         04/10/2007 09:52 PM
> > >
> > >
> > >         To
> > >                 <technology at laptop.org>
> > >         cc
> > >
> > >         Subject
> > >                 Urgent Request for Assistance for presentation to
> > >         potential funding source
> > >
> > >
> > >         I am writing on behalf of the OLPC project for Pacific island
> > >         countries.
> > >         We just upgraded the OS build for B2 models with us and we
> > >         couldn't see
> > >         one laptop from the other.
> > >
> > >         Please email me with any help you can on:
> > >
> > >         1) Getting mesh network working so that two laptops next to
> > >         each other
> > >         can see each other and share something
> > >
> > >         2) Can we change volume
> > >
> > >         Merci
> > >
> > >         Sam
> > >
> > >         samt at spc.int
> > >
> > >
> > >         --
> > >         Richard A. Smith
> > >         smithbone at gmail.com
> > >
> > >         _______________________________________________
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> > >
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