Suspend vs Network Traffic - blockers

[Ricardo Carrano]

Hi everyone,

On Fri, Aug 15, 2008 at 6:14 PM, John Gilmore <gnu at toad.com> wrote:
> Deepak,
>
>>>> Would this be considered a blocker for 8.2 ...
>
> (Not my call.)
>
>>>> or do we primarilly
>>>> care about collaboration in mesh mode for deployments?
>
> Very few deployments use mesh mode, because it currently doesn't scale
> up to more than about ten nearby laptops.  (It's due to many interactions
> between the mesh firmware, the use of multicast presence packets, and
> the limited bandwidth available on WiFi.  We have had numerous
> fundamental bugs in these areas -- many of which you've seen referred
> to in this thread -- and are only now being able to re-test after
> months of effort spent trying to fix some of those bugs.)
>
> So OLPC's recommended configuration with more than 10 laptops in a
> school is to have one (or more) 802.11 access point, and have the
> XO's use it in ordinary WiFi mode.  Some places have school servers,
> some don't.  When there is a school server, it's sitting on a
> wired Ethernet attached to the WiFi routers.
>
> Due to the mesh/multicast overload problems, very few Active Antennas
> are in use in deployments, as I understand it.  And I'm pretty sure
> that very few deployments use any kind of WiFi network interface
> directly inside the school server; they use Ethernet there.
>
> This page is the best reference for deployment scenarios:
>
>  http://wiki.laptop.org/go/Networking_scenarios
>
> (It even says ("Troublesome Scenario: Simple WiFi") that an access
> point without a school server is problematic with more than a few
> XO's, because the XO's will use multicast for presence detection, and
> 802.11 access points tend to use low speed 1Mbps transmissions for
> multicast packets.  With a school server there, the XO's will not use
> multicast, they'll use ordinary high speed unicast packets to and from
> the presence service in the school server.)


They are calling my flight so, I'll have to be quick. Actually in the
presence of an access point, multicast will scale better since it will
not be retransmitted by every node in the mesh. Wireless is inherently
a broadcast medium.

Also, many access points will allow you to change the multicast rate.

The question of scalability in infra mode is just a question of the
bandwidth demands of the application. Actually this is also true for
mesh mode (a chat will do better than a video based activity). In
short, the way things are implemented now, infra mode will always
scale better.

But I certainly agree that infra mode is important for us. With or
without a school server or a jabber server.

Sorry, for being in a hurry.

Cheers!
Ricardo
>
>        John
>