[Olsr-dev] Node hand-off and attach speed

[Dazz Dev]

Hi Henning,
Thanks for the reply. My responses are below:

On 3/26/08, Henning Rogge <(spam-protected)> wrote:
>
> On Wed, Mar 26, 2008 at 1:14 AM, Dazz Dev <(spam-protected)> wrote:
> > Hi all,
> > I am working on a project and would love to use OLSR but I have been
> unable
> > to find some information about a couple issues.
> >
> > 1) In an OLSR network in which 1 (or more) node is highly mobile, when
> that
> > node moves away from it's original location and connects to another
> node,
> > what happens with any of the currenly open connections?  Do they get
> > transfered gracefully and stay connected, or are they disconnected?
> A node can have as many connections to stations as it can
> (bidirectional) communicate with.
>
> So your fast moving node will aquire new links and notice that old
> ones will be lost.


In a situation in which the moving node currenly has an open TCP connection
with a remote host, will that connection be dropped, or will it persist?
e.g. if the moving node has someone telneted into it, would the user's
connection be dropped, or would the connection be re-routed without issue.
(i'm sorry if this is fairly basic, I'm still trying to determine if OLSR
meets my needs).

> 2) Do we know the average connection or transfer time when you have nodes
> > moving from one to another?  To give context, lets say you have a number
> of
> > nodes that are in fixed locations with mobile nodes (think vehicles)
> moving.
> > Based on node speed and range, the mobile nodes could move too fast to
> > connect.
> Connection speed depends on the timeout settings of the routing agent.
> A default OLSR router transmits a single HELLO packet every two
> seconds. You need a bidirectional connection, so it takes 2-4 seconds
> to establish a link (more if packets get lost).
>
> If you set olsrd to "0.2 seconds" intervals for Hellos you could
> establish a link within 0.2-0.4 seconds. Of course you pay with the
> higher overhead, but it might be a good idea. Of course you have to
> decrease the TC interval too (default is 5 seconds).
>
> > If anyone has any insight into this I would really appreciate it.  I'm
> at
> > the preliminary stages of development and testing and am unable to test
> > these 2 issues.  They are effectivly showstoppers (along with securing
> the
> > network).
> Maybe you should tell us a little bit more about your scenario...
> what's the maximum speed of the nodes relative to any other node ?


The very worst a relative speed of about 225 kmph, but that would be
exceedingly rare.  Most likely the maximum would be aproximately 112kmph and
more normally it would be 50kmph and slower (i.e. motor vehicles with both
stationary and mobile nodes).  Obviously range of the wireless transmitters
comes into play when we start talking about the very fast nodes.
In addition, I would like to lock down the network with some kind of
encryption for the data and with a shared private key for adding new nodes.
I have read some white papers hinting that WPA cannot be used in OLSR
networks.


> Henning


I appreciate your time.  If these issues can be mitigated, I think OLSR
would be a perfect fit and I hope I can contribute meaningfully to the
deamon.

--
> "Wo kämen wir hin, wenn alle sagten, wo kämem wir hin, und niemand
> ginge, um einmal zu schauen, wohin man käme, wenn man ginge." (Kurt
> Marti)
>
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