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

[Henning Rogge]

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.

> 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 ?

Henning

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