[Olsr-dev] OLSRd with ETT available

[Erik Tromp]

Hello All,

This is to announce the availability of the first release of OLSR-LC.

OLSR-LC is OLSR enhanced with link-cost extensions. OLSR-LC was initially
developed on version 0.4.10 of OLSRd, and was ported up to version 0.5.3 .
In the coming weeks I will put effort in porting the extensions up to the
most recent versions of OLSRD, versions 0.5.4 and 0.5.5 .

The link-cost extensions were developed at Thales Communication, Huizen,
Netherlands, and is currently maintained by Erik Tromp, Avantec Engineering
( www.avantec.nl )

You can get a copy of the source code at:

  http://sourceforge.net/projects/olsr-lc

How to install it: download the file olsrd-0.5.3-lc-0.1.tar.gz from the
above URL into a directory of your choice.

At the command prompt, cd to the directory in which you saved the downloaded
file, and type:

  tar -zxvf ./olsrd-0.5.3-lc-0.1.tar.gz

This will create the directory olsrd-0.5.3-lc-0.1 and unpack all source
files in that directory.

Then type:

  cd olsrd-0.5.3-lc-0.1
  make build_all

followed by:

  make install_all

In the lib directory you will find a sub-directory ett . This contains a
basic setup of a plugin that can be used to calculate link costs based on
Expected Transmission Time (ETT) . For ETT you need the medium speed
(Mbit/s). Then you can use the formula:

 ETT = ETX * #bits / bitspeed

The actual implementation of this plugin is still to be written. Currently
the plugin does nothing more than to set the link speed of each available
neighbor link every 10 seconds to a random value of either 1 or 2 Mbit/sec .

An actual implementation of the ETT plugin could be based on measuring, once
every so many minutes, the speed of the available links with all the
neighbors.
This could be done using the well-known packet-pair technique. That approach
would be purely layer-3, so no interfacing with layer-2 metrics.

An alternative to measuring (via RTT or packet-pair methods) would be to
write a plugin that retrieves layer 2 information. An existing
implementation might be found the XIAN framework; see
http://xian.sourceforge.net/ .

Of course there are many other ways to measure the speed. And, in absence of
any automatic measuring method, one could also fall back to setting the
speed values manually to a fixed (pre-configured) value. The initial speed
values, together with other link cost values, can be configured in the
olsrd.conf file; for an example see ...\files\olsrd.conf.default.lq .

If you have an example of source code that can read out layer-2 metrics I
would be very interested !

As always: have fun with it!

Erik Tromp