[Olsr-dev] Rounting

Henning Rogge (spam-protected)
Tue May 17 08:37:54 CEST 2011

On Tue May 17 2011 01:34:22 scolfield wrote:
> Hello again,
> ------ -------- ---------------------------
> | IP | UDP | OLSR Messages |
> ------ -------- ---------------------------
> The OLSR messages came from 698 port number and so, OLSR daemon begin
> processing this messages.
The IP stack of your operation systems parse the IP and then the UDP header 
and decides to forward the packet to the OLSR socket (because OLSRd has opened 
an UDP socket on prt 698).

> My first question is, can I affirm that the OLSR daemon is a
> protocol that belongs a application layer?
OLSRd is an userspace routing daemon, so it does work for the layer 3, but as 
most routing daemons it has been written as an application.

> Because it is started as daemon and not loaded as kernel
> module. I know that the OLSR is a routing protocol that determine which is
> a better path from origin to destine. And so, the data user application can
> flow on this better path.

> My second question is, consider the data user application over TCP. The
> packet format is:
> ------ -------- ---------------------------------
> | IP | TCP | User Data Application |
> ------ -------- ---------------------------------
> OLSR evaluate the IP header and detect that protocol and destine port is
> different of UDP/698?
The OLSR routing daemon never sees this packets.

> So, OLSR will not process and simply look at the routing table, look the
> next hope and forward it?
> It is OLSR protocol that perform this?
No, thats your operation system.

OLSR calculates a routing table and send this table to the operation system, 
which then forwards the incoming IP packets according to the table.
> In computer networks lessons, the basic that we learn is that routers may
> only to see for until layer 3, and not above it. But, the OLSR utilize the
> UDP protocol, and this confused me.
OLSRd does not route packets itself... it just calculate the table, the 
operation system (in the IP stack on layer 3) does all the routing/forwarding 

Henning Rogge

Diplom-Informatiker Henning Rogge , Fraunhofer-Institut für
Kommunikation, Informationsverarbeitung und Ergonomie FKIE
Kommunikationssysteme (KOM)
Neuenahrer Straße 20, 53343 Wachtberg, Germany
Telefon +49 228 9435-961,   Fax +49 228 9435 685
mailto:(spam-protected) http://www.fkie.fraunhofer.de
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