rohc team mailing list archive

[Didier Barvaux <didier.barvaux@xxxxxxxxxxxxxxxxxxxx>]

Hi Ramya,

My answer is below. Please, keep sending your questions on the mailing
list so that everyone might read the discussion and eventually learn
something from it.


> I tried to send it through eth0 but still when i execute the command :
> 
> ./rohctunnel eth0:rohc0 remote 192.168.1.4 local 192.168.1.2 port 5000
> the output goes as follows:
> 
> [...]
> 
> This keeps coming and there is no other output that i can see. I am
> new to this So I dont have much idea how to proceed. Can you pls help
> And can you also tell me where and how to check if the packets are
> compressed and decompressed and after executing which command the
> packets will b compressed.

The interface "eth0" is your normal Ethernet interface. The rochtunnel
tool creates a new virtual interface ("eth0:rohc0" in your case) that
you should use to send the network packets that you want to compress.
The virtual interface supersedes the normal interface for traffic you
want to compress.

Once started, the rohctunnel tool waits for packets on the "eth0:rohc0"
interface. Whenever it reads one packet, it compresses the packet to
create a ROHC packet and then sends this ROHC packet to the "eth0"
interface. The header of the rohctunnel source code contains a figure
that describes this, see
http://bazaar.launchpad.net/%7Edidier-barvaux/rohc/main/annotate/head%3A/app/tunnel/tunnel.c

So, on the "eth0:rohc0" interface, tcpdump may capture uncompressed
packets that will be soon compressed by the rohctunnel tool. On the
"eth0" interface tcpdump may capture compressed ROHC packets that the
rohctunnel tool just compressed.

Here is a figure to explain that (use a fixed font to read it):
        
 uncompressed     +------------+     +------------+
 packet to    --> | eth0:rohc0 | --> | rohctunnel |
 compress         +------------+     +------------+
                                          |
                                          | compressed ROHC packet
                                          | encapsulated in UDP
                                          |
                                          |    +------------+
                                          +--> |    eth0    |
                                               +------------+

Does it help you ?

Regards,

Didier Barvaux
Viveris Technologies
http://www.tech.viveris.com/opensource/