[Olsr-users] Discrepancy between ETX value and ping packet loss

[O'Keeffe, Daniel]

Hey Henning,
Thanks for the confirmation. Would there be any disadvantage to just pushing the broadcast rate all the way to 11 (spinal tap style :))? Also, off the top of your head can you think of any other typical Mac or transport layer tuning that people do for high throughput TCP?
Cheers,
Dan

On 18 Mar 2015 05:28, Henning Rogge <(spam-protected)> wrote:
Yes,

that is the reason... many mesh networks increase the basic multicast
rate to 6 MBit/s to ignore the old 802.11b rates.

Henning Rogge

On Tue, Mar 17, 2015 at 11:06 PM, Dan O'Keeffe <(spam-protected)> wrote:
> Hey again,
> Actually it's ok, I figured it out. Because the OLSR HELLO messages are
> broadcast at the 1Mbps data rate for 802.11, they experience a different
> packet loss to the 11Mbps unicast traffic.
> Cheers,
> Dan
> On 17/03/15 20:43, Dan O'Keeffe wrote:
>> Hello,
>> I'm trying to use the OLSR ETX extensions to determine the path quality
>> to different destinations (so my application can send data to the
>> destination with the best path as the quality changes over time).
>> However the ETX values I'm seeing don't seem to correspond particularly
>> well to the packet loss I observe when I manually ping the different
>> destinations.
>>
>> More specifically, I have a two node network with each node running
>> olsrd and one node pinging the other (using a ping payload size of 0
>> so that the actual ping is just a 28 byte header). At a certain distance
>> the ping packet loss goes to 40%, but the ETX I observe using the
>> txtinfo plugin is 1.000 (i.e. from the output of 'echo "/all" | nc
>> localhost 2006).
>>
>> Does anyone have an idea as to why I'm not seeing any packet loss
>> affecting the ETX? Using tshark I can see the OLSR control
>> messages being sent and received. However it's hard to tell whether
>> any of the control messages are actually being dropped, and so
>> I'm not sure whether the issue is that the OLSR control messages just
>> aren't experiencing packet loss or I haven't configured the ETX
>> calculation properly. From what I understand the ETX calculation should
>>  be based on the number of hello messages sucessfully sent and received
>> over a sliding window, but perhaps there's more to the implementation?
>>
>> The output of olsrd --version is:
>>
>> *** olsr.org -  0.6.3-git_-hash_e334b612adcb7c22239a9dcafaf5b7ba  - ***
>>  Build date: 2013-03-28 03:47:37 on marid
>>
>>
>> I have made a few tweaks to the default config (see attached), but
>> I don't see that they should make a difference.
>>
>>
>> Finally, I should note that I'm running in an emulated environment
>> (using the CORE EMANE wireless network emulator). The only way I could
>> see that making a difference is that perhaps the same packet loss isn't
>> being applied to broadcast traffic as to normal traffic, but before I
>> check that on the CORE EMANE mailing list I'd just like to be sure there
>> isn't an obvious issue with my olsrd configuration.
>>
>> Thanks for any help!
>> Dan
>>
>>
>>
>
>
> --
> Olsr-users mailing list
> (spam-protected)
> https://lists.olsr.org/mailman/listinfo/olsr-users
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.olsr.org/pipermail/olsr-users/attachments/20150318/903e3655/attachment.html>