[Olsr-dev] Seeking comments: OLSR+ETX v/s DSR+ETX

Sven-Ola Tuecke (spam-protected)
Wed Dec 19 15:14:09 CET 2007

Hi hannes,

(I think this was meant for the list - so I reply there)

you need exact time sync on all nodes for that. While we can define, that 
NTP (or better PTP) as a prerequisite - those protos will not synchronize to 
well via Wifi. These protocols insist on low-latency and stable connections. 
Same with grabbing the 64bit TSF from the wifi cards - we have a history 
with driver flaws on that...

// Sven-Ola

hi sven-ola,

Sven-Ola Tuecke wrote:
> For ETT we need a round trip time to calculate. To measure/evaluate the 
> difference between large and small packets. So basically, you will send 
> out
> a packet and listen for the answer, checking the time.

the response part does not reflect my understanding. -

what i am envisioning is:

1. a unicast small packet plus a unicast large packet.
2. both packets shall carry timestamps and be sequence
    number protected.
3. based on the arrival time the receiver can calculate the
    air-bandwidth and
4. attach that rx-bandwidth to a neighbor advertisement
    in a new TBD OLSRDv2 TLV
5. during SPF calculation the average bandwidth between
    a pair of neighbors is computed. the inverse
    average bandwidth is multiplied with ETX.


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