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

[Aaron Kaplan]

On Dec 19, 2007, at 12:15 PM, Sven-Ola Tuecke wrote:

> Hi Sebastian,
>
> don't know, what parts of the current olsrd implementation you  
> denote with
> the term "voodoo". Link quality is a number between 0.0 and 1.0 and it
> reflecs how many packages are lost between sender and receiver. How  
> LQ is
> evaluated/measured may #include <voodoo.h> (especially the 128er  
> bit mask
> array) but nothing that really deserves that term IMO.
>
> The rest is a formula, commonly known as ETX. Which is optimized /  
> meant for
> meshing with single interfaces. Because the plus operator in (1/LQ  
> + 1/NLQ)
> it favors routes with less hops (theres a magic '2' in there ;-).
>
> Current EXT overcomes a small weakness in LQ-only measurements: If  
> a certain
> amount of links in a path do not have packet loss, the second-level  
> criteria
> (Hops) works well for route decisions. Moreover - there where talks  
> about
> exchaning that plus with a multiplication operator (hence something  
> like
> 1/LQ * 1/NLQ) or introducing some "voodoo factors" to have a
> seamless/tweakable transition between '+' and '*'. But I think that's
> another story...

By the way: Markus Kittenberger write a visualization where you can  
see if different routes would have been chosen if you subsitute the +  
with a * in the path kost calculation. If he was correct, there is  
almost no change at all!

a.


>
> // Sven-Ola
>
> "sebastian sauer" <(spam-protected)> schrieb im Newsbeitrag
> news:(spam-protected)
>> Wed 12 Dec 2007 23:17, Hannes Gredler wrote:
>>> Sudheendra Murthy wrote:
>>>> It is clear that OLSR+ETX has additional overhead of sending TC
>>>> messages when compared with DSR+ETX. Does this overhead provide
>>>> significant benefits? I am interested in knowing the pros and  
>>>> cons of
>>>> the OLSR+ETX and DSR+ETX protocols.
>>>
>>> the overhead is next to nothing -
>> ACK.
>>
>>> ans yes it provides significant benefits.
>> ACK.
>>
>> further the ETX is the same in both OLSR and DSR.
>>
>> what differs greatly is the linkquality definition/implementation.
>> this part is not properly implemented in OLSR at the moment, in fact
>> the current implementation can only be explained by "voodoo-magic"  
>> but
>> not on the grounds of rational thought.
>>
>> i already worked on a patch, but never found time for testing it  
>> properly
>> or to bring this topic to this ML.
>>
>> cheers,
>> s.
>>
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