Re: [manet] Some comments on draft-funkfeuer-manet-olsrv2-etx-01

[Teco Boot <[e-mail]>]

Op 13 mei 2011, om 16:23 heeft Georg Wittenburg het volgende geschreven:

>>> 
>>> The problem is
>>> that packet delivery ratios differ depending on the size of the
>>> transmitted packet. If small packets are used to estimate link quality,
>>> this estimate will be flawed if the link is used for large packets later
>>> on, i.e, packets that make full use of the MTU. A workaround would be to
>>> require that if HELLO packets are to be used for link quality estimation
>>> then they must be padded to correspond in size to the average data
>>> packet, or MTU.
>> 
>> The funkfeuer metric drafts suggests to use all RFC 5444 packets for link
>> loss estimation, not only a certain message type. Your suggestion would
>> make it necessary to pad all RFC5444 packets to the maximum MTU, which
>> might be a considerable overhead.
> 
> I agree. However, it still remains true that link loss estimation that relies 
> excessively on small packets will lead to suboptimal results. I'm aware that 
> the original ETX paper doesn't cover this, but it doesn't mean that it 
> shouldn't be addressed in this draft.
> 
> How about, for example, only incrementing the respective counters for packets 
> whose size is above a certain threshold, say MTU / 2 (or even MTU / 4)?

How can packet sizes of lost packets be measured?

Teco