[olsr-dev] MRP selection (all OLSRd versions)

Sven-Ola Tuecke (spam-protected)
Thu Jan 12 11:43:16 CET 2006

Thomas, Andreas,

while I do not want you guys to disturb while playing with new features, I 
have a moderate urgent bugfix request. Normally, I would do it for my own, 
but this one evt. needs some internal data changes and I am not too familiar 
with that.

OK. I am not happy with the MPR selection done in LQ and in RFC mode. 
Investigated only the lq_mpr() so far, but the RFC mprselect() may do it the 
same way. With multihomed hosts (nodes with more than one radio or nodes 
bound to ether backbones and wifi) at least *one* MPR should be selected on 
each interface. Otherwise inter-suburb routing may be dead / unrealiable / 
really slow.

Example: We connect 2 suburbs with a long distance managed link running on a 
double radio node. Other radio is Ad-Hoc. If all MPRs (due to LQ/ETX values) 
are selected on the Ad-Hoc radio, no routing info is tranmitted over the 
managed link. Same for RFC, if e.g. all AdHoc neighbours have high 
willingness values configured. Very slow routing happens, if a really 
unreliable ad-hoc parallel link exists between those suburbs.

Investigated the code in lq_mpr(). There is a chance, that more than 
MPRCoverage MPRs are selected (due to hashing) but I would call that a 
feature not a bug. More neighbours, more MPRs. Thats OK :) But at least one 
MPR for every interface - that code does not guarantee this.



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