Hi all,
While going through the draft I've come up with a load of questions and
notes. Addressing these will make the draft more complete and resolve some
of the ambiguity which might affect an implementation.
I'm going to divide these into a number of emails so that it should be
easier to follow each discussion.
This email is about metrics (Section 7 in Version 9a or Section 5 in
Version 9b):
1. We refer to RFC6551. This defines more than just HopCount = 3. e.g.
node energy, link throughput, link latency, link reliability and ETX
reliability. Our IANA section doesn't list these under MetricTypes,
actually it says those numbers are unallocated. Should we change this?
2. "monotonically increasing" means increasing or remaining constant
(i.e. anything but decreasing), so is it more correct to say "strictly
increasing"? For hopcount at least, Cost(L) is always 1 and route cost will
always increase with number of links. We can support any strictly
increasing metric using Cost(R) = sum of Cost(L), and our current LoopFree
function, I think. Charlie previously said link cost could be less than one
for some metrics. Since alternate metrics are out of scope anyway, I don't
know if that's relevant. They would need different Cost and LoopFree
functions. Is "strictly increasing" the same as "additive"? From some
Google searching, "additive" seems to refer to metrics themselves, whereas
"monotonically" or "strictly increasing" would refer to the route cost
function.
3. Should we have a configuration option for MetricTypes in use? Or
should we support all metric types we see in received messages? Or is this
what is meant by "check that the metric type is known"?
4. We havent decided on whether to make default metric type 0 for
simplification.
Comments welcome :-)
Kind regards,
Vicky.
