Dear NSI WG colleagues,
I have read the version of the Policy document that was already reviewed
by Richard and tried to assess if the document is sufficiently clear to
actually implement the pathTrace extension in a aggregator or uPA. There
are three things that are not completely clear to me yet.
I agree with Richard that it is not clear how a uPA can determine the
order number for its segment, especially in the tree scenario. It is
stated in the document that an AG that has done additional path finding
must assemble the child path in topological order, that sounds
reasonable because the AG is the only one aware of the order of the
segments and not the uPA, and what about other AG down the tree that do
additional path finding and will return traces with more then one
segment, is any AG allowed to renumber segments or lists of segments
from its childeren before it sends the trace upstream?
It is not clear to me if in any NSI deployment it is mandatory for all
NSA to either do implement or do not implement the pathTrace extension
or if it is allowed to have a mixed deployment. If the latter is allowed
questions like the following come to mind:
* what if an uPA does not implement the pathTrace extension, does an
AG has to check the reserve.cf coming up if it contains an expected
pathTrace?
* what if an AG, not being the root AG, does not support the pathTrace
extension, and lets assume that this AG does transparently forward
all NSI header elements it does not know about, it cannot aggregate
the pathTrace information from its childeren and can only at best
collect all pathTrace's from its children and add them as separate
traces to the reserve.cf going up
* What if the root AG does not support pathTrace but a sub tree with
an AG with an associated set op uPA does, then that sub tree AG will
act as root AG and the uPA of that sub tree will only see part of
the path in the rsvcommit.rq coming down and not the complete end to
end path
It is not clear to me if both an AG and uRA are allowed to terminate an
reservation that has failed segments due to policy violations, or that
we just trust on normal reserveCommit.fl processing and leave the
termination of the request up to the uRA?
Cheers,
HansT.
