Hi,
This thread went suddenly very quiet in response to Igor's question which is
a shame because it is a good question.
When you are doing a path computation how do you know why you can't reach
the destination with sufficient bandwidth and low enough delay?
Is it because there is not enough bandwidth on the low delay path?
Or is it because there is too much delay on the high bandwidth path?
The issue becomes unmanageably complex when there are many constraints, and
is particularly difficult when those are absolute not relative constraints.
Of course, it is always possible to make some guesses, but usually these are
based on varying the constraints to see what could be achieved. The choice
of which constraints to vary, by how much, and in what order is very
suspect, and (as when we discussed constraint relaxation) should be the
subject of policy either at the PCC or the PCE.
For example, a response that says "If you relaxed the required bandwidth by
10% you could get a path" is no use to a PCC that MUST have the bandwidth,
but that would be happy to relax the delay constraint by 90%.
Adrian
----- Original Message -----
From: "Igor Bryskin" <[EMAIL PROTECTED]>
To: "JP Vasseur" <[EMAIL PROTECTED]>; "LE ROUX Jean-Louis RD-CORE-LAN"
<[EMAIL PROTECTED]>
Cc: <[EMAIL PROTECTED]>
Sent: Monday, July 17, 2006 5:03 PM
Subject: Re: [Pce] P & I flags
JP.
IB>> This is the whole my point. If there is a set of
mandatory constraints,
there is no way for a PCE to tell because of which particular
constraint(s)
the computation has failed,
Why, if it is clever enough to detect a blocking constraint?
I agree with JL here. There *are* many ways to figure out which
constraints could not be satisfied, in which case indicating this
information to the PCC is quite useful.
IB>> I am just curious. Could you (or anybody) describe just one of the
ways
how PCE can figure out which of mandatory constraints caused the path
computation to fail?
Thanks,
Igor
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