SONET UPSR questions


I don't know if this is the right forum but if someone could
shed some light on the following questions, I would really
appreciate that. I have read the standards but did not get
a clear understanding on the following:

1) Given a SONET ring with UPSR, is it required that all working
paths be in one direction (clockwise or anticlockwise) and all
protected paths be in the opposite direction? Can I provision
some working paths to be clockwise and some to be counterclockwise?
I couldn't find anything in the standards that says that this is not

If this can be done, what are the merits/demerits of this approach?

2) In UPSR, when provisioning a working path, my understanding is that
it is not "required" to provision the protected path as well. i.e. One
can provision only unprotected paths in a UPSR configuration. Is this

3) Given a deployment of 4 node UPSR configuration A, B, C, D.
Say I provision a working path in clockwise direction from node A to D. Say
am using timeslot 'x' for this path. Is timeslot 'x' also reserved in the
direction from D to A?

What is the rational behind reserving this timeslot 'x' from D to A?


No. It isn't.

A simple google search would have turned up:

A careful reading of the secion on UPSR would have answered
most of your questions. A little thought on how telco circuits
work would have answered the rest.