RE: Comparison of restoration requirements between transport and packet networks

[neil.2.harrison@bt.com]

Vishal.....wrt to your question (snipped to it).  regards, Neil

> > NH=> A laudable aim....but it will never be possible to set 
> hard bounds
> > *unless* we fix the hierarchical client/server relationships for
> > ever.  Let
> > me give you and example for you to answer wrt to the activities
> > in the PWE3
> > group.  What is the protection speed requirments for 
> SDHoverMPLS in the
> > client (SDH) and server (MPLS) case?  And now extend this to some
> > arbitrary
> > nested client/server stack where one operator may not own the
> > layers below a
> > certain point (and which he has no visibility of).......so what
> > is there to
> > control 'which' and 'how many' client/server transitions 
> exist below here?
> 
> Perhaps a clarification here. Do you mean that client/server
> relationships cannot be fixed for ever (because of structures
> like SDHoverMPLS) or do you mean that SDHoverMPLS shouldn't be
> defined?
NH=> There are 3 network modes....cnls, co-ps and co-cs.  These have 9
possible client/server permutations.  Some make far more sense
architecturally than others.  I would *not* wish to be prescriptive on this
if some people want to do 'odd things'.  However the point I was making was
simply this....at some layer network one may not have control/sight of which
lower layer trails support your link-connections.....and this behaviour
recurses (ie link-connections in layer N are created by trails in layer N-1)
to the duct.  So if (i) there is no control over the client/server
relationships and (ii) one may not have control or visibilty of this anyway
(ie leased capacity) then how can one set any sort of meaningful prot-sw
timing bounds between layer networks?  The simple example I was giving was
trying to illustrate this, eg assume SDH is designed to act faster than MPLS
(because SDH is always assumed to be a lower server layer to MPLS) then what
does this mean when carrying an SDH layer network over MPLS wrt to the
prot-sw speed of the MPLS layer now?