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[IP-Optical] GMPLS - Hierarchies

  • From: neil.2.harrison@bt.com
  • Date: Thu, 7 Dec 2000 11:18:04 -0000

	Hi Marten......just one small observation to clarify what is really
meant by service interworking....see below:
	<snipped>
> - service interworking has been added (section 5.5/G.805 (03/00) in  
>   the form of a generic definition of "layer network interworking".
>   The importance here is that not only the traffic is forwarded, but 
>   also the associated trail overhead/OAM information. 
>   
	 NH=> I would have put this slightly differently........
	-	Payload is moved from layer X trail to (peer) layer Y trail
intact and transparently, ie the payload area must be the same size.
	-	Overhead functionality is *mapped* between the specific O/H
of the layer X trail and the layer Y trail.  This mapping may not be 100%
complete, since there could be functionality provided in the layer X trail
that is not present in the layer Y trail (or vice versa).  For example, in
ATM there is an AIS function but this does not exist in FR.  In FR there is
a BECN function, but this does not exist in ATM.  ATM uses LLC-SNAP client
(ie payload) encapsulation but FR uses NPLID. etc.

	neil