ITU - Telecommunication Standardization Sector	from TD44(Plen)
STUDY GROUP 15

Geneva, 15-26 October 2001

QUESTIONS:	Q.11/15
SOURCE:		ITU-T Study Group 15
TITLE:		SDH Signal and Group Structures
_____________
COMMUNICATION STATEMENT
TO:		IETF ccamp Working Group
APPROVAL:	ITU-T Study Group 15
FOR:		Information and Action
DEADLINE:	30 October 2001
CONTACT:	Gilles Joncour	Tel:	+33 2 96 05 24 69
		Fax:	+33 2 96 05 12 52
		Email:	gilles.joncour@francetelecom.com 
	                
ITU-T SG15 has made been aware that the IETF ccamp working group is
discussing the automatic setup of SDH group signals (AUG and TUG) and also
the structure of the SDH label within its gmpls work.

SDH Group Signals
As responsible ITU-T Study Group for the SDH Recommendations, ITU-T SG15
want to make IETF aware that networking of SDH group signals (AUG and TUG),
including connection setup and automatic detection of the groups VC
structure is not a functionality standardized by the ITU-T for SDH. AUG and
TUG are conceptual entities for the explanation of the SDH multiplex
structure. The only path layer network signals in SDH supported by
standards are VC-n signals. If the IETF sees any need for any additional
functionality, it should be brought to the attention of ITU-T SG15 by
contribution or communication from the IETF (according to RFC 2436 or ITU-T
Recommendation A.4) for further consideration.
SDH/SONET Labels

ITU-T has defined SDH as a standard incorporating an AU4 and AU3 branch in
the multiplex structure. Networks optimised for either of the branches are
present in the world. SONET is a particular implementation of an AU3 branch
optimised SDH network. Early differences between SONET and SDH have been
eliminated as much as possible in recent years. The current proposal to use
different S,U,K,L,M information in the labels in case of SONET and SDH
signals with identical multiplex structures within the gmpls work suggests
differences that are not present and that should not be introduced.  From
the problems that occurred due to the early differences between SONET and
SDH we learned that such differences should be avoided in the future. ITU-T
SG15 therefore strongly requests to use the same S,U,K,L,M information in
the label in case of SONET and SDH signals with identical multiplex
structures.