RE: [T1X1.5] Re: [IP-Optical] concatenation extensions in sonet/sdh

["Bernstein, Greg" <GregB@ciena.com>]

Hi Huub, see the comments in line below. But first, a couple of points (as
usual):
(1)	Virtual Concatenation is a great feature in SONET/SDH and I'm very
much for it and I think it has a lot to offer.
(2)	Arbitrary Concatenation means (to me) three things: (a) arbitrary
size - don't know that this is that useful in a general network-(b)
arbitrary starting time slot, (c) arbitrary locations of successive
timeslots.
(3)	If we use arbitrary concatenation but restrict to standard sizes,
then we have the capability to avoid regrooming on a link by link basis
(note that the arbitrary placement doesn't preclude a restriction to
standard timeslot usage.
(4)	In line with Eric's comment do we want the signaling protocol to
include standard practice, possibly standard practice, features offered by
one quarter of the vendors, etc... Or strictly what is standardized?
Switching based on path groups certainly isn't in any standard (its not
precluded)but a few vendors provide it so we put it in. The additional
transparency feature was requested so we put it in (some of us put in a
bunch of work to fix it up from its initial form, even if we would have
preferred its deferal).  Hence it was my notion that we were making the
signaling specification a common language and not trying to redefine
SONET/SDH standards (which should aim for the least common denominator in
some sense.  BTW how did that extreme layer violation of in-band FEC get in
the OC-192 spec?).

Greg B.
I'll be taking a one week break from Sub-IP in exchange for Sub-Optic 2001
in Japan (that's submarine optics...).

	Dr. Greg M. Bernstein, Senior Scientist, Ciena 
	New phone: (510) 573-2237


		-----Original Message-----
		From:	Huub van Helvoort [mailto:hhelvoort@lucent.com]
		Sent:	Friday, May 18, 2001 4:28 AM
		To:	Zhi-Wei Lin
		Cc:	Bernstein, Greg; 'Maarten Vissers'; Anup Tirumala;
ccamp@ops.ietf.org; chickoo66@yahoo.com; ip-optical@lists.bell-labs.com;
t1x1.5; q11/15
		Subject:	Re: [T1X1.5] Re: [IP-Optical] concatenation
extensions in sonet/sdh


		Greg, 

		Would you please provide a little more detail:

		Are the timeslots in an arbitrary concatenated signal
contiguous? No, that's the point.

		-1- if they are not contiguous:
		    what is the difference with a virtual concatenated
signal with
		    the members following exactly the same path trough the
network? Well to get technical, these are still treated as a concatenated
signal at each switch (a weakness compared to virtual concatenation). On the
other hand this doesn't need to involve path overhead (I think of virtual
concatenation as a service offered by PTE boxes).

		-2- if they are contiguous: 
		    suppose we have an OC-48 filled with: A: an STS-9c, B:
an STS-11c,
		    C: an STS-13c, D: an STS-15c in that order.
		    At a certai time A and B are not needed anymore freeing
capacity 
		    of 22 STS-1.
		    Now if a new STS-17c is required, how would one proceed
without
		    grooming (as you claim under (2) below?

		Regards, Huub.

	
===============================================================
		"Bernstein, Greg" wrote:

		> (2)     Arbitrary concatenation offers a solution to a
		> real problem, i.e.,
		> eliminates the need for re-grooming on lines that support
		> it.  For those who
		> have invested non-trivial amounts of money in transoceanic
		> links this can be
		> a significant savings.

		and in the same email:

		> To be precise in the definition of arbitrary
concatenation:
		> As a concatenated signal within a single SONET Line (SDH
MS), with
		> potentially arbitrary timeslots used for its components.
		>
		> The current main application is: avoiding the need for
service impacting
		> re-grooming. Note that this applies to standard sized
		> signals and is a per link property.
		>
		> Other applications do exist and are somewhat competitive
with non-LCAS
		> virtual concatenation since the implementation of
arbitrary concatenation
		> for odd sized signals is simpler than that of virtual
concatenation.  Once
		> "odd" sized signals are used an entire path through the
network must exist
		> that supports them.

		-- 
	
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		| Huub van Helvoort    |     Lucent Technologies     | PO
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		| TEL: +31 35 687 4393 |     ONG Systems Engineer    | 1270
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