Re: [IP-Optical] concatenation extensions in sonet/sdh

[Zhi-Wei Lin <zwlin@lucent.com>]

Hi,

some observations:

in terms of re-grooming and such, I believe both virtual concatenation
and arbitrary concatenation can perform this. One method is
standardized, the other is proprietary.

In terms of routing of the individual connections that make up the
concatenated signal, virtual concatenation is more flexible than
arbitrary concatenation, since you can put each component VC in
different lines, and each component can be routed differently.

In terms of interworking, yes the SIGNALLING can defnititely be made to
interwork. However, the larger issue for interworking is support by the
transport equipment themselves. Thus interworking involves TWO parts:
signaling interworking and transport interworking. Having one without
the other doesn't really help...

Thus, in terms of solving real problems, either virtual or arbitrary can
accomplish that, but IMO, virtual seems more flexible...and
standardized...

In terms of standards as fostering interoperability and stifling of
innovation, in principle yes I agree. And therefore if arbitrary
concatenation should be standardized, it should be standardized in the
correct standards body. As Maarten mentioned, the relevant standards
bodies discussed arbitrary concatenation years ago, and decided
(hopefully based on their expert technical opinion - I wasn't involved)
not to include arbitrary but instead to include virtual. IMO, there must
be good reasons, and from what I can tell, I see virtual as been more
flexible so that is a pretty good reason...we at IETF, being protocol
experts (and budding transport experts?) should not try to second-guess
the decisions without fully understanding the ramifications...

As for stifling innovation, anytime you standardize anything there is
always some factor of development that gets fixed (is this something
that should not be said in a public forum??? -- sorry!!). Therefore
there is always a tradeoff between innovation and standardization. I
think the job of standards bodies is to try to balance these two factors
such that the industry in general can live with the result without
unduly burdening...

agree?

Zhi



"Bernstein, Greg" wrote:
> 
> A couple more points.
> (1)     GMPLS works well with arbitrary concatenations need to specify the
> time slots since it provides a signaling protocol that can do just that,
> i.e., GMPLS actually enables this feature to interoperate.
> (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.
> (3)     The goal is interoperability and to solve real problems.  We've got
> a real problem and with a minor edit to the GMPLS SONET specification we can
> have an interoperable method for solving it.
> 
> 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.
> 
> Folks I thought the role of standards organizations was to foster
> interoperability that enables the industry to move forward rather than as a
> means to stifle innovation. I think it is better for the marketplace to
> decide which features are desirable.
> 
> Greg B.
> 
>         Dr. Greg M. Bernstein, Senior Scientist, Ciena
>         New phone: (510) 573-2237
>