Actually floating point is overkill for
TDM. We'd like to use small
integers to describe and update them more frequently. The TDM multiplexing is straight forward
but unforgiving. We had this same discussion when we decided to breakout the
labels for SONET/SDH GMPLS signaling.
I want to know that I've got 14 STS-1 of capacity, XX unused
VT1.5, etc... For those
SONET/SDH systems that have to deal with timeslot inflexibility (i.e., fragementations issues) more complete information on time
slot usage is advantageous. For
example with rings that don't have Time Slot Interchange, a map of the
timeslots could be helpful. Eric
and I had a bunch of stuff about this in our earlier routing drafts.
Greg B.
--------------------------------------------------------------------------------------
Dr. Greg M. Bernstein, Sr. Director
Technology, Ciena Corp.
-----Original Message-----
From: Don Fedyk
[mailto:dwfedyk@nortelnetworks.com]
Sent: Monday, February 25, 2002
4:07 PM
To: Bernstein, Greg; Kireeti
Kompella; ccamp@ops.ietf.org
Subject: RE: Routing drafts
Greg you wrote:
> (b) Big issue -- The parameters for representing
bandwidth on
> a link are not
> very appropriate for TDM
signals or WDM signals. I've
> included below some
> more explanation taken from
the IPO working group draft.
> However, this is
> the same thing that led to us
breaking out the traffic
> descriptor stuff in
> GMPLS signaling for the
SONET/SDH case. This is really
> needed here too.
>
These bandwidths in our draft are
exact floating point numbers.
Are you saying that the resolution
of the floating point is an issue
with optical? Or are you implying
that bandwidths are percentages ?
The text below is implying that
statistical multiplexing can use
inexact bandwidth but optical can
(and should) use exact bandwidths.
I did not see problems with the
floating point range or our draft.
Don
> (From IPO working group draft on Inter-domain
optical routing)
> 2.3 Differences
between MPLS and Optical Circuit routing
>
> The bandwidth accounting needed
in optical circuit-switched
> networks is also
> different than in packet
networks. In packet networks using
> either ATM QoS
> or MPLS-TE, complex
statistical measures are used to
> characterize the load
> on a link, often with varying
degrees of accuracy. The
> inexactness of such
> measures and the
"compressibility" of statistically
> multiplexed traffic
> imply that a small percentage
change in link utilization can
> usually be
> absorbed by the network.
>
> By contrast, if an OC-192 link
has just one STS-1 path
> occupied (less than
> 1% of the link bandwidth), it
cannot accommodate an STS-192c
> path. Due to
> the relatively simple finite
multiplex structures currently
> use in optical
> networks tracking bandwidth
resources is much easier than
> packet switched
> networks, however much
stricter bandwidth accounting is
> required on circuit
> switched links. In particular,
it is expected that an
> individual optical
> circuit switched link can be
fully utilized, while due to
> queuing effects a
> packet switched link on
average can never be run at full
> capacity and is
> typically run at less then 80%
of capacity.
>
> Greg B.
>
>
>