Marcus,
Thanks for
clarifying. I certainly don’t mean to imply that this would require a
SONET/SDH or OTN infrastructure. As for packets over OTN, I’m not sure I
consider this a pure packet network. After all, isn’t OTN really just the
next evolution of concatenated SONET/SDH frame structure? This touches on
an interesting point – no matter how much people pooh-pooh the use of SONET,
ultimately we still need many of its features (fault management, etc.).
I also don’t see why
the same approach couldn’t be used for intra-office links as well as metro or
backbone – i.e., just use existing PMDs/port types.
Best wishes,
Jugnu
From: Marcus Duelk [mailto:duelk@xxxxxxxxxx]
Sent: Tuesday, August 08, 2006
12:44 PM
To: OJHA,JUGNU
Cc:
STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [HSSG] Topics for
Consideration
Hi Jugnu,
I think it is important to mention that the idea is to use
"VCAT-like" features
for certain types of networks, particularly when you go into the Metro space
or beyond (backbone). Many people may associate VCAT or OTN being
equivalent to an overlay network where you do Packet over SONET or Ethernet
over SONET. It should be clear that VCAT or OTN can be implemented in a
pure packet network and may give clear benefits. How this could look like in
terms
of physical ports or PMDs is exactly what you just mentioned in the last
paragraph,
i.e. VCAT (or whatever you wanna call it) will allow you to potentially reuse
existing 1G/10G PMDs to create a higher-speed *parallel* Ethernet PMD. You
wouldn't need to specify what the actual line/service rate is, similar to
today's provisioning
of a Virtual Concatenated Group (VCG) where you just specify the number N of
STS-1's that belong to your VCG.
Marcus
OJHA,JUGNU wrote:
Marcus,
Thank you for
elaborating – this is indeed what I meant. As for the increased
complexity increasing the cost, I find this a bit of a red herring. It
basically implies some extra design time for the IC that would do the physical-layer
aggregation. As you mention, much of this work will have to be done
anyway, to allow for member failure, deskew (synchronization), etc.
Making things flexible would add some extra work. However, I’m not
convinced it would make all that much difference relative to the NRE and
overall design costs associated with the IC development. Any difference
would, of course, be amortized over the number of ICs shipped. We have to
keep in mind that for a high-volume product, the optics cost outweighs the IC
cost. If the product is not high volume, then both optics and IC costs
per unit will be high in any case, particularly when you amortize development
costs.
Mike, as for what PMDs
this would work over, the answer is – any. They could be wavelengths,
different fibers, or some mix of these. Also, there’s no need for the
various PMDs to be bundled into a single package (although that is certainly
one implementation option).
The bottom line is,
the PMDs could stay the same as the ones we use now. The difference would
lie behind those PMDs, in the IC world.
I hope this answers
the questions.
Best wishes,
Jugnu
Mike,
good questions. I think that there is a general dilemma of making the
choice between a simple lower-cost and a more flexible, complex and
higher-cost solution. Probably one solution is more justified in certain
networks (e.g. LAN/SAN) while the other is more suitable for other
networks (e.g. MAN/WAN).
I think Jugnu's idea was to eventually decouple the service rate from
the physical line rate by using physical layer aggregation similar to VCAT.
If you work with parallel PHYs over a WDM MAN/WAN you probably
have to define VCAT features anyway (e.g. differential delay compensation,
protection against loss of members, etc.). In that scenario, you wouldn't
necessarily have to define what the final service rate is, similar to a virtual
concatenated group which consists of N bandwidth 'units' (e.g. STS-1's).
Today's VCAT scales up to 256 members for one group. If you define
something like that for Ethernet and allow your 'bandwidth units' to be 1GbE
or 10GbE then that would scale to 256 Gb/s or 2.56 Tb/s max. service rate.
These things are done nowadays for overlay networks (over TDM,
or OTN), but in principle you could also use other metrics.
Marcus
Mike Bennett wrote:
Jugnu,
OJHA,JUGNU wrote:
Mike,
It seems more reasonable to me to consider
finally decoupling the physical pipe size from the rigid hierarchy used in the
past. Why not simply define a scalable interface that allows inverse
multiplexing (physical layer aggregation – not the type of aggregation you have
described, which sounds like the current LAG) of an arbitrary (within some
bounds, obviously) number of physical channels (10G) into a single logical
link? The SONET/SDH and Digital Wrapper/OTN world already has mechanisms
to do this (VCAT, LCAS), and dynamically to boot.
This would provide a much more flexible,
scalable solution to customers.
On the surface, it seems
to me that with flexibility comes complexity which leads to higher cost.
It's also not clear to me how the physical layer aggregation you propose
translates to a port on a switch. Would I have to buy an N x 10G
transceiver? Would it be a WDM-like transceiver? Would this work
with a single fiber-pair or multi-strand? What would the relative
incremental cost be (in percentages, non monetary units) to scale
up? Also, are you proposing that this would scale beyond
100G? If so, how far? You mention boundaries - I'm curious what you
think the upper bound would be. I hope you're planning to present
something at the interim as it would help me understand what you're
really proposing and how that compares to other ideas.
Regards,
Mike
In particular, it would allow them to grow
capacity on any given link as needed, instead of having to install 10x10G
channels up front. Further, when they hit 100G, they wouldn’t be stuck
until some other solution is defined – they could continue to grow.
Respectfully,
Jugnu Ojha
Avago Technologies
John, et al.,
>During our first meeting, I anticipate spending a lot
of time focusing on objectives. At the >closing plenary I
highlighted two issues / objectives that the SG would have to consider:
>
> Tradition of
10x leap in speed
I think the speed
increase has to be 10x. The standards development process will take at
least 3.5 to 4 years to complete. Anything less than 100G will force
people who are currently aggregating 10G links to continue to use aggregation,
only using fewer higher-speed, and more expensive links. End users
prefer using a single link over aggregating physical-layer links into a logical
link because of the complications that come with aggregation. The data in
the CFI presentation was just a sample of cases in which network operators
we're aggregating 10G links to accommodate the demand on their networks.
There will be many more by 2011 (when I expect there would be 'real' products
on the market).
> Multiple
Reach Targets
>
It was also presented that the focus of this effort wasn’t for a desktop
application, and >that the cost model needs to be considered.
I believe we need to adjust the cost model in such a way that it is aligned
with the ecosystem. It is unreasonable, in my opinion, to expect a 10x/3x
model to apply to systems designed for wide-area/metro-area networks. I
also think it's short-sighted to ignore the rest of the ecosystem and develop
Ethernet only in the part of the ecosystem where the original cost model
applies.
Regards,
Mike
--
Michael J. Bennett
Sr. Network Engineer
LBLnet Services Group
Lawrence Berkeley Laboratory
Tel. 510.486.7913
--
Michael J. Bennett
Sr. Network Engineer
LBLnet Services Group
Lawrence Berkeley Laboratory
Tel. 510.486.7913
--
___________________________
Marcus Duelk
Bell Labs / Lucent Technologies
Data Optical Networks Research
Crawford Hill HOH R-237
791 Holmdel-Keyport Road
Holmdel, NJ 07733, USA
fon +1 (732) 888-7086
fax +1 (732) 888-7074
--
___________________________
Marcus Duelk
Bell Labs / Lucent Technologies
Data Optical Networks Research
Crawford Hill HOH R-237
791 Holmdel-Keyport Road
Holmdel, NJ 07733, USA
fon +1 (732) 888-7086
fax +1 (732) 888-7074