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Re: [HSSG] Topics for Consideration


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.


Mike Bennett wrote:




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.



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.  



Jugnu Ojha

Avago Technologies


From: Mike Bennett [mailto:mjbennett@xxxxxxx]
Sent: Wednesday, August 02, 2006 12:21 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [HSSG] Topics for Consideration


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.



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

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