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RE: [10GBASE-T] latency

It would be most helpful to have a survey of applications and latency requirements. It might be easier if we can restrict this survey to the space of interest. In short, if the question could be bounded (will do no worse than X, can do no better than Y), then it would be far simpler for said experts to respond.
We might anticipate responses:
1. Y is not good enough. Unless you can get to Y2 (< Y) my application won't run.
2. X is good enough. Make it as simple as possible.
3. I can run between X & Y, prefer Y, but don't want to pay much over X for it.
In order to help set these boundaries, there are certain classes of problems that can be moved to NUMA machines if the latency is sub-microsecond, process to process.
 -----Original Message-----
From: Bruce Tolley []
Sent: Monday, February 23, 2004 11:17 AM
To:; 'stds-802-3-10gbt'
Subject: RE: [10GBASE-T] latency


Thanks for the summary

I would argue that early 10GBASE_T switching products should be sold to early adopters at National Labs and other R&D sites building clusters. We need this community to come to the TF and state its latency requirement in the 2006 timeframe and determine the tradeoffs.


At 10:54 AM 2/23/2004 -0800, Jonathan Thatcher wrote:
There have been numerous interesting and correct comments made. A subset of these apply only in certain contexts. To that end, I will attempt to add some context.
There is little question that lower latency increases the market potential. There is little question that lower prices (read that less complexity), and earlier time to market also increases the potential market. The problem is that these fight against each other, and the optimization point is not clear.
I presume that there are two principal application spaces for 10GBASE-T in the near term: data center and enterprise (home and school will probably have to wait a couple of years :-). If you want a strict boundary between these two spaces, I can't provide it. So we will have to deal with some ambiguity. In the enterprise, it is difficult to argue that low latency is as critical as low price. The exception to this would be low latency applications that want to be set up as a "grid computer," which I will lump into the "data center" bucket.
The data center, on the other hand, has instances where both low latency is required (clustered computing) and higher latency is acceptable (most file serving). From a parallel computing perspective, there are classes of problems (applications) that range from low latency NUMA to those that are "embarrassingly parallel (e.g."
From the perspective of the upcoming "Data Center Ethernet" (may not be the best name) call for interest, the intent is to explore those means that can be used to decrease latency in Ethernet networks. If one is to presume that this should be a key application space for 10GBASE-T, then it would be interesting to understand the trade-off between latency and complexity. It may be the case, that even under the most complex scenario, that 10GBASE-T latency is simply insufficient for entire classes of low latency applications.
So, the question remains, what does the complexity vs latency curve look like? I expect that it is something like the left side of a bathtub curve (vertical axis is latency, horizontal axis is complexity). What is the inflection point? What is the slope of the falling portion of the curve? What is the asymptote?

Bruce Tolley
Senior Manager, Emerging Technologies
Gigabit Systems Business Unit
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134-1706
ip phone: 408-526-4534

"Don't put your hiking boots in the oven unless you plan on eating them."

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