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Re: [HSSG] 40G MAC Rate Discussion

Thanks Shimon,


Thanks for the answers, a couple of comments/questions:

On 5-Apr-07, at 2:08 PM, Shimon Muller wrote:

> Med,
> Excellent questions. See in-line:
>> 1) Application: 40GE vsus 4x10G LAG:
>> What application(s) do think will require a 40GE single pipe
>> and can  not be addressed by 4x 10GE LAG?
> Any application where round-trip latency (rather than bulk throughput)
> is of essence. These are request-response type of applications, such
> as Oracle. Both 40GE and 4x10GE LAG may be able to handle the same
> number of transactions, however from a single user's perspective, the
> 40GE network will respond 4 times faster. This has direct  
> correlation to
> the application's performance.

I was under the impression that packet in flight time was a smallish
fraction compared to the processing time of TCP/IP at both ends.

 From your experience in the field what is the percentage of the
propagation delay versus processing time at the end nodes?

>> Few people mentioned already that 4x LAG was manageable.
>> My understanding is high end server are going multi-core/multi-CPI,
>> I  would imagine that Network IOs (flows) would fit well within  
>> the 4x
>> 10GE model.
> Correct, but only if you get uniform spreading of the flows. And  
> how do
> you guarantee that? That's the "manageable" dilemma that applies for
> both carrier and server environments, and is regardless of how many
> links you have in the LAG. There is essentially no good way to control
> this at the network management level.
> For network environments where a link has lots (millions) of flows,  
> you
> can rely on statistical multiplexing for getting good spreading of  
> flows.
> I would imagine that this would happen more often in carrier links  
> rather
> that server links, since they would have a lot more aggregation of  
> users.
> Apparently it is a problem for both.
> Finally, in the database example that I described earlier (Oracle),  
> typically
> you get a few dozen flows at best, and the spreading is very poor.
>> 2) Relative cost:
>> What is the expected relative cost vsus 10GE ports (or 4x 10GE LAG)?
>> and in what time frame? Given that the idea is the 40GE  will  
>> fill  the gap
>> between 10G and 100G for servers (say between 2010-2015?).
> I will let the optical vendors speak for themselves, but what I have
> heard is that a 40Gb QSFP solution will be 2x of current 10Gb SFP in
> 2008. By 2010 I would expect it to be similar to SFP.
> On the MAC side it should be essentially free, since I expect by 2010
> quad 10Gb NICs being the highest volume NICs, and adding 1x40Gb
> capability will be trivial.

If I am deploying a 4x 10G, any 40GE solution at the same point in time
will be around the same cost (or a little extra).
If there is no serial PMD with a better cost for that time frame,  
there is no
cost advantage to doing 40GE vsus 4x 10G.


> Regards,
> Shimon.