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[HSSG] 10 x 4 = 40


There's been some discussion (!) around the existence of an MSA for a 
40G module format. The module is actually based on 4 x 10G channels, 
this leaves system implementors 2 choices:

1. Simply define the MSA to use LAG . The MAC & PCS are already defined 
for 10GBASE-R, the PMD definitions are already available for SR, LR & 
LRM. This could be incorporated into systems being developed 
immediately, exploiting existing MAC and fabric silicon. From a 
standards perspective, I would classify this as another 10G format (no 
fundamental difference to X2, XFP or SFP+).

Additionally, a breakout device could allow compatibility with discrete 
10G systems (using SFP+, XFP, X2 etc.) and also would allow the use of a 
40G socket to connect to multiple 10G destinations (redundant 
connections, multipath routing etc.).

2. Try to push through a new definition in 802.3 for 40G MAC and PCS. 
This would almost certainly be tied to the same schedule as the 100G MAC 
& PCS definition, it might be available to start development in 3-4 
years. It would require new MAC/fabric silicon, that would have to start 
development after the standard is in its last stages of development.

A socket using the single 40G approach could not be connected to a 
breakout for legacy compatibility.


If #1 happens (almost impossible to "prevent" it) then confusion will 
ensue as option #1 & option #2 products mix in the market. It will be 
very difficult to distinguish or differentiate between the two. I don't 
know how those who commit to the "proper" approach of #2 will be able to 
recoup their extra development costs compared to those who get a 3-4 
year headstart by implementing #1. Additionally, option #2 based 
products will hit the market at the same time as 100G products become 
available. They will start with the perception of being "low-end" and 
will not be able to command the "early adopter premium" that is often 
relied on to recover leading edge development costs.

Frankly, looking at this, I would not recommend to my employer that we 
should spend time (and money) to develop the silicon to support option 
#2 vs option #1. Of course, others may feel free to spend their 
development differently. Additionally, if I was a component vendor, I 
know which option I would pursue.

With regards,