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All, The breakout concept appears to me to be most important for usage scenarios of optical technology. I am not seeing the need for it to extend to the architecture
of the 400G MAC and PCS necessarily. I had originally put forward the concept of technology reuse to take technology from the current Ethernet rate to build optical interfaces for the next Ethernet rate. A common module implementation could be seen to be
N ports of current Ethernet rate or one port of the next Ethernet rate, where the next Ethernet rate is N time the current Ethernet rate. In all of this, it was forward looking. The industry has been working post-haste by enabling an optical interface for 40GE by reusing the optical technology found in 10GBASE-LR, where the 40GBASE-R
PCS is used to create a four-lane parallel single mode (PSM4) solution. No 40G Ethernet PMD has been defined in this regard. Its growing prevalence might justify its eventual inclusion in the 802.3 standard. We did not define this PMD in the 802.3ba task
force because, I believe, we were not aware there would be any market acceptance. We now have a much different understanding of potential market acceptance and potential market volume for parallel single mode fiber solutions. Jeff From: Kolesar, Paul [mailto:PKOLESAR@xxxxxxxxxxxxx]
Brad, There has been no suggestion that the break-out objective be an absolute requirement. All have language like “as appropriate” or “if appropriate”. I personally think break-out capability makes a lot of sense for solutions aimed at connectivity within data centers. In contrast, so far I have not seen arguments
supporting break-out functionality in the longer-reach applications. Paul From: Brad Booth [mailto:bbooth@xxxxxxxx]
Jonathan, Thank you for the summation of my concern. The selection of a PHY will be based on its ability to meet the objectives. For example, if there are two PHY/PMD proposals where #1 provides a significant cost and implementation benefit but #2 provides breakout capability, then this objective
could be used to defeat #1 in favor of #2. Maybe the question the study group needs to answer is: Is breakout a critical requirement for 400G that we wish to exclude proposals that do not support it? Thanks, Brad ‘Provide support if appropriate for breakout functionality to 40G and / or 100G’ To avoid locking out an otherwise compelling technology option…. From: John D'Ambrosia [mailto:John_DAmbrosia@xxxxxxxx]
All, Per our call last week, what are the thoughts on the wording of this as a proposed objective –
Provide appropriate support for breakout functionality to 40G and / or 100G There was some concern about potential impact or unintended consequences that people wanted to see this wording to discuss further. Regards, John |