John,
While I understand the intent of this objective (and agree implementation of this functionality would be good to have), I'm not sure how the task force satisfies this objective.
To provide breakout functionality such as 40G operating as 4x10G, the device operating in 40G mode complies with the 40G standard and when the device operates in 4x10G mode, does each 10G portion comply with the 10G standard? As an example, 40GBASE-SR4 has a different reach requirement than a 4x10GBASE-SR. Which reach requirement is required for compliance? This is strictly an implementation decision. There is nothing within the 40G specification or the 10G specification that implies any requirement for 40G to breakout to 4x10G, which permits some flexibility in implementations.
Considering there are already 40G MAC/PHY and 100G MAC/PHY drafts or specifications in 802.3, how does a 400G MAC/PHY standard create compliance with those specifications? Does the "provide appropriate support" give the task force the ability to create new 40G MAC/PHY or 100G MAC/PHY specifications that are derivatives of the 400G MAC/PHY specifications? For example, if the 400G SG has a 2 km SMF objective, does that mean that to provide appropriate support for breakout that there would be the ability to create a 100G 2km SMF PMD?
Implementation of breakout functionality is a great way to provide a migration path and I believe the TF should take that into consideration when selecting PHY proposals; I'm just not sure how the study group defines it as objective the TF can show has been met.
Your thoughts/feedback on this would be greatly appreciated.
Thanks,
Brad