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Re: [802.3_400G] Breakout Functinoality Objective



Tom,
 
I agree that if there is a proposal that offers this functionality to the task force (with or without the objective), then it is likely to receive very strong support.
 
Another good point that was made is the area of the market most likely to use this is the data center where we are witnessing use of 40G breakout to 4x10G today. We should note though 40GBASE-SR4 is only 100m/150m OM3/4; whereas, 10GBASE-SR is 300m/400m. PMDs designed to meet only the 40GBASE-SR4 specification will not meet the requirement for 10GBASE-SR; therefore, a "non-standard" port type was created based on the compliance requirements of 10GBASE-SR applied to 40G.
 
If we look at the existing 40G and 100G optical PMDs being considered for data centers today, we have the following list:
* 40GBASE-SR4 (100m on OM3, 150m on OM4)
* 40GBASE-LR4 (10km on SMF)
* 100GBASE-SR10 (100m on OM3, 150m on OM4)
* 100GBASE-SR4 (70m on OM3, 100m on OM4)
* 100GBASE-LR4 (10km on SMF)
At this point in time, the above list would appear to be the only PMDs that may be supported?
 
So what is "appropriate support"? Is it a MAC/PCS/PMA functionality as exists with 40G-4x10G today? Or is there any requirement on PMD?
 
The MAC is specified at 40G and 100G in a bit serial fashion; therefore, it is unlikely that .3bs task force would need to do anything to support the existing MAC specifications. Assuming the task force doesn't want to modify the 40G or 100G PMD list, this would leave the task force with only having to consider modifications to the PCS/PMA
 
Maybe the objective needs to be something like:
Provide appropriate PCS/PMA support for breakout functionality to 40 and/or 100G.
 
Thanks,
Brad


On Thu, Oct 17, 2013 at 1:23 PM, Tom Palkert <tpalkert@xxxxxxxx> wrote:

I like the wording and tend to support Mr. Dudek. The term “appropriate support for breakout” seems generic enough that it will not force us down the path of 40G SR compliance while at the same time it should force us to address the issue in any proposals that are made.

 

In response to Brad’s thoughtful comments I would like to think that a proposal that shows full backwards compatibility to an existing 40G or 100G variant at zero additional technical risk, zero additional cost etc to the 400G proposal would get strong support. The other extreme would be a high power, high risk, high relative cost proposal with no backwards compatibility that would not receive support.

If anyone has proposed wording that is better I would like to hear something.

 

Tom

 

 

From: Brad Booth [mailto:bbooth@xxxxxxxx]
Sent: Wednesday, October 16, 2013 12:36 PM
To: STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_400G] Breakout Functinoality Objective

 

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

 

 

On Wed, Oct 16, 2013 at 6:15 AM, John D'Ambrosia <John_DAmbrosia@xxxxxxxx> wrote:

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

 

 

 

 

 


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