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Hi Cedric,
The dispersion effects for 2km at 200G per CWDM4 lane are the same as dispersion effects for 8km at 100G per CWDM4 lane, all other variables being the same.
802.3 decided that there was not enough margin for 10km at 100G per CWDM4 lane, so created 6km 400GbE-LR4-6 standard. The 100G MSA reviewed recent results and decided that 10km at 100G per CWDM4 lane works just fine.
8km is between these two decisions, so pick your poison.
4x200G/800GbE-FR4, when we get to it in the future, should be defined for 1km reach. Cost is everything so why eat into the margin with higher dispersion penalty to support tail of the reach distribution.
200G/lane optical should wait until the Cu do electrical first. When 25G/lane optical went first, we lacked the imagination to include FEC. Industry had to wait for 802.3bj to give us KR4 FEC before getting 25G/lane optical right.
Chris
From: Cedric Lam (林 峯) <clam@xxxxxxxxxx>
Sent: Thursday, August 20, 2020 10:16 AM
To: Chris Cole <chris.cole@xxxxxxxxxxx>
Cc: STDS-802-3-NGECDC@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_NGECDC] Definition of "Breakout"?
Thank Chris and John. We are in the era of abundance. Abundance of bandwidths, standards and names, which sometimes can be confusing (maybe it is just me). Thank you guys for the education. When it comes to 800G, my colleague Xiang told me that dispersion will kill CWDM4 in the FR reach. So we may need to think about how we can be less confusing.
On Thu, Aug 20, 2020 at 10:11 AM Chris Cole <chris.cole@xxxxxxxxxxx> wrote:
Hi Cedric,
FR4 (2km) has always used CWDM4, at all rates.
LAN-WDM has been used for 10km or greater reaches, i.e. LRn and ERn
Chris
From: Cedric Lam (林 峯) <000011675c2a7243-dmarc-request@xxxxxxxxxxxxxxxxx>
Sent: Thursday, August 20, 2020 10:07 AM
To: STDS-802-3-NGECDC@xxxxxxxxxxxxxxxxx
Subject: [EXTERNAL]: Re: [802.3_NGECDC] Definition of "Breakout"?
Also, I was told that DR4 in IEEE is kind of like PSM4 with parallel fibers, and FR4 uses LAN-WDM. So there is no good way of discerning between PSM4 or FR4 (a WDM interface) in IEEE naming. Here D and F means the transmission distance, R is line coding and 4 means 4 lanes which could be 4 pairs of fibers or 4 wavelengths on a single pair of fibers. So we may need to think about how to fix that in IEEE naming.
On Thu, Aug 20, 2020 at 9:52 AM Jeffery Maki <00000d5963b8071f-dmarc-request@xxxxxxxxxxxxxxxxx> wrote:
John,
I disagree. The term “breakout” is used in a general sense whenever a module can be put into use as four independent interfaces supporting ingress signals on four independent time domains. The choice of reach does not change this understanding.
The following modules are in the market or in progress to be in the market.
QSFP+ for 4 x 10GBASE-LR
QSFP28 for 4 x 25GBASE-LR
QSFP-DD for 4 x 100GBASE-LR1
and also
QSFP-DD for 4 x 100GBASE-FR1
The QSFP-DD for 4 x 100GBASE-FR1 is also known as 400G-DR4+. It can also be used to support 400GBASE-DR4 with 500 meters of parallel cabling.
The QSFP-DD for 4 x 100GBASE-LR1 is also known as 400G-DR4++. It can also be used to support 400GBASE-DR4 with 500 meters of parallel cabling but is a less likely use case.
The relevance of breakout to the IEEE 802.3 process is when the high-capacity module supporting breakout is thought to be the prevalent implementation of the PMD for broad-market potential instead of a single implementation of the PMD in a given form factor. In companion with this is the definition of a multi-port MDI with demarcation of which Tx and which Rx go together. These definitions are usually left for form-factor MSAs to define. The QSFP-DD MSA defines MPO and four separate SN/MDC duplex connectors to support quad-port breakout. The QSFP-DD for 4 x 100GBASE-FR1 AKA 400G-DR4+ using SN connector is an example.
Jeff
From: David Ofelt <00000d9f58951f93-dmarc-request@xxxxxxxxxxxxxxxxx>
Sent: Thursday, August 20, 2020 8:50 AM
To: STDS-802-3-NGECDC@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_NGECDC] Definition of "Breakout"?
[External Email. Be cautious of content]
I think there are two different concepts that end up being colloquially referred to as breakout. The first is that case you detaiil below- a set of parallel media lanes that can be grouped in various ways- either as a single unified PHY or as a number of slower PHYs. The other case is a module that happens to hold a number of PHYs that are completely independent- like a QSFP-DD/OSFP module that has 4 x 100GBASE-LR optics.
I’m Ok with declaring that “breakout” just covers the first case and your list is a good start at scoping the definition, but if we do that, I’d like us to figure out a name for the other case. I find that when I talk to people about modules- it is important to clearly address both cases, since many folks have only one of the cases in mind and conversations can get confusing.
I am also Ok with defining “breakout” to cover both cases, but then we can make that explicit in the definition.
--
DaveO
From: John D'Ambrosia <jdambrosia@xxxxxxxxx>
Reply-To: "jdambrosia@xxxxxxxxx" <jdambrosia@xxxxxxxxx>
Date: Thursday, August 20, 2020 at 06:03
To: "STDS-802-3-NGECDC@xxxxxxxxxxxxxxxxx" <STDS-802-3-NGECDC@xxxxxxxxxxxxxxxxx>
Subject: [802.3_NGECDC] Definition of "Breakout"?
[External Email. Be cautious of content]
All,
As I explore the scope for the Beyond 400 GbE effort, I have been having a number of conversations related to “breakout”
While we all discuss it – I have never seen some actual formal definition that is agreed upon within 802.3. So I would like to get some input.
I am going to start with breakout actually does and solicit input before proposing some definition to potentially use.
I see break out of the following –
- AUI
- Related PHYs
- Backplane
- Twin-ax cabling based on multiple different pairs
- SR optics based on parallel MMF
- DR optics based on parallel SMF
FR / LR / ER optics – I don’t see as being part of breakout.
Thoughts?
John
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