Carlos Thanks for taking the time to go through the specification proposal in detail and share your feedback.
Regarding your comments: * Would it be possible to take the CWDM4 spec and update it with the CWDM4-lite specific information so it's all in one document? Response: We thought about this and it does sounds like a great idea, but has not been workable in practice. As an example of this, I point to the recent multi source agreement (MSA) which added 10km as a new link distance at 100G on CWDM wavelengths. This was not added into the CWDM4 spec as an additional reach, but was created as a separate new MSA called 4WDM (http://4wdm-msa.org/). Rather than creating yet another new MSA, we see the OCP Networking group as the best forum to share the relaxed specification. And to share details of the ecosystem of networking elements that work together. The idea is to help simplify deployment of 100G technology across data centers of all sizes and OCP seems the right place to do that. *What is the difference between CWDM4-lite and PSM4 and why is another short distance, single mode fiber spec warranted? Response: Both CWDM4-OCP and PSM4 target short reach data center links at <500m. The difference between them is the number of fiber strands and connections required to complete a link. A bi-directional link using CWDM4-OCP runs over 2 single-mode fibers, whereas PSM4 runs over 8 strands of fiber. PSM4 requires 4 times as much fiber and 4 times as many patch-panel connections in each link which burdens data center infrastructure with additional cost and complexity, given the similarity in cost between the optical transceivers. Katharine From: opencompute-networking [mailto:opencompute-networking-boun...@lists.opencompute.org] On Behalf Of Carlos Cardenas Sent: Friday, January 20, 2017 11:38 AM To: opencompute-networking@lists.opencompute.org Subject: [Opencompute-networking] CWDM4-lite questions Howdy Katharine. Thanks for presenting this a couple of weeks ago. Here's the following feedback I have: * From this spec on CWDM4-lite (http://files.opencompute.org/oc/public.php?service=files&t=8ee8934b1f1f57bec2f88f2fac804d03<https://urldefense.proofpoint.com/v2/url?u=http-3A__files.opencompute.org_oc_public.php-3Fservice-3Dfiles-26t-3D8ee8934b1f1f57bec2f88f2fac804d03&d=DwMFaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=i8c1XOsbULQg4wxarudoiw&m=cbKc6LbuDDMDE_o6H_r0nt639m7I9AI0FVkFI4Sa6Q0&s=o9YeLFeJXJ3GINwkbMkhaaCEiWAxmvxBUlT11Eu3foI&e=>), I've spent more time reading the CWDM4 spec (http://www.cwdm4-msa.org/wp-content/uploads/2015/12/CWDM4-MSA-Technical-Spec-1p1-1.pdf<https://urldefense.proofpoint.com/v2/url?u=http-3A__www.cwdm4-2Dmsa.org_wp-2Dcontent_uploads_2015_12_CWDM4-2DMSA-2DTechnical-2DSpec-2D1p1-2D1.pdf&d=DwMFaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=i8c1XOsbULQg4wxarudoiw&m=cbKc6LbuDDMDE_o6H_r0nt639m7I9AI0FVkFI4Sa6Q0&s=noqMkI87Ln-bvKPvuZvvgm2fI83VWz8NmR-ly9W8nEA&e=>) to really understand what's going on. Would it be possible to take the CWDM4 spec and update it with the CWDM4-lite specific information so it's all in one document? As it is today, it feels too much like an errata than a specification. * I understand the motiviation on wanting to do CWDM4-lite (same as LR4-lite and LR4-lite-lite). However, for doing single mode fiber for short (500m) distances, there's already a spec and MSA for that: PSM4 (http://psm4.org/<https://urldefense.proofpoint.com/v2/url?u=http-3A__psm4.org_&d=DwMFaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=i8c1XOsbULQg4wxarudoiw&m=cbKc6LbuDDMDE_o6H_r0nt639m7I9AI0FVkFI4Sa6Q0&s=rikOSkLssGbsPYagRkNlsVOSAPKnRKLAVJAJM9nYFw8&e=>). It's even the spec that folks of FB's size wanting single mode in the data center have deployed with others adopting it as well. What is the difference between CWDM4-lite and PSM4 and why is another short distance, single mode fiber spec warranted? Thanks in advance. +--+ Carlos
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