That’s because the DWDM solutions (at least the good ones, wisely) use single-wavelength 100Ghz coherent light (like, you know, normal optics from the rest of history), and do not play this 4x25g lane splitting game.  Unfortunately they are still quite expensive and physically large, smallest I know of right now is in CFP2.

- Ben Cannon, AS15206

On Nov 25, 2018, at 10:16 AM, Mike Hammett <nanog@ics-il.net> wrote:

I haven't seen anyone selling 25G or 50G transport.



-----
Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com

Midwest-IX
http://www.midwest-ix.com


From: "Saku Ytti" <saku@ytti.fi>
To: "Mike Hammett" <nanog@ics-il.net>
Cc: nanog@nanog.org
Sent: Sunday, November 25, 2018 9:45:58 AM
Subject: Re: Cheap switch with a couple 100G

The argument should be 50G is cheaper than 40G.

Because serdes is 25G typically, you get 25, 50, 100 without gearboxes
and retimers, so less pincount, less thermal, higher density, lower
cost.

But BOM impact to pricing isn't high anyhow, unless we're talking
about massive port counts.

If box DOES support 10GE and 40GE then the cost benefit is not there,
so you need to be targeting quite specific use case, use-case large
scale DCs are targeting.

On Sun, 25 Nov 2018 at 16:42, Mike Hammett <nanog@ics-il.net> wrote:
>
> I keep hearing how cheap 100G is compared to 40G and it doesn't seem to hold true. Prove me wrong.
>
> Cisco Nexus and Arista both have switches with 48x 10G ports and 2x - 6x 40G ports for under $1k. Swap those 40G for 100G and you're at $5k - $7k.
>
> Am I missing some cheap switches with 100G?
>
>
> I ask this because the transport companies seem to have given up on 40G.
>
>
> -----
> Mike Hammett
> Intelligent Computing Solutions
> http://www.ics-il.com
>
> Midwest-IX
> http://www.midwest-ix.com



-- 
  ++ytti