network engineer here: nobody connects a 200 or 400GbE interface linecard off a router to a single anything... The purpose is for ISP-to-ISP interconnections for truly huge amounts of traffic. For example direct peering in the same IX/carrier hotel between a huge source of content (youtube/google, netflix, etc) and a huge ISP (comcast, centurylink).

For a big ISP, also things like 100GbE connections from a city's pair of core routers to slightly smaller aggregation routers.

edit: I don't know that anything "consumes" data in the way that the questioner is asking. It's more about the aggregate amount of data. One netflix 4K stream to an xbox one s is about 15.75 Mbps. Now multiply that by a hundred thousand netflix subscribers in a typical comcast service area, any of whom at any given time might be sitting around and watching Altered Carbon or Breaking Bad.

Streaming uncompressed raw video over ethernet for TV production. It's still commonly done over dark fiber but people are slowly migrating towards IP. A single uncompressed 4K video stream is over 12Gbps, 1080p is 3Gbps and obviously when you're producing content you have a few of these running alongside each other (multiple cameras, feedback, big screens etc... Think something like the world cup or superbowl). It quickly adds up to a tremendous bandwidth. On top of that it needs very low latency and jitter to keep all the streams synchronized.

I'm not consuming it, but I can produce over 100Gb/s of traffic from a single CDN node if it is equipped with multiple 100GbE NICS. So 200GbE and 400GbE are exciting to me.

(for context: https://medium.com/netflix-techblog/serving-100-gbps-from-an...)

Network Engineer here as well - I support one of the world's largest enterprise organizations (although my area of 'expertise' is pretty far down the stack - somewhere between the internet and the WAN circuits) - I can see no personal use for a 400 GbE port on anything.

As far as my organization goes, there will always be a bottleneck somewhere else (speaking location to location across the WAN).

The only applications I could see this being useful would be maybe huge ISP interconnects or maybe some big players in the video streaming world. That doesn't mean that future-proofing is a bad thing - of course cost will probably be a very large concern in the case of 400GbE...I see a lot of 40 gig ports that go completely unused, personally.

disclaimer: I work at IBM Research

we have just finished setting up our new big data crunching system which sits on 48x100GbE links on the full flash storage side and on 32x100GbE on the client side (split 100GbE -> 4x25GbE).

at this point we are saturating most of the links.

Can’t you saturate 100GB easily with a single disk array these days?

Yes, in my company we generate and receive uncompressed video in software and get to these kinds of bandwidths from a couple of servers running dual 100GbE: https://www.youtube.com/watch?v=A4L5xEXXlas

Not working on anything like that myself, but if the direction going forward it to stream not just 4k TV, but also 4k video games (console in the cloud), you will need some healthy backbones (even if they still run only IPv4 in 5 years!)

5G base stations cite 50 Gbps bandwidth, connect a bunch of these together in an urban area and you might want 400G for their uplink/backbone/whatever it's called.