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Comment by fideloper | Hacker News Reader

So...we're all upvoting this hoping someone else understands networking at this level, right? And that maybe they'll do something awesome with it.

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I probably couldn't improve the actual code myself, but I do understand what is being talked about conceptually. I enjoyed the article and learned a bit from it, thus I upvoted.

I understood this article and it is relevant to my interests since 25G NICs are coming this year.

source? I thought the next step was 40G?

http://25gethernet.org/

40G has been out for a few years but it's fairly expensive since it uses four lanes. 25G will be the best option if you need something faster than 10G IMO.

To expand on that: On a switch chip today, like the common Trident 2, you have 10 and 40 gig interfaces. The 40 gig are just four lanes bonded together (10 being one). These 25 gig products runs each lane at 25G instead of 10, so you get a 25G port in the same density you used to have 10, 50G at double the density of 40, and 100gbit/s at the old 40 gig density.

I think this is largely being driven by the server folk, who want to connect at 25G instead of 10.

There was an attempt to do that with 2.5G, but it has been relegated to backplanes and was never formally standardised.

The atom server boards released last year actually have 4x 2.5g lanes. As far as ive seen everyone just uses 4x 1g serdes on them instead of the hybrid 10.

And to expand on that slightly, it is not just about density, but also latency. Since 40G is clocked the same as 10G (as it is 4x 10G lanes), upgrading from 10G infrastructure to 40G will not improve overall latency Whereas 25G is clocked faster and will have lower overall latency. [Overall meaning the first packet won't arrive relatively sooner, but the second one will.]

There may be latency improvements inherent from design improvements within newer packet processing / switching ASICs themselves, just like Intel's tick/tock. For example, NASDAQ offers a 10G handoff to their 40G infrastructure which is 5-9us faster because of topology and equipment upgrades [1].

The nice thing about 40G is that it is compatible with 10G so you can selectively upgrade your switches to 40G but keep your 10G NICs, using these neato QSFP+->SFP+ breakout cables [2].

[1] http://www.nasdaqtrader.com/content/Productsservices/trading...

[2] https://www.google.com/search?q=qsfp+breakout&tbm=isch

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