400G forwarding - how does it work?

Saku Ytti saku at ytti.fi
Wed Jul 27 06:10:56 UTC 2022

On Tue, 26 Jul 2022 at 23:15, Jeff Tantsura <jefftant.ietf at gmail.com> wrote:

> In general, if we look at the whole spectrum, on one side there’re massively parallelized “many core” RTC ASICs, such as Trio, Lightspeed, and similar (as the last gasp of Redback/Ericsson venture - we have built 1400 HW threads ASIC (Spider).
> On another side of the spectrum - fixed pipeline ASICs, from BCM Tomahawk at its extreme (max speed/radix - min features) moving with BCM Trident, Innovium, Barefoot(quite different animal wrt programmability), etc - usually shallow on chip buffer only (100-200M).
> In between we have got so called programmable pipeline silicon, BCM DNX and Juniper Express are in this category, usually a combo of OCB + off chip memory (most often HBM), (2-6G), usually have line-rate/high scale security/overlay encap/decap capabilities. Usually have highly optimized RTC blocks within a pipeline (RTC within macro). The way and speed to access DBs, memories is evolving with each generation, number/speed of non networking cores(usually ARM)  keeps growing - OAM, INT, local optimizations are primary users of it.

What do we call Nokia FP? Where you have a pipeline of identical cores
doing different things, and the packet has to hit each core in line in
order? How do we contrast this to NPU where a given packet hits
exactly one core?

I think ASIC, NPU, pipeline, RTC are all quite ambiguous. When we say
pipeline, usually people assume a purpose build unique HW blocks
packet travels through (like DNX, Express) and not fully flexible
identical cores pipeline like FP.

So I guess I would consider 'true pipeline', pipeline of unique HW
blocks and 'true NPU' where a given packet hits exactly 1 core. And
anything else as more or less hybrid.

I expect once you get to the details of implementation all of these
generalisations use communicative power.


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