High Touch / Low Touch
High touch means very general purpose NPU, with off-chip memory. Low touch means usually ASIC or otherwise simplified pipeline and on-chip memory. Granted Jericho can support off-chip memory too.
L3 switches are canonical example of low touch. EZchip, Trio, Solar, FP3 etc are examples of canonical high touch NPUs. What low touch can do, it can do fast and economically.
Your analogy makes some sense, but what you classify as high-touch / low-touch is just one dimension and could do with a more modern update. I'd suggest a more modern analogy would be that historically the difference between a L3 switch and a router is the former has a fixed processing pipeline, limited buffering (most are just on-chip buffer) and limited table sizes. But more modern packet processors with fixed pipelines often have blocks or sections that are programmable or flexible. e.g. with a flexible packet parser, its possible to support new overlay or tunnel mechanisms, flexible key generation makes it possible to reuse different table resources in different ways, flexible rewrite engine means egress encap or tunnels or logic can be done. There's also often more capacity for recirc or additional stages as required. Specific to Jericho, the underlying silicon has all these characteristics. We [*] used the flexibility in all of the stages both now and in previous iterations (Arad) to add new features/functionality that wasn't natively there to start with. And it uses a combination of on-chip & off-chip buffering with VoQ Its also not only Arista that call it a router cisco do too (NCS5K5). Sure, using a NPU for packet processing essentially provided a 100% programmable packet forwarding pipeline, and maybe even a "run to completion" kind of packet pipeline where the pipeline could have a long tail of processing. However, engineering is a zero sum game, and to do that means you sacrifice power or density, or most often, both. I agree the lines have been blurred as to the characteristics, and we'd openly state that its not going to be useful in every use case of where a router is deployed, but for specific use cases, it fits the bill and has compelling density, performance and cost dynamics. To the OPs question, there are people running with this in EFT and others in production. My suggestion would be that if you think its of interest, reach out to your friendly Arista person [*] and try it out or talk through what it is you're after. We are generally a friendly bunch and often we can be quite creative in enabling things in different ways to old.
Yeah they are certainly much behind in features, but if you don't need those features, it's probably actually an advantage. For my use-cases Arista's MPLS stack is not there.
We've historically had the data-plane but not the control-plane. Thats a work in progress. Again, often there are creative solutions to ways of doing things that aren't necessarily the same as old ways but achieve the same end result. cheers, lincoln. [*] disclosure: i work on said products described ltd@arista.com.