Re: [Coin] Fwd: The Future of P4, Revisited

[Haoyu Song <[e-mail]>]

Interesting discussion. See my comments below  [HS]

Haoyu

> For example, in the multicast drafts i write, we use C-pseudocode
> to specify behavior, but we do attempt to implemnt on Tofino in P4. Should we really
> use P4 code for the RFC specs... ? (much longer than C Pseudocode). Aka: quite selfish
> (but IETF relevant ;-) reason to highlight this point.

[EH]: This is an area I'm very interested in. Having a standardized and formal language to describe protocols and behavior can bring a lot of functionality and benefits to the IETF. 
My initial thinking is that having such a blueprint, the IETF could generate tools to create a reference implementation that can be used for interoperability purposes therefore decreasing time to test and implement protocols and therefore RFC publications.

[HS] P4 can only describe dataplane behaviors, so any control plane stuff is out of scope. For dataplane, if it's used to describe header format, it's not better than the "struct" in C. The language uses the match-action table abstraction with an implication of pipeline implementation which may make it cumbersome or even impossible to describe the  behavior (e.g.,  P4 has very limited support for stateful processing). In general, I don't think P4 at its current form can undertake the role for formal protocol specification.