[ovs-dev] [RFC PATCH v2 00/13] Add Network Service Header Support

[Jiri Benc]

On Wed, 13 Jul 2016 07:35:59 -0700, Jesse Gross wrote:
> I think history tells us how this will end - similar to IPv4 options,
> implementations that don't implement TLVs will become deployed and
> then when there is a use for them it's no longer possible. Since I
> don't want OVS to have a half implementation or contribute to this
> issue, I'd like to see the whole protocol implemented before I apply
> anything.

I see a big difference between this and IPv4. While in IPv4, the
options are extension to existing headers, here we're talking about a
completely different payload. It's more comparable to http vs. ftp (of
course, it's a poor comparison, but I hope it illustrates at least a
bit what I mean).

If NSH takes off (and it's a big "if" in my opinion), it's also well
possible we'll see more metadata types. The spec is pretty much open to
this. Obviously, the authors are aware of that and type 2 is optional.
As I guess will be type 3 and type 4 and whatever.

It's pretty much inevitable that applications and deployments built
around MD type 1 won't support MD type 2. And vice versa. This is
regardless whether ovs supports MD type 2 or not. They're just a
different protocol.

In my opinion, starting with MD type 1 is a good way to reduce the
initial scope. I see no problem with adding MD type 2 later.

 Jiri