Re: [Bier] BIER in IPv6 --- draft-zhang-bier-bierin6-04

On Thu, Mar 26, 2020 at 12:05:30PM -0700, Tony Przygienda wrote:
> On Thu, Mar 26, 2020 at 11:44 AM Toerless Eckert <tte@cs.fau.de> wrote:
> 
> > On Thu, Mar 26, 2020 at 09:11:16AM -0700, Tony Przygienda wrote:
> > > Yes, critical point. We are _not_ "tunneling" in case of LL to LL BIERin6
> > > in fact for all practical purposes (tunnel assumes fragmentation/security
> > > etc which BIER architecture does NOT presume from L2 header, we do not
> > > expect Ethernet to fragment or encrypt BIER).
> >
> > When you say "We" your hat is that of a co-author ?
> >
> >
> yepp, co-author of the original bierin6 draft obviously ...
> 
> Asking in wider scope: while reading the rest of your email: are you
> implying that BIER WG should be in the busines of, as a previous
> commentator put it, inventing yet another L3-routed source-specific
> multicast tunneling technology?

Until i know what you're trying to imply with the word tunneling, i
have to guess ... lets simply talk about the properties we
want/do-not-want.

The BIER architecture RFC very nicely points to the fact how BIER 
can automatically determine remote neighbors to hop over non-BIER
enabled routers. Benefit of relying on the IGP. I think it would
nice if this can be leveraged in our IPv6 solution, but it only
makes sense if we can reasonably expect that a good amount of
devices can do this in the "fast-path" like hop-by-hop. I think
thats possible with both drafts.

I am not persuased that link-local encap+decap on every hop is
faster in HW data-plane than rewriting IPv6 header elements. I
have seem many forwarding planes where encap/decap would cause
recycling.

Functionally, the main difference between the drafts IMHO is that Xie's draft
uses the IPv6 header to carry VPN info, whereas i do not understand
how we would do this in Sandy's draft.

Cheers
    Toerless

> -- tony

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