Re: [babel] About BIER in Babel

Hello Alia and Dave,

> Le 28 mars 2017 à 18:06, Alia Atlas <akatlas@gmail.com> a écrit :
> 
> Hi Dave,
> 
> Take a look at https://datatracker.ietf.org/doc/html/draft-ietf-bier-architecture <https://datatracker.ietf.org/doc/html/draft-ietf-bier-architecture>
> and https://datatracker.ietf.org/doc/html/draft-ietf-bier-mpls-encapsulation <https://datatracker.ietf.org/doc/html/draft-ietf-bier-mpls-encapsulation>.
> The latter allows use over Ethernet (despite the old draft title).  The IPv6 encapsulation does not have WG agreement to adopt and wasn't discussed this IETF.

It was not discussed this IETF indeed, but was discussed the ietf before, and very extensively during the design team meeting. I wouldn't dare contradicting the responsible AD, but although we can objectively say that the document hasn't been adopted (he has been presented only once), saying that it has no "WG agreement" is more prone to discussion. I would be happy to see more discussion on BIER ML about that.

Anyway... More interesting information for Dave inlined ...

> 
> Regards,
> Alia
> 
> On Tue, Mar 28, 2017 at 5:48 PM, Dave Taht <dave.taht@gmail.com <mailto:dave.taht@gmail.com>> wrote:
> ... up until this moment I was mostly ignorant of bier. I may well
> still be overly ignorant, but read on.
> 
> On Tue, Mar 28, 2017 at 1:47 PM, Juliusz Chroboczek <jch@irif.fr <mailto:jch@irif.fr>> wrote:
> > Dear Sandy, dear all,
> >
> > I think there are very good reasons why it would be interesting to
> > experiment with BIER and Babel.  As you explained, there are at least two
> > approaches worth considering:
> >
> >   - announce BIER routing directly in Babel, as your draft suggests;
> >   - use MLD with Babel.
> >
> > I am not competent to judge which approach is suitable, but it is clearly
> > attractive to run a single protocol.
> >
> > As I mentioned at the mike, there are a number of problems with your
> > encoding.  My personal intuition would be to use a new AE number for BIER,
> > but of course someone would need to write it down and check the details.
> 
> However, leveraging this encoding over the others in the core draft seems
> straightforward to encapsulate into an ae with no afteraffects
> elsewhere in babel.
> 
> https://datatracker.ietf.org/doc/html/draft-pfister-bier-over-ipv6 <https://datatracker.ietf.org/doc/html/draft-pfister-bier-over-ipv6>
> 
> 4096 bits (maximum requirement for bier), on the other hand, breaks
> everything (babel mtu requirement while still fitting in everything
> else),
> 
> while (the minimum requirement) of 256 bits may well look a lot like
> how the new source specific ae is formed.

256 is the minimum requirement for BIER over MPLS and Ethernet.
There was discussion and, IMHO, consensus, that the minimum bit-string length
requirement would depend on the encap used.
Obviously, in the case of bier-over-ipv6, 256 doesn't make sense. 4096 even less so.
Using BIERoIPv6, bitstring lengths between 32 and 64 are more reasonable.

> 
> if there are other docs in that wg worth reading, running code on
> linux, or other use cases, please point me at em!

I implemented a very rudimentary version of BIERoIPv6 a while ago, for testing and learning purposes:
https://github.com/Oryon/bier6 <https://github.com/Oryon/bier6>

But this implementation has nothing to do with Babel, or Zhang's proposal.

Cheers,

- Pierre

> 
> > As David mentioned, some of us would feel much more comfortable if there
> > were a prototype implementation before we are asked to adopt your draft.
> > I would be interested in helping, but I have neither the competence nor
> > the manpower to do the implementation on my own.
> >
> > -- Juliusz
> >
> > _______________________________________________
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> 
> 
> 
> --
> Dave Täht
> Let's go make home routers and wifi faster! With better software!
> http://blog.cerowrt.org <http://blog.cerowrt.org/>
> 
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