Re: [Bier] BIER v6 requirements draft comments: draft-ietf-bier-ipv6-requirements ...

[Robert Raszuk <[e-mail]>]

All,

I would tend to agree with Tony here. BIER is designed to construct optimal
replication trees with minimal state.

While there may be devices which do not support BIER IMHO the
right approach would be to use IGP forwarding adjaciencies across such
devices leaving BIER with no change and no such deep nesting like proposed
in this document. L2.5 can happily go over L2 :)

So what may be needed is to claim support for BIER over FAs + perhaps
define SR segments to be advertised as FAs in SPRING keeping both BIER and
its transport detached.

Best,
R.


wt., 19 lis 2019 o 06:51 Antoni Przygienda <prz=[e-mail]>
napisał(a):

> Finally getting to fire off some comments on
> draft-ietf-bier-ipv6-requirements draft
>
>
>
> 3.4: I see NO requirements to do anything with SR or SRv6 in BIER WG
> charter so I am not sure how it ended up so prominently in the draft. And
> BIER is a hop-by-hop technology, it already includes provisions to
> transition non-BIER nodes via correct algorithms so not sure how SRv6 is of
> any use or relevance here. Of course BIER could be tunneled with SRv6 but
> then a BIER frame should be carried natively inside a SRv6 frame.  Comingling
> two level layer 2.5 transport technologies into a single layer format as
> the draft seems to imply is unnecessary and a bad idea since there will be
> resulting cross-talk.
>
> 4.2: completely disagreed. BIER is a hop-by-hop layer 2.5 technology.
> Modifying IP options is arguably far more expensive than next-protocol
> frame.
>
> 4.3:
>
>    - fragmentation will only play in IPv6 case if the frame is longer
>       than IPv6 max frame size - BML roughly. No matter _where_ we stick the mask
>       we face the same problem until we start to do BIER fragmentation and
>       reassembly
>       - Again, SRv6 is neither in the charter nor an issue since BIER is
>       a L2.5 hop-by-hop technology and not, as the authors want it, all of a
>       sudden an implicit tunneling or multi-hop technology
>
> 4.11: and again BIER is hop-by-hop and it will rely on higher layers to
> re-assemble just like MPLS does.
>
> I-D.xie-bier-ipv6-encapsulatio: yes, IPv6 architecture has the loophole
> for in flight modification of hop-by-hop header options but it does not
> mean it’s a good idea
>
>
>
> Last, major objection is that by opening any IPv6 destination address to
> receive BIER frames from multiple hops away we are opening a completely
> security nightmare and argumenting that whole BIER layer has to be IPSEC’ed
> to close that hole is simply going into a seriously wrong direction IMO.
>
>
>
> --- tony
>
>
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