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

Hi Tony,

On Mon, Nov 18, 2019 at 9:51 PM Antoni Przygienda
<prz=40juniper.net@dmarc.ietf.org> wrote:
>
> Finally getting to fire off some comments on draft-ietf-bier-ipv6-requirements draft

MM: Yay! thank you, happy we are getting some feedback.

> 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.

MM: Unless my co-authors, or anyone else, disagrees, I say we simply
remove this section and any and all references to SRv6 if it's not
helpful. Focus should be on IPv6 related requirements.

> 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.

MM: You completely disagree with requirement 4.2? You believe that the
solution _should_ require hop-by-hop modification of the IP source
address field? Or just disagree with our explanation of it? This
requirement came from Eric Rosen long ago. Please suggest new
requirement wording that makes you happy.

> 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

MM: So the requirement "should not require the BFRs to inspect layer 4
or require any changes to layer 4." is fine but you don't like the
fragmentation wording? Or do you not like the requirement period? We
can certainly re-word it or remove it if it causes heartache. Again
this was another Rosen requirement I believe. Fragmentation is
optional for BIER, but, from an IPv6 point of view, it is a basic
capability and we figured we should support it. Maybe we don't but
let's get the requirement down.

> 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

MM: Consider SRv6 gone from this draft since having it in there is
causing pain.

> 4.11: and again BIER is hop-by-hop and it will rely on higher layers to re-assemble just like MPLS does.

MM: and again IPv6 does provide the fragmentation/assembly capability,
so we figured BIER should inherit such capability but we could
certainly be wrong. Are you in favor then of removing the 4.11
requirement involving fragmentation? Or re-wording it?

> 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

MM: This isn't a solutions document so whether it's a good idea or not
can be saved for that document to justify. We will move the solutions
overviews to an appendix.

> 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.

MM: Which requirement are you referring to? Perhaps you are referring
to requirement 4.3 involving L4 Inspection where we mention IPsec? We
figured the IPSEC architecture should be inherited from IPv6 if we are
considering BIER in IPv6 but it looks like you don't agree. We are
happy to modify/add/remove any requirement just needs specifics.

thanks,
mike

>
>
> --- tony
>
>
>
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