Re: [bess] draft-ietf-bess-evpn-overlay-10 PMSI with Ingress Replication

[Martin Vigoureux <[e-mail]>]

if the intent was to help people better understand the reasoning behind 
the design, is it really best to remove it?
Wouldn't a rephrasing be more appropriate?

-m

Le 2017-12-15 à 19:21, Ali Sajassi (sajassi) a écrit :
> Hi Thomas,
> 
> On 12/15/17, 8:42 AM, "BESS on behalf of Thomas Morin" <[e-mail] on behalf of [e-mail]> wrote:
> 
>      
>      Here I would suggest to authors to consider purely removing this
>      paragraph, not because it would be wrong or ambiguous (as said above, I
>      don't think it is), but because as far as I can tell it has never meant
>      to specify anything not already implied by RFC7432, but was here only
>    to help understand.
>    
> OK, I will remove it in the next rev.
>    
> Cheers,
> Ali
>      
>      Best,
>      
>      -Thomas
>      
>      
>      
>      
>      -----Original Message-----
>      > From: John E Drake [mailto:[e-mail]]
>      > Sent: Friday, December 15, 2017 9:52 AM
>      > To: EXT - [e-mail] <[e-mail]>; Fedyk,
>      > Don <[e-mail]>; Marco Marzetti <[e-mail]>
>      > Cc: [e-mail]
>      > Subject: RE: [bess] draft-ietf-bess-evpn-overlay-10 PMSI with Ingress
>      > Replication
>      >
>      > Thomas,
>      >
>      > I completely agree w/ your email, below.
>      >
>      > Yours Irrespectively,
>      >
>      > John
>      >
>      >
>      > > -----Original Message-----
>      > > From: BESS [mailto:[e-mail]] On Behalf Of Thomas Morin
>      > > Sent: Friday, December 15, 2017 5:42 AM
>      > > To: Fedyk, Don <[e-mail]>; Marco Marzetti <marco@lamehost.
>      > > it>
>      > > Cc: [e-mail]
>      > > Subject: Re: [bess] draft-ietf-bess-evpn-overlay-10 PMSI with
>      > > Ingress
>      > > Replication
>      > >
>      > > Hi Don,
>      > >
>      > > Fedyk, Don, 2017-12-14 20:33:
>      > > > I think the gray area is that this draft talks about BUM traffic
>      > > > and
>      > > > ingress replication and then has a section on Multicast tunnels
>      > > > which excludes ingress replication traffic from the tunnels.
>      > >
>      > > No, ingress replication is not excluded at all:
>      > >
>      > >    The following tunnel types as defined in [RFC6514] can be used
>      > > in
>      > >    the PMSI tunnel attribute for VXLAN/NVGRE:
>      > >
>      > >          + 3 - PIM-SSM Tree
>      > >          + 4 - PIM-SM Tree
>      > >          + 5 - BIDIR-PIM Tree
>      > >          + 6 - Ingress Replication
>      > >
>      > > > If you are using point to point VXLAN/NVGRE  tunnels then
>      > > > ingress
>      > > > replication is default [...]
>      > >
>      > > This formulation surprises me: that some implementations behave as
>      > > you
>      > > describe is possibly true (this seems to be the case of the
>      > > implementation that triggered this discussion), but I don't know
>      > > about
>      > > any text in the specs we are discussing that would imply such a
>      > > 'default'.
>      > >
>      > > You might have implementations that in the absence of any local
>      > > configuration for an EVPN instance on which type of tunnel to use
>      > > for
>      > > BUM, will default to ingress replication: this is fine, out of the
>      > > scope of what is specified for interop, and not breaking other
>      > > implementations (as long, of course, that what is chosen locally
>      > > is
>      > > then advertised as expected in a PMSI Tunnel Attribute).
>      > >
>      > >
>      > > > but IMET is being used to identify the NVE IP.    I read RFC7432
>      > > > and
>      > > > RFC6514 in this area and thought that the PMSI attribute MUST be
>      > > > set
>      > > > when there is an Inclusive Multicast Ethernet tag IMET.
>      > >
>      > > Yes!  (the text of RFC7432 quoted by Ali reminds us that)
>      > >
>      > >
>      > > > I can see two possible fixes:
>      > > > -          Specify that the PMSI attribute MUST be set if there
>      > > > is an
>      > > > IMET route and specify correct attribute.
>      > >
>      > > Given the content of RFC7432 and the fact that this is a normative
>      > > ref
>      > > of draft-ietf-bess-evpn-overlay, I think that we don't need to
>      > > repeat
>      > > this MUST in draft-ietf-bess-evpn-overlay.  That is, unless we
>      > > explicitly identify an ambiguous piece of text.
>      > >
>      > > > -          Allow that ingress replication is default when PMSI is
>      > > > absent but accept PMSI that specifies ingress replication.
>      > > >
>      > >
>      > > I don't think we should do that. It would overnight make non-
>      > > compliant
>      > > pre- standard implementation of draft-ietf-bess-evpn-overlay,
>      > > without
>      > > a rationale to do so except coping with an implementation that
>      > > assumed a bit too much.
>      > >
>      > > Best,
>      > >
>      > > -Thomas
>      > >
>      > >
>      > >
>      > > > From: BESS [mailto:[e-mail]] On Behalf Of Marco
>      > > > Marzetti
>      > > > Sent: Thursday, December 14, 2017 9:21 AM
>      > > > To: Thomas Morin <[e-mail]>
>      > > > Cc: [e-mail]
>      > > > Subject: Re: [bess] draft-ietf-bess-evpn-overlay-10 PMSI with
>      > > > Ingress Replication
>      > > >
>      > > > Hello,
>      > > >
>      > > > I have encountered an implementation that is not attaching any
>      > > > PMSI
>      > > > to the IMET.
>      > > > The authors think they don't really need it because they only
>      > > > support Ingress Replication.
>      > > > Such behavior breaks interoperability with other implementations
>      > > > that are dropping the NLRI if PMSI is not attached.
>      > > >
>      > > > So i looked at draft-ietf-bess-evpn-overlay-10 and noticed that
>      > > > there's no clear indication of what the proper behavior is.
>      > > > As said i assumed i had to look at RFC7432 and RFC6514 (and i
>      > > > did
>      > > > it), but i wasn't 100% sure and i preferred to ask.
>      > > >
>      > > > Onestly you already made my day by confirming what i thought.
>      > > > My suggestion was to make things more clear, but i admit that it
>      > > > could look redundant.
>      > > >
>      > > > Thanks
>      > > >
>      > > >
>      > > >
>      > > >
>      > > >
>      > > >
>      > > >
>      > > > On Thu, Dec 14, 2017 at 2:39 PM, Thomas Morin
>      > >
>      > > <[e-mail]
>      > > > m> wrote:
>      > > > > Hi Marco,
>      > > > >
>      > > > > Marco Marzetti, 2017-12-14 12:25:
>      > > > > > I am writing this email asking you to clarify what's the
>      > > > >
>      > > > > suggested
>      > > > > > behavior when PMSI Tunnel Type is set to "Ingress
>      > > > > > Replication"
>      > > > >
>      > > > > (type
>      > > > > > 6) as draft-ietf-bess-evpn-overlay-10 only suggests what to
>      > > > > > do
>      > > > >
>      > > > > with
>      > > > > > multicast tunnel trees.
>      > > > > >
>      > > > > > I think the originating PE should conform with RFC6514 and
>      > > > >
>      > > > > RFC7432
>      > > > > > (from which you've taken inspiration) and always (RFC2119
>      > > > > > MUST)
>      > > > > > attach PMSI Tunnel attribute with the Tunnel Type set to
>      > > > > > Ingress
>      > > > > > Replication and Tunnel Identifier set to a routable address
>      > > > > > of
>      > > > >
>      > > > > the PE
>      > > > > > itself (more specifically NVE's IP address).
>      > > > > >
>      > > > > > Is that correct?
>      > > > > > In that case i suggest to add the following line at the end
>      > > > > > of
>      > > > > > Section 9.
>      > > > > > """
>      > > > > > For Ingress Replication the PE should follow what's stated in
>      > > > >
>      > > > > RFC6514
>      > > > > > Section 5 .
>      > > > > > """
>      > > > >
>      > > > > The text of section 9 lists "Ingress Replication" in the list
>      > > > > of
>      > > > > tunnel types that can be used. My understanding is that, in
>      > > > > the
>      > > > > absence of anything being specifically said for Ingress
>      > > > > Replication, an implementation should follow what is said in
>      > > > > RFC7432 and RFC6514.
>      > > > > (What
>      > > > > other specs could it follow to implement this supported type ?
>      > > > > RFC7432
>      > > > > and RFC6514 are more than an inspiration here, these are specs
>      > > > > that the document refers to explicitly)
>      > > > >
>      > > > > So I'm not sure that it is useful or needed to add text.
>      > > > >
>      > > > > Can you perhaps expand on why the current text would possibly
>      > > > > be
>      > > > > ambiguous, misleading or incomplete...?
>      > > > >
>      > > > > -Thomas
>      > > > >
>      > > >
>      > > >
>      > > >
>      > > > --
>      > > > Marco
>      > >
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