Re: [bess] draft-ietf-bess-evpn-overlay / section 5.1.3 vs. section 9 (was Re: [Idr] draft-ietf-bess-evpn-overlay vs. draft-ietf-idr-tunnel-encaps)

[John E Drake <[e-mail]>]

Thomas,

Comments inline.

Yours Irrespectively,

John

> -----Original Message-----
> From: Thomas Morin [mailto:[e-mail]]
> Sent: Wednesday, June 15, 2016 8:47 AM
> To: John E Drake; Rabadan, Jorge (Nokia - US); BESS; draft-ietf-bess-evpn-
> [e-mail]; Ali Sajassi (sajassi)
> Subject: draft-ietf-bess-evpn-overlay / section 5.1.3 vs. section 9 (was Re: [Idr] draft-ietf-
> bess-evpn-overlay vs. draft-ietf-idr-tunnel-encaps)
> 
> Hi John, Ali,
> 
> Through the discussion below it appeared that section 9 and section
> 5.1.3 needed adjustments to be brought in sync, and indeed there were some changes in
> last revision.
> 
> However, I don't think the cleanup/precision is complete yet:
> - section 5.1.3 says "the MPLS label field in the [...] Inclusive Multicast Ethernet Tag routes is
> used to carry the VNI" although the "Inclusive Multicast Ethernet Tag Route" has no "MPLS
> label field"
> - (directly related to the above) none of these section talks about using the MPLS field of
> the PMSI Tunnel Attribute as the VNI, although the discussion below concluded that it is
> what implementations actually do


[JD] Accordingly, and specifically to support the option of locally assigned VNIs, the MPLS label1 field in the MAC Advertisement route, the MPLS label field in the Ethernet AD per EVI route, and the MPLS label field in the PMSI Tunnel Attribute of the Inclusive Multicast Ethernet Tag route are used to carry the VNI.


> - also, section 9 now says "The Ethernet Tag field of this route is set as described in section
> 5.1.3.", but I find this sentence useless and redundant (precisely because 5.1.3 already says
> it and nothing would indicate that section 9 would be exempt of what 5.1.3 says)


[JD]  We should strike the sentence.  


> 
> Additionally, it occurred to me that "the MPLS field" is not, strictly speaking, unambiguous
> for MAC Advertisement routes, because the route actually has two MPLS fields.  The text
> should just say "MPLS Label1 field" for the MAC/IP advertisement route.


[JD]  See above.
 

> 
> Best,
> 
> -Thomas
> 
> 
> 2016-05-04, John E Drake:
> > Jorge,
> >
> > We put the VNI value in the MPLS label field of the PMSI attribute for all service types,
> and we put a value in the Ethernet Tag field following the rules for each service type as
> described in 5.1.3 (https://tools.ietf.org/html/draft-ietf-bess-evpn-overlay-02#section-
> 5.1.3).
> >
> > You're right that we need to clean up section 9.
> >
> > Yours Irrespectively,
> >
> > John
> >
> >> -----Original Message-----
> >> From: Rabadan, Jorge (Nokia - US) [mailto:[e-mail]]
> >> Sent: Wednesday, May 04, 2016 3:53 PM
> >> To: John E Drake; EXT - [e-mail]; BESS; IDR;
> >> draft-ietf-bess-evpn- [e-mail]; Ali Sajassi (sajassi)
> >> Subject: Re: [Idr] draft-ietf-bess-evpn-overlay vs.
> >> draft-ietf-idr-tunnel-encaps
> >>
> >> Hi John,
> >>
> >> About this:
> >>
> >> [JD] For the IMET route the MPLS label field is carried in the PMSI
> >> attribute. I think we need to ask everyone whether they used the
> >> Ethernet Tag or the PMSI attribute to carry the VNI
> >>
> >>
> >> In case it helps, I’ve seen a few implementations running and they
> >> all encode the VNI in the MPLS label field in the PTA. And a couple
> >> of them, encode the VNI in the ethernet-tag, in addition to the MPLS
> >> label in the PTA. In any case, I think section 9 contradicts section 5.1.3 and should be
> clarified.
> >>
> >> "5.1.3 Constructing EVPN BGP Routes
> >> <snip>
> >> the MPLS label field in the MAC Advertisement, Ethernet AD per EVI,
> >> and **Inclusive Multicast Ethernet Tag** routes is used to carry the VNI or VSID."
> >>
> >> Thanks.
> >> Jorge
> >>
> >>
> >>
> >>
> >>
> >> On 5/4/16, 8:34 PM, "EXT John E Drake" <[e-mail]> wrote:
> >>
> >>> Thomas and Jorge,
> >>>
> >>> Snipped, comments inline.
> >>>
> >>> Yours Irrespectively,
> >>>
> >>> John
> >>>
> >>>>>
> >>>>> draft-ietf-bess-evpn-overlay (see section 9) relies on the BGP
> >>>>> Encapsulation extended to encode the tunnel encap to use for BUM
> >>>>> traffic, but contrary to other E-VPN routes, relies on the
> >>>>> Ethernet Tag field of the NLRI to encode the VNI/VSID.
> >>>>
> >>>> [JORGE] This is certainly a leftover from an old version where the
> >>>> VNI/VSID was encoded in the ethernet tag for all the routes. The
> >>>> VNI should be encoded in the Label field in all the routes. This has to be corrected.
> >>>>
> >>>> In fact, section 5.1.3 says:
> >>>>
> >>>> 5.1.3 Constructing EVPN BGP Routes
> >>>>
> >>>> <snip>
> >>>>
> >>>> Accordingly, and
> >>>>    specifically to support the option of locally assigned VNIs, the MPLS
> >>>>    label field in the MAC Advertisement, Ethernet AD per EVI, and
> >>>>    Inclusive Multicast Ethernet Tag routes is used to carry the VNI or
> >>>>    VSID.  For the balance of this memo, the MPLS label field will be
> >>>>    referred to as the VNI/VSID field. The VNI/VSID field is used for
> >>>>    both local and global VNIs/VSIDs, and for either case the entire 24-
> >>>>    bit field is used to encode the VNI/VSID value.
> >>>>
> >>>> <snip>
> >>>
> >>>
> >>> [JD]  For the IMET route the MPLS label field is carried in the PMSI
> >>> attribute.  I think we
> >> need to ask everyone whether they
> >>> used the Ethernet Tag or the PMSI attribute to carry the VNI
> >>>
> >>>
> >>>>>>
> >>>>>> There are minor things that could be improved in
> >>>>>> draft-ietf-bess-evpn-overlay wrt. consistency with
> >>>>>> draft-ietf-idr-tunnel-encaps :
> >>>>>>
> >>>>>> * since draft-ietf-idr-tunnel-encaps will deprecate RFC5512, it
> >>>>>> would be better that draft-ietf-bess-evpn-overlay refers to
> >>>>>> draft-ietf-idr-tunnel-encaps and not anymore to RFC5512.
> >>>>
> >>>> [JORGE] I agree, as long as draft-ietf-idr-tunnel-encaps keeps the
> >>>> encapsulation extended community. There are a few implementations
> >>>> using this community and it is enough when only the encapsulation type is needed.
> >>>
> >>>
> >>> [JD]   I agree and the tunnel encaps draft does keep the EC
> >>>
> >>>
> >>>>
> >>>>>>
> >>>>>> * I think it would be better to avoid the explicit list of encap
> >>>>>> types in section 5.1.3, and rather refer to
> >>>>>> draft-ietf-idr-tunnel-encaps instead
> >>>>
> >>>> [JORGE] I agree.
> >>>
> >>>
> >>> [JD]  According to IANA, it allocated the five tunnels types to the
> >>> overlay draft so I think we need to keep them
> >>>
> >>>
> >>>>
> >>>>>> * the following minor modification was proposed, but not yet incorporated:
> >>>>>>
> >>>>>>     John Drake, 2015-11-13 (to BESS ML):
> >>>>>>>     For the overlay draft, replace this text in section 5.1.3:
> >>>>>>>
> >>>>>>>     "If the BGP Encapsulation extended community is not present,
> >>>>>>> then the default MPLS encapsulation or a statically configured
> >>>>>>> encapsulation is assumed."
> >>>>>>>
> >>>>>>>     With the following:
> >>>>>>>
> >>>>>>>     "Note that the MPLS encapsulation tunnel type is needed in
> >>>>>>> order to distinguish between an advertising node that only
> >>>>>>> supports non-MPLS encapsulations and one that supports MPLS and
> >>>>>>> non-MPLS encapsulations.  An  advertising node that only
> >>>>>>> supports MPLS encapsulation does not need to advertise any
> >>>>>>> encapsulation tunnel types;  i.e.,  if the BGP Encapsulation
> >>>>>>> extended community is not present, then either MPLS
> >>>>>>> encapsulation or a statically configured encapsulation is assumed."
> >>>>>>
> >>>>>> I think this change is useful and should be incorporated,
> >>>>>> although skipping the last sentence would be wise if the full
> >>>>>> list of tunnel types is removed.
> >>>
> >>>
> >>> [JD]  Fine with me either w/ or w/o the last sentence
> >>>
> >>>