Re: [bess] [Idr] draft-ietf-bess-evpn-overlay vs. draft-ietf-idr-tunnel-encaps

["Rabadan, Jorge (Nokia - US)" <[e-mail]>]

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  
>
>