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
- 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)
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.
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:[email protected]]
Sent: Wednesday, May 04, 2016 3:53 PM
To: John E Drake; EXT - [email protected]; BESS; IDR;
draft-ietf-bess-evpn-
[email protected]; 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" <[email protected]> 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
_______________________________________________
BESS mailing list
[email protected]
https://www.ietf.org/mailman/listinfo/bess
