Re: [bess] WG Last Call on draft-ietf-bess-evpn-etree

"Ali Sajassi (sajassi)" <> Mon, 01 February 2016 07:03 UTC

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From: "Ali Sajassi (sajassi)" <>
To: "Jeffrey (Zhaohui) Zhang" <>, "EXT -" <>, BESS <>, "" <>
Thread-Topic: [bess] WG Last Call on draft-ietf-bess-evpn-etree
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Date: Mon, 1 Feb 2016 07:03:36 +0000
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Subject: Re: [bess] WG Last Call on draft-ietf-bess-evpn-etree
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Hi Jeffrey,

Thanks for the review. Your comments helps tighten the draft some more. I
have updated the draft and will publish it next (rev04). Majority of the
comments were editorial in nature for better clarifications. Since the
existing draft (rev03) reflects the consensus regarding our several rounds
of discussions where we have taken care of the technical items, it is
consistent with our expectation of not seeing any major issue during the
LC. Please refer to my replies in line.


On 1/27/16, 5:26 PM, "BESS on behalf of Jeffrey (Zhaohui) Zhang"
< on behalf of>; wrote:

>I was involved in relevant discussions, and have reviewed once more for
>this LC.
>I support the publication, but with the following questions/comments.
>2.1 Scenario 1: Leaf OR Root site(s) per PE
>   ... If the number of EVIs is very large
>   (e.g., more than 32K or 64K), then RT type 0 as defined in [RFC4360]
>   SHOULD be used; otherwise, RT type 2 is sufficient.
>RFC 7153 should be referenced for "Type 2".


>Additionally, why is 32K mentioned? I can understand the 64k part.

Removed 32K since the example is clear enough with 64K

>   ... the MPLS-encapsulated frames MUST be tagged with an
>   indication of whether they originated from a Leaf AC or not.
>Perhaps change the last line to "indication if they originated from a
>Leaf AC"? Packets from a root AC are not tagged with a leaf indication.

OK. Better yet. It should say ³indication when they originated from a leaf

>   Other mechanisms for identifying whether an egress AC is a root or
>   leaf is beyond the scope of this document.
>Should "egress" be "ingress" in the above paragraph? Or simply removed?

Nice catch! It is ³ingress². It is now corrected.

>   ... This Leaf MPLS label is advertised to other PE devices,
>   using a new EVPN Extended Community called E-TREE Extended Community
>   (section 5.1) along with an Ethernet A-D per ES route with ESI of
>   zero and a set of Route Targets (RTs) corresponding to all the leaf
>   ACs on the PE.
>Perhaps change the last sentence to "... corresponding to all EVIs that
>have leaf sites on the PE."

The second to last sentence of section 3.2.1 says the same thing. I
changed this sentence and removed the 2nd to last sentence.

>3.2.3 BUM traffic originated from a multi-homed site on a leaf AC
>   In this scenario, it is assumed that a multi-homed Ethernet Segment
>   (ES) can have a mixed of both leaf and root ACs with each AC
>   designating a subnet (e.g., a VLAN).
>I understand that different VLANs on the same ES could be roots or
>leaves. I suppose it's more important to say that for the same vlan,
>different PEs on the same ES must have the same root/leaf designation.

That¹s given.

>Perhaps the first sentence could be reworded as the following to capture
>the above point:
>   While different ACs (VLANs) on the same ES could have different
>   root/leaf designation (some being roots and some being leaves),
>   the same VLAN does have the same root/leaf designation on all
>   PEs on the same ES.

That¹s fine. It makes it more clear.

>For the following:
>   ... the PEs with Leaf sites perform MAC learning in the
>   data-path over their Ethernet Segments, and advertise reachability in
>   EVPN MAC Advertisement routes which are imported only by PEs with at
>   least one Root site in the EVI. A PE with only Leaf sites will not
>   import these routes. PEs with Root and/or Leaf sites may use the
>   Ethernet A-D routes for aliasing (in the case of multi-homed
>   segments) and for mass MAC withdrawal per [RFC 7432].
>The above seems to contradict with the recommendation in Section 2.2. If
>the context is the scenario described in section 2.1 then that's fine,
>but the text does not have a clear context.

Agreed. Updated the section to indicate the context is section 2.1.

>3.3.2 E-Tree without MAC Learning
>   The PEs implementing an E-Tree service need not perform MAC learning
>   when the traffic flows between Root and Leaf sites are multicast or
>   broadcast.
>I suppose an "only" word should be added at the end of the above sentence.


>   The fields of the IMET route are populated per the procedures defined
>   in [RFC7432], and the route import rules are as described in previous
>   sections.
>The route import rules described in previous sections are for MAC routes,
>not IMET routes. Additionally, those rules may not be recommended, so
>might as well delete the last sentence.

Changed the last sentence to ³Š, and the multicast tunnel setup criteria
are as described in the previous section.²

>Section 3.3.1 talks about BUM procedures. That is not specific to 3.3.1
>though. Perhaps extract that out to a separate section, and remove the
>BUM text from 3.3.2 as well.

I think it is OK.

>   The E-TREE Extended Community is encoded as an 8-octet value as
>   follows:
>        0                   1                   2                   3
>        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
>       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>       | Type=0x06     | Sub-Type=0x04 | Flags(1 Octet)|               |
>       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>       |  Reserved=0   |           Leaf Label                          |
>       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>I assume the octect after the flags octet is also reserved=0. Better mark
>it as "Reserved=0".


>When it is used with Ethernet A-D per ES route, the leaf flag SHOULD be
>set to 0 but ignored by the receiving routers. Therefore, why not set it
>to 1 to be consistent the MAC/IP route case?

Because the flag is used for known unicast traffic and Leaf label for BUM
traffic. We don¹t want to mix the two.


>> -----Original Message-----
>> From: BESS [] On Behalf Of Thomas Morin
>> Sent: Tuesday, January 19, 2016 3:51 AM
>> To: BESS <>;;
>> Subject: [bess] WG Last Call on draft-ietf-bess-evpn-etree
>> Hello Working Group,
>> This email starts a Working Group Last Call on
>> draft-ietf-bess-evpn-etree [1] which is considered mature and ready for
>> a final working group review.
>> Please read the document if you haven't read the most recent version yet
>> (-03), and send your comments to the list, no later than *February the
>> 2nd* (2016-02-02).
>> This is not only a call for comments on the document, but also a call of
>> support for its publication.
>> *Coincidentally*, we are also polling for knowledge of any IPR that
>> applies to draft-ietf-bess-evpn-etree, to ensure that IPR has been
>> disclosed in compliance with IETF IPR rules (see RFCs 3979, 4879, 3669
>> and 5378 for more details).
>> *If* you are listed as a document author or contributor of
>> draft-ietf-bess-evpn-etree please respond to this email and indicate
>> whether or not you are aware of any relevant IPR.
>> Thank you,
>> Thomas/Martin
>> [1]
>> _______________________________________________
>> BESS mailing list
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