Re: [bess] Eric Rescorla's Discuss on draft-ietf-bess-evpn-etree-13: (with DISCUSS)

"Ali Sajassi (sajassi)" <> Thu, 09 November 2017 21:42 UTC

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From: "Ali Sajassi (sajassi)" <>
To: "Ali Sajassi (sajassi)" <>, Eric Rescorla <>, The IESG <>, Alvaro Retana <>
CC: "" <>, "" <>, "" <>, "" <>
Thread-Topic: Eric Rescorla's Discuss on draft-ietf-bess-evpn-etree-13: (with DISCUSS)
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Subject: Re: [bess] Eric Rescorla's Discuss on draft-ietf-bess-evpn-etree-13: (with DISCUSS)
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Hi Eric,

Let me know if you have any further questions/comments.


From: Cisco Employee <<>>
Date: Friday, October 27, 2017 at 10:06 AM
To: "Alvaro Retana (aretana)" <<>>, Eric Rescorla <<>>, The IESG <<>>
Cc: "<>" <<>>, "<>" <<>>, "<>" <<>>, "<>" <<>>
Subject: Re: Eric Rescorla's Discuss on draft-ietf-bess-evpn-etree-13: (with DISCUSS)
Resent-From: <<>>
Resent-To: Cisco Employee <<>>, <<>>, <<>>, <<>>, <<>>, <<>>
Resent-Date: Friday, October 27, 2017 at 10:06 AM

Hi Eric,

The "leaf" or "root" designation of an Attachment Circuit (AC) is done by the operator / service provider on the PE device (and not on a CE). So, CE device has no control in changing a "leaf" designation to a "root". I added "the network operator / service provider" to the text. Furthermore, I added additional text to address your second concern (e.g., regarding how to avoid any exchange among leaf ACs):

"Furthermore, this document provides additional security check by allowing sites (or ACs) of an EVPN instance to be designated as "Root" or "Leaf" by the network operator/ service provider and thus preventing any traffic exchange among "Leaf" sites of that VPN through ingress filtering for known unicast traffic and egress filtering for BUM traffic. Since by default and for the purpose of backward compatibility, an AC that doesn't have a leaf designation is considered as a root AC, in order to avoid any  traffic exchange among leaf ACs, the operator SHOULD configure the AC with a proper role (leaf or root) before activating the AC."


From: "Alvaro Retana (aretana)" <<>>
Date: Tuesday, September 26, 2017 at 6:03 AM
To: Eric Rescorla <<>>, The IESG <<>>
Cc: "<>" <<>>, "<>" <<>>, "<>" <<>>, "<>" <<>>
Subject: Re: Eric Rescorla's Discuss on draft-ietf-bess-evpn-etree-13: (with DISCUSS)
Resent-From: <<>>
Resent-To: Cisco Employee <<>>, <<>>, <<>>, <<>>, <<>>, <<>>
Resent-Date: Tuesday, September 26, 2017 at 6:03 AM


I don't have anything in my archive either. :-(

I just poked the authors...


On 9/26/17, 5:59 AM, "Eric Rescorla" <<>> wrote:

I have some memory that someone responded that this wasn't a security requirement, but I can't find that now.


On Sat, Sep 9, 2017 at 11:35 AM, Eric Rescorla <<>> wrote:
Eric Rescorla has entered the following ballot position for
draft-ietf-bess-evpn-etree-13: Discuss

When responding, please keep the subject line intact and reply to all
email addresses included in the To and CC lines. (Feel free to cut this
introductory paragraph, however.)

Please refer to
for more information about IESG DISCUSS and COMMENT positions.

The document, along with other ballot positions, can be found here:


It's not clear to me if the prohibition on leaf-to-leaf communications is
intended to be a security requirement. If so, it seems like it needs to
explicitly state why it is not possible for ACs which are leaf to pretend to be
root. If not, then it should say so. Additionally, this solution appears to
rely very heavily on filtering, so I believe some text about what happens
during periods of filtering inconsistency (and what the impact on the security