Re: [bess] Opsdir last call review of draft-ietf-bess-evpn-etree-12

"Ali Sajassi (sajassi)" <sajassi@cisco.com> Fri, 18 August 2017 04:48 UTC

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From: "Ali Sajassi (sajassi)" <sajassi@cisco.com>
To: "Carlos Pignataro (cpignata)" <cpignata@cisco.com>
CC: "ops-dir@ietf.org" <ops-dir@ietf.org>, "draft-ietf-bess-evpn-etree.all@ietf.org" <draft-ietf-bess-evpn-etree.all@ietf.org>, "bess@ietf.org" <bess@ietf.org>
Thread-Topic: Opsdir last call review of draft-ietf-bess-evpn-etree-12
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Date: Fri, 18 Aug 2017 04:48:22 +0000
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Subject: Re: [bess] Opsdir last call review of draft-ietf-bess-evpn-etree-12
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Hi Carlos,

Thanks for additional comments. Please refer to my replies inline.

From: "Carlos Pignataro (cpignata)" <cpignata@cisco.com<mailto:cpignata@cisco.com>>
Date: Wednesday, August 16, 2017 at 6:57 PM
To: Cisco Employee <sajassi@cisco.com<mailto:sajassi@cisco.com>>
Cc: "ops-dir@ietf.org<mailto:ops-dir@ietf.org>" <ops-dir@ietf.org<mailto:ops-dir@ietf.org>>, "draft-ietf-bess-evpn-etree.all@ietf.org<mailto:draft-ietf-bess-evpn-etree.all@ietf.org>" <draft-ietf-bess-evpn-etree.all@ietf.org<mailto:draft-ietf-bess-evpn-etree.all@ietf.org>>, "bess@ietf.org<mailto:bess@ietf.org>" <bess@ietf.org<mailto:bess@ietf.org>>
Subject: Re: Opsdir last call review of draft-ietf-bess-evpn-etree-12

Thanks Ali. General Ack to all your responses, make sense.

A follow-up question, though:

I notice “Reserved” in a few places. For example in Figure 4, which seems to make sense as the Reserved is a Must Be Zero (MBZ)

However, on the Flags, it says:

          0 1 2 3 4 5 6 7
         +-+-+-+-+-+-+-+-+
         |  reserved   |L|
         +-+-+-+-+-+-+-+-+

…

 Initial registrations are as follows:

         bit               Name                         Reference

         0-6               Reserved                     This document
         7                 Leaf-Indication              This document

Do you mean “Reserved” for the unassigned bit flags, or “Unassigned” (see the different in RFC 8126).

WRT to IANA, I meant “Unassigned”.  I will update both the flag digram and the IANA section to indicate “unassigned".

Finally, in the sentence:

   The reserved bits should be set to zero by the transmitter and should
   be ignored by the receiver.

Do those two “should” mean “should”, “SHOULD”, or “MUST”?

I will change it to "The reserved and unassigned bits SHOULD be set to zero by the transmitter and SHOULD be ignored by the receiver."

Thanks again,
Ali

Thanks!

Carlos.

On Aug 16, 2017, at 8:54 PM, Ali Sajassi (sajassi) <sajassi@cisco.com<mailto:sajassi@cisco.com>> wrote:


Hi Carlos,

Thanks for your review and comments. Please see inline for my responses.

On 8/7/17, 2:46 PM, "Carlos Pignataro (cpignata)" <cpignata@cisco.com<mailto:cpignata@cisco.com>> wrote:

Reviewer: Carlos Pignataro
Review result: Has Issues

Reviewer: Carlos Pignataro
Review result: Has Nits (and one potential Issue)

I am the OPS-DIR reviewer and in general I do not have operational concerns
with this document.

The main issue I have is in regards to the redefinition of the MSB of the
Tunnel Type, and associated backwards/forward compatibility considerations.

I note that RFC 7385 is Normatively referenced by a number of I-Ds:
https://datatracker.ietf.org/doc/rfc7385/referencedby/
BUT draft-ietf-bess-evpn-etree is not:
https://datatracker.ietf.org/doc/draft-ietf-bess-evpn-etree/referencedby/

So would those former be pointing to old info? And what other Backwards Compat
considerations are there?

To maximize backward/forward compatibility, let's retain the value for "Experimental Use” and “Reserved” as before per [RFC7385] and reduce the range for Composite tunnel for this draft. So, the changes will be
>From existing IANA assignments:
0x0C - 0xFA Unassigned
0xFB - 0xFE Experimental [RFC7385]
0xFF Reserved [RFC7385]
To:
  0x0C – 0x3F Unassigned
  0x80 – 0xBF reserved for composite tunnel
  0xD0 – 0xFA Unassigned
  0xFB - 0xFE Experimental [RFC7385]
  0xFF Reserved [RFC7385]



Further, some nits and editorials for your consideration:

   The Metro Ethernet Forum (MEF) has defined a rooted-multipoint
   Ethernet service known as Ethernet Tree (E-Tree). A solution
   framework for supporting this service in MPLS networks is proposed in
   RFC7387 ("A Framework for Ethernet Tree (E-Tree) Service over a
   Multiprotocol Label Switching (MPLS) Network").

Proposed? Or Described / Defined?
OK, changed to “described"

Same comment for the first sentence of the second paragraph of the Intro.
Changed to “describes"

   This document makes use of the
   most significant bit of the scope governed by the IANA registry
   created by RFC7385, and hence updates RFC7385 accordingly.

RFC 7385 does not mention a "scope". This really talks about the Tunnel Type.
Please reword for unambiguous clarity.

Changed it to “This document makes use of the most significant bit of the PMSI tunnel type governed by the IANA …"

3.1 Known Unicast Traffic

   To support the above ingress filtering functionality, a new E-TREE
   Extended Community with a Leaf indication flag is introduced [section
   5.2]. This new Extended Community MUST be advertised with MAC/IP

Section 5.2 is not a referenced citation.

Changed it to “[5.1]”. Nice catch! Thanks.

Similar issue with [5.1] at:

   In PBB-EVPN, the PE advertises a Root/Leaf indication along with each
   B-MAC Advertisement route, to indicate whether the associated B-MAC
   address corresponds to a Root or a Leaf site. Just like the EVPN
   case, the new E-TREE Extended Community defined in section [5.1] is
   advertised with each MAC Advertisement route.

This paragraph refers to the correct section!

3.2 BUM Traffic

Please expand to Broadcast, Unkonwn, Multicast.

Done.

   When receiver ingress-replication label is needed, the high-order bit
   of the tunnel type field (Composite Tunnel bit) is set while the
   remaining low-order seven bits indicate the tunnel type as before.

I believe it would be useful to depict the Composite Tunnel bit in Figure 5 as
well... It's not only a 1-octet Type.

I believe the description is clear in the text and adding additional diagram and text to describe the diagram would make it too verbose.

Also, please note:

  ** Obsolete normative reference: RFC 5226

Changed it to RFC 8126.

  ** Downref: Normative reference to an Informational RFC: RFC 7387

That’s OK.

Thanks again for your review,
Ali


Thank you!

Carlos.