Hi Greg,

thanks – and it seems that we’re on the same page with regards to efficiency (4 
bytes of non-required overhead) and maturity (or lack of) of OOAM.

On the IOAM implementation: There are several implementations of IOAM. Some of 
which have recently been worked on and shown at an IETF hackathon, see 
 - where we’ve shown IPv6 and VXLAN-GPE with IOAM – on FD.io/VPP as well as on 
Barefoot Tofino. You probably also remember the Netronome/Broadcom demo - 
https://www.youtube.com/watch?v=j9FbD4a3F4E .
Below you seem to be specifically referring to the IOAM open source 
implementation in FD.io/VPP: There are protocol encapsulations for VXLAN-GPE, 
NSH, and IPv6 implemented in FD.io/VPP. The current code uses the “next header 
approach” for VXLAN-GPE and it leverages MD-Type 2 for NSH. As you’re well 
aware, there the discussion in SFC whether to use MD-Type 2 or next header 
encapsulating IOAM data in NSH isn’t yet settled, hence we’ll refrain from 
updating the code until SFC WG has come to a conclusion.

Could you provide a pointer to an OOAM implementation?


From: Greg Mirsky <gregimir...@gmail.com>
Sent: Donnerstag, 12. April 2018 18:54
To: Frank Brockners (fbrockne) <fbroc...@cisco.com>
Cc: IETF IPPM WG <i...@ietf.org>; NVO3 <n...@ietf.org>; Service Function 
Chaining IETF list <s...@ietf.org>; int-area@ietf.org
Subject: Re: [ippm] encapsulation of IOAM data in various protocols - follow up 
from WG discussion in London

Hi Frank,
thank you for sharing your points. Please find my notes in-line and tagged 
GIM>>. I believe that this is very much relevant to work of other working 
groups that directly work on the overlay encapsulations in the center of the 
discussion and hence I've added them to the list. Hope we'll have more opinions 
to reach the conclusion that is acceptable to all.


On Wed, Apr 11, 2018 at 12:02 PM, Frank Brockners (fbrockne) 
<fbroc...@cisco.com<mailto:fbroc...@cisco.com>> wrote:
Back at the IPPM meeting in London, we discussed several drafts dealing with 
the encapsulation of IOAM data in various protocols 
(draft-brockners-ippm-ioam-vxlan-gpe-00, draft-brockners-ippm-ioam-geneve-00, 
draft-weis-ippm-ioam-gre-00). One discussion topic that we decided to take to 
the list was the question on whether draft-ooamdt-rtgwg-ooam-header could be 
leveraged.  After carefully considering draft-ooamdt-rtgwg-ooam-header, I came 
to the conclusion that the “OOAM header” does not meet the needs of IOAM:
* Efficiency: IOAM adds data to live user traffic. As such, an encapsulation 
needs to be as efficient as possible. The “OOAM header” is 8 bytes long. The 
approach for IOAM data encapsulation in the above mentioned drafts only 
requires 4 bytes. Using the OOAM header approach would add an unnecessary 
overhead of 4 bytes – which is significant.
GIM>> The difference in four octets is because OOAM Header:

  *   provides more flexibility, e.g. Flags field and Reserved fields;
  *   supports larger OAM packets than iOAM header;
  *   is future proof by supporting versioning (Version field).
* Maturity: IOAM has several implementations, which were also shown at recent 
IETF hackathons – and we’re expecting additional implementations to be 
publicized soon. Interoperable implementations need timely specifications. 
Despite the question being asked, the recent thread on OOAM in the NVO3 list 
hasn’t revealed any implementation of the OOAM header. In addition, the thread 
revealed that several fundamental questions about the OOAM header are still 
open, such as whether or how active OAM mechanisms within protocols such as 
Geneve would apply to the OOAM header. This ultimately means that we won’t get 
to a timely specification.
GIM>> May I ask which encapsulations supported by the implementations you refer 
to. Until very recently all iOAM proposals were to use meta-data TLV in, e.g. 
Geneve and NSH. And if these or some of these implementations already updated 
to the newly proposed iOAM shim, I don't see problem in making them use OOAM 
Header. Would you agree?

* Scope: It isn’t entirely clear to which protocols the OOAM header would 
ultimately apply to. The way the OOAM header is defined, OOAM uses a 8-bit 
field for “Next Prot”, the next protocol. Some protocols that IOAM data needs 
to be encapsulated into use 16-bits for their next protocol code points. See 
e.g. the GRE encapsulation – as specified in draft-weis-ippm-ioam-gre-00.
GIM>> The first paragraph of the Introduction section states:
   New protocols that support overlay networks like VxLAN-GPE
   [I-D.ietf-nvo3-vxlan-gpe], GUE [I-D.ietf-nvo3-gue], Geneve
   [I-D.ietf-nvo3-geneve], BIER [I-D.ietf-bier-mpls-encapsulation], and
   NSH [I-D.ietf-sfc-nsh] support multi-protocol payload, e.g.
   Ethernet, IPv4/IPv6, and recognize Operations, Administration, and
   Maintenance (OAM) as one of distinct types.  That ensures that
   Overlay OAM (OOAM)packets are sharing fate with Overlay data packet
   traversing the underlay.
I'm updating the OOAM Header draft and along with cleaning nits will update 
reference to GUE. I think that the list and the statemnt are quite clear in 
identifying the scope of networks that may benefit from using not only common 
OOAM Header but common OOAM mechanisms, e.g. Echo 

With the above in mind, I’d suggest that the WG moves forward with specific 
definitions for encapsulating IOAM data into protocols – per the above 
mentioned drafts.

Regards, Frank

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