Re: [nvo3] AD review of draft-ietf-nvo3-vmm-16

[Martin Vigoureux <[e-mail]>]

Linda,

Le 2020-11-19 à 18:39, Linda Dunbar a écrit :
> [Linda] Is it better to call the draft "Solutions to preserve IP Addresses during VM mobility in Layer 2 and Layer 3 Networks"?
that would work

> That sort of confirms this is not NVO3 specific.
> [Linda] Do you suggest to go through independent RFC stream?
IMO, if the WG thinks that the content is worth publishing as an RFC and 
considers that this is not specific to NVO3 then the WG should consider 
that option.


> 
>> This document is said to describe solutions *commonly* used in data
>> centers. Also, it primarily only describes what needs to be done but
>> not how.
>> This makes me wonder what benefit does it bring to the community and
>> to operators of data centers.
>> [Linda] This document provides guidelines to DC operators if they want
>> to maintain VMs IP addresses during VM migration. Being able to move
>> VMs dynamically, from one server to another, makes it possible for
>> dynamic load balancing or work distribution. Therefore, dynamic VM
>> Mobility is highly desirable for large scale multi-tenant DCs
> possibly, but if those techniques are already in use, what is the benefit of having an RFC describing them? virtual machine mobility seems to be fairly well documented already and much more broadly than just about IP addressing preservation. It is also very challenging for the reader to determine whether all aspects of IP address preservation have been covered.
> [Linda] We have aimed to cover all aspects of IP address preservation. If we miss some aspects, can you elaborate?
I didn't say you were missing some.
In any case consistently with my previous point, I think the WG needs to 
discuss the added value this brings. It would be great to have feedback 
from DC operators as they are the targetted community of this document.

> 
>> This document refers to other specifications which themselves do not
>> provide the missing pieces e.g., RFC7666 does not describe how to
>> transfer VM states; [Linda] That is why we wrote this draft to
>> indicate that VMs states transferred are needed. But during the
>> numerous reviews, we had been advised to remote the actual protocols
>> of moving states and change the document to be “Informational” (from
>> Standard Track).
> I'm ok with that recommendation, because moving states has little to do with IP address preservation. The issue I point to is that you refer to
> RFC7666 for more information on moving states, but nothing in RFC7666 talks about that.
> 
>> RFC8014 is not a specification for an NVE-to-NVA protocol.
>> [Linda] RFC8014 describes the NVE-to-NVA functions.
> indeed but your document doesn't say clearly which functions need to be activated and how is effectively used the protocol to achieve the desired objective.
> [Linda] Thank you for the specific action. we can add.
> 
>> How section 7 relates to the rest of the document is unclear. It seems
>> to restate some elements described in 4.2 and 4.3 but not all.
>> [Linda] Section 4 is the Overview. Section 7 describes the details of
>> the Overview of Section 4.
> hmmm, then we can add this to the things that need to be clarified.
> Section 7 mas much less information than 4.2/4.3. In fact it is 42 lines long while 4.2+4.3 are 142 (and section 4, as a whole, 233). How can the overview be longer than the details?
> [Linda]Interesting point. Will ask the WG if more needs to be added or removed.
> 
>> Section 8 and 9 seem to be out of the scope of this document.
>> [Linda] Section 8 and 9 describes what triggers the VMs move. It was
>> suggested from Aera Directorates review comments.
> In the intro you say that this document covers planned VM moves.
> Section 8 talks about other reasons for a move (failover, load, ...).
> This is confusing and in fact doesn't add anything to IP address preservations. Section 9 itself says that it is outside the scope of the document.
> 
> [Linda] "failover, planned VM moves" are some of the reasons triggering the "VM Moving".
indeed but again, Section 8 is not clear. It is called "Other options". 
But it is not clear other options to what. Section 8 starts by talking 
about "unexpected events" so that leads me to thinking this is not in 
scope of the document because of the intro which says "planed moves".
But then Section 8 goes on talking about Hot Failover. Do you mean to 
cover in section 8 the "Hot" mobility and in Section 7 the Warm and Cold 
mobility? But Section 7 does have some text on "Hot".
All in all, at the very least, some clarifications are needed.

>> In its current state the document is not ready for review by the IESG
>> and I'm returning it to the WG. I encourage the WG to evaluate the
>> benefit of publishing this as an RFC, to discuss whether this should
>> be the product of NVO3 and would an alternate publication stream be
>> more appropriate. In any case this document needs more work.
>> [Linda] We are going around in circles.
> Not all drafts become RFCs and not all paths to RFC are straight.
> I'm not taking a decision here, I'm asking the WG to have a discussion.
> 
> [Linda] sure.
> 
> 
>> -m