Re: [RTG-DIR] Rtgdir last call review of draft-ietf-detnet-mpls-04

[Balázs Varga A <[e-mail]>]

Hi Carlos,

Many thanks for the feedback. Regarding the 2 remaining open topics:
- Referencing the framework document: We intend to keep it "informational" as these references are in the text “background” and “e.g.,”.
- OAM: We will change text to highlight that OAM is for further study. No reference to an individual draft.  " ... additional considerations on OAM are further study ..."

I will start to update the draft accordingly.

Thanks & Cheers
Bala'zs

-----Original Message-----
From: Carlos Pignataro (cpignata) <[e-mail]> 
Sent: Friday, January 10, 2020 4:12 PM
To: Balázs Varga A <[e-mail]>
Cc: Routing Directorate <[e-mail]>; [e-mail]; [e-mail]; [e-mail]
Subject: Re: Rtgdir last call review of draft-ietf-detnet-mpls-04

Thanks for the response, Balázs. Please see inline.

> 2020/01/10 午前8:56、Balázs Varga A <[e-mail]>のメール:
> 
> Hi Carlos,
> 
> Many thanks for the review and your mailing with Stewart. 
> Your former discussion points I tried to incorporate in this mail. 
> Proposed resolutions are described below (marked with "<Balazs> and/or 
> <Stewart>").
> 
> We will start to update the text if reactions are OK with You.
> 
> Thanks & Cheers
> Bala'zs
> 
> -----Original Message-----
> From: Carlos Pignataro via Datatracker <[e-mail]>
> Sent: Tuesday, December 24, 2019 1:03 AM
> To: [e-mail]
> Cc: [e-mail]; [e-mail]; 
> [e-mail]
> Subject: Rtgdir last call review of draft-ietf-detnet-mpls-04
> 
> Reviewer: Carlos Pignataro
> Review result: Has Issues
> 
> Hello,
> 
> I have been selected as the Routing Directorate reviewer for this draft. The Routing Directorate seeks to review all routing or routing-related drafts as they pass through IETF last call and IESG review, and sometimes on special request. The purpose of the review is to provide assistance to the Routing ADs.
> For more information about the Routing Directorate, please see 
> ​http://trac.tools.ietf.org/area/rtg/trac/wiki/RtgDir
> 
> Although these comments are primarily for the use of the Routing ADs, it would be helpful if you could consider them along with any other IETF Last Call comments that you receive, and strive to resolve them through discussion or by updating the draft.
> 
> Document: draft-ietf-detnet-mpls-04
> Reviewer: Carlos Pignataro
> Review Date: December 2019
> Intended Status: Proposed Standard
> 
> Summary:
> 
> I have some minor concerns about this document that I think should be resolved before publication.
> 
> [Resolving, in this context, means discussing and responding to, some 
> of these would and others would not imply changes]
> 
> This document specifies the Deterministic Networking data plane when operating over an MPLS Packet Switched Networks.
> 
> Major Issues:
> 
> Minor Issues:
> 
> The document lists 7 (i.e, more than 5) authors.
> 
> A am somewhat confused regarding how some of these DETNET dataplane 
> documents interact, interface, and intersect with each other. Where 
> are requirements ultimately coming from for any variety of dataplanes? 
> Specifically: *
> draft-ietf-detnet-data-plane-framework-03 targets Informational 
> (should be
> STD?) but seems to include foundational Reqs. * draft-ietf-detnet-ip for IP * draft-ietf-detnet-ip-over-mpls for IP over MPLS * draft-ietf-detnet-ip-over-tsn and draft-ietf-detnet-mpls-over-tsn for X over TSN * draft-ietf-detnet-mpls-over-udp-ip and draft-ietf-detnet-mpls for MPLS Among all of these, where are really the requirements for MPLS? and for IP? Is there a "Roadmap" or Rosetta Stone to understand these? There are many permutations of X-over-Y. I appreciate that, not having followed DETNET discussions, I am likely missing something.
> 
> <Balazs> One can group the drafts in three sets:
> 1, General overview
> The "draft-ietf-detnet-data-plane-framework" is intended to be used as a "Rosetta Stone".
> It provides an overall framework for the Deterministic Networking data 
> plane. Framework covers concepts and considerations that are generally 
> common to any Deterministic Networking data plane specification.

Maybe a question not only for you — but: if this is a fundamental document, how is it Informational?

> 2, DetNet Data Plane specifications
> Two drafts are dedicated to IP and to MPLS based DetNet data planes. 
> These drafts specifies the requirements for MPLS and for IP.  
> "draft-ietf-detnet-mpls" specifies the Deterministic Networking data plane when operating over an MPLS Packet Switched Networks.
> "draft-ietf-detnet-ip" specifies the Deterministic Networking data 
> plane when operating in an IP Packet Switched Networks.
> 3, Specifications for X-over-Y scenarios Remaining drafts cover the 
> X-over-Y scenarios. Some are called as "sub-network" scenarios for 
> DetNet. For example, if DetNet MPLS nodes are interconnected by and IP 
> sub-network, what is described "draft-ietf-detnet-mpls-over-udp-ip".

I have not looked at the details, but this sounds a bit strange. You might end up with an expanding permutation of drafts and gaps. Why not include the X-over-Y in the Y document?

> 
> 
> 3.1.  Layers of DetNet Data Plane
> 
>   The DetNet control word (d-CW)
>   conforms to the Generic PW MPLS Control Word (PWMCW) defined in
>   [RFC4385].
> 
> Yes, but why not the Preferred CW?
> 
> <Balazs>/<Stewart> Sum of mailing + proposed fixing:
> The PCW only supports a 16bit sequence number and it has the skip zero auto-signaling of active S/N feature.
> This was a problem for DetNet because:
> - We were worried about S/N rollover frequency in some applications and so we wanted the option of a larger S/N.
> - We wanted to have the option to propagate the S/N from the payload 
> to the transport to simplify the implementation in some cases. These 
> applications have a non-skip zero S/N. Skip zero is an irritation to implement and we should probably have signaled in in PWs.
> As you note in is only a preferred design for PWs, DetNet is not 
> constrained by that and there were good reasons to adopt this alternate approach.
> We assume to fix this with adding above information to the text.
> NEW text to be added in section 4.2.1:
>    "This format of the d-CW was created in order (1) to allow larger S/N space to 
>    avoid S/N rollover frequency in some applications and (2) to allow non-skip 
>    zero S/N what simplifies implementation."

Sounds good.

> 
> 4.1.  DetNet Over MPLS Encapsulation Components
> 
>   The LSP used to forward the DetNet packet may be of any type (MPLS-
>   LDP, MPLS-TE, MPLS-TP [RFC5921], or MPLS-SR
>   [I-D.ietf-spring-segment-routing-mpls]).
> 
> I am not sure of the value of this statement for an "MPLS Dataplane" document.
> Further, are these "LSP Types" and if so where are the different types ennumerated? Does this mean that static binding LSPs and BGP signaled cannto be used? T-LDP does not work? "SDN Assigned"? I recommend removing this, since it can confuse and does not add much.
> 
> <Balazs>/<Stewart> Text intends to say that any type of LSP can be used below DetNet. 
> DetNet design is not restricted to a single method of establishing an 
> LSP nor to the characteristics and constraints that go with those LSPs.
> We assume to fix this with adding “for example” to the text and avoid the term "type".
> CHANGE text to:
>   "The LSP used to forward the DetNet packet is not restricted regarding any method 
>   used for establishing that LSP (for example, MPLS-LDP, MPLS-TE, MPLS-TP [RFC5921],
>   MPLS-SR [RFC8660], etc.)."
> 

OK.

> 
> 4.3.  OAM Indication
> 
> It is important to have the OAM Indication, but what type of OAM packets can run on top of this AcH? I found it interesting that for example there is not reference or citation to RFC 8029.
> 
> <Balazs>/<Stewart> Sum of former mailing + proposed fixing Work has 
> started on OAM for DetNet. We have two drafts dealing with IP and with 
> MPLS based DetNet data planes (draft-mirsky-detnet-ip-oam-01, draft-mirsky-detnet-mpls-oam-01). We expect to cover OAM for DetNet with these two OAM documents.
> The OAM for DetNet will be more complex than the OAM for a classical 
> P2P or P2MP LSP (or PW) because of the PREOF function. There is 
> nothing in the data plane that precludes us using on of the existing OAM indicators (GAL or 0001 ACH), but I think that it is important to thing through the subtleties. Thus I think it is OK to make progress on the elements of the data plane that we can nail down, and leave. The OAM as follow-up work.
> We assume to fix issue this with adding reference to DetNet OAM drafts.
> Add text to section 4.3:
>   "DetNet specific OAM functions for MPLS based DetNet data plane are discussed 
>     in [draft-mirsky-detnet-mpls-oam-01]."

I disagree. This is an individual draft. I’d add “For further study” without pointing to any early individual documents.

> 
> 
> Nits:
> 
> 2.2.  Abbreviations
> 
>   The following abbreviations are used in this document:
> 
> Many of these abbreviations are well-known, many others have authoritative definitions and expansions. I believe this section should point to the appropriate RFCs for LSR, CW, PE, OAM, etc...
> Also, interesting, this section does not expand LSE, and I think it should use it.
> 
> <Balazs> OK. We will update.
> 
> 4.6.1.  Class of Service
> 
> Should this include "and TTL" in the title? I was looking for TTL specs in the Table of Contents but could not find it.
> 
> <Balazs> There are no new TTL related procedures defined for DetNet. 
> Regarding TTL the section just intends to say that existing stuff can be used.
> So, I think we can leave the title as it is (no reference to TTL)
> 
> 9.2.  Informative References
> 
> Are all the "draft-ietf-detnet-*" really Informative?
> <Balazs> No, we will fix and update.
> 
> Also, outdated reference: draft-ietf-spring-segment-routing-mpls has 
> been published as RFC 8660 <Balazs>/<Stewart> OK, We will update.
> 
>   [RFC8655]  Finn, N., Thubert, P., Varga, B., and J. Farkas,
>              "Deterministic Networking Architecture", RFC 8655,
>              DOI 10.17487/RFC8655, October 2019,
>              <https://protect2.fireeye.com/v1/url?k=7a40605f-26946939-7a4020c4-8610d8a762ca-97dd584868114772&q=1&e=42fa17eb-44f5-42d1-9898-4d6ba7365c47&u=https%3A%2F%2Fwww.rfc-editor.org%2Finfo%2Frfc8655>.
> 
> And is this also Informational?
> <Balazs> No, We will update.
> 

Thanks!

Carlos.

> Thank you!
> 
> Carlos Pignataro.
> 
>