Subject: Re: [spring] draft-ietf-spring-ipv6-use-cases - shepherd review

From: <[email-masked]>
Date: Tue, 7 Feb 2017 14:03:14 +0000

Hi Roberta,

Thanks for the update and for addressing my comments.
I'll write the write'up ASAP (ETA end of this week)

FYI some typo:
OLD: and the achieve larger scale
NEW: and to achieve larger scale

OLD: a solution relaying on IPv6
NEW: a solution relying on IPv6

No need to refresh the draft for this.
Thanks
--Bruno

 > -----Original Message-----
 > From: Roberta Maglione (robmgl) [mailto:[email-masked]]
 > Sent: Friday, December 23, 2016 10:37 AM
 > To: DECRAENE Bruno IMT/OLN; [email-masked]; [email-masked]
 > Cc: [email-masked]; Stefano Previdi (sprevidi); Christian Martin (martincj)
 > Subject: RE: draft-ietf-spring-ipv6-use-cases - shepherd review
 > 
 > Hello Bruno,
 > Thanks for your comments, we are going to address them and post an updated version of
 > the document after the Holidays.
 > Please see  initial answers inline.
 > Regards
 > Roberta
 > 
 > -----Original Message-----
 > From: [email-masked] [mailto:[email-masked]]
 > Sent: Friday, December 16, 2016 3:47 PM
 > To: [email-masked]; [email-masked]
 > Cc: [email-masked]
 > Subject: draft-ietf-spring-ipv6-use-cases - shepherd review
 > 
 > Hi authors,
 > 
 > As the document shepherd, I have reviewed draft-ietf-spring-ipv6-use-cases.
 > I'm generally fine with the document, but do have some comments. Please find them below.
 > 
 > Best regards,
 > Bruno
 > 
 > ===== Major comments
 > Section 2.3.0 (intro of 2.3) and 2.3.1 are related to Service Function Chaining and Data
 > Center Network Overlay use cases.
 > Hence they have an adherence with the SFC and NVO3 WG.
 > Have those WG been presented this document, kept up to date, and are aligned with the
 > requirements as written?
 > Besides, those texts are unchanged since early 2014, while the situation may have change
 > since then, especially since both SFC and NVO3 WG are "recent". Especially SFC which has
 > been formed at the same period (23/12/2013). A priori, their work is likely to have
 > progressed since then, which does not seem reflected in this draft.
 > 
 > [RM] we are going the re-work theses sections to update the text in there.
 > 
 > ===== Minor comments
 > 
 > §2 IPv6 SPRING use cases
 > There are a few paragraphs ("In addition....in the above use case.") which describes that the
 > lack of MPLS support for IPv6 only networks is a use case for the IPv6 SR dataplane.
 > However it seems to me that MPLS SR support IPv6 FEC/segment hence would have been a
 > solution for such use case. So it does not seem to me a use case mandating a new dataplane
 > (IPv6 SR).
 > 
 > [RM] Agree with you that  when MPLS is present MPLS SR with IPv6 FEC/segment is a viable
 > solution. However it was pointed out in the mailing list by Wes George
 > (https://www.ietf.org/mail-archive/web/spring/current/msg00832.html ) that MPLS in IPv6
 > only environment still has some gaps as described in RFC 7439. Specific text was added to
 > address that comment.
 > We can definitely re-word the text in this section, to clarify the meaning.
 > 
 > On a related point, the term "IPv6-only" does not seem well defined as it could sometime
 > means "non-IPv4" and sometimes "non-MPLS", which is different.
 > [RM] will clarify this point thanks
 > 
 > ---
 >   "In addition it is worth to note that in today's MPLS dual-stack
 >    networks IPv4 traffic is labeled while IPv6 traffic is usually
 >    natively routed, not label-switched.  Therefore in order to be able
 >    to provide Traffic Engineering "like" capabilities for IPv6 traffic
 >    additional/alternative encapsulation mechanisms would be required."
 > 
 > The first observation does not seem enough to require the new of a new data-plane. As
 > discussed above, this may be caused by a lack of support for IPv6 in existing MPLS signaling
 > protocols. MPLS SR seems to be a valid option. So it does not seem to be a use case
 > mandating a new dataplane (IPv6 SR).
 > 
 > 
 > [RM] agree with you, the intention here was to capture current common deployments for
 > dual-stack networks where most of the times IPv4 is labeled switched while IPv6 is natively
 > routed, given the current gaps for MPLS on IPv6 only networks.
 > 
 > 
 > ---
 > "   2.  There is a strict lack of an MPLS dataplane"
 > May be adding "in a portion of the end to end path". (as some may have MPLS in the core,
 > yet not in the access/DC/home network...)
 > 
 > [RM] okay
 > 
 > ---
 >    "This section will describe some scenarios where MPLS may not be
 >    present and it will highlight how the SPRING architecture could be
 >    used to address such use cases, particularly, when an MPLS data plane
 >    is neither present nor desired."
 > 
 > May be rephrasing to avoid saying twice in the same sentence that MPLS is not present.
 > 
 > [RM] will do
 > 
 > ---
 > "   In any environment with requirements such as those listed above, an
 >    IPv6 data plane provides a powerful combination of capabilities for a
 >    network operator to realize benefits in explicit routing, protection
 >    and restoration, high routing scalability, traffic engineering,
 >    service chaining, service differentiation and application flexibility
 >    via programmability."
 > 
 > [...]
 > 
 > "   In addition to the use cases described in this document the SPRING
 >    architecture can be applied to all the use cases described in
 >    [RFC7855] for the SPRING MPLS data plane, when an IPv6 data plane is
 >    present.  Here there is a summary of those use cases:
 > 
 >    1.  Traffic Engineering
 > 
 >    2.  Disjoint paths in dual-plane networks
 > 
 >    3.  Fast Reroute: Protecting node and adjacency segments
 > 
 >    4.  OAM/monitoring
 > 
 >    5.  Egress Peering Engineering"
 > 
 > 
 > I feel that there is redundancy with those 2 paragraphs. In particular the catalog of
 > usages/benefits is duplicated.
 > 
 > [RM] will simplify the text and remove redundant text
 > 
 > ---
 > §2.2
 > It's not clear to me what "egress vectoring" is. (May be because this Access Network section
 > seems to refer to a specific access techno (DOCSIS) which I'm not familiar with.) Could you
 > add a reference?
 > 
 > [RM] will add a reference
 > 
 > ---
 > §2.3
 > 
 >    "A service provider may choose to have these service functions
 >    performed external to the routing infrastructure, specifically on
 >    either dedicated physical servers or within VMs running on a
 >    virtualization platform."
 > 
 > It's not clear to me what is meant by "routing infrastructure", especially when opposed to
 > servers/VM. Indeed, routers can now run in servers/VM. So may be rephrasing the whole
 > point would help.
 > 
 > [RM] will re-phrase the sentence
 > 
 > ---
 > Introduction part (2.3.0) is mostly related to service chaining, although this is not reflected
 > by the title. It is referencing two WG documents from the SFC WG. Does this mean that the
 > SFC WG is presenting those requirements in the SPRING WG?  This may require involving
 > the SFC WG in this last call. And some elaboration why the SFC WG solutions are not
 > adequate/enough. (e.g. is this a need to combine both routing instructions and service
 > instruction in order to both choose the route and the sequence of services function? In
 > particular when NHS meta data is not needed?)
 > 
 > This service chaining text seems to originate from draft-martin-spring-segment-routing-ipv6-
 > use-cases-00 i.e .from march 2014. And the text is unchanged since draft-martin-spring-
 > segment-routing-ipv6-use-cases-01 i.e from April 4, 2014.This seems like a long time in this
 > domain: mostly the whole duration of the SFC WG. Is this still aligned with the work that the
 > SFC WG has done in that 2.5 years period?
 > 
 > [RM] will re-work the section and update the text
 > 
 > ---
 > 2.3.1 is mostly related to VPN overlay. In the IETF, this seem in scope to the NVO3 WG. Does
 > this mean that the NVO3 WG is presenting those requirements in the SPRING WG? This may
 > require involving the NVO3 WG in this last call. Especially since NVO3 seems to have enough
 > encapsulation techniques to deal with, and it's not clear to me that NVO3 needs one more.
 > 
 > Besides, this section seems to come from 2014 and draft-baker-openstack-ipv6-model
 > which has expired 18 month ago. 2014 may be a long time ago in the DC environment. Is
 > this approach still up to date/relevant?
 > 
 > [RM] will re-work the section and update the text
 > 
 > ----
 > "The 128-bit PE Ingress ID in the Segment Router Header (SRH) policy list"
 > Name of the field and structure seems to have changed in the 6MAN draft. possibly:
 > :s/PE Ingress ID/Ingress Node TLV
 > :s/policy list/Optional TLV objects
 > 
 > [RM] will fix this
 > 
 > ===== Nits:
 > 
 > Reference:
 > Some references are outdated (cf idnits), in particular [I-D.previdi-6man-segment-routing-
 > header].
 > 
 > §2.3
 > "The term "Service Function Chain", as defined in [RFC7498], it is used"
 > :s/it is/is
 > 
 > [RM] ok will fix both of them
 > 
 > Thanks again for the comments.
 > Regards
 > Roberta
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