Re: [Teas] Genart last call review of draft-ietf-teas-rsvp-te-scaling-rec-06

[Vishnu Pavan Beeram <[e-mail]>]

Elwyn, Hi!

Thanks for the detailed review and the text suggestions. We just posted a
new revision (-07) to address the concerns listed below. Please go through
the new diffs (
https://www.ietf.org/rfcdiff?url2=draft-ietf-teas-rsvp-te-scaling-rec-07)
and let us know if additional changes are required.

Please see inline for further responses (prefixed VPB).

Regards,
-Pavan

On Fri, Sep 22, 2017 at 6:06 PM, Elwyn Davies <[e-mail]> wrote:

> Reviewer: Elwyn Davies
> Review result: Not Ready
>
> I am the assigned Gen-ART reviewer for this draft. The General Area
> Review Team (Gen-ART) reviews all IETF documents being processed
> by the IESG for the IETF Chair.  Please treat these comments just
> like any other last call comments.
>
> For more information, please see the FAQ at
>
> <https://trac.ietf.org/trac/gen/wiki/GenArtfaq>.
>
> Document: draft-ietf-teas-rsvp-te-scaling-rec-06
> Reviewer: Elwyn Davies
> Review Date: 2017-09-22
> IETF LC End Date: 2017-09-22
> IESG Telechat date: 2017-09-28
>
> Summary: Not ready, primarily because the title and presentation give the
> impression that the content is really a BCP when it isn't.  This conceals
> the
> considerable amount of tweaking of RFC 2961 functionality and addition of
> new
> RSVP Capabilities described in the document.  There are also a couple of
> minor
> issues that need to be sorted out.
>
> Major issues:
> Title and way proposals are presented:  The document defines two new
> 'capabilities' for RSVP-TE and is indeed (as specified in the document
> header)
> correctly intended for Standards Track status.  However the title and the
> whole
> of the meat of the document in Section 2 presents the proposals as
> 'recommendations' which says to me that I am expecting a BCP where a
> profile of
> available options from existing standards is recommended as the best
> choice for
> implementation and deployment.  In my opinion, the title would be better as
> something like "Additional Capabilities Designed to Improve the
> Scalability of
> RSVP-TE Deployments".  Whilst the proposals are based on the techniques in
> RFC
> 2961, the document *requires* the implementor to conform to rules that were
> optional and constrains configurable values to different ranges in order
> to be
> able to deliver the capabilities defined in the document as well as
> defining
> new RSVP extensions modifying some of the behaviour defined in RFC 2961.
> Thus
> although some of the rules could be met by choosing particular values
> within
> the RFC 2961 set, the use of MUST, tweaking of functionality and variation
> of
> ranges takes it well beyond a set of recommendations for RFC 2961 options
> selections.  In view of this Section 1 needs to be written as an
> introduction
> to the definitions of the new capabilities rather than advocacy for
> selection
> of RFC 2961 options and the implication that the techniques mentioned in
> the
> last paragraph of s1 are just a matter of selecting a profile of option
> values.
>  In actuality new protocol values are introduced and ss2.2 and 2.3 define
> novel
> extensions to RSVP beyond what is available for RFC 2961 and requiring
> modification to basic RFC 2961 functionality..
>
>
[VPB] We changed the title to "Techniques to Improve the Scalability of
RSVP-TE Deployments". We also tweaked the text in the introduction section
as suggested. Please see if the new set of diffs address the comment above.

Minor issues:
> Interaction with RFC 5063:  The document does not explicitly state that an
> implementation would need to support (at least) the extra capability obect
> defined in s4.2 of RFC 5063.  Some words about interaction with RFC 5063
> are
> probably required in that s4.2.1 of RFC 5063 rather assumes that if there
> is a
> capability object, by default its S bit will be set.
>

[VPB] The CAPABILITY object in RFC5063 is meant for generic use and can be
used even when there are no Graceful Restart extensions in play (even when
no GR flags are set). As far as we can tell, there is nothing in RFC5063
that precludes this. We added a reference to RFC5063 when the new
Capability flags are introduced. Would this be sufficient to address this
concern?


>
> Behaviour if a node stops setting Refresh-Reduction-Capable bit:  The last
> para
> of s2 in RFC 2961 discusses behaviour if a node stops setting this bit in
> messages.  What would happen with the extensions defined in this document
> if
> this happened while either of the extensions is in use?  As a matter of
> interest, if a peer offers the capabilities defined in this draft, is it
> possible or sensible for it to stop setting the Refresh-Reduction-Capable
> bit
> without stopping offering the extensions?
>

[VPB]  If a peer sets the I or F bit in the CAPABILITY object but does not
set the Refresh-Reduction-capable bit, then the corresponding functionality
("RI-RSVP" or "Per-Peer Flow-Control") is not activated for that peer. In
other words, resetting the Refresh-Reduction-Capable bit immediately makes
the node incapable of supporting the two capabilities discussed in this
document. This is covered in Sections 3.1 and 4.1 ( -07 version).


> s2.1.3, para 2: As specified, it appears that the 'slower timer'
> transmission
> of Path and Resv messages can go on indefinitely if no ack arrives.  What
> puts
> an end to this repetition?  [It may be that I have forgotten how basic RSVP
> works, but since this is altering the behaviour it would be good to
> explain how
> it terminates, and whether this requires any additional modification to
> timers.]
>

[VPB]  There is nothing new about Path and Resv messages getting
transmitted indefinitely (this is normal soft-state signaling behavior) --
all that this section does is discuss how these transmissions are paced in
the absence of an ack. The slower timer transmission will go on until
either an ack is received (at which point the regular "refresh interval"
comes into play) or the corresponding LSP instance state is torn down.


> Nits/editorial comments:
> Abstract: RSVP-TE is not a 'well-known' abbreviation: s/RSVP-TE/RSVP
> Traffic
> Engineering (RSVP-TE)/
>

> Abstract and s1, first para:  This para is not future proof.  Suggest:
> OLD:
>    The scale at which RSVP-TE [RFC3209] Label Switched Paths (LSPs) get
>    deployed is growing continually and there is considerable onus on
>    RSVP-TE implementations across the board to keep up with this
>    increasing demand in scale.
> NEW:
>    At the time of writing, networks which utilise RSVP Traffic Engineering
>    (RSVP-TE) [RFC3209] Label Switched Paths (LSPs) are encountering
> limitations
>    in the ability of implementations to support the growth in the number
> of LSPs
>    deployed.  This document defines two additional RSVP-TE extensions that
>    are intended to reduce the number of messages needed to maintain RSVP-TE
>    soft state in routers and hence allow implementations to support larger
>    scale deployments.
> ENDS
> Note:  Omit reference from Abstract.
>
>
[VPB] Fixed in -07

s1, para 2: s/under certain/beyond a certain/
>

[VPB] Fixed in -07


> s1, para 3: s/makes a set of concrete implementation
> recommendations/defines
> two extensions/; s/- push higher/by increasing/; s/maintain LSP
> state./maintain
> LSP state by reducing the number of messages needed./
>
> Abstract, para 2 and s1, last para:  [Omit reference from Abstract]
> OLD:
>    This document advocates the use of a couple of techniques - "Refresh-
>    Interval Independent RSVP (RI-RSVP)" and "Per-Peer Flow-Control" -
>    for significantly cutting down the amount of processing cycles
>    required to maintain LSP state.
> NEW:
>    This document defines two RSVP Capabilities [RFC5063] "Refresh-
>    Interval Independent RSVP (RI-RSVP)" and "Per-Peer Flow-Control"
>    that will cut down the number of messsages and processing cycles
>    required to maintain LSP state.
> ENDS
>

[VPB] Fixed in -07


> s1, last para: Add new penultimate sentence:
>    Note that the "Per-Peer Flow-Control" capability requires the "RI-RSVP"
>    capability as a prerequisite.
>

[VPB] Fixed in -07


> s1, last para: s/RECOMMENDED/recommended/ - this isn't a recommendation
> about
> the protocol on the wire.
>

[VPB] Fixed in -07


> Subdivision of s2:  The issues regarding the nature of the document would
> be
> helped by altering s2 into four top level sections, thus: s2: Requirement
> for
> RFC 2961 Refresh Overhead Reduction Support and Specific Option Choices
> (from
> s2.1) s3: Requirement for RFC 5063 Capability Object support (see Minor
> Issues
> above) s4: Refresh-Interval Independent RSVP Capability (from s2.3) s5:
> Per-Peer RSVP Flow Control Capability (from s2.4) Subsequent major sections
> then renumbered as s6 onwards. References to s2.x will need to be updated
> throughout.
>

[VPB] We subdivided s2 into 3 top level sections. We did not add a separate
section for discussing RFC5063 Capability Object support.


> s2.1 (would be introduction of new s2):
> OLD:
>    The implementation recommendations discussed in this section are
>    based on the proposals made in [RFC2961] and act as prerequisites for
>    implementing the techniques discussed in Sections 2.2 and 2.3.
>
> NEW:
>    The Capabilities defined in Sections 4 and 5 of this document are based
> on
>    proposals made in [RFC2961].  Implementations of these Capabilities will
>    need to support the RSVP messages and techniques defined in [RFC2961]
> as set
>    out in Section 2.1 [was 2.1.1] with
>    some minor modifications and alterations to recommended time intervals
> and
>    iteration counts as defined in the remainder of this section.
> ENDS
>
>
[VPB] Fixed in -07

s2.1.1, title and para 1 [will be s2.1]:
> OLD:
> 2.1.1.  Basic Prerequisites
>
>    An implementation that supports the techniques discussed in Sections
>    2.2 and 2.3 must meet certain basic prerequisites.
> NEW:
> 2.1.  Required Functionality from RFC 2961 to be Implemented
>
>    An implementation that supports the capabiities discussed in Sections
>    4 and 5 must provide a large subset of the functionality described
>    in [RFC2961] as follows:
> ENDS
>

[VPB] Fixed in -07


> s2.1.2, para 2 [will be s2.2]: s/techniques discussed in Sections 2.2 and
> 2.3/Capabilities defined in Sections 4 and 5/
>

[VPB] Fixed in -07


> s2.1.2, para 2: s/MESSAGE ID/MESSAGE_ID/
>

[VPB] Fixed in -07


> s2.2, para 1: s/improvement on transmission overhead/improvement of
> transmission overhead/
>

[VPB] Fixed in -07


> s2.2, para 1: s/proposes sufficient recommendations/sets out additional
> requirements/
>

[VPB] Fixed in -07


> s2.2, last bullet: Add a reference to the proposed new Section 3 that
> discusses
> the Capability object.
>

[VPB] Added a direct reference to RFC5063


> s2.2.1, last para: s/set Refresh-Reduction-Capable bit in common
> header/set the
> Refresh-Reduction-Capable bit in the common header/
>

[VPB] Fixed in -07


> s2.3, para 1: s/set of recommendations/functionality/;
> s/provide/provides/;
> s/RSVP-TE control plane congestion/a significant portion of the RSVP-TE
> control
> message load/
>

[VPB] Fixed in -07


> s2.3.2: s/MESSAGE ID/MESSAGE_ID/
>

[VPB] Fixed in -07


>
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