Re: [mpls] Genart last call review of draft-ietf-mpls-base-yang-15

[Tarek Saad <[e-mail]>]

Hi Gyan,

Thanks for your review and feedback. Please see inline for response.

On 8/20/20, 4:21 PM, "Gyan Mishra via Datatracker" <[e-mail]> wrote:

    [External Email. Be cautious of content]


    Reviewer: Gyan Mishra
    Review result: Ready with Issues

    I am the assigned Gen-ART reviewer for this draft. The General Area
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    Document: draft-ietf-mpls-base-yang-??
    Reviewer: Gyan Mishra
    Review Date: 2020-08-20
    IETF LC End Date: 2020-08-19
    IESG Telechat date: Not scheduled for a telechat

    Summary:
    The draft is well written and provides a very basic augmentation of the Yang
    core data modeling for routing management (NDMA) defined in RFC 8349 which
    provides the framework for managing routing subsystems. This drafts provides a
    new MPLS base model framework for managing MPLS routing subsystems, reflecting
    the mpls protocol specifications defined in RFC 3031  for future extensibility
    to Segment Routing architecture RFC 8200 and beyond.

    Major issues:
    The base mpls model defined in very BASIC as defined in the draft and does not
    reflect the data modeling of all attributes and features of the MPLS
    architecture defined in RFC 3031.  I understand this draft defines the topmost
    transport label for MPLS forwarding however it does not fully represent all
    data models representing the LDP protocol.

[TS]: Yes, the MPLS base model is agnostic to the signaling protocol that used to populate the MPLS RIBs. As illustrate in Figure 1, we expect other models to be augmenting MPLS base model.

    If the goal of this draft is to reflect RFC 3031 in its entirety it does not
    appear to do so.  If the goal of the draft is to provide just the basics of the
    MPLS address family framework for future extensibility for MPLS specification
    as well and this draft is not the "end all be all" for the MPLS protocol
    specification and is just an introduction of the mpls base Yang model then I
    think this draft is ready for publication.

[TS]: Yes, this model serves as base augmentation for other MPLS models.

    Examples what I believe is missing in defining RFC 30301 in this MPLS base
    Yang model. Defining the Label stack and depth of the stack Since this topmost
    MPLS label can be LDP, Static or RSVP data model is mentioned but not in the
    context of label stack with multiple lables and that the topmost label based on
    LFIB forwwarding table could be either TE or LDP tompost label.

    Also mention of BOS -Bottom of Stack bit for the label stack.
[TS]: The MPLS label stack type is defined in RFC8294 (see rt-types:mpls-label-stack) and is being used by MPLS base model.

    Implicit null label value 3 & Explicit Null  label value 0 & QOS related to EXP
    marking related to uniform & pipe mode. I did not see any mention of EXP bits.

[TS]: these types are all are already defined in RFC8294 (please refer to traffic-class instead of EXP). See below:
    +--ro mpls-label-stack
          +--ro entry* [id]
             +--ro id               uint8
             +--ro label?           rt-types:mpls-label
             +--ro ttl?             uint8
             +--ro traffic-class?   uint8

    Also LDP Downstream on demand versus Downstream unsolicited label distribution
[TS]: As mentioned, these are outside the scope of this model.

    method MPLS LIB and FEC binding for LSP  and data structure for LFIB entry
    local label & remote label learned via label mapping message.

    LDP label advertise, allocate, accept policy for /32 FEC binding to be only the
    loopback of iBGP peer FEC Destination.

    Label Imposition, Label Swapping & Label Disposition.

    MPLS LDP   multicast extension mLDP - P2MP LSP

    Also BGP LU labeled unicast BGP being used for Label distribution and label
    binding for inter-as for topmost label binding inter-as stitching RFC 8277.

    Also context related to LDPv6 RFC 7552.  Also softwire mesh framework RFC 5565
    v6 edge over v4 core or v4 edge over v6 core and core transport being v4 or v6
    and not both.
[TS]: MPLS bindings (local/remote) for V4 and V6 prefixes will be found in the augmentation of entries of the respective IPv4 and IPv6 RIBs defined in RFC 8349.

Regards,
Tarek (on behalf of co-authors)

    Minor issues:
    None

    Nits/editorial comments:
    The draft is well written and serves a critical need to extend the Yang data
    modeling capabilities from existing IPv4 & IPv6 address families to MPLS
    address family framework. A XML file was not provided on the datatracker so I
    was not able to run idnits against the draft.





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