Re: [MBONED] Continued Review of multicast-yang-model

[Gyan Mishra <[e-mail]>]

Hi Sandy & Authors

Excellent work capturing all the complexity and nuances of all the
scenarios related to multicast deployments in the Yang model.


I just reviewed the Multicast Yang model and as this should capture I
believe existing and future PTA tunnels types I noticed a few missing.

The Yang framework diagram is quite complicated and maybe we can setup a
call to go over it below is confusing.

3.1 Diagram

This diagram provides a really nice flow chart for the overall multicast
Yang model.  Few comments

Multicast model has 3 categories underlay, transport and overlay.

The layering horizontally is a bit hard to follow in the diagram and here
are some ideas.

So there are two main cases fork in the road

1. Underlay-only  netwok
2. Underlay/Overlay network

The difficulty is how do you represent it all together in a homogeneous
Yang model hierarchy

Underlay/Overlay network - “BGP free” core with PIM option for MVPN Rosen
PTA

BGP is part of MVPN SAFI 129 so I don’t think we have to call our BGP in
overlay

MLD / MLD snooping is v6 underlay - Underlay only IP transport related

So here am showing both together as you have it in the diagram

Overlay

MVPN SAFI 129( RFC 6513 6514 procedures)

FEC TLV - Type, Root, Opaque

Ingress - FEC Root  Type 1-5
Egress  Type 6 7

Egress  triggered-mLDP
Ingress triggered- RSVP-TE /BIER Type 4 leaf-ad

Transport

IP - could be v4 or v6 and would be for Underlay only scenario

MPLS  / SR-MPLS

PTA = mLDP P2P MP2MP, P2MP TE, IR, BIER, Replication SID
PIM GRE - ASM, SSM, BIDIR

SRv6
PTA - Replication SID
BIER

Underlay v4 v6 dual stacked

L3

OSPF PIM or no PIM for non MVPN Rosen PTA
ISIS PIM no PIM for non MVPN Rosen PTA
BGP PIM no PIM for non MVPN Rosen PTA
BABEL PIM

L2

Snooping v4

MLD Snooping v6



Kind Regards


Gyan

On Sat, May 8, 2021 at 4:49 AM <[e-mail]> wrote:

> Hi Jake,
>
> Thank you very much for your review! And sorry for the late response.
>
> Please find my answer with Sandy> inline.
>
>
> 原始邮件
> *发件人：*Holland,Jake
> *收件人：*MBONED WG;张征00007940;
> *日 期 ：*2021年03月20日 11:01
> *主 题 ：**Continued Review of multicast-yang-model*
> Hi Sandy,
>
>
> During the mboned meeting I think you said you were waiting on a review from
> me, but I thought I had sent one here the day after IETF 109, so I didn't
> realize you were waiting:
> https://mailarchive.ietf.org/arch/msg/mboned/cjVQ_qM2yeboxY0i3vvjSe9g3Xo/
>
> Sandy> Appreciate for your review again! :-)
>
>
>
> Also, after a quick review of what I said during 109, I think I was expecting
> you to send something to the list detailing which parts of the model were
> well-proven with its use in production, and which parts of the model needed
> a closer look since nobody has used it yet:
> https://www.youtube.com/watch?v=K1FS3XqqWTw&t=3371s
>
> Sandy> Because we verified this model in ODL BIER project, so some other
> parts included in this model, such as mldp or p2mp-te, has not been
> verified yet.
>
> So experience with these protocols may do good help for the model review.
>
>
>
> Anyway, I see from my last review that there's parts of the document I didn't
> cover, so I guess I'll try to do that now:
>
> 0.
> I'm struggling with the high-level expectations of what happens in a
> network if I configure something with this model.  In Appendix A, a
> helpful example is given, but what happens when you set that data
> instance in a netconf instance?  Does it make the forwarding get
> configured, so this is mostly a transport path signaling mechanism?
>
> Sandy> The model can be used by netconf, but it won't affect the netconf
> running. When this model configured, some other model may be also
> configured. For example, when BIER is configured as transport, BIER model
> may also be configured if you have any parameter needs to be set in BIER
> model.
>
>
> What happens if the underlay does not match?  (For example, what if
> the underlay in the setting says ospf, but it's in fact the network
> between ingress and egress was running isis?)
>
> Sandy> Yes. The underlay may not match. So the nofitication can be used to
> report this situation to controller. But what the controller needs to do is
> out of scope of this draft.
>
>
> 1.
>
> There are errors in the yang rules validation, as reported on the datatracker
> page:
> https://datatracker.ietf.org/doc/draft-ietf-mboned-multicast-yang-model/
>
> [e-mail]
> :252: error: RFC 8407: 4.14: statement "grouping" must have a "description" substatement
> [e-mail]
> :363: error: RFC 8407: 4.14: statement "grouping" must have a "description" substatement
> [e-mail]
> :364: error: RFC 8407: 4.14: statement "choice" must have a "description" substatement
>
> These seem to need a fix.
>
> Sandy> Thank you very much for your reminder, I'll fix it.
>
> 2.
> In 3.2/3.3, the multicast-keys list seems to be a problem, especially with
> respect to vni-type and vni-value, because there's only 3 possibilities for
> virtual-type (vxlan, nvgre, and geneve), but a value is required in order
> to have it as a key.  Likewise, I'm not sure the vpn-rd and vni-value make
> sense for all (S,G)s, do these have a value?  (What about in a traditional
> PIM network?)
>
> Would it make sense to use a type that permits these to be blank where
> appropriate?
>
> Sandy> Yes. If these keys are not used, it can be set to blank or zero.
>
>
> 3.
> I'm confused about the multicast-underlay/ospf/ospf/toplogy location.  What
> is that, and why don't the other underlays have anythin analogous?
>
> Sandy> Thank you for your pointing out it. OSPF and ISIS support
> multi-topoloty feature, so the underlay can map to a specific topology.
> I'll also add it in ISIS underlay.
>
>
> 4.
> In section 3.3, there are a lot of grammar problems.  I'll list some of
> them here, do you need text suggestions for these?
>
> Sandy> Much appreciate if you make some suggestion for these. :-)
>
>
> 4.a.
>
>     ... Multicast keys include the features of multicast flow,
>    such as(vpnid, multicast source and multicast group) information.  In
>    data center network, for fine-grained to gather the nodes belonging
>    to the same virtual network, there may need VNI-related information
>    to assist.
>
> 4.b.
>
>     ... there may define BIER
>    information including (Subdomain, ingress-node BFR-id, egress-nodes
>    BFR-id).  If no (ingress-node, egress-nodes) information are defined
>    directly, there may need overlay multicast signaling technology, such
>    as MLD or MVPN, to collect these nodes information.
>
>
> 5.
> In section 3.3, I was confused by this bit:
>
>    ... One or
>    several transport technologies could be defined at the same time.
>
> What does it mean if several transport technologies are defined at
> the same time, are those for redundant paths or something?
>
> Likewise this about the underlay:
>
>     ... One or several underlay
>    technologies could be defined at the same time if there is protective
>    requirement.
>
> By "protective environment" do you mean a redundant setup that can
> forward the traffic through multiple paths?  (And if so, what if the
> redundant paths use the same type of underlay?  Or if not, what does
> it mean?)
> Sandy> Yes. But I am not sure if these usage is existed actually. Do you
> think it's better to only keep one for it?
>
> 6.
> As an overview comment:
>
> I still feel like I'm missing something when I read through this
> spec--am I understanding correctly that the whole purpose is to
> set up the forwarding for each of the given (S,G)s through the
> network?  If so, I'm confused about what the underlay and overlay
> properties are for, exactly.  How does the controller use the
> information that there's an OSPF underlay, when it has that info?
> Sandy> For example, if the OSPF topology is configured, the associated
> OSPF YANG should also be configured in the controller. And the controller
> will push the multicast model and OSPF model to the device. But as you
> said, the description needs to be updated. It's great if you have any
> suggestion for it.
>
> I hope that's helpful, and please let me know if you're expecting
> anything else from me on this revision.
>
> Sandy> Thank you very much again for your help!
>
> Best regards,
>
> Sandy
>
>
> Best regards,
> Jake
>
>
>
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*Gyan Mishra*

*Network Solutions A**rchitect *

*Email [e-mail] <[e-mail]>*



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