Re: [Lsr] 答复: A new version of I-D, draft-liu-lsr-isis-ifit-node-capability-02

[Greg Mirsky <[e-mail]>]

Hi Tianran,
thank you for your kind attention to my questions. Please find my notes
in-lined below under the GIM>> tag.

Kind regards,
Greg

On Thu, Apr 2, 2020 at 11:33 PM Tianran Zhou <[e-mail]> wrote:

> Hi Greg,
>
>
>
> Good questions. Please see my reply in line.
>
>
>
> Thanks,
>
> Tianran
>
>
>
> *From:* Greg Mirsky [mailto:[e-mail]]
> *Sent:* Friday, April 3, 2020 6:58 AM
> *To:* wangyali <[e-mail]>
> *Cc:* Acee Lindem (acee) <[e-mail]>; Les Ginsberg (ginsberg) <
> [e-mail]>; Christian Hopps <[e-mail]>; [e-mail];
> Tianran Zhou <[e-mail]>
> *Subject:* Re: [Lsr] 答复: A new version of I-D,
> draft-liu-lsr-isis-ifit-node-capability-02
>
>
>
> Hi Yali, et al,
>
> thank you for the interesting discussion. I have several questions about
> the purpose of advertising ifit capabilities in IGP (and in general):
>
>    - Do you see a capability to export telemetry information as a
>    mandatory or optional?
>
> What’s the context with this question? Frankly, I did not have a deep well
> thinking on this question. But in our case, I wish it’s mandatory.
>
GIM>> If it is mandatory, then all nodes in a domain support IFIT and,
consequently, there's no need to advertise the capability in the
homogeneous, IFIT-wise, domain. Would you agree?

>
>    - Do you expect that a segment route to be constructed to prefer
>    ifit-capable nodes comparing to nodes that are not?
>
> Yes. This is one use case. As my echo to Robert, we want to achieve the
> SLA assurance network. We think the capability for visibility to verify the
> SLA compliance, and also the capability to get the accurate measurement for
> path computation should be considered. Should be considered from the very
> beginning when we compute the path.
>
GIM>> I understand that IFIT-capability might be used as one of CSPF
constraints. But, as I think of it, it can simply be discovered in the
course of running on-path telemetry collection. Would you agree?

> Thank you for your kind consideration of my questions.
>
>
>
> Regards,
>
> Greg
>
>
>
> On Wed, Apr 1, 2020 at 8:13 PM wangyali <[e-mail]> wrote:
>
> Hi Acee, Chris and Les,
>
> This is Yali. Many thanks for your kind comments and suggestion.
>
> Besides of signaling MSD by IGP node CAPABILITY TLV, we learned that
> there's another RFC7883 that advertising S-BFD discriminators in IS-IS. In
> my understand, BFD is a protocol to detect faults in the bidirectional path
> between two forwarding engines, including interface, data links, etc.
>
> Similarly, IFIT provides a complete framework of a family of on-path
> telemetry techniques, which are used to monitoring performance metrics of
> service flows, e.g. packet loss, delay. So we consider there's a same
> methodology with S-BFD that advertising IFIT node capabilities.
>
> Please let us know your comments and opinion. Thanks.
>
> Best regards,
> Yali
>
> -----邮件原件-----
> 发件人: Acee Lindem (acee) [mailto:[e-mail]]
> 发送时间: 2020年4月1日 20:29
> 收件人: Tianran Zhou <[e-mail]>; Les Ginsberg (ginsberg) <
> [e-mail]>; Christian Hopps <[e-mail]>
> 抄送: [e-mail]; wangyali <[e-mail]>
> 主题: Re: [Lsr] A new version of I-D,
> draft-liu-lsr-isis-ifit-node-capability-02
>
> Speak as WG Member...
>
> On 4/1/20, 8:08 AM, "Acee Lindem (acee)" <[e-mail]> wrote:
>
>     There is also a difference between some of the existing applications
> advertised in IGP capabilities. For example, MSD is used with the routing
> information to construct SR paths. The information for all these OAM
> mechanisms doesn't share this affinity. Also, it seems like a slippery
> slope in what is needed for each of the mechanism.
>     Thanks,
>     Acee
>
>     On 4/1/20, 4:01 AM, "Lsr on behalf of Tianran Zhou" <
> [e-mail] on behalf of [e-mail]> wrote:
>
>         Hi Les,
>
>         Thanks very much for your suggestion. I have a quick look at
> rfc6823. Sounds like a good idea. I will think about it.
>
>         Cheers,
>         Tianran
>
>         -----Original Message-----
>         From: Les Ginsberg (ginsberg) [mailto:[e-mail]]
>         Sent: Wednesday, April 1, 2020 1:47 PM
>         To: Tianran Zhou <[e-mail]>; Christian Hopps <
> [e-mail]>
>         Cc: wangyali <[e-mail]>; [e-mail]
>         Subject: RE: [Lsr] A new version of I-D,
> draft-liu-lsr-isis-ifit-node-capability-02
>
>         Tianran -
>
>         I am very much in agreement with the points Chris has made.
>
>         IGPs do not exist to advertise capabilities/configure applications
> - which seems to me to be what you are proposing here.
>         The fact that you can easily define the encodings does not make it
> the right thing to do.
>
>         This issue was discussed at length in the context of
> https://tools.ietf.org/html/rfc6823 . If you were proposing to use GENAPP
> I would not object - though I do think Chris has correctly pointed out that
> NETCONF/YANG is likely a more appropriate solution for your use case.
>
>            Les
>
>
>         > -----Original Message-----
>         > From: Tianran Zhou <[e-mail]>
>         > Sent: Tuesday, March 31, 2020 7:53 PM
>         > To: Christian Hopps <[e-mail]>
>         > Cc: wangyali <[e-mail]>; Les Ginsberg (ginsberg)
>         > <[e-mail]>; [e-mail]
>         > Subject: RE: [Lsr] A new version of I-D,
>         > draft-liu-lsr-isis-ifit-node-capability-02
>         >
>         > Hi Chris,
>         > Thanks for your quick reply, and please see inline.
>         >
>         > Cheers,
>         > Tianran
>         >
>         > -----Original Message-----
>         > From: Christian Hopps [mailto:[e-mail]]
>         > Sent: Wednesday, April 1, 2020 10:00 AM
>         > To: Tianran Zhou <[e-mail]>
>         > Cc: Christian Hopps <[e-mail]>; wangyali
>         > <[e-mail]>; Les Ginsberg (ginsberg) <
> [e-mail]>;
>         > [e-mail]
>         > Subject: Re: [Lsr] A new version of I-D,
>         > draft-liu-lsr-isis-ifit-node-capability-02
>         >
>         >
>         >
>         > > On Mar 31, 2020, at 9:28 PM, Tianran Zhou <
> [e-mail]>
>         > wrote:
>         > >
>         > > ZTR> Let's not boil the ocean to compare NETCONF/YANG or
> routing
>         > protocol, which is better. But I did not see the modification to
>         > routing protocol with some TLVs is a heavy work, or more complex
> than
>         > NETCONF/YANG.  I see both are available and useful.
>         >
>         > I'm not sure what you mean by boiling the ocean. I'm saying that
> YANG
>         > is built and intended for querying capabilities and configuring
>         > routers. Why isn't that where you are looking first for
> configuring your monitoring application?
>         >
>         > ZTR> I know NETCONF can do both query and configuration. And I
> know
>         > resent YANG-Push improvements to reduce the polling.  But
> routing
>         > protocol solutions are also widely used for this. There are
> already
>         > many RFCs and implementation practices. We considered both ways,
> and
>         > aimed for different scenarios.
>         >
>         > You don't see the major difference between writing a YANG model
> vs
>         > modifying all of the standard IETF routing protocols?
>         >
>         > ZTR> I know many differences between NETCONF and routing
> protocol.
>         > There are many details on both interfaces, implementations,
> scenarios
>         > when comparing them. That's what I mean boil the ocean.
>         > Here I do not know what's the "major difference" you mean?
>         >
>         > Thanks,
>         > Chris.
>
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