Re: [Lsr] Comments on draft-wang-lsr-prefix-unreachable-annoucement

[Ketan Talaulikar <[e-mail]>]

Hi Aijun,

Please check inline below for a quick response.

On Wed, Jul 27, 2022 at 2:55 PM Aijun Wang <[e-mail]>
wrote:

> Hi, Ketan:
>
>
>
> Thanks for your comments.  But I should correct some of them:
>
> 1)     In the updated version, the indication of prefix unreachability is
> still the “NULL” value of prefix originator, not the LSInfinity.
>
KT> Right and I am suggesting you go one step further and remove all that
prefix originator "business" :-)


> 2)     The LSInfinity is used only for avoiding the misrouting by
> implementation not support this implementation, as you have also pointed
> out.  As pointed out also in the draft, when all the nodes within the area
> support such capabilities, the LSInfinity value can be ignored:
>

KT> Well, as indicated, the use of the prefix originator for this purpose
is broken in my view. The use of LSInfinity is helpful to navigate through
backward compatibility issues. With prefix originator aspects removed, we
don't need the capability anymore. What comes out at the other end of this
"pivot" for draft-wang is much similar to the other proposal ... and this
IMHO is good.


>
>
> “If not all of nodes within one area support the PUAM capabilities,
>
>    the PUAM message should be advertised with the associated prefix cost
>
>    set to LSInfinity.  According to the description in [RFC2328 <https://datatracker.ietf.org/doc/html/rfc2328>],
>
>    [RFC5305 <https://datatracker.ietf.org/doc/html/rfc5305>] and [RFC5308 <https://datatracker.ietf.org/doc/html/rfc5308>], the prefix advertised with such metric value
>
>    will not be considered during the normal SPF computation, then such
>
>    additional information will avoid the misbehavior of the nodes when
>
>    they don't recognize the PUAM message.
>
>
>
>    If all of nodes within one area support the PUAM capabilites, the
>
>    PUAM message can be safely advertised without the additional
>
>    LSInfinity metric information.”
>
>
>
>
>
> We are glad to cooperate with Peter to forward the solution, but want to
> say LSInfinity only can’t be used to indicate the unreachable information,
> we need some explicit indication method.
>

KT> There is some value in having an explicit indication in addition to the
use of LSInfinity in draft-ppsenak. Perhaps a prefix attribute flag as was
already suggested to the authors of draft-ppsenak (
https://mailarchive.ietf.org/arch/msg/lsr/Q9wU3Bo1uzhPd5C7bT_WE7k_3JI/).
But certainly not the prefix originator as proposed by draft-wang.

Thanks,
Ketan


>
>
>
>
> Best Regards
>
>
>
> Aijun Wang
>
> China Telecom
>
>
>
> *发件人:* [e-mail] [mailto:[e-mail]] *代表 *Ketan
> Talaulikar
> *发送时间:* 2022年7月27日 16:36
> *收件人:* [e-mail]
> *抄送:* lsr <[e-mail]>
> *主题:* [Lsr] Comments on draft-wang-lsr-prefix-unreachable-annoucement
>
>
>
> Hello Authors,
>
>
>
> I am sharing some comments on the latest version of this document since we
> seem to have a packed agenda in LSR this time.
>
>
>
> 1) I notice that in the latest update of the draft, there is a big change
> to start using LSInfinity for indicating prefix unreachability (similar
> to draft-ppsenak-lsr-igp-ureach-prefix-announce). I see this as a sign of a
> degree of convergence between the two drafts.
>
>
>
> 2) However, I then question the motivation of the authors to continue with
> the bad design of overloading Prefix Originator and the added capability
> stuff on top. I don't wish to repeat why that design was an absolute NO-GO
> for me and I am glad to see the authors acknowledge the problem with
> misrouting by implementations not supporting this specification. So I don't
> see the point of still retaining all that.
>
>
>
> Thanks,
>
> Ketan
>
>
>