Hi Robert,
On 25/07/2023 18:51, Robert Raszuk wrote:
Hey Peter,
I think the point Bruno is making is valid ... Imagine dual or triple
vendor network and hop by hop routing (no end to end SAFI).
That means that all nodes should be in synch in terms to react on UPA,
chapter 7 of the draft says:
"Processing of the received UPAs is optional and SHOULD be controlled by
the configuration at the receiver. The receiver itself, based on its
configuration, decides what the UPA will be used for and what
applications, if any, will be notified when UPA is received."
So we have a way to achieve consistency if it is ever needed. For most
cases, the network wide consistency is not needed.
thanks,
Peter
Of course you will say that this is up to wise operator to enable it
only when it makes sense ... but I think the point is still valid and
clearly for none tunneled networks (if ever to use UPA) this is NOT a
local decision,
For vast majority it is local as forwarding is using some sort of PE-PE
encapsulation.
Cheers,
R.
On Tue, Jul 25, 2023 at 9:11 AM Peter Psenak
<[email protected] <mailto:[email protected]>>
wrote:
Bruno,
On 25/07/2023 14:39, [email protected]
<mailto:[email protected]> wrote:
> Hi all,
>
> IP reachability advertised by IS-IS is often used by other
routing and
> signaling protocols (e.g., BGP, PIM (rpf vector) LDP,
RSVP-TE...). As
> such, UPA may affect those protocols.
>
> Has UPA been presented in other WGs in the routing areas?
>
> I believe this would be prudent if not required.
why do you believe so? How is this different to an IGP prefix becoming
unreachable without UPA?
>
> In particular, BGP is (heavily) using reachability of (loopbacks)
> addresses advertised in IS-IS in order to evaluate the
reachability of
> BGP routes and compute their preference.
>
> If UPA is not interpreted the same ways by all routers,
forwarding loops
> may occur in a hop by hop routed network. (because different routers
> would select different paths since they use different information to
> select their path)
I don't see a problem, please provide an example.
If an ingress PE decides to switch to an alternate BGP path, how does
that creates any potential loop? And why all egress PEs would need
to do
the same?
>
> This is not considered nor discussed in the draft. Quite the
contrary,
> draft says that recognition, processing and use of UPA is a local
> consideration.
yes, and we want to keep it that way.
thanks,
Peter
>
> I would suggest to at minimum present this draft to IDR and gets the
> feedback from the IDR WG.
>
> --Bruno
>
>
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