Re: [Lsr] Publication has been requested for draft-ietf-lsr-ip-flexalgo-06

[Robert Raszuk <[e-mail]>]

Ok cool - thx Peter !

More general question - for any FlexAlgo model (incl. SR):

Is fallback between topologies - say during failure of primary one - only
allowed on the ingress to the network ?

If so the repair must be setup on each topology, otherwise repair will be
long as it would need to wait for igp flooding and ingress switchover
trigger ?

Obviously for IP flex algo it would be much much longer as given prefix
needs to be completely reflooded network wide and purged from original
topo. Ouch considering time to trigger such action.

Many thanks,
R.

On Tue, May 17, 2022, 13:35 Peter Psenak <[e-mail]> wrote:

> Hi Robert,
>
>
> On 17/05/2022 12:11, Robert Raszuk wrote:
> >
> > Actually I would like to further clarify if workaround 1 is even doable
> ...
> >
> > It seems to me that the IP flexalgo paradigm does not have a way for
> > more granular then destination prefix forwarding.
>
> that is correct. In IP flex-algo the prefix itself is bound to the
> algorithm.
>
> >
> > So if I have http traffic vs streaming vs voice going to the same load
> > balancer (same dst IP address) there seems to be no way to map some
> > traffic (based on say port number) to take specific topology.
>
> no, you can not do that with IP flex-algo.
>
>
> >
> > That's pretty coarse and frankly very limiting for applicability of IP
> > flex-algo. If I am correct the draft should be very explicit about this
> > before publication.
>
> please look at the latest version of the draft, section 3:
>
>
> https://datatracker.ietf.org/doc/html/draft-ietf-lsr-ip-flexalgo#section-3
>
> thanks,
> Peter
>
> >
> > Kind regards
> > R.
> >
> > On Tue, May 17, 2022 at 12:01 PM Robert Raszuk <[e-mail]
> > <mailto:[e-mail]>> wrote:
> >
> >     Folks,
> >
> >     A bit related to Aijun's point but I have question to the text from
> >     the draft he quoted:
> >
> >         In cases where a prefix advertisement is received in both a IPv4
> >         Prefix Reachability TLV and an IPv4 Algorithm Prefix Reachability
> >         TLV, the IPv4 Prefix Reachability advertisement MUST be preferred
> >         when installing entries in the forwarding plane.
> >
> >     Does this really mean that I can not for a given prefix say /24 use
> >     default topology for best effort traffic and new flex-algo topology
> >     for specific application ?
> >
> >     Is the "workaround 1" to always build two new topologies for such
> >     /24 prefix (one following base topo and one new) and never advertise
> >     it in base topology ?
> >
> >     Is the "workaround 2" to forget about native forwarding and use for
> >     example SR and mark the packets such that SID pool corresponding to
> >     base topology forwarding will be separate from SID pool
> >     corresponding to new flex-algo topology ?
> >
> >     Many thx,
> >     Robert
> >
> >
> >     ---------- Forwarded message ---------
> >     From: *Acee Lindem via Datatracker* <[e-mail]
> >     <mailto:[e-mail]>>
> >     Date: Mon, May 16, 2022 at 3:36 PM
> >     Subject: [Lsr] Publication has been requested for
> >     draft-ietf-lsr-ip-flexalgo-06
> >     To: <[e-mail] <mailto:[e-mail]>>
> >     Cc: <[e-mail] <mailto:[e-mail]>>,
> >     <[e-mail] <mailto:[e-mail]>>,
> >     <[e-mail] <mailto:[e-mail]>>, <[e-mail]
> >     <mailto:[e-mail]>>
> >
> >
> >     Acee Lindem has requested publication of
> >     draft-ietf-lsr-ip-flexalgo-06 as Proposed Standard on behalf of the
> >     LSR working group.
> >
> >     Please verify the document's state at
> >     https://datatracker.ietf.org/doc/draft-ietf-lsr-ip-flexalgo/
> >     <https://datatracker.ietf.org/doc/draft-ietf-lsr-ip-flexalgo/>
> >
> >
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> >
>
>