Hi Peter, Enabling local protection on all nodes in all topologies may also not be the best thing to do (for various reasons).
While I agree that general fallback may be fragile, how about limited fallback and only to one special "protection topology" which would have few constraints allowing us to do such fallback safely ? I guess for ip flex-algo which is a subject of this thread this would not be possible, but for SR flex-algo I think this may work pretty well allowing N:1 fast connectivity restoration. Thx, Robert On Tue, May 17, 2022 at 2:19 PM Peter Psenak <ppse...@cisco.com> wrote: > Robert, > > On 17/05/2022 14:14, Robert Raszuk wrote: > > 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 ? > > no. Fallback between flex-algos has never been a requirement and is not > part of the flex-algo specification. > > I consider it a dangerous thing to do. It may work under certain > conditions, but may cause loops under different ones. > > thanks, > Peter > > > > > > 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 <ppse...@cisco.com > > <mailto:ppse...@cisco.com>> 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 > > < > 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 <rob...@raszuk.net > > <mailto:rob...@raszuk.net> > > > <mailto:rob...@raszuk.net <mailto:rob...@raszuk.net>>> 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* <nore...@ietf.org > > <mailto:nore...@ietf.org> > > > <mailto:nore...@ietf.org <mailto:nore...@ietf.org>>> > > > Date: Mon, May 16, 2022 at 3:36 PM > > > Subject: [Lsr] Publication has been requested for > > > draft-ietf-lsr-ip-flexalgo-06 > > > To: <j...@juniper.net <mailto:j...@juniper.net> > > <mailto:j...@juniper.net <mailto:j...@juniper.net>>> > > > Cc: <a...@cisco.com <mailto:a...@cisco.com> > > <mailto:a...@cisco.com <mailto:a...@cisco.com>>>, > > > <iesg-secret...@ietf.org <mailto:iesg-secret...@ietf.org> > > <mailto:iesg-secret...@ietf.org <mailto:iesg-secret...@ietf.org>>>, > > > <lsr-cha...@ietf.org <mailto:lsr-cha...@ietf.org> > > <mailto:lsr-cha...@ietf.org <mailto:lsr-cha...@ietf.org>>>, > > <lsr@ietf.org <mailto:lsr@ietf.org> > > > <mailto:lsr@ietf.org <mailto:lsr@ietf.org>>> > > > > > > > > > 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/> > > > <https://datatracker.ietf.org/doc/draft-ietf-lsr-ip-flexalgo/ > > <https://datatracker.ietf.org/doc/draft-ietf-lsr-ip-flexalgo/>> > > > > > > > > > _______________________________________________ > > > Lsr mailing list > > > Lsr@ietf.org <mailto:Lsr@ietf.org> <mailto:Lsr@ietf.org > > <mailto:Lsr@ietf.org>> > > > https://www.ietf.org/mailman/listinfo/lsr > > <https://www.ietf.org/mailman/listinfo/lsr> > > > <https://www.ietf.org/mailman/listinfo/lsr > > <https://www.ietf.org/mailman/listinfo/lsr>> > > > > > > >
_______________________________________________ Lsr mailing list Lsr@ietf.org https://www.ietf.org/mailman/listinfo/lsr
