Missed it - sorry: s/ control plane CPUs and data plane FIBs / control plane CPUs and data plane FIBs with LFA or R-LFA enabled per topo/
On Wed, May 18, 2022 at 10:53 AM Robert Raszuk <[email protected]> wrote: > Peter, > > It is not about someone thinking if this is a good idea or not. It is > about practical aspects of real deployments. > > But ok section 10 of the subject draft says something pretty interesting: > > > > > > > *10. Protection In many networks where IGP Flexible Algorithms are > deployed, IGP restoration will be fast and additional protection > mechanisms will not be required. * > > *Question:* What makes networks with IGP flex-algo running any better > then networks without it in terms of protection needed or not ? > > Sure when applicable ECMP can be used to locally protect the traffic. But > when you need to run flex-algo for mobile slicing requirements (as > discussed in section 3) the load on control plane CPUs and data plane FIBs > may become significant (especially when we are talking about lots of > "slices"). > > Thx, > R. > > > > > > > > > > > > On Wed, May 18, 2022 at 9:45 AM Peter Psenak <[email protected]> wrote: > >> Robert, >> >> I really do not want to get into fallback between algorithms. If someone >> really thinks it is a good idea, he can write a separate document and >> describe the use case and how to do that safely. But please not in the >> base flex-algo specification. >> >> thanks, >> Peter >> >> >> >> On 17/05/2022 19:58, Robert Raszuk wrote: >> > 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 <[email protected] >> > <mailto:[email protected]>> 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 <[email protected] >> > <mailto:[email protected]> >> > > <mailto:[email protected] <mailto:[email protected]>>> 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 >> > >> > > >> > < >> 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 >> > <[email protected] <mailto:[email protected]> >> > > <mailto:[email protected] <mailto:[email protected]>> >> > > > <mailto:[email protected] <mailto:[email protected]> >> > <mailto:[email protected] <mailto:[email protected]>>>> 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* <[email protected] >> > <mailto:[email protected]> >> > > <mailto:[email protected] <mailto:[email protected]>> >> > > > <mailto:[email protected] <mailto:[email protected]> >> > <mailto:[email protected] <mailto:[email protected]>>>> >> > > > Date: Mon, May 16, 2022 at 3:36 PM >> > > > Subject: [Lsr] Publication has been requested for >> > > > draft-ietf-lsr-ip-flexalgo-06 >> > > > To: <[email protected] <mailto:[email protected]> >> > <mailto:[email protected] <mailto:[email protected]>> >> > > <mailto:[email protected] <mailto:[email protected]> >> > <mailto:[email protected] <mailto:[email protected]>>>> >> > > > Cc: <[email protected] <mailto:[email protected]> >> > <mailto:[email protected] <mailto:[email protected]>> >> > > <mailto:[email protected] <mailto:[email protected]> >> > <mailto:[email protected] <mailto:[email protected]>>>>, >> > > > <[email protected] >> > <mailto:[email protected]> <mailto:[email protected] >> > <mailto:[email protected]>> >> > > <mailto:[email protected] >> > <mailto:[email protected]> <mailto:[email protected] >> > <mailto:[email protected]>>>>, >> > > > <[email protected] <mailto:[email protected]> >> > <mailto:[email protected] <mailto:[email protected]>> >> > > <mailto:[email protected] <mailto:[email protected]> >> > <mailto:[email protected] <mailto:[email protected]>>>>, >> > > <[email protected] <mailto:[email protected]> <mailto:[email protected] >> > <mailto:[email protected]>> >> > > > <mailto:[email protected] <mailto:[email protected]> >> > <mailto:[email protected] <mailto:[email protected]>>>> >> > > > >> > > > >> > > > 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/>> >> > > > >> > <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 >> > > > [email protected] <mailto:[email protected]> <mailto:[email protected] >> > <mailto:[email protected]>> <mailto:[email protected] <mailto:[email protected]> >> > > <mailto:[email protected] <mailto:[email protected]>>> >> > > > 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>> >> > > > <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>>> >> > > > >> > > >> > >> >>
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