Robert.
On 18/05/2022 13:18, Robert Raszuk wrote:
Peter,
This was not my question ...
Section 10 of soon to be published RFC clearly states that *"IGP
restoration will be fast and additional protection mechanisms will not
be required." *
We can remove that sentence if you don't like it.
Those "additional mechanisms" are listed further like LFA, FRR with all
its flavors which of course can be enabled in each topology.
yes, so what else is missing?
So if (as co-author) you make such bold statement in the document I am
asking what makes networks where IGP Flex-Algo is used so good in terms
of *native* connectivity restoration that "additional protection will
not be required" ?
I have not added that sentence and I'm fine removing it.
This is 2022 and while many folks still got locked into archaic model
that for connectivity/service restoration you need to wait for protocol
convergence I would actually observe that during failure you should
first repair base topology then worry about flex-algos.
that is a matter of implementation and any ordering can be supported by
it, even configurable one.
I'm still not sure what exactly is your point.
thanks,
Peter
- - -
See one of the valid deployment models which get's often presented for
flex-algo is ability to run some special function on each node of given
topology yet make no changes whatsoever to path selection criteria. With
that running 100s of compute cycles for LFA in each topologically
identical flex-algo seems like a huge waist. And that deployment model
IMO should get attention and be addressed in base flex-algo specs.
Cheers,
Robert
On Wed, May 18, 2022 at 11:46 AM Peter Psenak <[email protected]
<mailto:[email protected]>> wrote:
Robert,
On 18/05/2022 10:53, Robert Raszuk 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 ?
the protection is provided withing the same algo, not between them. And
one can use all existing LFA mechanisms to do so.
thanks,
Peter
>
> 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]
<mailto:[email protected]>
> <mailto:[email protected] <mailto:[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]>
> <mailto:[email protected] <mailto:[email protected]>>
> > <mailto:[email protected] <mailto:[email protected]>
<mailto:[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]>>
> > <mailto:[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>>
> > > <mailto:[email protected]
<mailto:[email protected]> <mailto:[email protected]
<mailto:[email protected]>>
> <mailto:[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>>
> >
>
<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>>>
> > >
> >
>
<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>> <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]>>>
> > > <mailto:[email protected]
<mailto:[email protected]> <mailto:[email protected]
<mailto:[email protected]>>
> <mailto:[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>>>
> > > > <mailto:[email protected]
<mailto:[email protected]>
> <mailto:[email protected] <mailto:[email protected]>>
<mailto:[email protected] <mailto:[email protected]>
> <mailto:[email protected] <mailto:[email protected]>>>
> > <mailto:[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]>>>
> > > <mailto:[email protected]
<mailto:[email protected]> <mailto:[email protected]
<mailto:[email protected]>>
> <mailto:[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>>>
> > > > <mailto:[email protected]
<mailto:[email protected]>
> <mailto:[email protected] <mailto:[email protected]>>
<mailto:[email protected] <mailto:[email protected]>
> <mailto:[email protected] <mailto:[email protected]>>>
> > <mailto:[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]>>>
> > <mailto:[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>
> <mailto:[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>>>
> > > <mailto:[email protected]
<mailto:[email protected]> <mailto:[email protected]
<mailto:[email protected]>>
> <mailto:[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>>
> > <mailto:[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]>>>
> > <mailto:[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>
> <mailto:[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>>>
> > > <mailto:[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>
> <mailto:[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>>
> > <mailto:[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]>>> <mailto:[email protected]
<mailto:[email protected]>
> <mailto:[email protected] <mailto:[email protected]>>
> > <mailto:[email protected]
<mailto:[email protected]>
> <mailto:[email protected]
<mailto:[email protected]>>>>
> > > <mailto:[email protected]
<mailto:[email protected]>
> <mailto:[email protected] <mailto:[email protected]>>
> > <mailto:[email protected]
<mailto:[email protected]>
> <mailto:[email protected]
<mailto:[email protected]>>> <mailto:[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]>>>
> > <mailto:[email protected]
<mailto:[email protected]> <mailto:[email protected]
<mailto:[email protected]>>
> <mailto:[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>>>
> > > <mailto:[email protected]
<mailto:[email protected]>
> <mailto:[email protected] <mailto:[email protected]>>
<mailto:[email protected] <mailto:[email protected]>
> <mailto:[email protected] <mailto:[email protected]>>>
> > <mailto:[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]>>> <mailto:[email protected]
<mailto:[email protected]>
> <mailto:[email protected] <mailto:[email protected]>>
> > <mailto:[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>>>
> > > > <mailto:[email protected]
<mailto:[email protected]> <mailto:[email protected] <mailto:[email protected]>>
> <mailto:[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>>
> > <mailto:[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/>>>
> > >
>
<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/>>>>
> > > >
> >
>
<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/>>>
> > >
>
<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/>>>>>
> > > >
> > > >
> > > >
_______________________________________________
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