Shraddha,
On 24/11/2021 06:19, Shraddha Hegde wrote:
WG,
MPLS egress protection framework RFC 8679 provides a mechanism to
locally protect the traffic during
PE failures. The concepts can be applied to SRv6 as well. This mechanism
is much more efficient and quick because it locally provides fast protection
it requires SID allocation to be synchronized between multiple egress
PEs. With per CE SID allocation and multiple next-hops on each PE, the
number of SIDs become large and keeping them in sync is challenging.
Using anycast SID approach, you are loosing overlay (BGP) ECMP performed
at the ingress and replace it with underlay (IGP) ECMP towards the
egress. This may prevent BGP to load balance across multiple PEs or even
pick one as a preferred one.
So while it is a alternative, it has its drawbacks. We are trying to
provide a solution which would not pose any extra requirement to SID
allocation, nor affect BGP in any way.
thanks,
Peter
And switchover to the other PE.
If you compare this to the mechanisms being discussed in this thread
where the failure information is being
propagated by the egress PE to ABR and then ABR to the ingress, the
failover is going to be much slower.
The egress protection technology does not flood any information outside
of the domain and hence does not
affect the IGP scale.
This is a valid alternate solution to solve the problem at hand IMO.
I would be interested to see if people have use cases where egress
protection can’t be applied.
Rgds
Shraddha
Juniper Business Use Only
*From:* Lsr <[email protected]> *On Behalf Of *Tony Li
*Sent:* Tuesday, November 23, 2021 10:22 PM
*To:* Aijun Wang <[email protected]>
*Cc:* Les Ginsberg (ginsberg) <[email protected]>; Gyan Mishra
<[email protected]>; Christian Hopps <[email protected]>; lsr
<[email protected]>; Acee Lindem (acee) <[email protected]>; Tony Przygienda
<[email protected]>
*Subject:* Re: [Lsr] 【Responses for Comments on PUAM Draft】RE: IETF
112 LSR Meeting Minutes
*[External Email. Be cautious of content]*
Hi Aijun,
I object to adding negative liveness to the LSDB because of the
scale and because it adds scale during failures.
*/[WAJ] If we have no such mechanism, operator should either
advertise the host routes across areas(which has scale problem), or
lose the fast convergences for some overlay services(which defeat
the user experiences)./*
*/Within the real network, there is very rare chance for the massive
failure. And even such thing happen accidently, the information
about node liveness is countable, is there any router can’t process
such information?/*
*/The received unreachable information does not trigger the SPF
calculation. Will they influence intensively the performance of the
router?/*
If the scale is equal, then I would prefer to see flooding positive
information rather than negative information. Operationally this is
key: if there is a failure and positive information doesn’t propagate,
then it’s a bug that will be found in due course and the operator can
react outside of a failure scenario.
Having a scale failure on top of a topology failure is a far more
painful scenario.
The odds of a mass failure may be low. The fact of the matter is that
they still happen. It is our job to ensure that the IGP performs well
when it does.
Increasing the size of the LSDB always affects performance. It slows
flooding. Some nodes may not realize that SPF is not needed. When LSP
fragments are rearranged, inferring that SPF is not necessary is
non-trivial. Impacting router and network performance is a given.
My understanding is that N node failures would result in O(N) bytes
added to the LSDB. If someone has a way to compress that
information to O(1), I (and Claude Shannon) would be interested.
*/[WAJ] Do you have other determined solutions except the PUB/SUB
mechanism that does not exist in current IGP?/*
None of the mechanisms being discussed currently exist.
I have no objections to Robert’s BGP propagation ideas if that’s workable.
This is simply not the IGP’s job and the IGP is not a dump truck.
Tony
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