Zhibo,
On 05/08/2022 05:49, Huzhibo wrote:
Peter:
-----Original Message-----
From: Peter Psenak [mailto:[email protected]]
Sent: Friday, August 5, 2022 1:55 PM
To: Huzhibo <[email protected]>
Cc: [email protected]
Subject: Re: Question about draft-ppsenak-lsr-igp-ureach-prefix-announce
Zhibo,
On 03/08/2022 21:09, Huzhibo wrote:
Hi Peter:
Please see inline.
-----Original Message-----
From: Peter Psenak [mailto:[email protected]]
Sent: Wednesday, August 3, 2022 11:20 PM
To: Huzhibo <[email protected]>
Cc: [email protected]
Subject: Re: Question about
draft-ppsenak-lsr-igp-ureach-prefix-announce
Hi Zhibo,
On 29/07/2022 20:49, Huzhibo wrote:
Hi Peter:
Supplement to yesterday's online questions, If a node that does not
support IP Flexalgo, which has a default route, should the node
process the IP Flexalgo prefix as a UPA?
- I assume you are talking about the algo 0 default route. Because IP
Flex-algo default route does not make much sense really.
- If the node does not support IP flex-algo, than it would not use
any IP algo prefix as BGP service endpoint or for any other purpose.
Which IP Algo prefix as BGP service endpoint is not determined by the ingress
node, Such as VXLAN and SRv6 VPN.
When the ingress node receives an BGP Service cayyied a IP algo prefix
as endpoint and it has a algo 0 default route, it should be process this BGP
service. and this can not be affected by the IGP Flexalgo prefix.
sorry, but above is completely wrong.
When you want to use IP flex-algo forwarding, you must advertise the prefix as
algo prefix, relying on the algo 0 default would not give you algo forwarding.
Advertising IP algo prefix at the egress and relying in algo 0 default at the
ingress is going to cause all sorts of problems. You CAN NOT mix/change algos
along the path through the network - if you do, you may end up in a permanent
loop.
If the ingress node does not support Flexalgo, the ingress node does not cause a
permanent loop because once the packet is forwarded to the Flexalgo node, it
always
follows Flexalgo forwarding. If the packet does not reach the Flexalgo node, it
always follows
Algo 0 forwarding.
well, flex-algo was design for end to end forwarding. Switching between
algos as packet traverses the network is not guaranteed to be loop free.
If you don't trust me, I let you figure that out yourself when you do
such a thing and it breaks.
Therefore,
the IGP does only not generate the RIB/Fib for LSinfinity Metric prefix, but can
not trigger BGP Service Down.
In addition, LSinfinity Metric may be applied to other scenarios in
the future. We cannot guarantee that LSinfinity Metric will not conflict with
other purposes when being processed as a UPA.
no, it can not, because the LSinfinity has a very strict definition - it means
unreachable, which is exactly what the UPA is about.
I believe you are confusing a concept. The LSInfinity metric defined in RFC 5308
can be considered as zero route, but PUA/UPA actually defines a negative route.
It's not consistent
I'm not confusing anything:
rfc2328:
LSInfinity
The metric value indicating that the destination described by an
LSA is unreachable.
regards,
Peter
Peter
- If such node receives the IP algo prefix and even if it treats it
as UPA, given that such IP algo prefix was never reachable before on
this node, the UPA would result in no action.
thanks,
Peter
Thanks
Zhibo
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