Robert,
On 05/08/2022 09:09, Robert Raszuk wrote:
Peter,
Side question ...
Assume PE participates in 10 end to end flex-algos.
However BGP advertises 100K service routes with base 0 nh 1.1.1.1/32
<http://1.1.1.1/32>
Are you stating that BGP should advertise 100K routes 10 times with
different IP address ?
absolutely not.
Note that mapping to flex-algo may not be prefix based on the number of
forwarding paradigms. Yet UPA seems to be only prefix based.
so far flex-algo has been documented for SR (MPLS and SRv6) and for IP
(v4/v6). For SR MPLS the algo forwarding is realized via unique algo
label, for SRv6 via unique algo locator and for IP via unique IP prefix.
If other "forwarding paradigms" want to use it, they would need to defne
how.
UPA is about prefix reachability, or more precisely about the loss of it.
thanks,
Peter
Was this case discussed in any document/thread so far ?
Thx,
R.
.
On Fri, Aug 5, 2022 at 12:16 PM Peter Psenak
<[email protected] <mailto:[email protected]>>
wrote:
Zhibo,
On 05/08/2022 05:49, Huzhibo wrote:
> Peter:
>
>> -----Original Message-----
>> From: Peter Psenak [mailto:[email protected]
<mailto:[email protected]>]
>> Sent: Friday, August 5, 2022 1:55 PM
>> To: Huzhibo <[email protected] <mailto:[email protected]>>
>> Cc: [email protected] <mailto:[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]
<mailto:[email protected]>]
>>>> Sent: Wednesday, August 3, 2022 11:20 PM
>>>> To: Huzhibo <[email protected] <mailto:[email protected]>>
>>>> Cc: [email protected] <mailto:[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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