Subject: Re: [Lsr] draft-ietf-lsr-flex-algo

From: Peter Psenak <[email-masked]>
Date: Wed, 1 Jul 2020 11:18:57 +0200

Hi Bruno,

please see inline:

On 30/06/2020 18:39, [email-masked] wrote:
> Hi Peter,
> 
>> From: Peter Psenak [mailto:[email-masked]]
>>
>> Hi Bruno,
>>
>> On 30/06/2020 18:08, [email-masked] wrote:
>>> Hi Peter,
>>>
>>> Thanks for your reply.
>>>
>>>> From: Peter Psenak [mailto:[email-masked]]
>>>>
>>>> Hi Bruno,
>>>>
>>>> please see inline:
>>>>
>>>> On 30/06/2020 16:53, [email-masked] wrote:
>>>>> Hi all,
>>>>>
>>>>> I can live with the current text, but I'm just raising the point for
>> discussion
>>>> (better safe than sorry).
>>>>>
>>>>> "16.1.1.  IGP Algorithm Types Registry
>>>>>
>>>>>       This document makes the following registrations in the "IGP Algorithm
>>>> Types" registry:
>>>>>
>>>>>          Type: 128-255.
>>>>>
>>>>>          Description: Flexible Algorithms.
>>>>> "
>>>>> https://tools.ietf.org/html/draft-ietf-lsr-flex-algo-07#section-16.1.1
>>>>>
>>>>> This is essentially burning half of the registry for flex-algo. Indeed, any
>>>> network operator could use any value, e.g. 222, hence the IETF could
>> never
>>>> define a different usage for this value without creating interop issues for
>> the
>>>> network operator.
>>>>
>>>> what is the real problem? Is the space 2-127 that is free not sufficient
>>>> for other standardized algorithms that may come?
>>>>
>>>>>
>>>>> We could discuss whether we really need 127 values for this. (i.e. a
>>>> network operator requiring 127 flex algo, typically multiplying its IGP FIB
>>>> entries by 127...).
>>>>
>>>> above is not necessarily true and more importantly completely irrelevant
>>>> to the number of algos we reserve for FA.
>>>>
>>>>
>>>>> We could also discuss whether this range could be change to the IANA
>> well-
>>>> known "Private Use" [1]. This would allow for alternative private usages in
>>>> the future (e.g. Flexible Alorithms v2).
>>>>> [1] https://tools.ietf.org/html/rfc8126#section-4.1
>>>>>
>>>>> It seems to me that the latter would equally work for flex algo, but
>> would
>>>> provide more flexibility :-) for the future.
>>>>
>>>> I don't think so. We need an allocated range of algos for FA for
>>>> compatibility.
>>>
>>> The allocated range of algos for FA would be the same. Just not dedicated
>> to FA.
>>
>> this would not work. If I have a mix of routers, one set using value 222
>> for flex-algo and another set for something else, how are they going to
>> interoperate?
> 
> My understanding is that the value of the flexalgo is chosen by the network operator and configured on the router.
> 
> " We want the mapping between the Flex-Algorithm and it's meaning to be flexible and defined by the user."
> [...]
> " Flexible-Algorithm is a numeric identifier in the range 128-255 that
>     is associated via provisioning with the Flexible-Algorithm
>     Definition."
> 
> 
> IOW, "private or local use only, with the type and
>     purpose defined by the local site.  No attempt is made to prevent
>     multiple sites from using the same value in different (and
>     incompatible) ways.  IANA does not record assignments from registries
>     or ranges with this policy (and therefore there is no need for IANA
>     to review them) and assignments are not generally useful for broad
>     interoperability.  It is the responsibility of the sites making use
>     of the Private Use range to ensure that no conflicts occur (within
>     the intended scope of use)."
> 
> Which is the definition of Private Use by IANA.
> 
> 
>> We need a standardized range, using Private Use is not an option here.
> 
> Yes we need a standardized range.
> I'm not sure that this range needs to be dedicated to FA. But I leave this to you/the WG.

for flex-algos the definition of the algo comes from the FAD.

For correct operation one need to ensure that the algo definition comes 
from a common source.

If half of the routers follow FAD for algo 222 and other half takes the 
definition somewhere else, things would break.

We basically need to ensure that for the algos reserved for FA, the 
definition comes only from FAD.

thanks,
Peter

> 
> And thanks again for your active engagement in the discussion.
> 
> -- Bruno
> 
>> thanks,
>> Peter
>>
>>>
>>> --Bruno
>>>
>>>>
>>>> thanks,
>>>> Peter
>>>>>
>>>>> Regards,
>>>>> --Bruno
>>>>>
>>>>>
>>>>
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> 
> _________________________________________________________________________________________________________________________
> 
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> a l'expediteur et le detruire ainsi que les pieces jointes. Les messages electroniques etant susceptibles d'alteration,
> Orange decline toute responsabilite si ce message a ete altere, deforme ou falsifie. Merci.
> 
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