Re: [Idr] [draft-ietf-idr-segment-routing-te-policy] Error handling for Explicit NULL Label Policy Sub-TLV

[Przemyslaw Krol <[e-mail]>]

Hi Mano,

Oh, I see. Thanks for clarification and apologies for my irrelevant comment
then.
FWIW, I support your proposal to consider these values as reserved and
fallback to local poli..., erm, behavior defined by config :-)

pk




On Fri, May 17, 2019, 17:09 Manoharan Sundaramoorthy <[e-mail]>
wrote:

> Hi Pk,
>
> In 2(b) we meant, "For values 0 and 5-255, treat as if the Sub-TLV was not
> received and take default ENLP action that is configured locally" (or) "if
> these values are to be treated as illegal, then do TAW".
>
> Thanks,
> Mano
>
> On Fri, May 17, 2019 at 11:20 PM Przemyslaw Krol <[e-mail]> wrote:
>
>> Hi Nandan,
>>
>> I personally agree with your proposal for handling multiple ENLP sub-TLV
>> (1). It's clear and consistent with other similar cases
>>
>> In terms of ENLP = 0 || >=5 (2), my concern regarding 2b (fallback to
>> static) is that there may be multiple instances of BGP policy (different
>> advertisers) with the same or lower preference and valid ENLP values.
>> Failing back to static would basically skip those BGP policies and "bypass"
>> policy selection. I suspect it's undesirable. For this reason, treating it
>> as reserved (2a) sounds to me like a better option. Unless you really meant
>> ignoring offending policy and moving to the next one (which can be static
>> or BGP, depending on the selection algo), but regardless, 2a) seems safer
>> and less disruptive in the future (if/when we need ENLP >=5 ).
>>
>>
>> thanks,
>> pk
>>
>> On Thu, May 16, 2019 at 12:42 AM Nandan Saha <[e-mail]> wrote:
>>
>>> Hi folks,
>>>  There error handling for the ENLP sub-TLV isn't defined in
>>> draft-ietf-idr-segment-routing-te-policy-05 [1].
>>>
>>> There are 2 things that need to be clarified:-
>>>
>>> 1. The behavior when ENLP sub-TLV occurs more than once:
>>>   For this, my preference is to add text like we have for policy
>>> priority sub-TLV [2] (and some other sub-TLVs), mandating only one
>>> occurrence and treat-as-withdraw when present more than once.
>>>
>>> 2. Behavior when ENLP value is either 0 or >= 5.
>>>   The only meaningful/legal values defined now are 1-4. My preference is
>>> to
>>> 2a: mark other values as reserved for future use. (We could mark them
>>> illegal but that'll rule out trying to extended them if ever needed)
>>> and
>>> 2.b: Upon receipt ENLP = 0 || >=5 the headend call fall back to local
>>> policy. (If we go down the route of marking 0 || >= 5 as illegal, we
>>> can do TAW)
>>>
>>> Please let me know what you think, and if this seems reasonable.
>>>
>>> [1] -
>>> https://tools.ietf.org/html/draft-ietf-idr-segment-routing-te-policy-05#section-2.4.4
>>> [2] -
>>> https://tools.ietf.org/html/draft-ietf-idr-segment-routing-te-policy-05#section-2.4.5
>>>
>>> Thanks,
>>> Nandan
>>>
>>
>>
>> --
>> Przemyslaw "PK" Krol |  Strategic Network Engineer ing | [e-mail]
>>
>>
>
>
> --
> Thanks,
> Manoharan
>