Re: draft-ietf-rtgwg-policy-model default reject-route

Adding rfc-editor@rfc-editor.org


> On Sep 27, 2021, at 11:58 AM, Acee Lindem (acee) <acee@cisco.com> wrote:
> 
> Hi Kris, 
> I agree with your analysis and proposal. Do others have comment? If not,  we should remove during AUTH48 (Chris Smiley copied). 
> Thanks,
> Acee
> 
> On 9/17/21, 10:55 AM, "rtgwg on behalf of Kris Lambrechts" <rtgwg-bounces@ietf.org on behalf of kris@netedge.plus> wrote:
> 
>    Hi,
> 
>    I have been working on an implementation of
>    ietf-routing-policy@2021-08-12.yang and
>    ietf-bgp-policy@2021-07-11.yang and I'm struggling to implement a
>    pattern that I think is very common among routing policies.
> 
>    The problem I'm seeing is with the policy-result leaf under actions.
>    It is of type policy-result-type meaning that it can be either
>    accept-route or reject-route with a default of reject-route. As per
>    section 5.  Policy evaluation, all processing ends when either of
>    these is encountered. That would mean only one statement in a policy
>    can ever be processed. The first paragraph of section 5 suggests the
>    presence of those actions is optional however:
>> If the actions include either accept-route or reject-route actions, evaluation of the current policy definition stops, and no further policy statement is evaluated.
> 
>    In any vendor implementation I'm familiar with it is possible, and
>    common in practice, to combine actions (i.e. set a BGP community or
>    local-preference) from various statements which are processed in order
>    by either implicitly or explicitly continuing on to the next
>    statement.
> 
>    So my proposal here is to remove the default statement from the
>    policy-result, which would signify an implicit continuation to the
>    next statement. Or with the same net effect, you could add a
>    next-statement enum to the policy-result-types to make the choice
>    explicit.
> 
>    I feel like either change would make it much easier to write elegant,
>    compact and easy-to-understand policies (and to port existing
>    policies). Still, if this goes against your intended design, it would
>    be good to fix any wording in the draft that implies that these
>    actions are optional.
> 
>    Thank you,
> 
>    Kris Lambrechts
> 
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