Re: [i2rs] Question on opstate/ephemeral update

"Susan Hares" <shares@ndzh.com> Thu, 17 November 2016 04:24 UTC

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From: Susan Hares <shares@ndzh.com>
To: "'Joel M. Halpern'" <jmh@joelhalpern.com>, 'Joe Clarke' <jclarke@cisco.com>, i2rs@ietf.org
References: <8419df8b-4861-edb7-0a66-c2c123148727@cisco.com> <015201d2404d$ef173260$cd459720$@ndzh.com> <d17fc9d5-3f94-a50c-817b-a1abeb30b094@joelhalpern.com>
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Date: Wed, 16 Nov 2016 23:21:48 -0500
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Subject: Re: [i2rs] Question on opstate/ephemeral update
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Joel: 

My description is one 1 way to implement 3.4.   -Resolve the multi-write
conflict via client priorities.   Then install configuration into node using
the data store priorities (config = priority 3, ephemeral = priority 4, dhcp
= priority 2).  

Your way is to assign the priorities so it is a complete scheme.    Common
algebra techniques indicates these are the same.  Let's see what happens
when we implemented both ways. 

Cheers, 

Seu 


-----Original Message-----
From: i2rs [mailto:i2rs-bounces@ietf.org] On Behalf Of Joel M. Halpern
Sent: Wednesday, November 16, 2016 8:21 PM
To: Susan Hares; 'Joe Clarke'; i2rs@ietf.org
Subject: Re: [i2rs] Question on opstate/ephemeral update

My read of the ephemeral state requirements in this regard (3.4) was that we
are simply assigning Intended Conifg and the specific other cynamic control
protocols priorities in the same space we are using for deciding between
I2RS clients in the case of conflict.

So if I2RS Clients have priorities ranging from min+2 to Max-2, then
assuming higher is better, to get the result in your first example, one
would set intended to min-1 and dhcp to min-2.
And the reverse for your second example.

As an operator, one could assign ones clients priorities in various ranges,
and arrange the dhcp and intended config priorities at other points to get
more complex results.
And of course, one could set dhcp to max+1 and intended config to max+2 to
max I2RS yield to all the others, and intended config take precedence over
everything.

Yours,
Joel

On 11/16/16 4:10 PM, Susan Hares wrote:
> Joe:
>
> I've updated the examples in the yang document.  Here's my 
> understanding with priorities (see ephemeral state requirements) with 
> highest priority winning.
>
> Set
> Intended configuration priority = 2
> Dhcp configuration priority = 1
> Ephemeral state = 3
>
> Dhcp - would never update things, and I2RS would win over intended 
> configuration.
>
> Set
> Intended configuration priority = 1
> Dhcp configuration priority = 2
> Ephemeral state = 3
>
> Dhcp takes precedence (wins) over intended configuration - so dhcp 
> received configurations are installed.  Ephemeral state wins over dhcp
values.
>
> Does this make sense?
>
> Sue
>
> -----Original Message-----
> From: i2rs [mailto:i2rs-bounces@ietf.org] On Behalf Of Joe Clarke
> Sent: Wednesday, November 16, 2016 1:56 AM
> To: i2rs@ietf.org
> Subject: [i2rs] Question on opstate/ephemeral update
>
> Given the tight timing of the meeting, I don't want to derail things.
> If we have time, I'll raise this at the mic.
>
> But I do have a question on slide 2 of 
> https://www.ietf.org/proceedings/97/slides/slides-97-i2rs-i2rs-opstate
> -and-e
> phemeral-00.pdf
> .  I see DHCP along side the [I2RS] control plane DSes.  I understand 
> that the I2RS agent will handle the resolution of multiple client 
> writes using priorities.
>
> But how does that play with DHCP or local config?  In our ephemeral 
> requirements draft we say that local config (<intended> in this 
> drawing) would have a priority.  And that in the <applied> state the 
> device would have to resolve the local priorities with the "winning" 
> config from the I2RS agent.  But then DHCP writes a route.  How will that
be handled?
>
> I would like some clarity with respect to our priority requirements in 
> the ephemeral state draft.
>
> Joe
>
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