Re: [Ibnemo] [Sdn] Defining a Common Model for intent

["Susan Hares" <[e-mail]>]

Bert and Tianran:

I believe that you are stating regarding the definition: 

Intent == (defines)  object, result, constraint 

An IDL (intent description Langague) would be a common way to express the
object, result, and constraints.  If you use roles, I suggest that roles
provide a grouping of objects, results, and constraints.   Do you agree? 

Sue 
-----Original Message-----
From: Ibnemo [mailto:[e-mail]] On Behalf Of Zhoutianran
Sent: Friday, June 05, 2015 2:42 AM
To: Bert Wijnen (IETF); STUART VENTERS; [e-mail]
Cc: [e-mail]
Subject: Re: [Ibnemo] [Sdn] Defining a Common Model for intent

Thanks Bert for your clarification.

That's another good description on the role based intent I think.


Terence

-----Original Message-----
From: Bert Wijnen (IETF) [mailto:[e-mail]]
Sent: Thursday, June 04, 2015 11:35 PM
To: Zhoutianran; STUART VENTERS; [e-mail]
Cc: [e-mail]
Subject: Re: [Ibnemo] [Sdn] Defining a Common Model for intent

On 04/06/15 14:26, Zhoutianran wrote:
> Hi Bert,
>
> Thanks for you comments.
> I agree with you that we'd better just focus on the top layer.
> But I am sorry, what do you mean in the last sentence?
> "A role -based intent model? I guess it would just boil down in different
types of intent that fit with the specific role, right?"
> Could you give more information on this?

Sorry for not being clear,

my thinking here is that
- intent model is basically the same for anyone.
- but based on your role, you express your intent with different (role
specific)
    statements. That possibly means you use similar language (IDL) but you
use
    different objects (data) to express it

So a customer/end-user says
   I want a link between location A and B, i.e. my intent is to use a
connection between A & B
   and I want 1GB with low delay
The service provider who needs to implement this says things like
   Create  a physical link between A&B
   or create a logical link between A&B with guaranteed 1GB capacity

So the customer/end-user does not care about physical or logical or
whatever.
Maybe he/she does not even want to know.

But the service provider of course needs to express intent about physical or
logical

Does that help?

Bert

> Best,
> Terence
>
> ________________________________________
> 发件人: Bert Wijnen (IETF) [[e-mail]]
> 发送时间: 2015年6月3日 21:08
> 收件人: Zhoutianran; STUART VENTERS; [e-mail]
> 抄送: [e-mail]
> 主题: Re: [Ibnemo] [Sdn] Defining a Common Model for intent
>
> Hi all,
>
> I like the idea of (at least for now) stick to the problem of "intent" for
one layer (the top layer).
> Let us not boil the ocean and try to do everything that comes up. If 
> we are successful in doing a model for IBNEMO for the top layer, we can
then see if we want to go at more layers.
>
> A role -based intent model? I guess it would just boil down in 
> different types of intent that fit with the specific role, right?
>
> Bert
>
>
> On 03/06/15 11:44, Zhoutianran wrote:
>> Hi Stuart,
>>
>> Thanks for this deep thinking with a set of examples. It's really
important to clarify this fuzzy intent.
>> I think all the concern and uncertainty is because of the layered
thinking. We think intent is a relatively higher level nested.
>> What if we think about intent with differnet roles? Just like a relative
detailed description in my "role based intent" email.
>> I think the essential of the role based intent is that there is only one
intent layer which is always on the top. Intent is dedicated for
corresponding roles. One role will not call other roles interfaces.
>> Then we can try to find way to express intent for various roles.
>>
>>
>> Regards,
>> Terence
>>
>> -----Original Message-----
>> From: sdn [mailto:[e-mail]] On Behalf Of STUART VENTERS
>> Sent: Wednesday, June 03, 2015 12:06 AM
>> To: [e-mail]
>> Cc: 'Dave Hood'; [e-mail]; Lifengkai (Fengkai); Zhoutianran; 
>> Xiayinben; Susan Hares
>> Subject: Re: [Sdn] Defining a Common Model for intent
>>
>>
>>
>> I have 2 cents to contribute for this fuzzy intent word and resulting
data model.
>> Perhaps 'intent'  is just a relatively high level service request.
>> The problem with this definition is what is that 'relatively high level'
appears to depend on your point of view.
>>
>> To help think about it, here's a long chain of command for the same
action.
>> It is long for fun and so that anybody can find part of it that they
recognize.
>>
>>
>> Chain of command:
>>
>> Investor says: make money
>> CEO says: make the network work
>> CIO says: give me bandwidths between sites A, B, and C Net engineer
>> says: I need these evc's to these endpoints Purchasing agent: Says 
>> use this product from this vendor Sales Person says: Here is the 
>> price and priority
>> Partitioner: divides the end to end circuit among administrative 
>> domains
>> Planner: picks the necessary resources to use, makes the truck rolls 
>> happen
>> Allocator: allocates the necessary bandwidth
>> Provisioner: decides what provisioning is necessary in each part of 
>> the path
>> Adaptor: tailors the provisioning to a specific box
>> Driver: pushes the provisioning into the forwarding tables Forwarding
>> engine: forwards according to the tables
>>
>> The Investor's statement at the top is clearly what and not how.
>> The forwarding engine's operations have a lot of how, but maybe little
global view of what we are doing overall.
>>
>> If we say that the top is intent and the bottom is a is service request,
>>     who's to say where intent stops and service requests start?
>>
>> Perhaps  'intent' means a service request coming from a higher layer for
refinement.
>>
>> That said, the data model for intent might/should be different at each
level.
>> Since each level is processing the same request at different levels of
detail, it might be similar at each level.
>> Perhaps the data model starts simple on top and gathers more and more
detail as it gets lower ?
>> Maybe like a tree with the root at the top and leaves at the forwarding
engines, except distributed.
>>
>> Perhaps a simple starting point near the top is a combination of
entities, endpoints, and connections.
>>
>>
>> Regards,
>>
>> Stuart Venters
>>
>>
>>
>>
>>
>>
>>
>> From: sdn [mailto:[e-mail]] On Behalf Of Dave Hood
>> Sent: Tuesday, June 02, 2015 8:26 AM
>> To: Lifengkai (Fengkai); Susan Hares; [e-mail]
>> Cc: Zhoutianran; Xiayinben; [e-mail]
>> Subject: Re: [Sdn] Defining a Common Model for intent
>>
>> I agree that the context matters, Fengkai (and Susan in earlier
response). What the I-D appears to be saying is that any interaction across
an NBI is intent: otherwise the app/tenant/customer wouldn't do it. That's
the root of my question from the beginning: how would we know what is *not*
intent?
>>
>> If I ask for some particular microscopically detailed configuration (a
"how"), it's because I care, for some reason, about that level of detail. It
is in fact part of my intent.
>>
>> In my IT example, I argue that intent need not be independent of
protocols and ports, and that it need not be portable. Your response about
context appears to agree.
>>
>> So as best I can tell, we can say precisely what an intent is, and we
can't say what an intent is not. If intent is just the latest buzzword,
which it certainly appears to be, can we just say so and leave it to the
marketing people?
>>
>> Dave
>>
>> From: Lifengkai (Fengkai) [mailto:[e-mail]]
>> Sent: Tuesday, June 02, 2015 12:47 AM
>> To: Dave Hood; Susan Hares; [e-mail]
>> Cc: Zhoutianran; Xiayinben; [e-mail]
>> Subject: RE: [Sdn] Defining a Common Model for intent
>>
>> Hi Dave and all,
>>
>> Thanks for proposing the two valuable intent use cases.
>>
>> For the use case 2, I agree that the IT employee needs to include the
details of ports/protocols into his/her intent descriptions, but those may
not be in the intent context scope of a non-IT employee. Have a further
consideration with this, different users of the network have their own
intent in a specific domain. Then the roles/actors of network users, such as
end users, application developers, tenant IT/network administrators,
operator network administrators, are valuable to be identified and
distinguished, thus fitting the intent requirements of the network users
with different roles.
>>
>> Any thoughts about this consideration?
>>
>>
>> Best Regards,
>> Fengkai
>>
>> From: sdn [mailto:[e-mail]] On Behalf Of Dave Hood
>> Sent: Tuesday, June 02, 2015 1:38 AM
>> To: Susan Hares; [e-mail]
>> Cc: Zhoutianran; Xiayinben; [e-mail]
>> Subject: Re: [Sdn] Defining a Common Model for intent
>>
>> An excerpt from an email I sent on the ONF NBI list, which may contain
some useful thoughts:
>>
>> I have always had trouble understanding what an intent really is, so I am
looking forward to making the concept more precise.
>>
>> When I click a link on a web page, I express an intent to invoke whatever
that link offers. Completely below the surface is a layer stack, on-demand
session establishment, DNS look-ups, server load balancers, and any number
of other technological features that are of no interest to me. Why not use
that as an example of intent?
>>
>> Better yet, we talk about negotiation and selection. Suppose I want to
buy a widget. I probably already have some idea whether I want to go to
Amazon or EBay or somewhere else. Suppose it's Amazon. I search Amazon's
catalog and receive an offer of several widgets, some new, some used, some
with a choice of colour or other pertinent features. If I see nothing I
like, I may open a new browser window and check out Best Buy or EBay (lots
more hidden technology to make that happen!). Maybe I come back to the
Amazon page, having found nothing I liked better somewhere else. Now I
accept one of the offered widgets and go through the checkout process.
>>
>> Do we agree that this is a fairly pure expression of intent as 
>> conceptualized in the paper? (If not, let's talk about making a Skype
>> call.)
>>
>> Ok, that's my intent as an internet user. Let's assume the network is all
SDN of one kind or another. I invoke my intent through a GUI onto software
local to my PC, but I don't think we can call the PC an SDN controller. It's
more an active mediator, a client to an SDN. As far as the network is
concerned, the client makes DNS queries and swaps opaque TCP packets over a
forwarding path that may already exist, or may need to be learned and set up
on demand. This is about right, because the session content may well be
encrypted end to end, and rightly.
>>
>> To the SDN controller, my intent is satisfied by directing DNS queries to
a known DNS server somewhere, and ensuring IP connectivity for the
subsequent session. Hmmm. what happened to our intent-based NBI? The SDN
offered my PC a packet interface with the properties of knowing how to
recognize and route DNS queries specially, and general IP connectivity. My
PC accepted the service offer implicitly by offering traffic to the
data-plane interface. The network could be performing associated auxiliary
services such as usage-based billing (think wireless roaming), so it's more
than just a dumb pipe.
>>
>> If this is not a legitimate example of intent, it would be good to write
the white paper in such a way that clearly excludes such cases.
>>
>> Use case 2: suppose I am a corporate IT employee, and suppose that my 
>> intent is to have an E-Line between two of my campi. I necessarily 
>> care about ports and protocols; talk about intent being portable and 
>> protocol independent continues to confuse me completely. How can I 
>> order an E-line without caring about such details? [Nor is this 
>> intent portable.]
>>
>> Obviously, an SDN controller is going to expose whatever actions and
elements of information are germane to the service it offers, and if ports
and protocols are germane to the service, so be it.
>>
>> The SDN architecture, being recursive, models the north side of any
controller as exposing an instance of an information model, customized for
the intended client/customer/app/user. That being the case, how do we
distinguish an NBI API that conveys intent (service: same thing?) from one
that does not?
>>
>> I have recently come to the view that granularity is the criterion by
which an intent or service invocation is distinguished. Colloquially
speaking, a service invocation is a single invocation across the API: give
me E-Line. Now of course this turns into constraint negotiation, offer and
acceptance, but what happens across the API is effectively one transaction.
In contrast, what we might agree is *not* an intent or a service is the
manipulation of a granular information model, the explicit visibility of
multiple objects, how they are interrelated, their attributes, and the like.
>>
>> .         Network as a single lump vs some non-trivial topology.
>>
>> .         Chauffeur vs driving a car. Legitimate reasons to choose one
option or the other, but the level of granularity is quite different. Shall
we agree that driving is too granular to be considered intent?
>>
>> This idea of granularity and detailed operations on the components (which
of course may be complex entities themselves, virtualized into
simple-appearing lumps) seems to me to capture the essence of what people
are talking about when they say intent or service. I am not comfortable with
the way I am expressing it, so if this is a step in a productive direction,
or even if it's not, I welcome suggestions to clarify the concept.
>>
>> Dave
>>
>> From: sdn [mailto:[e-mail]] On Behalf Of Susan Hares
>> Sent: Saturday, May 30, 2015 1:02 PM
>> To: [e-mail]
>> Cc: 'Zhoutianran'; 'Xiayinben'; [e-mail]
>> Subject: [Sdn] Defining a Common Model for intent
>>
>> On this mail list, there has been a discussion of two types of
information for Intent and Nemo:
(http://www.ietf.org/mail-archive/web/sdn/current/msg00646.html) :
>>
>> 1)      What information is needed to represent a service request,
>> 2)      How to represent and transport the information for a request.
>>
>> In order to define what information is needed to represent a 1) service
request that signals Intent from an application to a controller, it is
important to define Intent, and provide a clear model of Intent.  Also, in
describing real use-cases it is important that one uses the same definition
and model for Intent in each use case.
>>
>> In the current forums examining Intent (ODL NIC, ODL Nemo, OF NBI and
Keystone, OPNFV Movie, OpenStack) there is a realization that Intent occurs
at multiple layers.  The authors of draft-xia-ibnemo-icim have created a
definition for intent and a unified model for defining intent which can
handle 1 or multiple layers. The model suggest that:
>> 1)      A user has a intent that is expressed in a context.
>> 2)      Intent (usually) involves an object with a result, and optionally
includes operations toward that result.
>> 3)      Operations conditions perform actions within/modified by
constraints.
>>
>> We believe this defines clearly what others are calling "pure intent"
(objects + results) versus "constrained intent" (objects + operations +
constraints).   The draft can be found at:
https://datatracker.ietf.org/doc/draft-xia-ibnemo-icim/ .   The authors are
looking for feedback on the concepts in the draft.
>>
>> Sue Hares
>>
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>>
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