Internet DRAFT - draft-xia-ibnemo-icim
draft-xia-ibnemo-icim
Internet-Draft Y. Xia, Ed.
Intended status: Standards Track T. Zhou, Ed.
Expires: December 2, 2016 Y. Zhang, Ed.
S. Hares
Huawei
P. Aranda
D. Lopez
Telefornica
J. Crowcroft
Cambridge University
Y. Zhang
China Unicom
May 31, 2016
Intent Common Information Model
draft-xia-ibnemo-icim-02
Abstract
Intent Common Information Model (ICIM) defines a unified model for
expressing different layers' intent whatever role, responsibility,
knowledge, etc. This document provides an information model to be
inherited and expanded to construct specific intent model in
different areas. According to this information model, network intent
model is put forward which can satisfy users' need in different
layers, such as, end-users, business developers, and network
administers.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 2, 2016.
Xia, et al. Expires December 2, 2016 [Page 1]
Internet-Draft Abbreviated-Title May 2016
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Intent Common Information Model Overview . . . . . . . . . . 3
2.1. Elements . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Relationships in ICIM . . . . . . . . . . . . . . . . . . 6
2.3. Intent and Policy . . . . . . . . . . . . . . . . . . . . 7
2.4. Role-based Intent . . . . . . . . . . . . . . . . . . . . 7
2.5. Intent and FSM . . . . . . . . . . . . . . . . . . . . . 7
3. Intent Modeling . . . . . . . . . . . . . . . . . . . . . . . 8
3.1. Notation . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2. Intent overview . . . . . . . . . . . . . . . . . . . . . 9
3.3. Top level intent expression . . . . . . . . . . . . . . . 10
3.4. Objects in the network . . . . . . . . . . . . . . . . . 10
3.5. Type of result . . . . . . . . . . . . . . . . . . . . . 11
3.6. Operation composition . . . . . . . . . . . . . . . . . . 12
4. Security Considerations . . . . . . . . . . . . . . . . . . . 13
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
7. Informative References . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
Network operations have traditionally been designed bottom-up
starting with low level device interfaces designed by protocol
experts.In order that interfaces could be wildly used by various
users, information details are exposed as much as possible. It
enables better control of devices, but leaves huge burden of
selecting useful information to users without well training. Since
the north bound interface (NBI) is used by network users, a more
appropriate design is to express user intent and abstract the network
Xia, et al. Expires December 2, 2016 [Page 2]
Internet-Draft Abbreviated-Title May 2016
from the top down. The intent base NBI expresses what a network
service consumer (e.g., application, operator) requires from the
network but it does not completely specify or constrain how that
service may or should be delivered by the network. The intent is
expected to be independent of protocols, network interface styles,
vendor features, media attributes, or any other network
implementations.
Intent Common Information Model (ICIM) specifies a generic model for
expressing key components of intent interface and the relationship
between these components. This document provides a common model
which could be inherited from and expanded to construct specific
intent interface in dedicated areas. According to this information
model, intent interface in network area can satisfy users' intention
in different roles, such as, end-users, business developers, network
administers, etc.
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2. Intent Common Information Model Overview
Intent Common Information Model aims to specify a unified information
model which satisfied different areas, scenarios, and other
constraints. So, it is a complete and detailed information model to
define the constituent elements of intent. However, not all elements
need to be present when mapping this model to a specific data model,
since some of the elements can be obtained by system automatically.
From the overall perspective, construction elements of intent can be
described as:
-user of intent who author and own this intent
-intent content which is a desired purpose and
-the specific context which is the background circumstance
information.
Furthermore, in general, person's intent content usually describes
the ultimate state of some objects or applies actions to these
objects. So intent content can be abstracted into further:
-object which is the target for intent
-result which is a desired state and
Xia, et al. Expires December 2, 2016 [Page 3]
Internet-Draft Abbreviated-Title May 2016
-operation which is the specific actions to achieve a purpose.
2.1. Elements
2.1.1 Users
User is an abstract class which specifies the subject and owner to
express the intent. It is a performance of roles in real world, that
is, each user serves as a role or a combination of roles actually.
For example, end-users, business designers, network administrators
are all instances of User class which act as specific roles. When a
user is labeled as a role, he will have the desire and requirement to
express intent belonged to this role. Owning to different network
abstraction views, intent is different for specific user when this
information model is applied to specific scenario.
Though one user serves as one role in most cases, it is sensible and
acceptable that one user serves as multiple roles and intent of these
users may involve more functions and huge operation scope.
2.1.2 Context
Context is an abstraction class which refers to a set of specific
background information such as, timer, price, and so on. Context has
a huge influence on a person designing a detailed plan or selecting
the best program to achieve a purpose. For example, when an
enterprise plans to build a dedicated connection between two sites,
price and distance will be the context in this scenario. While may
not be part of how an entity expresses or executes some intent, it is
a factor that must be considered with the expression of intent.
2.1.3 Object
Object is an abstract class which refers an abstract class which
defines some entities affected or managed by intent. For the
management, users could manage life cycle of the objects through some
concrete operations, such as, create, update, delete, etc. In
addition, users could use other specific operations to affect the
behavior of managed objects. For example, a business designer want
all traffic be filtered by a special firewall. The object of this
business designers intent could be the all traffic flowing on a
specific network (e.g. L3VPN), and this intent impacts the
forwarding behavior of the traffic network. Object is different in
specific area. In network area, object is an aggregation class with
CustomerFacingNode, Connection and ServiceFlow. For objects, users
could construct some specific objects to achieve intent, and it is
also allowed for users to assign intent to existing resources which
is physical/virtual devices or defined by other ways.
Xia, et al. Expires December 2, 2016 [Page 4]
Internet-Draft Abbreviated-Title May 2016
2.1.4 Result
Result is a type of intent which refers to an final state or
something an individual wants to achieve. This type of intent
shields difference and diversity of an environment away from the
users' intent. The person just describes the final state of objects
without worrying about how to achieve it. For example, a result
could be that the company accesses any sites on the Internet safely.
It just defines a result that ignores technology details, such as,
firewall, ACL, and so on.
In addition to the expecting state, violation is another special
state which has an important status when achieving integral
compliance. For example, a typical scenario is that one specific
tenant does not want his virtual machines to share a some hypervisor
with other tenants. This type of result just shows the undesired
state which express users' intent, so this kind of intent should be
another type of result.
2.1.5 Operation
Operation is a type of intent which refers to some specific actions
an individual desires to take for realizing the purpose. This type
of intent formulates explicit plan to realize a purpose which may
take a better control of the whole system. According to the
diversity of system support capability, there are large sets of
operations for users to take.
Generally, operations can be divided into two categories. One is
action without condition. For example, create a virtual machine.
This kind of operation defines a concrete action which is executed
immediately without any trigger. The other is action with condition.
For this kind of operations, condition is a trigger for the action.
And actions will not be executed immediately until the condition
clause is tested to be true. For example, "do load balancing when
the utilization of a link exceeds 80%". In this example,
"utilization of a link > 80%" is the trigger, and "do load balancing"
is the action. Action will not be executed until the trigger is
true. Actions are different according to users' role which has
different abstraction views. And actions will not be detailed
configurations in devices, but high-level and packaged functions
which are translated into configurations. For example, the service
providers' action "do load balancing" is device independent, and
network operators' action may configure load balance pools depending
on specific devices.
Xia, et al. Expires December 2, 2016 [Page 5]
Internet-Draft Abbreviated-Title May 2016
2.2. Relationships in ICIM
2.2.1 Relationship between Result and Operation
Users are free to express their intent, no matter it is an final
result or specific operations in their mind, but there are some
relationships between these two basic types of intent. Result refers
to an ultimate and relatively permanent status, regardless which ways
to maintain it. However, operations specify what kinds of action
need to take explicitly, which more focus on temporary or specific
behavior to achieve some goal. One typical service scenario is that
all links' utilization should not exceed 80%. By way of Result, the
intent will be expecting all links' utilizations are smaller than 80%
(or avoiding any link' utilization exceeds 80%). By way of
Operation, the intent will be if links' utilization exceeds 80%,
redirect some flows to other links (or some other actions could
achieve this goal).
For result, users just need to express the goal without worrying how
to implement it in a specific system which allows users to focus on
real requirement. To achieve the result, it needs some reasoning
mechanisms to transfer it to real executable operations which are
supported by specific system. So in a specific scenario, a result
can generate a set of concrete operations. For the above example, if
user just expresses the result, that is, all links' utilizations are
smaller than 80%. The system will choose suitable operations to
achieve this status automatically, i.e., expand the capacity of links
whose utilization exceed 80%, or redirect flows to other links whose
capacities are far less than 80%.
2.2.2 Relationship between Object and Operation
Operation refers to some specific actions on some objects, so object
is the target of an action. In general, any action will include some
objects to execute this action. When users want to execute some
actions to achieve goals, they may construct the target objects and
assign specific actions on them, and it is allowed for users to use
existing resources to do some operations. Though object is the
target of action, it offers the constraint for optional operations.
For example, for a virtual machine, the optional operations are
create, delete, migrate, etc.
2.2.3 Relationship between Object and Result
Result refers to some final state for some objects. This type of
intent does not define which specific operations to take, but only
express the desired state of objects. So it is independent on
objects' concrete capability. For example, intent is all virtual
Xia, et al. Expires December 2, 2016 [Page 6]
Internet-Draft Abbreviated-Title May 2016
machines' CPU utilization could not exceed 80%. It does not assign
specific operations. So reasoning mechanism will choose suitable
operations to satisfy this intent, such as, migrate virtual machine
or expand it.
2.3. Intent and Policy
In industry, Policy already has a clear definition, such as in
RFC3060. Policy rule consists of an event, a set of conditions and a
set of actions. When an event occurs, actions will be taken until
condition clauses are evaluated to be true.
As mentioned above, intent refers to a purpose in achieving result or
performing operation. The intent has a larger scope compared with
the policy since Intent can express both result and operation. On
one hand if a result is described by intent, there may be no specific
action given to show how to achieve this intent. On the other hand,
if operation described by intent, conditions of action is optional.
Policy is a specific form of operation in intent.
2.4. Role-based Intent
In an integrated system, roles are divided into several categories
according to the division of work, architecture of system, etc. In
network system, network abstraction will be quite different in the
perspective of each role. So intent has strong dependencies on
roles. Intent expressed by different categories of roles will focus
on different points and have different intent expression.
For example, if an agent is labeled as service provider role, he may
just care about the high-level services, such as, security
communication. And if he is labeled as network architecture role, he
will care about the details of the whole architecture.
2.5. Intent and FSM
Intent, standing on the perspective of users, expresses intuitive
service requirement, including desired network services or means to
fulfill network goals. In other words, the Intent model defines a
series of FSMs(finite-state machines) and transition between these
state machines to implement the managment of service's life cycle.
Specifically, each state machine, combining with elements which
construct intent, represents a specific state of one or several
objects, for example, a normal-work state or exception state of a
connectivity service. Both current state(or initial state) and
result state(or desired state) are one type of state machines, the
main difference between which is that result state is an ultimate
Xia, et al. Expires December 2, 2016 [Page 7]
Internet-Draft Abbreviated-Title May 2016
state repects users' requirement, otherwise, current state represents
a initial state needs to be transited to others states to satisfy
users' intent.
Operation, including specific actions, represents the transition
between current state and result state that describe the state of
objects as mentioned above. The transition between service states
could be shown as below.
operation
+-------------------------+
| |
+------+------+ +------+-----+
|current state+-----------+result state|
+-------------+ +------------+
Figure 1 intent and FSMs
Just as mentioned in the section 2.2, operation is the mean to change
network service state to fulfill users' intent, namely, the result
state. For users, who clearly grasp how to reach result state or
have to assgin actions for other reasons, they could descibe specific
operations in intent to realize the result. Otherwise, users just
need to descibe what's the result or desired state, and the complier
system will produces specific operations to achive the result.
A typical scenario is the constraint for bandwidth utilization. For
user who does not know the ways to adjust bandwidth, he may express
his intent with desired state, namely, the result state is bandwidth-
utilization<80% and system will choose suitable ways to adjust
bandwidth, such as, expansion or changing route. But for users who
has experience with network operation, he may express his intent with
operaiton, namely, do load balancing if bandwidth-utilization>80%.
Both expressiones descibe service state machines and transition, but
operation could implement the transition between current state and
result state.
3. Intent Modeling
This section defines the concept and hierarchy of intent, and
describes the Intent Common Information Model.
3.1. Notation
The notation used in this document is adapted from the UML (United
Modeling Language). We will use the UML for the intent information
modeling. This section listed symbols that will be used in this
document for relationships among information models.
Xia, et al. Expires December 2, 2016 [Page 8]
Internet-Draft Abbreviated-Title May 2016
-->
Stands for the association relationship. Association represents the
static relationship shared among the objects of two classes.
--A
Stands for the aggregation relationship. Aggregation is a variant of
the "has a" association relationship; aggregation is more specific
than association. It is an association that represents a part-whole
or part-of relationship. Aggregation can occur when a class is a
collection or container of other classes, but the contained classes
do not have a strong lifecycle dependency on the container. The
contents of the container are not automatically destroyed when the
container is.
--C
Stands for the composition relationship. Composition is a stronger
variant of the "has a" association relationship. It is more specific
than aggregation. Composition usually has a strong lifecycle
dependency between instances of the container class and instances of
the contained class. If the container is destroyed, normally every
instance that it contains is destroyed as well.
--G
Stands for the generalization relationship. The Generalization
indicates that one of the two related classes (the subclass) is
considered to be a specialized form of the other (the super type) and
the super class is considered a 'Generalization' of the subclass. In
practice, this means that any instance of the subtype is also an
instance of the super class.
3.2. Intent overview
In general, intent is one's specific mental activity, so it strongly
depends on the subject. Different users may have different intent.
In addition, context, omitted usually, is an important factor when
achieving purpose, which offers necessary background information to
impact the decision. It illustrates the overview of the intent.
Figure 2 indicates that the user has intent in some context. For
example, an enterprise wants to block all http traffic in work time.
In this intent, the user is the enterprise, the intent is to block
all http traffic in the work hours, and the context includes the
definition of the "enterprise" and the "work hours".
Xia, et al. Expires December 2, 2016 [Page 9]
Internet-Draft Abbreviated-Title May 2016
+------+ has +------+ in +-------+
| user +---->+intent+---->+context|
+------+ +------+ +-------+
Figure 2 general prescription for intent
3.3. Top level intent expression
In Cambridge Dictionaries, the definition of "intent" is the fact
that you want and plan to do something. So, in general, intent
refers to an agent's purpose on getting the result or performing some
specific operation. In specific areas, these results or operations
will relate to some objects. Figure 3 describes the general
expression of intent.
+--------+
| intent |
+-C-A-A--+
| | |
+-----------+ | +-------------+
| | |
| | |
+---+---+ +--+---+ +-----+-----+
| object| |result| | operation |
+-------+ +------+ +-----------+
Figure 3 intent expression
One type of intent is to express key operations that a user wants to
execute. The underlying intent system can generate a complete
operation list from user's request. The other type of intent is to
express the result or state without dictating any operations.
For example, intent of a user may be a result without defining how to
realize it, such as, requiring security communication between two
sites, or dictate some detailed operations in order to achieve a
purpose, such as, filtering all traffics by firewall between these
two sites.
3.4. Objects in the network
Object is an abstraction class which can be inherited from and
expanded in different area. It, cared about by users, represents the
target of result and operations. In network area, the object, i.e.
the target of intent, can be generalized into
CustomerFacingNode(CFN), Connection and ServiceFlow, as shown in
Figure 4.
Xia, et al. Expires December 2, 2016 [Page 10]
Internet-Draft Abbreviated-Title May 2016
+------------------+
+---+CustomerFacingNode|
| +------------------+
+------+ |
| +G+--+ +----------+
|Object+G+------+Connection|
| +G+--+ +----------+
+------+ |
| +-----------+
+---+ServiceFlow|
+-----------+
Figure 4 common objects in network area
The CustomerFacingNode represents the functions a user-facing network
node may provide in a network such as network services, forwarding
functions (firewall, load balancer, virtual router, and others), or a
group of network elements. A group of network elements can be a
subnet, an autonomous system, or a confederation of autonomous
systems.
The Connection describes the link resources between two CFNs. These
link resources construct the foundation of communications between
different CFNs. User could take connection as physical link, and
assign bandwidth on it.
The ServiceFlow refers to the traffic in network which describes data
packets have some certain common characters. ServiceFlow model
describes the connectivity in virtual network, namely, if users want
to describe the communications between CFNs without direct
connection, they have to define the service flow and assign operation
to allow the service flow.
3.5. Type of result
Result refers to the final state which is expected or avoided.
Figure 5 describes two types of result. Both of the results just
show the performance of some objects, without caring about how to
reach them.
Result could be expressed as a set of logic clause connected with
propositional literals including AND, OR and NOT. The logic clause
could be described as an expression with relational operators, such
as equal, greater-than, less-than, belong-to.
With this model, users could express the desired state as an
expression. System will resolve the expression and seek ways to make
it true. The result will be achieved when the expression is
evaluated to be true. The typical examples are shown as follows:
Xia, et al. Expires December 2, 2016 [Page 11]
Internet-Draft Abbreviated-Title May 2016
- For example, a user may express an intent as the network link
utilization must less than 80%. This expression is a type of result
which describes an expected state. The left operand is the
utilization of all links, the right operand is 80%, and the operator
is less-than.
- Another example is an enterprise wants the development team and
sales team not to share a common link. In this intent, the left
operand is the union of the link set of development team occupied and
the link set of sales team occupied. The operation will be equal,
and the right operator is an empty set.
Though a unified information model for the Result is proposed in
here, it is still a preliminary version which just expresses the
basic components. The formalization and standardization are still
open issues need to be studied further. More comprehensive and
detailed manifestations will be added in the next version.
+--------+
| result |
+--G-G---+
| |
+-----+ +-----+
| |
+---+----+ +---+---+
| expect | | avoid |
+--------+ +-------+
Figure 5 expression of Result
3.6. Operation composition
Operation refers to some specific actions in order to achieve some
purposes. An operation must have some actions. However, if
condition and constraint can be optionally defined in operations, it
depends on specific scenario and users' requirement. Once a
condition is involved in operation, actions will not be executed
immediately until condition is true. In additional, constraint
restricts action itself or the scope of action.
For example, redirect traffic to back-up link when the utilization of
current link exceeds 80%, except the flow from VIP user. In this
scenario, the condition is link utilization exceeds 80%, the action
is redirect traffic, and the constraint is VIP flow could not be
redirected.
Xia, et al. Expires December 2, 2016 [Page 12]
Internet-Draft Abbreviated-Title May 2016
+---------+
|operation|
+--A-C-A--+
| | |
+---------+ | +------------+
| | |
| | |
+----+----+ +--+---+ +-----+----+
|condition| |action| |constraint|
+---------+ +------+ +----------+
Figure 6 composition of operation
4. Security Considerations
TBD
5. IANA Considerations
This draft includes no request to IANA.
6. Acknowledgements
The authors would like to thanks the valuable comments made by Wei
Cao, Sheng Jiang, Zhigang Ji, Xuewei Wang, Shixing Liu, Yan Zhang.
7. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Authors' Addresses
Yinben Xia
Huawei Technologies Co., Ltd
Q14, Huawei Campus, No.156 Beiqing Road Hai-Dian District
Beijing 100095
China
Email: xiayinben@huawei.com
Tianran Zhou
Huawei Technologies Co., Ltd
Q14, Huawei Campus, No.156 Beiqing Road Hai-Dian District
Beijing 100095
China
Email: zhoutianran@huawei.com
Xia, et al. Expires December 2, 2016 [Page 13]
Internet-Draft Abbreviated-Title May 2016
Yali Zhang
Huawei Technologies Co., Ltd
Q14, Huawei Campus, No.156 Beiqing Road Hai-Dian District
Beijing 100095
China
Email: zhangyali369@huawei.com
Susan Hares
Huawei Technologies Co., Ltd
7453 Hickory Hill Saline
MI 48176
USA
Email: shares@ndzh.com
Pedro Andres Aranda
Telefornica I+D
Don Ramon de la Cruz, 82 Street Madrid
28006
Spain
Email: pedroa.aranda@telefonica.com
Diego R. Lopez
Telefornica I+D
Don Ramon de la Cruz, 82 Street Madrid
28006
Spain
Email: diego.r.lopez@telefonica.com
Jon Crowcroft
University of Cambridge Computer Laboratory
William Gates Building, 15 JJ Thomson Avenue Cambridge
CB3 0FD UK
Email: jon.crowcroft@cl.cam.ac.uk
Xia, et al. Expires December 2, 2016 [Page 14]
Internet-Draft Abbreviated-Title May 2016
Yan Zhang
China Unicom P.R.
China
Email: zhangy1036@chinaunicom.cn
Xia, et al. Expires December 2, 2016 [Page 15]
