Internet Research Task Force (IRTF) N. Figueira
Internet Draft R. Krishnan
Category: Informational Brocade
Expires: May 2015 November 25, 2014
Policy Architecture and Framework for NFV and Cloud Services
draft-norival-nfvrg-nfv-policy-arch-00
Abstract
A policy architecture and framework is discussed to support NFV and
Cloud environments, where policies are used to enforce business
rules and to specify resource constraints in a number of subsystems.
This document approaches the policy framework and architecture from
the perspective of overall orchestration requirements for services
involving multiple subsystems. The analysis extends beyond compute,
network, and storage subsystems to also include energy conservation.
This document also analyses policy scope, global versus local
policies, policy actions and translations, policy conflict detection
and resolution, interactions among policies engines, and a
hierarchical policy architecture/framework to address the demanding
and growing requirements of NFV and Cloud environments.
Status of this Memo
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Conventions used in this document
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.
Table of Contents
1. Introduction...................................................2
2. Policy Statement and Actions...................................3
3. Global vs Local Policies.......................................5
4. Hierarchical Policy Framework..................................6
5. Policy Conflicts and Resolution................................9
6. Policy Pub/Sub Bus............................................10
7. Example of Policy-based NFV Placement.........................14
8. Summary.......................................................14
9. IANA Considerations...........................................14
10. Security Considerations......................................14
11. Acknowledgements.............................................14
12. References...................................................15
12.1. Normative References....................................15
12.2. Informative References..................................15
Authors' Addresses...............................................16
1. Introduction
This document discusses the policy architecture and framework to
support Network Function Virtualization (NFV) [1] and Cloud
services. In these environments, policies are used to enforce
business rules and to specify resource constraints in a number of
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subsystems, e.g., compute, storage, network, energy, and etc., and
across subsystems.
The current work in the area of policy for NFV and Cloud services is
typically focused on individual subsystems and addresses very
specific use cases or environments. For example, [1] addresses
network subsystem policy for network virtualization, [3] proposes an
open source project in the area of network policy as part of the
OpenDaylight software define networking (SDN) controller framework
[4], [5] specifies an information model for network policy, [6]
focuses on placement and migration policies for distributed virtual
computing, [7] is an open source project proposal in OpenStack [10]
to address policy for cloud environments.
This document approaches policy, policy framework, and policy
architecture for NFV and Cloud services from the perspective of
overall orchestration requirements for services involving multiple
subsystems. The analysis extends beyond compute, network, and
storage subsystems to also include energy conservation as it applies
to NFV, Cloud, and other environments. The analysis in this document
extends beyond a single data center (DC) or administrative domain to
include multiple data centers and networks forming hierarchical
domain architectures [22].
This focus of document is not general policy theory, which has been
intensively studied and documented on numerous publications over the
past 10 to 15 years (see [5], [14], [16], [17], and [18] to name a
few). This document's purpose is to discuss and document a policy
architecture (using known policy concepts and theories) to address
the unique requirements of NFV and Cloud services including multiple
data centers and networks forming hierarchical domain architectures
[22].
With the above goals, this document analyses policy scope, global
versus local policies, policy actions and translations of actions,
policy conflict detection and resolution, the interactions among
policies engines of the different data center and network
subsystems, and a hierarchical policy architecture/framework to
address the demanding and growing requirements of NFV and Cloud
environments.
2. Policy Statement and Actions
Policies define which states of deployment are in compliance, and,
by logic negation, which ones are not. The compliance statement in a
policy may define specific actions, e.g., "a given customer is [not
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allowed to deploy a VNF X]" or quasi-specific actions, e.g., "a
given customer [must be given platinum treatment]". Quasi-specific
actions differ from the specific ones in that the former requires an
additional level of translation or interpretation, which will depend
on the subsystem where the policy is being evaluated, while the
latter does not require further translation or interpretation.
In the previous examples, "VNF X" defines a specific VNF type, i.e.,
"X" in this case, while "platinum treatment" could be translated to
an appropriate resource type depending on the subsystem. For
example, in the compute subsystem this could be translated to
servers of a defined minimum performance specification, while in the
network subsystem this could be translated to a specific Quality of
Service (QoS) level treatment.
The actions defined in a policy may be translated to subsystem
configurations. For example, when "platinum treatment" is translated
to a specific QoS level treatment in a networking subsystem, one of
the outcomes (there can be multiple) of the policy could be the
configuration of network elements (physical or virtual) to mark that
customer's traffic to a certain DSCP (DiffServ Code Point) level
(Figure 1).
Some may refer to the QoS configuration above as a policy in itself,
e.g., [14], [17], [15], and [16]. In this document, such device
configurations are called policy enablement/enforcement technologies
to set them apart from the actually intended policy, i.e., "a given
customer must be given platinum treatment" in the above example.
The translation of a policy into appropriate subsystem
configurations requires additional information that is usually
subsystem dependent and technology dependent. Therefore, policies
should not be written in terms of policy enablement/enforcement
technologies. Policies should be translated at the subsystems using
the appropriate policy enablement/enforcement technologies employed
by the subsystems. Figure 1 provides a few examples where the policy
"a given customer must be given platinum treatment" is translated to
appropriate configurations at the respective subsystems.
This above may sound like a discussion about "declarative" versus
"imperative" policies. We are actually postulating that "imperative
policy" is just a derived device/subsystem configuration (using an
appropriate policy enablement/enforcement technology) to support an
actually intended policy.
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+----------------------------------------------------------------+
| Policy: "a given customer must be given Platinum treatment" |
+----------------------------------------------------------------+
^ ^ ^ ^
| | | |
V V V V
+-------------+ +-------------+ +-------------+ +-------------+
|Compute | |Network | |Storage | |Whatever |
|Subsystem | |Subsystem | |Subsystem | |Subsystem |
| | | | | | | |
|Policy | |Policy | |Policy | |Policy |
|translation: | |translation: | |translation: | |translation: |
| | | | | | | |
|Install | |Give customer| |Give customer| | |
|customer VMs | |the best QoS,| |the fastest | | |
|on servers | |which | |SSD storage. | | |
|with 3GHz | |translates | | | | |
|16-core Xeon | |here to set | | | | |
|processors, | |DHCP to xx, | | | | |
|and etc. | |and etc. | | | | |
+-------------+ +-------------+ +-------------+ +-------------+
Figure 1: Example of Subsystem Translations of Policy Actions
3. Global vs Local Policies
Some policies may be subsystem specific in scope, while others may
have broader scope and interact with multiple subsystems. For
example, a policy constraining certain customer types (or specific
customers) to only use certain server types for VNF or Virtual
Machine (VM) deployment would be within the scope of the compute
subsystem. A policy dictating that a given customer type (or
specific customers) must be given platinum treatment could have
different implications on different sub-systems. As shown in Figure
1, platinum treatment could be translated to servers of a given
performance specification in a compute subsystem and storage of a
given performance specification (SSD in this example) in a storage
subsystem.
Policies with broader scope, or global policies, would be defined
outside affected subsystems and enforced by a global policy engine
(Figure 2), while subsystem specific policies or local policies,
would be defined and enforced by a local policy engine of the
respective subsystems.
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+----------------------------------------------------------------+
| +----------------------------------------------+ |
| | Global Policy Engine | |
| +----------------------------------------------+ |
| |
| +----------------------------------------------+ |
| | Global Policies | |
| +----------------------------------------------+ |
+----------------------------------------------------------------+
^ ^ ^ ^
| | | |
V V V V
+-------------+ +-------------+ +-------------+ +-------------+
|Compute | |Network | |Storage | |Whatever |
|Subsystem | |Subsystem | |Subsystem | |Subsystem |
| | | | | | | |
|Local Policy | |Local Policy | |Local Policy | |Local Policy |
|Engine | |Engine | |Engine | |Engine |
| | | | | | | |
|Local | |Local | |Local | |Local |
|Policies: | |Policies | |Policies | |Policies |
| P0, P1, | | P0, P1, | | P0, P1, | | P0, P1, |
| | | | | | | |
+-------------+ +-------------+ +-------------+ +-------------+
Figure 2: Global versus Local Policy Engines
4. Hierarchical Policy Framework
So far, we have referenced compute, network, and storage as
subsystems examples. However, the following subsystems may also
support policy engines and subsystem specific policies:
o SDN Controllers, e.g., OpenDaylight [4].
o OpenStack [10] components such as, Neutron, Cinder, Nova, and
etc.
o Directories, e.g., LDAP, ActiveDirectory, and etc.
o Applications in general, e.g., Apps on top of OpenDaylight or
OpenStack and standalone Apps.
o Physical and virtual network elements, e.g., routers, firewalls,
ADCs, and etc.
o Energy, e.g., OpenStack Neat [8]
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Therefore, a policy framework may involve a multitude of subsystems.
Subsystems may include other lower level subsystems, e.g., Neutron
[9] would be a lower level subsystem in the OpenStack subsystem. In
other words, the policy framework is hierarchical in nature, where
the policy engine of a subsystem may be viewed as a higher level
policy engine by lower level subsystems. In fact, the global policy
engine in Figure 2 could be the policy engine of a Data Center
subsystem and multiple Data Center subsystems could be grouped in a
region containing a region global policy engine. In addition, one
could define regions inside regions, hierarchically, as shown in
Figure 3.
Metro and wide-area network (WAN) used to interconnect data centers
would also be independent subsystems with their own policy engines.
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To higher level domain
^
|
|
Region 1 Domain V
+-------------------+
| +---------------+ |
| |Region 1 Global| |
| |Policy Engine | | +-------------------+
| +---------------+ | | +---------------+ |
| |<------>| |WAN 1 Global | |
| +---------------+ | | |Policy Engine | |
| |Whatever | | | +---------------+ |
| |Subsystems | | | |
| | | | | +---------------+ |
| |Local Policy | | | |Whatever | |
| |Engines | | | |Subsystems | |
| +---------------+ | | | | |
+-------------------+ | |Local Policy | |
^ ^ | |Engines | |
| | | +---------------+ |
| | +-------------------+
| |
| +-------------------------+
| |
| |
DC 1 Domain V DC N Domain V
+-------------------+ +-------------------+
| +---------------+ | | +---------------+ |
| |DC 1 Global | | | |DC N Global | |
| |Policy Engine | | | |Policy Engine | |
| +---------------+ | | +---------------+ |
| | | |
| +---------------+ | | +---------------+ |
| |Whatever | | | |Whatever | |
| |Subsystems | | | |Subsystems | |
| | | | | | | |
| |Local Policy | | | |Local Policy | |
| |Engines | | | |Engines | |
| +---------------+ | | +---------------+ |
+-------------------+ +-------------------+
Figure 3: A Hierarchical Policy Framework
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5. Policy Conflicts and Resolution
Policies should be stored in databases accessible by the policy
engines. For example, the local policies defined for the Compute
subsystem in Figure 2 would be stored in a database accessible by
the local policy engine in that subsystem.
As a new policy is added to a subsystem, the subsystem's policy
engine should perform conflict checks. For example, a simple
conflict would be created if a new policy states that "customer A
must not be allowed to use VNF X", while an already existing policy
states that "customer A is allowed to use VNF X". In this case, the
conflict should be detected and an appropriate policy conflict
resolution mechanism should be initiated.
The nature of the policy conflict resolution mechanism would depend
on how the new policy is being entered into the database. If an
administrator is manually attempting to enter that policy, the
conflict resolution could entail a warning message and rejection of
the new policy. The administrator would then decide whether or not
to replace the existing policy with the new one.
When policies are batched for later inclusion in the database, the
administrator should run a preemptive conflict resolution check on
those policies before committing to include them in the database at
a future time. However, running a preemptive conflict resolution
check does not guarantee that there will be no conflicts at the time
the batched policies are actually included in the database, since
other policies could have been added in the interim that cause
conflicts with those batched policies.
To avoid conflicts with batched policies, one could run a preemptive
conflict resolution check against database policies and also batched
policies every time new policies are added to the database.
However, this may not be sufficient in case a service provider
defines separate administrative domains. The region administration
could define batched polices to be pushed to the Compute subsystem
of a Data Center. However, the Compute subsystem may be a separate
administrative domain from that of the region administrative domain.
In this case, the Compute subsystem may not be allowed to run
preemptive policy conflict checks against the batched policies
defined in the region administrative domain. Thus, there is a need
for a reactive policy conflict resolution mechanism besides
preemptive techniques.
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6. Policy Pub/Sub Bus
In the previous section, we considered policy conflicts within a
same level subsystem. For example, new local policies added to the
Compute subsystem conflicting with existing local policies at that
subsystem. However, more subtle conflicts are possible between
global and local policies.
A global policy may conflict with subsystems' local policies.
Consider the following Compute subsystem local policy: "Platinum
treatment must be provided using server of type A."
The addition of the Global policy "Platinum treatment must be
provided using server subtype A-1" would intrude into the Compute
subsystem by redefining the type of server to be used for a
particular service treatment. While one could argue that such global
policy should not be permitted, this is an event that requires
detection and proper resolution. A possible resolution is for the
Compute subsystem to import the more restrictive policy into its
local database. The original local policy would remain as is along
with the new restrictive policy. The local policy engine would
enforce the more restricted form of the policy. This could make
already existing resource allocations non-compliant and requiring
corrective actions. If the new Global policy reads "Platinum
treatment must be provided using server of types A or B", the
Compute subsystem would not need to do anything, since the Compute
subsystem has a more restrictive local policy in place.
The above example demonstrates the need for subsystems to subscribe
to policy updates at the Global policy level. Some sort of policy
publication/subscription (pub/sub) bus would be required as shown in
Figure 4.
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+----------------------------------------------------------------+
| +----------------------------------------------+ |
| | Global Policy Engine | |
| +----------------------------------------------+ |
| |
| +----------------------------------------------+ |
| | Global Policies | |
| +----------------------------------------------+ |
+----------------------------------------------------------------+
^
|
Policy Pub/Sub Bus |
V
--------------------------------------------------------------
^ ^ ^ ^
| | | |
| | | |
V V V V
+-------------+ +-------------+ +-------------+ +-------------+
|Compute | |Network | |Storage | |Whatever |
|Subsystem | |Subsystem | |Subsystem | |Subsystem |
| | | | | | | |
|Local Policy | |Local Policy | |Local Policy | |Local Policy |
|Engine | |Engine | |Engine | |Engine |
| | | | | | | |
|Local | |Local | |Local | |Local |
|Policies: | |Policies | |Policies | |Policies |
| P0, P1, | | P0, P1, | | P0, P1, | | P0, P1, |
| | | | | | | |
+-------------+ +-------------+ +-------------+ +-------------+
Figure 4: A Policy Pub/Sub Bus
A policy conflict may force policies to change scope. Consider the
following existing policies in a Data Center:
Compute subsystem policy: "Platinum treatment requires a server of
type A or B."
Storage subsystem policy: "Platinum treatment requires a server
storage of type X or Y."
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Now consider the outcome of adding the following new Global policy:
"Platinum treatment requires a server of type A when storage of type
X is used or a server of type B when storage of type Y is used."
This new Global policy intrudes into the Compute and Storage
subsystems. Again, one could argue that such global policy should
not be permitted. Nevertheless, this is an event that requires
detection and proper resolution. This Global policy causes a
conflict because the Compute and Storage subsystems can no longer
independently define whether to use a server of type A or B or
storage of type X or Y, respectively. If the Compute subsystem
selects server of type A for a customer and the Storage subsystem
selects storage of type Y for that same customer service the Global
policy is violated. The Compute and Storage subsystems can no longer
make such selections.
A possible conflict resolution is for the Compute and Storage
subsystems to relegate policy enforcement for such resources to the
Global policy engine.
The above example demonstrates again the need for subsystems to
subscribe to policy updates at the Global policy level as shown in
Figure 4.
If, as demonstrated, a Global policy may hijack or nullify local
policies of subsystems, what exactly makes the scope of a policy
local versus global then?
Proposition: A Local Policy does not affect the compliance state
imposed by global Policies or the local policies of other
subsystems.
The above non-exhaustive examples demonstrate that global and local
policies may conflict in subtle ways. Policy conflicts will also
arise in deeper hierarchical policy frameworks. A hierarchical
policy framework requires a policy pub/sub bus between all levels to
allow for conflict detection and resolution (Figure 5).
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Pub/Sub bus to higher level
^
|
|
Region 1 Domain V
+-------------------+
| +---------------+ |
| |Region 1 Global| |
| |Policy Engine | | +-------------------+
| +---------------+ | | | +---------------+ |
| | |<-->| |WAN 1 Global | |
| +---------------+ | | | |Policy Engine | |
| |Whatever | | | | +---------------+ |
| |Subsystems | | | | |
| | | | | | +---------------+ |
| |Local Policy | | | | |Whatever | |
| |Engines | | | | |Subsystems | |
| +---------------+ | | | | | |
+-------------------+ | | |Local Policy | |
^ | | |Engines | |
Region | | | +---------------+ |
Pub/Sub Bus V | +-------------------+
----------------------+
^ ^
| +-------------------------+
| |
DC 1 Domain V DC N Domain V
+-------------------+ +-------------------+
| +---------------+ | | +---------------+ |
| |DC 1 Global | | | |DC N Global | |
| |Policy Engine | | | |Policy Engine | |
| +---------------+ | | +---------------+ |
| | | |
| +---------------+ | | +---------------+ |
| |Whatever | | | |Whatever | |
| |Subsystems | | | |Subsystems | |
| | | | | | | |
| |Local Policy | | | |Local Policy | |
| |Engines | | | |Engines | |
| +---------------+ | | +---------------+ |
+-------------------+ +-------------------+
Figure 5: Pub/Sub Bus - Hierarchical Policy Framework
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7. Example of Policy-based NFV Placement
IRTF draft [19] describes a detailed example of a global policy in
Datalog [18] applicable to compute and energy sub-systems for the
NFVIaaS use case [20] in an OpenStack framework. The goal of this
policy is to address the energy efficiency requirements described in
the ETSI NFV Virtualization Requirements [21].
8. Summary
This document approached the policy framework and architecture from
the perspective of overall orchestration requirements for services
involving multiple subsystems. The analysis extended beyond compute,
network, and storage subsystems to also include energy conservation.
This document also analyzed policy scope, global versus local
policies, policy actions and translations, policy conflict detection
and resolution, interactions among policies engines, and a
hierarchical policy architecture/framework to address the demanding
and growing requirements of NFV and Cloud environments.
The concept of NFV and the proposed policy architecture is
applicable to service providers and also enterprises. For example,
an enterprise branch office could have capacity and energy
constraints similar to that of a service provider mini NFV DC. This
is an aspect which would be worth examining in detail in future
work.
9. IANA Considerations
This draft does not have any IANA considerations.
10. Security Considerations
Security issues due to exchanging policies across different
administrative domains are an aspect for further study.
11. Acknowledgements
The authors would like to acknowledge Steven Wright, Uwe Michel,
Klaus Martiny, Diego Lopez, Pedro Andres Aranda Gutierrez, Dilip
Krishnaswamy and Tim Hinrichs for the discussions on some of these
topics.
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12. References
12.1. Normative References
12.2. Informative References
[1] "ETSI NFV White Paper,"
http://portal.etsi.org/NFV/NFV_White_Paper.pdf
[2] Rahman, M. R. et al., "SVNE: Survivable Virtual Network
Embedding Algorithms for Network Virtualization, "IEEE Transactions
on Network and Service Management,(Volume: 10 , Issue: 2)
[3] "OpenDaylight Group Based Policy,"
https://wiki.opendaylight.org/view/Project_Proposals:Group_Based_Pol
icy_Plugin
[4] "OpenDaylight SDN Controller, "http://www.opendaylight.org/
[5] B. Moore et al., "Policy Core Information Model -- Version 1
Specification," RFC 3060, February 2001
[6] Grit, L. et al., "Virtual Machine Hosting for Networked Clusters:
Building the Foundations for "Autonomic" Orchestration,"
Virtualization Technology in Distributed Computing, 2006. VTDC 2006.
[7] "OpenStack Congress, "https://wiki.openstack.org/wiki/Congress
[8] "OpenStack Neat, "http://openstack-neat.org/
[9] "OpenStack Neutron, "https://wiki.openstack.org/wiki/Neutron
[10] "OpenStack, "http://www.openstack.org/
[11] "SPEC Benchmark Results: HP Proliant DL380p Rack
Server,"http://i.dell.com/sites/doccontent/shared-content/data-
sheets/en/Documents/Comparing-Dell-R720-and-HP-Proliant-DL380p-Gen8-
Servers.pdf
[12] "Convex Optimization,"
https://web.stanford.edu/~boyd/cvxbook/bv_cvxbook.pdf
[13] Dmitris Alevras and Manfred W. Padberg, "Linear Optimization
and Extensions: Problems and Solutions," Universitext, Springer-
Verlag, 2001
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[14] "Policy Framework Working Group," IETF,
http://www.ietf.org/wg/concluded/policy.html
[15] "Common Information Model (CIM)," DTMF,
http://www.dmtf.org/standards/cim
[16] More, B., et al, "Information Model for Describing Network
Device QoS Datapath Mechanisms," RFC 3670, January 2004
[17] A. Westerinen, et al, "Terminology for Policy-Based
Management," RFC 3198, November 2001
[18] Ceri, S. et al., "What you always wanted to know about Datalog
(and never dared to ask)," IEEE Transactions on Knowledge and Data
Engineering, (Volume: 1, Issue: 1), August 2002
[19] Krishnan, R. et al., "NFVIaaS Architectural Framework for
Policy Based Resource Placement and Scheduling,"
https://datatracker.ietf.org/doc/draft-krishnan-nfvrg-policy-based-
rm-nfviaas/
[20] "ETSI NFV Use Cases,"
http://www.etsi.org/deliver/etsi_gs/NFV/001_099/001/01.01.01_60/gs_N
FV001v010101p.pdf
[21] "ETSI NFV Virtualization Requirements,"
http://www.etsi.org/deliver/etsi_gs/NFV/001_099/004/01.01.01_60/gs_N
FV004v010101p.pdf
[22] "SDN Multi-Domain Orchestration and Control: Challenges and
Innovative Future Directions," IEEE International Conference on
Computing, Networking and Communications (ICNC) 2015 Workshop -
Accepted
Authors' Addresses
Norival Figueira
Brocade Communications
nfigueir@Brocade.com
Ram (Ramki) Krishnan
Brocade Communications
ramk@brocade.com
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