Internet DRAFT - draft-ietf-teas-actn-framework
draft-ietf-teas-actn-framework
TEAS Working Group Daniele Ceccarelli (Ed)
Internet Draft Ericsson
Intended status: Informational Young Lee (Ed)
Expires: November 28, 2018 Huawei
May 28, 2018
Framework for Abstraction and Control of Traffic Engineered Networks
draft-ietf-teas-actn-framework-15
Abstract
Traffic Engineered networks have a variety of mechanisms to
facilitate the separation of the data plane and control plane. They
also have a range of management and provisioning protocols to
configure and activate network resources. These mechanisms represent
key technologies for enabling flexible and dynamic networking. The
term "Traffic Engineered network" refers to a network that uses any
connection-oriented technology under the control of a distributed or
centralized control plane to support dynamic provisioning of end-to-
end connectivity.
Abstraction of network resources is a technique that can be applied
to a single network domain or across multiple domains to create a
single virtualized network that is under the control of a network
operator or the customer of the operator that actually owns
the network resources.
This document provides a framework for Abstraction and Control of
Traffic Engineered Networks (ACTN) to support virtual network
services and connectivity services.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with
the provisions of BCP 78 and BCP 79.
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at any time. It is inappropriate to use Internet-Drafts as
reference material or to cite them other than as "work in progress."
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This Internet-Draft will expire on November 3, 2018.
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Table of Contents
1. Introduction...................................................3
2. Overview.......................................................4
2.1. Terminology...............................................5
2.2. VNS Model of ACTN.........................................7
2.2.1. Customers............................................9
2.2.2. Service Providers...................................10
2.2.3. Network Operators...................................10
3. ACTN Base Architecture........................................10
3.1. Customer Network Controller..............................12
3.2. Multi-Domain Service Coordinator.........................13
3.3. Provisioning Network Controller..........................13
3.4. ACTN Interfaces..........................................14
4. Advanced ACTN Architectures...................................15
4.1. MDSC Hierarchy...........................................15
4.2. Functional Split of MDSC Functions in Orchestrators......16
5. Topology Abstraction Methods..................................17
5.1. Abstraction Factors......................................17
5.2. Abstraction Types........................................18
5.2.1. Native/White Topology...............................18
5.2.2. Black Topology......................................19
5.2.3. Grey Topology.......................................20
5.3. Methods of Building Grey Topologies......................21
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5.3.1. Automatic Generation of Abstract Topology by
Configuration..............................................21
5.3.2. On-demand Generation of Supplementary Topology via Path
Compute Request/Reply......................................21
5.4. Hierarchical Topology Abstraction Example................22
5.5. VN Recursion with Network Layers.........................24
6. Access Points and Virtual Network Access Points...............25
6.1. Dual-Homing Scenario.....................................27
7. Advanced ACTN Application: Multi-Destination Service..........28
7.1. Pre-Planned End Point Migration..........................29
7.2. On the Fly End-Point Migration...........................30
8. Manageability Considerations..................................30
8.1. Policy...................................................31
8.2. Policy Applied to the Customer Network Controller........32
8.3. Policy Applied to the Multi-Domain Service Coordinator...32
8.4. Policy Applied to the Provisioning Network Controller....32
9. Security Considerations.......................................33
9.1. CNC-MDSC Interface (CMI).................................34
9.2. MDSC-PNC Interface (MPI).................................34
10. IANA Considerations..........................................34
11. References...................................................35
11.1. Informative References..................................35
12. Contributors.................................................36
Authors' Addresses...............................................37
APPENDIX A - Example of MDSC and PNC Functions Integrated in A
Service/Network Orchestrator.....................................37
1. Introduction
The term "Traffic Engineered network" refers to a network that uses
any connection-oriented technology under the control of a
distributed or centralized control plane to support dynamic
provisioning of end-to-end connectivity. Traffic Engineered (TE)
networks have a variety of mechanisms to facilitate the separation
of data plane and control plane including distributed signaling for
path setup and protection, centralized path computation for planning
and traffic engineering, and a range of management and provisioning
protocols to configure and activate network resources. These
mechanisms represent key technologies for enabling flexible and
dynamic networking. Some examples of networks that are in scope of
this definition are optical networks, Multiprotocol Label Switching
(MPLS) Transport Profile (MPLS-TP) networks [RFC5654], and MPLS-TE
networks [RFC2702].
One of the main drivers for Software Defined Networking (SDN)
[RFC7149] is a decoupling of the network control plane from the data
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plane. This separation has been achieved for TE networks with the
development of MPLS/GMPLS [RFC3945] and the Path Computation Element
(PCE) [RFC4655]. One of the advantages of SDN is its logically
centralized control regime that allows a global view of the
underlying networks. Centralized control in SDN helps improve
network resource utilization compared with distributed network
control. For TE-based networks, a PCE may serve as a logically
centralized path computation function.
This document describes a set of management and control functions
used to operate one or more TE networks to construct virtual
networks that can be presented to customers and that are built from
abstractions of the underlying TE networks. For example, a link in
the customer's network is constructed from a path or collection of
paths in the underlying networks. We call this set of functions
"Abstraction and Control of Traffic Engineered Networks" (ACTN).
2. Overview
Three key aspects that need to be solved by SDN are:
. Separation of service requests from service delivery so that
the configuration and operation of a network is transparent
from the point of view of the customer, but remains responsive
to the customer's services and business needs.
. Network abstraction: As described in [RFC7926], abstraction is
the process of applying policy to a set of information about a
TE network to produce selective information that represents the
potential ability to connect across the network. The process
of abstraction presents the connectivity graph in a way that is
independent of the underlying network technologies,
capabilities, and topology so that the graph can be used to
plan and deliver network services in a uniform way
. Coordination of resources across multiple independent networks
and multiple technology layers to provide end-to-end services
regardless of whether the networks use SDN or not.
As networks evolve, the need to provide support for distinct
services, separated service orchestration, and resource abstraction
have emerged as key requirements for operators. In order to support
multiple customers each with its own view of and control of the
server network, a network operator needs to partition (or "slice")
or manage sharing of the network resources. Network slices can be
assigned to each customer for guaranteed usage which is a step
further than shared use of common network resources.
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Furthermore, each network represented to a customer can be built
from virtualization of the underlying networks so that, for example,
a link in the customer's network is constructed from a path or
collection of paths in the underlying network.
ACTN can facilitate virtual network operation via the creation of a
single virtualized network or a seamless service. This supports
operators in viewing and controlling different domains (at any
dimension: applied technology, administrative zones, or vendor-
specific technology islands) and presenting virtualized networks to
their customers.
The ACTN framework described in this document facilitates:
. Abstraction of the underlying network resources to higher-layer
applications and customers [RFC7926].
. Virtualization of particular underlying resources, whose
selection criterion is the allocation of those resources to a
particular customer, application, or service [ONF-ARCH].
. TE Network slicing of infrastructure to meet specific
customers' service requirements.
. Creation of an abstract environment allowing operators to view
and control multi-domain networks as a single abstract network.
. The presentation to customers of networks as a virtual network
via open and programmable interfaces.
2.1. Terminology
The following terms are used in this document. Some of them are
newly defined, some others reference existing definitions:
. Domain: A domain [RFC4655] is any collection of network
elements within a common sphere of address management or path
computation responsibility. Specifically within this document
we mean a part of an operator's network that is under common
management (i.e., under shared operational management using the
same instances of a tool and the same policies). Network
elements will often be grouped into domains based on technology
types, vendor profiles, and geographic proximity.
. Abstraction: This process is defined in [RFC7926].
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. TE Network Slicing: In the context of ACTN, a TE network slice
is a collection of resources that is used to establish a
logically dedicated virtual network over one or more TE
networks. TE network slicing allows a network operator to
provide dedicated virtual networks for applications/customers
over a common network infrastructure. The logically dedicated
resources are a part of the larger common network
infrastructures that are shared among various TE network slice
instances which are the end-to-end realization of TE network
slicing, consisting of the combination of physically or
logically dedicated resources.
. Node: A node is a vertex on the graph representation of a TE
topology. In a physical network topology, a node corresponds
to a physical network element (NE) such as a router. In an
abstract network topology, a node (sometimes called an abstract
node) is a representation as a single vertex of one or more
physical NEs and their connecting physical connections. The
concept of a node represents the ability to connect from any
access to the node (a link end) to any other access to that
node, although "limited cross-connect capabilities" may also be
defined to restrict this functionality. Network abstraction
may be applied recursively, so a node in one topology may be
created by applying abstraction to the nodes in the underlying
topology.
. Link: A link is an edge on the graph representation of a TE
topology. Two nodes connected by a link are said to be
"adjacent" in the TE topology. In a physical network topology,
a link corresponds to a physical connection. In an abstract
network topology, a link (sometimes called an abstract link) is
a representation of the potential to connect a pair of points
with certain TE parameters (see [RFC7926] for details).
Network abstraction may be applied recursively, so a link in
one topology may be created by applying abstraction to the
links in the underlying topology.
. Abstract Topology: The topology of abstract nodes and abstract
links presented through the process of abstraction by a lower
layer network for use by a higher layer network.
. A Virtual Network (VN) is a network provided by a service
provider to a customer for the customer to use in any way it
wants as though it was a physical network. There are two views
of a VN as follows:
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a) The VN can be abstracted as a set of edge-to-edge links (a
Type 1 VN). Each link is referred as a VN member and is
formed as an end-to-end tunnel across the underlying
networks. Such tunnels may be constructed by recursive
slicing or abstraction of paths in the underlying networks
and can encompass edge points of the customer's network,
access links, intra-domain paths, and inter-domain links.
b) The VN can also be abstracted as a topology of virtual nodes
and virtual links (a Type 2 VN). The operator needs to map
the VN to actual resource assignment, which is known as
virtual network embedding. The nodes in this case include
physical end points, border nodes, and internal nodes as well
as abstracted nodes. Similarly the links include physical
access links, inter-domain links, and intra-domain links as
well as abstract links.
Clearly a Type 1 VN is a special case of a Type 2 VN.
. Access link: A link between a customer node and a operator
node.
. Inter-domain link: A link between domains under distinct
management administration.
. Access Point (AP): An AP is a logical identifier shared between
the customer and the operator used to identify an access link.
The AP is used by the customer when requesting a VNS. Note that
the term "TE Link Termination Point" (LTP) defined in [TE-Topo]
describes the end points of links, while an AP is a common
identifier for the link itself.
. VN Access Point (VNAP): A VNAP is the binding between an AP and
a given VN.
. Server Network: As defined in [RFC7926], a server network is a
network that provides connectivity for another network (the
Client Network) in a client-server relationship.
2.2. VNS Model of ACTN
A Virtual Network Service (VNS) is the service agreement between a
customer and operator to provide a VN. When a VN is a simple
connectivity between two points, the difference between VNS and
connectivity service becomes blurred. There are three types of VNS
defined in this document.
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o Type 1 VNS refers to a VNS in which the customer is allowed
to create and operate a Type 1 VN.
o Type 2a and 2b VNS refer to VNSs in which the customer is
allowed to create and operates a Type 2 VN. With a Type
2a VNS, the VN is statically created at service
configuration time and the customer is not allowed to
change the topology (e.g., by adding or deleting abstract
nodes and links). A Type 2b VNS is the same as a Type 2a
VNS except that the customer is allowed to make dynamic
changes to the initial topology created at service
configuration time.
VN Operations are functions that a customer can exercise on a VN
depending on the agreement between the customer and the operator.
o VN Creation allows a customer to request the instantiation
of a VN. This could be through off-line pre-configuration
or through dynamic requests specifying attributes to a
Service Level Agreement (SLA) to satisfy the customer's
objectives.
o Dynamic Operations allow a customer to modify or delete the
VN. The customer can further act upon the virtual network
to create/modify/delete virtual links and nodes. These
changes will result in subsequent tunnel management in the
operator's networks.
There are three key entities in the ACTN VNS model:
- Customers
- Service Providers
- Network Operators
These entities are related in a three tier model as shown in Figure
1.
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+----------------------+
| Customer |
+----------------------+
|
VNS || | /\ VNS
Request || | || Reply
\/ | ||
+----------------------+
| Service Provider |
+----------------------+
/ | \
/ | \
/ | \
/ | \
+------------------+ +------------------+ +------------------+
|Network Operator 1| |Network Operator 2| |Network Operator 3|
+------------------+ +------------------+ +------------------+
Figure 1: The Three Tier Model.
The commercial roles of these entities are described in the
following sections.
2.2.1. Customers
Basic customers include fixed residential users, mobile users, and
small enterprises. Each requires a small amount of resources and is
characterized by steady requests (relatively time invariant). Basic
customers do not modify their services themselves: if a service
change is needed, it is performed by the provider as a proxy.
Advanced customers include enterprises and governments. Such
customers ask for both point-to point and multipoint connectivity
with high resource demands varying significantly in time. This is
one of the reasons why a bundled service offering is not enough and
it is desirable to provide each advanced customer with a customized
virtual network service. Advanced customers may also have the
ability to modify their service parameters within the scope of their
virtualized environments. The primary focus of ACTN is Advanced
Customers.
As customers are geographically spread over multiple network
operator domains, they have to interface to multiple operators and
may have to support multiple virtual network services with different
underlying objectives set by the network operators. To enable these
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customers to support flexible and dynamic applications they need to
control their allocated virtual network resources in a dynamic
fashion, and that means that they need a view of the topology that
spans all of the network operators. Customers of a given service
provider can in turn offer a service to other customers in a
recursive way.
2.2.2. Service Providers
In the scope of ACTN, service providers deliver VNSs to their
customers. Service providers may or may not own physical network
resources (i.e., may or may not be network operators as described in
Section 2.2.3). When a service provider is the same as the network
operator, this is similar to existing VPN models applied to a single
operator although it may be hard to use this approach when the
customer spans multiple independent network operator domains.
When network operators supply only infrastructure, while distinct
service providers interface to the customers, the service providers
are themselves customers of the network infrastructure operators.
One service provider may need to keep multiple independent network
operators because its end-users span geographically across multiple
network operator domains. In some cases, service provider is also a
network operator when it owns network infrastructure on which
service is provided.
2.2.3. Network Operators
Network operators are the infrastructure operators that provision
the network resources and provide network resources to their
customers. The layered model described in this architecture
separates the concerns of network operators and customers, with
service providers acting as aggregators of customer requests.
3. ACTN Base Architecture
This section provides a high-level model of ACTN showing the
interfaces and the flow of control between components.
The ACTN architecture is based on a 3-tier reference model and
allows for hierarchy and recursion. The main functionalities within
an ACTN system are:
. Multi-domain coordination: This function oversees the specific
aspects of different domains and builds a single abstracted
end-to-end network topology in order to coordinate end-to-end
path computation and path/service provisioning. Domain
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sequence path calculation/determination is also a part of this
function.
. Abstraction: This function provides an abstracted view of the
underlying network resources for use by the customer - a
customer may be the client or a higher level controller entity.
This function includes network path computation based on
customer service connectivity request constraints, path
computation based on the global network-wide abstracted
topology, and the creation of an abstracted view of network
resources allocated to each customer. These operations depend
on customer-specific network objective functions and customer
traffic profiles.
. Customer mapping/translation: This function is to map customer
requests/commands into network provisioning requests that can
be sent from the Multi-Domain Service Coordinator (MDSC) to the
Provisioning Network Controller (PNC) according to business
policies provisioned statically or dynamically at the Operations
Support System (OSS)/ Network Management System (NMS).
Specifically, it provides mapping and translation of a
customer's service request into a set of parameters that are
specific to a network type and technology such that network
configuration process is made possible.
. Virtual service coordination: This function translates customer
service-related information into virtual network service
operations in order to seamlessly operate virtual networks
while meeting a customer's service requirements. In the
context of ACTN, service/virtual service coordination includes
a number of service orchestration functions such as multi-
destination load balancing, guarantees of service quality,
bandwidth and throughput. It also includes notifications for
service fault and performance degradation and so forth.
The base ACTN architecture defines three controller types and the
corresponding interfaces between these controllers. The following
types of controller are shown in Figure 2:
. CNC - Customer Network Controller
. MDSC - Multi-Domain Service Coordinator
. PNC - Provisioning Network Controller
Figure 2 also shows the following interfaces:
. CMI - CNC-MDSC Interface
. MPI - MDSC-PNC Interface
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. SBI - Southbound Interface
+---------+ +---------+ +---------+
| CNC | | CNC | | CNC |
+---------+ +---------+ +---------+
\ | /
\ | /
Boundary ========\==================|=====================/=======
Between \ | /
Customer & ----------- | CMI --------------
Network Operator \ | /
+---------------+
| MDSC |
+---------------+
/ | \
------------ | MPI -------------
/ | \
+-------+ +-------+ +-------+
| PNC | | PNC | | PNC |
+-------+ +-------+ +-------+
| SBI / | / \
| / | SBI SBI / \
--------- ----- | / \
( ) ( ) | / \
- Control - ( Phys. ) | / -----
( Plane ) ( Net ) | / ( )
( Physical ) ----- | / ( Phys. )
( Network ) ----- ----- ( Net )
- - ( ) ( ) -----
( ) ( Phys. ) ( Phys. )
--------- ( Net ) ( Net )
----- -----
Figure 2: ACTN Base Architecture
Note that this is a functional architecture: an implementation and
deployment might collocate one or more of the functional components.
Figure 2 shows a case where service provider is also a network
operator.
3.1. Customer Network Controller
A Customer Network Controller (CNC) is responsible for communicating
a customer's VNS requirements to the network operator over the CNC-
MDSC Interface (CMI). It has knowledge of the end-points associated
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with the VNS (expressed as APs), the service policy, and other QoS
information related to the service.
As the Customer Network Controller directly interfaces to the
applications, it understands multiple application requirements and
their service needs. The capability of a CNC beyond its CMI role is
outside the scope of ACTN and may be implemented in different ways.
For example, the CNC may in fact be a controller or part of a
controller in the customer's domain, or the CNC functionality could
also be implemented as part of a service provider's portal.
3.2. Multi-Domain Service Coordinator
A Multi-Domain Service Coordinator (MDSC) is a functional block that
implements all of the ACTN functions listed in Section 3 and
described further in Section 4.2. Two functions of the MDSC,
namely, multi-domain coordination and virtualization/abstraction are
referred to as network-related functions while the other two
functions, namely, customer mapping/translation and virtual service
coordination are referred to as service-related functions. The MDSC
sits at the center of the ACTN model between the CNC that issues
connectivity requests and the Provisioning Network Controllers
(PNCs) that manage the network resources.
The key point of the MDSC (and of the whole ACTN framework) is
detaching the network and service control from underlying technology
to help the customer express the network as desired by business
needs. The MDSC envelopes the instantiation of the right technology
and network control to meet business criteria. In essence it
controls and manages the primitives to achieve functionalities as
desired by the CNC.
In order to allow for multi-domain coordination a 1:N relationship
must be allowed between MDSCs and PNCs.
In addition to that, it could also be possible to have an M:1
relationship between MDSCs and PNC to allow for network resource
partitioning/sharing among different customers not necessarily
connected to the same MDSC (e.g., different service providers) but
all using the resources of a common network infrastructure operator.
3.3. Provisioning Network Controller
The Provisioning Network Controller (PNC) oversees configuring the
network elements, monitoring the topology (physical or virtual) of
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the network, and collecting information about the topology (either
raw or abstracted).
The PNC functions can be implemented as part of an SDN domain
controller, a Network Management System (NMS), an Element Management
System (EMS), an active PCE-based controller [Centralized] or any
other means to dynamically control a set of nodes and implementing a
north bound interface from the standpoint of the nodes (which is out
of the scope of this document). A PNC domain includes all the
resources under the control of a single PNC. It can be composed of
different routing domains and administrative domains, and the
resources may come from different layers. The interconnection
between PNC domains is illustrated in Figure 3.
_______ _______
_( )_ _( )_
_( )_ _( )_
( ) Border ( )
( PNC ------ Link ------ PNC )
( Domain X |Border|========|Border| Domain Y )
( | Node | | Node | )
( ------ ------ )
(_ _) (_ _)
(_ _) (_ _)
(_______) (_______)
Figure 3: PNC Domain Borders
3.4. ACTN Interfaces
Direct customer control of transport network elements and
virtualized services is not a viable proposition for network
operators due to security and policy concerns. Therefore, the
network has to provide open, programmable interfaces, through which
customer applications can create, replace and modify virtual network
resources and services in an interactive, flexible and dynamic
fashion.
Three interfaces exist in the ACTN architecture as shown in Figure
2.
. CMI: The CNC-MDSC Interface (CMI) is an interface between a CNC
and an MDSC. The CMI is a business boundary between customer
and network operator. It is used to request a VNS for an
application. All service-related information is conveyed over
this interface (such as the VNS type, topology, bandwidth, and
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service constraints). Most of the information over this
interface is agnostic of the technology used by network
operators, but there are some cases (e.g., access link
configuration) where it is necessary to specify technology-
specific details.
. MPI: The MDSC-PNC Interface (MPI) is an interface between an
MDSC and a PNC. It communicates requests for new connectivity
or for bandwidth changes in the physical network. In multi-
domain environments, the MDSC needs to communicate with
multiple PNCs each responsible for control of a domain. The
MPI presents an abstracted topology to the MDSC hiding
technology specific aspects of the network and hiding topology
according to policy.
. SBI: The Southbound Interface (SBI) is out of scope of ACTN.
Many different SBIs have been defined for different
environments, technologies, standards organizations, and
vendors. It is shown in Figure 3 for reference reason only.
4. Advanced ACTN Architectures
This section describes advanced configurations of the ACTN
architecture.
4.1. MDSC Hierarchy
A hierarchy of MDSCs can be foreseen for many reasons, among which
are scalability, administrative choices, or putting together
different layers and technologies in the network. In the case where
there is a hierarchy of MDSCs, we introduce the terms higher-level
MDSC (MDSC-H) and lower-level MDSC (MDSC-L). The interface between
them is a recursion of the MPI. An implementation of an MDSC-H
makes provisioning requests as normal using the MPI, but an MDSC-L
must be able to receive requests as normal at the CMI and also at
the MPI. The hierarchy of MDSCs can be seen in Figure 4.
Another implementation choice could foresee the usage of an MDSC-L
for all the PNCs related to a given technology (e.g., Internet
Protocol (IP)/Multiprotocol Label Switching (MPLS)) and a different
MDSC-L for the PNCs related to another technology (e.g., Optical
Transport Network (OTN)/Wavelength Division Multiplexing (WDM)) and
an MDSC-H to coordinate them.
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+--------+
| CNC |
+--------+
| +-----+
| CMI | CNC |
+----------+ +-----+
-------| MDSC-H |---- |
| +----------+ | | CMI
MPI | MPI | |
| | |
+---------+ +---------+
| MDSC-L | | MDSC-L |
+---------+ +---------+
MPI | | | |
| | | |
----- ----- ----- -----
| PNC | | PNC | | PNC | | PNC |
----- ----- ----- -----
Figure 4: MDSC Hierarchy
The hierarchy of MDSC can be recursive, where an MDSC-H is in turn
an MDSC-L to a higher level MDSC-H.
4.2. Functional Split of MDSC Functions in Orchestrators
An implementation choice could separate the MDSC functions into two
groups, one group for service-related functions and the other for
network-related functions. This enables the implementation of a
service orchestrator that provides the service-related functions of
the MDSC and a network orchestrator that provides the network-
related functions of the MDSC. This split is consistent with the
Yet Another Next Generation (YANG) service model architecture
described in [Service-YANG]. Figure 5 depicts this and shows how
the ACTN interfaces may map to YANG models.
+--------------------+
| Customer |
| +-----+ |
| | CNC | |
| +-----+ |
+--------------------+
CMI | Customer Service Model
|
+---------------------------------------+
| Service |
********|*********************** Orchestrator |
* MDSC | +-----------------+ * |
* | | Service-related | * |
* | | Functions | * |
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* | +-----------------+ * |
* +----------------------*----------------+
* * | Service Delivery
* * | Model
* +----------------------*----------------+
* | * Network |
* | +-----------------+ * Orchestrator |
* | | Network-related | * |
* | | Functions | * |
* | +-----------------+ * |
********|*********************** |
+---------------------------------------+
MPI | Network Configuration
| Model
+------------------------+
| Domain |
| +------+ Controller |
| | PNC | |
| +------+ |
+------------------------+
SBI | Device Configuration
| Model
+--------+
| Device |
+--------+
Figure 5: ACTN Architecture in the Context of the YANG Service
Models
5. Topology Abstraction Methods
Topology abstraction is described in [RFC7926]. This section
discusses topology abstraction factors, types, and their context in
the ACTN architecture.
Abstraction in ACTN is performed by the PNC when presenting
available topology to the MDSC, or by an MDSC-L when presenting
topology to an MDSC-H. This function is different to the creation
of a VN (and particularly a Type 2 VN) which is not abstraction but
construction of virtual resources.
5.1. Abstraction Factors
As discussed in [RFC7926], abstraction is tied with policy of the
networks. For instance, per an operational policy, the PNC would
not provide any technology specific details (e.g., optical
parameters for Wavelength Switched Optical Network (WSON) in the
abstract topology it provides to the MDSC. Similarly, policy of the
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networks may determine the abstraction type as described in Section
5.2.
There are many factors that may impact the choice of abstraction:
- Abstraction depends on the nature of the underlying domain
networks. For instance, packet networks may be abstracted with
fine granularity while abstraction of optical networks depends on
the switching units (such as wavelengths) and the end-to-end
continuity and cross-connect limitations within the network.
- Abstraction also depends on the capability of the PNCs. As
abstraction requires hiding details of the underlying network
resources, the PNC's capability to run algorithms impacts the
feasibility of abstraction. Some PNC may not have the ability to
abstract native topology while other PNCs may have the ability to
use sophisticated algorithms.
- Abstraction is a tool that can improve scalability. Where the
native network resource information is of large size there is a
specific scaling benefit to abstraction.
- The proper abstraction level may depend on the frequency of
topology updates and vice versa.
- The nature of the MDSC's support for technology-specific
parameters impacts the degree/level of abstraction. If the MDSC
is not capable of handling such parameters then a higher level of
abstraction is needed.
- In some cases, the PNC is required to hide key internal
topological data from the MDSC. Such confidentiality can be
achieved through abstraction.
5.2. Abstraction Types
This section defines the following three types of topology
abstraction:
. Native/White Topology (Section 5.2.1)
. Black Topology (Section 5.2.2)
. Grey Topology (Section 5.2.3)
5.2.1. Native/White Topology
This is a case where the PNC provides the actual network topology to
the MDSC without any hiding or filtering of information, i.e., no
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abstraction is performed. In this case, the MDSC has the full
knowledge of the underlying network topology and can operate on it
directly.
5.2.2. Black Topology
A black topology replaces a full network with a minimal
representation of the edge-to-edge topology without disclosing any
node internal connectivity information. The entire domain network
may be abstracted as a single abstract node with the network's
access/egress links appearing as the ports to the abstract node and
the implication that any port can be 'cross-connected' to any other.
Figure 6 depicts a native topology with the corresponding black
topology with one virtual node and inter-domain links. In this
case, the MDSC has to make a provisioning request to the PNCs to
establish the port-to-port connection. If there is a large number
of inter-connected domains, this abstraction method may impose a
heavy coordination load at the MDSC level in order to find an
optimal end-to-end path since the abstraction hides so much
information that it is not possible to determine whether an end-to-
end path is feasible without asking each PNC to set up each path
fragment. For this reason, the MPI might need to be enhanced to
allow the PNCs to be queried for the practicality and
characteristics of paths across the abstract node.
.....................................
: PNC Domain :
: +--+ +--+ +--+ +--+ :
------+ +-----+ +-----+ +-----+ +------
: ++-+ ++-+ +-++ +-++ :
: | | | | :
: | | | | :
: | | | | :
: | | | | :
: ++-+ ++-+ +-++ +-++ :
------+ +-----+ +-----+ +-----+ +------
: +--+ +--+ +--+ +--+ :
:....................................
+----------+
---+ +---
| Abstract |
| Node |
---+ +---
+----------+
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Figure 6: Native Topology with Corresponding Black Topology Expressed
as an Abstract Node
5.2.3. Grey Topology
A grey topology represents a compromise between black and white
topologies from a granularity point of view. In this case, the PNC
exposes an abstract topology containing all PNC domains border nodes
and an abstraction of the connectivity between those border nodes.
This abstraction may contain either physical or abstract
nodes/links.
Two types of grey topology are identified:
. In a type A grey topology, border nodes are connected by a full
mesh of TE links (see Figure 7).
. In a type B grey topology, border nodes are connected over a
more detailed network comprising internal abstract nodes and
abstracted links. This mode of abstraction supplies the MDSC
with more information about the internals of the PNC domain and
allows it to make more informed choices about how to route
connectivity over the underlying network.
.....................................
: PNC Domain :
: +--+ +--+ +--+ +--+ :
------+ +-----+ +-----+ +-----+ +------
: ++-+ ++-+ +-++ +-++ :
: | | | | :
: | | | | :
: | | | | :
: | | | | :
: ++-+ ++-+ +-++ +-++ :
------+ +-----+ +-----+ +-----+ +------
: +--+ +--+ +--+ +--+ :
:....................................
....................
: Abstract Network :
: :
: +--+ +--+ :
-------+ +----+ +-------
: ++-+ +-++ :
: | \ / | :
: | \/ | :
: | /\ | :
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: | / \ | :
: ++-+ +-++ :
-------+ +----+ +-------
: +--+ +--+ :
:..................:
Figure 7: Native Topology with Corresponding Grey Topology
5.3. Methods of Building Grey Topologies
This section discusses two different methods of building a grey
topology:
. Automatic generation of abstract topology by configuration
(Section 5.3.1)
. On-demand generation of supplementary topology via path
computation request/reply (Section 5.3.2)
5.3.1. Automatic Generation of Abstract Topology by Configuration
Automatic generation is based on the abstraction/summarization of
the whole domain by the PNC and its advertisement on the MPI. The
level of abstraction can be decided based on PNC configuration
parameters (e.g., "provide the potential connectivity between any PE
and any ASBR in an MPLS-TE network").
Note that the configuration parameters for this abstract topology
can include available bandwidth, latency, or any combination of
defined parameters. How to generate such information is beyond the
scope of this document.
This abstract topology may need to be periodically or incrementally
updated when there is a change in the underlying network or the use
of the network resources that make connectivity more or less
available.
5.3.2. On-demand Generation of Supplementary Topology via Path Compute
Request/Reply
While abstract topology is generated and updated automatically by
configuration as explained in Section 5.3.1, additional
supplementary topology may be obtained by the MDSC via a path
compute request/reply mechanism.
The abstract topology advertisements from PNCs give the MDSC the
border node/link information for each domain. Under this scenario,
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when the MDSC needs to create a new VN, the MDSC can issue path
computation requests to PNCs with constraints matching the VN
request as described in [ACTN-YANG]. An example is provided in
Figure 8, where the MDSC is creating a P2P VN between AP1 and AP2.
The MDSC could use two different inter-domain links to get from
domain X to domain Y, but in order to choose the best end-to-end
path it needs to know what domain X and Y can offer in terms of
connectivity and constraints between the PE nodes and the border
nodes.
------- --------
( ) ( )
- BrdrX.1------- BrdrY.1 -
(+---+ ) ( +---+)
-+---( |PE1| Dom.X ) ( Dom.Y |PE2| )---+-
| (+---+ ) ( +---+) |
AP1 - BrdrX.2------- BrdrY.2 - AP2
( ) ( )
------- --------
Figure 8: A Multi-Domain Example
The MDSC issues a path computation request to PNC.X asking for
potential connectivity between PE1 and border node BrdrX.1 and
between PE1 and BrdrX.2 with related objective functions and TE
metric constraints. A similar request for connectivity from the
border nodes in domain Y to PE2 will be issued to PNC.Y. The MDSC
merges the results to compute the optimal end-to-end path including
the inter domain links. The MDSC can use the result of this
computation to request the PNCs to provision the underlying
networks, and the MDSC can then use the end-to-end path as a virtual
link in the VN it delivers to the customer.
5.4. Hierarchical Topology Abstraction Example
This section illustrates how topology abstraction operates in
different levels of a hierarchy of MDSCs as shown in Figure 9.
+-----+
| CNC | CNC wants to create a VN
+-----+ between CE A and CE B
|
|
+-----------------------+
| MDSC-H |
+-----------------------+
/ \
/ \
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+---------+ +---------+
| MDSC-L1 | | MDSC-L2 |
+---------+ +---------+
/ \ / \
/ \ / \
+----+ +----+ +----+ +----+
CE A o----|PNC1| |PNC2| |PNC3| |PNC4|----o CE B
+----+ +----+ +----+ +----+
Virtual Network Delivered to CNC
CE A o==============o CE B
Topology operated on by MDSC-H
CE A o----o==o==o===o----o CE B
Topology operated on by MDSC-L1 Topology operated on by MDSC-L2
_ _ _ _
( ) ( ) ( ) ( )
( ) ( ) ( ) ( )
CE A o--(o---o)==(o---o)==Dom.3 Dom.2==(o---o)==(o---o)--o CE B
( ) ( ) ( ) ( )
(_) (_) (_) (_)
Actual Topology
___ ___ ___ ___
( ) ( ) ( ) ( )
( o ) ( o ) ( o--o) ( o )
( / \ ) ( |\ ) ( | | ) ( / \ )
CE A o---(o-o---o-o)==(o-o-o-o-o)==(o--o--o-o)==(o-o-o-o-o)---o CE B
( \ / ) ( | |/ ) ( | | ) ( \ / )
( o ) (o-o ) ( o--o) ( o )
(___) (___) (___) (___)
Domain 1 Domain 2 Domain 3 Domain 4
Where
o is a node
--- is a link
=== border link
Figure 9: Illustration of Hierarchical Topology Abstraction
In the example depicted in Figure 9, there are four domains under
control of PNCs PNC1, PNC2, PNC3, and PNC4. MDSC-L1 controls PNC1
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and PNC2 while MDSC-L2 controls PNC3 and PNC4. Each of the PNCs
provides a grey topology abstraction that presents only border nodes
and links across and outside the domain. The abstract topology
MDSC-L1 that operates is a combination of the two topologies from
PNC1 and PNC2. Likewise, the abstract topology that MDSC-L2
operates is shown in Figure 9. Both MDSC-L1 and MDSC-L2 provide a
black topology abstraction to MDSC-H in which each PNC domain is
presented as a single virtual node. MDSC-H combines these two
topologies to create the abstraction topology on which it operates.
MDSC-H sees the whole four domain networks as four virtual nodes
connected via virtual links.
5.5. VN Recursion with Network Layers
In some cases the VN supplied to a customer may be built using
resources from different technology layers operated by different
operators. For example, one operator may run a packet TE network
and use optical connectivity provided by another operator.
As shown in Figure 10, a customer asks for end-to-end connectivity
between CE A and CE B, a virtual network. The customer's CNC makes
a request to Operator 1's MDSC. The MDSC works out which network
resources need to be configured and sends instructions to the
appropriate PNCs. However, the link between Q and R is a virtual
link supplied by Operator 2: Operator 1 is a customer of Operator 2.
To support this, Operator 1 has a CNC that communicates to Operator
2's MDSC. Note that Operator 1's CNC in Figure 10 is a functional
component that does not dictate implementation: it may be embedded
in a PNC.
Virtual CE A o===============================o CE B
Network
----- CNC wants to create a VN
Customer | CNC | between CE A and CE B
-----
:
***********************************************
:
Operator 1 ---------------------------
| MDSC |
---------------------------
: : :
: : :
----- ------------- -----
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| PNC | | PNC | | PNC |
----- ------------- -----
: : : : :
Higher v v : v v
Layer CE A o---P-----Q===========R-----S---o CE B
Network | : |
| : |
| ----- |
| | CNC | |
| ----- |
| : |
***********************************************
| : |
Operator 2 | ------ |
| | MDSC | |
| ------ |
| : |
| ------- |
| | PNC | |
| ------- |
\ : : : /
Lower \v v v/
Layer X--Y--Z
Network
Where
--- is a link
=== is a virtual link
Figure 10: VN recursion with Network Layers
6. Access Points and Virtual Network Access Points
In order to map identification of connections between the customer's
sites and the TE networks and to scope the connectivity requested in
the VNS, the CNC and the MDSC refer to the connections using the
Access Point (AP) construct as shown in Figure 11.
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-------------
( )
- -
+---+ X ( ) Z +---+
|CE1|---+----( )---+---|CE2|
+---+ | ( ) | +---+
AP1 - - AP2
( )
-------------
Figure 11: Customer View of APs
Let's take as an example a scenario shown in Figure 11. CE1 is
connected to the network via a 10 Gbps link and CE2 via a 40 Gbps
link. Before the creation of any VN between AP1 and AP2 the
customer view can be summarized as shown in Table 1.
+----------+------------------------+
|End Point | Access Link Bandwidth |
+-----+----------+----------+-------------+
|AP id| CE,port | MaxResBw | AvailableBw |
+-----+----------+----------+-------------+
| AP1 |CE1,portX | 10 Gbps | 10 Gbps |
+-----+----------+----------+-------------+
| AP2 |CE2,portZ | 40 Gbps | 40 Gbps |
+-----+----------+----------+-------------+
Table 1: AP - Customer View
On the other hand, what the operator sees is shown in Figure 12.
------- -------
( ) ( )
- - - -
W (+---+ ) ( +---+) Y
-+---( |PE1| Dom.X )----( Dom.Y |PE2| )---+-
| (+---+ ) ( +---+) |
AP1 - - - - AP2
( ) ( )
------- -------
Figure 12: Operator view of the AP
Which results in a summarization as shown in Table 2.
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+----------+------------------------+
|End Point | Access Link Bandwidth |
+-----+----------+----------+-------------+
|AP id| PE,port | MaxResBw | AvailableBw |
+-----+----------+----------+-------------+
| AP1 |PE1,portW | 10 Gbps | 10 Gbps |
+-----+----------+----------+-------------+
| AP2 |PE2,portY | 40 Gbps | 40 Gbps |
+-----+----------+----------+-------------+
Table 2: AP - Operator View
A Virtual Network Access Point (VNAP) needs to be defined as binding
between an AP and a VN. It is used to allow for different VNs to
start from the same AP. It also allows for traffic engineering on
the access and/or inter-domain links (e.g., keeping track of
bandwidth allocation). A different VNAP is created on an AP for
each VN.
In this simple scenario we suppose we want to create two virtual
networks. The first with VN identifier 9 between AP1 and AP2 with
bandwidth of 1 Gbps, while the second with VN identifier 5, again
between AP1 and AP2 and with bandwidth 2 Gbps.
The operator view would evolve as shown in Table 3.
+----------+------------------------+
|End Point | Access Link/VNAP Bw |
+---------+----------+----------+-------------+
|AP/VNAPid| PE,port | MaxResBw | AvailableBw |
+---------+----------+----------+-------------+
|AP1 |PE1,portW | 10 Gbps | 7 Gbps |
| -VNAP1.9| | 1 Gbps | N.A. |
| -VNAP1.5| | 2 Gbps | N.A |
+---------+----------+----------+-------------+
|AP2 |PE2,portY | 4 0Gbps | 37 Gbps |
| -VNAP2.9| | 1 Gbps | N.A. |
| -VNAP2.5| | 2 Gbps | N.A |
+---------+----------+----------+-------------+
Table 3: AP and VNAP - Operator View after VNS Creation
6.1. Dual-Homing Scenario
Often there is a dual homing relationship between a CE and a pair of
PEs. This case needs to be supported by the definition of VN, APs,
and VNAPs. Suppose CE1 connected to two different PEs in the
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operator domain via AP1 and AP2 and that the customer needs 5 Gbps
of bandwidth between CE1 and CE2. This is shown in Figure 12.
____________
AP1 ( ) AP3
-------(PE1) (PE3)-------
W / ( ) \ X
+---+/ ( ) \+---+
|CE1| ( ) |CE2|
+---+\ ( ) /+---+
Y \ ( ) / Z
-------(PE2) (PE4)-------
AP2 (____________)
Figure 12: Dual-Homing Scenario
In this case, the customer will request for a VN between AP1, AP2,
and AP3 specifying a dual homing relationship between AP1 and AP2.
As a consequence no traffic will flow between AP1 and AP2. The dual
homing relationship would then be mapped against the VNAPs (since
other independent VNs might have AP1 and AP2 as end points).
The customer view would be shown in Table 4.
+----------+------------------------+
|End Point | Access Link/VNAP Bw |
+---------+----------+----------+-------------+-----------+
|AP/VNAPid| CE,port | MaxResBw | AvailableBw |Dual Homing|
+---------+----------+----------+-------------+-----------+
|AP1 |CE1,portW | 10 Gbps | 5 Gbps | |
| -VNAP1.9| | 5 Gbps | N.A. | VNAP2.9 |
+---------+----------+----------+-------------+-----------+
|AP2 |CE1,portY | 40 Gbps | 35 Gbps | |
| -VNAP2.9| | 5 Gbps | N.A. | VNAP1.9 |
+---------+----------+----------+-------------+-----------+
|AP3 |CE2,portX | 50 Gbps | 45 Gbps | |
| -VNAP3.9| | 5 Gbps | N.A. | NONE |
+---------+----------+----------+-------------+-----------+
Table 4: Dual-Homing - Customer View after VN Creation
7. Advanced ACTN Application: Multi-Destination Service
A further advanced application of ACTN is in the case of Data Center
selection, where the customer requires the Data Center selection to
be based on the network status; this is referred to as Multi-
Destination in [ACTN-REQ]. In terms of ACTN, a CNC could request a
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VNS between a set of source APs and destination APs and leave it up
to the network (MDSC) to decide which source and destination access
points to be used to set up the VNS. The candidate list of source
and destination APs is decided by a CNC (or an entity outside of
ACTN) based on certain factors which are outside the scope of ACTN.
Based on the AP selection as determined and returned by the network
(MDSC), the CNC (or an entity outside of ACTN) should further take
care of any subsequent actions such as orchestration or service
setup requirements. These further actions are outside the scope of
ACTN.
Consider a case as shown in Figure 14, where three data centers are
available, but the customer requires the data center selection to be
based on the network status and the connectivity service setup
between the AP1 (CE1) and one of the destination APs (AP2 (DC-A),
AP3 (DC-B), and AP4 (DC-C)). The MDSC (in coordination with PNCs)
would select the best destination AP based on the constraints,
optimization criteria, policies, etc., and setup the connectivity
service (virtual network).
------- -------
( ) ( )
- - - -
+---+ ( ) ( ) +----+
|CE1|---+---( Domain X )----( Domain Y )---+---|DC-A|
+---+ | ( ) ( ) | +----+
AP1 - - - - AP2
( ) ( )
---+--- ---+---
| |
AP3-+ AP4-+
| |
+----+ +----+
|DC-B| |DC-C|
+----+ +----+
Figure 14: End-Point Selection Based on Network Status
7.1. Pre-Planned End Point Migration
Furthermore, in case of Data Center selection, customer could
request for a backup DC to be selected, such that in case of
failure, another DC site could provide hot stand-by protection. As
shown in Figure 15 DC-C is selected as a backup for DC-A. Thus, the
VN should be setup by the MDSC to include primary connectivity
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between AP1 (CE1) and AP2 (DC-A) as well as protection connectivity
between AP1 (CE1) and AP4 (DC-C).
------- -------
( ) ( )
- - __ - -
+---+ ( ) ( ) +----+
|CE1|---+----( Domain X )----( Domain Y )---+---|DC-A|
+---+ | ( ) ( ) | +----+
AP1 - - - - AP2 |
( ) ( ) |
---+--- ---+--- |
| | |
AP3-| AP4-| HOT STANDBY
| | |
+----+ +----+ |
|DC-D| |DC-C|<-------------
+----+ +----+
Figure 15: Pre-planned End-Point Migration
7.2. On the Fly End-Point Migration
Compared to pre-planned end point migration, on the fly end point
selection is dynamic in that the migration is not pre-planned but
decided based on network condition. Under this scenario, the MDSC
would monitor the network (based on the VN Service-level Agreement
(SLA) and notify the CNC in case where some other destination AP
would be a better choice based on the network parameters. The CNC
should instruct the MDSC when it is suitable to update the VN with
the new AP if it is required.
8. Manageability Considerations
The objective of ACTN is to manage traffic engineered resources, and
provide a set of mechanisms to allow customers to request virtual
connectivity across server network resources. ACTN supports
multiple customers each with its own view of and control of a
virtual network built on the server network, the network operator
will need to partition (or "slice") their network resources, and
manage the resources accordingly.
The ACTN platform will, itself, need to support the request,
response, and reservations of client and network layer connectivity.
It will also need to provide performance monitoring and control of
traffic engineered resources. The management requirements may be
categorized as follows:
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. Management of external ACTN protocols
. Management of internal ACTN interfaces/protocols
. Management and monitoring of ACTN components
. Configuration of policy to be applied across the ACTN system
The ACTN framework and interfaces are defined to enable traffic
engineering for virtual network services and connectivity services.
Network operators may have other Operations, Administration, and
Maintenance (OAM) tasks for service fulfillment, optimization, and
assurance beyond traffic engineering. The realization of OAM beyond
abstraction and control of traffic engineered networks is not
considered in this document.
8.1. Policy
Policy is an important aspect of ACTN control and management.
Policies are used via the components and interfaces, during
deployment of the service, to ensure that the service is compliant
with agreed policy factors and variations (often described in SLAs),
these include, but are not limited to: connectivity, bandwidth,
geographical transit, technology selection, security, resilience,
and economic cost.
Depending on the deployment of the ACTN architecture, some policies
may have local or global significance. That is, certain policies
may be ACTN component specific in scope, while others may have
broader scope and interact with multiple ACTN components. Two
examples are provided below:
o A local policy might limit the number, type, size, and
scheduling of virtual network services a customer may request
via its CNC. This type of policy would be implemented locally
on the MDSC.
o A global policy might constrain certain customer types (or
specific customer applications) to only use certain MDSCs, and
be restricted to physical network types managed by the PNCs. A
global policy agent would govern these types of policies.
The objective of this section is to discuss the applicability of
ACTN policy: requirements, components, interfaces, and examples.
This section provides an analysis and does not mandate a specific
method for enforcing policy, or the type of policy agent that would
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be responsible for propagating policies across the ACTN components.
It does highlight examples of how policy may be applied in the
context of ACTN, but it is expected further discussion in an
applicability or solution specific document, will be required.
8.2. Policy Applied to the Customer Network Controller
A virtual network service for a customer application will be
requested by the CNC. The request will reflect the application
requirements and specific service needs, including bandwidth,
traffic type and survivability. Furthermore, application access and
type of virtual network service requested by the CNC, will be need
adhere to specific access control policies.
8.3. Policy Applied to the Multi-Domain Service Coordinator
A key objective of the MDSC is to support the customer's expression
of the application connectivity request via its CNC as a set of
desired business needs, therefore policy will play an important
role.
Once authorized, the virtual network service will be instantiated
via the CNC-MDSC Interface (CMI); it will reflect the customer
application and connectivity requirements, and specific service
transport needs. The CNC and the MDSC components will have agreed
connectivity end-points; use of these end-points should be defined
as a policy expression when setting up or augmenting virtual network
services. Ensuring that permissible end-points are defined for CNCs
and applications will require the MDSC to maintain a registry of
permissible connection points for CNCs and application types.
Conflicts may occur when virtual network service optimization
criteria are in competition. For example, to meet objectives for
service reachability a request may require an interconnection point
between multiple physical networks; however, this might break a
confidentially policy requirement of specific type of end-to-end
service. Thus an MDSC may have to balance a number of the
constraints on a service request and between different requested
services. It may also have to balance requested services with
operational norms for the underlying physical networks. This
balancing may be resolved using configured policy and using hard and
soft policy constraints.
8.4. Policy Applied to the Provisioning Network Controller
The PNC is responsible for configuring the network elements,
monitoring physical network resources, and exposing connectivity
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(direct or abstracted) to the MDSC. It is therefore expected that
policy will dictate what connectivity information will be exported
between the PNC, via the MDSC-PNC Interface (MPI), and MDSC.
Policy interactions may arise when a PNC determines that it cannot
compute a requested path from the MDSC, or notices that (per a
locally configured policy) the network is low on resources (for
example, the capacity on key links become exhausted). In either
case, the PNC will be required to notify the MDSC, which may (again
per policy) act to construct a virtual network service across
another physical network topology.
Furthermore, additional forms of policy-based resource management
will be required to provide virtual network service performance,
security and resilience guarantees. This will likely be implemented
via a local policy agent and additional protocol methods.
9. Security Considerations
The ACTN framework described in this document defines key components
and interfaces for managed traffic engineered networks. Securing
the request and control of resources, confidentially of the
information, and availability of function, should all be critical
security considerations when deploying and operating ACTN platforms.
Several distributed ACTN functional components are required, and
implementations should consider encrypting data that flows between
components, especially when they are implemented at remote nodes,
regardless these data flows are on external or internal network
interfaces.
The ACTN security discussion is further split into two specific
categories described in the following sub-sections:
o Interface between the Customer Network Controller and Multi-
Domain Service Coordinator (MDSC), CNC-MDSC Interface (CMI)
o Interface between the Multi-Domain Service Coordinator and
Provisioning Network Controller (PNC), MDSC-PNC Interface (MPI)
From a security and reliability perspective, ACTN may encounter many
risks such as malicious attack and rogue elements attempting to
connect to various ACTN components. Furthermore, some ACTN
components represent a single point of failure and threat vector,
and must also manage policy conflicts, and eavesdropping of
communication between different ACTN components.
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The conclusion is that all protocols used to realize the ACTN
framework should have rich security features, and customer,
application and network data should be stored in encrypted data
stores. Additional security risks may still exist. Therefore,
discussion and applicability of specific security functions and
protocols will be better described in documents that are use case
and environment specific.
9.1. CNC-MDSC Interface (CMI)
Data stored by the MDSC will reveal details of the virtual network
services, and which CNC and customer/application is consuming the
resource. The data stored must therefore be considered as a
candidate for encryption.
CNC Access rights to an MDSC must be managed. The MDSC must
allocate resources properly, and methods to prevent policy
conflicts, resource wastage, and denial of service attacks on the
MDSC by rogue CNCs, should also be considered.
The CMI will likely be an external protocol interface. Suitable
authentication and authorization of each CNC connecting to the MDSC
will be required, especially, as these are likely to be implemented
by different organizations and on separate functional nodes. Use of
the AAA-based mechanisms would also provide role-based authorization
methods, so that only authorized CNC's may access the different
functions of the MDSC.
9.2. MDSC-PNC Interface (MPI)
Where the MDSC must interact with multiple (distributed) PNCs, a
PKI-based mechanism is suggested, such as building a TLS or HTTPS
connection between the MDSC and PNCs, to ensure trust between the
physical network layer control components and the MDSC. Trust
anchors for the PKI can be configured to use a smaller (and
potentially non-intersecting) set of trusted Certificate Authorities
(CAs) than in the Web PKI.
Which MDSC the PNC exports topology information to, and the level of
detail (full or abstracted), should also be authenticated, and
specific access restrictions and topology views should be
configurable and/or policy-based.
10. IANA Considerations
This document has no actions for IANA.
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11. References
11.1. Informative References
[RFC2702] Awduche, D., et. al., "Requirements for Traffic
Engineering Over MPLS", RFC 2702, September 1999.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", IETF RFC
4655, August 2006.
[RFC5654] Niven-Jenkins, B. (Ed.), D. Brungard (Ed.), and M. Betts
(Ed.), "Requirements of an MPLS Transport Profile", RFC
5654, September 2009.
[RFC7149] Boucadair, M. and Jacquenet, C., "Software-Defined
Networking: A Perspective from within a Service Provider
Environment", RFC 7149, March 2014.
[RFC7926] A. Farrel (Ed.), "Problem Statement and Architecture for
Information Exchange between Interconnected Traffic-
Engineered Networks", RFC 7926, July 2016.
[RFC3945] Manning, E., et al., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture2, RFC 3945, October 2004.
[ONF-ARCH] Open Networking Foundation, "SDN architecture", Issue
1.1, ONF TR-521, June 2016.
[Centralized] Farrel, A., et al., "An Architecture for Use of PCE
and PCEP in a Network with Central Control", draft-ietf-
teas-pce-central-control, work in progress.
[Service-YANG] Lee, Y., Dhody, D., and Ceccarelli, C., "Traffic
Engineering and Service Mapping Yang Model", draft-lee-
teas-te-service-mapping-yang, work in progress.
[ACTN-YANG] Lee, Y., et al., "A Yang Data Model for ACTN VN
Operation", draft-lee-teas-actn-vn-yang, work in progress.
[ACTN-REQ] Lee, Y., et al., "Requirements for Abstraction and
Control of TE Networks", draft-ietf-teas-actn-
requirements, work in progress.
[TE-Topo] X. Liu et al., "YANG Data Model for TE Topologies", draft-
ietf-teas-yang-te-topo, work in progress.
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12. Contributors
Adrian Farrel
Old Dog Consulting
Email: adrian@olddog.co.uk
Italo Busi
Huawei
Email: Italo.Busi@huawei.com
Khuzema Pithewan
Infinera
Email: kpithewan@infinera.com
Michael Scharf
Nokia
Email: michael.scharf@nokia.com
Luyuan Fang
eBay
Email: luyuanf@gmail.com
Diego Lopez
Telefonica I+D
Don Ramon de la Cruz, 82
28006 Madrid, Spain
Email: diego@tid.es
Sergio Belotti
Alcatel Lucent
Via Trento, 30
Vimercate, Italy
Email: sergio.belotti@nokia.com
Daniel King
Lancaster University
Email: d.king@lancaster.ac.uk
Dhruv Dhody
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
Email: dhruv.ietf@gmail.com
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Gert Grammel
Juniper Networks
Email: ggrammel@juniper.net
Authors' Addresses
Daniele Ceccarelli
Ericsson
Torshamnsgatan,48
Stockholm, Sweden
Email: daniele.ceccarelli@ericsson.com
Young Lee
Huawei Technologies
5340 Legacy Drive
Plano, TX 75023, USA
Phone: (469)277-5838
Email: leeyoung@huawei.com
APPENDIX A - Example of MDSC and PNC Functions Integrated in A
Service/Network Orchestrator
This section provides an example of a possible deployment scenario,
in which Service/Network Orchestrator can include a number of
functionalities, among which, in the example below, PNC
functionalities for domain 2 and MDSC functionalities to coordinate
the PNC1 functionalities (hosted in a separate domain controller)
and PNC2 functionalities (co-hosted in the network orchestrator).
Customer
+-------------------------------+
| +-----+ |
| | CNC | |
| +-----+ |
+-------|-----------------------+
|
Service/Network | CMI
Orchestrator |
+-------|------------------------+
| +------+ MPI +------+ |
| | MDSC |---------| PNC2 | |
| +------+ +------+ |
+-------|------------------|-----+
| MPI |
Domain Controller | |
+-------|-----+ |
| +-----+ | | SBI
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| |PNC1 | | |
| +-----+ | |
+-------|-----+ |
v SBI v
------- -------
( ) ( )
- - - -
( ) ( )
( Domain 1 )----( Domain 2 )
( ) ( )
- - - -
( ) ( )
------- -------
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