Network Working Group Young Lee
Internet Draft Huawei
Intended status: Informational Daniel King
Expires: December 10, 2015 Lancaster University
M. Boucadair
France Telecom
R. Jing
China Telecom
L. Contreras Murillo
Telefonica
June 9, 2015
Problem Statement for Abstraction and Control of Transport Networks
draft-leeking-teas-actn-problem-statement-00.txt
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Abstract
Transport networks that provide connectivity and bandwidth for
customer services have typically been static, lacking
flexibility, and requiring long planning times when deploying new
services. Network Providers and Service Providers have embraced
technologies that allow separation of data plane and control plane,
distributed signaling for path setup and protection, and centralized
path computation for service planning and traffic engineering.
Although these technologies provide significant benefits, they do
not meet the growing need for network programmability, automation,
resource sharing, and service elasticity necessary to meet
operators' requirements for virtual network operation.
Virtual network operation refers to the creation of a
virtualized environment allowing operators to view the
abstraction of the underlying multi-administration, multi-
vendor, multi-technology networks and to operate, control, and
manage these multiple networks as if a single virtualized network.
Another dimension of virtual network operation is the use of
common core transport network resources by multi-tenant service
networks as a way of providing a virtualized infrastructure to
flexibly offer new services and applications.
The work effort investigating this problem space is known as
Abstraction and Control of Transport Networks (ACTN). This
document provides an ACTN problem description, a scope of work,
and outlines the core objectives and requirements to facilitate
virtual network operation.
Table of Contents
1. Introduction..................................................4
1.1. Terminology..............................................5
2. Objectives and Functional Requirements........................7
2.1. Use Cases................................................7
2.1.1 Packet Transport Networks (PTN) in Mobile Backhaul
Networks................................................7
2.1.2 Packet Optical Integration (POI)....................7
2.1.3 Multi-domain Data Center Interconnect...............7
2.1.4 On-demand E2E Connectivity Services in Multiple Vendor
Domain Transport Networks...............................8
2.1.5 Multi Tenant Virtual Network Operators..............9
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2.1.6 Virtual Network Operation for Multiple Domains in a
Single Operator Network.................................10
2.1.7 Mobile Virtual Network Operation for Multiple Domains
in a Single Operator Network............................10
2.1.8 Dynamic Service Control based on Performance
Monitoring..............................................11
3. Relationship with Existing Technologies & Other Industry
Initiatives.............................................11
3.1. Virtual Private Networks.................................11
3.2. Overlay Networks.........................................12
3.3. Other Industry Initiatives...............................12
4. Motivations for Additional Functionality......................13
4.1. Business Objectives......................................13
4.2. Network Resource Recursiveness...........................14
4.3. Customer-Initiated Programmability.......................14
4.4. Resource Partitioning....................................14
4.5. Service Orchestration....................................14
5. ACTN Objectives and Requirements..............................15
5.1. Capability and Resource Visibility.......................15
5.2. Network Programmability..................................16
5.3. Common Data Models.......................................16
5.4. Scheduling...............................................17
5.5. Slicing..................................................17
5.6. Adaptability.............................................17
5.7. Allocation...............................................17
5.8. Isolation................................................18
5.9. Manageability............................................18
5.10. Resilience..............................................19
5.11. Security................................................19
5.12. Policy..................................................20
5.13. Technology Independence.................................20
5.14. Optimization............................................20
5.15. Multi-domain Support....................................20
5.16. Architecture Principles.................................20
5.16.1. Network Partitioning...............................21
5.16.2. Orchestration......................................21
5.16.3. Recursion..........................................21
5.16.4. Legacy Support and Interoperability................21
5.17. Other Related Work......................................21
5.17.1. Requirements for Automated (Configuration) Management
...........................................................21
5.17.2. Connectivity Provisioning Negotiation Protocol (CPNP)
...........................................................21
6. References....................................................22
6.1. Informative References...................................22
7. Acknowledgements..............................................24
8. IANA Considerations...........................................24
9. Authors' Addresses............................................24
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1. Introduction
Customers continue to demand new services that are time scheduled,
dynamic, and underpinned by a Pay As You Go billing model. These
services are provided to customers by network operators and service
providers and give rise to a variety of applications for office
automation, data backup and retrieval, distributed computing, and
high-quality media broadcasting. They offer Network and Service
Providers new revenue generation opportunities, and these services
typically have different traffic characteristics from established
network services such as file hosting, web, and email. Deploying and
operating these new applications and services using existing network
technologies and architectures limits network efficiency,
scalability, and elasticity (i.e., they do not offer sufficient
capability to adapt to customer and application demands).
Network virtualization has been a significant innovation towards
meeting customer demands and enabling new applications and services.
Separating network resources, and representing resources and
topologies via abstracted concepts, facilitates effective sharing
(or 'slicing') of physical infrastructure into virtual network
service instances corresponding to multiple virtual network
topologies that may be used by specific applications, services, and
users. Further development is required to allow customers to create,
modify, and delete virtual network services dynamically.
Transport networks that provide connectivity and bandwidth for
customer services have typically been static, lacking flexibility,
and requiring long planning times when deploying new services.
Network Providers and Service Providers have embraced technologies
that allow separation of data plane and control plane, distributed
signaling for path setup and protection, and centralized path
computation for service planning and traffic engineering. Although
these technologies provide significant benefits, they do not meet
the growing need for network programmability, automation, resource
sharing, and service elasticity necessary to meet operators'
requirements for virtual network operation.
Virtual network operation refers to the creation of a virtualized
environment allowing operators to view the abstraction of the
underlying multi-administration, multi-vendor, multi-technology
networks and to operate, control and manage these multiple networks
as single virtualized network. Another dimension of virtual network
operation is the use of common core transport network resources by
multi-tenant service networks as a way of providing a virtualized
infrastructure to flexibly offer new services and applications.
Abstraction and Control of Transport Networks (ACTN) defines new
methods and capabilities for the deployment and operation of
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transport network resource. These are summarized as follows.
o Coordination and abstraction of underlying transport network
resources to higher-layer applications and customers. Note
that higher-layer applications and customers could be
internal users of the core transport network resource such as
various service networks.
o Multi-domain virtual network operation that facilitates
multi-administration, multi-vendor, and multi-technology
networks as a single virtualized network.
o Multi-tenant virtual network operation that consolidates
different network services and applications to allow slicing
of network resources to meet specific service, application
and customer requirements.
o Provision of a computation scheme and virtual control
capability via a data model to customers who request
virtual network services. Note that these customers could,
themselves, be service providers.
This document first presents the summary of ACTN use-cases, then
provides an ACTN problem description and scope of work, and
outlines the core objectives and requirements to facilitate
virtual network operation.
1.1. Terminology
This document uses the terminology defined in [RFC4655] and
[RFC5440]. Additional terms are defined below.
o Customers:
Customers are users of virtual network services. They are
provided with an abstract view of the network resource (known as
"a slice") to support their users and applications. In some
cases, customers may have to support multiple virtual network
services with different service objectives and QoS requirements
to enable multiple types of users and applications. Customers
may also be considered to be trusted parties with respect to
the provider wholesale service department. A trust model will
be required and is discussed further later in this document.
o Service Providers (also Virtual Network Service Provider):
Service Providers are the providers of virtual network services
to their customers. Service Providers typically lease resources
from one or more Network Provider to create virtual network
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services or offer end-to-end services to their customers. A
Service Provider may be a Network Provider such that some or
all of the resources used are owned by the Service Provider. A
Virtual Network Service Provider is a special type of
Service Provider in that they might own no physical equipment
or infrastructure, or might have only limited physical
infrastructure and require virtual resources to be supplied to
them by another Service Provider to offer the final service. A
Virtual Network Service Provider only provide services built
upon a virtual network infrastructure. The rest of this
document does not distinguish between a Virtual Network Service
Provider and Service Provider.
o Network Providers:
Network Providers are the infrastructure providers that own the
physical network resources and provide transport network
resources to their customers. Service Providers can be the
customers of Network Providers or can be the Network Providers
themselves.
o Network Virtualization:
Network virtualization, refers to allowing the customers to
utilize certain network resources as if they owned them, and thus
allows the customers to control their allocated resources in a
way most optimal for higher layer or application processes.
This customer control facilitates the introduction of new
applications (on top of available services) as the customers
are given programmable interfaces to create, modify, and delete
their virtual network services.
o Transport Networks:
Transport networks are defined as network infrastructure that
provides connectivity and bandwidth for customer services. They
are characterized by their ability to support server layer
resources providing connectivity bandwidth and traffic engineering
for client layer services, such that resource guarantees may be
provided to customers. Transport networks discussed in this
document different types of connection-oriented networks
including both Connection-Oriented Circuit Switched (CO-CS)
networks and Connection-Oriented Packet Switched (CO-PS)
networks. This implies that at least the following transport
networks are in scope: Layer 1 (L1) and Layer 0 (L0) optical
networks (e.g., OTN, ODU, OCh/WSON), MPLS-TP, MPLS-TE, as well
as other emerging network technologies with connection-oriented
behavior.
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2. Objectives and Functional Requirements
2.1 Use Cases
A group of Service Providers and Network Providers have identified
a number of key use cases that identify key application scenarios for
how ACTN may be used.
2.1.1 Packet Transport Networks (PTN) in Mobile Backhaul Networks
The Packet Transport Networks (PTN) Network Provider may use ACTN to
improve efficiency of provision and operation, optimize the
resources utilization, and promote the customer's experiences.
The Internet-Draft [CHENG] discusses the key requirements for ACTN in
a PTN environment, these include:
o Faster End-to-End Enterprise services Provisioning
o Multi-layer coordination in L2/L3 Packet Transport Networks
o Optimizing the network resources utilization (supporting
various performances monitoring matrix, such as traffic flow
statistics, packet delay, delay variation, throughput and
packet-loss rate)
o Virtual Networks Operations for Multi-domain Packet Transport
Networks
2.1.2 Packet Optical Integration (POI)
Increasingly there is a need for packet and optical transport
networks to work together to provide accelerated services. Transport
networks can provide useful information to the packet network
allowing it to make intelligent decisions and control its allocated
resources. The Internet-Draft [DHODY] outlines the Packet Optical
Integration (POI) use case for ACTN,
The Internet-Draft [DHODY] discusses the key requirements for ACTN
for the Packet Optical Integration (POI) environment, requirements
include:
o Packet Optical Integration to support Traffic Planning,
performance Monitoring, automated congestion management and
Automatic Network Adjustments.
o Protection and Restoration Synergy in Packet Optical Multi-
layer network.
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o Service Awareness and Coordination between Multiple Network
Domains.
2.1.3 Multi-domain Data Center Interconnect
Data center operators need to interface multi-domain transport
networks to offer their global data center applications and
services. As data center providers face multi-domain and diverse
transport technology, interoperability based on standard-based
abstraction is required for dynamic and flexible applications and
services.
The Internet-Draft [FANG] discusses the key requirements for ACTN
for the data center interconnect environment, requirements
include:
o Multi-domain Data Center Interconnection to support VM
Migration, Global Load Balancing, Disaster Recovery, On-
demand Virtual Connection/Circuit Services.
o The interfaces between the Data Center Operation and each
transport network domain should support standards-based
abstraction with a common information/data model to support
the following:
- Network Query (Pull Model) from the Data Center
Operation to each transport network domain to collect
potential resource availability (e.g., BW availability,
latency range, etc.) between a few data center
locations.
- Network Path Computation Request from the Data Center
Operation to each transport network domain to estimate
the path availability.
- Network Virtual Connections/Circuits Request from the
Data Center Operation to each transport domain to
establish end-to-end virtual connections/circuits (with
type, concurrency, duration, SLA.QoS parameters,
protection.reroute policy options, policy constraints
such as peering preference, etc.).
- Network Virtual Connections/Circuits Modification
Request.
2.1.4 On-demand E2E Connectivity Services in Multiple Vendor
Domain Transport Networks
There is a need for creation and operation of a virtualized
environment supporting the viewing and controlling different
vendor domains, including on-demand network connectivity
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service across a single operator environment. This will accelerate
rapid service deployment of new services, including more dynamic
and elastic services, and improve overall network operations and
scaling of existing services.
The Internet-Draft [KLEE] highlights on-demand edge-to-edge (E2E)
connectivity service requirements in multiple vendor domain
transport networks, which include:
o Two-stage path computation capability in a hierarchical
control architecture (MDSC-PNC) and a hierarchical
composition of integrated network views.
o Coordination of signal flow for E2E connections.
o Abstraction of:
- Inter-connection data between domains
- Customer Endpoint data
- The multiple levels/granularities of the abstraction of
network resource (which is subject to policy and service
need).
- Any physical network constraints (such as SRLG, link
distance, etc.) should be reflected in abstraction.
- Domain preference and local policy (such as preferred
peering point(s), preferred route, etc.), Domain network
capability (e.g., support of push/pull model).
2.1.5 Multi-Tenant Virtual Network Operators
Creation and operation of multi-tenant virtual networks that use
the common core network resources is important to facilitate rapid
deployment of new services, including more dynamic and elastic
services, and improve overall network operations and scaling of
existing services.
The Internet-Draft [KUMAKI] discusses multi-tenant virtual networks
that use the common core network resources, requirements include:
o On-demand Virtual Network Service Creation
o Domain Control Plane/Routing Layer Separation
o Independent service Operation for Virtual Services from
control of other domains
o Multiple service level support for each VN (e.g., bandwidth
and latency for each VN service).
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o VN diversity/survivability should be met in physical network
mapping.
o VN confidentiality and sharing constraint should be supported.
2.1.6 Virtual Network Operation for Multiple Domains in a Single
Operator Network
Virtual network operation for multiple domains in a single
operator network is required. This would facilitate the
application of virtual network abstractions to network operations.
These abstractions will create a virtualized environment
supporting the viewing and controlling different domains as a
single virtualized network.
This use case is discussed in more detail in [LOPEZ], requirements
include:
o Creation of a global abstraction of network topology: The VNO
Coordinator assembles each domain level abstraction of
network topology into a global abstraction of the end-to-end
network.
o End-to-end connection lifecycle management.
o Invocation of path provisioning request to each domain
(including optimization requests).
o Invocation of path protection/reroute to the affected
domain(s).
o End-to-end network monitoring and fault management. This could
imply potential KPIs and alarm correlation capabilities.
o End-to-end accounting and generation of detailed records for
resource usage.
o End-to-end policy enforcement
2.1.7 Mobile Virtual Network Operation for Multiple Domains
in a Single Operator Network
The use-case for mobile virtual networks with single operator
Networks is discuss edin [SHIN].
o Resource abstraction: operational mechanisms in mobile
backhaul network to give the current network usage
information for dynamic and elastic applications be
provisioned dynamically with QoS guarantee.
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o Load balancing or for recovery, the selection of core DC
location from edge constitutes a data center selection
problem.
o Multi-layer routing and optimization, coordination between
these two layers.
2.1.8 Dynamic Service Control based on Performance
Monitoring
Transport networks support various performance monitoring
mechanisms, such as traffic flow statistics, packet delay, delay
variation, throughput and packet-loss rate for MPLS-TP and packet
OTN networks, BER, FEC error correction counters for OTN and DWDM
networks, etc. These mechanisms may be used to support
dynamic service control of network resources based on the
aforementioned performance monitoring. This use case is discussed in
[XU], requirements include:
o Dynamic Service Control Policy enforcement and Traffic/SLA
Monitoring:
- Customer service performance monitoring strategy,
including the traffic monitoring object (the service
need to be monitored)
- monitoring parameters (e.g., transmitted and received
bytes per unit time),
- traffic monitoring cycle (e.g., 15 minutes, 24 hours),
- threshold of traffic monitoring (e.g., high and low
threshold), etc.
3. Relationship with Existing Technologies & Other Industry Initiatives
3.1. Virtual Private Networks
A Virtual Private Network (VPN) is a well-known concept
[RFC4110], [RFC4664], and [RFC4847], and may be used to connect
multiple distributed sites via a variety of transport
technologies, sometimes over shared network infrastructure.
Typically VPNs are managed and provisioned directly by the
Network Provider or a VPN Service Provider. VPN systems may be
Classified by:
o Protocol mechanisms used to tunnel the traffic;
o Tunnel termination point and/or location;
o Type of connectivity, site-to-site or remote-access;
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o Quality of Service (QoS) capabilities;
o Level of security provided;
o Emulated service connectivity layer (layer 1, layer 2,
layer 3);
Existing VPN solutions are largely technology specific and offer
limited elasticity, although some technologies offer greater
flexibility (i.e., layer 2 VPNs [RFC4664] and layer 3 VPNs
[RFC4110]) when compared with layer 1 VPNs [RFC4847], all
technologies are often deployed using pre-defined configurations.
[RFC4847] describes virtual networks in terms of ITU-T [Y.1312]
and [Y.1313]. Those Recommendations address both the data plane
and control plane aspects of VPNs. Concepts of private and
shared VPNs are described.
The transport layer is achieved by utilizing a variety of
technology-specific interfaces - e.g. Gigabit Ethernet (GE),
Synchronous Digital Hierarchy (SDH), or Asynchronous Transfer
Mode (ATM) for wireless back-hauling, or optical networks OTN and
WSON.
VPNs offer a scalable tunnel solution for customer traffic;
However, they are wholly dependent on the Service Provider to
setup and manage the VPNs, lacking customer-initiated service
programmability: creation, resizing, and deletion.
3.2. Overlay Networks
An overlay network [RFC4208] provides an enhanced network
virtualization technique, with the overlay network providing a
topology comprised of virtual or logical links and nodes, which
are built on top of physical nodes and links, providing a
topology in which some of the links and nodes are virtual or
logical and are built from multiple nodes or links in a server
network.
Overlay networks are typically used in the multi-layer context
in which the packet layer is a client to the server transport
layer. The scope of network virtualization in overlay networks is
somewhat limited. Customers and applications which need
visibility or programmability, and the ability to resize or add
resources, may find that overlay network technologies do meet
their requirements.
3.3. Other Industry Initiatives
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ONF Architecture [ONF-SDN-ARCH] describes various arrangements of
SDN controllers.
TM Forum's [TR215] and [TR225] addresses a common information model
that can be applied to transport network in particular.
ITU-T [Y.1312] and [Y.1313] are a good reference to review for
Layer 1 VPN in terms of terminology and architecture.
4. Motivations for Additional Functionality
4.1. Business Objectives
The VPN and overlay network (ON) models are built on the premise
that one single Network Provider provides all virtual private or
overlay networks to its customers. This model is simple to
operate but has some disadvantages in accommodating the
increasing need for flexible and dynamic network virtualization
capabilities.
A Network Provider may provide end-to-end services and content
(i.e., web and email) to its customers. Other services,
applications, and content are typically provided via Service
Providers and Over the Top (OTT) (i.e., Video-on-demand, Social
Media) providers. We can further categorize Service Providers
as:
o A fixed or mobile Internet Service Provider (ISP) which
provides Internet connectivity and bandwidth to users;
o A service provider that leases network resources from one or
more network providers to create virtual network services
between ISPs and the core Internet.
o Data Center (DC)/content Network Provider and Service Providers
who provide connectivity and bandwidth to content servers and
application servers.
Network Providers and Service Providers of every type, all share
The common business and revenue objectives:
o Minimize time to plan and deploy new services;
o Reduce the reliance on highly skilled personnel to operate
their network;
o Reduce time to react to changing business demands and customer
applications;
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o Offer new, much more flexible services to their customers;
o Maximize network resource usage and efficiency.
All aforementioned objectives have the capability to
significantly increase revenue and reduce operational costs.
Network and Service Providers require capabilities that extend
the current landscape of network virtualization capabilities and
overall business objectives of the Network Provider, Service
Provider, and ultimately the Customer and their Applications.
4.2. Network Resource Recursiveness
A newly emerged network virtualization environment is a
collection of heterogeneous network architectures from different
players. VPNs and overlay networks are somewhat limited in
addressing programmable interfaces for application or customer
layers as well as for the service layer. The model must be
extended to address a recursive nature of layer interactions in
network virtualization across transport networks, service
networks, and customers/applications.
4.3. Customer-Initiated Programmability
Network-driven technologies such as VPNs and overlay networks
provide customers with a set of pre-defined programmatic
parameters to enable virtual networks. However, this model is
limited to only allow programmable interfaces in which customers
initiate and define virtual network services. This model must be
extended to allow customer-initiated network programmability.
4.4. Resource Partitioning
The ability to slice and allocate transport resources for Service
Providers would be beneficial. It would improve transport network
resource efficiency and provide a method for the transport
Network Provider to offer resource flexibility and control to
Service Providers and users.
4.5. Service Orchestration
Another dimension is diversity on the customer side. Customers in
this newly emerged network virtualization environment bring
different dynamics than the traditional VPNs or Overlay Networks.
There may be a multiple virtual slices that need to be created,
managed and deleted, each interfacing to a number of Service
Providers and Network Providers as the end-points of the clients
span across multiple network domains. Thus, multiple components
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will require automated co-ordination and management, this is
known as service orchestration and is therefore one of the key
capabilities that should be provided.
5. ACTN Objectives
The overall goal of enabling network abstraction and multiple
concurrent virtual networks to coexist on a shared physical
infrastructure comprised of multiple physical layers may
be subdivided into several smaller objectives. These are
outlined below and are required in order to fulfill the design
goals of ACTN.
The ACTN effort should utilize existing physical layer monitoring
capabilities, algorithmic representation, and modelling of
physical layer resources to consider transport metrics and
constraints. Moreover, the model of the physical layer resources
may need dynamic collection of the status and availability of
the underlying transport network infrastructure.
5.1. Capability and Resource Visibility
It may be necessary for the application or Customer to obtain
Information about available capabilities and available network
resources, for example, a view and control of abstracted resource.
The visibility of the capabilities and the resources can be
obtained either by resource discovery or by resource publishing.
In the former case, the customer performs resource collection
directly from the provider network by using discovery
mechanisms to get total information about the available resources
to be consumed. In the latter case, the network provider exposes
available resources to potential customers (e.g., through a
resource catalog) reducing the amount of detail of the
underlying network.
Furthermore, capabilities and resources will also include:
o Peering Points (may be based on business SLAs or policies);
o Transport Topology (i.e., transport switching type, topology
and connection points);
o Transport Capacity (i.e., current bandwidth and maximum
bandwidth).
o Policy Management (i.e., what resources and capabilities are
available, and what may be requested and by whom).
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o Information about the provider (i.e., informative data about
the resource owner)
o Geographical information about the resources to be
consumed (i.e., geolocation of the resources for preventing
legal concerns that could appear in the provision of some
services).
o Information about resource cost, consumption, etc. (i.e.,
energy efficiency per transmitted bit, monetary cost of the
resource usage per time unit, etc.).
o Information about achievable resiliency (i.e.,
protection/restoration capabilities, recovery time, etc.).
5.2. Network Programmability
The creation of a programmable abstraction layer for physical
network devices would provide information models which
would allow operators to manipulate the network resources. By
utilizing open programmable north-bound network interfaces, it
would enable access to virtual control layer by customer
interfaces and applications.
A programmable interface should provide customers with the
capabilities to dynamically create, deploy, and operate services
in response to customer and application demands.
5.3. Common Data Models
The data model that describes the abstraction of the underlying
transport network should be agnostic to each technology
type within the ACTN framework. The model will provide a uniform
structure which is extensible to support any future
technologies.
The model will represent the physical resources as a set of
attributes, characteristics and functionality, while adaptively
capturing the true real-time and dynamic (real-time) properties
of underlying physical resources.
The data model can be decomposed into the following elements.
o Attributes
o Metrics
o Control Actions
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o Semantics
o Administrative information (resource ownership)
Virtual infrastructure requests from ACTN customers will be
translated into network parameters according to aforementioned
network abstraction model. Utilizing this mechanism, a request is
translated into topology and multi-dimensional nodes, interfaces
and spectrum space with specific attributes such as bandwidth,
QoS, and node capability.
Apart from facilitating the request of resources, these data
models could be used for other tasks like network operation
(e.g., the management of the abstracted transport infrastructure
by the customer), configuration (e.g., the control of the
resources), monitoring (e.g., the uniform view of different
infrastructures in use), Service Level Agreements (SLA) customization
(e.g., the particularization of the collected metrics according to
the customer interests), etc.
5.4. Scheduling
When requesting network slices it should be possible to request
an immediate or scheduled service.
To enable such on-demand consumption of resources, the Network
Providers would be capable of employing appropriate scheduling
algorithms in a centralized entity, or alternatively distributed
across all of the network elements.
5.5. Slicing
It should be possible for transport network infrastructure to be
partitioned into multiple independent virtual networks through a
process known as "slicing". This partitioning is based on
provider service types, customers and application requirements.
5.6. Adaptability
Adaptability of services would allow the Service Provider, user,
and application to request modification of existing virtual network
resources that have been assigned. This may include resizing of
bandwidth, modification of the underlying topology, and
adding/removing connectivity points to modify the virtual network
topology itself.
5.7. Allocation
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When establishing a network slice, a customer may require
specific guarantees for the virtual node and link attributes.
This might include a request that guarantees minimum packet
processing times on a virtual node, and fixed loss and delay
characteristics on the virtual links. This should be governed by
SLAs and can have implications in the supportive transport
technologies, and in the properties of the service to be offered
to the customer (e.g., protected versus non-protected).
To provide such guarantees and to create an illusion of an
isolated and dedicated network slice to each customer, the
Network Providers must employ the necesssary scheduling capability.
5.8. Isolation
Isolation, both of physical underlay infrastructure and of co-
existing virtual networks, is required for management and
confidentiality reasons. Additionally there must be no leakage of
traffic between different customers.
Furthermore, there must be mechanisms that ensure that once
network slices are assigned, Customer and Application services do
not compete for the transport resources that support their
virtual networks.
Within their virtual networks, each customer or application
should be able to use arbitrary network topology, routing, or
forwarding functions as well as customized control mechanisms
independent of the underlying physical network and of other
coexisting virtual networks.
It must also be possible for many virtual networks to share the
underlying infrastructure (multi-tenant), without impacting
the performance of applications utilizing the virtual networks.
5.9. Manageability
A broad range of capabilities will need to be provided
through a set of well-defined interfaces. These capabilities
apply to the management of end-to-end services and include the
ability to request, control, provisioning, monitoring, resilience,
adapt,and re-optimize those services. Specifically it should
be possible to provide the following funcitons.
o Control of virtual network resources. This control must be
capable of delivering end-to-end services with optimization of
connectivity and virtual infrastructure. Such optimization is
based on client interface and application demands,
technology constraints (bandwidth, latency, jitter,
function, etc.), and commercial constraints (energy, customer
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SLA, etc.).
o Automation of virtual service and function requests and
objectives, and providing on-demand and self-service network
slicing subject to policy constraints set by the operators of
the underlying physical networks, and under the control of
commercial agreements between all parties.
o Infrastructure elasticity to allow rapid provisioning,
automatic scaling out, or in, of virtual resources.
o Virtual resource monitoring
o Control of bandwidth, energy consumption and quality of
service/packet scheduling.
5.10. Resilience
The resilience of the transport service provided to the customer
will depend on the requirements expressed by the customer. Two
different resilience scenarios may be considered: (i) the
resilience as observed from the point of view of the customer;
and (ii) the resilience as observed from the point of view of the
provider.
The former case refers to the situation in which the customer
requests specific resilience requirements on the offered
transport service. For instance, the customer can request
transport protection through the provision of disjoint paths
connecting service end-points. This specific requirement forces
the provider to explicitly assign transport resources to a
customer.
However there are other situations in which the provider has to
allocate resources for implicit resilience. For instance, the
customer could request a service with certain QoS or availability
for a single connection between service end-points according to
an SLA. In that case, the provider could trigger recovery actions
in the network, e.g. during a network outage, and according to
the conditions of the SLA. These measures may not be perceived by
the customer.
5.11. Security
Network programmability may introduce new security and
misconfiguration vulnerabilities. These must be investigated and
discussed, and then solved. ACTN-based
networks must be resilient to existing, and new, faults and
attacks.
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Failure or security breach in one ACTN slice should not impact
another virtual network. It must also be possible to separate
untrusted services and applications, along with confidential
services and applications that must be secured.
Some other aspects are relevant to security within the context of
ACTN are as follows.
o Security aspects from the service point of view. For instance,
encryption capabilities as part of the service capabilities that
could be requested by the customer.
o Security aspects from the customer/provider relationship point
of view. For instance aspects like authentication,
authorization, logging, etc.
5.12. Policy
To be discussed.
5.13. Technology Independence
ACTN must support a variety of underlay transport technologies,
providing the flexibility to manage a variety of heterogeneous
network technologies.
5.14. Optimization
The service provider must be able to
optimize the provided transport infrastructure without impacting
the customer services. As the resources become consumed some
fragmentation in the usage of the underlying infrastructure could
occur. The provider then can be interested in optimizing the
usage of its resources for several reasons (e.g., energy
consumption, re-utilization of vacant resources, etc.).
5.15. Multi-domain Support
A given customer could required to compose an end-to-end
transport service by using network capabilities from different
service providers that may be internal organizations or external
entities. Reasons for that could be geographical coverage of the
service (not fully served by a unique provider), resource
availability (not enough resources from a given provider), or
simply resiliency (provider diversity). ACTN should allow the
multi-domain approach to give the customer the possibility of
composing multi-provider transport services.
5.16. Architectural Principles
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5.16.1. Network Partitioning
Coexistence of multiple network slices will need to be supported.
It should also be possible for multiple network slices used by
different customers to coexist, spanning part or
all of the underlying physical networks.
5.16.2. Orchestration
ACTN should allow orchestration (automated co-ordination of
functions) for managing and controlling virtual network services
that may span multiple Service Providers and Network Providers.
5.16.3. Recursion
It should be possible for a network slice to be segmented to
allow a slicing hierarchy with parent child relationships.
Allowing a customer to become a virtual provider is known
as "recursion" or "nesting" of network slices.
5.16.4. Legacy Support and Interoperability
The ability to deploy ACTN should be transparent to existing
physical network control and management mechanisms and protocols.
Additionally, interoperability with non-ACTN based (i.e.,
conventional) networks should be guaranteed, thus allowing for
the coexistence of both kinds of network solutions from the
perspective of either the customer or the provider.
5.17. Other Related Work
5.17.1. Requirements for Automated (Configuration) Management
Given the ever-increasing complexity of the configuration tasks
required for the dynamic provisioning of IP networks and
services, [I-D.boucadair-network-automation-requirements] aims at
listing the requirements to drive the specification of an
automated configuration management framework, including the
requirements for a protocol to convey configuration information
towards the managed entities.
5.17.2. Connectivity Provisioning Negotiation Protocol (CPNP)
[I-D.boucadair-connectivity-provisioning-protocol] specifies
the Connectivity Provisioning Negotiation Protocol (CPNP) which
could be used to facilitate the dynamic negotiation of service
parameters between a Customer and a Provider. As such, CPNP is a
generic protocol that can be used for various negotiation
purposes that include (but are not necessarily limited to)
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connectivity provisioning services, storage facilities, CDN
(Content Delivery Networks) footprint, etc.
The generic Connectivity Provisioning Profile (CPP) template
allows for:
o Automating the process of service negotiation and activation,
thus accelerating service provisioning;
o Setting the (traffic) objectives of Traffic Engineering
functions and service management functions.
o Enriching service and network management systems with
'decision-making' capabilities based on negotiated/offered
CPPs.
6. References
6.1. Informative References
[RFC4208] Swallow, G., Drake, J., Ishimatsu, H., and Y. Rekhter,
"Generalized Multiprotocol Label Switching (GMPLS)
User-Network Interface (UNI): Resource ReserVation
Protocol-Traffic Engineering (RSVP-TE) Support for the
Overlay Model", RFC 4208, October 2005.
[RFC4110] R. Callon and M. Suzuki, "A Framework for Layer 3
Provider-Provisioned Virtual Private Networks
(PPVPNs)", RFC 4110, July 2005.
[RFC4847] T. Takeda, Ed., "Framework and Requirements for Layer 1
Virtual Private Networks", RFC 4847, April 2007.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC
4655, August 2006.
[RFC4664] L. Andersson, and E. Rosen, Eds., "Framework for Layer
2 Virtual Private Networks (L2VPNs)", RFC 4664, Sep
2006.
[RFC5440] JP. Vasseur, Ed. And JL. Le Roux, Ed. "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
March 2009.
[I-D.boucadair-connectivity-provisioning-protocol]
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Boucadair, M. and C. Jacquenet, "Connectivity
Provisioning Negotiation Protocol (CPNP)", draft-
boucadair-connectivity-provisioning-protocol-09 (work
in progress), March 2015.
[I-D.boucadair-network-automation-requirements]
Boucadair, M. and C. Jacquenet, "Requirements for
Automated (Configuration) Management", draft-
boucadair-network-automation-requirements-05 (work in
progress), February 2015.
[CHENG] W. Cheng, et. al., "ACTN Use-cases for Packet Transport
Networks in Mobile Backhaul Networks", draft-cheng-actn-
ptn-requirements, work in progress.
[DHODY] D. Dhody, et. al., "Packet Optical Integration (POI) Use
Cases for Abstraction and Control of Transport Networks
(ACTN)", draft-dhody-actn-poi-use-case, work in progress.
[FANG] L. Fang, "ACTN Use Case for Multi-domain Data Center
Interconnect", draft-fang-actn-multidomain-dci, work in
progress.
[KLEE] K. Lee, H. Lee, R. Vilata, V. Lopez, "ACTN Use-case for
On-demand E2E Connectivity Services in Multiple Vendor
Domain Transport Networks", draft-klee-actn-connectivity-
multi-vendor-domains, work in progress.
[KUMAKI] K. Kumaki, T. Miyasaka, "ACTN : Use case for Multi
Tenant VNO ", draft-kumaki-actn-multitenant-vno, work in
progress.
[LOPEZ] D. Lopez (Ed), "ACTN Use-case for Virtual Network
Operation for Multiple Domains in a Single Operator
Network", draft-lopez-actn-vno-multidomains, work in
progress.
[SHIN] J. Shin, R. Hwang, J. Lee, "ACTN Use-case for Mobile
Virtual Network Operation for Multiple Domains in a Single
Operator Network", draft-shin-actn-mvno-multi-domain, work
in progress.
[XU] Y. Xu, et. al., "Use Cases and Requirements of Dynamic
Service Control based on Performance Monitoring in ACTN
Architecture", draft-xu-actn-perf-dynamic-service-control,
work in progress.
[Y.1312] Y.1312 - Layer 1 Virtual Private Network Generic
requirements and architecture elements, ITU-T
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Recommendation, September 2003, available from
<http://www.itu.int>.
[Y.1313] Y.1313 - Layer 1 Virtual Private Network service and
network architectures, ITU-T Recommendation, July 2004,
available from <http://www.itu.int>.
[TR215] TM Forum TR251, Logical Resource Network Model
Advancements and Insights, August 2014,
<https://www.tmforum.org>.
[TR225] TM Forum TR225, Logical Resource: Network Function
Model, June 2015, <https://www.tmforum.org>.
[ONF-SDN-ARCH] Software Defined Network Architcture, ONF TR-502,
June 2014, <https://www.opennetworking.org/>.
7. Acknowledgements
The authors wish to thank the contributions on the IETF ACTN
mailing list.
8. IANA Considerations
This problem statement document makes no requests for IANA action.
9. Authors' Addresses
Young Lee
Huawei Technologies
5340 Legacy Drive
Plano, TX 75023, USA
Phone: (469)277-5838
Email: leeyoung@huawei.com
Daniel King
Lancaster University
Email: d.king@lancaster.ac.uk
Mohamed Boucadair
France Telecom
Rennes 35000
France
Email: mohamed.boucadair@orange.com
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Ruiquan Jing,
China Telecom Corporation Limited,
No. 118, Xizhimenneidajie, Xicheng District, Beijing, China
Email: jingrq@ctbri.com.cn
Luis Miguel Contreras Murillo
Telefonica I+D
Email: lmcm@tid.es
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