TEAS Working Group D. King (Ed.)
Internet-Draft Old Dog Consulting
Intended status: Informational Y. Lee (Ed.)
Expires: December 26, 2018 Huawei
June 26, 2018
Applicability of Abstraction and Control
of Traffic Engineered Networks (ACTN) to Network Slicing
draft-king-teas-applicability-actn-slicing-03
Abstract
Network abstraction is a technique that can be applied to a network
domain to select network resources by policy to obtain a view of
potential connectivity
Network slicing is an approach to network operations that builds on
the concept of network abstraction to provide programmability,
flexibility, and modularity. It may use techniques such as Software
Defined Networking (SDN) and Network Function Virtualization (NFV)
to create multiple logical (virtual) networks, each tailored for a
set of services that are sharing the same set of requirements, on
top of a common network.
These logical networks are referred to as transport network slices.
A transport network slice does not necessarily represent dedicated
resources in the network, but does constitute a commitment by the
network provider to provide a specific level of service.
The Abstraction and Control of Traffic Engineered Networks (ACTN)
defines an SDN-based architecture that relies on the concepts of
network and service abstraction to detach network and service
control from the underlying data plane.
This document outlines the applicability of ACTN to transport
network slicing in an IETF technology network. It also identifies
the features of network slicing not currently within the scope of
ACTN, and indicates where ACTN might be extended.
Status of This Memo
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This Internet-Draft will expire on December 26 2018.
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Table of Contents
1. Introduction....................................................3
1.1. Terminology................................................4
2. Requirements for Network Slicing................................4
2.1. Resource Slicing...........................................4
2.2. Network and Function Virtualization........................5
2.3. Resource Isolation.........................................5
2.4. Control and Orchestration..................................6
3. Abstraction and Control of Traffic Engineered (TE)
Networks (ACTN).................................................6
3.1. ACTN Virtual Network as a "Network Slice"..................8
3.2. Examples of ACTN Delivering Types of Network Slices........8
3.2.1. ACTN Used for Virtual Private Line Model...............9
3.2.2. ACTN Used for VPN Delivery Model.......................10
3.2.3. ACTN Used to Deliver a Virtual Customer Network........10
3.3. Network Slice Service Mapping from TE to ACTN VN Models....11
3.4. ACTN VN KPI Telemetry Models...............................12
4. IANA Considerations.............................................12
5. Security Considerations.........................................12
6. Acknowledgements................................................12
7. References......................................................13
8. Contributors....................................................15
Authors' Addresses.................................................15
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1. Introduction
The principles of network resource separation are not new. For
years, separated overlay and logical (virtual) networking have
existed, allowing multiple connectivity services to be deployed over
a single physical network comprised of single or multiple layers.
However, several key differences exist that differentiate overlay and
virtual networking from network slicing.
A transport network slice construct provides an end-to-end logical
network, often with compute functions and utilising shared underlying
(physical or virtual) network resources. This logical network is
separated from other, often concurrent, logical networks each with
independent control and management, and each of which can be created
or modified on demand.
At one end of the spectrum, a virtual private wire or a virtual
private network (VPN) may be used to build a network slice. In these
cases, the network slices do not require the service provider to
isolate network resources for the provision of the service - the
service is "virtual".
At the other end of the spectrum there may be a detailed description
of a complex service that will meet the needs of a set of
applications with connectivity and service function requirements that
may include compute resource, storage capability, and access to
content. Such a service may be requested dynamically (that is,
instantiated when an application needs it, and released when the
application no longer needs it), and modified as the needs of the
application change.
Each example represents a self-contained network that must be
flexible enough to simultaneously accommodate diverse business-driven
use cases from multiple players on a common network infrastructure.
This document outlines the application of the ACTN architecture
[actn-framework] and enabling technologies to provide transport
network slicing in an IETF technology network. It describes how the
ACTN functional components can be used to support model-driven
partitioning of variable-sized bandwidth to facilitate network
sharing and virtualization. Furthermore, the use of model-based
interfaces to dynamically request the instantiation of virtual
networks could be extended to encompass requesting and instantiation
of specific service functions (which may be both physical and/or
virtual), and to partition network resources such as compute
resource, storage capability, and access to content.
In an IETF context, there are works in progress that have some
bearing with network slicing such as Enhanced VPN (VPN+) and DetNet.
Both works are an independent work in their own scope while
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This document highlights how the ACTN approach might be extended to
address these other requirements of network slicing where TE is
required.
1.1. Terminology
Resource: Any features that can be delivered, including connectivity,
compute, storage, and content delivery.
Service Functions (SFs): Components that provide specific function
within a network. SFs are often combined in a specific sequence,
service function chain, to deliver services.
Infrastructure Resources: The hardware and necessary software for
hosting and connecting SFs. These resources may include computing
hardware, storage capacity, network resources (e.g. links and
switching/routing devices enabling network connectivity), and
physical assets for radio access.
Service Provider: A server network or collection of server
networks.
Consumer: Any application, client network, or customer of a network
provider.
Service Level Agreement (SLA): An agreement between a consumer and
network provider that describes the quality with which features
and functions are to be delivered. It may include measures of
bandwidth, latency, and jitter; the types of service (such as the
network service functions or billing) to be executed; the location,
nature, and quantities of services (such as the amount and location
of compute resources and the accelerators require).
Network Slice: An agreement between a consumer and a service
provider to deliver network resources according to a specific service
level agreement. A slice could span multiple technology (e.g., radio,
transport and cloud) and administrative domains.
IETF Technology: A TE network slice or transport network slice.
2. Requirements for Network Slicing
The concept of network slicing is considered a key capability for
future networks and, to serve customers with a wide variety of
different service needs, in term of latency, reliability, capacity,
and service function specific capabilities.
This section outlines the key capabilities required, and further
discussed in [ngmn-network-slicing], [network-slice-5g],
[3gpp.28.801] and [onf-tr526], to realise network slicing in an IETF
technology network.
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2.1. Resource Slicing
For network slicing, it is important to consider both infrastructure
resources and servic functions. This allows a flexible approach to
deliver a range of services both by partitioning (slicing) the
available network resources to present them for use by a consumer,
but also by providing instances of SFs at the right locations and in
the correct chaining logic, with access to the necessary hardware,
including specific compute and storage resources.
Mapping of resources to slices may 1-to-1, or resources may be shared
among multiple slices.
2.2. Network and Function Virtualization
Virtualization is the abstraction of resources where the abstraction
is made available for use by an operations entity, for example, by
the Network Management Station (NMS) of a consumer network. The
resources to be virtualized can be physical or already virtualized,
supporting a recursive pattern with different abstraction layers.
Therefore, Virtualization is critical for network slicing as it
enables effective resource sharing between network slices.
Just as server virtualization makes virtual machines (VMs)
independent of the underlying physical hardware, network
Virtualization enables the creation of multiple isolated virtual
networks that are completely decoupled from the underlying physical
network, and can safely run on top of it.
2.3. Resource Isolation
Isolation of data and traffic is a major requirement that must be
satisfied for certain applications to operate in concurrent network
slices on a common shared underlying infrastructure. Therefore,
isolation must be understood in terms of:
o Performance: Each slice is defined to meet specific service
requirements, usually expressed in the form of Key Performance
Indicators (KPIs). Performance isolation requires that service
delivery on one network slice is not adversely impacted by
congestion and performance levels of other slices;
o Security: Attacks or faults occurring in one slice must not have an
impact on other slices, or customer flows are not only isolated on
network edge, but multiple customer traffic is not mixed across the
core of the network. Moreover, each slice must have independent
security functions that prevent unauthorised entities to have read
or write access to slice-specific configuration, management,
accounting information, and able to record any of these attempts,
whether authorised or not;
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o Management: Each slice must be independently viewed, utilised and
managed as a separate network.
2.4. Control and Orchestration
Orchestration is the overriding control method for network slicing.
We may define orchestration as combining and coordinating multiple
control methods to provide an operational mechanism that can deliver
services and control underlying resources. In a network slicing
environment, an orchestrator is needed to coordinate disparate
processes and resources for creating, managing, and deploying the
end-to-end service. Two scenarios are outlined below where
orchestration would be required:
1. Multi-domain Orchestration: Managing connectivity setup of the
transport service, across multiple administrative domains;
2. End-to-end Orchestration: Combining resources for an "end-to-end
service (e.g., transport connectivity with firewalling and
guaranteed bandwidth and minimum delay for premium radio users
(spanning multiple domains).
In addition, 3GPP has also developed Release 14 "Study on
management and orchestration of network slicing for next generation
network" [3gpp.28.801], which defines an information model where the
network slice as well as physical and virtualized network functions
belong to the network operator domain, while the virtualized
resources belong to another domain operated by a Virtualization
infrastructure service provider.
3. Abstraction and Control of Traffic Engineered (TE) Networks (ACTN)
The framework for ACTN [actn-framework] includes a reference
architecture that has been adapted for Figure 1 in this document, it
describes the functional entities and methods for the coordination of
resources across multiple domains, to provide end-to-end services,
components include:
o Customer Network Controller (CNC);
o Multi-domain Service Coordinator (MDSC);
o Provisioning Network Controller (PNC).
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--------- --------- ---------
| CNC-A | | CNC-B | | CNC-C |
--------- --------- ---------
\ | /
\__________ |-CMI I/F __________/
\ | /
-------------------------
| MDSC |
-------------------------
/ / | \
/ / |-MPI I/F \
/ / | \
------- ------- ------- -------
| PNC | | PNC | | PNC | | PNC |
------- ------- ------- -------
CMI - (CNC-MDSC Interface )
MPI - (MDSC-PNC Interface)
Figure 1: ACTN Hierarchy
ACTN facilitates end-to-end connections and provides them to the
user. The ACTN framework highlights how:
o Abstraction of the underlying network resources are provided to
higher-layer applications and customers;
o Virtualization of underlying resources, whose selection criterion
is the allocation of those resources for the customer, application,
or service;
o Creation of a virtualized environment allowing operators to view
and control multi-domain networks as a single virtualized network;
o The presentation to customers of networks as a virtual network via
open and programmable interfaces.
The ACTN managed infrastructure are traffic engineered network
resources, which may include:
o Statistical packet bandwidth;
o Physical forwarding plane sources, such as: wavelengths and
time slots;
o Forwarding and cross connect capabilities.
The ACTN type of network virtualization provides customers and
applications (tenants) to utilise and independently control
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allocated virtual network resources as if resources as if they
were physically their own resource. The ACTN network is "sliced",
with tenants being given a different partial and abstracted
topology view of the physical underlying network. The capabilities
that ACTN provides to enable slicing are outlined in Section 2
(Requirements for Network Slicing).
3.1. ACTN Virtual Network as a "Network Slice"
To support multiple clients each with its own view of and control
of the server network, a network operator needs to partition (or
"slice") the network resources. The resulting slices can be
assigned to each client for guaranteed usage which is a step
further than shared use of common network resources. See
[actn-vn] for detailed ACTN VN and VNS.
An ACTN Virtual Network (VN) is a client view that may be considered
a "network slice" of the ACTN managed infrastructure, and is
presented by the ACTN provider as a set of abstracted resources.
Depending on the agreement between client and provider various VN
operations and VN views are possible.
o Network Slice Creation: A VN could be pre-configured and created
via static or dynamic request and negotiation between customer and
provider. It must meet the specified SLA attributes which satisfy
the customer's objectives.
o Network Slice Operations: The network slice may be further modified
and deleted based on customer request to request changes in the
network resources reserved for the customer, and used to construct
the network slice. The customer can further act upon the network
slice to manage traffic flow across the network slice.
o Network Slice View: The VN topology from a customer point of view.
These may be a variety of tunnels, or an entire VN topology. Such
connections may comprise of customer end points, access links,
intra domain paths and inter-domain links.
Primitives (capabilities and messages) have been provided to support
the different ACTN network control functions that will enable network
slicing. These include: topology request/query, VN service request,
path computation and connection control, VN service policy
negotiation, enforcement, routing options. [actn-info]
3.2. Examples of ACTN Delivering Types of Network Slices
In examples below the ACTN framework is used to provide
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control, management and orchestration for the network slice
life-cycle, the connectivity . These dynamic and highly flexible,
end-to-end and dedicated network slices utilising common physical
infrastructure, and according to vertical-specific requirements.
The rest of this section provides three examples of using ACTN to
achieve different scenarios of ACTN for network slicing. All three
scenarios can be scaled up in capacity or be subject to topology
changes as well as changes from customer requirements perspective.
3.2.1. ACTN Used for Virtual Private Line Model
ACTN Provides virtual connections between multiple customer
locations, requested via Virtual Private Line (VPL) requester
(CNC-A). Benefits of this model include:
o Automated: the service set-up and operation is network provider
managed;
o Virtual: the private line is seamlessly extended from customers
Site A (vCE1 to vCE2) and Site B (vCE2 to vCE3) across the
ACTN-managed WAN to Site C;
o Agile: on-demand where the customer needs connectivity and
fully adjustable bandwidth.
(Customer VPL Request)
|
---------
| CNC-A |
Boundary ---------
Between ====================|====================
Customer & |
Network Provider --------
| MDSC |
--------
__|__
Site A ( PNC ) Site B
------ ( ) ------
|vCE1|=============( Phys. )=============|vCE2|
------ ( Net ) ------
\ ----- /
\ || /
\ || /
VPL 1 \__ || __/ VPL 2
\ || /
\ || /
\ ------ /
------|vCE3|-----
------
Site C
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Figure 2: Virtual Private Line Model
3.2.2. ACTN Used for VPN Delivery Model
ACTN Provides VPN connections between multiple sites, requested via
a VPN requestor (CNC-A), which is managed by the customer
themselves. The CNC will then interact with the network providers
MDSC. Benefits of this model include:
o Provides edge-to-edge VPN multi-access connection;
o Mostly network provider managed, with some flexibility delegated to
the customer managed CNC.
---------------- ----------------
| Site-A Users |___________ ____________| Site-B Users |
---------------- | | ----------------
-------
|CNC-A|
Boundary -------
Between ==========================|==========================
Customer & |
Network Provider |
|
---------------
| MDSC |
---------------
_________/ | \__________
/ | \
/ | \
--------- --------- ---------
| PNC | | PNC | | PNC |
--------- --------- ---------
| | /
| | /
----- ----- -----
( ) ( ) ( )
<Site A>----( Phys. )------------( Phys. )-------( Phys. )----<Site B>
( Net ) ( Net ) ( Net )
----- ----- -----
Figure 3: VPN Model
3.2.3. ACTN Used to Deliver a Virtual Customer Network
In this example ACTN provides a virtual network resource to the
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customer. This resource is customer managed. Empowering the tenant
to control allocated slice (recursively). Benefits of this model
include:
o The MDSC provides the topology as part of the customer view so
that the customer can control their network slice to fit their
needs;
o Resource isolation, each customer network slice is fixed and will
not be affected by changes to other customer network slices;
o Applications can interact with their assigned network slice
directly, the customer may implement their own network control
method and traffic prioritization, manage their own addressing
scheme, and further slice their assigned network resource;
o The network slice may also include specific capability nodes,
delivered as Physical Network Functions (PNFs) or Virtual Network
Functions (VNFs).
___________
--------------- ( Network )
| CNC |---------->( Slice 2 )
--------------- _(_________ )
--------------- ( Network )_)
| CNC |----------->( Slice 1 ) ^
--------------- ( ) :
^ (___________) :
| ^ ^ :
Boundary | : : :
Between ==========|========================:====:====:========
Customer & | : : :
Network Provider | : : :
v : : :
--------------- : :....:
| MDSC | : :
--------------- : :
^ ---^------ ...
| ( ) .
v ( Physical ) .
---------------- ( Network ) .
| PNC |<------> ( ) ---^------
---------------- | -------- ( )
| |-- ( Physical )
| PNC |<------------------------->( Network )
--------------- ( )
--------
Figure 4: Network Slicing
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3.3. Network Slice Service Mapping from TE to ACTN VN Models
The role of TE-service mapping model [te-service-mapping] is to
create a binding relationship across a Layer-3 Service Model [l3sm],
Layer-2 Service Model and TE Tunnel model, via a generic ACTN Virtual
Network (VN) model [actn-vn].
The ACTN VN YANG model is a generic virtual network service
model that allows customers (internal or external) to create a VN
that meets the customer's service objective with various
constraints.
The TE-service mapping model is needed to bind L3VPN specific
service model with TE-specific parameters. This binding
will facilitate a seamless service operation with underlay-TE
network visibility. The TE-service model developed in this document
can also be extended to support other services including L2SM, and
L1CSM network service models.
----------- --------------- ------------
| L3SM | <------> | | <-----> | ACTN VN |
----------- | | ------^-----
----------- | TE-Service | |
| L2SM | <------> |Mapping Model| <-----> ------v-----
----------- | | | TE-topo |
----------- | | ------------
| L2CSM | <------> | | <-----> ------------
----------- --------------- | TE-tunnel|
------------
Figure 5: TE-Service Mapping ([te-service-mapping])
Editors note - We plan to provide a list of models available and
their relationships/dependencies. We will also provide a vertical
hierarchy of how these models may be used between functional
components in ACTN.
3.4. ACTN VN KPI telemetry Models
The role of ACTN VN KPI telemetry model [actn-pm-telemetry] is
to provide YANG models so that customer can define key
performance monitoring data relevant for its VN/network slicing
via the YANG subscription model.
Key characteristics of [actn-pm-telemetry] include:
o an ability to provide scalable VN-level telemetry aggregation
based on customer-subscription model for key performance
parameters defined by the customer;
o an ability to facilitate proactive re-optimization and
reconfiguration of VNs/Netork Slices based on network
autonomic traffic engineering scaling configuration
mechanism.
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5. IANA Considerations
This document makes no requests for action by IANA.
6. Security Considerations
Network slicing involves the control of network resources in order
to meet the service requirements of consumers. In some deployment
models, the consumer is able to directly request modification in
the behaviour of resources owned and operated by a service provider.
Such changes could significantly affect the service provider's
ability to provide services to other consumers. Furthermore, the
resources allocated for or consumed by a consumer will normally be
billable by the service provider.
Therefore, it is crucial that the mechanisms used in any network
slicing system allow for authentication of requests, security of
those requests, and tracking of resource allocations.
It should also be noted that while the partitioning or slicing of
resources is virtual, the consumers expect and require that there
is no risk of leakage of data from one slice to another, no
transfer of knowledge of the structure or even existence of other
slices, and that changes to one slice (under the control of one
consumer) should not have detrimental effects on the operation of
other slices (whether under control of different or the same
consumers) beyond the limits allowed within the SLA. Thus, slices
are assumed to be private and to provide the appearance of genuine
physical connectivity.
ACTN operates using the [netconf] or [restconf] protocols and
assumes the security characteristics of those protocols.
Deployment models for ACTN should fully explore the authentication
and other security aspects before networks start to carry live
traffic.
7. Acknowledgements
Thanks to Qin Wu, Andy Jones, Ramon Casellas, and Gert Grammel for
their insight and useful discussions about network slicing.
8. References
8.1. Normative References
8.2. Informative References
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[ngmn-network-slicing]
NGMN, "Description of Network Slicing Concept", 1 2016,
<https://www.ngmn.org/uploads/
media/160113_Network_Slicing_v1_0.pdf>.
[3gpp.28.801]
3GPP, "Study on management and orchestration of network
slicing for next generation network", 3GPP TR 28.801
0.4.0, 1 2017,
<http://www.3gpp.org/ftp/Specs/html-info/28801.htm>.
[network-slice-5g]
"Network Slicing for 5G with SDN/NFV: Concepts,
Architectures and Challenges", Jose Ordonez-Lucena,
Pablo Ameigeiras, Diego Lopez, Juan J. Ramos-Munoz,
Javier Lorca, Jesus Folgueira, IEEE Communications
Magazine 55, March 2017
[onf-tr526]
ONF TR-526, "Applying SDN Architecture to 5G Slicing",
April 2016.
[actn-framework]
Ceccarelli, D. and Y. Lee, "Framework for Abstraction and
Control of Traffic Engineered Networks", draft-ietf-teas-
actn-framework, work in progress, February 2017.
[te-service-mapping]
Y. Lee, D. Dhody, and D. Ceccarelli, "Traffic Engineering
and Service Mapping Yang Model",
draft-lee-teas-te-service-mapping-yang, work in progress.
[actn-vn] Y. Lee (Editor), "A Yang Data Model for ACTN VN
Operation", draft-lee-teas-actn-vn-yang, work in progress.
[actn-info] Y. Lee, S. Belotti (Editors), "Information Model for
Abstraction and Control of TE Networks (ACTN)", draft-ietf-
teas-actn-info-model, work in progress.
[actn-pm-elemetry] Y. Lee, et al, "YANG models for ACTN TE
Performance Monitoring Telemetry and Network Autonomics",
draft-lee- teas-actn-pm-telemetry-autonomics, work in
progress.
[l3sm] Litkowski, S., Tomotaki, L., and K. Ogaki, "YANG Data
Model for L3VPN Service Delivery", RFC 8049, February 2017
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[netconf] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241.
[restconf] A. Bierman, M. Bjorklund, and K. Watsen, "RESTCONF
Protocol", draft-ietf-netconf-restconf, work in progress.
[sf-topology] I. Bryskin, et al, "Use Cases for SF Aware Topology
Models", draft-ietf-teas-use-cases-sf-aware-topo-model, work
in progress.
[vpn+] S. Bryant and J. Dong, "Enhanced Virtual Private Networks
(VPN+)", draft-bryant-rtgwg-enhanced-vpn, work in progress.
9. Contributors
The following people contributed text to this document.
Adrian Farrel
Email: afarrel@juniper.net
Mohamed Boucadair
Email: mohamed.boucadair@orange.com
Sergio Belotti
Email: sergio.belotti@nokia.com
Daniele Ceccarelli
Email: daniele.ceccarelli@ericsson.com
Haomian Zheng
Email: zhenghaomian@huawei.com
Authors' Addresses
Daniel King
Email: daniel@olddog.co.uk
Young Lee
Email: leeyoung@huawei.com
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