A Framework for Enhanced Virtual Private Network (VPN+)
draft-ietf-teas-enhanced-vpn-15
| Document | Type | Active Internet-Draft (teas WG) | |
|---|---|---|---|
| Authors | Jie Dong , Stewart Bryant , Zhenqiang Li , Takuya Miyasaka , Young Lee | ||
| Last updated | 2023-10-23 | ||
| Replaces | draft-dong-teas-enhanced-vpn | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Informational | ||
| Formats | |||
| Reviews |
RTGDIR Early review
by Ketan Talaulikar
Has issues
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||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | Waiting for WG Chair Go-Ahead | |
| Document shepherd | Lou Berger | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | lberger@labn.net |
draft-ietf-teas-enhanced-vpn-15
TEAS Working Group J. Dong
Internet-Draft Huawei
Intended status: Informational S. Bryant
Expires: 25 April 2024 University of Surrey
Z. Li
China Mobile
T. Miyasaka
KDDI Corporation
Y. Lee
Samsung
23 October 2023
A Framework for Enhanced Virtual Private Network (VPN+)
draft-ietf-teas-enhanced-vpn-15
Abstract
This document describes the framework for Enhanced Virtual Private
Network (VPN+) to support the needs of applications with specific
traffic performance requirements (e.g., low latency, bounded jitter).
VPN+ leverages the VPN and Traffic Engineering (TE) technologies and
adds characteristics that specific services require beyond those
provided by conventional VPNs. Typically, VPN+ will be used to
underpin network slicing, but could also be of use in its own right
providing enhanced connectivity services between customer sites.
This document also provides an overview of relevant technologies in
different network layers, and identifies some areas for potential new
work.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 25 April 2024.
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Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Overview of the Requirements . . . . . . . . . . . . . . . . 7
3.1. Performance Guarantees . . . . . . . . . . . . . . . . . 7
3.2. Interaction between VPN+ Services . . . . . . . . . . . . 9
3.2.1. Requirements on Traffic Isolation . . . . . . . . . . 9
3.2.2. Limited Interaction with Other Services . . . . . . . 10
3.2.3. Realization of Limited Interaction Between VPN+
Services . . . . . . . . . . . . . . . . . . . . . . 11
3.3. Integration with Network Resources and Service
Functions . . . . . . . . . . . . . . . . . . . . . . . . 12
3.3.1. Abstraction . . . . . . . . . . . . . . . . . . . . . 12
3.4. Dynamic Changes . . . . . . . . . . . . . . . . . . . . . 12
3.5. Customized Control . . . . . . . . . . . . . . . . . . . 13
3.6. Applicability to Overlay Technologies . . . . . . . . . . 13
3.7. Inter-Domain and Inter-Layer Network . . . . . . . . . . 14
4. The Architecture of VPN+ . . . . . . . . . . . . . . . . . . 14
4.1. Layered Architecture . . . . . . . . . . . . . . . . . . 16
4.2. Connectivity Types . . . . . . . . . . . . . . . . . . . 19
4.3. Application-Specific Data Types . . . . . . . . . . . . . 19
4.4. Scalable Service Mapping . . . . . . . . . . . . . . . . 19
5. Candidate Technologies . . . . . . . . . . . . . . . . . . . 20
5.1. Forwarding Resource Partitioning . . . . . . . . . . . . 21
5.1.1. Flexible Ethernet . . . . . . . . . . . . . . . . . . 21
5.1.2. Dedicated Queues . . . . . . . . . . . . . . . . . . 21
5.1.3. Time Sensitive Networking . . . . . . . . . . . . . . 22
5.2. Data Plane Encapsulation and Forwarding . . . . . . . . . 22
5.2.1. Deterministic Networking . . . . . . . . . . . . . . 22
5.2.2. MPLS Traffic Engineering (MPLS-TE) . . . . . . . . . 23
5.2.3. Segment Routing . . . . . . . . . . . . . . . . . . . 23
5.2.4. New Encapsulation Extensions . . . . . . . . . . . . 24
5.3. Non-Packet Data Plane . . . . . . . . . . . . . . . . . . 24
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5.4. Control Plane . . . . . . . . . . . . . . . . . . . . . . 24
5.5. Management Plane . . . . . . . . . . . . . . . . . . . . 26
5.6. Applicability of Service Data Models to VPN+ . . . . . . 27
6. Applicability in Network Slice Realization . . . . . . . . . 27
6.1. NRP Planning . . . . . . . . . . . . . . . . . . . . . . 28
6.2. NRP Creation . . . . . . . . . . . . . . . . . . . . . . 28
6.3. Network Slice Service Provisioning . . . . . . . . . . . 29
6.4. Network Slice Traffic Steering and Forwarding . . . . . . 29
7. Scalability Considerations . . . . . . . . . . . . . . . . . 29
7.1. Maximum Stack Depth of SR . . . . . . . . . . . . . . . . 30
7.2. RSVP-TE Scalability . . . . . . . . . . . . . . . . . . . 30
7.3. SDN Scaling . . . . . . . . . . . . . . . . . . . . . . . 31
8. Manageability Considerations . . . . . . . . . . . . . . . . 31
8.1. OAM Considerations . . . . . . . . . . . . . . . . . . . 31
8.2. Telemetry Considerations . . . . . . . . . . . . . . . . 32
9. Enhanced Resiliency . . . . . . . . . . . . . . . . . . . . . 32
10. Operational Considerations . . . . . . . . . . . . . . . . . 33
11. Security Considerations . . . . . . . . . . . . . . . . . . . 33
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34
13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 34
14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 35
15. Informative References . . . . . . . . . . . . . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 43
1. Introduction
RFC Editor Note: Please replace "RFC XXXX" in this document with the
RFC number assigned to [I-D.ietf-teas-ietf-network-slices], and
remove this note.
Virtual Private Networks (VPNs) have served the industry well as a
means of providing different groups of users with logically isolated
connectivity over a common network. The common (base) network that
is used to provide the VPNs is often referred to as the underlay, and
the VPN is often called an overlay.
Customers of a network operator may request connectivity services
with advanced characteristics, such as low latency guarantees,
bounded jitter, or isolation from other services or customers so that
changes in some other services (e.g., changes in network load, or
events such as congestion or outages) have no or only acceptable
effect on the observed throughput or latency of the services
delivered to the customer. These services are referred to as
"enhanced VPNs" (known as VPN+), as they are similar to VPN services
providing the customer with the required connectivity, but in
addition they also provide enhanced characteristics.
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This document describes a framework for delivering VPN services with
enhanced characteristics, such as guaranteed resources, latency,
jitter, etc. This is not a closed list. It is expected that other
enhanced features may be added to VPN over time, and it is expected
this framework will support these additions with necessary changes or
enhancements in some network layers and network planes.
The requirements of VPN+ services cannot simply be met by overlay
networks, as VPN+ services require tighter coordination and
integration between the overlay and the underlay networks.
In the overlay network, VPN has been defined as the network construct
to provide the required connectivity for different services or
customers. Multiple VPN flavors can be considered to create that
construct [RFC4026]. In the underlay network, this document
introduces the concept Virtual Transport Network (VTN). A VTN is a
virtual underlay network that is associated with a network topology,
and is allocated with a set of dedicated or shared resources from the
underlay physical network.
A VPN+ service is realized by integrating a VPN in the overlay and a
VTN in the underlay. In doing so, a VPN+ service can provide
enhanced properties, such as guaranteed resources and assured or
predictable performance. A VPN+ service may also involve a set of
service functions (Section 1.4 of [RFC7665]). VPN+ techniques can be
used to instantiate a network slice service, and they can also be of
use in general cases to provide enhanced connectivity services
between customer sites or service endpoints.
The concept of network slicing has gained traction driven largely by
needs surfacing from 5G [NGMN-NS-Concept] [TS23501] [TS28530].
According to [TS28530], a 5G end-to-end network slice consists of
three major types of network segments: Radio Access Network (RAN),
Transport Network (TN), and Mobile Core Network (CN). The transport
network provides the connectivity between different entities in RAN
and CN segments of a 5G end-to-end network slice, with specific
performance commitments.
[I-D.ietf-teas-ietf-network-slices] defines the terminologies and the
characteristics of Network Slices. It also discusses the general
framework, the components and interfaces for requesting and operating
Network Slices. An RFC XXXX Network Slice Service enables
connectivity between a set of Service Demarcation Points (SDPs) with
specific Service Level Objectives (SLOs) and Service Level
Expectations (SLEs) over a common underlay network. An RFC XXXX
Network Slice can be realized as a logical network connecting a
number of endpoints and is associated with a set of shared or
dedicated network resources that are used to satisfy the Service
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Level Objectives (SLOs) and Service Level Expectations (SLEs)
requirements. In this document (which is solely about IETF
technologies) we refer to an "RFC XXXX Network Slice" simply as a
"network slice": a network slice is considered as one target use case
of VPN+.
[I-D.ietf-teas-ietf-network-slices] also introduces the concept of
Network Resource Partition (NRP), which is a subset of the
buffer/queuing/scheduling resources and associated policies on each
of a connected set of links in the underlay network. An NRP can be
associated with a dedicated or shared network topology to select or
specify the set of links and nodes involved. NRP can be seen as an
instantiation of VTN in the context of network slicing.
This document describes a framework for using existing, modified, and
potential new technologies as components to provide VPN+ services.
Specifically, this document provides:
* The functional requirements and service characteristics of a VPN+
service.
* The design of the data plane for VPN+.
* The necessary control and management protocols in both the
underlay and the overlay of VPN+.
* The mechanisms to achieve integration between the overlay network
and the underlay network.
* The necessary Operation, Administration, and Management (OAM)
methods to instrument a VPN+ to make sure that the required SLA
between the customer and the network operator is met, and to take
any corrective action (such as switching traffic to an alternate
path) to avoid SLA violation.
The required layered network structure to achieve these objectives is
shown in Section 4.1.
It is not envisaged that VPN+ services will replace conventional VPN
services. VPN services will continue to be delivered using existing
mechanisms and can co-exist with VPN+ services. Whether enriched
VPN+ features are added to an active VPN service is deployment
specific.
2. Terminology
In this document, the relationship of the four terms "VPN", "VPN+",
"VTN", and "Network Slice" are as follows:
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* A Virtual Private Network (VPN) refers to the overlay network
service that provides connectivity between different customer
sites, and that maintains traffic separation between different
customers. Examples of technologies to provide VPN services are:
IPVPN [RFC2764], L2VPN [RFC4664], L3VPN [RFC4364], and EVPN
[RFC7432].
* An enhanced VPN (VPN+) service is an evolution of the VPN service
that makes additional service-specific commitments. An enhanced
VPN is made by integrating a VPN with a set of network resources
allocated in the underlay network.
* A Virtual Transport Network (VTN) is a virtual underlay network
which is associated with a logical network topology, and is
allocated with a set of dedicated or shared network resources from
the underlay physical network. A VTN is designed to meet the
network resources and performance characteristics required by the
VPN+ services.
* A network slice service could be delivered by provisioning one or
more VPN+ services in the network. Other mechanisms for realizing
network slices may exist but are not in scope for this document.
The term "tenant" is used in this document to refer to the customers
of the VPN+ services.
The following terms are also used in this document. Some of them are
newly defined, some others reference existing definitions.
SLA: Service Level Agreement. See
[I-D.ietf-teas-ietf-network-slices].
SLO: Service Level Objective. See
[I-D.ietf-teas-ietf-network-slices].
SLE: Service Level Expectation. See
[I-D.ietf-teas-ietf-network-slices].
ACTN: Abstraction and Control of Traffic Engineered Networks
[RFC8453].
DetNet: Deterministic Networking. See [RFC8655].
FlexE: Flexible Ethernet [FLEXE].
TSN: Time Sensitive Networking [TSN].
VN: Virtual Network. See [RFC8453].
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VTP: Virtual Transport Path. A VTP is a path through the VTN which
provides the required connectivity and performance between two or
more customer sites.
3. Overview of the Requirements
This section provides an overview of the requirements of a VPN+
service.
3.1. Performance Guarantees
Performance guarantees are committed by network operators to their
customers in relation to the services delivered to the customers.
They are usually expressed in SLAs as a set of SLOs.
There are several kinds of performance guarantees, including
guaranteed maximum packet loss, guaranteed maximum delay, and
guaranteed delay variation. Note that these guarantees apply to
conformance traffic; out-of-profile traffic will be handled according
to a separate agreement with the customer (see, for example,
Section 3.6 of [RFC7297]).
Guaranteed maximum packet loss is usually addressed by setting packet
priorities, queues size, and discard policy. However, this becomes
more difficult when the requirement is combined with latency
requirements. The limiting case is zero congestion loss, and that is
the goal of Deterministic Networking (DetNet) [RFC8655] and Time-
Sensitive Networking (TSN) [TSN]. In modern optical networks, loss
due to transmission errors already approaches zero, but there is the
possibility of failure of the interface or the fiber itself. This
type of fault can be addressed by some form of signal duplication and
transmission over diverse paths.
Guaranteed maximum latency is required by a number of applications,
particularly real-time control applications and some types of
augumented reality and virtual reality (AR/VR) applications. DetNet
techniques may be considered [RFC8655], however additional methods of
enhancing the underlay to better support the delay guarantees may be
needed, and these methods will need to be integrated with the overall
service provisioning mechanisms.
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Guaranteed maximum delay variation is a performance guarantee that
may also be needed. [RFC8578] calls up a number of cases that need
this guarantee, for example in electrical utilities. Time transfer
is an example service that needs a performance guarantee, although it
is in the nature of time that the service might be delivered by the
underlay as a shared service and not provided through different
VPN+s. Alternatively, a dedicated VPN+ might be used to provide time
transfer as a shared service.
This suggests that a spectrum of service guarantees need to be
considered when designing and deploying a VPN+. For illustration
purposes and without claiming to be exhaustive, four types of
services are considered:
* Best effort
* Assured bandwidth
* Guaranteed latency
* Enhanced delivery
It is noted that some service may have mixed requirements of the
above, e.g., both assured bandwidth and guaranteed latency can be
required.
The best effort service is the basic connectivity service that can be
provided by current VPNs.
An assured bandwidth service is a connectivity service in which the
bandwidth over some period of time is assured. This could be
achieved either simply based on a best effort service with over-
capacity provisioning, or it can be based on MPLS traffic engineered
label switching paths (TE-LSPs) with bandwidth reservations.
Depending on the technique used, however, the bandwidth is not
necessarily assured at any instant. Providing assured bandwidth to
VPNs, for example by using per-VPN TE-LSPs, is not widely deployed at
least partially due to scalability concerns. The more common
approach of aggregating multiple VPNs onto common TE-LSPs results in
shared bandwidth and so may reduce the assurance of bandwidth to any
one service. VPN+ aims to provide a more scalable approach for such
services.
A guaranteed latency service has an upper bound to edge-to-edge
latency. Assuring the upper bound is sometimes more important than
minimizing latency. There are several new technologies that provide
some assistance with this performance guarantee. Firstly, the IEEE
TSN project [TSN] introduces the concept of scheduling of delay- and
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loss-sensitive packets. FlexE [FLEXE] is also useful to help provide
a guaranteed upper bound to latency. DetNet is also of relevance in
assuring an upper bound of end-to-end packet latency in network
layer. The use of these technologies to deliver VPN+ services needs
to be considered when a guaranteed latency service is required.
An enhanced delivery service is a connectivity service in which the
underlay network (at Layer 3) needs to ensure to eliminate or
minimize packet loss in the event of equipment or media failures.
This may be achieved by delivering a copy of the packet through
multiple paths. Such a mechanism may need to be used for VPN+
services.
3.2. Interaction between VPN+ Services
There is a fine distinction between how a customer requests limits on
interaction between VPN+ services, and how that is delivered by the
service provider. This section examines the requirements and
realization of limited interaction between VPN+ services.
3.2.1. Requirements on Traffic Isolation
Traffic isolation is a generic term that can be used to describe the
requirements on separating the services of different customers or
different service types in the network. In the context of network
slicing, traffic isolation is defined as an SLE of the network slice
service (Section 8.1 of [I-D.ietf-teas-ietf-network-slices]), which
is one element of the SLA. A customer may care about disruption
caused by other services, contamination by other traffic, or delivery
of their traffic to the wrong destinations.
A customer may want to specify (and thus pay for) the traffic
isolation provided by the service provider. Some customers (banking,
for example) may have strict requirements on how their flows are
handled when delivered over a shared network. Some professional
services are used to relying on specific certifications and audits to
ensure the compliancy of a network with traffic isolation
requirements, and specifically to prevent data leaks.
With traffic isolation, a customer expects that the service traffic
cannot be received by other customers in the same network. In
[RFC4176], traffic isolation is mentioned as one of the requirements
of VPN customers. Traffic isolation is also described in Section 3.8
of [RFC7297].
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There can be different expectations on traffic isolation. For
example, a customer may further request the protection of their
traffic by requesting specific encryption schemes at the VPN+ network
access and also when transported between PEs.
A VPN+ service customer may request traffic isolation together with
other operator defined service characteristics. The exact details
about the expected behavior need to be specified in the service
request, so that meaningful service assurance and fulfillment
feedback can be exposed to the customers. It is out of the scope of
this document to elaborate the service modeling considerations.
3.2.2. Limited Interaction with Other Services
[RFC2211] describes the Controlled Load Service. In that document,
the end-to-end behavior provided to an application by a series of
network elements providing controlled-load service is described as
closely approximating to the behavior visible to applications
receiving best-effort service when those network elements are not
carrying substantial traffic from other services.
Thus, a consumer of a Controlled Load Service may assume that:
* A very high percentage of transmitted packets will be successfully
delivered by the network to the receiving end-nodes.
* The transit delay experienced by a very high percentage of the
delivered packets will not greatly exceed the minimum transmit
delay experienced by any successfully delivered packet.
A VPN+ customer may request a Controlled Load Service in one of two
ways:
1. It may configure a set of SLOs (for example, for delay and loss)
such that the delivered enhanced VPN meets the behavioral
objectives of the customer.
2. As described in [RFC2211], a customer may request the Controlled
Load Service without reference to or specification of specific
target values for control parameters such as delay or loss.
Instead, acceptance of a request for Controlled Load Service is
defined to imply a commitment by the network element to provide
the requestor with service closely equivalent to that provided to
uncontrolled (best-effort) traffic under lightly loaded
conditions. This way of requesting the service is an SLE.
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Limited interaction between VPN+ services does not cover service
degradation due to non-interaction-related causes, such as link
errors.
3.2.3. Realization of Limited Interaction Between VPN+ Services
A service provider may translate the requirements related to limited
interaction into distinct engineering rules in its network. Honoring
the service requirement may involve tweaking a set of QoS, TE,
security, and planning tools, while traffic isolation will involve
adequately configuring routing and authorization capabilities.
Concretely, there are many existing techniques which can be used to
provide traffic isolation, such as IP and MPLS VPNs or other multi-
tenant virtual network techniques. Controlled Load Services may be
realized as described in [RFC2211]. Other tools may include various
forms of resource management and reservation techniques, such as
network capacity planning, allocating dedicated network resources,
traffic policing or shaping, prioritizing in using shared network
resources etc., so that a subset of bandwidth, buffers, and queueing
resources can be available in the underlay network to support the
VPN+ services.
To provide the required traffic isolation, or to reduce the
interaction with other VPN+ services, network resources may need to
be reserved in the data plane of the underlay network and dedicated
to traffic from a specific VPN+ service or a specific group of VPN+
services. This may introduce scalability concerns both in the
implementation (as each VPN+ may need to be tracked in the network)
and in how many resources need to be reserved and how the services
are mapped to the resources (Section 4.4). Thus, some trade-off
needs to be considered to provide the traffic isolation and limited
interaction between VPN+ services.
A dedicated physical network can be used to meet stricter SLO and SLE
requests, at the cost of allocating resources on a long-term and end-
to-end basis. On the other hand, where adequate traffic isolation
and limited interaction can be achieved at the packet layer, this
permits the resources to be shared amongst a group of services and
only dedicated to a service on a temporary basis. By combining
conventional VPNs with TE/QoS/security techniques, VPN+ offers a
variety of means to honor customer's requirements.
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3.3. Integration with Network Resources and Service Functions
The way to achieve the characteristics demand of a VPN+ service (such
as guaranteed or predictable performance) is by integrating the
overlay VPN with a particular set of resources in the underlay
network which are allocated to meet the service requirements. This
needs to be done in a flexible and scalable way so that it can be
widely deployed in operators' networks to support a good number of
VPN+ services.
Taking mobile networks and in particular 5G into consideration, the
integration of the network with service functions is likely a
requirement. The IETF's work on service function chaining (SFC)
[RFC7665] provides a foundation for this. Service functions in the
underlay network can be considered as part of the VPN+ services,
which means the service functions may need to be an integral part of
the corresponding VTN. The details of the integration between
service functions and VPN+ are out of the scope of this document.
3.3.1. Abstraction
Integration of the overlay VPN and the underlay network resources and
service functions does not always need to be a direct mapping. As
described in [RFC7926], abstraction is the process of applying policy
to a set of information about a traffic engineered (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.
With the approach of abstraction, VPN+ may be built on top of an
abstracted topology that represents the connectivity capabilities of
the underlay TE based network as described in the framework for
Abstraction and Control of TE Networks (ACTN) [RFC8453] as discussed
further in Section 5.5.
3.4. Dynamic Changes
VPN+s need to be created, modified, and removed from the network
according to service demands (including scheduled requests). A VPN+
that requires limited interaction with other services (Section 3.2.2)
must not be disrupted by the instantiation or modification of another
VPN+ service. As discussed in Section 3.1 of [RFC4176], the
assessment of traffic isolation is part of the management of a VPN
service. Determining whether modification of a VPN+ can be
disruptive to that VPN+ and whether the traffic in flight will be
disrupted can be a difficult problem.
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Dynamic changes both to the VPN+ and to the underlay network need to
be managed to avoid disruption to services that are sensitive to
changes in network performance.
In addition to non-disruptively managing the network during changes
such as the inclusion of a new VPN+ service endpoint or a change to a
link, VPN+ traffic might need to be moved because of changes to
traffic patterns and volumes. This means that during the lifetime of
a VPN+ service, closed-loop optimization is needed so that the
delivered service always matches the ordered service SLA.
The data plane aspects of this problem are discussed further in
Section 5.1, Section 5.2, and Section 5.3.
The control plane aspects of this problem are discussed further in
Section 5.4.
The management plane aspects of this problem are discussed further in
Section 5.5.
3.5. Customized Control
In many cases the customers are delivered with VPN+ services without
information about the underlying VTNs. However, depending on the
agreement between the operator and the customer, in some cases the
customer may also be provided with some information about the
underlying VTNs. Such information can be filtered or aggregated
according to the operator's policy. This allows the customer of a
VPN+ service to have some visibility and even control over how the
underlying topology and resources of the VTN are used. For example,
the customers may be able to specify the path or path constraints
within the VTN for specific traffic flows of their VPN+ service.
Depending on the requirements, a VPN+ customer may have their own
network controller, which may be provided with an interface to the
control or management system run by the network operator. Note that
such a control is within the scope of the customer's VPN+ service;
any additional changes beyond this would require some intervention by
the network operator.
A description of the control plane aspects of this problem are
discussed further in Section 5.4. A description of the management
plane aspects of this feature can be found in Section 5.5.
3.6. Applicability to Overlay Technologies
The concept of VPN+ can be applied to any existing and future multi-
tenancy overlay technologies including but not limited to:
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* Layer-2 point-to-point services, such as pseudowires [RFC3985]
* Layer-2 VPNs [RFC4664]
* Ethernet VPNs [RFC7209], [RFC7432]
* Layer-3 VPNs [RFC4364], [RFC2764]
Where such VPN service types need enhanced isolation and delivery
characteristics, the technologies described in Section 5 can be used
to tweak the underlay to provide the required enhanced performance.
3.7. Inter-Domain and Inter-Layer Network
In some scenarios, a VPN+ service may span multiple network domains.
A domain is considered to be any collection of network elements under
the responsibility of the same administrative entity, for example, an
Autonomous System (AS). In some domains the network operator may
manage a multi-layered network, for example, a packet network over an
optical network. When VPN+ services are provisioned in such network
scenarios, the technologies used in different network planes (data
plane, control plane, and management plane) need to provide
mechanisms to support multi-domain and multi-layer coordination and
integration, so as to provide the required service characteristics
for different VPN+ services, and improve network efficiency and
operational simplicity. The mechanisms for multi-domain VPNs
[RFC4364] may be reused, and some enhancement may be needed to meet
the additional requirements of VPN+ services.
4. The Architecture of VPN+
Multiple VPN+ services can be provided by a common network
infrastructure. Each VPN+ service is provisioned with an overlay VPN
and mapped to a corresponding VTN, which has a specific set of
network resources and service functions allocated in the underlay to
satisfy the needs of the customer. One VTN may support one of more
VPN+ services. The integration between the overlay connectivity and
the underlay resources ensures the required isolation between
different VPN+ services, and achieves the guaranteed performance for
different customers.
The VPN+ architecture needs to be designed with consideration given
to:
* An enhanced data plane.
* A control plane to create VPN+ and VTN, making use of the data
plane isolation and performance guarantee techniques.
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* A management plane for VPN+ service life-cycle management.
* The OAM mechanisms for VPN+ and the underlaying VTN.
* Telemetry mechanisms for VPN+ and the underlaying VTN.
These topics are expanded below.
* The enhanced data plane provides:
- The required packet latency and jitter characteristics.
- The required packet loss characteristics.
- The required resource isolation capability, e.g., bandwidth
guarantee.
- The mechanism to associate a packet with the set of resources
allocated to a VTN which the VPN+ service packet is mapped to.
* The control plane:
- Collects information about the underlying network topology and
network resources, and exports this to network nodes and/or a
centralized controller as required.
- Creates VTNs with the network resource and topology properties
needed by the VPN+ services.
- Distributes the attributes of VTNs to network nodes which
participate in the VTNs and/or a centralized controller.
- Computes and sets up network paths in each VTN.
- Maps VPN+ services to an appropriate VTN.
- Determines the risk of SLA violation and takes appropriate
avoiding/correction actions.
- Considers the right balance of per-packet and per-node state
according to the needs of the VPN+ services to scale to the
required size.
* The management plane provides:
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- An interface between the VPN+ service provider (e.g.,
operator's network management system) and the VPN+ customer
(e.g., an organization or a service with VPN+ requirement) such
that the operation requests and the related parameters can be
exchanged without the awareness of other VPN+ customers.
- An interface between the VPN+ service provider and the VPN+
customers to expose the network capability information toward
the customer.
- The service life-cycle management and operation of VPN+
services (e.g., creation, modification, assurance/monitoring,
and decommissioning).
* Operations, Administration, and Maintenance (OAM) provides:
- The tools to verify the connectivity and monitor the
performance of the VPN+ service.
- The tools to verify whether the underlay network resources are
correctly allocated and operating properly.
* Telemetry provides:
- Provides the mechanisms to collect network information about
the operation of the data plane, control plane, and management
plane. More specifically, telemetry provides the mechanisms to
collect network data:
o from the underlay network for overall performance evaluation
and for the planning of the VPN+ services.
o from each VPN+ service for monitoring and analytics of the
characteristics and SLA fulfillment of the VPN+ services.
4.1. Layered Architecture
The layered architecture of VPN+ is shown in Figure 1.
Underpinning everything is the physical network infrastructure layer
which provides the underlying resources used to provision the
separate VTNs. This layer is responsible for the partitioning of
link and/or node resources for different VTNs. Each subset of link
or node resource can be considered as a virtual link or virtual node
used to build the VTNs.
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/\
||
+-------------------+ Centralized
| Network Controller| Control & Management
+-------------------+
||
\/
o---------------------------o VPN+ #1
/-------------o
o____________/______________o VPN+ #2
_________________o
_____/
o___/ \_________________o VPN+ #3
\_______________________o
...... ...
o-----------\ /-------------o
o____________X______________o VPN+ #n
__________________________
/ o----o-----o /
/ / / / VTN-1
/ o-----o-----o----o----o /
/_________________________/
__________________________
/ o----o /
/ / / \ / VTN-2
/ o-----o----o---o------o /
/_________________________/
...... ...
___________________________
/ o----o /
/ / / / VTN-m
/ o-----o----o----o-----o /
/__________________________/
++++ ++++ ++++
+--+===+--+===+--+
+--+===+--+===+--+
++++ +++\\ ++++
|| || \\ || Physical
|| || \\ || Network
++++ ++++ ++++ \\+++ ++++ Infrastructure
+--+===+--+===+--+===+--+===+--+
+--+===+--+===+--+===+--+===+--+
++++ ++++ ++++ ++++ ++++
o Virtual Node ++++
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+--+ Physical Node with resource partition
-- Virtual Link +--+
++++
== Physical Link with resource partition
Figure 1: The Layered Architecture of VPN+
Various components and techniques discussed in Section 5 can be used
to enable resource partitioning of the physical network
infrastructure, such as FlexE, TSN, dedicated queues, etc. These
partitions may be physical or virtual so long as the SLA required by
the higher layers is met.
Based on the set of network resource partitions provided by the
physical network infrastructure, multiple VTNs can be created, each
with a set of dedicated or shared network resources allocated from
the physical underlay network, and each can be associated with a
customized logical network topology, so as to meet the requirements
of different VPN+ services or different groups of VPN+ services.
According to the associated logical network topology, each VTN needs
to be instantiated on a set of network nodes and links which are
involved in the logical topology. And on each node or link, each VTN
is associated with a set of local resources which are allocated for
the processing of traffic in the VTN. The VTN provides the
integration between the logical network topology and the required
underlying network resources.
According to the service requirements of connectivity, performance
and isolation, etc., VPN+ services can be mapped to the appropriate
VTNs in the network. Different VPN+ services can be mapped to
different VTNs, while it is also possible that multiple VPN+ services
are mapped to the same VTN. Thus, the VTN is an essential scaling
technique, as it has the potential of eliminating per-service per-
path state from the network. In addition, when a group of VPN+
services are mapped to a single VTN, only the network state of the
single VTN needs to be maintained in the network (see Section 4.4 for
more information).
The network controller is responsible for creating a VTN, instructing
the involved network nodes to allocate network resources to the VTN,
and provisioning the VPN+ services on the VTN. A distributed control
plane may be used for distributing the VTN resource and topology
attributes among nodes in the VTN.
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The process used to create VTNs and to allocate network resources for
use by the VTNs needs to take a holistic view of the needs of all of
the service provider's customers and to partition the resources
accordingly. However, within a VTN these resources can, if required,
be managed via a dynamic control plane. This provides the required
scalability and isolation with some flexibility.
4.2. Connectivity Types
At the VPN service level, the required connectivity for an MP2MP VPN
service is usually full or partial mesh. To support such VPN
services, the corresponding VTN also needs to provide MP2MP
connectivity among the end points.
Other service requirements may be expressed at different
granularities, some of which can be applicable to the whole service,
while some others may only be applicable to some pairs of end points.
For example, when a particular level of performance guarantee is
required, the point-to-point path through the underlying VTN of the
VPN+ service may need to be specifically engineered to meet the
required performance guarantee.
4.3. Application-Specific Data Types
Although a lot of the traffic that will be carried over VPN+ will
likely be IP based, the design must be capable of carrying other
traffic types, in particular Ethernet traffic. This is easily
accomplished through the various pseudowire (PW) techniques
[RFC3985].
Where the underlay is MPLS, Ethernet traffic can be carried over VPN+
encapsulated according to the method specified in [RFC4448]. Where
the underlay is IP, Layer Two Tunneling Protocol - Version 3 (L2TPv3)
[RFC3931] can be used with Ethernet traffic carried according to
[RFC4719]. Encapsulations have been defined for most of the common
layer-2 types for both PW over MPLS and for L2TPv3.
4.4. Scalable Service Mapping
VPNs are instantiated as overlays on top of an operator's network and
offered as services to the operator's customers. An important
feature of overlays is that they can deliver services without placing
per-service state in the core of the underlay network.
VPN+ may need to install some additional state within the network to
achieve the features that they require. Solutions must consider
minimizing and controlling the scale of such state, and deployment
architectures should constrain the number of VPN+ services so that
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the additional state introduced to the network is acceptable and
under control. It is expected that the number of VPN+ services will
be small at the beginning, and even in the future the number of VPN+
services will be fewer than conventional VPNs because existing VPN
techniques are good enough to meet the needs of most existing VPN-
type services.
In general, it is not required that the state in the network be
maintained in a 1:1 relationship with the VPN+ services. It will
usually be possible to aggregate a set or group of VPN+ services so
that they share the same VTN and the same set of network resources
(much in the same way that current VPNs are aggregated over transport
tunnels) so that collections of VPN+ services that require the same
behavior from the network in terms of resource reservation, latency
bounds, resiliency, etc. can be grouped together. This is an
important feature to assist with the scaling characteristics of VPN+
deployments.
[I-D.ietf-teas-nrp-scalability] provides more details of scalability
considerations for the network resource partitions used to
instantiate VTNs, and Section 7 includes a greater discussion of
scalability considerations.
5. Candidate Technologies
A VPN is a virtual network created by applying a demultiplexing
technique to the underlying network (the underlay) to distinguish the
traffic of one VPN from that of another. The connections of VPN are
supported by a set of underlay paths. A path that travels by other
than the shortest path through the underlay normally requires state
to specify that path. The state of the paths could be applied to the
underlay through the use of the RSVP-TE signaling protocol, or
directly through the use of an SDN controller. Based on Segment
Routing, state could be maintained at the ingress node of the path,
and carried in the data packet. Other techniques may emerge as this
problem is studied. This state gets harder to manage as the number
of paths increases. Furthermore, as we increase the coupling between
the underlay and the overlay to support the VPN+ service, this state
is likely to increase further.
VTN can be used to provide a group of virtual underlay paths (VTP)
with a common set of network resources. Through the use of VTNs, a
subset of underlay network resource can be either dedicated for a
particular VPN+ service or shared among a group of VPN+ services.
This section describes the candidate technologies in different
network planes which can be used to build VTNs.
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5.1. Forwarding Resource Partitioning
Several candidate layer-2 packet- or frame-based forwarding plane
mechanisms which can provide the required traffic isolation and
performance guarantees are described in the following sections.
5.1.1. Flexible Ethernet
FlexE [FLEXE] provides the ability to multiplex channels over an
Ethernet link to create point-to-point fixed-bandwidth connections in
a way that provides separation between VPN+ services. FlexE also
supports bonding links to create larger links out of multiple low-
capacity links.
However, FlexE is only a link level technology. When packets are
received by the downstream node, they need to be processed in a way
that preserves that traffic isolation in the downstream node. This
in turn requires a queuing and forwarding implementation that
preserves the end-to-end separation of enhanced VPNs.
If different FlexE channels are used for different services, then no
sharing is possible between the FlexE channels. This means that it
may be difficult to dynamically redistribute unused bandwidth to
lower priority services in another FlexE channel. If one FlexE
channel is used by one customer, the customer can use some methods to
manage the relative priority of their own traffic in the FlexE
channel.
5.1.2. Dedicated Queues
DiffServ based queuing systems are described in [RFC2475] and
[RFC4594]. This approach is not sufficient to provide separation of
VPN+ services because DiffServ does not provide enough markers to
differentiate between traffic of a large number of VPN+ services.
Nor does DiffServ offer the range of service classes that each VPN+
service needs to provide to its tenants. This problem is
particularly acute with an MPLS underlay, because MPLS only provides
eight traffic classes.
In addition, DiffServ, as currently implemented, mainly provides per-
hop priority-based scheduling, and it is difficult to use it to
achieve quantitative resource reservation for different VPN+
services.
To address these problems and to reduce the potential interactions
between VPN+ services, it would be necessary to steer traffic to
dedicated input and output queues per VPN+ service or per group of
VPN+ services: some routers have a large number of queues and
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sophisticated queuing systems which could support this, while some
routers may struggle to provide the granularity and level of
separation required by the applications of VPN+.
5.1.3. Time Sensitive Networking
Time Sensitive Networking (TSN) [TSN] is an IEEE project to provide a
method of carrying time sensitive information over Ethernet. It
introduces the concept of packet scheduling where a packet stream may
be given a time slot guaranteeing that it experiences no queuing
delay or increase in latency beyond the very small scheduling delay.
The mechanisms defined in TSN can be used to meet the requirements of
time sensitive traffic flows of VPN+ service.
Ethernet can be emulated over a layer-3 network using an IP or MPLS
pseudowire. However, a TSN Ethernet payload would be opaque to the
underlay and thus not treated specifically as time sensitive data.
The preferred method of carrying TSN over a layer-3 network is
through the use of deterministic networking as explained in
Section 5.2.1.
5.2. Data Plane Encapsulation and Forwarding
This section considers the problem of VPN+ service differentiation
and the representation of underlying network resources in the network
layer. More specifically, it describes the possible data plane
mechanisms to determine the network resources and the logical network
topology or paths associated with a VTN.
5.2.1. Deterministic Networking
Deterministic Networking (DetNet) [RFC8655] is a technique being
developed in the IETF to enhance the ability of layer-3 networks to
deliver packets more reliably and with greater control over the
delay. The design cannot use re-transmission techniques such as TCP
since that can exceed the delay tolerated by the applications.
DetNet pre-emptively sends copies of the packet over various paths to
minimize the chance of all copies of a packet being lost. It also
seeks to set an upper bound on latency, but the goal is not to
minimize latency. Detnet can be realized over IP data plane
[RFC8939] or MPLS data plane [RFC8964], and may be used to provide
Virtual Transport Paths (VTPs) for VPN+ services.
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5.2.2. MPLS Traffic Engineering (MPLS-TE)
MPLS-TE [RFC2702][RFC3209] introduces the concept of reserving end-
to-end bandwidth for a TE-LSP, which can be used to provide a point-
to-point Virtual Transport Path (VTP) across the underlay network to
support VPN services. VPN traffic can be carried over dedicated TE-
LSPs to provide reserved bandwidth for each specific connection in a
VPN, and VPNs with similar behavior requirements may be multiplexed
onto the same TE-LSPs. Some network operators have concerns about
the scalability and management overhead of MPLS-TE system, especially
with regard to those systems that use an active control plane, and
this has lead them to consider other solutions for traffic
engineering in their networks.
5.2.3. Segment Routing
Segment Routing (SR) [RFC8402] is a method that prepends instructions
to packets at the head-end of a path. These instructions are used to
specify the nodes and links to be traversed, and allow the packets to
be routed on paths other than the shortest path. By encoding the
state in the packet, per-path state is transitioned out of the
network. SR can be instantiated using MPLS data plane (SR-MPLS) or
IPv6 data plane (SRv6).
An SR traffic engineered path operates with a granularity of a link.
Hints about priority are provided using the Traffic Class (TC) field
in the packet header. However, to achieve the performance and
isolation characteristics that are sought by VPN+ customers, it will
be necessary to steer packets through specific virtual links and/or
queues on the same link and direct them to use specific resources.
With SR, it is possible to introduce such fine-grained packet
steering by specifying the queues and the associated resources
through an SR instruction list.
Note that the concept of a queue is a useful abstraction for
different types of underlay mechanism that may be used to provide
enhanced isolation and performance support. How the queue satisfies
the requirement is implementation specific and is transparent to the
layer-3 data plane and control plane mechanisms used.
With Segment Routing, the SR instruction list could be used to build
a P2P path, and a group of SR Segment Identifiers (SIDs) could also
be used to represent an MP2MP network. Thus, the SR based mechanism
could be used to provide both a Virtual Transport Path (VTP) and a
Virtual Transport Network (VTN) for VPN+ services.
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5.2.4. New Encapsulation Extensions
In contrast to reusing existing data plane for VPN+, another possible
approach is to introduce new encapsulations or extensions to existing
data plane to allow dedicated identifiers for the underlay network
resources of a VTN, and the logical network topology or paths
associated with a VTN. This may require more protocol work, while
the potential benefit is it can reduce the impact to existing network
operation and improve the scalability of VPN+. More details about the
encapsulation extensions are described in
[I-D.ietf-teas-nrp-scalability].
5.3. Non-Packet Data Plane
Non-packet underlay data plane technologies often have TE properties
and behaviors, and meet many of the key requirements in particular
for bandwidth guarantees, traffic isolation (with physical isolation
often being an integral part of the technology), highly predictable
latency and jitter characteristics, measurable loss characteristics,
and ease of identification of flows. The cost is that the resources
are allocated on a long-term and end-to-end basis. Such an
arrangement means that the full cost of the resources has to be borne
by the client to which the resources are allocated. When a VTN built
with this data plane is used to support multiple VPN+ services, the
cost could be distributed among such group of services.
5.4. Control Plane
The control plane of VPN+ would likely be based on a hybrid control
mechanism that takes advantage of a logically centralized controller
for on-demand provisioning and global optimization, whilst still
relying on a distributed control plane to provide scalability, high
reliability, fast reaction, automatic failure recovery, etc.
Extension to and optimization of the centralized and distributed
control plane is needed to support the enhanced properties of VPN+.
As described in Section 4, the VPN+ control plane needs to provide
the following functions:
* Collect information about the underlying network topology and
network resources, and exports this to network nodes and/or a
centralized controller as required.
* Create VTNs with the network resource and topology properties
needed by the VPN+ services.
* Distribute the attributes of VTNs to network nodes which
participate in the VTNs and/or the centralized controller.
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* Map VPN+ services to an appropriate VTN.
* Compute and set up VTPs in each VTN to meet VPN+ service
requirements.
The collection of underlying network topology and resource
information can be done using existing the IGP and Border Gateway
Protocol - Link State (BGP-LS) [RFC7752] based mechanisms. The
creation of VTN and the distribution of VTN attributes may need
further control protocol extensions. The computation of VTPs based
on the attributes and constraints of the VTN can be performed either
by the headend node of the path or a centralized Path Computation
Element (PCE) [RFC4655].
There are two candidate control plane mechanisms for the setup of
VTPs in the VTN: RSVP-TE and Segment Routing (SR).
* RSVP-TE [RFC3209] provides the signaling mechanism for
establishing a TE-LSP in an MPLS network with end-to-end resource
reservation. This can be seen as an approach of providing a
Virtual Transport Path (VTP) which could be used to bind the VPN
to specific network resources allocated within the underlay, but
there remain scalability concerns as mentioned in Section 5.2.2.
* The SR control plane [RFC8665] [RFC8667] [RFC9085] does not have
the capability of signaling resource reservations along the path.
On the other hand, the SR approach provides a potential way of
binding the underlay network resource and the VTNs without
requiring per-path state to be maintained in the network. A
centralized controller can perform resource planning and
reservation for VTNs, and it needs to instruct the network nodes
to ensure that resources are correctly allocated for the VTN. The
controller could provision the SR paths based on the mechanism in
[RFC9256] to the headend nodes of the paths.
According to the service requirements for connectivity, performance
and isolation, one VPN+ service may be mapped a dedicated VTN, or a
group of VPN+ services may be mapped to the same VTN. The mapping of
VPN+ services to VTN can be achieved using existing control
mechanisms with possible extensions, and it can be based on either
the characteristics of the data packet or the attributes of the VPN
service routes.
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5.5. Management Plane
The management plane provides the interface between the VPN+ service
provider and the customers for life-cycle management of the VPN+
service (i.e., creation, modification, assurance/monitoring, and
decommissioning). It relies on a set of service data models for the
description of the information and operations needed on the
interface.
As an example, in the context of 5G end-to-end network slicing
[TS28530], the management of the transport network segment of the 5G
end-to-end network slice can be realized with the management plane of
VPN+. The 3GPP management system may provide the connectivity and
performance related parameters as requirements to the management
plane of the transport network. It may also require the transport
network to expose the capabilities and status of the network slice.
Thus, an interface between the VPN+ management plane and the 5G
network slice management system, and relevant service data models are
needed for the coordination of 5G end-to-end network slice
management.
The management plane interface and data models for VPN+ services can
be based on the service models described in Section 5.6.
It is important that the management life-cycle supports in-place
modification of VPN+ services. That is, it should be possible to add
and remove end points, as well as to change the requested
characteristics of the service that is delivered. The management
system needs to be able to assess the revised VPN+ requests and
determine whether they can be provided by the existing VTNs or
whether changes must be made, and it will additionally need to
determine whether those changes to the VTN are possible. If not,
then the customer's modification request may be rejected.
When the modification of a VPN+ service is possible, the management
system must make every effort to make the changes in a non-disruptive
way. That is, the modification of the VPN+ service or the underlying
VTN must not perturbate traffic on the VPN+ service in a way that
causes the service level to drop below the agreed levels.
Furthermore, changes to one VPN+ service should not cause disruption
to other VPN+ services.
The network operator for the underlay network (i.e., the provider of
the VPN+ service) may delegate some operational aspects of the
overlay VPN and the underlying VTN to the customer. In this way, the
VPN+ is presented to the customer as a virtual network, and the
customer can choose how to use that network. Some mechanisms in the
operator's network is needed, so that a customer cannot exceed the
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capabilities of the virtual links and nodes, but can decide how to
load traffic onto the network, for example, by assigning different
metrics to the virtual links so that the customer can control how
traffic is routed through the virtual network. This approach
requires a management system for the virtual network, but does not
necessarily require any coordination between the management systems
of the virtual network and the physical network, except that the
virtual network management system might notice when the VTN is close
to capacity or considerably under-used and automatically request
changes in the service provided by the underlay network.
5.6. Applicability of Service Data Models to VPN+
This section describes the applicability of the existing and in-
progress service data models to VPN+. [RFC8309] describes the scope
and purpose of service models and shows where a service model might
fit into an SDN based network management architecture. New service
models may also be introduced for some of the required management
functions.
Service data models are used to represent, monitor, and manage the
virtual networks and services enabled by VPN+. The VPN customer
service models (e.g., the Layer 3 VPN Service Model (L3SM) [RFC8299],
the Layer 2 VPN Service Model (L2SM) [RFC8466]), or the ACTN Virtual
Network (VN) model [I-D.ietf-teas-actn-vn-yang]) are service models
which can provide the customer's view of the VPN+ service. The
Layer-3 VPN Network Model (L3NM) [RFC9182], the Layer-2 VPN network
model (L2NM) [RFC9291] provide the operator's view of the managed
infrastructure as a set of virtual networks and the associated
resources. The Service Attachment Points (SAPs) model [RFC9408]
provides an abstract view of the service attachment points (SAPs) to
various network services in the provider network, where VPN+ could be
one of the service types. Augmentation to these service models may
be needed to provide the VPN+ services. The NRP model
[I-D.wdbsp-teas-nrp-yang] further provides the management of the NRP
topology and resources both in the controller and in the network
devices to instantiate the VTNs needed for the VPN+ services.
6. Applicability in Network Slice Realization
This section describes the applicability of VPN+ for network slice
realization.
In order to provide network slices to customers, a technology-
agnostic network slice service model
[I-D.ietf-teas-ietf-network-slice-nbi-yang] is needed for the
customers to communicate the requirements of network slices (end
points, connectivity, SLOs, and SLEs). These requirements may be
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realized using technology specified in this document to instruct the
network to deliver a VPN+ service so as to meet the requirements of
the network slice customers.
6.1. NRP Planning
In the network slicing context, an NRP is considered as the
instantiation of VTN to support the network slice services.
According to the network operators' network resource planning policy,
or based on the requirements of one or a group of customers or
services, an NRP may need to be created to meet the requirements of
network slice services. One of the basic requirements for the NRP is
to provide a set of dedicated network resources to avoid unexpected
interference from other services in the same network. Other possible
requirements may include the required topology and connectivity,
bandwidth, latency, reliability, etc.
A centralized network controller can be responsible for calculating a
subset of the underlay network topology (which is called a logical
topology) to support the NRP requirement. And on the network nodes
and links within the logical topology, the set of network resources
to be allocated to the NRP can also be determined by the controller.
Normally such calculation needs to take the underlay network
connectivity information and the available network resource
information of the underlay network into consideration. The network
controller may also take the status of the existing NRPs into
consideration in the planning and calculation of a new NRP.
6.2. NRP Creation
According to the result of the NRP planning, the network nodes and
links involved in the logical topology of the NRP are instructed to
allocated the required set of network resources for the NRP. One or
multiple mechanisms as specified in section 5.1 can be used to
partition the forwarding plane network resources and allocate
different subsets of resources to different NRPs. In addition, the
data plane identifiers which are used to identify the set of network
resources allocated to the NRP are also provisioned on the network
nodes. Depending on the data plane technologies used, the set of
network resources of an NRP can be identified using e.g. either
resource aware SR segments as specified in
[I-D.ietf-spring-resource-aware-segments]
[I-D.ietf-spring-sr-for-enhanced-vpn], or a dedicated Resource ID as
specified in [I-D.ietf-6man-enhanced-vpn-vtn-id] can be introduced.
The network nodes involved in an NRP may distribute the logical
topology information, the NRP specific network resource information
and the Resource Identifier of the NRP using the control plane. Such
information could be used by the controller and the network nodes to
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compute the TE or shortest paths within the NRP, and install the NRP
specific forwarding entries to network nodes.
6.3. Network Slice Service Provisioning
According to the connectivity requirements of an network slice
service, an overlay VPN can be created using the existing or future
multi-tenancy overlay technologies as described in Section 3.6.
Then according to the SLO and SLE requirements of a network slice
service, the network slice service is mapped to an appropriate NRP as
the virtual underlay. The integration of the overlay VPN and the
underlay NRP together provide a network slice service.
6.4. Network Slice Traffic Steering and Forwarding
At the edge of the operator's network, traffic of network slices can
be classified based on the rules defined by the operator's policy, so
that the traffic which matches the rules for specific network slice
services can be mapped to the corresponding NRP. This way, packets
belonging to specific network slice service will be processed and
forwarded by network nodes based either the traffic-engineered paths
or the shortest paths in the associated network topology, using the
set of network resources of the corresponding NRP.
7. Scalability Considerations
VPN+ provides performance guaranteed services in packet networks, but
with the potential cost of introducing additional state into the
network. There are at least three ways that this additional state
might be brought into the network:
* Introduce the complete state into the packet, as is done in SR.
This allows the controller to specify the detailed series of
forwarding and processing instructions for the packet as it
transits the network. The cost of this is an increase in the
packet header size. The cost is also that systems will have to
provide VTN specific segments in case they are called upon by a
service. This is a type of latent state, and increases as the
segments and resources that need to be exclusively available to
VPN+ service are specified more precisely.
* Introduce the state to the network. This is normally done by
creating a path using signaling such as RSVP-TE. This could be
extended to include any element that needs to be specified along
the path, for example explicitly specifying queuing policy. It is
also possible to use other methods to introduce path state, such
as via an SDN controller, or possibly by modifying a routing
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protocol. With this approach there is state per path: per-path
characteristic that needs to be maintained over the life of the
path. This is more network state than is needed using SR, but the
packets are usually shorter.
* Provide a hybrid approach. One example is based on using binding
SIDs [RFC8402] to represent path fragments, and bind them together
with SR. Dynamic creation of a VPN service path using SR requires
less state maintenance in the network core at the expense of
larger packet headers. The packet size can be lower if a form of
loose source routing is used (using a few nodal SIDs), and it will
be lower if no specific functions or resources on the routers are
specified.
Reducing the state in the network is important to VPN+, as it
requires the overlay to be more closely integrated with the underlay
than with conventional VPNs. This tighter coupling would normally
mean that more state needs to be created and maintained in the
network, as the state about fine granularity processing would need to
be loaded and maintained in the routers. Aggregation is a well-
established approach to reduce the amount of state and improve
scaling, and VTN is considered as the network construct to aggregate
the states of VPN+ services. In addition, an SR approach allows much
of the state to be spread amongst the network ingress nodes, and
transiently carried in the packets as SIDs.
The following subsections describe some of the scalability concerns
that need to be considered. Further discussion of the scalability
considerations of the underlaying network construct of VPN+ can be
found in [I-D.ietf-teas-nrp-scalability].
7.1. Maximum Stack Depth of SR
One of the challenges with SR is the stack depth that nodes are able
to impose on packets [RFC8491]. This leads to a difficult balance
between adding state to the network and minimizing stack depth, or
minimizing state and increasing the stack depth.
7.2. RSVP-TE Scalability
The established method of creating a resource allocated path through
an MPLS network is to use the RSVP-TE protocol. However, there have
been concerns that this requires significant continuous state
maintenance in the network. Work to improve the scalability of RSVP-
TE LSPs in the control plane can be found in [RFC8370].
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There is also concern at the scalability of the forwarder footprint
of RSVP-TE as the number of paths through a label switching router
(LSR) grows. [RFC8577] addresses this by employing SR within a
tunnel established by RSVP-TE.
7.3. SDN Scaling
The centralized approach of SDN requires state to be stored in the
network, but does not have the overhead of also requiring control
plane state to be maintained. Each individual network node may need
to maintain a communication channel with an SDN controller, but that
compares favorably with the need for a control plane to maintain
communication with all neighbors.
However, SDN may transfer some of the scalability concerns from the
network to a centralized controller. In particular, there may be a
heavy processing burden at the controller, and a heavy load in the
network surrounding the controller. A centralized controller may
also present a single point of failure within the network.
8. Manageability Considerations
This section describes the considerations about the OAM and Telemetry
mechanisms used to support the verification, monitoring and
optimization of the characteristics and SLA fulfillment of the VPN+
services.
8.1. OAM Considerations
The design of OAM for VPN+ services needs to consider the following
requirements:
* Instrumentation of the underlay so that the network operator can
be sure that the resources committed to a customer are operating
correctly and delivering the required performance.
* Instrumentation of the overlay by the customer. This is likely to
be transparent to the network operator and to use existing
methods. Particular consideration needs to be given to the need
to verify the various committed performance characteristics.
* Instrumentation of the overlay by the service provider to
proactively demonstrate that the committed performance is being
delivered. This needs to be done in a non-intrusive manner,
particularly when the tenant is deploying a performance sensitive
application.
A study of OAM in SR networks is documented in [RFC8403].
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8.2. Telemetry Considerations
Network visibility is essential for network operation. Network
telemetry has been considered as an ideal means to gain sufficient
network visibility with better flexibility, scalability, accuracy,
coverage, and performance than conventional OAM technologies.
As defined in [RFC9232], the objective of Network Telemetry is to
acquire network data remotely for network monitoring and operation.
It is a general term for a large set of network visibility techniques
and protocols. Network telemetry addresses the current network
operation issues and enables smooth evolution toward intent-driven
autonomous networks. Telemetry can be applied on the forwarding
plane, the control plane, and the management plane in a network.
How the telemetry mechanisms could be used or extended for the VPN+
service is out of the scope of this document.
9. Enhanced Resiliency
Each VPN+ service has a life cycle, and may need modification during
deployment as the needs of its tenant change. This is discussed in
Section 5.5. Additionally, as the network evolves, there may need to
perform garbage collection to consolidate resources into usable
quanta.
Systems in which the path is imposed, such as SR or some form of
explicit routing, tend to do well in these applications, because it
is possible to perform an atomic transition from one path to another.
That is, a single action by the head-end that changes the path
without the need for coordinated action by the routers along the
path. However, implementations and the monitoring protocols need to
make sure that the new path is operational and meets the required SLA
before traffic is transitioned to it. It is possible for deadlocks
to arise as a result of the network becoming fragmented over time,
such that it is impossible to create a new path or to modify an
existing path without impacting the SLA of other paths. The global
concurrent optimization mechanisms as described in [RFC5557] and
discussed in [RFC7399] may be helpful, while complete resolution of
this situation is as much a commercial issue as it is a technical
issue.
There are, however, two manifestations of the latency problem that
are for further study in any of these approaches:
* The problem of packets overtaking one another if a path latency
reduces during a transition.
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* The problem of transient variation in latency in either direction
as a path migrates.
There is also the matter of what happens during failure in the
underlay infrastructure. Fast reroute is one approach, but that
still produces a transient loss with a normal goal of rectifying this
within 50ms [RFC5654]. An alternative is some form of N+1 delivery
such as has been used for many years to support protection from
service disruption. This may be taken to a different level using the
techniques of DetNet with multiple in-network replication and the
culling of later packets [RFC8655].
In addition to the approach used to protect high priority packets,
consideration should be given to the impact of best effort traffic on
the high priority packets during a transition. Specifically, if a
conventional re-convergence process is used there will inevitably be
micro-loops and whilst some form of explicit routing will protect the
high priority traffic, lower priority traffic on best effort shortest
paths will micro-loop without the use of a loop prevention
technology. To provide the highest quality of service to high
priority traffic, either this traffic must be shielded from the
micro-loops, or micro-loops must be prevented completely.
10. Operational Considerations
It is expected that VPN+ services will be introduced in networks
which already have conventional VPN services deployed. Depending on
service requirements, the tenants or the operator may choose to use a
VPN or a VPN+ to fulfill a service requirement. The information and
parameters to assist such a decision needs to be supplied on the
management interface between the tenant and the operator.
11. Security Considerations
All types of virtual network require special consideration to be
given to the isolation of traffic belonging to different tenants.
That is, traffic belonging to one VPN must not be delivered to end
points outside that VPN. In this regard VPN+ neither introduces, nor
experiences greater security risks than other VPNs.
However, in a VPN+ service the additional service requirements need
to be considered. For example, if a service requires a specific
upper bound to latency then it can be damaged by simply delaying the
packets through the activities of another tenant, i.e., by
introducing bursts of traffic for other services. In some respects
this makes the VPN+ more susceptible to attacks since the SLA may be
broken. But another view is that the operator must, in any case,
preform monitoring of the VPN+ to ensure that the SLA is met, and
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this means that the operator may be more likely to spot the early
onset of a security attack and be able to take pre-emptive protective
action.
The measures to address these dynamic security risks must be
specified as part of the specific solution to the isolation
requirements of a VPN+ service.
While a VPN+ service may be sold as offering encryption and other
security features as part of the service, customers would be well
advised to take responsibility for their own security requirements
themselves possibly by encrypting traffic before handing it off to
the service provider.
The privacy of VPN+ service customers must be preserved. It should
not be possible for one customer to discover the existence of another
customer, nor should the sites that are members of an VPN+ be
externally visible.
A VPN+ service (even one with traffic isolation requirements or with
limited interaction with other enhanced VPNs) does not provide any
additional guarantees of privacy for customer traffic compared to
regular VPNs: the traffic within the network may be intercepted and
errors may lead to mis-delivery. Users who wish to ensure the
privacy of their traffic must take their own precautions including
end-to-end encryption.
12. IANA Considerations
There are no requested IANA actions.
13. Contributors
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Daniel King
Email: daniel@olddog.co.uk
Adrian Farrel
Email: adrian@olddog.co.uk
Jeff Tansura
Email: jefftant.ietf@gmail.com
Zhenbin Li
Email: lizhenbin@huawei.com
Qin Wu
Email: bill.wu@huawei.com
Bo Wu
Email: lana.wubo@huawei.com
Daniele Ceccarelli
Email: daniele.ceccarelli@ericsson.com
Mohamed Boucadair
Email: mohamed.boucadair@orange.com
Sergio Belotti
Email: sergio.belotti@nokia.com
Haomian Zheng
Email: zhenghaomian@huawei.com
14. Acknowledgements
The authors would like to thank Charlie Perkins, James N Guichard,
John E Drake, Shunsuke Homma, Luis M. Contreras, and Joel Halpern
for their review and valuable comments.
This work was supported in part by the European Commission funded
H2020-ICT-2016-2 METRO-HAUL project (G.A. 761727).
15. Informative References
[FLEXE] "Flex Ethernet Implementation Agreement", March 2016,
<http://www.oiforum.com/wp-content/uploads/OIF-FLEXE-
01.0.pdf>.
[I-D.ietf-6man-enhanced-vpn-vtn-id]
Dong, J., Li, Z., Xie, C., Ma, C., and G. S. Mishra,
"Carrying Virtual Transport Network (VTN) Information in
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IPv6 Extension Header", Work in Progress, Internet-Draft,
draft-ietf-6man-enhanced-vpn-vtn-id-05, 6 July 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-6man-
enhanced-vpn-vtn-id-05>.
[I-D.ietf-spring-resource-aware-segments]
Dong, J., Bryant, S., Miyasaka, T., Zhu, Y., Qin, F., Li,
Z., and F. Clad, "Introducing Resource Awareness to SR
Segments", Work in Progress, Internet-Draft, draft-ietf-
spring-resource-aware-segments-07, 31 May 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-spring-
resource-aware-segments-07>.
[I-D.ietf-spring-sr-for-enhanced-vpn]
Dong, J., Bryant, S., Miyasaka, T., Zhu, Y., Qin, F., Li,
Z., and F. Clad, "Segment Routing based Virtual Transport
Network (VTN) for Enhanced VPN", Work in Progress,
Internet-Draft, draft-ietf-spring-sr-for-enhanced-vpn-05,
31 May 2023, <https://datatracker.ietf.org/doc/html/draft-
ietf-spring-sr-for-enhanced-vpn-05>.
[I-D.ietf-teas-actn-vn-yang]
Lee, Y., Dhody, D., Ceccarelli, D., Bryskin, I., and B. Y.
Yoon, "A YANG Data Model for Virtual Network (VN)
Operations", Work in Progress, Internet-Draft, draft-ietf-
teas-actn-vn-yang-20, 14 October 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
actn-vn-yang-20>.
[I-D.ietf-teas-ietf-network-slice-nbi-yang]
Wu, B., Dhody, D., Rokui, R., Saad, T., Han, L., and J.
Mullooly, "A YANG Data Model for the IETF Network Slice
Service", Work in Progress, Internet-Draft, draft-ietf-
teas-ietf-network-slice-nbi-yang-07, 20 October 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
ietf-network-slice-nbi-yang-07>.
[I-D.ietf-teas-ietf-network-slices]
Farrel, A., Drake, J., Rokui, R., Homma, S., Makhijani,
K., Contreras, L. M., and J. Tantsura, "A Framework for
Network Slices in Networks Built from IETF Technologies",
Work in Progress, Internet-Draft, draft-ietf-teas-ietf-
network-slices-25, 14 September 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
ietf-network-slices-25>.
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[I-D.ietf-teas-nrp-scalability]
Dong, J., Li, Z., Gong, L., Yang, G., Guichard, J.,
Mishra, G. S., Qin, F., Saad, T., and V. P. Beeram,
"Scalability Considerations for Network Resource
Partition", Work in Progress, Internet-Draft, draft-ietf-
teas-nrp-scalability-02, 2 June 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
nrp-scalability-02>.
[I-D.wdbsp-teas-nrp-yang]
Wu, B., Dhody, D., Beeram, V. P., Saad, T., and S. Peng,
"A YANG Data Model for Network Resource Partitions
(NRPs)", Work in Progress, Internet-Draft, draft-wdbsp-
teas-nrp-yang-02, 28 August 2023,
<https://datatracker.ietf.org/doc/html/draft-wdbsp-teas-
nrp-yang-02>.
[NGMN-NS-Concept]
hao ,, "NGMN NS Concept", 2016,
<https://www.ngmn.org/fileadmin/user_upload/161010_NGMN_Ne
twork_Slicing_framework_v1.0.8.pdf>.
[RFC2211] Wroclawski, J., "Specification of the Controlled-Load
Network Element Service", RFC 2211, DOI 10.17487/RFC2211,
September 1997, <https://www.rfc-editor.org/info/rfc2211>.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
<https://www.rfc-editor.org/info/rfc2475>.
[RFC2702] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J.
McManus, "Requirements for Traffic Engineering Over MPLS",
RFC 2702, DOI 10.17487/RFC2702, September 1999,
<https://www.rfc-editor.org/info/rfc2702>.
[RFC2764] Gleeson, B., Lin, A., Heinanen, J., Armitage, G., and A.
Malis, "A Framework for IP Based Virtual Private
Networks", RFC 2764, DOI 10.17487/RFC2764, February 2000,
<https://www.rfc-editor.org/info/rfc2764>.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>.
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[RFC3931] Lau, J., Ed., Townsley, M., Ed., and I. Goyret, Ed.,
"Layer Two Tunneling Protocol - Version 3 (L2TPv3)",
RFC 3931, DOI 10.17487/RFC3931, March 2005,
<https://www.rfc-editor.org/info/rfc3931>.
[RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
Edge-to-Edge (PWE3) Architecture", RFC 3985,
DOI 10.17487/RFC3985, March 2005,
<https://www.rfc-editor.org/info/rfc3985>.
[RFC4026] Andersson, L. and T. Madsen, "Provider Provisioned Virtual
Private Network (VPN) Terminology", RFC 4026,
DOI 10.17487/RFC4026, March 2005,
<https://www.rfc-editor.org/info/rfc4026>.
[RFC4176] El Mghazli, Y., Ed., Nadeau, T., Boucadair, M., Chan, K.,
and A. Gonguet, "Framework for Layer 3 Virtual Private
Networks (L3VPN) Operations and Management", RFC 4176,
DOI 10.17487/RFC4176, October 2005,
<https://www.rfc-editor.org/info/rfc4176>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <https://www.rfc-editor.org/info/rfc4364>.
[RFC4448] Martini, L., Ed., Rosen, E., El-Aawar, N., and G. Heron,
"Encapsulation Methods for Transport of Ethernet over MPLS
Networks", RFC 4448, DOI 10.17487/RFC4448, April 2006,
<https://www.rfc-editor.org/info/rfc4448>.
[RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration
Guidelines for DiffServ Service Classes", RFC 4594,
DOI 10.17487/RFC4594, August 2006,
<https://www.rfc-editor.org/info/rfc4594>.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
[RFC4664] Andersson, L., Ed. and E. Rosen, Ed., "Framework for Layer
2 Virtual Private Networks (L2VPNs)", RFC 4664,
DOI 10.17487/RFC4664, September 2006,
<https://www.rfc-editor.org/info/rfc4664>.
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[RFC4719] Aggarwal, R., Ed., Townsley, M., Ed., and M. Dos Santos,
Ed., "Transport of Ethernet Frames over Layer 2 Tunneling
Protocol Version 3 (L2TPv3)", RFC 4719,
DOI 10.17487/RFC4719, November 2006,
<https://www.rfc-editor.org/info/rfc4719>.
[RFC5557] Lee, Y., Le Roux, JL., King, D., and E. Oki, "Path
Computation Element Communication Protocol (PCEP)
Requirements and Protocol Extensions in Support of Global
Concurrent Optimization", RFC 5557, DOI 10.17487/RFC5557,
July 2009, <https://www.rfc-editor.org/info/rfc5557>.
[RFC5654] Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M., Ed.,
Sprecher, N., and S. Ueno, "Requirements of an MPLS
Transport Profile", RFC 5654, DOI 10.17487/RFC5654,
September 2009, <https://www.rfc-editor.org/info/rfc5654>.
[RFC7149] Boucadair, M. and C. Jacquenet, "Software-Defined
Networking: A Perspective from within a Service Provider
Environment", RFC 7149, DOI 10.17487/RFC7149, March 2014,
<https://www.rfc-editor.org/info/rfc7149>.
[RFC7209] Sajassi, A., Aggarwal, R., Uttaro, J., Bitar, N.,
Henderickx, W., and A. Isaac, "Requirements for Ethernet
VPN (EVPN)", RFC 7209, DOI 10.17487/RFC7209, May 2014,
<https://www.rfc-editor.org/info/rfc7209>.
[RFC7297] Boucadair, M., Jacquenet, C., and N. Wang, "IP
Connectivity Provisioning Profile (CPP)", RFC 7297,
DOI 10.17487/RFC7297, July 2014,
<https://www.rfc-editor.org/info/rfc7297>.
[RFC7399] Farrel, A. and D. King, "Unanswered Questions in the Path
Computation Element Architecture", RFC 7399,
DOI 10.17487/RFC7399, October 2014,
<https://www.rfc-editor.org/info/rfc7399>.
[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
2015, <https://www.rfc-editor.org/info/rfc7432>.
[RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
Chaining (SFC) Architecture", RFC 7665,
DOI 10.17487/RFC7665, October 2015,
<https://www.rfc-editor.org/info/rfc7665>.
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[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>.
[RFC7926] Farrel, A., Ed., Drake, J., Bitar, N., Swallow, G.,
Ceccarelli, D., and X. Zhang, "Problem Statement and
Architecture for Information Exchange between
Interconnected Traffic-Engineered Networks", BCP 206,
RFC 7926, DOI 10.17487/RFC7926, July 2016,
<https://www.rfc-editor.org/info/rfc7926>.
[RFC8172] Morton, A., "Considerations for Benchmarking Virtual
Network Functions and Their Infrastructure", RFC 8172,
DOI 10.17487/RFC8172, July 2017,
<https://www.rfc-editor.org/info/rfc8172>.
[RFC8299] Wu, Q., Ed., Litkowski, S., Tomotaki, L., and K. Ogaki,
"YANG Data Model for L3VPN Service Delivery", RFC 8299,
DOI 10.17487/RFC8299, January 2018,
<https://www.rfc-editor.org/info/rfc8299>.
[RFC8309] Wu, Q., Liu, W., and A. Farrel, "Service Models
Explained", RFC 8309, DOI 10.17487/RFC8309, January 2018,
<https://www.rfc-editor.org/info/rfc8309>.
[RFC8370] Beeram, V., Ed., Minei, I., Shakir, R., Pacella, D., and
T. Saad, "Techniques to Improve the Scalability of RSVP-TE
Deployments", RFC 8370, DOI 10.17487/RFC8370, May 2018,
<https://www.rfc-editor.org/info/rfc8370>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8403] Geib, R., Ed., Filsfils, C., Pignataro, C., Ed., and N.
Kumar, "A Scalable and Topology-Aware MPLS Data-Plane
Monitoring System", RFC 8403, DOI 10.17487/RFC8403, July
2018, <https://www.rfc-editor.org/info/rfc8403>.
[RFC8453] Ceccarelli, D., Ed. and Y. Lee, Ed., "Framework for
Abstraction and Control of TE Networks (ACTN)", RFC 8453,
DOI 10.17487/RFC8453, August 2018,
<https://www.rfc-editor.org/info/rfc8453>.
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[RFC8466] Wen, B., Fioccola, G., Ed., Xie, C., and L. Jalil, "A YANG
Data Model for Layer 2 Virtual Private Network (L2VPN)
Service Delivery", RFC 8466, DOI 10.17487/RFC8466, October
2018, <https://www.rfc-editor.org/info/rfc8466>.
[RFC8491] Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg,
"Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491,
DOI 10.17487/RFC8491, November 2018,
<https://www.rfc-editor.org/info/rfc8491>.
[RFC8568] Bernardos, CJ., Rahman, A., Zuniga, JC., Contreras, LM.,
Aranda, P., and P. Lynch, "Network Virtualization Research
Challenges", RFC 8568, DOI 10.17487/RFC8568, April 2019,
<https://www.rfc-editor.org/info/rfc8568>.
[RFC8577] Sitaraman, H., Beeram, V., Parikh, T., and T. Saad,
"Signaling RSVP-TE Tunnels on a Shared MPLS Forwarding
Plane", RFC 8577, DOI 10.17487/RFC8577, April 2019,
<https://www.rfc-editor.org/info/rfc8577>.
[RFC8578] Grossman, E., Ed., "Deterministic Networking Use Cases",
RFC 8578, DOI 10.17487/RFC8578, May 2019,
<https://www.rfc-editor.org/info/rfc8578>.
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>.
[RFC8665] Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler,
H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", RFC 8665,
DOI 10.17487/RFC8665, December 2019,
<https://www.rfc-editor.org/info/rfc8665>.
[RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C.,
Bashandy, A., Gredler, H., and B. Decraene, "IS-IS
Extensions for Segment Routing", RFC 8667,
DOI 10.17487/RFC8667, December 2019,
<https://www.rfc-editor.org/info/rfc8667>.
[RFC8939] Varga, B., Ed., Farkas, J., Berger, L., Fedyk, D., and S.
Bryant, "Deterministic Networking (DetNet) Data Plane:
IP", RFC 8939, DOI 10.17487/RFC8939, November 2020,
<https://www.rfc-editor.org/info/rfc8939>.
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[RFC8964] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., Bryant,
S., and J. Korhonen, "Deterministic Networking (DetNet)
Data Plane: MPLS", RFC 8964, DOI 10.17487/RFC8964, January
2021, <https://www.rfc-editor.org/info/rfc8964>.
[RFC9085] Previdi, S., Talaulikar, K., Ed., Filsfils, C., Gredler,
H., and M. Chen, "Border Gateway Protocol - Link State
(BGP-LS) Extensions for Segment Routing", RFC 9085,
DOI 10.17487/RFC9085, August 2021,
<https://www.rfc-editor.org/info/rfc9085>.
[RFC9182] Barguil, S., Gonzalez de Dios, O., Ed., Boucadair, M.,
Ed., Munoz, L., and A. Aguado, "A YANG Network Data Model
for Layer 3 VPNs", RFC 9182, DOI 10.17487/RFC9182,
February 2022, <https://www.rfc-editor.org/info/rfc9182>.
[RFC9232] Song, H., Qin, F., Martinez-Julia, P., Ciavaglia, L., and
A. Wang, "Network Telemetry Framework", RFC 9232,
DOI 10.17487/RFC9232, May 2022,
<https://www.rfc-editor.org/info/rfc9232>.
[RFC9256] Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
A., and P. Mattes, "Segment Routing Policy Architecture",
RFC 9256, DOI 10.17487/RFC9256, July 2022,
<https://www.rfc-editor.org/info/rfc9256>.
[RFC9291] Boucadair, M., Ed., Gonzalez de Dios, O., Ed., Barguil,
S., and L. Munoz, "A YANG Network Data Model for Layer 2
VPNs", RFC 9291, DOI 10.17487/RFC9291, September 2022,
<https://www.rfc-editor.org/info/rfc9291>.
[RFC9408] Boucadair, M., Ed., Gonzalez de Dios, O., Barguil, S., Wu,
Q., and V. Lopez, "A YANG Network Data Model for Service
Attachment Points (SAPs)", RFC 9408, DOI 10.17487/RFC9408,
June 2023, <https://www.rfc-editor.org/info/rfc9408>.
[TS23501] "3GPP TS23.501", 2016,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3144>.
[TS28530] "3GPP TS28.530", 2016,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3273>.
[TSN] "Time-Sensitive Networking", March ,
<https://1.ieee802.org/tsn/>.
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Authors' Addresses
Jie Dong
Huawei
Email: jie.dong@huawei.com
Stewart Bryant
University of Surrey
Email: stewart.bryant@gmail.com
Zhenqiang Li
China Mobile
Email: lizhenqiang@chinamobile.com
Takuya Miyasaka
KDDI Corporation
Email: ta-miyasaka@kddi.com
Young Lee
Samsung
Email: younglee.tx@gmail.com
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