TEAS Working Group
Internet Engineering Task Force (IETF) J. Dong
Internet-Draft
Request for Comments: 9732 Huawei
Intended status:
Category: Informational S. Bryant
Expires: 16 December 2024
ISSN: 2070-1721 University of Surrey
Z. Li
China Mobile
T. Miyasaka
KDDI Corporation
Y. Lee
Samsung
14 June 2024
January 2025
A Framework for Network Resource Partition (NRP) based Based Enhanced Virtual
Private Networks
draft-ietf-teas-enhanced-vpn-20
Abstract
This document describes the framework for enhanced Virtual Private
Networks (VPNs) that are Network Resource Partition (NRP) based Enhanced Virtual Private Networks (VPNs) in
order to support the needs of applications with specific traffic
performance requirements (e.g., low latency, bounded jitter). An NRP
represents a subset of network resources and associated policies in
the underlay network. NRP-based Enhanced enhanced VPNs leverage the VPN and
Traffic Engineering (TE) technologies and add characteristics that
specific services require beyond those provided by conventional VPNs.
Typically, an NRP-based enhanced VPN will be used to underpin network
slicing, but it 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, layers and identifies some areas for potential new work.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 16 December 2024.
https://www.rfc-editor.org/info/rfc9732.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Overview of the Requirements . . . . . . . . . . . . . . . . 7
3.1. Performance Guarantees . . . . . . . . . . . . . . . . . 7
3.2. Interaction between Between Enhanced 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 with Enhanced 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 . . . . . . . . . . 14
3.7. Inter-Domain and Inter-Layer Network . . . . . . . . . . 14
4. The Architecture of NRP-based NRP-Based Enhanced VPNs . . . . . . . . . 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. Underlay Forwarding Resource Partitioning . . . . . . . . 21
5.1.1. Flexible Ethernet . . . . . . . . . . . . . . . . . . 21
5.1.2. Dedicated Queues . . . . . . . . . . . . . . . . . . 21
5.1.3. Time Sensitive Time-Sensitive Networking . . . . . . . . . . . . . . 22
5.2. Network Layer Encapsulation and Forwarding . . . . . . . 22
5.2.1. Deterministic Networking . . . . . . . . . . . . . . 22 (DetNet)
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
5.4. Control Plane . . . . . . . . . . . . . . . . . . . . . . 24
5.5. Management Plane . . . . . . . . . . . . . . . . . . . . 26
5.6. Applicability of Service Data Models to Enhanced VPNs . . 27
6. Applicability in Network Slice Realization . . . . . . . . . 28
6.1. NRP Planning . . . . . . . . . . . . . . . . . . . . . . 28
6.2. NRP Creation . . . . . . . . . . . . . . . . . . . . . . 29
6.3. Network Slice Service Provisioning . . . . . . . . . . . 29
6.4. Network Slice Traffic Steering and Forwarding . . . . . . 29
7. Scalability Considerations . . . . . . . . . . . . . . . . . 30
7.1. Maximum Stack Depth of SR . . . . . . . . . . . . . . . . 31
7.2. RSVP-TE Scalability . . . . . . . . . . . . . . . . . . . 31
7.3. SDN Scaling . . . . . . . . . . . . . . . . . . . . . . . 31
8. Enhanced Resiliency . . . . . . . . . . . . . . . . . . . . . 32
9. Manageability Considerations . . . . . . . . . . . . . . . . 33
9.1. OAM Considerations . . . . . . . . . . . . . . . . . . . 33
9.2. Telemetry Considerations . . . . . . . . . . . . . . . . 34
10. Operational Considerations . . . . . . . . . . . . . . . . . 34
11. Security Considerations . . . . . . . . . . . . . . . . . . . 34
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 35
13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 35
14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 36
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 36
15.1.
13.1. Normative References . . . . . . . . . . . . . . . . . . 36
15.2.
13.2. Informative References . . . . . . . . . . . . . . . . . 37
Acknowledgements
Contributors
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 44
1. Introduction
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, "underlay",
and the VPN is often called an overlay. "overlay".
Customers of a network operator may request connectivity services
with advanced characteristics, such as low latency low-latency guarantees,
bounded jitter, or isolation from other services or customers customers, so
that changes in other services (e.g., changes in network load, or
events such as congestion or outages) have no effect or only
acceptable effects on the observed throughput or latency of the
services delivered to the customer. These services are referred to
as "enhanced VPNs", as they are similar to VPN services services, providing
the customer with the required connectivity, but in addition, they also provide
enhanced characteristics.
This document describes a framework for delivering VPN services with
enhanced characteristics, such as guaranteed resources, latency,
jitter, etc. This list is not exhaustive. It is expected that other
enhanced features may be added to VPN over time, time and it is expected that this
framework will support these additions with necessary changes or
enhancements in some network layers and network planes (data plane,
control plane, and management plane).
The concept of network slicing has gained traction traction, driven largely by
needs surfacing from 5G [NGMN-NS-Concept] [TS23501] [TS28530]. (see [NGMN-NS-Concept], [TS23501], and
[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 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.
[RFC9543] discusses the general framework, components, and interfaces
for requesting and operating network slices using IETF technologies.
These network slices may be referred to as RFC "RFC 9543 Network Slices, Slices",
but in this document (which is solely about IETF technologies) technologies), we
simply use the term "network slice" to refer to this concept. A
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. A 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
SLOs
SLO and SLEs SLE requirements. A network slice is considered as to be one
target use case of enhanced VPNs.
[RFC9543] 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.
The requirements of enhanced VPN services cannot simply be met by
overlay networks, as networks: enhanced VPN services require tighter coordination
and integration between the overlay and the underlay networks.
In the overlay network, the 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, the NRP is used to
represent a subset of the network resources and associated policies
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.
An enhanced VPN service can be realized by integrating a VPN in the
overlay and an NRP in the underlay. This is called an NRP-based "NRP-based
enhanced VPN. VPN". In doing so, an enhanced VPN service can provide
enhanced properties, such as guaranteed resources and assured or
predictable performance. An enhanced VPN service may also involve a
set of service functions (see Section 1.4 of [RFC7665] for the
definition of service function). The techniques for delivering an
NRP-based enhanced VPN can be used to instantiate a network slice
service (as described in Section 6), and they can also be of use in
general cases to provide enhanced connectivity services between
customer sites or service endpoints.
This document describes a framework for using existing, modified, and
potential new technologies as components to provide NRP-based
enhanced VPN services. Specifically, this document provides:
* The functional requirements and service characteristics of an
enhanced VPN service.
* The design of the data plane for NRP-based enhanced VPNs.
* The necessary control and management protocols in both the
underlay and the overlay of enhanced VPNs.
* The mechanisms to achieve integration between the overlay network
and the underlay network.
* The necessary Operation, Administration, and Management (OAM)
methods to instrument an enhanced VPN to make sure that the
required Service Level Agreement (SLA) between the customer and
the network operator is met, met and to take any corrective action
(such as switching traffic to an alternate path) to avoid SLA
violation.
One possible layered network structure to achieve these objectives is
shown in Section 4.1.
It is not envisaged that enhanced VPN services will replace
conventional VPN services. VPN services will continue to be
delivered using existing mechanisms and can co-exist coexist with enhanced VPN
services. Whether enhanced VPN features are added to an active VPN
service is deployment-specific. deployment specific.
2. Terminology
In this document, the relationship of the four terms "VPN", "enhanced
VPN", "NRP", and "Network Slice" are as follows:
* A Virtual Private Network (VPN) refers to the overlay network
service that provides connectivity between different customer
sites,
sites and that maintains traffic separation between different
customers. Examples of technologies to provide VPN services are: are
as follows: IPVPN [RFC2764], L2VPN [RFC4664], L3VPN [RFC4364], and
EVPN [RFC7432].
* An enhanced VPN service is an evolution of the VPN service that
makes additional service-specific commitments. An NRP-based
enhanced VPN is made by integrating a VPN with a set of network
resources allocated in the underlay network (i.e. (i.e., an NRP).
* A Network Resource Partition (NRP) (NRP), as defined in [RFC9543] [RFC9543], 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. An NRP is designed to meet the network resources and
performance characteristics required by the enhanced VPN services.
* A network slice service could be delivered by provisioning one or
more NRP-based enhanced VPNs in the network. Other mechanisms for
realizing network slices may exist but are not in the scope of
this document.
The term "tenant" is used in this document to refer to a customer of
the enhanced VPN services.
The following terms, defined in other documents, are also used in
this document.
SLA: Service Level Agreement. See [RFC9543]. Agreement (see [RFC9543])
SLO: Service Level Objective. See [RFC9543]. Objective (see [RFC9543])
SLE: Service Level Expectation. See [RFC9543]. Expectation (see [RFC9543])
ACTN: Abstraction and Control of Traffic Engineered TE Networks
[RFC8453]. (see [RFC8453])
DetNet: Deterministic Networking. See [RFC8655]. Networking (see [RFC8655])
FlexE: Flexible Ethernet [FLEXE]. (see [FLEXE])
TSN: Time Sensitive Time-Sensitive Networking [TSN]. (see [TSN])
VN: Virtual Network. See [RFC8453]. Network (see [RFC8453])
3. Overview of the Requirements
This section provides an overview of the requirements of an enhanced
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, queue sizes, and discard policies. 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
augmented reality and virtual reality (AR/VR) applications. DetNet
techniques may be considered [RFC8655], however [RFC8655]; however, additional methods
of enhancing the underlay to better support the delay guarantees may
be
needed, and these needed. These methods will need to be integrated with the overall
service provisioning mechanisms.
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 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
enhanced VPNs. Alternatively, a dedicated enhanced VPN might be used
to provide time transfer as a shared service.
This suggests that a spectrum of service guarantees needs to be
considered when designing and deploying an enhanced 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 services may have mixed requirements from this
list, e.g., both assured bandwidth and guaranteed latency can be
required.
The best effort 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 best-effort service with over-
capacity provisioning, provisioning or it can be based on MPLS traffic engineered
label switching paths (TE-LSPs) TE 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 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. Enhanced VPNs aim 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, guarantee:
* the IEEE TSN project [TSN] introduces the concept of scheduling of delay-
delay-sensitive and 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 the network layer.
The use of these technologies to deliver enhanced 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 enhanced
VPN services.
3.2. Interaction between Between Enhanced VPN Services
There is a fine distinction between how a customer requests limits on
interaction between an enhanced VPN service and other services
(whether they are other enhanced VPN services or any other network
service),
service) and how that is delivered by the service provider. This
section examines the requirements and realization of limited
interaction between an enhanced VPN service and other services.
3.2.1. Requirements on Traffic Isolation
Traffic isolation
"Traffic isolation" is a generic term that can be used to describe
the requirements for 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 [RFC9543]), 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 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].
There can be different expectations of traffic isolation. For
example, a customer may further request the protection of their
traffic by requesting specific encryption schemes at the enhanced VPN
network
access and also when transported between Provider Edge (PE)
Nodes. nodes.
An enhanced VPN service customer may request traffic isolation
together with other operator defined operator-defined service characteristics. The
exact details about the expected behavior need to be specified in the
service request, 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 service-modeling considerations.
3.2.2. Limited Interaction with Other Services
[RFC2211] describes the Controlled Load Service. 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 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. 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.
An enhanced VPN customer may request a Controlled Load Service 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 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 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.
Limited interaction between enhanced VPN services does not cover
service degradation due to non-interaction-related causes, such as
link errors.
3.2.3. Realization of Limited Interaction with Enhanced 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 that can be used to
provide traffic isolation, such as IP and MPLS VPNs or other multi-
tenant virtual network techniques. Controlled Load Services 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
resources, etc., so that a subset of bandwidth, buffers, and queueing
resources can be available in the underlay network to support the
enhanced VPN services.
To provide the required traffic isolation, or to reduce the
interaction with other enhanced VPN services, network resources may
need to be reserved in the data plane of the underlay network and
dedicated to traffic from a specific enhanced VPN service or a
specific group of enhanced VPN services. This may introduce
scalability concerns both in the implementation (as each enhanced 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 an
enhanced VPN services service and other 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, an enhanced VPN
offers a variety of means to honor customer's requirements.
3.3. Integration with Network Resources and Service Functions
The way to achieve the characteristics demand of an enhanced 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 that 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
enhanced VPN services.
Taking mobile networks and and, in particular particular, 5G into consideration, the
integration of the network with service functions is likely a
requirement. The IETF's work on service function chaining Service Function Chaining (SFC)
[RFC7665] provides a foundation for this. Service functions in the
underlay network can be considered as to be part of the enhanced VPN
services, which means the service functions may need to be an
integral part of the corresponding NRP. The details of the
integration between service functions and enhanced VPNs 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, an enhanced VPN may be built on top
of an abstracted topology that represents the connectivity
capabilities of the underlay TE based 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
Enhanced VPNs need to be created, modified, and removed from the
network according to service demands (including scheduled requests).
An enhanced VPN that requires limited interaction with other services
(Section 3.2.2) must not be disrupted by the instantiation or
modification of another enhanced 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 an enhanced VPN can be disruptive to that enhanced VPN and whether
the traffic in flight will be disrupted can be a difficult problem.
Dynamic changes both to the enhanced 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 without disruption during changes
such as the inclusion of a new enhanced VPN service endpoint or a
change to a link, enhanced VPN traffic might need to be moved because
of changes to traffic patterns and volumes. volume. This means that during
the lifetime of an enhanced 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
Sections 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 enhanced VPN services are delivered to customers
without information about the underlying NRPs. However, in some
cases, 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 NRPs. Such information can be filtered or
aggregated according to the operator's policy. This allows the
customer of an enhanced VPN service to have some visibility and even
control over how the underlying topology and resources of the NRP are
used. For example, the customers customer may be able to specify the path or
path constraints within the NRP for specific traffic flows of their
enhanced VPN service. Depending on the requirements, an enhanced 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 enhanced 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 an enhanced VPN can be applied to any existing and
future multi-tenancy overlay technologies including but not limited
to:
* Layer-2 Layer 2 point-to-point (P2P) services, such as pseudowires [RFC3985] (see
[RFC3985])
* Layer-2 Layer 2 VPNs [RFC4664] (see [RFC4664])
* Ethernet VPNs [RFC7209], [RFC7432] (see [RFC7209] and [RFC7432])
* Layer-3 Layer 3 VPNs [RFC4364], [RFC2764] (see [RFC4364] and [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, an enhanced 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 enhanced VPN services are
provisioned in such network scenarios, the technologies used in
different network planes (data (the data plane, control plane, and
management plane) need to provide mechanisms to support multi-domain
and multi-
layer multi-layer coordination and integration, so as integration; this is to provide the
required service characteristics for different enhanced VPN services, services
and improve network efficiency and operational simplicity. The
mechanisms for multi-domain VPNs [RFC4364] (see [RFC4364]) may be reused, and
some enhancement may be needed to meet the additional requirements of
enhanced VPN services.
4. The Architecture of NRP-based NRP-Based Enhanced VPNs
Multiple NRP-based enhanced VPN services can be provided by a common
network infrastructure. Each NRP-based enhanced VPN service is
provisioned with an overlay VPN and mapped to a corresponding NRP,
which has a specific set of network resources and service functions
allocated in the underlay to satisfy the needs of the customer. One
NRP may support one or more NRP-based enhanced VPN services. The
integration between the overlay connectivity and the underlay
resources ensures the required isolation between different enhanced
VPN services, services and achieves the guaranteed performance for different
customers.
The NRP-based enhanced VPN architecture needs to be designed with
consideration given to:
* An enhanced data plane.
* A control plane to create enhanced VPNs and NRPs, making use of
the data plane isolation and performance guarantee techniques.
* A management plane for to manage enhanced VPN service life-cycle management. life cycles.
* The OAM mechanisms for enhanced VPNs and the underlying NRPs.
* Telemetry mechanisms for enhanced VPNs and the underlying NRPs.
These topics are expanded below.
* The enhanced data plane provides:
- The required packet latency packet-latency and jitter characteristics.
- The required packet loss packet-loss characteristics.
- The required resource isolation resource-isolation capability, e.g., bandwidth
guarantee.
- The mechanism to associate a packet with the set of resources
allocated to an NRP to which the enhanced VPN service packet is
mapped to.
mapped.
* The control plane:
- Collects information about the underlying network topology and
network resources, resources and exports this to network nodes and/or a
centralized controller as required.
- Creates NRPs with the network resource and topology properties
needed by the enhanced VPN services.
- Distributes the attributes of NRPs to network nodes which that
participate in the NRPs and/or a centralized controller.
- Computes and sets up network paths in each NRP.
- Maps enhanced VPN services to an appropriate NRP.
- Determines the risk of SLA violation and takes appropriate
avoiding/correction
avoidance/correction actions.
- Considers the right balance of per-packet and per-node state
according to the needs of the enhanced VPN services to scale to
the required size.
* The management plane includes management interfaces, the
Operations, Administration, and Maintenance (OAM) and Telemetry telemetry
mechanisms. More specifically, it provides:
- An interface between the enhanced VPN service provider (e.g.,
the operator's network management system) and the enhanced VPN
customer (e.g., an organization or a service with an enhanced VPN
requirement) such that the operation requests and the related
parameters can be exchanged without the awareness of other
enhanced VPN customers.
- An interface between the enhanced VPN service provider and the
enhanced VPN customers to expose the network capability
information toward the customer.
- The service life-cycle management and operation of enhanced VPN
services (e.g., creation, modification, assurance/monitoring,
and decommissioning).
- The OAM tools to verify whether the underlay network resources
(i.e.
(i.e., NRPs) are correctly allocated and operating properly.
- The OAM tools to verify the connectivity and monitor the
performance of the enhanced VPN service.
- Telemetry of information in the underlay network for overall
performance evaluation and the planning of the enhanced VPN
services.
- Telemetry of information of enhanced VPN services for
monitoring and analytics of the characteristics and SLA
fulfillment of the enhanced VPN services.
4.1. Layered Architecture
The layered architecture of NRP-based enhanced VPNs is shown in
Figure 1.
Underpinning everything is the physical network infrastructure layer layer,
which provides the underlying resources used to provision the
separate NRPs. This layer is responsible for the partitioning of
link and/or node resources for different NRPs. Each subset of a link
or node resource can be considered as to be a virtual link or virtual
node used to build the NRPs.
/\
||
+-------------------+ Centralized
| Network Controller| Control & Management
+-------------------+
||
\/
o---------------------------o Enhanced VPN #1
/-------------o
o____________/______________o Enhanced VPN #2
_________________o
_____/
o___/ \_________________o Enhanced VPN #3
\_______________________o
...... ...
o-----------\ /-------------o
o____________X______________o Enhanced VPN #n
__________________________
/ o----o-----o /
/ / / / NRP-1
/ o-----o-----o----o----o /
/_________________________/
__________________________
/ o----o /
/ / / \ / NRP-2
/ o-----o----o---o------o /
/_________________________/
...... ...
___________________________
/ o----o /
/ / / / NRP-m
/ o-----o----o----o-----o /
/__________________________/
++++ ++++ ++++
+--+===+--+===+--+
+--+===+--+===+--+
++++ +++\\ ++++
|| || \\ || Physical
|| || \\ || Network
++++ ++++ ++++ \\+++ ++++ Infrastructure
+--+===+--+===+--+===+--+===+--+
+--+===+--+===+--+===+--+===+--+
++++ ++++ ++++ ++++ ++++
o Virtual Node ++++
+--+ Physical Node with resource partition
-- Virtual Link +--+
++++
== Physical Link with resource partition
Figure 1: The Layered Architecture of Enhanced VPNs
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 NRPs can be created, each
with created. Each
of these NRPs:
* has 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, topology so as
to meet the requirements of different enhanced VPN services or
different groups of enhanced VPN services.
According to the associated logical network topology, each NRP needs
to be instantiated on a set of network nodes and links
which that are
involved in the logical topology. And on On each node or link, each NRP is
associated with a set of local resources which that are allocated for the
processing of traffic in the NRP. The NRP provides the integration
between the logical network topology and the required underlying
network resources.
According to the service requirements of connectivity, performance
and performance,
isolation, etc., enhanced VPN services can be mapped to the
appropriate NRPs in the network. Different enhanced VPN services can
be mapped to different NRPs, while NRPs; it is also possible that multiple
enhanced VPN services are mapped to the same NRP. Thus, the NRP is
an essential scaling technique, technique as it has the potential of eliminating
per-service per-path state from the network. In addition, when a
group of enhanced VPN services are is mapped to a single NRP, only the
network state of the single NRP needs to be maintained in the network
(see Section 4.4 for more information).
The network controller is responsible for creating an NRP,
instructing the involved network nodes to allocate network resources
to the NRP, and provisioning the enhanced VPN services on the NRP. A
distributed control plane may be used for distributing the NRP
resource and topology attributes among nodes in the NRP. Extensions
to distributed control protocols (if any) are out of the scope of
this document.
The process used to create NRPs and to allocate network resources for
use by the NRPs 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 an NRP NRP, these resources can, if
required, can be managed
via a dynamic control plane. plane if required. 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 a Multipoint-
to-Multipoint (MP2MP) VPN service is usually full or partial mesh.
To support such VPN services, the corresponding NRP also needs to
provide MP2MP connectivity among the end points. endpoints.
Other service requirements may be expressed at different
granularities, some of which can be applicable to the whole service, service
while some others may only be applicable to some pairs of end points. endpoints. For
example, when a particular level of performance guarantee is
required, the point-to-point path through the underlying NRP of the
enhanced 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 enhanced VPN
will likely be IP-based, 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 an
enhanced VPN encapsulated according to the method specified in
[RFC4448]. Where the underlay is IP, Layer Two L2 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 L2 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.
An enhanced VPN may need to install some additional state within the
network to achieve the features that they require. Solutions need to
take the scale of such state into consideration, and deployment
architectures should constrain the number of enhanced VPN services so
that the additional state introduced to the network is acceptable and
under control. It is expected that the number of enhanced VPN
services will be small at the beginning, and beginning: even in the future future, the
number of enhanced 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 enhanced VPN services. It
will usually be possible to aggregate a set or group of enhanced VPN
services so that they share the same NRP and the same set of network
resources (much in the same way that current VPNs are aggregated over
transport tunnels) so that collections of enhanced 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 NRP-based enhanced VPN deployments.
[I-D.ietf-teas-nrp-scalability]
[NRP-SCALABILITY] provides more details of scalability considerations
for the NRPs used to instantiate NRPs, 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 a 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, protocol or directly through
the use of an SDN a Software-Defined Networking (SDN) controller. Based on
Segment
Routing, Routing (SR), state could be maintained at the ingress node
of the path, 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 enhanced
VPN service, this state is likely to increase further. Through the
use of NRP, a subset of underlay network resource resources can be either
dedicated for a particular enhanced VPN service or shared among a
group of enhanced VPN services. A group of underlay paths can be
established using the common set of network resources of the NRP.
This section describes the candidate technologies, technologies and examines them
in the context of the different network planes that may be used
together to build NRPs. Section 5.1 discusses the layer-2 packet-
based L2 packet-based or
frame-based forwarding plane forwarding-plane mechanisms for resource partitioning.
Section 5.2 discusses the corresponding encapsulation and forwarding
mechanisms in the network layer. Non-packet data plane mechanisms
are briefly discussed in Section 5.3. The control plane and
management plane mechanisms are discussed in Section Sections 5.4 and Section 5.5 5.5,
respectively.
5.1. Underlay Forwarding Resource Partitioning
Several candidate layer-2 L2 packet-based or frame-based forwarding
plane forwarding-plane
mechanisms which that 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 enhanced 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 In
turn, this 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 Thus, 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
Diffserv-based queuing systems are described in [RFC2475] and
[RFC4594]. This approach is not sufficient to provide separation of
enhanced VPN services because DiffServ Diffserv does not provide enough
markers to differentiate between traffic of a large number of
enhanced VPN services. Additionally, DiffServ Diffserv does not offer the
range of service classes that each enhanced VPN service needs to
provide to its tenants. This problem is particularly acute with an
MPLS underlay, underlay because MPLS only provides eight traffic classes.
In addition, DiffServ, 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 enhanced VPN
services.
To address these problems and to reduce the potential interactions
between enhanced VPN services, it would be necessary to steer traffic
to dedicated input and output queues per enhanced VPN service or per
group of enhanced VPN services: some routers have a large number of
queues and sophisticated queuing systems which that could support this, this
while some routers may struggle to provide the granularity and level
of separation required by the applications of an enhanced VPN.
5.1.3. Time Sensitive Networking Time-Sensitive Networking (TSN)
[TSN] is an IEEE project to provide a method of carrying time-sensitive 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 will experience no queuing delay or increase in
latency beyond the a very small scheduling delay. The mechanisms defined
in TSN can be used to meet the requirements of time-sensitive traffic
flows of enhanced VPN service.
Ethernet can be emulated over a layer-3 L3 network using an IP or MPLS
pseudowire. However, a TSN Ethernet payload would be opaque to the
underlay and thus
underlay; thus, it would not be treated specifically as time-sensitive time-
sensitive data. The preferred method of carrying TSN over a layer-3 L3
network is through the use of deterministic networking as explained
in Section 5.2.1.
5.2. Network Layer Encapsulation and Forwarding
This section considers the problem of enhanced 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 an NRP.
5.2.1. Deterministic Networking
Deterministic Networking (DetNet)
DetNet [RFC8655] is a technique being developed in the IETF to
enhance the ability of layer-3 L3 networks to deliver packets more reliably
and with greater control over the delay. The design cannot use re-transmission
retransmission techniques such as TCP
since because that can exceed the
delay tolerated by the applications. DetNet preemptively 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 the IP data plane [RFC8939] or the MPLS data plane
[RFC8964], and it may be used to provide deterministic paths for
enhanced VPN services.
5.2.2. MPLS Traffic Engineering (MPLS-TE)
MPLS-TE [RFC2702][RFC3209] (see [RFC2702] and [RFC3209]) introduces the concept of
reserving end-
to-end end-to-end bandwidth for a TE-LSP, which can be used to
provide a set of point-to-point resource reserved resource-reserved paths across the
underlay network to support VPN services. VPN traffic can be carried
over dedicated TE-
LSPs TE-LSPs to provide guaranteed 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 headend of a path. These instructions are used to
specify the nodes and links to be traversed, and they 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 the MPLS data plane
(SR-MPLS)
[RFC8660] (see [RFC8660]) or the IPv6 data plane (SRv6) [RFC8986]. (see
[RFC8986]).
An SR traffic engineered path operates with a the 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 enhanced 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. One approach to do this is described
in [I-D.ietf-spring-resource-aware-segments]. [RESOURCE-AWARE-SEGMENTS].
Note that the concept of a queue is a useful abstraction for
different types of underlay mechanism mechanisms 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
L3 data plane and control plane mechanisms used.
With Segment Routing, the SR instruction list could be used to build
a P2P SR path. In addition, a group of SR Segment Identifiers (SIDs)
could also be used to represent an MP2MP network. Thus, the SR based SR-based
mechanism could be used to provide both resource reserved resource-reserved paths and
NRPs for enhanced VPN services.
5.2.4. New Encapsulation Extensions
In contrast to reusing an existing data plane for enhanced VPN,
another possible approach is to introduce new encapsulations or
extensions to an existing data plane to allow dedicated identifiers
for the underlay network resources of an enhanced VPN, VPN and the logical
network topology or paths associated with an enhanced VPN. This may
require more protocol work, while work; however, the potential benefit is benefits are that
it can reduce the impact to existing network operation and improve
the scalability of enhanced VPN. More details about the
encapsulation extensions and the scalability concerns are described
in
[I-D.ietf-teas-nrp-scalability]. [NRP-SCALABILITY].
5.3. Non-Packet Data Plane
Non-packet underlay data plane technologies, such as optical based optical-based
data planes planes, often have TE properties and behaviors, and behaviors. They meet many
of the key requirements in particular for requirements, particularly those 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 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 an NRP built with this data plane is used to support
multiple enhanced VPN services, the cost could be distributed among
such a group of services.
5.4. Control Plane
The control plane of NRP-based enhanced VPNs is likely to be based on
a hybrid control mechanism that takes advantage of a logically
centralized controller for on-demand provisioning and global
optimization, whilst Global
Concurrent Optimization (GCO) while 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 an NRP-based enhanced
VPN.
As described in Section 4, the enhanced VPN control plane needs to
provide the following functions:
* Collect Collection of information about the underlying network topology
and network resources, resources and exports exportation of this to network nodes
and/or a centralized controller as required.
* Create Creation of NRPs with the network resource and topology properties
needed by NRP-based enhanced VPN services.
* Distribute Distribution of the attributes of NRPs to network nodes which that
participate in the NRPs and/or the centralized controller.
* Map Mapping of enhanced VPN services to an appropriate NRP.
* Compute Computation and set up of service paths in each NRP to meet
enhanced VPN service requirements.
The collection of underlying
Underlying network topology and resource information can be done collected
using mechanisms based on the existing IGP and Border Gateway
Protocol - Link State (BGP-LS) [RFC9552] based mechanisms. [RFC9552]. The creation of NRPs and
the distribution of NRP attributes may need further control protocol
extensions. The computation of service paths based on the attributes
and constraints of the NRP can be performed either by the headend
node of the path or by a centralized Path Computation Element (PCE)
[RFC4655].
Two candidate control plane mechanisms for path setup in the NRP are: are
RSVP-TE and Segment Routing (SR).
* RSVP-TE [RFC3209] RSVP-TE, as described in [RFC3209], provides the signaling
mechanism for establishing a TE-LSP in an MPLS network with end-to-end end-
to-end resource reservation. This can be seen as an approach of
providing resource-reserved paths which that could be used to bind the
VPN to a specific set of network resources allocated within the underlay,
but
underlay; however, there remain scalability concerns concerns, as mentioned
in Section 5.2.2.
* The SR control plane [RFC8665] [RFC8667] [RFC9085] plane, as described in [RFC8665], [RFC8667], and
[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 NRPs without requiring per-path state to be maintained in
the network. A centralized controller can perform resource
planning and reservation for NRPs, and it needs to instruct the
network nodes to ensure that resources are correctly allocated for
the NRP. 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 performance,
and isolation, one enhanced VPN service may be mapped to a dedicated
NRP,
NRP or a group of enhanced VPN services may be mapped to the same
NRP. The mapping of enhanced VPN services to an NRP can be achieved
using existing control mechanisms with possible extensions, and extensions; it can be
based on either the characteristics of the data packet or the
attributes of the VPN service routes.
5.5. Management Plane
The management plane provides the interface between the enhanced VPN
service provider and the customers for life-cycle management of the
enhanced 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
the enhanced 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 enhanced 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 enhanced VPN
services can be based on the service models described in Section 5.6.
It is important that the management life-cycle supports management support in-place
modification of enhanced VPN services. That is, it should be
possible to add and remove end points, endpoints, 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 enhanced VPN
requests and determine whether they can be provided by the existing
NRPs or whether changes must be made, and it made. It will additionally also need to determine
whether those changes to the NRP are possible. If not, then the
customer's modification request may be rejected.
When the modification of an enhanced 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 enhanced VPN
service or the underlying NRP must not perturb traffic on the
enhanced VPN service in a way that causes the service level to drop
below the agreed levels. Furthermore, changes to one enhanced VPN
service should not cause disruption to other enhanced VPN services.
The network operator for the underlay network (i.e., the provider of
the enhanced VPN service) may delegate some operational aspects of
the overlay VPN and the underlying NRP to the customer. In this way,
the enhanced 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 are needed, needed so that that:
* a customer cannot exceed the capabilities of the virtual links and
nodes, but
* it 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, 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 NRP 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 Enhanced VPNs
This section describes the applicability of the existing and in-
progress service data models to enhanced VPNs. [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 enhanced VPNs. The VPN
customer service models (e.g., the Layer 3 VPN L3VPN Service Model (L3SM) in
[RFC8299], the Layer 2 VPN L2VPN Service Model (L2SM) in [RFC8466]), or the ACTN
Virtual Network (VN) model [I-D.ietf-teas-actn-vn-yang]) in [RFC9731]) are service models which that can
provide the customer's view of the enhanced VPN service. The Layer-3 VPN L3VPN
Network Model (L3NM) [RFC9182], from [RFC9182] and the
Layer-2 VPN network model L2VPN Network Model
(L2NM) from [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 in [RFC9408]
provides an abstract view of the service attachment points Service Attachment Points (SAPs) to
various network services in the provider network, where enhanced VPN
could be one of the service types. [RFC9375] provides the data model
for performance monitoring of network and VPN services. Augmentation
to these service models may be needed to provide the enhanced VPN
services. The NRP model
[I-D.ietf-teas-nrp-yang] in [NRP-YANG] further provides the
management of the NRP topology and resources both in the controller
and in the network devices to instantiate the NRPs needed for the
enhanced VPN services.
6. Applicability in Network Slice Realization
This section describes the applicability of NRP-based enhanced VPN
for network slice realization.
In order to provide network slice services to customers, a
technology-agnostic network slice service model
[I-D.ietf-teas-ietf-network-slice-nbi-yang] [NETWORK-SLICE-YANG]
is needed for the customers to communicate the requirements of
network slices (SDPs, connectivity, SLOs, and SLEs). These
requirements may be realized using technology specified in this
document to instruct the network to deliver an enhanced VPN service
so as to meet the requirements of the network slice customers.
According to the location of SDPs used for the network slice service
(see Section 5.2 of [RFC9543]), an SDP can be mapped to a CE, Customer
Edge (CE), a PE, a port on a CE, or a customer-facing port on a PE,
any of which can be correlated to the end point endpoint of the enhanced VPN
service. The detailed approach for SDP mapping is described in [I-D.ietf-teas-ietf-network-slice-nbi-yang].
[NETWORK-SLICE-YANG].
6.1. NRP Planning
An NRP is used to support the SLOs and SLEs required by 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. 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
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
allocate the required set of network resources for the NRP. One or
multiple mechanisms as specified in section Section 5.1 can be used to
partition the forwarding plane forwarding-plane network resources and allocate
different subsets of resources to different NRPs. In addition, the
data plane identifiers which that 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 using, e.g., resource-
aware SR segments as specified in
[I-D.ietf-spring-resource-aware-segments]
[I-D.ietf-spring-sr-for-enhanced-vpn], [RESOURCE-AWARE-SEGMENTS] and
[SR-ENHANCED-VPN] or a dedicated Resource ID as specified in [I-D.ietf-6man-enhanced-vpn-vtn-id]
[IPv6-NRP-OPTION] can be introduced. The network nodes involved in
an NRP may distribute the logical topology information, the NRP-specific NRP-
specific network resource information information, and the Resource Identifier ID of the NRP
using the control plane. Such information could be used by the
controller and the network nodes to compute the TE or shortest paths
within the NRP, NRP and to install the NRP
specific NRP-specific forwarding entries to
network nodes.
6.3. Network Slice Service Provisioning
According to the connectivity requirements of an a 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
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 provides a network slice service.
6.4. Network Slice Traffic Steering and Forwarding
At the edge of the operator's network, traffic of network slices slice traffic can be
classified based on the rules defined by the operator's policy, policy; this
is so that the traffic which that matches the rules for specific network
slice services can be mapped to the corresponding NRP. This way, Thus, packets
belonging to a specific network slice service will be processed and
forwarded by network nodes based either on either:
* the traffic-engineered paths or
* the shortest paths in the associated network topology, topology
using the set of network resources of the corresponding NRP.
7. Scalability Considerations
NRP-based enhanced VPNs provide performance guaranteed services in
packet networks, but networks; however, this comes 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: added:
* Introduce by introducing 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 A further cost is also that systems will have to
provide NRP specific NRP-specific segments in case they are called upon by a
service. This is a type of latent state, and it increases as the
segments and resources that need to be exclusively available to
enhanced VPN service are specified more precisely.
* Introduce by introducing 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 example, explicitly specifying queuing policy. It
is also possible to use other methods to introduce path state,
such as via an SDN controller, controller or possibly by modifying a routing
protocol. With this approach approach, there is state per path: a 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 by providing a hybrid approach. One example is based on using
binding SIDs [RFC8402] (see [RFC8402]) to represent path fragments, fragments and bind
binding 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. For SRv6, the packet size may also
be reduced by utilizing the compression techniques as specified in
[I-D.ietf-spring-srv6-srh-compression].
[SRv6-SRH-COMPRESSION].
Reducing the state in the network is important to enhanced VPNs, 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 fine-granularity processing would need to be
loaded and maintained in the routers. Aggregation is a
well-established well-
established approach to reduce the amount of state and improve
scaling, and NRP is considered as to be the network construct to
aggregate the states of enhanced VPN services. In addition, an SR
approach allows much of the state to be spread amongst the network
ingress
nodes, 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 constructs of NRP-based
enhanced VPNs can be found in [I-D.ietf-teas-nrp-scalability]. [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
between:
* adding state to the network and minimizing stack depth, or depth and
* minimizing state and increasing the stack depth.
7.2. RSVP-TE Scalability
The established method of creating a resource-reserved 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].
There is also concern at the scalability of the forwarder footprint
of RSVP-TE as the number of paths through a label switching router 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 control plane state to be
stored in the network, but can reduce the overhead of control
channels to be maintained. Each individual network node may need to
maintain a control channel with an SDN controller, which is
considered more scalable comparing compared to the need of maintaining control
channels with a set of neighbor nodes.
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, 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. Enhanced Resiliency
Each enhanced VPN service has a life cycle, cycle and may need modification
during deployment as the needs of its tenant change. This is
discussed in change (see
Section 5.5. 5.5). Additionally, as the network evolves,
there garbage
collection may need to perform garbage collection be performed 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, applications because it is
possible to perform an atomic transition from one path to another.
That is, a single action by the head-end headend 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 GCO
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,
However, there are two manifestations of the latency problem that are
for further study in any of these approaches:
* The problem of packets Packets overtaking one another if a path latency reduces during a
transition.
* The problem of transient 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 50 ms [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 replications and the
culling of later packets [RFC8655].
In addition to the approach used to protect high priority high-priority packets,
consideration should be given to the impact of best effort best-effort traffic on
the high priority high-priority packets during a transition. Specifically, if a
conventional re-convergence process is used used, there will inevitably be
micro-loops and whilst and, while some form of explicit routing will protect the
high priority
high-priority traffic, lower priority lower-priority traffic on best effort best-effort shortest
paths will micro-loop without the use of a loop prevention loop-prevention
technology. To provide the highest quality of service to high high-
priority traffic, either this traffic must be shielded from the
micro-loops,
micro-loops or micro-loops must be prevented completely.
9. Manageability Considerations
This section describes the considerations about the OAM and Telemetry telemetry
mechanisms used to support the verification, monitoring monitoring, and
optimization of the characteristics and SLA fulfillment of NRP-based
enhanced VPN services. It should be read along with Section 5.5 that 5.5,
which gives consideration of to the management plane techniques that can
be used to build NRPs.
9.1. OAM Considerations
The design of OAM for enhanced VPN services needs to consider the
following requirements:
* Instrumentation of the NRP (the virtual underlay) so that the
network operator can be sure that the resources committed to a
customer are operating correctly and delivering the required
performance. It is important that the OAM packets follow the same
path and the set of resources as the service packets mapped to the
NRP.
* 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].
9.2. Telemetry Considerations
Network visibility is essential for network operation. Network
telemetry has been considered as to be 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 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.
Telemetry for enhanced VPN service needs to consider the following
requirements:
* Collecting data of NRPs for overall performance evaluation and the
planning of the enhanced VPN services.
* Collecting data of each enhanced VPN service for monitoring and
analytics of the service characteristics and SLA fulfillment.
How the telemetry mechanisms could be used or extended for enhanced
VPN services is out of the scope of this document.
10. Operational Considerations
It is expected that NRP-based enhanced VPN services will be
introduced in networks which that already have conventional VPN services
deployed. Depending on service requirements, the tenants or the
operator may choose to use a VPN or an enhanced 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. The management interface and data models as
(as described in Section 5.6 5.6) can be used for the life-cycle
management of enhanced VPN services, such as service creation,
modification, performance monitoring monitoring, and decommissioning.
11. Security Considerations
All types of virtual network networks 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
endpoints outside that VPN. In this regard regard, the enhanced VPN neither
introduces,
introduces nor experiences greater security risks than other VPNs.
However, in an enhanced VPN service service, the additional service
requirements need to be considered. For example, if a service
requires a specific upper bound to latency 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
respects, this makes the enhanced VPN more susceptible to attacks
since the SLA may be broken. But another Another view is that the operator must,
in any case, preform monitoring of the enhanced VPN to ensure that
the SLA is met, and this means that met; thus, the operator may be more likely to spot the
early onset of a security attack and be able to take preemptive
protective action.
The measures to address these dynamic security risks must be
specified as part of the specific solution to the isolation
requirements of an enhanced VPN service.
While an enhanced 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
themselves, possibly by encrypting traffic before handing it off to
the service provider.
The privacy of enhanced VPN service customers must be preserved. It
should not be possible for one customer to discover the existence of
another customer, customer nor should the sites that are members of an enhanced
VPN be externally visible.
An enhanced 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
This document has no requested IANA actions.
13. Contributors
Daniel King
Email: daniel@olddog.co.uk
Adrian Farrel
Email: adrian@olddog.co.uk
Jeff Tantsura
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.ietf@gmail.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. References
15.1.
13.1. Normative References
[RFC9543] Farrel, A., Ed., Drake, J., Ed., Rokui, R., Homma, S.,
Makhijani, K., Contreras, L., and J. Tantsura, "A
Framework for Network Slices in Networks Built from IETF
Technologies", RFC 9543, DOI 10.17487/RFC9543, March 2024,
<https://www.rfc-editor.org/info/rfc9543>.
15.2.
13.2. Informative References
[FLEXE] Optical Internetworking Forum, "Flex Ethernet
Implementation Agreement", IA # OIF-FLEXE-01.0, March
2016,
<https://www.oiforum.com/wp-content/uploads/2019/01/OIF-
FLEXE-01.0.pdf>.
[I-D.ietf-6man-enhanced-vpn-vtn-id] <https://www.oiforum.com/wp-content/uploads/2019/01/
OIF-FLEXE-01.0.pdf>.
[IPv6-NRP-OPTION]
Dong, J., Li, Z., Xie, C., Ma, C., and G. S. Mishra,
"Carrying Network Resource Partition (NRP) (NR) related Information in
IPv6 Extension Header", Work in Progress, Internet-Draft,
draft-ietf-6man-enhanced-vpn-vtn-id-06, 20 February 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-6man-
enhanced-vpn-vtn-id-06>.
[I-D.ietf-spring-resource-aware-segments]
Dong, J., Miyasaka, T., Zhu, Y., Qin, F., and Z. Li,
"Introducing Resource Awareness to SR Segments", Work in
Progress, Internet-Draft, draft-ietf-spring-resource-
aware-segments-09, 6 May 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-spring-
resource-aware-segments-09>.
[I-D.ietf-spring-sr-for-enhanced-vpn]
Dong, J., Miyasaka, T., Zhu, Y., Qin, F., and Z. Li,
"Segment Routing based Network Resource Partition (NRP)
for Enhanced VPN", Work in Progress, Internet-Draft,
draft-ietf-spring-sr-for-enhanced-vpn-07,
draft-ietf-6man-enhanced-vpn-vtn-id-09, 3 March 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-spring-
sr-for-enhanced-vpn-07>.
[I-D.ietf-spring-srv6-srh-compression]
Cheng, W., Filsfils, C., Li, Z., Decraene, B., and F.
Clad, "Compressed SRv6 Segment List Encoding", Work in
Progress, Internet-Draft, draft-ietf-spring-srv6-srh-
compression-17, 16 May 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-spring-
srv6-srh-compression-17>.
[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-28, 8 June November 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
actn-vn-yang-28>.
[I-D.ietf-teas-ietf-network-slice-nbi-yang]
<https://datatracker.ietf.org/doc/html/draft-ietf-6man-
enhanced-vpn-vtn-id-09>.
[NETWORK-SLICE-YANG]
Wu, B., Dhody, D., Rokui, R., Saad, T., and J. Mullooly,
"A YANG Data Model for the RFC 9543 Network Slice
Service", Work in Progress, Internet-Draft, draft-ietf-
teas-ietf-network-slice-nbi-yang-13, 9 May 2024,
teas-ietf-network-slice-nbi-yang-20, 27 January 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
ietf-network-slice-nbi-yang-13>.
[I-D.ietf-teas-nrp-scalability]
ietf-network-slice-nbi-yang-20>.
[NGMN-NS-Concept]
hao ,, "NGMN NS Concept", <https://www.ngmn.org/fileadmin/
user_upload/161010_NGMN_Network_Slicing_framework_v1.0.8.p
df>.
[NRP-SCALABILITY]
Dong, J., Li, Z., Gong, L., Yang, G., and G. S. Mishra,
"Scalability Considerations for Network Resource
Partition", Work in Progress, Internet-Draft, draft-ietf-
teas-nrp-scalability-04, 4 March
teas-nrp-scalability-06, 21 October 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
nrp-scalability-04>.
[I-D.ietf-teas-nrp-yang]
nrp-scalability-06>.
[NRP-YANG] Wu, B., Dhody, D., Beeram, V. P., Saad, T., and S. Peng,
"YANG Data Models for Network Resource Partitions (NRPs)",
Work in Progress, Internet-Draft, draft-ietf-teas-nrp-
yang-01, 16 March
yang-02, 5 July 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
nrp-yang-01>.
[NGMN-NS-Concept]
hao ,, "NGMN NS Concept", <https://www.ngmn.org/fileadmin/
user_upload/161010_NGMN_Network_Slicing_framework_v1.0.8.p
df>.
nrp-yang-02>.
[RESOURCE-AWARE-SEGMENTS]
Dong, J., Miyasaka, T., Zhu, Y., Qin, F., and Z. Li,
"Introducing Resource Awareness to SR Segments", Work in
Progress, Internet-Draft, draft-ietf-spring-resource-
aware-segments-10, 12 October 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-spring-
resource-aware-segments-10>.
[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>.
[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>.
[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>.
[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>.
[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>.
[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>.
[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>.
[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>.
[RFC8660] Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing with the MPLS Data Plane", RFC 8660,
DOI 10.17487/RFC8660, December 2019,
<https://www.rfc-editor.org/info/rfc8660>.
[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>.
[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>.
[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>.
[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>.
[RFC9375] Wu, B., Ed., Wu, Q., Ed., Boucadair, M., Ed., Gonzalez de
Dios, O., and B. Wen, "A YANG Data Model for Network and
VPN Service Performance Monitoring", RFC 9375,
DOI 10.17487/RFC9375, April 2023,
<https://www.rfc-editor.org/info/rfc9375>.
[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>.
[RFC9552] Talaulikar, K., Ed., "Distribution of Link-State and
Traffic Engineering Information Using BGP", RFC 9552,
DOI 10.17487/RFC9552, December 2023,
<https://www.rfc-editor.org/info/rfc9552>.
[RFC9731] Lee, Y., Ed., Dhody, D., Ed., Ceccarelli, D., Bryskin, I.,
and B. Y. Yoon, "A YANG Data Model for Virtual Network
(VN) Operations", RFC 9731, DOI 10.17487/RFC9731, January
2025, <https://www.rfc-editor.org/info/rfc9731>.
[SR-ENHANCED-VPN]
Dong, J., Miyasaka, T., Zhu, Y., Qin, F., and Z. Li,
"Segment Routing based Network Resource Partition (NRP)
for Enhanced VPN", Work in Progress, Internet-Draft,
draft-ietf-spring-sr-for-enhanced-vpn-08, 12 October 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-spring-
sr-for-enhanced-vpn-08>.
[SRv6-SRH-COMPRESSION]
Cheng, W., Ed., Filsfils, C., Li, Z., Decraene, B., and F.
Clad, Ed., "Compressed SRv6 Segment List Encoding", Work
in Progress, Internet-Draft, draft-ietf-spring-srv6-srh-
compression-18, 22 July 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-spring-
srv6-srh-compression-18>.
[TS23501] "3GPP TS23.501", 3GPP, "System architecture for the 5G system (5GS)", 3GPP
TS 23.501,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3144>.
[TS28530] "3GPP TS28.530", 3GPP, "Management and orchestration; Concepts, use cases
and requirements", 3GPP TS 28.530,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3273>.
[TSN] ""Time-Sensitive Networking", IEEE 802.1 Time-Sensitive Working Group, "Time-Sensitive Networking (TSN)
Task Group", <https://1.ieee802.org/tsn/>.
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).
Contributors
Daniel King
Email: daniel@olddog.co.uk
Adrian Farrel
Email: adrian@olddog.co.uk
Jeff Tantsura
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.ietf@gmail.com
Mohamed Boucadair
Email: mohamed.boucadair@orange.com
Sergio Belotti
Email: sergio.belotti@nokia.com
Haomian Zheng
Email: zhenghaomian@huawei.com
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