draft-ietf-teas-enhanced-vpn-04.txt   draft-ietf-teas-enhanced-vpn-05.txt 
TEAS working group J. Dong TEAS working group J. Dong
Internet-Draft Huawei Internet-Draft Huawei
Intended status: Informational S. Bryant Intended status: Informational S. Bryant
Expires: July 2020 Futurewei Expires: July 2020 Futurewei
Z. Li Z. Li
China Mobile China Mobile
T. Miyasaka T. Miyasaka
KDDI Corporation KDDI Corporation
Y.Lee Y.Lee
Sung Kyun Kwan University Sung Kyun Kwan University
January 23, 2020 February 18, 2020
A Framework for Enhanced Virtual Private Networks (VPN+) Services A Framework for Enhanced Virtual Private Networks (VPN+) Services
draft-ietf-teas-enhanced-vpn-04 draft-ietf-teas-enhanced-vpn-05
Abstract Abstract
This document describes the framework for Enhanced Virtual Private This document describes the framework for Enhanced Virtual Private
Network (VPN+) service. The purpose is to support the needs of new Network (VPN+) service. The purpose is to support the needs of new
applications, particularly applications that are associated with 5G applications, particularly applications that are associated with 5G
services, by utilizing an approach that is based on existing VPN and services, by utilizing an approach that is based on existing VPN and
TE technologies and adds features that specific services require TE technologies and adds features that specific services require
over and above traditional VPNs. over and above traditional VPNs.
Typically, VPN+ will be used to form the underpinning of network Typically, VPN+ will be used to form the underpinning of network
slicing, but could also be of use in its own right providing slicing, but could also be of use in its own right providing
enhanced connectivity services between customer sites. enhanced connectivity services between customer sites.
It is envisaged that enhanced VPNs will be delivered using a It is envisaged that enhanced VPNs will be delivered using a
combination of existing, modified, and new networking technologies. combination of existing, modified, and new networking technologies.
This document provides an overview of relevant technologies and This document provides an overview of relevant technologies and
identifies some areas for potential new work. identifies some areas for potential new work.
It is not envisaged that large numbers of VPN+ instances will be It is not envisaged that quite large numbers of VPN+ services will be
deployed in a network and, in particular, it is not intended that deployed in a network and, in particular, it is not intended that
all VPNs supported by a network will use VPN+ related techniques. all VPNs supported by a network will use VPN+ related techniques.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
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This Internet-Draft will expire on July 22, 2020. This Internet-Draft will expire on August 18, 2020.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction ................................................ 3 1. Introduction ................................................ 3
2. Overview of the Requirements ................................ 6 2. Terminologies ............................................... 6
2.1. Isolation between Virtual Networks ..................... 6 3. Overview of the Requirements ............................... 7
2.1.1. A Pragmatic Approach to Isolation ................. 8 3.1. Isolation between Enhanced VPN Services ................ 7
2.2. Performance Guarantee .................................. 8 3.1.1. A Pragmatic Approach to Isolation ................. 8
2.3. Integration ........................................... 10 3.2. Performance Guarantee .................................. 9
2.3.1. Abstraction ...................................... 11 3.3. Integration ........................................... 11
2.4. Dynamic Management .................................... 11 3.3.1. Abstraction ...................................... 11
2.5. Customized Control .................................... 12 3.4. Dynamic Management .................................... 12
2.6. Applicability ......................................... 12 3.5. Customized Control .................................... 12
2.7. Inter-Domain and Inter-Layer Network .................. 12 3.6. Applicability ......................................... 13
3. Architecture of Enhanced VPN ............................... 13 3.7. Inter-Domain and Inter-Layer Network .................. 13
3.1. Layered Architecture .................................. 15 4. Architecture of Enhanced VPN ............................... 13
3.2. Multi-Point to Multi-Point (MP2MP) Connectivity ....... 17 4.1. Layered Architecture ................................. 15
3.3. Application Specific Network Types .................... 18 4.2. Multi-Point to Multi-Point (MP2MP) Connectivity ....... 17
3.4. Scaling Considerations ................................ 18 4.3. Application Specific Network Types .................... 18
4. Candidate Technologies ..................................... 19 4.4. Scaling Considerations ................................ 18
4.1. Layer-Two Data Plane .................................. 19 5. Candidate Technologies ..................................... 19
4.1.1. Flexible Ethernet ................................ 19 5.1. Layer-Two Data Plane .................................. 19
4.1.2. Dedicated Queues ................................. 20 5.1.1. Flexible Ethernet ................................ 19
4.1.3. Time Sensitive Networking ........................ 20 5.1.2. Dedicated Queues ................................. 20
5.1.3. Time Sensitive Networking ........................ 20
4.2. Layer-Three Data Plane ................................ 21 5.2. Layer-Three Data Plane ................................ 21
4.2.1. Deterministic Networking ......................... 21 5.2.1. Deterministic Networking ......................... 21
4.2.2. MPLS Traffic Engineering (MPLS-TE) ............... 21 5.2.2. MPLS Traffic Engineering (MPLS-TE) ............... 21
4.2.3. Segment Routing .................................. 21 5.2.3. Segment Routing .................................. 21
4.3. Non-Packet Data Plane ................................. 22 5.3. Non-Packet Data Plane ................................. 22
4.4. Control Plane ......................................... 22 5.4. Control Plane ......................................... 22
4.5. Management Plane ...................................... 23 5.5. Management Plane ...................................... 23
4.6. Applicability of Service Data Models to Enhanced VPN .. 23 5.6. Applicability of Service Data Models to Enhanced VPN .. 23
4.6.1. Enhanced VPN Delivery in the ACTN Architecture ... 24 5.6.1. Enhanced VPN Delivery in the ACTN Architecture ... 24
4.6.2. Enhanced VPN Features with Service Data Models ... 25 5.6.2. Enhanced VPN Features with Service Data Models ... 25
4.6.3. 5G Transport Service Delivery via Coordinated Data 5.6.3. 5G Transport Service Delivery via Coordinated Data
Modules ................................................. 27 Modules ................................................. 27
5. Scalability Considerations ................................. 29 6. Scalability Considerations ................................. 29
5.1. Maximum Stack Depth of SR ............................. 30 6.1. Maximum Stack Depth of SR ............................. 30
5.2. RSVP Scalability ...................................... 30 6.2. RSVP Scalability ...................................... 30
5.3. SDN Scaling ........................................... 30 6.3. SDN Scaling ........................................... 30
6. OAM Considerations ......................................... 30 7. OAM Considerations ......................................... 30
7. Telemetry Considerations ................................... 31 8. Telemetry Considerations ................................... 31
8. Enhanced Resiliency ........................................ 31 9. Enhanced Resiliency ........................................ 31
9. Operational Considerations ................................. 33 10. Operational Considerations ................................ 33
10. Security Considerations ................................... 33 11. Security Considerations ................................... 33
11. IANA Considerations........................................ 33 12. IANA Considerations ....................................... 33
12. Contributors .............................................. 34 13. Contributors .............................................. 34
13. Acknowledgments ........................................... 34 14. Acknowledgments ........................................... 34
14. References ................................................ 34 15. References ................................................ 34
14.1. Normative References ................................. 34 15.1. Normative References ................................. 34
14.2. Informative References ............................... 36 15.2. Informative References ............................... 36
Authors' Addresses ............................................ 40 Authors' Addresses ............................................ 40
1. Introduction 1. Introduction
Virtual private networks (VPNs) have served the industry well as a Virtual private networks (VPNs) have served the industry well as a
means of providing different groups of users with logically isolated means of providing different groups of users with logically isolated
connectivity over a common network. The common or base network that connectivity over a common network. The common or base network that
is used to provide the VPNs is often referred to as the underlay, is used to provide the VPNs is often referred to as the underlay,
and the VPN is often called an overlay. and the VPN is often called an overlay.
Customers of a network operator may request a connectivity services Customers of a network operator may request a connectivity services
with advanced characteristics such as complete isolation from other with advanced characteristics such as enhanced isolation from other
services so that changes in some other service (such as changes in services so that changes in some other service (such as changes in
network load, or events such as congestion or outages) have no network load, or events such as congestion or outages) have no or
effect on the throughput or latency of the services provided to the acceptable effect on the throughput or latency of the services
customer. These services are "enhanced VPNs" (known as VPN+) in that provided to the customer. These services are "enhanced VPNs" (known
they are similar to VPN services as they provide the customer with as VPN+) in that they are similar to VPN services as they provide
required connectivity, but have enhanced characteristics. the customer with required connectivity, but have enhanced
characteristics.
Driven largely by needs surfacing from 5G, the concept of network Driven largely by needs surfacing from 5G, the concept of network
slicing has gained traction [NGMN-NS-Concept] [TS23501] [TS28530] slicing has gained traction [NGMN-NS-Concept] [TS23501] [TS28530]
[BBF-SD406]. According to [TS28530], a 5G end-to-end network slice [BBF-SD406]. According to [TS28530], a 5G end-to-end network slice
consists of three major types network segments: Radio Access Network consists of three major types network segments: Radio Access Network
(RAN), Transport Network (TN) and Mobile Core Network (CN). The (RAN), Transport Network (TN) and Mobile Core Network (CN). The
transport network provides the required connectivity between transport network provides the required connectivity between
different entities in RAN and CN segments of an end-to-end network different entities in RAN and CN segments of an end-to-end network
slice, with specific performance commitment. VPN+ could be used to slice, with specific performance commitment.
form the underpinning of network slicing, but could also be of use
in general cases providing enhanced connectivity services between
customer sites.
A transport network slice is a virtual (logical) network with a A transport network slice is a virtual (logical) network with a
particular network topology and a set of shared or dedicated network particular network topology and a set of shared or dedicated network
resources, which are used to provide the network slice consumer with resources, which are used to provide the network slice consumer with
the required connectivity, appropriate isolation and specific the required connectivity, appropriate isolation and specific
Service Level Agreement (SLA) or Service Level Objective (SLO). Service Level Agreement (SLA) or Service Level Objective (SLO).
A transport network slice could span multiple technologies (such as A transport network slice could span multiple technologies (such as
IP or Optical) and multiple administrative domains. Depending on the IP or Optical) and multiple administrative domains. Depending on the
consumer's requirement, a transport network slice could be isolated consumer's requirement, a transport network slice could be isolated
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network virtualization, and abstraction to provide performance network virtualization, and abstraction to provide performance
assurance, flexibility, programmability and modularity. It may use assurance, flexibility, programmability and modularity. It may use
techniques such as Software Defined Networking (SDN) [RFC7149], techniques such as Software Defined Networking (SDN) [RFC7149],
network abstraction [RFC7926] and Network Function Virtualization network abstraction [RFC7926] and Network Function Virtualization
(NFV) [RFC8172] [RFC8568] to create multiple logical (virtual) (NFV) [RFC8172] [RFC8568] to create multiple logical (virtual)
networks, each tailored for a set of services or a particular tenant networks, each tailored for a set of services or a particular tenant
or a group of tenants that share the same or similar set of or a group of tenants that share the same or similar set of
requirements, on top of a common network. How the network slices requirements, on top of a common network. How the network slices
are engineered can be deployment-specific. are engineered can be deployment-specific.
Thus, there is a need to create virtual networks with enhanced VPN+ could be used to form the underpinning of transport network
characteristics to support enhanced VPN services. The tenant of slice, but could also be of use in general cases providing enhanced
such a virtual network can require a degree of isolation and connectivity services between customer sites.
performance that previously could not be satisfied by traditional
overlay VPNs. Additionally, the tenant may ask for some level of
control to their virtual networks, e.g., to customize the service
paths in a network slice.
These enhanced properties cannot be met by simple overlay networks, The requirement of enhanced VPN services cannot be met by simple
as they require tighter coordination and integration between the overlay networks, as they require tighter coordination and
underlay and the overlay network. This document introduces the integration between the underlay and the overlay network. VPN+ is
Enhanced VPN (otherwise known as VPN+). VPN+ is built from a virtual built from a VPN overlay and a underlying Virtual Transport Network
network which has a customized network topology and a set of (VTN) which has a customized network topology and a set of dedicated
dedicated or shared network resources, optionally including invoked or shared network resources. It may optionally include a set of
service functions, allocated from the underlay network. Unlike a invoked service functions allocated from the underlay network. Thus
traditional VPN, an enhanced VPN can achieve greater isolation with an enhanced VPN can achieve greater isolation with strict
strict performance guarantees. These new properties, which have performance guarantees. These new properties, which have general
general applicability, may also be of interest as part of a network applicability, may also be of interest as part of a network slicing
slicing solution, but it is not envisaged that VPN+ services will solution. It is not envisaged that VPN+ services will replace
replace traditional VPN services that can continue to be deployed traditional VPN services that can continue to be deployed using pre-
using pre-existing mechanisms. Furthermore, it is not intended that existing mechanisms.
large numbers of VPN+ instances will be deployed within a single
network. See Section 5 for a discussion of scalability
considerations.
This document specifies a framework for using existing, modified, This document specifies a framework for using
and potential new technologies as components to provide a VPN+ existing, modified, and potential new technologies as components to
service. Specifically we are concerned with: provide a VPN+ service. Specifically we are concerned with:
o The design of the enhanced data plane. o The design of the enhanced data plane.
o The necessary protocols in both the underlay and the overlay o The necessary protocols in both the underlay and the overlay
of the enhanced VPN. of the enhanced VPN.
o The mechanisms to achieve integration between overlay and o The mechanisms to achieve integration between overlay and
underlay. underlay.
o The necessary Operation, Administration, and Management (OAM) o The necessary Operation, Administration, and Management (OAM)
methods to instrument an enhanced VPN to make sure that the required methods to instrument an enhanced VPN to make sure that the required
Service Level Agreement (SLA) is met, and to take any corrective Service Level Agreement (SLA) is met, and to take any corrective
action to avoid SLA violation, such as switching to an alternate action to avoid SLA violation, such as switching to an alternate
path. path.
The required layered network structure to achieve this is shown in The required layered network structure to achieve this is shown in
Section 3.1. Section 4.1.
Note that, in this document, the four terms "VPN", "Enhanced VPN" Note that, in this document, the relationship of the four terms
(or "VPN+"), "Virtual Network (VN)", and "Network Slice" may be "VPN", "Enhanced VPN" (or "VPN+"), "Virtual Transport Network (VTN)",
considered as describing similar concepts dependent on the viewpoint and "Network Slice" are described as below:
from which they are used.
o An enhanced VPN can be considered as an evolution of VPN, but o An enhanced VPN (VPN+) can be considered as an evolution of
with additional service-specific commitments. Thus, care must be VPN service, but with additional service-specific commitments. Thus,
taken with the term "VPN" to distinguish normal or legacy VPNs from care must be taken with the term "VPN" to distinguish normal or
VPN+ instances. legacy VPNs from VPN+ services.
o A Virtual Network (VN) is a type of service that connects o A Virtual Transport Network (VTN) is a virtual underlay
customer edge points with the additional possibility of requesting network that connects customer edge points with the additional
further service characteristics in the manner of an enhanced VPN. capability of providing the isolation and performance
characteristics required by an enhanced VPN customer.
o An enhanced VPN or VN is made by creating a slice through the o An enhanced VPN (VPN+) is made by integrating an overlay VPN
resources of the underlay network. and an VTN with a set of network resources allocated in the underlay
network.
o The general concept of network slicing in a TE network o A network slice in transport network could be provided with an
provides tools to address some aspects or realizations of enhanced enhanced VPN (VPN+).
VPN.
2. Overview of the Requirements 2. Terminologies
The following terms are used in this document. Some of them are
newly defined, some others reference existing definitions:
ACTN: Abstraction and Control of TE Networks [RFC8453]
Detnet: Deterministic Networking [DETNET]
FlexE: Flexible Ethernet [FLEXE]
TSN: Time Sensitive Networking [TSN]
VN: Virtual Network [I-D.ietf-teas-actn-vn-yang]
VPN: Virtual Private Network. IPVPN is defined in [RFC2764], L2VPN
is defined in [RFC4664]
VPN+: Enhanced VPN service. An enhanced VPN service (VPN+) can be
considered as an evolution of VPN service, but with additional
service-specific commitments such as enhanced isolation and
performance guarantee.
VTP: Virtual Transport Path. A VTP is a virtual underlay path which
connects two customer edge points with the capability of providing
the isolation and performance characteristics required by an
enhanced VPN customer. A VTP usually has a customized path with a
set of reserved network resources along the path.
VTN: Virtual Transport Network. A VTN is a virtual underlay network
that connects customer edge points with the capability of providing
the isolation and performance characteristics required by an
enhanced VPN customer. A VTN usually has a customized topology and a
set of dedicated or shared network resources.
3. Overview of the Requirements
In this section we provide an overview of the requirements of an In this section we provide an overview of the requirements of an
enhanced VPN service. enhanced VPN service.
2.1. Isolation between Virtual Networks 3.1. Isolation between Enhanced VPN Services
One element of the SLA demanded for an enhanced VPN is a guarantee One element of the SLA demanded for an enhanced VPN is a guarantee
that the service offered to the customer will not be perturbed by that the service offered to the customer will not be perturbed by
any other traffic flows in the network. One way for a service any other traffic flows in the network. One way for a service
provider to guarantee the customer's SLA is by controlling the provider to guarantee the customer's SLA is by controlling the
degree of isolation from other services in the network. Isolation degree of isolation from other services in the network. Isolation
is a feature that can be requested by customers. There are is a feature that can be requested by customers. There are different
different grades of how isolation may be enabled by a network grades of how isolation may be enabled by a network operator and
operator and that may result in different levels of service that may result in different levels of service perceived by the
perceived by the customer. These range from simple separation of customer. These range from simple separation of service traffic on
service traffic on delivery (ensuring that traffic is not delivered delivery (ensuring that traffic is not delivered to the wrong
to the wrong customer), all the way to complete separation within customer), all the way to complete separation within the underlay so
the underlay so that the traffic from different services use that the traffic from different services use distinct network
distinct network resources. resources.
The terms hard and soft isolation are used to identify different The terms hard and soft isolation are used to identify different
levels of isolation. A VPN has soft isolation if the traffic of one levels of isolation. A VPN has soft isolation if the traffic of one
VPN cannot be received by the customers of another VPN. Both IP and VPN cannot be received by the customers of another VPN. Both IP and
MPLS VPNs are examples of VPNs with soft isolation: the network MPLS VPNs are examples of VPNs with soft isolation: the network
delivers the traffic only to the required VPN endpoints. However, delivers the traffic only to the required VPN endpoints. However,
with soft isolation, traffic from VPNs and regular non-VPN traffic with soft isolation, traffic from VPNs and regular non-VPN traffic
may congest the network resulting in packet loss and delay for other may congest the network resulting in packet loss and delay for other
VPNs operating normally. The ability for a VPN service or a group VPNs operating normally. The ability for a VPN service or a group
of VPN services to be sheltered from this effect is called hard of VPN services to be sheltered from this effect is called hard
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these data plane issues. Firstly there is the IEEE project on Time these data plane issues. Firstly there is the IEEE project on Time
Sensitive Networking [TSN] which introduces the concept of packet Sensitive Networking [TSN] which introduces the concept of packet
scheduling of delay and loss sensitive packets. Then there is scheduling of delay and loss sensitive packets. Then there is
[FLEXE] which provides the ability to multiplex multiple channels [FLEXE] which provides the ability to multiplex multiple channels
over one or more Ethernet links in a way that provides hard over one or more Ethernet links in a way that provides hard
isolation. Finally there are advanced queueing approaches which isolation. Finally there are advanced queueing approaches which
allow the construction of virtual sub-interfaces, each of which is allow the construction of virtual sub-interfaces, each of which is
provided with dedicated resource in a shared physical interface. provided with dedicated resource in a shared physical interface.
These approaches are described in more detail later in this document. These approaches are described in more detail later in this document.
Section 2.1.1 explores pragmatic approaches to isolation in packet Section 3.1.1 explores pragmatic approaches to isolation in packet
networks. networks.
2.1.1. A Pragmatic Approach to Isolation 3.1.1. A Pragmatic Approach to Isolation
A key question is whether it is possible to achieve hard isolation A key question is whether it is possible to achieve hard isolation
in packet networks that were never designed to support hard in packet networks that were never designed to support hard
isolation. On the contrary, they were designed to provide isolation. On the contrary, they were designed to provide
statistical multiplexing, a significant economic advantage when statistical multiplexing, a significant economic advantage when
compared to a dedicated, or a Time Division Multiplexing (TDM) compared to a dedicated, or a Time Division Multiplexing (TDM)
network. However, there is no need to provide any harder isolation network. However, there is no need to provide any harder isolation
than is required by the applications. An approximation to this than is required by the applications. An approximation to this
requirement is sufficient in most cases. Pseudowires [RFC3985] requirement is sufficient in most cases. Pseudowires [RFC3985]
emulate services that would have had hard isolation in their native emulate services that would have had hard isolation in their native
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that has served the industry well and will continue to do so. At that has served the industry well and will continue to do so. At
the opposite end of the spectrum, we have the absolute isolation the opposite end of the spectrum, we have the absolute isolation
provided by dedicated transport networks. The goal of enhanced VPNs provided by dedicated transport networks. The goal of enhanced VPNs
is "pragmatic isolation". This is isolation that is better than is is "pragmatic isolation". This is isolation that is better than is
obtainable from pure statistical multiplexing, more cost effective obtainable from pure statistical multiplexing, more cost effective
and flexible than a dedicated network, but which is a practical and flexible than a dedicated network, but which is a practical
solution that is good enough for the majority of applications. solution that is good enough for the majority of applications.
Mechanisms for both soft isolation and hard isolation would be Mechanisms for both soft isolation and hard isolation would be
needed to meet different levels of service requirement. needed to meet different levels of service requirement.
2.2. Performance Guarantee 3.2. Performance Guarantee
There are several kinds of performance guarantee, including There are several kinds of performance guarantee, including
guaranteed maximum packet loss, guaranteed maximum delay, and guaranteed maximum packet loss, guaranteed maximum delay, and
guaranteed delay variation. Note that these guarantees apply to guaranteed delay variation. Note that these guarantees apply to
conformance traffic, out-of-profile traffic will be handled conformance traffic, out-of-profile traffic will be handled
according to other requirements. according to other requirements.
Guaranteed maximum packet loss is a common parameter, and is usually Guaranteed maximum packet loss is a common parameter, and is usually
addressed by setting packet priorities, queue size, and discard addressed by setting packet priorities, queue size, and discard
policy. However this becomes more difficult when the requirement is policy. However this becomes more difficult when the requirement is
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Networking (DetNet) Working Group [DETNET] is relevant; however Networking (DetNet) Working Group [DETNET] is relevant; however
additional methods of enhancing the underlay to better support the additional methods of enhancing the underlay to better support the
delay guarantees may be needed, and these methods will need to be delay guarantees may be needed, and these methods will need to be
integrated with the overall service provisioning mechanisms. integrated with the overall service provisioning mechanisms.
Guaranteed maximum delay variation is a service that may also be Guaranteed maximum delay variation is a service that may also be
needed. [RFC8578] calls up a number of cases where this is needed, needed. [RFC8578] calls up a number of cases where this is needed,
for example in electrical utilities. Time transfer is one example of for example in electrical utilities. Time transfer is one example of
a service that needs this, although it is in the nature of time that a service that needs this, although it is in the nature of time that
the service might be delivered by the underlay as a shared service the service might be delivered by the underlay as a shared service
and not provided through different virtual networks. Alternatively and not provided through different enhanced VPNs. Alternatively a
a dedicated virtual network may be used to provide this as a shared dedicated enhanced VPN may be used to provide this as a shared
service. service.
This suggests that a spectrum of service guarantee be considered This suggests that a spectrum of service guarantee be considered
when deploying an enhanced VPN. As a guide to understanding the when deploying an enhanced VPN. As a guide to understanding the
design requirements we can consider four types: design requirements we can consider four types:
o Best effort o Best effort
o Assured bandwidth o Assured bandwidth
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An enhanced delivery service is one in which the underlay network An enhanced delivery service is one in which the underlay network
(at Layer 3) attempts to deliver the packet through multiple paths (at Layer 3) attempts to deliver the packet through multiple paths
in the hope of eliminating packet loss due to equipment or media in the hope of eliminating packet loss due to equipment or media
failures. failures.
It is these last two characteristics (guaranteed upper bound to It is these last two characteristics (guaranteed upper bound to
latency and elimination of packet loss) that an enhanced VPN adds to latency and elimination of packet loss) that an enhanced VPN adds to
a VPN service. a VPN service.
2.3. Integration 3.3. Integration
The only way to achieve the enhanced characteristics provided by an The only way to achieve the enhanced characteristics provided by an
enhanced VPN (such as guaranteed or predicted performance) is by enhanced VPN (such as guaranteed or predicted performance) is by
integrating the overlay VPN with a particular set of network integrating the overlay VPN with a particular set of network
resources in the underlay network which are allocated to meet the resources in the underlay network which are allocated to meet the
service requirement. This needs be done in a flexible and scalable service requirement. This needs be done in a flexible and scalable
way so that it can be widely deployed in operator networks to way so that it can be widely deployed in operator networks to
support a reasonable number of enhanced VPN customers. support a reasonable number of enhanced VPN customers.
Taking mobile networks and in particular 5G into consideration, the Taking mobile networks and in particular 5G into consideration, the
integration of network and the service functions is a likely integration of network and the service functions is a likely
requirement. The work in IETF SFC working group [SFC] provides a requirement. The work in IETF SFC working group [SFC] provides a
foundation for this integration. foundation for this integration.
2.3.1. Abstraction 3.3.1. Abstraction
Integration of the overlay VPN and the underlay network resources Integration of the overlay VPN and the underlay network resources
does not need to be a tight mapping. As described in [RFC7926], does not need to be a tight mapping. As described in [RFC7926],
abstraction is the process of applying policy to a set of abstraction is the process of applying policy to a set of
information about a TE network to produce selective information that information about a TE network to produce selective information that
represents the potential ability to connect across the network. The represents the potential ability to connect across the network. The
process of abstraction presents the connectivity graph in a way that process of abstraction presents the connectivity graph in a way that
is independent of the underlying network technologies, capabilities, is independent of the underlying network technologies, capabilities,
and topology so that the graph can be used to plan and deliver and topology so that the graph can be used to plan and deliver
network services in a uniform way. network services in a uniform way.
Virtual networks can be built on top of an abstracted topology that Virtual networks can be built on top of an abstracted topology that
represents the connectivity capabilities of the underlay network as represents the connectivity capabilities of the underlay network as
described in the framework for Abstraction and Control of TE described in the framework for Abstraction and Control of TE Networks
Networks (ACTN) described in [RFC8453] as discussed further in (ACTN) [RFC8453] as discussed further in Section 5.5.
Section 4.5.
2.4. Dynamic Management 3.4. Dynamic Management
Enhanced VPNs need to be created, modified, and removed from the Enhanced VPNs need to be created, modified, and removed from the
network according to service demand. An enhanced VPN that requires network according to service demand. An enhanced VPN that requires
hard isolation (section 2.1) must not be disrupted by the hard isolation (section 3.1) must not be disrupted by the
instantiation or modification of another enhanced VPN. Determining instantiation or modification of another enhanced VPN. Determining
whether modification of an enhanced VPN can be disruptive to that whether modification of an enhanced VPN can be disruptive to that
VPN, and in particular whether the traffic in flight will be VPN, and in particular whether the traffic in flight will be
disrupted can be a difficult problem. disrupted can be a difficult problem.
The data plane aspects of this problem are discussed further in The data plane aspects of this problem are discussed further in
Sections 4.1, 4.2, and 4.3. Sections 5.1, 5.2, and 5.3.
The control plane aspects of this problem are discussed further in The control plane aspects of this problem are discussed further in
Section 4.4. Section 5.4.
The management plane aspects of this problem are discussed further The management plane aspects of this problem are discussed further
in Section 4.5 in Section 5.5.
Dynamic changes both to the VPN and to the underlay transport Dynamic changes both to the VPN and to the underlay transport
network need to be managed to avoid disruption to services that are network need to be managed to avoid disruption to services that are
sensitive to the change of network performance. sensitive to the change of network performance.
In addition to non-disruptively managing the network as a result of In addition to non-disruptively managing the network as a result of
gross change such as the inclusion of a new VPN endpoint or a change gross change such as the inclusion of a new VPN endpoint or a change
to a link, VPN traffic might need to be moved as a result of traffic to a link, VPN traffic might need to be moved as a result of traffic
volume changes. volume changes.
2.5. Customized Control 3.5. Customized Control
In some cases it is desirable that an enhanced VPN has a customized In some cases it is desirable that an enhanced VPN has a customized
control plane, so that the tenant of the enhanced VPN can have some control plane, so that the tenant of the enhanced VPN can have some
control of how the resources and functions allocated to this control of how the resources and functions allocated to this
enhanced VPN are used. For example, the tenant may be able to enhanced VPN are used. For example, the tenant may be able to
specify the service paths in his own enhanced VPN. Depending on the specify the service paths in his own enhanced VPN. Depending on the
requirement, an enhanced VPN may have its own dedicated controller, requirement, an enhanced VPN may have its own dedicated controller,
which may be provided with an interface to the control system which may be provided with an interface to the control system
provided by the network operator. Note that such control is within provided by the network operator. Note that such control is within
the scope of the tenant's enhanced VPN, any change beyond that would the scope of the tenant's enhanced VPN, any change beyond that would
require some intervention of the operator. require some intervention of the operator.
A description of the control plane aspects of this problem are A description of the control plane aspects of this problem are
discussed further in Section 4.4. A description of the management discussed further in Section 5.4. A description of the management
plane aspects of this feature can be found in Section 4.5. plane aspects of this feature can be found in Section 5.5.
2.6. Applicability 3.6. Applicability
The technologies described in this document should be applicable to The technologies described in this document should be applicable to
a number of types of VPN services such as: a number of types of VPN services such as:
o Layer 2 point-to-point services such as pseudowires [RFC3985] o Layer 2 point-to-point services such as pseudowires [RFC3985]
o Layer 2 VPNs [RFC4664] o Layer 2 VPNs [RFC4664]
o Ethernet VPNs [RFC7209] o Ethernet VPNs [RFC7209]
o Layer 3 VPNs [RFC4364], [RFC2764] o Layer 3 VPNs [RFC4364], [RFC2764]
Where such VPN types need enhanced isolation and delivery Where such VPN types need enhanced isolation and delivery
characteristics, the technologies described in section 4 can be used characteristics, the technologies described in section 5 can be used
to provide an underlay with the required enhanced performance. to provide an underlay with the required enhanced performance.
2.7. Inter-Domain and Inter-Layer Network 3.7. Inter-Domain and Inter-Layer Network
In some scenarios, an enhanced VPN services may span multiple In some scenarios, an enhanced VPN services may span multiple
network domains. A domain is considered to be any collection of network domains. A domain is considered to be any collection of
network elements within a common realm of address space or path network elements within a common realm of address space or path
computation responsibility [RFC5151]. In some domains the operator computation responsibility [RFC5151]. In some domains the operator
may manage a multi-layered network, for example, a packet network may manage a multi-layered network, for example, a packet network
over an optical network. When enhanced VPNs are provisioned in such over an optical network. When enhanced VPNs are provisioned in such
network scenarios, the technologies used in different network planes network scenarios, the technologies used in different network planes
(data plane, control plane, and management plane) need to provide (data plane, control plane, and management plane) need to provide
mechanisms to support multi-domain and multi-layer coordination and mechanisms to support multi-domain and multi-layer coordination and
integration, so as to provide the required service characteristics integration, so as to provide the required service characteristics
for different enhanced VPNs, and improve network efficiency and for different enhanced VPNs, and improve network efficiency and
operational simplicity. operational simplicity.
3. Architecture of Enhanced VPN 4. Architecture of Enhanced VPN
A number of enhanced VPN services will typically be provided by a A number of enhanced VPN services will typically be provided by a
common network infrastructure. Each enhanced VPN consists of both common network infrastructure. Each enhanced VPN consists of both
the overlay and a specific set of network resources and functions the overlay and a corresponding VTN with a specific set of network
allocated in the underlay to satisfy the needs of the VPN tenant. resources and functions allocated in the underlay to satisfy the
The integration between overlay and various underlay resources needs of the VPN tenant. The integration between overlay and
ensures the required isolation between different enhanced VPNs, and various underlay resources ensures the required isolation between
achieves the guaranteed performance for different services. different enhanced VPNs, and achieves the guaranteed performance for
different services.
An enhanced VPN needs to be designed with consideration given to: An enhanced VPN needs to be designed with consideration given to:
o An enhanced data plane o An enhanced data plane
o A control plane to create enhanced VPNs, making use of the
o A control plane to create enhanced VPNs, making use of the
data plane isolation and performance guarantee techniques data plane isolation and performance guarantee techniques
o A management plane for enhanced VPN service life-cycle o A management plane for enhanced VPN service life-cycle
management. management.
These required characteristics are expanded below: These required characteristics are expanded below:
o Enhanced data plane o Enhanced data plane
* Provides the required resource isolation capability, e.g. * Provides the required resource isolation capability, e.g.
bandwidth guarantee. bandwidth guarantee.
* Provides the required packet latency and jitter * Provides the required packet latency and jitter
characteristics. characteristics.
* Provides the required packet loss characteristics. * Provides the required packet loss characteristics.
* Provides the mechanism to associate a packet with the set * Provides the mechanism to associate a packet with the set
of resources allocated to the enhanced VPN which the packet belongs. of resources allocated to the enhanced VPN which the packet belongs.
o Control plane o Control plane
* Collect information about the underlying network topology * Collect information about the underlying network topology
and resources available and export this to nodes in the network and resources available and export this to nodes in the network
and/or the centralized controller as required. and/or the centralized controller as required.
* Create the required virtual networks with the resource and * Create the required virtual transport networks (VTNs) with
properties needed by the enhanced VPN services that are assigned to the resource and properties needed by the enhanced VPN services that
them. are assigned to them.
* Determine the risk of SLA violation and take appropriate * Determine the risk of SLA violation and take appropriate
avoiding action. avoiding action.
* Determine the right balance of per-packet and per-node * Determine the right balance of per-packet and per-node
state according to the needs of enhanced VPN service to scale to the state according to the needs of enhanced VPN service to scale to the
required size. required size.
o Management plane o Management plane
* Provides an interface between the enhanced VPN provider * Provides an interface between the enhanced VPN provider
(e.g., the Transport Network Manager) and the enhanced VPN clients (e.g., the Transport Network Manager) and the enhanced VPN clients
(e.g., the 3GPP Management System) such that some of the operation (e.g., the 3GPP Management System) such that some of the operation
requests can be met without interfering with the enhanced VPN of requests can be met without interfering with the enhanced VPN of
other clients. other clients.
* Provides an interface between the enhanced VPN provider and * Provides an interface between the enhanced VPN provider and
the enhanced VPN clients to expose transport network capability the enhanced VPN clients to expose transport network capability
information toward the enhanced VPN client. information toward the enhanced VPN client.
* Provides the service life-cycle management and operation of * Provides the service life-cycle management and operation of
enhanced VPN (e.g. creation, modification, assurance/monitoring and enhanced VPN (e.g. creation, modification, assurance/monitoring and
decommissioning). decommissioning).
o Operations, Administration, and Maintenance (OAM) o Operations, Administration, and Maintenance (OAM)
* Provides the OAM tools to verify the connectivity and * Provides the OAM tools to verify the connectivity and
performance of the enhanced VPN. performance of the enhanced VPN.
* Provide the OAM tools to verify whether the underlay * Provide the OAM tools to verify whether the underlay
network resources are correctly allocated and operated properly. network resources are correctly allocated and operated properly.
o Telemetry o Telemetry
* Provides the mechanism to collect data plane, control plane, * Provides the mechanism to collect data plane, control plane,
and management plane information about the network. More and management plane information about the network. More
specifically: specifically:
+ Provides the mechanism to collect network data from the + Provides the mechanism to collect network data from the
underlay network for overall performance evaluation and the enhanced underlay network for overall performance evaluation and the enhanced
VPN service planning. VPN service planning.
+ Provides the mechanism to collect network data about + Provides the mechanism to collect network data about
each enhanced VPN for monitoring and analytics of the each enhanced VPN for monitoring and analytics of the
characteristics and SLA fulfilment of enhanced VPN services. characteristics and SLA fulfilment of enhanced VPN services.
3.1. Layered Architecture 4.1. Layered Architecture
The layered architecture of an enhanced VPN is shown in Figure 2. The layered architecture of an enhanced VPN is shown in Figure 2.
Underpinning everything is the physical network infrastructure layer Underpinning everything is the physical network infrastructure layer
which provide the underlying resources used to provision the which provide the underlying resources used to provision the
separated virtual networks. This includes the partitioning of link separated virtual transport networks (VTNs). This includes the
and/or node resources. Each subset of link or node resource can be partitioning of link and/or node resources. Each subset of link or
considered as a virtual link or virtual node used to build the node resource can be considered as a virtual link or virtual node
virtual networks. used to build the VTNs.
A A
| | | |
+-------------------+ Centralized +-------------------+ Centralized
| Network Controller| Control& Management | Network Controller| Control& Management
+-------------------+ +-------------------+
|| ||
\/ \/
__________________________ __________________________
/ o----o----o / / o----o----o /
/ / / / Virtual / / / / VTN-1
/ o-----o-----o----o----o / Network-1 / o-----o-----o----o----o /
/_________________________/ /_________________________/
__________________________ __________________________
/ o----o / / o----o /
/ / / \ / Virtual / / / \ / VTN-2
/ o-----o----o----o-----o / Network-2 / o-----o----o----o-----o /
/_________________________/ /_________________________/
...... ... ...... ...
___________________________ ___________________________
/ o----o / / o----o /
/ / / / Virtual / / / / VTN-3
/ o-----o----o----o-----o / Network-N / o-----o----o----o-----o /
/__________________________/ /__________________________/
++++ ++++ ++++ ++++ ++++ ++++
+--+===+--+===+--+ +--+===+--+===+--+
+--+===+--+===+--+ +--+===+--+===+--+
++++ +++-\ ++++ Physical ++++ +++\\ ++++ Physical
|| || \\ || || || \\ ||
|| || \\ || Network || || \\ || Network
++++ ++++ ++++ \\+++ ++++ ++++ ++++ ++++ \\+++ ++++
+--+===+--+===+--+===+--+===+--+ Infrastructure +--+===+--+===+--+===+--+===+--+ Infrastructure
+--+===+--+===+--+===+--+===+--+ +--+===+--+===+--+===+--+===+--+
++++ ++++ ++++ ++++ ++++ ++++ ++++ ++++ ++++ ++++
O Virtual Node O Virtual Node
-- Virtual Link -- Virtual Link
++++ ++++
+--+ Physical Node with resource partition +--+ Physical Node with resource partition
+--+ +--+
++++ ++++
== Physical Link with resource partition == Physical Link with resource partition
Figure 2 The Layered Architecture Figure 2 The Layered Architecture
Various components and techniques discussed in Section 4 can be used Various components and techniques discussed in Section 5 can be used
to enable resource partition, such as FlexE, Time Sensitive to enable resource partition, such as FlexE, Time Sensitive
Networking, Deterministic Networking, Dedicated queues, etc. These Networking, Deterministic Networking, Dedicated queues, etc. These
partitions may be physical, or virtual so long as the SLA required partitions may be physical, or virtual so long as the SLA required
by the higher layers is met. by the higher layers is met.
Based on the network resources provided by the physical network Based on the network resources provided by the physical network
infrastructure, multiple virtual networks can be provisioned, each infrastructure, multiple VTNs can be provisioned, each with
with customized topology and other attributes to meet the customized topology and other attributes to meet the requirement of
requirement of different enhanced VPNs or different groups of different enhanced VPNs or different groups of enhanced VPNs. To get
enhanced VPNs. To get the required characteristic, each virtual the required characteristic, each VTN needs to be mapped to a set of
network needs to be mapped to a set of network nodes and links in network nodes and links in the network infrastructure. And on each
the network infrastructure. And on each node or link, the virtual node or link, the VTN is associated with a set of resources which
network is mapped to a set of resources which are allocated for the are allocated for the processing of traffic in the VTN. VTN provides
service processing of the virtual network. Such mapping provides the the integration between the virtual network topology and the
integration between the virtual networks and the required underlying required underlying network resources.
network resources.
The centralized controller is used to create the virtual networks, The centralized controller is used to create the VTN, and to
to instruct the network nodes to allocate the required resources to instruct the network nodes to allocate the required resources to
each virtual network and to provision the enhanced VPN services each VTN and to provision the enhanced VPN services on the VTNs. A
within the virtual networks. A distributed control plane may also distributed control plane may also be used for the distribution of
be used for the distribution of the topology and attribute the VTN topology and attribute information between nodes within the
information between nodes within the virtual networks. VTNs.
The process used to create virtual networks and to allocate physical The process used to create VTNs and to allocate network resources
resources for use by virtual networks needs to take a holistic view for use by VTNs needs to take a holistic view of the needs of all of
of the needs of all of its tenants (i.e., of all customers and their its tenants (i.e., of all customers and their associated VTNs), and
virtual networks), and to partition the resources accordingly. to partition the resources accordingly. However, within a VTN these
However, within a virtual network these resources can, if required, resources can, if required, be managed via a dynamic control plane.
be managed via a dynamic control plane. This provides the required This provides the required scalability and isolation.
scalability and isolation.
3.2. Multi-Point to Multi-Point (MP2MP) Connectivity 4.2. Multi-Point to Multi-Point (MP2MP) Connectivity
At the VPN service level, the required connectivity is usually mesh At the VPN service level, the required connectivity is usually mesh
or partial-mesh. To support such kinds of VPN service, the or partial-mesh. To support such kinds of VPN service, the
corresponding underlay is also an abstract MP2MP medium. Other corresponding VTN in underlay is also an abstract MP2MP medium.
service requirements may be expressed at different granularity, some Other service requirements may be expressed at different granularity,
of which can be applicable to the whole service, while some others some of which can be applicable to the whole service, while some
may be only applicable to some pairs of end points. For example, others may be only applicable to some pairs of end points. For
when performance guarantee is required, the point-to-point path example, when particular level of performance guarantee is
through the underlay of the enhanced VPN may need to be specifically required, the point-to-point path through the underlay of the
engineered to meet the required performance guarantee. enhanced VPN may need to be specifically engineered to meet the
required performance guarantee.
3.3. Application Specific Network Types 4.3. Application Specific Network Types
Although a lot of the traffic that will be carried over the enhanced Although a lot of the traffic that will be carried over the enhanced
VPN will likely be IPv4 or IPv6, the design has to be capable of VPN will likely be IPv4 or IPv6, the design has to be capable of
carrying other traffic types, in particular Ethernet traffic. This carrying other traffic types, in particular Ethernet traffic. This
is easily accomplished through the various pseudowire (PW) is easily accomplished through the various pseudowire (PW)
techniques [RFC3985]. Where the underlay is MPLS, Ethernet can be techniques [RFC3985]. Where the underlay is MPLS, Ethernet can be
carried over the enhanced VPN encapsulated according to the method carried over the enhanced VPN encapsulated according to the method
specified in [RFC4448]. Where the underlay is IP, Layer Two specified in [RFC4448]. Where the underlay is IP, Layer Two
Tunneling Protocol - Version 3 (L2TPv3) [RFC3931] can be used with Tunneling Protocol - Version 3 (L2TPv3) [RFC3931] can be used with
Ethernet traffic carried according to [RFC4719]. Encapsulations Ethernet traffic carried according to [RFC4719]. Encapsulations
have been defined for most of the common Layer 2 types for both PW have been defined for most of the common Layer 2 types for both PW
over MPLS and for L2TPv3. over MPLS and for L2TPv3.
3.4. Scaling Considerations 4.4. Scaling Considerations
VPNs are instantiated as overlays on top of an operator's network VPNs are instantiated as overlays on top of an operator's network
and offered as services to the operator's customers. An important and offered as services to the operator's customers. An important
feature of overlays is that they are able to deliver services feature of overlays is that they are able to deliver services
without placing per-service state in the core of the underlay without placing per-service state in the core of the underlay
network. network.
Enhanced VPNs may need to install some additional state within the Enhanced VPNs may need to install some additional state within the
network to achieve the additional features that they require. network to achieve the additional features that they require.
Solutions must consider minimizing and controlling the scale of such Solutions must consider minimizing and controlling the scale of such
state, and deployment architectures should constrain the number of state, and deployment architectures should constrain the number of
enhanced VPNs that would exist where such services would place enhanced VPNs that would exist where such services would place
additional state in the network. It is expected that the number of additional state in the network. It is expected that the number of
enhanced VPN would be small in the beginning, and even in future the enhanced VPN would be small in the beginning, and even in future the
number of enhanced VPN will be much fewer than traditional VPNs, number of enhanced VPN will be much fewer than traditional VPNs,
because pre-existing VPN techniques are be good enough to meet the because pre-existing VPN techniques are be good enough to meet the
needs of most existing VPN-type services. needs of most existing VPN-type services.
In general, it is not required that the state in the network be In general, it is not required that the state in the network be
maintained in a 1:1 relationship with the VPN+ instances. It will maintained in a 1:1 relationship with the VPN+ services. It will
usually be possible to aggregate a set of VPN+ services so that they usually be possible to aggregate a set of VPN+ services so that they
share the same virtual network and the same set of network resources share the same VTN and the same set of network resources (much in
(much in the way that current VPNs are aggregated over transport the way that current VPNs are aggregated over transport tunnels) so
tunnels) so that collections of enhanced VPNs that require the same that collections of enhanced VPNs that require the same behaviour
behaviour from the network in terms of resource reservation, latency from the network in terms of resource reservation, latency bounds,
bounds, resiliency, etc. are able to be grouped together. This is resiliency, etc. are able to be grouped together. This is an
an important feature to assist with the scaling characteristics of important feature to assist with the scaling characteristics of VPN+
VPN+ deployments. deployments.
See Section 5 for a further discussion of scalability considerations. See Section 6 for a further discussion of scalability considerations.
4. Candidate Technologies 5. Candidate Technologies
A VPN is a network created by applying a demultiplexing technique to A VPN is a network created by applying a demultiplexing technique to
the underlying network (the underlay) in order to distinguish the the underlying network (the underlay) in order to distinguish the
traffic of one VPN from that of another. A VPN path that travels by traffic of one VPN from that of another. A VPN path that travels by
other than the shortest path through the underlay normally requires other than the shortest path through the underlay normally requires
state in the underlay to specify that path. State is normally state in the underlay to specify that path. State is normally
applied to the underlay through the use of the RSVP signaling applied to the underlay through the use of the RSVP signaling
protocol, or directly through the use of an SDN controller, although protocol, or directly through the use of an SDN controller, although
other techniques may emerge as this problem is studied. This state other techniques may emerge as this problem is studied. This state
gets harder to manage as the number of VPN paths increases. gets harder to manage as the number of VPN paths increases.
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the overlay to support the enhanced VPN service, this state will the overlay to support the enhanced VPN service, this state will
increase further. increase further.
In an enhanced VPN different subsets of the underlay resources can In an enhanced VPN different subsets of the underlay resources can
be dedicated to different enhanced VPNs or different groups of be dedicated to different enhanced VPNs or different groups of
enhanced VPNs. An enhanced VPN solution thus needs tighter coupling enhanced VPNs. An enhanced VPN solution thus needs tighter coupling
with underlay than is the case with existing VPNs. We cannot, for with underlay than is the case with existing VPNs. We cannot, for
example, share the network resource between enhanced VPNs which example, share the network resource between enhanced VPNs which
require hard isolation. require hard isolation.
4.1. Layer-Two Data Plane 5.1. Layer-Two Data Plane
A number of candidate Layer 2 packet or frame-based data plane A number of candidate Layer 2 packet or frame-based data plane
solutions which can be used provide the required isolation and solutions which can be used provide the required isolation and
guarantees are described in following sections. guarantees are described in following sections.
4.1.1. Flexible Ethernet 5.1.1. Flexible Ethernet
FlexE [FLEXE] provides the ability to multiplex channels over an FlexE [FLEXE] provides the ability to multiplex channels over an
Ethernet link to create point-to-point fixed-bandwidth connections Ethernet link to create point-to-point fixed-bandwidth connections
in a way that provides hard isolation. FlexE also supports bonding in a way that provides hard isolation. FlexE also supports bonding
links to create larger links out of multiple low capacity links. links to create larger links out of multiple low capacity links.
However, FlexE is only a link level technology. When packets are However, FlexE is only a link level technology. When packets are
received by the downstream node, they need to be processed in a way received by the downstream node, they need to be processed in a way
that preserves that isolation in the downstream node. This in turn that preserves that isolation in the downstream node. This in turn
requires a queuing and forwarding implementation that preserves the requires a queuing and forwarding implementation that preserves the
end-to-end isolation. end-to-end isolation.
If different FlexE channels are used for different services, then no If different FlexE channels are used for different services, then no
sharing is possible between the FlexE channels. This means that it sharing is possible between the FlexE channels. This means that it
may be difficult to dynamically redistribute unused bandwidth to may be difficult to dynamically redistribute unused bandwidth to
lower priority services in another FlexE channel. If one FlexE lower priority services in another FlexE channel. If one FlexE
channel is used by one tenant, the tenant can use some methods to channel is used by one tenant, the tenant can use some methods to
manage the relative priority of his own traffic in the FlexE channel. manage the relative priority of his own traffic in the FlexE channel.
4.1.2. Dedicated Queues 5.1.2. Dedicated Queues
DiffServ based queuing systems are described in [RFC2475] and DiffServ based queuing systems are described in [RFC2475] and
[RFC4594]. This is considered insufficient to provide isolation for [RFC4594]. This is considered insufficient to provide isolation for
enhanced VPNs because DiffServ does not always provide enough enhanced VPNs because DiffServ does not always provide enough
markers to differentiate between traffic of many enhanced VPNs, or markers to differentiate between traffic of many enhanced VPNs, or
offer the range of service classes that each VPN needs to provide to offer the range of service classes that each VPN needs to provide to
its tenants. This problem is particularly acute with an MPLS its tenants. This problem is particularly acute with an MPLS
underlay, because MPLS only provides eight Traffic Classes. underlay, because MPLS only provides eight Traffic Classes.
In addition, DiffServ, as currently implemented, mainly provides In addition, DiffServ, as currently implemented, mainly provides
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achieve quantitive resource reservation. achieve quantitive resource reservation.
In order to address these problems and to reduce the potential In order to address these problems and to reduce the potential
interference between enhanced VPNs, it would be necessary to steer interference between enhanced VPNs, it would be necessary to steer
traffic to dedicated input and output queues per enhanced VPN: some traffic to dedicated input and output queues per enhanced VPN: some
routers have a large number of queues and sophisticated queuing routers have a large number of queues and sophisticated queuing
systems, which could support this, while some routers may struggle systems, which could support this, while some routers may struggle
to provide the granularity and level of isolation required by the to provide the granularity and level of isolation required by the
applications of enhanced VPN. applications of enhanced VPN.
4.1.3. Time Sensitive Networking 5.1.3. Time Sensitive Networking
Time Sensitive Networking (TSN) [TSN] is an IEEE project that is Time Sensitive Networking (TSN) [TSN] is an IEEE project that is
designing a method of carrying time sensitive information over designing a method of carrying time sensitive information over
Ethernet. It introduces the concept of packet scheduling where a Ethernet. It introduces the concept of packet scheduling where a
packet stream may be given a time slot guaranteeing that it packet stream may be given a time slot guaranteeing that it
experiences no queuing delay or increase in latency. The mechanisms experiences no queuing delay or increase in latency. The mechanisms
defined in TSN can be used to meet the requirements of time defined in TSN can be used to meet the requirements of time
sensitive services of an enhanced VPN. sensitive services of an enhanced VPN.
Ethernet can be emulated over a Layer 3 network using an IP or MPLS Ethernet can be emulated over a Layer 3 network using an IP or MPLS
pseudowire. However, a TSN Ethernet payload would be opaque to the pseudowire. However, a TSN Ethernet payload would be opaque to the
underlay and thus not treated specifically as time sensitive data. underlay and thus not treated specifically as time sensitive data.
The preferred method of carrying TSN over a Layer 3 network is The preferred method of carrying TSN over a Layer 3 network is
through the use of deterministic networking as explained in Section through the use of deterministic networking as explained in Section
4.2.1. 5.2.1.
4.2. Layer-Three Data Plane 5.2. Layer-Three Data Plane
We now consider the problem of slice differentiation and resource We now consider the problem of slice differentiation and resource
representation in the network layer. representation in the network layer.
4.2.1. Deterministic Networking 5.2.1. Deterministic Networking
Deterministic Networking (DetNet) [RFC8655] is a technique being Deterministic Networking (DetNet) [RFC8655] is a technique being
developed in the IETF to enhance the ability of Layer 3 networks to developed in the IETF to enhance the ability of Layer 3 networks to
deliver packets more reliably and with greater control over the deliver packets more reliably and with greater control over the
delay. The design cannot use re-transmission techniques such as TCP delay. The design cannot use re-transmission techniques such as TCP
since that can exceed the delay tolerated by the applications. Even since that can exceed the delay tolerated by the applications. Even
the delay improvements that are achieved with Stream Control the delay improvements that are achieved with Stream Control
Transmission Protocol Partial Reliability Extension (SCTP-PR) Transmission Protocol Partial Reliability Extension (SCTP-PR)
[RFC3758] do not meet the bounds set by application demands. DetNet [RFC3758] do not meet the bounds set by application demands. DetNet
pre-emptively sends copies of the packet over various paths to pre-emptively sends copies of the packet over various paths to
minimize the chance of all copies of a packet being lost. It also 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 seeks to set an upper bound on latency, but the goal is not to
minimize latency. minimize latency.
4.2.2. MPLS Traffic Engineering (MPLS-TE) 5.2.2. MPLS Traffic Engineering (MPLS-TE)
MPLS-TE [RFC2702] [RFC3209] introduces the concept of reserving end- MPLS-TE [RFC2702] [RFC3209] introduces the concept of reserving end-
to-end bandwidth for a TE-LSP, which can be used as connectivity to-end bandwidth for a TE-LSP, which can be used to provide point-
across the underlay network to support VPNs. VPN traffic can be to-point Virtual Transport Path (VTP) across the underlay network to
carried over dedicated TE-LSPs to provide reserved bandwidth for support VPNs. VPN traffic can be carried over dedicated TE-LSPs to
each specific connection in a VPN, and VPNs with similar behavior provide reserved bandwidth for each specific connection in a VPN,
requirements may be multiplexed onto the same TE-LSPs. Some network and VPNs with similar behaviour requirements may be multiplexed onto
operators have concerns about the scalability and management the same TE-LSPs. Some network operators have concerns about the
overhead of MPLS-TE system, and this has lead them to consider other scalability and management overhead of MPLS-TE system, and this has
solutions for their networks. lead them to consider other solutions for their networks.
4.2.3. Segment Routing 5.2.3. Segment Routing
Segment Routing (SR) [RFC8402] is a method that prepends Segment Routing (SR) [RFC8402] is a method that prepends
instructions to packets at the head-end of a path. These instructions to packets at the head-end of a path. These
instructions are used to specify the nodes and links to be traversed instructions are used to specify the nodes and links to be traversed
and allow the packets to be routed on paths other than the shortest and allow the packets to be routed on paths other than the shortest
path. By encoding the state in the packet, per-path state is path. By encoding the state in the packet, per-path state is
transitioned out of the network. transitioned out of the network.
An SR traffic engineered path operates with a granularity of a link An SR traffic engineered path operates with a granularity of a link
with hints about priority provided through the use of the traffic with hints about priority provided through the use of the traffic
skipping to change at page 22, line 15 skipping to change at page 22, line 15
required. With SR, it is possible to introduce such fine-grained required. With SR, it is possible to introduce such fine-grained
packet steering by specifying the queues and resources through an SR packet steering by specifying the queues and resources through an SR
instruction list. instruction list.
Note that the concept of queue is a useful abstraction for different Note that the concept of queue is a useful abstraction for different
types of underlay mechanism that may be used to provide enhanced types of underlay mechanism that may be used to provide enhanced
isolation and latency support. How the queue satisfies the isolation and latency support. How the queue satisfies the
requirement is implementation specific and is transparent to the requirement is implementation specific and is transparent to the
layer-3 data plane and control plane mechanisms used. layer-3 data plane and control plane mechanisms used.
4.3. Non-Packet Data Plane With Segment Routing, the SR instruction list could be used to build
a P2P path, a group of SR SIDs could also be used to represent a MP2MP
network. Thus the SR based mechanism could be used to provide both
Virtual Transport Path (VTP) and Virtual Transport Network (VTN) for
enhanced VPN services.
5.3. Non-Packet Data Plane
Non-packet underlay data plane technologies often have TE properties Non-packet underlay data plane technologies often have TE properties
and behaviors, and meet many of the key requirements in particular and behaviours, and meet many of the key requirements in particular
for bandwidth guarantees, traffic isolation (with physical isolation for bandwidth guarantees, traffic isolation (with physical isolation
often being an integral part of the technology), highly predictable often being an integral part of the technology), highly predictable
latency and jitter characteristics, measurable loss characteristics, latency and jitter characteristics, measurable loss characteristics,
and ease of identification of flows. The cost is the resources are and ease of identification of flows. The cost is the resources are
allocated on a long term and end-to-end basis. Such an arrangement allocated on a long term and end-to-end basis. Such an arrangement
means that the full cost of the resources has be borne by the means that the full cost of the resources has be borne by the
service that is allocated with the resources. service that is allocated with the resources.
4.4. Control Plane 5.4. Control Plane
Enhanced VPN would likely be based on a hybrid control mechanism, Enhanced VPN would likely be based on a hybrid control mechanism,
which takes advantage of the logically centralized controller for which takes advantage of the logically centralized controller for
on-demand provisioning and global optimization, whilst still relying on-demand provisioning and global optimization, whilst still relying
on a distributed control plane to provide scalability, high on a distributed control plane to provide scalability, high
reliability, fast reaction, automatic failure recovery, etc. reliability, fast reaction, automatic failure recovery, etc.
Extension to and optimization of the distributed control plane is Extension to and optimization of the distributed control plane is
needed to support the enhanced properties of VPN+. needed to support the enhanced properties of VPN+.
RSVP-TE [RFC3209] provides the signaling mechanism for establishing RSVP-TE [RFC3209] provides the signaling mechanism for establishing
a TE-LSP in an MPLS network with end-to-end resource reservation. a TE-LSP in an MPLS network with end-to-end resource reservation.
It could be used to bind the VPN to specific network resources This can be seen as a Virtual Transport Path (VTP), which could be
allocated within the underlay, but there remain scalability concerns used to bind the VPN to specific network resources allocated within
mentioned in Section 4.2.2. the underlay, but there remain scalability concerns mentioned in
Section 5.2.2.
The control plane of SR [RFC8665] [RFC8667] [I-D.ietf-idr-bgp-ls- The control plane of SR [RFC8665] [RFC8667] [I-D.ietf-idr-bgp-ls-
segment-routing-ext] does not have the capability of signaling segment-routing-ext] does not have the capability of signaling
resource reservations along the path. On the other hand, the SR resource reservations along the path. On the other hand, the SR
approach provides a potential way of binding the underlay network approach provides a potential way of binding the underlay network
resource and the enhanced VPN service without requiring per-path resource and the enhanced VPN service without requiring per-path
state to be maintained in the network. A centralized controller can state to be maintained in the network. A centralized controller can
perform resource planning and reservation for enhanced VPNs, while perform resource planning and reservation for enhanced VPNs, while
it needs to ensure that resources are correctly allocated in network it needs to ensure that resources are correctly allocated in network
nodes for the enhanced VPN service. nodes for the enhanced VPN service.
4.5. Management Plane 5.5. Management Plane
The management plane provides the interface between the enhanced VPN The management plane provides the interface between the enhanced VPN
provider and the clients for the service life-cycle management (e.g. provider and the clients for the service life-cycle management (e.g.
creation, modification, assurance/monitoring and decommissioning). creation, modification, assurance/monitoring and decommissioning).
It relies on a set of service data models for the description of the It relies on a set of service data models for the description of the
information and operations needed on the interface. information and operations needed on the interface.
In the context of 5G end-to-end network slicing [TS28530], the In the context of 5G end-to-end network slicing [TS28530], the
management of enhanced VPNs is considered as the management of the management of enhanced VPNs is considered as the management of the
transport network part of the end-to-end network slice. 3GPP transport network part of the end-to-end network slice. 3GPP
management system may provide the connectivity and performance management system may provide the connectivity and performance
related parameters as requirements to the management plane of the related parameters as requirements to the management plane of the
transport network. It may also require the transport network to transport network. It may also require the transport network to
expose the capability and status of the transport network slice. expose the capability and status of the transport network slice.
Thus, an interface between the enhanced VPN management plane and the Thus, an interface between the enhanced VPN management plane and the
3GPP network slice management system, and relevant service data 3GPP network slice management system, and relevant service data
models are needed for the coordination of end-to-end network slice models are needed for the coordination of end-to-end network slice
management. management.
The management plane interface and data models for enhanced VPN can The management plane interface and data models for enhanced VPN can
be based on the service models described in Section 4.6. be based on the service models described in Section 5.6.
4.6. Applicability of Service Data Models to Enhanced VPN 5.6. Applicability of Service Data Models to Enhanced VPN
ACTN supports operators in viewing and controlling different domains ACTN supports operators in viewing and controlling different domains
and presenting virtualized networks to their customers. The ACTN and presenting virtualized networks to their customers. The ACTN
framework [RFC8453] highlights how: framework [RFC8453] highlights how:
o Abstraction of the underlying network resources is provided to o Abstraction of the underlying network resources is provided to
higher-layer applications and customers. higher-layer applications and customers.
o Underlying resources are virtualized allocating those resources o Underlying resources are virtualized allocating those resources
for the customer, application, or service. for the customer, application, or service.
skipping to change at page 24, line 17 skipping to change at page 24, line 26
manage the virtual networks and services enabled by ACTN. The manage the virtual networks and services enabled by ACTN. The
Customer VPN model (e.g. L3SM [RFC8299]) or an ACTN Virtual Network Customer VPN model (e.g. L3SM [RFC8299]) or an ACTN Virtual Network
(VN) [I-D.ietf-teas-actn-vn-yang] model is a customer view of the (VN) [I-D.ietf-teas-actn-vn-yang] model is a customer view of the
ACTN managed infrastructure, and is presented by the ACTN provider ACTN managed infrastructure, and is presented by the ACTN provider
as a set of abstracted services or resources. The L3VPN network as a set of abstracted services or resources. The L3VPN network
model [I-D.ietf-opsawg-l3sm-l3nm] and the TE tunnel model [I-D.ietf- model [I-D.ietf-opsawg-l3sm-l3nm] and the TE tunnel model [I-D.ietf-
teas-yang-te] provide a network view of the ACTN managed teas-yang-te] provide a network view of the ACTN managed
infrastructure presented by the ACTN provider as a set of transport infrastructure presented by the ACTN provider as a set of transport
resources. resources.
4.6.1. Enhanced VPN Delivery in the ACTN Architecture 5.6.1. Enhanced VPN Delivery in the ACTN Architecture
ACTN provides VPN connections between multiple sites as requested ACTN provides VPN connections between multiple sites as requested
via the Customer Network Controller (CNC). The CNC is managed by via the Customer Network Controller (CNC). The CNC is managed by
the customer themselves, and interacts with the network provider's the customer themselves, and interacts with the network provider's
Multi-Domain Service Controller (MDSC). The Provisioning Network Multi-Domain Service Controller (MDSC). The Provisioning Network
Controllers (PNC) are responsible for network resource management, Controllers (PNC) are responsible for network resource management,
thus the PNCs are remain entirely under the management of the thus the PNCs are remain entirely under the management of the
network provider and are not visible to the customer so that network provider and are not visible to the customer so that
management is mostly performed by the network provider, with some management is mostly performed by the network provider, with some
flexibility delegated to the customer-managed CNC. flexibility delegated to the customer-managed CNC.
skipping to change at page 25, line 35 skipping to change at page 25, line 35
---------------- ( Network ) . ---------------- ( Network ) .
| PNC |<-------->( ) ---^------ | PNC |<-------->( ) ---^------
---------------- | -------- ( ) ---------------- | -------- ( )
| |-- ( Physical ) | |-- ( Physical )
| PNC |<------------------------->( Network ) | PNC |<------------------------->( Network )
--------------- ( ) --------------- ( )
-------- --------
Figure 3 Generic VPN+ Delivery in the ACTN Architecture Figure 3 Generic VPN+ Delivery in the ACTN Architecture
4.6.2. Enhanced VPN Features with Service Data Models 5.6.2. Enhanced VPN Features with Service Data Models
This section discusses how the service data models can fulfil the This section discusses how the service data models can fulfil the
enhanced VPN requirements described earlier in this document within enhanced VPN requirements described earlier in this document within
the scope of the ACTN architecture. the scope of the ACTN architecture.
4.6.2.1. Isolation Between VPNs 5.6.2.1. Isolation Between VPNs
The VN YANG model [I-D.ietf-teas-actn-vn-yang] and the TE-service The VN YANG model [I-D.ietf-teas-actn-vn-yang] and the TE-service
mapping model [I-D.ietf-teas-te-service-mapping-yang] fulfil the VPN mapping model [I-D.ietf-teas-te-service-mapping-yang] fulfil the VPN
isolation requirement by providing the following features for the isolation requirement by providing the following features for the
VPNs: VPNs:
o Each VPN is identified with a unique identifier (vpn-id) and o Each VPN is identified with a unique identifier (vpn-id) and
can be mapped to a specific VN. Multiple VPNs may mapped to the can be mapped to a specific VN. Multiple VPNs may mapped to the
same VN according to service requirements and operator's policy. same VN according to service requirements and operator's policy.
o Each VPN is managed and controlled independent of other VPNs. o Each VPN is managed and controlled independent of other VPNs.
o Each VPN is instantiated with an isolation requirement o Each VPN is instantiated with an isolation requirement
described by the TE-service mapping model [I-D.ietf-teas-te-service- described by the TE-service mapping model [I-D.ietf-teas-te-service-
mapping-yang]. This mapping supports all levels of isolation (hard mapping-yang]. This mapping supports all levels of isolation (hard
isolation with deterministic characteristics, hard isolation, soft isolation with deterministic characteristics, hard isolation, soft
isolation, or no isolation). isolation, or no isolation).
4.6.2.2. Guaranteed Performance 5.6.2.2. Guaranteed Performance
Performance objectives of a VPN [RFC8299][RFC8466] are expressed Performance objectives of a VPN [RFC8299][RFC8466] are expressed
through a QoS profile including the following properties: through a QoS profile including the following properties:
o Rate-limit o Rate-limit
o Bandwidth o Bandwidth
o Latency o Latency
skipping to change at page 26, line 42 skipping to change at page 26, line 42
o Objective function (e.g., min cost path, min load path, etc.) o Objective function (e.g., min cost path, min load path, etc.)
o Metric Types and their threshold: o Metric Types and their threshold:
* TE cost, IGP cost, Hop count, or Unidirectional Delay (e.g., * TE cost, IGP cost, Hop count, or Unidirectional Delay (e.g.,
can set all path delay <= threshold) can set all path delay <= threshold)
Once these requests are instantiated, the resources are committed Once these requests are instantiated, the resources are committed
and guaranteed through the life cycle of the VPN. and guaranteed through the life cycle of the VPN.
4.6.2.3. Integration 5.6.2.3. Integration
The L3VPN network model provides mechanism to correlate customer's The L3VPN network model provides mechanism to correlate customer's
VPN and the VPN service related resources (e.g., RT and RD) VPN and the VPN service related resources (e.g., RT and RD)
allocated in the provider's network. allocated in the provider's network.
The VPN/Network performance monitoring model [I-D.www-bess-yang-vpn- The VPN/Network performance monitoring model [I-D.www-bess-yang-vpn-
service-pm] provides mechanisms to monitor and manage network service-pm] provides mechanisms to monitor and manage network
Performance on the topology at different layer or the overlay Performance on the topology at different layer or the overlay
topology between VPN sites. topology between VPN sites.
These two models provide mechanisms to correlate the customer's VPN These two models provide mechanisms to correlate the customer's VPN
and the actual TE tunnels instantiated in the provider's network. and the actual TE tunnels instantiated in the provider's network.
Service function integration with network topology (L3 and TE Service function integration with network topology (L3 and TE
topology) is in progress in [I-D.ietf-teas-sf-aware-topo-model] topology) is in progress in [I-D.ietf-teas-sf-aware-topo-model]
which addresses a number of use-cases that show how TE topology which addresses a number of use-cases that show how TE topology
supports various service functions. supports various service functions.
4.6.2.4. Dynamic and Customized Management 5.6.2.4. Dynamic and Customized Management
The ACTN architecture allows the CNC to interact with the provider's The ACTN architecture allows the CNC to interact with the provider's
MDSC. This gives the customer dynamic control of their VPNs. MDSC. This gives the customer dynamic control of their VPNs.
For example, the ACTN VN model [I-D.ietf-teas-actn-vn-yang] allows For example, the ACTN VN model [I-D.ietf-teas-actn-vn-yang] allows
life-cycle management to create, modify, and delete VNs on demand. life-cycle management to create, modify, and delete VNs on demand.
Customers may also be allowed more customized control of the VN Customers may also be allowed more customized control of the VN
topology by provisioning tunnels to connect their endpoints, and topology by provisioning tunnels to connect their endpoints, and
even configuring the paths of those tunnels. even configuring the paths of those tunnels.
Another example is the L3VPN service model [RFC8299] which allows Another example is the L3VPN service model [RFC8299] which allows
VPN lifecycle management such as VPN creation, modification, and VPN lifecycle management such as VPN creation, modification, and
deletion on demand. deletion on demand.
4.6.3. 5G Transport Service Delivery via Coordinated Data Modules 5.6.3. 5G Transport Service Delivery via Coordinated Data Modules
The overview of network slice structure as defined in the 3GPP 5GS The overview of network slice structure as defined in the 3GPP 5GS
is shown in Figure 4. The terms are described in specific 3GPP is shown in Figure 4. The terms are described in specific 3GPP
documents [TS23501] [TS28530]. documents [TS23501] [TS28530].
<================== E2E-NSI =======================> <================== E2E-NSI =======================>
: : : : : : : : : :
: : : : : : : : : :
<====== RAN-NSSI ======><=TN-NSSI=><====== CN-NSSI ======>VL[APL] <====== RAN-NSSI ======><=TN-NSSI=><====== CN-NSSI ======>VL[APL]
: : : : : : : : : : : : : : : : : :
skipping to change at page 29, line 10 skipping to change at page 29, line 10
The TE Service mapping model can be used to map L3VPN service The TE Service mapping model can be used to map L3VPN service
requests onto underlying network resource and TE models to get the requests onto underlying network resource and TE models to get the
TE network provisioned. TE network provisioned.
For IP VPN service provisioning, the service parameters in the L3VPN For IP VPN service provisioning, the service parameters in the L3VPN
service model [RFC8299] can be decomposed into a set of service model [RFC8299] can be decomposed into a set of
configuration parameters described in the L3VPN network model [I- configuration parameters described in the L3VPN network model [I-
D.ietf-opsawg-l3sm-l3nm] which will get the VPN network provisioned. D.ietf-opsawg-l3sm-l3nm] which will get the VPN network provisioned.
5. Scalability Considerations 6. Scalability Considerations
Enhanced VPN provides performance guaranteed services in packet Enhanced VPN provides performance guaranteed services in packet
networks, but with the potential cost of introducing additional networks, but with the potential cost of introducing additional
states into the network. There are at least three ways that this states into the network. There are at least three ways that this
additional state might be presented in the network: additional state might be presented in the network:
o Introduce the complete state into the packet, as is done in SR. o Introduce the complete state into the packet, as is done in SR.
This allows the controller to specify a detailed series of This allows the controller to specify a detailed series of
forwarding and processing instructions for the packet as it transits forwarding and processing instructions for the packet as it transits
the network. The cost of this is an increase in the packet header the network. The cost of this is an increase in the packet header
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Reducing the state in the network is important to enhanced VPN, as Reducing the state in the network is important to enhanced VPN, as
it requires the overlay to be more closely integrated with the it requires the overlay to be more closely integrated with the
underlay than with traditional VPNs. This tighter coupling would underlay than with traditional VPNs. This tighter coupling would
normally mean that more state needed to be created and maintained in normally mean that more state needed to be created and maintained in
the network, as the state about fine granularity processing would the network, as the state about fine granularity processing would
need to be loaded and maintained in the routers. However, a segment need to be loaded and maintained in the routers. However, a segment
routed approach allows much of this state to be spread amongst the routed approach allows much of this state to be spread amongst the
network ingress nodes, and transiently carried in the packets as network ingress nodes, and transiently carried in the packets as
SIDs. SIDs.
5.1. Maximum Stack Depth of SR 6.1. Maximum Stack Depth of SR
One of the challenges with SR is the stack depth that nodes are able 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 to impose on packets [RFC8491]. This leads to a difficult balance
between adding state to the network and minimizing stack depth, or between adding state to the network and minimizing stack depth, or
minimizing state and increasing the stack depth. minimizing state and increasing the stack depth.
5.2. RSVP Scalability 6.2. RSVP Scalability
The traditional method of creating a resource allocated path through The traditional method of creating a resource allocated path through
an MPLS network is to use the RSVP protocol. However there have an MPLS network is to use the RSVP protocol. However there have
been concerns that this requires significant continuous state been concerns that this requires significant continuous state
maintenance in the network. Work to improve the scalability of maintenance in the network. Work to improve the scalability of
RSVP-TE LSPs in the control plane can be found in [RFC8370]. RSVP-TE LSPs in the control plane can be found in [RFC8370].
There is also concern at the scalability of the forwarder footprint There is also concern at the scalability of the forwarder footprint
of RSVP as the number of paths through an LSR grows. [RFC8577] of RSVP as the number of paths through an LSR grows. [RFC8577]
proposes to address this by employing SR within a tunnel established proposes to address this by employing SR within a tunnel established
by RSVP-TE. by RSVP-TE.
5.3. SDN Scaling 6.3. SDN Scaling
The centralized approach of SDN requires state to be stored in the The centralized approach of SDN requires state to be stored in the
network, but does not have the overhead of also requiring control network, but does not have the overhead of also requiring control
plane state to be maintained. Each individual network node may need plane state to be maintained. Each individual network node may need
to maintain a communication channel with the SDN controller, but to maintain a communication channel with the SDN controller, but
that compares favourably with the need for a control plane to that compares favourably with the need for a control plane to
maintain communication with all neighbors. maintain communication with all neighbors.
However, SDN may transfer some of the scalability concerns from the However, SDN may transfer some of the scalability concerns from the
network to the centralized controller. In particular, there may be network to the centralized controller. In particular, there may be
a heavy processing burden at the controller, and a heavy load in the a heavy processing burden at the controller, and a heavy load in the
network surrounding the controller. network surrounding the controller.
6. OAM Considerations 7. OAM Considerations
The enhanced VPN OAM design needs to consider the following The enhanced VPN OAM design needs to consider the following
requirements: requirements:
o Instrumentation of the underlay so that the network operator can o Instrumentation of the underlay so that the network operator can
be sure that the resources committed to a tenant are operating be sure that the resources committed to a tenant are operating
correctly and delivering the required performance. correctly and delivering the required performance.
o Instrumentation of the overlay by the tenant. This is likely to o Instrumentation of the overlay by the tenant. This is likely to
be transparent to the network operator and to use existing methods. be transparent to the network operator and to use existing methods.
skipping to change at page 31, line 26 skipping to change at page 31, line 26
delivered. This needs to be done in a non-intrusive manner, delivered. This needs to be done in a non-intrusive manner,
particularly when the tenant is deploying a performance sensitive particularly when the tenant is deploying a performance sensitive
application. application.
o Verification of the conformity of the path to the service o Verification of the conformity of the path to the service
requirement. This may need to be done as part of a commissioning requirement. This may need to be done as part of a commissioning
test. test.
A study of OAM in SR networks has been documented in [RFC8403]. A study of OAM in SR networks has been documented in [RFC8403].
7. Telemetry Considerations 8. Telemetry Considerations
Network visibility is essential for network operation. Network Network visibility is essential for network operation. Network
telemetry has been considered as an ideal means to gain sufficient telemetry has been considered as an ideal means to gain sufficient
network visibility with better flexibility, scalability, accuracy, network visibility with better flexibility, scalability, accuracy,
coverage, and performance than conventional OAM technologies. coverage, and performance than conventional OAM technologies.
As defined in [I-D.ietf-opsawg-ntf], the purpose of Network As defined in [I-D.ietf-opsawg-ntf], the purpose of Network
Telemetry is to acquire network data remotely for network monitoring Telemetry is to acquire network data remotely for network monitoring
and operation. It is a general term for a large set of network and operation. It is a general term for a large set of network
visibility techniques and protocols. Network telemetry addresses visibility techniques and protocols. Network telemetry addresses
the current network operation issues and enables smooth evolution the current network operation issues and enables smooth evolution
toward intent-driven autonomous networks. Telemetry can be applied toward intent-driven autonomous networks. Telemetry can be applied
on the forwarding plane, the control plane, and the management plane on the forwarding plane, the control plane, and the management plane
in a network. in a network.
How the telemetry mechanisms could be used or extended for the How the telemetry mechanisms could be used or extended for the
enhanced VPN service will be described in a separate document. enhanced VPN service will be described in a separate document.
8. Enhanced Resiliency 9. Enhanced Resiliency
Each enhanced VPN has a life-cycle, and may need modification during Each enhanced VPN has a life-cycle, and may need modification during
deployment as the needs of its tenant change. Additionally, as the deployment as the needs of its tenant change. Additionally, as the
network as a whole evolves, there may need to be garbage collection network as a whole evolves, there may need to be garbage collection
performed to consolidate resources into usable quanta. performed to consolidate resources into usable quanta.
Systems in which the path is imposed such as SR, or some form of Systems in which the path is imposed such as SR, or some form of
explicit routing tend to do well in these applications, because it explicit routing tend to do well in these applications, because it
is possible to perform an atomic transition from one path to another. is possible to perform an atomic transition from one path to another.
This is a single action by the head-end changes the path without the This is a single action by the head-end changes the path without the
skipping to change at page 33, line 5 skipping to change at page 33, line 5
consideration has to be given to the impact of best effort traffic consideration has to be given to the impact of best effort traffic
on the high priority packets during a transient. Specifically if a on the high priority packets during a transient. Specifically if a
conventional re-convergence process is used there will inevitably be conventional re-convergence process is used there will inevitably be
micro-loops and whilst some form of explicit routing will protect micro-loops and whilst some form of explicit routing will protect
the high priority traffic, lower priority traffic on best effort the high priority traffic, lower priority traffic on best effort
shortest paths will micro-loop without the use of a loop prevention shortest paths will micro-loop without the use of a loop prevention
technology. To provide the highest quality of service to high technology. To provide the highest quality of service to high
priority traffic, either this traffic must be shielded from the priority traffic, either this traffic must be shielded from the
micro-loops, or micro-loops must be prevented. micro-loops, or micro-loops must be prevented.
9. Operational Considerations 10. Operational Considerations
It is likely that enhanced VPN service will be introduced in It is likely that enhanced VPN service will be introduced in
networks which already have traditional VPN services deployed. networks which already have traditional VPN services deployed.
Depends on service requirement, the tenants or the operator may Depends on service requirement, the tenants or the operator may
choose to use traditional VPN or enhanced VPN to fulfil the service choose to use traditional VPN or enhanced VPN to fulfil the service
requirement. The information and parameters to assist such decision requirement. The information and parameters to assist such decision
needs to be reflected on the management interface between the needs to be reflected on the management interface between the
tenants and the operator. tenants and the operator.
10. Security Considerations 11. Security Considerations
All types of virtual network require special consideration to be All types of virtual network require special consideration to be
given to the isolation of traffic belonging to different tenants. given to the isolation of traffic belonging to different tenants.
That is, traffic belonging to one VPN must not be delivered to end That is, traffic belonging to one VPN must not be delivered to end
points outside that VPN. In this regard enhanced VPNs neither points outside that VPN. In this regard enhanced VPNs neither
introduce, no experience a greater security risks than other VPNs. introduce, no experience a greater security risks than other VPNs.
However, in an enhanced Virtual Private Network service the However, in an enhanced Virtual Private Network service the
additional service requirements need to be considered. For example, additional service requirements need to be considered. For example,
if a service requires a specific upper bound to latency then it can if a service requires a specific upper bound to latency then it can
skipping to change at page 33, line 45 skipping to change at page 33, line 45
other security features as part of the service, customers would be other security features as part of the service, customers would be
well advised to take responsibility for their own security well advised to take responsibility for their own security
requirements themselves possibly by encrypting traffic before requirements themselves possibly by encrypting traffic before
handing it off to the service provider. handing it off to the service provider.
The privacy of enhanced VPN service customers must be preserved. It The privacy of enhanced VPN service customers must be preserved. It
should not be possible for one customer to discover the existence of should not be possible for one customer to discover the existence of
another customer, nor should the sites that are members of an another customer, nor should the sites that are members of an
enhanced VPN be externally visible. enhanced VPN be externally visible.
11. IANA Considerations 12. IANA Considerations
There are no requested IANA actions. There are no requested IANA actions.
12. Contributors 13. Contributors
Daniel King Daniel King
Email: daniel@olddog.co.uk Email: daniel@olddog.co.uk
Adrian Farrel Adrian Farrel
Email: adrian@olddog.co.uk Email: adrian@olddog.co.uk
Jeff Tansura Jeff Tansura
Email: jefftant.ietf@gmail.com Email: jefftant.ietf@gmail.com
skipping to change at page 34, line 31 skipping to change at page 34, line 31
Mohamed Boucadair Mohamed Boucadair
Email: mohamed.boucadair@orange.com Email: mohamed.boucadair@orange.com
Sergio Belotti Sergio Belotti
Email: sergio.belotti@nokia.com Email: sergio.belotti@nokia.com
Haomian Zheng Haomian Zheng
Email: zhenghaomian@huawei.com Email: zhenghaomian@huawei.com
13. Acknowledgments Zhenbin Li
Email: lizhenbin@huawei.com
14. Acknowledgments
The authors would like to thank Charlie Perkins, James N Guichard, The authors would like to thank Charlie Perkins, James N Guichard,
John E Drake and Shunsuke Homma for their review and valuable John E Drake and Shunsuke Homma for their review and valuable
comments. comments.
This work was supported in part by the European Commission funded This work was supported in part by the European Commission funded
H2020-ICT-2016-2 METRO-HAUL project (G.A. 761727). H2020-ICT-2016-2 METRO-HAUL project (G.A. 761727).
14. References 15. References
14.1. Normative References 15.1. Normative References
[I-D.ietf-teas-actn-vn-yang] Lee, Y., Dhody, D., Ceccarelli, D., [I-D.ietf-teas-actn-vn-yang] Lee, Y., Dhody, D., Ceccarelli, D.,
Bryskin, I., and B. Yoon, "A Yang Data Model for VN Bryskin, I., and B. Yoon, "A Yang Data Model for VN
Operation", draft-ietf-teas-actn-vn-yang-07 (work in Operation", draft-ietf-teas-actn-vn-yang-07 (work in
progress), October 2019. progress), October 2019.
[I-D.ietf-teas-te-service-mapping-yang] Lee, Y., Dhody, D., Fioccola, [I-D.ietf-teas-te-service-mapping-yang] Lee, Y., Dhody, D., Fioccola,
G., Wu, Q., Ceccarelli, D., and J. Tantsura, "Traffic G., Wu, Q., Ceccarelli, D., and J. Tantsura, "Traffic
Engineering (TE) and Service Mapping Yang Model", draft- Engineering (TE) and Service Mapping Yang Model", draft-
ietf-teas-te-service-mapping-yang-02 (work in progress), ietf-teas-te-service-mapping-yang-02 (work in progress),
skipping to change at page 36, line 5 skipping to change at page 36, line 5
[RFC8453] Ceccarelli, D., Ed. and Y. Lee, Ed., "Framework for [RFC8453] Ceccarelli, D., Ed. and Y. Lee, Ed., "Framework for
Abstraction and Control of TE Networks (ACTN)", RFC 8453, Abstraction and Control of TE Networks (ACTN)", RFC 8453,
DOI 10.17487/RFC8453, August 2018, <https://www.rfc- DOI 10.17487/RFC8453, August 2018, <https://www.rfc-
editor.org/info/rfc8453>. editor.org/info/rfc8453>.
[RFC8466] Wen, B., Fioccola, G., Ed., Xie, C., and L. Jalil, "A YANG [RFC8466] Wen, B., Fioccola, G., Ed., Xie, C., and L. Jalil, "A YANG
Data Model for Layer 2 Virtual Private Network (L2VPN) Data Model for Layer 2 Virtual Private Network (L2VPN)
Service Delivery", RFC 8466, DOI 10.17487/RFC8466, October Service Delivery", RFC 8466, DOI 10.17487/RFC8466, October
2018, <https://www.rfc-editor.org/info/rfc8466>. 2018, <https://www.rfc-editor.org/info/rfc8466>.
14.2. Informative References 15.2. Informative References
[BBF-SD406] "BBF SD-406: End-to-End Network Slicing", 2016, [BBF-SD406] "BBF SD-406: End-to-End Network Slicing", 2016,
<https://wiki.broadband-forum.org/display/BBF/SD-406+End- <https://wiki.broadband-forum.org/display/BBF/SD-406+End-
to-End+Network+Slicing>. to-End+Network+Slicing>.
[DETNET] "Deterministic Networking", March , [DETNET] "Deterministic Networking", March ,
<https://datatracker.ietf.org/wg/detnet/about/>. <https://datatracker.ietf.org/wg/detnet/about/>.
[FLEXE] "Flex Ethernet Implementation Agreement", March 2016, [FLEXE] "Flex Ethernet Implementation Agreement", March 2016,
<https://www.oiforum.com/wp-content/uploads/2019/01/OIF- <https://www.oiforum.com/wp-content/uploads/2019/01/OIF-
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