TEAS Working Group J. Dong
Internet-Draft Huawei
Intended status: Informational S. Bryant
Expires: January 14, 2021 Futurewei
Z. Li
China Mobile
T. Miyasaka
KDDI Corporation
Y. Lee
Samsung
July 13, 2020
A Framework for Enhanced Virtual Private Networks (VPN+) Service
draft-ietf-teas-enhanced-vpn-06
Abstract
This document describes the framework for Enhanced Virtual Private
Network (VPN+) service. The purpose is to support the needs of new
applications, particularly applications that are associated with 5G
services, by utilizing an approach that is based on existing VPN and
Traffic Engineering (TE) technologies and adds features that specific
services require over and above traditional VPNs.
Typically, VPN+ will be used to form the underpinning of network
slicing, but could also be of use in its own right providing enhanced
connectivity services between customer sites.
It is envisaged that enhanced VPNs will be delivered using a
combination of existing, modified, and new networking technologies.
This document provides an overview of relevant technologies and
identifies some areas for potential new work.
Comparing to traditional VPNs, It is not envisaged that quite large
numbers of VPN+ services will be deployed in a network. In other
word, it is not intended that all existing VPNs supported by a
network will use VPN+ related techniques.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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working documents as Internet-Drafts. The list of current Internet-
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This Internet-Draft will expire on January 14, 2021.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Overview of the Requirements . . . . . . . . . . . . . . . . 6
3.1. Isolation between Enhanced VPN Services . . . . . . . . . 6
3.1.1. A Pragmatic Approach to Isolation . . . . . . . . . . 8
3.2. Performance Guarantee . . . . . . . . . . . . . . . . . . 9
3.3. Integration . . . . . . . . . . . . . . . . . . . . . . . 10
3.3.1. Abstraction . . . . . . . . . . . . . . . . . . . . . 11
3.4. Dynamic Management . . . . . . . . . . . . . . . . . . . 11
3.5. Customized Control . . . . . . . . . . . . . . . . . . . 12
3.6. Applicability . . . . . . . . . . . . . . . . . . . . . . 12
3.7. Inter-Domain and Inter-Layer Network . . . . . . . . . . 12
4. Architecture of Enhanced VPN . . . . . . . . . . . . . . . . 13
4.1. Layered Architecture . . . . . . . . . . . . . . . . . . 14
4.2. Multi-Point to Multi-Point (MP2MP) Connectivity . . . . . 17
4.3. Application Specific Network Types . . . . . . . . . . . 17
4.4. Scaling Considerations . . . . . . . . . . . . . . . . . 17
5. Candidate Technologies . . . . . . . . . . . . . . . . . . . 18
5.1. Layer-Two Data Plane . . . . . . . . . . . . . . . . . . 18
5.1.1. Flexible Ethernet . . . . . . . . . . . . . . . . . . 18
5.1.2. Dedicated Queues . . . . . . . . . . . . . . . . . . 19
5.1.3. Time Sensitive Networking . . . . . . . . . . . . . . 19
5.2. Layer-Three Data Plane . . . . . . . . . . . . . . . . . 20
5.2.1. Deterministic Networking . . . . . . . . . . . . . . 20
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5.2.2. MPLS Traffic Engineering (MPLS-TE) . . . . . . . . . 20
5.2.3. Segment Routing . . . . . . . . . . . . . . . . . . . 20
5.3. Non-Packet Data Plane . . . . . . . . . . . . . . . . . . 21
5.4. Control Plane . . . . . . . . . . . . . . . . . . . . . . 21
5.5. Management Plane . . . . . . . . . . . . . . . . . . . . 22
5.6. Applicability of Service Data Models to Enhanced VPN . . 22
5.6.1. Network Slice Delivery via Coordinated Service Data
Models . . . . . . . . . . . . . . . . . . . . . . . 23
6. Scalability Considerations . . . . . . . . . . . . . . . . . 24
6.1. Maximum Stack Depth of SR . . . . . . . . . . . . . . . . 25
6.2. RSVP Scalability . . . . . . . . . . . . . . . . . . . . 25
6.3. SDN Scaling . . . . . . . . . . . . . . . . . . . . . . . 25
7. OAM Considerations . . . . . . . . . . . . . . . . . . . . . 25
8. Telemetry Considerations . . . . . . . . . . . . . . . . . . 26
9. Enhanced Resiliency . . . . . . . . . . . . . . . . . . . . . 26
10. Operational Considerations . . . . . . . . . . . . . . . . . 27
11. Security Considerations . . . . . . . . . . . . . . . . . . . 27
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 28
14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 29
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 29
15.1. Normative References . . . . . . . . . . . . . . . . . . 29
15.2. Informative References . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35
1. Introduction
Virtual private networks (VPNs) have served the industry well as a
means of providing different groups of users with logically isolated
connectivity over a common network. The common or base network that
is used to provide the VPNs is often referred to as the underlay, and
the VPN is often called an overlay.
Customers of a network operator may request a connectivity services
with advanced characteristics such as enhanced isolation from other
services so that changes in some other service (such as changes in
network load, or events such as congestion or outages) have no or
acceptable effect on the throughput or latency of the services
provided to the customer. These services are "enhanced VPNs" (known
as VPN+) in that they are similar to VPN services as they provide the
customer with required connectivity, but have enhanced
characteristics.
Driven largely by needs surfacing from 5G, the concept of network
slicing has gained traction [NGMN-NS-Concept] [TS23501] [TS28530]
[BBF-SD406]. According to [TS28530], a 5G end-to-end network slice
consists of three major types network segments: Radio Access Network
(RAN), Transport Network (TN) and Mobile Core Network (CN). The
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transport network provides the required connectivity between
different entities in RAN and CN segments of an end-to-end network
slice, with specific performance commitment.
A transport network slice is a virtual (logical) network with a
particular network topology and a set of shared or dedicated network
resources, which are used to provide the network slice consumer with
the required connectivity, appropriate isolation and specific Service
Level Objective (SLO).
A transport network slice could span multiple technologies (such as
IP or Optical) and multiple administrative domains. Depending on the
consumer's requirement, a transport network slice could be isolated
from other, often concurrent transport network slices in terms of
data plane, control plane, and management plane resources.
In this document the term "network slice" refers to a transport
network slice, and is considered as one typical use case of enhanced
VPN.
Network slicing builds on the concept of resource management, network
virtualization, and abstraction to provide performance assurance,
flexibility, programmability and modularity. It may use techniques
such as Software Defined Networking (SDN) [RFC7149], network
abstraction [RFC7926] and Network Function Virtualization (NFV)
[RFC8172] [RFC8568] to create multiple logical (virtual) 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 requirements, on top
of a common network. How the network slices are engineered can be
deployment-specific.
VPN+ could be used to form the underpinning of transport network
slice, but could also be of use in general cases providing enhanced
connectivity services between customer sites.
The requirement of enhanced VPN services cannot be met by simple
overlay networks, as they require tighter coordination and
integration between the underlay and the overlay network. VPN+ is
built from a VPN overlay and a underlying Virtual Transport Network
(VTN) which has a customized network topology and a set of dedicated
or shared network resources. It may optionally include a set of
invoked service functions allocated from the underlay network. Thus
an enhanced VPN can achieve greater isolation with strict performance
guarantees. These new properties, which have general applicability,
may also be of interest as part of a network slicing solution. It is
not envisaged that VPN+ services will replace traditional VPN
services that can continue to be deployed using pre- existing
mechanisms.
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This document specifies a framework for using existing, modified, and
potential new technologies as components to provide a VPN+ service.
Specifically we are concerned with:
o The design of the enhanced data plane.
o The necessary protocols in both the underlay and the overlay of
the enhanced VPN.
o The mechanisms to achieve integration between overlay and
underlay.
o The necessary Operation, Administration, and Management (OAM)
methods to instrument an enhanced VPN to make sure that the
required Service Level Agreement (SLA) is met, and to take any
corrective action to avoid SLA violation, such as switching to an
alternate path.
The required layered network structure to achieve this is shown in
Section 4.1.
Note that, in this document, the relationship of the four terms
"VPN", "VPN+", "VTN", and "Transport Network Slice" are described as
below:
o A VPN refers to the overlay virtual private network which provides
the required service connectivity and traffic separation between
different VPN customers.
o A Virtual Transport Network (VTN) is a virtual underlay network
that connects customer edge points with the additional capability
of providing the isolation and performance characteristics
required by an enhanced VPN customer.
o An enhanced VPN (VPN+) can be considered as an evolution of VPN
service, but with additional service-specific commitments. An
enhanced VPN (VPN+) is made by integrating an overlay VPN and a
VTN with a set of network resources allocated in the underlay
network.
o A transport network slice could be provided with an enhanced VPN
(VPN+).
2. Terminologies
The following terms are used in this document. Some of them are
newly defined, some others reference existing definitions:
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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
enhanced VPN service.
3.1. Isolation between Enhanced VPN Services
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 any
other traffic flows in the network. One way for a service provider
to guarantee the customer's SLA is by controlling the degree of
isolation from other services in the network. Isolation is a feature
that can be requested by customers. There are different grades of
how isolation may be enabled by a network operator and that may
result in different levels of service perceived by the customer.
These range from simple separation of service traffic on delivery
(ensuring that traffic is not delivered to the wrong customer), all
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the way to complete separation within the underlay so that the
traffic from different services use distinct network resources.
The terms hard and soft isolation are used to illustrate different
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
MPLS VPNs are examples of VPNs with soft isolation: the network
delivers the traffic only to the required VPN endpoints. However,
with soft isolation, traffic from VPNs and regular non-VPN traffic
may congest the network resulting in packet loss and delay for other
VPNs operating normally. The ability for a VPN service or a group of
VPN services to be sheltered from this effect is called hard
isolation, and this property is required by some applications. Hard
isolation is needed so that applications with exacting requirements
can function correctly, despite other demands (perhaps a burst of
traffic in another VPN) competing for the underlying resources. In
practice isolation may be offered as a spectrum between soft and
hard, and in some cases soft and hard isolation may be used in a
hierarchical manner. An operator may offer its customers a choice of
different degrees of isolation ranging from soft isolation up to hard
isolation.
An example of the requirement for hard isolation is a network
supporting both emergency services and public broadband multi-media
services. During a major incident the VPNs supporting these services
would both be expected to experience high data volumes, and it is
important that both make progress in the transmission of their data.
In these circumstances the VPN services would require an appropriate
degree of isolation to be able to continue to operate acceptably. On
the other hand, VPNs servicing ordinary bulk data may expect to
contest for network resources and queue packets so that traffic is
delivered within SLAs, but with some potential delays and
interference.
In order to provide the required level of isolation, resources may
have to be reserved in the data plane of the underlay network and
dedicated to traffic from a specific VPN or a specific group of VPNs
to form different enhanced VPNs in the network. This may introduce
scalability concerns, thus some trade-off needs to be considered to
provide the required isolation between some enhanced VPNs while still
allowing reasonable sharing.
An optical layer can offer a high degree of isolation, at the cost of
allocating resources on a long term and end-to-end basis. On the
other hand, where adequate isolation can be achieved at the packet
layer, this permits the resources to be shared amongst a group of
services and only dedicated to a service on a temporary basis.
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There are several new technologies that provide some assistance with
these data plane issues. Firstly there is the IEEE project on Time
Sensitive Networking [TSN] which introduces the concept of packet
scheduling of delay and loss sensitive packets. Then there is
[FLEXE] which provides the ability to multiplex multiple channels
over one or more Ethernet links in a way that provides hard
isolation. Finally there are advanced queueing approaches which
allow the construction of virtual sub-interfaces, each of which is
provided with dedicated resource in a shared physical interface.
These approaches are described in more detail later in this document.
Section 3.1.1 explores pragmatic approaches to isolation in packet
networks.
3.1.1. A Pragmatic Approach to Isolation
A key question is whether it is possible to achieve hard isolation in
packet networks that were never designed to support hard isolation.
On the contrary, they were designed to provide statistical
multiplexing, a significant economic advantage when compared to a
dedicated, or a Time Division Multiplexing (TDM) network. However,
there is no need to provide any harder isolation than is required by
the applications. An approximation to this requirement is sufficient
in most cases. Pseudowires[RFC3985] emulate services that would have
had hard isolation in their native form.
This spectrum of isolation is shown in Figure 1:
O=================================================O
| \---------------v---------------/
Statistical Pragmatic Absolute
Multiplexing Isolation Isolation
(Traditional VPNs) (Enhanced VPN) (Dedicated Network)
Figure 1: The Spectrum of Isolation
Figure 1 shows the spectrum of isolation that may be delivered by a
network. At one end of the figure, we have traditional statistical
multiplexing technologies that support VPNs. This is a service type
that has served the industry well and will continue to do so. At the
opposite end of the spectrum, we have the absolute isolation provided
by dedicated transport networks. The goal of enhanced VPNs is
"pragmatic isolation". This is isolation that is better than is
obtainable from pure statistical multiplexing, more cost effective
and flexible than a dedicated network, but is a practical solution
that is good enough for the majority of applications. Mechanisms for
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both soft isolation and hard isolation would be needed to meet
different levels of service requirement.
3.2. Performance Guarantee
There are several kinds of performance guarantee, including
guaranteed maximum packet loss, guaranteed maximum delay, and
guaranteed delay variation. Note that these guarantees apply to
conformance traffic, out-of-profile traffic will be handled according
to other requirements.
Guaranteed maximum packet loss is a common parameter, and is usually
addressed by setting packet priorities, queue size, and discard
policy. However this becomes more difficult when the requirement is
combined with latency requirements. The limiting case is zero
congestion loss, and that is the goal of the Deterministic Networking
work that the IETF [DETNET] and IEEE [TSN] are pursuing. In modern
optical networks, loss due to transmission errors already approaches
zero, but there are the possibilities of failure of the interface or
the fiber itself. This can only be addressed by some form of signal
duplication and transmission over diverse paths.
Guaranteed maximum latency is required in a number of applications
particularly real-time control applications and some types of virtual
reality applications. The work of the IETF Deterministic Networking
(DetNet) Working Group [DETNET] is relevant, however additional
methods of enhancing the underlay to better support the delay
guarantees may be needed, and these methods will need to be
integrated with the overall service provisioning mechanisms.
Guaranteed maximum delay variation is a service that may also be
needed. [RFC8578] calls up a number of cases where this is needed,
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
the service might be delivered by the underlay as a shared service
and not provided through different enhanced VPNs. Alternatively a
dedicated enhanced VPN may be used to provide this as a shared
service.
This suggests that a spectrum of service guarantee be considered when
deploying an enhanced VPN. As a guide to understanding the design
requirements we can consider four types:
o Best effort
o Assured bandwidth
o Guaranteed latency
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o Enhanced delivery
Best effort service is the basic service that current VPNs can
provide.
An assured bandwidth service is one in which the bandwidth over some
period of time is assured. This can be achieved either simply based
on best effort with over-capacity provisioning, or it can be based on
TE-LSPs with bandwidth reservation. The instantaneous bandwidth is
however, not necessarily assured, depending on the technique used.
Providing assured bandwidth to VPNs, for example by using per-VPN TE-
LSPs, is not widely deployed at least partially due to scalability
concerns. VPN+ aims to provide a more scalable approach for such
kind of service.
A guaranteed latency service has a latency upper bound provided by
the network. Assuring the upper bound is sometimes more important
than minimizing latency. There are several new technologies that
provide some assistance with performance guarantee. Firstly there is
the IEEE project on Time Sensitive Networking [TSN] which introduces
the concept of packet scheduling of delay and loss sensitive packets.
Then the DetNet work is also of greater relevance in assuring upper
bound of end-to-end packet latency. Flex Ethernet [FLEXE] is also
useful to provide these guarantees. The usage of such underlying
technologies for VPN+ service needs to be considered.
An enhanced delivery service is one in which the underlay network (at
Layer 3) attempts to deliver the packet through multiple paths in the
hope of eliminating packet loss due to equipment or media failures.
Such mechanism may need to be used for VPN+ service.
3.3. Integration
The only way to achieve the enhanced characteristics provided by an
enhanced VPN (such as guaranteed or predicted performance) is by
integrating the overlay VPN with a particular set of network
resources in the underlay network which are allocated to meet the
service requirement. This needs be done in a flexible and scalable
way so that it can be widely deployed in operator networks to support
a reasonable number of enhanced VPN customers.
Taking mobile networks and in particular 5G into consideration, the
integration of network and the service functions is a likely
requirement. The work in IETF SFC working group [SFC] provides a
foundation for this integration.
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3.3.1. Abstraction
Integration of the overlay VPN and the underlay network resources
does not need to be a tight mapping. As described in [RFC7926],
abstraction is the process of applying policy to a set of information
about a TE network to produce selective information that represents
the potential ability to connect across the network. The process of
abstraction presents the connectivity graph in a way that is
independent of the underlying network technologies, capabilities, and
topology so that the graph can be used to plan and deliver network
services in a uniform way.
Virtual networks can be built on top of an abstracted topology that
represents the connectivity capabilities of the underlay network as
described in the framework for Abstraction and Control of TE Networks
(ACTN) [RFC8453] as discussed further in Section 5.5.
3.4. Dynamic Management
Enhanced VPNs need to be created, modified, and removed from the
network according to service demand. An enhanced VPN that requires
hard isolation (Section 3.1) must not be disrupted by the
instantiation or modification of another enhanced VPN. Determining
whether modification of an enhanced VPN can be disruptive to that
VPN, and in particular whether the traffic in flight will be
disrupted can be a difficult problem.
The data plane aspects of this problem are discussed further in
Sections Section 5.1,Section 5.2 and Section 5.3.
The control plane aspects of this problem are discussed further in
Section 5.4.
The management plane aspects of this problem are discussed further in
Section 5.5.
Dynamic changes both to the VPN and to the underlay transport network
need to be managed to avoid disruption to services that are sensitive
to the change of network performance.
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
to a link, VPN traffic might need to be moved as a result of traffic
volume changes.
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3.5. Customized Control
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 of how the resources and functions allocated to this enhanced
VPN are used. For example, the tenant may be able to specify the
service paths in his own enhanced VPN. Depending on the requirement,
an enhanced VPN may have its own dedicated controller, which may be
provided with an interface to the control system provided by the
network operator. Note that such control is within the scope of the
tenant's enhanced VPN, any change beyond that would require some
intervention of the operator.
A description of the control plane aspects of this problem are
discussed further in Section 5.4. A description of the management
plane aspects of this feature can be found in Section 5.5.
3.6. Applicability
The technologies described in this document should be applicable to a
number types of VPN overlay services such as:
o Layer 2 point-to-point services such as pseudowires [RFC3985]
o Layer 2 VPNs [RFC4664]
o Ethernet VPNs [RFC7209]
o Layer 3 VPNs [RFC4364], [RFC2764]
Where such VPN types need enhanced isolation and delivery
characteristics, the technologies described in Section 5 can be used
to provide an underlay with the required enhanced performance.
3.7. Inter-Domain and Inter-Layer Network
In some scenarios, an enhanced VPN services may span multiple network
domains. A domain is considered to be any collection of network
elements within a common realm of address space or path computation
responsibility [RFC5151]. In some domains the operator may manage a
multi-layered network, for example, a packet network over an optical
network. When enhanced VPNs are provisioned in such network
scenarios, the technologies used in different network planes (data
plane, control plane, and management plane) need to provide
mechanisms to support multi-domain and multi-layer coordination and
integration, so as to provide the required service characteristics
for different enhanced VPNs, and improve network efficiency and
operational simplicity.
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4. Architecture of Enhanced VPN
A number of enhanced VPN services will typically be provided by a
common network infrastructure. Each enhanced VPN consists of both
the overlay and a corresponding VTN with a specific set of network
resources and functions allocated in the underlay to satisfy the
needs of the VPN tenant. The integration between overlay and various
underlay resources ensures the required isolation between different
enhanced VPNs, and achieves the guaranteed performance for different
services.
An enhanced VPN needs to be designed with consideration given to:
o A enhanced data plane
o A control plane to create enhanced VPNs, making use of the data
plane isolation and performance guarantee techniques.
o A management plane for enhanced VPN service life-cycle management.
These required characteristics are expanded below:
o Enhanced data plane
* Provides the required resource isolation capability, e.g.
bandwidth guarantee.
* Provides the required packet latency and jitter
characteristics.
* Provides the required packet loss characteristics.
* Provides the mechanism to associate a packet with the set of
resources allocated to the enhanced VPN which the packet
belongs.
o Control plane
* Collect information about the underlying network topology and
resources available and export this to nodes in the network
and/or the centralized controller as required.
* Create the required virtual transport networks (VTNs) with the
resource and properties needed by the enhanced VPN services
that are assigned to them.
* Determine the risk of SLA violation and take appropriate
avoiding action.
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* Determine the right balance of per-packet and per-node state
according to the needs of enhanced VPN service to scale to the
required size.
o Management plane
* Provides an interface between the enhanced VPN provider (e.g.
the Transport Network (TN) Manager) and the enhanced VPN
clients (e.g. the 3GPP Management System) such that some of the
operation requests can be met without interfering with the
enhanced VPN of other clients.
* Provides an interface between the enhanced VPN provider and the
enhanced VPN clients to expose transport network capability
information toward the enhanced VPN client.
* Provides the service life-cycle management and operation of
enhanced VPN (e.g. creation, modification, assurance/monitoring
and decommissioning).
o Operations, Administration, and Maintenance (OAM)
* Provides the OAM tools to verify the connectivity and
performance of the enhanced VPN.
* Provide the OAM tools to verify whether the underlay network
resources are correctly allocated and operated properly.
o Telemetry
* Provides the mechanism to collect the data plane, control plane
and management plane data of the network, more specifically:
*
+ Provides the mechanism to collect network data from the
underlay network for overall performance evaluation and the
enhanced VPN service planning.
+ Provides the mechanism to collect network data of each
enhanced VPN for the monitoring and analytics of the
characteristics and SLA fulfilment of enhanced VPN services.
4.1. Layered Architecture
The layered architecture of an enhanced VPN is shown in Figure 2.
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Underpinning everything is the physical network infrastructure layer
which provide the underlying resources used to provision the
separated virtual transport networks (VTNs). This includes the
partitioning of link and/or node resources. Each subset of link or
node resource can be considered as a virtual link or virtual node
used to build the VTNs.
A
| |
+-------------------+ Centralized
| Network Controller| Control & Management
+-------------------+
||
\/
o---------------------------o
/-------------o
o____________/______________o VPN Services
...... (P2P,P2MP,MP2MP...)
o-----------\ /-------------o
o____________X______________o
__________________________
/ o----o----o /
/ / / / VTN-1
/ o-----o-----o----o----o /
/_________________________/
__________________________
/ o----o /
/ / / \ / VTN-2
/ o-----o----o----o-----o /
/_________________________/
...... ...
___________________________
/ o----o /
/ / / / VTN-3
/ o-----o----o----o-----o /
/__________________________/
++++ ++++ ++++
+--+===+--+===+--+
+--+===+--+===+--+
++++ +++\\ ++++ Physical
|| || \\ ||
|| || \\ || Network
++++ ++++ ++++ \\+++ ++++
+--+===+--+===+--+===+--+===+--+ Infrastructure
+--+===+--+===+--+===+--+===+--+
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++++ ++++ ++++ ++++ ++++
O Virtual Node
-- Virtual Link
++++
+--+ Physical Node with resource partition
+--+
++++
== Physical Link with resource partition
Figure 2: The Layered Architecture of VPN+
Various components and techniques discussed in Section 5 can be used
to enable resource partition, such as FlexE, Time Sensitive
Networking, Deterministic Networking, Dedicated queues, etc. These
partitions may be physical, or virtual so long as the SLA required by
the higher layers is met.
Based on the network resources provided by the physical network
infrastructure, multiple VTNs can be provisioned, each with
customized topology and other attributes to meet the requirement of
different enhanced VPNs or different groups of enhanced VPNs. To get
the required characteristic, each VTN needs to be mapped to a set of
network nodes and links in the network infrastructure. And on each
node or link, the VTN is associated with a set of resources which are
allocated for the processing of traffic in the VTN. VTN provides the
integration between the virtual network topology and the required
underlying network resources.
The centralized controller is used to create the VTN, and to instruct
the network nodes to allocate the required resources to each VTN and
to provision the enhanced VPN services on the VTNs. A distributed
control plane may also be used for the distribution of the VTN
topology and attribute information between nodes within the VTNs.
The process used to create VTNs and to allocate network resources for
use by VTNs needs to take a holistic view of the needs of all of its
tenants (i.e., of all customers and their associated VTNs), and to
partition the resources accordingly. However, within a VTN these
resources can, if required, be managed via a dynamic control plane.
This provides the required scalability and isolation.
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4.2. Multi-Point to Multi-Point (MP2MP) Connectivity
At the VPN service level, the required connectivity is usually mesh
or partial-mesh. To support such kinds of VPN service, the
corresponding VTN in underlay is also an abstract MP2MP medium.
Other service requirements may be expressed at different granularity,
some of which can be applicable to the whole service, while some
others may be only applicable to some pairs of end points. For
example, when particular level of performance guarantee is required,
the point-to-point path through the underlay of the enhanced VPN may
need to be specifically engineered to meet the required performance
guarantee.
4.3. Application Specific Network Types
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
carrying other traffic types, in particular Ethernet traffic. This
is easily accomplished through the various pseudowire (PW) techniques
[RFC3985]. Where the underlay is MPLS, Ethernet can be carried over
the enhanced VPN encapsulated according to the method specified in
[RFC4448]. Where the underlay is IP, Layer Two Tunneling Protocol -
Version 3 (L2TPv3) [RFC3931] can be used with Ethernet traffic
carried according to [RFC4719]. Encapsulations have been defined for
most of the common Layer 2 types for both PW over MPLS and for
L2TPv3.
4.4. Scaling Considerations
VPNs are instantiated as overlays on top of an operator's network and
offered as services to the operator's customers. An important
feature of overlays is that they are able to deliver services without
placing per-service state in the core of the underlay network.
Enhanced VPNs may need to install some additional state within the
network to achieve the additional features that they require.
Solutions must consider minimizing and controlling the scale of such
state, and deployment architectures should constrain the number of
enhanced VPNs that would exist where such services would place
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
number of enhanced VPN will be much fewer than traditional VPNs,
because pre-existing VPN techniques are be good enough to meet the
needs of most existing VPN-type services.
In general, it is not required that the state in the network be
maintained in a 1:1 relationship with the VPN+ services. It will
usually be possible to aggregate a set of VPN+ services so that they
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share the same VTN and the same set of network resources (much in the
way that current VPNs are aggregated over transport tunnels) so that
collections of enhanced VPNs that require the same behaviour from the
network in terms of resource reservation, latency bounds, resiliency,
etc. are able to be grouped together. This is an important feature
to assist with the scaling characteristics of VPN+ deployments.
See Section 6 for a greater discussion of scalability considerations.
5. Candidate Technologies
A VPN is a network created by applying a demultiplexing technique to
the underlying network (the underlay) in order to distinguish the
traffic of one VPN from that of another. A VPN path that travels by
other than the shortest path through the underlay normally requires
state in the underlay to specify that path. State is normally
applied to the underlay through the use of the RSVP signaling
protocol, or directly through the use of an SDN controller, although
other techniques may emerge as this problem is studied. This state
gets harder to manage as the number of VPN paths increases.
Furthermore, as we increase the coupling between the underlay and the
overlay to support the enhanced VPN service, this state will increase
further.
In an enhanced VPN different subsets of the underlay resources can be
dedicated to different enhanced VPNs or different groups of enhanced
VPNs. An enhanced VPN solution thus needs tighter coupling with
underlay than is the case with existing VPNs. We cannot, for
example, share the network resource between enhanced VPNs which
require hard isolation.
5.1. Layer-Two Data Plane
A number of candidate Layer 2 packet or frame-based data plane
solutions which can be used provide the required isolation and
guarantees are described in following sections.
5.1.1. Flexible Ethernet
FlexE [FLEXE] provides the ability to multiplex channels over an
Ethernet link to create point-to-point fixed-bandwidth connections in
a way that provides hard isolation. FlexE also supports bonding
links to create larger links out of multiple low capacity links.
However, FlexE is only a link level technology. When packets are
received by the downstream node, they need to be processed in a way
that preserves that isolation in the downstream node. This in turn
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requires a queuing and forwarding implementation that preserves the
end-to-end isolation.
If different FlexE channels are used for different services, then no
sharing is possible between the FlexE channels. This means that it
may be difficult to dynamically redistribute unused bandwidth to
lower priority services in another FlexE channel. If one FlexE
channel is used by one tenant, the tenant can use some methods to
manage the relative priority of his own traffic in the FlexE channel.
5.1.2. Dedicated Queues
DiffServ based queuing systems are described in [RFC2475] and
[RFC4594]. This is considered insufficient to provide isolation for
enhanced VPNs because DiffServ does not always provide enough markers
to differentiate between traffic of many enhanced VPNs, or offer the
range of service classes that each VPN needs to provide to its
tenants. This problem is particularly acute with an MPLS underlay,
because MPLS only provides eight Traffic Classes.
In addition, DiffServ, as currently implemented, mainly provides per-
hop priority-based scheduling, and it is difficult to use it to
achieve quantitive resource reservation.
In order to address these problems and to reduce the potential
interference between enhanced VPNs, it would be necessary to steer
traffic to dedicated input and output queues per enhanced VPN: some
routers have a large number of queues and sophisticated queuing
systems, which could support this, while some routers may struggle to
provide the granularity and level of isolation required by the
applications of enhanced VPN.
5.1.3. Time Sensitive Networking
Time Sensitive Networking (TSN) [TSN] is an IEEE project that is
designing a method of carrying time sensitive information over
Ethernet. It introduces the concept of packet scheduling where a
packet stream may be given a time slot guaranteeing that it
experiences no queuing delay or increase in latency. The mechanisms
defined in TSN can be used to meet the requirements of time sensitive
services of an enhanced VPN.
Ethernet can be emulated over a Layer 3 network using an IP or MPLS
pseudowire. However, a TSN Ethernet payload would be opaque to the
underlay and thus not treated specifically as time sensitive data.
The preferred method of carrying TSN over a Layer 3 network is
through the use of deterministic networking as explained in
Section 5.2.1.
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5.2. Layer-Three Data Plane
We now consider the problem of slice differentiation and resource
representation in the network layer.
5.2.1. Deterministic Networking
Deterministic Networking (DetNet) [RFC8655] is a technique being
developed in the IETF to enhance the ability of Layer 3 networks to
deliver packets more reliably and with greater control over the
delay. The design cannot use re-transmission techniques such as TCP
since that can exceed the delay tolerated by the applications. Even
the delay improvements that are achieved with Stream Control
Transmission Protocol Partial Reliability Extension (SCTP-PR)
[RFC3758] may not meet the bounds set by application demands. DetNet
pre-emptively sends copies of the packet over various paths to
minimize the chance of all copies of a packet being lost. It also
seeks to set an upper bound on latency, but the goal is not to
minimize latency.
5.2.2. MPLS Traffic Engineering (MPLS-TE)
MPLS-TE [RFC2702][RFC3209] introduces the concept of reserving end-
to-end bandwidth for a TE-LSP, which can be used to provide point-
to-point Virtual Transport Path (VTP) across the underlay network to
support VPNs. VPN traffic can be carried over dedicated TE-LSPs to
provide reserved bandwidth for each specific connection in a VPN, and
VPNs with similar behaviour requirements may be multiplexed onto the
same TE-LSPs. Some network operators have concerns about the
scalability and management overhead of MPLS-TE system, and this has
lead them to consider other solutions for their networks.
5.2.3. Segment Routing
Segment Routing (SR) [RFC8402] is a method that prepends instructions
to packets at the head-end of a path. These instructions are used to
specify the nodes and links to be traversed and allow the packets to
be routed on paths other than the shortest path. By encoding the
state in the packet, per-path state is transitioned out of the
network.
An SR traffic engineered path operates with a granularity of a link
with hints about priority provided through the use of the traffic
class (TC) or Differentiated Services Code Point (DSCP) field in the
header. However to achieve the latency and isolation characteristics
that are sought by the enhanced VPN users, steering packets through
specific queues and resources will likely be required. With SR, it
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is possible to introduce such fine-grained packet steering by
specifying the queues and resources through an SR instruction list.
Note that the concept of queue is a useful abstraction for different
types of underlay mechanism that may be used to provide enhanced
isolation and latency support. How the queue satisfies the
requirement is implementation specific and is transparent to the
layer-3 data plane and control plane mechanisms used.
With Segment Routing, the SR instruction list could be used to build
a P2P path, 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
and behaviours, and meet many of the key requirements in particular
for bandwidth guarantees, traffic isolation (with physical isolation
often being an integral part of the technology), highly predictable
latency and jitter characteristics, measurable loss characteristics,
and ease of identification of flows. The cost is the resources are
allocated on a long term and end-to-end basis. Such an arrangement
means that the full cost of the resources has be borne by the service
that is allocated with the resources.
5.4. Control Plane
Enhanced VPN would likely be based on a hybrid control mechanism,
which takes advantage of the logically centralized controller for on-
demand provisioning and global optimization, whilst still relying on
a distributed control plane to provide scalability, high reliability,
fast reaction, automatic failure recovery, etc. Extension to and
optimization of the distributed control plane is needed to support
the enhanced properties of VPN+.
RSVP-TE [RFC3209] provides the signaling mechanism for establishing a
TE-LSP in an MPLS network with end-to-end resource reservation. This
can be seen as an approach of providing Virtual Transport Path (VTP),
which could be used to bind the VPN to specific network resources
allocated within the underlay, but there remain scalability concerns
mentioned in Section 5.2.2.
The control plane of SR [RFC8665] [RFC8667]
[I-D.ietf-idr-bgp-ls-segment-routing-ext] does not have the
capability of signaling resource reservations along the path. On the
other hand, the SR approach provides a potential way of binding the
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underlay network resource and the enhanced VPN service without
requiring per-path state to be maintained in the network. A
centralized controller can perform resource planning and reservation
for enhanced VPNs, while it needs to ensure that resources are
correctly allocated in network nodes for the enhanced VPN service.
The controller could also compute the SR paths based on the planned
or collected network resource and other attributes, and provision the
SR paths based on the mechanism in
[I-D.ietf-spring-segment-routing-policy] to the ingress nodes of the
enhanced VPN services. The distributed control plane may be used to
advertise the network attributes associated with enhanced VPNs, and
compute the SR paths with specific constraints of enhanced VPN
services.
5.5. Management Plane
The management plane provides the interface between the enhanced VPN
provider and the clients for the service life-cycle management (e.g.
creation, modification, assurance/monitoring and decommissioning).
It relies on a set of service data models for the description of the
information and operations needed on the interface.
As an example, in the context of 5G end-to-end network slicing
[TS28530], the management of enhanced VPNs is considered as the
management of the transport network part of the end-to-end network
slice. 3GPP management system may provide the connectivity and
performance related parameters as requirements to the management
plane of the transport network. It may also require the transport
network to expose the capability and status of the transport network
slice. Thus, an interface between the enhanced VPN management plane
and the 3GPP network slice management system, and relevant service
data models are needed for the coordination of end-to-end network
slice management.
The management plane interface and data models for enhanced VPN can
be based on the service models described in Section 5.6
5.6. Applicability of Service Data Models to Enhanced VPN
ACTN supports operators in viewing and controlling different domains
and presenting virtualized networks to their customers. The ACTN
framework [RFC8453] highlights how:
o Abstraction of the underlying network resources is provided to
higher-layer applications and customers.
o Underlying resources are virtualized and allocated for the
customer, application, or service.
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o A virtualized environment is created allowing operators to view
and control multi-domain networks as a single virtualized network.
o Networks can be presented to customers as a virtual network via
open and programmable interfaces.
The type of network virtualization enabled by ACTN managed
infrastructure provides customers and applications (tenants) with the
capability to utilize and independently control allocated virtual
network resources as if they were physically their own resources.
Service Data models are used to represent, monitor, and manage the
virtual networks and services enabled by ACTN. The Customer VPN
model (e.g. L3SM [RFC8299], L2SM [RFC8466]) or an ACTN Virtual
Network (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 as a set of abstracted services or resources. The L3VPN
network model [I-D.ietf-opsawg-l3sm-l3nm] and [I-D.ietf-opsawg-l2nm]
provide a network view of the ACTN managed infrastructure presented
by the ACTN provider as a set of transport resources.
5.6.1. Network Slice Delivery via Coordinated Service Data Models
In order to support network slice service in transport network, a
Transport Slice (TS) Northbound Interface (NBI) data model may be
needed for a consumer to express the requirements for transport
slices, which can be technology-agnostic. Then these requirements
may be realized using technology-specific Southbound Interface (SBI).
As per [RFC8453] and [I-D.ietf-teas-actn-yang], the CNC-MDSC
Interface (CMI) of ACTN is used to convey the virtual network service
requirements, which is a generic interface to deliver various TE
based VN services. In the context of network slice northbound
interface, there may be some gaps in L3SM/L2SM or VN model, or the
combination of them. The TS NBI is required to communicate the
connectivity of the transport slice, along with the service level
objective (SLO) parameters and traffic selection rules, and provides
a way to monitor the state of the transport slice. This can be
described in a more abstracted manner, so as to reduce the
association with specific realization technologies of transport
network slice, such as the VPN and TE technologies. The transport
slice model as defined in [I-D.wd-teas-transport-slice-yang] provides
an abstracted and generic approach to meet the transport slice NBI
requirement.
The MDSC-PNC Interface (MPI) models in the ACTN architecture can be
used for the realization of transport slices, for example, in a TE
enabled transport network, and may also be used for cross-layer or
cross-domain implementation of transport slice.
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6. Scalability Considerations
Enhanced VPN provides performance guaranteed services in packet
networks, but with the potential cost of introducing additional
states into the network. There are at least three ways that this
additional state might be presented in the network:
o Introduce the complete state into the packet, as is done in SR.
This allows the controller to specify the detailed series of
forwarding and processing instructions for the packet as it
transits the network. The cost of this is an increase in the
packet header size. The cost is also that systems will have
capabilities enabled in case they are called upon by a service.
This is a type of latent state, and increases as we more precisely
specify the path and resources that need to be exclusively
available to a VPN.
o Introduce the state to the network. This is normally done by
creating a path using RSVP-TE, which can be extended to introduce
any element that needs to be specified along the path, for example
explicitly specifying queuing policy. It is possible to use other
methods to introduce path state, such as via a Software Defined
Network (SDN) controller, or possibly by modifying a routing
protocol. With this approach there is state per path, per path
characteristic that needs to be maintained over its life-cycle.
This is more state than is needed using SR, but the packets are
shorter.
o Provide a hybrid approach. One example is based on using binding
SIDs [RFC8402] to create path fragments, and bind them together
with SR. Dynamic creation of a VPN service path using SR requires
less state maintenance in the network core at the expense of
larger packet headers. The packet size can be lower if a form of
loose source routing is used (using a few nodal SIDs), and it will
be lower if no specific functions or resources on the routers are
specified.
Reducing the state in the network is important to enhanced VPN, as it
requires the overlay to be more closely integrated with the underlay
than with traditional VPNs. This tighter coupling would normally
mean that more state needed to be created and maintained in the
network, as the state about fine granularity processing would need to
be loaded and maintained in the routers. However, a segment routed
approach allows much of this state to be spread amongst the network
ingress nodes, and transiently carried in the packets as SIDs.
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6.1. Maximum Stack Depth of SR
One of the challenges with SR is the stack depth that nodes are able
to impose on packets [RFC8491]. This leads to a difficult balance
between adding state to the network and minimizing stack depth, or
minimizing state and increasing the stack depth.
6.2. RSVP Scalability
The traditional method of creating a resource allocated path through
an MPLS network is to use the RSVP protocol. However there have been
concerns that this requires significant continuous state maintenance
in the network. Work to improve the scalability of RSVP-TE LSPs in
the control plane can be found in [RFC8370].
There is also concern at the scalability of the forwarder footprint
of RSVP as the number of paths through an LSR grows. [RFC8577]
proposes to address this by employing SR within a tunnel established
by RSVP-TE.
6.3. SDN Scaling
The centralized approach of SDN requires state to be stored in the
network, but does not have the overhead of also requiring control
plane state to be maintained. Each individual network node may need
to maintain a communication channel with the SDN controller, but that
compares favourably with the need for a control plane to maintain
communication with all neighbors.
However, SDN may transfer some of the scalability concerns from the
network to the centralized controller. In particular, there may be a
heavy processing burden at the controller, and a heavy load in the
network surrounding the controller.
7. OAM Considerations
The enhanced VPN OAM design needs to consider the following
requirements:
o Instrumentation of the underlay so that the network operator can
be sure that the resources committed to a tenant are operating
correctly and delivering the required performance.
o Instrumentation of the overlay by the tenant. This is likely to
be transparent to the network operator and to use existing
methods. Particular consideration needs to be given to the need
to verify the isolation and the various committed performance
characteristics.
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o Instrumentation of the overlay by the network provider to
proactively demonstrate that the committed performance is being
delivered. This needs to be done in a non-intrusive manner,
particularly when the tenant is deploying a performance sensitive
application.
o Verification of the conformity of the path to the service
requirement. This may need to be done as part of a commissioning
test.
A study of OAM in SR networks has been documented in [RFC8403].
8. Telemetry Considerations
Network visibility is essential for network operation. Network
telemetry has been considered as an ideal means to gain sufficient
network visibility with better flexibility, scalability, accuracy,
coverage, and performance than conventional OAM technologies.
As defined in [I-D.ietf-opsawg-ntf], Network Telemetry is to acquire
network data remotely for network monitoring and operation. It is a
general term for a large set of network visibility techniques and
protocols. Network telemetry addresses the current network operation
issues and enables smooth evolution toward intent-driven autonomous
networks. Telemetry can be applied on the forwarding plane, the
control plane, and the management plane in a network.
How the telemetry mechanisms could be used or extended for the
enhanced VPN service is out of the scope of this document.
9. Enhanced Resiliency
Each enhanced VPN has a life-cycle, and may need modification during
deployment as the needs of its tenant change. Additionally, as the
network as a whole evolves, there may need to be garbage collection
performed to consolidate resources into usable quanta.
Systems in which the path is imposed such as SR, or some form of
explicit routing tend to do well in these applications, because it 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
need for coordinated action by the routers along the path. However,
implementations and the monitoring protocols need to make sure that
the new path is up and meets the required SLA before traffic is
transitioned to it. It is possible for deadlocks to arise as a
result of the network becoming fragmented over time, such that it is
impossible to create a new path or to modify an existing path without
impacting the SLA of other paths. Resolution of this situation is as
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much a commercial issue as it is a technical issue and is outside the
scope of this document.
There are, however, two manifestations of the latency problem that
are for further study in any of these approaches:
o The problem of packets overtaking one and other if a path latency
reduces during a transition.
o The problem of transient variation in latency in either direction
as a path migrates.
There is also the matter of what happens during failure in the
underlay infrastructure. Fast reroute is one approach, but that
still produces a transient loss with a normal goal of rectifying this
within 50ms [RFC5654]. An alternative is some form of N+1 delivery
such as has been used for many years to support protection from
service disruption. This may be taken to a different level using the
techniques proposed by the IETF deterministic network work with
multiple in-network replication and the culling of later packets
[RFC8655].
In addition to the approach used to protect high priority packets,
consideration has to be given to the impact of best effort traffic on
the high priority packets during a transient. Specifically if a
conventional re-convergence process is used there will inevitably be
micro-loops and whilst some form of explicit routing will protect the
high priority traffic, lower priority traffic on best effort shortest
paths will micro-loop without the use of a loop prevention
technology. To provide the highest quality of service to high
priority traffic, either this traffic must be shielded from the
micro-loops, or micro-loops must be prevented.
10. Operational Considerations
It is likely that enhanced VPN service will be introduced in networks
which already have traditional VPN services deployed. Depends on
service requirement, the tenants or the operator may choose to use
traditional VPN or enhanced VPN to fulfil the service requirement.
The information and parameters to assist such decision needs to be
reflected on the management interface between the tenants and the
operator.
11. Security Considerations
All types of virtual network require special consideration to be
given to the isolation of traffic belonging to different tenants.
That is, traffic belonging to one VPN must not be delivered to end
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points outside that VPN. In this regard enhanced VPNs neither
introduce, no experience a greater security risks than other VPNs.
However, in an enhanced Virtual Private Network service the
additional service requirements need to be considered. For example,
if a service requires a specific upper bound to latency then it can
be damaged by simply delaying the packets through the activities of
another tenant, i.e., by introducing bursts of traffic for other
services.
The measures to address these dynamic security risks must be
specified as part to the specific solution are form part of the
isolation requirements of a service.
While an enhanced VPN service may be sold as offering encryption and
other security features as part of the service, customers would be
well advised to take responsibility for their own security
requirements themselves possibly by encrypting traffic before handing
it off to the service provider.
The privacy of enhanced VPN service customers must be preserved. It
should not be possible for one customer to discover the existence of
another customer, nor should the sites that are members of an
enhanced VPN be externally visible.
12. IANA Considerations
There are no requested IANA actions.
13. Contributors
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Daniel King
Email: daniel@olddog.co.uk
Adrian Farrel
Email: adrian@olddog.co.uk
Jeff Tansura
Email: jefftant.ietf@gmail.com
Zhenbin Li
Email: lizhenbin@huawei.com
Qin Wu
Email: bill.wu@huawei.com
Bo Wu
Email: lana.wubo@huawei.com
Daniele Ceccarelli
Email: daniele.ceccarelli@ericsson.com
Mohamed Boucadair
Email: mohamed.boucadair@orange.com
Sergio Belotti
Email: sergio.belotti@nokia.com
Haomian Zheng
Email: zhenghaomian@huawei.com
14. Acknowledgements
The authors would like to thank Charlie Perkins, James N Guichard,
John E Drake and Shunsuke Homma for their review and valuable
comments.
This work was supported in part by the European Commission funded
H2020-ICT-2016-2 METRO-HAUL project (G.A. 761727).
15. References
15.1. Normative References
[RFC2764] Gleeson, B., Lin, A., Heinanen, J., Armitage, G., and A.
Malis, "A Framework for IP Based Virtual Private
Networks", RFC 2764, DOI 10.17487/RFC2764, February 2000,
<https://www.rfc-editor.org/info/rfc2764>.
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[RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
Edge-to-Edge (PWE3) Architecture", RFC 3985,
DOI 10.17487/RFC3985, March 2005,
<https://www.rfc-editor.org/info/rfc3985>.
[RFC4664] Andersson, L., Ed. and E. Rosen, Ed., "Framework for Layer
2 Virtual Private Networks (L2VPNs)", RFC 4664,
DOI 10.17487/RFC4664, September 2006,
<https://www.rfc-editor.org/info/rfc4664>.
15.2. Informative References
[BBF-SD406]
"BBF SD-406: End-to-End Network Slicing", 2016,
<https://wiki.broadband-forum.org/display/BBF/SD-406+End-
to-End+Network+Slicing>.
[DETNET] "Deterministic Networking", March ,
<https://datatracker.ietf.org/wg/detnet/about/>.
[FLEXE] "Flex Ethernet Implementation Agreement", March 2016,
<http://www.oiforum.com/wp-content/uploads/OIF-FLEXE-
01.0.pdf>.
[I-D.ietf-idr-bgp-ls-segment-routing-ext]
Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H.,
and M. Chen, "BGP Link-State extensions for Segment
Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-16
(work in progress), June 2019.
[I-D.ietf-opsawg-l2nm]
Barguil, S., Dios, O., Boucadair, M., Munoz, L., Jalil,
L., and J. Ma, "A Layer 2 VPN Network YANG Model", draft-
ietf-opsawg-l2nm-00 (work in progress), July 2020.
[I-D.ietf-opsawg-l3sm-l3nm]
Barguil, S., Dios, O., Boucadair, M., Munoz, L., and A.
Aguado, "A Layer 3 VPN Network YANG Model", draft-ietf-
opsawg-l3sm-l3nm-03 (work in progress), April 2020.
[I-D.ietf-opsawg-ntf]
Song, H., Qin, F., Martinez-Julia, P., Ciavaglia, L., and
A. Wang, "Network Telemetry Framework", draft-ietf-opsawg-
ntf-03 (work in progress), April 2020.
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[I-D.ietf-spring-segment-routing-policy]
Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
P. Mattes, "Segment Routing Policy Architecture", draft-
ietf-spring-segment-routing-policy-08 (work in progress),
July 2020.
[I-D.ietf-teas-actn-vn-yang]
Lee, Y., Dhody, D., Ceccarelli, D., Bryskin, I., and B.
Yoon, "A Yang Data Model for VN Operation", draft-ietf-
teas-actn-vn-yang-08 (work in progress), March 2020.
[I-D.ietf-teas-actn-yang]
Lee, Y., Zheng, H., Ceccarelli, D., Yoon, B., Dios, O.,
Shin, J., and S. Belotti, "Applicability of YANG models
for Abstraction and Control of Traffic Engineered
Networks", draft-ietf-teas-actn-yang-05 (work in
progress), February 2020.
[I-D.wd-teas-transport-slice-yang]
Bo, W., Dhody, D., Han, L., and R. Rokui, "A Yang Data
Model for Transport Slice NBI", draft-wd-teas-transport-
slice-yang-02 (work in progress), July 2020.
[NGMN-NS-Concept]
"NGMN NS Concept", 2016, <https://www.ngmn.org/fileadmin/u
ser_upload/161010_NGMN_Network_Slicing_framework_v1.0.8.pd
f>.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
<https://www.rfc-editor.org/info/rfc2475>.
[RFC2702] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J.
McManus, "Requirements for Traffic Engineering Over MPLS",
RFC 2702, DOI 10.17487/RFC2702, September 1999,
<https://www.rfc-editor.org/info/rfc2702>.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>.
[RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P.
Conrad, "Stream Control Transmission Protocol (SCTP)
Partial Reliability Extension", RFC 3758,
DOI 10.17487/RFC3758, May 2004,
<https://www.rfc-editor.org/info/rfc3758>.
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[RFC3931] Lau, J., Ed., Townsley, M., Ed., and I. Goyret, Ed.,
"Layer Two Tunneling Protocol - Version 3 (L2TPv3)",
RFC 3931, DOI 10.17487/RFC3931, March 2005,
<https://www.rfc-editor.org/info/rfc3931>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <https://www.rfc-editor.org/info/rfc4364>.
[RFC4448] Martini, L., Ed., Rosen, E., El-Aawar, N., and G. Heron,
"Encapsulation Methods for Transport of Ethernet over MPLS
Networks", RFC 4448, DOI 10.17487/RFC4448, April 2006,
<https://www.rfc-editor.org/info/rfc4448>.
[RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration
Guidelines for DiffServ Service Classes", RFC 4594,
DOI 10.17487/RFC4594, August 2006,
<https://www.rfc-editor.org/info/rfc4594>.
[RFC4719] Aggarwal, R., Ed., Townsley, M., Ed., and M. Dos Santos,
Ed., "Transport of Ethernet Frames over Layer 2 Tunneling
Protocol Version 3 (L2TPv3)", RFC 4719,
DOI 10.17487/RFC4719, November 2006,
<https://www.rfc-editor.org/info/rfc4719>.
[RFC5151] Farrel, A., Ed., Ayyangar, A., and JP. Vasseur, "Inter-
Domain MPLS and GMPLS Traffic Engineering -- Resource
Reservation Protocol-Traffic Engineering (RSVP-TE)
Extensions", RFC 5151, DOI 10.17487/RFC5151, February
2008, <https://www.rfc-editor.org/info/rfc5151>.
[RFC5654] Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M., Ed.,
Sprecher, N., and S. Ueno, "Requirements of an MPLS
Transport Profile", RFC 5654, DOI 10.17487/RFC5654,
September 2009, <https://www.rfc-editor.org/info/rfc5654>.
[RFC7149] Boucadair, M. and C. Jacquenet, "Software-Defined
Networking: A Perspective from within a Service Provider
Environment", RFC 7149, DOI 10.17487/RFC7149, March 2014,
<https://www.rfc-editor.org/info/rfc7149>.
[RFC7209] Sajassi, A., Aggarwal, R., Uttaro, J., Bitar, N.,
Henderickx, W., and A. Isaac, "Requirements for Ethernet
VPN (EVPN)", RFC 7209, DOI 10.17487/RFC7209, May 2014,
<https://www.rfc-editor.org/info/rfc7209>.
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[RFC7926] Farrel, A., Ed., Drake, J., Bitar, N., Swallow, G.,
Ceccarelli, D., and X. Zhang, "Problem Statement and
Architecture for Information Exchange between
Interconnected Traffic-Engineered Networks", BCP 206,
RFC 7926, DOI 10.17487/RFC7926, July 2016,
<https://www.rfc-editor.org/info/rfc7926>.
[RFC8172] Morton, A., "Considerations for Benchmarking Virtual
Network Functions and Their Infrastructure", RFC 8172,
DOI 10.17487/RFC8172, July 2017,
<https://www.rfc-editor.org/info/rfc8172>.
[RFC8299] Wu, Q., Ed., Litkowski, S., Tomotaki, L., and K. Ogaki,
"YANG Data Model for L3VPN Service Delivery", RFC 8299,
DOI 10.17487/RFC8299, January 2018,
<https://www.rfc-editor.org/info/rfc8299>.
[RFC8370] Beeram, V., Ed., Minei, I., Shakir, R., Pacella, D., and
T. Saad, "Techniques to Improve the Scalability of RSVP-TE
Deployments", RFC 8370, DOI 10.17487/RFC8370, May 2018,
<https://www.rfc-editor.org/info/rfc8370>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8403] Geib, R., Ed., Filsfils, C., Pignataro, C., Ed., and N.
Kumar, "A Scalable and Topology-Aware MPLS Data-Plane
Monitoring System", RFC 8403, DOI 10.17487/RFC8403, July
2018, <https://www.rfc-editor.org/info/rfc8403>.
[RFC8453] Ceccarelli, D., Ed. and Y. Lee, Ed., "Framework for
Abstraction and Control of TE Networks (ACTN)", RFC 8453,
DOI 10.17487/RFC8453, August 2018,
<https://www.rfc-editor.org/info/rfc8453>.
[RFC8466] Wen, B., Fioccola, G., Ed., Xie, C., and L. Jalil, "A YANG
Data Model for Layer 2 Virtual Private Network (L2VPN)
Service Delivery", RFC 8466, DOI 10.17487/RFC8466, October
2018, <https://www.rfc-editor.org/info/rfc8466>.
[RFC8491] Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg,
"Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491,
DOI 10.17487/RFC8491, November 2018,
<https://www.rfc-editor.org/info/rfc8491>.
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[RFC8568] Bernardos, CJ., Rahman, A., Zuniga, JC., Contreras, LM.,
Aranda, P., and P. Lynch, "Network Virtualization Research
Challenges", RFC 8568, DOI 10.17487/RFC8568, April 2019,
<https://www.rfc-editor.org/info/rfc8568>.
[RFC8577] Sitaraman, H., Beeram, V., Parikh, T., and T. Saad,
"Signaling RSVP-TE Tunnels on a Shared MPLS Forwarding
Plane", RFC 8577, DOI 10.17487/RFC8577, April 2019,
<https://www.rfc-editor.org/info/rfc8577>.
[RFC8578] Grossman, E., Ed., "Deterministic Networking Use Cases",
RFC 8578, DOI 10.17487/RFC8578, May 2019,
<https://www.rfc-editor.org/info/rfc8578>.
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>.
[RFC8665] Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler,
H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", RFC 8665,
DOI 10.17487/RFC8665, December 2019,
<https://www.rfc-editor.org/info/rfc8665>.
[RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C.,
Bashandy, A., Gredler, H., and B. Decraene, "IS-IS
Extensions for Segment Routing", RFC 8667,
DOI 10.17487/RFC8667, December 2019,
<https://www.rfc-editor.org/info/rfc8667>.
[SFC] "Service Function Chaining", March ,
<https://datatracker.ietf.org/wg/sfc/about>.
[TS23501] "3GPP TS23.501", 2016,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3144>.
[TS28530] "3GPP TS28.530", 2016,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3273>.
[TSN] "Time-Sensitive Networking", March ,
<https://1.ieee802.org/tsn/>.
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Authors' Addresses
Jie Dong
Huawei
Email: jie.dong@huawei.com
Stewart Bryant
Futurewei
Email: stewart.bryant@gmail.com
Zhenqiang Li
China Mobile
Email: lizhenqiang@chinamobile.com
Takuya Miyasaka
KDDI Corporation
Email: ta-miyasaka@kddi.com
Young Lee
Samsung
Email: younglee.tx@gmail.com
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