Network Working Group T. Takeda, Ed.
Request for Comments: 4847 NTT
Category: Informational April 2007
Framework and Requirements for Layer 1 Virtual Private Networks
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This document provides a framework and service level requirements for
Layer 1 Virtual Private Networks (L1VPNs). This framework is
intended to aid in developing and standardizing protocols and
mechanisms to support interoperable L1VPNs.
The document examines motivations for L1VPNs, high level (service
level) requirements, and outlines some of the architectural models
that might be used to build L1VPNs.
Table of Contents
1. Introduction ....................................................3
2. Terminology .....................................................3
3. Overview ........................................................5
3.1. Network Topology ...........................................5
3.2. Introducing Layer 1 VPNs ...................................5
3.3. Current Technologies for Dynamic Layer 1 Provisioning ......6
3.4. Relationship with ITU-T ....................................7
4. Motivations .....................................................8
4.1. Basic Layer 1 Services .....................................8
4.1.1. L1VPN for Dynamic Layer 1 Provisioning ..............9
4.2. Merits of L1VPN ............................................9
4.2.1. Customer Merits .....................................9
4.2.2. Provider Merits ....................................10
4.3. L1VPN Deployment Scenarios ................................10
4.3.1. Multi-Service Backbone .............................11
4.3.2. Carrier's Carrier ..................................11
4.3.3. Layer 1 Resource Trading ...........................12
4.3.4. Inter-AS and Inter-SP L1VPNs .......................12
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4.3.5. Scheduling Service .................................13
5. Reference Model ................................................14
5.1. Management Systems ........................................15
6. Generic Service Description ....................................15
6.1. CE Construct ..............................................15
6.2. Generic Service Features ..................................16
7. Service Models .................................................16
7.1. Management-Based Service Model ............................17
7.2. Signaling-Based Service Model (Basic Mode) ................17
7.2.1. Overlay Service Model ..............................18
7.3. Signaling and Routing Service Model (Enhanced Mode) .......19
7.3.1. Overlay Extension Service Model ....................20
7.3.2. Virtual Node Service Model .........................20
7.3.3. Virtual Link Service Model .........................21
7.3.4. Per-VPN Peer Service Model .........................22
8. Service Models and Service Requirements ........................22
8.1. Detailed Service Level Requirements .......................24
9. Recovery Aspects ...............................................25
9.1. Recovery Scope ............................................25
9.2. Recovery Resource Sharing Schemes .........................26
10. Control Plane Connectivity ....................................27
10.1. Control Plane Connectivity between a CE and a PE .........27
10.2. Control Plane Connectivity between CEs ...................28
11. Manageability Considerations ..................................29
12. Security Considerations .......................................31
12.1. Types of Information .....................................32
12.2. Security Features ........................................32
12.3. Scenarios ................................................33
13. Acknowledgements ..............................................34
14. Contributors ..................................................34
15. Normative References ..........................................35
16. Informative References ........................................35
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1. Introduction
This document examines motivations for Layer 1 Virtual Private
Networks (L1VPNs), provides high-level (service-level) requirements,
and outlines some of the architectural models that might be used to
build L1VPNs.
The objective of the document is mainly to present the requirements
and architecture based on the work undertaken within Question 11 of
Study Group 13 of the ITU-T.
L1VPNs provide services over layer 1 networks. This document
provides a framework for L1VPNs and the realization of the framework
by those networks being controlled by Generalized Multi-Protocol
Label Switching (GMPLS) protocols.
Use of GMPLS protocols for providing L1VPN services has several
advantages, such as:
- Flexible network operation.
- Use of standardized protocols.
- Use of common control and measurement plane protocols applicable to
various layer 1 networks, including Time Division Multiplexing
(TDM) networks and optical networks.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The reader is assumed to be familiar with the terminology in
[RFC3031], [RFC3209], [RFC3471], [RFC3473], [RFC4202], [RFC3945],
[RFC4208], and [RFC4026].
In this context, a Layer 1 Network is any transport network that has
connectivity and/or switching using spatial switching (e.g., incoming
port or fiber to outgoing port or fiber), lambda-switching, or time-
division-multiplex-switching.
A Layer 1 VPN (L1VPN) is a service offered by a core layer 1 network
to provide layer 1 connectivity between two or more customer sites,
and where the customer has some control over the establishment and
type of the connectivity. An alternative definition is simply to say
that an L1VPN is a VPN whose data plane operates at layer 1. Further
details of the essence of an L1VPN are provided in Section 3.
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In addition, the following new terms are used within this document:
- Virtual link: A provider network Traffic Engineering (TE) link
advertised to customers in routing information for purposes that
include path computation. A direct data link may or may not exist
between the two end points of a virtual link.
- Virtual node: A provider network logical node advertised to
customers in routing information. A virtual node may represent a
single physical node, or multiple physical nodes and the links
between them.
- VPN end point: A Customer Edge (CE) device's data plane interface,
which is connected to a Provider Edge (PE) device, and which is
part of the VPN membership. Note that a data plane interface is
associated with a TE link end point. For example, if a CE router's
interface is a channelized interface (defined in SONET/SDH), a
channel in the channelized interface can be a data plane interface.
- VPN connection (or connection in the L1VPN context): A connection
between a pair of VPN end points. Note that in some scenarios a
connection may be established between a pair of C (Customer)
devices using this CE-CE VPN connection as a segment or forwarding
adjacency defined in [RFC4206].
Note that the following terms are aligned with Provider Provisioned
VPN (PPVPN) terminology [RFC4026], and in this document, have a
meaning in the context of L1VPNs, unless otherwise specified.
- CE device: A CE device is a customer device that receives L1VPN
service from the provider. A CE device is connected to at least
one PE device. A CE device can be a variety of devices, for
example, Time Division Multiplexing (TDM) switch, router, and layer
2 switch. A CE device does not have to have the capability to
switch at layer 1, but it is capable of receiving a layer 1 signal
and either switching it or terminating it with adaptation. A CE
device may be attached to one or more C devices on the customer
site, and it may be a host using a layer 1 connection directly.
- PE device: A PE device is a provider device that provides L1VPN
service to the customer. A PE device is connected to at least one
CE device. A layer 1 PE device is a TDM switch, an Optical Cross-
Connect (OXC) (see [RFC3945]), or a Photonic Cross-Connect (PXC)
(see [RFC3945]). Alternatively, a PE device may be an Ethernet
Private Line (EPL) type of device that maps Ethernet frames onto
layer 1 connections (by means of Ethernet over TDM etc.).
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- P (Provider) device: A P device is a provider device that is
connected only to other provider devices (P or PE devices). A
layer 1 P is a TDM switch, OXC, or PXC.
- Customer: A customer has authority over a set of CE devices within
the same VPN (e.g., the owner of CE devices). Note that a customer
may outsource the management of CE devices to other organizations,
including to the provider itself.
- Provider: A provider has authority over the management of the
provider network.
- Membership information: A list of CE-PE TE link addresses belonging
to the same VPN. Membership information contains the association
of a CE, a PE, and a VPN.
3. Overview
3.1. Network Topology
The layer 1 network, made of OXCs, TDM switches, or PXCs may be seen
as consisting of PE devices that give access from outside of the
network, and P devices that operate only within the core of the
network. Similarly, outside the layer 1 network is the customer
network consisting of C devices with access to the layer 1 network
made through CE devices.
A CE and PE are connected by one or more links. A CE may also be
connected to more than one PE, and a PE may have more than one CE
connected to it.
A layer 1 connection is provided between a pair of CEs. Such a
connection follows the hierarchy defined in [RFC4206]. That is, a
CE-CE connection may be nested in a lower layer connection (e.g., VC3
connection over STM1 connection). Likewise, the switching
capabilities of the interfaces of the CEs, PEs, and Ps on which a
connection is routed, follow the hierarchy defined in [RFC4206].
3.2. Introducing Layer 1 VPNs
The concept of a PPVPN has been established through many previous
documents such as [RFC4664] and [RFC4110]. Terminology for PPVPNs is
set out in [RFC4026] with special reference to layer 2 and layer 3
VPNs.
The realization of L1VPNs can be based on extensions of the concepts
of the PPVPN to the layer 1 network. It must be understood that
meeting the requirements set out in this document may necessitate
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extensions to the existing mechanisms both for the control plane
within the layer 1 network and for service provisioning at the edge
of the network (CE and PE devices). It is at the interface between
CE and PE devices that the L1VPN service is provided.
Note that the fundamental difference between L1VPNs and L2/L3 VPNs is
that in L1VPNs, data plane connectivity does not guarantee control
plane connectivity (and vice versa). But CE-PE control plane
connectivity is required for L1VPN services provisioned through the
control plane, and CE-CE data plane connectivity is maintained by
signaling mechanisms based on this control plane connectivity.
Furthermore, the provision of CE-CE control plane connectivity over
the provider network is also required for certain levels of L1VPN
service, and this can be achieved by the exchange of control packets
between CEs over the control plane of the provider network. This
aspect is discussed further in Section 10.2.
3.3. Current Technologies for Dynamic Layer 1 Provisioning
Pre-existing efforts at standardization have focused on the provision
of dynamic connections within the layer 1 network (signaling and
routing) and the definition of interfaces for requesting services
between the user and the layer 1 network over the User-Network
Interface (UNI), and between networks across the External Network-
Network Interface (E-NNI) (see [RFC3945], [RFC4208], [RFC4139], and
[RFC4258]).
Current UNIs include features to facilitate requests for end-to-end
(that is, CE to CE) services that include the specification of
constraints such as explicit paths, bandwidth requirements,
protection needs, and (of course) destinations.
Current E-NNIs include features to exchange routing information, as
well as to facilitate requests for end-to-end services.
The UNIs and E-NNIs may be applied in the context of L1VPNs. For
example, the UNI may be applied between the CE and the PE, and the
E-NNI may be applied between PEs (inter-AS/SP L1VPNs), or between the
CE and the PE.
However, the existing UNI and E-NNI specifications do not provide
sufficient parameters to support VPNs without some additions. For
example, there is no way to distinguish between control messages
received over a shared control link (i.e., a control link shared by
multiple VPNs) at a UNI/E-NNI, and these messages must be
disambiguated to determine the L1VPN to which they apply. A control
link is an IP link used for establishing a control channel between
nodes.
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Another example is that there is no clearly defined way of
distributing membership information to be used in combination with
UNI/E-NNI. This function is necessary in order to discover the
existence and location of the CEs to be connected by L1 connections.
Distribution of membership information is typically done by the
provider, and may be realized by mechanisms such as static
provisioning, or by piggybacking on routing protocols (e.g., see
Section 4.2.1 of [RFC4110]). Note that the method chosen for
distribution of membership information depends on the solution used
for supporting L1VPNs, which is outside of the scope of this
document.
Furthermore, customer addressing realms may overlap with each other,
and may also overlap with the service provider addressing realm.
This requires address mapping mechanisms, but such mechanisms are not
well defined in existing UNI/E-NNI specifications.
Lastly, there is no clearly defined way to restrict connectivity
among CEs (or over a UNI/E-NNI). In addition, E-NNIs allow routing
information exchange, but there is no clearly defined way to allow
limited routing information exchange (i.e., a specific set of routing
information is distributed to a specific set of CEs).
In order for L1VPNs to be supported in a fully functional manner,
these additional capabilities and other requirements set out later in
this document must be addressed.
Note that inter-AS/SP L1VPNs require additional analysis beyond the
focus of this document.
3.4. Relationship with ITU-T
The foundation of this document is based on the work of the ITU-T
Study Group 13, Question 11, such as [Y.1312] and [Y.1313]. This
group has been researching and specifying both the requirements and
the architecture of L1VPNs for some time. In this context, the
foundation of this document is a representation of the findings of
the ITU-T, and a presentation of those findings in terms and format
that are familiar to the IETF.
In particular, this document is limited to the areas of concern of
the IETF. That is, it is limited to layer 1 networks that utilize IP
as the underlying support for their control plane.
The foundation of this document presents the requirements and
architectures developed within the ITU-T for better understanding
within the IETF and to further cooperation between the two bodies.
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Some work related to the L1VPN solution space has already been done
within the IETF.
4. Motivations
The general benefits and desirability of VPNs have been described
many times and in many places ([RFC4110] and [RFC4664]). This
document does not dwell on the merits of VPNs as such, but focuses
entirely on the applicability of the VPN concept to layer 1 networks.
Similarly, the utility and value of a control plane for the
configuration, management, and operation of a layer 1 network is
well-rehearsed [RFC3945].
4.1. Basic Layer 1 Services
Basic layer 1 services may be characterized in terms that include:
- Connectivity: Between a pair of CEs.
- Capacity: For example, the bit rate for a TDM service or the
capacity of a lambda.
- Transparency: For example, for an SDH network, overhead
transparency.
- Availability: The percentage of time that the offered service meets
the criteria that the provider defines, possibly agreed with each
customer. To achieve the required level of availability for the
customer connections the service provider's network may use
restoration or protected resources [RFC4427].
- Performance: The quality of the service delivered to customers,
e.g., the number of error-seconds per month.
The layer 1 services may be categorized based on the combination of
connectivity features (data plane) and service control capability
features (control plane) available to the customer. A CE is
associated with the service interface between a customer site and the
provider network, and the categorization can be seen in the context
of this service interface as follows.
1. A single connection between a pair of CEs.
- Static Service:
The classic private line service achieved through a permanent
connection.
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- Dynamic Service:
Either a switched connection service, or a customer-controlled
soft permanent connection service (i.e., the customer is in
control of when the signaled part is established).
2. Multiple connections among a set of CEs.
- Static Service:
A private network service consisting of a mesh of permanent
connections.
- Dynamic Service:
A dynamic private network service consisting of any combination
of switched connection services and customer-controlled soft
permanent connection services.
For service types 1 and 2, connections are point-to-point, and can be
permanent, soft-permanent, or switched. For a static service, the
management plane of the provider network is responsible for the
management of both the network infrastructure and the end-user
connections. For dynamic services, the management plane of the
provider network is only responsible for the configuration of the
infrastructure; end-user connections are established dynamically via
the control plane of the provider network upon customer request.
This document does not preclude other advanced services and topology
support, such as point-to-multipoint (P2MP) services, as part of the
layer 1 services, but these are for further study.
4.1.1. L1VPN for Dynamic Layer 1 Provisioning
Private network services in the second category in Section 4.1 can be
enhanced so that multiple private networks are supported across the
layer 1 network as virtual private networks. These are Layer 1
Virtual Private Networks (L1VPNs). Note that the first category in
Section 4.1 would include L1VPNs with only two CEs as a special case.
Compared to the first category of service, the L1VPN service has
features such as connectivity restriction, a separate policy, and
distribution of membership information applied to a specific group.
4.2. Merits of L1VPN
4.2.1. Customer Merits
From the customer's perspective, there are two main benefits to a
L1VPN. These benefits apply over and above the advantages of access
to a dynamically provisioned network.
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- The customer can outsource the direct management of a layer 1
network by placing the VPN management in the control of a third
party. This frees the customer from the need to configure and
manage the connectivity information for the CEs that participate in
the VPN.
- The customer can make small-scale use of a layer 1 network. So,
for example, by sharing the layer 1 network infrastructure with
many other users, the customer sites can be connected together
across the layer 1 network without bearing the full cost of
deploying and managing the layer 1 network.
To some extent, the customer may also gain from the provider's
benefits (see below). That is, if the provider is able to extract
more value from the layer 1 network, the customer will benefit from
lower priced services that are better tailored to the customer's
needs.
4.2.2. Provider Merits
The provider benefits from the customer's perception of benefits.
In particular, the provider can build on dynamic, on-demand services
by offering new VPN services and off-loading the CE-to-CE
configuration requirements from the customers.
Additionally, a more flexible VPN structure applied to the layer 1
network allows the provider to make more comprehensive use of the
spare (that is, previously unused) resources within the network.
This could be achieved by applying a network model where the provider
is responsible for deciding how resources are used and for
provisioning of the connection through the layer 1 network.
4.3. L1VPN Deployment Scenarios
In large carrier networks providing various kinds of service, it is
often the case that multiple service networks are supported over a
shared transport network. By applying L1VPNs, multiple internal
service networks (which may be managed and operated separately) can
be supported over a shared layer 1 transport network controlled and
managed using GMPLS. In addition, L1VPNs can support capabilities to
offer innovative services to external clients.
Some more specific deployment scenarios are as follows.
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4.3.1. Multi-Service Backbone
A multi-service backbone is characterized such that each service
department of a carrier that receives the carrier's L1VPN service
provides a different kind of higher-layer service. The customer
receiving the L1VPN service (i.e., each service department) can offer
its own services, whose payloads can be any layer (e.g., ATM, IP,
TDM). The layer 1 transport network and each service network belong
to the same organization, but may be managed separately. From the
L1VPN service provider's point of view, these services are not
visible and are not part of the L1VPN service. That is, the type of
service being carried within the layer 1 payload is not known by the
service provider.
The benefit is that the same layer 1 transport network resources are
shared by multiple services. A large capacity backbone network (data
plane) can be built economically by having the resources shared by
multiple services usually with flexibility to modify topologies,
while separating the control functions for each service department.
Thus, each customer can select a specific set of features that are
needed to provide their own service.
Note that it is also possible to control and manage these service
networks and the layer 1 transport network by using GMPLS in the
integrated model [RFC3945] instead of using L1VPNs. However, using
L1VPNs is beneficial in the following points:
- Independent address space for each of the service networks.
- Network isolation (topology information isolation, fault isolation
among service networks).
- Independent layer 1 resource view for each of the service networks.
- Independent policies that could be applied for each of the service
networks.
These points may apply to the management plane functionalities as
well as to the control plane functionalities.
4.3.2. Carrier's Carrier
A carrier's carrier is characterized such that one carrier that
receives another carrier's L1VPN service provides its own services.
In this scenario, two carriers are in different organizations. It
is, therefore, expected that the information provided at the service
demarcation points is more limited than in the multi-service backbone
case. Similarly, less control of the L1VPN service is given at the
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service demarcation points. For example, customers of an L1VPN
service receive:
- A more limited view of the L1VPN service provider network.
- More limited control over the L1VPN service provider network.
One of the merits is that each carrier can concentrate on a specific
service. For example, the customer of the L1VPN service may focus on
L3 services, e.g., providing secure access to the Internet, leaving
the L1VPN provider to focus on the layer 1 service, e.g., providing a
long-haul bandwidth between cities. The L1VPN customer can construct
its own network using layer 1 resources supplied by the L1VPN
provider, usually with flexibility to modify topologies, while
separating the control functions for each customer carrier.
4.3.3. Layer 1 Resource Trading
In addition to the scenarios where the second tier service provider
is using a single core service provider as mentioned in Section
4.3.2, it is possible for the second tier provider to receive
services from more than one core service provider. In this scenario,
there are some benefits for the second tier service provider such as
route redundancy and dynamic carrier selection based on the price.
The second tier service provider can support a function that enables
a layer 1 resource trading service. Using resource information
published by its core service providers, a second tier service
provider can decide how to best use the core providers. For example,
if one core service provider is no longer able to satisfy requests
for service, an alternate service provider can be used. Or the
second tier service provider could choose to respond to price changes
of service over time.
Another example of second tier service provider use is to reduce
exposure to failures in each provider (i.e., to improve
availability).
4.3.4. Inter-AS and Inter-SP L1VPNs
In addition to the scenarios where a single connection between two
CEs is routed over a single service provider as mentioned in Section
4.3.2, it is possible that a connection is routed over multiple ASes
within a service provider (called inter-AS L1VPN) or over multiple
service providers (called inter-SP L1VPN).
The inter-AS L1VPN scenario can be used to construct a single L1VPN
from network resources administered by different domains of a single
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service provider. These administrative domains might not usually
have a collaborative relationship at layer 1, and so the inter-AS
L1VPN offers a new business model for joint delivery of services to a
customer. Consideration of inter-AS L1VPNs requires further analysis
beyond the scope of this document.
The inter-SP scenario can be used to construct a single L1VPN from
services provided by multiple regional providers. There could be a
variety of business relationships among providers and customers, and
this scenario contains many more manageability, security, privacy,
policy, and commercial issues than the more simple inter-AS L1VPN
case. Consideration of inter-SP L1VPN requires further analysis
beyond the scope of this document.
4.3.5. Scheduling Service
In some deployment scenarios, customers of L1VPN services may wish to
set up layer 1 connections not on-demand, but at a planned time in
the future. Or, even though customers of L1VPN services may wish to
use layer 1 connections on-demand, they can tolerate some delay, for
example, due to lack of resources at that moment.
In those scenarios, the provider can reserve bandwidth at a specified
time in the future, and can establish the VPN connections according
to a schedule. This makes it possible to use bandwidth more
efficiently over time (i.e., support more demand). This service, the
scheduling service, may be used to support customers who use layer 1
connections for data backup applications, content delivery
applications, and some other applications.
Furthermore, customers may be able to specify when to release layer 1
connections in advance. By considering this information, the
provider may be able to further engineer scheduling, which leads to
still more efficient bandwidth usage.
Note that scheduling of L1VPN services requires time-scoped resource
management, which is not well considered in current GMPLS protocols
and requires the support of the management plane. In addition,
offering scheduling service and on-demand service on the same
infrastructure needs careful consideration.
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5. Reference Model
Figure 5.1 describes the L1VPN reference model.
: +--------------------+ :
: | +------------+ | :
: | | Management | | :
+------+ : | | system(s) | | : +------+
| C | : | +------------+ | : | CE | +------+
|device| : | | : |device|--| C |
+------+ : | +------+ : | of | |device|
| : | | |=:=|VPN A| +------+
| : | | | : +------+
+------+ : | | PE | : +------+
+------+ | CE | : | |device| : | CE | +------+
| C | |device| : +------+ +------+ | | : |device| | C |
|device|--| of |=:=| |==| |==| |-:-| of |--|device|
+------+ |VPN A| : | | | | +------+ : |VPN B| +------+
+------+ : | PE | | P | | : +------+
+------+ : |device| |device| | : +------+
+------+ | CE | : | | | | +------+ : | CE | +------+
| C |--|device|=:=| |==| |==| |-:-|device|--| C |
|device| | of | : +------+ +------+ | | : | of | |device|
+------+ |VPN B| : | | PE | : |VPN A| +------+
+------+ : | |device| : +------+
| : | | | : +------+
| : | | |=:=| CE | +------+
+------+ : | +------+ : |device| | C |
| C | : | | : | of |--|device|
|device| : | | : |VPN B| +------+
+------+ : | | : +------+
: | | :
Customer | | Customer
interface | | interface
+--------------------+
|<---- Provider ---->|
| network |
Key: ==== Layer 1 Connection -- link
Figure 5.1: L1VPN Reference Model
In an L1VPN, layer 1 connections are provided between CEs' data plane
interfaces within the same VPN. In Figure 5.1, a connection is
provided between the left-hand CE of VPN A and the upper right-hand
CE of VPN A, and another connection is provided between the left-hand
CE of VPN B and lower right-hand CE of VPN B (shown as "=" mark).
These layer 1 connections are called VPN connections.
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Note that as mentioned in Section 3.1, these VPN connections follow
the hierarchy defined in [RFC4206].
5.1. Management Systems
As shown in the reference model, a provider network may contain one
or more management systems. A management system may support
functions including provisioning, monitoring, billing, and recording.
Provider management systems may also communicate with customer
management systems in order to provide services. Sections 7 and 11
provide more detail.
6. Generic Service Description
This section describes generic L1VPN services. Detailed descriptions
are provided through specific service models in Section 7.
6.1. CE Construct
- The CE device may support more than one customer VPN.
- CE-PE data plane links (between data plane interfaces) may be
shared by multiple VPNs.
Note that it is necessary to disambiguate control plane messages
exchanged between CE and PE if the CE-PE relationship is applicable
to more than one VPN. This makes it possible to determine to which
VPN such control plane messages apply. Such disambiguation might be
achieved by allocating a separate control channel to each VPN (either
using a separate physical channel, a separate logical channel such as
IP tunnel, or using separate addressing).
A customer addressing realm consists of CE-PE TE link addresses and
CE-PE control channel addresses as well as customer site addresses (C
and CE addresses). Customer addressing realms may overlap, and may
also overlap with the service provider addressing realm.
NATs or firewalls might reasonably be placed at customer interfaces,
or between administrative domains within the core network.
Addressing in the L1VPN model must handle such eventualities.
Traversal of NATs and firewalls within the customer network might
have implications for L1VPN services that connect C devices, and is
for further study.
Takeda Informational [Page 15]RFC 4847 Layer 1 VPN Framework April 2007
6.2. Generic Service Features
L1VPN has the following two generic service features.
- Connectivity restriction: Layer 1 connectivity is provided to a
limited set of CEs' data plane interfaces, called VPN end points.
(This set forms the L1VPN membership.)
- Per VPN control and management: Some level of control and
management capability is provided to the customer. Details differ
depending on service models described in Section 7.
7. Service Models
This section describes Layer 1 VPN service models that can be
supported by GMPLS protocols enabled networks. These models are
derived from the generic service description presented above.
Such layer 1 networks are managed and controlled using GMPLS
signaling as described in [RFC3471] and [RFC3473], and GMPLS routing
as described in [RFC4202]. It must be understood that meeting the
requirements set out in this document may necessitate extensions to
the existing GMPLS protocols both for the control plane within the
layer 1 network and for service provisioning at the edge of the
network (CE and PE devices). A CE and a PE are connected by one or
more data links. The ends of each link are usually represented as
GMPLS-capable interfaces.
Note that in this document, service models are classified by the
semantics of information exchanged over the customer interface. The
customer interface may be instantiated by the CE-PE control plane
communication and/or the management plane communication between the
customer management systems(s) and the provider management system(s).
Note that how to realize a CE-PE control channel is discussed in
Section 10.1. Customer management system(s) and provider management
systems(s) may communicate by utilizing the CE-PE control channel(s).
Takeda Informational [Page 16]RFC 4847 Layer 1 VPN Framework April 2007
7.1. Management-Based Service Model
Figure 7.1 describes the Management-based service model.
+--------------------+
: | |
+----------+ : | +----------+ |
| Customer | : | | Provider | |
|Management| : | |Management| |
| system(s)|-:-----+----| system(s)| |
+----------+ : | +----------+ |
: | | :
: | | :
+----+ : +----+ +----+ +----+ : +----+
| CE |----:---| PE |----| P |----| PE |---:---| CE |
+----+ : +----+ +----+ +----+ : +----+
: | | :
: | | :
: +--------------------+ :
: | | :
: |<-Provider network->| :
Customer Customer
interface interface
Figure 7.1: Management-Based Service Model
In this service model, customer management systems and provider
management systems communicate with each other. Customer management
systems access provider management systems to request layer 1
connection setup/deletion between a pair of CEs. Customer management
systems may obtain additional information, such as resource
availability information and monitoring information, from provider
management systems. There is no control message exchange between a
CE and PE.
The provider network may be based on GMPLS. In this case, mechanisms
to support soft permanent connections can be applied. However,
interfaces between management systems are not within the scope of
this document.
7.2. Signaling-Based Service Model (Basic Mode)
In this service model, the CE-PE interface's functional repertoire is
limited to path setup signaling only. The provider's network is not
involved in distribution of customer network's routing information.
Takeda Informational [Page 17]RFC 4847 Layer 1 VPN Framework April 2007
Note in addition that there may be communication between customer
management system(s) and provider management system(s) in order to
provide customers with detailed monitoring, fault information, etc.
7.2.1. Overlay Service Model
Figure 7.2 describes the Overlay service model.
+--------------------+
: | | :
: | | :
+----+ : +----+ +----+ : +----+
| CE |---:---| PE | | PE |---:---| CE |
+----+ : +----+ +----+ : +----+
: | | :
: | | :
: +--------------------+ :
: | | :
: |<-Provider network->| :
Customer Customer
interface interface
Figure 7.2: Overlay Service Model
In this service model, the customer interface is based on the GMPLS
UNI Overlay [RFC4208]. The CE requests layer 1 connection
setup/deletion to a remote CE. There is no routing protocol running
(i.e., no routing neighbor/peering relationship) between a CE and a
PE. The CE does not receive routing information from remote customer
sites, nor routing information about the provider network.
The CE's interface may be assigned a public or private address, that
designates VPN end points.
In this model, membership information needs to be configured on PEs,
so that the PE that receives a Path message from the ingress CE can
identify the remote PE connected to the egress CE. Distribution of
membership information between PEs is typically done by the provider,
and may be realized by mechanisms such as static provisioning, or by
piggybacking on routing protocols (auto-discovery).
There are various ways that customers perceive the provider network.
In one example, the whole provider network may be considered as one
node -- the path specified and recorded in signaling messages
reflects this. Note that this is distinct from the Virtual Node
service model described in Section 7.3.2 because such a model
requires that the network is represented to the VPN sites as a
virtual node -- that is, some form of routing advertisement is
Takeda Informational [Page 18]RFC 4847 Layer 1 VPN Framework April 2007
implied, and this is not in scope for the Signaling-based service
model.
7.3. Signaling and Routing Service Model (Enhanced Mode)
In this service model, the CE-PE interface provides the signaling
capabilities as in the Basic Mode, plus permits limited exchange of
information between the control planes of the provider and the
customer to help such functions as discovery of customer network
routing information (i.e., reachability or TE information in remote
customer sites), or parameters of the part of the provider's network
dedicated to the customer.
By allowing CEs to obtain customer network routing information, a
so-called N-square routing problem could be solved.
In addition, by using the received traffic engineering-based routing
information, a customer can use traffic engineering capabilities.
For example, a customer can set up two disjoint connections between a
pair of CEs. Another example is that a customer can request a
connection between a pair of devices within customer sites, and not
necessarily between CEs, with more effective traffic engineering.
As such, the customer interface is based on GMPLS signaling and
mechanisms to exchange reachability/TE information. Typically, a
routing protocol is used between a CE and PE, or more precisely
between a CE and the VPN routing context instantiated on the PE.
Link state routing information would be needed to implement the above
two example scenarios. Some scenarios may be satisfied with
reachability routing information only.
Note that this service model does not preclude the use of mechanisms
other than routing protocols to exchange reachability/TE information.
As with the Signaling-based service model, there may be communication
between customer management system(s) and provider management
system(s) in order to provide detailed monitoring, fault information
etc. to customers.
Four specific types of the Signaling and Routing service model are
the Overlay Extension service model, the Virtual Node service model,
the Virtual Link service model and the Per-VPN Peer service model,
depending on how customers perceive the provider network in routing
and signaling (i.e., the level of information details that a customer
is allowed to receive in routing and signaling).
Takeda Informational [Page 19]
RFC 4847 Layer 1 VPN Framework April 2007
7.3.1. Overlay Extension Service Model
This service model complements the Overlay service model. In this
service model, a CE receives a list of CE-PE TE link addresses to
which it can request a VPN connection (i.e., membership information).
This may include additional information concerning these TE links
(e.g., switching type). Mechanisms other than routing could be used
to exchange reachability/TE information between the CE and the PE.
7.3.2. Virtual Node Service Model
Figure 7.3 describes the Virtual Node service model.
+--------------------+
: | | :
+----+ : | | : +----+
| CE |---:---| Virtual Node |---:---| CE |
+----+ : | | : +----+
: | | :
: +--------------------+ :
: | | :
: |<-Provider network->| :
Customer Customer
interface interface
Figure 7.3: Virtual Node Service Model
In this type of service model, the whole provider network is
represented as a virtual node (defined in Section 2). The customer
perceives the provider network as one single node. The CE receives
routing information about CE-PE links and the customer network (i.e.,
remote customer sites).
Note that in this service model, there must be one single virtual
node, and this virtual node must be connected with every CE in the
VPN.
Takeda Informational [Page 20]RFC 4847 Layer 1 VPN Framework April 2007
7.3.3. Virtual Link Service Model
Figure 7.4 describes the Virtual Link service model.
+--------------------+
: | | :
: | Virtual | :
+----+ : +----+ link +----+ : +----+
| CE |---:---| PE |**************| PE |---:---| CE |
+----+ : +----+ +----+ : +----+
: | | :
: +--------------------+ :
: | | :
: |<-Provider network->| :
Customer Customer
interface interface
Figure 7.4: Virtual Link Service Model
In this service model, a virtual link is constructed between PEs.
For the definition of a virtual link, please refer to terminology in
Section 2. A virtual link is assigned to each VPN and disclosed to
the corresponding CEs. As such, the CE receives routing information
about CE-PE links, customer network (i.e., remote customer sites), as
well as virtual links assigned to each VPN. A special property of
the virtual links used in this service model is that the provider
network allocates data plane link resources for the exclusive use of
each virtual link. The TE attributes of a virtual link are
determined according to data plane link resources allocated to this
virtual link. Virtual links are an abstraction of the provider
network to customers for administrative purposes as well as to
exclude "unnecessary information".
Note that in this service model, both end points of each virtual link
must be a PE device.
Takeda Informational [Page 21]RFC 4847 Layer 1 VPN Framework April 2007
7.3.4. Per-VPN Peer Service Model
Figure 7.5 describes the Per-VPN Peer service model.
+--------------------+
: | | :
+----+ : +----+ +----+ +----+ : +----+
| CE |---:---| PE |----| P |----| PE |---:---| CE |
+----+ : +----+ +----+ +----+ : +----+
: | | :
: +--------------------+ :
: | | :
: |<-Provider network->| :
Customer Customer
interface interface
Figure 7.5: Per-VPN Peer Service Model
This service model is a generalization and combination of the Virtual
Link service model and the Virtual Node service model mentioned in
Sections 7.3.2 and 7.3.3 respectively.
In this service model, the provider partitions the TE links within
the provider network per VPN, and discloses per-VPN TE link
information to corresponding CEs. As such, a CE receives routing
information about CE-PE links, customer network (i.e., remote
customer sites), as well as partitioned portions of the provider
network.
Note that PEs may advertise abstracted routing information about the
provider network to CEs for administrative purpose as well as to
exclude "unnecessary information". In other words, virtual links may
be constructed between two nodes where direct data links do not
exist, or virtual nodes may be constructed to represent multiple
physical nodes and links between them.
In the Per-VPN Peer service model, at least one virtual node
corresponding to P devices (one single P or a set of Ps) must be
visible to customers.
8. Service Models and Service Requirements
The service models mentioned in Section 7 are related to what
information is exchanged between CE and PE. In addition, service
models differ in how data plane resources are allocated for each VPN.
Note that in the ITU-T documents, the term "U-Plane" is used instead
of "data plane".
Takeda Informational [Page 22]RFC 4847 Layer 1 VPN Framework April 2007
o Data plane resource allocation
- Shared or dedicated:
Shared means that provider network data plane links are shared by
multiple (i.e., any or a specific set of) VPNs. (Data plane
links are dynamically allocated to a VPN when a VPN connection is
requested, and data plane links allocated to one VPN at one time
can be allocated to another VPN at another time.)
Dedicated means that provider network data plane links are
partitioned per VPN. (Data plane links are statically allocated
to one VPN and can not be used by other VPNs.)
o Information exchanged between CE and PE
- Signaling
- Membership information (optionally includes TE information of the
associated CE-PE TE links)
- Customer network routing information (reachability only, or may
include TE information)
- Provider network routing information (TE information)
Note that link management information (e.g., LMP [RFC4204]) may be
exchanged between a CE and a PE, but this is orthogonal to the
definition of the service models.
Table 1 shows combination of service requirements and service
models.
Takeda Informational [Page 23]RFC 4847 Layer 1 VPN Framework April 2007
| Data plane | Data plane
| shared | dedicated
---------------------------+------------------+-------------------
Signaling | Overlay | Overlay
---------------------------+------------------+-------------------
Signaling + | Overlay | Overlay
Membership information | Extension | Extension
---------------------------+------------------+-------------------
Signaling + | |
Membership information + | Virtual Node | Virtual Node
Customer network routing | |
information | |
---------------------------+------------------+-------------------
Signaling + | |
Membership information + | | Virtual Link
Customer network routing | Not applicable |
information + | | Per-VPN Peer
Provider network routing | |
information | |
Table 1: Combination of service requirements and service models
As described in previous sections, the difference between the Virtual
Link service model and the Per-VPN Peer service model is whether
customers have visibility of P devices. In the Virtual Link service
model, the end points of virtual links must be PE devices, thus P
devices are not visible to customers. In the Per-VPN Peer service
model, at least one virtual node corresponding to P devices (one
single P, or a set of Ps) is visible to customers.
Note that when customers receive provider network routing information
in the form of virtual link, customers must be able to specify such
links for a VPN connection over the provider network in signaling.
8.1. Detailed Service Level Requirements
In addition to the requirements set out in table 1, more detailed
service requirements are provided below. They are generally common
to the various service models, except where indicated.
- Selection of layer 1 service class: Customers MAY be allowed to
specify a layer 1 service class (e.g., availability level) for a
VPN connection. Further details are described in Section 9.
Takeda Informational [Page 24]RFC 4847 Layer 1 VPN Framework April 2007
- Reception of performance information: Customers MAY be allowed to
receive performance information for their VPN connections (e.g.,
performance monitoring data). When data plane links are dedicated,
customers MAY be allowed to receive performance information for
links dedicated to them.
- Reception of fault information: Customers MAY be allowed to receive
fault information for their VPN connections (e.g., failure
notification by RSVP-TE, data plane alarm notification through the
management plane, notification of connection setup rejection
causes). Note that this does not prevent customers from using
Operations and Management (OAM) mechanisms for, or on, their VPN
connections. When data plane links are dedicated, customers MAY be
allowed to receive fault information for links dedicated to them.
- Reception of connection information: Customers MAY be allowed to
receive information for current VPN connections (through the
management plane).
- Reception of accounting information: Customers MUST be able to
receive accounting information for each VPN.
- Specification of policy: Customers MAY be allowed to specify
policies (e.g., path computation policies, recovery policies
including parameters) for each VPN.
- Security: The communication between the customer and the provider
MUST be secure. Further details are described in Section 12.
- Filtering: Unnecessary information (e.g., information concerning
other VPNs) MUST NOT be provided to each customer. This applies
particularly to the Signaling and Routing service model, but is
also relevant to the Signaling-based service model and to the
Management-based service model. Further details are described in
Section 12.
9. Recovery Aspects
9.1. Recovery Scope
GMPLS provides various recovery techniques for use in different
recovery scenarios [RFC4427]. The provider network may apply these
recovery techniques to protect VPN connections as part of the L1VPN
service, for example as follows:
Takeda Informational [Page 25]RFC 4847 Layer 1 VPN Framework April 2007
o PE-PE recovery
The provider network constitutes a recovery domain, and the
recovery scope is the PE-PE part of the CE-CE VPN connection.
It should be possible for the provider network to hide the provider
network recovery operation from the customer. Namely, it should be
possible to configure the provider network to not notify the
customer when a failure occurs and a PE-PE recovery operation
successfully repairs the failure. Further, when PE-PE recovery
fails and the failure should be notified to the customer, it should
be possible for the provider network to hide its internal topology.
o CE-PE recovery
The recovery scope is either or both of the ingress and egress
CE-PE links of the CE-CE VPN connection.
o CE-CE recovery
The recovery scope is the entire CE-CE VPN connection.
When a failure needs to be notified to a customer so that the
customer can initiate recovery operation, it should be possible for
the provider network to hide its internal topology.
These recovery schemes may be applied in combination.
Customers may be allowed to specify the desired recovery level in a
connection setup request. Furthermore, the customer may be allowed
to specify the desired recovery level in a way that is agnostic of
the recovery technique (e.g., when the recovery operation does not
require cooperation between the provider network and the customer
network). In such cases, the provider network must translate the
specified recovery level into specific recovery techniques, based on
operational policies. This allows enhanced recovery techniques above
and beyond the GMPLS specifications to be used in the provider
network.
9.2. Recovery Resource Sharing Schemes
The provider network may support various recovery resource sharing
schemes, such as the following:
o Shared recovery
When the provider network supports shared recovery (e.g., shared
mesh restoration [RFC4427]), the provider network may provide
Takeda Informational [Page 26]RFC 4847 Layer 1 VPN Framework April 2007
sharing recovery resources between VPN connections that serve with
only the same VPN, a specific set of VPNs, or any VPN. The default
mode is sharing recovery resources with any VPN.
o Extra traffic
GMPLS recovery mechanisms support extra traffic. Extra traffic
allows the transfer of preemptable traffic on the recovery
resources when these resources are not being used for the recovery
of protected normal traffic [RFC4427].
In the context of L1VPNs, extra traffic is applied for CE-CE VPN
connections, or PE-PE part of CE-CE VPN connections. The latter
case may be applied only when there is hierarchy (i.e., CE-CE VPN
connection is nested on top of PE-PE connection). In this section,
the latter aspect is analyzed.
When the provider network allows a CE-CE VPN connection to be set
up as "extra traffic", it means that the VPN connection may use a
PE-PE connection that protects some other CE-CE VPN connection. In
such a case the provider network may restrict extra traffic CE-CE
VPN connection to use resources (i.e., the PE-PE connections) that:
- protect VPN connections from the same VPN as the extra traffic
connection.
- are used for a specific set of VPNs.
- are available for any VPN.
The default mode is to support preemptable traffic on recovery
resources reserved for any VPN.
10. Control Plane Connectivity
10.1. Control Plane Connectivity between a CE and a PE
In the Signaling-based service model and the Signaling and Routing
service model, there must be a control channel (IP-level
connectivity) between a CE and its PE. The instantiation of the
control channel may differ depending on addressing and security.
As stated in Section 6.1, it is necessary to disambiguate control
plane messages exchanged between the CE and PE if the CE-PE
relationship is applicable to more than one VPN. Furthermore,
private addresses may be assigned to CE-PE control channels.
Takeda Informational [Page 27]RFC 4847 Layer 1 VPN Framework April 2007
Security aspects of the CE-PE control channel are discussed in
Section 12.
10.2. Control Plane Connectivity between CEs
A customer network connected by VPN connections may be controlled by
MPLS or GMPLS, and the VPN connections may be treated as TE links
within the customer network. In such cases, there must be control
plane (IP-level) connectivity between the CEs, so that control
messages, such as signaling and routing messages, can be exchanged
between the CEs. Furthermore, in some recovery techniques, Notify
message exchange is needed between the ingress and egress of the VPN
connection, which requires control plane connectivity between the
CEs. There are several potential ways to achieve this.
o Use of VPN connections as in-band control channels
If the CEs have the ability to inject control messages into the VPN
connections and to extract the messages at the far end of the VPN
connections, then control messages can be exchanged in-band. For
example, when a VPN connection is a Packet Switch Capable (PSC) TE
link in the customer network, this operation is transparent to the
L1VPN service provider.
o Use of overhead associated with the VPN connections
If the VPN connection provides connectivity in the customer network
at a different switching capability (implying network technology
layer) from that used by the provider network to support the CE-PE
and PE-PE connectivity, then the customer network can utilize any
overhead available within the VPN connection as a control channel
to connect the CEs. For example, if a VPN connection provides a
TDM TE link in the customer network but is supported by a
technology such as lambda or fiber, then the CEs may utilize the
overhead (DCC) as a control channel, if the network supports
transparent transfer of such overhead. This operation is
transparent to the L1VPN service provider.
o Use of control-channel-specific VPN connections
A customer establishes VPN connections dedicated as control
channels. This operation is transparent to the L1VPN service
provider, but since control plane traffic is likely to be
relatively low compared with the capacity of VPN connections, this
may be an expensive solution for the customer.
Takeda Informational [Page 28]RFC 4847 Layer 1 VPN Framework April 2007
o Use of separate network
A customer may utilize another network and network service, such as
private line service, L3VPN service, L2VPN service, or Internet
access service, to establish CE-CE control channel connectivity.
This operation is transparent to the L1VPN service provider.
o Use of CE-PE control channels
In the Signaling-based service model, and the Signaling and Routing
service model, there must be control plane (IP-level) connectivity
between the CE and PE, as described in Section 10.1.
By utilizing this, CE-CE control message exchange could be realized
as part of the service provided by the L1VPN service provider.
Namely, the provider network transfers control messages received
over the CE-PE control channel to the other side of the provider
network and delivers them through the PE-CE control channel. The
realization of this within the provider network is up to the
operator, but where the provider network uses a GMPLS control
plane, the customer control plane messages could be forwarded
through the provider control plane, perhaps using IP tunnels.
Care must be taken to protect the provider network and other
customers from Denial of Service (DoS) attack. Traffic saturation
over the control plane network needs to be carefully managed as
well. Note that if private addresses are assigned to the CE-PE
control channels, the provider network must support VPN-scoped
routing and forwarding for control messages.
11. Manageability Considerations
Manageability considerations for GMPLS are described in existing
documents, such as [RFC3945]. Also, manageability considerations for
L3VPN are described in existing documents, such as [RFC4176]. These
manageability considerations should also be applied in L1VPNs, and
these aspects are described in this section. In addition, there are
some specific manageability considerations for L1VPNs, such as
configuration and accounting.
o Fault management
The provider network MUST support fault management. It MUST support
liveness detection, and monitoring and verification of correct
operation.
Takeda Informational [Page 29]RFC 4847 Layer 1 VPN Framework April 2007
When a failure occurs, the provider network SHOULD correlate the
failure. Also, it SHOULD be able to detect which customer is
affected by the failure.
If the provider network can resolve failures without intervention
from the customer network, it MUST be possible to configure the
provider network to not report failures to the customers. However,
it MAY be part of an agreement between a customer and provider that
failures are reported to the customer, regardless.
o Configuration management
The provider network MUST support configuration management, such as
the following.
- Service mode/model configuration.
- Network representation configuration: Configuration of virtual
node and virtual link.
- Resource allocation configuration: Dedicated, shared. See
Section 8 for more detail.
- Recovery policy configuration: For example, recovery resource
sharing schemes, such as shared recovery, extra traffic. See
Section 9 for more detail.
- Membership configuration.
- Network/Element level configuration: For example, TE link
configuration.
It SHOULD be possible for the provider network to verify that
configuration is correctly made.
o Accounting management
The provider network MUST support accounting management. It MUST
be able to record usage of VPN connections for each customer.
o Performance management
The provider network MUST support performance management.
In particular, it MUST support performance monitoring of parameters
associated with the Service Level Agreement (SLA), such as bit
error rate per VPN connection, and SLA verification.
Takeda Informational [Page 30]RFC 4847 Layer 1 VPN Framework April 2007
In addition, it MUST support performance monitoring and analysis of
parameters related to the network and equipment not directly
associated with the SLA, such as network resource utilization.
o Security management
The provider network MUST support security management. See Section
12 for details.
o Management systems
In order to support various management functionalities, the
provider network relies on management systems and related tools.
GMPLS protocols and potential extensions of GMPLS MUST be able to
work with management systems and related tools to provide such
functionalities.
In particular, MIB modules for GMPLS protocols and potential
extensions MUST be supported.
o Management of customer networks
Customers MAY outsource management of their network (especially CEs
and CE-CE links) to the provider network. In such case, the
provider MUST be able to manage the customer network, as well as
the provider network.
12. Security Considerations
Security is clearly one of the essential requirements in L1VPNs. In
this section, key security requirements are highlighted. Security
considerations for L3VPNs and L2VPNs are described in existing
documents, such as [RFC4110], [RFC4111], and [RFC4664]. These
security considerations should also be applied in L1VPNs, and these
aspects are described in this section. In addition, there are some
specific security considerations for L1VPNs, such as connectivity
restriction and shared control links.
This section first describes types of information to be secured.
Then, security features or aspects are described. Finally, some
considerations concerning scenarios where security mechanisms are
applied is described.
Takeda Informational [Page 31]RFC 4847 Layer 1 VPN Framework April 2007
12.1. Types of Information
It MUST be possible to secure the information exchanged between the
customer and the provider. This includes data plane information,
control plane information, and management plane information.
At layer 1, data plane information is normally assumed to be secured
once connections are established, since those connections are
dedicated to each VPN. That is, it is not possible to communicate
unless there is a connection. Therefore, in L1VPNs, the main concern
of data plane security is restricting VPN connections to be used only
within the same VPN, as described in Section 6.2. Note that a
customer may wish to assure data plane information security against
not only other customers, but also the provider. In such case, the
customer may wish to apply their own security mechanisms for data
plane information (CE-CE security), as later described.
In addition, information contained in the provider network MUST be
secured. This includes VPN service contract information, current VPN
connection information, VPN membership information, and system
information. Note these types of information MAY be accessible to
authorized entities.
12.2. Security Features
Security features include the following:
o Data integrity
The information exchanged between the customer and the provider
MUST be delivered unchanged.
o Confidentiality
The information exchanged between the customer and the provider
MUST NOT be disclosed to a third party.
o Authentication
The entity requesting the service to the provider MUST be
identified and have its identity authenticated, and the provider
providing the service MUST also be identified and have its identify
authenticated.
Takeda Informational [Page 32]RFC 4847 Layer 1 VPN Framework April 2007
o Access control
Access to the information contained in the provider network, which
may be information about the customer networks or the existence of
customers, as well as about the provider network, MUST be
restricted to the authorized entity.
o DoS attack detection and protection
The provider network MUST have mechanisms to detect DoS attack and
to protect against it reactively and proactively.
12.3. Scenarios
There are two scenarios (or occasions) in which security mechanisms
are applied. One is the service contract phase, where security
mechanisms are applied once. The other is the service access phase,
where security mechanisms are applied every time the service is
requested.
o Service contract scenario (static)
This scenario includes the addition of new physical devices, such
as CE devices, data links and control links. It MUST be guaranteed
that these physical devices are connected to the right entity. In
addition, authority to access specific information MAY be given to
each customer as a part of service contract.
o Service access scenario (dynamic)
This scenario includes the reception of connection requests,
routing information exchange requests (e.g., attempts to establish
a neighbor relationship in routing protocols, or command request
via the management plane interface), and management information
retrieval requests. If a communication channel between the
customer and the provider (control channel, management interface)
is physically separate per customer, and the entity connected over
this communication channel is identified in the service contract
phase, the provider can ensure who is requesting the service.
Also, the communication channel could be considered as secure.
However, when communication channel is physically shared among
customers, security mechanisms MUST be available and SHOULD be
enforced. Examples of such security mechanisms include IPsec
[RFC4302] and [RFC4303]. Note that even in the case of physically
separate communication channels, customers may wish to apply
security mechanisms to assure higher security, and such mechanisms
MUST be available.
Takeda Informational [Page 33]RFC 4847 Layer 1 VPN Framework April 2007
When the entity requesting the service is identified, the provider
MUST ensure that the request is authorized for that entity. This
includes assuring that connection request is between VPN end points
belonging to the same VPN.
Also note that customers may wish to apply their own security
mechanisms for data plane information (CE-CE security). This
includes IPsec [RFC4302] and [RFC4303] for IP traffic.
13. Acknowledgements
The material in this document is based on the work of the ITU-T Study
Group 13.
We would like to thank Dimitri Papadimitriou, Deborah Brungard, Yakov
Rekhter, Alex Zinin, Igor Bryskin, Adrian Farrel, and Ross Callon for
their useful comments and suggestions.
Thanks to Mark Townsley, Dan Romascanu, and Cullen Jennings for
helpful input during IESG review.
14. Contributors
The foundation of this document is based heavily on the work of ITU-T
Study Group 13, Question 11. SG13/Q11 has been investigating the
service requirements and architecture for Layer 1 VPNs for some time,
and the foundation of this document is a summary and development of
the conclusions they have reached. Based on such material, the IETF
and the L1VPN WG in particular have developed this framework and
requirements for the support of L1VPNs by use of GMPLS protocols.
The details of this document are the result of contributions from
several authors who are listed here in alphabetic order. Contact
details for these authors can be found in a separate section near the
end of this document.
Raymond Aubin (Nortel)
Marco Carugi (Nortel)
Ichiro Inoue (NTT)
Hamid Ould-Brahim (Nortel)
Tomonori Takeda (NTT)
Takeda Informational [Page 34]RFC 4847 Layer 1 VPN Framework April 2007
15. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC3471] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description", RFC
3471, January 2003.
[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation
Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC
3473, January 2003.
[RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945, October 2004.
[RFC4026] Andersson, L. and T. Madsen, "Provider Provisioned
Virtual Private Network (VPN) Terminology", RFC 4026,
March 2005.
[RFC4202] Kompella, K., Ed., and Y. Rekhter, Ed., "Routing
Extensions in Support of Generalized Multi-Protocol Label
Switching (GMPLS)", RFC 4202, October 2005.
[RFC4208] Swallow, G., Drake, J., Ishimatsu, H., and Y. Rekhter,
"Generalized Multiprotocol Label Switching (GMPLS) User-
Network Interface (UNI): Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Support for the Overlay
Model", RFC 4208, October 2005.
[Y.1312] Y.1312 - Layer 1 Virtual Private Network Generic
requirements and architecture elements, ITU-T
Recommendation, September 2003, available from
<http://www.itu.int>.
16. Informative References
[Y.1313] Y.1313 - Layer 1 Virtual Private Network service and
network architectures, ITU-T Recommendation, July 2004,
available from <http://www.itu.int>.
Takeda Informational [Page 35]RFC 4847 Layer 1 VPN Framework April 2007
[RFC4110] Callon, R. and M. Suzuki, "A Framework for Layer 3
Provider-Provisioned Virtual Private Networks (PPVPNs)",
RFC 4110, July 2005.
[RFC4111] Fang, L., Ed., "Security Framework for Provider-
Provisioned Virtual Private Networks (PPVPNs)", RFC 4111,
July 2005.
[RFC4139] Papadimitriou, D., Drake, J., Ash, J., Farrel, A., and L.
Ong, "Requirements for Generalized MPLS (GMPLS) Signaling
Usage and Extensions for Automatically Switched Optical
Network (ASON)", RFC 4139, July 2005.
[RFC4176] El Mghazli, Y., Ed., Nadeau, T., Boucadair, M., Chan, K.,
and A. Gonguet, "Framework for Layer 3 Virtual Private
Networks (L3VPN) Operations and Management", RFC 4176,
October 2005.
[RFC4204] Lang, J., Ed., "Link Management Protocol (LMP)", RFC
4204, October 2005.
[RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
Hierarchy with Generalized Multi-Protocol Label Switching
(GMPLS) Traffic Engineering (TE)", RFC 4206, October
2005.
[RFC4258] Brungard, D., Ed., "Requirements for Generalized Multi-
Protocol Label Switching (GMPLS) Routing for the
Automatically Switched Optical Network (ASON)", RFC 4258,
November 2005.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302, December
2005
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC
4303, December 2005.
[RFC4427] Mannie, E., Ed., and D. Papadimitriou, Ed., "Recovery
(Protection and Restoration) Terminology for Generalized
Multi-Protocol Label Switching (GMPLS)", RFC 4427, March
2006.
[RFC4664] Andersson, L., Ed., and E. Rosen, Ed., "Framework for
Layer 2 Virtual Private Networks (L2VPNs)", RFC 4664,
September 2006.
Takeda Informational [Page 36]RFC 4847 Layer 1 VPN Framework April 2007
Authors' Addresses
Raymond Aubin
Nortel Networks
P O Box 3511 Station C
Ottawa, ON K1Y 4H7 Canada
Phone: +1 (613) 763 2208
EMail: aubin@nortel.com
Marco Carugi
Nortel Networks S.A.
Parc d'activites de Magny-Chateaufort
Les Jeunes Bois - MS CTF 32B5 - Chateaufort
78928 YVELINES Cedex 9 - FRANCE
Phone: +33 1 6955 7027
EMail: marco.carugi@nortel.com
Ichiro Inoue
NTT Network Service Systems Laboratories, NTT Corporation
3-9-11, Midori-Cho
Musashino-Shi, Tokyo 180-8585 Japan
Phone: +81 422 59 6076
EMail: inoue.ichiro@lab.ntt.co.jp
Hamid Ould-Brahim
Nortel Networks
P O Box 3511 Station C
Ottawa, ON K1Y 4H7 Canada
Phone: +1 (613) 765 3418
EMail: hbrahim@nortel.com
Tomonori Takeda, Editor
NTT Network Service Systems Laboratories, NTT Corporation
3-9-11, Midori-Cho
Musashino-Shi, Tokyo 180-8585 Japan
Phone: +81 422 59 7434
EMail : takeda.tomonori@lab.ntt.co.jp
Takeda Informational [Page 37]
RFC 4847 Layer 1 VPN Framework April 2007
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Takeda Informational [Page 38]
