Request for Comments: 4176 Alcatel
Category: Informational T. Nadeau
Cisco
M. Boucadair
France Telecom
K. Chan
Nortel
A. Gonguet
Alcatel
October 2005
Framework for Layer 3 Virtual Private Networks (L3VPN)
Operations and Management
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 Internet Society (2005).
Abstract
This document provides a framework for the operation and management
of Layer 3 Virtual Private Networks (L3VPNs). This framework intends
to produce a coherent description of the significant technical issues
that are important in the design of L3VPN management solutions. The
selection of specific approaches, and making choices among
information models and protocols are outside the scope of this
document.
Table of Contents
1. Introduction ................................................. 2
1.1. Terminology ............................................ 2
1.2. Management functions ................................... 4
1.3. Reference Models ....................................... 5
2. Customer Service Operations and Management ................... 7
2.1. Customer Service Management Information Model .......... 7
2.2. Customer Management Functions .......................... 8
2.2.1. Fault Management ............................... 8
2.2.2. Configuration Management ....................... 9
2.2.3. Accounting ..................................... 9
2.2.4. Performance Management ......................... 10
2.2.5. Security Management ............................ 10
2.3. Customer Management Functional Description ............. 11
2.3.1. L3VPN Service Offering Management .............. 11
2.3.2. L3VPN Service Order Management ................. 12
2.3.3. L3VPN Service Assurance ........................ 12
3. Provider Network Manager ..................................... 12
3.1. Provider Network Management Definition ................. 12
3.2. Network Management Functions ........................... 13
3.2.1. Fault Management ............................... 13
3.2.2. Configuration Management ....................... 14
3.2.3. Accounting ..................................... 17
3.2.4. Performance Management ......................... 17
3.2.5. Security Management ............................ 17
4. L3VPN Devices ................................................ 18
4.1. Information Model ...................................... 18
4.2. Communication .......................................... 18
5. Security Considerations ...................................... 19
6. Acknowledgements ............................................. 19
7. Normative References ......................................... 19
1. Introduction
1.1. Terminology
In this document, the following terms are used and defined as
follows:
VPN:
Virtual Private Network. A set of transmission and switching
resources that will be used over a shared infrastructure to
process the (IP) traffic that characterizes communication services
between the sites or premises interconnected via this VPN. See
[RFC4026].
L3VPN:
An L3VPN interconnects sets of hosts and routers based on Layer 3
addresses. See [RFC4026].
VPN Instance:
From a management standpoint, a VPN instance is the collection of
configuration information associated with a specific VPN, residing
on a PE router.
VPN Site:
A VPN customer’s location that is connected to the Service
Provider network via a CE-PE link, which can access at least one
VPN.
VPN Service Provider (SP):
A Service Provider that offers VPN-related services.
VPN Customer:
Refers to a customer that bought VPNs from a VPN service provider.
Customer Agent:
Denotes the entity that is responsible for requesting VPN
customer-specific information.
Service Level Agreement(SLA):
Contractual agreement between the Service Provider and Customer,
which includes qualitative and quantitative metrics that define
service quality guarantees and retribution procedures when service
levels are not being met.
Service Level Specifications (SLS):
Internally-focused service performance specifications used by the
Service Provider to manage customer service quality levels.
1.2. Management functions
For any type of Layer-3 VPN (PE or CE-based VPNs), having a
management platform where the VPN-related information could be
collected and managed is recommended. The Service and Network
Management System may centralize information related to instances of
a VPN and allow users to configure and provision each instance from a
central location.
An SP must be able to manage the capabilities and characteristics of
their VPN services. Customers should have means to ensure
fulfillment of the VPN service to which they subscribed. To the
extent possible, automated operations and interoperability with
standard management protocols should be supported.
Two main management functions are identified:
A customer service management function:
This function provides the means for a customer to query,
configure, and receive (events/alarms) customer-specific VPN
service information. Customer-specific information includes data
related to contact, billing, site, access network, IP address,
routing protocol parameters, etc. It may also include
confidential data, such as encryption keys. Several solutions
could be used:
* Proprietary network management system
* SNMP manager
* PDP function
* Directory service, etc.
A provider network management function:
This function is responsible for planning, building, provisioning,
and maintaining network resources in order to meet the VPN
service-level agreements outlined in the SLA offered to the
customer. This mainly consists of (1) setup and configuration of
physical links, (2) provisioning of logical VPN service
configurations, and (3) life-cycle management of VPN service,
including the addition, modification, and deletion of VPN
configurations.
There may be relationships between the customer service and
provider network management functions, as the provider network is
managed to support/realize/provide the customer service. One
example use of this relationship is to provide the VPN-SLS
assurance for verifying the fulfillment of the subscribed VPN
agreement.
1.3. Reference Models
The ITU-T Telecommunications Management Network has the following
generic requirements structure:
o Engineer, deploy and manage the switching, routing, and
transmission resources supporting the service from a network
perspective (network element management);
o Manage the VPNs deployed over these resources (network
management);
o Manage the VPN service (service management);
- - - - - - - - - - - - - - - - - - - - - - - -:- - - - - - - - -
Service +-------------+ : +----------+
Management | Service |<------------------:----->| Customer |
Layer | Manager | : | Agent |
+-------------+ : +----------+
- - - - - - - - - - ^ - - - - - - - - - - - - -:- - - - - - - - -
Network | +------------+ :
Management | | Provider | :
Layer | | Network | Customer
+------>| Manager | Interface
+------------+ :
- - - - - - - - - - - - - - - - - ^ - - - - - -:- - - - - - - - -
Network Element | :
Management | +------+ : +------+
Layer | | | : | CE |
+->| PE | : |device|
|device| : | of |
| |--:--|VPN A|
+------+ : +------+
---------------------------------------------->:<----------------
SP network : Customer Network
Figure 1: Reference Model for PE-based L3VPN Management
- - - - - - - - - - - - - - - - - - - - - - - -:- - - - - - - - -
Service +-------------+ : +----------+
Management | Service |<------------------:----->| Customer |
Layer | Manager | : | Agent |
+-------------+ : +----------+
- - - - - - - - - - ^ - - - - - - - - - - - - -:- - - - - - - - -
Network | +------------+ :
Management | | Provider | :
Layer | | Network | Customer
+------>| Manager | Interface
+------------+ :
- - - - - - - - - - - - - - - -^- - - -^- - - -:- - - - - - - - -
Network Element | +-------:---------------+
Management | +------+ : +------+ |
Layer | | | : | CE | |
+---->| PE | : |device|<----+
|device| : | of |
| |--:--|VPN A|
+------+ : +------+
---------------------------------------------->:<----------------
SP network : Customer Network
Figure 2: Reference Model for CE-based L3VPN Management
Above, Figures 1 and 2 present the reference models for both PE and
CE-based L3VPN management, according to the aforementioned generic
structure.
In both models, the service manager administrates customer-specific
attributes, such as customer Identifier (ID), personal information
(e.g., name, address, phone number, credit card number, etc.),
subscription services and parameters, access control policy
information, billing and statistical information, etc.
In the PE-based reference model, the provider network manager
administrates device attributes and their relationships, covering PE
devices and other devices that construct the corresponding PE-based
VPN.
In the CE-based reference model, the provider network manager
administrates device attributes and their relationships, covering PE
and CE devices that construct the corresponding CE-based VPN.
Network and customer service management systems that are responsible
for managing VPN networks have several challenges, depending on the
type of VPN network(s) they are required to manage.
2. Customer Service Operations and Management
Services offered by providers can be viewed from the customer’s or
the provider’s perspective. This section describes service
management from the customer’s perspective, focusing on the Customer
Management function.
The Customer Management function’s goal is to manage the
service-based operations like service ordering, service subscription,
activation, etc.
The Customer Management function resides in the L3VPN service manager
at the Service Management Layer (SML). It mainly consists of
defining the L3VPN services offered by the SP, collecting and
consolidating the customer L3VPN services requirements, as well as
performing some reporting for the customer. This function is
correlated with the Network Management function at the Network
Management Layer (NML) for initiating the L3VPN services
provisioning, and getting some service reporting.
2.1. Customer Service Management Information Model
This section presents a framework that is used for L3VPN customer
service management at the SML. The information framework represents
the data that need to be managed, and the way they are represented.
At the SML, the information framework that is foreseen is composed of
Service Level Agreements (SLA) and Service Level Specifications
(SLS).
Services are described through Service Level Agreements (SLA), which
are contractual documents between customers and service providers.
The technical part of the service description is called the Service
Level Specification (SLS). The SLS groups different kinds of
parameters. Some are more related to the description of the
transport of the packets, and some to the specification of the
service itself.
A Service Level Specification (SLS) may be defined per access network
connection, per VPN, per VPN site, and/or per VPN route. The service
provider may define objectives and the measurement intervals, for at
least the SLS, using the following Service Level Objective (SLO)
parameters:
o QoS and traffic parameters
o Availability for the site, VPN, or access connection
o Duration of outage intervals per site, route, or VPN
o Service activation interval (e.g., time to turn up a new site)
o Trouble report response time interval
o Time to repair interval
o Total incoming/outgoing traffic from a site or a (VPN) route, or
that has transited through the whole VPN
o Measurement of non-conforming incoming/outgoing traffic
(compliance of traffic should deserve some elaboration because of
many perspectives - security, QoS, routing, etc.) from a site or a
(VPN) route, or that has transited through the whole VPN
The service provider and the customer may negotiate contractual
penalties in the case(s) where the provider does not meet a (set of)
SLS performance objective(s).
Traffic parameters and actions should be defined for incoming and
outgoing packets that go through the demarcation between the service
provider premises and the customer’s premises. For example, traffic
policing functions may be activated at the ingress of the service
provider’s network, while traffic shaping capabilities could be
activated at the egress of the service provider’s network.
2.2. Customer Management Functions
This section presents detailed customer management functions in the
traditional fault, configuration, accounting, performance, and
security (FCAPS) management categories.
2.2.1. Fault Management
The fault management function of the Customer Service Manager relies
upon the manipulation of network layer failure information, and it
reports incidents to the impacted customers. Such reports should be
based upon and related to the VPN service offering to which the
customer is subscribed. The Customer Management function support for
fault management includes:
o Indication of customer’s services impacted by failure
o Incident recording or logs
o Frequency of tests
o Ability to invoke probes from the customer and provider
o Ability to uncover faults before the customer notices them
2.2.2. Configuration Management
The configuration management function of the Customer Manager must be
able to configure L3VPN service parameters with the level of detail
that the customer is able to specify, according to service templates
defined by the provider.
A service template contains fields which, when instantiated, yield a
definite service requirement or policy. For example, a template for
an IPsec tunnel [RFC2401] would contain fields such as tunnel end
points, authentication modes, encryption and authentication
algorithms, shared keys (if any), and traffic filters.
Other examples: a BGP/MPLS-based VPN service template would contain
fields such as the customer premises that need to be interconnected
via the VPN, and a QoS agreement template would contain fields such
as one-way transit delay, inter-packet delay variation, throughput,
and packet loss thresholds.
2.2.3. Accounting
The accounting management function of the Customer Manager is
provided with network layer measurements information and manages this
information. The Customer Manager is responsible for the following
accounting functions:
o Retrieval of accounting information from the Provider Network
Manager
o Analysis, storage, and administration of measurements
Some providers may require near-real time reporting of measurement
information, and may offer this as part of a customer network
management service.
If an SP supports "Dynamic Bandwidth Management" service, then the
schedule and the amount of the bandwidth required to perform
requested bandwidth allocation change(s) must be traceable for
monitoring and accounting purposes.
Solutions should state compliance with accounting requirements, as
described in section 1.7 of [RFC2975].
2.2.4. Performance Management
From the Customer Manager’s perspective, performance management
includes functions involved in the determination of the conformance
level with the Service Level Specifications, such as QoS and
availability measurements. The objective is to correlate accounting
information with performance and fault management information to
produce billing that takes into account SLA provisions for periods of
time where the service level objectives are not met.
The performance information should reflect the quality of the
subscribed VPN service as perceived by the customer. This
information could be measured by the provider or controlled by a
third party. The parameters that will be used to reflect the
performance level could be negotiated and agreed upon between the
service provider and the customer during the VPN service negotiation
phase.
Performance management should also support analysis of important
aspects of an L3VPN, such as bandwidth utilization, response time,
availability, QoS statistics, and trends based on collected data.
2.2.5. Security Management
From the Customer Manager’s perspective, the security management
function includes management features to guarantee the security of
the VPN. This includes security of devices, configuration data, and
access connections. Authentication and authorization (access
control) also fall into this category.
2.2.5.1. Access Control
Management access control determines the privileges that a user has
for particular applications and parts of the network. Without such
control, only the security of the data and control traffic is
protected (leaving the devices providing the L3VPN network
unprotected) among other equipment or resources. Access control
capabilities protect these devices to ensure that users have access
to only those resources and applications they are granted to use.
2.2.5.2. Authentication
Authentication is the process of verifying the identity of a VPN
user.
2.3. Customer Management Functional Description
This section provides a high-level example of an architecture for the
L3VPN management framework, with regard to the SML layer. The goal
is to map the customer management functions described in Section 2.2
to architectural yet functional blocks, and to describe the
communication with the other L3VPN management functions.
+ - - - - - - - - - - - - - - - - - - - - - - - - - +
| Service +----------------+ +----------------+ |
| Management | VPN Offering| | VPN Order | |
| | Management | | Management | |