Service Requirements for Layer 3 Provider Provisioned Virtual Private Networks (PPVPNs)
draft-ietf-l3vpn-requirements-02
The information below is for an old version of the document that is already published as an RFC.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 4031.
|
|
|---|---|---|---|
| Authors | Marco Carugi , Dave McDysan | ||
| Last updated | 2015-10-14 (Latest revision 2004-07-20) | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | (None) | |
| Document shepherd | (None) | ||
| IESG | IESG state | RFC 4031 (Informational) | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | Dr. Thomas Narten | ||
| Send notices to | <rick@rhwilder.net>, <rcallon@juniper.net>, <ronald.p.bonica@mci.com> |
draft-ietf-l3vpn-requirements-02
INTERNET DRAFT M. Carugi
Internet Engineering Task Force Nortel Networks
Document: D. McDysan
draft-ietf-l3vpn-requirements-02.txt MCI
July 2004 (Co-Editors)
Category: Informational
Expires: January 2005
Service requirements for Layer 3 Virtual Private Networks:
<draft-ietf-l3vpn-requirements-02.txt>
Status of this memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026 ([RFC-2026]).
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
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Internet-Drafts are draft documents valid for a maximum of six
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The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This document is a product of the IETF's Layer 3 Virtual Private
Network (l3vpn) working group. Comments should be addressed to WG's
mailing list at l3vpn@ietf.org. The charter for l3vpn may be found
at http://www.ietf.org/html.charters/l3vpn-charter.html
Copyright (C) The Internet Society (2000). All Rights Reserved.
Distribution of this memo is unlimited.
Abstract
This document provides requirements for Layer 3 Virtual Private
Networks (L3VPNs). It identifies requirements applicable to a number
of individual approaches that a Service Provider may use for the
provisioning of a VPN service. This document expresses a service
provider perspective, based upon past experience of IP-based service
offerings and the ever-evolving needs of the customers of such
services. Toward this end, it first defines terminology and states
general requirements. Detailed requirements are expressed from a
customer as well as a service provider perspective.
Carugi, McDysan et al 1
Service requirements for Layer 3 PPVPNs July 2004
Conventions used in this document
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 RFC 2119 ([RFC-
2119]).
Table of Contents
1 Introduction....................................................5
1.1 Scope of this document.........................................5
1.2 Outline........................................................6
2 Contributing Authors............................................6
3 Definitions.....................................................6
3.1 Virtual Private Network........................................6
3.2 Users, Sites, Customers and Agents.............................7
3.3 Intranets, Extranets, and VPNs.................................7
3.4 Networks of Customer and Provider Devices......................7
3.5 Access Networks, Tunnels, and Hierarchical Tunnels.............8
3.6 Use of Tunnels and roles of CE and PE in L3 VPNs...............9
3.6.1 PE-Based Layer 3 VPNs and Virtual Forwarding Instances....9
3.6.2 CE-Based L3VPN Tunnel Endpoints and Functions............10
3.7 Customer and Provider Network Management......................11
4 Service Requirements Common to Customers and Service Providers.12
4.1 Isolated Exchange of Data and Routing Information.............12
4.2 Addressing....................................................12
4.3 Quality of Service............................................12
4.3.1 QoS Standards............................................13
4.3.2 Service Models...........................................14
4.4 Service Level Specification and Agreements....................14
4.5 Management....................................................15
4.6 Interworking..................................................15
5 Customer Requirements..........................................15
5.1 VPN Membership (Intranet/Extranet)............................15
5.2 Service Provider Independence.................................16
5.3 Addressing....................................................16
5.4 Routing Protocol Support......................................16
5.5 Quality of Service and Traffic Parameters.....................16
5.5.1 Application Level QoS Objectives.........................16
5.5.2 DSCP Transparency........................................17
5.6 Service Level Specification/Agreement.........................17
5.7 Customer Management of a VPN..................................18
5.8 Isolation.....................................................18
5.9 Security......................................................18
5.10 Migration Impact..............................................19
5.11 Network Access................................................19
5.11.1 Physical/Link Layer Technology...........................19
5.11.2 Temporary Access.........................................19
5.11.3 Sharing of the Access Network............................20
5.11.4 Access Connectivity......................................20
5.12 Service Access................................................22
5.12.1 Internet Access..........................................22
5.12.2 Hosting, Application Service Provider....................22
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5.12.3 Other Services...........................................22
5.13 Hybrid VPN Service Scenarios..................................22
6 Service Provider Network Requirements..........................23
6.1 Scalability...................................................23
6.2 Addressing....................................................23
6.3 Identifiers...................................................23
6.4 Discovering VPN Related Information...........................24
6.5 SLA and SLS Support...........................................24
6.6 Quality of Service (QoS) and Traffic Engineering..............25
6.7 Routing.......................................................25
6.8 Isolation of Traffic and Routing..............................26
6.9 Security......................................................26
6.9.1 Support for Securing Customer Flows......................26
6.9.2 Authentication Services..................................27
6.9.3 Resource Protection......................................27
6.10 Inter-AS (SP)VPNs.............................................28
6.10.1 Routing Protocols........................................28
6.10.2 Management...............................................28
6.10.3 Bandwidth and QoS Brokering..............................29
6.10.4 Security Considerations..................................29
6.11 L3VPN Wholesale...............................................29
6.12 Tunneling Requirements........................................30
6.13 Support for Access and Backbone Technologies..................30
6.13.1 Dedicated Access Networks................................31
6.13.2 On-Demand Access Networks................................31
6.13.3 Backbone Networks........................................31
6.14 Protection, Restoration.......................................31
6.15 Interoperability..............................................32
6.16 Migration Support.............................................32
7 Service Provider Management Requirements.......................33
7.1 Fault management..............................................33
7.2 Configuration Management......................................34
7.2.1 Configuration Management for PE-Based VPNs...............35
7.2.2 Configuration management for CE-based VPN................35
7.2.3 Provisioning Routing.....................................35
7.2.4 Provisioning Network Access..............................35
7.2.5 Provisioning Security Services...........................36
7.2.6 Provisioning VPN Resource Parameters.....................36
7.2.7 Provisioning Value-Added Service Access..................36
7.2.8 Provisioning Hybrid VPN Services.........................37
7.3 Accounting....................................................37
7.4 Performance Management........................................38
7.4.1 Performance Monitoring...................................38
7.4.2 SLA and QoS management features..........................38
7.5 Security Management...........................................38
7.5.1 Resource Access Control....................................38
7.5.2 Authentication...........................................39
7.6 Network Management Techniques.................................39
8 Security Considerations........................................40
9 Acknowledgements...............................................40
10 References.....................................................41
10.1 Normative References..........................................41
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10.2 Non-normative References......................................41
11 Authors' address...............................................43
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1 Introduction
This section describes the scope and outline of the document.
1.1 Scope of this document
This document provides requirements specific to Layer 3 Virtual
Private Networks (L3VPN) (requirements that are generic to L2 and L3
VPNs are contained in [PPVPN-GR]).
This document identifies requirements that may apply to one or more
individual approaches that a Service Provider may use for the
provisioning of a Layer 3 (e.g., IP) VPN service. It makes use of
the terminology and common components for Layer 3 VPNs defined in
[L3VPN-FR] and of the generic VPN terminology defined in [PPVPN-
TERM].
The specification of technical means to provide L3VPN services is
outside the scope of this document. Other documents, such as the L3
VPN framework document [L3VPN-FR] and several sets of documents, one
set per each individual technical approach for providing L3VPN
services, are intended to cover this aspect.
Technical approaches targeted by this document include the network-
based (PE-based) L3 VPN category (aggregated routing VPNs
[RFC2547bis] and virtual routers [PPVPN-VR]) and the CE-based L3
VPNs category [CE-PPVPN][IPsec-PPVPN]. The document distinguishes
L3VPN categories as to where the endpoints of tunnels exist as
detailed in the L3VPN framework document [L3VPN-FR]. Terminology
regarding whether equipment faces a customer or the service provider
network is used to define the various types of L3 VPN solutions.>
This document is intended as a "checklist" of requirements providing
a consistent way to evaluate and document how well each individual
approach satisfies specific requirements. The applicability
statement documents for each individual approach should present the
results of this evaluation. It is not the intent of this document to
state a comparison of one approach versus another.
This document provides requirements from several points of view. It
begins with some considerations from a common customer and service
provider point of view not covered in the generic provider
provisioned VPN requirement document [PPVPN-GR], followed by a
customer perspective, and concludes with specific needs of a Service
Provider (SP).
The following L3VPN deployment scenarios are considered within this
document:
1. Internet-wide: VPN sites attached to arbitrary points in
the Internet
2. Single SP/single AS: VPN sites attached to the network of a
single provider within the scope of a single AS
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3.Single SP/multiple ASs: VPN sites attached to the network
of a single provider consisting of multiple ASs
4.Cooperating SPs: VPN sites attached to networks of different
providers that cooperate with each other to provide the VPN
service
The above deployment scenarios have many requirements in common.
These common requirements include SP requirements for security,
privacy, manageability, interoperability and scalability, including
service provider projections for number, complexity, and rate of
change of customer VPNs over the next several years. When
requirements apply to a specific deployment scenario, the above
terminology is used to state the context of those particular
requirements.
1.2 Outline
The outline of the rest of the document is as follows. Section 2
mentions the contributing authors. Section 3 provides definitions of
terms and concepts. Section 4 provides requirements that are common
to both customers and service providers and are not covered in the
generic provider provisioned VPN requirement document [PPVPN-GR].
Section 5 states requirements from a customer perspective. Section 6
states network requirements from a service provider perspective.
Section 7 states service provider management requirements. Section 8
describes security considerations. Section 9 lists acknowledgements.
Section 10 provides a list of references cited herein. Section 11
lists the authors' addresses.
2 Contributing Authors
This document is the combined effort of the two co-editors and the
following contributing authors:
Luyuan Fang
Ananth Nagarajan
Junichi Sumimoto
Rick Wilder
3 Definitions
This section provides the definition of terms and concepts used
throughout the document. Terminology used herein is taken from
[PPVPN-TERM] and [L3VPN-FR].
3.1 Virtual Private Network
"L3 Virtual Private Network" (L3 VPN) refers to the L3 communication
between a set of sites, making use of a shared network
infrastructure.
"Provider Provisioned VPN" (PPVPN) refers to VPNs for which the
service provider participates in management and provisioning of the
VPN.
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3.2 Users, Sites, Customers and Agents
User: A user is an entity (e.g., a human being using a host, a
server, or a system) that has been authorized to use a VPN service.
Site: A site is a set of users that have mutual L3 (i.e., IP)
reachability without use of a specific service provider network. A
site may consist of a set of users that are in geographic proximity.
Note that a topological definition of a site (e.g., all users at a
specific geographic location) may not always conform to this
definition. For example, two geographic locations connected via
another provider's network would also constitute a single site since
communication between the two locations does not involve the use of
the service provider offering the L3 VPN service.
Customer: A single organization, corporation, or enterprise that
administratively controls a set of sites.
Agent: A set of users designated by a customer who has the
authorization to manage a customer's VPN service offering.
3.3 Intranets, Extranets, and VPNs
Intranet: An intranet restricts communication to a set of sites that
belong to one customer. An example is branch offices at different
sites that require communication to a headquarters site.
Extranet: An extranet allows the specification of communication
between a set of sites that belong to different customers. In other
words, two or more organizations have access to a specified set of
each other's sites. Examples of an extranet scenario include
multiple companies cooperating in joint software development, a
service provider having access to information from the vendors'
corporate sites, different companies, or universities participating
in a consortium. An extranet often has further restrictions on
reachability, for example, at a host and individual transport level.
Note that an intranet or extranet can exist across a single service
provider network with one or more ASs, or across multiple service
provider networks.
L3 Virtual Private Network (L3 VPN): An alternative definition of
VPN refers to a specific set of sites as either an intranet or an
extranet that have been configured to allow communication. Note that
a site is a member of at least one VPN, and may be a member of many
VPNs.
3.4 Networks of Customer and Provider Devices
L3VPNs are composed of the following types of devices.
Customer Edge (CE) device: A CE device faces the users at a customer
site. The CE has an access connection to a PE device. It may be a
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router or a switch that allows users at a customer site to
communicate over the access network with other sites in the VPN. In
a CE-based L3VPN, as intended in this document (provider provisioned
CE-based VPN), the service provider manages (at least partially) the
CE device.
Provider Edge (PE) device: A PE device faces the provider network on
one side and attaches via an access connection over one or more
access networks to one or more CE devices. It participates in the
Packet Switched Network (PSN) in performing routing and forwarding
functions.
Note that the definitions of Customer Edge and Provider Edge do not
necessarily map to the physical deployment of equipment on customer
premises or a provider point of presence.
Provider (P) device: A device within a provider network that
interconnects PE (or other P) devices, but does not have any direct
attachment to CE devices. The P router does not keep VPN state and
is VPN un-aware [PPVPN-TERM].
Packet Switched Network (PSN): A (IP or MPLS) network through which
the tunnels supporting the VPN services are set up [PPVPN-TERM].
Service Provider (SP) network: An SP network is a set of
interconnected PE and P devices administered by a single service
provider in one or more ASs.
3.5 Access Networks, Tunnels, and Hierarchical Tunnels
VPNs are built between CEs using access networks, tunnels, and
hierarchical tunnels across a PSN.
Access connection: An access connection provides connectivity
between a CE and a PE. This includes dedicated physical circuits,
virtual circuits, such as Frame Relay, ATM, Ethernet (V)LAN, or IP
tunnels (e.g., IPsec, L2TP).
Access network: An access network provides access connections
between CE and PE devices. It may be a TDM network, L2 network
(e.g. FR, ATM, and Ethernet), or an IP network over which access is
tunneled (e.g., using L2TP]).
Tunnel: A tunnel between two entities is formed by encapsulating
packets within another encapsulating header for purpose of
transmission between those two entities in support of a VPN
application. Examples of protocols commonly used for tunneling are:
GRE, IPsec, IP-in-IP tunnels, and MPLS.
Hierarchical Tunnel: Encapsulating one tunnel within another forms a
hierarchical tunnel. The innermost tunnel protocol header defines a
logical association between two entities (e.g., between CEs or PEs)
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[VPN TUNNEL]. Note that the tunneling protocols need not be the same
at different levels in a hierarchical tunnel.
3.6 Use of Tunnels and roles of CE and PE in L3 VPNs
This section summarizes the point where tunnels terminate and the
functions implemented in the CE and PE devices that differentiate
the two major categories of L3 VPNs for which requirements are
stated, namely PE-based and CE-based L3 VPNs. See the L3VPN
framework document for more detail [L3VPN-FR].
3.6.1 PE-Based Layer 3 VPNs and Virtual Forwarding Instances
In a PE-based layer 3 VPN service, a customer site receives IP layer
(i.e., layer 3) service from the SP. The PE is attached via an
access connection to one or more CEs. The PE performs forwarding of
user data packets based on information in the IP layer header, such
as an IPv4 or IPv6 destination address. The CE sees the PE as a
layer 3 device such as an IPv4 or IPv6 router.
Virtual Forwarding Instance (VFI): In a PE-based layer 3 VPN
service, the PE contains a VFI for each L3 VPN that it serves. The
VFI terminates tunnels for interconnection with other VFIs and also
terminates access connections for accommodating CEs. VFI contains
information regarding how to forward data received over the CE-PE
access connection to VFIs in other PEs supporting the same L3 VPN.
The VFI includes the router information base and the forwarding
information base for a L3 VPN [L3VPN-FR]. A VFI enables router
functions dedicated to serving a particular VPN, such as separation
of forwarding and routing and support for overlapping address
spaces. Routing protocols in the PEs and the CEs interact to
populate the VFI.
The following narrative and figures provide further explanation of
the way PE devices use tunnels and hierarchical tunnels. Figure 3.1
illustrates the case where a PE uses a separate tunnel for each VPN.
As shown in the figure, the tunnels provide communication between
the VFIs in each of the PE devices.
+----------+ +----------+
+-----+ |PE device | |PE device | +-----+
| CE | | | | | | CE |
| dev | Access | +------+ | | +------+ | Access | dev |
| of | conn. | |VFI of| | Tunnel | |VFI of| | conn. | of |
|VPN A|----------|VPN A |==================|VPN A |----------|VPN A|
+-----+ | +------+ | | +------+ | +-----+
| | | |
+-----+ Access | +------+ | | +------+ | Access +-----+
|CE | conn. | |VFI of| | Tunnel | |VFI of| | conn. | CE |
| dev |----------|VPN B |==================|VPN B |----------| dev |
| of | | +------+ | | +------+ | | of |
|VPN B| | | | | |VPN B|
+-----+ +----------+ +----------+ +-----+
Figure 3.1 PE Usage of Separate Tunnels to Support VPNs
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Figure 3.2 illustrates the case where a single hierarchical tunnel
is used between PE devices to support communication for VPNs. The
innermost encapsulating protocol header provides the means for the
PE to determine the VPN for which the packet is directed.
+----------+ +----------+
+-----+ |PE device | |PE device | +-----+
| CE | | | | | | CE |
| dev | Access | +------+ | | +------+ | Access | dev |
| of | conn. | |VFI of| | | |VFI of| | conn. | of |
|VPN A|----------|VPN A | | Hierarchical | |VPN A |----------|VPN A|
+-----+ | +------+\| Tunnel |/+------+ | +-----+
| >==============< |
+-----+ Access | +------+/| |\+------+ | Access +-----+
| CE | conn. | |VFI of| | | |VFI of| | conn. | CE |
| dev |----------|VPN B | | | |VPN B |----------| dev |
| of | | +------+ | | +------+ | | of |
|VPN B| | | | | |VPN B|
+-----+ +----------+ +----------+ +-----+
Figure 3.2 PE Usage of Shared Hierarchical Tunnels to Support VPNs
3.6.2 CE-Based L3VPN Tunnel Endpoints and Functions
Figure 3.3 illustrates the CE-based L3 VPN reference model. In this
configuration, typically a single level of tunnel (e.g., IPsec)
terminates at pairs of CEs. Usually, a CE serves a single customer
site and therefore the forwarding and routing is physically separate
from all other customers. Furthermore, the PE is not aware of the
membership of specific CE devices to a particular VPN. Hence, the
VPN functions are implemented using provisioned configurations on
the CE devices and the shared PE and P network is used to only
provide the routing and forwarding that supports the tunnel
endpoints on between CE devices. The tunnel topology connecting the
CE devices may be a full or partial mesh, depending upon VPN
customer requirements and traffic patterns.
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Service requirements for Layer 3 PPVPNs July 2004
+---------+ +--------------------------------+ +---------+
| | | | | |
| | | +------+ +------+ : +------+
+------+ : | | | | | | : | CE |
| CE | : | | | P | | PE | : |device|
|device| : +------+ Tunnel |router| |device| : | of |
| of |=:================================================:=|VPN A|
|VPN A| : | | +------+ +------+ : +------+
+------+ : | PE | | | : |
+------+ : |device| | | : |
| CE | : | | Tunnel +------+ : +------+
|device|=:================================================:=| CE |
| of | : +------+ | PE | : |device|
|VPN B| : | | |device| : | of |
+------+ : | | +----------+ +----------+ | | : |VPN B|
| : | | | Customer | | Network | +------+ : +------+
|Customer | | |management| |management| | | : |
|interface| | | function | | function | | |Customer |
| | | +----------+ +----------+ | |interface|
| | | | | |
+---------+ +--------------------------------+ +---------+
| Access | |<-------- SP network(s) ------->| | Access |
| network | | | | network |
Figure 3.3 CE-based L3 VPN
3.7 Customer and Provider Network Management
Customer Network Management Function: A customer network management
function provides the means for a customer agent to query or
configure customer specific information, or receive alarms regarding
his or her VPN. Customer specific information includes data related
to contact, billing, site, access network, IP address, routing
protocol parameters, etc. It may use a combination of proprietary
network management system, SNMP manager, or directory service (e.g.,
LDAP [RFC3377] [RFC2251]).
Provider Network Management Function: A provider network management
function provides many of the same capabilities as a customer
network management system across all customers. This would not
include customer confidential information, such as keying material.
The intent of giving the provider a view comparable to that of the
customer is to aid in troubleshooting and problem resolution. Such a
system also provides the means to query, configure, or receive
alarms regarding any infrastructure supporting the L3VPN service. It
may use a combination of proprietary network management system, SNMP
manager, or directory service (e.g., LDAP [RFC3377] [RFC2251]).
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4 Service Requirements Common to Customers and Service Providers
Many of the requirements that apply to both the customer and the
provider and are of an otherwise general nature, or apply to both L2
and L3 VPNs, are described in [PPVPN-GR]. This section contains
requirements specific to L3 VPNs which are not covered in [PPVPN-
GR].
4.1 Isolated Exchange of Data and Routing Information
A mechanism for isolating the distribution of reachability
information to only those sites associated with a VPN must be
provided.
L3VPN solutions shall define means that prevent routers in a VPN
from interaction with unauthorized entities and avoid introducing
undesired routing information that could corrupt the VPN
routing information base [VPN-CRIT].
A means to constrain, or isolate, the distribution of addressed data
to only those VPN sites determined either by routing data and/or
configuration must be provided.
A single site shall be capable of being in multiple VPNs. The VPN
solution must ensure that traffic is exchanged only with those sites
that are in the same VPN.
The internal structure of a VPN should not be advertised nor
discoverable from outside that VPN.
Note that isolation of forwarded data and/or exchange of
reachability information to only those sites that are part of a VPN
may be viewed as a form of security, for example, [Y.1311.1],[MPLS
SEC].
4.2 Addressing
IP addresses must be unique within the set of sites reachable from
the VPNs of which a particular site is a member.
A VPN solution must support IPv4 and IPv6 as both the encapsulating
and encapsulated protocol.
If a customer has private or non-unique IP addresses, then a VPN
service SHOULD be capable of translating such customer private or
non-unique IP addresses for communicating with IP systems having
public addresses.
4.3 Quality of Service
To the extent possible, L3 VPN QoS should be independent of the
access network technology.
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4.3.1 QoS Standards
A non-goal of the L3 VPN WG effort (as chartered) is the development
of new protocols or extension of existing ones. With regards to QoS
support, a L3 VPN shall be able to support QoS in one or more of the
following already defined modes:
- Best Effort (mandatory support for all L3VPN types)
- Aggregate CE Interface Level QoS ("hose" level QoS)
- Site-to-site ("pipe" level QoS)
- Intserv (i.e., RSVP) signaled
- Diffserv marked
- Across packet-switched access networks
Note that all cases involving QoS may require that the CE and/or PE
perform shaping and/or policing.
L3VPN CEs should be capable of supporting integrated services
(Intserv) for certain customers in support of session applications,
such as switched voice or video. Intserv-capable CE devices shall
support the following Internet standards:
- Resource reSerVation Protocol (RSVP) [RFC 2205]
- Guaranteed Quality of Service providing a strict delay bound
[RFC 2212]
- Controlled Load Service providing performance equivalent to that
of an unloaded network [RFC 2211]
L3VPN CE and PE should be capable of supporting differentiated
service (Diffserv). . Diffserv-capable L3VPN CE and PE shall
support the following per hop behavior (PHB) [RFC 2475] types:
- Expedited Forwarding (EF) - the departure rate of an aggregate
class of traffic from a device that must equal or exceed a
configured rate [RFC 3246].
- Assured Forwarding (AF) - a means for a provider Diffserv (DS)
domain to offer different levels of forwarding assurances for IP
packets received from a customer DS domain. Four AF classes are
defined, where each AF class implies allocation in each DS node of a
certain amount of forwarding resources (e.g., buffer space and
bandwidth) [RFC 2597].
A CE or PE device supporting a L3 VPN service may classify a packet
for a particular Intserv or Diffserv service based on upon one or
more of the following IP header fields: protocol ID, source port
number, destination port number, destination address, or source
address.
For a specifiable set of Internet traffic, L3 VPN devices should
support Random Early Detection (RED) to provide graceful degradation
in the event of network congestion.
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4.3.2 Service Models
A service provider must be able to offer QoS service to a customer
for at least the following generic service types: managed access VPN
service or edge-to-edge QoS VPN service [PPVPN-GR]. More detail
specific to L3 VPNs is provided below.
A managed access L3 VPN service provides QoS on the access
connection between the CE and the PE. For example, diffserv would be
enabled only on the CE router and the customer-facing ports of the
PE router. Note that this service would not require Diffserv
implementation in the SP backbone. The SP may use policing for
inbound traffic at the PE. The CE may perform shaping for outbound
traffic. Another example of a managed access L3 VPN service is where
the SP performs the packet classification and diffserv marking. An
SP may provide several packet classification profiles that customers
may select, or may offer custom profiles based upon customer
specific requirements. In general, more complex QoS policies should
be left to the customer for implementation.
An edge-to-edge QoS VPN service provides QoS from edge device to
edge device. The edge device may be either PE or CE depending upon
the service demarcation point between the provider and the customer.
Such a service may be provided across one or more provider
backbones. The CE requirements for this service model are the same
as the managed access VPN service. However, in this service QoS is
provided from one edge of the SP network(s) to the other edge.
4.4 Service Level Specification and Agreements
A generic discussion of SLAs is provided in [PPVPN-GR].
Additionally, SLS measurements for quality based on the DiffServ
scheme SHOULD be based upon the following classification:
. A Point-to-Point SLS [Y.1311.1], sometimes also referred to as
the "Pipe" model, defines traffic parameters in conjunction
with the QoS objectives for traffic exchanged between a pair
of VPN sites (i.e., points). A Point-to-Point SLS is analogous
to the SLS typically supported over point-to-point Frame Relay
or ATM PVCs or an edge-to-edge MPLS tunnel. The set of SLS
specifications to all other reachable VPN sites would define
the overall Point-to-Point SLS for a specific site.
. A Point-to-Cloud SLS [Y.1311.1], sometimes also referred as
the "Hose" model, defines traffic parameters in conjunction
with the QoS objectives for traffic exchanged between a CE and
a PE for traffic destined to a set (either all or a subset) of
other sites in the VPN (i.e., the cloud), as applicable. In
other words, a point-to-cloud SLS defines compliance in terms
of all packets transmitted from a given VPN site toward the SP
network on an aggregate basis (i.e., regardless of the
destination VPN site of each packet).
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. A Cloud-to-Point SLS (a case not covered by this SLS is where
flows originating from multiple sources may congest the
interface from the network toward a specific site).
Traffic parameters and actions SHOULD be defined for packets to and
from the demarcation between the service provider and the site. For
example, policing may be defined on ingress and shaping on egress.
4.5 Management
An SP and its customers MUST be able to manage the capabilities and
characteristics of their VPN services. To the extent possible,
automated operations and interoperability with standard management
platforms SHOULD be supported.
The ITU-T Telecommunications Management Network (TMN) model 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 VPN networks deployed over these resources (network
management);
o Manage the VPN service (service management);
o Manage the VPN business, mainly provisioning administrative and
accounting information related to the VPN service customers
(business management).
Service management should include the TMN 'FCAPS' functionalities,
as follows: Fault, Configuration, Accounting, Provisioning, and
Security, as detailed in section 7.
4.6 Interworking
Interworking scenarios among different solutions providing L3VPN
services is highly desirable. See the L3VPN framework document for
more details on interworking scenarios [L3VPN-FR]. Interworking
SHOULD be supported in a scalable manner.
Interworking scenarios MUST consider at least traffic and routing
isolation, security, QoS, access, and management aspects. This
requirement is essential in the case of network migration, to ensure
service continuity among sites belonging to different portions of
the network.
5 Customer Requirements
This section captures additional requirements from a customer
perspective.
5.1 VPN Membership (Intranet/Extranet)
When an extranet is formed, a customer agent from each of the
organizations first approves addition of a site to an extranet VPN
as a business decision between the parties involved. The solution
SHOULD provide a means such that these organizations can control
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extranet communication involving the L3VPN exchange of traffic and
routing information.
5.2 Service Provider Independence
Customers MAY require VPN service that spans multiple administrative
domains or service provider networks. Therefore, a VPN service MUST
be able to span multiple AS and SP networks, but still act and
appear as a single, homogenous VPN from a customer point of view.
A customer might also start with a VPN provided in a single AS with
a certain SLA but then ask for an expansion of the service spanning
multiple ASs/SPs. In this case, as well as for all kinds of multi-
AS/SP VPNs, VPN service SHOULD be able to deliver the same SLA to
all sites in a VPN regardless of the AS/SP to which it homes.
5.3 Addressing
A customer requires support from a L3 VPN for the following
addressing IP assignment schemes:
o customer assigned, non-unique, or RFC 1918 private addresses
o globally unique addresses obtained by the customer
o globally unique addresses statically assigned by the L3VPN
service provider
o on-demand, dynamically assigned IP addresses (e.g., DHCP),
irrespective of whether the access is temporary (e.g., remote) or
permanent (i.e., dedicated)
In the case of combined L3 VPN service with non-unique or private
addresses and Internet access, mechanisms that permit the exchange
of traffic between the customer's address space and the global
unique Internet address space MAY be supported. For example, NAT is
employed by many customers and some service providers today to meet
this need. A preferred solution would be to assign unique addresses,
either IPv4 or IPv6; however, some customers do not want to renumber
their networks.
5.4 Routing Protocol Support
There SHOULD be no restriction on the routing protocols used between
CE and PE routers, or between CE routers. At least the following
protocols MUST be supported: static routing, IGP protocols, such as
RIP, OSPF, IS-IS, and BGP [L3VPN-FR].
5.5 Quality of Service and Traffic Parameters
QoS is expected to be an important aspect of a L3VPN service for
some customers. QoS requirements cover scenarios involving an
intranet, an extranet, as well as shared access between a VPN site
and the Internet.
5.5.1 Application Level QoS Objectives
A customer is concerned primarily that the L3VPN service provide his
or her applications with the QoS and level of traffic such that the
applications perform acceptably. Voice and interactive video, and
multimedia applications are expected to require the most stringent
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QoS. These real-time applications are sensitive to delay, delay
variation, loss, availability and/or reliability. Another set of
applications, including some multimedia and interactive video
applications, high-performance web browsing and file transfer
intensive applications, requires near real time performance.
Finally, best effort applications are not sensitive to degradation,
that is are elastic and can adapt to conditions of degraded
performance.
The selection of appropriate QoS and service type to meet specific
application requirements is particularly important to deal with
periods of congestion in a SP network. Sensitive applications will
likely select per-flow Integrated service (Intserv) with precise SLA
guarantees measured on a per flow basis. On the other hand, non-
sensitive applications will likely rely on a Diffserv class-based
QoS.
The fundamental customer application requirement is that a L3VPN
solution MUST support both the Intserv QoS model for selected
individual flows, and Diffserv for aggregated flows.
A customer application SHOULD experience consistent QoS independent
of the access network technology used at different sites connected
to the same VPN.
5.5.2 DSCP Transparency
The Diffserv Code Point (DSCP) set by a user as received by the
ingress CE SHOULD be capable of being relayed transparently to the
egress CE [see section 2.6.2 of RFC 3270 and Y.1311.1]. Although RFC
2475 states that interior or boundary nodes within a DS domain can
change the DSCP, customer VPNs MAY have other requirements, such as:
o Applications that use the DSCP in a manner differently than the
DSCP solution supported by the SP network(s);
o Customers using more DSCPs within their sites than the SP
network(s) supports;
o Support for a carrier's carrier service where one SP is the
customer of another L3VPN SP. Such an SP should be able to resell
VPN service to his or her VPN customers independently of the DSCP
mapping solution supported by the carrier's carrier SP.
Note that support for DSCP transparency has no implication on the
QoS or SLA requirements. If an SP supports DSCP transparency, then
that SP needs to only carry the DSCP values across its domain, but
MAY map the received DSCP to some other value for QoS support across
its domain.
5.6 Service Level Specification/Agreement
Most customers simply want their applications to perform well. An
SLA is a vehicle for customer recourse in the event that SP(s) do
not perform or manage a VPN service well in a measurable sense.
Therefore, when purchasing service under an SLA, a customer agent
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MUST have access to the measures from the SP(s) that support the
SLA.
5.7 Customer Management of a VPN
A customer MUST have a means to view the topology, operational
state, order status, and other parameters associated with his or her
VPN.
Most aspects of management information about CE devices and customer
attributes of a L3VPN manageable by an SP SHOULD be capable of being
configured and maintained by an authenticated, authorized customer
agent. However, some aspects, such as encryption keys, SHALL NOT be
readable nor writable by management systems.
A customer agent SHOULD be able to make dynamic requests for changes
to traffic parameters. A customer SHOULD be able to receive real-
time response from the SP network in response to these requests.
One example of such service is a "Dynamic Bandwidth management"
capability, that enables real-time response to customer requests for
changes of allocated bandwidth allocated to his or her VPN
[Y.1311.1].
A customer who may not be able to afford the resources to manage his
own sites SHOULD be able to outsource the management of the entire
VPN to the SP(s) supporting the VPN network.
5.8 Isolation
These features include traffic and routing information exchange
isolation, similar to that obtained in VPNs based on Layer 1 and
Layer 2 (e.g., private lines, FR, or ATM) [MPLS SEC].
5.9 Security
The suite of L3VPN solutions SHOULD support a range of security
related features. Higher levels of security services, like edge-to-
edge encryption, authentication, or replay attack should be
supported. More details on customer requirements for security are
described in [VPNSEC].
Security in a L3VPN service SHOULD be as transparent as possible to
the customer, with the obvious exception of support for remote or
temporary user access, as detailed in section 5.11.2.
L3VPN customers MUST be able to deploy their own internal security
mechanisms in addition to those deployed by the SP, in order to
secure specific applications or traffic at a granularity finer than
a site-to-site basis.
If a customer requires QoS support in a L3 VPN, then this request
MUST be communicated to the SP either using unencrypted fields or
else via an agreed security association. For example, applications
could send RSVP messages in support of Intserv either in the clear
or encrypted using a key negotiated with the SP. Another case is
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where applications using an IPsec tunnel could copy the DSCP from
the encrypted IP header to the header of the tunnel's IP header.
5.10 Migration Impact
Often, customers are migrating from an already deployed private
network toward one or more L3 VPN solutions. A typical private
network scenario is CE routers connected via real or virtual
circuits. Ideally, minimal incremental cost SHOULD result during the
migration period. Furthermore, if necessary, any disruption of
service SHOULD also be minimized.
A range of scenarios of customer migration MUST be supported. Full
migration of all sites MUST be supported. Support for cases of
partial migration is highly desirable [Y.1311.1], that is, legacy
private network sites that belong to the L3VPN service SHOULD still
have L3 reachability to the sites that migrate to the L3VPN service.
5.11 Network Access
Every L3 packet exchanged between the customer and the SP over the
access connection MUST appear as it would on a private network
providing an equivalent service to that offered by the L3VPN.
5.11.1 Physical/Link Layer Technology
L3VPNs SHOULD support a broad range of physical and link layer
access technologies, such as PSTN, ISDN, xDSL, cable modem, leased
line, Ethernet, Ethernet VLAN, ATM, Frame Relay, Wireless local
loop, mobile radio access, etc. The capacity and QoS achievable may
be dependent on the specific access technology in use.
5.11.2 Temporary Access
The VPN service offering SHOULD allow both permanent and temporary
access to one or more L3VPNs for authenticated users across a broad
range of access technologies. Support for remote or temporary VPN
access SHOULD include ISDN, PSTN dial-in, xDSL or access via another
SP network. The customer SHOULD be able to choose from alternatives
for authentication of temporary access users. Choices for access
authentication are: SP-provided, third-party, or customer-provided
authentication.
A significant number of VPN users may not be permanently attached to
one VPN site : in order to limit access to a VPN to only authorized
users, it is first necessary to authenticate them. Authentication
SHALL apply as configured by the customer agent and/or SP where a
specific user may be part of one or more VPNs. The authentication
function SHOULD be used to automatically invoke all actions
necessary to join a user to the VPN.
A user SHOULD be able to access a L3VPN via a network having generic
Internet access.
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Mobile users may move within a L3VPN site. Mobile users may also
have temporary connections to different L3VPN site within the same
VPN. Authentication SHOULD be provided for both of these cases.
5.11.3 Sharing of the Access Network
In a PE-based L3VPN, if the site shares the access network with
other traffic (e.g., access to the Internet), then data security in
the access network is the responsibility of the L3VPN customer.
5.11.4 Access Connectivity
Various types of physical connectivity scenarios MUST be supported,
such as multi-homed sites, backdoor links between customer sites,
devices homed to two or more SP networks. L3VPN solutions SHOULD
support at least the types of physical or link-layer connectivity
arrangements shown in Figure 5.1. Support for other physical
connectivity scenarios with arbitrary topology is desirable.
Access arrangements with multiple physical or logical paths from a
CE to other CEs and PEs MUST support redundancy, and SHOULD support
load balancing. Resiliency uses redundancy to provide connectivity
between a CE site and other CE sites, and optionally, other
services. Load balancing provides a means to perform traffic
engineering such that capacity on redundant links is used to achieve
improved performance during periods when the redundant component(s)
are available.
For multi-homing to a single SP, load balancing capability SHOULD be
supported by the PE across the CE to PE links. For example, in case
(a), load balancing SHOULD be provided by the two PEs over the two
links connecting to the single CE. In case (c), load balancing
SHOULD be provided by the two PEs over the two links connecting to
the two CEs.
In addition, the load balancing parameters (e.g., the ratio of
traffic on the multiple load-balanced links, or the preferred link)
SHOULD be provisionable based on customer's requirements. The load
balancing capability may also be used to achieve resiliency in the
event of access connectivity failures. For example, in cases (b) a
CE may connect to two different SPs via diverse access networks.
Resiliency MAY be further enhanced as shown in case (d), where CEs
connected via a "back door" connection connect to different SPs.
Furthermore, arbitrary combinations of the above methods, with a few
examples shown in cases (e) and (f) should be supportable by any
L3VPN approach.
For multi-homing to multiple SPs, load balancing capability MAY also
be supported by the PEs in the different SPs (clearly, this is a
more complex type of load balancing to realize, and requires policy
and service agreements between the SPs to interoperate).
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+---------------- +---------------
| |
+------+ +------+
+---------| PE | +---------| PE |
| |router| | |router| SP network
| +------+ | +------+
+------+ | +------+ |
| CE | | | CE | +---------------
|device| | SP network |device| +---------------
+------+ | +------+ |
| +------+ | +------+
| | PE | | | PE |
+---------|router| +---------|router| SP network
+------+ +------+
| |
+---------------- +---------------
(a) (b)
+---------------- +---------------
| |
+------+ +------+ +------+ +------+
| CE |-----| PE | | CE |-----| PE |
|device| |router| |device| |router| SP network
+------+ +------+ +------+ +------+
| | | |
| Backdoor | | Backdoor +---------------
| link | SP network | link +---------------
| | | |
+------+ +------+ +------+ +------+
| CE | | PE | | CE | | PE |
|device|-----|router| |device|-----|router| SP network
+------+ +------+ +------+ +------+
| |
+---------------- +---------------
(c) (d)
+---------------- +---------------
| |
+------+ +------+ +------+ +------+
| CE |-----| PE | | CE |-----| PE |
|device| |router| |device| |router| SP network
+------+\ +------+ +------+\ +------+
| \ | | \ |
|Back \ | |Back \ +---------------
|door \ | SP network |door \ +---------------
|link \ | |link \ |
+------+ +------+ +------+ +------+
| CE | | PE | | CE | | PE |
|device|-----|router| |device|-----|router| SP network
+------+ +------+ +------+ +------+
| |
+---------------- +---------------
(e) (f)
Figure 5.1 Representative types of access arrangements.
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Service requirements for Layer 3 PPVPNs July 2004
5.12 Service Access
Customers MAY also require access to other services, as described in
this section.
5.12.1 Internet Access
Customers SHOULD be able to have L3 VPN and Internet access across
the same access network for one or more of the customer's sites.
Customers SHOULD be able to direct Internet traffic from the set of
sites in the L3VPN to one or more customer sites that have
firewalls, other security-oriented devices, and/or NAT that process
all traffic between the Internet and the customer's VPN.
L3 VPN Customers SHOULD be able to receive traffic from the Internet
addressed to a publicly accessible resource that is not part of the
VPN, such as an enterprise's public web server.
As stated in section 5.3, if a customer L3 VPN employs private or
non-unique IP addresses, then network address translation (NAT) or a
similar mechanism MUST be provided either by the customer or the SP
in order to be able to exchange traffic with devices outside the
customer's L3 VPN.
5.12.2 Hosting, Application Service Provider
A customer SHOULD be able to access hosting, other application
services, or other Application Service Providers (ASP) over a L3
L3VPN service. This MAY require that an ASP participates in one or
more VPNs with the customers that use such a service.
5.12.3 Other Services
In conjunction with a VPN service, a customer MAY also wish to have
access to other services, such as: DNS, FTP, HTTP, NNTP, SMTP, LDAP,
VoIP, NAT, LDAP, Videoconferencing, Application sharing, E-business,
Streaming, E-commerce, Directory, Firewall, etc. The resources that
implement these services could be physically dedicated to each VPN.
If the resources are logically shared, then they MUST have access
separated and isolated between VPNs in a manner consistent with the
L3VPN solution to meet this requirement.
5.13 Hybrid VPN Service Scenarios
Intranet or extranet customers have a number of reasons for wanting
hybrid networks that involve more than one VPN solution type. These
include migration, mergers, extranet customers with different VPN
types, the need for different capabilities between different sets of
sites, temporary access, different availability of VPN solutions as
provided by different service providers.
The framework and solution approaches SHOULD include provisions for
interworking, interconnection, and/or reachability between different
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L3VPN solutions in such a way that does not overly complicate
provisioning, management, scalability, or performance.
6 Service Provider Network Requirements
This section describes requirements from a service provider
perspective.
6.1 Scalability
[PPVPN-GR} lists projections regarding L3VPN sizing and scalability
requirements and metrics related to specific solutions.
6.2 Addressing
As described in section 4.2, SPs MUST have support for public and
private IP addresses, IPv4 and IPv6, for both unicast and multicast.
In order to support this range of addressing schemes, SPs require
the following support from L3VPN solutions.
A L3VPN solution MUST be able to assign blocks of addresses from its
own public IP address space to L3VPN customer sites in such a way
that advertisement of routes to other SPs and other sites aggregates
efficiently.
A L3VPN solution MUST be able to use address assignments made by a
customer. These customer assigned addresses may be public, or
private.
In the case where private IP addresses are used, a L3VPN solution
MUST provide a means for an SP to translate such addresses to public
IP addresses for communication with other VPNs using overlapping
addresses, or the Internet.
6.3 Identifiers
A number of identifiers MAY be necessary for SP use in management,
control, and routing protocols. Requirements for at least the
following identifiers are known.
An SP domain MUST be uniquely identified at least within the set of
all interconnected SP networks when supporting a VPN that spans
multiple SPs. Ideally, this identifier should be globally unique
(e.g., an AS number).
An identifier for each VPN SHOULD be unique, at least within each
SP's network. Ideally, the VPN identifier SHOULD be globally unique
to support the case where a VPN spans multiple SPs (e.g., [RFC
2685]).
A CE device SHOULD have a unique identifier, at least within each
SP's network.
A PE device SHOULD have a unique identifier, at least within each
SP's network.
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The identifier of a device interconnecting SP networks MUST be
unique within the set of aforementioned networks.
Each site interface SHOULD have a unique identifier, at least within
each PE router supporting such an interface.
Each tunnel SHOULD have a unique identifier, at least within each
router supporting the tunnel.
6.4 Discovering VPN Related Information
Configuration of CE and PE devices is a significant task for a
service provider. Solutions SHOULD strive to contain methods that
dynamically allow VPN information to be discovered (or learned) by
the PE and/or CE to reduce configuration complexity. The following
specific requirements apply to intra and inter-provider VPNs [VPN
DISC].
Every device involved in a VPN SHALL be able to identify and
authenticate itself to other devices in the VPN. After learning the
VPN membership, the devices SHOULD be able to securely exchange
configuration information. The VPN information MUST include at least
the IP address of the PE and may be extensible to provide additional
information.
Each device in a VPN SHOULD be able to determine which other devices
belong to the same VPN. Such a membership discovery scheme MUST
prevent unauthorized access and allow authentication of the source.
Distribution of VPN information SHOULD be limited to those devices
involved in that VPN.
In the case of a PE-based VPN, a solution SHOULD support the means
for attached CEs to authenticate each other and verify that the SP's
VPN network is correctly configured.
The mechanism SHOULD respond to VPN membership changes in a timely
manner. A "timely manner" is no longer than the provisioning
timeframe, typically on the order of minutes, and could be as short
as the timeframe required for "rerouting," typically on the order of
seconds.
Dynamically creating, changing, and managing multiple VPN
assignments to sites and/or customers is another aspect of
membership that MUST be addressed in a L3 VPN solution.
6.5 SLA and SLS Support
Typically, a Service Provider offering a L3VPN service commits to
specific Service Level Specifications (SLS) as part of a contract
with the customer, as described in section 4.4 and [PPVPN-GR]. Such
a Service Level Agreement (SLA) implies SP requirements for
measuring Specific Service Level Specifications (SLS) for quality,
availability, response time, and configuration intervals.
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6.6 Quality of Service (QoS) and Traffic Engineering
A significant aspect of a L3VPN is support for QoS. Since an SP has
control over the provisioning of resources and configuration of
parameters in at least the PE and P devices, and in some cases, the
CE device as well, the onus is on the SP to provide either managed
QoS access service, or edge-to-edge QoS service, as defined in
section 4.3.2.
Each L3VPN approach MUST describe the traffic engineering techniques
available for a SP to meet the QoS objectives. These descriptions of
traffic engineering techniques SHOULD quantify scalability and
achievable efficiency. Traffic engineering support MAY be on an
aggregate or per-VPN basis.
QoS policies MUST not be impacted by security mechanisms. For
example, Diffserv policies MUST not be impacted by the use of IPSec
tunnels, using the mechanisms explained in RFC 2983.
As stated in RFC 2475, a mapping function from customer provided
Diffserv marking to marking used in a SP network should be provided
for L3 VPN services.
In the case where a customer requires DSCP transparency, as
described in section 5.5.2, a L3 VPN service MUST deliver the same
value of DSCP field in the IP header received from the customer to
the egress demarcation of the destination.
6.7 Routing
The distribution of reachability and routing policy SHOULD be
constrained to the sites that are members of the VPN.
Optionally, the exchange of such information MAY use some form of
authentication (e.g., MD5).
Functions to isolate the SP network and customer VPNs from anomalous
routing behavior from a specific set of customer sites SHOULD be
provided. Examples of such functions are: controls for route flap
dampening, filters that accept only prefixes configured for a
specific CE, a maximum number of routes accepted for each CE, or a
maximum rate at which route updates can be received from a CE.
When VPN customers use overlapping, non-unique IP addresses, the
solution MUST define a means to distinguish between such overlapping
addresses on a per-VPN basis.
Furthermore, the solution SHOULD provide an option that either
allows, or prevents advertisement of VPN routes to the Internet.
Ideally, the choice of a SP's IGP SHOULD not depend on the routing
protocol(s) used between PE and CE routers in a PE-based VPN.
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Furthermore, it is desirable that an SP SHOULD have a choice with
regards to the IGP routing protocol.
The additional routing burden that an SP must carry should be
articulated in each specific L3 VPN solution.
6.8 Isolation of Traffic and Routing
The internal structure of a L3VPN network SHOULD not be visible to
outside networks (i.e., the Internet or any connected VPN).
From a high level SP perspective, a PE-based L3VPN MUST isolate the
exchange of traffic and routing information to only those sites that
are authenticated and authorized members of a VPN.
In a CE-based VPN, the tunnels that connect the sites effectively
meet this isolation requirement if both traffic and routing
information flow over the tunnels.
A L3VPN solution SHOULD provide a means for meeting L3VPN QoS SLA
requirements that isolates VPN traffic from the affects of traffic
offered by non-VPN customers. Also, L3VPN solutions SHOULD provide a
means to isolate the effects that traffic congestion produced by
sites as part of one VPN can have on another VPN.
6.9 Security
This section contains requirements related to securing customer
flows, providing authentication services for temporary, remote or
mobile users, and the need to protect service provider resources
involved in supporting a L3VPN. More detailed security requirements
are provided in [VPNSEC].
6.9.1 Support for Securing Customer Flows
In order to meet the general requirement for providing a range of
security options to a customer, each L3VPN solution MUST clearly
spell out the configuration options that can work together and how
the can do so.
When a VPN solution operates over a part of the Internet, it should
support a configurable option to support one or more of the
following standard IPsec methods for securing a flow for a specified
subset of a customer's VPN traffic:
o confidentiality, so that only authorized devices can decrypt it,
o integrity, to ensure that the data has not been altered,
o authentication, to ensure that the sender is indeed who he or she
claims to be,
o replay attack prevention.
The above functions SHOULD be capable of being applied to "data
traffic" of the customer, which includes the traffic exchanged
between sites, between temporary users and sites and even between
temporary users. It SHOULD also be possible to apply these functions
to "control traffic", such as routing protocol exchanges, that are
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Service requirements for Layer 3 PPVPNs July 2004
not necessarily perceived by the customer but nevertheless essential
to maintain his or her VPN.
Furthermore, such security methods MUST be configurable between
different end points, such as CE-CE, PE-PE, and CE-PE. It is also
desirable to configure security on a per-route or per-VPN basis [VPN
SEC].
A VPN solution MAY support one or more encryption schemes, including
AES, 3DES. Encryption, decryption, and key management SHOULD be
included in profiles as part of the security management system.
6.9.2 Authentication Services
A service provider MUST provide authentication services in support
of temporary user access requirements, as described in section
5.11.2.
Furthermore, traffic exchanged within the scope of VPN MAY involve
several categories of equipment that must cooperate together to
provide the service [Y.1311.1]. These network elements can be CE,
PE, firewalls, backbone routers, servers, management stations, etc.
These network elements learn about each others identity, either via
manual configuration or via discovery protocols, as described in
section 6.4. When network elements must cooperate, these network
elements SHALL authenticate peers before providing the requested
service. This authentication function MAY also be used to control
access to network resources.
The peer identification and authentication function described above
applies only to network elements participating in the VPN. Examples
include:
- traffic between a CE and a PE,
- traffic between CEs belonging to the same VPN,
- CE or PE routers dealing with route announcements for a VPN,
- policy decision point [RFC 3198] and a network element,
- management station and an SNMP agent.
Each L3VPN solution SHOULD describe for a peer authentication
function: where it is necessary, how it shall be implemented, how
secure it must be, and the way to deploy and maintain identification
and authentication information necessary to operate the service.
6.9.3 Resource Protection
Recall from the definitions in section 3.3, that a site can be part
of an intranet with sites from the only same organization, part of
an extranet involving sites from other organizations, have access to
the Internet, or any combination of these scopes of communication.
Within these contexts, a site might be subject to various attacks
coming from different sources. Potential sources of attack include:
- users connected to the supporting public IP backbone,
- users from the Internet,
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- users from temporary sites belonging to the intranet and/or
extranet VPN that the site is part of.
Security threats and risks that a site may encounter include the
following:
- denial of service, for example mail spamming, access connection
congestion, TCP SYN attacks, ping attacks, etc.
- intrusion attempts, which may eventually lead to denial of
service (e.g. a Trojan horse attack).
Additional threat scenarios are defined in [VPNSEC]. A L3 VPN
solution MUST state how it addresses each potential threat scenario.
The devices in the L3VPN network must provide some means of
reporting intrusion attempts to the service provider resources.
6.10 Inter-AS (SP)VPNs
The scenario for VPNs spanning multiple Autonomous Systems (AS) or
Service Providers (SP) requires standard solutions. The scenario
where multiple ASs are involved is the most general case, and is
therefore the one described here. The scenarios of concern are the
CE-based and PE-based L3 VPNs defined in section 3.
In each scenario, all applicable SP requirements, such as traffic
and routing isolation, SLA's, management, security, provisioning,
etc. MUST be preserved across adjacent ASs. The solutions MUST
describe the inter-SP network interface, encapsulation method(s),
routing protocol(s), and all applicable parameters [VPN IW].
An essential pre-condition for an inter-AS VPN is an agreement
between the ASs involved that spells out at least trust, economic,
and management responsibilities.
The overall scalability of the VPN service MUST allow the L3VPN
service to be offered across potentially hundreds of SPs, with the
overall scaling parameters per SP given in [PPVPN-GR].
6.10.1 Routing Protocols
If the link between ASs is not trusted, routing protocols running
between those ASs MUST support some form of authentication. For
example, the TCP option for carrying an MD5 digest may be used to
enhance security for BGP [RFC2385].
BGP MUST be supported as the standard inter-AS routing protocol to
control the path taken by L3VPN traffic.
6.10.2 Management
The general requirements for managing a single AS apply to a
concatenation of ASs. A minimum subset of such capabilities is the
following:
- Diagnostic tools (e.g., ping, traceroute)
- Secured access to one AS management system by another
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- Configuration request and status query tools
- Fault notification and trouble tracking tools
6.10.3 Bandwidth and QoS Brokering
When a VPN spans multiple ASs, there is a desire for a brokering
mechanism that requests certain SLA parameters, such as bandwidth
and QoS, from the other domains and/or networks involved in
transferring traffic to various sites. Although bandwidth and QoS
brokering across multiple ASs is not common in today's networks,
these may be desirable in order to maintain SLAs in inter-AS VPNs.
This section describes requirements for features that would
facilitate these mechanisms. The objective is that a solution SHOULD
be able to determine whether a set of ASs can establish and
guarantee uniform QoS in support of a L3VPN.
The brokering mechanism can be a manual one, for example, where one
provider requests from another provider a specific set of bandwidth
and QoS parameters for traffic going to and from a specific set of
sites. The mechanism could also be an automated one where a device
dynamically requests and receives certain bandwidth and SLA/QoS
parameters. For instance, in the case of a L3 VPN over MPLS, a PE
may negotiate the label for different traffic classes to reach a PE
residing in a neighboring AS. Or, it might be a combination of both.
For additional detailed requirements on the automated approach, see
[TE-INTERAS].
It is not desirable to perform brokering on a per VPN basis since
such an approach would not scale. A solution MUST provide some means
of aggregating QoS and bandwidth brokering requests between ASs. One
method could be for SP's to make an agreement specifying the maximum
amount of bandwidth for specific QoS parameters for all VPN
customers using the SP network. Alternatively, such aggregation
might be on a per hierarchical tunnel basis between PE routers in
different ASs supporting a L3 VPN service [TE-INTERAS].
6.10.4 Security Considerations
If a tunnel traverses multiple SP networks and it passes through an
unsecured SP, POP, NAP, or IX, then security mechanisms MUST be
employed. These security mechanisms include encryption,
authentication and resource protection as described in section 6.9
and security management of section 7.5. For example, a provider
should consider use of both authentication and encryption for a
tunnel used as part of a L3VPN that traverses another service
provider's network.
6.11 L3VPN Wholesale
The architecture MUST support the possibility of one service
provider offering VPN service to another service provider. Another
example is when one service provider sells L3VPN service at
wholesale to another service provider, who then resells that VPN
service to his or her customers.
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The wholesaler's VPN MUST be transparent to the addressing and
routing used by the reseller.
Support for additional levels of hierarchy, for example three levels
where a reseller can again resell the VPN service to yet another VPN
provider, SHOULD be provided.
The Carrier's Carrier scenario is the name used in this document for
this category of L3VPN wholesale (although some scenarios of Inter-
AS/Inter-Provider VPN could possibly fall in this L3VPN wholesale
category too). Various carrier's carrier scenarios should be
supported, such as:
- the customer Carriers do not operate L3VPN services for their
clients;
- the customer Carriers operate L3VPN services for their clients,
but these services are not linked with the L3VPN service offered
by the Carrier's Carrier;
- the customer Carriers operate L3VPN services for their clients and
these services are linked with the L3VPN service offered by the
Carrier's Carrier ("Hierarchical VPNs" scenario)
6.12 Tunneling Requirements
Connectivity between CE sites or PE devices in the backbone SHOULD
be able to use a range of tunneling technologies, such as L2TP,
IPSEC, GRE, IP-in-IP, MPLS, etc.
To set up tunnels between routers, every router MUST support static
configuration for tunneling and MAY support a tunnel setup protocol.
If employed, a tunnel establishment protocol SHOULD be capable of
conveying information, such as the following:
- Relevant identifiers
- QoS/SLA parameters
- Restoration parameters
- Multiplexing identifiers
- Security parameters
There MUST be a means to monitor the following aspects of tunnels:
- Statistics, such as amount of time spent in the up and down
state
- Count of transitions between the up and down state
- Events, such as transitions between the up and down states
The tunneling technology used by the VPN Service Provider and its
associated mechanisms for tunnel establishment, multiplexing, and
maintenance MUST meet the requirements on scaling, isolation,
security, QoS, manageability, etc.
6.13 Support for Access and Backbone Technologies
This section describes requirements for aspects of access and
backbone network technologies from an SP point of view.
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Some SPs MAY desire that a single network infrastructure should
suffice for all services, public IP, VPNs, traffic engineering, and
differentiated services [L2 VPN].
6.13.1 Dedicated Access Networks
Ideally, the L3VPN service SHOULD be independent of physical, link
layer or even network technology of the access network. However, the
characteristics of access networks MUST be accounted for when
specifying the QoS aspects of SLAs for VPN service offerings.
6.13.2 On-Demand Access Networks
Service providers SHOULD be able to support temporary user access,
as described in section 5.11.2 using dedicated or dial-in access
network technology.
L3VPN solutions MUST support the case where a VPN user directly
accesses the VPN service through an access network connected to the
service provider. They MUST also describe how they can support the
case where one or more other service provider networks are used as
access to the service provider supporting the L3VPN service.
Ideally, all information necessary to identify and authenticate
users for an intranet SHOULD be stored and maintained by the
customer. In an extranet, one customer SHOULD be able to maintain
the authentication server, or the customers involved in the extranet
MAY choose to outsource the function to a service provider.
Identification and authentication information could be made
available to the service provider for controlling access, or the
service provider may query a customer maintained server.
Furthermore, one SP may act as access for the SP providing the VPN
service. In the case where the access SP performs identification and
authentication on behalf of the VPN SP, an agreement MUST be reached
on a common specification.
Support for at least the following authentication protocols SHALL be
supported: PAP, CHAP and EAP, since they are currently used in a
wide range of equipment and services.
6.13.3 Backbone Networks
Ideally, the backbone interconnecting SP PE and P devices SHOULD be
independent of physical and link layer technology. Nevertheless, the
characteristics of backbone technology MUST be taken into account
when specifying the QoS aspects of SLAs for VPN service offerings.
6.14 Protection, Restoration
When primary and secondary access connections are available, a L3VPN
solution MUST provide restoration of access connectivity whenever
the primary access link from a CE site to a PE fails. This
restoration capability SHOULD be as automatic as possible, that is,
the traffic should be directed over the secondary link soon after
failure of the primary access link is detected. Furthermore,
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reversion to the primary link SHOULD be dynamic, if configured to do
so [VPN-NEEDS].
As mentioned in Section 5.11.4 above, in the case of multi-homing,
the load balancing capability MAY be used to achieve a degree of
redundancy in the network. In the case of failure of one or more
(but not all) of the multi-homed links, the load balancing
parameters MAY be dynamically adjusted to rapidly redirect the
traffic from the failed link(s) to the surviving links. Once the
failed link(s) is (are) restored, the original provisioned load
balancing ratio SHOULD be restored to its value prior to the
failure.
An SP SHOULD be able to deploy protection and restoration mechanisms
within his or her backbone infrastructure to increase reliability
and fault tolerance of the VPN service offering. These techniques
SHOULD be scalable, and therefore should strive to not perform such
function in the backbone on a per-VPN basis.
Appropriate measurements and alarms that indicate how well network
protection and restoration mechanisms are performing MUST be
supported.
6.15 Interoperability
Service providers are interested in interoperability in at least the
following scenarios:
- To facilitate use of PE and managed CE devices within a single SP
network
- To implement L3VPN services across two or more interconnected SP
networks
- To achieve interworking or interconnection between customer sites
using different L3VPN approaches or different implementations of
the same approach
Each approach MUST describe whether any of the above objectives can
be met. If an objective can be met, the approach MUST describe how
such interoperability could be achieved. In particular, the approach
MUST describe the inter-solution network interface, encapsulation
method(s), routing protocol(s), security, isolation, management, and
all other applicable aspects of the overall VPN solution provided
[VPN IW].
6.16 Migration Support
Service providers MUST have a graceful means to migrate a customer
with minimal service disruption on a site-by-site basis to a L3VPN
approach.
If L3VPN approaches can interwork or interconnect, then service
providers MUST have a graceful means to migrate a customer with
minimal service disruption on a site-by-site basis whenever changing
interworking or interconnection.
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7 Service Provider Management Requirements
A service provider MUST have a means to view the topology,
operational state, order status, and other parameters associated
with each customer's VPN. Furthermore, an SP MUST have a means to
view the underlying logical and physical topology, operational
state, provisioning status, and other parameters associated with the
equipment providing the VPN service(s) to its customers.
Currently, proprietary methods are often used to manage VPNs. The
additional expense associated with operators having to use multiple
proprietary management methods (e.g., command line interface (CLI)
languages) to access such systems is undesirable. Therefore, devices
SHOULD provide standards-based interfaces wherever feasible.
The remainder of this section presents detailed SP management
requirements for a Network Management System (NMS) in the
traditional fault, configuration, accounting, performance, and
security (FCAPS) management categories. Much of this text was
adapted from ITU-T Y.1311.1.
7.1 Fault management
Support for fault management includes:
- indication of customers impacted by failure,
- fault detection (incidents reports, alarms, failure
visualization),
- fault localization (analysis of alarms reports, diagnostics),
- incident recording or logs, creation and follow through of trouble
tickets),
- corrective actions (traffic, routing, resource allocation).
Since PE-based VPNs rely on a common network infrastructure, the NMS
MUST provide a means to inform the provider on the VPN customers
impacted by a failure in the infrastructure. The NMS SHOULD provide
pointers to the related customer configuration information to aid in
fault isolation and the determination of corrective action.
It is desirable to detect faults caused by configuration errors,
because these may cause VPN service to fail, or not meet other
requirements (e.g., traffic and routing isolation). This is a
likely case of compromised security [VPNSEC]. Detection of such
errors is inherently difficult because the problem involves more
than one node and may reach across a global perspective. One
approach could be a protocol that systematically checks that all
constraints and consistency checks hold among tunnel configuration
parameters at the various end points.
A capability to verify L3 reachability within a VPN MUST be provided
for diagnostic purposes.
A capability to verify the parameter configuration of a device
supporting a L3VPN MUST be provided for diagnostic purposes.
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7.2 Configuration Management
Overall, the NMS must support configuration necessary to realize
desired L3 reachability of a L3VPN. Toward this end, an NMS MUST
provide configuration management to provision at least the following
L3VPN components: PE,CE, hierarchical tunnels, access connections,
routing, and QoS, as detailed in this section. If shared access to
the Internet is provided, then this option MUST also be
configurable.
Since VPN configuration and topology are highly dependent upon a
customer's organization, provisioning systems MUST address a broad
range of customer specific requirements. The NMS MUST ensure that
these devices and protocols are provisioned consistently and
correctly.
Provisioning for adding or removing sites SHOULD be as localized and
automated as possible.
Configuration management for VPNs, according to service templates
defined by the provider MUST be supported. A service template
contains fields which, when instantiated, yield a definite service
requirement or policy. For example, a template for an IPSec tunnel
would contain fields such as tunnel end points, authentication
modes, encryption and authentication algorithms, pre-shared keys if
any, and traffic filters. An SLA template would contain fields such
as delay, jitter, throughput and packet loss thresholds as well as
end points over which the SLA has to be satisfied. In general, a
customer's service order can be regarded as a set of instantiated
service templates. This set can, in turn, be regarded as the logical
or service architecture of the customer's VPN.
Service templates can also be used by the provider to define the
service architecture of the provider's own network. For example,
OSPF templates could contain fields such as the subnets that form a
particular area, the area identifier and the area type. BGP service
template could contain fields which when instantiated would yield a
BGP policy, such as for expressing a preference about an exit router
for a particular destination.
The set of service templates SHOULD be comprehensive in that they
can capture all service orders in some meaningful sense.
The provider SHOULD provide means for translating instantiated
service templates into device configurations so that associated
services can be provisioned.
Finally, the approach SHOULD provide means for checking if a service
order is correctly provisioned. This would represent one method of
diagnosing configuration errors. Configuration errors can arise due
to a variety of reasons: manual configuration, intruder attacks, and
conflicting service requirements.
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7.2.1 Configuration Management for PE-Based VPNs
Requirements for configuration management unique to a PE-based VPN
are as follows.
o The NMS MUST support configuration of at least the following
aspects of a L3 PE routers: intranet and extranet membership, CE
routing protocol for each access connection, routing metrics,
tunnels, etc.
o The NMS SHOULD use identifiers for SPs, L3VPNs, PEs, CEs,
hierarchical tunnels and access connections as described in section
6.3.
o Tunnels MUST be configured between PE and P devices. This
requires coordination of identifiers of tunnels, hierarchical
tunnels, VPNs, and any associated service information, for example a
QoS/SLA service.
o Routing protocols running between PE routers and CE devices MUST
be configured per VPN.
O For multicast service, multicast routing protocols MUST also be
configurable.
o Routing protocols running between PE routers and between PE and P
routers MUST also be configured.
o The configuration of a PE-based L3VPN MUST be coordinated with the
configuration of the underlying infrastructure, including Layer 1
and 2 networks interconnecting components of a L3VPN.
7.2.2 Configuration management for CE-based VPN
Requirements for configuration management unique to a CE-based VPN
are as follows.
o Tunnels MUST be configured between CE devices. This requires
coordination of identifiers of tunnels, VPNs, and any associated
service information, for example, a QoS/SLA service.
o Routing protocols running between PE routers and CE devices MUST
be configured. For multicast service, multicast routing protocols
MUST also be configurable.
7.2.3 Provisioning Routing
A means for a service provider to provision parameters for the IGP
for a L3VPN MUST be provided. This includes link level metrics,
capacity, QoS capability, and restoration parameters.
7.2.4 Provisioning Network Access
A service provider MUST have the means to provision network access
between SP-managed PE and CE, as well as the case where the customer
manages the CE.
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7.2.5 Provisioning Security Services
When a security service is requested, an SP MUST have the means to
provision the entities and associated parameters involved with the
service. For example, for IPsec service, tunnels, options, keys, and
other parameters must be provisioned at either the CE and/or PE. In
the case of an intrusion detection service, the filtering and
detection rules must be provisioned on a VPN basis.
7.2.6 Provisioning VPN Resource Parameters
A service provider MUST have a means to dynamically provision
resources associated with VPN services. For example, in a PE-based
service, the number and size of virtual switching and forwarding
table instances must be provisionable.
Dynamic VPN resource assignment is crucial to cope with the frequent
changes requests from customer's (e.g., sites joining or leaving a
VPN), as well as to achieve scalability. The PEs SHOULD be able to
dynamically assign the VPN resources. This capability is especially
important for dial and wireless VPN services.
If an SP supports a "Dynamic Bandwidth management" service, then the
provisioning system MUST be able to make requested changes within
the ranges and bounds specified in the Service Level Agreement
(SLA). Examples of SLA parameters are response time and probability
of being able to service such a request.
7.2.7 Provisioning Value-Added Service Access
A L3VPN service provides controlled access between a set of sites
over a common backbone. However, many service providers also offer a
range of value-added services, for example: Internet access,
firewall services, intrusion protection, IP telephony and IP
Centrex, application hosting, backup, etc. It is outside of the
scope of this document to define if and how these different services
interact with the VPN in order to solve issues such as addressing,
integrity and security. However, the VPN service MUST be able to
provide access to these various types of value-added services.
A VPN service SHOULD allow the SP to supply the customer with
different kinds of standard IP services, like DNS, NTP and RADIUS
needed for ordinary network operation and management. The provider
SHOULD be able to provide IP services to multiple VPN customers.
A firewall function MAY be required to restrict access to the L3VPN
from the Internet [Y.1311].
A managed firewall service MUST be carrier grade. For redundancy and
failure recovery, a means for firewall fail-over should be provided.
Managed firewall services that may be provided include dropping
specified protocol types, intrusion protection, traffic-rate
limiting against malicious attacks, etc.
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Managed firewalls MUST be supported on a per-VPN basis, although
multiple VPNs may be supported by the same physical device (e.g., in
PE-based solution). Managed firewalls SHOULD be provided at the
major access point(s) for the L3VPN. Managed firewall services may
be embedded in CE or PE device, or implemented in standalone
devices.
The NMS SHOULD allow a customer to outsource the management of an IP
networking service to the SP providing the VPN or to a third party.
The NMS SHOULD support collection of information necessary for
optimal allocation of IP services in response to customer orders.
Reachability to and from the Internet to sites within a VPN MUST be
configurable by an SP. This could be controlled by configuring
routing policy to control distribution of VPN routes advertised to
the Internet.
7.2.8 Provisioning Hybrid VPN Services
Configuration of interworking or interconnection between L3VPN
solutions SHOULD be also supported. Ensuring that security and end-
to-end QoS issues are provided consistently SHOULD be addressed.
7.3 Accounting
Many service providers require collection of measurements regarding
resource usage for accounting purposes. The NMS MAY need 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 SLS is not met.
A L3VPN solution MUST describe how the following accounting
functions can be provided:
- measurements of resource utilization,
- collection of accounting information,
- 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 a "Dynamic Bandwidth management" service, then the
dates, times, amounts and interval required to perform requested
bandwidth allocation change(s) MUST be traceable for monitoring and
accounting purposes.
Solutions should state compliance to accounting requirements, as
described in section 1.7 of RFC 2975.
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7.4 Performance Management
Performance management MUST support functions involved with
monitoring and collecting performance data regarding devices,
facilities, and services, as well as determination of conformance to
Service Level Specifications (SLS), such as QoS and availability
measurements.
Performance management SHOULD also support analysis of important
aspects of a L3VPN , such as bandwidth utilization, response time,
availability, QoS statistics, and trends based on collected data.
7.4.1 Performance Monitoring
The NMS MUST monitor device behavior to evaluate performance metrics
associated with an SLA. Different measurement techniques may be
necessary depending on the service for which an SLA is provided.
Example services are QoS, security, multicast, and temporary access.
These techniques MAY be either intrusive or non-intrusive depending
on the parameters being monitored.
The NMS MUST also monitor aspects of the VPN not directly associated
with an SLA, such as resource utilization, state of devices and
transmission facilities, as well as control of monitoring resources
such as probes and remote agents at network access points used by
customers and mobile users.
7.4.2 SLA and QoS management features
The NMS SHOULD support SLAs between an SP and the various VPN
customers according to the corresponding SLSes by measurement of the
indicators defined within the context of the SLA, on a regular
basis.
The NMS SHOULD use the QOS parameter measurement definitions,
techniques, and methods as defined by the IETF IP Performance
Metrics (IPPM) working group for delay, loss, and delay variation.
The NMS SHOULD support allocation and measurement of end-to-end QoS
requirements to QoS parameters for one or more VPN network(s).
Devices supporting L3VPN SLAs SHOULD have real-time performance
measurements that have indicators and threshold crossing alerts.
Such thresholds should be configurable.
7.5 Security Management
The security management function of the NMS MUST include management
features to guarantee the security of devices, access connections,
and protocols within the L3VPN network(s), as well as the security
of customer data and control as described in section 6.9.
7.5.1 Resource Access Control
Resource access control determines the privileges that a user has to
access particular applications and VPN network resources. Without
such control, only the security of the data and control traffic is
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protected, leaving the devices providing the L3VPN network
unprotected. Access control capabilities protect these devices to
ensure that users have access to only the resources and applications
to which they are authorized to use.
In particular, access to the routing and switching resources managed
by the SP MUST be tightly controlled to prevent and/or effectively
mitigate a malicious attack. More detailed requirements in this area
are described in [VPNSEC].
7.5.2 Authentication
Authentication is the process of verifying that the sender is
actually who he or she claims to be. The NMS MUST support standard
methods for authenticating users attempting to access management
services.
Scalability is critical as the number of nomadic/mobile clients is
increasing rapidly. The authentication scheme implemented for such
deployments MUST be manageable for large numbers of users and VPN
access points.
Strong authentication schemes SHALL be supported to ensure the
security of both VPN access point-to-VPN access point (e.g., PE to
PE in a PE-based case) and client-to-VPN Access point (e.g., CE-to-
PE in a PE-based case) communications. This is particularly
important to prevent VPN access point spoofing. VPN Access Point
Spoofing is the situation where an attacker tries to convince a PE
or CE that the attacker is the VPN Access Point. If an attacker can
convince a PE or CE device of that, then that device will send VPN
traffic to the attacker (who could forward it to the true access
point after compromising confidentiality or integrity).In other
words, a non-authenticated VPN AP can be spoofed with a man-in-the-
middle attack, because the endpoints never verify each other. A
weakly-authenticated VPN AP may be subject to such an attack.
Strongly-authenticated VPN APs are not subject to such attacks,
because the man-in-the-middle cannot be authenticated as the real
AP, due to the strong authentication algorithms.
7.6 Basis and Presentation Techniques of Management Information
Each L3VPN solution approach MUST specify the management information
bases (MIB) modules for the network elements involved in L3VPN
services. This is an essential requirement in network provisioning.
The approach SHOULD identify any information not contained in a
standard MIB related to FCAPS that is necessary to meet a generic
requirement.
An IP VPN (Policy)Information model, when available, SHOULD reuse
the policy information models being developed in parallel for
specific IP network capabilities [IM-REQ]. This includes the QoS
Policy Information Model_[QPIM] and the IPSEC Configuration Policy
Model_ [IPSECIM]. The IP VPN Information model SHOULD provide the
OSS with adequate "hooks" to correlate service level specifications
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with traffic data collected from network elements. The use of
policies includes rules that control corrective actions taken by OSS
components responsible for monitoring the network and ensuring that
it meets service requirements.
Additional requirements on VPN information models are given in
reference [IM-PPVPN]. In particular, an information model MUST allow
an SP to change VPN network dimensions with minimal influence on
provisioning issues. The adopted model SHOULD be applicable to both
small/medium size and large-scale L3VPN scenarios.
Some service providers MAY require systems that visually, audibly,
or logically present FCAPS information to internal operators and/or
customers.
8 Security Considerations
Security considerations occur at several levels and dimensions
within L3 VPNs, as detailed within this document. This section
provides a summary with references to supporting detailed
information.
The requirements in this document separate the notion of traditional
security requirements, such as integrity, confidentiality, and
authentication from that of isolating (or separating) the exchange
of VPN data and control traffic between specific sets of sites (as
defined in sections 3.3 and 4.1). Further detail on security
requirements is given from the customer and service provider
perspectives in sections 5.9 and 6.9, respectively. In an analogous
manner, further detail on data and control traffic isolation
requirements are given from the customer and service provider
perspectives in sections 5.1 and 6.8, respectively. Additionally,
references to a document [VPNSEC] specifically addressing security
requirements are made where appropriate.
Furthermore, requirements regarding management of security from a
service provider perspective are described in section 7.5.
9 Acknowledgements
The authors of this document would like to acknowledge the
contributions from the people who launched the work on VPN
requirements inside ITU-T SG13, the authors of the original IP VPN
requirements and framework document [RFC 2764], as well as Tom
Worster, Ron Bonica, Sanjai Narain, Muneyoshi Suzuki, Tom Nadeau,
Nail Akar, Derek Atkins, Bryan Gleeson, Greg Burns, and Frederic Le
Garrec. The authors are also grateful to the helpful suggestions and
direction provided by the technical advisors, Alex Zinin, Scott
Bradner, Bert Wijnen and Rob Coltun. Finally, the authors also wish
to acknowledge the insights and requirements gleaned from the many
documents listed in the references section. Citations to these
documents were made only where the authors believed that additional
insight to the requirement could be obtained by reading the source
document.
Carugi, McDysan et al Informational - Expires January 2005 40
Service requirements for Layer 3 PPVPNs July 2004
10 References
10.1 Normative References
[RFC 3809] Nagarajan, A., "Generic Requirements for Provider
Provisioned VPN," Work in Progress.
[RFC 3377] Hodges, J., Morgan, R. "Lightweight Directory Access
Protocol (v3): Technical Specification," RFC 3377,
September 2002
[RFC 1918] Rekhter, Y., et al., "Address Allocation for Private
Internets," RFC 1918, February 1996.
[RFC 2026] Bradner, S., "The Internet Standards Process --
Revision 3", BCP 9, RFC 2026, October 1996.
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997
[RFC 2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S.,
Jamin, S. "Resource ReSerVation Protocol (RSVP) --
Version 1 Functional Specification," September 1997.
[RFC 2211] Wroclawski, J., Specification of the Controlled-Load
Network Element Service, RFC 2211, IETF, September
1997.
[RFC 2212] Shenker, S., Partridge, C., Guerin, R., Specification
of Guaranteed Quality of Service, RFC 2212, IETF,
September 1997.
[RFC 2251] Wahl, M. et al., "Lightweight Directory Access
Protocol (v3)," RFC 2251, December 1997.
[RFC 2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang,
Z., Weiss, W. "An Architecture for Differentiated
Services", RFC 2475, Dec. 1998.
[RFC 2597] Baker, F., Heinanen, J., Weiss, W., Wroclawski, J.
"Assured Forwarding PHB Group", RFC 2597, June 1999.
[RFC 2661] Townsley, W. et al., "Layer Two Tunneling Protocol
"L2TP"," RFC 2661, August 1999.
[RFC 2685] Fox B., et al, "Virtual Private Networks Identifier",
RFC 2685, September 1999.
[RFC 2983] Black, D. "Differentiated Services and Tunnels,"
RFC2983, October 2000
[RFC 3031] Rosen, E., Viswanathan, A., Callon, R. "Multiprotocol
Label Switching Architecture," January 2001.
[RFC 3246] Davie, B., et al., "An Expedited Forwarding PHB", RFC
3246, March 2002.
[RFC 3270] Le Faucheur, F., et al., "Multi-Protocol Label
Switching (MPLS) Support of Differentiated Services,"
RFC 3270, May 2002
10.2 Non-normative References
[2547bis] Rosen, E., Rekhter, Y. et al., "BGP/MPLS VPNs", work
in progress.
[2917bis] Muthukrishnan, K., et al., "A Core MPLS IP VPN
Architecture," work in progress
Carugi, McDysan et al Informational - Expires January 2005 41
Service requirements for Layer 3 PPVPNs July 2004
[DOCSIS 1.1] Data Over Cable Service Interface Specification
(DOCSIS), Cable Labs,
http://www.cablemodem.com/specifications.html
[FRF.13] Frame Relay Forum, "Service Level Definitions
Implementation Agreement," August, 1998.
[IM-PPVPN] Lago, P., et al., "An Information Model for Provider
Provisioned Virtual Private Networks," work in
progress.
[IM-REQ] Iyer, M., et al., "Requirements for an IP VPN Policy
Information Model," work in progress
[IPSECIM] Jason, J., "IPsec Configuration Policy Model," work
in progress.
[CE-PPVPN] De Clercq, J., Paridaens, O., Krywaniuk, A., Wang,
C., "An Architecture for Provider Provisioned CE-
based Virtual Private Networks using IPsec," work in
progress
[IPSEC-PPVPN] Gleeson, B., "Uses of IPsec with Provider
Provisioned VPNs," work in progress.
[L2 MPLS] Martini, L., et al., "Transport of Layer 2 Frames
Over MPLS," work in progress.
[L2 VPN] Rosen, E., et al., "An Architecture for L2VPNs,"
work in progress.
[L2 VPN] Kompella, K., Bonica, R., "Whither Layer 2 VPNs?,"
work in progress.
[MPLS SEC] Behringer, M., "Analysis of the Security of the MPLS
Architecture," work in progress
[PPVPN-TERM] Andersson, L., Madsen, T., "PPVPN Terminology," work
in progress
[L3VPN-SEC] Fang, L., et al., "Security Framework for Provider
Provisioned Virtual Private Networks," work in
progress.
[NBVPN-FR] Suzuki, M. and Sumimoto, J. (editors), "A framework
for Network-based VPNs", work in progress
[L3VPN-FR] Callon, R., Suzuki, M., et al. "A Framework for
Layer 3 Provider Provisioned Virtual Private
Networks ",work in progress
[PPVPN-VR] Knight, P., Ould-Brahim, H., Gleeson, B., "Network
based IP VPN Architecture using Virtual
Routers," work in progress
[QPIM] Snir, Ramberg, Strassner, Cohen and Moore, "Policy
QoS Information Model," work in progress.
[RFC 2547] Rosen, E., Rekhter, Y., "BGP/MPLS VPNs," RFC 2547,
March 1999.
[RFC 2764] Gleeson, B., et al., "A Framework for IP based Virtual
Private Networks", RFC 2764, February 2000.
[RFC 2975] Aboba, B., et al., "Introduction to Accounting
Management," October 2000.
[RFC 3198] Westerinen, A., et al., "Terminology for Policy-Based
Management," November, 2001.
[TE-INTERAS] Zhang, R., Vasssuer, J.P., "MPLS Inter-AS Traffic
Engineering requirements," work in progress.
[VPN DISC] Squire, M. et al., "VPN Discovery Discussions and
Carugi, McDysan et al Informational - Expires January 2005 42
Service requirements for Layer 3 PPVPNs July 2004
Options," work in progress.
[VPN IW] Kurakami, H., et al., "Provider-Provisioned VPNs
Interworking," work in progress.
[VPN SEC] De Clercq, J., et al., "Considerations about
possible security extensions to BGP/MPLS VPN," work
in progress.
[VPN TUNNEL] Worster, T., et al., "A PPVPN Layer Separation: VPN
Tunnels and Core Connectivity," work in progress
[VPN-CRIT] Yu, J., Jou, L., Matthews, A ., Srinivasan, V.,
"Criteria for Evaluating VPN Implementation
Mechanisms", work in progress
[VPN-NEEDS] Jacquenet, C., "Functional needs for the deployment
of an IP VPN service offering : a service provider
perspective ", work in progress
[Y.1241] "IP Transfer Capability for the support of IP based
Services", Y.1241 ITU-T Recommendation, January
2001.
[Y.1311.1] Carugi, M. (editor), "Network Based IP VPN over MPLS
architecture",Y.1311.1 ITU-T Recommendation,
July2001.
[Y.1311] Knightson, K. (editor), "Network based VPNs -
Generic Architecture and Service Requirements,"
Y.1311 ITU-T Recommendation, March 2002.
11 Authors' address
Marco Carugi (Co-editor)
Nortel Networks
Parc d'activit‰s de Magny-Les Jeunes Bois CHATEAUFORT
78928 YVELINES Cedex 9 - FRANCE
EMail: marco.carugi@nortelnetworks.com
Dave McDysan (Co-editor)
MCI
22001 Loudoun County Parkway
Ashburn, VA 20147, USA
EMail: dave.mcdysan@mci.com
Luyuan Fang
AT&T
200 Laurel Ave - Room C2-3B35
Middletown, NJ 07748 USA
EMail: Luyuanfang@att.com
Ananth Nagarajan
Juniper Networks
EMail: ananth@juniper.net
Junichi Sumimoto
NTT Communications Corporation
3-20-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo 163-1421, Japan
EMail: j.sumimoto@ntt.com
Carugi, McDysan et al Informational - Expires January 2005 43
Service requirements for Layer 3 PPVPNs July 2004
Rick Wilder
Alcatel
EMail: rick.wilder@alcatel.com
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