RFC5523: OSPFv3-Based Layer 1 VPN Auto-Discovery
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Related keywords:
(layer 1 virtual private network)
(open shortest path first)
Network Working Group L. Berger
Request for Comment: 5523 LabN Consulting, LLC
Category: Experimental April 2009
OSPFv3-Based Layer 1 VPN Auto-Discovery
Status of This Memo
This memo defines an Experimental Protocol for the Internet
community. It does not specify an Internet standard of any kind.
Discussion and suggestions for improvement are requested.
Distribution of this memo is unlimited.
Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents in effect on the date of
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Please review these documents carefully, as they describe your rights
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Abstract
This document defines an OSPFv3-based (Open Shortest Path First
version 3) Layer 1 Virtual Private Network (L1VPN) auto-discovery
mechanism. This document parallels the existing OSPF version 2 L1VPN
auto-discovery mechanism. The notable functional difference is the
support of IPv6.
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Table of Contents
1. Introduction ....................................................2
1.1. Terminology ................................................2
1.2. Conventions Used in This Document ..........................3
1.3. Overview ...................................................3
2. OSPFv3 L1VPN LSA and Its TLVs ...................................5
2.1. OSPFv3 L1VPN LSA ...........................................5
2.2. L1VPN IPv6 INFO TLV ........................................7
3. OSPFv3 L1VPN LSA Advertising and Processing .....................8
4. Backward Compatibility ..........................................9
5. Manageability Considerations ....................................9
5.1. Coexistence with and Migration from OSPFv2 .................9
6. Security Considerations ........................................10
7. IANA Considerations ............................................11
8. Acknowledgment .................................................11
9. References .....................................................11
9.1. Normative References ......................................11
9.2. Informative References ....................................12
1. Introduction
This document defines an OSPFv3-based (Open Shortest Path First
version 3) Layer 1 Virtual Private Network (L1VPN) auto-discovery
mechanism. This document parallels the existing OSPF version 2 L1VPN
auto-discovery mechanism. The notable functional difference is the
support of IPv6.
1.1. Terminology
The reader of this document should be familiar with the terms used in
[RFC4847] and [RFC5251]. The reader of this document should also be
familiar with [RFC5340], [RFC5329], and [RFC5252]. In particular,
the following terms:
L1VPN Layer 1 Virtual Private Network
CE Customer (edge) network element directly connected to the
Provider network (terminates one or more links to one or
more PEs); it is also connected to one or more Cs and/or
other CEs.
C Customer network element that is not connected to the
Provider network but is connected to one or more other Cs
and/or CEs.
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PE Provider (edge) network element directly connected to one
or more Customer networks (terminates one or more links to
one or more CEs associated with the same or different
L1VPNs); it is also connected to one or more Ps and/or
other PEs.
P Provider (core) network element that is not directly
connected to any of Customer networks; P is connected to
one or more other Ps and/or PEs.
LSA OSPF Link State Advertisement.
LSDB Link State Database: a data structure supported by an IGP
speaker.
PIT Port Information Table.
CPI Customer Port Identifier.
PPI Provider Port Identifier.
1.2. 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 [RFC2119].
1.3. Overview
The framework for Layer 1 VPNs is described in [RFC4847]. Basic mode
operation is further defined in [RFC5251]. [RFC5251] identifies the
information that is necessary to map customer information (port
identifiers) to provider information (identifiers). It also states
that this mapping information may be provided via provisioning or via
an auto-discovery mechanism. [RFC5252] provides such an auto-
discovery mechanism using Open Shortest Path First (OSPF) version 2.
This document provides the same functionality using OSPF version 3
and adds support for IPv6.
Figure 1 shows the L1VPN basic service being supported using OSPF-
based L1VPN auto-discovery. This figure shows two PE routers
interconnected over a GMPLS backbone. Each PE is attached to three
CE devices belonging to three different Layer 1 VPNs. In this
network, OSPF is used to provide the VPN membership, port mapping,
and related information required to support basic mode operation.
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PE PE
+---------+ +--------------+
+--------+ | +------+| | +----------+ | +--------+
| VPN-A | | |VPN-A || | | VPN-A | | | VPN-A |
| CE1 |--| |PIT || OSPF LSAs | | PIT | |-| CE2 |
+--------+ | | ||<----------->| | | | +--------+
| +------+| Distribution| +----------+ |
| | | |
+--------+ | +------+| | +----------+ | +--------+
| VPN-B | | |VPN-B || ------- | | VPN-B | | | VPN-B |
| CE1 |--| |PIT ||--( GMPLS )--| | PIT | |-| CE2 |
+--------+ | | || (Backbone) | | | | +--------+
| +------+| -------- | +----------+ |
| | | |
+--------+ | +-----+ | | +----------+ | +--------+
| VPN-C | | |VPN-C| | | | VPN-C | | | VPN-C |
| CE1 |--| |PIT | | | | PIT | |-| CE2 |
+--------+ | | | | | | | | +--------+
| +-----+ | | +----------+ |
+---------+ +--------------+
Figure 1: OSPF Auto-Discovery for L1VPNs
The approach used in this document to provide OSPFv3-based L1VPN
auto-discovery uses a new type of Link State Advertisement (LSA),
which is referred to as an OSPFv3 L1VPN LSA. The OSPFv3 L1VPN LSA
carries information in TLV (type, length, value) structures. An
L1VPN-specific TLV is defined below to propagate VPN membership and
port information. This TLV is referred to as the L1VPN Info TLV.
The OSPFv3 L1VPN LSA may also carry Traffic Engineering (TE) TLVs;
see [RFC3630], [RFC4203], and [RFC5329].
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2. OSPFv3 L1VPN LSA and Its TLVs
This section defines the OSPFv3 L1VPN LSA and its TLVs.
2.1. OSPFv3 L1VPN LSA
The format of a OSPFv3 L1VPN LSA is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | LS type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| L1VPN Info TLV |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TE Link TLV |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
LS age
As defined in [RFC5340].
LS type
As defined in [RFC5340]. The U-bit MUST be set to 1, and the S1
and S2 bits MUST be set to indicate either area or Autonomous
System (AS) scoping. The LSA Function Code portion of this field
MUST be set to 14, i.e., the OSPFv3 L1VPN LSA.
Advertising Router
As defined in [RFC5340].
LS Sequence Number
As defined in [RFC5340].
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LS checksum
As defined in [RFC5340].
Length
As defined in [RFC5340].
L1VPN Info TLV
A single L1VPN Info TLV, as defined in Section 2.2 of [RFC5252] or
Section 2.2 of this document, MUST be present. If more than one
L1VPN Info TLV is present, only the first TLV is processed and the
others MUST be ignored on receipt. If no L1VPN Info TLV is
present, the LSA is processed (and flooded) as normal, but the
L1VPN PIT table MUST NOT be modified in any way.
TE Link TLV
A single TE Link TLV MAY be included in an OSPFv3 L1VPN LSA. When
an L1VPN IPv4 Info TLV is present, a single TE Link TLV as defined
in [RFC3630] and [RFC4203] MAY be included. When an L1VPN IPv6
Info TLV is present, a single TE Link TLV as defined in [RFC5329]
MAY be included.
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2.2. L1VPN IPv6 INFO TLV
The following TLV is introduced:
Name: L1VPN IPv6 Info
Type: 32768
Length: Variable
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| L1VPN TLV Type | L1VPN TLV Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| L1VPN Globally Unique Identifier |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PE TE Address |
| ... |
| ... |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link-Local Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
| L1VPN Auto-Discovery Information |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| .| Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L1VPN TLV Type
The type of the TLV (see above).
TLV Length
The length of the TLV in bytes, excluding the four (4) bytes of
the TLV header and, if present, the length of the Padding field.
L1VPN Globally Unique Identifier
As defined in [RFC5251].
PE TE Address
This field MUST carry an address that has been advertised by the
LSA originator per [RFC5329] and is either the Router IPv6 Address
TLV or Local Interface IPv6 Address link sub-TLV. It will
typically carry the TE Router Address.
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Link-Local Identifier
This field is used to support unnumbered links. When an
unnumbered PE TE link is represented, this field MUST contain a
value advertised by the LSA originator per [RFC5340] in a Router
LSA. When a numbered link is represented, this field MUST be set
to zero (0).
L1VPN Auto-Discovery Information
As defined in [RFC5251].
Padding
A field of variable length and of sufficient size to ensure that
the TLV is aligned on a 4-byte boundary. This field is only
required when the L1VPN Auto-Discovery Information field is not
4-byte aligned. This field MUST be less than 4 bytes long, and
MUST NOT be present when the size of L1VPN Auto-Discovery
Information field is 4-byte aligned.
3. OSPFv3 L1VPN LSA Advertising and Processing
PEs advertise local <CPI, PPI> tuples in OSPFv3 L1VPN LSAs containing
L1VPN Info TLVs. Each PE MUST originate a separate OSPFv3 L1VPN LSA
with area or AS flooding scope, based on configuration, for each
local CE-PE link. The LSA MUST be originated each time a PE restarts
and every time there is a change in the PIT entry associated with a
local CE-PE link. The LSA MUST include a single L1VPN Info TLV and
MAY include a single TE Link TLV. The TE Link TLV carries TE
attributes of the associated CE-PE link. Note that because CEs are
outside of the provider TE domain, the attributes of CE-PE links are
not advertised via normal OSPF-TE procedures as described in
[RFC5329]. If more than one L1VPN Info TLVs and/or TE Link TLVs are
found in the LSA, the subsequent TLVs SHOULD be ignored by the
receiving PEs.
Every time a PE receives a new, removed, or modified OSPFv3 L1VPN
LSA, the PE MUST check whether it maintains a PIT associated with the
L1VPN specified in the L1VPN Globally Unique Identifier field. If
this is the case (the appropriate PIT will be found if one or more
local CE-PE links that belong to the L1VPN are configured), the PE
SHOULD add, remove, or modify the PIT entry associated with each of
the advertised CE-PE links accordingly. (An implementation MAY
choose to not remove or modify the PIT according to local policy or
management directives.) Thus, in the normal steady-state case, all
PEs associated with a particular L1VPN will have identical local PITs
for an L1VPN.
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4. Backward Compatibility
Neither the TLV nor the LSA introduced in this document present any
interoperability issues. Per [RFC5340], and due to the U-bit being
set, OSPFv3 speakers that do not support the OSPFv3 L1VPN LSA (Ps for
example) just participate in the LSA's flooding process but should
ignore the LSA's contents.
5. Manageability Considerations
The principal concern in operating an auto-discovery mechanism for an
L1VPN is that the PE needs to be configured with information about
which VPNs it supports. This information can be discovered from the
CEs using some form of membership negotiation, but is more likely to
be directly configured by the operator as described in [RFC4847],
[RFC5251], and [RFC5253]. No standardized mechanisms to configure
this information have been defined, and it is a matter for individual
implementations with input from operator policy how a PE is told
which L1VPNs it supports. It is probable that configuration of this
information is closely tied to the configuration of CE-facing ports
on the PE, which in turn causes PITs to be established in the PE.
Additionally, it may be of value to an operator to view the L1VPN
membership information that has been learned by a PE. An
implementation may supply this information through a proprietary
interface, or may allow it to be inspected through the OSPFv3 MIB
module [OSPFv3-MIB] or the Traffic Engineering Database MIB
[TED-MIB].
Note that the operation of the control plane has no impact on IP
network traffic because all of the user data is in Layer 1, while the
control plane is necessarily out of band in a Data Communications
Network (DCN).
5.1. Coexistence with and Migration from OSPFv2
It is expected that only a single routing protocol instance will be
used to operate auto-discovery within an L1VPN at any time. Thus,
coexistence issues only apply to the migration from OSPFv2 to OSPFv3
and can be expected to be transient.
Migration from OSPFv2 to OSPFv3 would be a once-only event for any
network and would probably depend on the migration of the routing
protocol used within the network for normal GMPLS procedures. The
migration process would not be any different from the process used to
migrate the normal GMPLS routing protocol. The steps to follow are
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clearly a matter for the operator of the network and are not a matter
for standardization, but the following sequence is provided to
illustrate the potential actions:
1. Assign IPv6 addresses to all control plane and data plane
resources.
2. Install and enable OSPFv3 on all controllers.
3. Use OSPFv3 to advertise IPv4 and IPv6 resource identifiers.
4. Manually verify the advertised membership and topology information
from the OSPFv2 and OSPFv3 databases.
5. Start a maintenance window where data continues to flow, but no
L1VPN connections can be changed.
6. Cut over to the OSPFv3 membership and topology information.
7. Close the maintenance window.
8. Turn off OSPFv2.
9. Remove/disable the IPv4 address for all control plane and data
plane resources.
6. Security Considerations
The approach presented in this document describes how PEs dynamically
learn L1VPN specific information. Mechanisms to deliver the VPN
membership information to CEs are explicitly out of scope of this
document. Therefore, the security issues raised in this document are
limited to within the OSPF domain.
This defined approach reuses mechanisms defined in [RFC5340].
Therefore, the same security approaches and considerations apply to
this approach. OSPF provides several security mechanisms that can be
applied. Specifically, OSPF supports multiple types of
authentication, limits the frequency of LSA origination and
acceptance, and provides techniques to avoid and limit the impact of
database overflow. In cases were end-to-end authentication is
desired, OSPF's neighbor-to-neighbor authentication approach can be
augmented with an approach similar to the experimental extension to
OSPF, see [RFC2154], which supports the signing and authentication of
LSAs.
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7. IANA Considerations
IANA has assigned an OSPFv3 LSA Function Code as described in Section
2.1 of this document. IANA has made an assignment in the form:
Value OSPFv3 LSA type function Type Reference
------- ----------------------------- ---------
14 OSPFv3 L1VPN LSA [RFC5523]
8. Acknowledgment
This document was created at the request of Pasi Eronen. Adrian
Farrel and Acee Lindem provided valuable reviews of this document.
Adrian also provided the text for Section 5.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, July 2008.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic
Engineering (TE) Extensions to OSPF Version 2", RFC
3630, September 2003.
[RFC4203] Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4203, October 2005.
[RFC5251] Fedyk, D., Ed., Rekhter, Y., Ed., Papadimitriou, D.,
Rabbat, R., and L. Berger, "Layer 1 VPN Basic Mode", RFC
5251, July 2008.
[RFC5252] Bryskin, I. and L. Berger, "OSPF-Based Layer 1 VPN
Auto-Discovery", RFC 5252, July 2008.
[RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed.,
"Traffic Engineering Extensions to OSPF Version 3", RFC
5329, September 2008.
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9.2. Informative References
[OSPFv3-MIB] Joyal, D., Ed. and V. Manral, Ed., "Management
Information Base for OSPFv3", Work in Progress, November
2008.
[RFC2154] Murphy, S., Badger, M., and B. Wellington, "OSPF with
Digital Signatures", RFC 2154, June 1997.
[RFC4847] Takeda, T., Ed., "Framework and Requirements for Layer 1
Virtual Private Networks", RFC 4847, April 2007.
[RFC5253] Takeda, T., Ed., "Applicability Statement for Layer 1
Virtual Private Network (L1VPN) Basic Mode", RFC 5253,
July 2008.
[TED-MIB] Miyazawa, M., Otani, T., Nadeau, T., and K. Kumaki,
"Traffic Engineering Database Management Information
Base in support of MPLS-TE/GMPLS", Work in Progress,
January 2009.
Author's Address
Lou Berger
LabN Consulting, LLC
EMail: lberger@labn.net
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