OSPFv3 TE: Traffic Engineering Extensions to OSPF Version 3
Letting an IPv6 network describe its links so that paths can be planned across it.
Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed., "Traffic Engineering Extensions to OSPF Version 3", RFC 5329, DOI 10.17487/RFC5329, September 2008, <https://www.rfc-editor.org/info/rfc5329>.
@misc{rfc5329,
series = {Request for Comments},
number = 5329,
howpublished = {RFC 5329},
publisher = {RFC Editor},
doi = {10.17487/RFC5329},
url = {https://www.rfc-editor.org/info/rfc5329},
author = {K. Ishiguro and V. Manral and A. Davey and A. Lindem},
title = {{Traffic Engineering Extensions to OSPF Version 3}},
pagetotal = 12,
year = 2008,
month = sep,
} RFC text
Contents
Network Working Group K. Ishiguro
Request for Comments: 5329 V. Manral
Category: Standards Track IP Infusion, Inc
A. Davey
Data Connection Limited
A. Lindem, Ed.
Redback Networks
September 2008
Traffic Engineering Extensions to OSPF Version 3
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This document describes extensions to OSPFv3 to support intra-area
Traffic Engineering (TE). This document extends OSPFv2 TE to handle
IPv6 networks. A new TLV and several new sub-TLVs are defined to
support IPv6 networks.
Table of Contents
1. Introduction ....................................................2
1.1. Requirements Notation ......................................2
2. Intra-Area-TE-LSA ...............................................3
2.1. Intra-Area-TE-LSA Payload ..................................4
3. Router IPv6 Address TLV .........................................4
4. Link TLV ........................................................5
4.1. Link ID Sub-TLV ............................................6
4.2. Neighbor ID Sub-TLV ........................................6
4.3. Local Interface IPv6 Address Sub-TLV .......................6
4.4. Remote Interface IPv6 Address Sub-TLV ......................7
5. Security Considerations .........................................8
6. Management Considerations .......................................8
7. IANA Considerations .............................................9
8. References ......................................................9
8.1. Normative References .......................................9
8.2. Informative References ....................................10
Acknowledgments ...................................................10
1. Introduction
OSPFv3 has a very flexible mechanism for adding new LS types.
Unknown LS types are flooded properly based on the flooding scope
bits in the LS type [OSPFV3]. This document defines the Intra-Area-
TE-LSA to OSPFv3.
For Traffic Engineering, this document uses "Traffic Engineering
Extensions to OSPF" [TE] as a base for TLV definitions. New TLVs and
sub-TLVs are added to [TE] to extend TE capabilities to IPv6
networks. Some existing TLVs and sub-TLVs require clarification for
OSPFv3 applicability.
GMPLS [GMPLS] and the Diff-Serv MPLS extensions [TE-DIFF] are based
on [TE]. These functions can also be extended to OSPFv3 by utilizing
the TLVs and sub-TLVs described in this document.
1.1. Requirements Notation
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-KEYWORDS].
2. Intra-Area-TE-LSA
A new LS type is defined for the Intra-Area-TE-LSA. This is
different from OSPFv2 Traffic Engineering [TE] where opaque LSAs are
used to advertise TE information [OPAQUE]. The LSA function code is
10, the U-bit is set, and the scope is set to 01 for area-scoping.
When the U-bit is set to 1, an OSPFv3 router must flood the LSA at
its defined flooding scope even if it does not recognize the LS type
[OSPFV3].
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 |1|0|1| 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+- TLVs -+
| ... |
OSPFv3 Intra-Area-TE-LSA
The Link State ID of an Intra-Area-TE-LSA is an arbitrary value used
to maintain multiple Traffic Engineering LSAs. The Link State ID has
no topological significance.
The format of the TLVs within the body of an Intra-Area-TE-LSA is the
same as the format used by the Traffic Engineering extensions to OSPF
[TE]. The LSA payload consists of one or more nested
Type/Length/Value (TLV) triplets. The format of each TLV is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Format
The Length field defines the length of the value portion in octets
(thus, a TLV with no value portion would have a length of 0). The
TLV is padded to 4-octet alignment; padding is not included in the
Length field (so a 3-octet value would have a length of 3, but the
total size of the TLV would be 8 octets). Nested TLVs are also 32-
bit aligned. For example, a 1-byte value would have the Length field
set to 1, and 3 octets of padding would be added to the end of the
value portion of the TLV. Unrecognized types are ignored.
2.1. Intra-Area-TE-LSA Payload
An Intra-Area-TE-LSA contains one top-level TLV. There are two
applicable top-level TLVs:
2 - Link TLV
3 - Router IPv6 Address TLV
3. Router IPv6 Address TLV
The Router IPv6 Address TLV advertises a reachable IPv6 address.
This is a stable IPv6 address that SHOULD be reachable if there is
connectivity to the OSPFv3 router.
The Router IPv6 Address TLV has type 3, length 16, and a value
containing a 16-octet local IPv6 address. A link-local address MUST
NOT be specified for this TLV. It MUST appear in exactly one Traffic
Engineering LSA originated by an OSPFv3 router supporting the TE
extensions. The Router IPv6 Address TLV is a top-level TLV as
defined in "Traffic Engineering Extensions to OSPF" [TE], and only
one top-level TLV may be contained in an LSA.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 | 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+- -+-+-+-+
| |
+-+-+-+- Router IPv6 Address -+-+-+-+
| |
+-+-+-+- -+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type A 16-bit field set to 3.
Length A 16-bit field that indicates the length of the value
portion in octets. For this TLV, it is always 16.
Value A stable and routable IPv6 address.
Router IPv6 Address TLV
4. Link TLV
The Link TLV describes a single link and consists of a set of sub-
TLVs [TE]. All of the sub-TLVs in [TE] other than the Link ID sub-
TLV are applicable to OSPFv3. The Link ID sub-TLV can't be used in
OSPFv3 since it is defined to use the OSPFv2 identification for the
Designated Router (DR) on multi-access networks. In OSPFv2,
neighbors on point-to-point networks and virtual links are identified
by their Router IDs while neighbors on broadcast, Non-Broadcast
Multi-Access (NBMA), and Point-to-Multipoint links are identified by
their IPv4 interface addresses (refer to section 8.2 in [OSPFV2]).
The IPv4 interface address is not known to OSPFv3. In contrast to
OSPFv2, OSPFv3 always identifies neighboring routers by their Router
IDs (refer to section 2.11 in [OSPFV3]).
Three new sub-TLVs for the Link TLV are defined:
18 - Neighbor ID (8 octets)
19 - Local Interface IPv6 Address (16N octets, where N is the
number of IPv6 addresses)
20 - Remote Interface IPv6 Address (16N octets, where N is the
number of IPv6 addresses)
The Neighbor ID sub-TLV is mandatory for OSPFv3 Traffic Engineering
support. It MUST appear exactly once in a Link TLV. All other sub-
TLVs defined in this document SHOULD NOT occur more than once in a
Link TLV. If a sub-TLV is specified more than once, instances
subsequent to the first are ignored.
4.1. Link ID Sub-TLV
The Link ID sub-TLV is used in OSPFv2 to identify the other end of
the link. In OSPFv3, the Neighbor ID sub-TLV MUST be used for link
identification. In OSPFv3, the Link ID sub-TLV SHOULD NOT be sent
and MUST be ignored upon receipt.
4.2. Neighbor ID Sub-TLV
In OSPFv2, the Link ID is used to identify the other end of a link.
In OSPFv3, the combination of Neighbor Interface ID and Neighbor
Router ID is used for neighbor link identification. Both are
advertised in the Neighbor ID sub-TLV.
Neighbor Interface ID and Neighbor Router ID values are the same as
described in RFC 5340 [OSPFV3], A.4.3 Router-LSAs.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 18 | 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type A 16-bit field set to 18.
Length A 16-bit field that indicates the length of the value
portion in octets. For this sub-TLV, it is always 8.
Value The neighbor's Interface ID and Router ID.
Neighbor ID Sub-TLV
4.3. Local Interface IPv6 Address Sub-TLV
The Local Interface IPv6 Address sub-TLV specifies the IPv6
address(es) of the interface corresponding to this link. If there
are multiple local addresses assigned to the link, then they MAY all
be listed in this sub-TLV. Link-local addresses MUST NOT be included
in this sub-TLV.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 19 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+- -+-+-+-+
| |
+-+-+-+- Local Interface IPv6 Address -+-+-+-+
| |
+-+-+-+- -+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| o |
| o |
| o |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+- -+-+-+-+
| |
+-+-+-+- Local Interface IPv6 Address -+-+-+-+
| |
+-+-+-+- -+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type A 16-bit field set to 19.
Length A 16-bit field that indicates the length of the value
portion in octets. For this sub-TLV, it MUST always be a
multiple of 16 octets dependent on the number of IPv6
global addresses advertised.
Value A list of one or more local IPv6 interface addresses each
consuming 16 octets.
Local Interface IPv6 Address Sub-TLV
4.4. Remote Interface IPv6 Address Sub-TLV
The Remote Interface IPv6 Address sub-TLV advertises the IPv6
address(es) associated with the neighbor's interface. This sub-TLV
and the Local Interface IPv6 Address sub-TLV are used to discern
amongst parallel links between OSPFv3 routers. If the link type is
multi-access, the Remote Interface IPv6 Address MAY be set to ::.
Alternately, an implementation MAY choose not to send this sub-TLV.
Link-local addresses MUST NOT be advertised in this sub-TLV.
Neighbor addresses advertised in link-LSAs with a prefix length of
128 and the LA-bit set MAY be advertised.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 20 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+- -+-+-+-+
| |
+-+-+-+- Remote Interface IPv6 Address -+-+-+-+
| |
+-+-+-+- -+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| o |
| o |
| o |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+- -+-+-+-+
| |
+-+-+-+- Remote Interface IPv6 Address -+-+-+-+
| |
+-+-+-+- -+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type A 16-bit field set to 20.
Length A 16-bit field that indicates the length of the value
portion in octets. For this sub-TLV, it MUST be a
multiple of 16 octets dependent on the number of IPv6
global addresses advertised.
Value A variable-length Remote Interface IPv6 Address list.
Remote Interface IPv6 Address Sub-TLV
5. Security Considerations
The function described in this document does not create any new
security issues for the OSPFv3 protocol. Security considerations for
the base OSPFv3 protocol [OSPFV3] and OSPFv2 Traffic Engineering [TE]
are applicable to OSPFv3 Traffic Engineering.
6. Management Considerations
The typical management interface for routers running the new
extensions to OSPF for intra-area Traffic Engineering is Simple
Network Management Protocol (SNMP) based. The extra management
objects for configuration operations and statistics are defined in
[OSPFV3-MIB], and an implementation of the extensions defined in this
document SHOULD provide for the appropriate hooks or instrumentation
that allow for the MIB objects to be implemented.
The following MIB variables have been added to the OSPFv3 MIB in
support of TE:
ospfv3AreaTEEnabled
This TruthValue MIB variable in the ospfv3AreaEntry table entry
indicates whether or not OSPFv3 TE advertisement for OSPFv3
interfaces is enabled for the corresponding area. The default
value is FALSE.
ospfv3IfTEDisabled
This TruthValue MIB variable in the ospfv3IfEntry table entry
indicates whether or not OSPFv3 TE advertisement for OSPFv3 for
the corresponding interface is disabled. This MIB variable is
only applicable if ospfv3AreaTEEnabled is TRUE for the interface's
area. The default value is FALSE.
7. IANA Considerations
The following IANA assignments have been made from existing
registries:
1. The OSPFv3 LSA type function code 10 has been assigned to the
OSPFv3 Intra-Area-TE-LSA.
2. The Router IPv6 Address TLV type 3 has been assigned from the
existing registry for OSPF TE TLVs.
3. The Neighbor ID (18), Local Interface IPv6 Address (19), and
Remote Interface IPv6 Address (20) sub-TLVs have been assigned
from the existing registry for OSPF TE sub-TLVs.
8. References
8.1. Normative References
[OSPFV2] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April
1998.
[OSPFV3] Coltun, R., Ferguson, D., Moy, J., and A. Lindem,
"OSPF for IPv6", RFC 5340, July 2008.
[RFC-KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[TE] Katz, D., Kompella, K., and D. Yeung, "Traffic
Engineering (TE) Extensions to OSPF Version 2", RFC
3630, September 2003.
8.2. Informative References
[GMPLS] Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF
Extensions in Support of Generalized Multi-Protocol
Label Switching (GMPLS)", RFC 4203, October 2005.
[OPAQUE] Berger, L., Bryskin, I., Zinin, A., and R. Coltun,
"The OSPF Opaque LSA Option", RFC 5250, July 2008.
[OSPFV3-MIB] Joyal, D. and V. Manral, "Management Information Base
for OSPFv3", Work in Progress, September 2007.
[TE-DIFF] Le Faucheur, F., Wu, L., Davie, B., Davari, S.,
Vaananen, P., Krishnan, R., Cheval, P., and J.
Heinanen, "Multi-Protocol Label Switching (MPLS)
Support of Differentiated Services", RFC 3270, May
2002.
Acknowledgments
Thanks to Kireeti Kompella, Alex Zinin, Adrian Farrell, and Mach Chen
for their comments.
Thanks to Vijay K. Gurbani for providing the General Area Review Team
(Gen-ART) review.
Thanks to Rob Austein for providing the Security Directorate (secdir)
review.
Thanks to Dan Romascanu for providing the text for the "Management
Considerations" section in the context of the IESG review.
Thanks to Dave Ward, Tim Polk, Jari Arkko, and Pasi Eronen for
comments and relevant discussion in the context of the IESG review.
The RFC text was produced using Marshall Rose's xml2rfc tool.
Authors' Addresses
Kunihiro Ishiguro
IP Infusion, Inc.
1188 East Arques Avenue,
Sunnyvale, CA 94085
USA
EMail: kunihiro@ipinfusion.com
Vishwas Manral
IP Infusion, Inc
#41, Ground Floor, 5th Cross Road
8th Main Road
Vasanth Nagar, Bangalore 560052
India
EMail: vishwas@ipinfusion.com
Alan Davey
Data Connection Limited
100 Church Street
Enfield
EN2 6BQ
UK
EMail: Alan.Davey@dataconnection.com
Acee Lindem
Redback Networks
102 Carric Bend Court
Cary, NC 27519
USA
EMail: acee@redback.com
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On this page
§1What the Document Extends
OSPFv3 has a very flexible mechanism for adding new link state types. Unknown types are flooded properly, based on the flooding scope bits in the link state type, so a router that does not understand a new type still passes it on. This document defines the Intra-Area-TE-LSA for OSPFv3.
For traffic engineering, the document uses the traffic engineering extensions to OSPF, RFC 3630, as the base for its TLV definitions. New TLVs and sub-TLVs are added to extend the traffic engineering capabilities to IPv6 networks, and some existing TLVs and sub-TLVs need clarification for OSPFv3 applicability. The GMPLS extensions to OSPF and the Diff-Serv MPLS extensions are themselves based on the same document, so those functions can be extended to OSPFv3 by using the TLVs and sub-TLVs described here.
The routing protocol for IPv6 already has a way to carry new kinds of information, and it already has a way to carry traffic engineering information for IPv4. This RFC joins the two: a new advertisement type for OSPFv3 that carries the IPv4-style traffic engineering information plus a few IPv6-specific additions.
§2The New Advertisement and Its TLVs
A new link state type is defined for the Intra-Area-TE-LSA. This is different from OSPFv2 traffic engineering, where opaque link state advertisements are used to advertise traffic engineering information. The link state function code is 10, the U-bit is set, and the scope is set to 01 for area scoping. When the U-bit is set to 1, an OSPFv3 router must flood the advertisement at its defined flooding scope even if it does not recognize the type.
The Link State ID of an Intra-Area-TE-LSA is an arbitrary value used to maintain several traffic engineering advertisements. It has no topological significance.
The format of the TLVs inside the advertisement is the same as in the traffic engineering extensions to OSPF. The payload consists of one or more nested Type, Length and Value triplets, where the Type field is 16 bits, the Length field is 16 bits, and the Value holds the content. The Length field gives the length of the value portion in octets, so a TLV with no value has a length of zero. The TLV is padded to 4-octet alignment, and the padding is not counted in the Length field: a 3-octet value has a length of 3 but the whole TLV is 8 octets. Nested TLVs are aligned the same way, so a 1-byte value has a length of 1 and 3 octets of padding are added to the end of the value. Unrecognised types are ignored.
The new advertisement is a container of typed fields, each with a type number, a length and a value. The length counts only the value, and the fields are padded so that each one starts on a four-octet boundary, which is how the nested fields line up inside it.
§2.1What the Advertisement Carries
An Intra-Area-TE-LSA contains one top-level TLV, and there are two applicable top-level types: type 2, the Link TLV, and type 3, the Router IPv6 Address TLV.
The Router IPv6 Address TLV advertises a reachable IPv6 address. It is a stable address that should be reachable if there is connectivity to the OSPFv3 router. The TLV has type 3 and length 16, and its value holds a 16-octet local IPv6 address. A link-local address must not be specified in it. It must appear in exactly one traffic engineering LSA originated by an OSPFv3 router that supports the traffic engineering extensions. It is a top-level TLV as defined in the traffic engineering extensions to OSPF, and only one top-level TLV may be contained in an advertisement.
Each advertisement carries one thing: either a description of a link, or the router's own IPv6 address so that the link can be traced back to it. That address must be one that can be reached from elsewhere, not a link-local one.
| Field | Name | Size | Value | Description |
|---|---|---|---|---|
TYPE | Type | 2 bytes | Set to 3 for the Router IPv6 Address TLV. | |
LENGTH | Length | 2 bytes | The length of the value in octets, always 16. | |
ADDRESS | Router IPv6 Address | 16 bytes | A stable, routable local IPv6 address. Link-local addresses are not allowed. |
§4The Link TLV and Three New Sub-TLVs
The Link TLV describes a single link and consists of a set of sub-TLVs. All of the sub-TLVs of the OSPFv2 traffic engineering extensions other than the Link ID sub-TLV apply to OSPFv3. The Link ID sub-TLV cannot be used in OSPFv3, because it is defined to use the OSPFv2 identification for the designated router on multi-access networks. In OSPFv2, neighbours on point-to-point networks and virtual links are identified by their Router IDs, while neighbours on broadcast, non-broadcast multi-access and point-to-multipoint links are identified by their IPv4 interface addresses. OSPFv3 does not know those IPv4 addresses. In contrast to OSPFv2, OSPFv3 always identifies neighbouring routers by their Router IDs.
Three new sub-TLVs are defined for the Link TLV. Type 18 is the Neighbor ID, 8 octets long. Type 19 is the Local Interface IPv6 Address, 16N octets where N is the number of IPv6 addresses. Type 20 is the Remote Interface IPv6 Address, also 16N octets.
One top-level field describes a link and holds a set of smaller fields. Most of the smaller fields from the IPv4 version still apply. The IPv4 way of naming the far end of a link cannot be used here, so three new smaller fields replace it, carrying the neighbour's identifiers and the two addresses of the two ends.
| Code | Name | Length | What it holds |
|---|---|---|---|
| 2 | Link TLV | Variable | One link and its sub-TLVs |
| 3 | Router IPv6 Address TLV | 16 | A local IPv6 address of the router |
| 18 | Neighbor ID sub-TLV | 8 | The neighbour's interface ID and router ID |
| 19 | Local Interface IPv6 Address sub-TLV | Multiple of 16 | The addresses of the local interface |
| 20 | Remote Interface IPv6 Address sub-TLV | Multiple of 16 | The addresses of the neighbour's interface |
§4.2The Sub-TLVs in Detail
The Neighbor ID sub-TLV is mandatory for OSPFv3 traffic engineering support and must appear exactly once in a Link TLV. All the other sub-TLVs defined in the document should not occur more than once in a Link TLV, and if one is specified more than once the instances after the first are ignored.
In OSPFv2 the Link ID identifies the other end of a link. In OSPFv3 the combination of the neighbour's interface ID and the neighbour's router ID is used for neighbour link identification, and both are advertised in the Neighbor ID sub-TLV. The values are the same as those described in RFC 5340 for Router-LSAs. The sub-TLV has type 18 and length 8, and its value holds the neighbour's interface ID and router ID.
The Link ID sub-TLV, which is used in OSPFv2 to identify the other end of a link, should not be sent in OSPFv3 and must be ignored when received.
The Local Interface IPv6 Address sub-TLV specifies the IPv6 addresses of the interface that corresponds to this link. If several local addresses are assigned to the link, they may all be listed. Link-local addresses must not be included. The sub-TLV has type 19, and its length must always be a multiple of 16 octets, depending on the number of IPv6 global addresses advertised, with each address taking 16 octets.
The Remote Interface IPv6 Address sub-TLV advertises the IPv6 addresses associated with the neighbour's interface. It and the local address sub-TLV are used to tell parallel links between OSPFv3 routers apart. If the link type is multi-access, the remote address may be set to ::. An implementation may also choose not to send the sub-TLV at all. Link-local addresses must not be advertised in it, though neighbour addresses advertised in link-LSAs with a prefix length of 128 and the LA-bit set may be.
The neighbour identifier is the one smaller field that must always be there, and it says both the neighbour's router identifier and its interface identifier. The two address fields list the addresses on each side of the link, and they are what tells two parallel links apart. Link-local addresses are not allowed in any of them.
- Neighbor ID sub-TLVMandatory, and it must appear exactly once in a Link TLV.
- Link ID sub-TLVNot sent in OSPFv3, and ignored when received. The Neighbor ID replaces it.
- Link-local addressesMust not appear in the router address field or in either interface address field.
- Repeated sub-TLVsNot expected; any instance after the first is ignored.
- Remote address on a multi-access linkMay be set to ::, or the field may be left out entirely.
§5Security Considerations
The function described in this document does not create any new security issues for the OSPFv3 protocol. The security considerations for the base OSPFv3 protocol and for OSPFv2 traffic engineering apply to OSPFv3 traffic engineering.
Nothing here changes the security picture of the routing protocol itself; the same rules that already apply to OSPFv3 and to its IPv4 traffic engineering counterpart apply here.
§6Management Considerations
The typical management interface for routers running the new intra-area traffic engineering extensions to OSPF is SNMP based. The extra management objects for configuration operations and statistics are defined in the OSPFv3 MIB, and an implementation of the extensions in this document should provide the hooks or instrumentation that allow those MIB objects to be implemented.
Two variables have been added to the OSPFv3 MIB in support of traffic engineering. The variable ospfv3AreaTEEnabled, a TruthValue in the ospfv3AreaEntry table, says whether traffic engineering advertisement for OSPFv3 interfaces is enabled for the corresponding area, and its default value is FALSE. The variable ospfv3IfTEDisabled, a TruthValue in the ospfv3IfEntry table, says whether traffic engineering advertisement is disabled for the corresponding interface. It applies only where the area's own variable is TRUE, and its default value is FALSE as well.
Routers are managed over SNMP, and two new switches are added so an operator can turn the new advertisements on for an area and off for a single interface. Both are off by default.
§7IANA Assignments
Three assignments were made from existing registries. The OSPFv3 link state type function code 10 has been assigned to the OSPFv3 Intra-Area-TE-LSA. The Router IPv6 Address TLV type 3 has been assigned from the existing registry for OSPF traffic engineering TLVs. The Neighbor ID sub-TLV 18, the Local Interface IPv6 Address sub-TLV 19 and the Remote Interface IPv6 Address sub-TLV 20 have been assigned from the existing registry for OSPF traffic engineering sub-TLVs.
The document asks IANA for three numbers: the code that names the new advertisement, the code for the router address field, and the codes for the three new smaller fields.