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IETF RFC 5786
Advertising a Router's Local Addresses in OSPF Traffic Engineering (TE) Extensions
Last modified on Thursday, March 4th, 2010
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Internet Engineering Task Force (IETF) R. Aggarwal
Request for Comments: 5786 K. Kompella
Updates: 3630 Juniper Networks
Category: Standards Track March 2010
ISSN: 2070-1721
Advertising a Router's Local Addresses
in OSPF Traffic Engineering (TE) Extensions
 Abstract
OSPF Traffic Engineering (TE) extensions are used to advertise TE
Link State Advertisements (LSAs) containing information about TE-
enabled links. The only addresses belonging to a router that are
advertised in TE LSAs are the local addresses corresponding to TE-
enabled links, and the local address corresponding to the Router ID.
In order to allow other routers in a network to compute Multiprotocol
Label Switching (MPLS) Traffic Engineered Label Switched Paths (TE
LSPs) to a given router's local addresses, those addresses must also
be advertised by OSPF TE.
This document describes procedures that enhance OSPF TE to advertise
a router's local addresses.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/RFC 5786.
Aggarwal & Kompella Standards Track PAGE 1 
RFC 5786 Advertising a Local Router's Addresses March 2010
Copyright Notice
Copyright (c) 2010 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
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Table of Contents
1. Introduction ....................................................3
1.1. Motivation .................................................3
2. Specification of Requirements ...................................3
3. Rejected Potential Solution .....................................4
4. Solution ........................................................4
4.1. Node Attribute TLV .........................................4
4.2. Operation ..................................................5
5. Security Considerations .........................................6
6. IANA Considerations .............................................6
7. Acknowledgements ................................................6
8. References ......................................................7
8.1. Normative References .......................................7
8.2. Informative References .....................................7
Aggarwal & Kompella Standards Track PAGE 2
RFC 5786 Advertising a Local Router's Addresses March 2010
1. Introduction
1.1. Motivation
In some cases, it is desirable to set up constrained shortest path
first (CSPF) computed Multiprotocol Label Switching (MPLS) Traffic
Engineered Label Switched Paths (TE LSPs) to local addresses of a
router that are not currently advertised in the TE LSAs, i.e.,
loopback and non-TE interface addresses.
For instance, in a network carrying VPN and non-VPN traffic, it is
often desirable to use different MPLS TE LSPs for the VPN traffic and
the non-VPN traffic. In this case, one loopback address may be used
as the BGP next-hop for VPN traffic while another may be used as the
BGP next-hop for non-VPN traffic. It is also possible that different
BGP sessions are used for VPN and non-VPN services. Hence, two
separate MPLS TE LSPs are desirable -- one to each loopback address.
However, current routers in an OSPF network can only use CSPF to
compute MPLS TE LSPs to the router ID or the local addresses of a
remote router's TE-enabled links. This restriction arises because
OSPF TE extensions [RFC 3630, RFC 5329] only advertise the router ID
and the local addresses of TE-enabled links of a given router. Other
routers in the network can populate their traffic engineering
database (TED) with these local addresses belonging to the
advertising router. However, they cannot populate the TED with the
advertising router's other local addresses, i.e., loopback and non-TE
interface addresses. OSPFv2 stub links in the router LSA [RFC 2328]
provide stub reachability information to the router but are not
sufficient to learn all the local addresses of a router. In
particular for a subnetted point-to-point (P2P) interface the stub,
link ID is the subnet address. While for a non-subnetted interface,
the stub link ID is the neighbor address. Intra-prefix LSAs in
OSPFv3 [RFC 5340] are also not sufficient to learn the local
addresses.
For the above reasons, this document defines an enhancement to OSPF
TE extensions to advertise the local addresses of a node.
2. Specification of Requirements
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].
Aggarwal & Kompella Standards Track PAGE 3
RFC 5786 Advertising a Local Router's Addresses March 2010
3. Rejected Potential Solution
A potential solution would be to advertise a TE link TLV for each
local address, possibly with a new link type. However, this is
inefficient since the only meaningful information is the address.
Furthermore, this would require implementations to process these TE
link TLVs differently from others; for example, the TE metric is
normally considered a mandatory sub-TLV, but would have no meaning
for a local address.
4. Solution
The solution is to advertise the local addresses of a router in a new
OSPF TE LSA Node Attribute TLV. It is anticipated that the Node
Attribute TLV will also prove more generally useful.
4.1. Node Attribute TLV
The Node Attribute TLV carries the attributes associated with a
router. The TLV type is 5 and the length is variable. It contains
one or more sub-TLVs. This document defines the following sub-TLVs:
1. Node IPv4 Local Address sub-TLV
2. Node IPv6 Local Address sub-TLV
The Node IPv4 Local Address sub-TLV has a type of 1 and contains one
or more local IPv4 addresses. It has the following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Len 1 | IPv4 Prefix 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Prefix 1 cont. | :
+-+-+-+-+-+-+-+-+ ~
: . :
~ . +-+-+-+-+-+-+-+-+
: . | Prefix Len n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Prefix n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Each local IPv4 address is encoded as a <Prefix Length, Prefix>
tuple. Prefix Length is encoded in 1 byte. It is the number of bits
in the Address and can be at most 32. Prefix is an IPv4 address
prefix and is encoded in 4 bytes with zero bits as necessary.
Aggarwal & Kompella Standards Track PAGE 4
RFC 5786 Advertising a Local Router's Addresses March 2010
The Node IPv4 Local Address sub-TLV length is in octets. It is the
sum of the lengths of all n IPv4 Address encodings in the sub-TLV,
where n is the number of local addresses included in the sub-TLV.
The Node IPv6 Local Address sub-TLV has a type of 2 and contains one
or more local IPv6 addresses. It has the following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 2 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Len 1 | Prefix 1 Opt. | IPv6 Prefix 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Prefix 1 cont. :
: . ~
~ .
: .
: +-+-+-+-+-++-+-+-+-+-++-+-+-+-+-+
: | Prefix Len n | Prefix n Opt. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Prefix n :
| :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--
Each local IPv6 address is encoded using the procedures in [RFC 5340].
Each IPv6 address MUST be represented by a combination of three
fields: PrefixLength, PrefixOptions, and Address Prefix.
PrefixLength is the length in bits of the prefix and is an 8-bit
field. PrefixOptions is an 8-bit field describing various
capabilities associated with the prefix [RFC 5340]. Address Prefix is
an encoding of the prefix itself as an even multiple of 32-bit words,
padding with zero bits as necessary. This encoding consumes
(PrefixLength + 31) / 32) 32-bit words.
The Node IPv6 Local Address sub-TLV length is in octets. It is the
sum of the lengths of all n IPv6 Address encodings in the sub-TLV,
where n is the number of local addresses included in the sub-TLV.
4.2. Operation
A router announces one or more local addresses in the Node Attribute
TLV. The local addresses that can be learned from TE LSAs, i.e.,
router address and TE interface addresses SHOULD NOT be advertised in
the node local address sub-TLV. The local addresses advertised will
depend on the local configuration of the advertising router. The
default behavior MAY be to advertise all the loopback interface
addresses.
Aggarwal & Kompella Standards Track PAGE 5
RFC 5786 Advertising a Local Router's Addresses March 2010
The Node Attribute TLV MUST NOT appear in more than one TE LSA
originated by a router. Furthermore, such an LSA MUST NOT include
more than one Node Attribute TLV. A Node Attribute TLV MUST NOT
carry more than one Node IPv4 Local Address sub-TLV. A Node
Attribute TLV MUST NOT carry more than one Node IPv6 Local Address
sub-TLV.
5. Security Considerations
This document does not introduce any further security issues other
than those discussed in [RFC 3630] and [RFC 5329].
6. IANA Considerations
IANA has assigned the Node Attribute TLV (value 5) type from the
range 3-32767 as specified in [RFC 3630], from the top level types in
TE LSAs registry maintained by IANA at http://www.iana.org.
IANA has created and now maintains the registry for the sub-TLVs of
the Node Attribute TLV. Value 1 is reserved for Node IPv4 Local
Address sub-TLV and value 2 for Node IPv6 Local Address sub-TLV.
The guidelines for the assignment of types for sub-TLVs of the Node
Attribute TLV are as follows:
o Types in the range 3-32767 are to be assigned via Standards
Action.
o Types in the range 32768-32777 are for experimental use; these
will not be registered with IANA, and MUST NOT be mentioned by
RFCs.
o Types in the range 32778-65535 are not to be assigned at this
time. Before any assignments can be made in this range, there
MUST be a Standards Track RFC that specifies IANA
Considerations that covers the range being assigned.
7. Acknowledgements
We would like to thank Nischal Sheth for his contribution to this
work. We would also like to thank Jean Philippe Vasseur, Acee
Lindem, Venkata Naidu, Dimitri Papadimitriou, and Adrian Farrel for
their comments.
Aggarwal & Kompella Standards Track PAGE 6
RFC 5786 Advertising a Local Router's Addresses March 2010
8. References
8.1. Normative References
[RFC 2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630, September
2003.
[RFC 5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, July 2008.
8.2. Informative References
[RFC 5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed.,
"Traffic Engineering Extensions to OSPF Version 3", RFC
5329, September 2008.
Authors' Addresses
Rahul Aggarwal
Juniper Networks
1194 North Mathilda Ave.
Sunnyvale, CA 94089
Phone: +1-408-936-2720
EMail: rahul@juniper.net
Kireeti Kompella
Juniper Networks
1194 North Mathilda Ave.
Sunnyvale, CA 94089
EMail: kireeti@juniper.net
Aggarwal & Kompella Standards Track PAGE 7
Advertising a Router's Local Addresses in OSPF Traffic Engineering (TE) Extensions
RFC TOTAL SIZE: 15541 bytes
PUBLICATION DATE: Thursday, March 4th, 2010
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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