Network Working Group R. Aggarwal
Internet Draft Juniper Networks
Expiration Date: November 2009
K. Kompella
Juniper Networks
May 04, 2009
Advertising a Router's Local Addresses in OSPF TE Extensions
draft-ietf-ospf-te-node-addr-06.txt
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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.
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Table of Contents
1 Specification of requirements ......................... 3
2 Introduction .......................................... 3
2.1 Motivation ............................................ 3
3 Rejected Potential Solution ........................... 4
4 Solution .............................................. 4
4.1 Node Attribute TLV .................................... 5
4.2 Operation ............................................. 6
5 Security Considerations ............................... 7
6 IANA Considerations ................................... 7
7 Acknowledgements ...................................... 7
8 References ............................................ 8
8.1 Normative References .................................. 8
8.2 Informative References ................................ 8
9 Authors' Addresses .................................... 8
1. 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 [RFC2119].
2. Introduction
2.1. 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
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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 [RFC3630, RFC5329] 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 [RFC2328],
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 [RFC5340] are also not sufficient to learn the local
addresses.
For the above reasons this document proposes an enhancement to OSPF
TE extensions to advertise the local addresses of a node.
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.
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4.1. Node Attribute TLV
The node attribute TLV carries the attributes associated with a
router. The TLV type is TBD 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.
The Node IPv4 Local Address sub-TLV length is in octets. It is the
sum 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. :
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: . ~
~ .
: .
: +-+-+-+-+-++-+-+-+-+-++-+-+-+-+-+
: | Prefix Len n | Prefix n Opt. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Prefix n :
| :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--
Each local IPv6 address is encoded using the procedures in [RFC5340].
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 [RFC5340]. 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 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.
The node attribute TLV must appear in exactly one TE LSA originated
by a router. Furthermore, only one node attribute TLV must be
advertised in such a LSA. A node attribute TLV must carry at most one
Node IPv4 Local Address sub-TLV and at most one Node IPv6 Local
Address sub-TLV.
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5. Security Considerations
This document does not introduce any further security issues other
than those discussed in [RFC3630, RFC5329].
6. IANA Considerations
The Node Attribute TLV type has to be IANA assigned from the range 3
- 32767 as specified in [RFC3630], from the top level types in TE
LSAs registry maintained by IANA at [IANA-OSPF-TE].
IANA is requested to maintain the registry for the sub-TLVs of the
node attribute TLV and reserve value 1 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.
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8. References
8.1. Normative References
[RFC2328] Moy, J., "OSPF Version 2", RFC 2328, April 1998.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3630] D. Katz, K. Kompella, D. Yeung, "Traffic Engineering
Extensions to OSPF version 2", RFC 3630,
September 2003.
[RFC5340] R. Coltun, et. al.,"OSPF for IPv6", RFC 5340.
8.2. Informative References
[RFC5329] K. Ishiguro, T. Takada, "Traffic Engineering
Extensions to OSPF version 3", RFC 5329
[IANA-OSPF-TE] http://www.iana.org/assignments/ospf-traffic-eng-tlvs
9. 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
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