Network Working Group Rahul Aggarwal
Internet Draft Kireeti Kompella
Expiration Date: October 2004 Juniper Networks
Advertising a Router's Local Addresses in OSPF TE Extensions
draft-ietf-ospf-te-node-addr-00.txt
1. Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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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and may be updated, replaced, or obsoleted by other documents at any
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The list of current Internet-Drafts can be accessed at
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The list of Internet-Draft Shadow Directories can be accessed at
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2. Abstract
This document describes procedures that enhance OSPF Traffic
Engineering (TE) extensions for advertising a router's local
addresses. This is needed to enable other routers in a network to
compute traffic engineered MPLS LSPs to a given router's local
addresses. Currently, 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.
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3. Motivation
In some cases it is desirable to setup constrained shortest path
first (CSPF) computed MPLS 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 currently routers in an OSPF network can only use CSPF to
compute MPLS TE LSPs to the router ID or the local addresses of TE
enabled links of a remote router. This restriction arises because
OSPF TE extensions [OSPF-TE, OSPFv3-TE] 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 other
local addresses of the advertising router i.e. loopback and non-TE
interface addresses. OSPFv2 stub links in the router LSA [OSPFv2],
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
[OSPFv3] 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.
4. A 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.
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5. Proposed Solution
The proposed solution is to advertise the local addresses of a router
in a new OSPF TE LSA node attribute TLV. node attribute TLV. It is
anticipated that a node attribute TLV will also prove more generally
useful.
5.1. 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. . .
. . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The length is set to 4 * n 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Address 1 |
| |
| |
| |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. . .
. . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Address n |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--
The length is set to 16 * n where n is the number of local addresses
included in the sub-TLV.
5.2. 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.
6. Security Considerations
This document does not introduce any further security issues other
than those discussed in [OSPF-TE, OSPFv3-TE].
7. IANA Considerations
The Node Attribute TLV type has to be IANA assigned from the range 3
- 32767 as specified in [OSPF-TE].
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8. Acknowledgments
We would like to thank Nischal Sheth for his contribution to this
work. We woud also like to thank Jean Philippe Vasseur, Acee Lindem,
Venkata Naidu and Dimitri Papadimitriou for their comments.
9. References
[OSPF] Moy, J., "OSPF Version 2", RFC 2328, April 1998.
[RFC] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[OSPF-TE] D. Katz, K. Kompella, D. Yeung, "Traffic Engineering
Extensions to OSPF version 2", RFC 3630,
September 2003.
[OSPFv3] R. Coltun, D. Ferguson, J. Moy, "OSPF for IPv6",
RFC 2740.
[OSPFv3-TE] K. Ishiguro, T. Takada, "Traffic Engineering
Extensions to OSPF version 3",
draft-ietf-ospf-ospfv3-traffic-01.txt.
[OSPF-TE-MESH] J. P. Vasseur, P. Psenak, "OSPF Traffic Engineering
Capability TLVs",
draft-vasseur-mpls-ospf-te-cap-00.txt.
10. Author Information
Rahul Aggarwal
Juniper Networks
1194 North Mathilda Ave.
Sunnyvale, CA 94089
Email: rahul@juniper.net
Kireeti Kompella
Juniper Networks
1194 North Mathilda Ave.
Sunnyvale, CA 94089
Email: kireeti@juniper.net
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