Network Working Group                                  Rahul Aggarwal
Internet Draft                                         Kireeti Kompella
Expiration Date: October 2004 January 2005                          Juniper Networks

      Advertising a Router's Local Addresses in OSPF TE Extensions




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   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.


1. 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.


2. 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.


3. 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


3.1. 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                        |
      |                                                               |
      |                                                               |
      |                                                               |
      .                               .                               .
      .                               .                               .
      |                         IPv6 Address n                        |
      |                                                               |
      |                                                               |
      |                                                               |

   The length is set to 16 * n where n is the number of local addresses
   included in the sub-TLV.


3.2. 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


4. Security Considerations

   This document does not introduce any further security issues other
   than those discussed in [OSPF-TE, OSPFv3-TE].


5. IANA Considerations

   The Node Attribute TLV type has to be IANA assigned from the range 3
   - 32767 as specified in [OSPF-TE].


6. 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.


7. References

7.1. Normative 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.

7.2. Informative References

   [OSPFv3-TE]    K. Ishiguro, T. Takada, "Traffic Engineering
                  Extensions to OSPF version 3",

   [OSPF-TE-MESH] J. P. Vasseur, P. Psenak, "OSPF Traffic Engineering
                  Capability TLVs",


8. Author Information

   Rahul Aggarwal
   Juniper Networks
   1194 North Mathilda Ave.
   Sunnyvale, CA 94089

   Kireeti Kompella
   Juniper Networks
   1194 North Mathilda Ave.
   Sunnyvale, CA 94089

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