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Versions: 00 01 02 03 04 05 06 07 08 09 RFC 3630

Network Working Group                                          Dave Katz
Internet Draft                                    Juniper Networks, Inc.
Expiration Date: April 2002                                  Derek Yeung
                                                  Procket Networks, Inc.
                                                        Kireeti Kompella
                                                  Juniper Networks, Inc.



                 Traffic Engineering Extensions to OSPF

                  draft-katz-yeung-ospf-traffic-06.txt

Status

   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
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   The list of Internet-Draft Shadow Directories can be accessed at
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Abstract

   This document describes extensions to the OSPF protocol to support
   Traffic Engineering, using opaque LSAs.













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1. Introduction

   This document specifies a method of adding traffic engineering
   capabilities to OSPF [1].  The architecture of traffic engineering is
   described in [2].  The semantic content of the extensions is
   essentially identical to the corresponding extensions to IS-IS [3].
   It is expected that the traffic engineering extensions to OSPF will
   continue to mirror those in IS-IS.

   The extensions provide a way of describing the traffic engineering
   topology (including bandwidth and administrative constraints).  This
   topology does not necessarily match the regular routed topology,
   though this proposal depends on Network LSAs to describe multiaccess
   links.


1.1. Applicability

   Many of the extensions specified in this document are in response to
   the requirements stated in [2], and thus are referred to as "traffic
   engineering extensions", and are also commonly associated with MPLS
   Traffic Engineering.  A more accurate (albeit bland) designation is
   "extended link attributes", as what is proposed is simply to add more
   attributes to links in OSPF advertisements.

   The information made available by these extensions can be used to
   build an extended link state database just as router LSAs are used to
   build a "regular" link state database; the difference is that the
   extended link state database (referred to below as the traffic
   engineering database) has additional link attributes.  Uses of the
   traffic engineering database include:

      o monitoring the extended link attributes;
      o local constraint-based source routing; and
      o global traffic engineering.

   For example, an OSPF-speaking device can participate in an OSPF area,
   build a traffic engineering database, and thereby report on the
   reservation state of links in that area.

   In "local constraint-based source routing", a router R can compute a
   path from a source node A to a destination node B; typically, A is R
   itself, and B is specified by a "router address" (see below).  This
   path may be subject to various constraints on the attributes of the
   links and nodes that the path traverses, e.g., use green links that
   have unreserved bandwidth of at least 10Mbps.  This path could then
   be used to carry some subset of the traffic from A to B, forming a
   simple but effective means of traffic engineering.  How the subset of



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   traffic is determined, and how the path is instantiated is beyond the
   scope of this document; suffice it to say that one means of defining
   the subset of traffic is "those packets whose IP destinations were
   learned from B", and one means of instantiating paths is using MPLS
   tunnels.  As an aside, note that constraint-based routing can be NP-
   hard, or even unsolvable, depending on the nature of the attributes
   and constraints and thus many implementations will use heuristics.
   Consequently, we don't attempt to sketch an algorithm here.

   Finally, for "global traffic engineering", a device can build a
   traffic engineering database, input a traffic matrix and an
   optimization function, crunch on the information, and thus compute
   optimal or near-optimal routing for the entire network.  The device
   can subsequently monitor the traffic engineering topology and react
   to changes by recomputing the optimal routes.


1.2. Limitations

   The extensions specified in this document capture the reservation
   state of point-to-point links.  The reservation state of multiaccess
   links is not accurately reflected, except in the special case that
   there are only two devices in the multiaccess subnetwork.

   This document also does not support unnumbered links.  This
   deficiency is addressed in [4]; see also [5] and [6].


2. LSA Format


2.1. LSA type

   This extension makes use of the Opaque LSA [7].

   Three types of Opaque LSAs exist, each of which has different
   flooding scope.  This proposal uses only Type 10 LSAs, which have
   area flooding scope.

   One new LSA is defined, the Traffic Engineering LSA.  This LSA
   describes routers, point-to-point links, and connections to
   multiaccess networks (similar to a Router LSA).  For traffic
   engineering purposes, the existing Network LSA suffices for
   describing multiaccess links, so no additional LSA is defined for
   this purpose.






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2.2. LSA ID

   The LSA ID of an Opaque LSA is defined as having eight bits of type
   and 24 bits of type-specific data.  The Traffic Engineering LSA uses
   type 1.  The remaining 24 bits are broken up into eight bits of
   reserved space (which must be zero) and sixteen bits of instance:

      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       |    Reserved   |           Instance            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Instance field is an arbitrary value used to maintain multiple
   Traffic Engineering LSAs.  A maximum of 65536 Traffic Engineering
   LSAs may be sourced by a single system.  The LSA ID has no
   topological significance.


2.3. LSA Format Overview


2.3.1. LSA Header

   The Traffic Engineering LSA starts with the standard LSA header:

      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             |    Options    |      10       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       1       |    Reserved   |           Instance            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                     Advertising Router                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                     LS sequence number                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         LS checksum           |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


2.3.2. TLV Header

   The LSA payload consists of one or more nested Type/Length/Value
   (TLV) triplets for extensibility.  The format of each TLV is:






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      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...                           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Length field defines the length of the value portion in octets
   (thus a TLV with no value portion would have a length of zero).  The
   TLV is padded to four-octet alignment;  padding is not included in
   the length field (so a three octet value would have a length of
   three, but the total size of the TLV would be eight octets).  Nested
   TLVs are also 32-bit aligned.  Unrecognized types are ignored.  All
   types between 32768 and 65535 are reserved for vendor-specific
   extensions.  All other undefined type codes are reserved for future
   assignment by IANA.


2.4. LSA payload details

   An LSA contains one top-level TLV.

   There are two top-level TLVs defined:

     1 - Router Address
     2 - Link


2.4.1. Router Address TLV

   The Router Address TLV specifies a stable IP address of the
   advertising router that is always reachable if there is any
   connectivity to it.  This is typically implemented as a "loopback
   address"; the key attribute is that the address does not become
   unusable if an interface is down.  In other protocols this is known
   as the "router ID," but for obvious reasons this nomenclature is
   avoided here.

   If IS-IS is also active in the domain, this address can also be used
   to compute the mapping between the OSPF and IS-IS topologies.  For
   example, suppose a router R is advertising both IS-IS and OSPF
   Traffic Engineering LSAs, and suppose further that some router S is
   building a single Traffic Engineering Database (TED) based on both
   IS-IS and OSPF TE information.  R may then appear as two separate
   nodes in S's TED; however, if both the IS-IS and OSPF LSAs generated
   by R contain the same Router Address, then S can determine that the
   IS-IS TE LSA and the OSPF TE LSA from R are indeed from a single



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   router.

   The router address TLV is type 1, and has a length of 4, and the
   value is the four octet IP address.  It must appear in exactly one
   Traffic Engineering LSA originated by a router.


2.4.2. Link TLV

   The Link TLV describes a single link.  It is constructed of a set of
   sub-TLVs.  There are no ordering requirements for the sub-TLVs.

   Only one Link TLV shall be carried in each LSA, allowing for fine
   granularity changes in topology.

   The Link TLV is type 2, and the length is variable.

   The following sub-TLVs are defined:

     1 - Link type (1 octet)
     2 - Link ID (4 octets)
     3 - Local interface IP address (4 octets)
     4 - Remote interface IP address (4 octets)
     5 - Traffic engineering metric (4 octets)
     6 - Maximum bandwidth (4 octets)
     7 - Maximum reservable bandwidth (4 octets)
     8 - Unreserved bandwidth (32 octets)
     9 - Resource class/color (4 octets)

     32768-32772 - Reserved for Cisco-specific extensions

   The Link Type and Link ID sub-TLVs are mandatory, i.e., must appear
   exactly once.  All other sub-TLVs defined here may occur at most
   once.  These restrictions need not apply to future sub-TLVs.
   Unrecognized sub-TLVs are ignored.


2.5. Sub-TLV Details


2.5.1. Link Type

   The Link Type sub-TLV defines the type of the link:

       1 - Point-to-point
       2 - Multiaccess

   The Link Type sub-TLV is TLV type 1, and is one octet in length.



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2.5.2. Link ID

   The Link ID sub-TLV identifies the other end of the link.  For point-
   to-point links, this is the Router ID of the neighbor.  For
   multiaccess links, this is the interface address of the designated
   router.  The Link ID is identical to the contents of the Link ID
   field in the Router LSA for these link types.

   The Link ID sub-TLV is TLV type 2, and is four octets in length.


2.5.3. Local Interface IP Address

   The Local Interface IP Address sub-TLV specifies the IP address(es)
   of the interface corresponding to this link.  If there are multiple
   local addresses on the link, they are all listed in this sub-TLV.

   The Local Interface IP Address sub-TLV is TLV type 3, and is 4N
   octets in length, where N is the number of local addresses.


2.5.4. Remote Interface IP Address

   The Remote Interface IP Address sub-TLV specifies the IP address(es)
   of the neighbor's interface corresponding to this link.  This and the
   local address are used to discern multiple parallel links between
   systems.

   The Remote Interface IP Address sub-TLV is TLV type 4, and is 4N
   octets in length, where N is the number of neighbor addresses.


2.5.5. Traffic Engineering Metric

   The Traffic Engineering Metric sub-TLV specifies the link metric for
   traffic engineering purposes.  This metric may be different than the
   standard OSPF link metric.

   The Traffic Engineering Metric sub-TLV is TLV type 5, and is four
   octets in length.


2.5.6. Maximum Bandwidth

   The Maximum Bandwidth sub-TLV specifies the maximum bandwidth that
   can be used on this link in this direction (from the system
   originating the LSA to its neighbor), in IEEE floating point format.
   This is the true link capacity.  The units are bytes per second.



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   The Maximum Bandwidth sub-TLV is TLV type 6, and is four octets in
   length.


2.5.7. Maximum Reservable Bandwidth

   The Maximum Reservable Bandwidth sub-TLV specifies the maximum
   bandwidth that may be reserved on this link in this direction, in
   IEEE floating point format.  Note that this may be greater than the
   maximum bandwidth (in which case the link may be oversubscribed).
   This SHOULD be user-configurable; the default value should be the
   Maximum Bandwidth.  The units are bytes per second.

   The Maximum Reservable Bandwidth sub-TLV is TLV type 7, and is four
   octets in length.


2.5.8. Unreserved Bandwidth

   The Unreserved Bandwidth sub-TLV specifies the amount of bandwidth
   not yet reserved at each of the eight priority levels, in IEEE
   floating point format.  The values correspond to the bandwidth that
   can be reserved with a setup priority of 0 through 7, arranged in
   increasing order with priority 0 occurring at the start of the sub-
   TLV, and priority 7 at the end of the sub-TLV.  The initial values
   (before any bandwidth is reserved) are all set to the Maximum
   Reservable Bandwidth.  Each value will be less than or equal to the
   Maximum Reservable Bandwidth.  The units are bytes per second.

   The Unreserved Bandwidth sub-TLV is TLV type 8, and is 32 octets in
   length.


2.5.9. Resource Class/Color

   The Resource Class/Color sub-TLV specifies administrative group
   membership for this link, in terms of a bit mask.  A link that is a
   member of multiple groups will have multiple bits set.

   The Resource Class/Color sub-TLV is TLV type 9, and is four octets in
   length.










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3. Elements of Procedure

   Routers shall originate Traffic Engineering LSAs whenever the LSA
   contents change, and whenever otherwise required by OSPF (an LSA
   refresh, for example).

   Upon receipt of a changed Traffic Engineering LSA or Network LSA
   (since these are used in traffic engineering calculations), the
   router should update its traffic engineering database.  No SPF or
   other route calculations are necessary.


4. Compatibility Issues

   There should be no interoperability issues with routers that do not
   implement these extensions, as the Opaque LSAs will be silently
   ignored.

   The result of having routers that do not implement these extensions
   is that the traffic engineering topology will be missing pieces;
   however, if the topology is connected, TE paths can still be
   calculated and ought to work.


5. Security Considerations

   This document raises no new security issues for OSPF.


6. References

   [1] Moy, J., "OSPF Version 2", RFC 2328, April 1998.

   [2] Awduche, D., et al, "Requirements for Traffic Engineering Over
       MPLS," RFC 2702, September 1999.

   [3] Smit, H. and T. Li, "ISIS Extensions for Traffic Engineering,"
       work in progress.

   [4] Kompella, K., Rekhter, Y., et al, "OSPF Extensions in Support of
       Generalized MPLS," work in progress.

   [5] Kompella, K., Rekhter, Y., and Kullberg, A., "Signalling
       Unnumbered Links in CR-LDP," work in progress.

   [6] Kompella, K., and Rekhter, Y., "Signalling Unnumbered Links in
       RSVP-TE," work in progress.




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   [7] Coltun, R., "The OSPF Opaque LSA Option," RFC 2370, July 1998.


7. Authors' Addresses

   Dave Katz
   Juniper Networks
   1194 N. Mathilda Ave.
   Sunnyvale, CA 94089 USA

   Phone:  +1 408 745 2000
   Email:  dkatz@juniper.net

   Derek M. Yeung
   Procket Networks, Inc.
   1100 Cadillac Court
   Milpitas, CA 95035 USA

   Phone:  +1 408 635-7900
   Fax:    +1 408 987-6166

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

   Phone:  +1 408 745 2000
   Email:  kireeti@juniper.net























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