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Versions: 00 01 02 03 04 05 06 07 08 RFC 4124

   TEWG
   Internet Draft                                  Francois Le Faucheur
                                                                 Editor
   Document: draft-ietf-tewg-diff-te-proto-08.txt        Cisco Systems,
                                                                   Inc.
   Expires: June 2005                                     December 2004


                   Protocol extensions for support of
           Differentiated-Service-aware MPLS Traffic Engineering


Status of this Memo

   This document is an Internet-Draft and is subject to all provisions
   of section 3 of RFC 3667.  By submitting this Internet-Draft, each
   author represents that any applicable patent or other IPR claims of
   which he or she is aware have been or will be disclosed, and any of
   which he or she become aware will be disclosed, in accordance with
   RFC 3668.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

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   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on June 13, 2005.


Copyright Notice

   Copyright (C) The Internet Society (2004).  All Rights Reserved.


Abstract

   This document specifies the protocol extensions for support of
   Differentiated-Service-aware MPLS Traffic Engineering (DS-TE). This
   includes generalization of the semantic of a number of IGP extensions


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   already defined for existing MPLS Traffic Engineering in RFC3630 and
   RFC-TBD as well as additional IGP extensions beyond those. This also
   includes extensions to RSVP-TE signaling beyond those already
   specified in RFC3209 for existing MPLS Traffic Engineering. These
   extensions address the Requirements for DS-TE spelt out in RFC3564.

   <RFC-Editor-note> To be removed by the RFC editor at the time of
   publication:        Please replace "TBD" above by the actual RFC
   number when
          an RFC number is allocated to [ISIS-TE]
   </RFC-Editor-note>

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].


Table of Contents

   1. Introduction...................................................3
   2. Contributing Authors...........................................4
   3. Definitions....................................................5
   4. Configurable Parameters........................................5
      4.1. Link Parameters...........................................5
         4.1.1. Bandwidth Constraints (BCs)  5
         4.1.2. Overbooking6
      4.2. LSR Parameters............................................6
         4.2.1. TE-Class Mapping 7
      4.3. LSP Parameters............................................8
         4.3.1. Class-Type 8
         4.3.2. Setup and Holding Preemption Priorities  8
         4.3.3. Class-Type/Preemption Relationship 8
      4.4. Examples of Parameters Configuration......................8
         4.4.1. Example 1  8
         4.4.2. Example 2  9
         4.4.3. Example 3  10
         4.4.4. Example 4  10
         4.4.5. Example 5  11
   5. IGP Extensions for DS-TE......................................11
      5.1. Bandwidth Constraints....................................11
      5.2. Unreserved Bandwidth.....................................14
   6. RSVP-TE Extensions for DS-TE..................................15
      6.1. DS-TE related RSVP Messages Format.......................15
         6.1.1. Path Message Format 15
      6.2. CLASSTYPE Object.........................................16
         6.2.1. CLASSTYPE object 16
      6.3. Handling CLASSTYPE Object................................16
      6.4. Non-support of the CLASSTYPE Object......................19


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      6.5. Error Codes For Diff-Serv-aware TE.......................19
   7. DS-TE support with MPLS extensions............................20
      7.1. DS-TE support and references to preemption priority......21
      7.2. DS-TE support and references to Maximum Reservable Bandwidth
      ..............................................................21
   8. Constraint Based Routing......................................21
   9. Diff-Serv scheduling..........................................22
   10. Existing TE as a Particular Case of DS-TE....................22
   11. Computing "Unreserved TE-Class [i]" and Admission Control Rules22
      11.1. Computing "Unreserved TE-Class [i]".....................23
      11.2. Admission Control Rules.................................23
   12. Security Considerations......................................24
   13. Acknowledgments..............................................24
   14. IANA Considerations..........................................24
      14.1. A new name space for Bandwidth Constraints Model Identifiers
      ..............................................................24
      14.2. A new name space for Error Values under the "Diff-Serv-aware
      TE Error".....................................................24
      14.3. Assignments made in this Document.......................25
         14.3.1. Bandwidth Constraints sub-TLV for OSPF version 2 25
         14.3.2. Bandwidth Constraints sub-TLV for ISIS  25
         14.3.3. CLASSTYPE object for RSVP26
         14.3.4. "Diff-Serv-aware TE Error" Error Code26
         14.3.5. Error Values for "Diff-Serv-aware TE Error"26
   15. Intellectual Property Considerations.........................27
   16. Normative References.........................................28
   17. Informative References.......................................28
   18. Editor's Address:............................................29
   19. Full Copyright Statement.....................................29
   Appendix A - Prediction for Multiple Path Computation............30
   Appendix B - Solution Evaluation.................................31
   Appendix C - Interoperability with non DS-TE capable LSRs........32
   Disclaimer of Validity...........................................35
   Copyright Statement..............................................35
   Acknowledgment...................................................35


1.Introduction

   [DSTE-REQ] presents the Service Providers requirements for support of
   Differentiated-Service (Diff-Serv)-aware MPLS Traffic Engineering
   (DS-TE). This includes the fundamental requirement to be able to
   enforce different bandwidth constraints for different classes of
   traffic.

   This document specifies the IGP and RSVP-TE signaling extensions
   (beyond those already specified for existing MPLS Traffic Engineering
   [OSPF-TE][ISIS-TE][RSVP-TE]) for support of the DS-TE requirements
   spelled out in [DSTE-REQ] including environments relying on



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   distributed Constraint Based Routing (e.g. path computation involving
   Head-end LSRs).

   [DSTE-REQ] provides a definition and examples of Bandwidth
   Constraints Models. The present document does not specify nor assume
   a particular Bandwidth Constraints model. Specific Bandwidth
   Constraints model are outside the scope of this document. While the
   extensions for DS-TE specified in this document may not be sufficient
   to support all the conceivable Bandwidth Constraints models, they do
   support the "Russian Dolls" Model specified in [DSTE-RDM], the
   "Maximum Allocation" Model specified in [DSTE-MAM] and the "Maximum
   Allocation with Reservation" Model specified in [DSTE-MAR].

   There may be differences between the quality of service expressed and
   obtained with Diffserv without DS-TE and with DS-TE. Because DS-TE
   uses Constraint Based Routing, and because of the type of admission
   control capabilities it adds to Diffserv, DS-TE has capabilities for
   traffic that Diffserv does not:  Diffserv does not indicate
   preemption, by intent, whereas DS-TE describes multiple levels of
   preemption for its Class Types. Also, Diffserv does not support any
   means of explicitly controlling overbooking, while DS-TE allows this.
   When considering a complete quality of service environment, with
   Diffserv routers and DS-TE, it is important to consider these
   differences carefully.


2.Contributing Authors

   This document was the collective work of several. The text and
   content of this document was contributed by the editor and the co-
   authors listed below. (The contact information for the editor appears
   in Section 18, and is not repeated below.)

   Jim Boyle                            Kireeti Kompella
   Protocol Driven Networks, Inc.       Juniper Networks, Inc.
   1381 Kildaire Farm Road #288         1194 N. Mathilda Ave.
   Cary, NC 27511, USA                  Sunnyvale, CA 94099
   Phone: (919) 852-5160                Email: kireeti@juniper.net
   Email: jboyle@pdnets.com

   William Townsend                     Thomas D. Nadeau
   Tenor Networks                       Cisco Systems, Inc.
   100 Nagog Park                       250 Apollo Drive
   Acton, MA 01720                      Chelmsford, MA 01824
   Phone: +1-978-264-4900               Phone: +1-978-244-3051
   Email:                               Email: tnadeau@cisco.com
   btownsend@tenornetworks.com

   Darek Skalecki
   Nortel Networks


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   3500 Carling Ave,
   Nepean K2H 8E9
   Phone: +1-613-765-2252
   Email: dareks@nortelnetworks.com



3.Definitions

   For readability a number of definitions from [DSTE-REQ] are repeated
   here:

   Traffic Trunk: an aggregation of traffic flows of the same class
   [i.e. which are to be treated equivalently from the DS-TE
   perspective] which are placed inside a Label Switched Path.

   Class-Type (CT): the set of Traffic Trunks crossing a link that is
   governed by a specific set of Bandwidth constraints. CT is used for
   the purposes of link bandwidth allocation, constraint based routing
   and admission control. A given Traffic Trunk belongs to the same CT
   on all links.

   TE-Class: A pair of:
             i. a Class-Type
            ii. a preemption priority allowed for that Class-Type. This
                means that an LSP transporting a Traffic Trunk from
                that Class-Type can use that preemption priority as the
                set-up priority, as the holding priority or both.

   Definitions for a number of MPLS terms are not repeated here. Those
   can be found in [MPLS-ARCH].


4.Configurable Parameters

   This section only discusses the differences with the configurable
   parameters supported for MPLS Traffic Engineering as per [TE-REQ],
   [ISIS-TE], [OSPF-TE], and [RSVP-TE]. All other parameters are
   unchanged.

4.1.Link Parameters

4.1.1.Bandwidth Constraints (BCs)

   [DSTE-REQ] states that "Regardless of the Bandwidth Constraints
   Model, the DS-TE solution MUST allow support for up to 8 BCs."

   For DS-TE, the existing "Maximum Reservable link bandwidth" parameter
   is retained but its semantic is generalized and interpreted as the



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   aggregate bandwidth constraints across all Class-Types, so that,
   independently of the Bandwidth Constraints Model in use:
     SUM (Reserved (CTc)) <= Max Reservable Bandwidth,
     where the SUM is across all values of "c" in the range 0 <= c <= 7.

   Additionally, on every link, a DS-TE implementation MUST provide for
   configuration of up to 8 additional link parameters which are the
   eight potential Bandwidth Constraints i.e. BC0, BC1 , ... BC7. The
   LSR MUST interpret these Bandwidth Constraints in accordance with the
   supported Bandwidth Constraints Model (i.e. what bandwidth constraint
   applies to what Class-Type and how).

   Where the Bandwidth Constraints Model imposes some relationship among
   the values to be configured for these Bandwidth Constraints, the LSR
   MUST enforce those at configuration time. For example, when the
   "Russian Doll" Bandwidth Constraints Model ([DSTE-RDM]) is used, the
   LSR MUST ensure that BCi is configured smaller or equal to BCj, where
   i is greater than j, and ensure that BC0 is equal to the Maximum
   Reservable Bandwidth. As another example, when the Maximum Allocation
   Model ([DSTE-MAM]) is used, the LSR MUST ensure that all BCi are
   configured smaller or equal to the Maximum Reservable Bandwidth.

4.1.2.Overbooking

   DS-TE enables a network administrator to apply different overbooking
   (or underbooking) ratios for different CTs.

   The principal methods to achieve this are the same as historically
   used in existing TE deployment, which are :
  (i)    To take into account the overbooking/underbooking ratio
          appropriate for the OA/CT associated with the considered LSP
          at the time of establishing the bandwidth size of a given
          LSP. We refer to this method as the "LSP Size Overbooking
          method".  AND/OR
  (ii)   To take into account the overbooking/underbooking ratio at
          the time of configuring the Maximum Reservable
          Bandwidth/Bandwidth Constraints and use values which are
          larger(overbooking) or smaller(underbooking) than actually
          supported by the link. We refer to this method as the "Link
          Size Overbooking method".

   The "LSP Size Overbooking" method and the "Link Size Overbooking"
   method are expected to be sufficient in many DS-TE environments and
   require no additional configurable parameters. Other overbooking
   methods may involve such additional configurable parameters but are
   beyond the scope of this document.

4.2.LSR Parameters




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4.2.1.TE-Class Mapping

   In line with [DSTE-REQ], the preemption attributes defined in [TE-
   REQ] are retained with DS-TE and applicable within, and across, all
   Class Types. The preemption attributes of setup priority and holding
   priority retain existing semantics, and in particular these semantics
   are not affected by the LSP Class Type. This means that if LSP1
   contends with LSP2 for resources, LSP1 may preempt LSP2 if LSP1 has a
   higher set-up preemption priority (i.e. lower numerical priority
   value) than LSP2 holding preemption priority regardless of LSP1 CT
   and LSP2 CT.

   DS-TE LSRs MUST allow configuration of a TE-Class mapping whereby the
   Class-Type and preemption level are configured for each of (up to) 8
   TE-Classes.

   This mapping is referred to as :

        TE-Class[i]  <-->  < CTc , preemption p >

   Where 0 <= i <= 7, 0 <= c <= 7, 0 <= p <= 7

   Two TE-Classes MUST NOT be identical (i.e. have both the same Class-
   Type and the same preemption priority).

   There are no other restrictions on how any of the 8 Class-Types can
   be paired up with any of the 8 preemption priorities to form a TE-
   class. In particular, one given preemption priority can be paired up
   with two (or more) different Class-Types to form two (or more) TE-
   classes. Similarly, one Class-Type can be paired up with two (or
   more) different preemption priorities to form two (or more) TE-
   Classes. Also, there is no mandatory ordering relationship between
   the TE-Class index (i.e. "i" above) and the Class-Type (i.e. "c"
   above) or the preemption priority (i.e. "p" above) of the TE-Class.

   Where the network administrator uses less than 8 TE-Classes, the DS-
   TE LSR MUST allow remaining ones to be configured as "Unused". Note
   that "Configuring all the 8 TE-Classes as "Unused" effectively
   results in disabling TE/DS-TE since no TE/DS-TE LSP can be
   established (nor even configured, since as described in section 4.3.3
   below, the CT and preemption priorities configured for an LSP MUST
   form one of the configured TE-Classes)".

   To ensure coherent DS-TE operation, the network administrator MUST
   configure exactly the same TE-Class Mapping on all LSRs of the DS-TE
   domain.

   When the TE-class mapping needs to be modified in the DS-TE domain,
   care ought to be exercised during the transient period of
   reconfiguration during which some DS-TE LSRs may be configured with


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   the new TE-class mapping while others are still configured with the
   old TE-class mapping. It is recommended that active tunnels do not
   use any of the TE-classes which are being modified during such a
   transient reconfiguration period.

4.3.LSP Parameters

4.3.1.Class-Type

   With DS-TE, LSRs MUST support, for every LSP, an additional
   configurable parameter which indicates the Class-Type of the Traffic
   Trunk transported by the LSP.

   There is one and only one Class-Type configured per LSP.

   The configured Class-Type indicates, in accordance with the supported
   Bandwidth Constraints Model, the Bandwidth Constraints that MUST be
   enforced for that LSP.

4.3.2.Setup and Holding Preemption Priorities

   As per existing TE, DS-TE LSRs MUST allow every DS-TE LSP to be
   configured with a setup and holding priority, each with a value
   between 0 and 7.

4.3.3.Class-Type/Preemption Relationship

   With DS-TE, the preemption priority configured for the setup priority
   of a given LSP and the Class-Type configured for that LSP MUST be
   such that, together, they form one of the (up to) 8 TE-Classes
   configured in the TE-Class Mapping specified in section 4.2.1 above.

   The preemption priority configured for the holding priority of a
   given LSP and the Class-Type configured for that LSP MUST also be
   such that, together, they form one of the (up to) 8 TE-Classes
   configured in the TE-Class Mapping specified in section 4.2.1 above.

   The LSR MUST enforce these two rules at configuration time.

4.4.Examples of Parameters Configuration

   For illustrative purposes, we now present a few examples of how these
   configurable parameters may be used. All these examples assume that
   different bandwidth constraints need to be enforced for different
   sets of Traffic Trunks (e.g. for Voice and for Data) so that two, or
   more, Class-Types need to be used.

4.4.1.Example 1




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   The Network Administrator of a first network using two Class Types
   (CT1 for Voice and CT0 for Data), may elect to configure the
   following TE-Class Mapping to ensure that Voice LSPs are never driven
   away from their shortest path because of Data LSPs:

        TE-Class[0]  <-->  < CT1 , preemption 0 >
        TE-Class[1]  <-->  < CT0 , preemption 1 >
        TE-Class[i]  <-->  unused,   for 2 <= i <= 7

   Voice LSPs would then be configured with:
        - CT=CT1, set-up priority =0, holding priority=0

   Data LSPs would then be configured with:
        - CT=CT0, set-up priority =1, holding priority=1

   A new Voice LSP would then be able to preempt an existing Data LSP in
   case they contend for resources. A Data LSP would never preempt a
   Voice LSP. A Voice LSP would never preempt another Voice LSP. A Data
   LSP would never preempt another Data LSP.

4.4.2.Example 2

   The Network Administrator of another network may elect to configure
   the following TE-Class Mapping in order to optimize global network
   resource utilization by favoring placement of large LSPs closer to
   their shortest path:

        TE-Class[0]  <-->  < CT1 , preemption 0 >
        TE-Class[1]  <-->  < CT0 , preemption 1 >
        TE-Class[2]  <-->  < CT1 , preemption 2 >
        TE-Class[3]  <-->  < CT0 , preemption 3 >
        TE-Class[i]  <-->  unused,   for 4 <= i <= 7

   Large size Voice LSPs could be configured with:
        - CT=CT1, set-up priority =0, holding priority=0

   Large size Data LSPs could be configured with:
        - CT=CT0, set-up priority = 1, holding priority=1

   Small size Voice LSPs could be configured with:
        - CT=CT1, set-up priority = 2, holding priority=2

   Small size Data LSPs could be configured with:
        - CT=CT0, set-up priority = 3, holding priority=3.

   A new large size Voice LSP would then be able to preempt a small size
   Voice LSP or any Data LSP in case they contend for resources.
   A new large size Data LSP would then be able to preempt a small size
   Data LSP or a small size Voice LSP in case they contend for



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   resources, but it would not be able to preempt a large size Voice
   LSP.

4.4.3.Example 3

   The Network Administrator of another network may elect to configure
   the following TE-Class Mapping in order to ensure that Voice LSPs are
   never driven away from their shortest path because of Data LSPs while
   also achieving some optimization of global network resource
   utilization by favoring placement of large LSPs closer to their
   shortest path:

        TE-Class[0]  <-->  < CT1 , preemption 0 >
        TE-Class[1]  <-->  < CT1 , preemption 1 >
        TE-Class[2]  <-->  < CT0 , preemption 2 >
        TE-Class[3]  <-->  < CT0 , preemption 3 >
        TE-Class[i]  <-->  unused,   for 4 <= i <= 7

   Large size Voice LSPs could be configured with:
        - CT=CT1, set-up priority = 0, holding priority=0.

   Small size Voice LSPs could be configured with:
        - CT=CT1, set-up priority = 1, holding priority=1.

   Large size Data LSPs could be configured with:
        - CT=CT0, set-up priority = 2, holding priority=2.

   Small size Data LSPs could be configured with:
        - CT=CT0, set-up priority = 3, holding priority=3.

   A Voice LSP could preempt a Data LSP if they contend for resources. A
   Data LSP would never preempt a Voice LSP. A Large size Voice LSP
   could preempt a small size Voice LSP if they contend for resources. A
   Large size Data LSP could preempt a small size Data LSP if they
   contend for resources.

4.4.4.Example 4

   The Network Administrator of another network may elect to configure
   the following TE-Class Mapping in order to ensure that no preemption
   occurs in the DS-TE domain:

        TE-Class[0]  <-->  < CT1 , preemption 0 >
        TE-Class[1]  <-->  < CT0 , preemption 0 >
        TE-Class[i]  <-->  unused,   for 2 <= i <= 7

   Voice LSPs would then be configured with:
        - CT=CT1, set-up priority =0, holding priority=0

   Data LSPs would then be configured with:


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        - CT=CT0, set-up priority =0, holding priority=0

   No LSP would then be able to preempt any other LSP.

4.4.5.Example 5

   The Network Administrator of another network may elect to configure
   the following TE-Class Mapping in view of increased network stability
   through a more limited use of preemption:

        TE-Class[0]  <-->  < CT1 , preemption 0 >
        TE-Class[1]  <-->  < CT1 , preemption 1 >
        TE-Class[2]  <-->  < CT0 , preemption 1 >
        TE-Class[3]  <-->  < CT0 , preemption 2 >
        TE-Class[i]  <-->  unused,   for 4 <= i <= 7

   Large size Voice LSPs could be configured with:
        - CT=CT1, set-up priority = 0, holding priority=0.

   Small size Voice LSPs could be configured with:
        - CT=CT1, set-up priority = 1, holding priority=0.

   Large size Data LSPs could be configured with:
        - CT=CT0, set-up priority = 2, holding priority=1.

   Small size Data LSPs could be configured with:
        - CT=CT0, set-up priority = 2, holding priority=2.

   A new large size Voice LSP would be able to preempt a Data LSP in
   case they contend for resources, but it would not be able to preempt
   any Voice LSP even a small size Voice LSP.

   A new small size Voice LSP would be able to preempt a small size Data
   LSP in case they contend for resources, but it would not be able to
   preempt a large size Data LSP or any Voice LSP.

   A Data LSP would not be able to preempt any other LSP.


5.IGP Extensions for DS-TE

   This section only discusses the differences with the IGP
   advertisement supported for (aggregate) MPLS Traffic Engineering as
   per [OSPF-TE] and [ISIS-TE]. The rest of the IGP advertisement is
   unchanged.

5.1.Bandwidth Constraints

   As detailed above in section 4.1.1, up to 8 Bandwidth Constraints
   ( BCb, 0 <= b <= 7) are configurable on any given link.


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   With DS-TE, the existing "Maximum Reservable Bandwidth" sub-TLV
   ([OSPF-TE], [ISIS-TE]) is retained with a generalized semantic so
   that it MUST now be interpreted as the aggregate bandwidth constraint
   across all Class-Types [ i.e.
   SUM (Reserved (CTc)) <= Max Reservable Bandwidth], independently of
   the Bandwidth Constraints Model.

   This document also defines the following new optional sub-TLV to
   advertise the eight potential Bandwidth Constraints (BC0 to BC7):

   "Bandwidth Constraints" sub-TLV:
        - Bandwidth Constraints Model Id (1 octet)
        - Reserved (3 octets)
        - Bandwidth Constraints (Nx4 octets)

   Where:

        - With OSPF, the sub-TLV is a sub-TLV of the "Link TLV" and its
          sub-TLV type is TBD

        - With ISIS, the sub-TLV is a sub-TLV of the "extended IS
          reachability TLV" and its sub-TLV type is TBD ().

   <IANA-note> To be removed by the RFC editor at the time of
   publication:        When the sub-TLV numbers are allocated by IANA
   for OSPF and ISIS, replace "TBD" in the two bullet points above by
   the respective assigned value. See IANA Considerations section for
   allocation request.
   </IANA-note>
        - Bandwidth Constraints Model Id: 1 octet identifier for the
          Bandwidth Constraints Model currently in use by the LSR
          initiating the IGP advertisement. See the IANA Considerations
          section below for assignment of values in this name space.

        - Reserved: a 3-octet field. This field should be set to zero
          by the LSR generating the sub-TLV and should be ignored by
          the LSR receiving the sub-TLV.

        - Bandwidth Constraints: contains BC0, BC1,... BC(N-1).
          Each Bandwidth Constraint is encoded on 32 bits in IEEE
          floating point format. The units are bytes (not bits!) per
          second. Where the configured TE-class mapping and the
          Bandwidth Constraints model in use are such that BCh+1,
          BCh+2, ...and BC7 are not relevant to any of the Class-Types
          associated with a configured TE-class, it is RECOMMENDED that
          only the Bandwidth Constraints from BC0 to BCh be advertised,
          in order to minimize the impact on IGP scalability.




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   All relevant generic TLV encoding rules (including TLV format,
   padding and alignment, as well as IEEE floating point format
   encoding) defined in [OSPF-TE] and [ISIS-TE] are applicable to this
   new sub-TLV.

   The "Bandwidth Constraints" sub-TLV format is illustrated below:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | BC Model Id   |           Reserved                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       BC0 value                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     //                       . . .                                 //
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       BCh value                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   A DS-TE LSR MAY optionally advertise Bandwidth Constraints.

   A DS-TE LSR which does advertise Bandwidth Constraints MUST use the
   new "Bandwidth Constraints" sub-TLV (in addition to the existing
   Maximum Reservable Bandwidth sub-TLV) to do so. For example,
   considering the case where a Service Provider deploys DS-TE with
   TE-classes associated with CT0 and CT1 only, and where the Bandwidth
   Constraints Model is such that only BC0 and BC1 are relevant to CT0
   and CT1: a DS-TE LSR which does advertise Bandwidth Constraints would
   include in the IGP advertisement the Maximum Reservable Bandwidth
   sub-TLV as well as the "Bandwidth Constraints" sub-TLV, where the
   former should contain the aggregate bandwidth constraint across all
   CTs and the latter would contain BC0 and BC1.

   A DS-TE LSR receiving the "Bandwidth Constraints" sub-TLV with a
   Bandwidth Constraints Model Id which does not match the Bandwidth
   Constraints Model it currently uses, SHOULD generate a warning to the
   operator/management-system reporting the inconsistency between
   Bandwidth Constraints Models used on different links. Also, in that
   case, if the DS-TE LSR does not support the Bandwidth Constraints
   Model designated by the Bandwidth Constraints Model Id, or if the DS-
   TE LSR does not support operations with multiple simultaneous
   Bandwidth Constraints Models, the DS-TE LSR MAY discard the
   corresponding TLV. If the DS-TE LSR does support the Bandwidth
   Constraints Model designated by the Bandwidth Constraints Model Id
   and if the DS-TE LSR does support operations with multiple
   simultaneous Bandwidth Constraints Models, the DS-TE LSR MAY accept
   the corresponding TLV and allow operations with different Bandwidth
   Constraints Models used in different parts of the DS-TE domain.



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5.2.Unreserved Bandwidth

   With DS-TE, the existing "Unreserved Bandwidth" sub-TLV is retained
   as the only vehicle to advertise dynamic bandwidth information
   necessary for Constraint Based Routing on Head-ends, except that it
   is used with a generalized semantic. The Unreserved Bandwidth sub-TLV
   still carries eight bandwidth values but they now correspond to the
   unreserved bandwidth for each of the TE-Class (instead of for each
   preemption priority as per existing TE).

   More precisely, a DS-TE LSR MUST support the Unreserved Bandwidth
   sub-TLV with a definition which is generalized into the following:

   The Unreserved Bandwidth sub-TLV specifies the amount of bandwidth
   not yet reserved for each of the eight TE-classes, in IEEE floating
   point format arranged in increasing order of TE-Class index, with
   unreserved bandwidth for TE-Class [0] occurring at the start of the
   sub-TLV, and unreserved bandwidth for TE-Class [7] at the end of the
   sub-TLV. The unreserved bandwidth value for TE-Class [i] ( 0 <= i <=
   7) is referred to as "Unreserved TE-Class [i]". It indicates the
   bandwidth that is available, for reservation, to an LSP which :
        - transports a Traffic Trunk from the Class-Type of TE-
          Class[i], and
        - has a setup priority corresponding to the preemption priority
          of TE-Class[i].

   The units are bytes per second.

   Since the bandwidth values are now ordered by TE-class index and thus
   can relate to different CTs with different bandwidth constraints and
   can relate to any arbitrary preemption priority, a DS-TE LSR MUST NOT
   assume any ordered relationship among these bandwidth values.

   With existing TE, since all preemption priorities reflect the same
   (and only) bandwidth constraints and since bandwidth values are
   advertised in preemption priority order, the following relationship
   is always true, and is often assumed by TE implementations:

       If i < j , then "Unreserved Bw [i]" >= "Unreserved Bw [j]"

   With DS-TE, no relationship is to be assumed so that:
        If i < j , then any of the following relationship may be true
                "Unreserved TE-Class [i]" = "Unreserved TE-Class [j]"
                    OR
                "Unreserved TE-Class [i]" > "Unreserved TE-Class [j]"
                    OR
                "Unreserved TE-Class [i]" < "Unreserved TE-Class [j]".

   Rules for computing "Unreserved TE-Class [i]" are specified in
   section 11.


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   If TE-Class[i] is unused, the value advertised by the IGP in
   "Unreserved TE-Class [i]" MUST be set to zero by the LSR generating
   the IGP advertisement, and MUST be ignored by the LSR receiving the
   IGP advertisement.


6.RSVP-TE Extensions for DS-TE

   In this section we describe extensions to RSVP-TE for support of
   Diff-Serv-aware MPLS Traffic Engineering. These extensions are in
   addition to the extensions to RSVP defined in [RSVP-TE] for support
   of (aggregate) MPLS Traffic Engineering and to the extensions to RSVP
   defined in [DIFF-MPLS] for support of Diff-Serv over MPLS.

6.1.DS-TE related RSVP Messages Format

   One new RSVP Object is defined in this document: the CLASSTYPE
   Object. Detailed description of this Object is provided below. This
   new Object is applicable to Path messages. This specification only
   defines the use of the CLASSTYPE Object in Path messages used to
   establish LSP Tunnels in accordance with [RSVP-TE] and thus
   containing a Session Object with a C-Type equal to LSP_TUNNEL_IPv4
   and containing a LABEL_REQUEST object.

   Restrictions defined in [RSVP-TE] for support of establishment of LSP
   Tunnels via RSVP-TE are also applicable to the establishment of LSP
   Tunnels supporting DS-TE. For instance, only unicast LSPs are
   supported and Multicast LSPs are for further study.

   This new CLASSTYPE object is optional with respect to RSVP so that
   general RSVP implementations not concerned with MPLS LSP set up do
   not have to support this object.

   An LSR supporting DS-TE MUST support the CLASSTYPE Object.

6.1.1.Path Message Format

   The format of the Path message is as follows:

   <Path Message> ::=      <Common Header> [ <INTEGRITY> ]
                           <SESSION> <RSVP_HOP>
                           <TIME_VALUES>
                           [ <EXPLICIT_ROUTE> ]
                           <LABEL_REQUEST>
                           [ <SESSION_ATTRIBUTE> ]
                           [ <DIFFSERV> ]
                           [ <CLASSTYPE> ]
                           [ <POLICY_DATA> ... ]
                           [ <sender descriptor> ]


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   <sender descriptor> ::=  <SENDER_TEMPLATE> [ <SENDER_TSPEC> ]
                           [ <ADSPEC> ]
                           [ <RECORD_ROUTE> ]

6.2.CLASSTYPE Object

   The CLASSTYPE object Class Name is CLASSTYPE. Its Class Number is
   TBD. Currently, there is only one defined C_Type which is C_Type 1.
   The CLASSTYPE object format is shown below.

   <IANA-note> To be removed by the RFC editor at the time of
   publication:        When the RSVP Class-Num is assigned by IANA
   replace "TBD"
           above by the assigned value. See IANA Considerations section
           for allocation request.
   </IANA-note>

6.2.1.CLASSTYPE object

   Class Number = TBD
   Class Type = 1


   <IANA-note> To be removed by the RFC editor at the time of
   publication:        When the RSVP Class Number is assigned by IANA
   replace "TBD"
           above by the assigned value. See IANA Considerations section
           for allocation request.
   </IANA-note>

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Reserved                                         |  CT |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Reserved : 29 bits
       This field is reserved. It MUST be set to zero on transmission
       and MUST be ignored on receipt.

   CT : 3 bits
       Indicates the Class-Type. Values currently allowed are
       1, 2, ... , 7. Value of 0 is Reserved.

6.3.Handling CLASSTYPE Object

   To establish an LSP tunnel with RSVP, the sender LSR creates a Path
   message with a session type of LSP_Tunnel_IPv4 and with a


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   LABEL_REQUEST object as per [RSVP-TE]. The sender LSR may also
   include the DIFFSERV object as per [DIFF-MPLS].

   If the LSP is associated with Class-Type 0, the sender LSR MUST NOT
   include the CLASSTYPE object in the Path message. This allows
   backward compatibility with non-DSTE-configured or non-DSTE-capable
   LSRs as discussed below in section 10 and Appendix C.

   If the LSP is associated with Class-Type N (1 <= N <=7), the sender
   LSR MUST include the CLASSTYPE object in the Path message with the
   Class-Type (CT) field set to N.

   If a path message contains multiple CLASSTYPE objects, only the first
   one is meaningful; subsequent CLASSTYPE object(s) MUST be ignored and
   MUST NOT be forwarded.

   Each LSR along the path MUST record the CLASSTYPE object, when
   present, in its path state block.

   If the CLASSTYPE object is not present in the Path message, the LSR
   MUST associate the Class-Type 0 to the LSP.

   The destination LSR responding to the Path message by sending a Resv
   message MUST NOT include a CLASSTYPE object in the Resv message
   (whether the Path message contained a CLASSTYPE object or not).

   During establishment of an LSP corresponding to the Class-Type N, the
   LSR MUST perform admission control over the bandwidth available for
   that particular Class-Type.

   An LSR that recognizes the CLASSTYPE object and that receives a path
   message which:
        - contains the CLASSTYPE object, but
        - which does not contain a LABEL_REQUEST object or which does
          not have a session type of LSP_Tunnel_IPv4,
   MUST send a PathErr towards the sender with the error code "Diff-
   Serv-aware TE Error" and an error value of "Unexpected CLASSTYPE
   object". Those are defined below in section 6.5.

   An LSR receiving a Path message with the CLASSTYPE object, which:
        - recognizes the CLASSTYPE object, but
        - does not support the particular Class-Type,
   MUST send a PathErr towards the sender with the error code "Diff-
   Serv-aware TE Error" and an error value of "Unsupported Class-Type".
   Those are defined below in section 6.5.

   An LSR receiving a Path message with the CLASSTYPE object, which:
        - recognizes the CLASSTYPE object, but
        - determines that the Class-Type value is not valid (i.e.
          Class-Type value 0),


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   MUST send a PathErr towards the sender with the error code "Diff-
   Serv-aware TE Error" and an error value of "Invalid Class-Type
   value". Those are defined below in section 6.5.

   An LSR receiving a Path message with the CLASSTYPE object, which:
        - recognizes the CLASSTYPE object,
        - supports the particular Class-Type, but
        - determines that the tuple formed by (i) this Class-Type and
          (ii) the set-up priority signaled in the same Path message,
          is not one of the eight TE-classes configured in the TE-class
          mapping,
   MUST send a PathErr towards the sender with the error code "Diff-
   Serv-aware TE Error" and an error value of "CT and setup priority do
   not form a configured TE-Class". Those are defined below in section
   6.5.

   An LSR receiving a Path message with the CLASSTYPE object, which:
        - recognizes the CLASSTYPE object,
        - supports the particular Class-Type, but
        - determines that the tuple formed by (i) this Class-Type and
          (ii) the holding priority signaled in the same Path message,
          is not one of the eight TE-classes configured in the TE-class
          mapping,
   MUST send a PathErr towards the sender with the error code "Diff-
   Serv-aware TE Error" and an error value of "CT and holding priority
   do not form a configured TE-Class". Those are defined below in
   section 6.5.

   An LSR receiving a Path message with the CLASSTYPE object, which:
        - recognizes the CLASSTYPE object,
        - supports the particular Class-Type, but
        - determines that the tuple formed by (i) this Class-Type and
          (ii) the setup priority signaled in the same Path message,
          is not one of the eight TE-classes configured in the TE-class
          mapping, AND
        - determines that the tuple formed by (i) this Class-Type and
          (ii) the holding priority signaled in the same Path message,
          is not one of the eight TE-classes configured in the TE-class
          mapping
   MUST send a PathErr towards the sender with the error code "Diff-
   Serv-aware TE Error" and an error value of "CT and setup priority do
   not form a configured TE-Class AND CT and holding priority do not
   form a configured TE-Class". Those are defined below in section 6.5.

   An LSR receiving a Path message with the CLASSTYPE object and with
   the DIFFSERV object for an L-LSP, which:
        - recognizes the CLASSTYPE object,
        - has local knowledge of the relationship between Class-Types
          and PSC (e.g. via configuration)



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        - based on this local knowledge, determines that the PSC
          signaled in the DIFFSERV object is inconsistent with the
          Class-Type signaled in the CLASSTYPE object,
   MUST send a PathErr towards the sender with the error code "Diff-
   Serv-aware TE Error" and an error value of "Inconsistency between
   signaled PSC and signaled CT". Those are defined below in section
   6.5.

   An LSR receiving a Path message with the CLASSTYPE object and with
   the DIFFSERV object for an E-LSP, which:
        - recognizes the CLASSTYPE object,
        - has local knowledge of the relationship between Class-Types
          and PHBs (e.g. via configuration)
        - based on this local knowledge, determines that the PHBs
          signaled in the MAP entries of the DIFFSERV object are
          inconsistent with the Class-Type signaled in the CLASSTYPE
          object,
   MUST send a PathErr towards the sender with the error code "Diff-
   Serv-aware TE Error" and an error value of "Inconsistency between
   signaled PHBs and signaled CT". Those are defined below in section
   6.5.

   An LSR MUST handle the situations where the LSP can not be accepted
   for other reasons than those already discussed in this section, in
   accordance with [RSVP-TE] and [DIFF-MPLS] (e.g. a reservation is
   rejected by admission control, a label can not be associated).

6.4.Non-support of the CLASSTYPE Object

   An LSR that does not recognize the CLASSTYPE object Class-Num MUST
   behave in accordance with the procedures specified in [RSVP] for an
   unknown Class-Num whose format is 0bbbbbbb (i.e. it MUST send a
   PathErr with the error code "Unknown object class" toward the
   sender).

   An LSR that recognizes the CLASSTYPE object Class-Num but does not
   recognize the CLASSTYPE object C-Type, MUST behave in accordance with
   the procedures specified in [RSVP] for an unknown C-type (i.e. it
   MUST send a PathErr with the error code "Unknown object C-Type"
   toward the sender).

   In both situations, this causes the path set-up to fail. The sender
   SHOULD notify the operator/management-system that an LSP cannot be
   established and possibly might take action to retry reservation
   establishment without the CLASSTYPE object.

6.5.Error Codes For Diff-Serv-aware TE





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   In the procedures described above, certain errors are reported as a
   "Diff-Serv-aware TE Error". The value of the "Diff-Serv-aware TE
   Error" error code is (TBD).

   <IANA-note> To be removed by the RFC editor at the time of
   publication:        When the "Diff-Serv-aware TE Error" Error Code is
   assigned by
           IANA, replace "TBD" above by the assigned value.
          See IANA Considerations section for allocation request.
   </IANA-note>
   The following defines error values for the Diff-Serv-aware TE Error:

     Value    Error

       1      Unexpected CLASSTYPE object
       2      Unsupported Class-Type
       3      Invalid Class-Type value
       4      Class-Type and setup priority do not form a configured
              TE-Class
       5      Class-Type and holding priority do not form a
              configured TE-Class
       6      Class-Type and setup priority do not form a configured
              TE-Class AND Class-Type and holding priority do not form
              a configured TE-Class
       7      Inconsistency between signaled PSC and signaled
              Class-Type
        8      Inconsistency between signaled PHBs and signaled
               Class-Type

   See the IANA Considerations section for allocation of additional
   Values.


7.DS-TE support with MPLS extensions.

   There are a number of extensions to the initial base specification
   for signaling [RSVP-TE] and IGP support for TE [OSPF-TE][ISIS-TE].
   Those include enhancements for generalization ([GMPLS-SIG] and
   [GMPLS-ROUTE]), as well as for additional functionality such as LSP
   hierarchy [HIERARCHY], link bundling [BUNDLE] and fast restoration
   [REROUTE]. These specifications may reference how to encode
   information associated with certain preemption priorities, how to
   treat LSPs at different preemption priorities, or otherwise specify
   encodings or behavior that have a different meaning for a DS-TE
   router.

   In order for an implementation to support both this specification for
   Diff-Serv-aware TE and a given MPLS enhancement such as those listed
   above (but not limited to those), it MUST treat references to



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   "preemption priority" and to "Maximum Reservable Bandwidth" in a
   generalized manner, such as it is used in this specification.

   Additionally, current and future MPLS enhancements may include more
   precise specification for how they interact with Diff-Serv-aware TE.

7.1.DS-TE support and references to preemption priority

   When a router supports both Diff-Serv-aware TE and one of the MPLS
   protocol extensions such as those mentioned above, encoding of values
   of preemption priority in signaling or encoding of information
   associated with preemption priorities in IGP defined for the MPLS
   extension, MUST be considered to be an encoding of the same
   information for the corresponding TE-Class. For instance, if an MPLS
   enhancement specifies advertisement in IGP of a parameter for routing
   information at preemption priority N, in a DS-TE environment it MUST
   actually be interpreted as specifying advertisement of the same
   routing information but for TE-Class [N].  On receipt, DS-TE routers
   MUST interpret it as such as well.

   When there is discussion on how to comparatively treat LSPs of
   different preemption priority, a DS-TE LSR MUST treat the preemption
   priorities in this context as the preemption priorities associated
   with the TE-Classes of the LSPs in question.

7.2.DS-TE support and references to Maximum Reservable Bandwidth

   When a router supports both Diff-Serv-aware TE and MPLS protocol
   extensions such as those mentioned above, advertisements of Maximum
   Reservable Bandwidth MUST be done with the generalized interpretation
   defined above in section 4.1.1 as the aggregate bandwidth constraint
   across all Class-Types and MAY also allow the optional advertisement
   of all Bandwidth Constraints.


8.Constraint Based Routing

   Let us consider the case where a path needs to be computed for an LSP
   whose Class-Type is configured to CTc and whose set-up preemption
   priority is configured to p.

   Then the pair of CTc and p will map to one of the TE-Classes defined
   in the TE-Class mapping. Let us refer to this TE-Class as TE-
   Class[i].

   The Constraint Based Routing algorithm of a DS-TE LSR is still only
   required to perform path computation satisfying a single bandwidth
   constraint which is to fit in "Unreserved TE-Class [i]" as advertised
   by the IGP for every link. Thus, no changes are required to the
   existing TE Constraint Based Routing algorithm itself.


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   The Constraint Based Routing algorithm MAY also take into account,
   when used, the optional additional information advertised in IGP such
   as the Bandwidth Constraints and the Maximum Reservable Bandwidth. As
   an example, the Bandwidth Constraints MIGHT be used as a tie-breaker
   criteria in situations where multiple paths, otherwise equally
   attractive, are possible.


9.Diff-Serv scheduling

   The Class-Type signaled at LSP establishment MAY optionally be used
   by DS-TE LSRs to dynamically adjust the resources allocated to the
   Class-Type by the Diff-Serv scheduler. In addition, the Diff-Serv
   information (i.e. the PSC) signaled by the TE-LSP signaling protocols
   as specified in [DIFF-MPLS], if used, MAY optionally be used by DS-TE
   LSRs to dynamically adjust the resources allocated to a PSC/OA within
   a Class Type by the Diff-Serv scheduler.


10.Existing TE as a Particular Case of DS-TE

   We observe that existing TE can be viewed as a particular case of
   DS-TE where:

        (i)    a single Class-Type is used,
        (ii)   all 8 preemption priorities are allowed for that Class-
                Type, and
        (iii)  the following TE-Class Mapping is used:
                    TE-Class[i]  <-->  < CT0 , preemption i >
                    Where 0 <= i <= 7.


   In that case, DS-TE behaves as existing TE.

   As with existing TE, the IGP advertises:
        - Unreserved Bandwidth for each of the 8 preemption priorities

   As with existing TE, the IGP may advertise:
        - Maximum Reservable Bandwidth containing a bandwidth
          constraint applying across all LSPs

   Since all LSPs transport traffic from CT0, RSVP-TE signaling is done
   without explicit signaling of the Class-Type (which is only used for
   other Class-Types than CT0 as explained in section 6) as with
   existing TE.


11.Computing "Unreserved TE-Class [i]" and Admission Control Rules



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11.1.Computing "Unreserved TE-Class [i]"

   We first observe that, for existing TE, details on admission control
   algorithms for TE LSPs, and consequently details on formulas for
   computing the unreserved bandwidth, are outside the scope of the
   current IETF work. This is left for vendor differentiation. Note that
   this does not compromise interoperability across various
   implementations since the TE schemes rely on LSRs to advertise their
   local view of the world in terms of Unreserved Bw to other LSRs. This
   way, regardless of the actual local admission control algorithm used
   on one given LSR, Constraint Based Routing on other LSRs can rely on
   advertised information to determine whether an additional LSP will be
   accepted or rejected by the given LSR. The only requirement is that
   an LSR advertises unreserved bandwidth values which are consistent
   with its specific local admission control algorithm and take into
   account the holding preemption priority of established LSPs.

   In the context of DS-TE, again, details on admission control
   algorithms are left for vendor differentiation and formulas for
   computing the unreserved bandwidth for TE-Class[i] are outside the
   scope of this specification. However, DS-TE places the additional
   requirement on the LSR that the unreserved bandwidth values
   advertised MUST reflect all of the Bandwidth Constraints relevant to
   the CT associated with TE-Class[i] in accordance with the Bandwidth
   Constraints Model. Thus, formulas for computing "Unreserved TE-Class
   [i]" depend on the Bandwidth Constraints Model in use and MUST
   reflect how bandwidth constraints apply to CTs. Example formulas for
   computing "Unreserved TE-Class [i]" Model are provided for the
   Russian Dolls Model and Maximum Allocation Model respectively in
   [DSTE-RDM] and [DSTE-MAM].

   As with existing TE, DS-TE LSRs MUST consider the holding preemption
   priority of established LSPs (as opposed to their set-up preemption
   priority) for the purpose of computing the unreserved bandwidth for
   TE-Class [i].

11.2.Admission Control Rules

   A DS-TE LSR MUST support the following admission control rule:

   Regardless of how the admission control algorithm actually computes
   the unreserved bandwidth for TE-Class[i] for one of its local link,
   an LSP of bandwidth B, of set-up preemption priority p and of
   Class-Type CTc is admissible on that link if, and only if,:

        B <= Unreserved Bandwidth for TE-Class[i]

        Where




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        - TE-Class [i] maps to  < CTc , p > in the TE-Class mapping
          configured on the LSR.


12.Security Considerations

   This document does not introduce additional security threats beyond
   those described for Diff-Serv ([DIFF-ARCH]) and MPLS Traffic
   Engineering ([TE-REQ], [RSVP-TE], [OSPF-TE], [ISIS-TE]) and the same
   security measures and procedures described in these documents apply
   here. For example, the approach for defense against theft- and
   denial-of-service attacks discussed in [DIFF-ARCH], which consists of
   the combination of traffic conditioning at DS boundary nodes along
   with security and integrity of the network infrastructure within a
   Diff-Serv domain, may be followed when DS-TE is in use. Also, as
   stated in [TE-REQ], it is specifically important that manipulation of
   administratively configurable parameters (such as those related to
   DS-TE LSPs) be executed in a secure manner by authorized entities.


13.Acknowledgments

   We thank Martin Tatham, Angela Chiu and Pete Hicks for their earlier
   contribution in this work. We also thank Sanjaya Choudhury for his
   thorough review and suggestions.


14.IANA Considerations

   This document creates two new name spaces which are to be managed by
   IANA. Also, a number of assignments from existing name spaces have
   been made by IANA in this document. Those are discussed below.

14.1.A new name space for Bandwidth Constraints Model Identifiers

   This document defines in section 5.1 a "Bandwidth Constraints Model
   Id" field (name space) within the "Bandwidth Constraints" sub-TLV,
   both for OSPF and ISIS. IANA is requested to create and maintain this
   new name space. The field for this namespace is 1 octet, and IANA
   guidelines for assignments for this field are as follows:

          o values in the range 0-239 are to be assigned according to
   the "Specification Required" policy defined in [IANA-CONS].

         o values in the range 240-255 are reserved for "Private Use" as
   defined in [IANA-CONS].

14.2.A new name space for Error Values under the "Diff-Serv-aware TE
    Error"



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   An Error Code is an 8-bit quantity defined in [RSVP] that appears in
   an ERROR_SPEC object to broadly define an error condition.  With each
   Error Code there may be a 16-bit Error Value (which depends on the
   Error Code) that further specifies the cause of the error.

   This document defines in section 6.5 a new RSVP error code, the
   "Diff-Serv-aware TE Error" (see section 14.3.4). The Error Values for
   the "Diff-Serv-aware TE Error" constitute a new name space to be
   managed by IANA.

   This document defines, in section 6.5, values 1 through 7 in that
   name space (see section 14.3.5).

   Future allocations of values in this name space are to be assigned by
   IANA using the "Specification Required" policy defined in
   [IANA-CONS].

14.3.Assignments made in this Document

14.3.1.Bandwidth Constraints sub-TLV for OSPF version 2

   [OSPF-TE] creates a name space for the sub-TLV types within the "Link
   TLV" of the Traffic Engineering LSA and rules for management of this
   name space by IANA.

   This document defines in section 5.1 a new sub-TLV, the "Bandwidth
   Constraints" sub-TLV, for the OSPF "Link" TLV. In accordance with the
   IANA considerations provided in [OSPF-TE], a sub-TLV type in the
   range 10 to 32767 was requested and the value TBD has been assigned
   by IANA for the "Bandwidth Constraints" sub-TLV.

   <IANA-note> To be removed by the RFC editor at the time of
   publication:
   When the sub-TLV Type is assigned by IANA replace "TBD" above by the
   assigned value.
   </IANA-note>

14.3.2.Bandwidth Constraints sub-TLV for ISIS

   [ISIS-TE] creates a name space for the sub-TLV types within the ISIS
   "Extended IS Reachability" TLV and rules for management of this name
   space by IANA.

   This document defines in section 5.1 a new sub-TLV, the "Bandwidth
   Constraints" sub-TLV, for the ISIS "Extended IS Reachability" TLV. In
   accordance with the IANA considerations provided in [ISIS-TE], a
   sub-TLV type was requested and the value TBD has been assigned by
   IANA for the "Bandwidth Constraints" sub-TLV.




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   <IANA-note> To be removed by the RFC editor at the time of
   publication:
   When the sub-TLV Type is assigned by IANA replace "TBD" above by the
   assigned value.
   </IANA-note>

14.3.3.CLASSTYPE object for RSVP

   [RSVP] defines the Class Number name space for RSVP object which is
   managed by IANA. Currently allocated Class Numbers are listed at
   "http://www.iana.org/assignments/rsvp-parameters"

   This document defines in section 6.2.1 a new RSVP object, the
   CLASSTYPE object. IANA was requested to assign a Class Number for
   this RSVP object from the range defined in section 3.10 of [RSVP] for
   those objects which, if not understood, cause the entire RSVP message
   to be rejected with an error code of "Unknown Object Class". Such
   objects are identified by a zero in the most significant bit of the
   class number (i.e.
   Class-Num = 0bbbbbbb).
   IANA assigned Class-Number TBD to the CLASSTYPE object. C_Type 1 is
   defined in this document for the CLASSTYPE object.

   <IANA-note> To be removed by the RFC editor at the time of
   publication:
   When the RSVP Class-Num is assigned by IANA replace "TBD" above by
   the assigned value.
   </IANA-note>

14.3.4."Diff-Serv-aware TE Error" Error Code

   [RSVP] defines the Error Code name space and rules for management of
   this name space by IANA. Currently allocated Error Codes are listed
   at "http://www.iana.org/assignments/rsvp-parameters"

   This document defines in section 6.5 a new RSVP Error Code, the
   "Diff-Serv-aware TE Error". In accordance with the IANA
   considerations provided in [RSVP], Error Code TBD was assigned by
   IANA to the "Diff-Serv-aware TE Error".

   <IANA-note> To be removed by the RFC editor at the time of
   publication:
   When the RSVP Class-Num is assigned by IANA replace "TBD" above by
   the assigned value.
   </IANA-note>

14.3.5.Error Values for "Diff-Serv-aware TE Error"

   An Error Code is an 8-bit quantity defined in [RSVP] that appears in
   an ERROR_SPEC object to broadly define an error condition.  With each


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   Error Code there may be a 16-bit Error Value (which depends on the
   Error Code) that further specifies the cause of the error.

   This document defines in section 6.5 a new RSVP error code, the
   "Diff-Serv-aware TE Error" (see section 14.3.4). The Error Values for
   the "Diff-Serv-aware TE Error" constitute a new name space to be
   managed by IANA.

   This document defines, in section 6.5, the following Error Values for
   the "Diff-Serv-aware TE Error":

     Value    Error

       1 Unexpected CLASSTYPE object
       2 Unsupported Class-Type
       3 Invalid Class-Type value
       4 Class-Type and setup priority do not form a configured
               TE-Class
       5 Class-Type and holding priority do not form a
               configured TE-Class
       6 Class-Type and setup priority do not form a configured
               TE-Class AND Class-Type and holding priority do not form
                a configured TE-Class
       7 Inconsistency between signaled PSC and signaled
               Class-Type
        8 Inconsistency between signaled PHBs and signaled
                Class-Type

   See section 14.2 for allocation of other values in that name space.


15.   Intellectual Property Considerations

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights. Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.




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                   Protocols for Diffserv-aware TE      December 2004

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard. Please address the information to the IETF at
   ietf-ipr@ietf.org.


16.Normative References

   [DSTE-REQ] Le Faucheur et al, Requirements for support of Diff-Serv-
   aware MPLS Traffic Engineering, RFC3564.

   [MPLS-ARCH] Rosen et al., "Multiprotocol Label Switching
   Architecture", RFC3031.

   [DIFF-ARCH] Blake et al., "An Architecture for Differentiated
   Services", RFC2475.

   [TE-REQ] Awduche et al., "Requirements for Traffic Engineering Over
   MPLS", RFC2702.

   [OSPF-TE] Katz et al., "Traffic Engineering (TE) Extensions to OSPF
   Version 2", RFC3630.

   [ISIS-TE] Smit, Li, "Intermediate System to Intermediate System
   (IS-IS) extensions for Traffic Engineering (TE)", RFC 3784.

   [RSVP-TE] Awduche et al, "RSVP-TE: Extensions to RSVP for LSP
   Tunnels", RFC 3209.

   [RSVP] Braden et al, "Resource ReSerVation Protocol (RSVP) - Version
   1 Functional Specification", RFC 2205.

   [DIFF-MPLS] Le Faucheur et al, "MPLS Support of Diff-Serv", RFC3270.

   [RFC2119] S. Bradner, Key words for use in RFCs to Indicate
   Requirement Levels, RFC2119.

   [IANA-CONS], T. Narten et al, "Guidelines for Writing an IANA
   Considerations Section in RFCs", RFC2434.


17.Informative References

   [DSTE-RDM] Le Faucheur et al., "Russian Dolls Bandwidth Constraints
   Model for DS-TE", draft-ietf-tewg-diff-te-russian-07.txt, work in
   progress.





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   [DSTE-MAM] Le Faucheur, Lai, "Maximum Allocation Bandwidth
   Constraints Model for DS-TE", draft-ietf-tewg-diff-te-mam-04.txt,
   work in progress .

   [DSTE-MAR] Ash, "Max Allocation with Reservation Bandwidth
   Constraints Model for MPLS/DiffServ TE & Performance Comparisons",
   draft-ietf-tewg-diff-te-mar-03.txt, work in progress .

   [GMPLS-SIG] Berger et. al., "Generalized Multi-Protocol Label
   Switching (GMPLS) Signaling Functional Description", RFC3471

   [GMPLS-ROUTE] Kompella et. al., "Routing Extensions in Support of
   Generalized MPLS", draft-ietf-ccamp-gmpls-routing-09.txt, work in
   progress.

   [BUNDLE] Kompella, Rekhter, Berger, "Link Bundling in MPLS Traffic
   Engineering", draft-ietf-mpls-bundle-04.txt, work in progress.

   [HIERARCHY] Kompella, Rekhter, "LSP Hierarchy with Generalized MPLS
   TE", draft-ietf-mpls-lsp-hierarchy-08.txt, work in progress.

   [REROUTE] Pan et. al., "Fast Reroute Extensions to RSVP-TE for LSP
   Tunnels", draft-ietf-mpls-rsvp-lsp-fastreroute-07.txt, work in
   progress.


18.Editor's Address:

   Francois Le Faucheur
   Cisco Systems, Inc.
   Village d'Entreprise Green Side - Batiment T3
   400, Avenue de Roumanille
   06410 Biot-Sophia Antipolis
   France
   Phone: +33 4 97 23 26 19
   Email: flefauch@cisco.com


19.Full Copyright Statement

   Copyright (C) The Internet Society (2004).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other


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                   Protocols for Diffserv-aware TE      December 2004

   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Appendix A - Prediction for Multiple Path Computation

   There are situations where a Head-End needs to compute paths for
   multiple LSPs over a short period of time. There are potential
   advantages for the Head-end in trying to predict the impact of the n-
   th LSP on the unreserved bandwidth when computing the path for the
   (n+1)-th LSP, before receiving updated IGP information. One example
   would be to perform better load-distribution of the multiple LSPs
   across multiple paths. Another example would be to avoid CAC
   rejection when the (n+1)-th LSP would no longer fit on a link after
   establishment of the n-th LSP. While there are also a number of
   conceivable scenarios where doing such predictions might result in a
   worse situation, it is more likely to improve the situation. As a
   matter of fact, a number of network administrators have elected to
   use such predictions when deploying existing TE.

   Such predictions are local matters, are optional and are outside the
   scope of this specification.

   Where such predictions are not used, the optional Bandwidth
   Constraint sub-TLV and the optional Maximum Reservable Bandwidth sub-
   TLV need not be advertised in IGP for the purpose of path computation
   since the information contained in the Unreserved Bw sub-TLV is all
   that is required by Head-Ends to perform Constraint Based Routing.

   Where such predictions are used on Head-Ends, the optional Bandwidth
   Constraints sub-TLV and the optional Maximum Reservable Bandwidth
   sub-TLV MAY be advertised in IGP. This is in order for the Head-ends
   to predict as accurately as possible how an LSP affects unreserved
   bandwidth values for subsequent LSPs.

   Remembering that actual admission control algorithms are left for
   vendor differentiation, we observe that predictions can only be


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   performed effectively when the Head-end LSR predictions are based on
   the same (or a very close) admission control algorithm as used by
   other LSRs.


Appendix B - Solution Evaluation

1.   Satisfying Detailed Requirements

   This DS-TE Solution addresses all the scenarios presented in [DSTE-
   REQ].

   It also satisfies all the detailed requirements presented in [DSTE-
   REQ].

   The objective set out in the last paragraph of section "4.7
   overbooking" of [DSTE-REQ] is only partially addressed by this DS-TE
   solution. Through support of the "LSP Size Overbooking" and "Link
   Size Overbooking" methods, this DS-TE solution effectively allows CTs
   to have different overbooking ratios and simultaneously allows
   overbooking to be tweaked differently (collectively across all CTs)
   on different links. But, in a general sense, it does not allow the
   effective overbooking ratio of every CT to be tweaked differently in
   different parts of the network independently of other CTs, while
   maintaining accurate bandwidth accounting of how different CTs
   mutually affect each other through shared Bandwidth Constraints (such
   as the Maximum Reservable Bandwidth).

2.   Flexibility

   This DS-TE solution supports 8 CTs. It is entirely flexible as to how
   Traffic Trunks are grouped together into a CT.

3.   Extendibility

   A maximum of 8 CTs is considered by the authors of this document as
   more than comfortable. A maximum of 8 TE-classes is considered by the
   authors of this document as sufficient. However, this solution could
   be extended to support more CTs or more TE-classes if deemed
   necessary in the future; This would necessitate additional IGP
   extensions beyond those specified in this document.

   Although the prime objective of this solution is support of Diff-
   Serv-aware Traffic Engineering, its mechanisms are not tightly
   coupled with Diff-Serv. This makes the solution amenable, or more
   easily extendable, for support of potential other future Traffic
   Engineering applications.

4.   Scalability



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   This DS-TE solution is expected to have a very small scalability
   impact compared to existing TE.

   From an IGP viewpoint, the amount of mandatory information to be
   advertised is identical to existing TE. One additional sub-TLV has
   been specified, but its use is optional and it only contains a
   limited amount of static information (at most 8 Bandwidth
   Constraints).

   We expect no noticeable impact on LSP Path computation since, as with
   existing TE, this solution only requires CSPF to consider a single
   unreserved bandwidth value for any given LSP.

   From a signaling viewpoint we expect no significant impact due to
   this solution since it only requires processing of one additional
   information (the Class-Type) and does not significantly increase the
   likelihood of CAC rejection. Note that DS-TE has some inherent impact
   on LSP signaling in the sense that it assumes that different classes
   of traffic are split over different LSPs so that more LSPs need to be
   signaled; but this is due to the DS-TE concept itself and not to the
   actual DS-TE solution discussed here.

5.   Backward Compatibility/Migration

   This solution is expected to allow smooth migration from existing TE
   to DS-TE. This is because existing TE can be supported as a
   particular configuration of DS-TE. This means that an "upgraded" LSR
   with a DS-TE implementation can directly interwork with an "old" LSR
   supporting existing TE only.

   This solution is expected to allow smooth migration when increasing
   the number of CTs actually deployed since it only requires
   configuration changes. However, these changes need to be performed in
   a coordinated manner across the DS-TE domain.


Appendix C - Interoperability with non DS-TE capable LSRs

   This DSTE solution allows operations in a hybrid network where some
   LSRs are DS-TE capable while some LSRs are not DS-TE capable, which
   may occur during migration phases. This Appendix discusses the
   constraints and operations in such hybrid networks.

   We refer to the set of DS-TE capable LSRs as the DS-TE domain. We
   refer to the set of non DS-TE capable (but TE capable) LSRs as the
   TE-domain.

   Hybrid operations requires that the TE-class mapping in the DS-TE
   domain is configured so that:



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        - a TE-class exist for CT0 for every preemption priority
          actually used in the TE domain
        - the index in the TE-class mapping for each of these TE-
          classes is equal to the preemption priority.

   For example, imagine the TE domain uses preemption 2 and 3. Then, DS-
   TE can be deployed in the same network by including the following TE-
   classes in the TE-class mapping:
           i   <--->       CT      preemption
         ====================================
           2               CT0     2
           3               CT0     3

   Another way to look at this is to say that, the whole TE-class
   mapping does not have to be consistent with the TE domain, but the
   subset of this TE-Class mapping applicable to CT0 has to effectively
   be consistent with the TE domain.

   Hybrid operations also requires that:
        - non DS-TE capable LSRs be configured to advertise the Maximum
          Reservable Bandwidth
        - DS-TE capable LSRs be configured to advertise Bandwidth
          Constraints (using the Max Reservable Bandwidth sub-TLV as
          well as the Bandwidth Constraints sub-TLV, as specified in
          section 5.1 above).
   This allows DS-TE capable LSRs to unambiguously identify non DS-TE
   capable LSRs.

   Finally hybrid operations require that non DS-TE capable LSRs be able
   to accept Unreserved Bw sub-TLVs containing non decreasing bandwidth
   values (ie with Unreserved [p] < Unreserved [q] with p <q).

   In such hybrid networks :
        - CT0 LSPs can be established by both DS-TE capable LSRs and
          non-DSTE capable LSRs
        - CT0 LSPs can transit via (or terminate at) both DS-TE capable
          LSRs and non-DSTE capable LSRs
        - LSPs from other CTs can only be established by DS-TE capable
          LSRs
        - LSPs from other CTs can only transit via (or terminate at)
          DS-TE capable LSRs


   Let us consider, the following example to illustrate operations:

   LSR0--------LSR1----------LSR2
        Link01       Link12

   Where:
      LSR0 is a non-DS-TE capable LSR


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      LSR1 and LSR2 are DS-TE capable LSRs

   Let"s assume again that preemption 2 and 3 are used in the TE-domain
   and that the following TE-class mapping is configured on LSR1 and
   LSR2:
           i   <--->       CT      preemption
         ====================================
           0               CT1     0
           1               CT1     1
           2               CT0     2
           3               CT0     3
      rest          unused

   LSR0 is configured with a Max Reservable bandwidth=m01 for Link01.
   LSR1 is configured with a BC0=x0 a BC1=x1(possibly=0), and a Max
   Reservable Bandwidth=m10(possibly=m01) for Link01.

   LSR0 will advertise in IGP for Link01:
        - Max Reservable Bw sub-TLV = <m01>
        - Unreserved Bw sub-TLV =
          <CT0/0,CT0/1,CT0/2,CT0/3,CT0/4,CT0/5,CT0/6,CT0/7>

   On receipt of such advertisement, LSR1 will:
        - understand that LSR0 is not DS-TE capable because it
          advertised a Max Reservable Bw sub-TLV and no Bandwidth
          Constraints sub-TLV
        - conclude that only CT0 LSPs can transit via LSR0 and that
          only the values CT0/2 and CT0/3 are meaningful in the
          Unreserved Bw sub-TLV. LSR1 may effectively behave as if the
          six other values contained in the Unreserved Bw sub-TLV were
          set to zero.

   LSR1 will advertise in IGP for Link01:
        - Max Reservable Bw sub-TLV = <m10>
        - Bandwidth Constraints sub-TLV = <BC Model ID, x0,x1>
        - Unreserved Bw sub-TLV = <CT1/0,CT1/1,CT0/2,CT0/3,0,0,0,0>

   On receipt of such advertisement, LSR0 will:
        - Ignore the Bandwidth Constraints sub-TLV (unrecognized)
        - Correctly process CT0/2 and CT0/3 in the Unreserved Bw sub-
          TLV and use these values for CTO LSP establishment
        - Incorrectly believe that the other values contained in the
          Unreserved Bw sub-TLV relates to other preemption priorities
          for CT0, but will actually never use those since we assume
          that only preemption 2 and 3 are used in the TE domain.







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Disclaimer of Validity

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Copyright Statement

   Copyright (C) The Internet Society (2004).  This document is subject
   to the rights, licenses and restrictions contained in BCP 78, and
   except as set forth therein, the authors retain all their rights.


Acknowledgment

   Funding for the RFC Editor function is currently provided by the
   Internet Society.






























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