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Versions: 00 01 02 03 04 05 06 07 rfc4127                   Experimental
   TEWG
   Internet Draft                                  Francois Le Faucheur
                                                                 Editor
   draft-ietf-tewg-diff-te-russian-07.txt                Cisco Systems,
                                                                   Inc.
   Expires: June 2005                                     December 2004


             Russian Dolls Bandwidth Constraints Model for
                 Diff-Serv-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
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   This Internet-Draft will expire on June 13, 2005.


Copyright Notice

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


Abstract





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                    Russian Dolls Model for DS-TE       December 2005


   This document provides specification for one Bandwidth Constraints
   Model for Diff-Serv-aware MPLS Traffic Engineering, which is referred
   to as the Russian Dolls Model.

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...................................................2
   2. Contributing Authors...........................................3
   3. Definitions....................................................3
   4. Russian Dolls Model Definition.................................4
   5. Example Formulas for Computing "Unreserved TE-Class [i]" with
   Russian Dolls Model...............................................6
   6. Receiving both Maximum Reservable Bandwidth and Bandwidth
   Constraints sub-TLVs..............................................7
   7. Security Considerations........................................8
   8. Acknowledgments................................................8
   9. IANA Considerations............................................8
   10. Normative References..........................................8
   11. Informative References........................................9
   12. Intellectual Property Considerations.........................10
   13. Editor's Address:............................................10
   14. Full Copyright Statement.....................................10
   Appendix A - Addressing [DSTE-REQ] Scenarios.....................11
   Disclaimer of Validity...........................................12
   Copyright Statement..............................................13
   Acknowledgment...................................................13


1.Introduction

   [DSTE-REQ] presents the Service Providers requirements for support of
   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.

   [DSTE-REQ] also defines the concept of Bandwidth Constraints Model
   for DS-TE and states that "The DS-TE technical solution MUST specify
   at least one Bandwidth Constraints Model and MAY specify multiple
   Bandwidth Constraints Models."





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                    Russian Dolls Model for DS-TE       December 2005


   This document provides a detailed description of one particular
   Bandwidth Constraints Model for DS-TE which is introduced in [DSTE-
   REQ] and called the Russian Dolls Model (RDM).

   [DSTE-PROTO] specifies the IGP and RSVP-TE signaling extensions for
   support of DS-TE. These extensions support RDM.


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 11, 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
   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:

   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.


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   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.

   A number of recovery mechanisms under investigation or specification
   in the IETF take advantage of the concept of bandwidth sharing across
   particular sets of LSPs. "Shared Mesh Restoration" in [GMPLS-RECOV]
   and "Facility-based Computation Model" in [MPLS-BACKUP] are example
   mechanisms which increase bandwidth efficiency by sharing bandwidth
   across backup LSPs protecting against independent failures. To ensure
   that the notion of "Reserved (CTc)" introduced in [DSTE-REQ] is
   compatible with such a concept of bandwidth sharing across multiple
   LSPs, the wording of the "Reserved (CTc)" definition provided in
   [DSTE-REQ] is generalized into the following:

   Reserved (CTc): For a given Class-Type CTc ( 0 <= c <= MaxCT ) ,let
   us define "Reserved(CTc)" as the total amount of the bandwidth
   reserved by all the established LSPs which belong to CTc.

   With this generalization, the Russian Dolls Model definition provided
   in this document is compatible with Shared Mesh Restoration defined
   in [GMPLS-RECOV], so that DS-TE and Shared Mesh Protection can
   operate simultaneously, under the assumption that Shared Mesh
   Restoration operates independently within each DS-TE Class-Type and
   does not operate across Class-Types (for example back up
   LSPs protecting Primary LSPs of CTx need to also belong to CTx;
   Excess Traffic LSPs sharing bandwidth with Backup LSPs of CTx need to
   also belong to CTx).

   We also introduce the following definition:

   Reserved(CTb,q) : let us define "Reserved(CTb,q)" as the total amount
   of the bandwidth reserved by all the established LSPs which belong to
   CTb and have a holding priority of q. Note that if q and CTb do not
   form one of the 8 possible configured TE-Classes, then there can not
   be any established LSP which belong to CTb and have a holding
   priority of q, so in that case, Reserved(CTb,q)=0.


4.Russian Dolls Model Definition

   RDM is defined in the following manner:
             o Maximum Number of Bandwidth Constraints (MaxBC)=
               Maximum Number of Class-Types (MaxCT) = 8
             o for each value of b in the range 0 <= b <= (MaxCT - 1):


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                     SUM (Reserved (CTc)) <= BCb,
                     Where the SUM is across all values of c in the
                     range b <= c <= (MaxCT - 1)
            o BC0= Maximum Reservable Bandwidth, so that
                    SUM (Reserved(CTc)) <= Max-Reservable-Bw,
                     where the SUM is across all values of c in the
                     range  0 <= c <= (MaxCT - 1)

   A DS-TE LSR implementing RDM MUST support enforcement of Bandwidth
   Constraints in compliance with this definition.

   Both preemption within a Class-Type and across Class-Types is
   allowed.

   Where 8 Class-Types are active, the RDM Bandwidth Constraints can
   also be expressed in the following way:
        - All LSPs from CT7 use no more than BC7
        - All LSPs from CT6 and CT7 use no more than BC6
        - All LSPs from CT5, CT6 and CT7 use no more than BC5
        - etc.
        - All LSPs from CT0, CT1,... CT7 use no more than
          BC0 = "Maximum Reservable Bandwidth"

   Purely for illustration purposes, the diagram below represents the
   Russian Dolls Bandwidth Constraints Model in a pictorial manner when
   3 Class-Types are active:

   I------------------------------------------------------I
   I-------------------------------I                      I
   I--------------I                I                      I
   I    CT2       I    CT2+CT1     I      CT2+CT1+CT0     I
   I--------------I                I                      I
   I-------------------------------I                      I
   I------------------------------------------------------I

   I-----BC2------>
   I----------------------BC1------>
   I------------------------------BC0=Max Reservable Bw--->


   While simpler Bandwidth Constraints models or, conversely, more
   flexible/sophisticated Bandwidth Constraints models can be defined,
   the Russian Dolls Model is attractive in some DS-TE environments for
   the following reasons:
       - Although a little less intuitive than the Maximum Allocation
          Model (see[DSTE-MAM]), RDM is still a simple model to
          conceptualize.




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       - RDM can be used to simultaneously ensure bandwidth efficiency
          and protection against QoS degradation of all Class-Types,
          whether preemption is used or not.
       - RDM can be used in conjunction with preemption to
          simultaneously achieve isolation across Class-Types (so that
          each Class-Type is guaranteed its share of bandwidth no
          matter the level of contention by other classes), bandwidth
          efficiency and protection against QoS degradation of all
          Class-Types.
       - RDM only requires limited protocol extensions such as the
          ones defined in [DSTE-PROTO].

   RDM may not be attractive in some DS-TE environments for the
   following reasons:
       - if the usage of preemption is precluded for some
          administrative reason, while RDM can still ensure bandwidth
          efficiency and protection against QoS degradation of all CTs,
          RDM cannot guarantee isolation across Class-Types.

   Additional considerations on the properties of RDM can be found in
   [BC-CONS] and [BC-MODEL].

   As a simple example usage of the "Russian Dolls" Bandwidth
   Constraints Model, a network administrator using one CT for Voice
   (CT1) and one CT for data (CT0) might configure on a given link:
        - BC0 = Max-Reservable-Bw= 2.5 Gb/s (i.e. Voice + Data is
          limited to 2.5 Gb/s)
        - BC1= 1.5 Gb/s (i.e. Voice is limited to 1.5 Gb/s).


5.Example Formulas for Computing "Unreserved TE-Class [i]" with Russian
   Dolls Model

   As specified in [DSTE-PROTO], formulas for computing "Unreserved TE-
   Class [i]" MUST reflect all of the Bandwidth Constraints relevant to
   the CT associated with TE-Class[i], and thus, depend on the Bandwidth
   Constraints Model. Thus, a DS-TE LSR implementing RDM MUST reflect
   the RDM Bandwidth Constraints defined in section 4 above when
   computing "Unreserved TE-Class [i]".

   Keeping in mind, as explained in [DSTE-PROTO], that details of
   admission control algorithms as well as formulas for computing
   "Unreserved TE-Class [i]" are outside the scope of the IETF work, we
   provide in this section, for illustration purposes, an example of how
   values for the unreserved bandwidth for TE-Class[i] might be computed
   with RDM, assuming the basic admission control algorithm which simply
   deducts the exact bandwidth of any established LSP from all of the
   Bandwidth Constraints relevant to the CT associated with that LSP.



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   We assume that:
        TE-Class [i] <--> < CTc , preemption p>
   in the configured TE-Class mapping.

   For readability, formulas are first shown assuming only 3 CTs are
   active. The formulas are then extended to cover the cases where more
   CTs are used.

   If CTc = CT0, then "Unreserved TE-Class [i]" =
      [ BC0 - SUM ( Reserved(CTb,q) ) ] for q <= p and 0 <= b <= 2


   If CTc = CT1, then "Unreserved TE-Class [i]" =
      MIN  [
      [ BC1 - SUM ( Reserved(CTb,q) ) ] for q <= p and 1 <= b <= 2,
      [ BC0 - SUM ( Reserved(CTb,q) ) ] for q <= p and 0 <= b <= 2
             ]


   If CTc = CT2, then "Unreserved TE-Class [i]" =
      MIN  [
      [ BC2 - SUM ( Reserved(CTb,q) ) ] for q <= p and 2 <= b <= 2,
      [ BC1 - SUM ( Reserved(CTb,q) ) ] for q <= p and 1 <= b <= 2,
      [ BC0 - SUM ( Reserved(CTb,q) ) ] for q <= p and 0 <= b <= 2
             ]


   The formula can be generalized to 8 active CTs and expressed in a
   more compact way in the following:

     "Unreserved TE-Class [i]" =
      MIN  [
    [ BCc - SUM ( Reserved(CTb,q) ) ] for q <= p and c <= b <= 7,
    [ BC(c-1) - SUM ( Reserved(CTb,q) ) ] for q <= p and (c-1)<= b <= 7,
        . . .
    [ BC0 - SUM ( Reserved(CTb,q) ) ] for q <= p and 0 <= b <= 7,
           ]
      where:
        TE-Class [i] <--> < CTc , preemption p>
        in the configured TE-Class mapping.


6.Receiving both Maximum Reservable Bandwidth and Bandwidth Constraints
   sub-TLVs

   [DSTE-PROTO] states that
   " 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."


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   With RDM, BC0 is equal to the Maximum Reservable Bandwidth since they
   both represent the aggregate constraint across all Class-Types. Thus,
   a DS-TE LSR receiving both the "Maximum Reservable Bw" sub-TLV and
   the new "Bandwidth Constraints" sub-TLV (which contains BC0) for a
   given link where the RDM model is used, MAY ignore the "Maximum
   Reservable Bw" sub-TLV.


7.Security Considerations

   Security considerations related to the use of DS-TE are discussed in
   [DSTE-PROTO]. Those apply independently of the Bandwidth Constraints
   Model, including RDM specified in this document.


8.Acknowledgments

   We thank Martin Tatham for his key contribution in this work. Tatiana
   Renko is also warmly thanked for her instantiation of the Russian
   Doll.


9.IANA Considerations

   [DSTE-PROTO] defines a new name space for "Bandwidth Constraints
   Model Id". The guidelines for allocation of values in that name space
   are detailed in section 14.1 of [DSTE-PROTO]. In accordance with
   these guidelines, IANA was requested to assign a Bandwidth
   Constraints Model Id for RDM from the range 0-127 (which is to be
   managed as per the "Specification Required" policy defined in [IANA-
   CONS]).

   Bandwidth Constraints Model Id = TBD was allocated by IANA to RDM.

   <IANA-note> To be removed by the RFC editor at the time of
   publication
        We request IANA to assign value 0 for the RDM model.
      Once the value has been assigned, please replace "TBD" above
        by the assigned value.
   </IANA-note>


10.Normative References

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




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   [DSTE-PROTO] Le Faucheur et al, Protocol extensions for support of
   Diff-Serv-aware MPLS Traffic Engineering, draft-ietf-tewg-diff-te-
   proto-08.txt, work in progress.

   [RFC2119] S. Bradner, Key words for use in RFCs to Indicate
   Requirement Levels, RFC2119, March 1997.

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


11.Informative References

   [BC-CONS] Le Faucheur, "Considerations on Bandwidth Constraints Model
   for DS-TE", draft-lefaucheur-tewg-russian-dolls-00.txt, June 2002.

   [BC-MODEL] Lai, "Bandwidth Constraints Models for DS-TE",
   draft-wlai-tewg-bcmodel-03.txt, work in progress.

   [DSTE-MAM] Le Faucheur, Lai, "Maximum Allocation Bandwidth
   Constraints Model for Diff-Serv-aware MPLS Traffic Engineering",
   draft-ietf-tewg-diff-tet-mam-04.txt, work in progress.

   [DSTE-MAR] Ash, "Max Allocation with Reservation Bandwidth
   Constraints Model for MPLS/DiffServ TE & Performance Comparisons",
   work in progress.

   [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.

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

   [GMPLS-RECOV] Lang et al, "Generalized MPLS Recovery Functional
   Specification", draft-ietf-ccamp-gmpls-recovery-functional-02.txt,
   work in progress.

   [MPLS-BACKUP] Vasseur et al, "MPLS Traffic Engineering Fast reroute:
   bypass tunnel path computation for bandwidth protection", draft-
   vasseur-mpls-backup-computation-02.txt, work in progress.






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12.   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.

   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.


13.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


14.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



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                    Russian Dolls Model for DS-TE       December 2005


   the copyright notice or references to the Internet Society or other
   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 - Addressing [DSTE-REQ] Scenarios

   This Appendix provides examples of how the Russian Dolls Bandwidth
   Constraints Model can be used to support each of the scenarios
   described in [DSTE-REQ].

1.   Scenario 1: Limiting Amount of Voice

   By configuring on every link:
        - Bandwidth Constraint 1 (for CT1=Voice) = "certain percentage"
          of link capacity
        - BC0 (for CT1=Voice + CT0= Data) =  link capacity

   By configuring:
        - every CT1/Voice TE-LSP with preemption =0
        - every CT0/Data TE-LSP with preemption =1

   DS-TE with the Russian Dolls Model will address all the requirements:
        - amount of Voice traffic limited to desired percentage on
          every link
        - data traffic capable of using all remaining link capacity
        - voice traffic capable of preempting other traffic

2.   Scenario 2: Maintain Relative Proportion of Traffic Classes

   By configuring on every link:
        - BC2 (for CT2) = e.g. 45%
        - BC1 (for CT1+CT2) = e.g. 80%
        - BC0 (for CT0+CT1+CT2) = e.g.100%




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   DS-TE with the Russian Dolls Model will ensure that the amount of
   traffic of each Class Type established on a link is within acceptable
   levels as compared to the resources allocated to the corresponding
   Diff-Serv PHBs regardless of which order the LSPs are routed in,
   regardless of which preemption priorities are used by which LSPs and
   regardless of failure situations.

   By also configuring:
        - every CT2/Voice TE-LSP with preemption =0
        - every CT1/Premium Data TE-LSP with preemption =1
        - every CT0/Best-Effort TE-LSP with preemption =2

   DS-TE with the Russian Dolls Model will also ensure that:
        - CT2 Voice LSPs always have first preemption priority in order
          to use the CT2 capacity
        - CT1 Premium Data LSPs always have second preemption priority
          in order to use the CT1 capacity
        - Best-Effort can use up to link capacity whatever is left by
          CT2 and CT1.

   Optional automatic adjustment of Diff-Serv scheduling configuration
   could be used for maintaining very strict relationship between amount
   of established traffic of each Class Type and corresponding Diff-Serv
   resources.

3.   Scenario 3: Guaranteed Bandwidth Services

   By configuring on every link:
        - BC1 (for CT1) = "given" percentage of link bandwidth
          (appropriate to achieve the Guaranteed Bandwidth service's
          QoS objectives)
        - BC0 (for CT0+CT1) = 100% of link bandwidth

   DS-TE with the Russian Dolls Model will ensure that the amount of
   Guaranteed Bandwidth Traffic established on every link remains below
   the given percentage so that it will always meet its QoS objectives.
   At the same time it will allow traffic engineering of the rest of the
   traffic such that links can be filled up.


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.


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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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