TEWG Internet Draft Francois Le Faucheur Cisco Systems, Inc. Waisum Lai AT&T Labs draft-ietf-tewg-diff-te-mam-04.txt Expires: June 2005 December 2004 Maximum Allocation 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 Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference 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. The list of Internet-Draft Shadow Directories can be accessed at 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 Le Faucheur, et al. [Page 1] Maximum Allocation Model for DS-TE December 2004 This document provides specification for one Bandwidth Constraints Model for Diff-Serv-aware MPLS Traffic Engineering, which is referred to as the Maximum Allocation 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. Definitions....................................................3 3. Maximum Allocation Model Definition............................4 4. Example Formulas for Computing "Unreserved TE-Class [i]" with Maximum Allocation Model..........................................6 5. Security Considerations........................................7 6. Acknowledgments................................................7 7. Intellectual Property Considerations...........................7 8. IANA Considerations............................................8 9. Normative References...........................................8 10. Informative References........................................9 11. Authors' Address:.............................................9 12. Full Copyright Statement.....................................10 Appendix A - Addressing [DSTE-REQ] Scenarios.....................10 Disclaimer of Validity...........................................12 Copyright Statement..............................................12 Acknowledgment...................................................12 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." This document provides a detailed description of one particular Bandwidth Constraints Model for DS-TE which is introduced in [DSTE- REQ] and called the Maximum Allocation Model (MAM). Le Faucheur, et al. [Page 2] Maximum Allocation Model for DS-TE December 2004 [DSTE-PROTO] specifies the IGP and RSVP-TE signaling extensions for support of DS-TE. These extensions support MAM. 2.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. TE-Class: A pair of: i. a Class-Type ii. a preemption priority allowed for that Class-Type. This Formatted: Bullets and 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 Maximum Allocation 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: Le Faucheur, et al. [Page 3] Maximum Allocation Model for DS-TE December 2004 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. 3.Maximum Allocation Model Definition MAM 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 c in the range 0 <= c <= (MaxCT - 1): Reserved (CTc) <= BCc <= Max-Reservable-Bandwidth, o SUM (Reserved(CTc)) <= Max-Reservable-Bandwidth where the SUM is across all values of c in the range 0 <= c <= (MaxCT - 1) A DS-TE LSR implementing MAM MUST support enforcement of Bandwidth Constraints in compliance with this definition. To increase the degree of bandwidth sharing among the different CTs, the sum of Bandwidth Constraints may exceed the Maximum Reservable Bandwidth, so that the following relationship may hold true: o SUM (BCc) > Max-Reservable-Bandwidth, where the SUM is across all values of c in the range 0 <= c <= (MaxCT - 1) The sum of Bandwidth Constraints may also be equal to (or below) the Maximum Reservable Bandwidth. In that case, the Maximum Reservable Bandwidth does not actually constrain CT bandwidth reservations (in other words, the 3rd bullet item of the MAM definition above will never effectively come into play). This is because the 2nd bullet item of the MAM definition above implies that: SUM (reserved(CTc)) <= SUM (BCc) and we assume here that SUM (BCc) <= Maximum Reservable Bandwidth therefore, it will always be true that: SUM (Reserved(CTc)) <= Max-Reservable-Bandwidth. Both preemption within a Class-Type and across Class-Types is allowed. Le Faucheur, et al. [Page 4] Maximum Allocation Model for DS-TE December 2004 Where 8 Class-Types are active, the MAM Bandwidth Constraints can also be expressed in the following way: - All LSPs from CT7 use no more than BC7 - All LSPs from CT6 use no more than BC6 - All LSPs from CT5 use no more than BC5 - etc. - All LSPs from CT0 use no more than BC0 - All LSPs from all CTs collectively use no more than the Maximum Reservable Bandwidth Purely for illustration purposes, the diagram below represents MAM in a pictorial manner when 3 Class-Types are active: I----------------------------I <---BC0---> I I---------I I I I I I CT0 I I I I I I---------I I I I I I <-------BC1-------> I I-----------------I I I I I I CT1 I I I I I I-----------------I I I I I I <-----BC2-----> I I-------------I I I I I I CT2 I I I I I I-------------I I I I I CT0+CT1+CT2 I I I I----------------------------I <--Max Reservable Bandwidth--> (Note that, in this illustration, the sum BC0 + BC1 + BC2 exceeds the Max Reservable Bandwidth.) Le Faucheur, et al. [Page 5] Maximum Allocation Model for DS-TE December 2004 While more flexible/sophisticated Bandwidth Constraints Models can be defined (and are indeed defined - see [DSTE-RDM]), the Maximum Allocation Model is attractive in some DS-TE environments for the following reasons: - Network administrators generally find MAM simple and intuitive - MAM matches simple bandwidth control policies that Network Administrators may want to enforce such as setting individual Bandwidth Constraint for a given type of traffic (aka. Class- Type) and simultaneously limit the aggregate of reserved bandwidth across all types of traffic. - MAM can be used in a way which ensures isolation across Class-Types, whether preemption is used or not. - MAM can simultaneously achieve isolation, bandwidth efficiency and protection against QoS degradation of the premium CT. - MAM only requires limited protocol extensions such as the ones defined in [DSTE-PROTO]. MAM may not be attractive in some DS-TE environments because: - MAM cannot simultaneously achieve isolation, bandwidth efficiency and protection against QoS degradation of CTs other than the Premium CT. Additional considerations on the properties of MAM and its comparison with RDM can be found in [BC-CONS] and [BC-MODEL]. As a very simple example usage of the MAM Model, a network administrator using one CT for Voice (CT1) and one CT for Data (CT0) might configure on a given 2.5 Gb/s link: - BC0 = 2 Gb/s (i.e. Data is limited to 2 Gb/s) - BC1 = 1 Gb/s (i.e. Voice is limited to 1 Gb/s) - Maximum Reservable Bandwidth = 2.5 Gb/s (i.e. aggregate Data + Voice is limited to 2.5 Gb/s) 4.Example Formulas for Computing "Unreserved TE-Class [i]" with Maximum Allocation 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 MAM MUST reflect the MAM Bandwidth Constraints defined in section 3 above when computing "Unreserved TE-Class [i]". Le Faucheur, et al. [Page 6] Maximum Allocation Model for DS-TE December 2004 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 MAM, 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. Then: "Unreserved TE-Class [i]" = MIN [ [ BCc - SUM ( Reserved(CTc,q) ) ] for q <= p , [ Max-Res-Bw - SUM (Reserved(CTb,q)) ] for q <= p and 0 <= b <= 7, ] where: TE-Class [i] <--> < CTc , preemption p> in the configured TE-Class mapping. 5.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 MAM specified in this document. 6.Acknowledgments A lot of the material in this document has been derived from ongoing discussions within the TEWG work. This involved many people including Jerry Ash and Dimitry Haskin. 7. 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. Le Faucheur, et al. [Page 7] Maximum Allocation Model for DS-TE December 2004 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. 8.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 MAM 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 MAM. To be removed by the RFC editor at the time of publication We request IANA to assign value 1 for the MAM model. Once the value has been assigned, please replace "TBD" above by the assigned value. 9.Normative References [DSTE-REQ] Le Faucheur et al, Requirements for support of Diff-Serv- aware MPLS Traffic Engineering, RFC3564. [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 [IANA-CONS], T. Narten et al, "Guidelines for Writing an IANA Considerations Section in RFCs", RFC2434. Le Faucheur, et al. [Page 8] Maximum Allocation Model for DS-TE December 2004 10.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-RDM] Le Faucheur et al., "Russian Dolls Bandwidth Constraints Model for Diff-Serv-aware MPLS Traffic Engineering", draft-ietf-tewg-diff-te-russian-07.txt, work in progress. [OSPF-TE] Katz et al., "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC3630. [ISIS-TE] Smit et al., "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, May 2002. [DSTE-MAR] Ash, G., "Max Allocation with Reservation Bandwidth Constraints Model for MPLS/DiffServ TE & Performance Comparisons", Work In Progress. [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. 11.Authors' 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 Field Code Le Faucheur, et al. [Page 9] Maximum Allocation Model for DS-TE December 2004 Wai Sum Lai AT&T Labs 200 Laurel Avenue Middletown, New Jersey 07748, USA Phone: (732) 420-3712 Email: wlai@att.com 12.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 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 Maximum Allocation 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 Le Faucheur, et al. [Page 10] Maximum Allocation Model for DS-TE December 2004 - Bandwidth Constraint 0 (for CT0=Data) = link capacity (or a constraint specific to data traffic) - Max Reservable Bandwidth = link capacity By configuring: - every CT1/Voice TE-LSP with preemption =0 - every CT0/Data TE-LSP with preemption =1 DS-TE with the Maximum Allocation 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 (or up to its own specific constraint) - 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% of link capacity - BC1 (for CT1) = e.g. 35% of link capacity - BC0 (for CT0) = e.g.100% of link capacity - Max Reservable Bandwidth = link capacity DS-TE with the Maximum Allocation 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 Maximum Allocation 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. Le Faucheur, et al. [Page 11] Maximum Allocation Model for DS-TE December 2004 3. Scenario 3: Guaranteed Bandwidth Services By configuring on every link: - BC1 (for CT1) = "given" percentage of link bandwidth (appropriate to achieve the QoS objectives of the Guaranteed Bandwidth service) - BC0 (for CT0=Data) = link capacity (or a constraint specific to data traffic) - Max Reservable Bandwidth = link capacity DS-TE with the Maximum Allocation 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 (or limited to the specific constraint for such traffic). 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. Le Faucheur, et al. [Page 12]