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                                                    Francois Le Faucheur
                                                        Thomas D. Nadeau
                                                     Cisco Systems, Inc.

                                                             Angela Chiu
                                                         celion Networks

                                                        William Townsend
                                                          Tenor Networks

                                                          Darek Skalecki
                                                         Nortel Networks



IETF Internet Draft
Expires: August, 2001
Document: draft-ietf-isis-diff-te-00.txt         February, 2001


                           Extensions to ISIS
        for support of Diff-Serv-aware MPLS Traffic Engineering


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026. Internet-Drafts are
   Working documents of the Internet Engineering 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.


Abstract

   A companion document [DIFF-TE-REQTS] defines the requirements for
   support of Diff-Serv-aware MPLS Traffic Engineering on a per-Class-
   Type basis, as discussed in the Traffic Engineering Working Group
   Framework document [TEWG-FW].

   This document proposes corresponding extensions to ISIS for support
   of Traffic Engineering on a per-Class-Type basis.


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          ISIS Extensions for Diff-Serv Traffic Engineering   Feb 2001

   Two companion documents [DIFF-TE-EXT] [DIFF-TE-OSPF] propose
   corresponding extensions to RSVP and CR-LDP and to OSPF for support
   of Traffic Engineering on a per-Class-Type basis.


1.      Introduction

   As Diffserv becomes prominent in providing scalable multi-class of
   services in IP networks, performing traffic engineering at a per-
   class level instead of an aggregated level is needed in networks
   where fine optimisation of resources is sought in order to further
   enhance performance and efficiency. By mapping a traffic trunk in a
   given class on a separate LSP, it allows the traffic trunk to
   utilize resources available on both shortest path(s) and non-
   shortest paths and follow paths that meet constraints which are
   specific to the given class. It also allows each class to select the
   proper protection/restoration mechanism(s) that satisfy its
   survivability requirements in a cost effective manner.

   Besides the set of parameters defined for the general aggregate TE
   [TE-REQ], a new set of per-class parameters needs to be provided at
   each LSR interface and propagated via extensions to the IGP
   (ISIS/OSPF)  [TEWG-FW]. Furthermore, the per-class parameters can be
   aggregated into per-Class-Type parameters. The main motivation for
   grouping a set of classes into a Class-Type is to improve the
   scalability of the IGP link state advertisements by propagating
   information on a per-Class-Type basis instead of on a per-class
   basis. This approach also has the benefit of allowing better
   bandwidth sharing between classes in the same Class-Type.

   A Class-Type [TEWG-FW] is defined as a set of classes that satisfy
   the following two conditions:

     1) Classes in the same Class-Type possess common aggregate maximum
       and minimum bandwidth requirements to guarantee the required
       performance level.

     2) There is no maximum or minimum bandwidth requirement to be
       enforced at the level of an individual class within the Class-
       Type. One can still implement some "priority" policies for
       classes within the same Class-Type in terms of accessing the
       Class-Type bandwidth (e.g. via the use of preemption
       priorities).

   An example of Class-Type comprising multiple Diff-Serv classes is a
   low-loss Class-Type that includes both AF1-based and AF2-based
   Ordering Aggregates.

   Note that with per Class-Type TE, Constraint-Based Routing is
   performed with bandwidth constraints on a per Class-Type basis but
   LSPs may carry a single Diff-Serv class (Ordered Aggregate) with
   Diff-Serv scheduling (i.e. PHB) performed separately for each class.

 Le Faucheur et. al                                                  2

          ISIS Extensions for Diff-Serv Traffic Engineering   Feb 2001


   In this document, we will only discuss "per Class-Type TE" because
   "per Class TE" can be viewed as a special case of per Class-Type TE
   (where each Class-Type is degenerated into a single Diff-Serv
   class).

   This document focuses on intra-domain operations. Inter-domain
   operations is for further study.

   A companion document [DIFF-TE-REQTS] defines the requirements for
   support of MPLS Traffic Engineering on a per-Class-Type basis. The
   following sections propose detailed extensions to ISIS that meet
   those requirements.

   Two companion documents [DIFF-TE-EXT] [DIFF-TE-OSPF] propose
   corresponding extensions to RSVP and CR-LDP and to OSPF for support
   of Traffic Engineering on a per-Class-Type basis.


2.      ISIS Extensions

   In this section we describe extensions to IS-IS for support of Diff-
   Serv Traffic Engineering on a per-Class-Type basis which meet the
   requirements defined in [DIFF-TE-REQTS]. These extensions are in
   addition to the extensions required to support (aggregate) MPLS
   Traffic Engineering defined in [ISIS-TE].

2.1.    Existing TE sub-TLVs

   [ISIS-TE] defines new extended TLVs for support of (aggregate)
   Traffic Engineering. One of these extended TLV is referred to as the
   extended IS reachability TLV (TLV type 22). This TLV contains a
   number of new sub-TLVs.

   In this document we refer to the sub-TLV 10 (Maximum reservable link
   bandwidth) of the extended IS reachability TLV (as defined in [ISIS-
   TE]) as the "Maximum Reservable Aggregate Bandwidth".

   We also refer to the sub-TLV 11 (unreserved bandwidth) of the
   extended IS reachability TLV (as defined in [ISIS-TE]) as the
   "Unreserved Bandwidth for Class-Type 0".

2.2.    New Sub-TLVs

   The following additional sub-TLVs are defined for the extended IS
   reachability TLV (sub-TLV numbers to be allocated):

     TBD1 - Unreserved bandwidth for Class-Type 1
     TBD2 - Unreserved bandwidth for Class-Type 2
     TBD3 - Unreserved bandwidth for Class-Type 3

   Each sub-TLV may occur only once. Unrecognized types are ignored.

 Le Faucheur et. al                                                  3

          ISIS Extensions for Diff-Serv Traffic Engineering   Feb 2001


   The additional sub-TLVs defined above are optional so that they may
   or may not be included in the extended IS reachability TLV.

   The extended IS reachability TLV may include the sub-TLVs for any
   subset of the three additional Class-Types. In other words, the IS
   reachability TLV may contain none of the three sub-TLVs defined
   above, any one of those, any two of those, or the three sub-TLVs.

   As discussed in [DIFF-TE-REQTS], where a Class-Type is not
   effectively used in a network, it is recommended that the
   corresponding sub-TLV is not included in the IS reachability TLV.
   Therefore, the Class-Types to be advertised in ISIS should be
   configurable. For instance, a Network Administrator may elect to use
   Diff-Serv Traffic Engineering in order to compute separate routes
   for data traffic and voice traffic (and apply different bandwidth
   constraints to the route computation for those). In that case, the
   IGP would be configured to only advertise the sub-TLV for one
   additional Class-Type (i.e. the extended IS reachability TLV would
   contain sub-TLV 10 for the Maximum Reservable Aggregate Bandwidth,
   sub-TLV 11 for the Unreserved Bandwidth for Class-Type 0 and sub-TLV
   TBD1 for Unreserved Bandwidth for Class-Type 1).

   An LSR which supports Class-Type N and receiving an extended IS
   reachability TLV without the sub-TLV corresponding to Class-Type N,
   must interpret this as meaning that the corresponding link does not
   support Class-Type N. For Constraint Based Routing purposes, the LSR
   may consider this equivalent to the case where the extended IS
   reachability TLV contains an Unreserved Bandwidth Class-Type N sub-
   TLV with bandwidth values set to zero.

   An LSR which does not support Class-Type N and which receives an
   extended IS reachability TLV containing the sub-TLV corresponding to
   Class-Type N, must ignore this sub-TLV. However, the IS reachability
   TLV must be flooded transparently, so that the sub-TLV for Class-
   Type N is kept in the IS reachability TLV when reflooded by this
   LSR.

2.3.    Sub-TLV Details

   The Unreserved Bandwidth for Class-Type N (N= 1,2,3) sub-TLVs
   specifies the amount of bandwidth not yet reserved for Class-Type N
   at each of the eight preemption priority levels. Each value will be
   less than, or equal to, the Maximum Reservable Bandwidth for Class-
   Type N.

   When the bandwidth value for preemption Z (Z > 0) is identical to
   the bandwidth value for preemption Z-1, the bandwidth value for
   preemption Z is not explicitly repeated in the sub-TLV. Rather, the
   fact that it is identical to the value of preemption Z-1, is encoded
   in a "repetition octet".


 Le Faucheur et. al                                                  4

          ISIS Extensions for Diff-Serv Traffic Engineering   Feb 2001

   Thus, the sub-TLV comprises:

        - P (1<=P<=8) bandwidth values. These values correspond to the
   bandwidth that can be reserved with a holding priority of 0 through
   7, arranged in increasing order with priority 0 occurring at the
   start of the sub-TLV, and priority 7 towards the end of the sub-TLV,
   but omitting all repeated values. The units are bytes per second and
   the values are encoded in IEEE floating point format.

        - a "repetition octet" where each bit is referred to as bitZ ,
   0 <= Z < 8, and is defined to have the following meaning:
             * if bitZ = 0 then "Unreserved Bandwidth" for preemption
        level Z is explicitely included in the sub-TLV,
             * if bitZ = 1 then "Unreserved Bandwidth" for preemption
        level Z is not explicitely included in the sub-TLV but is
        defined to be equal to "Unreserved Bandwidth" for preemption
        level Z-1.

   Note that the highest preemption level (level 0) is always
   advertised and the first bit (Bit0) in the "repetition octet" is
   always set to 0.

   [Editor's note: should the "repetition octet" be moved before the
   bandwidth values?]

   The Unreserved Bandwidth for Class-Type N sub-TLV is TLV type
   (TBDN). Its length is (P*4 +1), where 1<=P<=8 and where P is the
   number of non-equal bandwidth values across all preemption levels
   for that Class-Type.

   For example, when a link supports LSPs of preemption levels 2 and 4
   only (for a particular Class-Type) with "Unreserved Bandwidth" (for
   the particular Class-Type) on that link for preemption levels 0, 2,
   and 4 currently of 10Mb/s, 5Mb/s and 3Mb/s, respectively, then
   "Unreserved Bandwidth" (for the particular Class-Type) for
   preemption levels 0, 2, and 4 of 10Mb/s, 5Mb/s and 3Mb/s,
   respectively, are explicitly advertised for that link as well as
   "repetition octet" of 01010111 in binary form. The sub-TLV length is
   13.


3.      Security Considerations

   This document raises no new security issues for IS-IS. The security
   mechanisms already proposed for ISIS may be used.


4.      Acknowledgments

   This document has benefited from discussions with Carol Iturralde .



 Le Faucheur et. al                                                  5

          ISIS Extensions for Diff-Serv Traffic Engineering   Feb 2001

References

   [TE-REQ] Awduche et al, Requirements for Traffic Engineering over
   MPLS, RFC2702, September 1999.

   [TEWG-FW] Awduche et al, A Framework for Internet Traffic
   Engineering, draft-ietf-tewg-framework-02.txt, July 2000.

   [DIFF-TE-REQTS] Le Faucheur et al, Requirements for support of
   Diff-Serv-aware MPLS Traffic Engineering, draft-ietf-tewg-diff-te-
   reqts-00.txt, February 2001.

   [DIFF-TE-OSPF] Le Faucheur et al,  Extension to OSPF for support of
   Diff-Serv-aware MPLS Traffic Engineering, draft-ietf-ospf-diff-te-
   00.txt, February 2001.

   [DIFF-TE-EXT] Le Faucheur et al,  Extension to RSVP and CR-LDP for
   support of Diff-Serv-aware MPLS Traffic Engineering, draft-ietf-
   mpls-diff-te-ext-01.txt, February 2001.

   [ISIS-TE] Smit, Li, IS-IS extensions for Traffic Engineering, draft-
   ietf-isis-traffic-02.txt, September 2000.


Authors' Address:

   Francois Le Faucheur
   Cisco Systems, Inc.
   Petra B - Les Lucioles - 291, rue Albert Caquot - 06560 Valbonne -
   France
   Phone: +33 4 92 96 75 64
   Email: flefauch@cisco.com

   Angela Chiu
   Celion Networks
   1 Sheila Drive, Suite 2
   Tinton Falls, NJ 07724
   Phone: +1-732 747 9987
   Email: angela.chiu@celion.com


   William Townsend
   Tenor Networks
   100 Nagog Park
   Acton, MA 01720
   Phone: +1-978-264-4900
   Email: btownsend@tenornetworks.com

   Thomas D. Nadeau
   Cisco Systems, Inc.
   250 Apollo Drive
   Chelmsford, MA 01824

 Le Faucheur et. al                                                  6

          ISIS Extensions for Diff-Serv Traffic Engineering   Feb 2001

   Phone: +1-978-244-3051
   Email: tnadeau@cisco.com

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












































 Le Faucheur et. al                                                  7


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