Francois Le Faucheur
                                                                Liwen Wu
                                                             Bruce Davie
                                                           Cisco Systems

                                                          Shahram Davari
                                                         PMC-Sierra Inc.

                                                           Pasi Vaananen
                                                                   Nokia

                                                            Ram Krishnan
                                                        Nexabit Networks

                                                         Pierrick Cheval
                                                                 Alcatel

                                                           Juha Heinanen
                                                           Telia Finland

IETF Internet Draft
Expires: April, October, 2000
Document: draft-ietf-mpls-diff-ext-02.txt              October, 1999 draft-ietf-mpls-diff-ext-03.txt              February, 2000

                MPLS Support of Differentiated Services

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

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Abstract

   This document defines a flexible solution for support of
   Differentiated Services (Diff-Serv) over Multi-Protocol Label
   Switching (MPLS) networks.

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                      MPLS Support of Diff-Serv            February 00

   This solution allows the MPLS network administrator to flexibly
   define select how
   Diff-Serv Behavior Aggregates (BAs) are mapped onto Label Switched
   Paths so that he/she can best match the Diff-Serv, Traffic

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                      MPLS Support of Diff-Serv             October 99
   Engineering and Fast Restoration objectives within his/her
   particular network. For instance, this solution allows the network
   administrator to decide whether different sets of BAs are to be
   mapped onto the same LSP or mapped onto separate LSPs.

   This solution relies on combined use of two types of LSPs:
     - LSPs where both the Behavior Aggregate's scheduling treatment
   and its drop precedence are conveyed to the LSR in which can transport multiple Ordered Aggregates, so that
       the EXP field of the MPLS Shim Header. Header conveys to the LSR the PHB
       to be applied to the packet (covering both information about the
       packet's scheduling treatment and its drop precedence).
     - LSPs where which only transport a single Ordered Aggregate, so that
       the Behavior Aggregate's packet's scheduling treatment is inferred by the LSR
       exclusively from the packet's label value while the Behavior
   Aggregate's packet's
       drop precedence is indicated conveyed in the EXP field of the MPLS Shim
       Header or in the encapsulating link layer specific selective
       drop mechanism (ATM, Frame Relay, 802.1).

1. Introduction

   In an MPLS domain [MPLS_ARCH], when a stream of data traverses a
   common path, a Label Switched Path (LSP) can be established using
   MPLS signaling protocols. At the ingress Label Switch Router (LSR),
   each packet is assigned a label and is transmitted downstream. At
   each LSR along the LSP, the label is used to forward the packet to
   the next hop.

   In a Differentiated Service (Diff-Serv) domain [DIFF_ARCH] all the
   IP packets crossing a link and requiring the same Diff-Serv behavior
   are said to constitute a Behavior Aggregate (BA). At the ingress
   node of the Diff-Serv domain the packets are classified and marked
   with a Diff-Serv Code Point (DSCP) which corresponds to their
   Behavior Aggregate. At each transit node, the DSCP is used to select
   the Per Hop Behavior (PHB) that determines the scheduling treatment
   and, in some cases, drop probability for each packet.

   This document specifies a solution for supporting the Diff-Serv
   Behavior Aggregates whose corresponding PHBs are currently defined
   (in [DIFF_HEADER], [DIFF_AF], [DIFF_EF]) over an MPLS network. This
   solution also offers flexibility for easy support of PHBs that may
   be defined in the future.

   As mentioned in [DIFF_HEADER], "Service providers are not required
   to use the same node mechanisms or configurations to enable service
   differentiation within their networks, and are free to configure the
   node parameters in whatever way that is appropriate for their
   service offerings and traffic engineering objectives". Thus, the
   solution defined in this document gives Service Providers
   flexibility in selecting how Diff-Serv classes of service are Routed

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                      MPLS Support of Diff-Serv            February 00

   or Traffic Engineered within their domain (eg. separate classes of
   services supported via separate LSPs and Routed separately, all
   classes of service supported on the same LSP and Routed or Traffic
   Engineered together).
   Similarly, the solution gives Service Providers flexibility in how
   Diff-Serv classes of service can be protected via MPLS Fast
   Restoration (eg. some classes of service supported via LSPs which
   are protected via MPLS Fast Restoration

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                      MPLS Support of Diff-Serv             October 99 while some other classes of
   service are supported via LSPs which are not protected).

   Beside, the solution specified in this document achieves label space
   conservation and reduces the volume of label set-up/tear-down
   signaling where possible by only mandating set-up of resorting to multiple LSPs for a
   given Forwarding Equivalent Class (FEC) [MPLS_ARCH] when useful or
   required.

   This specification allows support of Differentiated Services for
   both IPv4 and IPv6 traffic transported over an MPLS network.

   This document only describes operations for unicast. Multicast
   support is for future study

1.1  Ordered Aggregate (OA) and PHB Scheduling Class (PSC)

   The Diff-Serv model defines [APPENDIX A] [DIFF_NEW] the set of Behavior
   Aggregates which share an ordering constraint to constitute an
   "Ordered Aggregate (OA)". It also defines the set of one or more
   PHBs that are applied to the this set of Behavior Aggregates forming a given OA,
   as to
   constitute a "PHB Scheduling Class (PSC)".

1.2 EXP-Inferred-PSC LSPs (E-LSP)

   Section 2 below specifies how a

   A single LSP can be used to support up to eight BAs, BAs of a given FEC,
   regardless of how many OAs these BAs span. With such LSPs, the packet DSCP value gets entirely mapped into the EXP
   field of the MPLS Shim Header [MPLS_ENCAPS] at is used by the Edge of LSR to
   determine the MPLS Diff-
   Serv Cloud (thus encoding both drop precedence and PSC/scheduling
   information). In other words, PHB to be applied to the packet. This includes both
   the PSC and Drop Precedence are
   conveyed in each labeled packet using the EXP field of the MPLS Shim
   Header [MPLS_ENCAPS]. drop preference.

   We refer to such LSPs as "EXP-inferred-PSC LSPs" (E-LSP). Detailed
   operations of E-LSPs are specified in section 2 below.

   E-LSPs have (E-LSP), since the following benefits:
        - label space is conserved by allowing "packing"
   PSC of up to eight
   BAs per label (eg. when there are fewer than eight BAs in the
   network, this method maintains the same label space as in a non
   Diff-Serv capable MPLS network).
        - label establishment signaling is then reduced since a single
   LSP is established for up to eight BAs (eg. when there are fewer
   than eight BAs in the network, packet transported on this method maintains the same level
   of signaling as in a non-Diff-Serv capable MPLS network)
        - the amount of forwarding state is also reduced, as a single
   forwarding entry can support up to 8 BAs.
        - operation of Diff-Serv MPLS over E-LSPs is analogous to
   operations of Diff-Serv in non-MPLS networks in LSP depends on the sense EXP field
   value for that the
   Diff-Serv packet.

   The mapping from EXP field to PHB is triggered exclusively by (ie to PSC and drop precedence)
   for a field given such LSP, is either explicitly encoded
   in every packet based signaled at label set-up
   or relying on locally configured PHB a pre-configured mapping. This is
   expected to facilitate migration from non-MPLS Diff-Serv to MPLS
   Diff-Serv

   Detailed operations in some networks.
        - some early implementations of E-LSPs exist today and
   experiments have confirmed proper operations and usefulness.

   E-LSPs only allow support of eight BAs or less.

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                      MPLS Support of Diff-Serv             October 99 below.

1.3 Label-Inferred-PSC Label-Only-Inferred-PSC LSPs (L-LSP)

   Section 3 below specifies how a

   A separate LSP can be established for
   each a single <FEC, OA> pair between two LSR neighbors. pair.

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                      MPLS Support of Diff-Serv            February 00

   With such LSPs, the PSC is explicitly signaled at label
   establishment time so that, after label establishment, the LSR can
   infer exclusively from the label value the PSC to be applied to a
   labeled packet. When the Shim Header is used, the Drop Precedence to
   be applied by the LSR to the labeled packet packet, is conveyed inside the
   labeled packet MPLS Shim Header using the EXP field [MPLS_ENCAPS].
   When the Shim Header is not used (eg. MPLS Over ATM), the Drop
   Precedence to be applied by the LSR to the labeled packet is
   conveyed inside the link layer header encapsulating the labeled
   packet encapsulation using link layer
   specific drop precedence fields (eg. ATM Cell Loss Priority).

   We refer to such LSPs as "Label-Inferred-PSC "Label-Only-Inferred-PSC LSPs" (L-LSP). (L-LSP)
   since the PSC can be fully inferred from the label without any other
   information (eg. regardless of the EXP field value). Detailed
   operations of L-LSPs are specified in section 3 4 below.

   L-LSPs allow support of any number of Behavior Aggregates.

   L-LSPs have the following drawbacks:
        - they require the use of a separate label for support of each
   PSC,   and
        - they require more signaling operations to set up the
   corresponding L-LSPs.

1.4 Overall Operations

   For a given FEC, and unless media specific restrictions apply as
   identified in the corresponding sections below (eg. `MPLS Support of
   Diff-Serv by ATM LSRs'), 7, 8, 9 and 10 below, this specification
   allows any one of the following set of combinations within an MPLS Diff-Serv Diff-
   Serv domain:
     - zero or any number of E-LSPs, and
     - zero or any number of L-LSPs.

   The network administrator selects the actual combination of LSPs
   from the set of allowed combinations and selects how the Behavior
   Aggregates are actually transported over this combination of LSPs,
   in order to best match his/her environment and objectives in terms
   of Diff-Serv support, Traffic Engineering and Fast Restoration.
   Criteria for selecting such a combination are outside the scope of
   this specification; However in order to respect ordering
   constraints, all packets of a given microflow, possibly spanning
   multiple BAs of a given Ordered Aggregate, MUST be transported over
   the same LSP. Conversely, each LSP MUST be capable of supporting all
   the (active) PHBs of a given PSC.

   Examples of deployment scenarios are provided for information in
   APPENPIX B. A.

1.5 Label Forwarding Model for Diff-Serv LSRs

   In order to describe Label Forwarding by Diff-Serv LSRs, we model
   the LSR Diff-Serv label switching behavior as comprising three
   stages:
        -A- incoming PHB and FEC determination

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                      MPLS Support of Diff-Serv             October 99

        -B- Optional outgoing PHB determination via Local Policy and
   Traffic Conditioning
        -C- Outgoing EXP(and possibly CLP/DE) and label determination,
   enforcement of outgoing PHB's forwarding behavior

   This model is used below for specifying LSR Label Forwarding using
   L-LSPs and E-LSPs for Diff-Serv support over MPLS.

1.6 Relationship between Label and FEC

   [MPLS_ARCH] states in section `2.1. Overview' that:
   `Some routers analyze a packet's network layer header not merely to
   choose the packet's next hop, but also to determine a packet's
   "precedence" or "class of service".  They may then apply different
   discard thresholds or scheduling disciplines to different packets.
   MPLS allows (but does not require) the precedence or class of
   service to be fully or partially inferred from the label.  In this
   case, one may say that the label represents the combination of a FEC
   and a precedence or class of service.'

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                      MPLS Support of Diff-Serv            February 00

   In line with this, we observe that:
     - With E-LSPs, the label represents the combination of a FEC and
       the set of E-LSP transported Behavior Aggregates (BAs). (BAs) transported over the E-
       LSP). Where all the MPLS supported BAs are transported over E-LSPs, an E-LSP,
       the label then represents the complete FEC.
     - With L-LSPs, the label represents the combination of a FEC and
       an Ordered Aggregate (OA).

2. Detailed Operations of E-LSPs

2.1 E-LSP Establishment

      Recognizing that:

      - Certain MPLS encapsulations (such as PPP and LAN) make use Label Forwarding Model for Diff-Serv LSRs

   Since different Ordered Aggregates of a
   Shim Header which consists given FEC may be transported
   over different LSPs, the label swapping decision of a label stack with one or more entries
   [MPLS_ENCAPS];

      - the Diff-Serv Code Point field (DSCP) is 6-bit long
   [DIFF_HEADER] but when 8 (or less) BAs are used, LSR
   clearly depends on the DSCP values can
   be mapped entirely into forwarded packet's Behavior Aggregate. Also,
   since the 3-bit long EXP IP DS field of the MPLS label
   stack entry;

      We define that:

      - one LSP established for a given Forwarding Equivalent Class
   (FEC) forwarded packet may not be used for transport of up directly
   visible to eight BAs of that FEC;

      - such an LSP is referred LSR, the way to as an "EXP-inferred-PSC" LSP or
   "E-LSP" because determine the PSC PHB to be applied to a labeled
   received packet and to encode the PHB into a transmitted packet is
   different to a non-MPLS Diff-Serv Router.

   In order to describe Label Forwarding by Diff-Serv LSRs, we model
   the LSR Diff-Serv label switching behavior as comprising four
   stages:
     - Incoming PHB Determination (A)
     - Optional Outgoing PHB Determination via Local Policy and Traffic
       Conditioning (B)
     - Label Swapping (C)
     - Encoding of Diff-Serv information into Encapsulation Layer
       (EXP,CLP,DE,User_Priority)  (D)

   Obviously, to enforce the Diff-Serv service differentiation the LSR
   MUST also apply the forwarding treatment corresponding to the
   Outgoing PHB.

   This model is inferred from illustrated below:

   --Inc_label(*)--------------------------->I===I---Outg_label (**)-->
     \                                       I   I \
      \---->I===I                            I C I  \-->I===I--Encaps->
            I A I           I===I--Outg_PHB->I===I      I D I   (**)
   -Encaps->I===I--Inc_PHB->I B I         \          /->I===I
      (*)                   I===I          \--------/

   `Encaps' designates the EXP field of Diff-Serv related information encoded in the
   MPLS Shim Header; Encapsulation layer (eg EXP field, ATM CLP, Frame Relay DE,
   802.1 User_Priority)

   (*) when the LSR performs label imposition, the incoming packet is
   received unlabelled.

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                      MPLS Support of Diff-Serv             October 99

      -            February 00

   (**) when the set of transported BAs can span one or multiple OAs;

      - packets belonging to this given (FEC) and from LSR performs label disposition, the
   corresponding set of BAs are sent down this E-LSP.

      - multiple BAs belonging outgoing packet is
   transmitted unlabelled.

   This model is presented here to the same FEC illustrate operations of Diff-Serv
   LSRs and transported over the
   same E-LSP are granted different scheduling treatment and different
   drop precedence by the MPLS LSR based on the EXP field does not constrain actual implementation.

2.1 Incoming PHB Determination

   This stage determines which is
   appropriately encoded to reflect both the PSC and the drop
   precedence of Behavior Aggregate the received packet
   belongs to.

   2.1.1 Incoming PHB corresponding to the packet's BA.

   MPLS specifies how LSPs can be established via multiple signaling
   protocols. Those include the Label Distribution Protocol (LDP),
   RSVP, BGP and PIM. Determination for received labelled packets

   This document specifies below, respectively in
   section 4 and section 5, how RSVP and LDP are to be used specification defines one default method for
   establishment this determination
   which allows for regular support of E-LSPs.

2.2 Label Forwarding

2.2.1 Incoming PHB and FEC Determination On Ingress E-LSP

   When receiving a labeled packet Diff-Serv over a E-LSP of an MPLS ingress
   interface, MPLS. This method
   considers only the LSR: outer encapsulation (ie outer label entry or ATM
   encapsulation or Frame Relay encapsulation) and ignores other label
   entries which may be present in the stack. It combines:
     - determines the FEC based on Diff-Serv context associated with the incoming label and
       stored in the Incoming Label Map (ILM). See section 2.3 below
       for details on information comprising the Diff-Serv context.
     - determines the incoming PHB by looking at Diff-Serv related information that is encoded in the
       corresponding encapsulation layer (ie in EXP field of MPLS Shim
       layer or in CLP/DE field of the top level link layer encapsulation) of the
       received label entry packet.

   The details of this method depend on the incoming LSP type and then by looking up on
   the PHB<-->EXP
   mapping incoming MPLS encapsulation and are defined below in section 2.3.

   If the EXP field value of a packet received on an E-LSP sections
   3.3 and 4.3.

   Support for this default method is not
   listed in the mapping defined in section 2.3, mandatory for compliance to this EXP value should
   specification.

   Optionally, other methods for Incoming PHB Determination may also be considered invalid. LSR behavior
   supported. Other methods may take into account other information in such situation is
   addition to, or instead of, the information used by the mandatory
   method. For instance, other method could take into account the DS
   field of the encapsulated packet or the EXP field of a local
   matter and is outside label header
   deeper in the label stack. Such methods are beyond the scope of this document.

2.2.2
   specification.

2.1.2 Incoming PHB Determination for received unlabelled packets

   For packets received unlabelled, this stage operates exactly as with
   a non-MPLS IP Diff-Serv Router and uses the DS field.

2.2 Optional Outgoing PHB Determination Via Local Policy And Traffic
Conditioning

   This stage of Diff-Serv label switching is optional and may be used
   on an LSR to perform traffic conditioning including Behavior
   Aggregate demotion or promotion inside
   an promotion. It is outside the scope of this

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                      MPLS Support of Diff-Serv domain.            February 00

   specification. For the purpose of specifying Diff-Serv over MPLS
   forwarding, we simply note that the PHB to be actually enforced, and
   conveyed to downstream LSRs, by an LSR (referred to as "outgoing
   PHB") may be different to the PHB which had been associated with the
   packet by the previous LSR (referred to as "incoming PHB").

2.2.3   Outgoing EXP Field And Label Determination On Egress E-LSP

   Once

   When this stage is not present, the outgoing PHB has been determined by "outgoing PHB" is simply
   identical to the LSR "incoming PHB".

   For packets received unlabelled, this stage operates as with a function
   of the incoming PHB and of the optional Local Policy and Traffic
   Conditioning, the LSR:

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   MPLS Support of IP Diff-Serv             October 99

        - determines via local configuration that the outgoing PHB Router.

2.3 Label Swapping

   [MPLS_ARCH] describes how label swapping is
   one of the PHBs supported performed by the E-LSP and determines the egress E-
   LSP LSRs on
   incoming labeled packets using an Incoming Label Map (ILM), where
   each incoming label for the packet's FEC
        - determines the value is mapped to be written in the EXP field of the
   top level label entry (and possibly of other level one or multiple NHLFEs. [MPLS_ARCH]
   also describes how label entries in
   the case of a hierarchical tunnel entry) by looking up the
   PHB<-->EXP mapping defined below in section 2.3 for the outgoing
   PHB.
        - SHALL apply the scheduling/dropping behavior corresponding to
   the Outgoing PHB in compliance with the corresponding Diff-Serv PHB
   specification.

2.2.4 Simplified Forwarding

   When Local Policy and Traffic Conditioning are not to be imposition is performed by the LSR and the labeled packet is received LSRs on incoming
   unlabelled packets using a E-LSP and FEC-to-NHLFEs Map (FTN), where each
   incoming FEC is
   forwarded onto an E-LSP, the Forwarding operation mapped to one or multiple NHLFEs.

   A Diff-Serv Context for a label is simplified
   since: defined as comprising:
     - the EXP field does not need to be modified `LSP type (ie E-LSP or L-LSP)'
     - the outgoing label determination depends exclusively on the `supported PHBs'
     - `Encaps-->PHB mapping' for an incoming label (ie does not depend on Local Policy and Traffic
   Conditioning). The
     - `Set of PHB-->Encaps mappings' for an outgoing label

   The present specification defines that a Diff-Serv Context is determined from stored
   in the Incoming
   Label Map (ILM) using ILM for each incoming label.

   [MPLS_ARCH] states that the same procedures as `NHLFE may also contain any other
   information needed in order to properly dispose of the packet'. In
   accordance with non Diff-Serv LSPs
   (ie this, the incoming label present specification defines that a Diff-
   Serv context is used as stored in the index NHLFE for each outgoing label which is
   swapped or pushed.

   This Diff-Serv context information is populated into the ILM to identify
   the NHLFE independently of and the Diff-Serv operations)
        -
   FTN at label establishment time.

   If the scheduling/dropping behavior label corresponds to be applied is determined
   exclusively from the unmodified EXP field value.

2.3 PHB<-->EXP field an E-LSP for which no EXP<-->PHB mapping

   Like
   has been explicitly signaled at LSP setup, the mapping between `supported PHBs' is
   populated with the set of PHBs and DSCPs in a Diff-Serv network, of the
   mapping between PHB and EXP field preconfigured
   EXP<-->PHB Mapping, which is a local matter to be defined by
   the Service Provider and configured on every LSR.

   LSRs supporting E-LSPs must allow configuration of PHB<-->EXP
   mapping. This mapping applies to all discussed below in section 3.2.1.

   If the E-LSPs established on this
   LSR (over interfaces belonging label corresponds to a given MPLS Diff-Serv domain).

   The PHB<-->EXP an E-LSP for which an EXP<-->PHB mapping must be consistent
   has been explicitly signaled at every LSP hop
   throughout the MPLS Diff-Serv domain spanned by setup, the LSP. This `supported PHBs' is
   achieved via consistent configuration by the network operator within
   the MPLS Diff-Serv domain.

   Clearly, if different Behavior Aggregates transported over an E-LSP
   are to be treated differently in
   populated with the MPLS Diff-Serv cloud, different
   values set of PHBs of the EXP field are signaled EXP<-->PHB mapping.

   If the label corresponds to configured in an L-LSP, the PHB<-->EXP mapping
   for `supported PHBs' is
   populated with the corresponding PHBs.

2.4 E-LSP Merging set of PHBs forming the PSC that is signaled at
   LSP set-up.

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                      MPLS Support of Diff-Serv             October 99

   In an MPLS domain, two            February 00

   The details of how the `Encaps-->PHB mapping' or more LSPs can be merged into one LSP at
   one LSR. E-LSPs `Set of
   PHB-->Encaps mappings' are compatible with LSP Merging under populated are defined below in sections 3
   and 4.

   [MPLS_ARCH] also states that:
   "If the following
   condition:

   E-LSPs can only be merged into ILM [respectively, FTN] maps a particular label to a set of
   NHLFEs that contains more than one LSP if they support element, exactly one element of
   the exact
   same set of BAs.

   Since must be chosen before the BAs/PHBs supported over an E-LSP packet is not signalled at
   establishment time, forwarded.  The
   procedures for choosing an LSR can not rely on signaling information to
   enforce the above merge condition (ie that merged LSPs do support element from the exact same set of BAs). However all E-LSPs are to use the same
   PHB<-->EXP mapping, and transport beyond the same set scope
   of Behavior
   Aggregates, within this document.  Having the ILM [respectively, FTN] map a given MPLS Diff-Serv domain. Thus, E-LSP
   merging is allowed within label
   [respectively, a given MPLS Diff-Serv domain.

   E-LSP Merging at FEC] to a boundary between two MPLS Diff-Serv domains set containing more than one NHLFE may be
   useful if, e.g., it is desired to do load balancing over multiple
   equal-cost paths."
   In accordance with this, the present specification allows that an
   incoming label [respectively FEC] is mapped, for further study.

3.  Detailed Operation Diff-Serv purposes,
   to multiple NHLFEs (for instance where different NHLFEs correspond
   to egress labels supporting different sets of L-LSPs

3.1 L-LSP Establishment

      Recognizing that:

      - All currently defined MPLS encapsulation methods have PHBs). When a field
   of 3 bits or less for label
   [respectively FEC] maps to multiple NHLFEs, the Diff-Serv encoding (i.e., 3-bit EXP field in
   case of Shim Header and 1-bit CLP/DE bit in case LSR MUST
   choose one of ATM/Frame
   Relay).

      - The the NHLFEs whose Diff-Serv Code Point (DSCP) is 6-bit long [DIFF_HEADER]. So context indicates that when more than it
   supports the Outgoing PHB of the forwarded packet.

   When a certain number label [respectively FEC] maps to multiple NHLFEs which
   supports the Outgoing PHB, the procedure for choosing one among
   those is outside the scope of BAs are used (i.e., more
   than 8 BAs in case this document. This situation may be
   encountered where it is desired to do load balancing of Shim Header and more than 2 BAs a Behavior
   Aggregate over multiple LSPs. In such situations, in case order to
   respect ordering constraints, all packets of
   ATM/Frame Relay), the DS field can not a given microflow MUST
   be mapped entirely transported over the same LSP.

2.4 Encoding Diff-Serv information into Encapsulation Layer

   This stage determines how to encode the
   appropriate field fields of the MPLS
   encapsulation header (i.e., EXP field in
   case of layer which convey Diff-Serv information (eg MPLS Shim Header and CLP/DE field in case of ATM/Frame Relay);

        - Some Service Providers have a requirement
   EXP, ATM CLP, Frame Relay DE, 802.1 User_Priority).

2.4.1 Encoding Diff-Serv information for fine grain
   Traffic Engineering (such as per OA Traffic Engineering)

      We propose that:

      - All transmitted labeled packets belonging to a single OA and

   This specification defines one default method for this encoding
   which allows regular support of Diff-Serv over MPLS. This method
   takes into account:
     - the same Forwarding
   Equivalent Class (FEC) be sent down a single LSP; Outgoing PHB
     - One LSP be established per <FEC, OA> pair (rather than simply
   one LSP per FEC as in an MPLS network the Diff-Serv context associated with each swapped/pushed label
       of the selected NHLFE (`Set of PHB-->Encaps mappings').

   This method defines that does not support Diff-
   Serv). Such an LSP the Outgoing PHB is referred to as a "Label-inferred-PSC" LSP reflected into:
     - the EXP field value of all the swapped or
   "L-LSP"; pushed label entries
     - Multiple BAs belonging to the same OA be granted different Drop
   Precedence (DP) values through appropriate coding CLP/DE bit when the packet is encapsulated into ATM/Frame
       Relay,
     - the 802.1 User_Priority field of the relevant 802.1 Tag Control
       Information when the packet is encapsulated into LAN interfaces
       supporting multiple Traffic Classes,

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                      MPLS Support of Diff-Serv             October 99

   field of MPLS encapsulation header (EXP field            February 00

   The details of this method depend on the top label entry
   for outgoing LSP type and on
   the shim header, CLP/DE bit in case of ATM/Frame Relay). outgoing MPLS specifies how LSPs can be established via multiple signaling
   protocols. Those include the Label Distribution Protocol (LDP),
   RSVP, BGP encapsulation and PIM. This document specifies, respectively are defined below in section
   4 and section 5, how RSVP sections
   3.5 and LDP are to be used 4.5.

   Support for establishment
   of L-LSPs.

3.2 Label Forwarding

3.2.1 Incoming PHB and FEC Determination On Ingress L-LSP

   When receiving a labeled packet this default method is mandatory for compliance to this
   specification.

   Optionally, other methods for encoding Diff-Serv information into
   the Encapsulation layer may also be supported to allow for more
   sophisticated Diff-Serv operations over an L-LSP MPLS. Other methods may
   affect encapsulation fields differently.

2.4.2 Encoding Diff-Serv information for transmitted unlabelled packets

   This specification defines one default method for this encoding
   which allows regular support of an MPLS ingress
   interface, the LSR:
        - determines the FEC based on the incoming Diff-Serv over MPLS.

   Support for this default method is mandatory for compliance to this
   specification.

   For packets transmitted unlabelled (ie LSR performing label
        - determines
   disposition), the PSC from the incoming label among default encoding method writes the set DSCP of
   LSPs established for that FEC
        - determines the incoming
   Outgoing PHB from into the PSC and DS field.

   Optionally, other encoding methods may also be supported to allow
   for more sophisticated Diff-Serv operations over MPLS. Other methods
   may affect the EXP/CLP/DLE DS field of differently. One example would be a method
   where the top level label entry in accordance with IP packet's DS field is left unchanged regardless of the
   PSC/EXP(resp PSC/CLP, PSC/DE) -->PHB mappings defined below in
   sections 6.3 (resp 7.2 and 8.2).

3.2.2 Optional
   Outgoing PHB Determination Via Local Policy And Traffic
Conditioning

   This stage of PHB. Such a method would allow `MPLS Diff-Serv label switching is independent
   Transparency' ie it would allow support of Differentiated Services
   in the
   ingress/egress interface media type and method used for MPLS Diff-
   Serv support. It is optional and may be used backbone based on an LSR a Diff-Serv policy which is specific
   to perform
   Behavior Aggregate demotion or promotion inside an the MPLS Diff-Serv
   domain. For cloud (and different from the purpose of specifying a Diff-Serv over policy applied
   in the non-MPLS clouds around the MPLS method,
   we simply note that cloud) since the PHB to be actually enforced by an LSR
   (referred to as "outgoing PHB") may IP DS field
   would be different to the PHB which
   had been associated with the packet at the previous LSR (referred to
   as "incoming PHB").

3.2.3   Outgoing EXP/CLP/DE Field and Label Determination on Egress L-
LSP

   Once the outgoing PHB has been determined by transported transparently through the LSR as a function MPLS cloud. Details
   of such methods are outside the incoming PHB and scope of the optional Local Policy and Traffic
   Conditioning, the LSR:
        - determines via local configuration that the outgoing PHB is
   one this specification.

3. Detailed Operations of the PHBs supported by a L-LSP and determines the egress
   L-LSP label for the packet's FEC E-LSPs

3.1 E-LSP Definition

    Recognizing that:

     - determines the value to be written in the EXP/CLP/DLE field Certain MPLS encapsulations (such as PPP and LAN) make use of the top level label entry (and possibly a
       Shim Header which consists of other level a label stack with one or more
       entries in the case of [MPLS_ENCAPS] each with a hierarchical tunnel entry) by performing 3-bit EXP field;

     - the outgoing PHB-->EXP/PSC (resp CLP/PSC, DE/PSC) mapping defined in
   sections 6.4 (resp 7.3 and 8.3). Differentiated-Service (DS) field is 6-bit long
       [DIFF_HEADER] potentially allowing support of up to 64 Behavior
       Aggregates

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                      MPLS Support of Diff-Serv             October 99            February 00

     - SHALL apply the scheduling/dropping behavior corresponding to
   the "Outgoing PHB" in compliance with the corresponding Diff-Serv
   PHB specification.

3.2.4 Simplified Forwarding

   When Local Policy and Traffic Conditioning are not to any subset of 8 (or less) DSCP values can be performed
   by mapped entirely
       into the LSR, and when 3-bit long EXP field of the labeled packet is received on MPLS label stack entry;

    We define that:

     - an LSP established for a L-LSP on given Forwarding Equivalent Class (FEC)
       may be used for transport of up to eight BAs of that FEC;

     - the ingress interface and is going out onto a L-LSP on an egress
   interface set of transported BAs can span multiple OAs;

     - for a given OA transported over the same type, LSP, all supported BAs of
       this OA are transported over the Forwarding operation is simplified
   since: LSP;

     - such an LSP is referred to as an "EXP-inferred-PSC" LSP or
       "E-LSP" because the EXP/CLP/DE field does not need PSC to be modified
        - applied to a labeled packet by the outgoing label determination
       LSR depends exclusively on the
   incoming label (ie does not depend on Local Policy EXP field value in the MPLS Shim Header;

     - packets belonging to this given (FEC) and Traffic
   Conditioning). The outgoing label is determined from the Incoming
   Label Map (ILM) using corresponding
       set of BAs are sent down this E-LSP.

     - multiple BAs belonging to the same procedures as with non Diff-Serv LSPs
   (ie FEC and transported over the incoming label is used as
       same E-LSP are granted different scheduling treatment and
       different drop precedence by the index into MPLS LSR based on the ILM EXP field
       which is appropriately encoded to identify reflect both the NHLFE independently of PSC and the Diff-Serv operations)
        -
       drop precedence of the scheduling behavior PHB corresponding to be applied is  determined
   exclusively from the Diff-Serv information stored in the NHLFE for the incoming label packet's BA.

     - the dropping behavior mapping between EXP field and PHB to be applied is determined exclusively
   from by the LSR
       for a given E-LSP is either explicitly signaled at label set-up
       or relies on a preconfigured mapping.

   Within a given MPLS Diff-Serv information stored in domain, all the NHLFE for E-LSPs relying on the incoming
   label and from
   pre-configured mapping are capable of transporting the incoming EXP/CLP/DE field
   More information is provided below in the sections titled `RSVP
   extensions for Diff-Serv Support' and `LDP extensions for Diff-Serv
   Support' on what is the Diff-Serv information stored in NHLFEs.

3.3 Merging

   In an MPLS domain, two same common
   set of 8, or more LSPs less, BAs. Each of those E-LSPs may actually transport
   this full set of BAs or any arbitrary subset of it.

   For a given FEC, two given E-LSPs using signaled EXP<-->PHB mapping
   can be merged into one LSP at
   one LSR. The proposed support of Diff-Serv in MPLS is compatible
   with LSP Merging under the following condition:

   L-LSPs can only same or different sets of Ordered Aggregates.

   For a given FEC, there may be merged into more than one L-LSP if they are associated with E-LSP carrying the same PSC.

   Note that when L-LSPs merge, the bandwidth that is available
   OA, for the
   PSC downstream example for purposes of the merge point must be sufficient to carry the
   sum load balancing of the merged traffic. This is particularly important OA. In that
   case, in the
   case order to respect ordering constraints, all packets of EF traffic. This a
   given microflow must be transported over the same LSP.

   MPLS specifies how LSPs can be ensured in multiple ways (for
   instance via provisioning or established via bandwidth multiple signaling
   protocols. Those include the Label Distribution Protocol (LDP),
   RSVP, BGP and explicit
   admission control).

4. PIM. Sections 5 and 6 below specify how RSVP Extension and LDP
   are to be used for Diff-Serv Support

   The MPLS architecture does not assume a single label distribution
   protocol. [RSVP_MPLS_TE] defines establishment of E-LSPs.

3.2 Populating the extension to RSVP `Encaps-->PHB mapping' for
   establishing label switched paths (LSPs) in an incoming E-LSP

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                      MPLS networks. Support of Diff-Serv            February 00

   This section specifies the extensions to RSVP, beyond those defined in

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                      MPLS Support defines how the `Encaps-->PHB mapping' of the Diff-Serv             October 99

   [RSVP_MPLS_TE], to establish label switched path (LSPs) supporting
   Differentiated Services in MPLS networks.

4.1 Diff-Serv related RSVP Messages Format

   One new RSVP Object
   context is defined populated for an incoming E-LSP in this document: the DIFFSERV_PSC
   Object. Detailed description of this Object is provided below. This
   new Object is applicable order to Path messages. This specification only
   defines support the use
   mandatory default method for Incoming PHB determination.

   The `Encaps-->PHB mapping' is always of the DIFFSERV_PSC Object in Path messages used to
   establish LSP Tunnels in accordance with [RSVP_MPLS_TE] and thus
   containing a Session Object with a C-Type equal form `EXP-->PHB
   mapping'.

   If the label corresponds to LSP_TUNNEL_IPv4
   and containing a LABEL_REQUEST object.

   Restrictions defined in [RSVP_MPLS_TE] an E-LSP for support of establishment
   of which no EXP<-->PHB mapping
   has been explicitly signaled at LSP Tunnels via RSVP are also applicable to setup, the establishment of
   LSP Tunnels supporting Diff-Serv: for instance, only unicast LSPs
   are supported and Multicast LSPs are for further study.

   This new DIFFSERV_PSC object `EXP-->PHB mapping'
   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.

   The DIFFSERV_PSC Object populated based on the Preconfigured EXP<-->PHB Mapping which is optional
   discussed below in section 3.2.1.

   If the label corresponds to an E-LSP for support of which an EXP<-->PHB mapping
   has been explicitly signaled at LSP Tunnels setup, the `EXP-->PHB mapping'
   is populated as
   defined in [RSVP_MPLS_TE]. A Diff-Serv capable LSR per the signaled EXP<-->PHB mapping.

3.2.1 Preconfigured EXP<-->PHB mapping

   LSRs supporting E-LSPs
   in compliance with which uses the preconfigured EXP<-->PHB
   mapping must allow local configuration of this specification MAY support EXP<-->PHB mapping.
   This mapping applies to all the DIFFSERV_PSC
   Object. A Diff-Serv capable LSR supporting L-LSPs in compliance with E-LSPs established on this specification MUST support the DIFFSERV_PSC Object.

4.1.1 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_PSC> ]
                                  [ <POLICY_DATA> ... ]
                                  [ <sender descriptor> ]

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

4.2 DIFFSERV_PSC Object

   As stated earlier, the PHB Scheduling Class associated with an L-LSP
   is to be specified through LSR
   without a new DIFFSERV_PSC object in RSVP Path
   messages. mapping explicitly signaled at set-up time.

   The DIFFSERV_PSC object has preconfigured EXP<-->PHB mapping must either be consistent at
   every E-LSP hop throughout the following format :

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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         Length                |   Class-Num   |    C-Type     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        Reserved     | T |PSCnb|              PSC              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Length

      This is set to 4.

     Class-Num

      The Class-Num for a DIFFSERV_PSC object is [TBD] and identifies
      a new object Class called domain spanned by the "Class Of Service" Class (COS
      Class). (The Class-Num is to
   LSP or appropriate remarking of the EXP field must be allocated performed by IANA with
   the form
      0bbbbbbb)

     C-Type

      The C-Type for LSR whenever a DIFFSERV_PSC object is 1.

     Reserved

      This field different preconfigured mapping is set to all zeros

     T

      This indicates used on the `LSP Type'. The following values are
      specified:

           T Value      LSP type
           00
   ingress and egress interfaces.

3.3 Incoming PHB Determination On Incoming E-LSP
           01           L-LSP

     PSCnb

      Indicates the number of PSC values included in the PSC object.

   This is set to 001.

     PSC

      The PSC indicates section defines the mandatory default method for Incoming PHB Scheduling Class to be supported by
   determination for a labeled packet received on an E-LSP. This method
   requires that the
      L-LSP. The 16-bit PSC `Encaps-->PHB mapping' is encoded populated as specified defined
   above in section 2 3.2.

   When receiving a labeled packet over an E-LSP of
      [PHBID]: an MPLS ingress
   interface, the LSR:

     -determines the EXP-->PHB mapping by looking up the
       `Encaps-->PHB mapping' of the Diff-Serv context associated with
       the incoming label in the ILM.
     - Where determines the PSC comprises a single incoming PHB defined by standards
      action, looking up the encoding for EXP field of the PSC is
       top level label entry into the encoding for this single
      PHB. It is EXP-->PHB mapping table.

   If the recommended DSCP EXP field value for that PHB, left-
      justified of a packet received on an E-LSP is not
   included in the 16-bit field, EXP-->PHB mapping associated with bits 6 through 15 set to
      zero. this LSP, this EXP
   value should be considered invalid. LSR behavior in such situation
   is a local matter and is outside the scope of this document.

3.4 Populating the `Set of PHB-->Encaps mappings' for an outgoing E-LSP

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                      MPLS Support of Diff-Serv             October 99

        - Where            February 00

   This section defines how the PSC comprises multiple PHBs defined by standards
      action, `Set of PHB-->Encaps mappings' of the PSC encoding
   Diff-Serv context is populated for an outgoing E-LSP in order to
   support the encoding mandatory default method for this set Encoding of PHB. It Diff-Serv
   information in the Encapsulation Layer.

3.4.1 `PHB-->EXP mapping'

   One `PHB-->EXP mapping' is always added to the smallest numerical value `Set of PHB-->Encaps
   mappings' of the recommended DSCP Diff-Serv context for an outgoing E-LSP.

   If the
      various PHBs in the PSC, left-justified in the 16 bit field, with
      bits 6 through 13 and bit 15 set label corresponds to zero and with bit 14 set to
      one.

      For instance, the encoding of the EF PSC an E-LSP for which no EXP<-->PHB mapping
   has been explicitly signaled at LSP setup, this `PHB-->EXP mapping'
   is :
        0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15
      +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
      | 1  0  1  1  1  0| 0  0  0  0  0  0  0  0  0  0|
      +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

      For instance, the encoding of populated based on the AF1 PSC Preconfigured EXP<-->PHB Mapping which is :
        0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15
      +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
      | 0  0  1  0  1  0| 0  0  0  0  0  0  0  0  1  0|
      +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

4.3 Handling Diff-Serv_PSC Object

   To establish
   discussed above in section 3.2.1.

   If the label corresponds to an E-LSP for which an EXP<-->PHB mapping
   has been explicitly signaled at LSP tunnel with RSVP, setup, the sender creates a Path
   message with a session type of LSP_Tunnel_IPv4 and with a
   LABEL_REQUEST object `PHB-->EXP mapping'
   is populated as per [RSVP_MPLS_TE].

   Where the sender supports Diff-Serv using E-LSPs, to establish an
   E-LSP tunnel with RSVP, signaled EXP<-->PHB mapping.

3.4.2 `PHB-->802.1 mapping'

   If the sender creates a Path message with outgoing interface is a
   session type of LSP_Tunnel_IPv4, with the LABEL_REQUEST object and
   without the DIFFSERV_PSC object.

   Optionally, to establish an E-LSP over LAN interface on which a single Ordered
   Aggregate multiple 802.1
   Traffic Classes are supported as per [IEEE_802.1], one `PHB-->802.1
   mapping' is going added to be transported, the sender MAY create a Path
   message which contains a session type `Set of LSP_Tunnel_IPv4, contains
   the LABEL_REQUEST object and contains the DIFFSERV_PSC object with
   its LSP-Type field set to `E-LSP' and its PSC field set to the value PHB-->Encaps mappings' of the PSC to be supported on Diff-
   Serv context for the outgoing E-LSP.

   The destination node of an E-LSP responds to the Path message
   containing This mapping is populated at
   label set-up based on the LABEL_REQUEST object by sending a Resv message
   containing Preconfigured PHB-->802.1 mapping defined
   below in section 3.4.2.1.

   Notice that the LABEL object and no DIFFSERV_PSC object.

   When receiving a Resv message containing `Set of PHB-->Encaps mappings' then contains both a LABEL object
   `PHB-->EXP mapping' and
   associated with a Path message which contained a LABEL_REQUEST
   object and no DIFFSERV_PSC object (or which contained `PHB-->802.1 mapping'.

3.4.2.1 Preconfigured `PHB-->802.1 Mapping'

   At the
   DIFFSERV_PSC object with its LSP-Type set time of producing this specification, there are no
   standardized mapping from PHBs to E-LSP), assuming the
   reservation can be accepted and a label can be associated with the
   reservation, a Diff-Serv E-LSP capable 802.1 Traffic Classes.

   Consequently, an LSR must:
        - update its Incoming Label Map (ILM) [MPLS_ARCH] supporting multiple 802.1 Traffic Classes over
   LAN interfaces must allow local configuration of a `PHB-->802.1
   Mapping'. This mapping applies to store all the outgoing LSPs established
   by the
   necessary LSR on such LAN interfaces.

3.5 Encoding Diff-Serv information. information into Encapsulation Layer On Outgoing
E-LSP

   This includes section defines the fact that mandatory default method for encoding of
   Diff-Serv related information into the
   Next Hop Label Forwarding Entry (NHLFE) corresponds MPLS encapsulation Layer to
   be used when a packet is transmitted onto an E-LSP. This method
   requires that the `Set of PHB-->Encaps mappings' is populated as
   defined above in accordance section 3.4.

   The LSR first determines the `Set of PHB-->Encaps Mapping'
   associated with [MPLS_ARCH] which states that the `NHLFE outer label of the NHLFE.

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                      MPLS Support of Diff-Serv             October 99

   may also contain any other information needed in order to properly
   dispose of            February 00

3.5.1 `PHB-->EXP mapping'

   For all the packet'. labels which are swapped or pushed, the LSR:
     - install determines the PHB-->EXP mapping by looking up the
       `Set of PHB-->Encaps mapping' of the required scheduling and dropping behavior for
   this NHLFE in order to support Diff-Serv context
       associated with the corresponding label forwarding as
   specified for E-LSPs in section 2.2.

   Where the sender supports Diff-Serv using L-LSPs, to establish an
   L-LSP tunnel with RSVP, the sender creates a Path message with a
   session type of LSP_Tunnel_IPv4, with the LABEL_REQUEST object and
   with the DIFFSERV_PSC object. The DIFFSERV_PSC object has its LSP-
   Type set to L-LSP and its NHLFE.
     - determines the PSC value indicating the PHB
   Scheduling Class to be supported written in the EXP field of the
       corresponding level label entry by looking up the L-LSP.

   An RSVP router that does recognizes "outgoing PHB"
       in this PHB-->EXP mapping table.

3.5.2 `PHB-->802.1 mapping'

   If the DIFFSERV_PSC object and that
   receives a path message which contains `Set of PHB-->Encaps mapping' of the DIFFSERV_PSC object but
   which does not contain a LABEL_REQUEST object or which does not have outer label contains a session type
   mapping of LSP_Tunnel_IPv4, sends a PathErr towards the
   sender with form `PHB-->802.1 mapping', then the LSR:
     - determines the error code `Diff-Serv Error' and an error value of
   `Unexpected DIFFSERV_PSC object'. Those are defined below to be written in the
   section titled `Diff-Serv Errors'.

   A node receiving a Path message with User_Priority field of
     the DIFFSERV_PSC object, which
   recognizes Tag Control Information of the DIFFSERV_PSC object but does not support 802.1 encapsulation header
     [IEEE_802.1], by looking up the
   particular PSC encoded "outgoing PHB" in the PSC field, sends a PathErr towards the
   sender with the error code `Diff-Serv Error' and this PHB-->802.1
     mapping table.

3.6 E-LSP Merging

   In an error value of
   `Unsupported PSC Value'. Those MPLS domain, two or more LSPs can be merged into one LSP at
   one LSR. E-LSPs are defined below in compatible with LSP Merging under the section
   titled `Diff-Serv Errors'.

   If a path message contains multiple DIFFSERV_PSC objects, following
   condition:

        E-LSPs can only the
   first one is meaningful; subsequent DIFFSERV_PSC object(s) must be
   ignored and not forwarded.

   Each node along merged into one LSP if they support the path records the DIFFSERV_PSC object, when
   present, in its path state block.

   The destination node
        exact same set of an L-LSP responds to BAs.

   For E-LSPs using signaled EXP<-->PHB mapping, the Path message
   containing above merge
   condition MUST be enforced by LSRs through explicit checking at
   label setup that the LABEL_REQUEST object and exact same set of PHBs is supported on the DIFFSERV_PSC object by
   sending a Resv message containing
   merged LSPs.

   For E-LSPs using the LABEL object and no
   DIFFSERV_PSC object.

   When receiving a Resv message containing a LABEL object and
   associated with a Path message which contained a LABEL_REQUEST
   object and preconfigured EXP<-->PHB mapping, since the DIFFSERV_PSC object with its LSP-Type set
   PHBs supported over an E-LSP is not signaled at establishment time,
   an LSR can not rely on signaling information to L-LSP,
   assuming enforce the reservation can be accepted and a label can be
   associated with above
   merge. However all E-LSPs using the reservation, a Diff-Serv L-LSP capable LSR must:
        - update its ILM preconfigured EXP<-->PHB mapping
   are required to store support the necessary same set of Behavior Aggregates within a
   given MPLS Diff-Serv information.
   This includes the fact that domain. Thus, merging of E-LSPs using the NHLFE corresponds to an
   preconfigured EXP<-->PHB mapping is allowed within a given MPLS
   Diff-Serv domain.

4.  Detailed Operation of L-LSPs

4.1 L-LSP and
   its PSC. Definition

    Recognizing that:

     - install the required scheduling and dropping behavior All currently defined MPLS encapsulation methods have a field of
       3 bits or less for
   this NHLFE to support Diff-Serv label forwarding as specified for L-
   LSPs encoding (i.e., 3-bit EXP field in section 3.2.

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                      MPLS Support of Diff-Serv             October 99

   A Diff-Serv LSR MUST handle the situations where the reservation can
   not be accepted for other reasons than those already discussed in
   this section,            February 00

       case of Shim Header and 1-bit CLP/DE bit in accordance with [RSVP_MPLS_TE] (eg. reservation
   rejected by admission control, case of ATM/Frame
       Relay).

     - The Differentiated-Services (DS) field is 6-bit long
       [DIFF_HEADER] potentially allowing support of up to 64 Behavior
       Aggregates. So that when more than a label certain number of BAs are
       used (i.e., more than 8 BAs in case of Shim Header and more than
       2 BAs in case of ATM/Frame Relay), the DS field can not be associated).

   [RSVP_MPLS_TE] identifies
       mapped entirely into the conditions where LSPs can be merged to
   constitute appropriate field of MPLS encapsulation
       header (i.e., EXP field in case of Shim Header and CLP/DE field
       in case of ATM/Frame Relay);

    We define that:

     - an LSP established for a multipoint-to-point LSP. When the LSPs to be merged are
   L-LSPs, those can only given Forwarding Equivalent Class (FEC)
       may be merged if an additional condition is met: used for transport of the DIFFSERV_PSC object BAs comprised in their respective path messages must one Ordered
       Aggregate (OA) for that FEC;

     - all
   be strictly identical.

4.4 Non-support BAs of this OA can be transported over the Diff-Serv_PSC Object

   An RSVP router that does LSP;

     - BAs from other OAs can not recognize the COS Class's Class-Num
   sends a PathErr with the error code "Unknown object class" toward
   the sender. An RSVP router that recognizes transported over the COS Class's Class-Num
   but does not recognize LSP;

     - BAs from the DIFFSERV_PSC object C-Type, sends a
   PathErr with OA transported over the error code "Unknown object C-Type" toward LSP are given the
   sender. This causes
       appropriate scheduling treatment based on the path PSC which is
       explicitly signaled at label set-up time.

     - Such an LSP is referred to fail. The sender should
   notify management that as a L-LSP cannot be established and possibly
   take action to retry reservation establishment without "Label-Only-inferred-PSC" LSP or
       "L-LSP";

     - Multiple BAs from OA transported over the
   DIFFSERV_PSC object (eg. attempt use LSP are granted
       different drop precedence by the MPLS LSR based on the
       appropriately encoded relevant field of MPLS encapsulation
       header (EXP field of E-LSPs as a back-up
   strategy).

4.5 Error Codes For Diff-Serv

   In the procedures described above, certain errors must be reported
   as a `Diff-Serv Error'. top label entry for the shim header,
       CLP/DE bit in case of ATM/Frame Relay); The value mapping between the
       relevant field of the `Diff-Serv Error' error
   code MPLS encapsulation and the drop precedence
       is 26 (TBD).

   The following defines error values a well-known mapping.

   For a given FEC, there may be more than one L-LSP carrying the same
   OA, for example for purposes of load balancing of the Diff-Serv Error:

       Value    Error

       1       Unsupported PSC value
       2       Unexpected DIFFSERV_PSC object

4.6 Use OA. In that
   case, in order to respect ordering constraints, all packets of COS Service with E-LSPs and L-LSPs

   Both E-LSPs and L-LSPs a
   given microflow must be transported over the same LSP.

   MPLS specifies how LSPs can be established with bandwidth reservation
   or without bandwidth reservation.

   To establish an E-LSP or via multiple signaling
   protocols. Those include the Label Distribution Protocol (LDP),
   RSVP, BGP and PIM. Sections 5 and 6 below specify how RSVP and LDP
   are to be used for establishment of L-LSPs.

4.2 Populating the `Encaps-->PHB mapping' for an incoming L-LSP with bandwidth reservation, Int-
   Serv's Controlled Load service (or possibly Guaranteed Service) is
   used and

   This section defines how the bandwidth is signaled in `Encaps-->PHB mapping' of the SENDER_TSPEC (respectively
   FLOWSPEC) of the path (respectively Resv) message.

   To establish an E-LSP or Diff-Serv
   context is populated for an incoming L-LSP without bandwidth reservation, the
   Class for support of Service service defined in [RSVP_MPLS_TE] is used. the
   mandatory default method for Incoming PHB determination.

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                      MPLS Support of Diff-Serv             October 99

   A Path message containing a COS SENDER_TSPEC and not containing a
   DIFFSERV_PSC object indicates to a Diff-Serv capable LSR that            February 00

4.2.1 `EXP-->PHB mapping'

   If the
   LSP to be established in an E-LSP without any bandwidth reservation.

   A Path message containing a COS SENDER_TSPEC and containing a
   DIFFSERV_PSC object with its LSP-Type set to E-LSP indicates to a
   Diff-Serv capable LSR that terminates the LSP to be established in MPLS Shim Layer (i.e. it is not an E-LSP
   without any bandwidth reservation.

   A Path message containing a COS SENDER_TSPEC and containing a
   DIFFSERV_PSC object with its LSP-Type set to L-LSP indicates to a
   Diff-Serv capable LSR that the LSP to be established
   ATM-LSR or FR-LSR as defined in an L-LSP [MPLS ATM][MPLS FR], and it does not
   receive packets without any bandwidth reservation.

   The above an MPLS shim layer on an LC-ATM or LC-FR
   interface) then the `Encaps-->PHB mapping' is summarized populated at label
   setup in the following table:

           Path Message            LSP type
     Service   DIFFSERV_PSC  LSP
                 Object      Type

     GS/CL         No               E-LSP with bandwidth reservation
     GS/CL         Yes       E-LSP  E-LSP with bandwidth reservation
     GS/CL         Yes       L-LSP  L-LSP with bandwidth reservation
     COS           No               E-LSP without bandwidth reservation
     COS           Yes       E-LSP  E-LSP without bandwidth reservation
     COS           Yes       L-LSP  L-LSP without bandwidth reservation

   Where:
        - GS stands for Guaranteed Service
        - CL stands for Controlled Load way:
     - COS stands for COS service

   When processing it is actually a path (respectively Resv) message for an E-LSP or
   an L-LSP using `EXP-->PHB mapping'
     - the COS service, mapping is a Diff-Serv capable LSR must ignore
   the value function of the COS field within a COS SENDER_TSPEC (respectively a
   COS FLOWSPEC).

5. LDP Extensions PSC which is carried on this
       LSP, and uses the relevant `EXP->PHB mapping' for Diff-Serv Support

   The MPLS architecture does not assume a single this PSC as
       defined in Section 4.2.1.1 below.

   For example if the incoming label distribution
   protocol. [LDP] defines corresponds to an L-LSP supporting
   the Label Distribution Protocol AF1 PSC, then the `Encaps-->PHB mapping' will be populated with:

      EXP Field              PHB

        000        ---->    AF11
        001        ---->    AF12
        010        ---->    AF13

4.2.1.1 EXP/PSC --> PHB mapping

   In order to populate the `Encaps-->PHB mapping', the mapping from
   the L-LSP PSCs and its
   usage for establishment the EXP field of label switched paths (LSPs) in the shim header into PHBs is
   specified as follows:

      EXP Field      PSC             PHB

        000          DF    <---->    DF
        000          CSn   <---->    CSn
        000          AFn   <---->    AFn1
        001          AFn   <---->    AFn2
        010          AFn   <---->    AFn3
        000          EF    <---->    EF

4.2.2 `CLP-->PHB mapping'

   If the LSR does not terminate an MPLS
   networks. This section specifies Shim Layer over this incoming
   label and uses ATM encapsulation (i.e. it is an ATM-LSR or it
   receives packets without a shim on an LC-ATM interface), then the extensions to LDP to establish
   `Encaps-->PHB mapping' of the Diff-Serv context for this incoming
   L-LSP is populated at label switched path (LSPs) supporting Differentiated Services in
   MPLS networks.

   Two new LDP TLVs are defined setup in this document:
        - the `DIFF-SERV_PSC' TLV following way:
     - it is actually a `CLP-->PHB mapping'
     - the `Release Status' TLV
   Detailed descriptions mapping is a function of these TLV are provided the PSC which is carried on this
       LSP, and uses the relevant `CLP-->PHB mapping' for this PSC as
       defined in Section 4.2.2.1 below.

   For example if the incoming label corresponds to an L-LSP supporting
   the AF1 PSC, then the `Encaps-->PHB mapping' will be populated with:

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                      MPLS Support of Diff-Serv             October 99

   As described in [LDP], there are two modes for label distribution:
   Downstream Unsolicited and Downstream on Demand.

   When an E-LSP is established using Downstream on Demand mode, the
   Label Request message and the Label Mapping message usually do not
   include the new Diff-Serv_PSC.            February 00

      CLP Field              PHB

        0          ---->    AF11
        1          ---->    AF12

4.2.2.1 CLP/PSC --> PHB mapping

   In the case where, a single Ordered
   Aggregate is order to be transported over populate the E-LSP, `Encaps-->PHB mapping', the Label Request
   message mapping from
   the L-LSP PSCs and the Label Mapping message may optionally include CLP bit of the new
   Diff-Serv_PSC (with its LSP-type defined below set to `E-LSP').

   When an E-LSP ATM cell header into PHBs is established using Downstream Unsolicited mode,
   specified as follows:

      CLP Bit      PSC             PHB

         0          DF    ---->    DF
         0          CSn   ---->    CSn
         0          AFn   ---->    AFn1
         1          AFn   ---->    AFn2
         0          EF    ---->    EF

4.2.3 `DE-->PHB mapping'

   If the
   new Diff-Serv_PSC MUST LSR does not be carried in the Label Request message
   nor in the Label Mapping message.

   When terminate an L-LSP MPLS Shim Layer over this incoming
   label and uses Frame Relay encapsulation(i.e. it is established using Downstream a FR-LSR or it
   receives packets without a shim on Demand mode, an LC-FR interface), then the
   new DIFF-SERV_PSC TLV MUST be carried
   `Encaps-->PHB mapping' of the Diff-Serv context for this incoming
   L-LSP is populated at label setup in the Label Request Message
   to indicate following way:
     - it is actually a `DE-->PHB mapping'
     - the PHB Scheduling Class (PSC) mapping is a function of the LSP and may
   optionaly be PSC which is carried on this
       LSP, and uses the relevant `DE-->PHB mapping' for this PSC as
       defined in Section 4.2.3.1 below.

4.2.3.1 DE/PSC --> PHB mapping

   In order to populate the Label Mapping message.

   When an L-LSP is established using Downstream Unsolicited mode, `Encaps-->PHB mapping', the
   new DIFF-SERV_PSC TLV MUST be carried in mapping from
   the Label Mapping Message
   to indicate L-LSP PSCs and the PHB Scheduling Class (PSC) DE bit of the LSP.

   The Release Status TLV is to be used to include diagnostic
   information in Label Release messages when handling Diff-Serv
   related errors.

   The new Diff-Serv_PSC and Release Status TLVs are optional with
   respect to LDP. A Diff-Serv capable LSR supporting E-LSPs in
   compliance with this specification MAY support the Diff-Serv_PSC TLV
   and the Release Status TLV. A Diff-Serv capable LSR supporting
   L-LSPs in compliance with this specification MUST support the Diff-
   Serv_PSC TLV and the Release Status TLV.

5.1 Diff-Serv related TLVs

5.1.1 Diff-Serv_PSC TLV

   As stated earlier, the PHB Scheduling Class associated with an L-LSP Frame Relay header into PHBs is to be
   specified through a new Diff-Serv_PSC TLV in LDP messages.
   The Diff-Serv_PSC TLV has the following format:

     0                   1                   2                   3 as follows:

      DE Bit      PSC             PHB

         0 1 2 3 4 5 6 7 8 9          DF    ---->    DF
         0 1 2 3 4 5 6 7 8 9          CSn   ---->    CSn
         0          AFn   ---->    AFn1
         1 2 3 4 5 6 7 8 9          AFn   ---->    AFn2
         0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |U|F| Type = PSC (0x901)        |      Length                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |        Reserved     | T |PSCnb|              PSC              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   U BIT =0          EF    ---->    EF

4.3 Incoming PHB Determination On Incoming L-LSP

   This section defines the mandatory default method for Incoming PHB
   determination for a labeled packet received on an L-LSP. This method
   requires that the `Encaps-->PHB mapping' is populated as defined
   above in section 4.2.

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                      MPLS Support of Diff-Serv             October 99

     If this new TLV is unknown to the LSR,            February 00

   When receiving a labeled packet over an L-LSP of an MPLS ingress
   interface, the LSR must reject first determines the
     whole message and return a notification

   F BIT = 0 `Encaps-->PHB mapping'
   associated with the incoming label.

4.3.1 `EXP-->PHB mapping'

   If this TLV is unknown to a LSR, this new TLV the `Encaps-->PHB mapping' is NOT forwarded.

   Type

     The Type of the PSC TLV is: 0x901.

   Length

     This is set to 4.

   Reserved

     This field is set to all zeros

   T

      This indicates form `EXP-->PHB mapping',
   then the `LSP Type'. The following values are
      specified:

           T Value      LSP type
           00           E-LSP
           01           L-LSP

   PSCnb

     Indicates LSR:
     - determines the number of PSC values included in incoming PHB by looking at the TSC TLV. This
     is set to 001

   PSC Value

     Encoding EXP field of the PSC
       top level label entry and by using the EXP-->PHB mapping.

   If the received EXP field value is as specified in section 4.2.

5.1.2 Release Status TLV

   As stated earlier, error codes are to specified through a new
   Release Status TLV not included in LDP Label Release messages when E-LSP or L-LSP
   set-up fails. The Release Status TLV has the following format:

     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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |U|F| Type = PSC (0x304)        |      Length                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                        Status Code                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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                      MPLS Support of Diff-Serv             October 99

   U BIT =0

     If EXP-->PHB
   mapping, this new TLV is unknown to the LSR, the EXP value should be considered invalid. LSR must reject the
     whole message and return a notification

   F BIT = 0

     If this TLV behavior
   in such situation is unknown to a LSR, local matter and is outside the scope of this new TLV
   document.

4.3.2 `CLP-->PHB mapping'

   If the `Encaps-->PHB mapping' is NOT forwarded.

   Type

     The Type of the PSC TLV is: 0x304.

   Status Code

     Indicates form `CLP-->PHB mapping',
   then the reason why LSR:
     - determines the label was released. This incoming PHB by looking at the CLP field uses of the same encoding
       ATM Layer encapsulation and values as by using the `Status Code' word defined for CLP-->PHB mapping.

   If the Notification message. Additional values are defined below, received CLP field value is not included in the section titled `Status Code Values', for CLP-->PHB
   mapping, this Status Code
     field CLP value should be considered invalid. LSR behavior
   in addition to such situation is a local matter and is outside the values currently defined in [LDP].

5.1.3 Status Code Values

   The following values are defined for scope of this
   document.

4.3.3 `DE-->PHB mapping'

   If the Status Code field which `Encaps-->PHB mapping' is
   used in Notification message of the form `DE-->PHB mapping',
   then the LSR:
     - determines the incoming PHB by looking at the DE field of the
       Frame Relay encapsulation and may be used in Label Release
   messages:

        Status Code             E   Status Data

        Unsupported PSC value   0   0x00000016
        Unexpected PSC by using the DE-->PHB mapping.

   If the received DE field value    0   0x00000017
        Unexpected PSC TLV      0   0x00000018
        Unexpected LSP-Type     0   0x00000019

5.2 Diff-Serv Related LDP Messages

5.2.1 Label Request Message

   In Downstream on Demand mode, is not included in the Diff-Serv capable DE-->PHB
   mapping, this DE value should be considered invalid. LSR requesting behavior in
   such situation is a
   label local matter and is outside the scope of this
   document.

4.4 Populating the `Set of PHB-->Encaps mappings' for an outgoing L-LSP includes the new Diff-Serv_PSC TLV in

   This section defines how the Label
   Request message to signal that `Set of PHB-->Encaps mappings' of the LSP
   Diff-Serv context is populated for an outgoing L-LSP and to indicate
   the PSC associated with the LSP.

   The format for support of
   the Label Request message mandatory default method for an L-LSP in Downstream Encoding Diff-Serv Information into
   Encapsulation on Demand mode, Outgoing L-LSP.

4.4.1 `PHB-->EXP mapping'

   If the LSR uses an MPLS Shim Layer over this outgoing label (i.e. it
   is as follows:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|   Label Request (0x0401)    |      Message Length           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ not an ATM-LSR or FR-LSR and it does not transmit packets without
   an MPLS Shim Layer on a LC-ATM or LC-FR interface), then one

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                      MPLS Support of Diff-Serv             October 99

   |                     Message ID                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     FEC TLV                                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     PSC TLV                                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

5.2.2 Label Mapping Message

   In Downstream Unsolicited mode,            February 00

   `PHB-->EXP mapping' is added at label setup to the `Set of
   PHB-->Encaps mapping' in the Diff-Serv capable LSR allocating context for this outgoing
   L-LSP. This `PHB-->EXP mapping' is populated in the following way:
     - it is a label function of the PSC supported on this LSP, and uses the
       relevant `PHB-->EXP mapping' for this PSC as defined in section
       4.4.1.1 below.

   For example if the outgoing label corresponds to an L-LSP includes supporting
   the Diff-Serv_PSC TLV in AF1 PSC, then the Label
   Mapping message following `PHB-->EXP mapping' is added into
   the `Set of PHB-->Encaps mappings':

        PHB                EXP Field

        AF11       ---->      000
        AF12       ---->      001
        AF13       ---->      010

4.4.1.1 PHB-->PSC/EXP mapping

   In order to signal that populate the `Set of PHB-->Encaps mappings', the mapping
   from the PHBs into the LSP is an L-LSP PSC and to indicate the EXP field of the shim
   header is specified as follows:

        PHB                     PSC associated with           EXP Field

        DF         ---->        DF              000
        CSn        ---->        CSn             000
        AFn1       ---->        AFn             000
        AFn2       ---->        AFn             001
        AFn3       ---->        AFn             010
        EF         ---->        EF              000

4.4.2 `PHB-->CLP mapping'

   If the LSP.

   The format LSR uses ATM encapsulation (i.e. it is an ATM-LSR or sends
   packets on an LC-ATM interface), then one `PHB-->CLP mapping' is
   added at label setup to the `Set of PHB-->Encaps mappings' in the Label Mapping message
   Diff-Serv context for an L-LSP this outgoing L-LSP. This `PHB-->CLP mapping'
   is populated in Downstream
   Unsolicited mode, the following way:
     - it is as follows:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|   Label Mapping (0x0400)    |      Message Length           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Message ID                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     FEC TLV                                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Label TLV                                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | a function of the PSC TLV                                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   In Downstream supported on Demand mode, this LSP, and uses the Diff-Serv capable LSR allocating a
   label
       relevant `PHB-->CLP mapping' for an L-LSP in response to a Label Request message containing
   the Diff-Serv_PSC TLV, may optionally include the same Diff-Serv_PSC
   TLV this PSC as defined below in
       section 4.4.2.1.

   For example if the Label Mapping message outgoing label corresponds to confirm the PSC associated with
   the LSP.

   The format of the Label Mapping message for an L-LSP in Downstream
   Unsolicited mode, is as follows:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 supporting
   the AF1 PSC, then the `PHB-->Encaps mapping' will be populated with:

        PHB                CLP Field

        AF11       ---->      0
        AF12       ---->      1 2 3 4 5 6 7 8 9 0
        AF13       ---->      1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|   Label Mapping (0x0400)    |      Message Length           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Message ID                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     FEC TLV                                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Label TLV                                 |

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                      MPLS Support of Diff-Serv             October 99

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     PSC TLV (optional)                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

5.2.3 Label Release Message

   [LDP] specifies            February 00

   Notice that `an the if the LSR sends is transmitting packets over a Label Release message to an LDP
   peer to signal LC-ATM
   interface using the peer that MPLS Shim Header, then the LSR no longer needs specific FEC-
   label mappings previously requested `Set of and/or advertised by PHB-->Encaps
   mappings' contains both a `PHB-->EXP mapping' and a `PHB-->CLP
   mapping'.

4.4.2.1 PHB-->PSC/CLP mapping

   In order to populate the
   peer.'

   This specification extends `Set of PHB-->Encaps mappings', the use mapping
   from the PHBs into the L-LSP PSC and the CLP bit of the Label Release message so
   that, when an ATM cell
   header is specified as follows:

        PHB              PSC       CLP Bit

         DF       ---->   DF         0
         CSn      ---->  CSn         0
         AFn1     ---->  AFn         0
         AFn2     ---->  AFn         1
         AFn3     ---->  AFn         1
         EF       ---->   EF         0

4.4.3 `PHB-->DE mapping'

   If the LSR cannot accept uses Frame Relay encapsulation (i.e. it is a label mapping for an E-LSP FR-LSR or
   sends packets on an
   L-LSP, LC-FR interface), one `PHB-->DE mapping' is
   added at label setup to the LSR should send `Set of PHB-->Encaps mapping' in the
   Diff-Serv context for this outgoing L-LSP and is populated in the
   following way:
     - it is a Label Release message to function of the LDP Peer
   to signal PSC supported on this LSP, and uses the peer
       relevant `PHB-->DE mapping' for this PSC as defined below in
       section 4.4.3.1.

   Notice that if the LSR cannot accept is sending packets over a LC-FR interfaces
   using the label mapping.

   This specification also extends MPLS Shim Header, then the encoding `Set of PHB-->Encaps mappings'
   contains both a `PHB-->EXP mapping' and a `PHB-->DE mapping'.

4.4.3.1 PHB-->PSC/DE mapping

   In order to populate the Label Release
   message so that `Set of PHB-->Encaps mappings', the new Release Status TLV can optionally be
   included in mapping
   from the message. Thus PHBs into the encoding L-LSP PSC and the DE bit of the Label Release
   message is: Frame Relay
   header is specified as follows:

        PHB              PSC       DE Bit

         DF       ---->   DF         0                   1                   2                   3
         CSn      ---->  CSn         0 1 2 3 4 5 6 7 8 9
         AFn1     ---->  AFn         0
         AFn2     ---->  AFn         1 2 3 4 5 6 7 8 9 0
         AFn3     ---->  AFn         1 2 3 4 5 6 7 8 9
         EF       ---->   EF         0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|   Label Release (0x0403)   |      Message Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Message ID                                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     FEC TLV                                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Label TLV (optional)                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Release Status TLV (optional)                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

5.2.4 Notification Message

   This specification allows inclusion of the Diff-Serv_PSC TLV in the
   Notification. Thus the encoding of the Notification message is:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|   Notification (0x0001)     |      Message Length           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Message ID                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Status TLV                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Optional Parameters                       |

4.4.4 `PHB-->802.1 mapping'

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                      MPLS Support of Diff-Serv             October 99

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Diff-Serv_PSC TLV (optional)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

5.3 Handling of the Diff-Serv_PSC TLV

5.3.1 Handling of the Diff-Serv_PSC TLV in Downstream Unsolicited Mode

   This section describes operations when            February 00

   If the Downstream Unsolicited
   Mode outgoing interface is used.

   When allocating a LAN interface on which multiple
   Traffic Classes are supported as defined in [IEEE_802.1], then one
   `PHB-->802.1 mapping' is added at label for an E-LSP, a Diff-Serv capable LSR issues
   a Label Mapping message without the Diff-Serv_PSC TLV.

   A Diff-Serv capable LSR receiving a Label Mapping message without
   the Diff-Serv_PSC TLV, must:
        - update its Incoming Label Map (ILM) [MPLS_ARCH] setup to store the
   necessary `Set of
   PHB-->Encaps mappings' in the Diff-Serv information. context for this outgoing
   L-LSP. This includes the fact that `PHB-->802.1 mapping' is populated in the
   Next Hop Label Forwarding Entry (NHLFE) corresponds to an E-LSP. following way:
     - install it is a function of the required scheduling PSC supported on this LSP, and dropping behavior uses the
       relevant `PHB-->802.1 mapping' for this NHLFE to support Diff-Serv forwarding as specified for E-LSPs PSC from the
       Preconfigured `PHB-->802.1 mapping' defined above in section 2.2.

   When allocating a label for an L-LSP, a Diff-Serv capable
       3.4.2.1.

   Notice that if the LSR issues is transmitting packets over a Label Mapping message which contains the Diff-Serv_PSC TLV with
   its PSC field indicating LAN interface
   supporting multiple 802.1 Traffic Classes, then the PSC `Set of the L-LSP.

   A Diff-Serv capable LSR receiving
   PHB-->Encaps mappings' contains both a Label Mapping message containing
   the Diff-Serv_PSC TLV, must:
        - update its ILM to store the necessary `PHB-->EXP mapping' and a
   `PHB-->802.1 mapping'.

4.5     Encoding Diff-Serv information. Information into Encapsulation on Outgoing
L-LSP

   This includes section defines the fact that mandatory default method for encoding of
   Diff-Serv related information into the NHLFE corresponds MPLS encapsulation Layer to
   be used when a packet is transmitted onto an L-LSP and
   its PSC.
        - install L-LSP.  This method
   requires that the required scheduling and dropping behavior for
   this LSP to support Diff-Serv forwarding `Set of PHB-->Encaps mappings' is populated as specified for L-LSPs
   defined above in section 3.2.

   A Diff-Serv capable 4.4.

   The LSR receiving a Label Mapping message first determines the `Set of PHB-->Encaps mapping'
   associated with the
   Diff-Serv_PSC TLV containing outer label of the NHLFE.

4.5.1 `PHB-->EXP mapping'

   If the `Set of PHB-->Encaps mapping' of the outer label contains a PSC value
   mapping of the form `PHB-->EXP mapping', then, for all the labels
   which is not supported,
   must reject are swapped or pushed, the LSR:
     - determines the PHB-->EXP mapping by sending a Label Release message which
   includes the Label TLV and looking up the Release Status TLV with a Status Code
       `PHB-->Encaps mapping' of `Unsupported PSC Value'.

   A the Diff-Serv capable LSR receiving a Label Mapping message context associated with
   multiple Diff-Serv_PSC TLVs only considers
       the first one as
   meaningful. The LSR must ignore and not forward corresponding label in the subsequent Diff-
   Serv_PSC TLV(s).

5.3.2 Handling of NHLFE.
     - determines the Diff-Serv_PSC TLV value to be written in Downstream on Demand Mode

   This section describes operations when the Downstream on Demand Mode
   is used.

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                      MPLS Support EXP field of Diff-Serv             October 99

   When requesting a the
       corresponding level label for an E-LSP, a Diff-Serv capable LSR sends
   a Label Request message without entry by looking up the Diff-Serv_PSC TLV.

   Optionally, when requesting a lebel for an E-LSP over which a single
   Ordered Aggregate is to going to be transported, "outgoing PHB"
       in this PHB-->EXP mapping table.

4.5.2 `PHB-->CLP mapping'

   If the Diff-Serv
   capable LSR may send `Set of PHB-->Encaps mapping' of the outer label contains a Label Request message containing
   mapping of the Diff-
   Serv_PSC TLV with its LSP type set to E-LSP and its PSC field set to form `PHB-->CLP mapping', then the value of LSR:
     - determines the PSC value to be supported on the E-LSP.

   A Diff-Serv capable LSR sending a Label Mapping message written in response
   to a Label Request message which did not contain the Diff-Serv_PSC
   TLV, must not include Diff-Serv_PSC TLV CLP field of the ATM
       Layer encapsulation by looking up the "outgoing PHB" in this Label Mapping
   message.

   A Diff-Serv capable LSR sending a Label Mapping message in response
   to a Label Request message which contained
       PHB-->CLP mapping table.

4.5.3 `PHB-->DE mapping'

   If the Diff-Serv_PSC TLV
   with its E-LSP type set to E-LSP, may send this Label Mapping
   message without `Set of PHB-->Encaps mapping' of the Diff-Serv_PSC TLV. Optionally, outer label contains a
   mapping  of the LSR may send
   this Label Mapping message with form `PHB-->DE mapping', then the Diff-Serv_PSC TLV with its LSP-
   Type set LSR:

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                      MPLS Support of Diff-Serv            February 00

     - determines the value to E-LSP and its PSC be written in the DE field set to of the same value as Frame
       Relay encapsulation by looking up the one
   received "outgoing PHB" in this
       PHB-->DE mapping table.

4.5.4 `PHB-->802.1 mapping'

   If the Label Request message.

   A Diff-Serv capable LSR receiving `Set of PHB-->Encaps mapping' of the outer label contains a Label Mapping message without
   mapping  of the Diff-Serv_PSC TLV in response to its Label Request message for
   an E-LSP, must: form `PHB-->802.1 mapping', then the LSR:
     - update its ILM determines the value to store be written in the necessary Diff-Serv information.
   This includes User_Priority field of
       the fact that Tag Control Information of the NHLFE corresponds to an E-LSP.
        - install 802.1 encapsulation header
       [IEEE_802.1] by looking up the required scheduling and dropping behavior for "outgoing PHB" in this NHLFE to
       PHB-->802.1 mapping table.

4.6 L-LSP Merging

   In an MPLS domain, two or more LSPs can be merged into one LSP at
   one LSR. The proposed support of Diff-Serv forwarding as specified for E-LSPs
   in section 2.2.

   A Diff-Serv capable LSR receiving a Label Mapping message containing
   the Diff-Serv_PSC TLV in response to its Label Request message for
   an E-LSP which did not contain MPLS is compatible
   with LSP Merging under the Diff-Serv_PSC TLV, must reject following condition:

        L-LSPs can only be merged into one L-LSP if they support the label mapping
        same PSC.

   The above merge condition MUST be enforced by sending a Label Release message which includes
   the Label TLV and LSRs through explicit
   checking at label setup that the Release Status TLV with a Status Code of
   `Unexpected same PSC TLV'.

   A Diff-Serv capable LSR receiving a Label Mapping message containing is supported on the Diff-Serv_PSC TLV in response to its Label Request message for
   an E-LSP which contained merged
   LSPs.

   Note that when L-LSPs merge, the Diff-Serv_PSC TLV, must compare bandwidth that is available for the
   received and sent Diff-Serv_PSC TLVs.

   If those are equal,
   PSC downstream of the LSR must:
        - update its ILM merge point must be sufficient to store the necessary Diff-Serv information.
   This includes carry the fact that
   sum of the NHLFE corresponds to an E-LSP.
        - install merged traffic. This is particularly important in the required scheduling and dropping behavior for
   this NHLFE to support Diff-Serv forwarding as specified for E-LSPs
   case of EF traffic. This can be ensured in section 2.2.

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                      MPLS Support of multiple ways (for
   instance via provisioning, or via bandwidth signaling and explicit
   admission control).

5. RSVP Extension for Diff-Serv             October 99

   If those are Support

   The MPLS architecture does not equal because they have a different LSP-Type, the
   LSR must reject the Label Mapping by sending assume a Label Release message
   which includes single label distribution
   protocol. [RSVP_MPLS_TE] defines the Label TLV and extension to RSVP for
   establishing label switched paths (LSPs) in MPLS networks. This
   section specifies the Release Status TLV with a
   Status Code of `Unexpected LSP-Type'.

   If extensions to RSVP, beyond those are not equal because they have a different PSC value, the
   LSR must reject the Label Mapping by sending a Label Release message
   which includes the Label TLV and the Release Status TLV with a
   Status Code of `Unexpected PSC Value'.

   When requesting a defined in
   [RSVP_MPLS_TE], to establish label for an L-LSP, a switched path (LSPs) supporting
   Differentiated Services in MPLS networks.

5.1 Diff-Serv capable LSR sends
   a Label Request message with related RSVP Messages Format

   One new RSVP Object is defined in this document: the Diff-Serv_PSC TLV which indicates DIFFSERV
   Object. Detailed description of this Object is provided below. This
   new Object is applicable to Path messages. This specification only
   defines the PSC use of the L-LSP.

   A Diff-Serv capable LSR receiving a Label Request message DIFFSERV Object in Path messages used to
   establish LSP Tunnels in accordance with the
   Diff-Serv_PSC TLV [RSVP_MPLS_TE] and thus
   containing a PSC value which is not supported or
   for which no EXP/PSC<-->PHB mapping is configured, must send a
   Notification message Session Object with a Status Code of `Unsupported PSC Value'.

   A Diff-Serv capable LSR that recognizes the Diff-Serv_PSC TLV Type
   in a Label Request message C-Type equal to LSP_TUNNEL_IPv4
   and supports containing a LABEL_REQUEST object.

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                      MPLS Support of Diff-Serv            February 00

   Restrictions defined in [RSVP_MPLS_TE] for support of establishment
   of LSP Tunnels via RSVP are also applicable to the requested PSC but establishment of
   LSP Tunnels supporting Diff-Serv: for instance, only unicast LSPs
   are supported and Multicast LSPs are for further study.

   This new DIFFSERV object is optional with respect to RSVP so that
   general RSVP implementations not
   able concerned with MPLS LSP set up do
   not have to satisfy the label request support this object.

   The DIFFSERV Object is optional for other reasons (eg no label
   available), must send a Notification message support of LSP Tunnels as
   defined in accordance with
   existing LDP procedures [LDP] (eg. with a `No Label Resource' Status
   Code). This Notification message must include the requested
   Diff-Serv_PSC TLV. [RSVP_MPLS_TE]. A Diff-Serv capable LSR sending a Label Mapping message in response
   to a Label Request message which contained the Diff-Serv_PSC TLV,
   may optionally include supporting E-LSPs
   using the exact same Diff-Serv_PSC TLV preconfigured EXP<-->PHB mapping in compliance with this
   Label Mapping message.
   specification MAY support the DIFFSERV Object. A Diff-Serv capable
   LSR receiving supporting E-LSPs using a Label Mapping message without
   the Diff-Serv_PSC TLV signaled EXP<-->PHB mapping in response to its Label Request message for
   an L-LSP, must:
        - update its ILM to store the necessary Diff-Serv information.
   This includes the fact that the NHLFE corresponds to an L-LSP and
   its PSC.
        - install the required scheduling and dropping behavior for
   compliance with this NHLFE to specification MUST support Diff-Serv forwarding as specified for L-LSPs
   in section 3.2. the DIFFSERV Object.
   A Diff-Serv capable LSR receiving a Label Mapping message with the
   Diff-Serv_PSC TLV supporting L-LSPs in response to its Label Request message for an L-
   LSP, must verify that compliance with this
   specification MUST support the Diff-Serv_PSC TLV received in DIFFSERV Object.

5.1.1 Path Message Format

   The format of the Label
   Mapping Path message is equal to the Diff-Serv_PSC TLV sent in the Label
   Request message.

   If those as follows:

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

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

5.2 DIFFSERV Object

   The DIFFSERV object formats are equal, the LSR must:
        - update its ILM shown below. Currently there are two
   possible C_Types. Type 1 is a DIFFSERV object for an E-LSP. Type 2
   is a DIFFSERV object for an L-LSP.

   5.2.1. DIFFSERV object for an E-LSP:

   class = TBD, C_Type = 1  (need to store the necessary Diff-Serv information.
   This includes get an official class num from the fact that
   IANA with the NHLFE corresponds to an L-LSP and
   its PSC form 0bbbbbbb)

     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                                       | MAPnb |

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                      MPLS Support of Diff-Serv             October 99

        - install the required scheduling and dropping behavior for
   this NHLFE            February 00

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                            MAP (1)                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    //                               ...                            //
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                            MAP (MAPnb)                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Reserved : 28 bits
       This field is reserved. It must be set to support Diff-Serv forwarding as specified for L-LSPs
   in section 3.2.

   If those are not equal because they have a different LSP-Type, the
   LSR zero on transmission
       and must reject the Label Mapping by sending a Label Release message
   which includes the Label TLV and be ignored on receipt.

     MAPnb : 4 bits
       Indicates the Release Status TLV with a
   Status Code number of `Unexpected LSP-Type'.

   If those are not equal because they have a different PSC value, the
   LSR must reject MAP entries included in the Label Mapping by sending a Label Release message
   which includes DIFFSERV
       Object. This can be set to any value from 1 to 8 (decimal).

     MAP : 32 bits
       Each MAP entry defines the Label TLV mapping between one EXP field value
       and the Release Status TLV with a
   Status Code of `Unexpected PSC Value'.

   A Diff-Serv capable LSR receiving a Label Mapping message with
   multiple Diff-Serv_PSC TLVs only considers the first one as
   meaningful. PHB. The LSR MAP entry has the following format:

     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     | EXP |             PHBID             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Reserved : 13 bits
               This field is reserved. It must ignore be set to zero on
               transmission and not forward must be ignored on receipt.

           EXP : 3 bits
               This field contains the subsequent Diff-
   Serv_PSC TLV(s).

5.4 Non-Handling value of the Diff-Serv_PSC TLV

   An LSR that does not recognize EXP field for the Diff-Serv_PSC TLV Type, on
   receipt
               EXP<-->PHB mapping defined in this MAP entry.

           PHBID : 16 bits
               This field contains the PHBID of a Label Request message or a Label Mapping message
   containing the Diff-Serv_PSC TLV, must ignore PHB for the message and return
   a Notification message with _Unknown TLV_ Status.

5.5 Bandwidth Information

   Bandwidth information may also be signaled at establishment time of
   E-LSP and L-LSP, for instance for the purpose of Traffic
   Engineering, using the Traffic Parameters TLV as described
               EXP<-->PHB mapping defined in
   [MPLS CR LDP].

6. MPLS Support of Diff-Serv over PPP this MAP entry. The general operations for MPLS support of Diff-Serv, including
   label forwarding and LSP setup operations was PHBID
               is encoded as specified in the
   previous sections. This section describes 2 of [PHBID].

   5.2.2 DIFFSERV object for an L-LSP:

   class = TBD, C_Type = 2  (class num is the specific operations
   required same as DIFFSERV object
   for MPLS support of Diff-Serv over PPP links. While
   sections 7, E-LSP))

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 and 9 focus on other media specific operations, namely
   ATM, Frame Relay and LAN respectively.

   This document allows the following set of LSP setup combinations per
   FEC within an MPLS PPP Diff-Serv domain:

        - Zero or any number of E-LSP, and
        - Zero or any number of L-LSPs.

6.1. E-LSP Operations over PPP 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        Reserved               |             PSC               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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                      MPLS Support of Diff-Serv             October 99

   Since MPLS uses the Shim Header for encapuslation over PPP, E-LSPs
   are supported over PPP. The E-LSP setup, label forwarding            February 00

     Reserved : 16 bits
       This field is reserved. It must be set to zero on transmission
       and
   merging operations over PPP follows exactly must be ignored on receipt.

     PSC : 16 bits
        The PSC indicates a PHB Scheduling Class to be supported by the procedures defined
        LSP. The PSC is encoded as specified in section 2. No additional PPP specific procedures are defined for
   E-LSPs.

6.2  L-LSP Operations over PPP

   L-LSPs are also supported over PPP. The L-LSP operations over PPP
   follows the general procedures 2 of section 3. However, [PHBID]:
            - Where the following
   PPP specific procedures are also PSC comprises a single PHB defined by standards
        action, the encoding for L-LSP operations over
   PPP : the PSC is the encoding for this
        single PHB. It is the recommended DSCP value for that PHB,
        left-justified in the 16-bit field, with bits 6 through 15 set
        to zero.
           - An MPLS PPP ingress interface determines Where the incoming PHB
   from PSC comprises multiple PHBs defined by standards
        action, the PSC encoding is the encoding for this set of PHB.
        It is the smallest numerical value of the recommended DSCP for
        the various PHBs in the PSC, left-justified in the 16 bit
        field, with bits 6 through 13 and bit 15 set to zero and with
        bit 14 set to one.

       For instance, the EXP field encoding of the EF PSC is :
              0                   1
              0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |1 0 1 1 1 0|0 0 0 0 0 0 0 0 0 0|
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       For instance, the encoding of the AF1 PSC is :
              0                   1
              0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |0 0 1 0 1 0|0 0 0 0 0 0 0 0 1 0|
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

5.3 Handling Diff-Serv Object

   To establish an LSP tunnel with RSVP, the sender creates a Path
   message with a session type of LSP_Tunnel_IPv4 and with a
   LABEL_REQUEST object as per [RSVP_MPLS_TE].

   Where the sender supports Diff-Serv, to establish with RSVP an E-LSP
   tunnel which uses the Preconfigured EXP<-->PHB mapping, the sender
   creates a Path message:
     - with a session type of LSP_Tunnel_IPv4,
     - with the LABEL_REQUEST object, and
     - without the DIFFSERV object.

   Where the sender supports Diff-Serv, to establish with RSVP an E-LSP
   tunnel which uses a signaled EXP<-->PHB mapping, the sender creates
   a Path message :
     - with a session type of LSP_Tunnel_IPv4,
     - with the LABEL_REQUEST object,

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                      MPLS Support of Diff-Serv            February 00

     - with the DIFFSERV object for an E-LSP containing one MAP entry
       for each EXP value to be supported on this E-LSP.

   Where the sender supports Diff-Serv, to establish with RSVP an L-LSP
   tunnel, the sender creates a Path message:
     - with a session type of LSP_Tunnel_IPv4,
     - with the LABEL_REQUEST object,
     - with the DIFFSERV object for an L-LSP containing the PHB
       Scheduling Class (PSC) supported on this L-LSP.

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

   Each node along the path records the DIFFSERV object, when present,
   in its path state block.

   The destination node of an E-LSP or L-LSP responds to the Path
   message containing the LABEL_REQUEST object by sending a Resv
   message:
     - with the LABEL object
     - without a DIFFSERV object.

   Assuming the reservation is accepted and a label is associated with
   the reservation, the Diff-Serv LSRs (sender, destination,
   intermediate nodes) must:
     - update the Diff-Serv context associated with the established
       LSPs in their ILM/FTN as specified in previous sections
       (incoming and outgoing label),
     - install the required Diff-Serv forwarding treatment (scheduling
       and dropping behavior) for this NHLFE (outgoing label).

   An RSVP router that does recognizes the DIFFSERV object and that
   receives a path message which contains the DIFFSERV object but which
   does not contain a LABEL_REQUEST object or which does not have a
   session type of LSP_Tunnel_IPv4, sends a PathErr towards the sender
   with the error code `Diff-Serv Error' and an error value of
   `Unexpected DIFFSERV object'. Those are defined below in section
   5.5.

   A node receiving a Path message with the DIFFSERV object for E-LSP,
   which recognizes the DIFFSERV object but does not support the
   particular PHB encoded in one, or more, of the MAP entries, sends a
   PathErr towards the sender with the error code `Diff-Serv Error' and
   an error value of `Unsupported PHB'. Those are defined below in
   section 5.5.

   A node receiving a Path message with the DIFFSERV object for E-LSP,
   which recognizes the DIFFSERV object but determines that the
   signaled EXP<-->PHB mapping is invalid, sends a PathErr towards the
   sender with the error code `Diff-Serv Error' and an error value of
   `Invalid EXP<-->PHB mapping'. Those are defined below in section

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                      MPLS Support of Diff-Serv            February 00

   5.5. The EXP<-->PHB mapping signaled in the DIFFSERV Object for an
   E-LSP is invalid when:
     - the MAPnb field is not within the range 1 to 8 decimal, or
     - a given EXP value appears in more than one MAP entry, or
     - the PHBID encoding is invalid

   A node receiving a Path message with the DIFFSERV object for L-LSP,
   which recognizes the DIFFSERV object but does not support the
   particular PSC encoded in the PSC field, sends a PathErr towards the
   sender with the error code `Diff-Serv Error' and an error value of
   `Unsupported PSC'. Those are defined below in section 5.5.

   A Diff-Serv LSR MUST handle the situations where the reservation can
   not be accepted for other reasons than those already discussed in
   this section, in accordance with [RSVP_MPLS_TE] (eg. reservation
   rejected by admission control, a label can not be associated).

5.4 Non-support of the Diff-Serv Object

   An RSVP router that does not recognize the DIFFSERV object Class-Num
   must behave in accordance with the procedures specified in [RSVP]
   for an unknown Class-Num whose format is 0bbbbbbb ie. it must send a
   PathErr with the error code `Unknown object class' toward the
   sender.

   An RSVP router that recognizes the DIFFSERV object Class-Num but
   does not recognize the DIFFSERV object C-Type, must behave in
   accordance with the procedures specified in [RSVP] for an unknown C-
   type ie. 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 management that a L-LSP cannot be established and
   possibly take action to retry reservation establishment without the
   DIFFSERV object (eg. attempt to use E-LSPs with Preconfigured
   EXP<-->PHB mapping as a fall-back strategy).

5.5 Error Codes For Diff-Serv

   In the procedures described above, certain errors must be reported
   as a `Diff-Serv Error'. The value of the `Diff-Serv Error' error
   code is 26 (TBD).

   The following defines error values for the Diff-Serv Error:

       Value    Error

        1       Unexpected DIFFSERV object
        2       Unsupported PHB
        3       Invalid EXP<-->PHB mapping
        4       Unsupported PSC

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                      MPLS Support of Diff-Serv            February 00

5.6 Use of COS Service with E-LSPs and L-LSPs

   Both E-LSPs and L-LSPs can be established with bandwidth reservation
   or without bandwidth reservation.

   To establish an E-LSP or an L-LSP with bandwidth reservation, Int-
   Serv's Controlled Load service (or possibly Guaranteed Service) is
   used and the bandwidth is signaled in the SENDER_TSPEC (respectively
   FLOWSPEC) of the path (respectively Resv) message.

   To establish an E-LSP or an L-LSP without bandwidth reservation, the
   Class of Service service defined in [RSVP_MPLS_TE] is used.

   A Path message containing a COS SENDER_TSPEC and not containing a
   DIFFSERV object indicates to a Diff-Serv capable LSR that the LSP to
   be established in an E-LSP using the Preconfigured mapping and
   without any bandwidth reservation.

   A Path message containing a COS SENDER_TSPEC and containing a
   DIFFSERV object for E-LSP indicates to a Diff-Serv capable LSR that
   the LSP to be established in an E-LSP using a signaled mapping and
   without any bandwidth reservation.

   A Path message containing a COS SENDER_TSPEC and containing a
   DIFFSERV object for LSP indicates to a Diff-Serv capable LSR that
   the LSP to be established in an L-LSP without any bandwidth
   reservation.

   The above is summarized in the following table:

           Path Message  LSP type
    Service  DIFFSERV
              Object

     GS/CL     No        E-LSP + preconf mapping + bandw reservation
     GS/CL   Yes/E-LSP   E-LSP + signaled mapping + bandw reservation
     GS/CL   Yes/L-LSP   L-LSP + bandw reservation
     COS       No        E-LSP + preconf mapping + no bandw reservation
     COS     Yes/E-LSP   E-LSP + signaled mapping + no band reservation
     COS     Yes/L-LSP   L-LSP + no bandw reservation

   Where:
        - GS stands for Guaranteed Service
        - CL stands for Controlled Load
        - COS stands for COS service

   When processing a path (respectively Resv) message for an E-LSP or
   an L-LSP using the COS service, a Diff-Serv capable LSR must ignore
   the value of the COS field within a COS SENDER_TSPEC (respectively a
   COS FLOWSPEC).

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                      MPLS Support of Diff-Serv            February 00

6. LDP Extensions for Diff-Serv Support

   The MPLS architecture does not assume a single label distribution
   protocol. [LDP] defines the Label Distribution Protocol and its
   usage for establishment of label switched paths (LSPs) in MPLS
   networks. This section specifies the extensions to LDP to establish
   label switched path (LSPs) supporting Differentiated Services in
   MPLS networks.

   One new LDP TLV is defined in this document:
        - the Diff-Serv TLV
   Detailed description of this TLV is provided below.

   The new Diff-Serv TLV is optional with respect to LDP. A Diff-Serv
   capable LSR supporting E-LSPs which uses the Preconfigured
   EXP<-->PHB mapping in compliance with this specification MAY support
   the Diff-Serv TLV. A Diff-Serv capable LSR supporting E-LSPs which
   uses the signaled EXP<-->PHB mapping in compliance with this
   specification MUST support the Diff-Serv TLV. A Diff-Serv capable
   LSR supporting L-LSPs in compliance with this specification MUST
   support the Diff-Serv TLV.

6.1 Diff-Serv TLV

   The Diff-Serv TLV has the following formats:

   Diff-Serv TLV for an E-LSP:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |U|F| Type = PSC (0x901)        |      Length                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |T|        Reserved                                     | MAPnb |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            MAP (1)                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                    ...

     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            MAP (MAPnb)                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     T:1 bit
       LSP Type. This is set to 0 for an E-LSP

     Reserved : 28 bits
       This field is reserved. It must be set to zero on transmission
       and must be ignored on receipt.

     MAPnb : 4 bits

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                      MPLS Support of Diff-Serv            February 00

       Indicates the number of MAP entries included in the DIFFSERV
       Object. This can be set to any value from 1 to 8 (decimal).

     MAP : 32 bits
       Each MAP entry defines the mapping between one EXP field value
       and one PHB. The MAP entry has the following format:

     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     | EXP |             PHBID             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Reserved : 13 bits
               This field is reserved. It must be set to zero on
               transmission and must be ignored on receipt.

           EXP : 3 bits
               This field contains the value of the EXP field for the
               EXP<-->PHB mapping defined in this MAP entry.

           PHBID : 16 bits
               This field contains the PHBID of the PHB for the
               EXP<-->PHB mapping defined in this MAP entry. The PHBID
               is encoded as specified in section 2 of [PHBID].

   Diff-Serv TLV for an L-LSP:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |U|F| Type = PSC (0x901)        |      Length                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |T|        Reserved             |              PSC              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     T:1 bit
       LSP Type. This is set to 1 for an L-LSP

     Reserved : 16 bits
       This field is reserved. It must be set to zero on transmission
       and must be ignored on receipt.

     PSC : 16 bits
        The PSC indicates a PHB Scheduling Class to be supported by the
        LSP. The PSC is encoded as specified in section 2 of [PHBID]:
            - Where the PSC comprises a single PHB defined by standards
        action, the encoding for the PSC is the encoding for this
        single PHB. It is the recommended DSCP value for that PHB,
        left-justified in the 16-bit field, with bits 6 through 15 set
        to zero.

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                      MPLS Support of Diff-Serv            February 00

           - Where the PSC comprises multiple PHBs defined by standards
        action, the PSC encoding is the encoding for this set of PHB.
        It is the smallest numerical value of the recommended DSCP for
        the various PHBs in the PSC, left-justified in the 16 bit
        field, with bits 6 through 13 and bit 15 set to zero and with
        bit 14 set to one.

       For instance, the encoding of the EF PSC is :
              0                   1
              0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |1 0 1 1 1 0|0 0 0 0 0 0 0 0 0 0|
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       For instance, the encoding of the AF1 PSC is :
              0                   1
              0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |0 0 1 0 1 0|0 0 0 0 0 0 0 0 1 0|
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

6.2 Diff-Serv Status Code Values

   The following values are defined for the Status Code field of the
   Status TLV:

        Status Code                     E   Status Data

        Unsupported PHB                 0   0x00000016
        Invalid EXP<-->PHB mapping      0   0x00000017
        Unsupported PSC                 0   0x00000018
        Unexpected Diff-Serv TLV        0   0x00000019

6.3 Diff-Serv Related LDP Messages

6.3.1 Label Request Message

   The format of the Label Request message is extended as follows, to
   optionally include the Diff-Serv TLV:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|   Label Request (0x0401)    |      Message Length           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Message ID                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     FEC TLV                                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Diff-Serv TLV (optional)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 Le Faucheur et. al                                                 30

                      MPLS Support of Diff-Serv            February 00

6.3.2 Label Mapping Message

   The format of the Label Mapping message is extended as follows, to
   optionally include the Diff-Serv TLV:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|   Label Mapping (0x0400)    |      Message Length           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Message ID                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     FEC TLV                                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Label TLV                                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Diff-Serv TLV (optional)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

6.3.3 Label Release Message

   The format of the Label Release message is extended as follows, to
   optionally include the Status TLV:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|   Label Release (0x0403)   |      Message Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Message ID                                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     FEC TLV                                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Label TLV (optional)                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Status TLV (optional)                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

6.3.4 Notification Message

   The format of the Notification message is extended as follows, to
   optionally include the Diff-Serv TLV:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|   Notification (0x0001)     |      Message Length           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Message ID                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Status TLV                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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                      MPLS Support of Diff-Serv            February 00

   |                     Optional Parameters                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Diff-Serv TLV (optional)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

6.4 Handling of the top level label entry in
   accordance with Diff-Serv TLV

6.3.1 Handling of the PSC/EXP -->PHB mappings defined below Diff-Serv TLV in Downstream Unsolicited Mode

   This section
   6.3.

        - If describes operations when the EXP field value of Downstream Unsolicited
   Mode is used.

   When allocating a packet received on label for an L-LSP is
   such that the PSC/EXP combination E-LSP which is not listed in to use the mapping of
   section 6.3, this PSC/EXP combination should be considered invalid.
   preconfigured EXP<-->PHB mapping, a downstream Diff-Serv LSR behavior in such situation is issues
   a local matter and is outside Label Mapping message without the
   scope of this document.

        - An MPLS PPP egress interface determines Diff-Serv TLV.

   When allocating a label for an E-LSP which is to use a signaled
   EXP<-->PHB mapping, a downstream Diff-Serv LSR issues a Label
   Mapping message with the Diff-Serv TLV for an E-LSP which contains
   one MAP entry for each EXP value to be
   written in the EXP field of the top level label entry (and possibly
   of other level supported on this E-LSP.

   When allocating a label entries in the case of for an L-LSP, a hierarchical tunnel
   entry) by performing the outgoing PHB-->EXP/PSC mapping defined
   below in section 6.4.

6.3 PSC/EXP --> PHB mapping

   The mapping from the L-LSP PSC and the EXP field of the shim header
   into PHBs is as follows:

      EXP Field      PSC             PHB

        000          DF    ----->    DF
        000          CSn   ----->    CSn
        000          AFCn  ----->    AFn1
        001          AFCn  ----->    AFn2
        010          AFCn  ----->    AFn3
        000          EF    ----->    EF

6.4 PHB --> PSC/EXP mapping

   The mapping from PHBs into downstream Diff-Serv LSR
   issues a Label Mapping message with the Diff-Serv TLV for an L-LSP PSC and
   which contains the EXP field of PHB Scheduling Class (PSC) to be supported on
   this L-LSP.

   Assuming the
   shim header label set-up is successful, the downstream and upstream
   LSRs must:
     - update the Diff-Serv context associated with the established
       LSPs in their ILM/FTN as follows:

      PHB              EXP Field     PSC

      DF     ----->     000          DF

 Le Faucheur et. al                                                 26

                      MPLS Support of specified in previous sections
       (incoming and outgoing label),
     - install the required Diff-Serv forwarding treatment (scheduling
       and dropping behavior) for this NHLFE (outgoing label).

   An upstream Diff-Serv             October 99

      CSn    ----->     000          CSn
      AFn1   ----->     000          AFCn
      AFn2   ----->     001          AFCn
      AFn3   ----->     010          AFCn
      EF     ----->     000          EF

6.5 LSR implementation receiving a Label Mapping message with PPP interfaces

   For an
   multiple Diff-Serv TLVs only considers the first one as meaningful.
   The LSR implementation must ignore and not forward the subsequent Diff-Serv TLV(s).

   An upstream Diff-Serv LSR which receives a Label Mapping message
   with PPP interfaces, the Diff-Serv TLV for an E-LSP and does not support the
   particular PHB encoded in one, or more, of E-LSPs
   over the PPP interfaces is mandatory MAP entries, must
   reject the mapping by sending a Label Release message which includes
   the Label TLV and the Status TLV with respect to this
   specification. A a Status Code of `Unsupported
   PHB'.

   An upstream Diff-Serv capable LSR receiving a Label Mapping message with PPP interfaces MUST
   support E-LSPs over these PPP interfaces in compliance the
   Diff-Serv TLV for an E-LSP and determining that the signaled
   EXP<-->PHB mapping is invalid, must reject the mapping by sending a
   Label Release message which includes the Label TLV and the Status
   TLV with this
   specification.

   Support a Status Code of L-LSPs over PPP interfaces by `Invalid EXP<-->PHB Mapping'. The
   EXP<-->PHB mapping signaled in the DIFFSERV Object for an LSR implementation E-LSP is
   optional. A
   invalid when:

 Le Faucheur et. al                                                 32

                      MPLS Support of Diff-Serv capable LSR MAY support L-LSPs over PPP
   interfaces. However, if            February 00

     - the MAPnb field is not within the range 1 to 8 decimal, or
     - a Diff-Serv LSR does support L-LSPs over PPP
   interfaces, then it MUST do so given EXP value appears in compliance with all more than one MAP entry, or
     - the material
   from this specification pertaining to L-LSPs. PHBID encoding is invalid

   An upstream Diff-Serv LSR running MPLS over PPP over receiving a traditional ATM connection (ie
   where Label Mapping message with the ATM switches do
   Diff-Serv TLV for an L-LSP containing a PSC value which is not participate in MPLS
   supported, must reject the mapping by sending a Label Release
   message which includes the Label TLV and where the ATM
   connection VPI/VCI values have not been established via any Status TLV with a
   Status Code of `Unsupported PSC'.

6.3.2 Handling of the Diff-Serv TLV in Downstream on Demand Mode

   This section describes operations when the Downstream on Demand Mode
   is used.

   When requesting a label
   distribution protocol) for an E-LSP which is to be considered as use the
   preconfigured EXP<-->PHB mapping, an upstream Diff-Serv LSR with PPP
   interfaces from sends a
   Label Request message without the point of view of compliance Diff-Serv TLV.

   When requesting a label for an E-LSP which is to this
   specification.

   Similarly, use a signaled
   EXP<-->PHB mapping, an upstream Diff-Serv LSR running MPLS over PPP over sends a traditional Frame
   Relay connection (ie where the Frame Realy switches do not
   participate in MPLS and where Label Request
   message with the Frame Relay connection DLCI values
   have not been established via any label distribution protocol) is Diff-Serv TLV for an E-LSP which contains one MAP
   entry for each EXP value to be considered as supported on this E-LSP.

   When requesting a label for an L-LSP, an upstream Diff-Serv LSR
   sends a Label Request message with PPP interfaces from the point of view
   of compliance Diff-Serv TLV for an L-LSP
   which contains the PSC to be supported on this specification.

7. MPLS Support of L-LSP.

   A downstream Diff-Serv by ATM LSRs

   The general operations LSR sending a Label Mapping message in
   response to a Label Request message for MPLS support of Diff-Serv, including an E-LSP or an L-LSP must
   not include a Diff-Serv TLV in this Label Mapping message.

   Assuming the label forwarding set-up is successful, the downstream and LSP setup operations was upstream
   LSRs must:
     - update the Diff-Serv context associated with the established
       LSPs in their ILM/FTN as specified in the previous sections. This section describes sections
       (incoming and outgoing label),
     - install the specific operations required Diff-Serv forwarding treatment (scheduling
       and dropping behavior) for MPLS support of this NHLFE (outgoing label).

   An upstream Diff-Serv over ATM links.

   This document allows LSR receiving a Label Mapping message
   containing a Diff-Serv TLV in response to its Label Request message,
   must reject the following set label mapping by sending a Label Release message
   which includes the Label TLV and the Status TLV with a Status Code
   of LSP setup combinations per
   FEC within an MPLS ATM `Unexpected Diff-Serv domain:

        - any number of L-LSPs.

7.1 L-LSP Operations over ATM TLV'.

   A downstream Diff-Serv LSR receiving a Label Request message with
   multiple Diff-Serv TLVs only considers the first one as meaningful.
   The L-LSP operations over ATM follows LSR must ignore and not forward the general procedures of
   section 3. However, subsequent Diff-Serv TLV(s).

   A downstream Diff-Serv LSR which receives a Label Request message
   with the following ATM specific procedures are also
   defined Diff-Serv TLV for L-LSP operations over ATM links : an E-LSP and does not support the

 Le Faucheur et. al                                                 27                                                 33

                      MPLS Support of Diff-Serv             October 99

        - An MPLS ATM ingress interface determines the incoming            February 00

   particular PHB
        from the PSC and the ATM Cell Loss Probability (CLP) bit encoded in
        accordance with one (or more) of the incoming PSC/CLP-->PHB mapping defined
        below in section 7.2;

       - If MAP entries, must
   reject the CLP value request by sending a Notification message which includes
   the Status TLV with a Status Code of `Unsupported PHB'.

   A downstream Diff-Serv LSR receiving a packet received on Label Request message with
   the Diff-Serv TLV for an L-LSP is such E-LSP and determining that the PSC/CLP combination signaled
   EXP<-->PHB mapping is not listed in invalid, must reject the mapping request by sending a
   Notification message which includes the Status TLV with a Status
   Code of section
       7.2, this PSC/CLP combination should be considered invalid. LSR
       behavior `Invalid EXP<-->PHB Mapping'. The EXP<-->PHB mapping
   signaled in such situation the DIFFSERV TLV for an E-LSP is a local matter and invalid when:
     - the MAPnb field is outside not within the
       scope of this document. range 1 to 8 decimal, or
     - An MPLS ATM egress interface determines the a given EXP value to be
        written appears in more than one MAP entry, or
     - the ATM Cell Loss Probability (CLP) bit by
        performing the outgoing PHB-->PSC/CLP mapping defined below in
        section 7.3. This PHBID encoding is performed by an invalid

   A downstream Diff-Serv LSR on the Edge of receiving a Label Request message with
   the ATM Diff-Serv MPLS Cloud and TLV for an L-LSP containing a PSC value which is performed not
   supported, must reject the request by an ATM sending a Notification message
   which includes the Status TLV with a Status Code of `Unsupported
   PSC'.

   A downstream Diff-Serv LSR in the
        middle of that recognizes the ATM Diff-Serv MPLS cloud when doing optional
        Local Policy TLV Type in
   a Label Request message and Traffic Conditioning. When supports the requested PSC but is not doing optional
        Local Policy and Traffic Conditioning, an LSR
   able to satisfy the label request for other reasons (eg. no label
   available), must send a Notification message in accordance with
   existing LDP procedures [LDP] (eg. with a `No Label Resource' Status
   Code). This Notification message must include the middle requested
   Diff-Serv TLV.

6.4 Non-Handling of the ATM Diff-Serv MPLS cloud may simply leave TLV

   An LSR that does not recognize the CLP bit
        untouched;

        - when packet is segmented to cells Diff-Serv TLV Type, on edge LSR, all cells receipt of
   a Label Request message or a Label Mapping message containing the packet SHOULD be encoded
   Diff-Serv TLV, must behave in accordance with the same CLP bit value.

7.2 PSC/CLP --> PHB mapping

   The mapping from L-LSP PSC and CLP bit of the ATM cell header into
   PHBs is as follows:

      CLP Bit      PSC             PHB

         0          DF    ----->    DF
         0          CSn   ----->    CSn
         0          AFCn  ----->    AFn1
         1          AFCn  ----->    AFn2 / AFn3
         0          EF    ----->    EF

   Since there is only one bit for encoding the PHB drop precedence
   value over ATM links, only two different drop precedence levels are
   supported in ATM LSRs. The behaviour for AF MUST comply to procedures described
   specified in [DIFF_AF] [LDP] for the case when only two drop
   precedence levels an unknown TLV whose U Bit and F Bit are supported.

7.3 PHB --> PSC/CLP mapping

   The mapping from PHBs into set
   to 0 ie. it must ignore the L-LSP PSC message, return a Notification message
   with `Unknown TLV' Status.

6.5 Bandwidth Information

   Bandwidth information may also be signaled at establishment time of
   E-LSP and L-LSP, for instance for the CLP bit purpose of Traffic
   Engineering, using the ATM
   cell header is Traffic Parameters TLV as follows:

      PHB             CLP Bit     PSC

 Le Faucheur et. al                                                 28 described in
   [MPLS CR LDP].

7. MPLS Support of Diff-Serv             October 99

      DF     ----->      0         DF
      CSn    ----->      0         CSn
      AFn1   ----->      0         AFCn
      AFn2   ----->      1         AFCn
      AFn3   ----->      1         AFCn
      EF     ----->      0         EF

7.4 Merging over PPP

   The use of merging is optional. In case that merging general operations for MPLS support of ATM LSPs is
   used, procedures described Diff-Serv, including
   label forwarding and LSP setup operations are specified in the
   previous sections. This section 3.5. describes the specific operations
   required for MPLS support of this specification
   apply. Additionally, to avoid cell interleaving problems with AAL-5
   merging, procedures specified in [MPLS ATM] MUST be followed.

7.5 Use Diff-Serv over PPP links. While

 Le Faucheur et. al                                                 34

                      MPLS Support of ATM Traffic Classes Diff-Serv            February 00

   sections 8, 9 and Traffic Management mechanisms

   The use 10 focus on other media specific operations,
   namely ATM, Frame Relay and LAN respectively.

   This document allows any of the ATM traffic classes as specified by ITU-T and ATM-
   Forum following LSP combinations per FEC
   within an MPLS PPP Diff-Serv domain:

     - Zero or any number of vendor specific ATM traffic classes is outside of the
   scope E-LSP, and
     - Zero or any number of this specification. The only requirement for compliant
   implementation is that the forwarding behaviour experienced by a
   Behavior Aggregate forwarded over an L-LSP by the ATM L-LSPs.

7.1 LSR MUST be
   compliant implementation with the corresponding PPP interfaces

   A Diff-Serv PHB specifications.

   To avoid discarding parts of capable LSR with PPP interfaces MUST support, over these
   PPP interfaces, E-LSPs which use the packets, frame discard mechanisms,
   such as Early Packet Discard (EPD) SHOULD be enabled pre-configured EXP<-->PHB
   mapping, in the ATM-LSRs
   for compliance with all PHBs described in the material from this document.

7.6 LSR Implementation With ATM Interfaces

   For an specification
   pertaining to those types of LSPs.

   A Diff-Serv capable LSR implementation with ATM PPP interfaces running native ATM
   MPLS, MAY support, over these
   PPP interfaces, E-LSPs which use a signaled EXP<-->PHB mapping. If a
   Diff-Serv LSR does support of L-LSPs E-LSPs which use a signaled EXP<-->PHB
   mapping over the ATM interfaces is mandatory PPP interfaces, then it MUST do so in compliance with
   respect to
   all the material from this specification. specification pertaining to those types
   of LSPs.

   A Diff-Serv capable LSR with ATM PPP interfaces MUST MAY support L-LSPs over
   these ATM interfaces PPP interfaces. If a Diff-Serv LSR does support L-LSPs over
   PPP interfaces, then it MUST do so in compliance with all the
   material from this specification. Additionally, procedures
   specified in [MPLS ATM] MUST be followed by compliant
   implementation.

   Support of E-LSPs specification pertaining to L-LSPs.

   An LSR running MPLS over PPP over a traditional ATM connection (ie.
   where the ATM switches do not participate in MPLS and where the ATM
   connection VPI/VCI values have not been established via any label
   distribution protocol) is to be considered as an LSR with PPP
   interfaces from the point of view of compliance to this
   specification.

   Similarly, an LSR running native ATM MPLS by over PPP over a traditional Frame
   Relay connection (ie. where the Frame Relay switches do not
   participate in MPLS and where the Frame Relay connection DLCI values
   have not been established via any label distribution protocol) is to
   be considered as an LSR implementation is not allowed. with PPP interfaces from the point of view
   of compliance to this specification.

8. MPLS Support of Diff-Serv by Frame Relay ATM LSRs

   The general operations for MPLS support of Diff-Serv, including
   label forwarding and LSP setup operations was specified in the
   previous sections. This section describes the specific operations
   required for MPLS support of Diff-Serv over Frame Relay ATM links.

   This document allows the following set of LSP setup combinations per FEC
   within an MPLS Frame Relay ATM Diff-Serv domain:

        - any number of L-LSPs.

 Le Faucheur et. al                                                 29                                                 35

                      MPLS Support of Diff-Serv             October 99            February 00

        - any number of L-LSPs.

8.1 L-LSP Operations over Frame Relay Merging

   The L-LSP operations over Frame Relay follows the general procedures use of merging is optional. In case that merging of ATM LSPs is
   used, procedures described in section 3. However, 3.6 of this specification
   apply. Additionally, to avoid cell interleaving problems with AAL-5
   merging, procedures specified in [MPLS ATM] MUST be followed.

8.2 Use of ATM Traffic Classes and Traffic Management mechanisms

   The use of the following Frame Relay ATM traffic classes as specified by ITU-T and ATM-
   Forum or of vendor specific procedures
   are also defined ATM traffic classes is outside of the
   scope of this specification. The only requirement for L-LSP operations over Frame Relay links :

        - An MPLS Frame Relay ingress interface determines compliant
   implementation is that the incoming
        PHB from forwarding behavior experienced by a
   Behavior Aggregate forwarded over an L-LSP by the PSC and ATM LSR MUST be
   compliant with the Frame Relay Discard Eligible(DE) corresponding Diff-Serv PHB specifications.

   Since there is only one bit
        in accordance with for encoding the incoming PSC/CLP-->PHB mapping defined
        below PHB drop precedence
   value over ATM links, only two different drop precedence levels are
   supported in section 8.2;

       - If ATM LSRs. The behavior for AF MUST comply to procedures
   described in [DIFF_AF] for the DE value of a packet received on an L-LSP is such that case when only two drop precedence
   levels are supported.

   To avoid discarding parts of the PSC/DE combination is not listed packets, frame discard mechanisms,
   such as Early Packet Discard (EPD) SHOULD be enabled in the mapping of section
       8.2, ATM-LSRs
   for all PHBs described in this PSC/DE combination should be considered invalid. document.

8.3 LSR
       behavior Implementation With ATM Interfaces

   A Diff-Serv capable LSR with ATM interfaces MUST support L-LSPs over
   these ATM interfaces in such situation is a local matter and is outside compliance with all the
       scope of material from this document.

        - An MPLS Frame Relay egress interface determines the value
   specification pertaining to
        be written in the Frame Relay Discard Eligible (DE) bit by
        performing the outgoing PHB-->PSC/DE mapping defined below those types of LSPs. Additionally,
   procedures specified in
        section 8.3. This is performed [MPLS ATM] MUST be followed by an LSR on the Edge compliant
   implementation.

   Support of the
        Frame Relay Diff-Serv E-LSPs over ATM interfaces running native ATM MPLS Cloud and is performed by an Frame
        Relay
   LSR in the middle implementation is not allowed.

9. MPLS Support of the Diff-Serv by Frame Relay Diff-Serv LSRs

   The general operations for MPLS cloud
        when doing optional Local Policy and Traffic Conditioning. When
        not doing optional Local Policy support of Diff-Serv, including
   label forwarding and Traffic Conditioning, an
        LSR LSP setup operations was specified in the middle of the Frame Relay Diff-Serv MPLS cloud may
        simply leave the DE bit untouched;

8.2 PSC/DE --> PHB mapping

   The mapping from L-LSP PSC and DE bit of
   previous sections. This section describes the Frame Relay header into
   PHBs is as follows:

      DE Bit       PSC             PHB

         0          DF    ----->    DF
         0          CSn   ----->    CSn
         0          AFCn  ----->    AFn1
         1          AFCn  ----->    AFn2 / AFn3
         0          EF    ----->    EF

   Since there is only one bit specific operations
   required for encoding the PHB drop precedence
   value MPLS support of Diff-Serv over Frame Relay links, only two different drop precedence
   levels are supported in Frame Relay LSRs. The behaviour for AF MUST
   comply to procedures described in [DIFF_AF] for the case when only
   two drop precedence levels are supported.

8.3 PHB --> PSC/DE mapping

   The mapping from PHBs into the L-LSP PSC and links.

   This document allows the DE bit following set of the LSP combinations per FEC
   within an MPLS Frame Relay header is as follows: Diff-Serv domain:

        - any number of L-LSPs.

9.1 Merging

 Le Faucheur et. al                                                 30                                                 36

                      MPLS Support of Diff-Serv             October 99

      PHB               DE Bit     PSC

      DF     ----->      0         DF
      CSn    ----->      0         CSn
      AFn1   ----->      0         AFCn
      AFn2   ----->      1         AFCn
      AFn3   ----->      1         AFCn
      EF     ----->      0         EF

8.4 Merging            February 00

   The use of merging is optional. In case that merging of Frame Relay
   LSPs is used, procedures described in section 3.5. 3.6 of this
   specification apply as well as procedures in [MPLS FR].

8.5

9.2 Use of Frame Relay Traffic parameters and Traffic Management
mechanisms

   The use of the Frame Relay traffic parameters as specified by ITU-T
   and Frame Relay-Forum or of vendor specific Frame Relay traffic
   management mechanisms is outside of the scope of this specification.
   The only requirement for compliant implementation is that the
   forwarding behavior experienced by a Behavior Aggregate forwarded
   over an L-LSP by the Frame Relay LSR MUST be compliant with the
   corresponding Diff-Serv PHB specifications.

8.6 LSR Implementation With Frame Relay Interfaces

   For an LSR implementation with

   Since there is only one bit for encoding the PHB drop precedence
   value over Frame Relay interfaces running native links, only two different drop precedence
   levels are supported in Frame Relay MPLS, support of L-LSPs over LSRs. The behavior for AF MUST
   comply to procedures described in [DIFF_AF] for the case when only
   two drop precedence levels are supported.

9.3 LSR Implementation With Frame Relay interfaces
   is mandatory with respect to this specification. Interfaces

   A Diff-Serv capable LSR with Frame Relay interfaces MUST support
   L-LSPs over these Frame Relay interfaces in compliance with all the
   material from this specification. specification pertaining to those types of LSPs.

   Support of E-LSPs over Frame Relay interfaces running native Frame
   Relay MPLS by an LSR implementation is not allowed.

9.

10. MPLS Support of Diff-Serv over LAN Media

   The general operations for MPLS support of Diff-Serv, including
   label forwarding and LSP setup operations was specified in the
   previous sections. This section describes the specific operations
   required for MPLS support of Diff-Serv over LAN.

   This document allows the following set of LSP setup combinations per
   FEC over an MPLS link:

     - Zero or any number of E-LSP, and
        - Zero or any number of L-LSPs.

 Le Faucheur et. al                                                 31

                      MPLS Support of Diff-Serv             October 99

9.1. E-LSP Operations over PPP

   Text to be written (in particular regarding use of 802.1 COS field).

9.2  L-LSP Operations over PPP

   Text to be written (in particular regarding use any number of 802.1 COS field).

9.3 E-LSP, and
     - Zero or any number of L-LSPs.

10.1 LSR Implementation With LAN Interfaces

   For an

   A Diff-Serv capable LSR implementation with LAN interfaces MUST support, over these
   LAN interfaces, support of E-LSPs
   over which use the LAN interfaces is mandatory pre-configured EXP<-->PHB
   mapping, in compliance with respect to all the material from this
   specification. specification
   pertaining to those types of LSPs.

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                      MPLS Support of Diff-Serv            February 00

   A Diff-Serv capable LSR with LAN interfaces MUST MAY support, over these
   LAN interfaces, E-LSPs which use a signaled EXP<-->PHB mapping. If a
   Diff-Serv LSR does support E-LSPs which use a signaled EXP<-->PHB
   mapping over these LAN interfaces interfaces, then it MUST do so in compliance with
   all the material from this
   specification.

   Support specification pertaining to those types
   of L-LSPs over LAN interfaces by an LSR implementation is
   optional. LSPs.

   A Diff-Serv capable LSR MAY support L-LSPs over LAN interfaces. However, if If a
   Diff-Serv LSR does support L-LSPs over LAN interfaces, then it MUST
   do so in compliance with all the material from this specification
   pertaining to L-LSPs.

10. Operations at MPLS Diff-Serv Boundaries

10.1 Operations at E-LSP/L-LSP Boundary Within Single MPLS Diff-Serv
Domain

   Text to be added

10.2 Operations At Boundary across Diff-Serv domains

   Text to be added

11. Explicit Congestion Notification

   Explicit Congestion Notification is described in [ECN] and is
   proposed as an Experimental extension to the IP protocol.

   [MPLS_ECN] discusses deployment of ECN in an MPLS network using the
   Shim Header as the MPLS encapsulation. It demonstrates that,
   provided a given LSP is identified as ECN-capable or as non-ECN-
   capable (and consistently recognized as such by all the involved
   LSRs), then ECN can be supported in an MPLS domain where the Shim
   Header is used as the MPLS encapsulation via a single bit of the EXP
   field.

   The details of how a given LSP is to be identified as ECN-capable or
   non-ECN-capable (whether via extensions to the LSP establishment
   signaling and procedures, via configuration or via other means) are
   outside the scope of this specification.

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                      MPLS Support of Diff-Serv             October 99

   However, this specification recognizes that, within an ECN-capable
   MPLS domain where LSPs are identified as ECN-capable or not-ECN-
   capable:

     - Support of ECN does not require that any bit(s) from the EXP
       field be reserved for ECN operations across all LSPs even when
       those LSPs are not ECN-capable. Consequently, LSPs identified as non-ECN-
   capable
       non-ECN-capable (regardless of whether this is because at least
       one LSR on the LSP does not support ECN operations or whether
       this is because the network administrator does not wish to use
       ECN on this LSP) can make use of the full 3-bit EXP field for
       Diff-Serv purposes. Thus, non-ECN-capable E-LSPs and non-ECN-capable non-ECN-
       capable L-LSPs can operate as defined earlier in this document
       without any restriction imposed by the fact that the MPLS domain is ECN-capable. In particular, up to 8
   BAs can still be transported over a non-ECN-capable E-LSP within an
   ECN-capable MPLS domain. Similarly, non-ECN-capable L-LSPs within an
   ECN-capable MPLS domain can support all the drop precedence levels
   of currently defined PSCs. Should a future PSC involve more than 4
   drop precedence levels, non-ECN-capable L-LSPs within an ECN-capable
   MPLS domain could still use the full 3-bit field EXP.

        - Because a single bit is required to encode the ECN
   information inside the ECN-capable MPLS domain, LSPs identified as
   ECN-capable can make use of two bits of fact that the EXP field value. MPLS domain
       is ECN-capable. In particular, up to 4 8 BAs can still be
       transported over a non-ECN-capable E-LSP within an ECN-capable E-
   LSP.
       MPLS domain. Similarly, up to 4 drop precedence levels can be supported over non-ECN-capable L-LSPs within an ECN-capable L-LSP; since ECN-
       capable MPLS domain can support all the PSCs corresponding to PHBs
   currently defined through standards action involve less than 4 drop precedence levels, ECN support does not levels
       of currently restrict Diff-Serv
   operations over L-LSPs. defined PSCs. Should a PSC corresponding to future PHBs
   defined by standards action or corresponding to local use or
   experimental PHBs, PSC involve more than
       4 drop precedence levels, then
   ECN support over the corresponding LSP would constrain the PSC to 4
   drop precedence levels; relative benefits of additional precedence
   levels beyond 4, would then be weighted by the network administrator
   over the benefits of ECN, to determine whether it is preferable to
   support this PSC over an ECN-capable or non-ECN-capable LSP.

11.1 MPLS ECN bit with Shim Header

   Where the Shim Header is used as the MPLS encapsulation, ECN
   information is to be encoded on ECN-capable LSPs in the first bit of
   the 3-bit EXP field in the following way:

     EXP field          MPLS ECN Meaning

     0xx        -->     `ECT, not CE'
     1xx        -->     `not ECT, or ECT+CE'

   where ECT stands for `ECN Capable Transport' and `CE' stands for
   `Congestion experienced'. L-LSPs within an ECN-

 Le Faucheur et. al                                                 33                                                 38

                      MPLS Support of Diff-Serv             October 99

   Detailed specification for usage of this MPLS ECN bit is outside the
   scope of this specification.

   For ECN-capable E-LSPs, the PHB<-->EXP mapping defined above in the
   section titled `PHB<-->EXP Field Mapping' and configured on the LSR
   is only operating over the last 2 bits of            February 00

       capable MPLS domain could still use the full 3-bit EXP field. Thus
   it has the following format:

      EXP Field                 PHB

        e00     <----->         a given PHB
        e01     <----->         a given PHB
        e10     <----->         a given PHB
        e11     <-----> field EXP.

     - Because a given PHB

   where `e' single bit is required to encode the MPLS ECN bit and can take information
       inside the value zero or one
   depending on ECN operations.

   For ECN-capable L-LSPs, the PSC/EXP-->PHB mapping defined above in
   the section titled `PSC/EXP-->PHB is only operating over the last 2 MPLS domain, LSPs identified as ECN-
       capable can make use of two bits of the 3-bit EXP field and is the following:

      EXP Field      PSC             PHB

        e00          DF    ----->    DF
        e00          CSn   ----->    CSn
        e00          AFCn  ----->    AFn1
        e01          AFCn  ----->    AFn2
        e10          AFCn  ----->    AFn3
        e00          EF    ----->    EF

   where `e' is the MPLS ECN bit and value for
       Diff-Serv purposes. In particular, up to 4 BAs can take be
       transported over an ECN-capable E-LSP. Similarly, up to 4 drop
       precedence levels can be supported over an ECN-capable L-LSP;
       since all the value zero PSCs corresponding to PHBs currently defined
       through standards action involve less than 4 drop precedence
       levels, ECN support does not currently restrict Diff-Serv
       operations over L-LSPs. Should a PSC corresponding to future
       PHBs defined by standards action or one
   depending on corresponding to local use
       or experimental PHBs, involve more than 4 drop precedence
       levels, then ECN operations.

   For ECN-capable L-LSPs, support over the PHB--> PSC/EXP mapping defined above in corresponding LSP would
       constrain the section titled `PHB--> PSC/EXP Mapping' is only operating PSC to 4 drop precedence levels; relative benefits
       of additional precedence levels beyond 4, would then be weighted
       by the network administrator over the last 2 bits benefits of the 3-bit EXP field and ECN, to
       determine whether it is the following:

        PHB              EXP Field preferable to support this PSC

        DF     ----->     e00          DF
        CSn    ----->     e00          CSn
        AFn1   ----->     e00          AFCn
        AFn2   ----->     e01          AFCn
        AFn3   ----->     e10          AFCn
        EF     ----->     e00          EF

   where `e' is the over an
       ECN-capable or non-ECN-capable LSP.

11.1 MPLS ECN bit and can take with Shim Header

   Where the Shim Header is used as the value zero or one
   depending on ECN operations.

 Le Faucheur et. al                                                 34 MPLS Support of Diff-Serv             October 99

   For non-ECN-capable LSPs, encapsulation, ECN
   information is to be encoded on ECN-capable LSPs in the first bit of
   the 3-bit EXP field is
   NOT reserved for ECN and can be used to encode any Diff-Serv
   information. In particular, for non-ECN-capable E-LSPs, the
   PHB<-->EXP mapping defined in the section titled `PHB<-->EXP Field
   Mapping' and configured on the LSR is operating over the 3 bits of
   the following way:

     EXP field.

12. Security Considerations

   This document does not introduce any new security issues beyond
   those inherent in Diff-Serv, field          MPLS and RSVP, and may use the same
   mechanisms proposed ECN Meaning

     0xx        -->     `ECT, not CE'
     1xx        -->     `not ECT, or ECT+CE'

   where ECT stands for those technologies.

13. Acknowledgments

   This document has benefited from discussions with K. K.
   Ramakrishnan, Eric Rosen, Angela Chiu and Carol Iturralde.

APPENDIX A. Ordered Aggregate (OA) `ECN Capable Transport' and PHB Scheduling Class (PSC)

   This Appendix contains the definition of two Diff-Serv concepts:
        - the Ordered Aggregate (OA)
        - the PHB Scheduling Class (PSC)
   In the future, it is expected that these definitions will be
   incorporated in new versions `CE' stands for
   `Congestion experienced'.

   Detailed specification for usage of this MPLS ECN bit is outside the Diff-Serv specifications.

A.1 Ordered Aggregate (OA)

   [DIFF_AF] states that "a DS node does not reorder IP packets
   scope of this document.

   For ECN-capable E-LSPs using preconfigured mapping, the
   same microflow if they belong to the same AF class" (even if
   different packets of
   Preconfigured EXP<-->PHB mapping defined above in section 3.2.1 is
   only operating over the microflow contain different AF codepoints last 2 bits of the same AF class). 3-bit EXP field. For ECN-
   capable E-LSPs using signaled mapping, the sake of generality, we define a set of Behavior Aggregates
   which share such an ordering constraint to constitute a "Ordered
   Aggregate" (OA).

A.2 PHB Scheduling Class (PSC)

   We refer to signaled EXP<-->PHB
   mapping is only operating over the set last 2 bits of one or more PHBs applied to the set of
   Behavior Aggregates forming 3-bit EXP
   field. Thus it has the following format:

      EXP Field                 PHB

        e00     <----->         a given OA, as a "PHB Scheduling Class"
   (PSC).

   The PHBs currently specified are Default PHB (DF), Class Selector
        e01     <----->         a given PHB group (CSx), Assured Forwarding
        e10     <----->         a given PHB group (AFxy), Expedited
   Forwarding
        e11     <----->         a given PHB (EF).

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                      MPLS Support of Diff-Serv             October 99

A.2.1 DF PSC

   The Default PHB            February 00

   where `e' is a single PHB specified in [DIFF_Header]. Thus, the corresponding PSC comprises a single PHB MPLS ECN bit and thus coincides with can take the DF PHB.

A.2.2 CSn PSC

   [DIFF_HEADER] defines up to 8 CS Codepoints referred to as CSn,
   where 1 <= i <= 8. [DIFF_HEADER] states that "... PHBs selected by
   distinct Class Selector Codepoints SHOULD be independently
   forwarded; that is, packets marked with different Class Selector
   Codepoints MAY be re-ordered". Thus, there is value zero or one
   depending on ECN operations.

   For ECN-capable L-LSPs, the `EXP/PSC-->PHB mapping' defined above in
   section 4.2.1.1 is only operating over the last 2 bits of the 3-bit
   EXP field and is the following:

      EXP Field      PSC corresponding
   to each CSn PHB. Each CSn PSC comprises a single             PHB and thus
   coincides with this

        e00          DF    ----->    DF
        e00          CSn PHB.

A.2.3   ----->    CSn
        e00          AFn PSC

   As described in [DIFF_AF],   ----->    AFn1
        e01          AFn   ----->    AFn2
        e10          AFn   ----->    AFn3
        e00          EF    ----->    EF

   where `e' is the Assured Forwarding (AF) PHB group
   provides forwarding of IP packets MPLS ECN bit and can take the value zero or one
   depending on ECN operations.

   For ECN-capable L-LSPs, the `PHB--> PSC/EXP mapping' defined above
   in N independent AF classes.
   Within each AF class, an IP packet the section 4.4.1.1 is assigned one of M different
   levels only operating over the last 2 bits of drop precedence. An IP packet that belongs to an AF class
   i the
   3-bit EXP field and has drop precedence j is marked with the AF codepoint AFij, following:

        PHB              EXP Field     PSC

        DF     ----->     e00          DF
        CSn    ----->     e00          CSn
        AFn1   ----->     e00          AFn
        AFn2   ----->     e01          AFn
        AFn3   ----->     e10          AFn
        EF     ----->     e00          EF

   where 1 <= i <= N `e' is the MPLS ECN bit and 1 <= j <= M. Currently, four classes (N=4)
   with three levels of drop precedence in each class (M=3) are
   defined for general use.

   [DIFF_AF] states that "a DS node does not reorder IP packets of can take the
   same microflow if they belong to value zero or one
   depending on ECN operations.

   For non-ECN-capable LSPs, the same AF class" (even if
   different packets first bit of the microflow contain different AF codepoints
   of 3-bit EXP field is
   NOT reserved for ECN and can be used to encode any Diff-Serv
   information. In particular, for non-ECN-capable E-LSPs, the same AF class). As noted above, each AF class
   EXP<-->PHB mapping defined in the AF PHB
   group is the primary example of a PSC. Each PSC comprises 3 PHBs section titled `EXP<-->PHB Field
   Mapping' and
   coincides with configured on the AF Class. Those PSCs are thus referred to as AFn,
   where 1 <= n <= 4.

A.2.4 EF PSC

   [DIFF_EF] defines LSR is operating over the Expedited Forwarding (EF) PHB for traffic
   requiring forwarding with low loss, low latency, low jitter.
   [DIFF_EF] defines a single PHB. Thus, 3 bits of
   the corresponding PSC
   comprises a single PHB EXP field.

12. Security Considerations

   This document does not introduce any new security issues beyond
   those inherent in Diff-Serv, MPLS and thus coincides with RSVP, and may use the DF PHB.

A.2.5 Summary list of PSC

   The following PSCs have thus been identified:
        - DF
        - CSn , 1 <= i <= 8
        - AFn, 1 <= i <= 4
        - EF

APPENDIX B. Example Deployment Scenarios same
   mechanisms proposed for those technologies.

13. Acknowledgments

 Le Faucheur et. al                                                 36                                                 40

                      MPLS Support of Diff-Serv             October 99            February 00

   This document has benefited from discussions with K. K.
   Ramakrishnan, Eric Rosen, Angela Chiu and Carol Iturralde.

APPENDIX A. Example Deployment Scenarios

   This section does not provide additional specification and is only
   here to provide examples of how this flexible approach for Diff-Serv
   support over MPLS may be deployed. Pros and cons of various
   deployment options for particular environments are beyond the scope
   of this document.

B.1

A.1 Scenario 1: 8 (or less) BAs, no Traffic Engineering, no Fast
Reroute

   A Service Provider running 8 (or less) BAs over MPLS, not performing
   Traffic engineering, not performing protection via Fast Reroute and
   using MPLS Shim Header encapsulation in his/her network, may elect
   to run Diff-Serv over MPLS using a single E-LSP per FEC established
   via LDP. Furthermore the Service Provider may elect to use the
   preconfigured EXP<-->PHB mapping.

   Operations can be summarized as follows:
     - the Service Provider configures at every LSR the bi-
   directional bi-directional
       mapping between each PHB and a value of the EXP field
       (eg. 000<-->AF11, 001<-->AF12, 010<-->AF13)
     - the Service Provider configures at every LSR, and for every
       interface, the scheduling behavior for each PSC (eg bandwdith bandwidth
       allocated to AF1) and the dropping behavior for each PHB (eg
       drop profile for AF11, AF12, AF13)
     - LSRs signal establishment of a single E-LSP per FEC using LDP in
       accordance with the specification above (ie no Diff-Serv_PSC Diff-Serv TLV in
       LDP Label Request/Label Mapping messages to implicitly indicate
       that the LSP is an E-LSP)

B.2 E-LSP and that it uses the preconfigured
       mapping)

A.2 Scenario 2: More than 8 BAs, no Traffic Engineering, no Fast
Reroute

   A Service Provider running more than 8 BAs over MPLS, not performing
   Traffic Engineering and not performing protection via Fast Reroute
   and using MPLS Shim encapsulation in his/her network may elect to
   run Diff-Serv over MPLS using for each FEC:
     - one E-LSP established via LDP and using the preconfigured
       mapping to support a set of 8 (or less) BAs, AND
     - one L-LSP per <FEC,OA> established via LDP for support of the
       other BAs.

   Operations can be summarized as follows:

 Le Faucheur et. al                                                 41

                      MPLS Support of Diff-Serv            February 00

     - the Service Provider configures at every LSR the bi-
   directional bi-directional
       mapping between each PHB and a value of the EXP field for the
       BAs transported over the E-LSP
     - the Service Provider configures at every LSR, and for every
       interface, the scheduling behavior for each PSC supported over
       the E-LSP and the dropping behavior for each corresponding PHB
     - the Service Provider configures at every LSR, and for every
       interface, the scheduling behavior for each PSC supported over
       the L-LSPs and the dropping behavior for each corresponding PHB

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                      MPLS Support of Diff-Serv             October 99
     - LSRs signal establishment of a single E-LSP per FEC for the set
       of E-LSP transported BAs using LDP as specified above (ie no
   Diff-Serv_PSC
       Diff-Serv TLV in LDP Label Request/Label Mapping messages to
       implicitly indicate that the LSP is an E-LSP) E-LSP and that it uses
       the preconfigured mapping)
     - LSRs signal establishment of one L-LSP per <FEC,OA> for the
       other BAs using LDP as specified above (ie Diff-Serv_PSC Diff-Serv TLV in LDP
       Label Request/Label Mapping messages to indicate the L-LSP's
       PSC).

B.3

A.3 Scenario 3: 8 BAs, Aggregate Traffic Engineering, Aggregate Fast
Reroute

   A Service Provider running 8 (or less) BAs over MPLS, performing
   aggregate Traffic Engineering (ie performing a single common path
   selection for all BAs), performing aggregate protection via Fast
   Reroute (ie performing Fast Reroute for all PSCs jointly) and using
   MPLS Shim Header encapsulation in his/her network, may elect to run
   Diff-Serv over MPLS using a single E-LSP per FEC established via
   RSVP [RSVP_MPLS_TE] or CR-LDP [CR-LDP_MPLS_TE]. [CR-LDP_MPLS_TE] and using the
   preconfigured mapping.

   Operations can be summarized as follows:
     - the Service Provider configures at every LSR the
   bidirectional bi-directional
       mapping between each PHB and a value of the EXP field
       (eg. 000<-->AF11, 001<-->AF12, 010<-->AF13)
     - the Service Provider configures at every LSR, and for every
       interface, the scheduling behavior for each PSC (eg bandwidth
       allocated to AF1) and the dropping behavior for each PHB (eg
       drop profile for AF11, AF12, AF13)
     - LSRs signal establishment of a single E-LSP per FEC: FEC which will
       use the preconfigured mapping:
           * using the RSVP protocol as specified above (ie no
   DIFFSERV_PSC DIFFSERV
       RSVP Object in the PATH message containing the LABEL_REQUEST
       Object), OR
           * using the CR-LDP protocol as specified above (ie no Diff-
   Serv_PSC
       Serv TLV in LDP Label Request/Label Mapping messages).

B.4

A.4 Scenario 4: per-OA Traffic Engineering/Fast Reroute

   A Service Provider running any number of BAs over MPLS, performing
   per-OA Traffic Engineering (ie performing a separate path selection
   for each OA) and performing per-OA protection via Fast Reroute (ie

 Le Faucheur et. al                                                 42

                      MPLS Support of Diff-Serv            February 00

   performing protection with different Fast Reroute policies for the
   different OAs) in his/her network, may elect to run Diff-Serv over
   MPLS using one L-LSP per <FEC,OA> pair established via RSVP or
   CR-LDP.

   Operations can be summarized as follows:
     - the Service Provider configures at every LSR, and for every
       interface, the scheduling behavior for each PSC (eg bandwidth
       allocated to AF1) and the dropping behavior for each PHB (eg
       drop profile for AF11, AF12, AF13)
     - LSRs signal establishment of one L-LSP per <FEC,OA>:

 Le Faucheur et. al                                                 38

                      MPLS Support of Diff-Serv             October 99
                * using the RSVP as specified above to signal the
       L-LSP's PSC (ie DIFFSERV_PSC DIFFSERV RSVP Object in the PATH message
       containing the LABEL_REQUEST), OR
                * using the CR-LDP protocol as specified above to
       signal the L-LSP PSC (ie Diff-Serv_PSC Diff-Serv TLV in LDP Label
       Request/Label Mapping messages).

B.5

A.5 Scenario 5: less than 8 (or less) BAs, per-OA Traffic Engineering/Fast
Reroute

   A Service Provider running less than 8 (or less) 8 BAs over MPLS, performing
   per-OA Traffic Engineering (ie performing a separate path selection
   for each OA) and performing per-OA protection via Fast Reroute (ie
   performing protection with different Fast Reroute policies for the
   different OAs) in his/her network, may elect to run Diff-Serv over
   MPLS using one E-LSP per <FEC,OA> pair established via RSVP or
   CR-LDP. Furthermore, the Service Provider may elect to use the
   preconfigured mapping on all the E-LSPs.

   Operations can be summarized as follows:
     - the Service Provider configures at every LSR the
   bidirectional bi-directional
       mapping between each PHB and a value of the EXP field
       (eg. 000<-->AF11, 001<-->AF12, 010<-->AF13)
     - the Service Provider configures at every LSR, and for every
       interface, the scheduling behavior for each PSC (eg bandwidth
       allocated to AF1) and the dropping behavior for each PHB (eg
       drop profile for AF11, AF12, AF13)
     - LSRs signal establishment of one L-LSP E-LSP per <FEC,OA>:
                * using the RSVP protocol as specified above to signal
       that the LSP is an E-LSP which uses the preconfigured mapping
       (ie no DIFFSERV_PSC DIFFSERV RSVP Object in the PATH message containing the
       LABEL_REQUEST), OR
                * using the CR-LDP protocol as specified above to
       signal that the LSP is an E-LSP  which uses the preconfigured
       mapping (ie no Diff-Serv_PSC Diff-Serv TLV in LDP Label Request/Label Mapping
       messages)
     - the Service Provider configures, for each E-LSP, at the head-
   end head-end
       of that E-LSP, a filtering/forwarding criteria so that only the
       packets belonging to a given OA are forwarded on the E-LSP
       established for the corresponding FEC and corresponding OA.

B.6

 Le Faucheur et. al                                                 43

                      MPLS Support of Diff-Serv            February 00

A.6 Scenario 6: no Traffic Engineering/Fast Reroute on 8 BAs, per-OA
Traffic Engineering/Fast Reroute on other BAs.

   A Service Provider not performing Traffic Engineering/Fast Reroute
   on 8 (or less) BAs, performing per-OA Traffic Engineering/Fast
   Reroute on the other BAs (ie performing a separate path selection
   for each OA corresponding to the other BAs and performing protection
   with a different policy for each of these OA) and using the MPLS
   Shim encapsulation in his/her network may elect to run Diff-Serv
   over MPLS, using for each FEC:
     - one E-LSP using the preconfigured mapping established via LDP to
       support the set of 8 (or less) non-traffic-engineered/non-fast-rerouted non-traffic-engineered/non-fast-
       rerouted BAs, AND

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                      MPLS Support of Diff-Serv             October 99
     - one L-LSP per <FEC,OA> pair established via RSVP or CR-LDP for
       support of the other BAs.

   Operations can be summarized as follows:
     - the Service Provider configures at every LSR the bi-
   directional bi-directional
       mapping between each PHB and a value of the EXP field for the
       BAs supported over the E-LSP
     - the Service Provider configures at every LSR, and for every
       interface, the scheduling behavior for each PSC supported over
       the E-LSP and the dropping behavior for each corresponding PHB
     - the Service Provider configures at every LSR, and for every
       interface, the scheduling behavior for each PSC supported over
       the L-LSPs and the dropping behavior for each corresponding PHB
     - LSRs signal establishment of a single E-LSP per FEC for the
   non-traffic non-
       traffic engineered BAs using LDP as specified above (ie no Diff-
   Serv_PSC
       Serv TLV in LDP Label Request/Label Mapping messages)
     - LSRs signal establishment of one L-LSP per <FEC,OA> for the
       other BAs:
                * using the RSVP protocol as specified above to signal
       the L-LSP PSC (ie DIFFSERV_PSC DIFFSERV RSVP Object in the PATH message
       containing the LABEL_REQUEST Object), OR
                * using the CR-LDP protocol as specified above to
       signal the L-LSP PSC (ie Diff-Serv_PSC Diff-Serv TLV in LDP Label
       Request/Label Mapping messages).

A.7 Scenario 7: More than 8 BAs, no Traffic Engineering, no Fast
Reroute

   A Service Provider running more than 8 BAs over MPLS, not performing
   Traffic engineering, not performing protection via Fast Reroute and
   using MPLS Shim Header encapsulation in his/her network, may elect
   to run Diff-Serv over MPLS using two E-LSPs per FEC established via
   LDP and using signaled EXP<-->PHB mapping.

   Operations can be summarized as follows:
     - the Service Provider configures at every LSR, and for every
       interface, the scheduling behavior for each PSC (eg bandwidth
       allocated to AF1) and the dropping behavior for each PHB (eg
       drop profile for AF11, AF12, AF13)

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                      MPLS Support of Diff-Serv            February 00

     - LSRs signal establishment of two E-LSPs per FEC using LDP in
       accordance with the specification above (ie Diff-Serv TLV in LDP
       Label Request/Label Mapping messages to explicitly indicate that
       the LSP is an E-LSP and its EXP<--> mapping). The signaled
       mapping will indicate the subset of 8 (or less) BAs to be
       transported on each E-LSP and what EXP values are mapped to each
       BA on each E-LSP.

References

   [MPLS_ARCH] Rosen et al., "Multiprotocol label switching
   Architecture", work in progress, (draft-ietf-mpls-arch-06.txt),
   August 1999.

   [MPLS ATM] Davie et al., _MPLS using LDP and ATM VC Switching_, work
   in progress, (draft-ietf-mpls-atm-02.txt), April 1999

   [MPLS FR] Conta et al., _Use of Label Switching on Frame Relay
   Networks Specification_, (draft-ietf-mpls-fr-03.txt), November 1998

   [DIFF_ARCH] Blake et al., "An architecture for Differentiated
   Services", RFC-2475, December 1998.

   [DIFF_AF] Heinanen et al., "Assured Forwarding PHB Group", RFC-2597,
   June 1999.

   [DIFF_EF] Jacobson et al., "An Expedited Forwarding PHB", RFC-2598,
   June 1999.

   [DIFF_HEADER] Nichols et al., "Definition of the Differentiated
   Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC-2474,
   December 1998.

 Le Faucheur et. al                                                 40

                      MPLS Support of Diff-Serv             October 99

   [ECN] Ramakrishnan et al., "A Proposal to add Explicit Congestion
   Notification (ECN) to IP", RFC-2481, January 1999.

   [MPLS_ECN] Ramakrishnan et al., "A Proposal to Incorporate ECN in
   MPLS", draft-ietf-mpls-ecn-00.txt, June 1999.

   [LDP] Andersson et al., "LDP Specification", draft-ietf-mpls-ldp-
   05.txt, June 99

   [RSVP_MPLS_TE] Awduche et al, "Extensions to RSVP for LSP Tunnels",
   draft-ietf-mpls-rsvp-lsp-tunnel-03.txt, September 1999

   [CR-LDP_MPLS_TE] Jamoussi et al., "Constraint-Based LSP Setup using
   LDP", draft-ietf-mpls-cr-ldp-03.txt, October 1999

   [PHBID] Brim et al., "Per Hop Behavior Identification Codes
   draft-ietf-diffserv-phbid-00.txt, October 99

 Le Faucheur et. al                                                 45

                      MPLS Support of Diff-Serv            February 00

   [DIFF_NEW] Grossman, _New Terminology for Diffserv_, draft-ietf-
   diffserv-new-terms-02.txt, November 99

   [IEEE_802.1] ISO/IEC 15802-3: 1998 ANSI/IEEE Std 802.1D, 1998
   Edition (Revision and redesignation of ISO/IEC 10038:98
   [ANSI/IEEE Std 802.1D, 1993 Edition], incorporating IEEE
   supplements P802.1p, 802.1j-1996, 802.6k-1992, 802.11c-1998, and
   P802.12e)

Author's Addresses:

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

   Liwen Wu
   Cisco Systems
   250 Apollo Drive, Chelmsford, MA 01824,
   USA
   Phone: (978)-244-3087 +1 (978) 244-3087
   Email: liwwu@cisco.com

   Bruce Davie
   Cisco Systems
   250 Apollo Drive, Chelmsford, MA 01824
   USA
   Phone: (978)-244-8000 +1 (978) 244-8000
   Email: bsd@cisco.com

   Shahram Davari
   PMC-Sierra Inc.
   105-8555 Baxter Place
   Burnaby, BC V5A 4V7
   Canada
   E-mail: Shahram_Davari@pmc-sierra.com

   Pasi Vaananen
   Nokia
   3 Burlington Woods Drive, Suit 250
   Burlington, MA 01803

 Le Faucheur et. al                                                 41

                      MPLS Support of Diff-Serv             October 99
   USA
   Phone +1 (781) 238-4981
   Email: pasi.vaananen@nokia.com

   Ram Krishnan
   Nexabit Networks
   200 Nickerson Road,
   Marlboro, MA 01752

 Le Faucheur et. al                                                 46

                      MPLS Support of Diff-Serv            February 00

   USA
   E-mail: ram@nexabit.com

   Pierrick Cheval
   Alcatel
   5 rue Noel-Pons
   92734 Nanterre Cedex
   France
   E-mail: pierrick.cheval@alcatel.fr

   Juha Heinanen
   Telia Finland
   E-mail: jh@lohi.eng.telia.fi

 Le Faucheur et. al                                                 42                                                 47