Differentiated Services                               Y.Bernet, et al
   Internet Draft                                         February, 1999
   Document: draft-ietf-diffserv-framework-02.txt
                                                 Yoram Bernet, Microsoft
                                                     James Binder, 3-Com
                           Steven Blake, Torrent Networking Technologies
                                          Mark Carlson, Redcape Software
                                                 Brian E. Carpenter, IBM
                                   Srinivasan Keshav, Cornell University
                                           Elwyn Davies, Nortel Networks
                                                  Borje Ohlman, Ericsson
                                                       Dinesh Verma, IBM
                               Zheng Wang, Bell Labs Lucent Technologies
                                       Walter Weiss, Lucent Technologies
                    A Framework for 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),
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      requested.  This document will expire before September, 1999.
      Distribution of this draft is unlimited.
   Copyright Notice
      Copyright (C) The Internet Society (1999).  All Rights Reserved.
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                    Draft-ietf-diffserv-framework-02.txt   February, 1999
      1. Abstract......................................................4
      2. Structure of this Draft.......................................4
      3. Differentiated Services - Motivation and Definition...........4
      4. Services......................................................5
         4.1 Customer/Provider Boundaries..............................5
         4.2 SLSs and TCSs.............................................6
         4.3 Service Taxonomy: Quantitative through Qualitative and
         4.4 The Scope of a Service....................................8
             4.4.1 Services where the Scope is Tied to the Receiver....8
         4.5 Dynamic vs. Static SLSs...................................9
         4.6 Provisioning Traffic Conditioners in Boundary Devices to
                 Provide Services.....................................10
             4.6.1 Minimal Functionality at Provider's Ingress........11
             4.6.2 Functionality at Provider's Ingress for Double-ended
             4.6.3 Added Value Functionality at Provider's Ingress....12
             4.6.4 Functionality at Customer's Egress.................13
             4.6.5 Functionality at Provider's Egress.................13
         4.7 Internal Provisioning....................................14
         4.8 End-to-End Service Construction..........................14
      5. Service Examples.............................................14
         5.1 Better than Best-Effort (BBE) Service....................14
             5.1.1 Service Implementation.............................15
         5.2 Leased Line Emulation Service............................16
             5.2.1 Service Implementation.............................16
         5.3 Quantitative Assured Media Playback Service..............17
             5.3.1 Service Implementation.............................17
         5.4 Superposition of Quantitative and Qualitative Services in
                 the Same Network.....................................18
      6. Provisioning and Configuration...............................18
         6.1 Boundary vs. Interior Provisioning and Configuration.....19
             6.1.1 Boundary Provisioning..............................19
             6.1.2 Interior Provisioning..............................20
          Quantitative Provisioning of the Interior..21
          Qualitative Provisioning of the Interior...22
         6.2. Static vs. Dynamic Provisioning.........................23
         6.3 Distributing Configuration Information...................24
             6.3.1 Top Down Distribution of Configuration Information.24
             6.3.2 Distribution of Configuration Information via
             6.3.3 Modification of Configuration Information Based on
                     Real-Time Measurement............................26
      7. Inter-Domain Considerations and End-to-End Services..........26
         7.1 TCSs.....................................................27
         7.2 Inter-Domain Provisioning................................27
         7.3 Service, PHB and Codepoint Mapping.......................28
         7.4 Host-Domain Boundaries...................................29
      8. Deployment Scenarios.........................................29
      9. Inter-operability with RSVP/Integrated Services..............31
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         9.1 RSVP/Integrated Services Over Differentiated Services....31
         9.2 Parallel Operation.......................................32
      10. Multicast Services..........................................32
         10.1  Codepoints and PHBs for Multicast Services.............33
         10.2  Provisioning Multicast Services........................33
      11. Security and Tunneling Considerations.......................34
      12. Acknowledgements............................................35
      13. References..................................................35
      14. Author's Addresses..........................................36
   Changes from previous version
      -  Terminology made consistent with architecture _ particularly
         boundary (node) used in place of edge (node) where appropriate.
      -  Table of contents added.
      -  Traffic Conditioning Agreement (TCA) replaced by Traffic
         Conditioning Specification (TCS) throughout to avoid
         connotations of contractual agreement.
      -  Most instances of Service Level Agreement (SLA) replaced by
         Service Level Specification (SLS) where it is clear that we are
         talking about the technical specification of the services.  The
         SLS is defined as the technical specification part of the
         contractual SLA.  Emphasized that this document discusses the
         technical aspects of the SLA whilst acknowledging that it fits
         in a wider contractual framework which is outside the scope of
         technical standards.
      -  Deployment scenarios section added.
      -  Whole document coordinated with [DiffEdge] and [E2EQoS].
      -  Service scope added as a component of TCS.
      -  Connections made to work of MPLS and IP Performance Metrics
      -  Pointed out that dealing with the interactions of multiple end-
         to-end services is an open question and is unlikely to have a
         computable answer in common cases.
      -  Multicast section improved:
         -  Added preamble pointing out that DS should be good for
            multicast except that provisioning is difficult
         -  Application level unicast is dealt with by multiple
            instances of point-to-point services
         -  Pointed out that provisioning multiple source  mpt-to-mpt is
            not a straight generalisation of pt-to-mpt
      -  Emphasised that TC for a quantitative service in an IPsec
         tunnel will be difficult to realize because the relevant packet
         fields are hidden.
      -  Updated references to reflect current drafts.  Added a few new
         references including [ROTZY] for bandwidth broker.
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   1. Abstract
      This document provides a general description of issues related to
      the definition, configuration and management of services enabled
      by the differentiated services architecture [DSARCH]. This
      document should be read along with its companion documents, the
      differentiated services architecture [DSARCH] and the definition
      of the DS field [DSHEAD]. A glossary of specialist terms used may
      be found in [DSARCH].
   2. Structure of this Draft
      Section 3 defines Differentiated Services and explains the
      motivation behind its deployment. Section 4 defines the concept of
      a service and the components that comprise a service. Section 5
      discusses several service examples. Section 6 examines intra-
      domain provisioning, configuration and management issues. Section
      7 examines inter-domain provisioning, configuration and
      management. Section 8 describes some possible deployment
      scenarios.  Section 9 addresses interoperability with Integrated
      Services and RSVP. Section 10 discusses the interaction of
      differentiated services with multicast and tunneling. Section 11
      addresses security concerns.
   3. Differentiated Services - Motivation and Definition
      Traditionally, network service providers (both enterprise and
      traditional ISPs) provide all customers with the same level of
      performance (best-effort service). Most service differentiation
      has been in the pricing structure (individual vs. business rates)
      or the connectivity type (dial-up access vs. leased line, etc.).
      However, in recent years, increased usage of the Internet has
      resulted in scarcity of network capacity, compromising performance
      of traditional, mission critical applications. At the same time,
      new applications have emerged which demand much improved service
      quality. As a result, service providers are finding it necessary
      to offer their customers alternative levels of service. As well as
      meeting new customer expectations, this allows service providers
      to improve their revenues through premium pricing and competitive
      differentiation of service offerings, which in turn can fund the
      necessary expansion of the network.
      The Differentiated Services architecture offers a framework within
      which service providers can offer each customer a range of network
      services which are differentiated on the basis of performance in
      addition to pricing tiers used in the past. Customers request a
      specific performance level on a packet by packet basis, by marking
      the DS field of each packet with a specific value (see [DSHEAD]
      for more details). This value specifies the Per-hop Behavior (PHB)
      to be allotted to the packet within the provider's network.
      Typically, the customer and provider negotiate a profile (policing
      profile) describing the rate at which traffic can be submitted at
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      each service level. Packets submitted in excess of this profile
      may not be allotted the service level requested. A salient feature
      of differentiated services is its scalability, which allows it to
      be deployed in very large networks.  This scalability is achieved
      by forcing as much complexity out of the core of the network into
      boundary devices which process lower volumes of traffic and lesser
      numbers of flows, and offering services for aggregated traffic
      rather than on a per-micro-flow basis.
   4. Services
      [DSARCH] defines a Service as "the overall treatment of a defined
      subset of a customer's traffic within a DS-domain, or end-to-end".
      Although PHBs are at the heart of the differentiated services
      architecture, it is the service obtained as a result of marking
      traffic for a specific PHB, which is of value to the customer.
      PHBs are merely building blocks for services. Service providers
      combine PHB implementations with traffic conditioners,
      provisioning strategies and billing models which enable them to
      offer services to their customers. Providers and customers
      negotiate agreements with respect to the services to be provided
      at each customer/provider boundary. These are commonly referred to
      as Service Level Agreements (SLAs).  Many of the aspects of SLAs
      (such as payment terms) are beyond the scope of technical
      standards and are therefore not considered in this document;  the
      subset of the SLA which provides the technical specification of
      the service will be referred to as the Service Level Specification
      Bear in mind when considering the services that are offered in a
      DS-domain that:
      * DS services are all for unidirectional traffic only
      * DS services are for traffic aggregates, not individual micro-
   4.1 Customer/Provider Boundaries
      Present day network traffic generally traverses a concatenation of
      networks which may include hosts, home or office networks, campus
      or corporate networks and several large transit networks. Home and
      office networks are typically customers of campus or corporate
      networks, which are in turn customers of large transit networks.
      While one would expect the initial deployment of differentiated
      services to be within large transit networks, its deployment may
      also be extended to the smaller campus and corporate networks and
      in special cases, all the way to individual hosts. As such, there
      may be numerous customer/provider boundaries at which the concept
      of a 'service' applies.
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   4.2 SLSs and TCSs
      At each differentiated service customer/provider boundary, the
      technical aspects of the service provided is defined in the form
      of an SLS which specifies the overall features and performance
      which can be expected by the customer. Because DS services are
      unidirectional the two directions of flow across the boundary will
      need to be considered separately.  An important subset of the SLS
      is the traffic conditioning specification, or TCS. The TCS
      specifies detailed service parameters for each service level. Such
      parameters include:
      1. Detailed service performance parameters such as expected
         throughput, drop probability, latency.
      2. Constraints on the ingress and egress points at which the
         service is provided, indicating the `scope' of the service.
         Service scopes are discussed further in Sec. 4.4.
      3. Traffic profiles which must be adhered to for the requested
         service to be provided, such as token bucket parameters.
      4. Disposition of traffic submitted in excess of the specified
      5. Marking services provided.
      6. Shaping services provided.
      The TCS, the logical components needed to implement it and the
      configuration needed for those components are discussed in more
      detail in [DiffEdge].
      In addition to the details in the TCS, the SLS may specify more
      general service characteristics such as:
      1. Availability/Reliability, which may include behavior in the
         event of failures resulting in rerouting of traffic
      2. Encryption services
      3. Routing constraints
      4. Authentication mechanisms
      5. Mechanisms for monitoring and auditing the service
      6. Responsibilities such as location of the equipment and
         functionality, action if the contract is broken, support
      7. Pricing and billing mechanisms
      These additional characteristics are important, and in the case of
      pricing and billing, fundamental to the service offering but they
      do not affect the service itself and are not considered further
      Metrics which can be used to validate the delivery of the service
      specified by a TCS have been studied by the IP Performance Metrics
      Working Group of the IETF and are being published as Informational
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   4.3 Service Taxonomy: Quantitative through Qualitative and
      The Differentiated Services architecture can support a broad
      spectrum of different kinds of service.  Categorizing these
      services provides some constraints on the corresponding SLSs that
      can be offered for the service.
      Some services can be clearly categorized as qualitative or
      quantitative depending on the type of performance parameters
      offered. Examples of qualitative services are as follows:
      1. Traffic offered at service level A will be delivered with low
      2. Traffic offered at service level B will be delivered with low
      The assurances offered in examples 1 and 2 are relative and can
      only be verified by comparison.
      Examples of quantitative services are as follows:
      3. 90% of in profile traffic delivered at service level C will
         experience no more than 50 msec latency.
      4. 95% of in profile traffic delivered at service level D will be
      Examples 3 and 4 both provide concrete guarantees that could be
      verified by suitable measurements on the example service
      irrespective of any other services offered in parallel with it.
      There are also services which are not readily categorized as
      qualitative or quantitative as in the following examples:
      5. Traffic offered at service level E will be allotted twice the
         bandwidth of traffic delivered at service level F.
      6. Traffic with drop precedence AF12 has a higher probability of
         delivery than traffic with drop precedence AF13 [AF].
      In example 5, the provider is quantifying the relative benefit of
      submitting traffic at service level E vs. service level F, but the
      customer cannot expect any particular quantifiable throughput.
      This can be described as a `Relative Quantification Service'.
      In general, when a provider offers a quantitative service, it will
      be necessary to specify quantitative policing profiles. In many
      cases, quantitative policing profiles will be specified even for
      services that do not offer quantitative performance.
      Determining how to monitor and audit the delivery of a qualitative
      or relative quantification service in such a way as to convince
      the user that he has received fair measure requires careful
      attention.  It will be up to the customer to determine if the
      advantage offered is sufficient to make the service worthwhile.
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      The SLS must clearly avoid making quantitative commitments for
      these services.
   4.4 The Scope of a Service
      The scope of a service refers to the topological extent over which
      the service is offered. For example, assume that a provider offers
      a service to a customer which connects to their network at ingress
      point A. The service may apply to:
      1. all traffic from ingress point A to any egress point
      2. all traffic between ingress point A and egress point B
      3. all traffic from ingress point A to a set of egress points
      Egress points may be in the same DS Domain as the ingress point or
      may be in other domains which are either directly or indirectly
      connected to the ingress domain. If the egress point is in another
      domain, it will be necessary for the ingress provider to negotiate
      SLAs with the relevant peer domains, which will recursively
      negotiate with their peers to ensure that the service offered at
      ingress point A can indeed be extended to the egress points
      specified. The scope of a service is part of the TCS governing
      ingress point A.
      In general, providers will be able to offer quantitative services
      most efficiently when a specific set of egress points is
      specified. Quantitative services which span multiple domains also
      require tighter coupling between the SLA offered to the customer
      at ingress point A and the SLAs negotiated with intermediate
      domains. Qualitative services can more readily be offered to
      arbitrary sets of egress points and require looser coupling
      between the SLA at ingress point A and SLAs at intermediate domain
   4.4.1 Services where the Scope is Tied to the Receiver
      A special case of service scope is a service that governs all
      traffic between any ingress point and egress point B. The SLS that
      defines this service would be at egress point B and would
      effectively allow the customer to control the mix of traffic
      received from the provider. While such a service is theoretically
      possible, it appears to be a mismatch with the more usual
      specification of Differentiated Services  which governs the
      quality with which traffic is sent, rather than received.
      A number of concerns would have to be addressed by such a service,
      -  Traffic going to point B from an ingress point A under the
         terms of the SLS of this service may also be governed by an SLS
         for traffic submitted at point A.  The SLSs may conflict and it
         will not, in general, be possible to resolve all such conflicts
         across all the ingress points
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      -  Establishing a traffic profile for this service at every
         possible ingress which prevents overload of the receiver can be
         more complex than for other service scopes: Static profiles are
         likely to be either inefficient (e.g. dividing the egress
         profile into fixed proportions) or risky (e.g. allowing every
         ingress to send the whole profile) whilst dynamic profiles
         require processes and communication mechanisms to coordinate
         the settings.  For example, the sources may offer 1Mb/s when
         the receiver can only accept 9.6Kb/s.
      -  Without effective ingress profiles for the service, denial of
         service attacks will be a serious problem.
      Some of the characteristics of receiver oriented services can be
      provided by local policies and the SLS for the domain to which
      traffic is sent via the egress point as described in Sec. 4.6.4.
   4.5 Dynamic vs. Static SLSs
      SLSs may be static or dynamic. Static SLSs are the norm at the
      present time. These are instantiated as a result of negotiation
      between human agents representing provider and customer. A static
      SLS is first instantiated at the agreed upon service start date
      and may periodically be renegotiated (on the order of days or
      weeks or months). The SLS may specify that service levels change
      at certain times of day or certain days of the week, but the
      agreement itself remains static.
      Dynamic SLSs, on the other hand, may change frequently. Such
      changes may result for example, from variations in offered traffic
      load relative to preset thresholds or from changes in pricing
      offered by the provider as the traffic load fluctuates. Dynamic
      SLSs change without human intervention and thus require an
      automated agent and protocol, for example, a bandwidth broker to
      represent the differentiated service provider's domain (such as
      suggested in [ROTZY]).
      Dynamic SLSs also present challenging problems to both end users
      and network providers:
      -  Network providers have to balance frequently changing loads on
         different routes within the provider network. This requires the
         provider to adopt dynamic, automated resource provisioning
         mechanisms rather than relying on static provisioning.
      -  Customer equipment will have to adapt to dynamic SLSs in order
         to make the most out of the changing SLS.
      -  End user applications may have to adapt their behavior during a
         session to make the most of (or even, cope with) dynamic SLSs.
      It is worth reiterating that the SLSs in Differentiated Services
      apply to aggregates of traffic and not individual flows.  For
      scalability, it is undesirable to envisage modifying an SLS every
      time a new micro-flow is added or removed from an aggregate.
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   4.6 Provisioning Traffic Conditioners in Boundary Devices to Provide
      Once an SLS has been negotiated, the service provider (and
      optionally the customer) will configure traffic conditioning
      components at the boundary between the two networks. The service
      provider does so with the goal of protecting the provider's
      network such that the resources granted to the customer meet but
      do not exceed the terms of the TCS. The customer does so with the
      goal of making the best use of the service purchased from the
      provider. In this section, we will briefly describe configuration
      of traffic conditioners in boundary devices.  Traffic conditioners
      and their configuration are described in greater detail in
      Note that the provider's self interests require only that the
      provider identify
      -  for which service level specific traffic is submitted,
      -  by which customer it is submitted, and
      -  for traffic with double-ended SLSs (i.e. SLS scope is type 2 or
         3 of Sec. 4.4) only, the destination address to which the
         traffic is directed.
      Customer traffic may be authenticated either by the physical
      connection on which it arrives or by some sophisticated
      cryptographic means which is beyond the scope of this draft. The
      provider need not be concerned with the customer's individual
      micro-flows in delivering basic Differentiated Services (see Sec.
      4.6.3 for additional services).
      [DSARCH] identifies four traffic conditioning components:
      1. Meters
      2. Markers
      3. Shapers
      4. Droppers
      The combination and interaction of the traffic conditioning
      components is selected on a packet-by-packet basis by the DS
      codepoint.  The configuration parameters for the components at
      each codepoint are determined by the policies and profiles
      applied, so that the conditioner polices the traffic in the BA
      specified by the codepoint.  Meters measure submitted traffic for
      conformance to a profile, providing control input for the other
      components which implement the policing:
      -  Shapers police by delaying submitted traffic such that it does
         not exceed the traffic rate specified in a profile.
      -  Droppers police by dropping traffic that is submitted at a rate
         exceeding that specified in a profile.
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      -  Markers police by re-marking the traffic with a different
         codepoint either
         -  to demote out-of-profile traffic to a different PHB,
         -  as a result of an SLS which specifies codepoint mutation, or
         -  to ensure that only valid codepoints are used within the
      In addition to these four components, traffic classifiers are
      required in order to separate submitted traffic into different
      classes. Classifiers may separate traffic based only on the DS-
      field of submitted packets (BA classifiers) or may do so based on
      multiple fields within the packet header and even the packet
      payload (MF classifiers).  MF classifiers may be used at
      boundaries to provide certain per-micro-flow services to
      customers. Examples of such services include per-flow marking or
      shaping.  Typically, traffic will arrive at the boundary of a DS
      domain pre-marked and pre-shaped. However, at interfaces with some
      non-DS customer networks, it is possible that traffic will require
      marking and shaping.
      Even if a customer has pre-marked and pre-shaped, the service
      provider will wish to police the traffic at the ingress boundary
      to meet the domain's self-interests.  This may result in traffic
      being re-marked or dropped.
      Traffic conditioning components (in particular, meters) will also
      be the primary source of accounting information for a
      Differentiated Services network.
   4.6.1 Minimal Functionality at Provider's Ingress
      At the very least, the service provider must limit traffic carried
      on behalf of the customer to the constraints specified in the TCS.
      A simplified TCS can be represented in the form of a table wherein
      each row has the format:
      DS-Mark : Profile  : Scope : Disposition of non-conforming traffic
      This row indicates that the provider commits to carry traffic
      marked with 'DS-Mark' at the corresponding service level, provided
      that it conforms to the 'Profile'. Traffic that is submitted with
      'DS-Mark' and which does not conform to the 'Profile', is
      subjected to 'Disposition of non-conforming traffic'. This is
      generally a policing action such as re-marking to a lower service
      level, delaying in a shaper, or dropping. Alternatively, it may be
      carried at the requested service level, but subjected to a
      surcharge.  The scope for this type of service would normally be
      expected to be of type 1 of Sec. 4.4.1, where the traffic
      destination can take it through any egress point of the domain.
      To provide this minimal functionality, the provider must configure
      a BA classifier to separate traffic into the different service
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      level requested, based on DS-Mark. Following the BA classifier,
      each class must be metered for conformance to the corresponding
      profile. Following the profiler, either a dropper, shaper or re-
      marker is likely to be employed.  The Better than Best Efforts
      service described in Sec. 5.1 is an example of a service for which
      this functionality is sufficient.
   4.6.2 Functionality at Provider's Ingress for Double-ended SLSs
      If quantitative or other services needing double-ended SLSs (types
      2 and 3 of Sec. 4.4.1) are implemented in a DS Domain, these
      services specify the possible egress port(s) for traffic
      conforming to the SLS.  The traffic conditioner needs to consider
      the destination address of the packet as additional input to the
      policing process, so that traffic is not accepted for egress ports
      for which an SLS does not exist.  The Virtual Leased Line service
      described in Sec. 5.2 is an example of a service that would
      require this functionality.
      A QoS VPN can be constructed by provisioning multiple instances of
      services of type 2, building in effect, a mesh of point to point
      QoS links.
      Services of type 3 are most likely to be used for multicast
      applications (see Sec. 10).
   4.6.3 Added Value Functionality at Provider's Ingress
      The functionality described in Secs. 4.6.1 and 4.6.2 serves only
      to protect the provider's network resources in line with the terms
      of the TCS. It provides no assistance to the customer. The burden
      of marking packets and shaping traffic falls entirely on the
      customer. In some cases, the SLS may call for the provider to
      provide additional services to the customer. Such services may
      1. Marking traffic from specific micro-flows to a specific
         behaviour aggregate (marking the DS-field).
      2. Policing traffic from specific micro-flows or sets of micro-
         flows, either in the form of dropping or shaping.
      In order to provide such services, the provider must generally
      employ an MF classifier in addition to the BA classifier. The need
      for an MF classifier arises only when the customer requires the
      provider to provide some form of traffic separation or
      authentication on behalf of the customer. The provider may charge
      dearly for these services depending on the degree of granularity
      and the amount of work required. For example, shaping thousands of
      customer micro-flows might consume considerable resources in the
      provider's boundary device. On the other hand marking based on
      source subnet addresses would consume considerably fewer
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   4.6.4 Functionality at Customer's Egress
      Strictly speaking, the customer need not apply any specific
      traffic conditioning. In this case, the customer relies on the
      provider to mark as per negotiated MF classification criteria. In
      many cases it is preferable for the customer to mark. Customer
      marking may be necessary when customer packets are encrypted (as
      in the case of end-to-end IPSec). Customer marking enables the
      customer to direct specific traffic from specific users or
      applications to specific service classes. This may be difficult or
      impossible for a provider to do on behalf of a customer when, for
      example,  applications use volatile ports and users are assigned
      IP addresses based on DHCP.
      In addition to marking, it is in the customer's best interest to
      at least shape per service level, at the customer network's egress
      point. Otherwise, customer traffic may be policed by the service
      provider with undesirable consequences (e.g. dropped packets).
      Shaping per service level does not however, provide for micro-flow
      traffic separation. As a consequence, a renegade traffic source
      may cause the profile to be exceeded for a specific service level,
      negatively impacting all customer flows which are marked for that
      service level. Therefore, it is often in the customer's interest
      to meter and shape or at least to police, with micro-flow
   4.6.5 Functionality at Provider's Egress
      At the egress from a provider's domain there may be an SLA in
      place with a peer DS domain, which might be either another
      provider or an end user domain.  As in Sec. 4.6.4, it is in the
      provider's best interests to shape the traffic leaving the domain.
      Depending on the SLA, the egress may be required to remark and/or
      police or shape the traffic.  Note that the forwarding treatment
      applied to the packet in the egress node of the domain would be
      that selected by the codepoint before it was remarked (otherwise,
      the egress node has to support multiple codepoint to PHB
      If the peer domain is a non-DS domain the egress may be required
      to remark all packets to conform to one of the previous standards
      for the use of the TOS byte [RFC791,RFC1349].
      The provider may also wish to offer additional services to a
      customer by policing egress traffic with micro-flow granularity if
      the customer might expect to receive excessive traffic in a single
      BA and wishes to apply greater control than could be achieved by
      normal policing of the aggregate.  This would be specified via an
      SLS in the usual way.
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   4.7 Internal Provisioning
      The provider must provision internal nodes in the provider network
      to meet the assurances offered by SLSs negotiated at the
      boundaries of the network. To do so, the provider may use similar
      traffic conditioning mechanisms to those used at the network
      boundaries. However, providers are unlikely to apply MF
      classification within the interior of the network.  The provider
      may police periodically within the network, by reshaping,
      remarking or discarding traffic.
      Service providers are experienced in provisioning large networks
      which offer uniform service.  They are assisted in this by
      predictive tools, traffic modeling tools and real time
      measurements. Current techniques will likely be applied to
      differentiated services networks, although, the complexity of
      provisioning will increase significantly.  In a differentiated
      service network, the provider must ensure that resources granted
      to traffic of one service level does not inappropriately
      compromise assurances regarding traffic at other service levels
      (for example, in example service 6, traffic in AF12 can
      legitimately compromise traffic in AF13 if an increase in AF12
      traffic causes more AF13 traffic to be dropped).  As mentioned
      previously, internal provisioning in the case of dynamic SLSs will
      likely require dynamic resource allocation protocols.
   4.8 End-to-End Service Construction
      The Differentiated Services architecture proposes that an end-to-
      end service can be constructed by the concatenation of domain
      services and their associated customer-provider SLAs for each of
      the domains which the service traffic has to cross.
      Clearly, not all PHBs and services can be meaningfully
      concatenated, and the definition of suitable services and their
      associated PHBs will be a major focus of future Differentiated
      Services development.  This is discussed at greater length in Sec.
   5. Service Examples
      In this section, we describe service examples and show how they
      can be supported by specific PHBs.  We base these examples on PHBs
      which are defined in [AF]and [EF].  These examples are intended to
      be illustrative of the wide range of services that can be employed
      using the differentiated services model, and are not intended to
      be an exhaustive list.  Further examples can be found in the
      Appendix of [AF] (`Olympic' service _ related gold, silver and
      bronze service levels, a proportional bandwidth service and an
      alternative for a low latency service) and [2BIT].
   5.1 Better than Best-Effort (BBE) Service
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      This is a qualitative service which promises to carry specific web
      server traffic at a higher priority than competing best-effort
      traffic. Such a service offers relatively loose (not quantifiable)
      performance from a given ingress point to any egress point. Such a
      service is suitable for example for businesses offering access to
      web based content. The BBE service enables the web content
      provider to provide content at a generally higher rate than other
      content providers are able to, in so reducing the latency
      experienced by consumers of  the web site.
   5.1.1 Service Implementation
      In this example, we assume that there is an SLS which defines the
      service at the customer's ingress point. This is the point at
      which the customer injects web server responses into  the
      differentiated services network. The information in the TCS can be
      represented in the following form [AF]:
      AF11 Mark : 1 Mbps : Any egress point : Excess traffic handled by
      marking with AF13 mark : .
      Packets submitted for the BBE service should be marked with the
      DS- field codepoint corresponding to the AF11 PHB. The provider is
      promising to carry up to 1 Mbps of traffic from the ingress point
      to any egress point at a higher priority than best-effort traffic.
      A lesser class of service corresponding to the AF13 PHB will be
      applied to traffic submitted for the AF11 PHB, in excess of 1
      The provider will provision a policer at the ingress point.
      Traffic submitted up to the 1 Mbps limit will be directed to the
      AF11 PHB. Traffic submitted in excess of 1 Mbps will be remarked
      for the AF13 PHB. Note that the scheme will preserve ordering of
      packets since AF11 and AF13 use a single queue..
      In order to provide this service, the provider will have to
      implement the AF11 and AF13 PHBs in core network equipment. The
      AF11 and AF13 PHBs can be implemented for example, using a single
      RIO queue. The provider will also have to provision equipment
      within the core of the provider's network to provide the AF11/AF13
      service. By provisioning the appropriate RED parameters, for
      example, the provider is able to control the priority of AF11
      traffic relative to AF13 traffic at each network node. Since there
      are no quantitative guarantees, the provider can be quite liberal
      in its provisioning strategy and may realize significant
      statistical multiplexing gains. Also, the absence of quantitative
      guarantees makes it easy to provide this type of service across
      multiple DS provider domains. This is because is not necessary to
      negotiate, then provision and enforce quantitative guarantees at
      multiple boundaries.
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   5.2 Leased Line Emulation Service
      This is a quantitative service which emulates traditional leased
      line service. As such, it promises to deliver customer traffic
      with very low latency and very low drop probability, up to a
      negotiated rate. Above this rate, traffic is dropped. Such a
      service is typically offered between two specific points. It is
      suitable for many customer applications. However, due to the high
      quality guarantees, it is likely to be priced higher than
      alternate services and therefore, to be used only for applications
      which really require this type of service. An example of such an
      application is IP telephony. A corporate customer might purchase
      leased line emulation service between each pair of a number of
      corporate network sites.
   5.2.1 Service Implementation
      In this example, we consider a customer with three geographically
      dispersed networks interconnected via a single provider network.
      Customer attachment points are represented as A, B and C. At each
      attachment point, an SLS describes the leased line service to be
      provided to the other two points. The table below represents the
      information required in the TCS at attachment point A:
      EF-Mark : 100 Kbps : Egress point B : Discard non-conforming
      EF-Mark : 50 Kbps : Egress point C : Discard non-conforming
      Packets submitted for leased line service should be marked with
      the DS-field codepoint corresponding to the EF PHB [EF]. From the
      ingress point A, to the egress point B, the provider is promising
      to carry up to 100 Kbps of traffic. Excess traffic will be
      discarded. From ingress point A, to egress point C, the provider
      promises to carry 50 Kbps of traffic. Of course, there is some
      tolerance required in policing the traffic and thus, there may be
      a specification of tolerated jitter or burst size. However, for a
      leased line service, the primary traffic profile parameter would
      be the sustained traffic rate.
      The provider will provision a policer at ingress point A to limit
      traffic destined for egress point B, to 100 Kbps. Similarly, a
      policer will be configured to limit traffic destined for egress
      point C, to 50 Kbps. These policers will require classification
      based on the DS-Mark and the destination address in each packet.
      In order to provide this service, the provider will have to
      implement the EF PHB in core network equipment. The EF PHB can be
      implemented using strict priority queuing or alternatively, by
      assigning EF marked packets to a heavily weighted queue in a WFQ
      scheme. The provider will have to provision equipment within the
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      core of the provider's network. For example, routers carrying
      traffic between point A and points B and/or C will have to be
      provisioned considering the resources committed by the TCS at
      point A. This means that a router which is both in the path from A
      to B and from A to C, will have to be considered to have committed
      150 Kbps of bandwidth as a result of the TCS in place at A. A
      router that is only in the path from A to B, will have to be
      considered to have committed 100 Kbps as a result of this TCS, and
      so on. Of course, routing is subject to change and so, failover
      paths may have to be provisioned as well. These may be provisioned
      to provide some fraction of the service in the case of failover or
      alternatively, the SLS at point A might reflect appropriate
      service availability parameters. To enhance the assurances offered
      by EF service, providers may employ route pinning mechanisms or
      QoS routing mechanisms.
   5.3 Quantitative Assured Media Playback Service
      This service offers looser assurances than the leased line service
      described above, but is still considered a quantitative service.
      In particular, it promises to deliver traffic with a high degree
      of reliability and with variable but bounded latency, up to a
      negotiated rate. Above this rate, traffic is subject to
      significant delay or drop. Such a service is typically offered
      between a specific set of points. It is suitable for many customer
      applications. It would likely be priced lower than a leased line
      service, due to the latency variability. However, due to the
      latency bound and high degree of delivery, it is likely to be
      priced higher than alternate services. This service is
      particularly suitable for video or audio playback, in which
      considerable bandwidth is required on a continual basis, but the
      non-interactive nature of the traffic makes it somewhat delay
   5.3.1 Service Implementation
      In this example, we again consider a customer with three
      geographically dispersed networks interconnected via a single
      provider network. The table below represents the information
      required in the TCS at attachment point A:
      AF11-Mark : 100 Kbps sustained, 100 Kb bursts tolerated at up to
      200 Kbps : Egress point B : Excess burst traffic over sustained
      rate marked with AF12-mark : Non-conforming traffic marked with
      AF13-mark : Max latency = 1 second
      AF11-Mark : 50 Kbps sustained, 100 Kb bursts tolerated at up to
      100 Kbps : Egress point C : Excess burst traffic over sustained
      rate marked with AF12-mark : Non-conforming traffic marked with
      AF13-mark : Max latency = 2 seconds
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      Packets submitted for the assured playback service should be
      marked with the DS-field codepoint corresponding to the AF11 PHB.
      From the ingress point A, to the egress point B, the provider is
      promising to carry up to 100 Kbps of sustained traffic with bursts
      of 100 Kb in size at a peak rate of 200 Kbps. Excess burst traffic
      will be marked with the codepoint for AF12 and out of profile
      traffic will be carried but with the AF13 codepoint. So long as
      these conditions are met, latency will be limited to 1 second.
      Note that for this service, the traffic profile is described using
      a full set of token bucket parameters. Since the latency bounds
      for such a service are less strict than those required for the
      leased line service, a certain degree of traffic burstiness can be
      The provider must support the AF11, AF12 and AF13 PHBs in core
      network routers. These PHBs might be provided, for example, by
      assigning AF11, AF12 and AF13 marked traffic to a single RIO queue
      with high drop thresholds. The policers at the boundary would
      limit competing traffic in line with the TCS, in order to assure
      that the latency bounds can be met. In addition, the service
      provider will have to provision devices in the core of the
      network. The provisioning considerations discussed in the context
      of the leased line service apply here as well, however, in
      general, the service provider has the liberty of being less
      conservative in provisioning and realizing better statistical
   5.4 Superposition of Quantitative and Qualitative Services in the
   Same Network
      A compelling model would provide both quantitative and qualitative
      services in the same differentiated service network(s) as follows.
      A number of corporate campus networks would be interconnected by a
      differentiated service network providing quantitative services
      between the sites. For example, a mesh of leased line services
      would enable IP telephony between the sites. A mesh of media
      playback service using the AF11 PHB would enable audio/video
      playback between the sites. In addition, each corporate site would
      be allotted some level of BBE service to arbitrary destinations.
      In this model, the differentiated service network is effectively
      providing a mesh of quantitative services between fixed locations
      (similar to a VPN). This mesh is superimposed on a cloud
      supporting BBE service.
   6. Provisioning and Configuration
      The provision of differentiated services requires careful network
      wide provisioning and configuration. Provisioning refers to the
      determination and allocation of the resources needed at various
      points in the network. Provisioning may dictate the addition or
      removal of physical resources at various points (physical
      provisioning). Provisioning may also dictate the modification of
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      operating parameters within existing physical network equipment to
      alter the relative share of the equipment's resources which are
      allotted to one or another class of traffic (logical
      provisioning). Configuration refers to the distribution of the
      appropriate operating parameters to network equipment to realize
      the provisioning objectives.
      In Secs. 4.6 and 4.7, we briefly discussed provisioning and
      configuration requirements both at the network boundaries and in
      the network interior. In this section we will focus primarily on
      the coordination of provisioning and configuration throughout the
      network, such that end-to-end services can be provided reliably.
      We will discuss the roles of protocols such as SNMP, CLI, RSVP,
      COPS and LDAP in the provisioning process.
   6.1 Boundary vs. Interior Provisioning and Configuration
      For the sake of brevity, consider the term 'provisioning' to refer
      both to provisioning and configuration, except where otherwise
      noted. It is helpful to consider provisioning at the network
      boundaries, separately from provisioning of the interior. Since
      the differentiated service provider is selling a contract (SLA) at
      the network boundary, we can consider the boundary provisioning
      which supports SLSs, to drive the interior provisioning. The two
      are not entirely separable in that each affects the other. For
      example, a network operator cannot offer an SLS which cannot be
      met by the resources available in the interior of the network. In
      general, the overall provisioning process iterates between the
      boundaries and the interior. From here on we will refer to
      provisioning with respect to the TCS rather than the SLS, since
      the TCS is the component of the SLS that defines detailed traffic
      handling parameters.
   6.1.1 Boundary Provisioning
      Boundary provisioning was considered briefly in Sec. 2.6. We
      discussed the minimal provisioning that a provider must implement
      to enforce a TCS. We also discussed additional configuration which
      a provider may use to provide additional (especially per-flow)
      services to a customer. The latter is not actually related to the
      provisioning of resources within the differentiated services
      network, but rather assists the customer by determining which
      subsets of the customer's traffic make use of the resources
      provisioned within the differentiated services network. As such,
      it is out of the scope of this section. Here, we consider only the
      minimal provisioning required at the boundary.
      At a minimum, the provider must assure that sufficient physical
      resources are provisioned at the boundary to meet the requirements
      of the TCS. For example, if the sum of the profiles supported at a
      particular ingress point would allow 10 Mbps of traffic to be
      supported, it is unacceptable to provision a T-1 access link. A T-
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      3 however, would be sufficient. Once the physical provisioning is
      implemented, it is necessary to apply the appropriate logical
      provisioning. This is achieved by configuring policers which limit
      the amount of traffic accepted from the T-3 access link, at each
      service level and, for double ended TCSs, for the appropriate
      egress points.  It may also be necessary to set up the amount of
      buffering available for the queues used for the service.  Similar
      provisioning is also appropriate at each egress point if the
      aggregate of profiles provisioned to the egress exceeds the
      capacity of the output link.
   6.1.2 Interior Provisioning
      For the purpose of provisioning the interior of the network, it is
      desirable to understand or to control the volume of traffic of
      each class which traverses each network node. The greater this
      understanding, the more efficiently the network can be provisioned
      while still meeting the requirements of the TCSs. It is feasible
      to understand the volume of traffic traversing each node if this
      traffic is admitted according to a TCS which dictates egress point
      as well as ingress point. (This case generally applies to
      quantitative services and was discussed in the context of the EF
      PHB and the leased line service in Sec. 3.2.1). While traffic
      volumes cannot be anticipated with 100% accuracy, it is possible
      to approximate them quite well, especially with the help of route
      pinning mechanisms. It is therefore possible to provision the
      network reasonably accurately for traffic submitted for
      quantitative services. Although such provisioning may be quite
      difficult in a large network, it is nonetheless a tractable
      problem. We will refer to this component of the provisioning
      problem as quantitative provisioning.
      On the other hand, many (if not most) of the services offered by
      differentiated service networks will not specify egress points (as
      is the case for qualitative services) and will not restrict
      submitted traffic to specific egress points, let alone specific
      routes. Thus, interior nodes will have to be provisioned without
      an a-priori understanding of the volume of traffic submitted for
      qualitative services which will arrive at each node. It is
      necessary to be able to provision differentiated service networks
      to support both quantitative services with specific egress points
      as well as qualitative services, which do not have specific egress
      points on the same physical resources. To this end, it is
      necessary to isolate the impact of qualitative traffic on the
      resources reserved for quantitative traffic. This can only be
      achieved if the former is treated with lower priority than the
      latter. Thus, in general, resources will have to be provisioned
      first for quantitative traffic, using quantitative provisioning
      mechanisms. Then, qualitative provisioning can be used to allocate
      remaining resources to qualitative traffic.  Qualitative
      provisioning can also be applied to services which offer a
      relative quantification of traffic volumes.
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      The impact of the two types of traffic will have to be isolated by
      ensuring that they do not share PHB codepoints. PHBs used for
      quantitative services will always have higher priority access to
      resources than those used for qualitative services. As a result,
      it is necessary to carefully police traffic submitted for
      quantitative PHBs. Failure to do so can result in the starvation
      of lower priority traffic. In general it can be expected that only
      a small fraction of the resources at each node will be provisioned
      for quantitative traffic.
      Similarly, a significant fraction of the traffic capacity should
      remain for best-efforts service to provide a 'soft' target for
      traffic dropping if congestion occurs or it is necessary to
      redirect non-best efforts traffic in the event of failure. Quantitative Provisioning of the Interior
      As discussed previously, quantitative provisioning is a difficult
      but tractable problem. With knowledge of the network routing
      topology and the TCSs at the boundaries, it is possible to compute
      the resources required at each interior node to carry the
      quantitative traffic offered at the edges. Based on the results of
      this computation, interior nodes must be provisioned and
      configured with sufficient capacity to accommodate the
      quantitative traffic which will arrive at the node, while leaving
      sufficient capacity remaining to accommodate some amount of
      qualitative traffic.
      The provisioning mechanism described assumes a top-down approach,
      in which the network administrator studies the network topology
      and traffic routing and computes the provisioning requirements. An
      alternative approach uses signaling to automate the process
      [MPLS]. For example, RSVP messages could be launched along the
      paths that will be followed by submitted quantitative traffic. If
      a TCS calls for 100 Kbps of leased-line service from ingress point
      A to egress point B, an RSVP message could be transmitted from
      point A towards point B, with a flowspec specifying 100 Kbps. This
      message would traverse each node at which resources would have to
      be committed. Conventional RSVP routers would install a
      reservation. In a differentiated service network, RSVP could be
      adapted to provision the resources required per the differentiated
      services model. In a network which offers a number of static TCSs,
      such RSVP messages could be launched from the TCS ingress point at
      the time the TCS is initially instantiated with the effect of
      instantiating the appropriate cumulative provisioning in routers
      along the various routes. The advantage of this approach is that
      it does not require explicit knowledge of the network topology. We
      will revisit these two approaches to quantitative provisioning of
      the interior in a later section.
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      Once the resources required for quantitative traffic at each node
      have been determined, provisioning of the node consists of
      installing or configuring interfaces of the appropriate capacity
      to easily accommodate the quantitative traffic that will traverse
      the node. Note that we do not state the precise meaning of 'to
      easily accommodate'. A number of factors must be considered when
      determining the appropriate capacity, given a certain volume of
      predicted quantitative traffic. These include:
      1. Margin of error
      2. Statistical gain desired
      3. Capacity remaining for qualitative (including best efforts)
      The first, margin of error, accommodates mistakes in computation,
      effects of transient route changes which are not otherwise
      accounted for, effects of traffic clustering as it moves through
      the network and so on. The statistical gain desired refers to the
      degree to which a provider is willing to gamble that not all
      sources of quantitative traffic will be simultaneously active at
      the limit dictated by the TCSs at the ingress points (vs. the
      penalty the provider would be willing to pay in terms of refunded
      charges or lost customers). Finally, the provider must determine
      how much capacity will be reserved for qualitative traffic at each
      node. Thus, if it is determined that 1 Mbps of quantitative
      traffic might traverse a specific node in a specific direction,
      the provider might install a 10 Mbps interface in the node, to
      serve the corresponding traffic direction. This would leave 9 Mbps
      of capacity quite safely for qualitative traffic. In this case,
      the provider would be assuming that statistical gains which might
      be realized will be used to offset the margin of error which would
      compromise the resources available.
      In addition to installing or configuring the appropriate capacity
      at each interface, it may be desirable to configure policers to
      assure that the resources actually consumed by the higher priority
      quantitative traffic do not exceed expectations. This is
      especially important if the provider is attempting to achieve a
      high degree of statistical gain or has not allowed for a
      reasonable margin of error. Policers need not be configured at
      each interior node, but should probably be configured at certain
      key nodes.  It may also be necessary to configure the internal
      resources of the router (queues and buffers) to deliver the
      services required. Qualitative Provisioning of the Interior
      As explained previously, it is necessary first to determine the
      resources which must be provisioned at each node for quantitative
      traffic. Once these have been determined, interfaces must be
      installed or provisioned to accommodate the required resources
      while leaving sufficient capacity for qualitative traffic. In
      order to do so, it is necessary to determine the resources
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      required at the node for qualitative traffic. Since qualitative
      traffic cannot be assumed to follow specific routes with the same
      degree of predictability as quantitative traffic, this
      provisioning problem is far more difficult and provisioning
      parameters must be estimated based on heuristics, experience and
      possibly on real time measurement.
      Once physical interfaces have been selected to accommodate the
      resources required by the computed quantitative traffic load and
      the estimated qualitative traffic load, additional configuration
      is required to support qualitative traffic. Such configuration
      amounts to the selection of relative weights for queues for
      different service levels (in a WFQ scheme), or the selection of
      RIO or RED thresholds or alternate logical resource provisioning
      parameters. It is assumed that if quantitative traffic is
      accommodated via similar queuing mechanisms (as opposed to strict
      priority queuing), that the weighting parameters chosen for
      quantitative traffic isolate it effectively from the effects of
      qualitative traffic. However, the configuration parameters which
      differentiate the various qualitative services may not provide
      such a degree of isolation among the qualitative services. Thus,
      it may be necessary to attempt to estimate the relative traffic
      arriving for each qualitative service and to anticipate the
      interaction between traffic of different qualitative services. It
      may be impossible to both efficiently and conservatively provision
      a network for certain combinations of qualitative services. To aid
      in the provisioning of a network for qualitative services, it may
      be useful to configure policers to control the volume of traffic
      arriving at a given node. However, such policing might have to be
      restricted to shaping (rather than discarding) in order to avoid
      violating TCSs in place at the network boundaries.
   6.2. Static vs. Dynamic Provisioning
      So far, we have considered static provisioning techniques. Even
      the example of RSVP usage for provisioning assumed that the RSVP
      messages were launched at the time a TCS was instantiated as
      opposed to dynamically. In the case that TCSs are static, static
      provisioning is adequate for quantitative traffic. However, since
      qualitative traffic offers less predictable patterns, it is likely
      to cause traffic volumes at different nodes in the network to
      change dynamically, even when the TCS is static. For this reason,
      dynamic provisioning techniques are desirable and may assist the
      service provider in making better use of network resources. In
      addition, dynamic provisioning may enable the service provider to
      provision more liberally for quantitative services, realizing
      statistical gains. If we consider further, that it may be
      desirable to provide dynamically changing TCSs, then the appeal of
      dynamic provisioning techniques is even stronger.
      Dynamic provisioning may be signaling based, measurement based or
      both. For example, a conventional RSVP router supports signaling
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      based dynamic provisioning. Hosts signal the router to request
      more or less resources and the router adjusts accordingly. The
      host may or may not actually submit traffic at the rate at which
      it signaled it would, but regardless, the resources are committed
      in case it does. Measurement based provisioning would adjust the
      resources committed in response to the traffic loads actually
      measured at the device. While differentiated services does not
      specify any form of signaled or measurement based provisioning,
      both may be useful.
   6.3 Distributing Configuration Information
      The process of physical provisioning is by necessity relatively
      static and cannot be automated since it requires installation of
      physical equipment. However, logical provisioning and
      configuration can and should be automated to the degree possible.
      In this section, we look at techniques for distributing
      configuration information.
   6.3.1 Top Down Distribution of Configuration Information
      In the simplest case, TCSs are static and both the boundaries and
      interior of the network are provisioned statically by 'pushing'
      configuration information down to the appropriate network nodes.
      Configuration of boundary nodes requires primarily the pushing of
      policing information to enforce the TCSs in place. (Additional
      fine grain information may be pushed to provide traffic separation
      services on behalf of the customer, but these are not addressed in
      this context). Configuration information for boundary nodes is
      determined at the time the TCS is negotiated. At this time, the
      nodes are configured by the provider. The network administrator
      may use one of several protocols to do so, including for example
      SNMP or CLI.
      In order to accommodate the traffic submitted by the provisioning
      of new TCSs, it is necessary to provision the interior of the
      network. As discussed previously, it is possible to compute the
      resources required for quantitative traffic. Assuming that
      sufficient physical capacity has been provisioned, configuration
      amounts to logically provisioning sufficient capacity at each
      interior interface and to configuring policers for the
      quantitative traffic at various interior nodes. In addition,
      qualitative provisioning requires the configuration of queues, WFQ
      weights and/or RIO parameters at various interior nodes, and may
      also include the configuration of some number of policers. In the
      case, of static, top down configuration, interior configuration
      information is also pushed down via a configuration protocol such
      as SNMP or CLI.
      The difficulty of such top down provisioning is that it requires
      the network administrator to coordinate the provisioning of each
      network node, at boundaries as well as in the interior, such that
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      the network is provisioned end-to-end in a consistent manner and
      is able to efficiently deliver the services promised by the TCSs.
      In order to assist the network administrator in this task, it is
      useful to consider a database which holds both current topology
      information as well as the current TCSs instantiated at the
      network boundaries. This information is stored in a format
      dictated by a standard schema as suggested in [Ellesson].
      Of course, the database is ideally maintained in a way which is
      logically centralized (for ease of programming and modifying) but
      is physically distributed (for the sake of robustness and fault
      tolerance). Policy servers may be used to extract information from
      the database and to convert it to configuration information which
      is pushed down to individual nodes. In this scenario, policy
      servers would likely use a directory access protocol such as LDAP
      to retrieve information from the directory and would use a
      configuration protocol such as SNMP or CLI to push the
      configuration information down to the network nodes. Note that in
      this example, the policy servers and the directory schemas are in
      effect fulfilling the role of bandwidth broker [ROTZY]. In
      particular, the policy servers use an awareness of the network
      topology to provision interior nodes such that certain end-to-end
      QoS routes can be constructed and assurances implied by the TCSs
      at the boundaries can be delivered.
   6.3.2 Distribution of Configuration Information via Signaling
      An alternate mechanism of distributing configuration information
      is via signaling messages transmitted between boundary nodes of
      the same differentiated service domain (intra-domain signaling).
      It is also interesting to consider inter-domain signaling, but
      this will be addressed separately. An example of such signaling
      was described previously, in the usage of a modified form of RSVP.
      Such signaling is particularly useful for the purpose of
      installing configuration information for quantitative services
      which affect specific paths and is somewhat less useful (though
      not useless) for the purpose of configuring qualitative services.
      It is likely that such a signaling approach would be used in
      conjunction with top down provisioning. For example, the directory
      schema might dictate the amount of resources to be available for
      high priority quantitative services at each node. These limits
      might be pushed down to individual nodes a-priori. Signaling from
      the network boundaries, at TCS instantiation time, would then be
      used to claim resources from the pool of quantitative resources
      available at each node. Alternatively, nodes might consult policy
      servers as the signaling resource requests arrive at each node.
      The latter model is similar to the use of per- flow RSVP signaling
      and PEP/PDP policy usage in traditional RSVP networks. Qualitative
      configuration information would still be pushed in a top down
      manner. The advantage of the latter model is that policy servers
      would be dynamically updated with information regarding the
      current usage of network resources. In this model, it is likely
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      that a variant of COPS would be used to communicate between
      network nodes and the policy servers. Note that COPS may be used
      for distribution of top down configuration information as well,
      though it is not specifically designed for this purpose.
      One of the advantages of configuration via signaling, is that it
      facilitates the support of dynamic TCSs. TCSs could be dynamically
      renegotiated using inter-domain signaling. Such renegotiation
      would require dynamically modifying the provisioning within the
      affected domain, a process which requires some automated signaling
      protocol such as an aggregated form of RSVP signaling between
      boundary nodes in a provider's domain. This protocol would in
      effect, represent a distributed bandwidth broker [ROTZY] for the
   6.3.3 Modification of Configuration Information Based on Real-Time
      A third mechanism for the configuration of interior nodes would be
      based on measurement of current traffic loads at key network
      nodes. Measurement based configuration is less necessary for
      quantitative provisioning, since quantitative traffic patterns are
      relatively predictable. However, it can significantly enhance the
      efficiency with which qualitative provisioning can be achieved.
      For example, network nodes may feed policy servers with current
      qualitative traffic load measurements. In response, bandwidth
      brokers and policy servers might recompute the relative weights
      for different service queues in a WFQ node and push the new
      configuration information to the routers. It is likely that
      measurement based configuration for qualitative services would be
      used in conjunction with signaling based configuration for
      quantitative services.
   7. Inter-Domain Considerations and End-to-End Services
      So far we have considered differentiated service primarily in the
      context of a single DS domain providing service to a single
      customer. The ultimate customers of the differentiated service
      network are hosts and end users residing on peripheral stub
      networks. In general, these are interconnected by multiple domains
      and require service which spans these domains. Therefore, it is
      important to consider the interaction of services provided by a
      concatenation of differentiated service domains and the peripheral
      stub networks, rather than the service provided by a single
      domain.  The interactions of the services and the network
      concatenation present a serious challenge to providers seeking to
      provision the services scientifically.  Whether algorithms or
      heuristics can be developed to cover the full spectrum of service
      combinations is an open question, but by analogy with QoS Routing
      it is very likely that some of the problems are not computable.
      In this section, we discuss inter-domain issues related to TCSs,
      provisioning and service and PHB mapping.
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   7.1 TCSs
      Each service provider is expected to negotiate bilateral
      agreements at each boundary node at which it connects to an
      adjacent provider's network. Such The technical aspects of these
      agreements that relate to delivering differentiated services are
      captured in the form of two TCSs, one specifying the services
      provided to provider A's traffic by provider B and the other
      specifying the services provided to provider B's traffic by
      provider A. Note that provider A serves as a provider to provider
      B with respect to traffic flowing from provider B to provider A.
      On the other hand provider A is a customer of provider B with
      respect to traffic flowing from provider A to provider B. The two
      TCSs can be considered separately.
      In general, the TCSs needed by a provider at any boundary will be
      dictated by TCSs negotiated at other boundaries. For example,
      assume that provider A offers leased line service to a customer
      with an ingress point in provider A's domain, but an egress point
      in provider B's domain. In this case, it is necessary that the TCS
      between provider A and provider B be sufficient to accommodate the
      assurance made by provider A to its leased line service customer.
      Provider A may serve a number of customers with leased line
      services terminating at various boundary points in provider B's
      network. Thus, the TCS between provider A and provider B must
      represent the aggregate requirements of the TCSs of all of
      provider A's customers.
   7.2 Inter-Domain Provisioning
      The inter-domain provisioning problem is not unlike the intra-
      domain provisioning problem. The provider would generally begin by
      evaluating the TCSs it has negotiated with its customers, and then
      computing the impact of each of these TCSs on the TCSs it has
      negotiated with its providers. For quantitative services, the
      provider can compute the quantitative requirements of TCSs at each
      of its provider's boundary nodes, as described above in the
      context of the leased line service. For qualitative services, the
      process of determining the requirements from its providers is
      fuzzier, since the volume of qualitative traffic expected to be
      carried through any boundary is less deterministic.
      In the simplest case, provisioning is based on static TCSs. In
      this case, provisioning is an iterative process in which providers
      negotiate TCSs with each of their customers, then apply the
      appropriate internal provisioning techniques to meet these
      requirements. In the process of internal provisioning, a provider
      might determine that a particular TCS cannot be met due to
      internal resource constraints. The provider would then either have
      to add internal resources or renegotiate one or more customer
      TCSs. Although the process may be somewhat iterative, it is
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      relatively static in that changes in boundary TCSs and internal
      provisioning occur relatively infrequently (on the order of hours,
      days or months) and require human intervention.
      Internal provisioning to meet the requirements of TCSs relies on
      provisioning techniques described previously. As TCSs are
      negotiated, the provider must check that the existing internal
      provisioning is sufficient to meet the requirements of the new
      TCS, or must alter the internal provisioning. Recall that internal
      provisioning might be pushed in a top down manner, from a domain's
      logically centralized point of administration, or alternatively
      might be distributed from the boundaries via signaling. In the
      former case, some form of a bandwidth broker would be directly
      consulted or notified regarding changes in TCSs negotiated at the
      domain boundaries. In the case that signaling is used,
      provisioning messages (such as described previously) would be
      launched from the boundary at which the new TCS is negotiated.
      These would claim a share of existing provisioned resources, or
      would notify the bandwidth broker in the case that additional
      resources are required.
      A more sophisticated model would allow TCSs to be renegotiated
      dynamically. In this case, the process would be automatic, and
      would not require human intervention. Each domain would in effect,
      represent a bandwidth broker, via one protocol or another. A
      specific inter-domain protocol might be used to communicate
      between centralized bandwidth broker agents, or alternatively, an
      inter- domain variant of RSVP might be used.  In the latter case,
      there is no direct interaction with a bandwidth broker per-se.
      However, the collection of network nodes, policy servers and
      directory behave collectively as a bandwidth broker which
      communicates using RSVP. In either case, TCS renegotiations would
      be triggered by load measurements at boundary nodes. These could
      be in the form of changes in actual measured traffic volume, or
      alternatively, based on explicit fine grain RSVP resource requests
      from hosts at the periphery. Domains would approve renegotiations
      based both on resource constraints as well as predetermined policy
   7.3 Service, PHB and Codepoint Mapping
      In order to provide end-to-end service to customers, it must be
      possible to extend services across multiple domains. Several
      complexities may arise at inter-domain boundaries, as follows:
      1. The services provided by a certain domain may not be compatible
         with the services provided by a neighbour domain.
      2. The services provided by a certain domain may be compatible
         with those provided by the neighbour domain, but the PHB used
         to obtain the service might be different.
      3. The PHB might be the same, but the codepoint used to request
         the PHB might be different.
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      4. The PHB and codepoint are the same but differences in
         provisioning and charging models results in different services.
      Resolution of these complexities requires determination of the
      compatible services and negotiation of the PHB codepoints which
      will be used to request the services. This process is greatly
      simplified by the provision of a set of universal services using
      universally recognized codepoints. The leased line service and the
      recommended EF codepoint is likely to be one such example.
      Generally, extension of quantitative services across multiple
      domains will require more uniformity in the nature of the services
      provided. Qualitative services on the other hand, may be extended
      end-to-end by a concatenation of services which vary from domain
      to domain. For example, one domain may base a qualitative service
      on a WFQ scheme with RED while another may use priority queuing
      with RIO. Since the assurances provided by qualitative services
      tend to be looser, it is possible that a meaningful service can be
      provided end-to-end by concatenating these two service types.
   7.4 Host-Domain Boundaries
      In certain cases, a host may be directly attached to a
      differentiated service domain. This is likely both in the case of
      campus networks that provide differentiated services within the
      network or in the case of dial-up users connecting to a
      differentiated service provider. In these cases, the host can be
      considered the customer of the differentiated service network.
      Legacy hosts are unlikely to mark their own packets for the
      appropriate DS-field and are also unlikely to shape or police
      their traffic. In the case of legacy hosts, the differentiated
      service provider will have to provide these services on behalf of
      the customer. In the case of campus networks, some network wide
      policy would likely be used to configure these services in the DS
      boundary devices. In the case of dial-up hosts, marking, shaping
      and resources provided would likely be negotiated at the time the
      customer signs up with the provider.
      Newer hosts may be capable both of marking and of traffic shaping.
      In this case, the overall per-host resource constraints are still
      likely to be somewhat static. However, the manner in which the
      host shares these resources among its various traffic flows is
      determined by the host. Of course, the provider will have to
      configure policers to assure that the host does not seize more
      than its share of resources in the differentiated service network.
   8. Deployment Scenarios
      A number of scenarios can be envisaged for the junction of a non-
      DS Domain and a DS Domain, and hence for deployment scenarios:
      1. A service provider runs a DS Domain which offers Differentiated
         Services to a customer who has a network which has no DS
         capability - the junction occurs at the ingress to the service
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         provider's network.  The service provider would provide
         classification, marking and shaping of traffic as a value-added
         service using information provided by the customer.
      2. A service provider runs a DS Domain for a customer who has a
         network which has mostly no DS capability except that the
         customer's  first hop or demarcation router acts as a
         degenerate, one node DS Domain.  The only (boundary) node in
         this domain performs classification, marking and shaping,
         whilst the provider's equipment just has to police the incoming
         aggregate traffic.
      3. The customer and provider both have fully capable DS Domains.
         Hosts are embedded in the customer's DS Domain - the junction
         between the non-DS and DS Domains is logically at the boundary
         between the Operating System and the application.
      Scenarios 1 and 2 provide simple initial deployment mechanisms for
      DS as they do not require general modification of hosts.  The
      advantage of Scenario 2 over Scenario 1 is that the customer can
      use, and keep private, local administrative knowledge to improve
      the classification of packets.  In Scenario 1 this information
      would have to be made available in the service provider's domain
      to achieve the same granularity of classification requiring that
      the customer have greater trust in the provider.
      Scenario 3 requires modification of hosts.  Direct interaction
      between applications and the DS Ingress node would therefore be
      possible giving scope for sophisticated application of the DS
      capabilities;  even without such interaction, extremely fine-
      grained classification of traffic packets would be possible in the
      operating system kernel.  Authentication of the application/host
      and authorization to use DS services requires particular attention
      in this case, although care has to be taken to avoid denial of
      service attacks in all cases (see Sec. 11 and [DSARCH] for further
      discussion of security).
      A customer might also deploy a network of DS capable routers
      before some or any of the associated hosts were DS capable.
      Classification, marking and shaping would be provided by the
      `first hop' router which the packet encounters on the first hop
      after leaving the host;  the core of the customer's network is
      fully DS capable and the packets are forwarded in accordance with
      their DSCP to another host in the same DS Domain or on to a
      provider's domain.
      It might be possible to utilize non-DS capable routers in the
      interior of a DS Domain without compromising the QoS delivered
      -  The non-DS capable routers forward unchanged TOS byte all
         packets marked with the values of DSCP used in the DS Domain.
      -  The non-DS capable routers forward these packets as if they
         were best efforts traffic
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      -  The non-DS capable routers are used only at points which rarely
         or never experience congestion.
   9. Inter-operability with RSVP/Integrated Services
      In this section, we discuss alternatives for inter-operability
      between differentiated services and RSVP/Integrated services.
   9.1 RSVP/Integrated Services Over Differentiated Services
      This scenario is discussed in detail in [E2EQOS]. It assumes a
      model in which peripheral stub networks are RSVP and Intserv
      aware. These are interconnected by differentiated service
      networks. In this model, the scalability of differentiated service
      networks helps to extend the reach of RSVP/Integrated service
      (Intserv)networks. Intervening differentiated service networks
      appear as a single RSVP hop to the RSVP/Intserv networks. Hosts
      attached to the peripheral RSVP/Intserv networks signal to each
      other for per-flow resource requests across the differentiated
      service networks. Standard RSVP/Intserv processing is applied
      within the RSVP/Intserv peripheral networks. RSVP signaling
      messages are carried transparently through the differentiated
      service networks. Devices at the boundaries between the
      RSVP/Intserv networks and the differentiated service networks
      process the RSVP messages and provide admission control based on
      the availability of appropriate resources within the
      differentiated service network.
      This model is predicated on the availability of services within
      the differentiated service network which can extend the reach of
      intserv type services. For example, the leased line service can
      extend the intserv guaranteed service across a differentiated
      service network. Multiple guaranteed service micro-flows which
      exist in peripheral networks are aggregated into the EF behaviour
      aggregate at the boundary of the diffserv network. When an RSVP
      request for guaranteed service arrives at the boundary of a
      differentiated service network, RSVP style admission control is
      applied based on the amount of resources requested in the intserv
      flowspec and the availability of differentiated services at the
      corresponding service level (per the TCS). If admission control
      succeeds, the originating host (or its agent) marks traffic on the
      signaled microflow, for the appropriate differentiated service
      The RSVP/Intserv over differentiated service model is especially
      suitable for providing quantitative end-to-end services. The use
      of differentiated services eliminates the scalability concerns of
      RSVP/Intserv networks. The use of RSVP signaling provides
      admission control to the differentiated service network, based on
      resource availability and policy decisions. It also greatly
      simplifies the configuration of differentiated service
      classifiers, policers and other traffic conditioning components.
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      Variations on this theme would enable some number of nodes within
      the differentiated service networks to process the per-flow RSVP
      messages passing through. These could be used to aid in dynamic
      provisioning without necessarily requiring any per-flow state or
      processing within the differentiated service network. In yet
      another model, the transition of per-flow RSVP messages through
      the differentiated service network might trigger aggregated RSVP
      signaling between differentiated service domain boundaries, for
      the purpose of renegotiating TCSs and adjusting provisioning
      dynamically [GBH97, CLASSY].
   9.2 Parallel Operation
      Another alternative for the interoperation of differentiated
      service and RSVP/Intserv networks is simple parallel operation. In
      this mode, each node within the differentiated service network may
      also be an RSVP capable node. Some strategy would have to be
      selected for determining which packets are handled using RSVP and
      which are handled using differentiated services. For example,
      those that classify to an RSVP installed filter might be handled
      using RSVP, while those not classifying to specific RSVP filters
      would be handled according to the DS-field using differentiated
      service mechanisms. Such a model is likely to be deployed in
      smaller networks (since the RSVP/Intserv component is less suited
      for large networks). In particular, the stub networks cited in
      [E2EQOS] would likely provide differentiated services for those
      qualitative applications which do not signal, while providing
      RSVP/Intserv services for those quantitative applications which do
   10. Multicast Services
      The basic concept of Differentiated Services appears to offer an
      excellent fit with a multicast service insofar as traffic may be
      forwarded from an ingress to several egresses.  Unfortunately, as
      we shall see, provisioning a multicast service is extremely
      Because the Differentiated Services Architecture deals only with
      unidirectional flows, a 'multicast' service in a DS network will
      in fact offer a point-to-multipoint unidirectional service.  Each
      source of traffic that wishes to send to the multicast group using
      this service needs a separate SLS which applies at the ingress
      point where the traffic enters the network.
      The network resources that must be provisioned for a multicast
      service will be affected by the mechanisms used by the routers to
      provide the service.  Depending on the capabilities of the routers
      and the multicast routing protocol employed, sub-optimal
      replication of a packet may result in multiple copies travelling
      over the same link.
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      If receivers can be added dynamically to a multicast group whilst
      a flow is in progress, the complexity of provisioning grows
      considerably:  The amount of network resources that will be
      consumed by multicast traffic originating from a particular
      upstream network may be difficult to forecast in advance.
      Consequently, it may not be possible to offer quantitative
      services where dynamic addition of receivers adds to the paths
      through the network already used by the flow.
      All multicast receivers must also be capable of handling the
      existing or proposed traffic on the multicast tree.  This is an
      extension of the receiver control problem discussed in Sec. 4.4.1
      where it is clearly not desirable for a single inadequate receiver
      to limit the traffic on a complete tree.  It is therefore
      essential that a multicast service specify a minimum receiver
      capacity _ where the service passes from one domain to another the
      TCS on the receiving domain must offer at least this capacity.
      Note that application level multicast does not normally fall into
      the multicast service category because it is normally realised as
      a number of independent unicasts each of which is delivered by a
      unicast service.
   10.1  Codepoints and PHBs for Multicast Services
      To achieve resource isolation of multicast traffic from unicast
      traffic, it may be necessary to use separate codepoints and
      separate instances of a PHB or different PHBs for the multicast
      and unicast services.  If the multicast traffic is not adequately
      isolated, dynamic addition of new members of the multicast group
      can adversely affect existing unicast traffic.
      Because a multicast service traffic flow can exit from a domain to
      several peer domains, care must be taken to use a codepoint and
      PHB that is compatible with the peering SLSs at the egress points.
      This may be a more stringent requirement than for a unicast
      service where a flow need only be compatible with a single egress
      point SLS.
   10.2  Provisioning Multicast Services
      The scope of a multicast service would normally be either case 1
      (any egress point) or case 3 (a pre-defined set of egress points)
      of Sec. 4.4.
      For a quantitative service the scope will, in general, need to be
      case 3.  The service can be provisioned in a similar way to
      corresponding unicast services with the same volume of traffic
      along each of the paths from ingress to egress, but taking into
      account that all paths will be used simultaneously and allowing
      for multiple copies of traffic if necessary.  If the multicast
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      routing protocol used can generate different multicast trees
      depending on the order in which members join the group,
      provisioning may not be possible.  Solving this problem may
      require pinning of the multicast tree branch points; the solution
      of this problem is outside the scope of this framework.
      For a qualitative service, provisioning is essentially the same as
      the unicast case, but statistical multiplexing gains are likely to
      be less because all paths may be used at once.
      The traffic conditioning mechanisms for multicast services are not
      significantly different from those for the unicast services but
      multiple shapers may be required where traffic exits from several
      interfaces on a single router or multiple replicas exit from one
      An additional problem arises when a service is actually used as
      part of a multipoint-to-multipoint service.  The traffic patterns
      resulting from this usage and the required provisioning cannot be
      easily generalised from the point-to-multipoint case, with the
      result that it is difficult to determine how much extra capacity
      should be provisioned when a link is a common path for traffic
      from several sources.
   11. Security and Tunneling Considerations
      The security and tunneling implications for the actual data
      transport of the services of the Differentiated Services
      Architecture have been extensively discussed in [DSARCH] and
      [DSHEAD] to which the reader is referred.
      Additional security considerations arise from the services
      overlaid on the data transport:
      1. The services maybe the subject of differential charging.
         Accordingly, the service users have to be authenticated and
         authorized, and the accounting data needed must be secured.
      2. The mechanisms used to create and distribute the policy and
         resource allocations must be secured.
      3. Statistical data needed to audit service delivery must be
      The mechanisms used to provide this security are outside the scope
      of this framework, but are under consideration by the AAA working
      The use of tunnels in general and IPsec tunnels in particular
      impedes the work of MF Classifiers by concealing the fields used
      by L4 and higher layer classifiers.  Thus traffic conditioners
      within the area where IPsec encryption is used will need to rely
      only on IP header fields, including the DS Field (BA Classifiers
      will work normally).  If more sophisticated MF classification is
      required it will have to take place before the tunnel ingress and
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      the application of IPsec encryption.  If IPsec encryption is used
      end-to-end, then Differentiated Services may require host marking
      Similarly, there is a constraint on quantitative services in
      general because IPsec hides the final destination address, so that
      it may be difficult to police quantitative services when IPsec is
      used because the traffic conditioner cannot determine the egress
      address easily.
      If a tunnel carries multiple flows with different traffic types,
      they may be marked with different DS codepoints so that they are
      subjected to appropriate behaviors in the network interior.  This
      may be considered to be a security breach as it allows traffic
      patterns to become visible.  If just one codepoint is used for all
      traffic it should be selected carefully to be appropriate for all
      the traffic in the tunnel.
   12. Acknowledgements
      The authors would like to acknowledge the helpful comments and
      suggestions of the following individuals:  Kathleen Nichols, David
      Black, Konstantinos Dovrolis, Shivkumar Kalyana, Wu-chang Feng,
      Marty Borden, and Ronald Bonica.
   13. References
      [2BIT] K. Nichols, V. Jacobson, and L. Zhang, "A Two-bit
      Differentiated Services Architecture for the Internet", Internet
      [CLARK] D. Clark and J. Wroclawski, "An Approach to Service
      Allocation in the Internet", Internet Draft
      [CLASSY] S. Berson and S. Vincent, "Aggregation of Internet
      Integrated Services State", Internet Draft, November 1997.
      [COPS] J. Boyle, R. Cohen, D. Durham, S. Herzog, R. Rajan, and A.
      Sastry, "COPS (Common Open Policy Service) Protocol", March 1998.
      [DSARCH]  D. Black, S. Blake, M. Carlson, E. Davies, Z. Wang, and
      W. Weiss, "An Architecture for Differentiated Services", Internet
      Draft, May 1998.
      [DSHEAD]  K. Nichols and S. Blake, "Definition of the
      Differentiated Services Field (DS Byte) in the IPv4 and IPv6
      Headers", Internet Draft, May 1998.
      [AF]  J.Heinanen, _Assured Forwarding PHB Group_Internet Draft,
      August 1998.
      [EF]  V.Jacobson, _Expedited Forwarding Per Hop Behavior_,
      Internet Draft, August 1998.
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                    Draft-ietf-diffserv-framework-02.txt   February, 1999
      [Ellesson]  E. Ellesson and S. Blake, "A Proposal for the Format
      and Semantics of the TOS Byte and Traffic Class Byte in IPv4 and
      IPv6", Internet Draft, November 1997.
      [E2EQOS]  Y. Bernet, R. Yavatkar, P. Ford, F. Baker, L. Zhang, K.
      Nichols and M. Speer, "A Framework for the Use of RSVP with Diff-
      serv Networks", Internet Draft, November 1998.
      [DiffEdge]  Y. Bernet, D. Durham and F. Reichmeyer, _Requirements
      of Diff-serv Boundary Routers_, Internet Draft, November 1998.
      [ROTZY]  F. Reichmeyer, L. Ong, A. Terzis, L. Zhang, and
      R. Yavatkar, _A Two-Tier Resource Management Model for
      Differentiated Services Networks_, Internet Draft, November 1998
      [MPLS] B. Thomas, N. Feldman, P. Doolan, L. Andersson and
      A. Fredette, "Label Distribution Protocol Specification", Internet
      Draft, January 1999.
      [GBH97] R. Guerin, S. Blake, and S. Herzog, "Aggregating RSVP-
      based QoS Requests", Internet Draft, November 1997.
      [IntServ]  R. Braden, D. Clark, and S. Shenker, "Integrated
      Services in the Internet Architecture:  An Overview", Internet RFC
      1633, July 1994.
      [RSVP] B. Braden et. al., "Resource ReSerVation Protocol (RSVP) --
      Version 1 Functional Specification", Internet RFC 2205, September
      [RFC791] Information Sciences Institute, "Internet Protocol",
      Internet RFC 791, September 1981.
      [RFC1349] P. Almquist, "Type of Service in the Internet Protocol
      Suite", Internet RFC 1349, July 1992.
   14. Author's Addresses
      Bernet, Yoram
      One Microsoft Way
      Redmond, WA 98052
      Phone: +1 (425) 936-9568
      Email: yoramb@microsoft.com
   Bernet, et al          Expires: September 1999                      36
                    Draft-ietf-diffserv-framework-02.txt   February, 1999
      Binder, James
      3Com Corp.
      5400 Bayfront Plaza
      Santa Clara, CA 95052
      Phone: +1 (408) 326-6051
      Email: james_binder@3com.com
      Blake, Steven
      Torrent Networking Technologies
      3000 Aerial Center, Suite 140
      Morrisville, NC  27560
      Phone:  +1-919-468-8466 x232
      Fax:    +1-919-468-0174
      Email: slblake@torrentnet.com
      Carlson, Mark
      RedCape Software Inc.
      2990 Center Green Court South
      Boulder, CO 80301
      Phone: +1 (303) 448-0048 x115
      Email: mac@redcape.com
      Carpenter, Brian E
      IBM United Kingdom Laboratories
      Hursley Park
      Hampshire SO21 2JN
      Phone: +44 1962 816833
      Email: brian@hursley.ibm.com
      Davies, Elwyn
      Nortel Networks
      London Road
      Harlow, Essex CM17 9NA, UA
      Phone: +44-1279-405498
      Email: elwynd@nortelnetworks.com
      Ohlman, Borje
      Ericsson Radio
      Dialoggatan 1 (Kungens Kurva)
      S-126 25 Stockholm
      Phone: +46-8-719 3187
      Email: Borje.Ohlman@ericsson.com
   Bernet, et al          Expires: September 1999                      37
                    Draft-ietf-diffserv-framework-02.txt   February, 1999
      Srinivasan Keshav
      4107B Uspon Hall
      Cornell University
      Ithaca, NY 14853
      Phone: +607-255-5395
      Email: skeshav@cs.cornell.edu
      Dinesh Verma IBM T. J. Watson Research Center
      P.O. Box 704
      Yorktown Heights, NY 10598
      Phone: +1 (914) 784-7466
      Email: dverma@watson.ibm.com
      Zheng Wang
      Bell Labs Lucent Tech
      101 Crawfords Corner Road
      Holmdel, NJ 07733
      Email: zhwang@bell-labs.com
      Walter Weiss
      Lucent Technologies
      300 Baker Avenue, Suite 100 Concord, MA 01742-2168
      Email: wweiss@lucent.com
   Bernet, et al          Expires: September 1999                      38