TSVWG                                                       R. Geib, Ed.
Internet-Draft                                          Deutsche Telekom
Intended status: Informational                              July 4, 2014
Expires: January 5, 2015

             DiffServ interconnection classes and practice


   This document proposes a limited and well defined set of QoS PHBs and
   PHB groups to be applied at (inter)connections of two separately
   administered and operated networks.  Many network providers operate
   Treatment Aggregate of different DiffServ classes.  This draft offers
   a simple and constrained interconnection concept which may simplify
   operation and negotiation of DiffServ at interconnection points.

Status of this Memo

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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Related work . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  An Interconnection class and codepoint scheme  . . . . . . . .  5
     3.1.  Limitations arising from the MPLS Short Pipe model . . . .  9
     3.2.  Treatment of Network Control traffic at carrier
           interconnection interfaces . . . . . . . . . . . . . . . .  9
   4.  DiffServ Intercon relation to other QoS standards
       (revision may be required) . . . . . . . . . . . . . . . . . . 10
     4.1.  MPLS, Ethernet and DSCP Precedence Prefixes for
           aggregated classes . . . . . . . . . . . . . . . . . . . . 11
     4.2.  Proposed GSMA IR.34 to DiffServ Intercon mapping . . . . . 11
     4.3.  Proposed MEF 23.1 to DiffServ Intercon mapping . . . . . . 12
   5.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 13
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 14
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 15
   Appendix A.  Change log  . . . . . . . . . . . . . . . . . . . . . 16
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 16

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1.  Introduction

   DiffServ has been deployed in many networks.  As described by section of RFC 2475, remarking of packets at domain boundaries is a
   DiffServ feature [RFC2475].  This draft proposes a set of standard
   QoS classes and code points at interconnection points to which and
   from which locally used classes and code points should be mapped.

   Many providers operate MPLS based backbones.  RFC 5127 assumes
   backbone engineering to ensure that a major link, switch, or router
   can fail, and the result will be a routed network that still meets
   ambient Service Level Agreements classes(SLAs) [RFC5127].  Based on
   it, RFC5127 introduces the concept of Treatment Aggregates, which
   allow to forward multiple DSCPs by a single MPLS Traffic Class.  This
   draft shares the assumption of RFC 5127 on backbone engineering.
   RFC3270 adds the Short Pipe Models to the Pipe and Uniform Model
   already defined for Differentiated Services and Tunnels [RFC2983] ,
   [RFC3270].  It was required due to the presence of Pen-ultimate hop
   popping (PHP) of MPLS Labels.  RFC3270 expects the Short Pipe model
   only to be deployed for IP tunnels and VPNs.  If it used to transport
   non tunneled IP traffic, some restrictions may apply for DSCP
   transparency.  The Short Pipe model is popular with many network
   providers operating MPLS.

   RFC2474 specifies the DiffServ Codepoint Field [RFC2474].
   Differentiated treatment is based on the specific DSCP.  Once set, it
   may change, but any DSCP rewrite is always a one by one mapping.
   What is not allowed is remarking n received DSCPs to a single
   transmitted DSCP.  If unknown DSCPs are received, RFC2474 recommends
   transmitting them unchanged by default forwarding.  An MPLS network
   supporting the Short Pipe model for not tunneled IPv4 traffic may
   need to be able to correctly classify or rewrite the IP DSCP on
   interfaces between the last Label Switch Router and a Label Edge
   Router.  In that case, it may not be possible to transmit 64 DSCPs
   through this domain.

   RFC5127 proposes to transmit DSCPs as they are received in general.
   This is not possible, if the receiving and the transmitting domain
   use different DSCPs for the PHBs to which traffic is mapped if both

   This draft adresses IP interconnection supporting DiffServ to or
   between providers operating MPLS in their backbone.  It proposes
   operational simplifications and methods to match IP DiffServ
   requirements with MPLS limitations (especially regarding the Short
   Pipe Model if applied for non tunnel IPv4 traffic).  The scope of
   this draft is limited to 4 specified interconnection Treatment
   Aggregates.  To ease operation and to ensure traffic to leave a

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   domain with the DSCPs received, small sets of specific DSCPs and a
   definition of their Treatment Aggregate PHB are suggested.  The
   mechanism proposed here may be extended.  This is relevant only if it
   sees some deployment, and it is preferred to start with a limited and
   simple approach to clarify the concept.

   At first glance, the interconnection codepoint scheme may look like
   an additional effort.  But there are some obvious benefits: each
   party sending or receiving traffic has to specify the mapping from or
   to the interconnection class and code point scheme only once.
   Without it, this is to be negotiated per interconnection party
   individually.  Further, end-to-end QoS in terms of traffic being
   classified for say, for a sufficiently similar PHB in all passed
   domains is more likely to result if an interconnection code point
   scheme is used.  This draft supports a remarking of one DSCP only to
   one other DSCPs (no n DSCP to one DSCP remarking).

   The example given in RFC 5127 on aggregation of DiffServ service
   classes picks 4 Treatment Aggregates.  This draft also favours 4
   Treatment Aggregates.  Reasons to favour working with 4 DiffServ
   Treatment Aggregates:

   o  There should be a coding reserve for interconnection classes.
      This leaves space for future standards, for private bilateral
      agreements and for provider internal classes.

   o  The fields available for carrying QoS information (e.g., DiffServ
      PHB) in MPLS and Ethernet are only 3 bits in size, and are
      intended for more than just QoS purposes (see e.g.  [RFC5129]).

   o  Migrations from one code point scheme to another may require spare
      QoS code points.

   RFC5127 provides recommendations on aggregation of IP DSCPs into MPLS
   Treatment Aggregates and offers a deployment example [RFC5127].
   RFC5127 seems to be based on an assumption the the MPLS Short Pipe
   model is only deployed for tunneled IP products or VPNs.  This draft
   assumes presence of non tunneled IPv4 traffic and deployment of the
   MPLS Short Pipe model.  That requires deviating from the RFC5127
   example as follows:

   o  DSCP remarking is to be expected at provider edges, if the domain
      is terminating this traffic.

   o  This draft follows RFC4594 in the proposed marking of provider
      Network Control traffic and expands RFC4594 on treatment of CS6
      marked traffic at interconnection points (see section 5.2).

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   The proposed Interconnection class and code point scheme tries to
   reflect and consolidate related DiffServ and QoS standardisation
   efforts outside of the IETF, namely MEF [MEF 23.1], GSMA [IR.34] and
   ITU [Y.1566].  GSMAs IR.34 specifies an inter provider VPN, but it is
   nevertheless specifying a kind of DiffServ aware IP based carrier

1.1.  Related work

   In addition to the standardisation activities which triggered this
   work, other authors published RFCs or drafts which may benefit from
   an interconnection class- and codepoint scheme.  RFC 5160 suggests
   Meta-QoS- Classes to enable deployment of standardised end to end QoS
   classes [RFC5160].  The authors agree that the proposed
   interconnection class- and codepoint scheme as well as the idea of
   standardised end to end classes would complement their own work.
   Work on signaling Class of Service at interconnection interfaces by
   BGP [I-D.knoll-idr-cos-interconnect], [ID.idr-sla] is beyond the
   scope of this draft.  Should the basic transport and class properties
   be standardised as proposed here, signaled access to QoS classes may
   be of interest.  The current BGP drafts focus on exchanging SLA and
   traffic conditioning parameters.  They seem to assume that common
   interpretation of the PHB properties identified by DSCPs has been
   established prior to exchanging further details by BGP signaling.

2.  Terminology

   This draft reuses existing terminology of RFCs 2474 and 5127.

3.  An Interconnection class and codepoint scheme

   Interconnecting parties face the problem of matching classes to be
   interconnected and then to agree on code point mapping.  As stated by
   the DiffServ Architecture [RFC2475], remarking is a standard
   behaviour at interconnection interfaces.  If the MPLS Short Pipe
   model is deployed by the receiving domain, the Label Switch Router
   prior to and the destination Label Edge Router may have to correctly
   classify traffic by its DSCP.  To avoid DSCPs being misused, only
   domain internal DSCPs may be tolerated there.  This means, that
   traffic terminating within this domain will be delivered with the
   DSCP matching the properties of the PHB at interconnection, but with
   the DSCP assigned by the terminating domain.  This draft proposes a
   standard interconnection set of 4 Treatment Aggregates with well
   defined DSCPs to be aggregated by them.  A sending party remarks
   DSCPs from internal schemes to the Interconnection code points.  The
   receiving party remarks DSCPs to her internal scheme.  The

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   interconnection code point scheme fully complies with the DiffServ
   architecture.  DiffServ compliance does not allow for a rewrite of
   several received DSCPs with a single DSCP to be transmitted.  The set
   of DSCPs and PHBs supported accross the two interconnected domains
   and the treatment of PHBs and DSCPs not recognised by any of both
   domains should be part of an SLA.  DiffServ transit to a third party
   network is excluded for initial versions of this draft (but may be
   added if there's interest).

   This draft picks up the DiffServ interconnection class defintions
   proposed by ITU-T Y.1566 [Y.1566].  The classes defined there, are
   used as MPLS Treatment Aggregates here.  This draft proposes a set of
   Treatment Aggregate PHBs and DSCPs to be aggregated.  Their
   properties differ slightly from those of the RFC5127 example:

   Class Priority:  PHB EF, DSCP 101 110.  The figures of merit
           describing the PHB to be in the range of low single digit
           milliseconds.  See [RFC3246].  This class corresponds to RFC
           5127's real time class, but it is limited to traffic for
           which node configuration "ensures that the service rate of EF
           packets on a given output interface exceeds their arrival
           rate at that interface over long and short time intervals"
           (see RFC 3246).

   Bulk inelastic:  The Treatment Aggregate is initially designed only
           to transport PHB AF41, DSCP 100 010 (the other AF4 PHB group
           PHB's and DSCPs should be reserved for future extension of
           the set of DSCPs carried by this Treatment Aggregate).
           Optimised for low loss, low delay, low jitter at high
           bandwidth.  Traffic load in this class must be controlled,
           e.g. by application servers.  One example could be flow
           admission control.  There may be infrequent retransmissions
           requested by the application layer to mitigate low levels of
           packet losses.  Discard of packets through active queue
           management should be avoided in this class.  Congestion in
           this class may result in bursty packet loss.  If used to
           carry multimedia traffic, it is recommended to carry audio
           and video traffic in a single PHB (note that video
           conferencing may require separate PHBs for audio and video
           traffic, which could also be realised by utilising two AF 4
           PHBs).  All of these properties influence the buffer design.
           This class is designed to transport those parts of RFC 5127's
           Real Time class, which consume considerable QoS bandwidth at
           the interconnection interface.

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   Assured:  The complete PHB group AF3, DSCPs 011 010, 011 100 and 011
           110 is transmitted by this Treatment Aggregate.  It may be
           optimised to transport traffic without bandwidth
           requirements.  It aims on very low loss at high bandwidths.
           Retransmissions after losses characterise the class and
           influence the buffer design.  Active queue management with
           probabilistic dropping may be deployed.  The RFC 5127 example
           calls this class Assured Elastic.

   Default:  The Treatment Aggregate for the default PHB, CS0 with DSCP
           000 000.  This class may be optimised to transport traffic
           without bandwidth requirements.  Retransmissions after losses
           characterise the class and influence the buffer design.
           Active queue management with probabilistic dropping may be
           deployed.  The RFC 5127 example calls this class Elastic.

   RFC2474 recommends leaving DSCPs unknown to a receiving domain
   unchanged while default PHB transport is provided.  If there's
   community interest in this draft, current carrier deployments should
   be checked for support of this RFC2474 recommendation.

   The idea is illustrated by an example.  Provider O and provider W are
   peer with provider T. They have agreed upon a QoS interconnection.
   Traffic of provider O terminates within provider Ts network, while
   the GSMA IR.34 traffic transits through the netwirk of provider T to
   provider F. Assume all providers to run their own internal codepoint
   schemes for a class with properties of the DiffServ Intercon Assured
   Treatment Aggregate.  See below for a description of GSMA IR.34.

           Provider-O             Provider-W
           RFC5127                GSMA 34.1
               |                      |
          +----------+           +----------+
          |AF21, AF22|           |AF31, AF21|
          +----------+           +----------+
               |                      |
               V                      V
           +++++++++              +++++++++
           |Rtr PrO|              |Rtr PrW|
           +++++++++              +++++++++
               |        DiffServ      |
          +----------+           +----------+
          |AF31, AF32|           |AF31, AF32|
          +----------+           +----------+
               |        Intercon      |

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               V                      V
           +++++++++                  |
               |     Provider-T domain
          | MPLS TC 2 |
          | DSCP rew. |
          | AF21, AF22|
             |      |  Local DSCPs Provider-T
             |      |  +----------+   +++++++++
             V      +->|AF21, AF22|->-|RtrDstH|
             |         +----------+   +++++++++
         |AF21, AF22|
             |        DiffServ
         |AF31, AF32|
             |        Intercon
         |AF31, AF21|
         GSM IR.34

   DiffServ Intercon example

                                 Figure 1

   It is easily visible that all providers only need to deploy internal
   DSCP to DiffServ Intercon DSCP mappings to exchange traffic in the
   desired classes.

   RFC5127 specifies a separate Treatment Aggregate for network control

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   traffic.  It may be present at interconnection interfaces too, but
   depending on the agreement between providers, Network Control traffic
   may also be classified for another interconnection class.  See below
   for a detailed discussion on the treatment of Network Control

   The proposed class and code point scheme is designed for point to
   point IP layer interconnections.  Other types of interconnections are
   out of scope of this document.  The basic class and code point scheme
   is applicable on Ethernet layer too.

3.1.  Limitations arising from the MPLS Short Pipe model

   If non tunneled IPv4 traffic is transmitted by deploying the MPLS
   Short Pipe model as specified by RFC3270, then IP DSCPs may be used
   for classification or they may be remarked at interfaces between the
   destination Label Edge Router and the Label Switch Router.  Domain
   internal Treatment Aggregates may be applicable, e.g. for domain
   internal network control traffic.  This Treatment Aggregate and the
   DSCPs which are aggregated by it, may not be available for customer
   traffic.  A domain supporting such an internal Treatment Aggregate
   can't support a set of 64 DSCPs in that case.  As mentioned below,
   the number of PHBs and their DSCPs supported end-to-end should be as
   well defined as the treatment of not recognised DSCPs when
   negotiating interconnection.

   The situation is more relaxed for tunneled IPv4 traffic, IPv6 traffic
   in general (for the time being) and for VPN traffic.  If there's
   community interest, a later version of this discuss this in more

3.2.  Treatment of Network Control traffic at carrier interconnection

   As specified by RFC4594, section 3.2, Network Control (NC) traffic
   marked by CS6 is to be expected at interconnection interfaces.  This
   document does not change NC specifications of RFC4594.  The latter
   specification is detailed on domain internal NC traffic and on
   traffic exchanged between peering points.  Further, it recommends not
   to forward CS6 marked traffic originating from user-controlled end
   points by the NC class of a provider domain.

   As a minor clarification to RFC4594, "peering" shouldn't be
   interpreted in a commercial sense.  The NC PHB is applicable also in
   the case of a purchased network service based on a transit agreement
   with an upstream provider.  RFC4594 recommendations on NC traffic are
   applicable for IP carrier interconnections in general.

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   Some CS6 traffic exchanged accross carrier interconnections will
   terminate at the domain ingress node (e.g., if BGP is running between
   the two routers on opposite ends of the interconnection link).

   If the MPLS Short Pipe model is deployed for non tunneled IPv4
   traffic, an IP carrier may limit access to the NC PHB for traffic
   which is recognised as network control traffic relevant to the own
   domain.  Interconnecting carriers should specify treatment of CS6
   marked traffic received at a carrier interconnection which is to be
   forwarded beyond the ingress node.  An SLA covering the following
   cases is recommended, if a carrier wishes to send CS6 marked traffic
   accross an interconnection link which isn't terminating at the
   interconnected ingress node:

   o  classification of traffic which is network control traffic for
      both domains.  This traffic should be classified and marked for
      the NC PHB.

   o  classification of traffic which is network control traffic for the
      sending domain only.  This traffic should be classified for a PHB
      offering similar properties as the NC class (e.g.  AF31 as
      specified by this document).  As an example GSMA IR.34 proposes an
      Interactive class / AF31 to carry SIP and DIAMETER traffic.  While
      this is service control traffic of high importance to the
      interconnected Mobile Network Operators, it is certainly no
      Network Control traffic for a fixed network providing transit.
      The example may not be perfect.  It was picked nevertheless
      because it refers to an existing standard.

   o  any other CS6 marked traffic should be remarked or dropped.

4.  DiffServ Intercon relation to other QoS standards (revision may be

   This sections provides suggestions how to aggregate traffic by DSCP
   Precedence Prefexies to Ethernet and MPLS.  Other Standardisation
   Organsiations deal with QoS aware provider interconnection.  As IP is
   the state of the art realisation of provider interconnections, these
   standards bodies specify DiffServ aware interconnections.  Some of
   these bodies are industry alliances chartered also to promote
   interconnection of wireless or Ethernet technology including the
   exchange of IP datagrams at interconnection points.  Examples are the
   Metro Ethernet Forum (MEF) or the GSM Alliance (GSMA).  The ITU was
   mentioned earlier.  ITU works across and between responsibilities of
   different Standardisation Organisations and liaising with them, if
   their responsibilities are touched, is traditional part of that

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4.1.  MPLS, Ethernet and DSCP Precedence Prefixes for aggregated classes

   The interconnection class and code point scheme respects properties
   and limits of a 3 bit PHB coding space in different ways:

   o  it allows to classify four interconnection classes based on the
      DSCP Precedence Prefix.

   o  it supports a single PHB group (AF3), whose DSCPs may be
      aggregated into a sinle MPLS TC (or Ethernet priority) based on
      their joint DSCP Precedence Prefix.  This kind of aggregation will
      work for the AF4 PHB group, if the PHBs AF42 and AF43 need to be
      supported in addition to AF41.

   o  Applying only 4 aggregated classes at interconnection allows for
      bilateral extensions, if desired.  Should two carriers agree to
      map AF32 and AF33 to an additional individual MPLS TC and offer an
      Ordered Aggregate across the interconnecting domain, this proposal
      at leaves some MPLS TC coding space for such an extension
      (although this draft doesn't recommend interconnections of that

   The above statement is no requirement to depricate any DSCP to MPLS
   TC or Ethernet P-Bit mapping functionality.  In the opposite, by
   limiting the interconnection scheme to 6 PHBs, each PHB may be mapped
   to an individual Traffic Class or Priority also within MPLS or
   Ethernet (if desired).

4.2.  Proposed GSMA IR.34 to DiffServ Intercon mapping

   GSMA IR.34 provides guidelines on how to set up and interconnect
   Internet Protocol (IP) Packet eXchange (IPX) Networks [IR.34].  An
   IPX network is an inter-Service Provider IP backbone which comprises
   the interconnected networks of IPX Providers.  IPX is a
   telecommunications interconnection model for the exchange of IP based
   traffic between customers of separate mobile and fixed operators as
   well as other types of service provider (such as ISP), via IP based
   network-to-network interface.  Note that IPX is not a public
   interconnection model however, it is designed as a private IP
   Backbone of the interconnected parties.  Two IPX partners may
   interconnect using transit offered by an Inter-Service Provider IP
   Backbone.  This requires an IP QoS aware interconnection as described
   by this draft between IPX provider and Inter-Service Provider IP

   GSMA IR.34 specifies 4 aggregated classes and 7 PHBs.  Mapping to
   DiffServ Intercon is smooth apart from the GSMA aggregated class
   Interactive, which consistfs of 4 PHBs.  The table below lists a

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   suggested mapping to DiffServ Intercon.

   |      GSMA IR.34       |  DiffServ-Intercon    |
   |                       |                       |
   |  Agg. Class   |  PHB  |  Agg. Class  |  PHB   |
   |Conversational |  EF   |   Priority   |   EF   |
   | Streaming     | AF41  |Bulk inelastic|  AF41  |
   | Interactive   | AF31  |    Assured   |  AF31  |
   +               +-------+              +--------+
   |  (ordered by  | AF32  |              |        |
   +   priority,   +-------+              +  AF32  +
   | AF3 highest)  | AF21  |              |        |
   +               +-------+              +--------+
   |               | AF11  |              |  AF33  |
   | Background    | CS0   |    Default   |   CS0  |

   Suggested mapping of GSMA IR.34 classes and PHBs to DiffServ Intercon

                                 Figure 2

   The motivation resulting in the design of the IR.34 Intercative class
   are unknown to the author of this draft.  It is out of scope of this
   draft to decide how 4 PHBs can be mapped to a to single aggregated
   class.  The suggested mapping is pragmatic and tries to come as close
   as possible to other design criteria pursued by GSMA IR.34.

4.3.  Proposed MEF 23.1 to DiffServ Intercon mapping

   MEF 23.1 is an implemenation agreement facilitating Ethernet service
   interoperability and consistency between Operators and the use of a
   common CoS Label set for Subscribers [MEF23.1].  It pursues the same
   aims and method on Ethernet layer as this draft does on IP layer
   (i.e. providing an interconnection class and codepoint scheme).  MEF
   23.1 addresses external network to network interfaces typically
   interconnecting metro ethernet providers.  This may typically involve
   Ethernet Network Sections associated with typical Operator domains
   that interconnect at external network to network interfaces.  MEF
   23.1 specifies three aggregated CoS classes.  In addition, the usage
   of a subset of Ethernet PCP and IP DSCP values is specifiedthus
   facilitating synergies between Ethernet and IP services and networks.

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   The main purpose is specifying operator virtual (Ethernet)
   connections.  As an IP QoS model is added, this draft proposes an IP
   class and codepoint mapping.

   MEF 23.1 QoS mapping requires some thought as 3 classes are supported
   of which two are Ordered Aggregates.  MEF 23.1s section 8.5.1 example
   on IP DSCP mapping may suggest supporting classification based on the
   DSCP Precedence Prefix.  MEF 23.1 section allows the
   conclusion that MEF class M is best mapped to this drafts Bulk
   inelastic class.  The suggested mapping MEF to DiffServ Intercon is
   limited to the the MEF color blind mode (3 classes, no sub-classes):

   |        MEF 23.1       |  DiffServ-Intercon    |
   |                       |                       |
   |  Agg. Class   |  PHB  |  Agg. Class  |  PHB   |
   |    High       |  EF   |   Priority   |   EF   |
   |   Medium      | AF3   |Bulk inelastic|  AF41  |
   |     Low       | CS1   |    Default   |   CS0  |

   Suggested mapping of MEF 23.1 color blind mode classes and PHBs to
   DiffServ Intercon

                                 Figure 3

   The MEF color aware mode supports Ordered Aggregates in the MEF
   classes M and L. The MEF L specification classifies AF1 and Best
   Effort for the same Ordered Aggregate.  A Better than Best Effort
   service produced in the same queue as best effort traffic can be
   realized, but hasn't been standardized by IETF.  This document
   doesn't suggest any mapping.  Diffserv Intercon also doesn't suggest
   an Ordered Aggregate in the Bulk Inelastic class.  Later versions of
   this document may do so and specify a solution.  Both issues are left
   for bilateral negotiation.

5.  Contributors

   David Black provided many helpful comments and inputs to this work.

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6.  Acknowledgements

   Al Morton and Sebastien Jobert provided feedback on many aspects
   during private discussions.  Mohamed Boucadair and Thomas Knoll
   helped adding awareness of related work.  David Black, Fred Baker and
   Brian Carpenter provided intensive feedback and discussion.

7.  IANA Considerations

   This memo includes no request to IANA.

8.  Security Considerations

   This document does not introduce new features, it describes how to
   use existing ones.  The security section of RFC 2475 [RFC2475] and
   RFC 4594 [RFC4594] apply.

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2474]  Nichols, K., Blake, S., Baker, F., and D. Black,
              "Definition of the Differentiated Services Field (DS
              Field) in the IPv4 and IPv6 Headers", RFC 2474,
              December 1998.

   [RFC2475]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
              and W. Weiss, "An Architecture for Differentiated
              Services", RFC 2475, December 1998.

   [RFC2597]  Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski,
              "Assured Forwarding PHB Group", RFC 2597, June 1999.

   [RFC3246]  Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec,
              J., Courtney, W., Davari, S., Firoiu, V., and D.
              Stiliadis, "An Expedited Forwarding PHB (Per-Hop
              Behavior)", RFC 3246, March 2002.

   [RFC3260]  Grossman, D., "New Terminology and Clarifications for
              Diffserv", RFC 3260, April 2002.

   [RFC3270]  Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen,

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Internet-Draft              Abbreviated Title                  July 2014

              P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi-
              Protocol Label Switching (MPLS) Support of Differentiated
              Services", RFC 3270, May 2002.

   [RFC5129]  Davie, B., Briscoe, B., and J. Tay, "Explicit Congestion
              Marking in MPLS", RFC 5129, January 2008.

   [RFC5462]  Andersson, L. and R. Asati, "Multiprotocol Label Switching
              (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic
              Class" Field", RFC 5462, February 2009.

   [min_ref]  authSurName, authInitials., "Minimal Reference", 2006.

9.2.  Informative References

              Knoll, T., "BGP Class of Service Interconnection",
              draft-knoll-idr-cos-interconnect-12 (work in progress),
              May 2014.

              IETF, "Inter-domain SLA Exchange", IETF,  http://

              IEEE, "IEEE Standard for Local and Metropolitan Area
              Networks - Virtual Bridged Local Area Networks", 2005.

   [IR.34]    GSMA Association, "IR.34 Inter-Service Provider IP
              Backbone Guidelines Version 7.0", GSMA,  GSMA IR.34 http:/
              ir.34.pdf, 2012.

   [MEF23.1]  MEF, "Implementation Agreement MEF 23.1 Carrier Ethernet
              Class of Service Phase 2", MEF,  MEF23.1 http://
              technical-specifications/MEF_23.1.pdf, 2012.

   [RFC2983]  Black, D., "Differentiated Services and Tunnels",
              RFC 2983, October 2000.

   [RFC4594]  Babiarz, J., Chan, K., and F. Baker, "Configuration
              Guidelines for DiffServ Service Classes", RFC 4594,
              August 2006.

   [RFC5127]  Chan, K., Babiarz, J., and F. Baker, "Aggregation of
              Diffserv Service Classes", RFC 5127, February 2008.

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   [RFC5160]  Levis, P. and M. Boucadair, "Considerations of Provider-
              to-Provider Agreements for Internet-Scale Quality of
              Service (QoS)", RFC 5160, March 2008.

   [Y.1566]   ITU-T, "Quality of service mapping and interconnection
              between Ethernet, IP and multiprotocol label switching
              networks", ITU,
               http://www.itu.int/rec/T-REC-Y.1566-201207-I/en, 2012.

Appendix A.  Change log

   00 to 01  Added terminology and references.  Added details and
           information to interconnection class and codepoint scheme.
           Editorial changes.

   01 to 02  Added some references regarding related work.  Clarified
           class definitions.  Further editorial improvements.

   02 to 03  Consistent terminology.  Discussion of Network Management
           PHB at interconnection interfaces.  Editorial review.

   03 to 04  Again improved terminology.  Better wording of Network
           Control PHB at interconnection interfaces.

   04 to 05  Large rewrite and re-ordering of contents.

   05 to 06  Description of IP and MPLS related requirements and
           constraints on DSCP rewrites.

Author's Address

   Ruediger Geib (editor)
   Deutsche Telekom
   Heinrich Hertz Str. 3-7
   Darmstadt,   64295

   Phone: +49 6151 5812747
   Email: Ruediger.Geib@telekom.de

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