TSVWG                                                       R. Geib, Ed.
Internet-Draft                                          Deutsche Telekom
Intended status: Informational                         February 14, 2014
Expires: August 18, 2014

             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
   Aggregated DiffServ classes.  This draft contains DiffServ
   aggregation friendly interconnection concepts.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on August 18, 2014.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Related work . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Aggregating PHBs of a class by a DSCP Precedence Prefix  . . .  6
   4.  An Interconnection class and codepoint scheme  . . . . . . . .  6
     4.1.  Treatment of Network Control traffic at carrier
           interconnection interfaces . . . . . . . . . . . . . . . .  9
   5.  DiffServ Intercon relation to other QoS standards  . . . . . . 10
     5.1.  MPLS, Ethernet and DSCP Precedence Prefixes for
           aggregated classes . . . . . . . . . . . . . . . . . . . . 11
     5.2.  Proposed GSMA IR.34 to DiffServ Intercon mapping . . . . . 11
     5.3.  Proposed MEF 23.1 to DiffServ Intercon mapping . . . . . . 12
   6.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 14
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 14
     10.2. 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.

   IP precedence has been deprecated.  MPLS and Ethernet support 3 bit
   code point fields to differentiate service quality (see MPLS TC /
   Traffic Class [RFC5462] and PCP, Priority Code Point [IEEE802.1Q]).
   The concept of classifying DiffServ traffic classes by the bits 0-2
   of a DSCP has been part of Diffserv from start on.  This is also
   reflected by the DiffServ codepoint definitions of AF and EF.  It is
   common practice today also to copy these three DSCP bits into MPLS TC
   or Ethernet P-Bits.  PHBs based on DSCP bit 0-2 classification may be
   applied in core network sections rather than then DSCP based PHBs.
   Network providers make use of this feature for their own IP QoS
   concepts.  This draft suggests to expand it to interconnections
   between operators of different domains in a simple manner while each
   operator may maintain the own class and codepoint scheme within the
   own domain.

   The scope of this draft is limited to 4 specified interconnection
   classes having four different 3 bit code points in DSCP bits 0-2.
   Using more than the 4 proposed IP precedences at interconnection
   could result in non-revertible IP Precedence or DSCP rewrites and
   avoid sustaining end-to-end QoS classes, if a receiving provider
   operates more than 4 MPLS TCs.  Assume a provider operating 4 QoS
   classes available at interconnection and MPLS within his backbone.
   Further assume this carrier to support MPLS based ECN marking and
   assume this carrier to operate a newtork control class with an own
   MPLS TC.  Two codepoints are left for future use.  If 5 or more PHBs
   each with different DSCP bits 0-2 are offerd at an interconnection
   point and no more than a single MPLS label needs to be pushed, two
   (or more) PHBs will carry the same DSCP bits 0-2 after re-marking to
   the provider internal QoS scheme.  Due to MPLS pen ultimate hop
   popping, DSCPs must be re-written in this case.  That may work if
   bits 3-5 of the DSCP can be varied without introducing ambiguities.
   Should this traffic later pass another QoS interconnection point
   further downstream, the orginal sending domain may not be able to
   ensure proper class mapping for the PHBs merged into a single class
   by the receiving domain.

   At first glance, the interconnection codepoint scheme looks 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

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   it, this is to be negotiated per interconnection party individually.
   Further, end-to-end QoS in terms of traffic being classified for the
   same class in all passed domains is more likely to result if an
   interconnection code point scheme is used.  It is not necessarily
   resulting from individual per provider mapping negotiations, as can
   be seen from the example given above.

   The standards and deployments known to the author of this draft are
   limited to 4 DiffServ classes at interconnection points (or less).
   The example given in RFC 5127 on aggregation of DiffServ service
   classes picks 4 Treatment aggregates (note that this document prefers
   class instead of treatment aggregate).  Reasons to favour working
   with 4 DiffServ interconnection classes:

   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.

   IP Precedence has been deprecated when DiffServ was standardised.  It
   is common practice today however to copy the DSCPs Bits 0-2 (called
   DSCP Precedence Prefix in the following) into MPLS TC or Ethernet
   P-Bits.  This is also reflected by the DiffServ codepoint definitions
   of AF and EF.  Class based PHBs may be applied in core network
   sections rather than then DSCP based PHBs.

   The set of available router and traffic management tools to configure
   and operate DiffServ classes is limited.  This should be reflected by
   class definitions.  These may in the end be more related to transport
   properties (e.g., whether the traffic in a class is congestion
   controlled or not) than to application requirements.

   RFC5127 provides recommendations on domain internal aggregation of
   DiffServ traffic and offers a deployment example [RFC5127].  This
   draft differs from the RFC5127 aggregation deployment example in the
   following points:

   o  the basic concept of this draft is to maintain classes, while
      expecting DSCP remarking at provider edges.

   o  This draft follows RFC4594 in the proposed marking of provider
      Network Control traffic and expands RFC4594 on treatment of CS6

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      marked traffic at interconnection points (see section 5.2).

   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 re-uses existing terminology.

   DSCP Precedence Prefix  Bits 0-2 of the DSCP ("x" in this generic
           DSCP: xxxddd) are called the DSCP Precedence Prefix.  Section
           4.2 of [RFC2474] discusses the role of these bits in enabling
           use of DiffServ with network equipment that is not fully
           DiffServ- compliant; this term provides a formal for these
           bits that is preferable to referring to them as "the former
           IP Precedence field".

   DSCP Precedence Class  This is a set of one or more PHBs that utilize
           the same DSCP Precedence Prefix on an interconnection between
           two networks.

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3.  Aggregating PHBs of a class by a DSCP Precedence Prefix

   Configuration and operation of MPLS networks is simplified, if a DSCP
   Precedence Class can be aggregated into a single PSC by classifying
   them on their DSCP Precedence Prefix.  The DSCP Precedence Prefix of
   an interconnection DSCP Precedence Class may be rewritten at the
   ingress edge router and then simply be copied into the MPLS TC field
   of one or more labels to be pushed.

   To allow for simple carrier interconnection agreements, carriers
   sending traffic belonging to the same class but marked by DSCPs with
   differing DSCP Precedence Prefixes should apply the interconnection
   marking and code point scheme specified below, if they interconnect
   to a carrier applying DSCP Precedence Prefix based traffic
   aggregation.  An example where this may be applicable is the
   Interactive Class of GSMA IR.34 [IR.34]).  Another option is to
   negotiate a customised interconnection agreement of course.

   Classification by DSCP Precedence Prefix is useful for links
   aggregating DiffServ traffic.  DSCP Precedence Prefix based
   classification is not recommended as a general mode of operation.
   Edge systems, QoS policy enforcement nodes, service areas and hosts
   benefit from fine grained DSCP based classification and should
   continue to do so.

   RFC 2474 specifies the Class Selector Codepoints [RFC2474].  These
   offer a similar concept, but they are strictly limited to xxx000
   DSCPs.  The Class Selector Code points don't offer aggregation, they
   just simplify classification.  This draft intents to aggregate
   several PHBs of a single class by a DSCP Precedence Prefix, which a
   different concept than that of the Class Selector Code points.

4.  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.  This draft proposes a
   standard interconnection set of 4 DSCP precedence classes with well
   defined DSCP and DSCP Precedence Prefix values.  A sending party
   remarks DSCPs from internal schemes to the Interconnection code
   points.  The receiving party remarks DSCP Precedence Prefixes and /
   or DSCPs to her internal scheme.  Thus the interconnection code point
   scheme fully complies with the DiffServ architecture.

   This draft picks up the DiffServ interconnection class defintions
   proposed by ITU-T Y.1566 [Y.1566].  In addition to the classes

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   defined there, this draft proposes a complete set of PHBs and DSCPs.
   Like in the example given by RFC 5127 for domain internal class
   aggregation, Y.1566 specifies four PHB scheduling classes (for
   provider interconnection however).  Their properties 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:  PHB AF41, DSCP 100 010 (the other AF4 PHB group
           PHB's and DSCPs should be reserved for future extension of
           this DSCP scheduling class).  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 utlising 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.

   Assured:  The complete PHB group AF3, DSCPs 011 010, 011 100 and 011
           110.  This class 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:  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.

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   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
   class.  See section 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      |
               V                      V
           +++++++++                  |
               |     Provider-T domain
          | MPLS TC 2 |
          |and  rewr. |
          |DSCP pref 2|
             |      |  Local DSCPs Provider-T
             |      |  +----------+   +++++++++
             V      +->|AF21, AF22|->-|RtrDstH|
             |         +----------+   +++++++++
         |AF21, AF22|

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             |        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 PHB scheduling class for network control
   traffic.  This class may be present at interconnection interfaces
   too, but depending on the agreement between providers, it may also be
   classified for another interconnection class.  See section 4.2 for a
   detailed discussion.

   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.

4.1.  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.

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   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.

   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).

   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.

5.  DiffServ Intercon relation to other QoS standards

   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

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   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

5.1.  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).

5.2.  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

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   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
   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.

5.3.  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

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   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.
   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.

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6.  Contributors

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

7.  Acknowledgements

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

8.  IANA Considerations

   This memo includes no request to IANA.

9.  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.

10.  References

10.1.  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.

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Internet-Draft              Abbreviated Title              February 2014

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

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

10.2.  Informative References

              Knoll, T., "BGP Class of Service Interconnection",
              draft-knoll-idr-cos-interconnect-11 (work in progress),
              November 2013.

              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.

   [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

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              Diffserv Service Classes", RFC 5127, February 2008.

   [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.

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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