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Versions: 00 02 03 04 05 06 07 08 draft-ietf-tsvwg-diffserv-intercon

TSVWG                                                       R. Geib, Ed.
Internet-Draft                                          Deutsche Telekom
Intended status: Informational                          October 18, 2013
Expires: April 21, 2014


             DiffServ interconnection classes and practice
                 draft-geib-tsvwg-diffserv-intercon-04

Abstract

   This document proposes a limited set of interconnection QoS PHBs and
   PHB groups.  It further introduces some DiffServ deployment aspects.
   The proposals made here should be integrated into a revised version
   of RFC5127.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 21, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Aggregating PHBs of a class by a DSCP Precedence Prefix  . . .  5
   4.  An Interconnection class and codepoint scheme  . . . . . . . .  6
   5.  Consolidation of QoS standards by the interconnection
       codepoint scheme . . . . . . . . . . . . . . . . . . . . . . .  7
   6.  Treatment of Network Control traffic at carrier
       interconnection interfaces . . . . . . . . . . . . . . . . . .  9
   7.  MPLS, Ethernet and DSCP Precedence Prefixes for aggregated
       classes  . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   8.  QoS class name selection . . . . . . . . . . . . . . . . . . . 11
   9.  Allow for DiffServ extendibility on MPLS and Ethernet level  . 12
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
   11. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   12. Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     13.1. Normative References . . . . . . . . . . . . . . . . . . . 12
     13.2. Informative References . . . . . . . . . . . . . . . . . . 13
   Appendix A.  Change log  . . . . . . . . . . . . . . . . . . . . . 14
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14




























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1.  Introduction

   This draft proposes a DiffServ interconnection class and codepoint
   scheme.  At least one party of an interconnection often is a network
   provider.  Many network providers operate Aggregated DiffServ
   classes.  This draft contains concepts and current practice relevant
   for a revised version of RFC5127 [RFC5127].  Its main purpose is to
   be considered as an input for the latter task.

   DiffServ sees deployment in many networks for the time being.  As
   described in the introduction of the draft DiffServ problem statement
   [I-D.polk-tsvwg-diffserv-stds-problem-statement], remarking of
   packets at domain boundaries is a DiffServ feature.  This draft
   proposes a set of standard QoS classes and codepoints at
   interconnection points to which and from which locally used classes
   and codepoints should be mapped.  Such a scheme simplifies
   interconnection negotiations and ensures that end to end class
   properties remain roughly the same while codepoints may change.

   The proposed Interconnection class and codepoint scheme tries to
   reflect and consolidate related DiffServ and QoS standardisation
   efforts outside of the IETF, namely MEF, GSMA and ITU.

   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 than to application requirements.  Please interpret
   transport properties as "congestion aware" and "not congestion aware"
   rather then TCP or UDP.

   Finally, this draft proposes to leave some lass Selector Codepoint
   and by that MPLS TC codepoint space to allow for future DiffServ
   extensions like ECN/PCN and domain internal classes.  An example for
   an internal PHB may be CS6.  Some operators protect their network
   internal routing and / or management traffic by CS6.  This PHB is
   possibly not available to transport customer or interconnection
   partner signaling and management traffic.

   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



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   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.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].


2.  Terminology

   This draft re-uses existing terminology.

   DSCP Precedence Prefix  The bits 0-2 of the DSCP (marked "x" in this
           generic DSCP field: xxxddd) are called the DSCP Precedence
           Prefix [RFC2474] in the following.  By ignoring the value of
           bits 3-6 ( d stands for don' care), a simple aggregation of
           PHBs differed by DSCP is possible in IP and MPLS backbones,
           but also if Ethernet transport is applied.  This is discussed
           in more detail below.

   Class   A class is a set of one or more PHBs utilising the same PHB
           if classified by a single identical DSCP Precedence Prefix
           (e.g. an AF class [RFC2597]).  It is a PHB Scheduling Class
           [RFC3260] or an Ordered Aggregate.  A class is a PHB group
           [RFC2575].  Different classes must not be aggregated.

   PHB     On IP layer, a single DSCP identifies a single PHB.  In
           addition, this document proposes an MPLS like classification
           of traffic for a single PHB based on the DSCP Precedence
           Prefix (see [RFC3270]).

   The above references may be incomplete and mostly refer to the early
   DiffServ RFCs only.

   To gain clarity, "DSCP based PHB selection" is only meant if
   expressed exactly that way in the remaining document.  "PHB" here



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   relates to DSCP Precedence Prefix based PHB selection.

   The following current practice issues relate to the concept of the
   DiffServ interconnection class proposal rather than to terminology.
   They serve as additional motivation of this activity:

   o  Abstract class names like "EF" are preferential over those being
      close to an application, like "Voice".  Unfortunately, non QoS
      experts can't handle abstract class names.  Hence and usually
      sooner than later, classes are named for applications or groups of
      them.  One consequence however is, that people tend to combine
      application group class names and SLA parameters.  Based on an
      application specific name and some worst case performance numbers
      on a paper, they often decide that their application needs a
      separate new QoS class.

   o  Worse than that, but very present in practice, is the class
      abstraction level which is preferred by those dealing with QoS (as
      experts or non experts): the DSCPs or the DSCP Precedence Prefix
      values.  These are the commodity abstractions applied for QoS
      classes.  Most of these persons have fixed class to codepoint
      mappings in their minds, which they can't easily adapt on per
      customer or per interconnection partner basis.

   While these issues aren't to be solved by IETF (QoS experts could and
   should of course teach staff to use proper Diffserv terminology and
   concepts), a simple and comprehensible QoS interconnection class
   scheme also is helpful in this area.


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

   Operation of IP and MPLS networks and router configuration is
   simplified, if DSCP based PHBs can be aggregated into a single class
   by simply classifying them by their DSCP Precedence Prefix.  As
   specified above, the DSCP Precedence Prefix are the bits 0-2 od the
   DSCP.  If classification based on DSCP Precedence Prefix is applied
   in an MPLS domain, the DSCP Precedence Prefix my simply be copied
   into the MPLS TC field.  This is very useful in domains operating
   Pen-ultimate hop popping.  Also in this case, operation and
   configuration of routers can be simplified significantly as compared
   to aggregation schemes based on configuring individual DSCPs.

   A network provider applying DSCP Precedence Prefix based aggregation
   MAY remark incoming DSCPs so that they can be aggregated by their
   DSCP Precedence Prefix.  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



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   the interconnection marking and codepoint scheme specified below, if
   they interconnect to a carrier applying DSCP Precedence Prefix based
   traffic aggregation.  An example where this may be required is the
   Interactive Class of GSMA IR.34 [IR.34] (note that the author of this
   draft believes that the GSMA specification is breaking RFC 2597).
   Another option is to negotiate a customised interconnection agreement
   of course.

   A node forwarding traffic based the DSCP Precedence Prefix MUST
   classify this traffic by the DSCP bits 0-2 and it MUST ignore the
   bits 4-6 of DSCP for classification.  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 Codepoints 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 Codepoints.


4.  An Interconnection class and codepoint scheme

   DiffServ deployments mostly follow loose class specification schemes
   (often one or two AF classes, EF and Best Effort).  Especially DSCP
   assignment for the AF classes varies between deployments.  Basic AF
   class property definitions are often similar however.  Applying
   provider specific DSCPs is in line with the DiffServ architecture.
   This document doesn't propose to change that.

   Interconnecting parties face the problem of matching classes to be
   interconnected and then to agree on codepoint mapping.  As stated by
   draft DiffServ problem statement
   [I-D.polk-tsvwg-diffserv-stds-problem-statement], remarking is a
   standard behaviour at interconnection interfaces.  This draft
   proposes a standard interconnection set of 4 QoS classes with well
   defined DSCP and DSCP Precedence Prefix values.  A sending party
   remarks DSCPs from internal schemes to the Interconnection
   codepoints.  The receiving party remarks DSCP Precedence Prefixes and
   / or DSCPs to her internal scheme.  Thus the interconnection
   codepoint scheme fully complies with the DiffServ architecture.  An
   interconnection class and codepoint scheme was introduced by ITU-T
   [Y.1566] (there also including Ethernet).  It is specified to a
   higher level of detail in this document.



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   At first glance, this looks like an additional effort.  But there are
   obvious benefits: each party sending or receiving traffic has to
   specify the mapping from or to the interconnection class and
   codepoint 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 the same class in all passed domains
   is likely to result if an interconnection codepoint scheme is used.
   It is not necessarily resulting from individual per network mapping
   negotiations.

   The standards and deployments known to the author of this draft are
   limited to 4 DiffServ classes at interconnection points (or
   less).Draft RFC 4597 update [I-D.polk-tsvwg-rfc4594-update]doesn't
   seem to generally contradict to this, as it proposes to standardise
   "many services classes, not all will be used in each network at any
   period of time."  Some reasons 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  MPLS and Ethernet support only 8 PHBs, classes or ECN indications.
      Assignment of 3 bit codepoints for whatever purpose must be well
      thought through.  Limiting interconnection QoS to four classes is
      MPLS and Ethernet friendly in that sense.

   o  Migrations from one codepoint scheme to another may require spare
      QoS codepoints.

   The proposed class and codepoint 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 codepoint scheme
   is applicable on Ethernet layer too.


5.  Consolidation of QoS standards by the interconnection codepoint
    scheme

   The interconnection class and codepoint scheme proposed by Y.1566
   also tries to consolidate related DiffServ and QoS standardisation
   efforts outside of the IETF [Y.1566].  The interconnection class and
   codepoint scheme may be a suitable approach to consolidate these
   standards.  MEF 23.1 specifies 3 aggregated classes, consuming up to
   5 codepoints on Ethernet layer (EF, AF3, AF1 and Best Effort) and 5
   PHBs [MEF23.1].  MEF aggregates AF1 and Default PHB in a single
   class.  This is not recommended for interconnection, as it is not in
   line with RFC 2597 (which requires separate forwarding resources for



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   each AF class and doesn't foresee aggregation of Default PHB and an
   AF class).

   GSMA IR.34 proposes four classes, EF, AF4, another AF class and Best
   Effort with 7 PHBs in sum [IR.34].  IR.34 specifies an "Interactive"
   class consisting of 3 PHBs with different priorities.  IR.34 assigns
   the PHBS AF31, AF21 and AF11 to this Interactive class.  This breaks
   RFC 2597.  The proposed interconnection class and codepoint scheme
   supports an GSMA Interactive like class but assigns AF3 with PHBs
   AF31, AF32 and AF33.

   If IETF picks up this draft, it may be a good idea to inform MEF and
   GSMA about conflicts of their standards with DiffServ and suggest
   joint activities to improve the situation.  Information on
   interworking with MEF 23 and GSMA IR.34 with the interconnection QoS
   scheme could be given by a later version of this draft.

   The classes to be supported at interconnection interfaces are
   specified by Y.1566 as:

   Class Priority:  EF, expecting the figures of merit describing the
           PHB to be in the range of low single digit milliseconds.  See
           [RFC3246].

   Bulk inelastic:  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.  All of
           these properties influence the buffer design.

   Assured:  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.

   Default:  Default.  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.




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   Note that other DiffServ related standards trim down class
   requirements to SLA parameters.  To quote e.g.  RFC 4594-update, "A
   "service class" represents a similar set of traffic characteristics
   for delay, loss, and jitter as packets traverse routers in a
   network."  This draft adds traffic PHB properties corresponding to
   expected transport layer characteristics as a key factor to a class
   definition: the desired class performance like delay, jitter and
   worst case loss are met only if PHB and transport properties meet the
   ones described by the class definition.  This is not to say, the
   other standards ignore PHB properties.  They are e.g. a core part of
   RFC 4594-update.  They do not directly refer to transport protocol
   properties, as most existing QoS standards prefer the approach of
   assigning QoS classes to applications or application sets.  This may
   result in undesirable class mappings, if an e.g.  IP TV application
   demanding low loss is matched to a class whose low loss guarantees
   depend on AQM mechanisms.

   Y.1566 does not define a complete set of DSCP based PHBs to be
   supported at an interconnection interface.  This information is added
   by this draft.  At interconnection points, the following DSCP based
   PHBs should be accepted between interconnected parties:

   Class:  PHB (one or more)

   Class Priority:  EF

   Bulk inelastic:  AF41 (AF42 and AF43 are reserved for extension)

   Assured:  AF31, AF32 and AF33

   Default:  Default (i.e.  Best Effort)

   Class names (and property specification) have been picked from Y.1566
   above.


6.  Treatment of Network Control traffic at carrier interconnection
    interfaces

   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



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   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 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).

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


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

   Ethernet and MPLS support 3 bit codepoint fields to differentiate
   service quality.  Mapping of the DSCP Precedence Prefix to these 3
   Bit fields has been a configuration restriction in the early days of
   DiffServ.  The concept of classifying DiffServ traffic classes by the
   bits 0-2 of a DSCP has however been part of Diffserv from start on.
   EF's DSCP Precedence Prefix is 5, that of AF4 is 4 and so on.  The
   interconnection class and codepoint 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 Class
      Selector Codepoints.

   o  it supports a single PHB group (AF3), whose DSCP based PHBs may be
      mapped to up to three different MPLS TC's or Ethernet P-Bits.
      Note that this draft doesn's favour or recommend doing that, but
      it is possible.  The author isn't aware of deployed service offers
      with 3 different drop levels in a single class.



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   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 7 DSCP based PHBs, each PHB
   may be mapped to a 3 Bit based PHB scheme.


8.  QoS class name selection

   This is more of an informational discussion, proposed best practice,
   and mainly relates to human behaviour (including QoS experts) rather
   than technical issues.  Above the human preference for conceivable
   class names has been mentioned.  Network engineers (including the
   former Diffserv WG authors) recommend avoiding application related
   QoS class names.  Focus should be put on class properties.  These can
   be irritating again.  Just looking at SLA parameters like Delay,
   Jitter and packet loss doesn't tell the reader, which transport
   properties guided the related scheduler engineering of a PHB.  A
   router produces QoS with a scheduling mechanism, a settable queue
   depth and optional active queue management (including ECN), and may
   be a policer.  Some kind of resource management may be present (also
   in Diffserv domains).  It's beyond the imagination of the author how
   one would engineer more than half a dozen classes with
   distinguishable properties using this set of tools.

   There's no perfect solution to the problem, as PHB configurations are
   not comprehensible to most readers, even if they were communicated
   (they are operational secrets of course).  There are (or should be)
   engineering assumptions, when designing QoS PHBs.  They closer relate
   to layer 3 or layer 4 level properties than to specific applications.
   In most cases, an application responds to congestion by reducing
   traffic, or it ignores congestion.  Active queue management doesn't
   help to avoid congestion in the latter case, only resource management
   does.  EF may be a special case.  If the EF traffic is not responsive
   to congestion, and packets are assumed to be short, rather small
   jitter values can be reached if engineering ensures that the packet
   arrival rate never exceeds the transmission rate of that queue (see
   RFC 3246 [RFC3246]).  There's other non congestion-responsive
   traffic, for which the EF engineering assumptions may not fit.  So
   support of a PHB like bulk inelastic is reasonable.

   Active queue management may be deployed for QoS classes designed to
   transport traffic responding to congestion by traffic reduction.

   The class names of this document follow Y.1566.  TCP_optimised and
   especially UDP_optimised are inappropriate class names, as some UDP
   based applications are or may be expected to become TCP friendly.





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9.  Allow for DiffServ extendibility on MPLS and Ethernet level

   Any aggregated Diffserv deployment faces codepoint depletion issues
   rather soon, if deployed on MPLS or Ethernet.  Coding space should be
   left for new features, like ECN, PCN or Conex.  In addition to
   carrying customer traffic, internal routing and network management
   traffic may be protected by using a separate class.  Offering
   interconnection with up to four classes and 4 - 6 MPLS TC's (or
   Ethernet P-bits) to that respect is probably at least a fair
   compromise.


10.  Acknowledgements

   David Black gave many helpful comments to this work.  Al Morton and
   Sebastien Jobert provided feedback on many aspects during private
   discussions.  Brian Carpenter, Mohamed Boucadair and Thomas Knoll
   helped adding awareness of further potentially related work.


11.  IANA Considerations

   This memo includes no request to IANA.


12.  Security Considerations

   This document does not introduce new features, it describes how to
   use existing ones.  The security section of RFC 4597 [RFC4597]
   applies.


13.  References

13.1.  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.

   [RFC2575]  Wijnen, B., Presuhn, R., and K. McCloghrie, "View-based
              Access Control Model (VACM) for the Simple Network
              Management Protocol (SNMP)", RFC 2575, April 1999.




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

   [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.

13.2.  Informative References

   [I-D.knoll-idr-cos-interconnect]
              Knoll, T., "BGP Class of Service Interconnection",
              draft-knoll-idr-cos-interconnect-10 (work in progress),
              May 2013.

   [I-D.polk-tsvwg-diffserv-stds-problem-statement]
              Polk, J., "The Problem Statement for the Standard
              Configuration of DiffServ Service Classes",
              draft-polk-tsvwg-diffserv-stds-problem-statement-00 (work
              in progress), July 2012.

   [I-D.polk-tsvwg-rfc4594-update]
              Polk, J., "Standard Configuration of DiffServ Service
              Classes", draft-polk-tsvwg-rfc4594-update-03 (work in
              progress), March 2013.

   [ID.idr-sla]
              IETF, "Inter-domain SLA Exchange", IETF,  http://
              datatracker.ietf.org/doc/draft-ietf-idr-sla-exchange/,
              2013.

   [IR.34]    GSMA Association, "IR.34 Inter-Service Provider IP
              Backbone Guidelines Version 7.0", GSMA,  GSMA IR.34 http:/
              /www.gsma.com/newsroom/wp-content/uploads/2012/03/



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              ir.34.pdf, 2012.

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

   [RFC4597]  Even, R. and N. Ismail, "Conferencing Scenarios",
              RFC 4597, August 2006.

   [RFC5127]  Chan, K., Babiarz, J., and F. Baker, "Aggregation of
              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.














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Author's Address

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

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









































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