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Inter-Domain Routing Working Group                             Th. Knoll
Internet-Draft
Intended status: Standards Track                        January 23, 2017
Expires: July 27, 2017


                 BGP Extended Community for QoS Marking
                    draft-knoll-idr-qos-attribute-19

Abstract

   This document specifies a simple signalling mechanism for inter-
   domain QoS marking using several instances of a new BGP Extended
   Community.  Class based packet marking and forwarding is currently
   performed independently within ASes.  The new QoS marking community
   makes the targeted Per Hop Behaviour within the IP prefix advertising
   AS and the currently applied marking at the interconnection point
   known to all access and transit ASes.  This enables individual
   (re-)marking and possibly forwarding treatment adaptation to the
   original QoS class setup of the respective originating AS.  The
   extended community provides the means to signal QoS markings on
   different layers, which are linked together in QoS Class Sets.  It
   provides inter-domain and cross-layer insight into the QoS class
   mapping of the source AS with minimal signalling traffic.

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].

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 July 27, 2017.




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Copyright Notice

   Copyright (c) 2017 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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Related Work  . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Definition of the QoS Marking Community . . . . . . . . . . .   7
     4.1.  Extended Community Type . . . . . . . . . . . . . . . . .   7
     4.2.  Structure of the QoS Marking Community  . . . . . . . . .   7
     4.3.  Technology Type Enumeration . . . . . . . . . . . . . . .  11
   5.  Community Usage . . . . . . . . . . . . . . . . . . . . . . .  11
     5.1.  QoS Marking Example . . . . . . . . . . . . . . . . . . .  12
     5.2.  AS Border Packet Forwarding . . . . . . . . . . . . . . .  12
     5.3.  IP Prefix Aggregation . . . . . . . . . . . . . . . . . .  13
   6.  Confidentiality Considerations  . . . . . . . . . . . . . . .  13
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  15
   Appendix A.  QoS Marking Example  . . . . . . . . . . . . . . . .  16
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   A new BGP Extended Community is defined in this document, which
   carries QoS marking information for different network layer
   technologies across ASes.  This extended community is called "QoS
   Marking".  This new community provides a mechanism within BGP-4
   [RFC4271] for associating all advertised prefixes of the AS with its
   differentiated QoS Class Marking information.  It allows for the
   consistent exchange of class encoding values between BGP peers for
   physical, data link and network QoS mechanisms.  These labels can be
   used to control the distribution of this information, for the



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   encoding and for treatment adjustments within the AS or for other
   applications.  One globally seen QoS Class Set per AS is required for
   scalability reasons.  It is the AS provider's responsibility to
   enforce the globally signalled Set throughout the AS.

   Several QoS Marking communities MAY be included in a single BGP
   UPDATE message.  They are virtually linked together by means of an
   identical "QoS Set Number" field.  Each QoS Marking community is
   encoded as 8-octet tuple, as defined in Section 4.  Signalled QoS
   Class Sets are assumed to be valid for traffic crossing this AS.  If
   different QoS strategies are used with an AS, its provider is
   responsible for consistent transport of transit traffic across this
   inhomogeneous domain.  In all transit forwarding cases, QoS based
   tunnelling mechanisms are the means of choice for transparent traffic
   transport.

   The availability of the "Best Effort" forwarding class is implied and
   defaults to a zero encoding on all signalled layers.  It is therefore
   not necessary to include QoS Marking communities for the Best Effort
   Class as long as the default encoding is in place.

   Class overload prevention can be achieved by means of the signalling
   described in [I-D.knoll-idr-cos-interconnect].  It is a complementary
   concept to limit the usage of advertised classes in a fair and square
   manner.

2.  Problem Statement

   Current inter-domain interconnection is "best effort" interconnection
   only.  That is, traffic forwarding between ASes is without traffic
   class differentiation and without any forwarding guarantee.  It is
   common for network providers to reset any IP packet class markings to
   zero, the best effort DSCP marking, at the AS ingress router, which
   eliminates any traffic differentiation.  Some providers perform
   higher layer classification at the ingress in order to guess the
   forwarding requirements and to match on their AS internal QoS
   forwarding policy.  There is no standardized set of classes, no
   standardized marking (class encoding) and no standardized forwarding
   behaviour, which cross-domain traffic could rely on.  QoS policy
   decisions are taken by network providers independently and in an
   uncoordinated fashion.

   This general statement does not cover the existing individual
   agreements, which do offer quality based interconnection with strict
   QoS guarantees.  However, such SLA based agreements are of bilateral
   or multilateral nature and do not offer a means for a general "better
   than best effort" interconnection.  This draft does not aim for
   making such SLA based agreements become void.  On the contrary, those



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   agreements are expected to exist for special traffic forwarding paths
   with strictly guaranteed QoS.

   There are many approaches, which propose proper inter-domain QoS
   strategies including inter-domain parameter signalling, metering,
   monitoring and misbehaviour detection.  Such complex strategies get
   close to guaranteed QoS based forwarding at the expense of dynamic
   measurements and adjustments, of state keeping on resource usage vs.
   traffic load and in particular of possibly frequent inter-domain
   signalling.

   The proposed QoS Class marking approach dissociates from the complex
   latter solutions and targets the general "better than best effort"
   interconnection in coexistence with SLA based agreements.  It enables
   ASes to make their supported Class Sets and their encoding globally
   known.  In other words, this support information constitutes a simple
   map of QoS enabled roads in transit and destination ASes.

   Signalling the coarse information about the supported class set and
   its cross-layer encoding within the involved forwarding domains of
   the selected AS path removes the lack of knowledge about the over-all
   available traffic differentiation.  AS providers are enabled to make
   an informed decision about supported class encodings and might adopt
   to them.  No guarantees are offered by this "better than best effort"
   approach, but as much as easily possible traffic differentiation
   without the need for frequent inter-domain signalling and for costly
   ingress re-classification will be achieved.

   Remarking the class encoding of customer traffic in order to match
   neighbouring class set encodings is reasonable at AS interconnection
   points.  For AS internal forwarding, the encapsulation within any
   kind of QoS supporting tunnelling technology is highly recommended.
   The cross-layer signalling of QoS encoding will further ease the
   setup of QoS based inter-domain tunnelling.

   The general confidentiality concern of disclosing AS internal policy
   information is addressed in Section 6.  In short, network providers
   can signal a different class set in the QoS Marking communities to
   the one actually used internally.  The different class sets
   (externally signalled vs. internally applied one) require an
   undisclosed strictly defined mapping at the AS borders between the
   two.  This way, a distinction between internal and external QoS Class
   Sets can be achieved.

   The general need for class based accounting is not addressed by this
   draft.  MIB extensions are also required, which separate traffic
   variables by traffic marking.  It is expected for both that existing
   procedures can be reused in a class based manner.



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3.  Related Work

   A number of QoS improvement approaches have been proposed before and
   a selection will be briefly mentioned in this section.

   Most of the approaches perform parameter signalling.
   [I-D.jacquenet-bgp-qos] defines the QOS_NLRI attribute, which is used
   for propagating QoS-related information associated to the NLRI
   (Network Layer Reachability Information) information conveyed in a
   BGP UPDATE message.  Single so called "QoS routes" are signalled,
   which fulfil certain QoS requirements.  Several information types are
   defined for the attribute, which concentrate on rate and delay type
   parameters.

   [I-D.boucadair-qos-bgp-spec] is based on the specified QOS_NLRI
   attribute and introduces some modifications to it.  The notion of AS-
   local and extended QoS classes is used, which effectively describes
   the local set of QoS performance parameters or their cross-domain
   combined result.  Two groups of QoS delivery services are
   distinguished, where the second group concentrates on ID associated
   QoS parameter propagation between adjacent peers.  The first group is
   of more interest for this draft since it concentrates on the
   "identifier propagation" such as the DSCP value for example.
   However, this signalling is specified for the information exchange
   between adjacent peers only and assumes the existence of extended QoS
   classes and offline traffic engineering functions.

   Another approach is described in [I-D.liang-bgp-qos].  It associates
   a list of QoS metrics with each prefix by extending the existing
   AS_PATH attribute format.  Hop-by-hop metric accumulation is
   performed as the AS_PATH gets extended in relaying ASes.  Metrics are
   generically specified as a list of TLV-style attribute elements.  The
   metrics such as bandwidth and delay are exemplary mentioned in the
   draft.

   One contribution specialized in the signalling of Type Of Service
   (TOS) values which are in turn directly mapped to DSCP values in
   section 3.2 of the draft [I-D.zhang-idr-bgp-extcommunity-qos].  The
   TOS value is signalled within an Extended Community Attribute and, if
   it is understood correctly, will be applied to a certain route.  An
   additional value field is used to identify, which routes belong to
   which signalled TOS community.  Who advertises such attributes and
   whether they are of transitive or non-transitive type remains
   unspecified.

   The most comprehensive analysis (although not an IETF draft) is given
   in [MIT_CFP].  This "Inter- provider Quality of Service" white paper
   examines the inter-domain QoS requirements and derives a



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   comprehensive approach for the introduction of at least one QoS class
   with guaranteed delay parameters.  The implementation aspects of
   metering, monitoring, parameter feedback and impairment allocations
   are all considered in the white paper.  However, QoS guarantees and
   parameter signalling is beyond the intention of this QoS Marking
   draft.

   Other drafts may also be considered as related work as long as they
   convey QoS marking information and might be "misused" for QoS class
   signalling.

   One example is the usage of the "Traffic Engineering Attribute" as
   defined in [RFC5543].  However, the attribute is non-transitive and
   the LSP encoding types are not generally applicable to inter-domain
   interconnection types.  Its usage of the targeted QoS Marking
   signalling is not possible.  The included maximum bandwidth of each
   of eight priority classes, could however be used in future draft
   extensions.

   The second example is the current "Dissemination of flow
   specification rules" draft [RFC5575].  It defines a new BGP NLRI
   encoding format, which can be used to distribute traffic flow
   specifications.  Such flow specification can also include DSCP values
   as type 11 in the NLRI.  Furthermore, one could signal configuration
   actions together with the DSCP encoding, which could be used for
   filtering purposes or even trigger remarking and route selection with
   it.  Such usage is not defined in the draft and can hardly be
   achieved because of the following reasons.  The flow specification is
   focused on single flows, which might even be part of an aggregate.
   Such fine grained specification is counterproductive for the coarse
   grained general QoS Marking approach of this draft.  The novel
   approach of cross-layer QoS Marking could also not be incorporated,
   which might be essential for future tunnelled inter-domain
   interconnection.

















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4.  Definition of the QoS Marking Community

4.1.  Extended Community Type

   The new QoS Marking community is encoded in a BGP Extended Community
   Attribute [RFC4360].  It is therefore a transitive optional BGP
   attribute with Type Code 16.  An adoption to the simple BGP Community
   Attribute encoding [RFC1997] is not defined in this document.  The
   actual encoding within the BGP Extended Community Attribute is as
   follows.

   The QoS Marking community is of regular type which results in a 1
   octet Type field followed by 7 octets for the QoS marking structure.
   The Type is IANA-assignable and marks the community as transitive
   across ASes.  The type number has been assigned by IANA to 0x04
   [IANA_EC].

   Optionally, a non-transitive Type value assignment of 0x44 is
   provided, which allows for the AS internal marking information
   exchange.  The community format remains untouched for the non-
   transitive version.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0|                                               |
   +-+-+-+-+-+-+-+-+   7 octet QoS Marking community structure     |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 1

4.2.  Structure of the QoS Marking Community

   The QoS Marking community provides a flexible encoding structure for
   various QoS Markings on different layers.  This flexibility is
   achieved by a Flags, a QoS Set Number and a Technology Type field
   within the 7 octet structure as defined below.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Flags      | QoS Set Number|Technology Type| QoS Marking Oh|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | QoS Marking Ol| QoS Marking A |0 0 0 0 0 0 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 2



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   Flags:

    0  1  2  3  4  5  6  7
   +--+--+--+--+--+--+--+--+
   |0  0 |P |R |I |A |0 |0 |
   +--+--+--+--+--+--+--+--+

                                 Figure 3

      All used and unused flags default to a value of '0'.  The
      following table shows the bit encoding of the Flags field.

   +-----+--------+----------------------------------------+
   | Bit | Flag   | Encoding                               |
   +-----+--------+----------------------------------------+
   | 0-1 | unused | Default to '0'                         |
   | 2   | P      | '1' ... Marking is preserved           |
   | 3   | R      | '1' ... Remarking occurred             |
   | 4   | I      | '1' ... QoS marking ignored            |
   | 5   | A      | '1' ... QoS class aggregation occurred |
   | 6,7 | unused | Default to '0'                         |
   +-----+--------+----------------------------------------+

                                  Table 1

      The 'P' flag indicates the preservation of incoming markings
      during the transit forwarding process.  The IP prefix originating
      AS SHOULD set the flag to '1', which is otherwise implied by an
      AS_PATH length of 1 ASN.  Transit ASes MUST set the flag to '1',
      if the advertised Marking A is accepted at the ingress and is sent
      out unchanged at the egress.  That is, no remarking occurs -
      neither for marking adoption with the neighbouring downstream AS
      nor by resetting the markings.  This flag field is set and cleared
      by each relaying AS according to its handling of markings -
      irrespective of the possible ignorance of the particular Marking A
      in the internal per hop forwarding behaviour.

      The Flags "R, I and A" are set to '0' in the advertisement by the
      IP prefix originating AS.  Transit ASes MUST change the flag value
      to '1' once the respective event occurred.  If the QoS marking
      actively used in the transit AS internal forwarding is different
      from the advertised original one, the 'Remarking (R)' flag is set
      to '1'.  This MUST be done separately for each technology type
      community within the community set.  The same applies to the
      'Ignore (I)' flag, if the respective advertised QoS marking is
      ignored in the transit AS internal forwarding.





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      The 'Aggregation (A)' flag MUST be set to '1' by the UPDATE
      message relaying transit AS, if the respective IP prefixes will be
      advertised inside an IP prefix aggregate constituted from
      differing Class Sets.

      If the defined "R, I and A" flags are cleared - and by means of
      the cleared 'Partial' flag of the BGP attribute it is shown, that
      no "QoS Class ignorant" AS is involved in the forwarding path - a
      consistent class based overall traffic separated forwarding is
      available along this path.

   QoS Set Number:

      Several single QoS Marking communities can be logically grouped
      into a QoS Marking community Set characterized by a identical QoS
      Set Number.  This grouping of the single QoS Marking communities
      into a set provides cross-layer linking between the QoS class
      encodings.  It can also be used for the specification of behaviour
      sets as given in the [RFC3140].  The number of signalled QoS
      Marking communities as well as QoS Marking community Sets is at
      the operator's choice of the originating AS.  The enumerated QoS
      set numbers have BGP UPDATE message local significance starting
      with set number 0x00.

   Technology Type:

   The technology type encoding uses the enumeration list in
   (Section 4.3).  Future version of this draft will need an extended
   enumeration list administered by IANA.

   QoS Marking / Enumeration O & A:

   The interpretation of these fields depends on the selected layer and
   technology.  ASes, which process the community and support the given
   QoS Class by means of a QoS mechanism using bit encodings for the
   targeted behaviour (e.g. IP DSCP, Ethernet User Priority, MPLS TC
   etc.)  MUST use a copy of the encoding in the "QoS Marking A"
   community field.  Unused higher order bits default to '0'.  Other
   technologies, which use separate forwarding channels for different
   classes (such as L-LSPs, VPI/VCI inferred ATM classes, lambda
   inferred priority, etc.)  SHALL use class enumerations as encoding in
   this community field.  The enumeration count starts with zero for the
   best effort traffic class and rises by one with each available higher
   priority class.







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   There are two QoS Marking fields within the QoS Marking community for
   the "original (O)" and the "active (A)" QoS marking.  Higher order
   bits of those fields, which are not used for the respective behaviour
   encoding, default to zero.

   QoS Marking O (Original QoS Marking):

      This field is a 16 bit QoS Marking field, which consists of of a
      high ("Oh") and a low ("Ol") octet.  The IP prefix originating AS
      copies the internally associated QoS encoding of the given
      Technology Type into this one octet field.  The field value is
      right-aligned depending on the number of encoded bits.  For the IP
      technology, the encoding of Per Hop Behaviour Codes has to follow
      the definitions stated in [RFC3140].  The field MUST remain
      unchanged in BGP UPDATE messages of relaying nodes.

   QoS Marking A (Active QoS Marking):

      QoS Marking A and O MUST be identically encoded by the prefix
      originating AS, except for the case, where IP technology Per Hop
      Behaviours are addressed.  "QoS Marking A" will always contain the
      locally applied encoding for the targeted PHB.

      All other ASes use this Active QoS Marking field to advertise
      their locally applied internal QoS encoding of the given class and
      technology at the interconnection point.  The field value is
      right-aligned depending on the number of encoded bits.  A cleared
      Marking field (all zero) signals that this traffic class
      experiences default traffic treatment within the transit AS
      forwarding technology.





















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4.3.  Technology Type Enumeration

   A small list of technologies is provided in the table below for the
   direct encoding of common technology types.  The mapping of all
   virtual channel technologies into a single technology type value is
   for limiting the number of different communities in an UPDATE
   message.  It is therefore a contribution to scalability.

   +---------+---------------------------------------------------------+
   | Value   | Technology Type                                         |
   +---------+---------------------------------------------------------+
   | 0x00    | DiffServ enabled IP (DSCP encoding)                     |
   | 0x01    | Ethernet using 802.1q priority tag                      |
   | 0x02    | MPLS using E-LSP                                        |
   | 0x03    | Virtual Channel (VC) encoding using separate channels   |
   |         | for QoS forwarding / one channel per class (e.g. ATM    |
   |         | VCs, FR VCs, MPLS L-LSPs)                               |
   | 0x04    | GMPLS - time slot encoding                              |
   | 0x05    | GMPLS - lambda encoding                                 |
   | 0x06    | GMPLS - fibre encoding                                  |
   +---------+---------------------------------------------------------+

                                  Table 2

5.  Community Usage

   Providers MAY choose to process the QoS Marking communities and adopt
   the behaviour encoding and tunnel selection according to their local
   policy.  Whether this MAY also lead to different IGP routing
   decisions or even effect BGP update filters is out of scope for the
   community definition.

   Only the IP prefix originating AS is allowed to signal the QoS
   Marking communities and Sets.  AS providers, which make use of this
   signalling mechanism MUST make sure, that only one external Class Set
   will be advertised for the AS.  All advertised prefixes, which
   originate from that AS will be sent with the same QoS Marking
   community Set in the respective UPDATE message.  Transit ASes MUST
   NOT modify or extend the QoS Marking community Set except for the
   update of each 'QoS Marking A' field contained in the community Set
   and the respective "P, R, I, A" flags.  Prefixes with associated
   identical QoS Marking community Sets are to be advertised together in
   common UPDATE messages in relaying nodes.

   Figure 4 shows an AS interconnection example with different Class
   Sets.  It shows the case in AS 5 where different Class Sets are used
   internally and externally.  The proposed QoS Class Set signalling
   will always use the external definitions within the UPDATE message



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   QoS Marking communities.  The example also shows, that IP prefixes,
   which originate in AS 5 and AS 3 can be advertised together with the
   same QoS Marking community Set as long as their Layer 2 encoding is
   identical.

                      AS 5 = Transit AS
   +------------+     =================     +------------+
   +   AS 1     +      AS internal:         +   AS 3     +
   + 4 classes  +         5 classes         + 3 classes  +
   +   L2/L3    +         L2/L3             +   L2/L3    +
   +(EF,2xAF,BE)+      AS external:         +(EF,AF1,BE)+
   +         [] +         3 classes         +[]          +
   +------------+         L3 (EF,AF1,BE)   +------------+
                 \    +---------------+    /
                  \   |       []      |   /
                   \  |      /  \     |  /
                    \ |  --()---()--  | /
                     \| /   |    |  \ |/
                      |[]   |    |  []|
                     /| \   |    |  / |\
                    / |  --()---()--  | \
                   /  |      \  /     |  \
                  /   |       []      |   \
                 /    +---------------+    \
   +------------+                           +------------+
   +         [] +                           +[]          +
   +   AS 2     +                           +   AS 4     +
   + 2 classes  +                           + 6 classes  +
   +   L2/L3    +                           +  L1/L2/L3  +
   +  (EF,BE)   +                           +(EF,4xAF,BE)+
   +------------+                           +------------+
   [] ... AS Border Router
   () ... AS internal Router

                                 Figure 4

5.1.  QoS Marking Example

   See Appendix A for an example QoS Marking community Set.

5.2.  AS Border Packet Forwarding

   IP packet forwarding based on packet header QoS encoding might
   require remarking of packets in order to match AS internal policies
   and encodings of neighbouring ASes.






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   Identical QoS class sets and encodings between neighbouring ASes do
   not require any remarking.  Different encodings will be matched on
   the outgoing traffic.

   Outgoing traffic for a given IP prefix uses the 'QoS Marking A'
   information of the respective BGP UPDATE message QoS Marking
   community for adopted remarking of the forwarded packet.

   If the 'I' flag is set for a given encoding, the outgoing traffic
   remarking SHOULD still be applied despite of the signalled lack of
   QoS Class forwarding support.  This is particularly important, if the
   preserve flag 'P' is signalled together with the 'I' flag.

5.3.  IP Prefix Aggregation

   Several IP prefixes of different IP prefix originating ASes MAY be
   aggregated to a shorter IP prefix in transit ASes.  If the original
   Class Sets of the aggregated prefixes are identical, the aggregate
   will use the same Set. In all other cases, the resulting IP prefix
   aggregate is handled the same as if the transit AS were the
   originating AS for this aggregated prefix.  The transit AS provider
   MAY care for AS internal mechanisms, which map the signalled
   aggregate QoS Class Set to the different original Class Sets in the
   internal forwarding path.

   In case of IP prefix aggregation with different QoS Class Sets, the
   'Aggregation (A)' flag of each QoS Marking community within the Set
   MUST be set to '1'.

6.  Confidentiality Considerations

   The disclosure of confidential AS intrinsic information is of no
   concern since the signalled marking for QoS class encodings can be
   adopted prior to the UPDATE advertisement of the IP prefix
   originating AS.  This way, a distinction between internal and
   external QoS Class Sets can be achieved.  AS internal cross-layer
   marking adaptation and policy based update filtering allows for
   consistent QoS class support despite made up QoS Class Set and
   encoding information within UPDATE advertisements.  In case of such
   policy hiding strategy, the required AS internal ingress and egress
   adaptation SHALL be done transparently without explicit "Active
   Marking" and 'R' flag signalling.









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7.  IANA Considerations

   This document defines a new BGP Extended Community, which includes a
   "Technology Type" field.  Section 4.3 enumerates a number of popular
   technologies.  This list is expected to suffice for first
   implementations.  However, future or currently uncovered technologies
   may arise, which will require an extended "Technology Type"
   enumeration list administered by IANA.

   A new extended community QoS Marking community is defined, which has
   been assigned a Type value of 0x04 for a transitive and 0x44 for a
   non-transitive usage.

8.  Security Considerations

   This extension to BGP does not change the underlying security issues
   inherent in the existing BGP.

   Malicious signalling behaviour of QoS Marking community advertising
   ASes can result in misguided neighbours about non existing or
   maliciously encoded Class Sets.  Removal of QoS Marking community
   Sets leads to the current best effort interconnection, which is no
   stringent security concern.

   The IP prefix originating AS MAY place a copy of its marking
   information into the Internet Routing Registry (IRR) for global
   reference.

   The strongest threat is the advertisement of numerous very fine
   grained Class Sets, which could limit the scalability of this
   approach.  However, neighbouring ASes are free to set the ignore flag
   of single communities or to stop processing the QoS Marking
   communities of a certain routing advertisement, once a self-set
   threshold has been crossed.  By means of this self defence mechanism
   it should not be possible to crash neighbouring peers due to the
   excessive use of the new community.

9.  References

9.1.  Normative References

   [IANA_EC]  IANA, , "Border Gateway Protocol (BGP) Data Collection
              Standard Communities", June 2008, <http://www.iana.org/
              assignments/bgp-extended-communities>.

   [RFC1997]  Chandra, R., Traina, P., and T. Li, "BGP Communities
              Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996,
              <http://www.rfc-editor.org/info/rfc1997>.



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   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
              RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3140]  Black, D., Brim, S., Carpenter, B., and F. Le Faucheur,
              "Per Hop Behavior Identification Codes", RFC 3140, DOI
              10.17487/RFC3140, June 2001,
              <http://www.rfc-editor.org/info/rfc3140>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI 10.17487
              /RFC4271, January 2006,
              <http://www.rfc-editor.org/info/rfc4271>.

   [RFC4360]  Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
              Communities Attribute", RFC 4360, DOI 10.17487/RFC4360,
              February 2006, <http://www.rfc-editor.org/info/rfc4360>.

   [RFC5543]  Ould-Brahim, H., Fedyk, D., and Y. Rekhter, "BGP Traffic
              Engineering Attribute", RFC 5543, DOI 10.17487/RFC5543,
              May 2009, <http://www.rfc-editor.org/info/rfc5543>.

   [RFC5575]  Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J.,
              and D. McPherson, "Dissemination of Flow Specification
              Rules", RFC 5575, DOI 10.17487/RFC5575, August 2009,
              <http://www.rfc-editor.org/info/rfc5575>.

9.2.  Informative References

   [I-D.boucadair-qos-bgp-spec]
              Boucadair, M., "QoS-Enhanced Border Gateway Protocol",
              draft-boucadair-qos-bgp-spec-01 (work in progress), July
              2005.

   [I-D.jacquenet-bgp-qos]
              Cristallo, G., "The BGP QOS_NLRI Attribute", draft-
              jacquenet-bgp-qos-00 (work in progress), February 2004.

   [I-D.knoll-idr-cos-interconnect]
              Knoll, T., "BGP Class of Service Interconnection", draft-
              knoll-idr-cos-interconnect-17 (work in progress), November
              2016.

   [I-D.liang-bgp-qos]
              Benmohamed, L., "QoS Enhancements to BGP in Support of
              Multiple Classes of Service", draft-liang-bgp-qos-00 (work
              in progress), June 2006.



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   [I-D.zhang-idr-bgp-extcommunity-qos]
              Zhang, Z., "ExtCommunity map and carry TOS value of IP
              header", draft-zhang-idr-bgp-extcommunity-qos-00 (work in
              progress), November 2005.

   [MIT_CFP]  Amante, S., Bitar, N., Bjorkman, N., and others, "Inter-
              provider Quality of Service - White paper draft 1.1",
              November 2006,
              <http://cfp.mit.edu/docs/interprovider-qos-nov2006.pdf>.

Appendix A.  QoS Marking Example

   The example AS is advertising several IP prefixes, which experience
   equal QoS treatment from AS internal networks.  The IP packet
   forwarding policy within this originating AS defines e.g. 3 traffic
   classes for IP traffic (DSCP1, DSCP2 and DSCP3).  These three classes
   are also consistently taken care of within a TC bit supporting MPLS
   tunnel forwarding.  The BGP UPDATE message for the announced IP
   prefixes will contain the following QoS Marking community Set
   together with the IP prefix NLRI.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 1 0 0 0 0 0|0 0 0 0 0 0 0 0|0 0 0 0 0 0 0 0|1 0 1 1 1 0 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0|0 0 1 0 1 1 1 0|0 0 0 0 0 0 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 1 0 0 0 0 0|0 0 0 0 0 0 0 0|0 0 0 0 0 0 1 0|0 0 0 0 0 0 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 1 0 1|0 0 0 0 0 1 0 1|0 0 0 0 0 0 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 1 0 0 0 0 0|0 0 0 0 0 0 0 1|0 0 0 0 0 0 0 0|0 0 1 0 1 0 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 1 0|0 0 0 0 1 0 1 0|0 0 0 0 0 0 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 1 0 0 0 0 0|0 0 0 0 0 0 0 1|0 0 0 0 0 0 1 0|0 0 0 0 0 0 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 1|0 0 0 0 0 0 0 1|0 0 0 0 0 0 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 1 0 0 0 0 0|0 0 0 0 0 0 1 0|0 0 0 0 0 0 0 0|0 1 0 0 1 0 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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   |0 0 0 0 0 0 1 0|0 0 0 1 0 0 1 0|0 0 0 0 0 0 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 1 0 0 0 0 0|0 0 0 0 0 0 1 0|0 0 0 0 0 0 1 0|0 0 0 0 0 0 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 1 0|0 0 0 0 0 0 1 0|0 0 0 0 0 0 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The class set as well as the example encodings are arbitrarily chosen.

                                 Figure 5

Author's Address

   Thomas Martin Knoll

   Email: thomas.m.knoll@gmail.com


































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