Inter-Domain Routing Working Group                             Th. Knoll
Internet-Draft                         Chemnitz University of Technology
Intended status: Standards Track                         January 7, 2009
Expires: July 11, 2009


            BGP Extended Community Attribute for QoS Marking
                    draft-knoll-idr-qos-attribute-03

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Abstract

   This document specifies a simple signalling mechanism for inter-
   domain QoS marking using several instances of a new BGP Extended



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   Community Attribute.  Class based packet marking and forwarding is
   currently performed independently within ASes.  The new QoS marking
   attribute 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 attribute 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].


































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Table of Contents

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






























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1.  Introduction

   A new BGP Extended Community Attribute is defined in this document,
   which carries QoS marking information for different network layer
   technologies across ASes.  This attribute is called "QoS Marking".
   This new attribute 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 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 attributes 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 attribute 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 attributes for the Best Effort
   Class as long as the default encoding is in place.


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 AS providers independently and in an
   uncoordinated fashion.




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   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
   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, AS providers can
   signal a different class set in the QoS Marking attributes 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



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   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.


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



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   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
   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
   attribute 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 [I-D.ietf-softwire-bgp-te-attribute].  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 [I-D.ietf-idr-flow-spec].  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.


4.  Definition of the QoS Marking Attribute






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4.1.  Extended Community Type

   The new QoS Marking attribute is encoded as 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 attribute 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 interconnection local marking
   information exchange.  The attributes 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 attribute structure     |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 1

4.2.  Structure of the QoS Marking Attribute

   The QoS Marking attribute 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

   Flags:





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    0  1  2  3  4  5  6  7
   +--+--+--+--+--+--+--+--+
   |0  0  0 |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                                |
   +-----+--------+-----------------------------------------+
   | 0-2 | unused | Default to '0'                          |
   | 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 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
      attribute within the attribute set.  The same applies to the
      'Ignore (I)' flag, if the respective advertised QoS marking is
      ignored in the transit AS internal forwarding.

      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 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:







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      Several single QoS Marking attributes can be logically grouped
      into a QoS Marking attribute Set characterized by a identical QoS
      Set Number.  This grouping of the single QoS Marking attributes
      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 attributes as well as QoS Marking attribute 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 Attribute 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 EXP
   etc.)  MUST use a copy of the encoding in the "QoS Marking A"
   attribute 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 attribute field.  The enumeration count starts with zero for the
   best effort traffic class and rises by one with each available higher
   priority class.

   There are two QoS Marking fields within the QoS Marking attribute 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.




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   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.

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 attributes 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.  Attribute Usage

   Providers MAY choose to process the QoS Marking attributes 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
   attribute definition.




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   Only the IP prefix originating AS is allowed to signal the QoS
   Marking attributes 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
   attribute Set in the respective UPDATE message.  Transit ASes MUST
   NOT modify or extend the QoS Marking attribute Set except for the
   update of each 'QoS Marking A' field contained in the Attribute Set
   and the respective "R, I, A" flags.  Prefixes with associated
   identical QoS Marking attribute 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
   QoS Marking attributes.  The example also shows, that IP prefixes,
   which originate in AS 5 and AS 3 can be advertised together with the
   same QoS Marking attribute Set as long as their Layer 2 encoding is
   identical.































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                      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 Attribute Example

   See Appendix A for an example QoS Marking attribute 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.

   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
   attribute for adopted remarking of the forwarded packet.



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   If the 'I' flag is set for a given encoding, the outgoing traffic
   remarking can not be applied due to this signalled lack of QoS Class
   forwarding support.

   There is no outgoing remarking, if the targeted class is not
   supported by the neighbouring AS.

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 attribute 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.


7.  IANA Considerations

   This document defines a new BGP Extended Community Attribute, 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.




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   A new extended community QoS Marking attribute 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 attribute advertising
   ASes can result in misguided neighbours about non existing or
   maliciously encoded Class Sets.  Removal of QoS Marking attribute
   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 thread 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 attributes or to stop processing the QoS Marking attributes
   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 attribute.


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]  Chandrasekeran, R., Traina, P., and T. Li, "BGP
              Communities Attribute", RFC 1997, August 1996.

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

   [RFC3140]  Black, D., Brim, S., Carpenter, B., and F. Le Faucheur,
              "Per Hop Behavior Identification Codes", RFC 3140,
              June 2001.



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   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.

   [RFC4360]  Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
              Communities Attribute", RFC 4360, February 2006.

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.ietf-idr-flow-spec]
              Marques, P., Sheth, N., Raszuk, R., Greene, B., and D.
              McPherson, "Dissemination of flow specification rules",
              draft-ietf-idr-flow-spec-03 (work in progress),
              November 2008.

   [I-D.ietf-softwire-bgp-te-attribute]
              Fedyk, D., Rekhter, Y., and H. Ould-Brahim, "BGP Traffic
              Engineering Attribute",
              draft-ietf-softwire-bgp-te-attribute-04 (work in
              progress), December 2008.

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

   [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.

   [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>.







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Appendix A.  QoS Marking Attribute 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 an EXP bit supporting MPLS
   tunnel forwarding.  The BGP UPDATE message for the announced IP
   prefixes will contain the following QoS Marking attribute 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 0 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 0 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 0 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 0 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 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 0 1 0 0 0|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |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 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 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









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Author's Address

   Thomas Martin Knoll
   Chemnitz University of Technology

   Email: knoll@etit.tu-chemnitz.de













































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