[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits] [IPR]

Versions: (draft-svshah-interdomain-sla-exchange) 00 01 02 03 04 05 06 07 08 09 10 11 12 13

Network Working Group                                            S. Shah
Internet-Draft                                                  K. Patel
Intended status: Standards Track                           Cisco Systems
Expires: May 4, 2016                                            S. Bajaj
                                                        Juniper Networks
                                                             L. Tomotaki
                                                                 Verizon
                                                            M. Boucadair
                                                          France Telecom
                                                       November 01, 2015


                       Inter-domain SLA Exchange
                     draft-ietf-idr-sla-exchange-06

Abstract

   Network administrators typically enforce Quality of Service (QoS)
   policies according to Service Level Agreement (SLA) with their
   providers.  The enforcement of such policies often relies upon
   vendor-specific configuration language.  Both learning of SLA, either
   thru SLA documents or via some other out-of-band method, and
   translating them to vendor specific configuration language is a
   complex, many times manual, process and prone to errors.  This
   document proposes an in-band method of SLA signaling, which can help
   to simplify some of the complexities, where BGP is available as the
   routing protocol.

   This document defines an optional transitive attribute to signal SLA
   parameters in-band, across administrative boundaries (considered as
   Autonomous Systems (AS)), thus simplifying and facilitating some of
   the complex provisioning tasks.

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."




Shah, et al.               Expires May 4, 2016                  [Page 1]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


   This Internet-Draft will expire on May 4, 2016.

Copyright Notice

   Copyright (c) 2015 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.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  QoS Attribute Definition  . . . . . . . . . . . . . . . . . .   4
     3.1.  SLA, QoS attribute sub-type, Definition . . . . . . . . .   5
   4.  Originating SLA Notification  . . . . . . . . . . . . . . . .  15
     4.1.  SLA Contexts  . . . . . . . . . . . . . . . . . . . . . .  15
       4.1.1.  SLA Advertisement for Point-to-Point Connection . . .  16
       4.1.2.  SLA Advertisement for Destination AS Multiple Hops
               Away  . . . . . . . . . . . . . . . . . . . . . . . .  16
   5.  SLA Attribute Handling at Forwarding Nodes  . . . . . . . . .  16
     5.1.  BGP Node Capable of Processing QoS Attribute  . . . . . .  16
     5.2.  SLA Attribute Handling at Receiver  . . . . . . . . . . .  17
   6.  Error Handling  . . . . . . . . . . . . . . . . . . . . . . .  18
   7.  Traffic Class Mapping . . . . . . . . . . . . . . . . . . . .  18
   8.  Deployment Considerations . . . . . . . . . . . . . . . . . .  18
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  20
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  20
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  21
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  21
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  21
     12.2.  Informative References . . . . . . . . . . . . . . . . .  22
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  23

1.  Introduction

   Typically there is a contractual Service Level Agreement (SLA) for
   QoS established between a customer and a provider or between
   providers.  This QoS SLA defines the nature of the various traffic
   classes and services needed within each traffic class.  The contract



Shah, et al.               Expires May 4, 2016                  [Page 2]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


   may include full line-rate or sub line-rate without additional
   traffic classes, or it may contain additional traffic classes and
   service definitions for those traffic classes.  Finer granular
   traffic classes may be based on some standard code points (like DSCP)
   or specific set of prefixes.

   Once the SLA is established, QoS SLA parameters are enforced in some
   or all participating devices by deriving those parameters into
   configuration information on respective devices.  SLA parameters may
   have to be exchanged through organizational boundaries, thru SLA
   documents or via some other off-band method to an administrator
   provisioning actual devices.  In a subsequent step, administrator
   requires to translate SLA to QoS policies using router (vendor)
   specific provisioning language.  In a multi-vendor network,
   translating SLAs into technology-specific and vendor-specific
   configuration requires to consider specificities of each vendor.
   There does not exist any standard protocol to translate SLA
   agreements into technical clauses and configurations and thus both
   the steps of out of band learning of negotiated SLA and provisioning
   them in a vendor specific language can be complex and error-prone.
   As an example for voice service, the Provider may negotiate QoS
   parameters (like min/max rates) for such traffic based upon the EF
   code-point in Diffserv-enabled [RFC2475] networks.  The Administrator
   at the CE side not only will have to know that Provider's service for
   voice traffic is EF-based but will also have to know how to implement
   DSCP EF classification rule along with Low Latency Service, and
   possibly min/max rate enforcement for the optimal use of bandwidth,
   as per vendor specific provisioning language.

   An in-band signaling method of propagating SLA parameters from the
   provider, PE in an example above, to contractual devices, CE in an
   example above, can help eliminate manual administrative process
   described above.  The provider may have SLA negotiated with the
   Customer via some defined off-band method (based on the specifics
   defined by the Provider or using protocols like [CPNP]).  The Inter-
   domain SLA exchange proposal described in this document does not pre-
   requisite any specific method of establishing SLAs).  The Provider
   provisions established SLA on the Provider device.  This SLA instance
   then can be signaled to the Customer via in-band signaling protocol.
   In reaction to this signal, receiver router may translate that to
   relevant QoS policy definition on the device.

   For an in-band signaling, we propose to use BGP as a transport.  The
   details of SLA parameters are specific to the granularity of traffic
   classes and their respective treatment, which is independent of the
   BGP protocol itself.  Though we find BGP as a suitable transport for
   inter-domain SLA exchange for the following reasons:




Shah, et al.               Expires May 4, 2016                  [Page 3]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


        - The need to exchange SLA parameters between domains(Autonomous
          Systems (AS)), where in use-cases described in this document,
          BGP is a suitable protocol for inter-domain exchange [RFC4271]
          [RFC4364].
        - There is no specifically defined protocol available today for
          SLA exchange.
        - BGP updates already advertise specific set of prefixes (flow
          or flow-group). Other QoS-related attributes, apart from the
          the use of SLA advertisement, can be added to these updates
          in the future.

   The proposal is to define a new BGP attribute to advertise/learn SLA
   details in-band.  The proposed attribute is intended to advertise SLA
   from one AS to a list of destined ASes.  The advertised QoS
   information could be for the incoming traffic to the advertiser, that
   is advertising SLA or could be for the outgoing traffic from the
   advertiser or could be for both directions.  Reception of and
   reaction to advertised SLAs are optional for the receiver.

   We propose QoS as an optional transitive attribute, keeping SLA
   advertisement as one of the sub-types of QoS attribute.  This is to
   keep the QoS attribute open for extensions.  For example, SLA
   Negotiation and Assurance is out of scope of this document but can be
   envisioned as another sub-type.

2.  Terminology

   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 [RFC2119].

3.  QoS Attribute Definition

   The QoS Attribute proposed here is an optional transitive attribute
   (attribute type code to be assigned by IANA).  SLA is defined as one
   of the sub-types in the QoS attribute.  The QoS attribute is only
   applicable to the NLRI advertised in the BGP update message.














Shah, et al.               Expires May 4, 2016                  [Page 4]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


       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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   Attr flag   | Attr type QoS |                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
       ~                                                               ~
       |                     QoS Attr length/Value                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+..........................


    Attribute flags
        highest order bit (bit 0) -
            MUST be set to 1, since this is an optional attribute

        2nd higher order bit (bit 1) -
            MUST be set to 1, since this is a transitive attribute



3.1.  SLA, QoS attribute sub-type, Definition

   The value field of the QoS Attribute contains TLVs, followed to QoS
   Attribute flags described in the previous section.  One of the TLVs
   that we define is a tuple of (SLA sub-type, Length, Value).

       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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | QoS Attr flags|      subType  |         subtype Length        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                                                               ~
       |                               Value                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+..........................

    QoS Attr flags
        8-bit = 0000-0000, All the bits are currently un-used. The space
                is made available for the purpose of future use. For now
                they all MUST be set to 0 when QoS attribute is added in
                the BGP update message and MUST be ignored when received


    subType
        8-bit
        0x00        = reserved
        0x01        = SLA
        0x02 - 0x0f = for future use





Shah, et al.               Expires May 4, 2016                  [Page 5]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


    subType Length
        16-bit
        Length of the content to follow pertaining to specified
        subType.

    Value for the SLA sub-type is as described below. These details
    contain information about 1) sender and receiver(s) and 2) SLA
    parameters. SLA Parameters include SLA event type (such as
    Advertise) and contents associated to that event type.

    The format of SLA message is,

       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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                    32-bit Source AS (Advertiser)              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                  32-bit Destination AS count                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                variable list of destination AS                |
       ~                            ....                               ~
       |                            ....                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Event |             SLA id            |      SLA length       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                    Content as per SLA Event                   |
       ~                                                               ~
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


    Source AS
        32-bit source AS number. This is the AS that is advertising SLA
        0 = ignore Source and Destination AS list from this Value field

            Note that AS = 0, used in message outside of QoS attribute,
            is illegal in normal BGP operations. AS = 0 inside the QoS
            attribute may be used simply as a flag to tell receiver to
            ignore Source and Destination AS list from inside the QoS
            attribute.

    Destination AS count
        32-bit destination AS count to take variable length AS list.
        This count has no functional value when Source AS is 0.

        0 = QoS attribute is relevant to every receiver of the message

    Destination AS list



Shah, et al.               Expires May 4, 2016                  [Page 6]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


        32-bit destination AS number
        ....
        .... [as many as AS count]

    SLA Event
        4-bits
        0x0 = reserved
        0x1 = ADVERTISE
        0x2 to 0xf, for future use

    SLA Id
        16-bit identifier unique within the scope of source AS

        The significance of an SLA identifier is in the context of the
        source that is advertising SLA parameters. The SLA identifier
        is not globally unique but it MUST be unique within the source
        AS (advertiser).


        If advertised SLA id is different from earlier advertised one,
        for the same prefix, previous SLA content MUST be replaced
        with the new advertised one.

        SLA is aggregate for all the traffic to prefixes for a given
        AFI/SAFI that share same source AS and SLA id.

    SLA Length
        12-bits - Total length of the SLA content to follow


    Content as per SLA event

        The SLA content is optional for an advertised SLA id. The
        value of the SLA length field in such case would be 0. If SLA
        content does not exist in BGP update messages with advertised
        QoS attribute, that contains the SLA sub-type, then receiver
        MUST inherit prior advertised SLA content for the same SLA id
        from the same Source AS. If there does not exist any prior SLA
        to relate to the advertised SLA id, then receiver can ignore
        the SLA advertisement and continue with the rest of the BGP
        message processing and forwarding rules. Note that such
        condition MUST not discard the attribute. All defined
        forwarding rules for this attribute still MUST apply.


      The only event prescribed in this document is ADVERTISE.
      The format of SLA ADVERTISE event message is,




Shah, et al.               Expires May 4, 2016                  [Page 7]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


       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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |dir|       Traffic Class count     | Class Desc Len|           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+           ~
       |                                                               |
       ~                  Traffic Class Description                    ~
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Elements Count|                                               |
       +-+-+-+-+-+-+-+-+                                               ~
       |                                                               |
       ~              Traffic Class Elements TLVs                      ~
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Service  Count|                                               |
       +-+-+-+-+-+-+-+-+                                               ~
       |               Traffic Class Service TLVs                      |
       ~                                                               ~
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       ~  Repeat from Traffic Class Description for next Traffic Class ~
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       ~    Repeat from direction for SLA in the other direction       ~
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


    dir (Direction)
        02-bit for incoming traffic to source AS or outgoing traffic
                   from source AS,
        0x0 = reserved
        0x1 = incoming, to source AS from destination AS
        0x2 = outgoing, from source AS towards destination AS
        0x3 = for future use


    Traffic Class count (Classifier Groups count)
        16-bit, count of number of classifier groups
        00 = Advertisement to invalidate previous advertised SLA if any

    Traffic Class Descr Length
        08-bit, length of the description

        0 = No description



Shah, et al.               Expires May 4, 2016                  [Page 8]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


    Traffic Class Description
        Description of the Traffic Class in UTF-8 encoding


    Traffic Class Elements Count in a Traffic Class,

        08-bit count of classifier elements in a specific Traffic Class

        00 = this has relative definition. It means classify rest all
             traffic that is not classified via earlier described
             Traffic Classes.
             It is RECOMMENDED that Traffic Class that has 0 elements
             is present last in the advertised list of Traffic Classes.
             If Advertised message has it positioned somewhere else,
             then receiver MUST re-order it, for the forwarding purpose,
             to the last position in the advertised list of Traffic
             Classes from a given source AS. QoS attribute advertised
             from a specific source MUST NOT have more than one such
             Traffic Classes (Traffic Class with 0 elements count). If
             there are more than one such Traffic Classes present then
             it is an error condition which should follow handling of
             such BGP message as described in Error handling section.



    Classifier Element values (optional),

        08-bit                = IPFIX Element Identifier
        08-bit                = size, in octets, of the value field
        variable-length field = contains actual value

        Given IPFIX [RFC5102] has well defined identifier set for a
        large number of packet attributes, IPFIX IANA registry is
        ("https://www.ietf.org/assignments/ipfix") chosen to specify
        packet classification attributes. However, since not all
        identifiers from IPFIX would be applicable to this proposal,
        only a limited set identified here can be supported by BGP
        SLA exchange. Any new element identifier, in the future added
        to the IPFIX IANA registry, is not automatically supported
        for this proposal. Only the IPFIX elements indicated in this
        document below remain supported.


       +----+----------------------------+
       | ID | Name                       |
       +----+----------------------------+
       |195 | ipDiffServCodePoint        |
       |203 | mplsTopLabelExp            |



Shah, et al.               Expires May 4, 2016                  [Page 9]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


       |244 | dot1qPriority              |
       |  8 | sourceIPv4Address          |
       | 27 | sourceIPv6Address          |
       |  9 | sourceIPv4PrefixLength     |
       | 29 | sourceIPv6PrefixLength     |
       | 44 | sourceIPv4Prefix           |
       |170 | sourceIPv6Prefix           |
       | 12 | destinationIPv4Address     |
       | 28 | destinationIPv6Address     |
       | 13 | destinationIPv4PrefixLength|
       | 30 | destinationIPv6PrefixLength|
       | 45 | destinationIPv4Prefix      |
       |169 | destinationIPv6Prefix      |
       |  4 | protocolIdentifier         |
       |  7 | sourceTransportPort        |
       | 11 | destinationTransportPort   |
       +----+----------------------------+

       Any traffic classifier element advertised in the QoS attribute
       is only applicable to the NLRI advertised for a given AFI/SAFI
       within the BGP update message. If a receiver receives a BGP
       update message with QoS/SLA attribute for an NLRI that is not
       supported by a receiver then receiver MUST not install an
       advertised SLA and continue to forward this attribute further
       if it is not the last receiver of an attribute.



    Traffic Class Service count (for a Traffic Class under definition)
        08-bit count of service attributes fields to follow with
               type/value pair
        List of service types and relevant values are discussed below

        00 = no bounded service (also means Best Effort)



    Traffic Class Service (optional),
        16-bit                = Traffic Class Service Type
        08-bit                = size, in octets, of the value field
        variable-length field = contains actual value


    - 0x00 = reserved


    - 0x01 = TRAFFIC_CLASS_TSPEC
      160-bits TSpec Parameter



Shah, et al.               Expires May 4, 2016                 [Page 10]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


      The TRAFFIC_CLASS_TSPEC parameter consists of the (r), (b), (p),
      (m) and (M) parameters as described in Invocation Information
      section of [RFC2212]. Note that inheriting the definition of
      TSpec here does not enable RFC2212 functionality. Only the
      values of the Traffic Specification are used in this
      specification.

       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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Minimum Rate (r) (32-bit IEEE floating point number)         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Burst Size (b) (32-bit IEEE floating point number)           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Maximum Rate (p) (32-bit IEEE floating point number)         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Minimum Policed Unit (m) (32-bit integer)                    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Maximum Packet Size (M)  (32-bit integer)                    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Parameter (r) indicates min-rate of the traffic class. This rate
      indicates the minimum rate, measured in octets of Layer 2 (L2)
      datagrams per second, that the service advertiser is providing
      for a given class of traffic on advertiser's hop. Note that it
      does not necessarily translate to a minimum rate service to the
      receiver of an SLA unless the traffic class definition clearly
      represents a sole receiver of an SLA. If there is no SLA for
      min-rate, the value of (r) MUST be set to 0.

      Parameter (b) indicates maximum burst size, measured in octets of
      L2 datagram size. Since queuing delay can be considered a
      function of burst size (b) and min-rate (r), in presence of non-
      zero parameter (r), parameter (b) represents bounded delay for
      the Traffic Class. This delay is a single hop queuing delay when
      SLA is to be implemented at the resource constrained bottleneck.
      In other words this burst size can be considered as a buffer
      size. Value of 0 for parameter (b) means the advertiser does not
      mandate specific bounded delay.

      Parameter (p) indicates max-rate of the traffic class. Just like
      min-rate, max-rate, measured in octets of L2 packets per second,
      field here also indicates service provided by advertiser. If
      advertiser does not have any specific value to set for a given
      class of traffic, it MAY be set to physical interface line rate
      or any other indirect limit that may affect this class' maximum
      rate. In absence of any such known value, it MUST be set to
      positive infinity. Value 0 is considered an error.



Shah, et al.               Expires May 4, 2016                 [Page 11]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


      Parameters (r), (b) and (p) are each set as 32-bit IEEE floating
      point numbers. Positive infinity is represented as an IEEE single
      precision floating-point number with an exponent of all ones and
      a sign mantissa of all zeros.  The format of IEEE floating-point
      numbers is further summarized in [RFC4506].

      The minimum policed unit (m) and maximum packet size (M)
      parameters have no relevance for the purpose of SLA exchange.
      Thus they MUST be ignored.


    - 0x02, L2_OVERHEAD
      08-bit, value

      By default specification of rate and other packet size related
      parameters, advertised in an SLA, includes L2 overhead. For the
      receiver next hop,this overhead is the L2 overhead of the local
      link where advertised SLA is received. However, in cases where
      advertised SLA is for a receiver multiple hops away, L2 overhead
      consideration from the source perspective may be different from
      the local L2 overhead at the receiver. Explicit notification of
      size of L2 overhead from a sender, in such cases, is useful for
      a receiver to distinguish local L2 overhead from the sender
      advertised one. When receiver choose to react to an advertised
      SLA and if this service type is present in advertised SLA,
      receiver MUST use advertised L2 overhead over local L2 overhead.

      If SLA is required to consider only IP packet size, sender may
      advertise this service with a value of 0.


    - 0x03 = MINRATE_IN_PROFILE_MARKING
      08-bit                = IPFIX Element Identifier
      08-bit                = size, in octets, of the value field
      variable-length field = contains actual value

      00 Identifier = drop, variable-length for this id is 0.

       +----+----------------------------+
       | ID | Name                       |
       +----+----------------------------+
       |195 | ipDiffServCodePoint        |
       |203 | mplsTopLabelExp            |
       |244 | dot1qPriority              |
       +----+----------------------------+


    - 0x04 = MINRATE_OUT_PROFILE_MARKING



Shah, et al.               Expires May 4, 2016                 [Page 12]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


      08-bit                = IPFIX Element Identifier
      08-bit                = size, in octets, of the value field
      variable-length field = contains actual value

      00 Identifier = drop, variable-length for this id is 0.

       +----+----------------------------+
       | ID | Name                       |
       +----+----------------------------+
       |195 | ipDiffServCodePoint        |
       |203 | mplsTopLabelExp            |
       |244 | dot1qPriority              |
       +----+----------------------------+


    - 0x05 = MAXRATE_IN_PROFILE_MARKING
      08-bit                = IPFIX Element Identifier
      08-bit                = size, in octets, of the value field
      variable-length field = contains actual value

      00 Identifier = drop, variable-length for this id is 0.

       +----+----------------------------+
       | ID | Name                       |
       +----+----------------------------+
       |195 | ipDiffServCodePoint        |
       |203 | mplsTopLabelExp            |
       |244 | dot1qPriority              |
       +----+----------------------------+


    - 0x06 = MAXRATE_OUT_PROFILE_MARKING
      08-bit                = IPFIX Element Identifier
      08-bit                = size, in octets, of the value field
      variable-length field = contains actual value

      00 Identifier = drop, variable-length for this id is 0.

       +----+----------------------------+
       | ID | Name                       |
       +----+----------------------------+
       |195 | ipDiffServCodePoint        |
       |203 | mplsTopLabelExp            |
       |244 | dot1qPriority              |
       +----+----------------------------+


      In the case when MINRATE_IN_PROFILE_MARKING,



Shah, et al.               Expires May 4, 2016                 [Page 13]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


      MINRATE_OUT_PROFILE_MARKING, MAXRATE_IN_PROFILE_MARKING and
      MAXRATE_OUT_PROFILE_MARKING are all advertised,
          - MINRATE_IN_PROFILE_MARKING takes highest precedence
            (that is over MAXRATE_IN_PROFILE_MARKING)

          - MAXRATE_IN_PROFILE_MARKING takes precedence over
            MINRATE_OUT_PROFILE_MARKING

          - and MAXRATE_OUT_PROFILE_MARKING takes precedence over
            MINRATE_OUT_PROFILE_MARKING


    - 0x07  = DROP_THRESHOLD
      03-bit count of drop-priority fields to follow with
               (type, type-value, burst size) tuple

      04-bit, drop priority type
        08-bit                = IPFIX Element Identifier
        08-bit                = size, in octets, of the value field
        variable-length field = contains actual value
        32-bit                = Burst Size
                                (32-bit IEEE floating point number)

       +----+----------------------------+
       | ID | Name                       |
       +----+----------------------------+
       |195 | ipDiffServCodePoint        |
       |203 | mplsTopLabelExp            |
       |244 | dot1qPriority              |
       +----+----------------------------+

      This finer granular drop threshold does not require separate
      buffer space from the aggregate buffer space. It is just an
      indicator beyond which code-point specific traffic to be
      discarded when occupancy of aggregate buffers reached to that
      threshold.

    - 0x08 = RELATIVE_PRIORITY
      04-bit, priority value
              lower the value, higher the priority

      Relative priority indicates scheduling priority. For example
      voice traffic, which requires lowest latency compared to any
      other traffic, may have lowest value advertised in relative
      priority. For two different traffic classification groups
      where one application group may be considered more important
      than the other but from a scheduling perspective does not
      require to be distinguished with a different priority, relative



Shah, et al.               Expires May 4, 2016                 [Page 14]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


      priority for those classification groups may be advertised with
      the same value.



    - 0x09 = SUB_TRAFFIC_CLASSES
      variable-length, repeats all content described above from Traffic
                       Class count onwards.

      For SLAs where a specific Traffic Class may further have
      different sub-services for a sub-group of Classifier Elements,
      this service type SHOULD be used to further divide Traffic Class
      in multiple sub-classes. Each sub-class is then defined with
      their own classifier elements and service types.


4.  Originating SLA Notification

   The QoS attribute MUST only be added by the originator and MUST NOT
   be added during BGP propagation.

   SLA messages SHOULD NOT be sent periodically just for the purpose of
   keep alive.  Some sort of SLA policy change may be considered as a
   trigger for the advertisement.

   For any modified SLA parameters, the originator MUST re-advertise the
   entire set of SLA parameters.  There is no provision to advertise
   partial set of parameters.  To invalidate previously advertised SLA
   parameters, a message MUST be sent with the same SLA id for the same
   source with the Traffic Class count set to 0.

4.1.  SLA Contexts

   In certain cases, the advertisement may relate to an SLA for
   aggregate traffic over a point-to-point connection between a specific
   destination and a specific source.  A point-to-point connection may
   be the physical link, that connects two BGP peers, or may be a
   virtual link (e.g. a tunnel).  A BGP update message, in such cases,
   with source AS number and NLRI prefix of source end-point can
   uniquely identify physical/virtual link and so establishes advertised
   SLA's context for that point to point link.

   In the simplest case where Provider (e.g.  PE) and Customer (e.g.
   CE) devices are directly connected via a physical link and have only
   a single link between them, CE can uniquely identify the forwarding
   link to PE with AS number of the PE and NLRI prefix being an IP
   address of PE, to CE (that is the next hop address from CE to PE).
   SLA advertised thru BGP update message from PE to CE, with PE's AS



Shah, et al.               Expires May 4, 2016                 [Page 15]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


   number and IP address, establishes SLA context for the aggregate
   traffic through link CE to PE.  SLA advertised thru BGP update
   message from PE to CE, with PE's AS number and any other prefix
   establishes SLA for that specific prefix, subset of traffic under CE
   to PE link.

   Even though this example is in the context of IP prefixes, SLA
   exchange does not have to be limited to the IP address family (IPv4
   and IPv6).  SLA advertisement is generic to all forms of NLRI types
   that are supported by the BGP protocol specification (like IPv4,
   IPv6, VPN-IPv4, VPN-IPv6).

4.1.1.  SLA Advertisement for Point-to-Point Connection

   When SLA messages are intended to be advertised for the point-to-
   point connection (physical or logical), the message is destined for
   the next hop and advertised message is in the context of the prefix
   of the source end-point of the point to point connection.

   The destination AS number set to, within QoS SLA attribute, typically
   is of the neighbor BGP speaker's.  Alternatively, source AS and
   destination AS count MAY be set to 0.

4.1.2.  SLA Advertisement for Destination AS Multiple Hops Away

   When SLA messages are to be advertised beyond next hop, value of
   source AS, in the QoS attribute, MUST be set by the originator of the
   update message.  If such an update is meant to be for a specific list
   of AS(es) as receivers, then the list of destination AS MUST be
   explicitly described in the QoS attribute message to avoid flooding
   of the QoS attribute data in the network beyond those destinations.

   When a new prefix is added in the AS, AS for which SLA parameters
   have already been advertised before for other existing prefixes, and
   if traffic to this new prefix is subject to the same SLA advertised
   earlier then BGP update for this new prefix may include QoS attribute
   containing just an SLA id, an id that was advertised earlier.  The
   corresponding Update message does not require to have the whole SLA
   content.  SLA id is sufficient to relate SLA parameters to new
   advertised prefix.

5.  SLA Attribute Handling at Forwarding Nodes

5.1.  BGP Node Capable of Processing QoS Attribute

   If a BGP node is capable of processing QoS attribute, it optionally
   MAY process the QoS attribute.  If advertised SLA has a list of
   destination ASes, it MAY trim the list and so count of destination AS



Shah, et al.               Expires May 4, 2016                 [Page 16]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


   to exclude ones that are not required in further announcement of BGP
   updates.

   BGP node MUST drop SLA related sub-type from the QoS attribute, if
   there is no more AS from the destination list in the forwarding path.
   The rest of the QoS attribute contents MAY be forwarded if there
   exist other sub-types of QoS attribute and forwarding rules meets
   other sub-types requirements.  If there is no other sub-types in the
   QoS attribute content then the node MUST drop the entire QoS
   attribute all together.  The other attributes and NLRI information
   may be announced further if they meet rules defined by other
   attributes and BGP protocol.

   Except extracting the entire SLA sub-type of the QoS attribute and
   trimming the list of destination AS list, all other content MUST NOT
   be modified by any intermediate receivers of the message.

5.2.  SLA Attribute Handling at Receiver

   Reception of and processing of advertised QoS SLA content are
   optional for the receiver.

      While reacting to SLA advertisement
      - receiver SHOULD invalidate previous advertised SLA parameters if
        one exists for the same SLA id and source AS. If the new
        advertised SLA has a non-zero traffic count, then the new
        advertised SLA SHOULD be installed. If new advertised SLA update
        is with Traffic Class count 0, then no action is required.

      - When BGP update messages are triggered only as a result of SLA
        policy change, BGP update message forwarding beyond intended
        receivers are not necessary. If receiver device implementation
        supports policy based filtering then receiver MAY implement a
        policy to filter such messages based on prefix and attribute.

   If SLA advertised to the next hop neighbor, the receiver may
   implement advertised SLA for the whole link, where the link could be
   physical or virtual link, connected to the neighbor.  If SLA
   advertised to is not the next hop neighbor then receiver may
   establish advertised SLA for that specific prefix list under the
   relevant link.  It is completely up to the receiver to decide for
   which prefixes it should accept advertised SLA and for which ones it
   won't.








Shah, et al.               Expires May 4, 2016                 [Page 17]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


6.  Error Handling

   Error conditions, while processing of the QoS attribute, SHALL be
   handled with the approach of attribute-discard as described in [IDR-
   ERR].  In such condition, receiver SHOULD also cleanup any previously
   installed SLA state for the same prefix.

7.  Traffic Class Mapping

   It is possible that switching/routing methods used in 2 different
   ASes could be different.  For example, Provider may tunnel Customer's
   IP traffic thru MPLS cloud.  In such cases traffic class definition
   for QoS services may differ in both ASes.  For the meaningful use of
   advertised SLA in such cases, receiver is required to map traffic
   class from one type to the other.

   In the example given, traffic classification in Customer AS could be
   IP Diffserv-based whereas traffic classification in Provider AS could
   be MPLS TC-based.  Thus for advertised MPLS TC-based SLA would
   require to map traffic class from IP Diffserv-based to MPLS TC type
   [RFC3270].

   There are well-defined recommendations that exist for traffic class
   mapping between two technologies, eg.  RFC3270 for mapping between
   DSCP and MPLS TC.  Receiver MAY use those defined recommendations for
   traffic class mapping or MAY define its own as per its network
   Traffic Class service definition to map to advertised Traffic
   Classes.  It is completely up to the receiver how to define such
   traffic class mapping.

8.  Deployment Considerations

   One of the use cases is for a Provider to advertise contracted SLA
   parameters to Customer Edge (CE) in cases where eBGP is deployed
   between PE and CE.  The SLA parameters may already be provisioned by
   the provider on the PE device (facing CE).  This provisioned SLA
   parameters are then advertised thru proposed BGP QoS attribute to the
   CE device.  CE device may read the attribute and SLA sub-type content
   to implement the QoS policy on the device.

   Contracted SLA from PE to CE may be full line-rate or sub line-rate
   or finer granular controlled services.  SLA advertise can be useful
   when contracted service is sub-rate of a link and/or when for finer
   granular traffic classes that are controlled (e.g. voice, video
   services may be capped to certain rate)






Shah, et al.               Expires May 4, 2016                 [Page 18]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


                                    _______________
                __________         /               \
               /          \       /                 \
              /            \     /                   \
              |CustomerSite|-----|      Provider     |
              \           C/E   P\E                  /
               \__________/       \                 /
                                   \_______________/
                   AS 3                   AS 2


                                  SLA_ADVERTISE: AS2 to AS3
                                                 NLRI = PE ip address


   Another use case can be to advertise SLAs among different network
   sites within one Enterprise network.  In Hub and Spoke deployments,
   Administrator may define SLAs at spoke and advertise QoS SLA
   parameters to the Hub thru BGP updates.  In the figure below, each
   spoke (AS1 and AS2) are connected to Hub (AS3) via a VPN tunnel.  As
   shown, AS2 can advertise SLA to AS3 in the context of that tunnel ip
   address.



                                                       AS 2
                              _______________        ________
                             /               \      /        \
           __________       /                 \-----| Spoke2 |
          /          \     /                   \    \________/
          |    Hub   |-----|      Provider     |     ________
          \__________/     \                   /    /        \
                            \                 /-----| Spoke1 |
              AS 3           \_______________/      \________/

                                                       AS 1


                                SLA_ADVERTISE: AS2 to AS3
                                               NLRI = AS2 tunnel address

                                SLA_ADVERTISE: AS1 to AS3
                                               NLRI = AS1 tunnel address


   Deployment options are not limited to involving CEs, PE-to-CE or CE-
   to-CE, only.  For any contract between two providers, SLA parameters
   may be advertised from one to the other.



Shah, et al.               Expires May 4, 2016                 [Page 19]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


9.  Acknowledgements

   Thanks to Fred Baker, David Black, Sue Hares and Benoit Claise for
   their suggestions and to Christian Jacquenet, Ken Briley, Rahul
   Patel, Fred Yip, Lou Berger, Brian Carpenter, Bertrand Duvivier,
   Bruno Decraene for the review.

10.  IANA Considerations

   This document defines a new BGP optional transitive path attribute,
   called QoS Attribute.  IANA action is required to allocate a new
   code-point in the BGP path Attributes registry.

   IANA is requested to create a registry for QoS Attribute subTypes.
   This is a registry of 1 octet value, to be assigned on a standards
   action/early allocation basis.  The initial assignments are:

             QoS Attribute subTypes
             - - - - - - - - - - - -
             Reserved                        0x00
             SLA                             0x01


   IANA is requested to create a registry for SLA Event Types.  This is
   a registry of 4-bits value, to be assigned on a standards action/
   early allocation basis.  The initial assignments are:

             QoS Attribute SLA Event Types
             - - - - - - - - - - - - - - -
             Reserved                        0x00
             ADVERTISE                       0x01


   IANA is requested to create a registry to define QoS SLA Direction.
   This is the direction in forwarding path, advertised QoS SLA is
   applicable to.

             QoS SLA Direction
             - - - - - - - - -
             Reserved                          0x00
             to Source AS from destination AS  0x01
             from source AS to destination AS  0x02


   QoS SLA Traffic Class Element Types will be referring to existing
   IPFIX IANA types as described in section 3.1.





Shah, et al.               Expires May 4, 2016                 [Page 20]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


   IANA is requested to create a registry for QoS SLA Traffic Class
   Service Types.  This is a registry of 2 octet values, to be assigned
   on a standards action/early allocation basis.  The initial
   assignments are:

             Traffic Class Service Type
             - - - - - - - - - - - - - -
             Reserved                        0x00
             TRAFFIC_CLASS_TSPEC             0x01
             L2_OVERHEAD                     0x02
             MINRATE_IN_PROFILE_MARKING      0x03
             MINRATE_OUT_PROFILE_MARKING     0x04
             MAXRATE_IN_PROFILE_MARKING      0x05
             MAXRATE_OUT_PROFILE_MARKING     0x06
             DROP_THRESHOLD                  0x07
             RELATIVE_PRIORITY               0x08
             SUB_TRAFFIC_CLASSES             0x09


11.  Security Considerations

   The QOS attribute defined in this document SHOULD be used by the
   managed networks for enforcing Quality of Service Policies and so
   there should not be any risks for identity thefts.  To strengthen the
   security for the QOS attribute, RPKI based origin validation
   [RFC7115] MAY be used.  In addition to the RPKI based origin
   validation, BGP Path Validation [I-D.ietf-sidr-bgpsec-protocol]
   procedures could be used over BGP QOS attribute and its associated
   prefix in producing the digital signature that can be carried within
   the signature SLA for the messages.  This would help prevent any man-
   in-the-middle attracks.

12.  References

12.1.  Normative References

   [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>.

   [RFC2212]  Shenker, S., Partridge, C., and R. Guerin, "Specification
              of Guaranteed Quality of Service", RFC 2212,
              DOI 10.17487/RFC2212, September 1997,
              <http://www.rfc-editor.org/info/rfc2212>.






Shah, et al.               Expires May 4, 2016                 [Page 21]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


   [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, DOI 10.17487/RFC3270, May 2002,
              <http://www.rfc-editor.org/info/rfc3270>.

   [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>.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
              2006, <http://www.rfc-editor.org/info/rfc4364>.

   [RFC4506]  Eisler, M., Ed., "XDR: External Data Representation
              Standard", STD 67, RFC 4506, DOI 10.17487/RFC4506, May
              2006, <http://www.rfc-editor.org/info/rfc4506>.

   [RFC5102]  Quittek, J., Bryant, S., Claise, B., Aitken, P., and J.
              Meyer, "Information Model for IP Flow Information Export",
              RFC 5102, DOI 10.17487/RFC5102, January 2008,
              <http://www.rfc-editor.org/info/rfc5102>.

   [RFC7115]  Bush, R., "Origin Validation Operation Based on the
              Resource Public Key Infrastructure (RPKI)", BCP 185,
              RFC 7115, DOI 10.17487/RFC7115, January 2014,
              <http://www.rfc-editor.org/info/rfc7115>.

   [IDR-ERR]  Scudder, J., Chen, E., Mohapatra, P., and K. Patel,
              "Revised Error Handling for BGP UPDATE Message, I-D.draft-
              ietf-idr-error-handling", June 2012.

12.2.  Informative References

   [RFC2475]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
              and W. Weiss, "An Architecture for Differentiated
              Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
              <http://www.rfc-editor.org/info/rfc2475>.

   [RFC7297]  Boucadair, M., Jacquenet, C., and N. Wang, "IP
              Connectivity Provisioning Profile (CPP)", RFC 7297,
              DOI 10.17487/RFC7297, July 2014,
              <http://www.rfc-editor.org/info/rfc7297>.

   [BGP-SEC]  Lepinski, M., "BGPsec Protocol Specification, I-D.draft-
              ietf-sidr-bgpsec-protocol", June 2015.




Shah, et al.               Expires May 4, 2016                 [Page 22]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


   [CPNP]     Boucadair, M. and C. Jacquenet, "Connectivity Provisioning
              Negotiation Protocol (CPNP), I-D.boucadair-connectivity-
              provisioning-protocol", Sep 2014.

   [BGPSLA-IMPL]
              Shah, S. and K. Patel, "Inter-domain SLA Exchange
              Implementation Report, I-D.draft-svshah-idr-sla-exchange-
              impl", Feb 2015.

Authors' Addresses

   Shitanshu Shah
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   US

   Email: svshah@cisco.com


   Keyur Patel
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   US

   Email: keyupate@cisco.com


   Sandeep Bajaj
   Juniper Networks
   1194 N. Mathilda Avenue
   Sunnyvale, CA  94089
   US

   Email: sbajaj@juniper.net


   Luis Tomotaki
   Verizon
   400 International
   Richardson, TX  75081
   US

   Email: luis.tomotaki@verizon.com






Shah, et al.               Expires May 4, 2016                 [Page 23]


Internet-Draft     Inter-domain SLA Exchange attribute     November 2015


   Mohamed Boucadair
   France Telecom
   Rennes 35000
   France

   Email: mohamed.boucadair@orange.com













































Shah, et al.               Expires May 4, 2016                 [Page 24]


Html markup produced by rfcmarkup 1.129c, available from https://tools.ietf.org/tools/rfcmarkup/