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Versions: (draft-boschi-ipfix-reducing-redundancy) 00 01 02 03 04 RFC 5473

IPFIX Working Group                                            E. Boschi
Internet-Draft                                            Hitachi Europe
Intended status: Informational                                   L. Mark
Expires: September 1, 2007                              Fraunhofer FOKUS
                                                               B. Claise
                                                     Cisco Systems, Inc.
                                                       February 28, 2007


             Reducing Redundancy in IPFIX and PSAMP Reports
              draft-ietf-ipfix-reducing-redundancy-03.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
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Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document describes a bandwidth saving method for exporting flow
   or packet information using the IP Flow Information Export (IPFIX)
   protocol.  As the PSAMP protocol is based on IPFIX, these
   considerations are valid for PSAMP exports as well.




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   This method works by separating information common to several flow
   records from information specific to an individual flow record.
   Common flow information is exported only once in a data record
   defined by an option template, while the rest of the specific flow
   information is associated with the common information via a unique
   identifier.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  IPFIX Documents Overview . . . . . . . . . . . . . . . . .  3
     1.2.  PSAMP Documents Overview . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Terminology Summary Table  . . . . . . . . . . . . . . . .  8
     2.2.  IPFIX Flows versus PSAMP Packets . . . . . . . . . . . . .  9
   3.  Specifications for bandwidth saving information export . . . .  9
     3.1.  Problem Statement and High Level Solution  . . . . . . . .  9
     3.2.  Data Reduction technique . . . . . . . . . . . . . . . . . 11
   4.  Transport Protocol Choice  . . . . . . . . . . . . . . . . . . 12
     4.1.  PR-SCTP  . . . . . . . . . . . . . . . . . . . . . . . . . 12
     4.2.  UDP  . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     4.3.  TCP  . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
   5.  commonPropertiesID Management  . . . . . . . . . . . . . . . . 13
   6.  The Collecting Process Side  . . . . . . . . . . . . . . . . . 14
     6.1.  UDP  . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     6.2.  TCP  . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
   7.  Advanced Techniques  . . . . . . . . . . . . . . . . . . . . . 16
     7.1.  Multiple Data Reduction  . . . . . . . . . . . . . . . . . 16
     7.2.  Cascading Common Properties  . . . . . . . . . . . . . . . 19
   8.  Export and Evaluation Considerations . . . . . . . . . . . . . 19
     8.1.  Transport Protocol Choice  . . . . . . . . . . . . . . . . 20
     8.2.  Reduced Size Encoding  . . . . . . . . . . . . . . . . . . 20
     8.3.  Efficiency Gain  . . . . . . . . . . . . . . . . . . . . . 20
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 21
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 21
   11. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 21
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 22
     12.2. Informative References . . . . . . . . . . . . . . . . . . 22
   Appendix A.  Examples  . . . . . . . . . . . . . . . . . . . . . . 23
     A.1.  Per Flow Data Reduction  . . . . . . . . . . . . . . . . . 23
     A.2.  Per Packet Data Reduction  . . . . . . . . . . . . . . . . 27
     A.3.  commonPropertiesID Template Withdrawal Message . . . . . . 30
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31
   Intellectual Property and Copyright Statements . . . . . . . . . . 32





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1.  Introduction

   The IPFIX working group has specified a protocol to export IP Flow
   information [I-D.ietf-ipfix-protocol].  This protocol is designed to
   export information about IP traffic flows and related measurement
   data, where a flow is defined by a set of key attributes (e.g. source
   and destination IP address, source and destination port, etc.).
   However, thanks to its template mechanism, the IPFIX protocol can
   export any type of information, as long as the information element is
   specified in the IPFIX Information Model [I-D.ietf-ipfix-protocol] or
   registered with IANA.

   Regardless of the fields content, flow records with common properties
   export the same fields in every single data record.  These common
   properties may represent values common to a collection of flows or
   packets, or values that are invariant over time.  Note that the
   common properties don't represent the list of flow keys, which are
   used to define a flow definition: however, the common properties may
   contain some of the flow keys.  The reduction of redundant data from
   the export stream can result in a significant reduction of the
   transferred data.

   This draft specifies a way to export these invariant or common
   properties only once, while the rest of the flow specific properties
   are exported in regular data records.  Unique common properties
   identifiers are used to link data records and the common attributes.

   The proposed method is applicable to IPFIX flow and to PSAMP per
   packet information, without any changes to both the IPFIX and PSAMP
   protocol specifications.

1.1.  IPFIX Documents Overview

   The IPFIX Protocol [I-D.ietf-ipfix-protocol] provides network
   administrators with access to IP flow information.  The architecture
   for the export of measured IP flow information out of an IPFIX
   exporting process to a collecting process is defined in the IPFIX
   Architecture [I-D.ietf-ipfix-architecture], per the requirements
   defined in RFC 3917 [RFC3917].  The IPFIX Architecture
   [I-D.ietf-ipfix-architecture] specifies how IPFIX data record and
   templates are carried via a congestion-aware transport protocol from
   IPFIX exporting processes to IPFIX collecting process.  IPFIX has a
   formal description of IPFIX information elements, their name, type
   and additional semantic information, as specified in the IPFIX
   Information Model [I-D.ietf-ipfix-info].  Finally the IPFIX
   Applicability Statement [I-D.ietf-ipfix-as] describes what type of
   applications can use the IPFIX protocol and how they can use the
   information provided.  It furthermore shows how the IPFIX framework



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   relates to other architectures and frameworks.

1.2.  PSAMP Documents Overview

   The document "A Framework for Packet  Selection and Reporting"
   [I-D.ietf-psamp-framework], describes the PSAMP framework for network
   elements to select subsets of packets by statistical and other
   methods, and to export a stream of reports on the selected packets to
   a collector.  The set of packet selection techniques (sampling,
   filtering, and hashing) supported by PSAMP are described in "Sampling
   and Filtering Techniques for IP Packet Selection"
   [I-D.ietf-psamp-sample-tech].  The PSAMP protocol
   [I-D.ietf-psamp-protocol] specifies the export of packet information
   from a PSAMP exporting process to a PSAMP collecting process.  Like
   IPFIX, PSAMP has a formal description of its information elements,
   their name, type and additional semantic information.  The PSAMP
   information model is defined in [I-D.ietf-psamp-info].  Finally
   [I-D.ietf-psamp-mib] describes the PSAMP Management Information Base.


2.  Terminology

   The terms in this section are in line with the IPFIX terminology
   section in the IPFIX [I-D.ietf-ipfix-protocol], and PSAMP
   [I-D.ietf-psamp-protocol] protocol specifications.  Note that this
   document selected the IPFIX definition of the term Exporting Process
   [I-D.ietf-ipfix-protocol], as this definition is more generic than
   the PSAMP definition [I-D.ietf-psamp-protocol].

   Observation Point:   An Observation Point is a location in the
      network where IP packets can be observed.  Examples include: a
      line to which a probe is attached, a shared medium, such as an
      Ethernet-based LAN, a single port of a router, or a set of
      interfaces (physical or logical) of a router.  Note that every
      Observation Point is associated with an Observation Domain
      (defined below), and that one Observation Point may be a superset
      of several other Observation Points.  For example one Observation
      Point can be an entire line card.  That would be the superset of
      the individual Observation Points at the line card's interfaces.

   Observation Domain:   An Observation Domain is the largest set of
      Observation Points for which Flow information can be aggregated by
      a Metering Process.  For example, a router line card may be an
      Observation Domain if it is composed of several interfaces, each
      of which is an Observation Point.  In the IPFIX Message it
      generates, the Observation Domain includes its Observation Domain
      ID, which is unique per Exporting Process.  That way, the
      Collecting Process can identify the specific Observation Domain



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      from the Exporter that sends the IPFIX Messages.  Every
      Observation Point is associated with an Observation Domain.  It is
      RECOMMENDED that Observation Domain IDs are also unique per IPFIX
      Device.

   IP Traffic Flow or Flow:   There are several definitions of the term
      'flow' being used by the Internet community.  Within the context
      of IPFIX we use the following definition:

      A Flow is defined as a set of IP packets passing an Observation
      Point in the network during a certain time interval.  All packets
      belonging to a particular Flow have a set of common properties.
      Each property is defined as the result of applying a function to
      the values of:

      1.  one or more packet header field (e.g. destination IP address),
          transport header field (e.g. destination port number), or
          application header field (e.g.  RTP header fields [RFC3550])

      2.  one or more characteristics of the packet itself (e.g. number
          of MPLS labels, etc...)

      3.  one or more of fields derived from packet treatment (e.g. next
          hop IP address, the output interface, etc...)

      A packet is defined to belong to a Flow if it completely satisfies
      all the defined properties of the Flow.

      This definition covers the range from a Flow containing all
      packets observed at a network interface to a Flow consisting of
      just a single packet between two applications.  It includes
      packets selected by a sampling mechanism.

   Flow Record:   A Flow Record contains information about a specific
      Flow that was observed at an Observation Point.  A Flow Record
      contains measured properties of the Flow (e.g. the total number of
      bytes for all the Flow's packets) and usually characteristic
      properties of the Flow (e.g. source IP address).

   Metering Process:   The Metering Process generates Flow Records.
      Inputs to the process are packet headers and characteristics
      observed at an Observation Point, and packet treatment at the
      Observation Point (for example the selected output interface).

      The Metering Process consists of a set of functions that includes
      packet header capturing, timestamping, sampling, classifying, and
      maintaining Flow Records.




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      The maintenance of Flow Records may include creating new records,
      updating existing ones, computing Flow statistics, deriving
      further Flow properties, detecting Flow expiration, passing Flow
      Records to the Exporting Process, and deleting Flow Records.

   Exporting Process:   The Exporting Process sends Flow Records to one
      or more Collecting Processes.  The Flow Records are generated by
      one or more Metering Processes.

   Exporter:   A device which hosts one or more Exporting Processes is
      termed an Exporter.

   IPFIX Device:   An IPFIX Device hosts at least one Exporting Process.
      It may host further Exporting processes and arbitrary numbers of
      Observation Points and Metering Process.

   Collecting Process:   A Collecting Process receives Flow Records from
      one or more Exporting Processes.  The Collecting Process might
      process or store received Flow Records, but such actions are out
      of scope for this document.

   Template:   Template is an ordered sequence of (type, length) pairs,
      used to completely specify the structure and semantics of a
      particular set of information that needs to be communicated from
      an IPFIX Device to a Collector.  Each Template is uniquely
      identifiable by means of a Template ID.

   Template Record:   A Template Record defines the structure and
      interpretation of fields in a Data Record.

   Data Record:   A Data Record is a record that contains values of the
      parameters corresponding to a Template Record.

   Options Template Record:   An Options Template Record is a Template
      Record that defines the structure and interpretation of fields in
      a Data Record, including defining how to scope the applicability
      of the Data Record.

   Set:   Set is a generic term for a collection of records that have a
      similar structure.  In an IPFIX Message, one or more Sets follow
      the Message Header.  There are three different types of Sets:
      Template Set, Options Template Set, and Data Set.

   Template Set:   A Template Set is a collection of one or more
      Template Records that have been grouped together in an IPFIX
      Message.





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   Options Template Set:   An Options Template Set is a collection of
      one or more Options Template Records that have been grouped
      together in an IPFIX Message.

   Data Set:   A Data Set is one or more Data Records, of the same type,
      that are grouped together in an IPFIX Message.  Each Data Record
      is previously defined by a Template Record or an Options Template
      Record.

   Information Element:   An Information Element is a protocol and
      encoding independent description of an attribute which may appear
      in an IPFIX Record.  The IPFIX information  model
      [I-D.ietf-ipfix-info] defines the base set of Information Elements
      for IPFIX.  The type associated with an Information Element
      indicates constraints on what it may contain and also determines
      the valid encoding mechanisms for use in IPFIX.

   Observed Packet Stream:   The Observed Packet Stream is the set of
      all packets observed at the Observation Point.

   Packet content:   The packet content denotes the union of the packet
      header (which includes link layer, network layer and other
      encapsulation headers) and the packet payload.

   Selection Process:   A Selection Process takes the Observed Packet
      Stream as its input and selects a subset of that stream as its
      output.

   Selector:   A Selector defines the action of a Selection Process on a
      single packet of its input.  If selected, the packet becomes an
      element of the output Packet Stream.

      The Selector can make use of the following information in
      determining whether a packet is selected:

      1.  the Packet Content;

      2.  information derived from the packet's treatment at the
          Observation Point;

      3.  any selection state that may be maintained by the Selection
          Process.

   PSAMP Device:   A PSAMP Device is a device hosting at least an
      Observation Point, a Selection Process and an Exporting Process.
      Typically, corresponding Observation Point(s), Selection
      Process(es) and Exporting Process(es) are co-located at this
      device, for example at a router.



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   Filtering:   A filter is a Selector that selects a packet
      deterministically based on the Packet Content, or its treatment,
      or functions of these occurring in the Selection State.  Examples
      include field match Filtering, and Hash-based Selection.

   Transport Session:   In SCTP, the transport session is known as the
      SCTP association, which is uniquely identified by the SCTP
      endpoints [RFC2960]; in TCP, the transport session is known as the
      TCP connection, which is uniquely identified by the combination of
      IP addresses and TCP ports used; In UDP, the transport session is
      known as the UDP session, which is uniquely identified by the
      combination of IP addresses and UDP ports used.

   commonPropertiesID:   The commonPropertiesID is an identifier of a
      set of common properties that is locally unique per Observation
      Domain and Transport Session.  Typically, this Information Element
      is used to link to information reported in separate Data Records.
      See the IPFIX information model [I-D.ietf-ipfix-info] for the
      Information Element definition.

   Common Properties:   Common Properties are a collection of one or
      more attributes shared by a set of different Flow Records.  Each
      set of Common Properties is uniquely identifiable by means of a
      commonPropertiesID.

   Specific Properties:   Specific Properties are a collection of one or
      more attributes reported in a Flow Record that are not included in
      the Common Properties defined for that Flow Record.

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

2.1.  Terminology Summary Table

   +------------------+---------------------------------------------+
   |                  |                 Contents                    |
   |                  +--------------------+------------------------+
   |       Set        |      Template      |         Record         |
   +------------------+--------------------+------------------------+
   |     Data Set     |          /         |     Data Record(s)     |
   +------------------+--------------------+------------------------+
   |   Template Set   | Template Record(s) |           /            |
   +------------------+--------------------+------------------------+
   | Options Template | Options Template   |           /            |
   |       Set        | Record(s)          |                        |
   +------------------+--------------------+------------------------+




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                         Terminology Summary Table

   A Data Set is composed of Data Record(s).  No Template Record is
   included.  A Template Record or an Options Template Record defines
   the Data Record.

   A Template Set contains only Template Record(s).

   An Options Template Set contains only Options Template Record(s).

2.2.  IPFIX Flows versus PSAMP Packets

   As described in the PSAMP protocol specification
   [I-D.ietf-psamp-protocol], the major difference between IPFIX and
   PSAMP is that the IPFIX protocol exports Flow Records while the PSAMP
   protocol exports Packet Records.  From a pure export point of view,
   IPFIX will not distinguish a Flow Record composed of several packets
   aggregated together from a Flow Record composed of a single packet.
   So the PSAMP export can be seen as special IPFIX Flow Record
   containing information about a single packet.

   For this document clarity, the term Flow Record represents a generic
   term expressing an IPFIX Flow Record or a PSAMP packet record, as
   foreseen by its definition.  However, when appropriate, a clear
   distinction between Flow Record or packet Record will be made.


3.  Specifications for bandwidth saving information export

   Several Flow Records often share a set of Common Properties.
   Repeating the information about these Common Properties for every
   Flow Record introduces a huge amount of redundancy.  This document
   proposes a method to reduce this redundancy.

   The PSAMP specifications are used for the export of per-packet
   information, exporting the specific observed packet in an IPFIX Flow
   Record.  This can be considered as a special Flow Record case,
   composed of a single packet.  Therefore, the method described in this
   document is also applicable to per packet data reduction, e.g. for
   export of One Way Delay (OWD) measurements (see Appendix), trajectory
   sampling, etc.

3.1.  Problem Statement and High Level Solution

   Consider a set of properties "A", e.g. common sourceAddressA and
   sourcePortA, equivalent for each Flow Records exported.  Figure 2
   shows how this information is repeated with classical IPFIX Flow
   Records, expressing the waste of bandwidth to export redundant



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   information.

   +----------------+-------------+---------------------------+
   | sourceAddressA | sourcePortA |     <Flow1 information>   |
   +----------------+-------------+---------------------------+
   | sourceAddressA | sourcePortA |     <Flow2 information>   |
   +----------------+-------------+---------------------------+
   | sourceAddressA | sourcePortA |     <Flow3 information>   |
   +----------------+-------------+---------------------------+
   | sourceAddressA | sourcePortA |     <Flow4 information>   |
   +----------------+-------------+---------------------------+
   |      ...       |     ...     |            ...            |
   +----------------+-------------+---------------------------+

        Figure 2: Common and Specific Properties exported together

   Figure 3 shows how this information is exported when applying the
   specifications of this document.  The Common Properties are separated
   from the Specific Properties for each Flow Record.  The Common
   Properties would be exported only once in a specific Data Record
   (defined by an Option Template), while each Flow Record contains a
   pointer to the Common Properties A, along with its Flow specific
   information.  In order to maintain the relationship between these
   sets of properties, we introduce indices (in this case: index for
   properties A) for the Common Properties that are unique for all
   Common Properties entries within an Observation Domain.  The purpose
   of the indices is to serve as a "key" identifying "rows" of the
   Common Properties table.  The rows are then referenced by the
   Specific Properties by using the appropriate value for the Common
   Properties identifier.

   +------------------------+-----------------+-------------+
   | index for properties A | sourceAddressA  | sourcePortA |
   +------------------------+-----------------+-------------+
   |          ...           |      ...        |     ...     |
   +------------------------+-----------------+-------------+


   +------------------------+---------------------------+
   | index for properties A |     <Flow1 information>   |
   +------------------------+---------------------------+
   | index for properties A |     <Flow2 information>   |
   +------------------------+---------------------------+
   | index for properties A |     <Flow3 information>   |
   +------------------------+---------------------------+
   | index for properties A |     <Flow4 information>   |
   +------------------------+---------------------------+




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       Figure 3: Common and Specific Properties exported separately

   This unique export of the Common Properties results in a decrease of
   the bandwidth requirements for the path between the Exporter and the
   Collector.

3.2.  Data Reduction technique

   The IPFIX protocol [I-D.ietf-ipfix-protocol] is Template based.
   Templates define how data should be exported, describing data fields
   together with their type and meaning.  IPFIX specifies two types of
   Templates: the Template Record and the Options Template Record.  The
   difference between the two is that the Options Template Record
   includes the notion of scope, defining how to scope the applicability
   of the Data Record.  The scope, which is only available in the
   Options Template Record, gives the context of the reported
   Information Elements in the Data Records.  The Template Records and
   Options Template Records are necessary to decode the Data Records.
   Indeed, by only looking at the Data Records themselves, this is
   impossible to distinguish a Data Record defined by Template Record
   from a Data Record defined by an Option Template Record.  To export
   information more efficiently, this specification proposes to group
   Flow Records by their common properties.  We define Common Properties
   as a collection of attributes shared by a set of different Flow
   Records.

   An implementation using the proposed specification MUST follow the
   IPFIX transport protocol specifications defined in the IPFIX protocol
   [I-D.ietf-ipfix-protocol].

   As explained in Figure 4, the information is split into two parts,
   using two different Data Records.  Common Properties MUST be exported
   via Data Records defined by an Option Template Record.  Like Template
   Records, they MUST be sent only once per SCTP association or TCP
   connection, and MUST be sent reliably via SCTP if SCTP is the
   transport protocol.  These properties represent values common to
   several Flow Records (e.g.  IP source and destination address).  The
   Common Properties Data Records MUST be sent prior to the
   corresponding Specific Properties Data Records.  The Data Records
   reporting Specific Properties MUST be associated with the Data
   Records reporting the Common Properties using a unique identifier for
   the Common Properties, the commonPropertiesID Information Element
   [I-D.ietf-ipfix-info].  The commonPropertiesID MUST be exported as
   the scope in the Options Template Record, and also exported in the
   associated Template Record.






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  +---------------------------+      +---------------------+
  | Common Properties         |      | Specific Properties |  Template
  | Option Template Record    |      | Template Record     |  Definition
  |                           |      |                     |
  | scope: commonPropertiesID |      | commonPropertiesID  |
  | Common Properties         |      | Specific Properties |
  +------------+--------------+      +---------+-----------+
  .............|...............................|.......................
               |                               |
  +------------v-------------+      +----------v----------+
  | Common Properties        |      | Specific Properties |+  Exported
  | Data Record              |------> Data Records        ||  Data
  +--------------------------+      +---------------------+|  Records
                                     +---------------------+


          Figure 4: Template Record and Data Record dependencies

   From the IPFIX protocol, there are no differences between the per
   Flow or per packet data reduction, except maybe the terminology where
   the Specific Properties could be called packet Specific Properties in
   the previous figure.


4.  Transport Protocol Choice

   This document follows the IPFIX transport protocol specifications
   defined in the IPFIX protocol [I-D.ietf-ipfix-protocol].  However,
   depending on the transport protocol choice, this document imposes
   some more constraints.  If PR-SCTP is selected as the IPFIX protocol,
   the SCTP sub-section specifications MUST be respected.  If UDP is
   selected as the IPFIX protocol, the UDP sub-section specifications
   MUST be respected.  If TCP is selected as the IPFIX protocol, the TCP
   sub-section specifications MUST be respected.

4.1.  PR-SCTP

   The active Common Properties MUST be sent after the SCTP association
   establishment before the corresponding Specific Properties Data
   Records.  In case of SCTP association re-establishment, all active
   Common Properties MUST be re-sent before the corresponding Specific
   Properties Data Records.

   The Common Properties Data Records MUST be sent reliably.







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4.2.  UDP

   Common Properties Data Records MUST be re-sent at regular intervals,
   whose frequency MUST be configurable.  The default value for the
   frequency of Common Properties transmission (refresh timeout) is 10
   minutes.

   The Exporting Process SHOULD transmit the Common Properties
   definition in advance of any Data Record that use these Common
   Properties, to help ensure that the Collector has the Common
   Properties definition before receiving the first associated Data
   Record.

   If a commonPropertiesID is not used anymore the Exporting Process
   stops re-sending the related Common Properties Data Record.  The old
   commonPropertiesID MUST NOT be used until its lifetime (see
   Section 6.1) has expired.

4.3.  TCP

   Common Properties MUST be sent after the TCP connection establishment
   before the corresponding Specific Properties Data Records.  In case
   of TCP connection re-establishment, all active Common Properties MUST
   be re-sent before the corresponding Specific Properties Data Records.


5.  commonPropertiesID Management

   The commonPropertiesId is an identifier of a set of common properties
   that is locally unique per Observation Domain and Transport Session.
   The Exporting Process MUST manage the commonPropertiesIDs allocations
   for its Observation Domains and Transport Session.  Different
   Observation Domains from the same Exporter MAY use the same
   commonPropertiesID value to refer to different sets of Common
   Properties.

   The commonPropertiesID values MAY be assigned sequentially, but it is
   NOT REQUIRED.  Particular commonPropertiesID ranges or values MAY
   have explicit meanings for the IPFIX Device.  For example,
   commonPropertiesID values may be assigned based on the result of a
   hash function, etc...

   Using a 64 bit commonPropertiesID Information Element allows the
   export of 2**64 active sets of Common Properties, per Observation
   Domain and per Transport Session.

   commonPropertiesIDs that are not used anymore SHOULD be withdrawn.
   The Common Properties ID withdrawal message is a Data Record defined



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   by an Option Template consisting of only one scope field namely the
   commonPropertiesID (with a type of 137 [I-D.ietf-ipfix-info]) and no
   non-scope fields.


   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Set ID = 3            |      Length = 14 octets       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Template ID N           |       Field Count = 1         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Scope Field count = 1    |0|  commonPropertiesID = 137   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Scope 1 Field Length = 8     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                   commonPropertiesID Withdrawal Message

   If UDP is selected as the transport protocol, the commonPropertiesID
   Template Withdraw Messages MUST not be used, as this method is
   inefficient due to the unreliable nature of UDP.


6.  The Collecting Process Side

   This section describes the Collecting Process when using SCTP and PR-
   SCTP as the transport protocol.  Any necessary changes to the
   Collecting Process specifically related to TCP or UDP transport
   protocols are specified in the subsections.

   The Collecting Process MUST store the commonPropertiesId information
   for the duration of the association so that it can interpret the
   corresponding Data Records that are received in subsequent Data Sets.
   The Collecting Process can either store the Data Records as they
   arrive, without reconstructing the initial Flow Record, or
   reconstruct the initial Flow Record.  In the former case, there might
   be less storage capacity required at the Collector side.  In the
   latter case, the collector job is more complex and time-consuming due
   to the higher resource demand for record processing in real time.

   If the Collecting Process has received the Specific Properties Data
   Record before the associated Common Properties Data Record, the
   Collecting Process SHOULD store the Specific Properties Data Record
   and await the retransmission or out-of-order arrival of the Common
   Properties Data Record.




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   Common Properties IDs are unique per SCTP association and per
   Observation Domain.  If the Collecting Process receives a Common
   Properties ID which has already been received but which has not
   previously been withdrawn (i.e. a commonPropertiesID from the same
   Exporter Observation Domain received on the SCTP association), then
   the Collecting Process MUST shutdown the association.

   When an SCTP association is closed, the Collecting Process MUST
   discard all Common Properties IDs received over that association and
   stop decoding IPFIX Messages that use those Common Properties IDs.

   If a Collecting Process receives a Common Properties Withdrawal
   message, the Collecting Process MUST delete the corresponding Common
   Properties associated with the specific SCTP association and specific
   Observation Domain, and stop interpreting Data Records referring to
   those Common Properties.  The receipt of Data Records referring to
   Common Properties that have been withdrawn MUST be ignored and SHOULD
   be logged by the Collecting Process.

   If the Collecting Process receives a Common Properties Withdrawal
   message for a Common Properties that it has not received before on
   this SCTP assocation, it MUST reset the SCTP association, discard the
   IPFIX Message, and SHOULD log the error as it does for malformed
   IPFIX Messages.

6.1.  UDP

   The Collecting Process MUST associate a lifetime with each Common
   Property received via UDP.  Common Properties not refreshed by the
   Exporting Process within the lifetime are expired at the Collecting
   Process.

   If the Common Properties are not refreshed before that lifetime has
   expired, the Collecting Process MUST discard the corresponding
   definition of the commonPropertiesID and any current and future
   associated Data Records.  In which case, an alarm MUST be logged.

   The Collecting Process MUST NOT decode any further Data Records which
   are associated with the expired Common Properties.  If a Common
   Property is refreshed with a definition that differs from the
   previous definition, the Collecting Process SHOULD log a warning and
   replace the previous received Common Property with the new one.  The
   Common Property lifetime at the Collecting Process MUST be at least 3
   times higher than the refresh timeout of the Template used to export
   the Common Property definition, configured on the Exporting Process.

   The Collecting Process SHOULD accept Data Records without the
   associated Common Properties required to decode the Data Record.  If



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   the Common Properties have not been received at the time Data Records
   are received, the Collecting Process SHOULD store the Data Records
   for a short period of time and decode them after the Common
   Properties definitions are received.  The short period of time MUST
   be lower than the lifetime of definitions associated with identifiers
   considered unique within the UDP session.

6.2.  TCP

   When the TCP connection is reset, either gracefully or abnormally,
   the Collecting Processes MUST delete all commonPropertiesID values
   and associated Common Properties data corresponding to that
   connection.

   If a Collection Process receives a commonPropertiesID Withdraw
   message, the Collection Process MUST expire the related Common
   Properties data.


7.  Advanced Techniques

7.1.  Multiple Data Reduction

   A Flow Record can refer to one or more Common Properties sets; the
   use of multiple Common Properties can lead to more efficient exports.
   When sets of Common Properties are identified in the data, it may be
   found that there is more than one set of non-overlapping properties.

   Note that in the case of multiple Common Properties in one Data
   Record, the different sets of Common Properties MUST be disjoint
   (i.e.  MUST NOT have Information Elements in common), to avoid
   potential collisions.

   Consider a set of properties "A", e.g. common sourceAddressA and
   sourcePortA, and another set of properties "B", e.g.
   destinationAddressB and destinationPortB.  Figure 6 shows how this
   information is repeated with classical IPFIX export in several Flow
   Records.













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   +--------+--------+---------+---------+---------------------+
   |srcAddrA|srcPortA|destAddrB|destPortB| <Flow1 information> |
   +--------+--------+---------+---------+---------------------+
   |srcAddrA|srcPortA|destAddrC|destPortC| <Flow2 information> |
   +--------+--------+---------+---------+---------------------+
   |srcAddrD|srcPortD|destAddrB|destPortB| <Flow3 information> |
   +--------+--------+---------+---------+---------------------+
   |srcAddrD|srcPortD|destAddrC|destPortC| <Flow4 information> |
   +--------+--------+---------+---------+---------------------+
   |   ...  |   ...  |   ...   |   ...   |        ...          |
   +--------+--------+---------+---------+---------------------+



        Figure 6: Common and Specific Properties exported together

   Besides that other sets of Properties might be repeated as well (e.g.
   properties C and D in the figure above).

   We can separate the Common Properties into the properties A composed
   of sourceAddressA and sourcePortA, properties D composed of
   sourceAddressD and sourcePortD, and into the properties B composed of
   destinationAddressB and destinationPortB and properties C composed of
   destinationAddressC and destinationPortC,.  These four records can be
   expanded to four combinations of Data Records to reduce redundancy
   without the need to define four complete sets of Common Properties
   (see the figure below).  The more Common Properties sets are defined,
   the more combinations are available.























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   +-------------------+-----------------+-------------+
   | index for prop. A | sourceAddressA  | sourcePortA |
   +-------------------+-----------------+-------------+
   | index for prop. D | sourceAddressD  | sourcePortD |
   +-------------------+-----------------+-------------+

   +-------------------+---------------------+------------------+
   | index for prop. B | destinationAddressB | destinationPortB |
   +-------------------+---------------------+------------------+
   | index for prop. C | destinationAddressC | destinationPortC |
   +-------------------+---------------------+------------------+


   +-----------------+-----------------+-----------------------+
   |index for prop. A|index for prop. B|  <Flow1 information>  |
   +-----------------+-----------------+-----------------------+
   |index for prop. A|index for prop. C|  <Flow2 information>  |
   +-----------------+-----------------+-----------------------+
   |index for prop. D|index for prop. B|  <Flow3 information>  |
   +-----------------+-----------------+-----------------------+
   |index for prop. D|index for prop. C|  <Flow4 information>  |
   +-----------------+-----------------+-----------------------+


     Multiple Common (above) and Specific Properties (below) exported
                                separately

   The advantage of the multiple Common Properties is that the objective
   of reducing the bandwidth is met while the number of indexes is kept
   to a minimum.  Defining an extra index for all records would not
   bring to save bandwidth in the case of Figure 6 and is generally a
   less efficient solution.

   If a set of Flow Records share multiple sets of Common Properties,
   multiple commonPropertiesID instances MAY be used to increase export
   efficiency even further, as displayed in Figure 8.















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  +--------------------------- +      +---------------------+
  | Common Properties          |      | Specific Properties | Template
  | Option Template Record     |      | Template Record     | Definition
  |                            |      |                     |
  | Scope: commonPropertiesID1 |      | commonPropertiesID1 |
  | Scope: commonPropertiesID2 |      | commonPropertiesID2 |
  | Common Properties          |      | Specific Properties |
  +------------+---------------+      +--------+------------+
  .............|...............................|.......................
               |                               |
  +------------v-------------+      +----------v----------+
  | Common Properties        |      | Specific Properties |+  Exported
  | Data Record              |------> Data Records        ||  Data
  +------------------------- +      +---------------------+|  Records
                                     +---------------------+



                     Figure 8: Multiple Data Reduction

7.2.  Cascading Common Properties

   An Exporting Process MUST NOT export any set of Common Properties
   which contains, either directly or via other cascaded Common
   Properties, references to itself in its own definition (i.e., a
   circular definition).  When the Collecting Process receives Common
   Properties that reference other Common Properties, it MUST resolve
   the references to Common Properties.  If the Common Properties aren't
   available at the time Data Records are received, the Collecting
   Process SHOULD store the Data Records for a short period of time and
   decode them after the Common Properties are received.

   If the Collecting Process could not decode a cascading Common
   Properties definition because the referenced Common Properties are
   not available before the short period of time, then the Collecting
   Process SHOULD log the error.

   If the Collecting Process could not decode a cascading Common
   Properties definition because it detects a circular definition, then
   the Collecting Process SHOULD log the error.

   Information Element ordering MUST be preserved when creating and
   expanding Common Properties.


8.  Export and Evaluation Considerations

   The objective of the method specified in this document is the



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   reduction in the amount of measurement data that has to be
   transferred from the Exporter to the Collector.  Note that the
   efficiency of this method may vary, as discussed in this section.  In
   addition there might be less storage capacity required at the
   Collector side if the Collector decides to store the Data Records as
   they arrive, without reconstructing the initial Flow Record.

   On the other hand, this method requires additional resources on both
   the Exporter and the Collector.  The Exporter has to manage Common
   Properties information and to assign commonPropertiesId values.  The
   Collector has to process records described by two templates instead
   of just one.  Additional effort is also required when post processing
   the measurement data, in order to correlate Flow Records with Common
   Properties information.

8.1.  Transport Protocol Choice

   The proposed method is most effective using a reliable transport
   protocol for the transfer of the Common Properties.  Therefore the
   use of SCTP-PR with the reliable mode or TCP is recommended.
   However, if the path from the Exporting Process to the Collecting
   Process is not fully reliable, the SCTP or TCP retransmission might
   reduce the benefits of this specification.  If the path from the
   Exporting Process to the Collecting Process is full reliable, the use
   of UDP is less effective because the Common Properties have to be re-
   sent regularly.

8.2.  Reduced Size Encoding

   The transfer of the commonPropertiesIDs originates some overhead and
   might even increase the amount of exported data if the length of the
   commonPropertiesID field is not shorter than the length of the
   replaced fields.

   In cases where the range of the commonPropertiesID can be restricted,
   it is RECOMMENDED to apply reduced-size encoding to the
   commonPropertiesID, to achieve a further bandwidth efficiency gain.

8.3.  Efficiency Gain

   While the goal of this specification is to reduce the bandwidth, the
   efficiency might be limited.  Indeed, the efficiency gain is based on
   the numerous redundant information in Flows and would be directly
   proportional to the re-use of the defined commonPropertiesID values
   (In other words, the more we re-use a commonPropertiesID value, the
   better the efficiency gain), with a theoretical limit where all the
   Data Records would use a single commonPropertiesID.  While the
   Exporting Process can evaluate the direct gain for the Flow Records



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   to be exported, it cannot predict whether future Flow Records would
   contain the information specified by active commonPropertiesID
   values.  This implies that the efficiency factor of this
   specification is higher for specific applications where filtering is
   involved, such as one-way delay or trajectory sampling.

   Note that this technique might even lead to an increase in bandwidth
   usage under certain conditions.  Taking into account the overhead of
   exporting the commonPropertiesID values, if the commonPropertiesID
   values are not used in future Data Records, this technique would
   actually increase the export bandwidth.  A typical case would be the
   assignments of Common Properties based on past observed traffic,
   hoping that future Flows would contain the same characteristics.

   The efficiency gain depends also on the difference between the length
   of the replaced fields and the length of the commonPropertiesID.  The
   shorter is the length of commonPropertiesID with respect to the total
   length of the Common Properties fields, the bigger is the gain.

   The example in section Appendix A.2 below uses IPFIX to export
   measurement data for each received packet.  In that case, for a Flow
   of 1000 packets the amount of data can be decreased more than 26
   percent.


9.  IANA Considerations

   This document has no actions for IANA.


10.  Security Considerations

   The same security considerations as for the IPFIX Protocol
   [I-D.ietf-ipfix-protocol] apply.


11.  Acknowledgments

   The authors would like to thank Guido Pohl for initiating this work
   and for his contribution to early versions of this document.  Thanks
   also to Andrew Johnson, Gehrard Muenz, Brian Trammell and Paul Aitken
   for their comments and feedback.


12.  References






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12.1.  Normative References

   [I-D.ietf-ipfix-protocol]
              Claise, B., "Specification of the IPFIX Protocol for the
              Exchange", draft-ietf-ipfix-protocol-24 (work in
              progress), November 2006.

   [I-D.ietf-ipfix-info]
              Quittek, J., "Information Model for IP Flow Information
              Export", draft-ietf-ipfix-info-15 (work in progress),
              February 2007.

   [I-D.ietf-psamp-protocol]
              Claise, B., "Packet Sampling (PSAMP) Protocol
              Specifications", draft-ietf-psamp-protocol-07 (work in
              progress), October 2006.

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

12.2.  Informative References

   [I-D.ietf-ipfix-as]
              Zseby, T., "IPFIX Applicability", draft-ietf-ipfix-as-11
              (work in progress), February 2007.

   [I-D.ietf-ipfix-architecture]
              Sadasivan, G., "Architecture for IP Flow Information
              Export", draft-ietf-ipfix-architecture-12 (work in
              progress), September 2006.

   [I-D.ietf-psamp-info]
              Dietz, T., "Information Model for Packet Sampling
              Exports", draft-ietf-psamp-info-05 (work in progress),
              October 2006.

   [I-D.ietf-psamp-sample-tech]
              Zseby, T., "Sampling and Filtering Techniques for IP
              Packet Selection", draft-ietf-psamp-sample-tech-07 (work
              in progress), July 2005.

   [I-D.ietf-psamp-mib]
              Dietz, T. and B. Claise, "Definitions of Managed Objects
              for Packet Sampling", draft-ietf-psamp-mib-06 (work in
              progress), June 2006.

   [I-D.ietf-psamp-framework]
              Duffield, N., "A Framework for Packet Selection and



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              Reporting", draft-ietf-psamp-framework-10 (work in
              progress), January 2005.

   [RFC2960]  Stewart, R., Xie, Q., Morneault, K., Sharp, C.,
              Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M.,
              Zhang, L., and V. Paxson, "Stream Control Transmission
              Protocol", RFC 2960, October 2000.

   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
              Jacobson, "RTP: A Transport Protocol for Real-Time
              Applications", STD 64, RFC 3550, July 2003.

   [RFC3917]  Quittek, J., Zseby, T., Claise, B., and S. Zander,
              "Requirements for IP Flow Information Export (IPFIX)",
              RFC 3917, October 2004.


Appendix A.  Examples

A.1.  Per Flow Data Reduction

   In this section we show how Flow information can be exported
   efficiently using the method described in this draft.  Let's suppose
   we have to periodically export data about two IPv6 Flows.

   In this example we report the following information:



   Flow|        dstIPv6Address                 | dst- |nPkts|nBytes
       |                                       | Port |     |
   ----------------------------------------------------------------
    A  |2001:DB8:80AD:5800:0058:0800:2023:1D71 |  80  | 30  |  6000
       |                                       |      |     |
    A  |2001:DB8:80AD:5800:0058:0800:2023:1D71 |  80  | 50  |  9500
       |                                       |      |     |
    B  |2001:DB8:80AD:5800:0058:00AA:00B7:AF2B | 1932 | 60  |  8000
       |                                       |      |     |
    A  |2001:DB8:80AD:5800:0058:0800:2023:1D71 |  80  | 40  |  6500
       |                                       |      |     |
    A  |2001:DB8:80AD:5800:0058:0800:2023:1D71 |  80  | 60  |  9500
       |                                       |      |     |
    B  |2001:DB8:80AD:5800:0058:00AA:00B7:AF2B | 1932 | 54  |  7600



   The Common Properties in this case are the destination IPv6 address
   and the destination port.  We first define an Option Template that



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   contains the following Information Elements:

   o  Scope: commonPropertiesID in [I-D.ietf-ipfix-info], with a type of
      137 and a length of 8 octets.

   o  The destination IPv6 address: destinationIPv6Address in
      [I-D.ietf-ipfix-info], with a type of 28 and a length of 16
      octets.

   o  The destination port: destinationTransportPort in
      [I-D.ietf-ipfix-info], with a type of 11, and a length of 2 octets

   Figure 10 shows the Option template defining the Common Properties
   with commonPropertiesID as scope:

     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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Set ID = 3            |      Length = 24 octets       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Template ID = 257       |       Field Count = 3         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Scope Field count = 1    |0|  commonPropertiesID = 137   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Scope 1 Field Length = 8     |0|  destinationIPv6Address = 28|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Field Length = 16        |0|destinationTransportPort = 11|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Field Length = 2         |        (Padding)              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


               Figure 10: Common Properties Option Template

   The Specific Properties Template consists of the information not
   contained in the Option Templates, i.e.  Flow specific information, n
   this case the number of packets and the number of bytes to be
   reported.  Additionally, this Template contains the
   commonPropertiesID.  In Data Records, the value of this field will
   contain one of the unique indices of the Option Records exported
   before.  It contains the following Information Elements (see also
   Figure 11):

   o  commonPropertiesID with a length of 8 octets

   o  The number of packets of the Flow: inPacketDeltaCount in
      [I-D.ietf-ipfix-info], with a length of 4 octets.




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   o  The number of octets of the Flow: inOctetDeltaCount in
      [I-D.ietf-ipfix-info], with a length of 4 octets


     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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Set ID = 2            |      Length = 20 octets       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Template ID = 258       |       Field Count = 3         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|  commonPropertiesID = 137   |       Field Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|    inPacketDeltaCount = 2   |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|    inOctetDeltaCount = 1    |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                  Figure 11: Specific Properties Template

   Considering the data shown at the beginning of this example, the
   following two Data Records will be exported:



   Common-      |           dstAddress                    | dst-
   PropertiesID |                                         | Port
   -------------+-----------------------------------------+-------
       101      | 2001:DB8:80AD:5800:0058:0800:2023:1D71  |  80
                |                                         |
       102      | 2001:DB8:80AD:5800:0058:00AA:00B7:AF2B  | 1932




   The Data Records reporting the Common Properties will look like:














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   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Set ID = 257          |      Length = 60 octets       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +-                             101                             -+
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +-                                                             -+
   |                                                               |
   +-           2001:DB8:80AD:5800:0058:0800:2023:1D71            -+
   |                                                               |
   +-                                                             -+
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            80                 |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-                             -+
   |                              102                              |
   +-                             -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                              -+
   |                                                               |
   +-                                                             -+
   |            2001:DB8:80AD:5800:0058:00AA:00B7:AF2B             |
   +-                                                             -+
   |                                                               |
   +-                             -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |          1932                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



            Figure 13: Data Records reporting Common Properties

   The Data Records will in turn be:



   commonPropertiesID  |  inPacketDeltaCount  | inOctetDeltaCount
   ---------------------------------------------------------------
           101         |          30          |       6000
           101         |          50          |       9500
           102         |          60          |       8000
           101         |          40          |       6500
           101         |          60          |       9500
           102         |          54          |       7600



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   Figure 15 shows the first Data Record listed in the table:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Set ID = 258         |          Length = 16          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +-                             101                             -+
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               30              |             6000              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


            Figure 15: Data Records reporting Common Properties

A.2.  Per Packet Data Reduction

   An example of the per packet data reduction is the measurement of
   One-Way Delay (OWD), where the exact same specific packet must be
   observed at the source and destination of the path to be measured.
   By subtracting the time of observation of the same packet at the two
   end points with synchronized clocks, the OWD is computed.  As the OWD
   is measured for a specific application on which a Service Level
   Agreement (SLA) is bound, this translates into the observation of
   multiple packets with Specific Properties, results of filtering.  In
   order to match the identical packet at both Observation Points, a
   series of packets with a set of properties (For example, all the
   packets of a specific source and destination IP addresses, of a
   specific DSCP value, and of a specific destination transport port)
   must be observed at both ends of the measurements.  This implies that
   the source and destination must export of a series of Flow Records
   composed of two types of information: some common information for all
   packets, and some unique information about packets in order to
   generate a unique identifier for each packet passing this Observation
   Point (for example, a hash value on the invariant fields of the
   packet).  So, the source and destination composing the measurements
   end points can individually and independently apply the redundancy
   technique described in this draft in order to save some bandwidth for
   their respective Flow Records export.

   The Templates required for exporting measurement data of this kind
   are illustrated in the figures below.  Figure 16 shows the Option
   Template containing the information concerning Flows using the
   commonPropertiesID as scope.  In the Common Properties Template we
   export the following Information Elements:




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   o  The source IPv4 Address: sourceIPv4Address in
      [I-D.ietf-ipfix-info], with a type of 8 and a length of 4 octets.

   o  The destination IPv4 Address: destinationIPv4Address in
      [I-D.ietf-ipfix-info], with a type of 12 and a length of 4 octets.

   o  The Class of Service field: ClassOfServiceIPv4 in
      [I-D.ietf-ipfix-info], with a type of 5 and a length of 1 octet

   o  The Protocol Identifier: protocolIdentifier in
      [I-D.ietf-ipfix-info], with a type of 4 and a length of 1 octet

   o  The source port: sourceTransportPort in [I-D.ietf-ipfix-info],
      with a type of 7 and a length of 2 octets.

   o  The destination port: destinationTransportPort in
      [I-D.ietf-ipfix-info], with a type of 11 and a length of 2 octets.

   The commonPropertiesID Information Element is used as the Scope
   Field.

     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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Set ID = 3            |      Length = 40 octets       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Template ID = 256       |       Field Count = 7         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Scope Field count = 1    |0|  commonPropertiesID = 137   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Scope 1 Field Length = 4     |0|    sourceIPv4Address = 8    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Field Length = 4         |0| destinationIPv4Address = 12 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Field Length = 4         |0|  classOfServiceIPv4 = 5     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Field Length = 1         |0|  protocolIdentifier = 4     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Field Length = 1         |0|  transportSourcePort = 7    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Field Length = 2         |0|transportDestinationPort = 11|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Field Length = 2         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                Figure 16: Example Flow Properties Template



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   For passive One Way Delay measurement, the Packet Properties
   Template, or Specific Properties Template, consists of at least
   Timestamp and Packet ID.  Additionally, this template contains a
   commonPropertiesId field to associate the packet with a Flow.

   Figure 17 displays the template with the packet properties.  In this
   example we export the following Information Elements:

   o  commonPropertiesID.  In this case reduced size encoding is used,
      and the Information Element is declared with a length of 4 octets
      instead of 8.

   o  The packet timestamp: observationTimeMilliseconds in the PSAMP
      Information Model [I-D.ietf-psamp-info], with a type of 323 and a
      length of 8 octets.

   o  digestHashValue in the PSAMP Information Model
      [I-D.ietf-psamp-info], with a type of 326 and a length of 8 octets

   o  The packet length: ipTotalLength in the IPFIX Information Model
      [I-D.ietf-ipfix-info], with a type of 224 and a length of 8 octets


      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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         Set ID = 2            |      Length = 36 octets       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |       Template ID = 257       |       Field Count = 4         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |0|  commonPropertiesID = 137   |       Field Length = 4        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |0| observationTimeMillis.= 323 |       Field Length = 8        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |0|    digestHashValue = 326    |       Field Length = 8        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |0|    ipTotalLength = 224      |       Field Length = 8        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



               Figure 17: Example Packet Properties Template

   At the collection point, packet records from the two measurement
   points are gathered and correlated by means of the packet ID.  The
   resulting delay data records are exported in a similar manner as the
   packet data.  One-way delay data is associated with Flow information
   by the commonPropertiesId field.  The OWD properties contain the



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   Packet Pair ID (which is the packet ID of the two contributing packet
   records), the timestamp of the packet passing the reference monitor
   point in order to reconstruct a time series, the calculated delay
   value, and the commonPropertiesID.

   In this example using IPFIX to export the measurement data for each
   received packet 38 bytes have to be transferred (sourceAddressV4=4,
   destinationAddressV4=4, classOfServiceV4=1, protocolIdentifier=1,
   sourceTransportPort=2, destionationTransportPort=2,
   observationTimeMilliseconds=8, digestHashValue=8, ipTotalLength=8).
   Without considering the IPFIX protocol overhead a Flow of 1000
   packets produces 38000 bytes of measurement data.  Using the proposed
   optimization each packet produces an export of only 28 bytes
   (observationTimeMilliseconds=8, digestHashValue=8, ipTotalLength=8,
   commonPropertiesID=4).  The export of the Flow information produces
   18 bytes (sourceAddressV4=4, destinationAddressV4=4,
   classOfServiceV4=1, protocolIdentifier=1, sourceTransportPort=2,
   destionationTransportPort=2, commonPropertiesID=4).  For a Flow of
   1000 packets this sums up to 28018 bytes.  This is a decrease of more
   than 26 percent.

A.3.  commonPropertiesID Template Withdrawal Message

   This section shows an example commonPropertiesID Withdrawal message.
   Figure 18 depicts the Option Template Record with the
   commonPropertiesID as unique scope field, and no non-scope fields.


     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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Set ID = 3            |      Length = 14 octets       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Template ID 259         |       Field Count = 1         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Scope Field count = 1    |0|  commonPropertiesID 137     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Scope 1 Field Length = 8     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


         Figure 18: example commonPropertiesID withdrawal template

   Figure 19 shows the Option Data Record withdrawing commonPropertiesID
   N:






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    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Set ID = 259          |      Length = 12 octets       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +-                              N                              -+
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



       Figure 19: commonPropertiesID withdrawal record, withdrawing
                           commonPropertiesID N


Authors' Addresses

   Elisa Boschi
   Hitachi Europe SAS
   Immeuble Le Theleme
   1503 Route les Dolines
   06560 Valbonne
   France

   Phone: +33 4 89874100
   Email: elisa.boschi@hitachi-eu.com


   Lutz Mark
   Fraunhofer FOKUS
   Kaiserin Augusta Allee 31
   10589 Berlin
   Germany

   Phone: +49 30 34637306
   Email: mark@fokus.fraunhofer.de


   Benoit Claise
   Cisco Systems
   De Kleetlaan 6a b1
   Diegem  1813
   Belgium

   Phone: +32 2 704 5622
   Email: bclaise@cisco.com




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Full Copyright Statement

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