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   IPFIX working group
   Internet Draft                               EDITOR:      B. Claise
   draft-ietf-ipfix-protocol-23.txt                       Cisco Systems
   Expires: April 12, 2006                                 October 2006





           Specification of the IPFIX Protocol for the Exchange
                      of IP Traffic Flow Information


 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
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
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   at any time.  It is inappropriate to use Internet-Drafts as
   reference material or to cite them other than as "work in progress".

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt
   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html

   This Internet-Draft will expire on April 12, 2007.

 Copyright Notice

   Copyright (C) The Internet Society (2006).

 Abstract

   This document specifies the IPFIX protocol that serves for
   transmitting IP traffic flow information over the network.  In order
   to transmit IP traffic flow information from an exporting process to
   an information collecting process, a common representation of flow


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                   IPFIX Protocol Specification           October 2006

   data and a standard means of communicating them is required. This
   document describes how the IPFIX data and templates records are
   carried over a number of transport protocols from an IPFIX exporting
   process to an IPFIX collecting process.

 Conventions used in this document

   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].

 Table of Contents

     1. Introduction...................................................4
     1.1 IPFIX Documents Overview......................................4
     2. Terminology....................................................5
     2.1 Terminology Summary Table....................................10
     3. IPFIX Message Format..........................................10
     3.1 Message Header Format........................................12
     3.2 Field Specifier Format.......................................13
     3.3 Set and Set Header Format....................................14
     3.3.1   Set Format...............................................15
     3.3.2   Set Header Format........................................16
     3.4 Record Format................................................16
     3.4.1   Template Record Format...................................16
     3.4.2   Options Template Record Format...........................19
     3.4.2.1  Scope...................................................19
     3.4.2.2  Options Template Record Format..........................20
     3.4.3   Data Record Format.......................................22
     4. Specific Reporting Requirements...............................23
     4.1 The Metering Process Statistics Option Template..............24
     4.2 The Metering Process Reliability Statistics Option Template..24
     4.3 The Exporting Process Reliability Statistics Option Template.26
     4.4 The Flow Keys Option Template................................27
     5. IPFIX Message Header "Export Time" and Flow Record Time.......27
     6. Linkage with the Information Model............................28
     6.1 Encoding of IPFIX Data Types.................................28
     6.1.1   Integral Data Types......................................28
     6.1.2   Address Types............................................29
     6.1.3   float32..................................................29
     6.1.4   float64..................................................29
     6.1.5   boolean..................................................29
     6.1.6   string and octetarray....................................29
     6.1.7   dateTimeSeconds..........................................29
     6.1.8   dateTimeMilliseconds.....................................29
     6.1.9   dateTimeNanoseconds......................................30
     6.1.10  dateTimeMicroseconds.....................................30
     6.2 Reduced Size Encoding of Integer and Float Types.............30
     7. Variable Length Information Element...........................31


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     8. Template Management...........................................32
     9. The Collecting Process's Side.................................35
     10. Transport Protocol...........................................37
     10.1 Transport Compliance and Transport Usage....................37
     10.2 SCTP........................................................38
     10.2.1  Congestion Avoidance.....................................38
     10.2.2  Reliability..............................................38
     10.2.3  MTU......................................................38
     10.2.4  Exporting Process........................................39
     10.2.4.1 Association Establishment...............................39
     10.2.4.2 Association Shutdown....................................39
     10.2.4.3 Stream..................................................40
     10.2.4.4 Template Management.....................................40
     10.2.5  Collecting Process.......................................40
     10.2.6  Failover.................................................40
     10.3 UDP.........................................................41
     10.3.1  Congestion Avoidance.....................................41
     10.3.2  Reliability..............................................41
     10.3.3  MTU......................................................41
     10.3.4  Port Numbers.............................................42
     10.3.5  Exporting Process........................................42
     10.3.6  Template Management......................................42
     10.3.7  Collecting Process.......................................43
     10.3.8  Failover.................................................44
     10.4 TCP.........................................................44
     10.4.1  Connection Management....................................44
     10.4.1.1 Connection Establishment................................44
     10.4.1.2 Graceful Connection Release.............................44
     10.4.1.3 Restarting Interrupted Connections......................45
     10.4.1.4 Failover................................................45
     10.4.2  Data Transmission........................................45
     10.4.2.1 IPFIX Message Encoding..................................45
     10.4.2.2 Templates Management....................................46
     10.4.2.3 Congestion Handling and Reliability.....................46
     11. Security Considerations......................................47
     11.1 Applicability of TLS and DTLS...............................48
     11.2 Usage.......................................................48
     11.3 Authentication..............................................49
     11.4 Protection against DoS attacks..............................49
     11.5 When DTLS or TLS is not an option...........................50
     11.6 Logging an IPFIX Attack.....................................51
     11.7 Securing the Collector......................................51
     12. IANA Considerations..........................................51
     13. Appendix A...................................................52
     13.1 Message Header Example......................................52
     13.2 Template Set Examples.......................................53
     13.2.1  Template Set using IETF specified Information Elements...53
     13.2.2  Template Set using Enterprise Specific Information
     Elements.........................................................54
     13.3 Data Set Example............................................55


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     13.4 Options Template Set Examples..............................56
     13.4.1  Options Template Set using IETF specified Information
     Elements........................................................56
     13.4.2  Options Template Set using enterprise-specific
     Information Elements............................................57
     13.4.3  Options Template Set using an enterprise-specific scope.57
     13.4.4  Data Set using an enterprise-specific scope.............58
     13.5 Variable length Information Element examples...............59
     13.5.1  Example of Variable Length Information Element with
     Length inferior to 255 octets...................................59
     13.5.2  Example of Variable Length Information Element with
     Length 255 to 65535 octets......................................59
     14. References..................................................59
     14.1 Normative References.......................................59
     14.2 Informative References.....................................60
     15. Acknowledgments.............................................61


 1.     Introduction

   A data network with IP traffic, primarily consists of IP Flows
   passing through the network elements of the network.  It is often
   interesting, useful or even a requirement to have access to
   information about these flows that pass through the network elements
   for administrative or other purposes.  The IPFIX collecting process
   should be able to receive the flow information passing through
   multiple network elements within the data network.  This requires
   uniformity in the method of representing the flow information and
   the means of communicating the flows from the network elements to
   the collection point.  This document specifies the protocol to
   achieve these aforementioned requirements.  This document specifies
   in detail the representation of different flows, the additional data
   required for flow interpretation, packet format, transport
   mechanisms used, security concerns, etc.

 1.1      IPFIX Documents Overview

   The 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 [IPFIX-ARCH], per the requirements defined in
   [RFC3917].  This document specifies how IPFIX data records and
   templates are carried via a number of transport protocols 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 [IPFIX-INFO].



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   Finally [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 relates to other
   architectures and frameworks.

 2.    Terminology

   The definitions of the basic terms like IP Traffic Flow, Exporting
   Process, Collecting Process, Observation Points, etc. are
   semantically identical with those found in the IPFIX requirements
   document [RFC3917].  Some of the terms have been expanded for more
   clarity when defining the protocol.  Additional terms required for
   the protocol has also been defined.  Definitions in this document
   and in [IPFIX-ARCH] are equivalent, except that definitions which
   are only relevant to the IPFIX protocol only appear here.

   The terminology summary table in Section 2.1 gives a quick overview
   of the relationships between some of the different terms defined.

 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 from the Exporter that sends the IPFIX Messages.
   Every Observation Point is associated with an Observation Domain.  .


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   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 fields (e.g. destination IP
      address), transport header fields (e.g. destination port number),
      or application header fields (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 Key

   Each of the fields which

   1.  Belong to the packet header (e.g. destination IP address)

   2.  Are a property of the packet itself (e.g. packet length)

   3.  Are derived from packet treatment (e.g. AS number)

   and which are used to define a Flow are termed Flow Keys.




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 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.

   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





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   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.

 Collector

   A device which hosts one or more Collecting Processes is termed a
   Collector.

 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.

 IPFIX Message

   An IPFIX Message is a message originating at the Exporting Process
   that carries the IPFIX records of this Exporting Process and whose
   destination is a Collecting Process.  An IPFIX Message is
   encapsulated at the transport layer.

 Message Header

   The Message Header is the first part of an IPFIX Message, which
   provides basic information about the message such as the IPFIX
   version, length of the message, message sequence number, etc.

 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




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   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.

 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 [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.

 Transport Session

   In SCTP, the transport session is known as the SCTP association,
   which is uniquely identified by the SCTP endpoints [RFC2960]; in TCP,



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   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.


 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)          |                        |
    +------------------+--------------------+------------------------+

      Figure A: 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).

 3.     IPFIX Message Format

   An IPFIX Message consists of a Message Header followed by one or
   more Sets.  The Sets can be any of the possible three types: Data
   Set, Template Set or Options Template Set.

   The format of the IPFIX Message is shown in Figure B.

      +----------------------------------------------------+
      | Message Header                                     |
      +----------------------------------------------------+
      | Set                                                |
      +----------------------------------------------------+


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      | Set                                                |
      +----------------------------------------------------+
        ...
      +----------------------------------------------------+
      | Set                                                |
      +----------------------------------------------------+

         Figure B: IPFIX Message format

   The Exporter MUST code all binary integers of the Message Header and
   the different Sets in network byte order (also known as the big-
   endian byte ordering).

   Following are some examples of IPFIX Messages:

   1. An IPFIX Message consisting of interleaved Template, Data, and
   Options Template Sets - A newly created Template is exported as soon
   as possible.  So if there is already an IPFIX Message with a Data
   Set that is being prepared for export, the Template and Option
   Template Sets are interleaved with this information, subject to
   availability of space.

   +--------+--------------------------------------------------------+
   |        | +----------+ +---------+     +-----------+ +---------+ |
   |Message | | Template | | Data    |     | Options   | | Data    | |
   | Header | | Set      | | Set     | ... | Template  | | Set     | |
   |        | |          | |         |     | Set       | |         | |
   |        | +----------+ +---------+     +-----------+ +---------+ |
   +--------+--------------------------------------------------------+

      Figure C: IPFIX Message example 1

   2. An IPFIX Message consisting entirely of Data Sets - After the
   appropriate Template Records have been defined and transmitted to
   the Collecting Process, the majority of IPFIX Messages consist
   solely of Data Sets.

   +--------+----------------------------------------------+
   |        | +---------+     +---------+      +---------+ |
   |Message | | Data    |     | Data    |      | Data    | |
   | Header | | Set     | ... | Set     | ...  | Set     | |
   |        | +---------+     +---------+      +---------+ |
   +--------+----------------------------------------------+



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      Figure D: IPFIX Message example 2

   3. An IPFIX Message consisting entirely of Template and Options
   Template Sets.

   +--------+-------------------------------------------------+
   |        | +----------+     +----------+      +----------+ |
   |Message | | Template |     | Template |      | Options  | |
   | Header | | Set      | ... | Set      | ...  | Template | |
   |        | |          |     |          |      | Set      | |
   |        | +----------+     +----------+      +----------+ |
   +--------+-------------------------------------------------+

      Figure E: IPFIX Message example 3

 3.1      Message Header Format

   The format of the IPFIX Message Header is shown in Figure F.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Version Number          |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Export Time                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Sequence Number                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Observation Domain ID                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Figure F: IPFIX Message Header format

   Message Header Field Descriptions

   Version
           Version of Flow Record format exported in this message.  The
           value of this field is 0x000a for the current version,
           incrementing by one the version used in the NetFlow services
           export version 9 [RFC3954].

   Length
           Total length of the IPFIX Message, measured in octets,
           including Message Header and Set(s).


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   Export Time
           Time in seconds since 0000 UTC Jan 1st 1970, at which the
           IPFIX Message Header leaves the Exporter.

   Sequence Number
           Incremental sequence counter modulo 2^32 of all IPFIX Data
           Records sent on this PR-SCTP stream from the current
           Observation Domain by the Exporting Process.  Check the
           specific meaning of this field in the sub-sections of
           section 10 when UDP or TCP is selected as the transport
           protocol.  This value SHOULD be used by the Collecting
           Process to identify whether any IPFIX Data Records have been
           missed.  Template and Options Template Records do not
           increase the Sequence Number.

   Observation Domain ID
           A 32-bit identifier of the Observation Domain that is
           locally unique to the Exporting Process.  The Exporting
           Process uses the Observation Domain ID to uniquely identify
           to the Collecting Process the Observation Domain that
           metered the Flows.  It is RECOMMENDED that this identifier
           is also unique per IPFIX Device.  Collecting Processes
           SHOULD use the Transport Session and the Observation Domain
           ID field to separate different export streams originating
           from the same Exporting Process.  The Observation Domain ID
           SHOULD be 0 when no specific Observation Domain ID is
           relevant for the entire IPFIX Message.  For example, when
           exporting the Exporting Process Statistics, or in case of
           hierarchy of Collector when aggregated data records are
           exported.

 3.2      Field Specifier Format

   Vendors need the ability to define proprietary Information Elements,
   because, for example, they are delivering a pre-standards product,
   or the Information Element is in some way commercially sensitive.
   This section describes the Field Specifier format for both IETF
   specified Information Elements [IPFIX-INFO] and enterprise-specific
   Information Elements.

   The Information Elements are identified by the Information Element
   identifier. When the Enterprise bit is set to 0, the corresponding
   Information Element identifier will report an IETF specified
   Information Element, and the Enterprise Number MUST NOT be present.
   When the Enterprise bit is set to 1, the corresponding Information
   Element identifier will report an enterprise-specific Information


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   Element and the Enterprise Number MUST be present.  An example of
   this is shown in section 13.4.2

   The Field Specifier format is shown in Figure G.

       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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |E|  Information Element ident. |        Field Length           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                      Enterprise Number                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Figure G: Field Specifier format

        Where:

       E
          Enterprise bit.  This is the first bit of the Field
          Specifier. If this bit is zero, the Information Element
          Identifier identifies an IETF specified Information Element,
          and the four octet Enterprise Number field MUST NOT be
          present.  If this bit is one, the Information Element
          identifier identifies an enterprise-specific Information
          Element, and the Enterprise Number filed MUST be present.

       Information Element identifier
           A numeric value that represents the type of the Information
           Element.  Refer to [IPFIX-INFO].

       Field Length
           The length of the corresponding encoded Information Element,
           in octets.  Refer to [IPFIX-INFO].  The field length may be
           smaller than the definition in [IPFIX-INFO] if reduced size
           encoding is used (see section 6.2).  The value 65535 is
           reserved for variable length Information Element (see
           section 7).

      Enterprise Number
         IANA enterprise number [PEN] of the authority defining the
         Information Element identifier in this Template Record.

 3.3      Set and Set Header Format



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   A Set is a generic term for a collection of records that have a
   similar structure.  There are three different types of Sets:
   Template Sets, Options Template Sets, and Data Sets. Each of these
   Sets consists of a Set Header and one or more Records. The Set
   Format and the Set Header Format are defined in the following
   sections.

 3.3.1   Set Format

   A Set has the format shown in figure H. The records types can be
   either Template Records, Options Template Records or Data Records.
   The record types MUST NOT be mixed within a Set.

         +--------------------------------------------------+
         | Set Header                                       |
         +--------------------------------------------------+
         | record                                           |
         +--------------------------------------------------+
         | record                                           |
         +--------------------------------------------------+
          ...
         +--------------------------------------------------+
         | record                                           |
         +--------------------------------------------------+
         | Padding (opt.)                                   |
         +--------------------------------------------------+

              Figure H: Set Format

      The Set Field Definitions are as follows:

      Set Header
          The Set Header Format is defined in section 3.3.2.

      Record
          One of the Record Formats: Template Record or Options Template
          Record or Data Record Format.

      Padding
          The Exporting Process MAY insert some padding octets, so that
          the subsequent Set starts at an aligned boundary.  For
          security reasons, the padding octet(s) MUST be composed of
          zero (0) valued octets.  The padding length MUST be shorter
          than any allowable Record in this Set.  If padding of the
          IPFIX Message is desired in combination with very short


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          Records, then the padding Information Element 'paddingOctets'
          [IPFIX-INFO] can be used for padding Records such that their
          length is increased to a multiple of 4 or 8 octets.  Because
          Template Sets are always 4-octet aligned by definition,
          padding is only needed in case of other alignments e.g. on 8-
          octet boundaries.

 3.3.2   Set Header Format

   Every Set contains a common header. This header is defined in figure
   I.

      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               |          Length               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure I: Set Header Format

   The Set Header Field Definitions are as follows:

      Set ID
         Set ID value identifies the Set.  A value of 2 is reserved for
         the Template Set.  A value of 3 is reserved for the Option
         Template Set.  All other values from 4 to 255 are reserved
         for future use.  Values above 255 are used for Data Sets. The
         Set ID values of 0 and 1 are not used for historical reasons
         [RFC3954].

      Length
          Total length of the Set in octets including the Set Header,
          all records and the optional padding.  Because an individual
          Set MAY contain multiple records, the Length value MUST be
          used to determine the position of the next Set.

 3.4      Record Format

   IPFIX defines three record formats, defined in the next sections:
   the Template Record Format, the Options Template Record Format and
   the Data Record Format.

 3.4.1   Template Record Format




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   One of the essential elements in the IPFIX record format is the
   Template Record.  Templates greatly enhance the flexibility of the
   record format because they allow the Collecting Process to process
   IPFIX Messages without necessarily knowing the interpretation of all
   Data Records. A Template Record contains any combination of IANA-
   assigned and/or enterprise-specific Information Elements
   identifiers.

   The format of the Template Record is shown in Figure J.  It consists
   of a Template Record Header and one or more Field Specifiers.  The
   definition of the Field Specifiers is given in figure G above.

         +--------------------------------------------------+
         | Template Record Header                           |
         +--------------------------------------------------+
         | Field Specifier                                  |
         +--------------------------------------------------+
         | Field Specifier                                  |
         +--------------------------------------------------+
          ...
         +--------------------------------------------------+
         | Field Specifier                                  |
         +--------------------------------------------------+

               Figure J: Template Record Format

   The format of the Template Record Header is shown in Figure K.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Template ID (> 255)      |         Field Count           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure K: Template Record Header Format

   The Template Record Header Field Definitions are as follows:

      Template ID
          Each of the newly generated Template Records is given a unique
          Template ID.  This uniqueness is local to the Transport
          Session and Observation Domain that generated the Template ID.
          Template IDs 0-255 are reserved for Template Sets, Options
          Template Sets, and other reserved Sets yet to be created.



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          Template IDs of Data Sets are numbered from 256 to 65535.
          There are no constraints regarding the order of the Template
          ID allocation.

      Field Count
         Number of fields in this Template Record.

   The example in Figure L shows a Template Set with mixed standard and
   enterprise-specific Information Elements. It consists of Set Header,
   Template Header and several Field Specifiers.

       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               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Template ID = 256        |         Field Count = N       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1| Information Element id. 1.1 |        Field Length 1.1       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Enterprise Number  1.1                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0| Information Element id. 1.2 |        Field Length 1.2       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             ...               |              ...              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1| Information Element id. 1.N |        Field Length 1.N       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Enterprise Number  1.N                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Template ID = 257        |         Field Count = M       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0| Information Element id. 2.1 |        Field Length 2.1       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1| Information Element id. 2.2 |        Field Length 2.2       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Enterprise Number  2.2                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             ...               |              ...              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1| Information Element id. 2.M |        Field Length 2.M       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Enterprise Number  2.M                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


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      |                          Padding (opt)                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure L: Template Set Example

   Information Element Identifiers 1.2 and 2.1 are defined by the IETF
   (Enterprise bit = 0) and therefore do not need an Enterprise Number
   to identify them.

 3.4.2   Options Template Record Format

   Thanks to the notion of scope, The Options Template Record gives the
   Exporter the ability to provide additional information to the
   Collector which would not be possible with Flow Records alone.

   One Options Template Record example is the "Flow Keys", which
   reports the Flow Keys for a Template, which is defined as the scope.
   Another example is the "Template configuration", which reports the
   configuration sampling parameter(s) for the Template, which is
   defined as the scope.

 3.4.2.1 Scope

   The scope, which is only available in the Options Template Set,
   gives the context of the reported Information Elements in the Data
   Records.  Note that the IPFIX Message Header already contains the
   Observation Domain ID (the identifier of the Observation Domain). If
   not zero, this Observation Domain ID can be considered as an
   implicit scope for the Data Records in the IPFIX Message.  The
   Observation Domain ID MUST be zero when the IPFIX Message contains
   data records with different Observation Domain ID values defined as
   scopes.

   Multiple scope fields MAY be present in the Options Template Record,
   in which case, the composite scope is the combination of the scopes.
   For example, if the two scopes are defined as "metering process" and
   "template", the combined scope is this Template for this metering
   process.  The order of the scope fields, as defined in the Options
   Template Record, is irrelevant in this case. However, if the order
   of the scope fields in the Options Template Record is relevant, the
   order of the scope fields MUST be used.  For example, if the first
   scope defines the filtering function, while the second scope defines
   the sampling function, the order of the scope is important. Applying



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   the sampling function first, followed by the filtering function,
   would lead to potentially different Data Records than applying the
   filtering function first, followed by the sampling function.  In
   this case, the Collector deduces the function order by looking at
   the order of the scope in the Options Template Record.

   The scope is an Information Element specified in the IPFIX
   Information Model [IPFIX-INFO].  An IPFIX compliant implementation
   of the Collecting Process SHOULD support this minimum set of
   Information Elements as scope: LineCardId, TemplateId,
   exporterIPv4Address, exporterIPv6Address, and ingressInterface.
   Note that other Information Elements such as meteringProcessId,
   exportingProcessId, observationDomainId, etc. are also valid scopes.
   The IPFIX protocol doesn't prevent the use of any Information
   Elements for scope.  However some Information Element types don't
   make sense if specifed as scope.  For example: the counter
   Information Elements.

   Finally, note that the Scope Field Count MAY NOT be zero.

 3.4.2.2 Options Template Record Format

   An Options Template Record contains any combination of IANA-assigned
   and/or enterprise-specific Information Elements identifiers.

   The format of the Options Template Record is shown in Figure M. It
   consists of an Options Template Record Header and one or more Field
   Specifiers. The definition of the Field Specifiers is given in
   figure G above.

         +--------------------------------------------------+
         | Options Template Record Header                   |
         +--------------------------------------------------+
         | Field Specifier                                  |
         +--------------------------------------------------+
         | Field Specifier                                  |
         +--------------------------------------------------+
          ...
         +--------------------------------------------------+
         | Field Specifier                                  |
         +--------------------------------------------------+

             Figure M: Options Template Record Format



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   The format of the Options Template Record Header is shown in Figure
   N.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Template ID (> 255)   |         Field Count           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Scope Field Count        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure N: Options Template Record Header Format

   The Options Template Record Header Field Definitions are as follows:

      Template ID
         Template ID of this Options Template Record.  This value is
         greater than 255.

      Field Count
         Number of all fields in this Options Template Record,
         including the Scope Fields.

      Scope Field Count
         Number of scope fields in this Options Template Record.  The
         Scope Fields are normal Fields except that they are
         interpreted as Scope at the Collector.  The Scope Field Count
         MAY NOT be zero.

   The example in Figure O shows an Option Template Set with mixed IETF
   and enterprise-specific Information Elements.  It consists of Set
   Header, Option Template Header and several Field Specifiers.

      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               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Template ID = 258     |         Field Count = N + M   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Scope Field Count = N     |0|  Scope 1 Infor. Element Id. |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Scope 1 Field Length      |0|  Scope 2 Infor. Element Id. |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


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      |     Scope 2 Field Length      |             ...               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            ...                |1|  Scope N Infor. Element Id. |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Scope N Field Length      |   Scope N Enterprise Number ...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ...  Scope N Enterprise Number   |1| Option 1 Infor. Element Id. |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Option 1 Field Length      |  Option 1 Enterprise Number ...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ... Option 1 Enterprise Number   |              ...              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             ...               |0| Option M Infor. Element Id. |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Option M Field Length     |      Padding (optional)       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure O: Option Template Set Example

 3.4.3   Data Record Format

   The Data Records are sent in Data Sets. The format of the Data
   Record is shown in Figure P.  It consists only of one or more Field
   Values.  The Template ID to which the Field Values belong is encoded
   in the Set Header field "Set ID" i.e., "Set ID" = "Template ID".

         +--------------------------------------------------+
         | Field Value                                      |
         +--------------------------------------------------+
         | Field Value                                      |
         +--------------------------------------------------+
          ...
         +--------------------------------------------------+
         | Field Value                                      |
         +--------------------------------------------------+

               Figure P: Data Record Format

   Note that Field Values do not necessarily have a length of 16 bits.
   Field Values are encoded according to their data type specified in
   [IPFIX-INFO].





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   Interpretation of the Data Record format can be done only if the
   Template Record corresponding to the Template ID is available at the
   Collecting Process.

   The example in Figure Q shows a Data Set. It consists of a Set
   Header several Field Values.

       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 = Template ID        |          Length               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Record 1 - Field Value 1    |   Record 1 - Field Value 2    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Record 1 - Field Value 3    |             ...               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Record 2 - Field Value 1    |   Record 2 - Field Value 2    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Record 2 - Field Value 3    |             ...               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Record 3 - Field Value 1    |   Record 3 - Field Value 2    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Record 3 - Field Value 3    |             ...               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              ...              |      Padding (optional)       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Figure Q: Data Set, containing Data Records

 4.     Specific Reporting Requirements

   Some specific Options Templates and Options Template Records are
   necessary to provide extra information about the Flow Records and
   about the Metering Process.

   The Option Template and Options Template Records defined in these
   sub-sections, which impose some constraints on the Metering Process
   and Exporting Process implementations, MAY be implemented.  If
   implemented, the specific Option Templates SHOULD be implemented as
   specified in these sub-sections.

   The minimum set of Information Elements is always specified in these
   Specific IPFIX Options Templates.  Nevertheless, extra Information
   Elements may be used in these specific Options Templates.


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 4.1      The Metering Process Statistics Option Template

   The Metering Process Statistics Option Template specifies the
   structure of a Data Record for reporting Metering Process
   statistics.  It SHOULD contain the following Information Elements
   that are defined in [IPFIX-INFO]:

        observationDomainId     An identifier of an Observation Domain
                                that is locally unique to the Exporting
                                Process.  This Information Element MUST
                                be defined as a Scope Field.

        exportedMessageTotalCount
                                The total number of IPFIX Messages
                                that the Exporting Process successfully
                                sent to the Collecting Process since
                                the Exporting Process re-
                                initialization.

        exportedFlowTotalCount  The total number of Flow Records that
                                the Exporting Process successfully sent
                                to the Collecting Process since the
                                Exporting Process re-initialization.

        exportedOctetTotalCount The total number of octets that the
                                Exporting Process successfully sent to
                                the Collecting Process since the
                                Exporting Process re-initialization.

   The Exporting Process SHOULD export the Data Record specified by the
   Metering Process Statistics Option Template on a regular basis or
   based on some export policy.  This periodicity or export policy
   SHOULD be configurable.

   Note that if several Metering Processes are available on the
   Exporter Observation Domain, the Information Element
   meteringProcessId MUST be specified as an additional Scope Field.

 4.2      The Metering Process Reliability Statistics Option Template

   The Metering Process Reliability Option Template specifies the




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   structure of a Data Record for reporting lack of reliability in the
   Metering Process.  It SHOULD contain the following Information
   Elements that are defined in [IPFIX-INFO]:

        observationDomainId     An identifier of an Observation Domain
                                that is locally unique to the Exporting
                                Process.  This Information Element MUST
                                be defined as a Scope Field.

        ignoredPacketTotalCount The total number of IP packets that the
                                Metering Process did not process.

        ignoredOctetTotalCount  The total number of octets in observed
                                IP packets that the Metering Process
                                did not process.

        time first ignored      The time stamp of the first IP packet
                                that was ignored by the Metering
                                Process.  For this time stamp, any of
                                the "flowStart" time stamp Information
                                Elements flowStartMilliseconds,
                                flowStartMicroseconds,
                                flowStartNanoseconds, and
                                flowStartDeltaMicroseconds can be used.

        time last ignored       The time stamp of the last IP packet
                                that was ignored by the Metering
                                Process.  For this time stamp, any of
                                the "flowEnd" time stamp Information
                                Elements flowEndMilliseconds,
                                flowEndMicroseconds,
                                flowEndNanoseconds, and
                                flowEndDeltaMicroseconds can be used.

   The Exporting Process SHOULD export the Data Record specified by the
   Metering Process Reliability Statistics Option Template on a regular
   basis or based on some export policy.  This periodicity or export
   policy SHOULD be configurable.

   Note that if several Metering Processes are available on the
   Exporter Observation Domain, the Information Element
   meteringProcessId MUST be specified as an additional Scope Field.




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 4.3      The Exporting Process Reliability Statistics Option Template

   The Exporting Process Reliability Option Template specifies the
   structure of a Data Record for reporting lack of reliability in the
   Exporting process.  It SHOULD contain the following Information
   Elements that are defined in [IPFIX-INFO]:

        Exporting Process ID     The identifier of the Exporting Process
                                 for which lack of reliability is
                                 reported.  There are three Information
                                 Elements specified in [IPFIX-INFO] that
                                 can be used for this purpose:
                                 exporterIPv4Address,
                                 exporterIPv6Address, or
                                 exportingProcessId.  This
                                 Information Element MUST be defined
                                 as a Scope Field.

         notSentFlowTotalCount   The total number of Flows that were
                                 generated by the Metering Process and
                                 but dropped by the Metering Process or
                                 by the Exporting Process instead of
                                 sending it to the Collecting Process.

         notSentPacketTotalCount The total number of packets in Flow
                                 Records that were generated by the
                                 Metering Process and but dropped by
                                 the Metering Process or by the
                                 Exporting Process instead of sending
                                 it to the Collecting Process.

         notSentOctetTotalCount  The total number of octets in packets
                                 in Flow Records that were generated by
                                 the Metering Process and but dropped
                                 by the Metering Process or by the
                                 Exporting Process instead of sending
                                 it to the Collecting Process.

        time first flow dropped  The time stamp of the first Flow
                                 was dropped by the Metering
                                 Process.  For this time stamp, any of
                                 the "flowStart" time stamp Information
                                 Elements flowStartMilliseconds,
                                 flowStartMicroseconds,


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                                 flowStartNanoseconds, and
                                 flowStartDeltaMicroseconds can be used.

        time last flow dropped   The time stamp of the last IP packet
                                 that was ignored by the Metering
                                 Process.  For this time stamp, any of
                                 the "flowEnd" time stamp Information
                                 Elements flowEndMilliseconds,
                                 flowEndMicroseconds,
                                 flowEndNanoseconds, and
                                 flowEndDeltaMicroseconds can be used.

   The Exporting Process SHOULD export the Data Record specified by the
   Exporting Process Reliability Statistics Option Template on a
   regular basis or based on some export policy.  This periodicity or
   export policy SHOULD be configurable.

 4.4      The Flow Keys Option Template

   The Flow Keys Option Template specifies the structure of a Data
   Record for reporting the Flow Keys of reported Flows.  A Flow Keys
   Data Record extends a particular Template Record that is referenced
   by its templateId identifier.  The Template Record is extended by
   specifying which of the Information Elements contained in the
   corresponding Data Records describe Flow properties that server as
   Flow Keys of the reported Flow.

   The Flow Keys Option Template SHOULD contain the following
   Information Elements that are defined in [IPFIX-INFO]:

        templateId              An identifier of a Template. This
                                Information Element MUST be defined as
                                a Scope Field.

        flowKeyIndicator        Bitmap with the positions of the Flow
                                Keys in the Data Records.

 5.     IPFIX Message Header "Export Time" and Flow Record Time

   The IPFIX Message Header "Export Time" field is the time in seconds
   since 0000 UTC Jan 1st, 1970, at which the IPFIX Message Header
   leaves the Exporter.  The time-related Information Elements
   specified in [IPFIX-INFO] MAY use this "Export Time" as base time
   and specify an offset relative to it, instead of using a common base



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   time, such as 0000 UTC Jan 1st, 1970.  All Information Elements that
   do not have their base time defined by their data type, MUST have
   the base time clearly specified in their description.

   For example, Data Records requiring a microsecond precision can
   export the flow start and end times with the flowStartMicroseconds
   and flowEndMicroseconds Information Elements [IPFIX-INFO],
   containing the time since 0000 UTC Jan 1st 1970.  An alternate
   solution is to export the flowStartDeltaMicroseconds and
   flowEndDeltaMicroseconds Information Elements [IPFIX-INFO] in the
   Data Record, which respectively report the flow start and end time
   offsets compared to the IPFIX Message Header "Export Time".  The
   latter solution lowers the export bandwidth requirement while it
   increases the load on the Exporter as the Exporting Process must
   calculate the flowStartDeltaMicroseconds and
   flowEndDeltaMicroseconds of every single Data Record before
   exporting the IPFIX Message.

   It must be noted that using time-related Information Elements with
   offset times compared to the IPFIX Message Header "Export Time"
   imposes some time constraints on the Data Records contained in the
   IPFIX Message.  In the example of flowStartDeltaMicroseconds and
   flowEndDeltaMicroseconds Information Elements [IPFIX-INFO], the Data
   Record must be exported within a maximum of 71 minutes after its
   creation. Otherwise, the 32-bits counter would not be sufficient to
   contain the flow start time offset.

 6.     Linkage with the Information Model

   The Information Elements [IPFIX-INFO] MUST be sent in canonical
   format in network byte order (also known as the big-endian byte
   ordering).

 6.1
     Encoding of IPFIX Data Types

   The following sections will define the encoding of the data types
   specified in [IPFIX-INFO].

 6.1.1   Integral Data Types

   Integral data types - octet, signed8, unsigned16, signed16,
   unsigned32, signed32, signed64 and unsigned64 - MUST be encoded
   using the default canonical format in network byte order.  Signed
   Integral data types are represented in two's complement notation.



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 6.1.2   Address Types

   Address types - macAddress, ipv4Address and ipv6Address - MUST be
   encoded the same way as the integral data types. The macAddress is
   treated as a 6-octet integer, the ipv4Address as a 4-octet integer
   and the ipv6Address as a 16-octet integer.

 6.1.3   float32

   The float32 data type MUST be encoded as an IEEE single-precision 32-
   bit floating point-type, as specified in [IEEE.754.1985].

 6.1.4   float64

   The float64 data type MUST be encoded as an IEEE double-precision
   64-bit floating point-type, as specified in [IEEE.754.1985].

 6.1.5   boolean

   The boolean data type is specified according to the TruthValue in
   [RFC2579]: that is an integer with the value 1 for true and a value
   2 for false. Every other value is undefined. The boolean data type
   MUST be encoded in a single octet.


 6.1.6   string and octetarray

   The data type string represents a finite length string of valid
   characters of the Unicode character encoding set.  The string data
   type MUST be encoded in UTF-8 format.  The string is sent as an
   array of octets using an information element of fixed or variable
   length. The length of the information element specifies the length
   of the octetarray.


 6.1.7   dateTimeSeconds

   The data type dateTimeseconds represents a time value in units of
   seconds normalised to the GMT timezone.  It MUST be encoded in a 32-
   bit integer containing the number of seconds since 0000 UTC Jan 1st
   1970.  The 32-bit integer allows the time encoding up to 136 years.

 6.1.8   dateTimeMilliseconds



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   The data type dateTimeMilliseconds represents a time value in units
   of milliseconds normalized to the GMT timezone.  It MUST be encoded
   in a 64-bit integer containing the number of milliseconds since 0000
   UTC Jan 1st 1970.

 6.1.9   dateTimeNanoseconds

   The data type of dateTimeNanoseconds represents a time value in
   units of nanoseconds normalized to the GMT timezone.  It MUST be
   encoded in a 64-bit integer according to the NTP format given in
   [RFC1305].

 6.1.10  dateTimeMicroseconds

   The data type dateTimeMicroseconds represents a time value in units
   of microseconds normalized to the GMT timezone.  It MUST be encoded
   in a 64-bit integer according to the NTP format given in [RFC1305].

 6.2      Reduced Size Encoding of Integer and Float Types

   Information Elements containing integer, string, float, and
   octetarray types in the information model MAY be encoded using
   fewer octets than those implied by their type in the information
   model definition [IPFIX-INFO], based on the assumption that the
   smaller size is sufficient to carry any value the Exporter may need
   to deliver.  This reduces the network bandwidth requirement
   between the Exporter and the Collector.  Note that the Information
   Element definitions [IPFIX-INFO] will always define the maximum
   encoding size.

   For instance the information model [IPFIX-INFO] defines byteCount as
   an unsigned64 type, which would require 64-bits.  However if the
   Exporter will never locally encounter the need to send a value
   larger than 4294967295, it may chose to send the value instead as an
   unsigned32.  For example, a core router would require an unsigned64
   byteCount while an unsigned32 might be sufficient for an access
   router.

   This behavior is indicated by the Exporter by specifying a type size
   with a smaller length than that associated with the assigned type of
   the Information Element.  In the example above the Exporter would
   place a length of 4 versus 8 in the Template.




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   If reduced sizing is used, it MUST only be applied to the following
   integer types: unsigned64, signed64, unsigned32, signed32,
   unsigned16, signed16.  The signed versus unsigned property of the
   reported value MUST be preserved.  The reduction in size can be to
   any number of octets smaller than the original type if the data
   value still fits, i.e. so that only leading zeroes are dropped. For
   example, an unsigned64 can be reduced in size to 7, 6, 5, 4, 3, 2,
   or 1 octet(s).

   Reduced sizing can also be used to reduce float64 to float32.  The
   float32 not only has a reduced number range, but due to the smaller
   mantissa is also less precise.

   The reduced size encoding MUST NOT be applied to
   dateTimeMicroseconds or to dateTimeNanoseconds because these
   represent an inherent structure that would be destroyed by using
   less than the original number of bytes.

 7.     Variable Length Information Element

   The IPFIX Template mechanism is optimized for fixed length
   Information Elements [IPFIX-INFO].  Where an Information Element has
   a variable length the following mechanism MUST be used to carry the
   length information, for both the IETF and proprietary Information
   Elements.

   In the Template Set the Information Element Field Length is recorded
   as 65535.  This reserved length value notifies the Collecting
   Process that length of the Information Element will be carried in
   the Information Element content itself.

   In most cases the length of the Information Element will be less
   than 255 octets.  The following length encoding mechanism optimizes
   the overhead of carrying the Information Element length in this
   majority case.  The length is carried in the octet before the
   Information Element, as shown in Figure R.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Length (< 255)|          Information element                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      ... continuing as needed                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    Figure R: Variable Length Information Element (length < 255 octets)


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   If the length of the Information Element is greater than or equal to
   255 octets, the length is encoded into 3 octets before the
   Information Element. The first octet is 255 and the length is
   carried in the second and third octets, as shown in Figure S.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      255      |      Length (0 to 65535)      |       IE      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      ... continuing as needed                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Figure S: Variable Length Information Element
               (length 0 to 65535) octets

   The octets carrying the length (either the first or the first three
   octets) MUST NOT be included in the length of the Information
   Element.

 8.     Template Management

   This section describes Template management when using SCTP and PR-
   SCTP as the transport protocol. Any necessary changes to Template
   management specifically related to TCP or UDP transport protocols are
   specified in section 10.

   The Exporting Process assigns and maintains the Template IDs per SCTP
   association for the Exporter's Observation Domains.  A newly created
   Template Record is assigned an unused Template ID by the Exporting
   Process.

   If a specific Information Element is required by a Template but is
   not available in observed packets, the Exporting Process MAY choose
   to export Flow Records without this Information Element in a Data
   Record defined by a new Template.

   If an Information Element is required more than once in Template, the
   different occurrences of this Information Element SHOULD follow the
   logical order of their treatments by the Metering Process.  For
   example, if a selected packet goes through two hash functions, and if
   the two hash values are sent within a single Template, the first
   occurrence of the hash value should belong to the first hash function
   in the Metering Process.  For example, when exporting the two source
   IP addresses of an IPv4 in IPv4 packets, the first sourceIPv4Address
   Information Element occurrence should be the IPv4 address of the


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   outer header, while the second occurrence should be the inner header
   one.

   Template Sets and Option Template Sets MUST be only sent once on SCTP
   stream zero with full reliability.  As such, the Collecting Process
   MUST store the Template Record information for the duration of the
   association so that it can interpret the corresponding Data Records
   that are received in subsequent Data Sets.

   The Exporting Process SHOULD transmit the Template Set and Options
   Template Set in advance of any Data Sets that use that (Options)
   Template ID, to help ensure that the Collector has the Template
   Record before receiving the first Data Record.  Data Records that
   correspond to a Template Record MAY appear in the same and/or
   subsequent IPFIX Message(s).

   Different Observation Domains from the same SCTP association may use
   the same Template ID value to refer to different Templates.

   The Templates that are not used anymore SHOULD be deleted.  Before
   reusing a Template ID, the Template MUST be deleted.  In order to
   delete an allocated Template, the Template is withdrawn through the
   use of a Template Withdraw Message.

   The Template Withdraw Message MUST not be sent until sufficient time
   has elapsed to allow the Collecting Process to receive and process
   the last Data Record using this Template information. This time MUST
   be configurable.  A suitable default value is 5 seconds after the
   last Data Record has been sent.

   The Template ID from a withdrawn Template MUST NOT be reused until
   sufficient time has elapsed to allow for the Collecting Process to
   receive and process the Template withdraw message.

   A Template Withdraw Message is a Template Record for that Template ID
   with a Field Count of 0. The format of the Template Withdrawal
   Message is shown in figure T.

      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 or 3)       |          Length = 16          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          Template ID N        |        Field Count = 0        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          Template ID ...      |        Field Count = 0        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          Template ID M        |        Field Count = 0        |



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     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure T: Template Withdrawal Message format

   The Set ID field MUST contain the value 2 for Template Set withdrawal
   and the value 3 for Options Template Set withdrawal.  Multiple
   Template IDs MAY be withdrawn with a single Template Withdrawal
   Message: in that case, padding MAY be used.

   The Template Withdraw Message withdraws the Template IDs for the
   Observation Domain ID specified in the IPFIX Message header.

   The Template Withdraw Message MUST be sent on the SCTP stream zero
   with full reliability.

   The Template Withdraw Message MUST NOT contain new Template or
   Options Template Records.

   If the measurement parameters change, the Template MUST be withdrawn
   (using a Template Withdraw Message and a new Template definition) or
   an unused Template ID MUST be used. Examples of the measurement
   changes are: a new sampling rate, a new flow expiration process, a
   new filtering definition, etc. If a Template is changed, a Template
   Withdraw Message MUST be sent to delete the Template.

   When the SCTP association shuts down or the Exporting Process
   restarts, all Template assignments are lost and Template IDs MUST be
   re-assigned.

   If the Metering Process restarts, the Exporting Process MUST either
   reuse the previously assigned Template ID for each Template, or it
   MUST withdraw the previously issued Template IDs by sending Template
   Withdraw Message(s) before reusing them.

   A Template Withdrawal Message to withdraw all Templates for the
   Observation Domain ID specified in the IPFIX Message header MAY be
   used. Its format is shown in figure U.

      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 = 8           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Template ID = 2       |        Field Count = 0        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure U: All Data Templates Withdrawal Message format



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   A Template Withdrawal Message to withdraw all Options Templates for
   the Observation Domain ID specified in the IPFIX Message header MAY
   be used. Its format is shown in figure V.

      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 = 8           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Template ID = 3       |        Field Count = 0        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure V: All Options Templates Withdrawal Message format

   When the SCTP association restarts, the Exporting Process MUST resend
   all the Template Records.

 9.     The Collecting Process's 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 section 10.

   The Collecting Process SHOULD listen for a new association request
   from the Exporting Process.  The Exporting Process will request a
   number of streams to use for export.  A Collecting Process MUST
   support at least two inbound streams per association.  An Exporting
   Process MAY ask for and support more than two streams.

   If the Collecting Process receives a malformed IPFIX Message, it
   MUST reset the SCTP association, discard the IPFIX Message, and
   SHOULD log the error.

   Template Sets and Option Template Sets are only sent once.  The
   Collecting Process MUST store the Template Record information for
   the duration of the association so that it can interpret the
   corresponding Data Records that are received in subsequent Data
   Sets.

   Template IDs are unique per SCTP association and per Observation
   Domain.  If the Collecting Process receives a Template which has
   already been received but which has not previously been withdrawn
   (i.e. a Template Record from the same Exporter Observation Domain



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   with the same Template ID 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 Templates received over that association and stop
   decoding IPFIX Messages that use those Templates.

   The Collecting Process normally receives Template Records from the
   Exporting Process before receiving Data Records.  The Data Records
   are then decoded and stored by the Collector. If the Template
   Records have not been received at the time Data Records are
   received, the Collecting Process MAY store the Data Records for a
   short period of time and decode them after the Template Records are
   received.  A Collecting Process MUST NOT assume that the Data Set
   and the associated Template Set (or Options Template Set) are
   exported in the same IPFIX Message.

   The Collecting Process MUST note the Information Element identifier
   of any Information Element that it does not understand and MAY
   discard that Information Element from the Flow Record.

   The Collector MUST accept padding in Data Records and Template
   Records.  The padding size is the Set Length minus the size of the
   Set Header (4 octets for the Set ID and the Set Length), modulo the
   Record size deduced from the Template Record.

   The IPFIX protocol has a Sequence Number field in the Export header
   which increases with the number of IPFIX Data Records in the IPFIX
   Message.  A Collector may detect out of sequence, dropped, or
   duplicate IPFIX Messages by tracking the Sequence Number.  A
   collector SHOULD provide a logging mechanism for tracking out of
   sequence IPFIX Messages.  Such out of sequence IPFIX Messages may be
   due to Exporter resource exhaustion where it can not transmit
   messages at their creation rate, an Exporting Process reset,
   congestion on the network link between the Exporter and Collector,
   Collector resource exhaustion where it can not process the IPFIX
   Messages at their arrival rate, out of order packet reception,
   duplicate packet reception, or an attacker injecting false messages.

   If a Collecting Process receives a Template Withdraw Message, the
   Collecting Process MUST delete the corresponding Template Records
   associated with the specific SCTP association and specific
   Observation Domain, and stop decoding IPFIX Messages that use the
   withdrawn Templates.



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   If the Collecting Process receives a Template Withdraw message for a
   Template Record 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.

   A Collecting Process that receives IPFIX Messages from several
   Observation Domains on the same Transport Session MUST be aware that
   the uniqueness of the Template ID is not guaranteed across
   Observation Domains.
   The Collector MUST support the use of Templates containing multiple
   occurrences of the similar Information Elements.


 10.      Transport Protocol

   The IPFIX Protocol Specification has been designed to be transport
   protocol independent.  Note that the Exporter can export to multiple
   Collecting Processes, using independent transport protocols.

   The IPFIX Message Header 16-bit Length field limits the length of a
   IPFIX Message to 65535 octets including the header.  A Collecting
   Process MUST be able to handle IPFIX Message lengths of up to 65535
   octets.

 10.1       Transport Compliance and Transport Usage

   We need to differentiate between what must be implemented (so that
   operators can interoperably deploy compliant implementations from
   different vendors) and what should or could be used in various
   operational environments. We must also make sure that ALL
   implementations can operate in a congestion-aware and congestion
   avoidance mode.

   SCTP [RFC2960] and PR-SCTP [RFC3758] MUST be implemented by all
   compliant implementations.  UDP [UDP] MAY also be implemented by
   compliant implementations.  TCP [TCP] MAY also be implemented by
   compliant implementations.

   PR-SCTP SHOULD be used in deployments where Exporters and Collectors
   are communicating over links that are susceptible to congestion.
   PR-SCTP is capable of providing any required degree of reliability.

   TCP MAY be used in deployments where Exporters and Collectors
   communicate over links that are susceptible to congestion, but PR-
   SCTP is preferred, due to its ability to limit back pressure on
   Exporters and its message versus stream orientation.


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   UDP MAY be used although it is not a congestion aware protocol.
   However, the IPFIX traffic between Exporter and Collector MUST run
   in an environment where IPFIX traffic has been provisioned for or is
   contained through some other means.

 10.2       SCTP

   This section describes how IPFIX can be transported over SCTP
   [RFC2960] using the PR-SCTP [RFC3758] extension.

 10.2.1  Congestion Avoidance

   The SCTP transport protocol provides the required level of
   congestion avoidance by design.

   SCTP will detect congestion in the end-to-end path between
   the IPFIX Exporting Process and the IPFIX Collecting Process,
   and limit the transfer rate accordingly.  When an IPFIX
   Exporting Process has records to export, but detects that
   transmission by SCTP is temporarily impossible, it can either
   wait until sending is possible again, or it can decide to drop the
   record.  In the latter case, the dropped export data MUST
   be accounted for, so that the amount of dropped export data can be
   reported.

 10.2.2  Reliability

   The SCTP transport protocol is by default reliable, but has the
   capability to operate in unreliable and partially reliable modes
   [RFC3758].

   Using reliable SCTP streams (referred to hereafter as "streams") for
   the IPFIX export is not in itself a guarantee that all Data Records
   are delivered.  If there is congestion on the link from the
   Exporting Process to the Collecting Process, or if a significant
   number of retransmissions are required, the send queues on the
   Exporting Process may fill up: the Exporting Process MAY either
   suspend export or discard the IPFIX Messages.  If Data Records are
   discarded the sequence numbers used for export MUST reflect the loss
   of data.

 10.2.3  MTU



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   SCTP provides the required IPFIX Message fragmentation service based
   on path MTU discovery.

 10.2.4  Exporting Process

 10.2.4.1 Association Establishment

   The IPFIX Exporting Process SHOULD initiate an SCTP association with
   the IPFIX Collecting Process.  By default, the Collecting Process
   listens for connections on SCTP port 4739.  By default the Exporting
   Process tries to connect to this port.  It MUST be possible to
   configure both the Exporting and Collecting Processes to use a
   different SCTP port.

   The Exporting Process MAY establish more than one association
   (connection "bundle" in SCTP terminology) to the Collecting Process.

   An Exporting Process MAY support more than one active association
   to different Collecting Processes (including the case of different
   Collecting Processes on the same host).


 10.2.4.2 Association Shutdown

   When an Exporting Process is shutdown, it SHOULD shutdown the SCTP
   association.

   When a Collecting Process no longer wants to receive IPFIX
   Messages, it SHOULD shutdown its end of the association.  The
   Collecting Process SHOULD continue to receive and process
   IPFIX Messages until the Exporting Process has closed its end of the
   association.

   When a Collecting Process detects that the SCTP association has been
   abnormally terminated, it MUST continue to listen for a new
   association establishment.

   When an Exporting Process detects that the SCTP association to the
   Collecting Process is abnormally terminated, it SHOULD try to re-
   establish the association.

   Association timeouts SHOULD be configurable.




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 10.2.4.3 Stream

   An Exporting Process MUST request at least two outbound streams per
   association.  The first stream (referred to as stream zero in the
   rest of this document), is used to send the Template Set and the
   Options Template Set.  Stream zero MUST be fully reliable.  Data
   Sets MUST NOT be sent on stream zero.

   Depending on the application requirement, the Exporting Process
   selects the mode (unreliable, partially reliable, or fully reliable)
   of the stream, used to send the Data Sets.  Unreliable mode MAY be
   used where the application does not require reliable transmission
   and the use of a retransmission queue is impractical.

   An Exporter MAY use multiple streams to export Data Sets, in some
   cases different applications will have different requirements in
   terms of reliability.  In such a case, the Observation Domain MUST
   use the same Observation Domain ID value on all of the multiple
   streams it uses.

   When Data Sets are exported over a partially reliable stream, they
   SHOULD be marked for retransmission as long as there is room in the
   SCTP send queues.  However, if the queue overflows during times of
   congestion or other retransmission events, the oldest Data Record
   that has been transmitted and marked as partially reliable should be
   freed and marked to be skipped per the PR-SCTP [RFC3758]
   specification.  The freed buffer space should then be re-used for
   the new Data Sets being exported.

 10.2.4.4 Template Management

   When the transport protocol is SCTP the default Template Management
   described in Section 8 is used.

 10.2.5  Collecting Process

   When the transport protocol is SCTP, the default Collector
   processing described in Section 9 is used.

 10.2.6  Failover

   If the Collecting Process does not acknowledge the attempt by the
   Exporting Process to establish an association the Exporting Process



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   should retry using the SCTP exponential backoff feature.  The
   Exporter MAY log an alarm if the time to establish the association
   exceeds a specified threshold, configurable on the Exporter.

   If Collecting Process failover is supported by the Exporting Process
   a second SCTP association MAY be opened in advance.

 10.3       UDP

   This section describes how IPFIX can be transported over UDP
   [UDP]

 10.3.1  Congestion Avoidance

   UDP has no integral congestion avoidance mechanism.  Its use
   over congestion sensitive network paths is therefore not
   recommended.  UDP MAY be used in deployments where Exporters and
   Collectors always communicate over dedicated links that are not
   susceptible to congestion, i.e. over provisioned links compared to
   the maximum export rate from the Exporters.

 10.3.2  Reliability

   UDP is not a reliable transport protocol, and cannot guarantee
   delivery of messages.  IPFIX Messages sent from the Exporting
   Process to the Collecting Process using UDP may therefore be lost.
   UDP MUST NOT be used unless the application can tolerate some
   loss of IPFIX Messages.

   The Collecting Process SHOULD deduce the loss and reordering of
   IPFIX Data Records by looking at the discontinuities in the IPFIX
   Message sequence number. In the case of UDP, the IPFIX Message
   sequence number contains the total number of IPFIX Data Records
   received for the UDP association, prior to the receipt of this IPFIX
   Message, modulo 2^32.  A Collector SHOULD detect out of sequence,
   dropped, or duplicate IPFIX Messages by tracking the Sequence
   Number.

   Templates sent from the Exporting Process to the Collecting
   Process using UDP as a transport MUST be resent at regular
   intervals in case previous copies were lost.

 10.3.3  MTU

   The maximum size of exported messages MUST be configured such that


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   the total packet size does not exceed the path MTU.  If the path MTU
   is unknown, a maximum packet size of 512 octets SHOULD be used.

 10.3.4  Port Numbers

   By default, the Collecting Process listens on the UDP port 4739.  By
   default the Exporting Process tries to connect to this port.  It
   MUST be possible to configure both the Exporting and Collecting
   Processes to use a different UDP port.

 10.3.5  Exporting Process

   The Exporting Process MAY duplicate the IPFIX Message to the several
   Collecting Processes.

 10.3.6  Template Management

   When IPFIX uses UDP as the transport protocol, Template Sets and
   Option Template Sets MUST be re-sent at regular intervals.  The
   frequency of (Options) Template transmission MUST be configurable.
   The default value for the frequency of (Options) Template
   transmission is 10 minutes. The Exporting Process SHOULD transmit
   the Template Set and Options Template Set in advance of any Data
   Sets that use that (Options) Template ID, to help ensure that the
   Collector has the Template Record before receiving the first Data
   Record.

   In the event of configuration changes, the Exporting Process SHOULD
   send multiple copies of the new Template definitions, in different
   IPFIX Messages, at an accelerated rate.  In such a case, it SHOULD
   transmit the changed Template Record(s) and Options Template
   Record(s), without any data, in advance to help ensure that the
   Collector will have the correct Template information before
   receiving the first data.

   If the Option Template scope is defined in another Template, then
   both Templates SHOULD be sent in the same IPFIX Message. For
   example: if a Flow Key Option Template (see section 4.4) is sent in
   an Option Template, then the associated Template SHOULD be sent in
   the same IPFIX Message.

   Following a configuration change that can modify the interpretation
   of the Data Records (for example, a sampling rate change) a new



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   Template ID MUST be used and the old Template ID MUST NOT be reused
   until its lifetime (see section 10.3.7) has expired.

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


 10.3.7  Collecting Process

   The Collecting Process MUST associate a lifetime with each
   Template (or another of definition of an identifier considered unique
   within the Transport Session) received via UDP.  Templates (and
   similar definitions) not refreshed by the Exporting Process within
   the lifetime are expired at the Collecting Process.  If the Template
   (or other definition) is not refreshed before that lifetime has
   expired, the Collecting Process MUST discard that definition 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 Template.  If a
   Template is refreshed with a Template Record that differs from the
   previous received Template Record, the Collecting Process SHOULD log
   a warning and replace the previous received Template Record with the
   new one.  The Template lifetime at the Collecting Process MUST be at
   least 3 times higher than the Template refresh timeout configured on
   the Exporting Process.

   Template IDs are unique per UDP session and per Observation Domain.
   At any given time the Collecting Process SHOULD maintain the
   following for all the current Template Records and Options Template
   Records: <IPFIX Device, Exporter source UDP port, Observation Domain
   ID, Template ID, Template Definition, Last Received>.

   The Collecting Process SHOULD accept Data Records without the
   associated Template Record (or other definitions) required to decode
   the Data Record.  If the Template Records (or other definitions such
   as 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 Template Records
   (or other 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.

   If the Collecting Process receives a malformed IPFIX Message, it MUST
   discard the IPFIX Message, and SHOULD log the error.






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 10.3.8  Failover

   Because UDP is not a connection oriented protocol, the Exporting
   Process is unable to determine from the transport protocol that the
   Collecting Process is no longer able to receive the IFPIX Messages.
   Therefore, it can not invoke a failover mechanism.  However, the
   Exporting Process MAY duplicate the IPFIX Message to several
   Collecting Processes.

 10.4      TCP

   This section describes how IPFIX can be transported over TCP [TCP].

 10.4.1  Connection Management

 10.4.1.1 Connection Establishment

   The IPFIX Exporting Process initiates a TCP connection to the
   Collecting Process.  By default, the Collecting Process listens for
   connections on TCP port 4739. By default the Exporting Process tries
   to connect to this port.  It MUST be possible to configure both the
   Exporting Process and the Collecting Process to use a different TCP
   port.

   An Exporting Process MAY support more than one active connection to
   different Collecting Processes (including the case of different
   Collecting Processes on the same host).

   The Exporter MAY log an alarm if the time to establish the
   connection exceeds a specified threshold, configurable on the
   Exporter.


 10.4.1.2 Graceful Connection Release

   When an Exporting Process is shutdown, it SHOULD shutdown the TCP
   connection.

   When a Collecting Process no longer wants to receive IPFIX Messages,
   it SHOULD close its end of the connection.  The Collecting Process
   SHOULD continue to read IPFIX Messages until the Exporting Process
   has closed its end.




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 10.4.1.3 Restarting Interrupted Connections

   When a Collecting Process detects that the TCP connection to the
   Exporting Process has terminated abnormally, it MUST continue to
   listen for a new connection.

   When an Exporting Process detects that the TCP connection to the
   Collecting Process has terminated abnormally, it SHOULD try to re-
   establish the connection.  Connection timeouts and retry schedules
   SHOULD be configurable.  In the default configuration, an Exporting
   Process MUST NOT attempt to establish a connection more frequently
   than once per minute.

 10.4.1.4 Failover

   If the Collecting Process does not acknowledge the attempt by the
   Exporting Process to establish a connection it will retry using the
   TCP exponential backoff feature.

   If Collecting Process failover is supported by the Exporting Process
   a second TCP connection MAY be opened in advance.

 10.4.2  Data Transmission

   Once a TCP connection is established, the Exporting Process starts
   sending IPFIX Messages to the Collecting Process.

 10.4.2.1 IPFIX Message Encoding

   IPFIX Messages are sent over the TCP connection without any special
   encoding.  The Length field in the IPFIX Message header defines the
   end of each IPFIX Message and thus the start of the next IPFIX
   Message.  This means that IPFIX Messages cannot be interleaved.

   In the case of TCP, the IPFIX Message sequence number contains the
   total number of IPFIX Data Records received for the TCP connection,
   prior to the receipt of this IPFIX Message, modulo 2^32.

   If an Exporting Process exports data from multiple Observation
   Domains, it should be careful to choose IPFIX Message lengths
   appropriately to minimize head-of-line blocking between different
   Observation Domains.  Multiple TCP connections MAY be used to avoid
   head-of-line between different Observation Domains.



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 10.4.2.2 Templates Management

   For each Template, the Exporting Process MUST send the Template
   Record before exporting Data Records that refer to that Template.

   Template IDs are unique per TCP connection and per Observation
   Domain.  A Collecting Process MUST record all Template and Options
   Template Records for the duration of the connection, as an Exporting
   Process is not required to re-export Template Records.

   When the TCP connection restarts, the Exporting Process MUST resend
   all the Template Records.

   When a TCP connection is closed, the Collecting Process MUST discard
   all Templates received over that connection and stop decoding IPFIX
   Messages that use those Templates.

   The Templates that are not used anymore SHOULD be deleted.  Before
   reusing a Template ID, the Template MUST be deleted.  In order to
   delete an allocated Template, the Template is withdrawn through the
   use of a Template Withdrawal Message over the TCP connection.

   If the Collecting Process receives a malformed IPFIX Message, it
   MUST reset the TCP connection, discard the IPFIX Message, and SHOULD
   log the error.

 10.4.2.3 Congestion Handling and Reliability

   TCP ensures reliable delivery of data from the Exporting Process to
   the Collecting Process.  TCP also controls the rate at which data
   can be sent from the Exporting Process to the Collecting Process,
   using a mechanism that takes into account both congestion in the
   network and the capabilities of the receiver.

   Therefore an IPFIX Exporting Process may not be able to send IPFIX
   Messages at the rate that the Metering Process generates it, either
   because of congestion in the network or because the Collecting
   Process cannot handle IPFIX Messages fast enough.  As long as
   congestion is transient, the Exporting Process can buffer IPFIX
   Messages for transmission.  But such buffering is necessarily
   limited, both because of resource limitations and because of
   timeliness requirements, so ongoing and/or severe congestion may
   lead to a situation where the Exporting Process is blocked.



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   When an Exporting Process has Data Records to export but the
   transmission buffer is full, and it wants to avoid blocking, it can
   decide to drop some Data Records.  The dropped Data Records MUST be
   accounted for, so that the amount can later be exported.

   When an Exporting Process finds that the rate at which records
   should be exported is consistently higher than the rate at which TCP
   sending permits, it should provide back pressure to the metering
   processes.  The metering process could then adapt by temporarily
   reducing the amount of data it generates, for example using sampling
   or aggregation.

 11.      Security Considerations

   The security considerations for the IPFIX protocol have been derived
   from an analysis of potential security threats, as discussed in the
   security consideration section of IPFIX requirements [RFC3917].  The
   requirements for IPFIX security are as follows:

     1. IPFIX must provide a mechanism to ensure the confidentiality of
     IPFIX data transferred from an Exporting Process to a Collecting
     Process, in order to prevent disclosure of flow data transported
     via IPFIX.

     2. IPFIX must provide a mechanism to ensure the integrity of IPFIX
     data transferred from an Exporting Process to a Collecting Process,
     in order to prevent the injection of incorrect data or control
     information (e.g. Templates) into an IPFIX Message stream.

     3. IPFIX must provide a mechanism to authenticate IPFIX Collecting
     and Exporting Processes, to prevent the collection of data from an
     unauthorized Exporting Process, or the export of data to an
     unauthorized Collecting Process

   Because IPFIX can be used to collect information for network
   forensics and billing purposes, attacks designed to confuse, disable,
   or exfiltrate information from an IPFIX collection system may be seen
   as a prime objective during a sophisticated network attack.

   An attacker in a position to inject false messages into an IPFIX
   Message stream can either affect the application using IPFIX (by
   falsifying data), or the IPFIX Collecting Process itself (by
   modifying or revoking Templates, or changing options); for this
   reason, IPFIX Message integrity is important.

   The IPFIX Messages themselves may also contain information of value
   to an attacker, including information about the configuration of the
   network as well as end-user traffic and payload data, so care must be


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   taken to confine their visibility to authorized users.  When an
   Information Element containing end-user payload information is
   exported, it SHOULD be transmitted to the Collecting Process using a
   means that secures its contents against eavesdropping.  Suitable
   mechanisms include the use of either a direct point-to-point
   connection or the use of an encryption mechanism.  It is the
   responsibility of the Collecting Process to provide a satisfactory
   degree of security for this collected data, including, if necessary,
   anonymization of any reported data.


 11.1       Applicability of TLS and DTLS

   TLS [RFC4346] and DTLS [RFC4347] were designed to provide the
   confidentiality, integrity, and authentication assurances required by
   the IPFIX protocol, without the need for pre-shared keys.

   With the mandatory SCTP and PR-SCTP transport protocols for IPFIX,
   DTLS [RFC4347] MUST be implemented.  If UDP is selected as the IPFIX
   transport protocol, DTLS [RFC4347] MUST be implemented.  If TCP is
   selected as the IPFIX transport protocol, TLS [RFC4346] MUST be
   implemented.

   Note that DTLS is selected as the security mechanism for SCTP and
   PR-SCTP. Though TLS bindings to SCTP are defined in [RFC3436], they
   require all communication to be over reliable streams, and require
   one session per stream.  This arrangement is not compatible with the
   rationale behind the choice of SCTP as an IPFIX transport protocol.

   Note that using RFC 4347 has a vulnerability, i.e. a true man in the
   middle may attempt to take data out of an association and fool the
   sender into thinking that the data was actually received by the peer.
   In generic TLS for SCTP (and/or TCP) this is not possible.  This
   means that the removal of a message may become hidden from the sender
   or receiver.  Another vulnerability of using PR-SCTP with DTLS is
   that someone could inject SCTP control information to shut down the
   SCTP association, effectively generating a loss of IPFIX Messages if
   those are buffered outside of the SCTP association.


 11.2       Usage

   The IPFIX Exporting Process initiates the communication IPFIX to the
   Collecting Process, and acts as a TLS or DTLS client according to
   [RFC4346] and [RFC4347], while the IPFIX Collecting Process acts as a
   TLS or DTLS server.  The DTLS client opens a secure connection on the
   SCTP port 4740 of the DTLS server if SCTP or PR-SCTP is selected as
   the transport protocol.  The TLS client opens a secure connection on
   the TCP port 4740 of the TLS server if TCP is selected as the
   transport protocol.  The DTLS client opens a secure connection on the


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   UDP port 4740 of the DTLS server if UDP is selected as the transport
   protocol.


 11.3       Authentication

   IPFIX Exporting Processes and IPFIX Collecting Processes are
   identified by the fully-qualified domain name of the interface on
   which IPFIX Messages are sent or received, for purposes of X.509
   client and server certificates as in [RFC3280].

   To prevent man-in-the-middle attacks from impostor Exporting or
   Collecting Processes, the acceptance of data from an unauthorized
   Exporting Process, or the export of data to an unauthorized
   Collecting Process, strong mutual authentication via asymmetric keys
   MUST be used for both TLS and DTLS.  Each of the IPFIX Exporting and
   Collecting Processes MUST verify the identity of its peer against its
   authorized certificates, and MUST verify that the peer's certificate
   matches its fully-qualified domain name, or, in the case of SCTP, the
   fully-qualified domain name of one of its endpoints.


 11.4       Protection against DoS attacks

   An attacker may mount a denial of service attack against an IPFIX
   collection system either directly, by sending large amounts of
   traffic to a Collecting Process, or indirectly, by generating large
   amounts of traffic to be measured by a Metering Process.

   Direct denial of service attacks can also involve state exhaustion,
   whether at the transport layer (e.g., by creating a large number of
   pending connections), or within the IPFIX Collecting Process itself
   (e.g., by sending Flow Records pending Template or Scope information,
   a large amount of Options Template Records, etc.)

   SCTP mandates a cookie exchange mechanism designed to defend against
   SCTP state exhaustion denial of service attacks. Similarly, TCP
   provides the "SYN cookie" mechanism to mitigate state exhaustion; SYN
   cookies SHOULD be used by any Collecting Process accepting TCP
   connections.  DTLS also provides cookie exchange to protect against
   DTLS server state exhaustion.

   The reader should note that there is no way to prevent fake IPFIX
   Messages processing (and states creation) for UDP & SCTP
   communication.  The use of TLS and DTLS can obviously prevent the
   creation of fake states but they are themselves prone to states
   exhaustion attacks.  Therefore, a Collector rate limiting SHOULD be
   used to protect TLS & DTLS (like limiting the number of new TLS or
   DTLS session per second to a sensible number).



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   IPFIX state exhaustion attacks can be mitigated by limiting the rate
   at which new connections or associations will be opened by the
   Collecting Process, the rate at IPFIX Messages will be accepted by
   the Collecting Process, and adaptively limiting the amount of state
   kept, particularly data records pending Templates or scope.  These
   rate and state limits MAY be provided by a Collecting Process; if
   provided, the limits SHOULD be user-configurable.

   Additionally, an IPFIX Collecting Process can eliminate the risk of
   state exhaustion attacks from untrusted nodes by requiring TLS or
   DTLS mutual authentication, causing the Collecting Process to accept
   IPFIX Messages only from trusted sources.

   With respect to indirect denial of service, the behavior of IPFIX
   under overload conditions depends on the transport protocol in use.
   For IPFIX over TCP, TCP congestion control would cause the flow of
   IPFIX Messages to back off and eventually stall, blinding the IPFIX
   system.  PR-SCTP improves upon this situation somewhat, as some IPFIX
   Messages would continue to be received by the Collecting Process due
   to the avoidance of head-of-line blocking by SCTP's multiple streams
   and partial reliability features, possibly affording some visibility
   of the attack.  The situation is similar with UDP, as some datagrams
   may continue to be received at the Collecting Process, effectively
   applying sampling to the IPFIX Message stream, implying that some
   forensics may be left.

   To minimize IPFIX Message loss under overload conditions, some
   mechanism for service differentiation could be used to prioritize
   IPFIX traffic over other traffic on the same link.  Alternatively,
   IPFIX Messages can be transported over a dedicated network.  In this
   case, care must be taken to ensure the dedicated network can handle
   the expected peak IPFIX Message traffic.


 11.5       When DTLS or TLS is not an option

   The use of DTLS or TLS might not be possible in some cases due to
   performance issues or other operational concerns.

   Without TLS or DTLS mutual authentication, IPFIX Exporting Processes
   and Collecting Processes can fall back on using IP source addresses
   to authenticate their peers.  A policy of allocating Exporting
   Process and Collecting Process IP addresses from specified address
   ranges, and using ingress filtering to prevent spoofing, can improve
   the usefulness of this approach.  Again, completely segregating IPFIX
   traffic on a dedicated network, where possible, can improve security
   even further.  In any case, the use of open Collecting Processes
   (those which will accept IPFIX Messages from any Exporting Process
   regardless of IP address or identity) is discouraged.


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   Modern TCP and SCTP implementations are resistent to blind insertion
   attacks (see [RFC1948], [RFC2960]); however, UDP offers no such
   protection.  For this reason, IPFIX Message traffic transported via
   UDP and not secured via DTLS SHOULD be protected via segregation to a
   dedicated network.

 11.6       Logging an IPFIX Attack

   IPFIX Collecting Processes MUST detect potential IPFIX Message
   insertion or loss conditions by tracking the IPFIX Sequence Number,
   and SHOULD provide a logging mechanism for reporting out of sequence
   messages.  Note that an attacker may be able to exploit the handling
   of out of sequence messages at the Collecting Process, so care should
   be taken in handling these conditions.  For example, a Collecting
   Process that simply resets the expected Sequence Number upon receipt
   of a later Sequence Number could be temporarily blinded by deliberate
   injection of later Sequence Numbers.

   IPFIX Exporting and Collecting Processes SHOULD log any connection
   attempt that fails due to authentication failure, whether due to
   being presented an unauthorized or mismatched certificate during TLS
   or DTLS mutual authentication, or due to a connection attempt from an
   unauthorized IP address when TLS or DTLS are not in use.

   IPFIX Exporting and Collecting Processes SHOULD detect and log any
   SCTP association reset or TCP connection reset.


 11.7       Securing the Collector

   The security of the Collector and its implementation is important to
   achieve overall security. However, it is outside the scope of this
   document.


 12.      IANA Considerations

   IPFIX Messages use two fields with assigned values.  These are the
   IPFIX Version Number, indicating which version of the IPFIX Protocol
   was used to export an IPFIX Message, and the IPFIX Set ID,
   indicating the type for each set of information within an IPFIX
   Message.

   The IPFIX Version Number value of 10 is reserved for the IPFIX
   Protocol specified in this document.  Set ID values of 0 and 1 are
   not used for historical reasons [RFC3954].  The Set ID value of 2 is
   reserved for the Template Set.  The Set ID value of 3 is reserved


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   for the Option Template Set.  All other Set ID values from 4 to 255
   are reserved for future use. Set ID values above 255 are used for
   Data Sets.

   New assignments in either IPFIX Version Number or IPFIX Set ID
   assignments require a Standards Action [RFC2434], i.e. they are to
   be made via Standards Track RFCs approved by the IESG.


13.     Appendix A

   This appendix, which is a not a normative reference, contains IPFIX
   encoding examples.

   Let's consider the example of an IPFIX Message composed of a
   Template Set, a Data Set (which contains three Data Records), an
   Options Template Set and a Data Set (which contains 2 Data Records
   related to the previous Options Template Record).

   IPFIX Message:

   +--------+------------------------------------------. . .
   |        | +--------------+ +------------------+
   |Message | | Template     | | Data             |
   | Header | | Set          | | Set              |   . . .
   |        | | (1 Template) | | (3 Data Records) |
   |        | +--------------+ +------------------+
   +--------+------------------------------------------. . .

        . . .-------------------------------------------+
              +------------------+ +------------------+ |
              | Options          | | Data             | |
       . . .  | Template Set     | | Set              | |
              | (1 Template)     | | (2 Data Records) | |
              +------------------+ +------------------+ |
        . . .-------------------------------------------+

 13.1       Message Header Example

   The Message Header is composed of:
    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Version = 0x000a          |         Length = 152          |



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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Export Time                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Sequence Number                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Observation Domain ID                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


 13.2       Template Set Examples

 13.2.1  Template Set using IETF specified Information Elements

   We want to report the following Information Elements:

   - The IPv4 source IP address: sourceIPv4Address in [IPFIX-INFO],
   with a length of 4 octets
   - The IPv4 destination IP address: destinationIPv4Address in [IPFIX-
   INFO], with a length of 4 octets

   - The next-hop IP address (IPv4): ipNextHopIPv4Address in [IPFIX-
   INFO], with a length of 4 octets

   - The number of packets of the Flow: inPacketDeltaCount in [IPFIX-
   INFO], with a length of 4 octets

   - The number of octets of the Flow: inOctetDeltaCount in [IPFIX-
   INFO], with a length of 4 octets

   Therefore, the Template Set will be composed of the following:

    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 = 28 octets       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Template ID 256         |       Field Count = 5         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|    sourceIPv4Address = 8    |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0| destinationIPv4Address = 12 |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|  ipNextHopIPv4Address = 15  |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


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   |0|   inPacketDeltaCount = 2    |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|   inOctetDeltaCount =  1    |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


 13.2.2  Template Set using Enterprise Specific Information Elements

      We want to report the following Information Elements:

      - The IPv4 source IP address: sourceIPv4Address in [IPFIX-INFO],
        with a length of 4 octets

      - The IPv4 destination IP address: destinationIPv4Address in
        [IPFIX-INFO], with a length of 4 octets

      - An enterprise-specific Information Element representing
        proprietary information, with a type of 15 and a length of 4

      - The number of packets of the Flow: inPacketDeltaCount in
        [IPFIX-INFO], with a length of 4 octets

      - The number of octets of the Flow: inOctetDeltaCount in
        [IPFIX-INFO], with a length of 4 octets

    Therefore, the Template Set will be composed of the following:

       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 = 32 octets       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       Template ID 257         |       Field Count = 5         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|    sourceIPv4Address = 8    |       Field Length = 4        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0| destinationIPv4Address = 12 |       Field Length = 4        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1| Information Element Id. = 15|       Field Length = 4        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Enterprise number                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|   inPacketDeltaCount = 2    |       Field Length = 4        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


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      |0|   inOctetDeltaCount = 1     |       Field Length = 4        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 13.3       Data Set Example

   In this example, we report the following three Flow Records:

   Src IP addr. | Dst IP addr.  | Next Hop addr. | Packet | Octets
                |               |                | Number | Number
   ------------------------------------------------------------------
   192.0.2.12   | 192.0.2.254   | 192.0.2.1      | 5009   | 5344385
   192.0.2.27   | 192.0.2.23    | 192.0.2.2      | 748    | 388934
   192.0.2.56   | 192.0.2.65    | 192.0.2.3      | 5      | 6534

    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 = 256         |          Length = 64          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          192.0.2.12                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          192.0.2.254                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          192.0.2.1                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             5009                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            5344385                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          192.0.2.27                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          192.0.2.23                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          192.0.2.2                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              748                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             388934                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          192.0.2.56                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          192.0.2.65                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          192.0.2.3                            |


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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               5                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              6534                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Note that padding is not necessary in this example.

 13.4       Options Template Set Examples

 13.4.1  Options Template Set using IETF specified Information Elements

   Per line card (the router being composed of two line cards), we want
   to report the following Information Elements:

      - Total number of IPFIX Messages: exportedPacketCount
        [IPFIX-INFO], with a length of 2 octets

      - Total number of exported Flows: exportedFlowCount [IPFIX-INFO],
        with a length of 2 octets

   The line card, which is represented by the lineCardId Information
   Element [IPFIX-INFO], is used as the Scope Field.

   Therefore, the Options Template Set will be:

    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          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Template ID 258         |        Field Count = 3        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Scope Field Count = 1     |0|     lineCardId = 141        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Scope 1 Field Length = 4    |0|  exportedPacketCount = 41   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Field Length = 2        |0|   exportedFlowCount = 42    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Field Length = 2        |           Padding             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+





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 13.4.2  Options Template Set using enterprise-specific Information
          Elements
   Per line card (the router being composed of two line cards), we want
   to report the following Information Elements:

     - Total number of IPFIX Messages: exportedPacketCount
       [IPFIX-INFO], with a length of 2 octets

     - An enterprise-specific number of exported Flows,
       with a type of 42 and a length of 4 octets

   The line card, which is represented by the lineCardId Information
   Element [IPFIX-INFO], is used as the Scope Field.

   The format of the Options Template Set is as follows:

       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 = 28          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       Template ID 259         |        Field Count = 3        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Scope Field Count = 1     |0|     lineCardId = 141        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Scope 1 Field Length = 4    |0|  exportedPacketCount = 41   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       Field Length = 2        |1|Information Element Id. = 42 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       Field Length = 4        |       Enterprise number     ...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ...      Enterprise number      |           Padding             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


 13.4.3  Options Template Set using an enterprise-specific scope

   In this example, we want to export the same information as in the
   example in section 13.4.1:

      - Total number of IPFIX Messages: exportedPacketCount
        [IPFIX-INFO], with a length of 2 octets




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      - Total number of exported Flows: exportedFlowCount
        [IPFIX-INFO], with a length of 2 octets

   But this time, the information pertains to a proprietary scope,
   identified by enterprise-specific Information Element number 123.

   The format of the Options Template Set is now as follows:

    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 = 28          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Template ID 260         |        Field Count = 3        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Scope Field Count = 1     |1|Scope 1 Infor. El. Id. = 123 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Scope 1 Field Length = 4   |       Enterprise Number      ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  ...       Enterprise Number      |0|  exportedPacketCount = 41   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Field Length = 2        |0|   exportedFlowCount = 42    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Field Length = 2        |           Padding             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


 13.4.4  Data Set using an enterprise-specific scope

   In this example, we report the following two Data Records:

   Line Card ID               | IPFIX Message  | Exported Flow Records
   -------------------------------------------------------------------
   Line Card 1 (lineCardId=1) | 345            | 10201
   Line Card 2 (lineCardId=2) | 690            | 20402

     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 = 260             |         Length = 20           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                               1                               |



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    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |             345               |            10201              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                               2                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |             690               |            20402              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 13.5      Variable length Information Element examples

 13.5.1  Example of Variable Length Information Element with Length
          inferior to 255 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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       5       |          5 octet Information Element          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


 13.5.2  Example of Variable Length Information Element with Length 255
          to 65535 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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      255      |             1000              |    IE ...     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                1000 octet Information Element                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     :                              ...                              :
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                             ... IE            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


 14.     References

 14.1      Normative References






  Claise, et. al            Standard Track                   [Page 59]

                   IPFIX Protocol Specification           October 2006

   [IPFIX-ARCH] Sadasivan, G., Brownlee, N., Claise, B., Quittek, J.,
   "Architecture Model for IP Flow Information Export" draft-ietf-ipfix-
   architecture-12, September 2006

   [IPFIX-INFO] Quittek, J., Bryant S., Claise, B., Meyer, J.
   "Information Model for IP Flow Information Export" draft-ietf-ipfix-
   info-12, June 2006

   [UDP]  Postel, J., "User Datagram Protocol" RFC 768, August 1980

   [TCP]  "TRANSMISSION CONTROL PROTOCOL DARPA INTERNET PROGRAM PROTOCOL
   SPECIFICATION" RFC 793, September 1981

   [RFC1305]  Mills, D., "Network Time Protocol (Version 3)
   Specification, Implementation and Analysis", RFC 1305, May 1992

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

   [RFC2402] Kent, S., Atkinson, R., "IP Authentication Header ", RFC
   2402, November 1998

   [RFC2406] Kent, S., Atkinson, R., "IP Encapsulating Security Payload
   (ESP)", RFC 2406, November 1998

   [RFC2434] Alvestrand, H. and T. Narten, "Guidelines for Writing an
   IANA Considerations Section in RFCs", RFC 2434, October 1998.

   [RFC2960] Stewart, R. (ed.) "Stream Control Transmission Protocol",
   RFC 2960, October 2000

   [RFC3436] Rescorla, E., Tuexen, M., "Transport Layer Security over
   Stream Control Transmission Protocol", RFC 3436, December 2002

   [RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., Conrad, P.
   "Stream Control Transmission Protocol (SCTP) Partial Reliability
   Extension", RFC 3758, May 2004

   [RFC4346] Dierks, T. and C. Allen, "The TLS Protocol Version 1.1",
   RFC 4346, April 2006.

   [RFC4347] Rescola, E., Modadugy, N. "Datagram Transport Layer
   Security", RFC 4347, April 2006


 14.2      Informative References

   [IKE] Harkins, D. and D. Carrel, "The Internet Key Exchange (IKE)",
   RFC 2409, November 1998.



  Claise, et. al            Standard Track                   [Page 60]

                   IPFIX Protocol Specification           October 2006


   [IPFIX-AS] Zseby, T., Boschi, E., Brownlee, N., Claise, B., "IPFIX
   Applicability", draft-ietf-ipfix-as-06.txt, May 2005

   [PEN] IANA Private Enterprise Numbers registry
   http://www.iana.org/assignments/enterprise-numbers


   [RFC1948]  Bellovin, S., "Defending Against Sequence Number
   Attacks", RFC 1948, May 1996

   [RFC2579] McCloghrie, K., et al "Textual Conventions for SMIv2", RFC
   2579, April 1999

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

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

   [RFC3954] Claise, B., et al "Cisco Systems NetFlow Services Export
   Version 9", RFC 3954, October 2004

   [IEEE.754.1985] Institute of Electrical and Electronics Engineers,
              "Standard for Binary Floating-Point Arithmetic", IEEE
              Standard 754, August 1985.


 15.      Acknowledgments

   We would like to thank the following persons: Juergen Quittek for
   the coordination job within IPFIX and PSAMP; Nevil Brownlee, Dave
   Plonka, Paul Aitken, and Andrew Johnson for the thorough reviews;
   Randall Stewart and Peter Lei for their SCTP expertise and
   contributions; Martin Djernaes for the first essay on the SCTP
   section; Michael Behringer and Eric Vyncke for their advices and
   knowledge in security; Brian Trammell for his technical feedback and
   contribution throughout the document; Mark Fullmer, Sebastian
   Zander, Jeff Meyer, Maurizio Molina, Carter Bullard, Tal Givoly,
   Lutz Mark, David Moore, Robert Lowe, Paul Calato, and many more, for
   the technical review and feedback.

 Authors' Addresses

   Benoit Claise
   Cisco Systems



  Claise, et. al            Standard Track                   [Page 61]

                   IPFIX Protocol Specification           October 2006

   De Kleetlaan 6a b1
   1831 Diegem
   Belgium
   Phone: +32 2 704 5622
   E-mail: bclaise@cisco.com

   Stewart Bryant
   Cisco Systems, Inc.
   250, Longwater,
   Green Park,
   Reading, RG2 6GB,
   United Kingdom
   Phone: +44 (0)20 8824-8828
   Email: stbryant@cisco.com

   Ganesh Sadasivan
   Cisco Systems, Inc.
   170 W. Tasman Dr.
   San Jose, CA 95134
   USA
   Phone: +1 (408) 527-0251
   Email: gsadasiv@cisco.com

   Simon Leinen
   SWITCH
   Limmatquai 138
   P.O. Box
   CH-8021 Zurich
   Switzerland
   Phone: +41 1 268 1536
   EMail: simon@switch.ch

   Thomas Dietz
   NEC Europte Ltd.
   Network Laboratories
   Kurfuersten-Anlage 36
   69115 Heidelberg
   Germany
   Phone: +49 6221 90511-28
   Email: dietz@netlab.nec.de

Intellectual Property Statement




  Claise, et. al            Standard Track                   [Page 62]

                   IPFIX Protocol Specification           October 2006

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