path: root/doc/rfc/rfc7011.txt

Internet Engineering Task Force (IETF)                    B. Claise, Ed.
Request for Comments: 7011                           Cisco Systems, Inc.
STD: 77                                                 B. Trammell, Ed.
Obsoletes: 5101                                               ETH Zurich
Category: Standards Track                                      P. Aitken
ISSN: 2070-1721                                      Cisco Systems, Inc.
                                                          September 2013


    Specification of the IP Flow Information Export (IPFIX) Protocol
                  for the Exchange of Flow Information

Abstract

   This document specifies the IP Flow Information Export (IPFIX)
   protocol, which serves as a means for transmitting Traffic Flow
   information over the network.  In order to transmit Traffic Flow
   information from an Exporting Process to a Collecting Process, a
   common representation of flow data and a standard means of
   communicating them are required.  This document describes how the
   IPFIX Data and Template Records are carried over a number of
   transport protocols from an IPFIX Exporting Process to an IPFIX
   Collecting Process.  This document obsoletes RFC 5101.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7011.














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Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................5
      1.1. Changes since RFC 5101 .....................................5
      1.2. IPFIX Documents Overview ...................................6
   2. Terminology .....................................................7
      2.1. Terminology Summary Table .................................13
   3. IPFIX Message Format ...........................................13
      3.1. Message Header Format .....................................15
      3.2. Field Specifier Format ....................................16
      3.3. Set and Set Header Format .................................18
           3.3.1. Set Format .........................................18
           3.3.2. Set Header Format ..................................19
      3.4. Record Format .............................................20
           3.4.1. Template Record Format .............................20
           3.4.2. Options Template Record Format .....................23
                  3.4.2.1. Scope .....................................23
                  3.4.2.2. Options Template Record Format ............24
           3.4.3. Data Record Format .................................27
   4. Specific Reporting Requirements ................................28
      4.1. The Metering Process Statistics Options Template ..........29
      4.2. The Metering Process Reliability Statistics
           Options Template ..........................................29
      4.3. The Exporting Process Reliability Statistics
           Options Template ..........................................31
      4.4. The Flow Keys Options Template ............................32
   5. Timing Considerations ..........................................32
      5.1. IPFIX Message Header Export Time and Flow Record Time .....32
      5.2. Supporting Timestamp Wraparound ...........................33







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   6. Linkage with the Information Model .............................34
      6.1. Encoding of IPFIX Data Types ..............................34
           6.1.1. Integral Data Types ................................34
           6.1.2. Address Types ......................................34
           6.1.3. float32 ............................................34
           6.1.4. float64 ............................................34
           6.1.5. boolean ............................................35
           6.1.6. string and octetArray ..............................35
           6.1.7. dateTimeSeconds ....................................35
           6.1.8. dateTimeMilliseconds ...............................35
           6.1.9. dateTimeMicroseconds ...............................35
           6.1.10. dateTimeNanoseconds ...............................36
      6.2. Reduced-Size Encoding .....................................36
   7. Variable-Length Information Element ............................37
   8. Template Management ............................................38
      8.1. Template Withdrawal and Redefinition ......................40
      8.2. Sequencing Template Management Actions ....................42
      8.3. Additional Considerations for Template Management
           over SCTP .................................................43
      8.4. Additional Considerations for Template Management
           over UDP ..................................................44
   9. The Collecting Process's Side ..................................45
      9.1. Collecting Process Handling of Malformed IPFIX Messages ...46
      9.2. Additional Considerations for SCTP Collecting Processes ...46
      9.3. Additional Considerations for UDP Collecting Processes ....46
   10. Transport Protocol ............................................47
      10.1. Transport Compliance and Transport Usage .................47
      10.2. SCTP .....................................................48
           10.2.1. Congestion Avoidance ..............................48
           10.2.2. Reliability .......................................49
           10.2.3. MTU ...............................................49
           10.2.4. Association Establishment and Shutdown ............49
           10.2.5. Failover ..........................................50
           10.2.6. Streams ...........................................50
      10.3. UDP ......................................................50
           10.3.1. Congestion Avoidance ..............................50
           10.3.2. Reliability .......................................51
           10.3.3. MTU ...............................................51
           10.3.4. Session Establishment and Shutdown ................51
           10.3.5. Failover and Session Duplication ..................51
      10.4. TCP ......................................................52
           10.4.1. Congestion Avoidance ..............................52
           10.4.2. Reliability .......................................52
           10.4.3. MTU ...............................................52
           10.4.4. Connection Establishment and Shutdown .............53
           10.4.5. Failover ..........................................53





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   11. Security Considerations .......................................54
      11.1. Applicability of TLS and DTLS ............................55
      11.2. Usage ....................................................56
      11.3. Mutual Authentication ....................................56
      11.4. Protection against DoS Attacks ...........................57
      11.5. When DTLS or TLS Is Not an Option ........................58
      11.6. Logging an IPFIX Attack ..................................58
      11.7. Securing the Collector ...................................59
      11.8. Privacy Considerations for Collected Data ................59
   12. Management Considerations .....................................60
   13. IANA Considerations ...........................................61
   Appendix A. IPFIX Encoding Examples ...............................62
      A.1. Message Header Example ....................................62
      A.2. Template Set Examples .....................................63
        A.2.1. Template Set Using IANA Information Elements ..........63
        A.2.2. Template Set Using Enterprise-Specific Information
               Elements ..............................................64
      A.3. Data Set Example ..........................................65
      A.4. Options Template Set Examples .............................66
        A.4.1. Options Template Set Using IANA Information Elements ..66
        A.4.2. Options Template Set Using Enterprise-Specific
               Information Elements ..................................66
        A.4.3. Options Template Set Using an Enterprise-Specific
               Scope .................................................67
        A.4.4. Data Set Using an Enterprise-Specific Scope ...........68
      A.5. Variable-Length Information Element Examples ..............69
        A.5.1. Example of Variable-Length Information Element with
               Length Less Than 255 Octets ...........................69
        A.5.2. Example of Variable-Length Information Element with
               3-Octet Length Encoding ...............................70
   Normative References ..............................................71
   Informative References ............................................71
   Acknowledgments ...................................................74
   Contributors ......................................................75

















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1.  Introduction

   Traffic on a data network can be seen as consisting of flows passing
   through network elements.  For administrative or other purposes, it
   is often interesting, useful, or even necessary to have access to
   information about these flows that pass through the network elements.
   A 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 a protocol
   to achieve these requirements.  This document specifies in detail the
   representation of different flows, as well as the additional data
   required for flow interpretation, packet format, transport mechanisms
   used, security concerns, etc.

1.1.  Changes since RFC 5101

   This document obsoletes the Proposed Standard revision of the IPFIX
   Protocol Specification [RFC5101].  The protocol specified by this
   document is interoperable with the protocol as specified in
   [RFC5101].  The following changes have been made to this document
   with respect to the previous document:

   - All outstanding technical and editorial errata on [RFC5101] have
     been addressed.

   - As the [IANA-IPFIX] registry is now the normative reference for all
     Information Element definitions (see [RFC7012]), all definitions of
     Information Elements in Section 4 have been replaced with
     references to that registry.

   - The encoding of the dateTimeSeconds, dateTimeMilliseconds,
     dateTimeMicroseconds, and dateTimeNanoseconds data types, and the
     related encoding of the IPFIX Message Header Export Time field,
     have been clarified, especially with respect to the epoch upon
     which the timestamp data types are based.

   - A new Section 5.2 has been added to address wraparound of these
     timestamp data types after they overflow in the years 2032-2038.

   - Clarifications on encoding, especially in Section 6, have been
     made: all IPFIX values are encoded in network byte order.








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   - Template management, as described in Section 8, has been simplified
     and clarified: the specification has been relaxed with respect to
     [RFC5101], especially concerning potential failures in Template ID
     reuse.  Additional corner cases in template management have been
     addressed.  The new template management language is interoperable
     with that in [RFC5101] to the extent that the behavior was defined
     in the prior specification.

   - Section 11.3 (Mutual Authentication) has been improved to refer to
     current practices in Transport Layer Security (TLS) mutual
     authentication; references to Punycode were removed, as these are
     covered in [RFC6125].

   - Editorial improvements, including structural changes to Sections 8,
     9, and 10 to improve readability, have been applied.  Behavior
     common to all transport protocols has been separated out, with
     exceptions per transport specifically noted.  All template
     management language (on both Exporting and Collecting Processes)
     has been unified in Section 8.

   - A new Section 12 on management considerations has been added.

1.2.  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 [RFC5470], 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 Processes.

   Four IPFIX optimizations/extensions are currently specified: a
   bandwidth-saving method for the IPFIX protocol [RFC5473], an
   efficient method for exporting bidirectional flows [RFC5103], a
   method for the definition and export of complex data structures
   [RFC6313], and the specification of the Protocol on IPFIX Mediators
   [IPFIX-MED-PROTO] based on the IPFIX Mediation Framework [RFC6183].

   A "file-based transport" for IPFIX, which defines how IPFIX Messages
   can be stored in files for document-based workflows and for archival
   purposes, is discussed in [RFC5655].

   IPFIX has a formal description of IPFIX Information Elements -- their
   names, data types, and additional semantic information -- as
   specified in [RFC7012].  The registry is maintained by IANA
   [IANA-IPFIX].  The inline export of the Information Element type
   information is specified in [RFC5610].



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   The framework for packet selection and reporting [RFC5474] enables
   network elements to select subsets of packets by statistical and
   other methods, and to export a stream of reports on the selected
   packets to a Collector.  The set of packet selection techniques
   (Sampling, Filtering, and hashing) standardized by the Packet
   Sampling (PSAMP) protocol is described in [RFC5475].  The PSAMP
   protocol [RFC5476], which uses IPFIX as its export protocol,
   specifies the export of packet information from a PSAMP Exporting
   Process to a PSAMP Collector.  Instead of exporting PSAMP Packet
   Reports, the stream of selected packets may also serve as input to
   the generation of IPFIX Flow Records.  Like IPFIX, PSAMP has a formal
   description of its Information Elements: their names, types, and
   additional semantic information.  The PSAMP information model is
   defined in [RFC5477].

   [RFC6615] specifies a MIB module for monitoring, and [RFC6728]
   specifies a data model for configuring and monitoring IPFIX and
   PSAMP-compliant devices using the Network Configuration Protocol
   (NETCONF).  [RFC6727] specifies the PSAMP MIB module as an extension
   of the IPFIX SELECTOR MIB module defined in [RFC6615].

   In terms of development, [RFC5153] provides guidelines for the
   implementation and use of the IPFIX protocol, while [RFC5471]
   provides guidelines for testing.  Finally, [RFC5472] describes what
   types 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 key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   RFC 2119 [RFC2119].

   The definitions of the basic terms like Traffic Flow, Exporting
   Process, Collecting Process, Observation Points, etc. are
   semantically identical to 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 have also been defined.  Definitions in this document
   and in [RFC5470] are equivalent; definitions that are only relevant
   to the IPFIX protocol only appear here.








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

   Observation Point

      An Observation Point is a location in the network where 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.  It is RECOMMENDED that Observation Domain IDs
      also be unique per IPFIX Device.

   Packet Treatment

      "Packet Treatment" refers to action(s) performed on a packet by a
      forwarding device or other middlebox, including forwarding,
      dropping, delaying for traffic-shaping purposes, etc.














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   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 packets or frames 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 the fields derived from Packet Treatment (e.g.,
         next-hop IP address, the output interface, etc.).

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

      Note that the set of packets represented by a Flow may be empty;
      that is, a Flow may represent zero or more packets.  As sampling
      is a Packet Treatment, this definition includes packets selected
      by a sampling mechanism.

   Flow Key

      Each of the fields that:

      1. belong to the packet header (e.g., destination IP address), or

      2. are a property of the packet itself (e.g., packet length), or

      3. are derived from Packet Treatment (e.g., Autonomous System (AS)
         number),

      and that are used to define a Flow (i.e., are the properties
      common to all packets in the Flow) are termed Flow Keys.  As an
      example, the traditional '5-tuple' Flow Key of source and
      destination IP address, source and destination transport port, and
      transport protocol, groups together all packets belonging to a
      single direction of communication on a single socket.



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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 contains 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, characteristics, and Packet Treatment
      observed at one or more Observation Points.

      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 IPFIX Messages to one or more
      Collecting Processes.  The Flow Records in the Messages are
      generated by one or more Metering Processes.

   Exporter

      A device that 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 as well as arbitrary numbers of
      Observation Points and Metering Processes.

   Collecting Process

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





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   Collector

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

   Template

      A 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 that originates at the Exporting
      Process and 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; the
      Message Header 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

      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.









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   Set

      A Set is a collection of records that have a similar structure,
      prefixed by a header.  In an IPFIX Message, zero or more Sets
      follow the Message Header.  There are three different types of
      Sets: Template Sets, Options Template Sets, and Data Sets.

   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 that may appear in an IPFIX Record.
      Information Elements are defined in the IANA "IPFIX Information
      Elements" registry [IANA-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 the Stream Control Transmission Protocol (SCTP), the Transport
      Session is known as the SCTP association, which is uniquely
      identified by the SCTP endpoints [RFC4960]; in TCP, the Transport
      Session is known as the TCP connection, which is uniquely
      identified by the combination of IP addresses and TCP ports used.
      In UDP, the Transport Session is known as the UDP session, which
      is uniquely identified by the combination of IP addresses and UDP
      ports used.






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2.1.  Terminology Summary Table

   Figure A shows a summary of IPFIX terminology.

    +------------------+---------------------------------------------+
    |                  |                 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 zero or
   more Sets.  The Sets can be any of these three possible types:
   Data Set, Template Set, or Options Template Set.

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

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

                      Figure B: IPFIX Message Format



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   Following are some examples of IPFIX Messages:

   1. An IPFIX Message consisting of interleaved Template, Data, and
      Options Template Sets, as shown in Figure C.  Here, Template and
      Options Template Sets are transmitted "on demand", before the
      first Data Set whose structure they define.

     +--------+--------------------------------------------------------+
     |        | +----------+ +---------+     +-----------+ +---------+ |
     |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, sent after the
      appropriate Template Records have been defined and transmitted to
      the Collecting Process, as shown in Figure D.

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

                    Figure D: IPFIX Message: Example 2

   3. An IPFIX Message consisting entirely of Template and Options
      Template Sets, as shown in Figure E.  Such a message can be used
      to define or redefine Templates and Options Templates in bulk.

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

                    Figure E: IPFIX Message: Example 3








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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

   Each Message Header field is exported in network byte order.  The
   fields are defined as follows:

   Version

      Version of IPFIX to which this Message conforms.  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).

   Export Time

      Time at which the IPFIX Message Header leaves the Exporter,
      expressed in seconds since the UNIX epoch of 1 January 1970 at
      00:00 UTC, encoded as an unsigned 32-bit integer.













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   Sequence Number

      Incremental sequence counter modulo 2^32 of all IPFIX Data Records
      sent in the current stream from the current Observation Domain by
      the Exporting Process.  Each SCTP Stream counts sequence numbers
      separately, while all messages in a TCP connection or UDP session
      are considered to be part of the same stream.  This value can 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 also be 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 Exporter.  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 the case of a hierarchy of
      Collectors 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 IANA-registered
   Information Elements [IANA-IPFIX] 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 appears in [IANA-IPFIX], and the Enterprise
   Number MUST NOT be present.  When the Enterprise bit is set to 1, the
   corresponding Information Element identifier identified an
   enterprise-specific Information Element; the Enterprise Number MUST
   be present.  An example of this is shown in Appendix A.2.2.









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   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
      Information Element in [IANA-IPFIX], 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 field MUST be
      present.

   Information Element identifier

      A numeric value that represents the Information Element.  Refer to
      [IANA-IPFIX].

   Field Length

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

   Enterprise Number

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










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3.3.  Set and Set Header Format

   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 record 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

   Set Header

      The Set Header Format is defined in Section 3.3.2.

   Record

      One of the record formats: Template Record, 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 octets with
      value zero (0).  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 records, then the padding
      Information Element 'paddingOctets' can be used for padding



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      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 the 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

   Each Set Header field is exported in network format.  The fields are
   defined as follows:

   Set ID

      Identifies the Set.  A value of 2 is reserved for Template Sets.
      A value of 3 is reserved for Options Template Sets.  Values from 4
      to 255 are reserved for future use.  Values 256 and above 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.
















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3.4.  Record Format

   IPFIX defines three record formats, as 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

   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 Element 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.  Field
   Specifiers are defined 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









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   The Template Record Header Field definitions are as follows:

   Template ID

      Each Template Record is given a unique Template ID in the range
      256 to 65535.  This uniqueness is local to the Transport Session
      and Observation Domain that generated the Template ID.  Since
      Template IDs are used as Set IDs in the Sets they describe (see
      Section 3.4.3), values 0-255 are reserved for special Set types
      (e.g., Template Sets themselves), and Templates and Options
      Templates (see Section 3.4.2) cannot share Template IDs within a
      Transport Session and Observation Domain.  There are no
      constraints regarding the order of the Template ID allocation.  As
      Exporting Processes are free to allocate Template IDs as they see
      fit, Collecting Processes MUST NOT assume incremental Template
      IDs, or anything about the contents of a Template based on its
      Template ID alone.

   Field Count

      Number of fields in this Template Record.






























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   The example in Figure L shows a Template Set with mixed IANA-assigned
   and enterprise-specific Information Elements.  It consists of a Set
   Header, a 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                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          Padding (opt)                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure L: Template Set Example

   Information Element id.s 1.2 and 2.1 appear in [IANA-IPFIX]
   (Enterprise bit = 0) and therefore do not need an Enterprise Number
   to identify them.






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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 that would not be possible with Flow Records alone.

   See Section 4 for specific Options Templates used for reporting
   metadata about IPFIX Exporting and Metering Processes.

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.

   The scope is one or more Information Elements, specified in the
   Options Template Record.  At a minimum, Collecting Processes SHOULD
   support as scope the observationDomainId, exportingProcessId,
   meteringProcessId, templateId, lineCardId, exporterIPv4Address,
   exporterIPv6Address, and ingressInterface Information Elements.  The
   IPFIX protocol doesn't prevent the use of any Information Elements
   for scope.  However, some Information Element types don't make sense
   if specified as scope (for example, the counter Information
   Elements).

   The IPFIX Message Header already contains the Observation Domain ID.
   If not zero, this Observation Domain ID can be considered as an
   implicit scope for the Data Records in the IPFIX Message.

   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 meteringProcessId and templateId,
   the combined scope is this Template for this Metering Process.  If a
   different order of Scope Fields would result in a Record having a
   different semantic meaning, then the order of Scope Fields MUST be
   preserved by the Exporting Process.  For example, in the context of
   PSAMP [RFC5476], if the first scope defines the filtering function,
   while the second scope defines the sampling function, the order of
   the scope is important.  Applying 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.










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3.4.2.2.  Options Template Record Format

   An Options Template Record contains any combination of IANA-assigned
   and/or enterprise-specific Information Element 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.  Field Specifiers are defined in Figure G above.

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

                 Figure M: Options Template Record Format

   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
















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   The Options Template Record Header Field definitions are as follows:

   Template ID

      Each Options Template Record is given a unique Template ID in the
      range 256 to 65535.  This uniqueness is local to the Transport
      Session and Observation Domain that generated the Template ID.
      Since Template IDs are used as Set IDs in the sets they describe
      (see Section 3.4.3), values 0-255 are reserved for special Set
      types (e.g., Template Sets themselves), and Templates and Options
      Templates cannot share Template IDs within a Transport Session and
      Observation Domain.  There are no constraints regarding the order
      of the Template ID allocation.  As Exporting Processes are free to
      allocate Template IDs as they see fit, Collecting Processes MUST
      NOT assume incremental Template IDs, or anything about the
      contents of an Options Template based on its Template ID alone.

   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.  A scope field count of N specifies that
      the first N Field Specifiers in the Template Record are Scope
      Fields.  The Scope Field Count MUST NOT be zero.






















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   The example in Figure O shows an Options Template Set with mixed
   IANA-assigned and enterprise-specific Information Elements.  It
   consists of a Set Header, an Options 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. |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     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: Options Template Set Example

















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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 as specified in
   [RFC7012].

   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.

























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   The example in Figure Q shows a Data Set.  It consists of a Set
   Header and 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 Options Template and Options Template Records defined in these
   subsections, which impose some constraints on the Metering Process
   and Exporting Process implementations, MAY be implemented.  If
   implemented, the specific Options Templates SHOULD be implemented as
   specified in these subsections.

   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.

   The Collecting Process MUST check the possible combinations of
   Information Elements within the Options Template Records to correctly
   interpret the following Options Templates.







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4.1.  The Metering Process Statistics Options Template

   The Metering Process Statistics Options Template specifies the
   structure of a Data Record for reporting Metering Process statistics.
   It SHOULD contain the following Information Elements, as defined in
   [IANA-IPFIX]:

      (scope) observationDomainId

         This Information Element MUST be defined as a Scope Field and
         MUST be present, unless the Observation Domain ID of the
         enclosing Message is non-zero.

      (scope) meteringProcessId

         If present, this Information Element MUST be defined as a Scope
         Field.

      exportedMessageTotalCount

      exportedFlowRecordTotalCount

      exportedOctetTotalCount

   The Exporting Process SHOULD export the Data Record specified by the
   Metering Process Statistics Options 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 Options Template

   The Metering Process Reliability Statistics Options Template
   specifies the structure of a Data Record for reporting lack of
   reliability in the Metering Process.  It SHOULD contain the following
   Information Elements, as defined in [IANA-IPFIX]:

      (scope) observationDomainId

         This Information Element MUST be defined as a Scope Field and
         MUST be present, unless the Observation Domain ID of the
         enclosing Message is non-zero.






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      (scope) meteringProcessId

         If present, this Information Element MUST be defined as a Scope
         Field.

      ignoredPacketTotalCount

      ignoredOctetTotalCount

      time first packet ignored

         The timestamp of the first packet that was ignored by the
         Metering Process.  For this timestamp, any of the following
         timestamp Information Elements can be used:

            observationTimeSeconds,
            observationTimeMilliseconds,
            observationTimeMicroseconds, or
            observationTimeNanoseconds.

      time last packet ignored

         The timestamp of the last packet that was ignored by the
         Metering Process.  For this timestamp, any of the following
         timestamp Information Elements can be used:

            observationTimeSeconds,
            observationTimeMilliseconds,
            observationTimeMicroseconds, or
            observationTimeNanoseconds.

   The Exporting Process SHOULD export the Data Record specified by the
   Metering Process Reliability Statistics Options 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.

   Since the Metering Process Reliability Statistics Options Template
   contains two identical timestamp Information Elements, and since the
   order of the Information Elements in the Template Records is not
   guaranteed, the Collecting Process interprets the time interval of
   ignored packets as the range between the two values; see Section 5.2
   for wraparound considerations.





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4.3.  The Exporting Process Reliability Statistics Options Template

   The Exporting Process Reliability Statistics Options Template
   specifies the structure of a Data Record for reporting lack of
   reliability in the Exporting Process.  It SHOULD contain the
   following Information Elements, as defined in [IANA-IPFIX]:

      (scope) Exporting Process Identifier

         The identifier of the Exporting Process for which reliability
         is reported.  Any of the exporterIPv4Address,
         exporterIPv6Address, or exportingProcessId Information Elements
         can be used for this field.  This Information Element MUST be
         defined as a Scope Field.

      notSentFlowTotalCount

      notSentPacketTotalCount

      notSentOctetTotalCount

      time first flow dropped

         The time at which the first Flow Record was dropped by the
         Exporting Process.  For this timestamp, any of the following
         timestamp Information Elements can be used:

            observationTimeSeconds,
            observationTimeMilliseconds,
            observationTimeMicroseconds, or
            observationTimeNanoseconds.

      time last flow dropped

         The time at which the last Flow Record was dropped by the
         Exporting Process.  For this timestamp, any of the following
         timestamp Information Elements can be used:

            observationTimeSeconds,
            observationTimeMilliseconds,
            observationTimeMicroseconds, or
            observationTimeNanoseconds.

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




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   Since the Exporting Process Reliability Statistics Options Template
   contains two identical timestamp Information Elements, and since the
   order of the Information Elements in the Template Records is not
   guaranteed, the Collecting Process interprets the time interval of
   dropped packets as the range between the two values; see Section 5.2
   for wraparound considerations.

4.4.  The Flow Keys Options Template

   The Flow Keys Options 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.  The Template Record is extended by specifying
   which of the Information Elements contained in the corresponding Data
   Records describe Flow properties that serve as Flow Keys of the
   reported Flow.

   The Flow Keys Options Template SHOULD contain the following
   Information Elements, as defined in [IANA-IPFIX]:

      (scope) templateId

         This Information Element MUST be defined as a Scope Field.

      flowKeyIndicator

5.  Timing Considerations

5.1.  IPFIX Message Header Export Time and Flow Record Time

   The IPFIX Message Header Export Time field is the time at which the
   IPFIX Message Header leaves the Exporter, using the same encoding as
   the dateTimeSeconds abstract data type [RFC7012], i.e., expressed in
   seconds since the UNIX epoch, 1 January 1970 at 00:00 UTC, encoded as
   an unsigned 32-bit integer.

   Certain time-related Information Elements may be expressed as an
   offset from this Export Time.  For example, Data Records requiring a
   microsecond precision can export the flow start and end times with
   the flowStartMicroseconds and flowEndMicroseconds Information
   Elements, which encode the absolute time in microseconds in terms of
   the NTP epoch, 1 January 1900 at 00:00 UTC, in a 64-bit field.  An
   alternate solution is to export the flowStartDeltaMicroseconds and
   flowEndDeltaMicroseconds Information Elements in the Data Record,
   which respectively report the flow start and end time as negative
   offsets from the Export Time, as an unsigned 32-bit integer.  This
   latter solution lowers the export bandwidth requirement, saving
   four bytes per timestamp, while increasing the load on the Exporter,



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   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 timestamps based on the Export Time impose some
   time constraints on the Data Records contained within the IPFIX
   Message.  In the example of flowStartDeltaMicroseconds and
   flowEndDeltaMicroseconds Information Elements, the Data Record can
   only contain records with timestamps within 71 minutes of the Export
   Time.  Otherwise, the 32-bit counter would not be sufficient to
   contain the flow start time offset.

5.2.  Supporting Timestamp Wraparound

   The dateTimeSeconds abstract data type [RFC7012] and the Export Time
   Message Header field (Section 3.1) are encoded as 32-bit unsigned
   integers, expressed as seconds since the UNIX epoch, 1 January 1970
   at 00:00 UTC, as defined in [POSIX.1].  These values will wrap around
   on 7 February 2106 at 06:28:16 UTC.

   In order to support continued use of the IPFIX protocol beyond this
   date, Exporting Processes SHOULD export dateTimeSeconds values and
   the Export Time Message Header field as the number of seconds since
   the UNIX epoch, 1 January 1970 at 00:00 UTC, modulo 2^32.  Collecting
   Processes SHOULD use the current date, or other contextual
   information, to properly interpret dateTimeSeconds values and the
   Export Time Message Header field.

   There are similar considerations for the NTP-based
   dateTimeMicroseconds and dateTimeNanoseconds abstract data types
   [RFC7012].  Exporting Processes SHOULD export dateTimeMicroseconds
   and dateTimeNanoseconds values as if the NTP era [RFC5905] is
   implicit; Collecting Processes SHOULD use the current date, or other
   contextual information, to determine the NTP era in order to properly
   interpret dateTimeMicroseconds and dateTimeNanoseconds values in
   received Data Records.

   The dateTimeMilliseconds abstract data type will wrap around in
   approximately 500 billion years; the specification of the behavior of
   this abstract data type after that time is left as a subject of a
   future revision of this specification.

   The long-term storage of files [RFC5655] for archival purposes is
   affected by timestamp wraparound, as the use of the current date to
   interpret timestamp values in files stored on the order of multiple
   decades in the past may lead to incorrect values; therefore, it is
   RECOMMENDED that such files be stored with contextual information to
   assist in the interpretation of these timestamps.



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6.  Linkage with the Information Model

   As with values in the IPFIX Message Header and Set Header, values of
   all Information Elements [RFC7012], except for those of the string
   and octetArray data types, are encoded in canonical format in network
   byte order (also known as big-endian byte ordering).

6.1.  Encoding of IPFIX Data Types

   The following sections define the encoding of the data types
   specified in [RFC7012].

6.1.1.  Integral Data Types

   Integral data types -- unsigned8, unsigned16, unsigned32, unsigned64,
   signed8, signed16, signed32, and signed64 -- MUST be encoded using
   the default canonical format in network byte order.  Signed integral
   data types are represented in two's complement notation.

6.1.2.  Address Types

   Address types -- macAddress, ipv4Address, and ipv6Address -- MUST be
   encoded the same way as the integral data types, as six, four, and
   sixteen octets in network byte order, respectively.

6.1.3.  float32

   The float32 data type MUST be encoded as an IEEE binary32 floating
   point type as specified in [IEEE.754.2008], in network byte order as
   specified in Section 3.6 of [RFC1014].  Note that on little-endian
   machines, byte swapping of the native representation is necessary
   before export.  Note that the method for doing this may be
   implementation platform dependent.

6.1.4.  float64

   The float64 data type MUST be encoded as an IEEE binary64 floating
   point type as specified in [IEEE.754.2008], in network byte order as
   specified in Section 3.7 of [RFC1014].  Note that on little-endian
   machines, byte swapping of the native representation is necessary
   before export.  Note that the method for doing this may be
   implementation platform dependent.









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6.1.5.  boolean

   The boolean data type is specified according to the TruthValue in
   [RFC2579].  It is encoded as a single-octet integer per
   Section 6.1.1, with the value 1 for true and value 2 for false.
   Every other value is undefined.

6.1.6.  string and octetArray

   The "string" data type represents a finite-length string of valid
   characters of the Unicode character encoding set.  The string data
   type MUST be encoded in UTF-8 [RFC3629] format.  The string is sent
   as an array of zero or more octets using an Information Element of
   fixed or variable length.  IPFIX Exporting Processes MUST NOT send
   IPFIX Messages containing ill-formed UTF-8 string values for
   Information Elements of the string data type; Collecting Processes
   SHOULD detect and ignore such values.  See [UTF8-EXPLOIT] for
   background on this issue.

   The octetArray data type has no encoding rules; it represents a raw
   array of zero or more octets, with the interpretation of the octets
   defined in the Information Element definition.

6.1.7.  dateTimeSeconds

   The dateTimeSeconds data type is an unsigned 32-bit integer in
   network byte order containing the number of seconds since the UNIX
   epoch, 1 January 1970 at 00:00 UTC, as defined in [POSIX.1].
   dateTimeSeconds is encoded identically to the IPFIX Message Header
   Export Time field.  It can represent dates between 1 January 1970 and
   7 February 2106 without wraparound; see Section 5.2 for wraparound
   considerations.

6.1.8.  dateTimeMilliseconds

   The dateTimeMilliseconds data type is an unsigned 64-bit integer in
   network byte order containing the number of milliseconds since the
   UNIX epoch, 1 January 1970 at 00:00 UTC, as defined in [POSIX.1].  It
   can represent dates beginning on 1 January 1970 and for approximately
   the next 500 billion years without wraparound.

6.1.9.  dateTimeMicroseconds

   The dateTimeMicroseconds data type is a 64-bit field encoded
   according to the NTP Timestamp format as defined in Section 6 of
   [RFC5905].  This field is made up of two unsigned 32-bit integers in
   network byte order: Seconds and Fraction.  The Seconds field is the
   number of seconds since the NTP epoch, 1 January 1900 at 00:00 UTC.



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   The Fraction field is the fractional number of seconds in units of
   1/(2^32) seconds (approximately 233 picoseconds).  It can represent
   dates between 1 January 1900 and 8 February 2036 in the current
   NTP era; see Section 5.2 for wraparound considerations.

   Note that dateTimeMicroseconds and dateTimeNanoseconds share an
   identical encoding.  The dateTimeMicroseconds data type is intended
   only to represent timestamps of microsecond precision.  Therefore,
   the bottom 11 bits of the Fraction field SHOULD be zero and MUST
   be ignored for all Information Elements of this data type
   (as 2^11 x 233 picoseconds = .477 microseconds).

6.1.10.  dateTimeNanoseconds

   The dateTimeNanoseconds data type is a 64-bit field encoded according
   to the NTP Timestamp format as defined in Section 6 of [RFC5905].
   This field is made up of two unsigned 32-bit integers in network byte
   order: Seconds and Fraction.  The Seconds field is the number of
   seconds since the NTP epoch, 1 January 1900 at 00:00 UTC.  The
   Fraction field is the fractional number of seconds in units of
   1/(2^32) seconds (approximately 233 picoseconds).  It can represent
   dates between 1 January 1900 and 8 February 2036 in the current
   NTP era; see Section 5.2 for wraparound considerations.

   Note that dateTimeMicroseconds and dateTimeNanoseconds share an
   identical encoding.  There is no restriction on the interpretation of
   the Fraction field for the dateTimeNanoseconds data type.

6.2.  Reduced-Size Encoding

   Information Elements encoded as signed, unsigned, or float data types
   MAY be encoded using fewer octets than those implied by their type in
   the information model definition, 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 [IANA-IPFIX] always define the maximum encoding size.

   For instance, the information model defines octetDeltaCount 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 choose to send the value as unsigned32
   instead.

   This behavior is indicated by the Exporter by specifying a size in
   the Template 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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   Reduced-size encoding MAY be applied to the following integer types:
   unsigned64, signed64, unsigned32, signed32, unsigned16, and 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-size encoding MAY 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.  In this case, the float64 would be
   reduced in size to 4 octets.

   Reduced-size encoding MUST NOT be applied to any other data type
   defined in [RFC7012] that implies a fixed length, as these types
   either have internal structure (such as ipv4Address or
   dateTimeMicroseconds) or restricted ranges that are not suitable for
   reduced-size encoding (such as dateTimeMilliseconds).

   Information Elements of type octetArray and string may be exported
   using any length, subject to restrictions on length specific to each
   Information Element, as noted in that Information Element's
   description.

7.  Variable-Length Information Element

   The IPFIX Template mechanism is optimized for fixed-length
   Information Elements [RFC7012].  Where an Information Element has a
   variable length, the following mechanism MUST be used to carry the
   length information for both the IANA-assigned and enterprise-specific
   Information Elements.

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















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   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 more
   common 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 (IE)
                           (Length < 255 Octets)

   The length may also be encoded into 3 octets before the Information
   Element, allowing the length of the Information Element to be greater
   than or equal to 255 octets.  In this case, the first octet of the
   Length field MUST be 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 (IE)
                        (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 the management of Templates and Options
   Templates at the Exporting and Collecting Processes.  The goal of
   Template management is to ensure, to the extent possible, that the
   Exporting Process and Collecting Process have a consistent view of
   the Templates and Options Templates used to encode and decode the
   Records sent from the Exporting Process to the Collecting Process.





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   Achieving this goal is complicated somewhat by two factors: 1) the
   need to support the reuse of Template IDs within a Transport Session
   and 2) the need to support unreliable transmission for Templates when
   UDP is used as the transport protocol for IPFIX Messages.

   The Template Management mechanisms defined in this section apply to
   the export of IPFIX Messages on SCTP, TCP, or UDP.  Additional
   considerations specific to SCTP and UDP transport are given in
   Sections 8.3 and 8.4, respectively.

   The Exporting Process assigns and maintains Template IDs per
   Transport Session and Observation Domain.  A newly created Template
   Record is assigned an unused Template ID by the Exporting Process.
   The Collecting Process MUST store all received Template Record
   information for the duration of each Transport Session until reuse or
   withdrawal as described in Section 8.1, or expiry over UDP as
   described in Section 8.4, so that it can interpret the corresponding
   Data Records.

   The Collecting Process MUST NOT assume that the Template IDs from a
   given Exporting Process refer to the same Templates as they did in
   previous Transport Sessions from the same Exporting Process; a
   Collecting Process MUST NOT use Templates from one Transport Session
   to decode Data Sets in a subsequent Transport Session.

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

   If an Information Element is required more than once in a 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 packet, the first sourceIPv4Address
   Information Element occurrence should be the IPv4 address of the
   outer header, while the second occurrence should be the address of
   the inner header.  Collecting Processes MUST properly handle
   Templates with multiple identical Information Elements.

   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



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   subsequent IPFIX Message(s).  However, 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.

   Though a Collecting Process normally receives Template Records from
   the Exporting Process before receiving Data Records, this is not
   always the case, e.g., in the case of reordering or Collecting
   Process restart over UDP.  In these cases, the Collecting Process MAY
   buffer Data Records for which it has no Templates, to wait for
   Template Records describing them; however, note that in the presence
   of Template withdrawal and redefinition (Section 8.1) this may lead
   to incorrect interpretation of Data Records.

   Different Observation Domains within a Transport Session MAY use the
   same Template ID value to refer to different Templates; Collecting
   Processes MUST properly handle this case.

   Options Templates and Templates that are related or interdependent
   (e.g., by sharing common properties as described in [RFC5473]) SHOULD
   be sent together in the same IPFIX Message.

8.1.  Template Withdrawal and Redefinition

   Templates that will not be used further by an Exporting Process MAY
   be withdrawn by sending a Template Withdrawal.  After receiving a
   Template Withdrawal, a Collecting Process MUST stop using the
   Template to interpret subsequently exported Data Sets.  Note that
   this mechanism does not apply when UDP is used to transport IPFIX
   Messages; for that case, see Section 8.4.

   A Template Withdrawal consists of a Template Record for the Template
   ID to be withdrawn, with a Field Count of 0.  The format of a
   Template Withdrawal 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        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure T: Template Withdrawal Format




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

   Template Withdrawals MAY appear interleaved with Template Sets,
   Options Template Sets, and Data Sets within an IPFIX Message.  In
   this case, the Templates and Template Withdrawals shall be
   interpreted as taking effect in the order in which they appear in the
   IPFIX Message.  An Exporting Process SHOULD NOT send a Template
   Withdrawal until sufficient time has elapsed to allow receipt and
   processing of any Data Records described by the withdrawn Templates;
   see Section 8.2 for details regarding the sequencing of Template
   management actions.

   The end of a Transport Session implicitly withdraws all the Templates
   used within the Transport Session, and Templates must be resent
   during subsequent Transport Sessions between an Exporting Process and
   Collecting Process.  This applies to SCTP and TCP only; see
   Sections 8.4 and 10.3.4 for discussions of Transport Session and
   Template lifetime over UDP.

   All Templates for a given Observation Domain MAY also be withdrawn
   using an All Templates Withdrawal, as shown in Figure U.  All Options
   Templates for a given Observation Domain MAY likewise be withdrawn
   using an All Options Templates Withdrawal, as 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 = 2        |          Length = 8           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Template ID = 2       |        Field Count = 0        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure U: All Templates Withdrawal Set Format

      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 Set Format





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   Template IDs MAY be reused for new Templates by sending a new
   Template Record or Options Template Record for a given Template ID
   after withdrawing the Template.

   If a Collecting Process receives a Template Withdrawal for a Template
   or Options Template it does not presently have stored, this indicates
   a malfunctioning or improperly implemented Exporting Process.  The
   continued receipt and interpretation of Data Records are still
   possible, but the Collecting Process MUST ignore the Template
   Withdrawal and SHOULD log the error.

   If a Collecting Process receives a new Template Record or Options
   Template Record for an already-allocated Template ID, and that
   Template or Options Template is identical to the already-received
   Template or Options Template, it SHOULD log the retransmission;
   however, this is not an error condition, as it does not affect the
   interpretation of Data Records.

   If a Collecting Process receives a new Template Record or Options
   Template Record for an already-allocated Template ID, and that
   Template or Options Template is different from the already-received
   Template or Options Template, this indicates a malfunctioning or
   improperly implemented Exporting Process.  The continued receipt and
   unambiguous interpretation of Data Records for this Template ID are
   no longer possible, and the Collecting Process SHOULD log the error.
   Further Collecting Process actions are out of scope for this
   specification.

8.2.  Sequencing Template Management Actions

   Since there is no guarantee of the ordering of exported IPFIX
   Messages across SCTP Streams or over UDP, an Exporting Process MUST
   sequence all Template management actions (i.e., Template Records
   defining new Templates and Template Withdrawals withdrawing them)
   using the Export Time field in the IPFIX Message Header.

   An Exporting Process MUST NOT export a Data Set described by a new
   Template in an IPFIX Message with an Export Time before the Export
   Time of the IPFIX Message containing that Template.  If a new
   Template and a Data Set described by it appear in the same IPFIX
   Message, the Template Set containing the Template MUST appear before
   the Data Set in the Message.

   An Exporting Process MUST NOT export any Data Sets described by a
   withdrawn Template in IPFIX Messages with an Export Time after the
   Export Time of the IPFIX Message containing the Template Withdrawal
   withdrawing that Template.




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   Put another way, a Template describes Data Records contained in IPFIX
   Messages when the Export Time of such messages is between a specific
   start and end time, inclusive.  The start time is the Export Time of
   the IPFIX Message containing the Template Record.  The end time is
   one of two times: if the template is withdrawn during the session,
   then it is the Export Time of the IPFIX Message containing the
   Template Withdrawal for the template; otherwise, it is the end of the
   Transport Session.

   Even if sent in order, IPFIX Messages containing Template management
   actions could arrive at the Collecting Process out of order, i.e., if
   sent via UDP or via different SCTP Streams.  Given this, Template
   Withdrawals and subsequent reuse of Template IDs can significantly
   complicate the problem of determining Template lifetimes at the
   Collecting Process.  A Collecting Process MAY implement a buffer and
   use Export Time information to disambiguate the order of Template
   management actions.  This buffer, if implemented, SHOULD be
   configurable to impart a delay on the order of the maximum reordering
   delay experienced at the Collecting Process.  Note, in this case,
   that the Collecting Process's clock is irrelevant: it is only
   comparing the Export Times of Messages to each other.

8.3.  Additional Considerations for Template Management over SCTP

   The specifications in this section apply only to SCTP; in cases of
   contradiction with specifications in Section 8 or Section 8.1, this
   section takes precedence.

   Template Sets and Options Template Sets MAY be sent on any SCTP
   Stream.  Data Sets sent on a given SCTP Stream MAY be represented by
   Template Records exported on any SCTP Stream.

   Template Sets and Options Template Sets MUST be sent reliably, using
   SCTP ordered delivery.

   Template Withdrawals MAY be sent on any SCTP Stream.  Template
   Withdrawals MUST be sent reliably, using SCTP ordered delivery.
   Template IDs MAY be reused by sending a Template Withdrawal and/or a
   new Template Record on a different SCTP Stream than the stream on
   which the original Template was sent.

   Additional Template Management considerations are provided in
   [RFC6526], which specifies an extension to explicitly link Templates
   with SCTP Streams.  In exchange for more restrictive rules on the
   assignment of Template Records to SCTP Streams, this extension allows
   fast, reliable reuse of Template IDs and estimation of Data Record
   loss per Template.




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8.4.  Additional Considerations for Template Management over UDP

   The specifications in this section apply only to UDP; in cases of
   contradiction with specifications in Section 8 or Section 8.1, this
   section takes precedence.

   Since UDP provides no method for reliable transmission of Templates,
   Exporting Processes using UDP as the transport protocol MUST
   periodically retransmit each active Template at regular intervals.
   The Template retransmission interval MUST be configurable via, for
   example, the templateRefreshTimeout and optionsTemplateRefreshTimeout
   parameters as defined in [RFC6728].  Default settings for these
   values are deployment- and application-specific.

   Before exporting any Data Records described by a given Template
   Record or Options Template Record, especially in the case of Template
   ID reuse as described in Section 8.1, the Exporting Process SHOULD
   send multiple copies of the Template Record in a separate IPFIX
   Message, in order to help ensure that the Collecting Process has
   received it.

   In order to minimize resource requirements for Templates that are no
   longer being used by the Exporting Process, the Collecting Process
   MAY associate a lifetime with each Template received in a Transport
   Session.  Templates not refreshed by the Exporting Process within the
   lifetime can then be discarded by the Collecting Process.  The
   Template lifetime at the Collecting Process MAY be exposed by a
   configuration parameter or MAY be derived from observation of the
   interval of periodic Template retransmissions from the Exporting
   Process.  In this latter case, the Template lifetime SHOULD default
   to at least 3 times the observed retransmission rate.

   Template Withdrawals (Section 8.1) MUST NOT be sent by Exporting
   Processes exporting via UDP and MUST be ignored by Collecting
   Processes collecting via UDP.  Template IDs MAY be reused by
   Exporting Processes by exporting a new Template for the Template ID
   after waiting at least 3 times the retransmission delay.  Note that
   Template ID reuse may lead to incorrect interpretation of Data
   Records if the retransmission and lifetime are not properly
   configured.

   When a Collecting Process receives a new Template Record or Options
   Template Record via UDP for an already-allocated Template ID, and
   that Template or Options Template is identical to the already-
   received Template or Options Template, it SHOULD NOT log the
   retransmission, as this is the normal operation of Template refresh
   over UDP.




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   When a Collecting Process receives a new Template Record or Options
   Template Record for an already-allocated Template ID, and that
   Template or Options Template is different from the already-received
   Template or Options Template, the Collecting Process MUST replace the
   Template or Options Template for that Template ID with the newly
   received Template or Options Template.  This is the normal operation
   of Template ID reuse over UDP.

   As 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, Collector IP
   address, Collector destination UDP port, Observation Domain ID,
   Template ID, Template Definition, Last Received>.

9.  The Collecting Process's Side

   This section describes the handling of the IPFIX protocol at the
   Collecting Process common to all transport protocols.  Additional
   considerations for SCTP and UDP are provided in Sections 9.2 and 9.3,
   respectively.  Template management at Collecting Processes is covered
   in Section 8.

   The Collecting Process MUST listen for association requests /
   connections to start new Transport Sessions from the Exporting
   Process.

   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 received Data Records.

   The Collecting Process 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 minimum Record size deduced from the Template Record.

   The IPFIX protocol has a Sequence Number field in the Export header
   that increases with the number of IPFIX Data Records in the IPFIX
   Message.  A Collector can 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 cannot 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 cannot process the IPFIX Messages at their
   arrival rate, out-of-order packet reception, duplicate packet
   reception, or an attacker injecting false messages.



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9.1.  Collecting Process Handling of Malformed IPFIX Messages

   If the Collecting Process receives a malformed IPFIX Message, it MUST
   discard the IPFIX Message and SHOULD log the error.  A malformed
   IPFIX Message is one that cannot be interpreted due to nonsensical
   length values (e.g., a variable-length Information Element longer
   than its enclosing Set, a Set longer than its enclosing IPFIX
   Message, or an IPFIX Message shorter than an IPFIX Message Header) or
   a reserved Version value (which may indicate that a future version of
   IPFIX is being used for export but in practice occurs most often when
   non-IPFIX data is sent to an IPFIX Collecting Process).  Note that
   non-zero Set padding does not constitute a malformed IPFIX Message.

   As the most likely cause of malformed IPFIX Messages is a poorly
   implemented Exporting Process, or the sending of non-IPFIX data to an
   IPFIX Collecting Process, human intervention is likely necessary to
   correct the issue.  In the meantime, the Collecting Process MAY
   attempt to rectify the situation any way it sees fit, including:

   - terminating the TCP connection or SCTP connection

   - using the receiver window to reduce network load from the
     malfunctioning Exporting Process

   - buffering and saving malformed IPFIX Message(s) to assist in
     diagnosis

   - attempting to resynchronize the stream, e.g., as described in
     Section 10.3 of [RFC5655]

   Resynchronization should only be attempted if the Collecting Process
   has reason to believe that the error is transient.  On the other
   hand, the Collecting Process SHOULD stop processing IPFIX Messages
   from clearly malfunctioning Exporting Processes (e.g., those from
   which the last few IPFIX Messages have been malformed).

9.2.  Additional Considerations for SCTP Collecting Processes

   As an Exporting Process may request and support more than one stream
   per SCTP association, the Collecting Process MUST support the opening
   of multiple SCTP Streams.

9.3.  Additional Considerations for UDP Collecting Processes

   A Transport Session for IPFIX Messages transported over UDP is
   defined from the point of view of the Exporting Process and roughly
   corresponds to the time during which a given Exporting Process sends
   IPFIX Messages over UDP to a given Collecting Process.  Since this is



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   difficult to detect at the Collecting Process, the Collecting Process
   MAY discard all Transport Session state after no IPFIX Messages are
   received from a given Exporting Process within a given Transport
   Session during a configurable idle timeout.

   The Collecting Process SHOULD accept Data Records without the
   associated Template Record (or other definitions such as Common
   Properties) required to decode the Data Record.  If the Template
   Records or other definitions 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 or other definitions are received, comparing Export Times of
   IPFIX Messages containing the Template Records with those containing
   the Data Records as discussed in Section 8.2.  Note that this
   mechanism may lead to incorrectly interpreted records in the presence
   of Template ID reuse or other identifiers with limited lifetimes.

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 an
   IPFIX Message to 65535 octets, including the header.  A Collecting
   Process MUST be able to handle IPFIX Message lengths of up to
   65535 octets.

   While an Exporting Process or Collecting Process may support multiple
   transport protocols, Transport Sessions are bound to a transport
   protocol.  Transport Session state MUST NOT be migrated by an
   Exporting Process or Collecting Process among Transport Sessions
   using different transport protocols between the same Exporting
   Process and Collecting Process pair.  In other words, an Exporting
   Process supporting multiple transport protocols is conceptually
   multiple Exporting Processes, one per supported transport protocol.
   Likewise, a Collecting Process supporting multiple transport
   protocols is conceptually multiple Collecting Processes, one per
   supported transport protocol.

10.1.  Transport Compliance and Transport Usage

   SCTP [RFC4960] using the Partially Reliable SCTP (PR-SCTP) extension
   as specified in [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.




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

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

   UDP may be used, although it is not a congestion-aware protocol.
   However, in this case the IPFIX traffic between the Exporter and
   Collector must be separately contained or provisioned to minimize the
   risk of congestion-related loss.

   By default, the Collecting Process listens for connections on SCTP,
   TCP, and/or UDP port 4739.  By default, the Collecting Process
   listens for secure connections on SCTP, TCP, and/or UDP port 4740
   (refer to the Security Considerations section).  By default, the
   Exporting Process attempts to connect to one of these ports.  It MUST
   be possible to configure both the Exporting and Collecting Processes
   to use different ports than the default.

10.2.  SCTP

   This section describes how IPFIX is transported over SCTP [RFC4960]
   using the PR-SCTP [RFC3758] extension.

10.2.1.  Congestion Avoidance

   SCTP provides the required level of congestion avoidance by design.

   SCTP detects congestion in the end-to-end path between the IPFIX
   Exporting Process and the IPFIX Collecting Process, and limits 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 decide to drop the record.  In the latter case, the dropped
   export data SHOULD be accounted for, so that the amount of dropped
   export data can be reported using the mechanism described in
   Section 4.3.










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10.2.2.  Reliability

   The SCTP transport protocol is by default reliable but has the
   capability to deliver messages with partial reliability [RFC3758].

   Using reliable SCTP messages for IPFIX export is not in itself a
   guarantee that all Data Records will be 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 IPFIX Sequence Numbers used for
   export MUST reflect the loss of data.

10.2.3.  MTU

   SCTP provides the required IPFIX Message fragmentation service based
   on Path MTU (PMTU) discovery.

10.2.4.  Association Establishment and Shutdown

   The IPFIX Exporting Process initiates an SCTP association with the
   IPFIX Collecting Process.  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).

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

   When a Collecting Process no longer wants to receive IPFIX Messages,
   it SHOULD shut down 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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10.2.5.  Failover

   If the Collecting Process does not acknowledge an attempt by the
   Exporting Process to establish an association, SCTP will
   automatically retry association establishment using exponential
   backoff.  The Exporter MAY log an alarm if the underlying SCTP
   association establishment times out; this timeout should be
   configurable on the Exporter.

   The Exporting Process MAY open a backup SCTP association to a
   Collecting Process in advance, if it supports Collecting Process
   failover.

10.2.6.  Streams

   An Exporting Process MAY request more than one SCTP Stream per
   association.  Each of these streams may be used for the transmission
   of IPFIX Messages containing Data Sets, Template Sets, and/or Options
   Template Sets.

   Depending on the requirements of the application, the Exporting
   Process may send Data Sets with full or partial reliability, using
   ordered or out-of-order delivery, over any SCTP Stream established
   during SCTP association setup.

   An IPFIX Exporting Process MAY use any PR-SCTP service definition as
   per Section 4 of the PR-SCTP specification [RFC3758] when using
   partial reliability to transmit IPFIX Messages containing only
   Data Sets.

   However, Exporting Processes SHOULD mark such IPFIX Messages for
   retransmission for as long as resource or other constraints allow.

10.3.  UDP

   This section describes how IPFIX is 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., links that are over-provisioned compared to the
   maximum export rate from the Exporters.






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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 Sequence
   Number.  In the case of UDP, the IPFIX Sequence Number contains the
   total number of IPFIX Data Records sent for the Transport Session
   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.

   Exporting Processes exporting IPFIX Messages via UDP MUST include a
   valid UDP checksum [UDP] in UDP datagrams including IPFIX Messages.

10.3.3.  MTU

   The maximum size of exported messages MUST be configured such that
   the total packet size does not exceed the PMTU.  If the PMTU is
   unknown, a maximum packet size of 512 octets SHOULD be used.

10.3.4.  Session Establishment and Shutdown

   As UDP is a connectionless protocol, there is no real session
   establishment or shutdown for IPFIX over UDP.  An Exporting Process
   starts sending IPFIX Messages to a Collecting Process at one point in
   time and stops sending them at another point in time.  This can lead
   to some complications in Template management, as outlined in
   Section 8.4 above.

10.3.5.  Failover and Session Duplication

   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 IPFIX Messages.
   Therefore, it cannot invoke a failover mechanism.  However, the
   Exporting Process MAY duplicate the IPFIX Message to several
   Collecting Processes.









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10.4.  TCP

   This section describes how IPFIX is transported over TCP [TCP].

10.4.1.  Congestion Avoidance

   TCP 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 them, 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.

   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 number of lost records can later be
   reported as described in Section 4.3.

10.4.2.  Reliability

   TCP ensures reliable delivery of data from the Exporting Process to
   the Collecting Process.

10.4.3.  MTU

   As TCP offers a stream service instead of a datagram or sequential
   packet service, IPFIX Messages transported over TCP are instead
   separated using the Length field in the IPFIX Message Header.  The
   Exporting Process can choose any valid length for exported IPFIX
   Messages, as TCP handles segmentation.

   Exporting Processes may choose IPFIX Message lengths lower than the
   maximum in order to ensure timely export of Data Records.









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10.4.4.  Connection Establishment and Shutdown

   The IPFIX Exporting Process initiates a TCP connection to the
   Collecting Process.  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).  An
   Exporting Process MAY support more than one active connection to the
   same Collecting Process to avoid head-of-line blocking across
   Observation Domains.

   The Exporter MAY log an alarm if the underlying TCP connection
   establishment times out; this timeout should be configurable on the
   Exporter.

   When an Exporting Process is shut down, it SHOULD shut down 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.

   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.

10.4.5.  Failover

   If the Collecting Process does not acknowledge an attempt by the
   Exporting Process to establish a connection, TCP will automatically
   retry connection establishment using exponential backoff.  The
   Exporter MAY log an alarm if the underlying TCP connection
   establishment times out; this timeout should be configurable on the
   Exporter.

   The Exporting Process MAY open a backup TCP connection to a
   Collecting Process in advance, if it supports Collecting Process
   failover.






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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 Considerations section of the IPFIX requirements document
   [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 Records
      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), or the duplication of
      Messages, in 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 take 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 affect either 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
   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 assumed to be unavailable to attackers, 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, encryption and/or
   anonymization of any reported data; see Section 11.8.




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11.1.  Applicability of TLS and DTLS

   Transport Layer Security (TLS) [RFC5246] and Datagram Transport Layer
   Security (DTLS) [RFC6347] were designed to provide the
   confidentiality, integrity, and authentication assurances required by
   the IPFIX protocol, without the need for pre-shared keys.

   IPFIX Exporting Processes and Collecting Processes using TCP MUST
   support TLS version 1.1 and SHOULD support TLS version 1.2 [RFC5246],
   including the mandatory ciphersuite(s) specified in each version.
   IPFIX Exporting Processes and Collecting Processes using UDP or SCTP
   MUST support DTLS version 1.0 and SHOULD support DTLS version 1.2
   [RFC6347], including the mandatory ciphersuite(s) specified in each
   version.

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

   Note that using DTLS has a man-in-the-middle vulnerability not
   present in TLS, allowing a message to be removed from the stream
   without the knowledge of either the sender or receiver.
   Additionally, when using DTLS over SCTP, an attacker could inject
   SCTP control information and shut down the SCTP association, causing
   a loss of IPFIX Messages if those messages are buffered outside of
   the SCTP association.  Techniques such as those described in
   [RFC6083] could be used to overcome these vulnerabilities.

   When using DTLS over SCTP, the Exporting Process MUST ensure that
   each IPFIX Message is sent over the same SCTP Stream that would be
   used when sending the same IPFIX Message directly over SCTP.  Note
   that DTLS may send its own control messages on stream 0 with full
   reliability; however, this will not interfere with the processing of
   stream 0 IPFIX Messages at the Collecting Process, because DTLS
   consumes its own control messages before passing IPFIX Messages up to
   the application layer.

   When using DTLS over SCTP or UDP, the Heartbeat Extension [RFC6520]
   SHOULD be used, especially on long-lived Transport Sessions, to
   ensure that the association remains active.

   Exporting and Collecting Processes MUST NOT request, offer, or use
   any version of the Secure Socket Layer (SSL), or any version of TLS
   prior to 1.1, due to known security vulnerabilities in prior versions
   of TLS; see Appendix E of [RFC5246] for more information.



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11.2.  Usage

   The IPFIX Exporting Process initiates the communication to the IPFIX
   Collecting Process and acts as a TLS or DTLS client according to
   [RFC5246] and [RFC6347], while the IPFIX Collecting Process acts as a
   TLS or DTLS server.  The DTLS client opens a secure connection on
   SCTP port 4740 of the DTLS server if SCTP is selected as the
   transport protocol.  The TLS client opens a secure connection on TCP
   port 4740 of the TLS server if TCP is selected as the transport
   protocol.  The DTLS client opens a secure connection on UDP port 4740
   of the DTLS server if UDP is selected as the transport protocol.

11.3.  Mutual Authentication

   When using TLS or DTLS, IPFIX Exporting Processes and IPFIX
   Collecting Processes SHOULD be identified by a certificate containing
   the DNS-ID as discussed in Section 6.4 of [RFC6125]; the inclusion of
   Common Names (CN-IDs) in certificates identifying IPFIX Exporting
   Processes or Collecting Processes is NOT RECOMMENDED.

   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, mutual authentication MUST be used for both TLS
   and DTLS.  Exporting Processes MUST verify the reference identifiers
   of the Collecting Processes to which they are exporting IPFIX
   Messages against those stored in the certificates.  Likewise,
   Collecting Processes MUST verify the reference identifiers of the
   Exporting Processes from which they are receiving IPFIX Messages
   against those stored in the certificates.  Exporting Processes MUST
   NOT export to non-verified Collecting Processes, and Collecting
   Processes MUST NOT accept IPFIX Messages from non-verified Exporting
   Processes.

   Exporting Processes and Collecting Processes MUST support the
   verification of certificates against an explicitly authorized list of
   peer certificates identified by Common Name and SHOULD support the
   verification of reference identifiers by matching the DNS-ID or CN-ID
   with a DNS lookup of the peer.

   IPFIX Exporting Processes and Collecting Processes MUST use non-NULL
   ciphersuites for authentication, integrity, and confidentiality.









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11.4.  Protection against DoS Attacks

   An attacker may mount a denial-of-service (DoS) 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 DoS 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, or a
   large amount of Options Template Records, etc.).

   SCTP mandates a cookie-exchange mechanism designed to defend against
   SCTP state exhaustion DoS 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
   Message processing (and state creation) for UDP and SCTP
   communication.  The use of TLS and DTLS can obviously prevent the
   creation of fake states, but they are themselves prone to state
   exhaustion attacks.  Therefore, Collector rate limiting SHOULD be
   used to protect TLS and DTLS (like limiting the number of new TLS or
   DTLS sessions per second to a sensible number).

   IPFIX state exhaustion attacks can be mitigated by limiting the rate
   at which new connections or associations will be opened by the
   Collecting Process; limiting the rate at which IPFIX Messages will be
   accepted by the Collecting Process; and adaptively limiting the
   amount of state kept, particularly for records waiting for Templates.
   These rate and state limits MAY be provided by a Collecting Process,
   and 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.  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



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   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 and implying that some
   information about the attack will be available.

   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 that 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 that will accept IPFIX Messages from any Exporting Process
   regardless of IP address or identity) is discouraged.

   Modern TCP and SCTP implementations are resistant to blind insertion
   attacks (see [RFC4960] and [RFC6528]); 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.





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   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 is 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, a complete set of security
   guidelines for Collector implementation is outside the scope of this
   document.

   As IPFIX uses length-prefix encodings, Collector implementors should
   take care to ensure the detection of inconsistent values that could
   impact IPFIX Message decoding, and proper operation in the presence
   of such inconsistent values.

   Specifically, IPFIX Message, Set, and variable-length Information
   Element lengths must be checked for consistency to avoid buffer-
   sizing vulnerabilities.

   Collector implementors should also pay special attention to UTF-8
   encoding of string data types, as vulnerabilities may exist in the
   interpretation of ill-formed UTF-8 values; see Section 6.1.6.

11.8.  Privacy Considerations for Collected Data

   Flow data exported by Exporting Processes and collected by Collecting
   Processes typically contains information about traffic on the
   observed network.  This information may be personally identifiable
   and privacy-sensitive.  The storage of this data must be protected
   via technical as well as policy means to ensure that the privacy of
   the users of the measured network is protected.  A complete
   specification of such means is out of scope for this document and is
   specific to the application and storage technology used.












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12.  Management Considerations

   [RFC6615] specifies a MIB module that defines managed objects for
   monitoring IPFIX Devices, including basic configuration.  This MIB
   can be used to measure the impact of IPFIX export on the monitoring
   network; it contains tables covering:

      Transport Session,
      Cache definition,
      Observation Point definition,
      Template and Options Template definition,
      export features (failover, load-balancing, duplicate), and
      export statistics per Process, Session, and Template

   From an operational aspect, an important function of this MIB module
   is provided by the Transport Session Statistical table, which
   contains the rate (in bytes per second) at which the Collector
   receives or the Exporter sends out IPFIX Messages.  Of particular
   interest to operations, the Transport Session Statistical table in
   Section 5.8.1 of this MIB module exposes the rate of collection or
   export of IPFIX Messages, which allows the measurement of the
   bandwidth used by IPFIX export.

   [RFC6727] describes extensions to the IPFIX-SELECTOR-MIB module
   specified in [RFC6615] and contains managed objects for providing
   information on applied packet selection functions and their
   parameters (filtering and sampling).

   Since the IPFIX-SELECTOR-MIB [RFC6615] and PSAMP-MIB [RFC6727]
   modules only contain read-only objects, they cannot be used for
   configuration of IPFIX Devices.  [RFC6728] specifies a configuration
   data model for the IPFIX and PSAMP protocols, using the Network
   Configuration Protocol (NETCONF).  This data model covers Selection
   Processes, Caches, Exporting Processes, and Collecting Processes on
   IPFIX and PSAMP Devices, and is defined using UML (Unified Modeling
   Language) class diagrams and formally specified using YANG.  The
   configuration data is encoded in Extensible Markup Language (XML).

   A few mechanisms specified alongside the IPFIX protocol can help
   monitor and reduce bandwidth used for IPFIX Export:

   - a bandwidth-saving method for exporting redundant information in
     IPFIX [RFC5473]

   - an efficient method for exporting bidirectional flows [RFC5103]

   - a method for the definition and export of complex data structures
     [RFC6313]



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   Alternatively, PSAMP [RFC5474] can be used to export packets sampled
   by statistical and other methods, which may be applicable to many
   monitoring areas for which IPFIX is also suited.  PSAMP also provides
   control over the impact on the measured network through its sampling
   rate.  The set of packet selection techniques (Sampling, Filtering,
   and hashing) standardized by PSAMP is described in [RFC5475].  PSAMP
   also defines an explicitly configurable export rate limit in
   Section 8.4 of [RFC5474].

13.  IANA Considerations

   IANA has updated the "IPFIX Information Elements" registry
   [IANA-IPFIX] so that all references that previously pointed to
   RFC 5101 now point to this document instead.

   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 Information Elements used by IPFIX, and sub-registries of
   Information Element values, are managed by IANA [IANA-IPFIX], as are
   the Private Enterprise Numbers used by enterprise-specific
   Information Elements [IANA-PEN].  This document makes no changes to
   these registries.

   The IPFIX Version Number value of 0x000a (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 for the Options 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 the "IPFIX Version Number" or "IPFIX Set
   IDs" sub-registries require a Standards Action [RFC5226], i.e., they
   are to be made via Standards Track RFCs approved by the IESG.














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Appendix A.  IPFIX Encoding Examples

   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 another Data Set (which contains two 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) | |
               +------------------+ +------------------+ |
         . . .-------------------------------------------+

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








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A.2.  Template Set Examples

A.2.1.  Template Set Using IANA Information Elements

   We want to report the following Information Elements:

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

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

   - Next-hop IP address (IPv4): ipNextHopIPv4Address [IANA-IPFIX], with
     a length of 4 octets

   - Number of packets of the Flow: packetDeltaCount [IANA-IPFIX], with
     a length of 4 octets

   - Number of octets of the Flow: octetDeltaCount [IANA-IPFIX], 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        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|    packetDeltaCount = 2     |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|    octetDeltaCount = 1      |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+











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A.2.2.  Template Set Using Enterprise-Specific Information Elements

   We want to report the following Information Elements:

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

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

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

   - Number of packets of the Flow: packetDeltaCount [IANA-IPFIX], with
     a length of 4 octets

   - Number of octets of the Flow: octetDeltaCount [IANA-IPFIX], 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|    packetDeltaCount = 2     |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|    octetDeltaCount = 1      |       Field Length = 4        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+











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A.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                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                               5                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                              6534                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Note that padding is not necessary in this example.



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A.4.  Options Template Set Examples

A.4.1.  Options Template Set Using IANA 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: exportedMessageTotalCount
     [IANA-IPFIX], with a length of 2 octets

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

   The line card, which is represented by the lineCardId Information
   Element [IANA-IPFIX], 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|exportedMessageTotalCount=41 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       Field Length = 2        |0|exportedFlowRecordTotalCo.=42|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       Field Length = 2        |           Padding             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

A.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: exportedMessageTotalCount
     [IANA-IPFIX], 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 [IANA-IPFIX], is used as the Scope Field.



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   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|exportedMessageTotalCount=41 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       Field Length = 2        |1|Information Element id. = 42 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       Field Length = 4        |       Enterprise number      ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ...       Enterprise number      |           Padding             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

A.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 Appendix A.4.1:

   - Total number of IPFIX Messages: exportedMessageTotalCount
     [IANA-IPFIX], with a length of 2 octets

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

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


















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   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|exportedMessageTotalCount=41 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       Field Length = 2        |0|exportedFlowRecordTotalCo.=42|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       Field Length = 2        |           Padding             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

A.4.4.  Data Set Using an Enterprise-Specific Scope

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

     Enterprise field 123   | IPFIX Message  | Exported Flow Records
     ---------------------------------------------------------------
     1                      | 345            | 10201
     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                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |             345               |            10201              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                               2                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |             690               |            20402              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+









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A.5.  Variable-Length Information Element Examples

A.5.1.  Example of Variable-Length Information Element with Length
        Less Than 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          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

A.5.2.  Example of Variable-Length Information Element with 3-Octet
        Length Encoding

     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            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
























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Normative References

   [IANA-IPFIX]
              IANA, "IP Flow Information Export (IPFIX) Entities",
              <http://www.iana.org/assignments/ipfix/>.

   [RFC1014]  Sun Microsystems, Inc., "XDR: External Data Representation
              Standard", RFC 1014, June 1987.

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

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

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of
              ISO 10646", STD 63, RFC 3629, November 2003.

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

   [RFC4960]  Stewart, R., Ed., "Stream Control Transmission Protocol",
              RFC 4960, September 2007.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

   [RFC5905]  Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
              "Network Time Protocol Version 4: Protocol and Algorithms
              Specification", RFC 5905, June 2010.

   [RFC6125]  Saint-Andre, P. and J. Hodges, "Representation and
              Verification of Domain-Based Application Service Identity
              within Internet Public Key Infrastructure Using X.509
              (PKIX) Certificates in the Context of Transport Layer
              Security (TLS)", RFC 6125, March 2011.

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, January 2012.






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   [RFC6520]  Seggelmann, R., Tuexen, M., and M. Williams, "Transport
              Layer Security (TLS) and Datagram Transport Layer Security
              (DTLS) Heartbeat Extension", RFC 6520, February 2012.

   [RFC7012]  Claise, B., Ed., and B. Trammell, Ed., "Information Model
              for IP Flow Information Export (IPFIX)", RFC 7012,
              September 2013.

   [TCP]      Postel, J., "Transmission Control Protocol", STD 7,
              RFC 793, September 1981.

   [UDP]      Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              August 1980.

Informative References

   [IEEE.754.2008]
              Institute of Electrical and Electronics Engineers, "IEEE
              Standard for Floating-Point Arithmetic", IEEE
              Standard 754, August 2008.

   [IPFIX-MED-PROTO]
              Claise, B., Kobayashi, A., and B. Trammell, "Operation of
              the IP Flow Information Export (IPFIX) Protocol on IPFIX
              Mediators", Work in Progress, July 2013.

   [IANA-PEN]
              IANA, "Private Enterprise Numbers",
              <http://www.iana.org/assignments/enterprise-numbers/>.

   [POSIX.1]  IEEE 1003.1-2008, "IEEE Standard for Information
              Technology - Portable Operating System Interface
              (POSIX(R))", 2008.

   [RFC2579]  McCloghrie, K., Ed., Perkins, D., Ed., and J.
              Schoenwaelder, Ed., "Textual Conventions for SMIv2",
              STD 58, RFC 2579, April 1999.

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

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

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



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   [RFC5101]  Claise, B., Ed., "Specification of the IP Flow Information
              Export (IPFIX) Protocol for the Exchange of IP Traffic
              Flow Information", RFC 5101, January 2008.

   [RFC5103]  Trammell, B. and E. Boschi, "Bidirectional Flow Export
              Using IP Flow Information Export (IPFIX)", RFC 5103,
              January 2008.

   [RFC5153]  Boschi, E., Mark, L., Quittek, J., Stiemerling, M., and P.
              Aitken, "IP Flow Information Export (IPFIX) Implementation
              Guidelines", RFC 5153, April 2008.

   [RFC5470]  Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,
              "Architecture for IP Flow Information Export", RFC 5470,
              March 2009.

   [RFC5471]  Schmoll, C., Aitken, P., and B. Claise, "Guidelines for IP
              Flow Information Export (IPFIX) Testing", RFC 5471,
              March 2009.

   [RFC5472]  Zseby, T., Boschi, E., Brownlee, N., and B. Claise, "IP
              Flow Information Export (IPFIX) Applicability", RFC 5472,
              March 2009.

   [RFC5473]  Boschi, E., Mark, L., and B. Claise, "Reducing Redundancy
              in IP Flow Information Export (IPFIX) and Packet Sampling
              (PSAMP) Reports", RFC 5473, March 2009.

   [RFC5474]  Duffield, N., Ed., Chiou, D., Claise, B., Greenberg, A.,
              Grossglauser, M., and J. Rexford, "A Framework for Packet
              Selection and Reporting", RFC 5474, March 2009.

   [RFC5475]  Zseby, T., Molina, M., Duffield, N., Niccolini, S., and F.
              Raspall, "Sampling and Filtering Techniques for IP Packet
              Selection", RFC 5475, March 2009.

   [RFC5476]  Claise, B., Ed., Johnson, A., and J. Quittek, "Packet
              Sampling (PSAMP) Protocol Specifications", RFC 5476,
              March 2009.

   [RFC5477]  Dietz, T., Claise, B., Aitken, P., Dressler, F., and G.
              Carle, "Information Model for Packet Sampling Exports",
              RFC 5477, March 2009.

   [RFC5610]  Boschi, E., Trammell, B., Mark, L., and T. Zseby,
              "Exporting Type Information for IP Flow Information Export
              (IPFIX) Information Elements", RFC 5610, July 2009.




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   [RFC5655]  Trammell, B., Boschi, E., Mark, L., Zseby, T., and A.
              Wagner, "Specification of the IP Flow Information Export
              (IPFIX) File Format", RFC 5655, October 2009.

   [RFC6083]  Tuexen, M., Seggelmann, R., and E. Rescorla, "Datagram
              Transport Layer Security (DTLS) for Stream Control
              Transmission Protocol (SCTP)", RFC 6083, January 2011.

   [RFC6183]  Kobayashi, A., Claise, B., Muenz, G., and K. Ishibashi,
              "IP Flow Information Export (IPFIX) Mediation: Framework",
              RFC 6183, April 2011.

   [RFC6313]  Claise, B., Dhandapani, G., Aitken, P., and S. Yates,
              "Export of Structured Data in IP Flow Information Export
              (IPFIX)", RFC 6313, July 2011.

   [RFC6526]  Claise, B., Aitken, P., Johnson, A., and G. Muenz, "IP
              Flow Information Export (IPFIX) Per Stream Control
              Transmission Protocol (SCTP) Stream", RFC 6526,
              March 2012.

   [RFC6528]  Gont, F. and S. Bellovin, "Defending against Sequence
              Number Attacks", RFC 6528, February 2012.

   [RFC6615]  Dietz, T., Ed., Kobayashi, A., Claise, B., and G. Muenz,
              "Definitions of Managed Objects for IP Flow Information
              Export", RFC 6615, June 2012.

   [RFC6727]  Dietz, T., Ed., Claise, B., and J. Quittek, "Definitions
              of Managed Objects for Packet Sampling", RFC 6727,
              October 2012.

   [RFC6728]  Muenz, G., Claise, B., and P. Aitken, "Configuration Data
              Model for the IP Flow Information Export (IPFIX) and
              Packet Sampling (PSAMP) Protocols", RFC 6728,
              October 2012.

   [UTF8-EXPLOIT]
              Davis, M. and M. Suignard, "Unicode Technical Report #36:
              Unicode Security Considerations", The Unicode Consortium,
              July 2012.










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Acknowledgments

   We would like to thank Ganesh Sadasivan for his significant
   contribution during the initial phases of the protocol specification.
   Additional thanks go to Juergen Quittek for coordination between
   IPFIX and PSAMP; Nevil Brownlee, Dave Plonka, 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 advice
   and knowledge in security; Michael Tuexen for his help regarding the
   DTLS section; Elisa Boschi for her contribution regarding the
   improvement of SCTP sections; Mark Fullmer, Sebastian Zander, Jeff
   Meyer, Maurizio Molina, Carter Bullard, Tal Givoly, Lutz Mark, David
   Moore, Robert Lowe, Paul Calato, Andrew Feren, Gerhard Muenz, Sue
   Hares, and many more, for the technical reviews and feedback.
   Finally, a special mention to Adrian Farrel for his attention to
   management and operational aspects.


































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Contributors

   Stewart Bryant
   Cisco Systems
   10 New Square, Bedfont Lakes
   Feltham, Middlesex  TW18 8HA
   United Kingdom

   EMail: stbryant@cisco.com


   Simon Leinen
   SWITCH
   Werdstrasse 2
   P.O. Box 8021
   Zurich
   Switzerland

   Phone: +41 44 268 1536
   EMail: simon.leinen@switch.ch


   Thomas Dietz
   NEC Europe Ltd.
   NEC Laboratories Europe
   Network Research Division
   Kurfuersten-Anlage 36
   69115 Heidelberg
   Germany

   Phone: +49 6221 4342-128
   EMail: Thomas.Dietz@nw.neclab.eu



















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Authors' Addresses

   Benoit Claise (editor)
   Cisco Systems, Inc.
   De Kleetlaan 6a b1
   1831 Diegem
   Belgium

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


   Brian Trammell (editor)
   Swiss Federal Institute of Technology Zurich
   Gloriastrasse 35
   8092 Zurich
   Switzerland

   Phone: +41 44 632 70 13
   EMail: trammell@tik.ee.ethz.ch


   Paul Aitken
   Cisco Systems, Inc.
   96 Commercial Quay
   Commercial Street, Edinburgh EH6 6LX
   United Kingdom

   Phone: +44 131 561 3616
   EMail: paitken@cisco.com





















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