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Versions: (draft-claise-ipfix-protocol-rfc5101bis) 00 01 02 03 04 05 06 07 08 09 10 RFC 7011

Network Working Group                                     B. Claise, Ed.
Internet Draft                                       Cisco Systems, Inc.
Obsoletes: 5101                                         B. Trammell, Ed.
Category: Standards Track                                     ETH Zurich
Expires: May 24, 2013                                  November 20, 2012


   Specification of the IP Flow Information eXport (IPFIX) Protocol
                  for the Exchange of Flow Information
                draft-ietf-ipfix-protocol-rfc5101bis-03


Abstract

   This document specifies the IP Flow Information Export (IPFIX)
   protocol that serves for transmitting Traffic Flow information over
   the network.  In order to transmit Traffic Flow information from an
   Exporting Process to an information Collecting Process, a common
   representation of flow data and a standard means of communicating
   them is 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 Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 23, 2012.

Copyright Notice

   Copyright (c) 2011 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



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   (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

     1.1.  Changes since RFC 5101 . . . . . . . . . . . . . . . . . .  4
     1.2.  IPFIX Documents Overview . . . . . . . . . . . . . . . . .  5
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  6
     2.1.  Terminology Summary Table  . . . . . . . . . . . . . . . . 11
   3.  IPFIX Message Format . . . . . . . . . . . . . . . . . . . . . 11
     3.1.  Message Header Format  . . . . . . . . . . . . . . . . . . 14
     3.2.  Field Specifier Format . . . . . . . . . . . . . . . . . . 15
     3.3.  Set and Set Header Format  . . . . . . . . . . . . . . . . 16
       3.3.1.  Set Format . . . . . . . . . . . . . . . . . . . . . . 16
       3.3.2.  Set Header Format  . . . . . . . . . . . . . . . . . . 17
     3.4.   Record Format . . . . . . . . . . . . . . . . . . . . . . 18
       3.4.1.  Template Record Format . . . . . . . . . . . . . . . . 18
       3.4.2.  Options Template Record Format . . . . . . . . . . . . 20
         3.4.2.1.  Scope  . . . . . . . . . . . . . . . . . . . . . . 21
         3.4.2.2.  Options Template Record Format . . . . . . . . . . 22
       3.4.3.  Data Record Format . . . . . . . . . . . . . . . . . . 24
   4.  Specific Reporting Requirements  . . . . . . . . . . . . . . . 25
     4.1.  The Metering Process Statistics Options Template . . . . . 25
     4.2.  The Metering Process Reliability Statistics Options
           Template . . . . . . . . . . . . . . . . . . . . . . . . . 26
     4.3.  The Exporting Process Reliability Statistics Options
           Template . . . . . . . . . . . . . . . . . . . . . . . . . 28
     4.4.  The Flow Keys Options Template . . . . . . . . . . . . . . 29
   5.  IPFIX Message Header Export Time and Flow Record Time  . . . . 30
   6.  Linkage with the Information Model . . . . . . . . . . . . . . 30
     6.1.  Encoding of IPFIX Data Types . . . . . . . . . . . . . . . 31
       6.1.1. Integral Data Types . . . . . . . . . . . . . . . . . . 31
       6.1.2. Address Types . . . . . . . . . . . . . . . . . . . . . 31
       6.1.3. float32 . . . . . . . . . . . . . . . . . . . . . . . . 31
       6.1.4. float64 . . . . . . . . . . . . . . . . . . . . . . . . 31
       6.1.5. boolean . . . . . . . . . . . . . . . . . . . . . . . . 31
       6.1.6. string and octetArray . . . . . . . . . . . . . . . . . 31
       6.1.7. dateTimeSeconds . . . . . . . . . . . . . . . . . . . . 31
       6.1.8. dateTimeMilliseconds  . . . . . . . . . . . . . . . . . 32
       6.1.9  dateTimeMicroseconds  . . . . . . . . . . . . . . . . . 32



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       6.1.10 dateTimeNanoseconds . . . . . . . . . . . . . . . . . . 32
     6.2.  Reduced Size Encoding  . . . . . . . . . . . . . . . . . . 33
   7.  Variable-Length Information Element  . . . . . . . . . . . . . 34
   8.  Template Management  . . . . . . . . . . . . . . . . . . . . . 36
     8.1. Template Withdrawal and Redefinition  . . . . . . . . . . . 37
     8.2   Sequencing Template Management Actions . . . . . . . . . . 39
     8.3.  Additional considerations for Template Management over
           SCTP . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
     8.4.  Additional considerations for Template Management over
           UDP  . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
   9. The Collecting Process's Side . . . . . . . . . . . . . . . . . 41
     9.1.  Additional considerations for SCTP Collecting Processes  . 42
     9.2.  Additional considerations for UDP Collecting Processes . . 42
   10.  Transport Protocol  . . . . . . . . . . . . . . . . . . . . . 42
     10.1.  Transport Compliance and Transport Usage  . . . . . . . . 44
     10.2.  SCTP  . . . . . . . . . . . . . . . . . . . . . . . . . . 44
       10.2.1.  Congestion Avoidance  . . . . . . . . . . . . . . . . 44
       10.2.2.  Reliability . . . . . . . . . . . . . . . . . . . . . 44
       10.2.3.  MTU . . . . . . . . . . . . . . . . . . . . . . . . . 45
       10.2.4.  Association Establishment and Shutdown  . . . . . . . 45
       10.2.5.  Failover  . . . . . . . . . . . . . . . . . . . . . . 46
       10.2.6.  Streams . . . . . . . . . . . . . . . . . . . . . . . 46
     10.3.  UDP . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
       10.3.1.  Congestion Avoidance  . . . . . . . . . . . . . . . . 46
       10.3.2.  Reliability . . . . . . . . . . . . . . . . . . . . . 46
       10.3.3.  MTU . . . . . . . . . . . . . . . . . . . . . . . . . 47
       10.3.4.  Session Establishment and Shutdown  . . . . . . . . . 47
       10.3.5.  Failover and Session Duplication  . . . . . . . . . . 47
     10.4.  TCP . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
       10.4.1.  Congestion Avoidance  . . . . . . . . . . . . . . . . 48
       10.4.2.  Reliability . . . . . . . . . . . . . . . . . . . . . 49
       10.4.3.  MTU . . . . . . . . . . . . . . . . . . . . . . . . . 49
       10.4.4.  Connection Establishment, Shutdown, and Restart . . . 49
       10.4.5.  Failover  . . . . . . . . . . . . . . . . . . . . . . 50
   11.  Security Considerations . . . . . . . . . . . . . . . . . . . 50
     11.1.  Applicability of TLS and DTLS . . . . . . . . . . . . . . 51
     11.2.  Usage . . . . . . . . . . . . . . . . . . . . . . . . . . 52
     11.3.  Authentication  . . . . . . . . . . . . . . . . . . . . . 52
     11.4.  Protection against DoS Attacks  . . . . . . . . . . . . . 53
     11.5.  When DTLS or TLS Is Not an Option . . . . . . . . . . . . 54
     11.6.  Logging an IPFIX Attack . . . . . . . . . . . . . . . . . 55
     11.7.  Securing the Collector  . . . . . . . . . . . . . . . . . 55
   12.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . 55
   Appendix A.  IPFIX Encoding Examples . . . . . . . . . . . . . . . 56
     A.1.  Message Header Example . . . . . . . . . . . . . . . . . . 56
     A.2.  Template Set Examples  . . . . . . . . . . . . . . . . . . 57
       A.2.1.  Template Set Using IETF-Specified Information
               Elements . . . . . . . . . . . . . . . . . . . . . . . 57



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       A.2.2.  Template Set Using Enterprise-Specific Information
               Elements . . . . . . . . . . . . . . . . . . . . . . . 57
     A.3.  Data Set Example . . . . . . . . . . . . . . . . . . . . . 59
     A.4.  Options Template Set Examples  . . . . . . . . . . . . . . 60
       A.4.1.  Options Template Set Using IETF-Specified
               Information Elements . . . . . . . . . . . . . . . . . 60
       A.4.2.  Options Template Set Using Enterprise-Specific
               Information  . . . . . . . . . . . . . . . . . . . . . 60
       A.4.3.  Options Template Set Using an Enterprise-Specific
               Scope  . . . . . . . . . . . . . . . . . . . . . . . . 61
       A.4.4.  Data Set Using an Enterprise-Specific Scope  . . . . . 62
     A.5.  Variable-Length Information Element Examples . . . . . . . 63
       A.5.1.  Example of Variable-Length Information Element with
               Length . . . . . . . . . . . . . . . . . . . . . . . . 63
       A.5.2.  Example of Variable-Length Information Element with
               3 Octet Length Encoding  . . . . . . . . . . . . . . . 63
   References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
   Normative References . . . . . . . . . . . . . . . . . . . . . . . 63
   Informative References . . . . . . . . . . . . . . . . . . . . . . 64
   Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . . . 66
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 67




   1.  Introduction

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

1.1.  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:



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   - EDITOR'S NOTE: not sure if we need to this information
      Errata ID: 1655 (technical)
      Errata ID: 2791 (technical)
      Errata ID: 2814 (editorial)
      Errata ID: 1818 (editorial)
      Errata ID: 2792 (editorial)
      Errata ID: 2888 (editorial)
      Errata ID: 2889 (editorial)
      Errata ID: 2890 (editorial)
      Errata ID: 2891 (editorial)
      Errata ID: 2892 (editorial)
      Errata ID: 2903 (editorial)
      Errata ID: 2761 (editorial)
      Errata ID: 2762 (editorial)
      Errata ID: 2763 (editorial)
      Errata ID: 2764 (editorial)
      Errata ID: 2852 (editorial)
      Errata ID: 2857 (editorial)

   - 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.

   - Clarifications on encoding, especially in Section 6: all IPFIX
   values encoded big-endian.

   - Template management in section 8 has been simplified, and made as
   independent of transport protocol as is interoperably possible, by
   relaxing restrictions on template management actions.

   - Editorial changes, including structural changes to sections 8, 9,
   and 10 to improve readability.


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 in [RFC5473], an



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   efficient method for exporting bidirectional flow in [RFC5103], a
   method for the definition and export of complex data structures in
   [RFC6313], and the specification of the Protocol for IPFIX Mediations
   [IPFIX-MED-PROTO] based on the IPIFX Mediation Framework [RFC6183].

   IPFIX has a formal description of IPFIX Information Elements, their
   name, type and additional semantic information, as specified in
   [RFC5102bis], with the export of the Information Element types
   specified in [RFC5610].

   [IPFIX-CONF] specifies a data model for configuring and monitoring
   IPFIX and PSAMP compliant devices using the NETCONF protocol, while
   the [RFC5815bis] specifies a MIB module for monitoring.

   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 type of applications can use the
   IPFIX protocol and how they can use the information provided.  It
   furthermore shows how the IPFIX framework relates to other
   architectures and frameworks.

2.  Terminology

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

   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, except that definitions that are
   only relevant to the IPFIX protocol only appear here.

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

   Observation Point

      An Observation Point is a location in the network where 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.



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      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.

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

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

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

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

      A packet is defined 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;



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      that is, a Flow may represent zero or more packets. Note also that
      as sampling is a packet treatent, 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),

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

      3.  are derived from packet treatment (e.g., Autonomous System
          (AS) number),

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

   Flow Record

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

   Metering Process

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

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

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

   Exporting Process

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

   Exporter



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      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 and arbitrary numbers of Observation
      Points and Metering Processes.

   Collecting Process

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

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

   Message Header

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

   Template Record

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

   Data Record



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

   Options Template Record

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

   Set

      Set is a generic term for a collection of records that have a
      similar structure.  In an IPFIX Message, one or more Sets follow
      the Message Header.

      There are three different types of Sets: Template Set, Options
      Template Set, and Data Set.

   Template Set

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

   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.
      The IPFIX information model [RFC5102bis] defines the base set of
      Information Elements for IPFIX.  The type associated with an
      Information Element indicates constraints on what it may contain
      and also determines the valid encoding mechanisms for use in
      IPFIX.

   Transport Session




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      In 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.

2.1.  Terminology Summary Table

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

   Figure A: Terminology Summary Table

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

   A Template Set contains only Template Record(s).

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

3.  IPFIX Message Format

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

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

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



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

   Figure B: IPFIX Message Format

   The Exporter MUST encode all integers in the Message Header and the
   Set Headers in network byte order (also known as big-endian byte
   order).

   Following are some examples of IPFIX Messages:

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































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

   Figure C: IPFIX Message, Example 1

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

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

   Figure D: IPFIX Message, Example 2

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

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

   Figure E: IPFIX Message, Example 3















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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

   Message Header Field Descriptions:

   Version

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

   Length

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

   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.

   Sequence Number

      Incremental sequence counter modulo 2^32 of all IPFIX Data Records
      sent in a 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
      transport session are considered to be part of the same stream.
      This value SHOULD be used by the Collecting Process to identify
      whether any IPFIX Data Records have been missed. Template and
      Options Template Records do not increase the Sequence Number.



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      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 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
   IETF-specified Information Elements [RFC5102bis] and enterprise-
   specific Information Elements.

   The Information Elements are identified by the Information Element
   identifier.  When the Enterprise bit is set to 0, the corresponding
   Information Element identifier will report an IETF-specified
   Information Element, and the Enterprise Number MUST NOT be present.
   When the Enterprise bit is set to 1, the corresponding Information
   Element identifier will report an enterprise-specific Information
   Element; the Enterprise Number MUST be present.  An example of this
   is shown in Section A.4.2.

   The Field Specifier format is shown in Figure G.

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |E|  Information Element ident. |        Field Length           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Enterprise Number                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure G: Field Specifier Format









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   Where:

   E

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

   Information Element identifier

      A numeric value that represents the type of Information Element.
      Refer to [RFC5102bis].

   Field Length

      The length of the corresponding encoded Information Element,  in
      octets.  Refer to [RFC5102bis].  The field length may be smaller
      than the definition in [RFC5102bis] 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 [PEN] of the authority defining the
      Information Element identifier in this Template Record.

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.








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

   Figure H: Set Format

   The Set Field Definitions are as follows:

   Set Header

      The Set Header Format is defined in Section 3.3.2.

   Record

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

   Padding

      The Exporting Process MAY insert some padding octets, so that the
      subsequent Set starts at an aligned boundary.  For security
      reasons, the padding octet(s) MUST be composed of zero (0) valued
      octets.  The padding length MUST be shorter than any allowable
      record in this Set.  If padding of the IPFIX Message is desired in
      combination with very short records, then the padding Information
      Element 'paddingOctets' [RFC5102bis] can be used for padding
      records such that their length is increased to a multiple of 4 or
      8 octets.  Because Template Sets are always 4-octet aligned by
      definition, padding is only needed in case of other alignments
      e.g., on 8-octet boundaries.

3.3.2.  Set Header Format

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






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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Set ID               |          Length               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure I: Set Header Format

   The Set Header Field Definitions are as follows:

   Set ID

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

   Length

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

3.4.   Record Format

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

3.4.1.  Template Record Format

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

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







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

   Figure J: Template Record Format

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

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Template ID (> 255)      |         Field Count           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure K: Template Record Header Format

   The Template Record Header Field Definitions are as follows:

   Template ID

      Each of the newly generated Template Records is given a unique
      Template ID.  This uniqueness is local to the Transport Session
      and Observation Domain that generated the Template ID.  Template
      IDs 0-255 are reserved for Template Sets, Options Template Sets,
      and other reserved Sets yet to be created.  Template IDs of Data
      Sets are numbered from 256 to 65535.  There are no constraints
      regarding the order of the Template ID allocation.

   Field Count

      Number of fields in this Template Record.

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








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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Set ID = 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 Identifiers 1.2 and 2.1 are defined by the IETF
   (Enterprise bit = 0) and, therefore, do not need an Enterprise Number
   to identify them.

3.4.2.  Options Template Record Format

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




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

3.4.2.1.  Scope

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

   Multiple Scope Fields MAY be present in the Options Template Record,
   in which case, the composite scope is the combination of the scopes.
   For example, if the two scopes are defined as "metering process" and
   "template", the combined scope is this Template for this Metering
   Process.  The order of the Scope Fields, as defined in the Options
   Template Record, is irrelevant in this case.  However, if the order
   of the Scope Fields in the Options Template Record is relevant, the
   order of the Scope Fields MUST be used.  For example, if the first
   scope defines the filtering function, while the second scope defines
   the sampling function, the order of the scope is important.  Applying
   the sampling function first, followed by the filtering function,
   would lead to potentially different Data Records than applying the
   filtering function first, followed by the sampling function.  In this
   case, the Collector deduces the function order by looking at the
   order of the scope in the Options Template Record.

   The scope is an Information Element specified in the IPFIX
   Information Model [RFC5102bis].  An IPFIX-compliant implementation of
   the Collecting Process SHOULD support this minimum set of Information
   Elements as scope: LineCardId, TemplateId, exporterIPv4Address,
   exporterIPv6Address, and ingressInterface.  Note that other
   Information Elements, such as meteringProcessId, exportingProcessId,
   observationDomainId, etc. are also valid scopes.  The IPFIX protocol
   doesn't prevent the use of any Information Elements for scope.
   However, some Information Element types don't make sense if specified
   as scope; for example, the counter Information Elements.

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






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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 Elements identifiers.

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

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

   Figure M: Options Template Record Format

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

    0                  1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Template ID (> 255)   |         Field Count           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Scope Field Count        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure N: Options Template Record Header Format

   The Options Template Record Header Field Definitions are as follows:

   Template ID

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








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   Field Count

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

   Scope Field Count

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

   The example in Figure O shows an Options Template Set with mixed IETF
   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 specified in
   [RFC5102bis].

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

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






















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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Set ID = 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.

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 that are
   defined in [RFC5102bis]:



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

   (scope) meteringProcessId
                           An identifier of the Metering Process for
                           which statistics are reported. This
                           Information Element MUST be defined as a
                           Scope Field.

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

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

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

   The Exporting Process SHOULD export the Data Record specified by the
   Metering Process Statistics 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 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 that are defined in [RFC5102bis]:






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

   (scope) meteringProcessId
                           The identifier of the Metering Process for
                           which lack of reliability is reported. This
                           Information Element MUST be defined as a
                           Scope Field.

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

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

   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 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 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.




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   Since the Metering Process Reliability Option Template will logically
   contain two identical timestamp Information Elements, and since the
   order of the Information Elements in the Template Records is not
   guaranteed, the Collecting Process MUST determine which is the oldest
   and the most recent timestamp in order the determine the right
   semantic behind the time first packet ignored and time last packet
   ignored Information Elements. Note that the counters wrap-around for
   the timestamps SHOULD also be taken into account.

4.3.  The Exporting Process Reliability Statistics Options Template

   The Exporting Process Reliability 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 that are defined in [RFC5102bis]:

   (scope) Exporting Process ID
                        The identifier of the Exporting Process for
                        which lack of reliability is reported.  There
                        are three Information Elements specified in
                        [RFC5102bis] that can be used for this purpose:
                        exporterIPv4Address, exporterIPv6Address, or
                        exportingProcessId.  This Information Element
                        MUST be defined as a Scope Field.

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

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

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







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   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 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 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.

   Since the Exporting Process Reliability Option Template will
   logically contain two identical timestamp Information Elements, and
   since the order of the Information Elements in the Template Records
   is not guaranteed, the Collecting Process MUST determine which is the
   oldest and the most recent timestamp in order the determine the right
   semantic behind the time first packet ignored and time last packet
   ignored Information Elements. Note that the counters wrap-around for
   the timestamps SHOULD also be taken into account.

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 identifier.  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 that are defined in [RFC5102bis]:







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

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

5.  IPFIX Message Header Export Time and Flow Record Time

   The IPFIX Message Header Export Time field is the time at which the
   IPFIX Message Header leaves the Exporter, expressed in seconds since
   the UNIX epoch, 1 January 1970 at 00:00 UTC, encoded in 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 [RFC5102bis], 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 [RFC5102bis] 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 two bytes per timestamp, while
   increasing the load on the Exporter, as the Exporting Process must
   calculate the flowStartDeltaMicroseconds and flowEndDeltaMicroseconds
   of every single Data Record before exporting the IPFIX Message.

   It must be noted that 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 [RFC5102bis], 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.


6.  Linkage with the Information Model

   As with values in the IPFIX Message Header and Set Header, values of
   all Information Elements [RFC5102bis], 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).






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6.1.  Encoding of IPFIX Data Types

   The following sections will define the encoding of the data types
   specified in [RFC5102bis].

6.1.1. Integral Data Types

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

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 single-precision
   32-bit floating point-type, as specified in [IEEE.754.1985], in
   network byte order.

6.1.4. float64

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

6.1.5. boolean

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

6.1.6. string and octetArray

   The data type string represents a finite length string of valid
   characters of the Unicode character encoding set. The string data
   type MUST be encoded in UTF-8 format. The string is sent as an array
   of octets using an Information Element of fixed or variable length.
   The data type octetArray has no encoding rules; it represents a raw
   array of octets, with the intepretation of the octets defined in the
   Information Element definition.

6.1.7. dateTimeSeconds



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   The data type dateTimeSeconds 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
   8 February 2106.

6.1.8. dateTimeMilliseconds

   The data type dateTimeMilliseconds 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 for approximately the
   next 500 billion years.

6.1.9  dateTimeMicroseconds

   The data type dateTimeMicroseconds 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 beginning between 1 January 1900 and 8 February 2036.

   Note that dateTimeMicroseconds and dateTimeNanoseconds share an
   identical encoding. The dataTimeMicroseconds data type is intended
   only to represent timestamps of microsecond precision. Therefore, the
   bottom 11 bits of the fraction field MAY contain any value 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 data type dateTimeNanoseconds 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 beginning between 1 January 1900 and 8 February 2036.

   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.




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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 [RFC5102bis], 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 [RFC5102bis] will always define the
   maximum encoding size.

   For instance, the information model [RFC5102bis] 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 chose to send the value
   instead as an unsigned32. For example, a core router would require an
   unsigned64 byteCount, while an unsigned32 might be sufficient for an
   access router.

   This behavior is indicated by the Exporter by specifying a 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.

   If reduced size encoding MAY be 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 [RFC5102bis] 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 length 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.




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7.  Variable-Length Information Element

   The IPFIX Template mechanism is optimized for fixed-length
   Information Elements [RFC5102bis].  Where an Information Element has
   a variable length, the following mechanism MUST be used to carry the
   length information for both the IETF and proprietary Information
   Elements.

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

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

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Length (< 255)|          Information Element                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      ... continuing as needed                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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

   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, 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 (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



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   Element.


















































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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.
   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
   IPFIX Message export on any supported Transport Protocol. Additional
   considerations specific to SCTP and UDP transport are given in
   sections 8.3 and 8.4, respectively.

   The Exporting Process assigns and maintains the Template IDs per
   Transport Session for the Exporter's Observation Domains. 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 in section 8.1, except as noted
   in section 8.4, so that it can interpret the corresponding Data
   Records that are received in subsequent Data Sets. 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. When a Transport Session is
   closed, the Collecting Process MUST discard all Templates received
   over that association and stop decoding IPFIX Messages that use those
   Templates.

   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
   defined 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 packets, the first sourceIPv4Address
   Information Element occurrence should be the IPv4 address of the
   outer header, while the second occurrence should be the address of



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   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
   subsequent IPFIX Message(s).

   This ensures that the Collecting Process normally receives Template
   Records from the Exporting Process before receiving Data Records.
   However, if the Template Records have not been received at the time
   Data Records are received, the Collecting Process MAY store the Data
   Records for a short period of time and decode them after the Template
   Records are received. In any case, 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.

   Different Observation Domains from the same 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 which are related or interdependent
   (e.g. by sharing common properties as in [RFC5473]) SHOULD be sent
   together in the same IPFIX Message.

8.1. Template Withdrawal and Redefinition

   Since a Template may have a lifetime at the Exporting Process
   independent of the Transport Session, IPFIX provides a mechanism for
   the withdrawal of templates and for the reuse of template IDs. This
   mechanism does not apply when UDP is used to transport IPFIX
   messages; for this case, see Section 8.4.

   Templates that will not be used further by an Exporting Process MUST
   be withdrawn by sending a Template Withdrawal Message. After
   receiving a Template Withdrawal, a Collecting Process MUST discard
   the Template and stop using it to interpret Data Sets.

   A Template Withdrawal consists of a Template Record for the Template
   ID to be with a Field Count of 0. The format of a Template Withdrawal
   is shown in Figure T.








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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Set ID = (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 Set Format


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

   A Template Withdrawal Message is an IPFIX Message containing Template
   Withdrawals. It withdraws Template IDs for the Observation Domain ID
   specified in the IPFIX Message Header. It MUST NOT contain new
   Template or Options Template Records, or any Data Sets. The Exporting
   Process SHOULD NOT send a Template Withdrawal Message until
   sufficient time has elapsed to allow receipt and processing of and
   Data Records described by the withdrawn Templates; see section 8.2
   for more information on sequencing Template Withdrawals.

   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. All Templates for a given Observation Domain MAY
   also be withdrawn using an All Templates Withdrawal, which withdraws
   the special Template ID 2; this is shown in Figure U. All Options
   Templates for a given observation Domain MAY likewise be withdrawn
   using an All Options Templates Withdrawal, which withdraws the
   special Template ID 3. Each of these Withdrawals MUST appear in a
   Template Withdrawal Message with no other Withdrawals.












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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Set ID = 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


   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 new Template Record or Options
   Template Record for an already-allocated Template ID, without having
   received a withdrawal, it MUST ignore the new Template Record and
   discard the old Template Record for the allocated ID; it SHOULD log
   the error.

   If a Collecting Process receives a Template Withdrawal for a Template
   or Options Template it does not presently have stored, it MUST ignore
   the Template Withdrawal and SHOULD log the error.

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



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   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.

   Put another way, a Template only describes Records contained in IPFIX
   Messages with the same Export Time as the IPFIX Message containing
   Template Record, or a subsequent export time. Likewise, a Template
   Withdrawal is only in effect for IPFIX Messages with the same Export
   Time as the Template Withdrawal, or a subsequent Export Time.

   Collecting Processes MAY implement a buffer to handle out-of-order
   Template management events.

8.3.  Additional considerations for Template Management over SCTP

   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 and in
   order.

   Template Withdrawal Messages MAY be sent on any SCTP stream. Template
   Withdrawal Messages MUST be sent reliably, using SCTP-ordered
   delivery. Template IDs MAY be reused by sending a Template Withdrawal
   Message 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 given in [IPFIX-
   PER-SCTP-STREAM], 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.

8.4.  Additional considerations for Template Management over UDP

   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, as via the
   the templateRefreshTimeout and optionsTemplateRefreshTimeout defined
   in [IPFIX-CONF]. Default settings for these values are deployment-
   and application-specific.



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

   In order to minimize resource requirements for templates which have
   expired at the Exporting Process without being withdrawn, or in cases
   when the Template Withdrawal Message was lost between the Exporting
   Process and the Collecting Process, the Collecting Process MAY
   associate a lifetime with each Template received in a UDP 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.

   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, 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 given in Sections 9.1 and 9.2
   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 the Flow Record.

   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 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



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   Message. The Collecting Process MAY detect out-of-sequence, dropped,
   or duplicate IPFIX Messages using this the Sequence Number. If it
   supports this mechanism, the Collecting Process SHOULD log
   out-of-sequence IPFIX Messages, as these could indicate resource
   exhaustion at the Exporting Process or the Collecting Process, an
   Exporting Process reset, packet loss due to congestion between the
   Exporting Process and the Collecting Process, or message injection.

   If the Collecting Process receives a malformed IPFIX Message, it MUST
   discard the IPFIX Message and SHOULD log the error. Note that non-
   zero Set padding does not constitute a malformed IPFIX Message.

9.1.  Additional considerations for SCTP Collecting Processes

   The Exporting Process requests a number of streams to use for export
   at association setup time. An Exporting Process MAY request and
   support more than one stream per SCTP association.

9.2.  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
   difficult to detect at the Collecting Process, the Collecting Process
   MAY expire all Transport Session state after no IPFIX Messages are
   received from a given Exporting Process during a configurable idle
   timeout.

   The Collecting Process SHOULD accept Data Records without the
   associated Template Record (or other definitions) required to decode
   the Data Record.  If the Template Records (or other definitions such
   as Common Properties) have not been received at the time Data Records
   are received, the Collecting Process SHOULD store the Data Records
   for a short period of time and decode them after the Template Records
   (or other definitions) are received.  The short period of time MUST
   be lower than the lifetime of definitions associated with identifiers
   considered unique within the UDP session.

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



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   octets.


















































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10.1.  Transport Compliance and Transport Usage

   SCTP [RFC4960] using the PR-SCTP extension 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.

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

   TCP MAY be used in deployments where Exporters and Collectors
   communicate over links that are susceptible to congestion, but 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 Exporter and
   Collector MUST be separately contained or provisioned to minimize the
   risk of congestion-related loss.

10.2.  SCTP

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

10.2.1.  Congestion Avoidance

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

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

10.2.2.  Reliability

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

   Using reliable SCTP messages for the 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



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   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 discovery.

10.2.4.  Association Establishment and Shutdown

   The IPFIX Exporting Process SHOULD initiate an SCTP association with
   the IPFIX Collecting Process.  By default, the Collecting Process
   listens for connections on SCTP port 4739.  By default, the
   Collecting Process listens for secure connections on SCTP port 4740
   (refer to the Security Considerations section).  By default, the
   Exporting Process tries to connect to one of these ports.  It MUST be
   possible to configure both the Exporting and Collecting Processes to
   use a different SCTP port.

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

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

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

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

10.2.6.  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 [RFC3758] specification 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.

10.3.2.  Reliability

   UDP is not a reliable transport protocol, and cannot guarantee
   delivery of messages.  IPFIX Messages sent from the Exporting Process



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

   Exporting Processes exporting IPFIX Messages via UDP MUST include a
   valid UDP checksum.

10.3.3.  MTU

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

10.3.4.  Session Establishment and Shutdown

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

   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 leads to
   some complications in template management, which are 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

   The IPFIX Exporting Process initiates a TCP connection to the
   Collecting Process.  By default, the Collecting Process listens for
   connections on TCP port 4739.  By default, the Collecting Process
   listens for secure connections on TCP port 4740 (refer to the
   Security Considerations section).  By default, the Exporting Process
   tries to connect to one of these ports.  It MUST be possible to
   configure both the Exporting Process and the Collecting Process to
   use a different TCP port.

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

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

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

   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
   exported as in Section 4.3.

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




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10.4.2.  Reliability

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

   In the case of TCP, the IPFIX Sequence Number contains the total
   number of IPFIX Data Records sent from this TCP connection, from the
   current Observation Domain by the Exporting Process, prior to the
   receipt of this IPFIX Message, modulo 2^32.

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.

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

10.4.4.  Connection Establishment, Shutdown, and Restart

   The IPFIX Exporting Process initiates a TCP connection to the
   Collecting Process.  By default, the Collecting Process listens for
   connections on TCP port 4739.  By default, the Collecting Process
   listens for secure connections on TCP port 4740 (refer to the
   Security Considerations section).  By default, the Exporting Process
   tries to connect to one of these ports.  It MUST be possible to
   configure both the Exporting Process and the Collecting Process to
   use a different TCP port.

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

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

   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



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   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 the attempt by the
   Exporting Process to establish a connection, it will retry using the
   TCP exponential backoff feature.

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

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 IPFIX requirements [RFC3917].
   The requirements for IPFIX security are as follows:

   1. IPFIX must provide a mechanism to ensure the confidentiality of
      IPFIX data transferred from an Exporting Process to a Collecting
      Process, in order to prevent disclosure of Flow 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) into an IPFIX Message
      stream.

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

   Because IPFIX can be used to collect information for network
   forensics and billing purposes, attacks designed to confuse, disable,
   or take information from an IPFIX collection system may be seen as a



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   prime objective during a sophisticated network attack.

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

   The IPFIX Messages themselves may also contain information of value
   to an attacker, including information about the configuration of the
   network as well as end-user traffic and payload data, so care must be
   taken to confine their visibility to authorized users.  When an
   Information Element containing end-user payload information is
   exported, it SHOULD be transmitted to the Collecting Process using a
   means that secures its contents against eavesdropping.  Suitable
   mechanisms include the use of either a direct point-to-point
   connection or the use of an encryption mechanism.  It is the
   responsibility of the Collecting Process to provide a satisfactory
   degree of security for this collected data, including, if necessary,
   anonymization of any reported data.

11.1.  Applicability of TLS and DTLS

   Transport Layer Security (TLS) [RFC5246] and Datagram Transport Layer
   Security (DTLS) [RFC4347] were designed to provide the
   confidentiality, integrity, and authentication assurances required by
   the IPFIX protocol, without the need for pre-shared keys.

   With the mandatory SCTP transport protocol for IPFIX, DTLS [RFC4347]
   MUST be implemented.  If UDP is selected as the IPFIX transport
   protocol, DTLS [RFC4347] MUST be implemented.  If TCP is selected as
   the IPFIX transport protocol, TLS [RFC5246] MUST be implemented.

   Note that DTLS is selected as the security mechanism for SCTP.
   Though TLS bindings to SCTP are defined in [RFC3436], they require
   all communication to be over reliable, bidirectional streams, and
   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 [RFC4347] has a vulnerability, i.e., a true man
   in the middle may attempt to take data out of an association and fool
   the sender into thinking that the data was actually received by the
   peer. In generic TLS for SCTP (and/or TCP), this is not possible.
   This means that the removal of a message may become hidden from the
   sender or receiver. Another vulnerability of using SCTP with DTLS is
   that someone could inject SCTP control information to shut down the
   SCTP association, effectively generating a loss of IPFIX Messages if



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   those are buffered outside of the SCTP association. Techniques such
   as [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 Extention [RFC6520]
   SHOULD be used, especially on long-lived Transport Sessions, to
   ensure that the association remains active.

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 [RFC4347], while the IPFIX Collecting Process acts as a
   TLS or DTLS server.  The DTLS client opens a secure connection on the
   SCTP port 4740 of the DTLS server if SCTP is selected as the
   transport protocol.  The TLS client opens a secure connection on the
   TCP port 4740 of the TLS server if TCP is selected as the transport
   protocol.  The DTLS client opens a secure connection on the UDP port
   4740 of the DTLS server if UDP is selected as the transport
   protocol.

11.3.  Authentication

   IPFIX Exporting Processes and IPFIX Collecting Processes are
   identified by the fully qualified domain name of the interface on
   which IPFIX Messages are sent or received, for purposes of X.509
   client and server certificates as in [RFC5280].

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






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   The fully qualified domain name used to identify an IPFIX Collecting
   Process or Exporting Process may be stored either in a subjectAltName
   extension of type dNSName, or in the most specific Common Name field
   of the Subject field of the X.509 certificate.  If both are present,
   the subjectAltName extension is given preference.

   Internationalized domain names (IDN) in either the subjectAltName
   extension of type dNSName or the most specific Common Name field of
   the Subject field of the X.509 certificate MUST be encoded using
   Punycode [RFC3492] as described in [RFC5891], "Conversion
   Operations".

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

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

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

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




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   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
   and partial reliability features, possibly affording some visibility
   of the attack.  The situation is similar with UDP, as some datagrams
   may continue to be received at the Collecting Process, effectively
   applying sampling to the IPFIX Message stream, implying that some
   forensics may be left.

   To minimize IPFIX Message loss under overload conditions, some
   mechanism for service differentiation could be used to prioritize
   IPFIX traffic over other traffic on the same link.  Alternatively,
   IPFIX Messages can be transported over a dedicated network.  In this
   case, care must be taken to ensure 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 [RFC1948], [RFC4960]); 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.





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11.6.  Logging an IPFIX Attack

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

   IPFIX Exporting and Collecting Processes SHOULD log any connection
   attempt that fails due to authentication failure, whether due to
   being presented an unauthorized or mismatched certificate during TLS
   or DTLS mutual authentication, or due to a connection attempt from an
   unauthorized IP address when TLS or DTLS 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, it is outside the scope of this
   document.

12.  IANA Considerations

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

   The IPFIX Version Number value of 10 is reserved for the IPFIX
   protocol specified in this document.  Set ID values of 0 and 1 are
   not used for historical reasons [RFC3954].  The Set ID value of 2 is
   reserved for the Template Set.  The Set ID value of 3 is reserved 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 IPFIX Version Number or IPFIX Set ID
   assignments 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 a Data Set (which contains 2 Data Records
   related to the previous Options Template Record).

   IPFIX Message:

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

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

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 IETF-Specified Information Elements


   We want to report the following Information Elements:

   - The IPv4 source IP address: sourceIPv4Address in [RFC5102bis],
     with a length of 4 octets

   - The IPv4 destination IP address: destinationIPv4Address in
     [RFC5102bis], with a length of 4 octets

   - The next-hop IP address (IPv4): ipNextHopIPv4Address in
     [RFC5102bis], with a length of 4 octets

   - The number of packets of the Flow: packetDeltaCount in
     [RFC5102bis], with a length of 4 octets

   - The number of octets of the Flow: octetDeltaCount in
     [RFC5102bis], 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        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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

   We want to report the following Information Elements:

   - The IPv4 source IP address: sourceIPv4Address in [RFC5102bis], with
     a length of 4 octets



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   - The IPv4 destination IP address: destinationIPv4Address in
     [RFC5102bis], with a length of 4 octets

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

   - The number of packets of the Flow: packetDeltaCount in
     [RFC5102bis], with a length of 4 octets

   - The number of octets of the Flow: octetDeltaCount in  [RFC5102bis],
     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 IETF-Specified Information Elements


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

   - Total number of IPFIX Messages: exportedMessageTotalCount
     [RFC5102bis], with a length of 2 octets

   - Total number of exported Flows: exportedFlowRecordTotalCount
     [RFC5102bis], with a length of 2 octets

   The line card, which is represented by the lineCardId Information
   Element [RFC5102bis], 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
        [RFC5102bis], 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



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   Element [RFC5102bis], is used as the Scope Field.

   The format of the Options Template Set is as follows:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         Set ID = 3            |          Length = 28          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |       Template ID 259         |        Field Count = 3        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |     Scope Field Count = 1     |0|     lineCardId = 141        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Scope 1 Field Length = 4    |0|exportedFlowRecordTotalCo.=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 Section A.4.1:

      - Total number of IPFIX Messages: exportedMessageTotalCount
        [RFC5102bis], with a length of 2 octets

      - Total number of exported Flows: exportedFlowRecordTotalCount
        [RFC5102bis], 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
        Inferior to 255 Octets

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       5       |          5 octet Information Element          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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

References

Normative References


   [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.

   [RFC3492]      Costello, A., "Punycode: A Bootstring encoding of
                   Unicode for Internationalized Domain Names in
                   Applications (IDNA)", RFC 3492, March 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.




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   [RFC4347]      Rescorla, E. and N. Modadugu, "Datagram Transport
                   Layer Security", RFC 4347, April 2006.

   [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.

   [RFC5280]      Cooper, D., Santesson, S., Farrell, S. Boeyen, S.
                   Housley, R., and W. Polk, "Internet X.509 Public Key
                   Infrastructure Certificate and Certificate Revocation
                   List (CRL) Profile", RFC 5280, April 2008.

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

   [RFC5891]      J. Klensin, "Internationalized Domain Names in
                   Applications (IDNA): Protocol", RFC 5891, August
                   2010.

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

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

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

   [RFC5102bis]   Quittek, J., Bryant S., Claise, B., Aitken, P., and J.
                   Meyer, "Information Model for IP Flow Information
                   Export", draft-claise-ipfix-information-model-
                   rfc5102bis-01.txt, Work in Progress, October 2011.

Informative References

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




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

   [RFC2579]      McCloghrie, K., Perkins, D., and J. Schoenwaelder,
                   "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.

   [RFC5101]      Claise, B., Ed., "Bidirectional Flow Export Using IP
                   Flow Information Export (IPFIX)", RFC 5103, January
                   2008.

   [RFC5103]      Trammell, B., and E. Boschi, "Specification of the IP
                   Flow Information Export (IPFIX) Protocol for the
                   Exchange of IP Traffic Flow Information", RFC 5101,
                   January 2008.

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

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

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

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

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

   [RFC5610]      Boschi, E., Trammell, B., Mark, L., and T. Zseby,



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                   "Exporting Type Information for IP Flow Information
                   Export (IPFIX) Information Elements", July 2009.

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

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

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

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

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

   [IPFIX-CONF]   Muenz, G., Claise, B., and P. Aitken, "Configuration
                   Data Model for IPFIX and PSAMP", draft-ietf-ipfix-
                   configuration-model-10, Work in Progress, July 2011.

   [IPFIX-PER-SCTP-STREAM] Claise, B., Aitekn, P., Johnson, A. and G.
                   Muenz, "IPFIX Export per SCTP Stream", draft-ietf-
                   ipfix-export-per-sctp-stream-08, Work in Progress,
                   May 2010.

   [IPFIX-MED-PROTO] Claise, B., Kobayashi, A., and B. Trammell,
                   "Specification of the Protocol for IPFIX Mediations",
                   draft-claise-ipfix-mediation-protocol-04, Work in
                   Progress, July 2011.

   [RFC5815bis]   Dietz, T., Kobayashi, A., Claise, B., and G. Muenz,
                   "Definitions of Managed Objects for IP Flow
                   Information Export", draft-dkcm-ipfix-rfc5815bis-
                   00.txt, Work in Progress, October 2011.

Acknowledgments

   We would like to thank the following persons: Ganesh Sadasivan for
   his significant contribution during the initial phases of the
   protocol specification; Juergen Quittek for the coordination job
   within IPFIX and PSAMP; Nevil Brownlee, Dave Plonka, Paul Aitken, and



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   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, and many more, for the technical
   reviews and feedback.

Authors' Addresses

   Benoit Claise (Ed.)
   Cisco Systems
   De Kleetlaan 6a b1
   1831 Diegem
   Belgium

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


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

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


   Stewart Bryant
   Cisco Systems, Inc.
   250, Longwater,
   Green Park,
   Reading, RG2 6GB,
   United Kingdom

   Phone: +44 (0)20 8824-8828
   EMail: stbryant@cisco.com









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   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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