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IP Flow Information Export WG                               G. Sadasivan
(ipfix)                                              Cisco Systems, Inc.
Internet-Draft                                               N. Brownlee
Expires: April 9, 2005                CAIDA | The University of Auckland
                                                               B. Claise
                                                     Cisco Systems, Inc.
                                                              J. Quittek
                                                         NEC Europe Ltd.
                                                         October 9, 2004


              Architecture for IP Flow Information Export
                    draft-ietf-ipfix-architecture-04

Status of this Memo

   This document is an Internet-Draft and is subject to all provisions
   of section 3 of RFC 3667.  By submitting this Internet-Draft, each
   author represents that any applicable patent or other IPR claims of
   which he or she is aware have been or will be disclosed, and any of
   which he or she become aware will be disclosed, in accordance with
   RFC 3668.

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

   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."

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

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on April 9, 2005.

Copyright Notice

   Copyright (C) The Internet Society (2004).

Abstract

   This memo defines the IPFIX architecture for the selective monitoring
   of IP flows, and for the export of measured IP flow information from



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   an IPFIX device to a collector, as per the requirements set out in
   the IPFIX requirements document.

Table of Contents

   1.   Architecture Issues  . . . . . . . . . . . . . . . . . . . .   4
   2.   Changes/Issues from the -03 Draft  . . . . . . . . . . . . .   5
   3.   Introduction . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.   Scope  . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.   Terminology  . . . . . . . . . . . . . . . . . . . . . . . .   6
   6.   Examples of Flows  . . . . . . . . . . . . . . . . . . . . .  10
   7.   IPFIX Reference Model  . . . . . . . . . . . . . . . . . . .  12
   8.   IPFIX Functional and Logical Blocks  . . . . . . . . . . . .  13
     8.1  Metering Process . . . . . . . . . . . . . . . . . . . . .  13
       8.1.1  Flow Expiration and Export . . . . . . . . . . . . . .  14
     8.2  Observation Point  . . . . . . . . . . . . . . . . . . . .  15
     8.3  Selection Criteria for Packets . . . . . . . . . . . . . .  15
       8.3.1  Filter Functions, Fi . . . . . . . . . . . . . . . . .  15
       8.3.2  Sampling Functions, Si . . . . . . . . . . . . . . . .  16
     8.4  Observation Domain . . . . . . . . . . . . . . . . . . . .  16
     8.5  Exporting Process  . . . . . . . . . . . . . . . . . . . .  16
     8.6  Collecting Process . . . . . . . . . . . . . . . . . . . .  17
     8.7  Summary  . . . . . . . . . . . . . . . . . . . . . . . . .  17
   9.   Overview of the IPFIX Protocol . . . . . . . . . . . . . . .  19
     9.1  Information Model Overview . . . . . . . . . . . . . . . .  19
     9.2  Flow records . . . . . . . . . . . . . . . . . . . . . . .  20
     9.3  Control Information  . . . . . . . . . . . . . . . . . . .  20
     9.4  Exporting Control Information  . . . . . . . . . . . . . .  20
     9.5  Reporting Responsibilities . . . . . . . . . . . . . . . .  21
   10.  IPFIX Protocol Details . . . . . . . . . . . . . . . . . . .  21
     10.1   The IPFIX Basis Protocol . . . . . . . . . . . . . . . .  21
     10.2   IPFIX Protocol on the Collecting Process . . . . . . . .  22
     10.3   Support for Applications . . . . . . . . . . . . . . . .  22
   11.  Export Models  . . . . . . . . . . . . . . . . . . . . . . .  23
     11.1   Export with Reliable Control Connection  . . . . . . . .  23
     11.2   Collector Failure Detection and Recovery . . . . . . . .  23
     11.3   Collector Redundancy . . . . . . . . . . . . . . . . . .  24
   12.  IPFIX Flow Collection for Special Traffic  . . . . . . . . .  24
   13.  IPFIX Flow Collection from Special Devices . . . . . . . . .  25
   14.  Security Considerations  . . . . . . . . . . . . . . . . . .  25
     14.1   Data Security  . . . . . . . . . . . . . . . . . . . . .  25
       14.1.1   No Security  . . . . . . . . . . . . . . . . . . . .  26
       14.1.2   Authentication-only  . . . . . . . . . . . . . . . .  26
       14.1.3   Encryption . . . . . . . . . . . . . . . . . . . . .  26
     14.2   IPFIX End-point Authentication . . . . . . . . . . . . .  27
   15.  IPFIX Overload . . . . . . . . . . . . . . . . . . . . . . .  27
     15.1   Denial of Service (DoS) Attack Prevention  . . . . . . .  27
       15.1.1   Network Under Attack . . . . . . . . . . . . . . . .  27



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       15.1.2   Generic DoS Attack on the IPFIX System . . . . . . .  28
       15.1.3   IPFIX Specific DoS Attack  . . . . . . . . . . . . .  28
   16.  IANA Considerations  . . . . . . . . . . . . . . . . . . . .  28
     16.1   Numbers used in the Protocol . . . . . . . . . . . . . .  28
     16.2   Numbers used in the Information Model  . . . . . . . . .  29
   17.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . .  29
   18.  References . . . . . . . . . . . . . . . . . . . . . . . . .  29
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . .  30
        Intellectual Property and Copyright Statements . . . . . . .  32










































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1.  Architecture Issues

   ARCH-01:

      Reduce confusion between 'information element' and 'field:' use
      'field' when it referring to an element's field within a packet,
      use 'information element' everywhere else.  (DONE)

   ARCH-02:

      Add 'Exporter' to terminology section (then we'll have Exporter,
      Collector, Device.  (DONE)

   ARCH-03:

      Not clear how Options Template and Options Data should be used.
      Add text to explain that

      *  data templates specify flow records,

      *  option templates specify options data records, and

      *  options data fields hold information which does not refer to
         specific flows, e.g.  config data or statistics.

   ARCH-04:

      Make sure Terminology definitions are consistent with protocol
      (and requirements) drafts.  (DONE)

   ARCH-05:

      Change IP addresses in 'Flows' examples to use "documentation
      prefixes," as per RFC 3330.  (DONE, using 198.18/15, network
      interconnect testing)

   ARCH-06:

      Flow aggregates.  Remove text, remove Flow Recording Process from
      'reference model' diagram.  (DONE)

   ARCH-07:

      There is no `Collecting Process' section.  Add one to section 7.5,
      using relevant text from sections 7.1 and 9.2.  (DONE)






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   ARCH-08:

      There is no Information Model Overview section.  Add one.

      *  Info Model defines fields for flow records and option data
         records

      *  Protocol document describes how fields are encoded in IPFIX
         messages

      *  Other systems - e.g.  PSAMP - may add data or options fields;
         need to decide on ranges of element ids for each protocol.

      (DONE)

   ARCH-09:

      IPFIX System Overview section needs rewriting.  (DONE)

   ARCH-10:

      No mention of transport protocols.  Need to say "IPFIX designed to
      be independent of transport, see protocol document for
      advantages/costs of various protocols." (DONE)

   ARCH-11:

      Need text for IANA Considerations section.  Nevil and Benoit
      agreed to write some, including ranges for IPFIX, PSAMP, etc.

      Suggest the  IPFIX chairs and document editors review requests for
      new field ID numbers.  (DONE)

   ARCH-12:

      Security Considerations.  Can anyone offer more/better text for
      this section?


2.  Changes/Issues from the -03 Draft

   MUST vs must:

      Since this will be an informational RFC, we now use
      must/may/should instead of MUST/MAY/SHOULD.






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   Capitals for IPFIX terms:

      Text changed so that these terms use lower-case before the
      'terminology' section, where they're defined.  After that we
      always upper-case their first letters.

   Small editorial changes:

      Lots of these to fix typos, reorder sections to improve document
      structure, etc.


3.  Introduction

   There are several applications e.g., usage-based accounting, traffic
   profiling, traffic engineering, attack/intrusion detection, QoS
   monitoring, that require flow-based IP traffic measurements.  It is
   therefore important to have a standard way of exporting information
   related to IP flows.  This document defines an architecture for IP
   traffic flow monitoring, measuring and exporting.  It provides a
   high-level description of an IPFIX device's key components and their
   functions.


4.  Scope

   This document defines the architecture for IPFIX.  Its main
   objectives are to:

   o  Describe the key architectural components of IPFIX systems,
      consisting of (at least) IPFIX exporters and collectors
      communicating using the IPFIX protocol.

   o  Define the architectural requirements, e.g., recovery, security,
      etc., for an IPFIX system.

   o  Describe the characteristics of the IPFIX (flow export) protocol.

   Note that the IPFIX system does not provide for remote configuration
   of an IPFIX device.  Instead, IPFIX devices are configured by network
   operations staff.

5.  Terminology

   The definitions of basic IPFIX terms such as IP Traffic Flow,
   Exporting Process, Collecting Process, Observation Point, etc.  are
   semantically identical with those found in the IPFIX requirements
   document IPFIX-REQS [1].  Some of the terms have been expanded for



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   more clarity when defining the protocol.  Additional terms required
   for the architecture have also been defined.  For the same terms
   defined here and in IPFIX-PROTO [4] the definitions are equivalent in
   both documents.

   * Observation Point

      An Observation Point is a location in the network where IP packets
      can be observed.  Examples include: a line to which a probe is
      attached, a shared medium, such as an Ethernet-based LAN, a single
      port of a router, or a set of interfaces (physical or logical) of
      a router.

      Note that 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

      The set of Observation Points which is the largest aggregatable
      set of Flow information at the Metering Process is termed an
      Observation Domain.  Each Observation Domain presents itself using
      a unique ID to the Collecting Process to identify the IPFIX
      Messages it generates.  For example, a router line card may be
      composed of several interfaces with each interface being an
      Observation Point.  Every Observation Point is associated with an
      Observation Domain.

   * IP Traffic Flow or Flow

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

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

      1.  One or more packet header field (e.g.  destination IP
          address), transport header field (e.g.  destination port
          number), or application header field (e.g.  RTP header fields
          [RFC1889])

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



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

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

      This definition covers the range from a Flow containing all
      packets observed at a network interface to a Flow consisting of
      just a single packet between two applications with a specific
      sequence number.

   * Flow Key

      Each of the fields which

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

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

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

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

   * 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

      A Metering Process generates Flow Records.  Input to the process
      are packet headers observed at an Observation Point, and packet
      treatment at the Observation Point.

      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.






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   * Exporting Process

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

   * Exporter

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

   * IPFIX Device

      An IPFIX Device hosts at least one Observation Point, a Metering
      Process and an Exporting Process.  Typically, corresponding
      Observation Point(s), Metering Process(es) and Exporting
      Process(es) are co-located at such a device, for example at a
      router.

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

   * Template

      A Template is an ordered sequence of <type, length> pairs, used to
      completely identify 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.

   * Control Information, Data Stream

      The information that needs to be exported from the IPFIX Device
      can be classified into the following categories:

      Control Information






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         This includes the Flow definition, selection criteria for
         packets within the Flow sent by the Exporting Process, and any
         IPFIX protocol messages.  The Control Information carries all
         the information needed for the end-points to understand the
         IPFIX protocol, and specifically for the receiver (Collector)
         to understand and interpret the data sent by the sender
         (Exporter).

      Data Stream

         This includes Flow Records carrying the field values for the
         various observed Flows at each of the Observation Points.

      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 within a transport layer header.


6.  Examples of Flows

   Some examples of Flows are listed below:

   Example 1: To create Flows, the different fields to distinguish Flows
   are defined.  The different combination of the field values creates
   unique Flows.  If the Flow Key is defined as {source IP address,
   destination IP address, DSCP}, then all of these are different Flows.

     1. {198.18.40.1, 198.18.23.5, 4}
     2. {198.18.40.23, 198.18.23.67, 4}
     3. {198.18.40.23, 198.18.23.67, 2}
     4. {198.18.20.200, 198.18.23.67, 4}

   Example 2: To create Flows, a match function can be applied to all
   the packets that pass through an Observation Point, in order to
   aggregate some values.  This could be done by defining the Flow Key
   as {source IP address, destination IP address, DSCP} as in example 1
   above, and applying a function which masks out the least significant
   8 bits of the source IP address and destination IP address (i.e.  the
   result is a /24 address).  The four Flows from example 1 would now be
   aggregated into three Flows by merging the Flows 1 and 2 into a
   single Flow.

     1. {198.18.40.0/24, 198.18.23.0/24, 4}
     2. {198.18.40.0/24, 198.18.23.0/24, 2}
     3. {198.18.20.0/24, 198.18.23.0/24, 4}



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   Example 3: To create Flows, a filter defined by some field values can
   be applied on all packets that pass the Observation Point, in order
   to select only certain Flows.  The filter is defined by choosing
   fixed values for specific fields from the packet.

   All the packets that go from a customer network 198.18.40.0/24 to
   another customer network 198.18.23.0/24 with DSCP value of 4 define a
   Flow.  All other combinations don't define a Flow and are not taken
   into account.  The three Flows from example 2 would now be reduced to
   one Flow by filtering away the second and the third Flow, leaving
   only {198.18.40.0/24, 198.18.23.0/24, 4}.

   The above example can be thought of as a function F() taking as input
   {source IP address, destination IP address, DSCP}.  The function
   selects only the packets which satisfy all three of the following
   conditions:

   1.  Mask out the least significant 8 bits of source IP address, match
       against 198.18.40.0.

   2.  Mask out the least significant 8 bits of destination IP address,
       match against 198.18.23.0.

   3.  Only accept DSCP value equal to 4.

   Depending on the values of {source IP address, destination IP
   address, DSCP} of the different observed packets, the Metering
   Process function F() would choose/filter/aggregate different sets of
   packets, which would create different Flows.  For example, various
   combination of values of {source IP address, destination IP address,
   DSCP}, F(source IP address, destination IP address, DSCP) would
   result in the definition of one or more Flows.



















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7.  IPFIX Reference Model

   The figure below shows the reference model for IPFIX.  This figure
   covers the various possible scenarios that can exist in an IPFIX
   system.

                              +----------------+   +----------------+
                              |[*Application 1]| ..|[*Application n]|
                              +--------+-------+   +-------+--------+
                                       ^                   ^
                                       ~                   ~
                                       +~~~~~~~~~~+~~~~~~~~+
                                                  ^
                                                  ~
   +------------------------+             +-------+------------------+
   |IPFIX Device(1)         |             | Collector(1)             |
   |[Exporting Process(es)] |<----------->| [Collecting Process(es)] |
   +------------------------+             +--------------------------+
           ....                                 ....
   +------------------------+            +---------------------------+
   |IPFIX Device(i)         |            | Collector(j)              |
   |[Obsv Point(s)]         |<---------->| [Collecting Process(es)]  |
   |[Metering Process(es)]  |      +---->| [*Application(s)]         |
   |[Exporting Process(es)] |      |     +---------------------------+
   +------------------------+      .
          ....                     .          ....
   +------------------------+      |     +--------------------------+
   |IPFIX Device(m)         |      |     | Collector(n)             |
   |[Obsv Point(s)]         |<-----+---->| [Collecting Process(es)] |
   |[Metering Process(es)]  |            | [*Application(s)]        |
   |[Exporting Process(es)] |            +--------------------------+
   +------------------------+

   The various functional components are indicated within brackets [].
   The functional components within [*] are not part of the IPFIX
   framework.  The interfaces shown by "<-->" are defined by the IPFIX
   framework but those shown by "<~~>" are not.

   The figure below shows a typical IPFIX Device.

          +--------------------------------------------------+
          |                 IPFIX Device                     |
          |                                          +-----+ |
          |        +---......--+------------+--------->    | |
          |        |                        |        |     | |
          |   +----+----+              +----+----+   |     | |
          |   |Metering |              |Metering |   |  E  | |
          |   |Process 1|              |Process N|   |  x  | |



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          |   |(Packet  |              |(Packet  |   |  p  | |
          |   | Level)  |              | Level)  |   |  o  | |
          |   +---------+              +---------+   |  r  | |
          |        ^                       ^         |  t  | |
          |+-------+-----------------------+-------+ |  i  | |
          ||       | Observation Domain 1  |       | |  n  | |
          || +-----+------+          +-----+------+| |  g  | |
          || |Obsv Point 1|  ...     |Obsv Point M|| |     | |
          || +------------+          +------------+| |     | |
   Packets|+-------^-------------------------^-----+ |     | | Export
   --->---+--------+----------.....----------+       |     | | Pkts to
      In  |                                          |     +------->
          |        . . . . .                         |     | |Collector
          |                                          |     | |
          |        +---......--+------------+--------->    | |
          |        |                        |        |     | |
          |   +----+----+              +----+----+   |  P  | |
          |   |Metering |              |Metering |   |  r  | |
          |   |Process 1|              |Process N|   |  o  | |
          |   +---------+              +---------+   |  c  | |
          |        ^                       ^         |  e  | |
          |+-------+-----------------------+-------+ |  s  | |
          ||       | Observation Domain K  |       | |  s  | |
          || +-----+------+          +-----+------+| |     | |
          || |Obsv Point 1|   ...    |Obsv Point M|| |     | |
          || +------------+          +------------+| |     | |
   Packets|+-------^-------------------------^-----+ +-----+ |
   --->---+--------+---------- ... ----------+               |
      In  |                                                  |
          +--------------------------------------------------+

   In the above figure the IPFIX components are shown in rectangular
   boxes.  Note that in case of multiple Observation Domains, a unique
   ID per Observation Domain must be transmitted as a parameter to the
   exporting function.  That unique ID is referred to as the IPFIX
   Soutrce ID.  The Exporting Process includes IPFIX protocol and
   underlying transport layer.

8.  IPFIX Functional and Logical Blocks


8.1  Metering Process

   Every Observation Point in an IPFIX Device, participating in Flow
   measurements, must be associated with at least one Metering Process.
   Every packet coming into an Observation Point goes into each of the
   Metering Processes associated with the Observation Point.  Broadly,
   each Metering Process extracts the packet headers that come into an



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   Observation Point, does timestamping and classifies the packet into
   Flow(s) based on the selection criteria.

   The Metering Process is a functional block which manages all the
   Flows generated from an Observation Domain.  The typical functions of
   a Metering Process may include:

   o  Maintain database(s) of all the Flows Records from an Observation
      Domain.  This includes creating new Flow Records, updating
      existing ones, computing Flow Records statistics, deriving further
      Flow properties, adding non-flow-specific information based on the
      packet treatment (in some cases fields like AS numbers, router
      state, etc.)

   o  Maintain aggregate statistics like flows generated, flows exported
      etc.


8.1.1  Flow Expiration and Export

   A Flow is considered to have expired, and may be exported, under the
   following conditions:

   1.  If the Metering Process can deduce the end of a Flow, that Flow
       should be exported when the end of the Flow is detected.  For
       example, a Flow generated by TCP traffic where the FIN or RST
       bits indicate the end of the Flow.

   2.  If no packets belonging to the Flow have been observed for a
       certain period of time.  This time period should be configurable
       at the Metering Process, with a minimum value of 0 seconds for
       immediate expiration.  Note that a zero timeout would report a
       Flow as a sequence of single-packet Flows.

   3.  If the IPFIX Device experiences resource constraints, a Flow may
       be prematurely expired (e.g.  lack of memory to store Flow
       Records)

   4.  For long-running Flows, the Exporting Process should export the
       Flow Records on a regular basis or based on some export policy.
       This periodicity or export policy should be configurable at the
       Metering Process.

   When a long-running Flow is exported, that Flow may still be
   maintained by the Metering Process so that, for incoming packets
   which continue to come on the same Flow, the Metering Process does
   not need to create a new Flow.




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8.2  Observation Point

   A Flow Record can be better analyzed if the Observation Point from
   which it was measured is known.  As such it is recommended that
   Exporters send this information to Collectors.  In cases where there
   is a single Observation Point or where the Observation Point
   information is not relevant, the Metering Process may choose not to
   add this to the Flow Records.

8.3  Selection Criteria for Packets

   A Metering Process may define rules so that only certain packets
   within an incoming stream of packets are chosen for measurement at an
   Observation Point.  This may be done by one of the two methods
   defined below or a combination of them.  A combination of each of
   these methods can be adopted to select the packets, i.e.  one can
   define a set of methods {F1, S1, F2, S2, S3} executed in a specified
   sequence at an Observation Point to select particular Flows.

   The figure below shows the operations which may be applied as part of
   a typical Metering Process.

                 packet header capturing
                           |
                      timestamping
                           |
                           v
                    +----->+
                    |      |
                    | sampling Si (1:1 in case of no sampling)
                    |      |
                    | filtering Fi (select all when no criteria)
                    |      |
                    +------+
                           |
                           v
                         Flows


8.3.1  Filter Functions, Fi

   A Filter Function selects only those incoming packets that satisfy a
   function on fields defined by the packet header fields, fields
   obtained while doing the packet processing, or properties of the
   packet itself.

   Example: Mask/Match of the fields that define a filter.  A filter
   might be defined as {Protocol == TCP, Destination Port between 80 and



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   120}.

   Several such filters could be used in any sequence to select packets.
   Note that packets selected by a (sequence of) filter functions may be
   further classified by other filter functions, i.e.  the selected
   packets may belong to several Flows, all of which are exported.

8.3.2  Sampling Functions, Si

   A sampling function determines which packets within a stream of
   incoming packets is selected for measurement, i.e.  packets that
   satisfy the sampling criteria for this Metering Process.

   Example: sample every 100th packet that was received at an
   Observation Point and collect the Flow Records selected by a
   particular filter function.  Choosing all the packets is a special
   case where the sampling rate is 1:1.

   Note that filtering and sampling functions may also be used in an
   Exporting Process to select Flow Records to be exported.

8.4  Observation Domain

   The Observation Domain is a logical block that presents a single
   identity for a group of Observation Points within an IPFIX Device.
   Each {Observation Point, Metering Process} pair belongs to a single
   Observation Domain.  An IPFIX Device could have multiple Observation
   Domains each of which has a subset of the total set of Observation
   Points in it.  Each Observation Domain must carry a unique ID within
   the context of an IPFIX Device.

8.5  Exporting Process

   The Exporting Process is the functional block that sends data to one
   or more IPFIX Collectors using the IPFIX protocol.  On one side it
   interfaces with Metering Process to get Flow Records, while on the
   other side the Exporting Process talks to a Collecting Process on the
   Collector(s).

   There may be additional rules defined within the context Observation
   Domain so that only certain Flows Records are picked up for export.
   This may be done by either one or a combination of Si, Fi, as
   described in the section on "Selection Criteria for Packets".

   Example: Only the Flow Records which meet the following selection
   criteria are exported.

   1.  All Flow Records whose destination IP address matches



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       {198.18.33.5}.

   2.  Every other (.i.e.  sampling rate 1 in 2) Flow Record whose
       destination IP address matches {198.18.11.30}.


8.6  Collecting Process

   Collecting Processes use a Flow Record's Template ID to interpret
   that Record's Information Elements.  To allow this, an IPFIX Exporter
   must ensure that an IPFIX Collector knows the Template ID for each
   incoming Flow Record.  To interpret incoming Flow Records, an IPFIX
   Collector may also need to know the function F() that was used by the
   Metering Process for each Flow.

   An IPFIX Collector may also use the selection criteria for packets to
   interpret the Flow Records further.

   The functions of the Collecting Process must include:

   o  Identifying, accepting and decoding the IPFIX Messages from
      different <Exporting Process, Observation Domain> pairs.

   o  Storing the Control Information and Flow Records received from an
      IPFIX Device.

   At a high level, the IPFIX protocol at the Collecting Process:

   1.  Receives and stores the Control Information.

   2.  Decodes and stores the Flow Records using the Control
       Information.

   3.  May optionally monitor the status of the Collecting Process and
       execute a failover should any problem arise.


8.7  Summary

   The figure below shows the functions performed in sequence by the
   various functional blocks in an IPFIX Device.

                    Packet(s) coming into Observation Point(s)
                      |                                   |
                      v                                   v
     +----------------+-------------------------+   +-----+-------+
     |          Metering Process on an          |   |             |
     |             Observation Point            |   |             |



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     |   packet header capturing                |   |             |
     |        |                                 |   | Metering    |
     |   timestamping                           |   | Process     |
     |        |                                 |   | on an       |
     | +----->+                                 |   | Observation |
     | |      |                                 |   | Point       |
     | |   sampling Si (1:1 in case of no       |   |             |
     | |      |          sampling)              |   |             |
     | | classifying Fi (select all when        |   |             |
     | |      |          no criteria)           |   |             |
     | +------+                                 |   |             |
     |        |                                 |   |             |
     |        |        Timing out Flows         |   |             |
     |        |    Handle resource overloads    |   |             |
     +--------|---------------------------------+   +-----|-------+
              |                                           |
      Flow Records (identified by Observation Domain)  Flow Records
              |                                           |
              +---------+---------------------------------+
                        |
   +--------------------|----------------------------------------------+
   |                    |     Exporting Process                        |
   |+-------------------|-------------------------------------------+  |
   ||                   v       IPFIX Protocol                      |  |
   ||+-----------------------------+  +----------------------------+|  |
   |||Rules for                    |  |Functions                   ||  |
   ||| Picking/sending Templates   |  |-Packetize selected Control ||  |
   ||| Picking/sending Flow Records|->|  & data Information into   ||  |
   ||| Encoding Template & data    |  |  IPFIX export packet.      ||-->
   ||| Selecting Flows to export(*)|  |-Handle export errors       ||  |
   ||+-----------------------------+  +----------------------------+|  |
   |+----------------------------+----------------------------------+  |
   |                             |                                     |
   |                     IPFIX exported packet                         |
   |                             |                                     |
   |                +------------+-----------------+                   |
   |                |  Anonymize export packet(*)  |                   |
   |                +------------+-----------------+                   |
   |                             |                                     |
   |                +------------+-----------------+                   |
   |                |       Transport  Protocol    |                   |
   |                +------------+-----------------+                   |
   |                             |                                     |
   +-----------------------------+-------------------------------------+
                                 |
                                 v
                    IPFIX export packet to Collector




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   (*) indicates that the block is optional.


9.  Overview of the IPFIX Protocol

   An IPFIX Device consists of a set of co-operating processes that
   implement the functional blocks described in the previous section.
   Alternatively, an IPFIX Device can be viewed simply as a network
   entity which implements the IPFIX protocol.  At the IPFIX Device, the
   protocol functionality resides in the Exporting Process.  The IPFIX
   Exporting Process gets Flow Records from a Metering Process, and
   carries them to the Collector(s).

   At a high level, an IPFIX Device performs the following tasks:

   1.  Encode Control Information into Templates.

   2.  Encode packets observed at the Observation Points into Flow
       Records.

   3.  Packetize the selected Templates and Flow Records into IPFIX
       Messages.

   4.  Send control and data packets to the Collector.

   The IPFIX protocol communicates information from an IPFIX Exporter to
   an IPFIX Collector.  That information includes not only Flow Records,
   but also information about the Metering Process.  Such information
   (referred to as Control Information) includes details of the data
   fields in Flow Records.  It may also include statistics from the
   Metering Process, such as the number of packets lost (i.e.  not
   metered).

   For details of the IPFIX protocol please refer to IPFIX-PROTO [4].

9.1  Information Model Overview

   The IP Flow Information eXport (IPFIX) protocol serves for
   transmitting information related to measured IP traffic over the
   Internet.  The protocol specification in IPFIX-PROTO [4] defines how
   information elements are transmitted.  For information elements, it
   specifies the encoding of a set of basic data types.  However, the
   list of fields that can be transmitted by the protocol, such as flow
   attributes (source IP address, number of packets, etc.) and
   information about the metering and exporting process (packet
   observation point, sampling rate, flow timeout interval, etc.), is
   not specified in IPFIX-PROTO [4].  Instead, it is defined in the
   IPFIX Information Model document IPFIX-INFO [3].



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   The Information Model provides a complete description of the
   properties of every IPFIX information element.  It does this by
   specifying each element's name, Field Type, data type, etc., and
   providing a description of each element.  Element descriptions give
   the semantics of the element, i.e.  say how it is derived from a Flow
   or other information available within an IPFIX Device.

9.2  Flow records

   The following rules provide guidelines to be followed while encoding
   the Flow's information:

   A Flow Record contains enough information so that the Collecting
   Process can identify the corresponding <Per-Flow Control Information,
   Configuration Control Information>.

   The Exporter encodes a given field (as specified in IPFIX-INFO [3],
   based on the encoding standards prescribed by IPFIX-PROTO [4].

9.3  Control Information

   The following rules provide guidelines to be followed while encoding
   the Control Information:

   o  Per-Flow Control Information should be encoded such that the
      Collecting Process can capture the structure and semantics of the
      corresponding Flow data for each of the Flows exported by the
      IPFIX Device.

   o  Configuration Control Information is conveyed to a Collector so
      that its Collecting Process can capture the structure and
      semantics of the corresponding configuration data.  The
      configuration data which is also Control Information should carry
      additional information on the Observation Domain within which the
      configuration takes effect.  For example, sampling using the same
      sampling algorithm, say 1 in 100 packets, is configured on two
      Observation Points O1 and O2.  The configuration in this case may
      be encoded as <ID, configuration domain (O1,O2), sampling
      algorithm, interval (1 in 100)>, where ID uniquely identifies this
      configuration.


9.4  Exporting Control Information

   The Control Information is used by the Collecting Process to:

   o  Decode and interpret Flow Records.




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   o  Understand the state of the Exporting Process.

   Sending Control Information from the Exporting Process in a timely
   and reliable manner is critical to the proper functioning of the
   IPFIX Collecting Process.  The following approaches may be taken for
   the export of Control Information.

   1.  Send all the Control Information pertaining to Flow Records prior
       to sending the Flow Records themselves.  This includes any
       incremental changes to the definition of the Flow Records.

   2.  Notify on a near real time basis the state of the IPFIX Device to
       the Collecting Process.  This includes all changes such as a
       configuration change that affects the Flow behavior, changes to
       Exporting Process resources that alter export rates, etc., which
       the Collector needs to be aware of.

   3.  Since it is vital that a Collecting Process maintains accurate
       knowledge of the Exporter's state, the export of the Control
       Information should be done such that that it reaches the
       Collector reliably.  One way to achieve this would be to send the
       Control Information over a reliable transport.


9.5  Reporting Responsibilities

   From time to time an IPFIX Device may not be able to observe all the
   packets reaching one of its Observation Points.  This could occur if
   a Metering Process finds itself temporarily short of resources, for
   example it might run out of packet buffers for IPFIX export, or it
   might detect errors in its underlying transport layer.

   In such situations, the IPFIX Device must report to its Collector(s)
   the number of packet losses that have occurred.

10.  IPFIX Protocol Details

   When the IPFIX Working Group was chartered there were existing common
   practices in the area of Flow export, for example NetFlow, CRANE,
   LFAP, RTFM, etc.  IPFIX's charter required the Working Group to
   consider those existing practices, and select the one that was the
   closest fit to the IPFIX requirements IPFIX-REQS [1].  Additions or
   modifications would then be made to the selected protocol to fit it
   exactly into the IPFIX architecture.

10.1  The IPFIX Basis Protocol

   The working group went through an extensive evaluation of the various



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   existing protocols that were available, weighing the level of
   compliance with the requirements, and selected one of the candidates
   as the basis for the IPFIX protocol.  For more details of the
   evaluation process please see IPFIX-EVAL [2].

   In the basis protocol Flow Records are defined by Templates, where a
   Template is an ordered set of the information elements appearing in a
   Flow Record, together with their field sizes within those records.

   This approach provides the following advantages:

   o  Using the Template mechanism, new fields can be added to IPFIX
      Flow Records without changing the structure of the export record
      format.

   o  Templates that are sent to the Collecting Process carry structural
      information about the exported Flow Record fields.  Therefore, if
      the Collector does not understand the semantics of new fields it
      can ignore them, but still interpret the Flow Record.

   o  Because the template mechanism is flexible, it allows the export
      of only the required fields from the Flows to the Collecting
      Process.  This helps to reduce the exported Flow data volume and
      possibly provide memory savings at the Exporting Process and
      Collecting Process.  Sending only the required information can
      also reduce network load.


10.2  IPFIX Protocol on the Collecting Process

   The Collecting process is responsible for:

   1.  Receiving and decoding Flow Records from the IPFIX Devices.

   2.  Indicating Flow Record losses to the exporting IPFIX Device
       and/or IPFIX users.

   3.  Optionally notifying status and overload conditions to the IPFIX
       Device.

   Complete details of the IPFIX protocol are given in IPFIX-PROTO [4].

10.3  Support for Applications

   Applications that use the information collected by IPFIX may be
   Billing or Intrusion Detection sub-systems, etc.  These applications
   may be an integral part of the Collecting Process or they may be
   co-located with the Collecting Process.  The way by which these



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   applications interface with IPFIX system to get the desired
   information is out of scope for this document.

11.  Export Models

11.1  Export with Reliable Control Connection

   As mentioned in the IPFIX-REQS [1] document, an IPFIX Device must be
   able to transport its Control Information and Data Stream over a
   congestion-aware transport protocol.

   If the network in which the IPFIX Device and Collecting Process are
   located does not guarantee reliability, at least the Control
   Information should be exported over a reliable transport.  The Data
   Stream may be exported over a reliable or unreliable transport
   protocol.

   Possible transport protocols include:

   o  SCTP: Supports reliable and unreliable transport.  Some of SCTP's
      features (e.g.  session failover) may prove unfamiliar to IPFIX
      implementors.

   o  TCP: Provides reliable transport only.  Simple to implement, may
      require large buffers to cope with periods of network congestion.

   o  UDP: Provides unreliable transport only.  Network operators would
      need to avoid congestion by keeping traffic within their own
      administrative domains.


11.2  Collector Failure Detection and Recovery

   The transport connection (in the case of a connection oriented
   protocol) is pre-configured between the IPFIX Device and the
   Collector.  The IPFIX protocol does not provide any mechanism for
   configuring the Metering or Exporting Processes.

   Once connected, an IPFIX Collector receives Control Information and
   uses that information to interpret Flow Records.  The IPFIX Device
   should set a keepalive (e.g.  the keepalive timeout in the case of
   TCP, the HEARTBEAT interval in the case of SCTP, or an IPFIX protocol
   level keepalive if any) to a sufficiently low value so that it can
   quickly detect a Collector failure.

   Collector failure refers to the crash or restart of the Collecting
   Process, or of the Collector itself.  A Collector failure is detected
   at the IPFIX Device by the break in control connection (depending on



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   the transport protocol - the connection timeout mechanisms differ).
   On detecting a keepalive timeout, the IPFIX Device should stop
   sending the Flow export data to the Collector and try to reestablish
   the transport connection.  This is valid for a single Collector
   scenario.  If there are multiple Collectors for the same IPFIX
   Device, the IPFIX Device opens control connections to each of the
   Collectors.  However, data gets sent only to one of the Collectors
   which is chosen as the primary.

   There could be one or more Collectors configured as secondary and a
   priority assigned to them.  The primary Collector crash is detected
   at the IPFIX Device by the break in control connection (depending on
   the transport protocol - the connection timeout mechanisms differ).
   On detecting loss of connectivity, the IPFIX Device opens a Data
   Stream with the secondary Collector of the next highest priority.
   That Collector now becomes the primary.  The maximum export data loss
   would be the amount of data exported in the time between when the
   loss of connectivity to the Collector happened, and the time at which
   this was detected by the IPFIX Device.

11.3  Collector Redundancy

   Since the IPFIX protocol requires a congestion-aware transport,
   achieving redundancy using multicast is not an option.  Multiple
   <Control Information, Data Stream> pairs could be set up, each to a
   different Collector from the same IPFIX Device.  The Control and data
   Information would then be replicated on each of the Control
   Information and Data Streams.

12.  IPFIX Flow Collection for Special Traffic

   An IPFIX Device could be doing one or more of generating, receiving,
   altering special types of traffic which are listed below.

   Tunnel traffic:

      The IPFIX Device could be the head, midpoint or endpoint of a
      tunnel.  In such cases the IPFIX could be handling GRE, IPinIP or
      UTI traffic.

   VPN traffic:

      The IPFIX Device could be a provider edge device which receives
      traffic from customer sites belonging to different Virtual Private
      Networks.

   In the cases above, there should be clear guidelines as to:




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   o  How and when to classify the packets as Flows in the IPFIX Device.

   o  If multiple encapsulations are used to define Flows, how to convey
      the same fields (e.g.  IP address) in different layers.

   o  How to differentiate Flows based on different private domains.
      For example, overlapping IP addresses in Layer-3 VPNs


13.  IPFIX Flow Collection from Special Devices

   IPFIX could be implemented on devices which perform one or more of
   the following special services:

   o  Explicitly drop packets.  For example a device which provides
      firewall service drops packets based on some administrative
      policy.

   o  Alter the values of fields used as IPFIX Flow keys of interest.
      For example a device which provides NAT service can change source
      or(and) destination IP address.

   In the cases above, there should be clear guidelines as to:

   o  How and when to classify the packets as Flows in the IPFIX Device.

   o  What extra information be exported so that the Collector can make
      a clear interpretation of the received Flow Records.


14.  Security Considerations

   IP Flow information can be used for various purposes, such as usage
   accounting, traffic profiling, traffic engineering, and intrusion
   detection.  The security requirement may differ significantly for
   such applications.  To be able to satisfy the security needs of
   various IPFIX users, an IPFIX system must provide different levels of
   security protection.

14.1  Data Security

   IPFIX data comprises Control Information and Data Stream generated by
   the IPFIX Device.

   The IPFIX data may exist in both the IPFIX Device and the Collector.
   In addition, the data is also transferred on the wire from the IPFIX
   Device to the Collector when it is exported.  To provide security,
   the data should be protected from common network attacks.



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   The protection of IPFIX data within the end system (IPFIX Device and
   Collector) is out of scope for this document.  It is assumed that the
   end system operator will provide adequate security for the IPFIX
   data.

   The IPFIX architecture must allow different levels of protection to
   the IPFIX data on the wire.  Wherever security functions are required
   it is recommended that users should leverage lower layers using
   either IPSEC or TLS, if these can successfully satisfy the security
   requirement of IPFIX data protection.

   To protect the data on the wire, three levels of granularity should
   be supported ..

14.1.1  No Security

   Security may not be required when the transport between the IPFIX
   Device and the Collector is perceived as safe.  This option allows
   the protocol to run most efficiently without extra overhead and an
   IPFIX system must support it.

14.1.2  Authentication-only

   Authentication-only protection provides IPFIX users with the
   assurance of data integrity and authenticity.  The data exchanged
   between the IPFIX Device and the Collector is protected by an
   authentication signature.  Any modification of the IPFIX data will be
   detected by the recipient, resulting in discarding of the received
   data.  However, the authentication-only option doesn't offer data
   confidentiality.

   The IPFIX user should avoid use authentication-only when sensitive or
   confidential information is being exchanged.  An IPFIX solution
   should support this option.  The authentication-only option should
   provide replay attack protection.  Some means to achieve this level
   of security are:

   o  TCP with MD5 options.

   o  IP Authentication Header


14.1.3  Encryption

   Data encryption provides the best protection for IPFIX data.  The
   IPFIX data is encrypted at the sender and only the intended recipient
   can decrypt and have access to the data.  This option must be used
   when the transport between the IPFIX Device and the Collector are



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   unsafe and the IPFIX data needs to be protected.  It is recommended
   that the underlying transport layer's security functions be used for
   this purpose.  Some means to achieve this level of security are:

   o  Encapsulating Security Payload.

   o  Transport Layer Security Protocol

   The data encryption option adds overhead to the IPFIX data transfer.
   It may limit the rate that an Exporter can report its Flow to the
   Collector due to the resource requirement for running encryption.

14.2  IPFIX End-point Authentication

   It is important to make sure that the IPFIX Device is talking to the
   "right" Collector rather than to a masquerading Collector.  The same
   logic also holds true from the Collector point of view, i.e.  it may
   want to make sure it is collecting the Flow information from the
   "right" IPFIX Device.  An IPFIX system should allow the end point
   authentication capability so that either one-way or mutual
   authentication can be performed between the IPFIX Device and
   Collector.

   The IPFIX architecture should use any existing transport protection
   protocols such as TLS or IPSEC to fulfill the authentication
   requirement.

15.  IPFIX Overload

   An IPFIX Device could become overloaded under various conditions.
   This may be because of exhaustion of internal resources used for Flow
   generation and/or export.  Such overloading may cause loss of data
   from the Exporting Process, either from lack of export bandwidth
   (possibly caused by an unusually high number of observed Flows) or
   from network congestion in the path from Exporter to Collector.

   IPFIX Collectors should be able to detect the loss of exported Flow
   Records, and should at least record the number of lost Flow Records.

15.1  Denial of Service (DoS) Attack Prevention

   Since one of the potential usages for IPFIX is for intrusion
   detection, it is important for the IPFIX architecture to support some
   kind of DoS resistance.

15.1.1  Network Under Attack

   The Network itself may be under attack, resulting in an overwhelming



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   number of IPFIX Messages.  An IPFIX system should try to capture as
   much information as possible.  However, when a large number of IPFIX
   Messages are generated in a short period of time, the IPFIX system
   may become overloaded.

15.1.2  Generic DoS Attack on the IPFIX System

   The IPFIX system may subject to generic DoS attacks, just as any
   system on any open network.  These types of attacks are not IPFIX
   specific.  Preventing and responding to such types of attacks are out
   of the scope of this document.

15.1.3  IPFIX Specific DoS Attack

   There are some specific attacks on the IPFIX portion of the IPFIX
   Device or Collector.

   o  The attacker could pound the Collector with spoofed IPFIX export
      packets.  One way to solve this problem is to periodically
      synchronize the sequence numbers of the Flow Records between the
      Exporting and Collecting Processes.

   o  The attacker could provide false reports to the IPFIX Device by
      sending spoofed control packets.

   The problems mentioned above can be solved to a large extent if the
   control packets are encrypted both ways.


16.  IANA Considerations

   The IPFIX Architecture, as set out in this document, has two sets of
   assigned numbers.  Considerations for assigning them are discussed in
   this section, using the example policies as set out in the
   "Guidelines for IANA Considerations" document IANA-RFC [5].

16.1  Numbers used in the Protocol

   IPFIX Messages, as described in IPFIX-PROTO [4], 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 Template Number, indicating the type for each
   set of information within an IPFIX message.

   Changes in either IPFIX Version Number or IPFIX Template Number
   assignments require an IETF Consensus, i.e.  they are to be made via
   RFCs approved by the IESG.




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16.2  Numbers used in the Information Model

   Fields of the IPFIX protocol carry information about traffic
   measurement.  They are modeled as elements of the IPFIX information
   model IPFIX-INFO [3].  Each information element describes a field
   which may appear in an IPFIX Message.  Within an IPFIX message the
   field type is indicated by its Field Type.

   Changes in IPFIX Field Type will be administered by IANA, subject to
   Expert Review, i.e.  review by one of a group of experts designated
   by an IETF Operations and Management Area Director.  Those experts
   will initially be drawn from the Working Group Chairs and document
   editors of the IPFIX and PSAMP Working Groups.

17.  Acknowledgements

   The document editors wish to thank all the people contributing to the
   discussion of this document on the mailing list, and the design teams
   for many valuable comments.  In particular, the following made
   significant contributions:

      Tanja Zseby
      Paul Calato
      Dave Plonka
      Jeffrey Meyer
      Benoit Claise
      Ganesh Sadasivan
      K.C.Norseth
      Vamsi Valluri
      Cliff Wang
      Ram Gopal
      Jc Martin
      Carter Bullard
      Juergen Quittek
      Reinaldo Penno
      Nevil Brownlee
      Simon Leinen
      Kevin Zhang


18  References

   [1]  Quittek, J., Zseby, T. and B. Claise, "Requirements for IP Flow
        Information Export",  (work in progress), Internet Draft,
        draft-ietf-ipfix-reqs-16.txt, June 2004.

   [2]  Leinen, S., "Evaluation of Candidate Protocols for IP Flow
        Information Export",  (work in progress), Internet Draft,



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        draft-leinen-ipfix-eval-contrib-03.txt, May 2004.

   [3]  Quittek, J., Meyer, J. and P. Calato, "IPFIX: Information
        Model",  (work in progress), Internet Draft,
        draft-ietf-ipfix-info-03.txt, February 2004.

   [4]  Fulmer, M., Claise, B., Calato, P. and R. Penno, "IPFIX:
        Protocol",  (work in progress), Internet Draft,
        draft-ietf-ipfix-protocol-03.txt, January 2004.

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


Authors' Addresses

   Ganesh Sadasivan
   Cisco Systems, Inc.
   170  West Tasman Drive
   San Jose, CA  95134
   USA

   Phone: +1 408 527-0251
   EMail: gsadasiv@cisco.com


   Nevil Brownlee
   CAIDA | The University of Auckland
   Private Bag 92019
   Auckland
   New Zealand

   Phone: +64 9 373 7599 x8941
   EMail: n.brownlee@auckland.ac.nz


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

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







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   Juergen Quittek
   NEC Europe Ltd.
   Adenauerplatz 6
   69225 Heidelberg
   Germany

   Phone: +49 6221 90511-15
   EMail: quittek@ccrle.nec.de
   URI:










































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Acknowledgment

   Funding for the RFC Editor function is currently provided by the
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