Internet Draft                                              Tanja Zseby
 Document: <draft-ietf-ipfix-as-02.txt>                     Elisa Boschi
 Expires:  January 2005                                 Fraunhofer FOKUS
                                                          Reinaldo Penno
                                                         Nortel Networks
                                                          Nevil Brownlee
                                                           Benoit Claise
                                                           Cisco Systems
                                                               July 2004
                           IPFIX Applicability
    Status of this Memo
    This document is an Internet-Draft and is in full conformance
    with all provisions of Section 10 of RFC2026.
    Internet-Drafts are working documents of the Internet
    Engineering Task Force (IETF), its areas, and its working
    groups. Note that other groups may also distribute working
    documents as Internet-Drafts. Internet-Drafts are draft
    documents valid for a maximum of six 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 The list of
    Internet-Draft Shadow Directories can be accessed at
    This document describes what type of applications can use the IP
    Flow Information Export (IPFIX) protocol and how they can use
    the information provided by IPFIX. It furthermore shows how the
    IPFIX framework relates to other architectures and frameworks.
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 Table of Contents
    1.   Introduction.............................................2
    2.   Applications of IPFIX....................................2
    2.1  Accounting...............................................3
    2.2  Security Analysis and Intrusion detection with IPFIX.....3
    2.3  Network Planning.........................................4
    2.4  Peering Agreements.......................................5
    2.5  Traffic Engineering......................................5
    2.6  Data Warehousing and Mining..............................5
    2.7  SLA validation...........................................5
    2.8  Traffic Monitoring.......................................5
    2.8.1 Measurement of Round-trip-time (RTT)....................6
    2.8.2 Measurement of One-way-delay (OWD)......................7
    2.8.3 Measurement of One-way-loss (OWL).......................7
    2.8.4 Measurement of IP delay variation (IPDV)................8
    3.   Relation of IPFIX to other frameworks and protocols......8
    3.1  IPFIX and AAA............................................8
    3.1.1 Connecting via an AAA Client............................8
    3.1.2 Connecting via an Application Specific Module (ASM).....9
    3.2  IPFIX and RTFM..........................................10
    3.2.1 Definition of 'flow'...................................10
    3.2.2 Configuration and Management...........................11
    3.2.3 Data Model details.....................................12
    3.2.4 Application/transport protocol.........................13
    3.3  IPFIX and IPPM..........................................13
    3.4  IPFIX and IDMEF.........................................14
    4.   Security Consideration..................................14
    5.   References..............................................14
    6.   Acknowledgements........................................16
    7.   Author's Addresses......................................16
    8.   Full Copyright Statement................................17
 1. Introduction
    The IPFIX protocol defines how IP Flow information can be
    exported from routers, measurement probes or other devices. It
    is intended to provide this information as input for various
    applications. This document describes what applications can use
    the IPFIX protocol and how they can use it. Furthermore, the
    relationship of IPFIX to other frameworks and architectures is
 2. Applications of IPFIX
    IPFIX data enables several critical customer applications. This
    section describes how different applications can use IPFIX.
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 2.1 Accounting
    Usage based accounting is one of the major applications for
    which the IPFIX protocol has been developed. IPFIX data provide
    fine-grained metering (for example, flow records include details
    such as IP addresses, packet and byte counts, timestamps, Type
    of Service (ToS), application ports, etc.) for highly flexible
    and detailed resource usage accounting. ISPs can use this
    information to migrate from single fee, flat-rate billing to
    more flexible charging mechanisms based on time of day,
    bandwidth usage, application usage, quality of service, etc.
    Enterprise customers can use this information for departmental
    chargeback or cost allocation for resource usage.
    In order to realize usage-based accounting with IPFIX the flow
    definition has to be chosen in accordance to the tariff model. A
    tariff can for instance be based on individual end-to-end
    streams. In that case accounting can be realized with a flow
    definition determined by the quintuple that consists of source
    address, destination address, protocol and portnumbers. Another
    example is a class-dependent tariff (e.g. in a DiffServ
    network). For this flows could be distinguished just by DiffServ
    codepoint (DSCP) and source address.
    The essential elements needed for accounting are the number of
    transferred packets and bytes per flow which are contained in
    IPFIX flow records. Furthermore IPFIX provides a very flexible
    definition of flows, so arbitrary flow-based accounting models
    can be realized without any extensions to the IPFIX protocol.
    Nevertheless the configuration of flow definitions is out of
    scope of the IPFIX definition.
    For accounting purposes, it would be advantageous to have the
    ability to use IPFIX flow records as accounting input in a AAA
    infrastructure. AAA servers then could provide the mapping
    between user and flow information.
 2.2 Security Analysis and Intrusion detection with IPFIX
    Intrusion detection systems (IDS) monitor and control security
    incidents. A typical IDS system includes components like sensor,
    event collector, and management stations. Sensors monitor
    network and system traffic for attacks and other security-
    related events. Sensors respond to and notify the administrator
    about these events as they occur. Event collectors are a middle-
    tier component responsible for transmitting events from sensors
    to the console and database. The management component serves the
    following purposes:
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    _ - visually monitors events (with a console)
    _ - collects data from sensors (with one or more event
    _ - stores data from sensors (in a database)
    IPFIX can report events of interest to the sensor either by the
    collecting process or directly by the exporting process. It
    depends on the scenario and the events of interest which
    solution is better. Getting information directly from the
    exporting process has the advantage that the sensor gets the
    information faster. It does not need to wait for collector
    processing time or until the collector has all relevant data.
    Getting the information from a collector allows correlating data
    from different exporting processes (e.g. from different routers)
    to get a better picture about what is going on in the network.
    IPFIX provides useful input data for basic intrusion detection
    functions (e.g. detecting unusual high loads) such as details on
    source and destination addresses, along with the start time of
    flows, TCP flags, application ports and flow volume. This data
    can be used to analyze network security and identify
    attacks. Nevertheless, for some scenarios intrusion detection
    may require further insight into packet content. Since IPFIX
    allows a flexible report definition the metering process and the
    IPFIX report format could be extended to support other data
    needed for intrusion detection systems.
    Detecting security incidents in real-time would require a
    preprocessing of data already at the measurement device and
    immediate data export in case a possible incident has been
    identified. This means that IPFIX reports must be generated upon
    incident detection events and not only upon flow end or fixed
    time intervals.
 2.3 Network Planning
    IPFIX data captured over a long period of time can be used to
    track and anticipate network growth and plan upgrades to
    increase the number of routing devices, ports, or higher-
    bandwidth interfaces. IPFIX data optimizes both strategic
    network planning (peering, backbone upgrade planning, and
    routing policy planning) as well as tactical network engineering
    decisions (upgrading the router or link capacity). This helps to
    minimize the total cost of network operations while maximizing
    network performance, capacity, and reliability.
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 2.4 Peering Agreements
    IPFIX data enables ISP peering partners to measure the volume
    and characteristics of traffic exchanged with other ISP peers.
    Different domains often have different tools. In order to
    achieve interoperability in such heterogeneous environment, it
    becomes necessary to have a common format to share measurement
    data. IPFIX provides the format through which data can be
    exchanged and consequently compared, between different ISPs.
    This makes also possible to provide End-to-End (E2E)
    measurements spanning multiple domains.
 2.5 Traffic Engineering
    IPIFX data provides traffic engineering details for a set of
    prefixes. This data can be used in network optimization for load
    balancing traffic across alternate paths, or for forwarding
    traffic of a certain set of prefixes on a preferred route.
 2.6 Data Warehousing and Mining
    IPFIX data (or derived information) can be stored for later
    retrieval and analysis to support proactive marketing and
    customer service programs. An example of this would be to
    determine which applications and services are being used by
    internal and external users and then target them for improved
    services such as advertising. This is especially useful for ISPs
    because IPFIX data enables them to create better service
 2.7 SLA validation
    The performance of QoS monitoring is one target application for
    using the IPFIX protocol. QoS monitoring is the passive
    observation of transmission quality for single flows or traffic
    aggregates in the network. One example of its usefulness is the
    validation of QoS guarantees in service level agreements (SLAs).
    Some QoS metrics require the correlation of data from multiple
    measurement points. For this the clocks of the involved
    exporting devices must be synchronized. Furthermore, such
    measurements would benefit from post-processing functions (e.g.
    packet ID generation and mapping) at the exporter and/or
 2.8 Traffic Monitoring
    IPFIX data can be used for extensive near real-time traffic
    monitoring. Traffic patterns associated with routing devices and
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    switches on an individual or network wide basis can be displayed
    enabling proactive problem detection, efficient troubleshooting,
    and rapid problem resolution.
    IPFIX data enables content and service providers to perform a
    detailed, time-based, and application-based usage analysis of a
    network. They also provide detailed information for
    understanding customer or end-user usage of network and
    application resources. This information can then be used to
    efficiently plan and allocate access, backbone, and application
    resources, as well as to detect and resolve potential security
    and policy violations.
    This section describes how the monitoring of different metrics
    can be performed with IPFIX. All of the metrics require at least
    an extension of the IPFIX information model because currently
    the necessary information such as e.g. round-trip-time, packet
    IDs etc. is not part of the model. However given the
    extensibility and flexibility of IPFIX the missing attributes
    can be easily defined.
 2.8.1   Measurement of Round-trip-time (RTT)
    The passive measurement of round-trip-times (RTT) can be
    performed by using packet pair matching techniques as described
    in [Brow00]. For the measurements, request/response packet pairs
    from protocols like DNS, ICMP, SNMP or TCP (syn/syn-ack,
    data/ack) are utilized to passively observe the RTT [Brow00]. As
    always for passive measurements this only works if the required
    traffic of interest is actually present in the network.
    Furthermore, if the observed protocol supports retransmissions
    (e.g. TCP) the RTT is not the network RTT but rather the RTT of
    the network and the network stack of the receiver. In case the
    reply packet is lost or can not be observed the RTT can not be
    In order to use this measurement technique, the IPFIX metering
    process needs to measure both directions. A classification of
    the protocols mentioned above has to be done. That means parts
    of the transport header are used for the classification. Since a
    differentiation of flows in accordance to the transport header
    is one of the requirements for IPFIX, such classification can be
    performed without extensions. Nevertheless, the meter needs to
    recognize request and response packets for the given protocols
    and therefore needs to look further into the packets. The
    capability to do this analysis is not part of the IPFIX
    requirements but can be achieved by optional extensions to the
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    classification process. The exporting device needs to assign a
    timestamp for the arrival of the packets. The calculation of the
    RTT can be done directly at the exporter or at the collector. In
    the first case IPFIX would transfer the calculated RTT to the
    collector. In the second case IPFIX needs to send the observed
    packet types and the timestamps to the collector. The round-
    trip-time-delay metric is defined in [RFC2681].
 2.8.2   Measurement of One-way-delay (OWD)
    Passive one-way-delay measurements require the collection of
    data at two measurement points. It is necessary to recognize
    packets at the second measurement point to correlate packet
    arrival events from both points. This can be done by capturing
    packet header and parts of the packet that can be used to
    recognize the same packet at the subsequent measurement point
    [MaPZ03]. To reduce the amount of measurement data a unique
    packet ID can be calculated from the header and part and/of the
    content e.g. by using a CRC or hash function [GrDM98, DuGr00,
    ZsZC01]. The capability of using content information is out of
    scope of IPFIX but can be achieved by an optional extension.
    Nevertheless, in some scenarios it might even be sufficient to
    calculate a packet ID based on header fields (including datagram
    ID and maybe sequence numbers from transport protocols) only
    without looking at parts of the packet content. If packet IDs
    need to be unique only for a certain time interval or a certain
    amount of packet ID collisions is tolerable this is a sufficient
    solution. The second issue is the export of packet IDs. IPFIX
    exports per flow information. However, it is possible to extend
    IPFIX with a scheme to export per-packet information by
    providing special templates for that purpose. The one way delay
    metric is defined in [RFC2679].
 2.8.3   Measurement of One-way-loss (OWL)
    Passive loss measurements for single flows can be performed at
    one measurement point by using sequence numbers that are present
    in protocols (e.g. IP identification, TCP sequence numbers)
    similar to the approach described in section 2.8.1. This
    requires the capturing of the sequence numbers of subsequent
    packets of the observed flow by the IPFIX metering process.
    An alternative to this is to perform a two-point measurement as
    described in section 2.8.2 and consider packets as lost that do
    not arrive at the second measurement point in a given time
    frame. This approach assumes that a packet observed at the first
    point should also be observed at the second point (known
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    The one-way loss metric is defined in [RFC2680].
 2.8.4Measurement of IP delay variation (IPDV)
    IP Delay variation is defined as the difference of one-way-delay
    values for selected packets [RFC3393]. Therefore, this metric
    can be calculated by performing passive measurement of one-way-
    delay for subsequent packets (e.g. of a flow) and then
    calculating the differences.
 3. Relation of IPFIX to other frameworks and protocols
 3.1 IPFIX and AAA
    AAA defines a protocol and architecture for authentication,
    authorization and accounting for service usage. The DIAMETER
    protocol is used for AAA communication for network access
    services (Mobile IP, NASREQ, and ROAMOPS). The AAA architecture
    [RFC2903] provides a framework for extending the AAA support
    also for other services. DIAMETER defines the exchange of
    messages between AAA entities, e.g. between AAA clients at
    access devices and AAA servers and among AAA servers. It is used
    also for the transfer of accounting records. Usage-based
    accounting requires measurement data from the network. IPFIX
    defines a protocol to export such data from routers, measurement
    probes and other devices.
    The provisioning of accounting with IPFIX can be realized
    without an AAA infrastructure. The collector can directly
    forward the measurement information to an accounting
    application. Nevertheless, if an AAA infrastructure is in place,
    IPFIX can provide the input for the generation of accounting
    records and several features of the AAA architecture can be
    used. Features include the mapping of a user ID to the flow
    information (by using authentication information), the
    generation of DIAMETER accounting records and the secure
    exchange of accounting records between domains with DIAMETER.
    Two possibilities to connect IPFIX and AAA can be distinguished:
 3.1.1Connecting via an AAA Client
    One possibility to connect IPFIX and AAA is to run an AAA client
    on the IPFIX collector. This client can generate DIAMETER
    accounting messages and send them to an AAA server. The mapping
    of the flow information to a user ID can be done in the AAA
    server by using data from the authentication process. DIAMETER
    accounting messages can be sent to the accounting application or
    to other AAA servers (e.g. in roaming scenarios).
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           +---------+  DIAMETER    +---------+
           |  AAA-S  |------------->|  AAA-S  |
           +---------+              +---------+
                | DIAMETER
         |  |  AAA-C |  |
         +  +--------+  |
         |              |
         |  Collector   |
                | IPFIX
          |  Exporter  |
    Figure 2: IPFIX collector connects to AAA server via AAA client
 3.1.2Connecting via an Application Specific Module (ASM)
    Another possibility is to directly connect the IPFIX collector
    with the AAA server via an application specific module (ASM).
    Application specific modules have been proposed by the IRTF AAA
    architecture research group (AAARCH) in [RFC2903]. They act as
    an interface between AAA server and service equipment. In this
    case the IPFIX collector is part of the ASM. The ASM acts as an
    interface between the IPFIX protocol and the input interface of
    the AAA server. The ASM translates the received IPFIX data into
    an appropriate format for the AAA server. The AAA server then
    can add information about the user ID and generate a DIAMETER
    accounting record. This accounting record can be sent to an
    accounting application or to other AAA servers.
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           +---------+  DIAMETER    +---------+
           |  AAA-S  |------------->|  AAA-S  |
           +---------+              +---------+
        |     ASM          |
        |  +------------+  |
        |  |  Collector |  |
                | IPFIX
          |  Exporter  |
    Figure 3: IPFIX connects to AAA server via ASM
 3.2 IPFIX and RTFM
    This section compares the Real-time Traffic Flow Measurement
    (RTFM) framework with the IPFIX framework.
 3.2.1Definition of 'flow'
    RTFM and IPFIX both use the same definition of flow; a flow is a
    set of packets which share a common set of end-point address
    attribute values. A flow is therefore completely specified by
    that set of values, together with an inactivity timeout.  A flow
    is considered to have ended when no packets are seen for at
    least the inactivity time.
    RTFM flows are bidirectional, which has given rise to some
    At the simplest level, a flow information exporter may achieve
    this by maintaining two unidirectional flows, one for each
    direction.  To export bidirectional flow information, e.g. to-
    and from- packet counts, for a flow from A to B, the exporter
    has only to search its flow table to find the matching flow from
    B to A.
    RTFM, however, takes bi-directionality a stage further, by
    including in the RTFM architecture [RFC 2722] a fully-detailed
    algorithm for real-time matching of the two directions of a
    flow.  This was done for two reasons, to reduce the memory
    required to store each flow (common address attributes for each
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    direction), and to allow for attributes which required fine
    detail for the two directions, e.g. short-term bit rate
    distributions [RFC 2724].
    ** So far there has been no suggestion that IPFIX should do
 3.2.2Configuration and Management
    The RTFM architecture specifies a complete system for gathering
    flow information.  It defines three entities,
     - Meters are very similar to IPFIX exporters.
     - Meter Readers are very similar to IPFIX collectors.
     - Managers co-ordinate the activities of meters and meter
    readers, and download configuration to them.
    Note that the whole RTFM system is asynchronous, many readers
    may collector flow data from a meter, and any reader may collect
    flow data from many meters.
    Rulesets allow the user to specify which flows are of interest,
    which are the source and destination ends of each flow, and what
    level of address granularity is required in the metered flows.
    For example, one may select all packets from 192.168/16, but
    build flow information for 192.168/24.  RTFM selection is done
    by testing under masks, and the masks do not have to use
    consecutive ones from the left.  Non-contiguous masks were
    considered important for handling some OSI protocols, but the
    need for that has diminished considerably.
    The RTFM approach is based on RMON, in that if a user wants to
    collect flow data for some particular set of flows, this can be
    achieved by writing a ruleset, i.e. an SRL program [RFC 2723],
    to specify what flows are of interest, requesting a manager to
    download that ruleset to a meter, and requesting the manager to
    have a meter reader collect the flow data at specified
    The details of how the manager communicates this information to
    meters and meter readers are not specified in the architecture.
    RTFM has a Meter MIB [RFC 2720], which is a standard which can
    be used to configure a meter, but nothing is said about how to
    configure a meter reader.
    The extent to which IPFIX should specify how meters or exporters
    should be configured is, at this stage, an open question.
    Clearly a collector needs some way to be sure of what it's
    collecting, e.g. by receiving 'templates' from the meter.
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    RTFM and IPFIX both leave parts of the system unspecified.  For
    RTFM flow data to be useful one must know the ruleset used to
    configure the meter, but a user can specify the ruleset.  For
    IPFIX one knows what the data is from the templates, but we have
    yet to determine whether in-band configuration will be
 3.2.3Data Model details  Count in one bucket
    Within a ruleset, a packet may only be counted on one bucket,
    i.e. it may only be included in one flow.  This means that the
    meter does not have to keep track of overlapping flows - if such
    aggregation is required, it must be done after the raw flow data
    has been read by a meter reader.
    From time to time one may wish to collect flow data for
    different levels of aggregation at the same time.  RTFM allows a
    meter to run several rulesets at the same time, and meter
    readers must specify which rulesets they are collecting data
    The 'count in one bucket' rule, together with the ability to run
    multiple rulesets, has proved very simple and effective in
    practice.  Counter wrapping
    For its packet- and byte-count attributes RTFM uses
    continuously-incrementing 64-bit counters, which are never
    reset.  This makes asynchronous meter reading easy, any reader
    simply has to remember its previous reading and compute the
    difference.  The only caveat is that the meter should be read
    often enough to avoid situations when the counter has cycled
    more than once between readings.  Sampling issues
    RTFM provides 1 out of N sampling as a configuration option, so
    that some metering interfaces may only process every Nth packet.
    The RTFM Architecture [RFC 2722] does not discuss the
    statistical implications of this, merely saying that users will
    need to satisfy themselves that sampling makes sense in their
    RTFM makes no provision for flow sampling.  Recently there has
    been a lot of interest in flow sampling schemes which favour the
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    'most important' flows, perhaps we need to consider this for
 3.2.4Application/transport protocol
    RTFM has a standards-track Meter MIB [RFC 2720], which can be
    used both to configure a meter and to read flow data from it.
    The MIB provides a way to read lists of attributes with a single
    Object Identifier (called a 'package'), which dramatically
    reduces the SNMP overhead for flow data collection.  NeTraMet, a
    widely-used open-source RTFM implementation, uses SNMPv2C for
    configuration and data collection.
    SNMP, of course, normally uses UDP as its transport protocol.
    Since RTFM requires a reliable flow data transport system, an
    RTFM meter reader must time out and resend unanswered SNMP
    requests. Apart from being clumsy, this can limit the maximum
    data transfer rate from meter to meter reader.  SNMP over TCP
    would be a better approach, but that is currently an IRTF
    On the other hand, RTFM does not specify an application protocol
    in its architecture, leaving this as an implementation issue.
    For example, a team at IBM Research implemented a RTFM meter and
    meter reader in a single host, with the reader storing the flow
    data directly into a large database system. Similarly, many
    NeTraMet users run the meter and meter reader on the same host
    A need for high flow data rates highlights the need for careful
    systems design when building a flow data collection system.
    When data rates are high, and it is not possible to use a high
    level of aggregation, then it makes sense to have the collectors
    very close to their exporters.  Once the data is safely on a
    dedicated host machine, large volumes of it can be moved using
    'background' techniques such as FTP.
    The RTFM architecture only specifies a pull model for getting
    data out of a meter.  To implement push mode data transfer would
    require specification of triggers to indicate when data should
    be sent for each flow.
 3.3 IPFIX and IPPM
    The IPFIX protocol can be used to carry IPPM network performance
    metrics or information that can be used to calculate those
    metrics (see section 2.7).
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 3.4 IPFIX and IDMEF
    The Intrusion Detection Message Exchange Format (IDMEF) [CuDF04]
    is a standard data format developed within the IDWG Working
    Group to exchange data alerts between automated Intrusion
    Detection Systems (IDS). IDMEF provides a standard
    representation of the alert information that an Intrusion
    Detection analyzer reports when a suspicious event is detected.
    These alerts may be simple or complex depending on analyzers
    capabilities, commercial vendor objectives, and intrusion
    detection environments. IDMEF messages are implemented in XML
    and composed by a basic schema and extension modules to define
    alerts that are more complex. Once the kind of alert that should
    be sent has been determined by the analyzer, it must be
    formatted following the IDMEF rules.
    Generally, alerts are sent when analyzers detect an event that
    they have been configured to look for.
    The IPFIX protocol can be used complementarily to IDMEF for
    providing detailed information of intrusions traffic, suspect
    events or anomalous traffic that differs from the normal network
 4. Security Consideration
    This document describes the usage of IPFIX in various scenarios.
    The security requirements for the IPFIX target applications are
    addressed in the IPFIX requirements draft. These requirements
    must be considered for the specification of the IPFIX protocol.
    The IPFIX extensions proposed in this document do not induce
    further security hazards.
    Section 3 of this document describes how IPFIX can be used in
    combination with other frameworks. New security hazards can
    arise when two individually secure frameworks are combined. For
    the combination of AAA with IPFIX an ASM or an IPFIX collector
    can function as transit point for the messages. It has to be
    ensured that at this point the applied security mechanisms (e.g.
    encryption of messages) are maintained.
 5. References
    [Awdu02] Daniel O. Awduche, et. al.," Overview and Principles of
             Internet Traffic Engineering", (work in progress),
             Internet Draft, Internet Engineering Task Force, draft-
             ietf-tewg-principles-02.txt, May 2002
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    [Brow00] Nevil Brownlee: Packet Matching for NeTraMet
    [CuDF04] D.Curry, H. Debar, H. Feinstein: ææThe Intrusion
             Detection Message Exchange FormatÆÆ,(work in progress),
             Internet Draft, Internet Engineering Task Force, <draft-
             ietf-idwg-idmef-xml-11.txt>, January 2004
    [DuGr00] Nick Duffield, Matthias Grossglauser: "Trajectory
             Sampling for Direct Traffic Observation", Proceedings of
             ACM SIGCOMM 2000, Stockholm, Sweden, August 28 -
             September 1, 2000.
    [GrDM98] Ian D. GRAHAM, Stephen F. DONNELLY, Stele MARTIN, Jed
             MARTENS, John G. CLEARY: Nonintrusive and Accurate
             Measurement of Unidirectional Delay and Delay Variation
             on the Internet, INET'98, Geneva, Switzerland,  21-24
             July, 1998
    [MaPZ03] L. Mark, G. Pohl, T. Zseby, K. Sugauchi: Passive One-
             way Delay Measurements, (work in progress), Internet
             Draft <draft-mark-powd-00.txt>, June 2003
    [QuZC03] J. Quittek ,et. Al "Requirements for IP Flow
             Information Export ", (work in progress) ,Internet
             Draft, Internet Engineering Task Force, <draft-ietf-
             ipfix-reqs-10.txt>, June 2003
    [RFC2679] G. Almes, S. Kalidindi, M. Zekauskas: A One-way Delay
             Metric for IPPM, Request for Comments: 2679, September
    [RFC2680] G. Almes, S. Kalidindi, M. Zekauskas: A One-way Packet
             Loss Metric for IPPM, September 1999
    [RFC2681]G. Almes, S. Kalidindi, M. Zekauskas, "A Round-trip
             Delay Metric for IPPM.", RFC 2681, September 1999
    [RFC2903] C. de Laat, G. Gross, L. Gommans, J. Vollbrecht, D.
             Spence, "Generic AAA Architecture", RFC 2903, August
    [RFC3393] C. Demichelis, P. Cimento: IP Packet Delay Variation
             Metric for IPPM, RFC 3393, November 200
    [ZsZC01] Tanja Zseby, Sebastian Zander, Georg Carle: Evaluation
             of Building Blocks for Passive One-way-delay
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                      IPFIX Applicability               July 2004
             Measurements, Proceedings of Passive and Active
             Measurement Workshop (PAM 2001), Amsterdam, The
             Netherlands, April 23-24, 2001
 6. Acknowledgements
    We would like to thank the following persons for their
    contribution, discussion on the mailing list and valuable
    - Sebastian Zander
    - Robert Loewe
    Part of the work has been developed in the research project 6QM
    co-funded with support from the European Commission.
 7. Author's Addresses
    Tanja Zseby
    Fraunhofer Institute for Open Communication Systems (FOKUS)
    Kaiserin-Augusta-Allee 31
    10589 Berlin, Germany
    Phone: +49 30 3463 7153
    Elisa Boschi
    Fraunhofer Institute for Open Communication Systems (FOKUS)
    Kaiserin-Augusta-Allee 31
    10589 Berlin, Germany
    Phone: +49 30 3463 7366
    Reinaldo Penno
    Nortel Networks, Inc.
    2305 Mission College Boulevard
    Building SC9-B1240, Santa Clara, CA 95134
    Nevil Brownlee
    9500 Gilman Drive
    La Jolla, CA 92093-0505
    Phone : +1 858 534 8338
    Email :
    Benoit Claise
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                      IPFIX Applicability               July 2004
    Cisco Systems
    De Kleetlaan 6a b1
    1831 Diegem
    Phone: +32 2 704 5622
 8. Full Copyright Statement
    "Copyright (C) The Internet Society (date). All Rights Reserved.
    This document and translations of it may be copied and furnished
    to others, and derivative works that comment on or otherwise
    explain it or assist in its implementation may be prepared,
    copied, published and distributed, in whole or in part, without
    restriction of any kind, provided that the above copyright
    notice and this paragraph are included on all such copies and
    derivative works. However, this document itself may not be
    modified in any way, such as by removing the copyright notice or
    references to the Internet Society or other Internet
    organizations, except as needed for the purpose of developing
    Internet standards in which case the procedures for copyrights
    defined in the Internet Standards process must be followed, or
    as required to translate it into.
                        Expires January 2005              [Page 17]