





Network Working Group                                         J. Quittek
Request for Comments: 3917                               NEC Europe Ltd.
Category: Informational                                         T. Zseby
                                                        Fraunhofer FOKUS
                                                               B. Claise
                                                           Cisco Systems
                                                               S. Zander
                                                    Swinburne University
                                                            October 2004


          Requirements for IP Flow Information Export (IPFIX)

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2004).

Abstract

   This memo defines requirements for the export of measured IP flow
   information out of routers, traffic measurement probes, and
   middleboxes.

Table of Contents

   1.   Introduction. . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.   Terminology . . . . . . . . . . . . . . . . . . . . . . . . .  3
        2.1.   IP Traffic Flow. . . . . . . . . . . . . . . . . . . .  3
        2.2.   Observation Point. . . . . . . . . . . . . . . . . . .  4
        2.3.   Metering Process . . . . . . . . . . . . . . . . . . .  4
        2.4.   Flow Record. . . . . . . . . . . . . . . . . . . . . .  5
        2.5.   Exporting Process. . . . . . . . . . . . . . . . . . .  5
        2.6.   Collecting Process . . . . . . . . . . . . . . . . . .  5
   3.   Applications Requiring IP Flow Information Export . . . . . .  6
        3.1.   Usage-based Accounting . . . . . . . . . . . . . . . .  6
        3.2.   Traffic Profiling. . . . . . . . . . . . . . . . . . .  7
        3.3.   Traffic Engineering. . . . . . . . . . . . . . . . . .  7
        3.4.   Attack/Intrusion Detection . . . . . . . . . . . . . .  7
        3.5.   QoS Monitoring . . . . . . . . . . . . . . . . . . . .  8
   4.   Distinguishing Flows. . . . . . . . . . . . . . . . . . . . .  8
        4.1.   Encryption . . . . . . . . . . . . . . . . . . . . . .  9
        4.2.   Interfaces . . . . . . . . . . . . . . . . . . . . . .  9



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        4.3.   IP Header Fields . . . . . . . . . . . . . . . . . . .  9
        4.4.   Transport Header Fields. . . . . . . . . . . . . . . . 10
        4.5.   MPLS Label . . . . . . . . . . . . . . . . . . . . . . 10
        4.6.   DiffServ Code Point. . . . . . . . . . . . . . . . . . 10
   5.   Metering Process. . . . . . . . . . . . . . . . . . . . . . . 10
        5.1.   Reliability. . . . . . . . . . . . . . . . . . . . . . 10
        5.2.   Sampling . . . . . . . . . . . . . . . . . . . . . . . 11
        5.3.   Overload Behavior. . . . . . . . . . . . . . . . . . . 11
        5.4.   Timestamps . . . . . . . . . . . . . . . . . . . . . . 12
        5.5.   Time Synchronization . . . . . . . . . . . . . . . . . 12
        5.6.   Flow Expiration. . . . . . . . . . . . . . . . . . . . 13
        5.7.   Multicast Flows. . . . . . . . . . . . . . . . . . . . 13
        5.8.   Packet Fragmentation . . . . . . . . . . . . . . . . . 13
        5.9.   Ignore Port Copy . . . . . . . . . . . . . . . . . . . 13
   6.   Data Export . . . . . . . . . . . . . . . . . . . . . . . . . 14
        6.1.   Information Model. . . . . . . . . . . . . . . . . . . 14
        6.2.   Data Model . . . . . . . . . . . . . . . . . . . . . . 16
        6.3.   Data Transfer. . . . . . . . . . . . . . . . . . . . . 16
               6.3.1. Congestion Awareness. . . . . . . . . . . . . . 16
               6.3.2. Reliability . . . . . . . . . . . . . . . . . . 17
               6.3.3. Security. . . . . . . . . . . . . . . . . . . . 18
        6.4.   Push and Pull Mode Reporting . . . . . . . . . . . . . 18
        6.5.   Regular Reporting Interval . . . . . . . . . . . . . . 18
        6.6.   Notification on Specific Events. . . . . . . . . . . . 18
        6.7.   Anonymization. . . . . . . . . . . . . . . . . . . . . 18
   7.   Configuration . . . . . . . . . . . . . . . . . . . . . . . . 19
        7.1.   Configuration of the Metering Process. . . . . . . . . 19
        7.2.   Configuration of the Exporting Process . . . . . . . . 19
   8.   General Requirements. . . . . . . . . . . . . . . . . . . . . 20
        8.1.   Openness . . . . . . . . . . . . . . . . . . . . . . . 20
        8.2.   Scalability. . . . . . . . . . . . . . . . . . . . . . 20
        8.3.   Several Collecting Processes . . . . . . . . . . . . . 20
   9.   Special Device Considerations . . . . . . . . . . . . . . . . 20
   10.  Security Considerations . . . . . . . . . . . . . . . . . . . 23
        10.1.  Disclosure of Flow Information Data. . . . . . . . . . 23
        10.2.  Forgery of Flow Records. . . . . . . . . . . . . . . . 24
        10.3.  Denial of Service (DoS) Attacks. . . . . . . . . . . . 24
   11.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 25
   12.  Appendix: Derivation of Requirements from Applications. . . . 26
   13.  References  . . . . . . . . . . . . . . . . . . . . . . . . . 31
        13.1.  Normative References . . . . . . . . . . . . . . . . . 31
        13.2.  Informative References . . . . . . . . . . . . . . . . 31
   14. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 32
   15. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 33







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1.  Introduction

   There are several applications that require flow-based IP traffic
   measurements.  Such measurements could be performed by a router while
   forwarding the traffic, by a middlebox [RFC3234], or by a traffic
   measurement probe attached to a line or a monitored port.  This memo
   defines requirements for exporting traffic flow information out of
   these boxes for further processing by applications located on other
   devices.  They serve as input to the standardization of the IPFIX
   protocol specifications.

   In section 3, a selection of such applications is presented.  The
   following sections list requirements derived from these applications.

   In its early discussions the IPFIX Working Group chose to evaluate
   existing flow export protocols at the same time it was developing
   this 'requirements' document.

   Flow export, however, is not performed by a protocol acting alone, it
   also requires a system of co-operating processes.  In producing IPFIX
   requirements, therefore, the Working Group decided to specify what
   was required by these various processes - the metering process, the
   exporting process, etc.  In these specifications we use lower-case
   for the words must, may, and should, to indicate that IPFIX
   implementors have some freedom as to how to meet the requirements.

   The Working Group's goal is to produce standards-track RFCs
   describing the IPFIX information model and export protocol RFCs.  As
   well as meeting the requirements set out in this document, the
   information model and protocol documents will provide a full
   specification of the IPFIX system, and will use uppercase keywords as
   in [RFC 2119].

2.  Terminology

   The following terminology is used in this document:

2.1.  IP Traffic Flow

   There are several definitions of the term 'flow' being used by the
   Internet community.  Within this document we use the following one:

   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:





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      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 [RFC3550])

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

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

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

   This definition covers the range from a flow containing all packets
   observed at a network interface to a flow consisting of just a single
   packet between two applications with a specific sequence number.
   Please note that the flow definition does not necessarily match a
   general application-level end-to-end stream.  However, an application
   may derive properties of application-level streams by processing
   measured flow data.  Also, please note that although packet
   properties may depend on application headers, there is no requirement
   defined in this document related to application headers.

2.2.  Observation Point

   The observation point is a location in the network where IP packets
   can be observed.  Examples are 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.  This would be the superset of the individual
   observation points at the line card's interfaces.

2.3.  Metering Process

   The metering process generates flow records.  Input to the process
   are packet headers observed at an observation point and packet
   treatment at the observation point, for example the selected output
   interface.  The metering process consists of a set of functions that
   includes packet header capturing, timestamping, sampling,
   classifying, and maintaining flow records.

   The maintenance of flow records may include creating new records,
   updating existing ones, computing flow statistics, deriving further
   flow properties, detecting flow expiration, passing flow records to
   the exporting process, and deleting flow records.



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   The sampling function and the classifying function may be applied
   more than once with different parameters.  Figure 1 shows the
   sequence in which the functions are applied.  Sampling is not
   illustrated in the figure; it may be applied before any other
   function.

                           packet header capturing
                                     |
                                timestamping
                                     |
                                     v
                              +----->+
                              |      |
                              | classifying
                              |      |
                              +------+
                                     |
                          maintaining flow records
                                     |
                                     v

                 Figure 1: Functions of the metering process

2.4.  Flow Record

   A flow record contains information about a specific flow that was
   metered at an observation point.  A flow record contains measured
   properties of the flow (e.g., the total number of bytes of all
   packets of the flow) and usually characteristic properties of the
   flow (e.g., source IP address).

2.5.  Exporting Process

   The exporting process sends flow records to one or more collecting
   processes.  The flow records are generated by one or more metering
   processes.

2.6.  Collecting Process

   The collecting process receives flow records from one or more
   exporting processes.  The collecting process might store received
   flow records or further process them, but these actions are out of
   the scope of this document.








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3.  Applications Requiring IP Flow Information Export

   This section describes a selection of applications requiring IP flow
   information export.  Because requirements for flow export listed in
   further sections below are derived from these applications, their
   selection is crucial.  The goal of this requirements document is not
   to cover all possible applications with all their flow export
   requirements, but to cover applications which are considered to be of
   significant importance in today's and/or future IP networks, and for
   which requirements can be met with reasonable technical effort.

   The list of applications should lead to a better understanding of the
   requirements which is particularly important when designing or
   implementing traffic flow metering functions.  A detailed overview of
   which requirement was derived from which application(s) is given in
   the appendix.

   Please note that the described applications can have a large number
   of differing implementations.  Requirement details or requirement
   significance (required (must), recommended (should), optional (may))
   could differ for specific implementations and/or for specific
   application scenarios.  Therefore we derive the requirements from the
   general functionality of the selected applications.  Some particular
   cases will even mandate more stringent requirements than the ones
   defined in this document.  For example, usage-based accounting is
   certainly the application that will probably mandate the highest
   degree of reliability amongst the applications discussed below.  The
   reliability requirements defined in sections 5.1 and 6.3.2. are not
   sufficient to guarantee the level of reliability that is needed for
   many usage-based accounting systems.  Particular reliability
   requirements for accounting systems are discussed in [RFC2975].

3.1.  Usage-based Accounting

   Several new business models for selling IP services and IP-based
   services are currently under investigation.  Beyond flat rate
   services which do not need accounting, accounting can be based on
   time or volume.  Accounting data can serve as input for billing
   systems.  Accounting can be performed per user or per user group, it
   can be performed just for basic IP service or individually per high-
   level service and/or per content type delivered.  For advanced/future
   services, accounting may also be performed per class of service, per
   application, per time of day, per (label switched) path used, etc.








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3.2.  Traffic Profiling

   Traffic profiling is the process of characterizing IP flows by using
   a model that represents key parameters of the flows such as flow
   duration, volume, time, and burstiness.  It is a prerequisite for
   network planning, network dimensioning, trend analysis, business
   model development, and other activities.  It depends heavily on the
   particular traffic profiling objective(s), which statistics, and
   which accuracy are required from the measurements.  Typical
   information needed for traffic profiling is the distribution of used
   services and protocols in the network, the amount of packets of a
   specific type (e.g., percentage of IPv6 packets) and specific flow
   profiles.

   Since objectives for traffic profiling can vary, this application
   requires a high flexibility of the measurement infrastructure,
   especially regarding the options for measurement configuration and
   packet classification.

3.3.  Traffic Engineering

   Traffic Engineering (TE) comprises methods for measurement,
   modelling, characterization and control of a network.  The goal of TE
   is the optimization of network resource utilization and traffic
   performance [RFC2702].  Since control and administrative reaction to
   measurement results requires access to the involved network nodes, TE
   mechanisms and the required measurement function usually are
   performed within one administrative domain.  Typical parameters
   required for TE are link utilization, load between specific network
   nodes, number, size and entry/exit points of the active flows and
   routing information.

3.4.  Attack/Intrusion Detection

   Capturing flow information plays an important role for network
   security, both for detection of security violation, and for
   subsequent defense.  In case of a Denial of Service (DOS) attack,
   flow monitoring can allow detection of unusual situations or
   suspicious flows.  In a second step, flow analysis can be performed
   in order to gather information about the attacking flows, and for
   deriving a defense strategy.

   Intrusion detection is a potentially more demanding application which
   would not only look at specific characteristics of flows, but may
   also use a stateful packet flow analysis for detecting specific,
   suspicious activities, or unusually frequent activities.  Such
   activities may be characterized by specific communication patterns,
   detectable by characteristic sequences of certain packet types.



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3.5.  QoS Monitoring

   QoS monitoring is the passive measurement of quality parameters for
   IP flows.  In contrast to active measurements, passive measurements
   utilize the existing traffic in the network for QoS analysis.  Since
   no test traffic is sent, passive measurements can only be applied in
   situations where the traffic of interest is already present in the
   network.  One example application is the validation of QoS parameters
   negotiated in a service level specification.  Note that
   passive/active measurement is also referred to as non-
   intrusive/intrusive measurement or as measurement of
   observed/synthetic traffic.

   Passive measurements cannot provide the kind of controllable
   experiments that can be achieved with active measurements.  On the
   other hand passive measurements do not suffer from undesired side
   effects caused by sending test traffic (e.g., additional load,
   potential differences in treatment of test traffic and real customer
   traffic).

   QoS monitoring often requires the correlation of data from multiple
   observation points (e.g., for measuring one-way metrics).  This
   requires proper clock synchronization of the involved metering
   processes.  For some measurements, flow records and/or notifications
   on specific events at the different observation points must be
   correlated, for example the arrival of a certain packet.  For this,
   the provisioning of post-processing functions (e.g., the generation
   of packet IDs) at the metering processes would be useful.  Since QoS
   monitoring can lead to a huge amount of measurement result data, it
   would highly benefit from mechanisms to reduce the measurement data,
   like aggregation of results and sampling.

   Please note that not all requirements for QoS monitoring are covered
   by the IPFIX requirements specified in the following sections.  The
   IPFIX requirements are targeted at per flow information including
   summaries of per-packet properties for packets within a flow, but not
   per-packet information itself.  For example jitter measurement
   requires timestamping each packet and reporting of all timestamps of
   a flow, but the IPFIX requirements only cover timestamps of first and
   last packet of a flow.

4.  Distinguishing Flows

   Packets are mapped to flows by evaluating their properties.  Packets
   with common properties are considered to belong to the same flow.  A
   packet showing at least one difference in the set of properties is
   considered to belong to a different flow.




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   The following subsections list a set of properties which a metering
   process must, should, or may be able to evaluate for mapping packets
   to flows.  Please note that requiring the ability to evaluate a
   certain property does not imply that this property must be evaluated
   for each packet.  In other words, meeting the IPFIX requirements
   means that the metering process in general must be able, via its
   configuration, to somehow support to distinguish flows via all the
   must fields, even if in certain circumstances/for certain
   applications, only a subset of the must fields is needed and
   effectively used to distinguish flows.

   Which combination of properties is used for distinguishing flows and
   how these properties are evaluated depends on the configuration of
   the metering process.  The configured choice of evaluated properties
   strongly depends on the environment and purpose of the measurement
   and on the information required by the collecting process.  But in
   any case, a collecting process must be able to clearly identify, for
   each received flow record, which set of properties was used for
   distinguishing this flow from other ones.

   For specific deployments, only a subset of the required properties
   listed below can be used to distinguish flows. For example, in order
   to aggregate the flow records and reduce the number of flow records
   exported.  On the other hand, some other deployments will require
   distinguishing flows by some extra parameters, such as the TTL field
   of the IP header or the BGP Autonomous System number [RFC1771] of the
   IP destination address.

4.1.  Encryption

   If encryption is used, the metering process might not be able to
   access all header fields.  A metering process must meet the
   requirements stated in this section 4 only for packets that have the
   relevant header fields not encrypted.

4.2.  Interfaces

   The metering process must be able to separate flows by the incoming
   interface or by the outgoing interface or by both of them.

4.3.  IP Header Fields

   The metering process must be able to separate flows by the following
   fields of the IP header:

      1. source IP address

      2. destination IP address



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      3. protocol type (TCP, UDP, ICMP, ...)

   For source address and destination address, separating by full match
   must be supported as well as separation by prefix match.

   The metering process should be able to separate flows by the IP
   version number if the observation point is located at a device that
   is supporting more than one IP version.

4.4.  Transport Header Fields

   The metering process must be able to separate flows by the port
   numbers of the transport header in case of TCP or UDP being used as
   transport protocol.  The metering process should be able to separate
   flows by the port numbers of the transport header in case of SCTP
   [RFC2960].

   For separation, both, source and destination port number must be
   supported for distinguishing flows, individually as well as in
   combination.

4.5.  MPLS Label

   If the observation point is located at a device supporting
   Multiprotocol Label Switching (MPLS, see [RFC3031]) then the metering
   process must be able to separate flows by the MPLS label.

4.6.  DiffServ Code Point

   If the observation point is located at a device supporting
   Differentiated Services (DiffServ) then the metering process must be
   able to separate flows by the DiffServ Code Point (DSCP, see
   [RFC2474]).

5.  Metering Process

   The following are requirements for the metering process.  All
   measurements must be conducted from the point of view of the
   observation point.

5.1.  Reliability

   The metering process must either be reliable or the absence of
   reliability must be known and indicated.  The metering process is
   reliable if each packet passing the observation point is metered
   according to the configuration of the metering process.  If, e.g.,





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   due to some overload, not all passing packets can be included into
   the metering process, then the metering process must be able to
   detect this failure and to report it.

5.2.  Sampling

   Sampling describes the systematic or random selection of a subset of
   elements (the sample) out of a set of elements (the parent
   population).  Usually the purpose of applying sampling techniques is
   to estimate a parameter of the parent population by using only the
   elements of the subset.  Sampling techniques can be applied for
   instance to select a subset of packets out of all packets of a flow
   or to select a subset of flows out of all flows on a link.  Sampling
   methods differ in their sampling strategy (e.g., systematic or
   random) and in the event that triggers the selection of an element.
   The selection of one packet can for instance be triggered by its
   arrival time (time-based sampling), by its position in the flow
   (count-based sampling) or by the packet content (content-based
   sampling).

   The metering process may support packet sampling.  If sampling is
   supported, the sampling configuration must be well defined.  The
   sampling configuration includes the sampling method and all its
   parameters.

   If the sampling configuration is changed during operation, the new
   sampling configuration with its parameters must be indicated to all
   collecting processes receiving the affected flow records.  Changing
   the sampling configuration includes: adding a sampling function to
   the metering process, removing a sampling function from the metering
   process, change sampling method, and change sampling parameter(s).

   In case of any change in the sampling configuration, all flow records
   metered by the previous sampling configuration must be terminated and
   exported according to the export configuration.  The metering process
   must not merge the flow records generated with the new sampling
   configuration with the flow records generated with the previous
   sampling configuration.

5.3.  Overload Behavior

   In case of an overload, for example lack of memory or processing
   power, the metering process may change its behavior in order to cope
   with the lack of resources.  Possible reactions include:







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         -  Reduce the number of flows to be metered.  This can be
            achieved by more coarse-grained flow measurement or by a
            restriction of the flow records to a subset of the set of
            original ones.

         -  Start sampling packets before they are processed by the
            metering process or - if sampling is already performed -
            reduce the sampling frequency.

         -  Stop metering.

         -  Reducing the resource usage of competing processes on the
            same device.  Example: reducing the packet forwarding
            throughput

   Overload behavior is not restricted to the four options listed above.
   But in case the overload behavior induces a change of the metering
   process behavior, the overload behavior must be clearly defined.

   For some flows, the change of behavior might have an impact on the
   data that would be stored in the associated flow records after the
   change, for example if the packet classification is changed or the
   sampling frequency.  These flows must be considered as terminated and
   the associated flow records must be exported separately from new ones
   generated after the behavior change.  The terminated flow records and
   new ones generated after the behavior change must not be merged by
   the metering process.  The collecting process must be able to
   distinguish the affected flow records generated before and after the
   change of behavior.  This requirement does not apply to flows and
   associated flow records not affected by the change of metering
   process behavior.

5.4.  Timestamps

   The metering process must be able to generate timestamps for the
   first and the last observation of a packet of a flow at the
   observation point.  The timestamp resolution must be at least the one
   of the sysUpTime [RFC3418], which is one centisecond.

5.5.  Time Synchronization

   It must be possible to synchronize timestamps generated by a metering
   process with Coordinated Universal Time (UTC).

   Note that the possibility of synchronizing timestamps of each single
   metering process with UTC implies the possibility of synchronizing
   timestamps generated by different metering processes.




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   Note that this does not necessarily imply that timestamps generated
   by the metering process are UTC timestamps.  For example, this
   requirement can be met by using local system clock values as
   timestamps and adding an additional timestamp when exporting a report
   to a collecting process.  Then the collecting process can synchronize
   the timestamps by calculating the offset between UTC and the system
   clock of the metering process.

5.6.  Flow Expiration

   The metering process must be able to detect flow expirations.  A flow
   is considered to be expired if no packet of this flow has been
   observed for a given timeout interval.  The metering process may
   support means for detecting the expiration of a flow before a timeout
   occurs, for example by detecting the FIN or RST bits in a TCP
   connection.  The procedure for detecting a flow expiration must be
   clearly defined.

5.7.  Multicast Flows

   For multicast flows containing packets replicated to multiple output
   interfaces, the metering process should be able to maintain discrete
   flow records per different output interface.  For example, the
   metering process should be able to report an incoming multicast
   packet that is replicated to four output interfaces in four different
   flow records that differ by the output interface.

5.8.  Packet Fragmentation

   In case of IP packet fragmentation and depending on the
   classification scheme, only the zero-offset fragment of a single
   initial packet might contain sufficient information to classify the
   packet.  Note that this fragment should be the first one generated by
   the router imposing the fragmentation [RFC791], but might not be the
   first one observed by the IPFIX device, due to reordering reasons.
   The metering process may keep state of IP packet fragmentation in
   order to map fragments that do not contain sufficient header
   information correctly to flows.

5.9.  Ignore Port Copy

   The metering process may be able to ignore packets which are
   generated by a port copy function acting at the device where the
   observation point of a flow is located.







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6.  Data Export

   The following are requirements for exporting flow records out of the
   exporting process.  Beside requirements on the data transfer, we
   separate requirements concerning the information model from
   requirements concerning the data model.  Furthermore, we list
   requirements on reporting times and notification on specific events,
   and on anonymization of flow records.

6.1.  Information Model

   The information model for the flow information export is the list of
   attributes of a flow to be contained in the report (including the
   semantics of the attributes).

   This section lists attributes an exporting process must, should or
   may be able to report.  This does not imply that each exported flow
   record must contain all required attributes.  But it implies that it
   must be possible to configure the exporting process in a way that the
   information of all required attributes can be transmitted from the
   exporting process to the receiving collecting process(es) for each
   exported flow.

   In other words, meeting the IPFIX requirements means that the
   exporting process in general must be able, via its configuration, to
   somehow support to report all the must fields, even if in certain
   circumstances or for certain applications, only a subset of the set
   of all must fields is needed and effectively reported.

   Beyond that, the exporting process might offer to report further
   attributes not mentioned here.  A particular flow record may contain
   some of the "required" attributes as well as some additional ones,
   for example covering future technologies.

   This document does not impose that the following attributes are
   reported for every single flow record, especially for repetitive
   attributes.  For example, if the observation point is the incoming
   packet stream at the IP interface with the ifIndex value 3, then this
   observation point does not have to be exported as part of every
   single flow record.  Exporting it just once might give sufficient
   information to the collecting process.

   The exporting process must be able to report the following attributes
   for each metered flow:

      1.  IP version number
          This requirement only applies if the observation point is
          located at a device supporting more than one version of IP.



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      2.  source IP address
      3.  destination IP address
      4.  IP protocol type (TCP,UDP,ICMP,...)
      5.  if protocol type is TCP or UDP: source TCP/UDP port number
      6.  if protocol type is TCP or UDP: destination TCP/UDP port
          number
      7.  packet counter
          If a packet is fragmented, each fragment is counted as an
          individual packet.
      8.  byte counter
          The sum of the total length in bytes of all IP packets
          belonging to the flow.  The total length of a packet covers IP
          header and IP payload.
      9.  type of service octet (in case of IPv4), traffic class octet
          (in case of IPv6).  According to [RFC2474], these octets
          include the DiffServ Code Point that has a length of 6 bits.
      10. in case of IPv6: Flow Label
      11. if MPLS is supported at the observation point: the top MPLS
          label or the corresponding forwarding equivalence class (FEC,
          [RFC3031]) bound to that label.  The FEC is typically defined
          by an IP prefix.
      12. timestamp of the first packet of the flow
      13. timestamp of the last packet of the flow
      14. if sampling is used: sampling configuration
      15. unique identifier of the observation point
      16. unique identifier of the exporting process

   The exporting process should be able to report the following
   attributes for each metered flow:

      17. if protocol type is ICMP: ICMP type and code
      18. input interface (ifIndex)
          This requirement does not apply if the observation point is
          located at a probe device.
      19. output interface (ifIndex)
          This requirement does not apply if the observation point is
          located at a probe device.
      20. multicast replication factor
          the number of outgoing packets originating from a single
          incoming multicast packet.  This is a dynamic property of
          multicast flows, that may change over time.  For unicast flows
          it has the constant value 1.  The reported value must be the
          value of the factor at the time the flow record is exported.

   The exporting process may be able to report the following attributes
   for each metered flow:

      21. Time To Live (in case of IPv4) or Hop Limit (in case of IPv6)



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      22. IP header flags
      23. TCP header flags
      24. dropped packet counter at the observation point
          If a packet is fragmented, each fragment must be counted as an
          individual packet.
      25. fragmented packet counter
          counter of all packets for which the fragmented bit is set in
          the IP header
      26. next hop IP address
      27. source BGP Autonomous System number (see [RFC1771])
      28. destination BGP Autonomous System number
      29. next hop BGP Autonomous System number

6.2.  Data Model

   The data model describes how information is represented in flow
   records.

   The data model must be extensible for future attributes to be added.
   Even if a set of attributes is fixed in the flow record, the data
   model must provide a way of extending the record by configuration or
   for certain implementations.

   The data model used for exporting flow information must be flexible
   concerning the flow attributes contained in flow records.  A flexible
   record format would offer the possibility of defining records in a
   flexible (customizable) way regarding the number and type of
   contained attributes.

   The data model should be independent of the underlying transport
   protocol, i.e., the data transfer.

6.3.  Data Transfer

   Requirements for the data transfer include reliability, congestion
   awareness, and security requirements.  For meeting these requirements
   the exporting process can utilize existing security features provided
   by the device hosting the process and/or provided by the transport
   network.  For example it can use existing security technologies for
   authentication and encryption or it can rely on physical protection
   of a separated network for transferring flow information.

6.3.1.  Congestion Awareness

   For the data transfer, a congestion aware protocol must be supported.






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6.3.2.  Reliability

   Loss of flow records during the data transfer from the exporting
   process to the collecting process must be indicated at the collecting
   process.  This indication must allow the collecting process to gauge
   the number of flow records lost.  Possible reasons for flow records
   loss include but are not limited to:

      1. Metering process limitations: lack of memory, processing power,
         etc.  These limitations are already covered in section 5.1.

      2. Exporting process limitations: lack of memory, processing
         power, etc.

      3. Data transfer problems: packets that carry flow records sent
         from the exporting process to the collecting process, are
         dropped by the network.  Examples are connection failures and
         losses by a transport protocol that specifically offers
         congestion avoidance without persistent transport-level
         reliability.

      4. Collecting process limitations: it may be experiencing
         congestion and not able to buffer new flows records.

      5. Operation and Maintenance: the collecting process is taken down
         for maintenance or other administrative purposes.

   Please note that if an unreliable transport protocol is used,
   reliability can be provided by higher layers.  If reliability is
   provided by higher layers, only lack of overall reliability must be
   indicated.  For example reordering could be dealt with by adding a
   sequence number to each packet.

   The data transfer between exporting process and collecting process
   must be open to reliability extensions including at least

      - retransmission of lost flow records,
      - detection of disconnection and fail-over, and
      - acknowledgement of flow records by the collecting process.

   This extensibility may be used to provide additional reliability.
   The extended protocol must still meet the requirements described in
   this section, particularly, it must still be congestion aware.
   Therefore, extensions using retransmissions must use exponential
   backoff.






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6.3.3.  Security

   Confidentiality of IPFIX data transferred from an exporting process
   to a collecting process must be ensured.

   Integrity of IPFIX data transferred from an exporting process to a
   collecting process must be ensured.

   Authenticity of IPFIX data transferred from an exporting process to a
   collecting process must be ensured.

   The security requirements have been derived from an analysis of
   potential security threads.  The analysis is summarized in Section
   10.

6.4.  Push and Pull Mode Reporting

   In general, there are two ways of deciding on reporting times: push
   mode and pull mode.  In push mode, the exporting process decides
   without an external trigger when to send flow records.  In pull mode,
   sending flow records is triggered by an explicit request from a
   collecting process.  The exporting process must support push mode
   reporting, it may support pull mode reporting.

6.5.  Regular Reporting Interval

   The exporting process should be capable of reporting measured traffic
   data regularly according to a given interval length.

6.6.  Notification on Specific Events

   The exporting process may be capable of sending notifications to a
   collecting process, if a specific event occurs.  Such an event can
   be, for instance, the arrival of the first packet of a new flow, or
   the termination of a flow after flow timeout.

6.7.  Anonymization

   The exporting process may be capable of anonymizing source and
   destination IP addresses in flow data before exporting them.  It may
   support anonymization of port numbers and other fields.  Please note
   that anonymization is not originally an application requirement, but
   derived from general requirements for treatment of measured traffic
   data within a network.

   For several applications anonymization cannot be applied, for example
   for accounting and traffic engineering.  However, for protecting the
   network user's privacy, anonymization should be applied whenever



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   possible.  In many cases it is sufficient if anonymization is
   performed at the collecting process after flow information has been
   exported.  This provides a reasonable protection of privacy as long
   as confidentiality of the export is provided.

   It would be desirable to request that all IPFIX exporters provide
   anonymization of flow records, but algorithms for anonymization are
   still a research issue.  Several are known but the security they
   provide and their other properties are not yet studied sufficiently.
   Also, there is no standardized method for anonymization.  Therefore,
   the requirement for the exporting process supporting anonymization is
   qualified with 'may' and not with 'must'.

   If anonymized flow data is exported, this must be clearly indicated
   to all receiving collecting processes, such that they can distinguish
   anonymized data from non-anonymized data.

7.  Configuration

   If configuration is done remotely, security should be provided for
   the configuration process covering confidentiality, integrity, and
   authenticity.  The means used for remote configuration are out of the
   scope of this document.

7.1.  Configuration of the Metering Process

   The metering process must provide a way of configuring traffic
   measurement.  The following parameters of the metering process should
   be configurable:

         1. specification of the observation point
            e.g., an interface or a list of interfaces to be monitored.
         2. specifications of flows to be metered
         3. flow timeouts

   The following parameters may be configurable:

         4. sampling method and parameters, if feature is supported
         5. overload behavior, if feature is supported

7.2.  Configuration of the Exporting Process

   The exporting process must provide a way of configuring the data
   export.  The following parameters of the exporting process should be
   configurable:

         1. reporting data format
            Specifying the reporting data format must include a



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            selection of attributes to be reported for each flow.
         2. the collecting process(es) to which flows are reported
         3. the reporting interval
            This requirement only applies if the exporting process
            supports reporting in regular intervals.
         4. notifications to be sent to the collecting process(es)
            This requirement only applies if the exporting process
            supports notifications.
         5. flow anonymization
            This requirement only applies if the exporting process
            supports flow anonymization.

8.  General Requirements

8.1.  Openness

   IPFIX specifications should be open to future technologies.  This
   includes extensibility of configuration of the metering process and
   the exporting process.

   Openness is also required concerning the extensibility of the data
   model, as stated in section 6.2.

8.2.  Scalability

   Data collection from hundreds of different exporting processes must
   be supported.  The collecting process must be able to distinguish
   several hundred exporting processes by their identifiers.

8.3.  Several Collecting Processes

   The exporting process may be able to export flow information to more
   than one collecting process.  If an exporting process is able to
   export flow records to multiple collecting processes then it must be
   able to ensure that the flow records can be identified so that
   duplicates can be detected between different collecting processes and
   double counting problems can be avoided.

9.  Special Device Considerations

   This document intends to avoid constraining the architecture of
   probes, routers, and other devices hosting observation points,
   metering processes, exporting processes, and/or collecting processes.
   It can be expected that typically observation point, metering
   process, and exporting process are co-located at a single device.
   However, the requirements defined in this document do not exclude
   devices that derive from this configuration.  Figure 2 shows some
   examples.



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   All examples are composed of one or more of the following elements:
   observation point (O), metering process (M), exporting process (E),
   and collecting process (C).  The observation points shown in the
   figure are always the most fine-granular ones supported by the
   respective device.

         +---+     +-----+     +---------+       +---------+
         | E-+->   |  E--+->   |    E----+->   <-+--E   E--+->
         | | |     |  |  |     |   / \   |       |  |   |  |
         | M |     |  M  |     |  M   M  |       |  M   M  |
         | | |     | /|\ |     | /|\ /|\ |       | /|\ /|\ |
         | O |     | OOO |     | OOO OOO |       | OOO OOO |
         +---+     +-----+     +---------+       +---------+
         Probe      Basic        Complex          Multiple
                    Router       Router           Exporting
                                                  Processes

       +---+     +---+     +---+
       | E-+->   | E-+->   | E-+------------->---+
       | | |     | | |     | | | +---+         +-+-----+
       +-+-+     | M |     | M | | E-+------->-+-C-M-E-+->
         |       | | |     | | | | | | +---+   +-+-----+
       +-+-+     +-+-+     | O | | M | | E-+->---+
       | | |       |       +---+ | | | | | |
       | M |     +-+-+           | O | | M |
       | | |     | | |           +---+ | | |           +-----+
       | O |     | O |                 | O |        ->-+-C-E-+->
       +---+     +---+                 +---+           +-----+

      Protocol   Remote             Concentrator        Proxy
      Converter  Observation

                   Figure 2: IPFIX-related Devices

   A very simple device is a probe.  A typical probe contains a single
   observation point, a single metering process, and a single exporting
   process.

   A basic router extends this structure by multiple observation points.
   Here, the observation point of a particular flow may be one of the
   displayed most fine-granular observation points, but also it may be a
   set of them.

   A more complex router may host more than one metering process, for
   example one per line card.  Please note that here, the observation
   point of a single flow cannot exceed the set of most fine-granular
   observation points linked to a single metering process, because only
   the metering process can merge packets observed at different fine-



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   granular observation points to a joint flow.  An observation point
   containing all most fine-granular observation points of this router
   is not possible with this structure.  Alternatively, a complex router
   may host different exporting processes for flow records generated by
   different metering processes.

   A protocol converter makes use of a metering process that can be
   accessed only by protocol(s) other than the one defined for IPFIX,
   for example, the SNMP and the Meter MIB module [RFC2720].  Then the
   exporting process receives flow records from a remote metering
   process and exports these records using the IPFIX protocol.  Please
   note that this document does not make any particular assumption on
   how metering processes and export processes exchange information, as
   long as all individual requirements for these processes are met.
   Also the locations of metering processes are not of any relevance for
   this document (in contrast to the locations of observation points and
   the exporting processes).

   In the example of remote packet observation in Figure 2 the metering
   process and the observation point are not co-located.  Packet headers
   captured at an observation point may be exported as raw data to a
   device hosting metering process and exporting process.  Again, this
   document does not make any particular assumption on how packet
   headers are transferred from observation points to metering
   processes, as long as all requirements for the metering processes are
   met.

   An intermediate structure between protocol converter and remote
   observation (not shown in the Figure) would be a split metering
   process, for example performing timestamping and sampling at the
   device hosting the observation point and performing packet
   classification at another device hosting the exporting process.

   A concentrator receives flow records via the IPFIX protocol, merges
   them into more aggregated flow records, and exports them again using
   the IPFIX protocol.  Please note that for the final flow records the
   resulting observation point may be a superset of the more fine-
   granular observation points at the first level devices.  The metering
   process of the final flow records is composed by the (partial)
   metering processes at the first level devices and the partial
   metering process at the concentrator.

   Finally, a very simple IPFIX-related device is a proxy.  It just
   receives flow records using the IPFIX protocol and sends them further
   using the same protocol.  A proxy might be useful for traversing
   firewalls or other gateways.





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10.  Security Considerations

   An IPFIX protocol must be capable of transporting data over the
   public Internet.  Therefore it cannot be excluded that an attacker
   captures or modifies packets or inserts additional packets.

   This section describes security requirements for IPFIX.  Like other
   requirements, the security requirements differ among the considered
   applications.  The incentive to modify collected data for accounting
   or intrusion detection for instance is usually higher than the
   incentive to change data collected for traffic profiling.  A detailed
   list of the required security features per application can be found
   in the appendix.

   The suggestion of concrete solutions for achieving the required
   security properties should be part of an IPFIX architecture and
   protocol.  It is out of scope of this document.  Also methods for
   remote configuration of the metering processes and exporting
   processes are out of scope.  Therefore, threats that are caused by
   data exchange for remote configuration are not considered here.

   The following potential security hazards for an IPFIX protocol have
   been identified: disclosure of IP flow information, forgery of flow
   records, and Denial of Service (DoS) attacks.

10.1.  Disclosure of Flow Information Data

   The content of data exchanged by an IPFIX protocol (for example IPFIX
   flow records) should be kept confidential between the involved
   parties (exporting process and collecting process).  Observation of
   IPFIX flow records gives an attacker information about the active
   flows in the network, communication endpoints and traffic patterns.
   This information cannot only be used to spy on user behavior but also
   to plan and conceal future attacks.  Therefore, the requirements
   specified in section 6.3.3. include confidentiality of the
   transferred data.  This can be achieved for instance by encryption.

   Also the privacy of users acting as sender or receiver of the
   measured traffic needs to be protected when they use the Internet.
   In many countries the right to store user-specific data (including
   the user's traffic profiles) is restricted by law or by regulations.

   In addition to encryption, this kind of privacy can also be protected
   by anonymizing flow records.  For many traffic flow measurements,
   anonymized data is as useful as precise data.  Therefore, it is
   desirable to support anonymization in IPFIX implementations.  It is
   beyond the scope of the IPFIX Working Group to develop and




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   standardize anonymization methods.  However, the requirements for
   extensibility of the IPFIX protocol are sufficient to support
   anonymized flow records when appropriate methods are standardized.

10.2.  Forgery of Flow Records

   If flow records are used in accounting and/or security applications,
   there are potentially strong incentives to forge exported IPFIX flow
   records (for example, to save money or prevent the detection of an
   attack).  This can be done either by altering flow records on the
   path or by injecting forged flow records that pretend to be
   originated by the original exporting process.

   Special caution is required if security applications rely on flow
   measurements.  With forged flow records it is possible to trick
   security applications.  For example, an application may be lead to
   falsely conclude that a DoS attack is in progress.  If such an
   injection of IPFIX traffic flow records fools the security
   application, causing it to erroneously conclude that a DoS attack is
   underway, then the countermeasures employed by the security
   application may actually deny useful non-malicious services.

   In order to make an IPFIX protocol resistant against such attacks,
   authentication and integrity must be provided, as specified in
   section 6.3.3.

10.3.  Denial of Service (DoS) Attacks

   DoS attacks on routers or other middleboxes that have the IPFIX
   protocol implemented would also affect the IPFIX protocol and impair
   the sending of IPFIX records.  Nevertheless, since such hazards are
   not induced specifically by the IPFIX protocol the prevention of such
   attacks is out of scope of this document.

   However, IPFIX itself also causes potential hazards for DoS attacks.
   All processes that expect the reception of traffic can be target of a
   DoS attack.  With the exporting process this is only the case if it
   supports the pull mode (which can be an optional feature of the IPFIX
   protocol according to this document).  The collecting process always
   expects data and therefore can be flooded by flow records.











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11.  Acknowledgments

   Many thanks to Georg Carle for contributing to the application
   analysis, to K.C. Norseth for several fine-tunings, to Sandra
   Tartarelli for checking the appendix, and to a lot of people on the
   mailing list for providing valuable comments and suggestions
   including Nevil Brownlee, Carter Bullard, Paul Calato, Ram Gopal, Tal
   Givoly, Jeff Meyer, Reinaldo Penno, Sonia Panchen, Simon Leinen,
   David Plonka, Ganesh Sadasivan, Kevin Zhang, and many more.










































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12.  Appendix: Derivation of Requirements from Applications

   The following table documents, how the requirements stated in
   sections 3-7 are derived from requirements of the applications listed
   in section 2.

   Used abbreviations:
      M = must
      S = should
      O = may (optional)
      - = DONT CARE

-----------------------------------------------------------------------.
   IPFIX                                                               |
----------------------------------------------------------------.      |
E: QoS Monitoring                                               |      |
----------------------------------------------------------.     |      |
D: Attack/Intrusion Detection                             |     |      |
----------------------------------------------------.     |     |      |
C: Traffic Engineering                              |     |     |      |
----------------------------------------------.     |     |     |      |
B: Traffic Profiling                          |     |     |     |      |
----------------------------------------.     |     |     |     |      |
A: Usage-based Accounting               |     |     |     |     |      |
----------------------------------.     |     |     |     |     |      |
                                  |     |     |     |     |     |      |
| Sect. |    Requirement          |  A  |  B  |  C  |  D  |  E  | IPFIX|
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 4.    | DISTINGUISHING FLOWS                                         |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 4.    | Combination of          |  M  |  M  |  M  |  M  |  M  |  M   |
|       | required attributes     |     |     |     |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 4.1.  | in/out IF               |  S  |  M  |  M  |  S  |  S  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 4.2.  | src/dst address         |  M  |  M  |  M  |  M  |  M  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 4.2.  | Masking of IP addresses |  M  |  M  |  M  |  M  |  M  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 4.2.  | transport protocol      |  M  |  M  |  -  |  M  |  M  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 4.2.  | version field           |  -  |  S  |  S  |  O  |  O  |  S   |
|       |                         |     |     | (b) |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|







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|-------+-------------------------+-----+-----+-----+-----+-----+------|
| Sect. |    Requirement          |  A  |  B  |  C  |  D  |  E  | IPFIX|
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 4.3.  | src/dst port            |  M  |  M  |  -  |  M  |  M  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 4.4.  | MPLS label (a)          |  S  |  S  |  M  |  O  |  S  |  M   |
|       |                         |     |     | (c) |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 4.5.  | DSCP (a)                |  M  |  S  |  M  |  O  |  M  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 5.    | METERING PROCESS                                             |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 5.1.  | Reliability             |  M  |  S  |  S  |  S  |  S  |      |
|-------+-------------------------+-----+-----+-----+-----+-----+  M   |
| 5.1.  | Indication of           |  -  |  M  |  M  |  M  |  M  |      |
|       | missing reliability     |     |     |     |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 5.2.  | Sampling (d,e)          |  O  |  O  |  O  |  O  |  O  |  O   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 5.3.  | Overload Behavior (f)   |  O  |  O  |  O  |  O  |  O  |  O   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 5.4.  | Timestamps              |  M  |  O  |  O  |  S  |  M  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 5.5.  | Time synchronization    |  M  |  S  |  S  |  S  |  M  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 5.6.  | Flow timeout            |  M  |  S  |  -  |  O  |  O  |  M   |
|       |                         | (g) |     |     |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 5.7.  | Multicast flows         |  S  |  O  |  O  |  O  |  S  |  S   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 5.8.  | Packet fragmentation    |  O  |  O  |  -  |  -  |  -  |  O   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 5.9.  | Ignore port copy        |  O  |  O  |  O  |  O  |  O  |  O   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.    | DATA EXPORT                                                  |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | INFORMATION MODEL                                            |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | IP Version              |  -  |  M  |  M  |  O  |  O  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | src/dst address         |  M  |  M  |  M  |  M  |  M  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | transport protocol      |  M  |  M  |  -  |  M  |  M  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | src/dst port            |  M  |  M  |  -  |  M  |  M  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | Packet counter (h)      |  S  |  M  |  M  |  S  |  S  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|



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|-------+-------------------------+-----+-----+-----+-----+-----+------|
| Sect. |    Requirement          |  A  |  B  |  C  |  D  |  E  | IPFIX|
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | Byte counter            |  M  |  M  |  M  |  S  |  S  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | ToS (IPv4) or traffic   |  M  |  S  |  M  |  O  |  M  |  M   |
|       | class octet (IPv6)      |     |     |     |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | Flow Label (IPv6)       |  M  |  S  |  M  |  O  |  M  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | MPLS label (a)          |  S  |  S  |  M  |  O  |  S  |  M   |
|       |                         |     |     | (c) |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | Timestamps for          |  M  |  O  |  O  |  S  |  S  |  M   |
|       | first/last packet       |     |     |     |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | Sampling configuration  |  M  |  M  |  M  |  M  |  M  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | observation point       |  M  |  M  |  M  |  M  |  M  |  M   |
|       | identifier              |     |     |     |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | export process          |  M  |  M  |  M  |  M  |  M  |  M   |
|       | identifier              |     |     |     |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | ICMP type and code (i)  |  S  |  S  |  -  |  S  |  S  |  S   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | input/output interface  |  S  |  S  |  S  |  S  |  S  |  S   |
|       | (j)                     |     |     |     |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | Multicast               |  O  |  S  |  S  |  -  |  S  |  S   |
|       | replication factor      |     |     |     |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | TTL                     |  O  |  O  |  O  |  O  |  O  |  O   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | IP header flags         |  -  |  O  |  O  |  O  |  O  |  O   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | TCP header flags        |  -  |  O  |  O  |  O  |  -  |  O   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | Dropped Packet          |  O  |  O  |  O  |  O  |  O  |  O   |
|       | Counter (h,k)           |     |     |     |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | Fragment counter        |  -  |  O  |  O  |  O  |  O  |  O   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | next hop IP address     |  O  |  O  |  O  |  O  |  -  |  O   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.1.  | src / dst / next hop    |  -  |  O  |  O  |  -  |  -  |  O   |
|       | BGP AS #                |     |     |     |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|



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RFC 3917                   IPFIX Requirements               October 2004


|-------+-------------------------+-----+-----+-----+-----+-----+------|
| Sect. |    Requirement          |  A  |  B  |  C  |  D  |  E  | IPFIX|
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.2.  | DATA MODEL                                                   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.2.  | Flexibility             |  M  |  S  |  M  |  M  |  M  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.2.  | Extensibility           |  M  |  S  |  M  |  M  |  M  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.3.  | DATA TRANSFER                                                |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.3.1.| Congestion aware        |  M  |  M  |  M  |  M  |  M  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.3.2.| Reliability             |  M  |  S  |  S  |  S  |  S  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.3.3.| Confidentiality         |  M  |  S  |  S  |  M  |  S  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.3.4.| Integrity               |  M  |  M  |  M  |  M  |  M  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.3.5.| Authenticity            |  M  |  M  |  M  |  M  |  M  |  M   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.4.  | REPORTING TIMES                                              |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.4.  | Push mode               |  M  |  O  |  O  |  M  |  S  |  M   |
|       |                         |     | (l) | (l) |     |(l,m)|      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.4.  | Pull mode               |  O  |  O  |  O  |  O  |  O  |  O   |
|       |                         |     | (l) | (l) |     | (l) |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.4.1.| Regular interval        |  S  |  S  |  S  |  S  |  S  |  S   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.6.  | Notifications           |  O  |  O  |  O  |  O  |  O  |  O   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 6.7.  | Anonymization (n)       |  O  |  O  |  O  |  O  |  O  |  O   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 7.    | CONFIGURATION                                                |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 7.    | Secure remote           |  S  |  S  |  S  |  S  |  S  |  S   |
|       | configuration (a)       |     |     |     |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 7.1.  | Config observation point|  S  |  S  |  S  |  S  |  S  |  S   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 7.1.  | Config flow             |  S  |  S  |  S  |  S  |  S  |  S   |
|       | specifications          |     |     |     |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 7.1.  | Config flow timeouts    |  S  |  S  |  S  |  S  |  O  |  S   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|




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|-------+-------------------------+-----+-----+-----+-----+-----+------|
| Sect. |    Requirement          |  A  |  B  |  C  |  D  |  E  | IPFIX|
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 7.1.  | Config sampling         |  O  |  O  |  O  |  O  |  O  |  O   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 7.1.  | Config overload         |  O  |  O  |  O  |  O  |  O  |  O   |
|       | behavior (a)            |     |     |     |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 7.2.  | Config report           |  S  |  S  |  S  |  S  |  S  |  S   |
|       | data format             |     |     |     |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 7.2.  | Config                  |  S  |  S  |  S  |  S  |  S  |  S   |
|       | notifications           |     |     |     |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 8.    | GENERAL REQUIREMENTS                                         |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 8.1.  | Openness                |  S  |  S  |  S  |  S  |  S  |  S   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 8.2.  | Scalability:            |     |     |     |     |     |      |
|       | data collection         |  M  |  S  |  M  |  O  |  S  |  M   |
|       | from hundreds of        |     |     |     |     |     |      |
|       | measurement devices     |     |     |     |     |     |      |
|-------+-------------------------+-----+-----+-----+-----+-----+------|
| 8.3.  | Several collectors      |  O  |  O  |  O  |  O  |  O  |  O   |
|-------+-------------------------+-----+-----+-----+-----+-----+------|

   Remarks:

      (a) If feature is supported.
      (b) The differentiation of IPv4 and IPv6 is for TE of importance.
          So we tended to make this a must.  Nevertheless, a should
          seems to be sufficient to perform most TE tasks and allows us
          to have a should for IPFIX instead of a must.
      (c) For TE in an MPLS network the label is essential.  Therefore a
          must is given here leading to a must in IPFIX.
      (d) If sampling is supported, the methods and parameters must be
          well defined.
      (e) If sampling is supported, sampling configuration changes must
          be indicated to all collecting processes.
      (f) If overload behavior is supported and it induces changes in
          the metering process behavior, the overload behavior must be
          clearly defined.
      (g) Precise time-based accounting requires reaction to a flow
          timeout.
      (h) If a packet is fragmented, each fragment is counted as an
          individual packet.
      (i) If protocol type is ICMP.




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      (j) This requirement does not apply if the observation point is
          located at a probe device.
      (k) Only if measurement is done on data path i.e., has access to
          forwarding decision.
      (l) Either push or pull has to be supported.
      (m) Required, in order to immediately report drop indications for
          SLA validation.
      (n) Anonymization must be clearly indicated to all receiving
          collecting processes.

13.  References

13.1.  Normative References

   [RFC2960]   Stewart, R., Xie, Q., Morneault, K., Sharp, C.,
               Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M.,
               Zhang, L., and V. Paxson, "Stream Control Transmission
               Protocol", RFC 2960, October 2000.

   [RFC3031]   Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
               Label Switching Architecture", RFC 3031, January 2001.

   [RFC2474]   Nichols, K., Blake, S., Baker, F., and D. Black,
               "Definition of the Differentiated Services Field (DS
               Field) in the IPv4 and IPv6 Headers", RFC 2474, December
               1998.

   [RFC791]    Postel, J., "Internet Protocol", STD 5, RFC 791,
               September 1981.

13.2.  Informative References

   [RFC3234]   Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and
               Issues", RFC 3234, February 2002.

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

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

   [RFC2975]   Aboba, B., Arkko, J., and D. Harrington, "Introduction to
               Accounting Management", RFC 2975, October 2000.

   [RFC2702]   Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J.
               McManus, "Requirements for Traffic Engineering Over
               MPLS", RFC 2702, September 1999.



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RFC 3917                   IPFIX Requirements               October 2004


   [RFC1771]   Rekhter, Y. and T. Li, "A Border Gateway Protocol 4
               (BGP-4)", RFC 1771, March 1995.

   [RFC3418]   Presuhn, R., "Management Information Base (MIB) for the
               Simple Network Management Protocol (SNMP)", STD 62, RFC
               3418, December 2002.

   [RFC2720]   Brownlee, N., "Traffic Flow Measurement: Meter MIB", RFC
               2720, October 1999.

14.  Authors' Addresses

   Juergen Quittek
   NEC Europe Ltd., Network Laboratories
   Kurfuersten-Anlage 36
   69115 Heidelberg
   Germany

   Phone: +49 6221 90511 15
   EMail: quittek@netlab.nec.de

   Tanja Zseby
   Fraunhofer Institute for Open Communication Systems (FOKUS)
   Kaiserin-Augusta-Allee 31
   10589 Berlin
   Germany

   Phone: +49 30 3463 7153
   EMail: zseby@fokus.fhg.de

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

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

   Sebastian Zander
   Centre for Advanced Internet Architectures, Mail H31
   Swinburne University of Technology
   PO Box 218
   John Street, Hawthorn
   Victoria 3122, Australia

   Phone: +61 3 9214 8089
   EMail: szander@swin.edu.au



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15.  Full Copyright Statement

   Copyright (C) The Internet Society (2004).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

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   The IETF invites any interested party to bring to its attention any
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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.







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