IPFIX Working Group A. Kobayashi
Internet-Draft NTT PF Lab.
Intended status: Informational B. Claise
Expires: April 19, 2010 Cisco Systems, Inc.
K. Ishibashi
NTT PF Lab.
October 16, 2009
IPFIX Mediation: Framework
draft-ietf-ipfix-mediators-framework-04
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Abstract
This document describes a framework for IPFIX Mediation. This
framework details the IPFIX Mediation reference model and IPFIX
Mediator components.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology and Definitions . . . . . . . . . . . . . . . . . 5
3. IPFIX/PSAMP Documents Overview . . . . . . . . . . . . . . . . 9
3.1. IPFIX Documents Overview . . . . . . . . . . . . . . . . . 9
3.2. PSAMP Documents Overview . . . . . . . . . . . . . . . . . 9
4. IPFIX Mediation Reference Model . . . . . . . . . . . . . . . 10
5. IPFIX Mediation Functional Blocks . . . . . . . . . . . . . . 15
5.1. Collecting Process . . . . . . . . . . . . . . . . . . . . 15
5.2. Exporting Process . . . . . . . . . . . . . . . . . . . . 16
5.3. Intermediate Process . . . . . . . . . . . . . . . . . . . 16
5.3.1. Data Record Expiration . . . . . . . . . . . . . . . . 17
5.3.2. Specific Intermediate Processes . . . . . . . . . . . 18
6. Component Combination . . . . . . . . . . . . . . . . . . . . 23
6.1. Data-based Collector Selection . . . . . . . . . . . . . . 23
6.2. Flow Selection and Aggregation . . . . . . . . . . . . . . 24
6.3. IPFIX File Writer/Reader . . . . . . . . . . . . . . . . . 25
7. Encoding for IPFIX Message Header . . . . . . . . . . . . . . 26
8. Information Model . . . . . . . . . . . . . . . . . . . . . . 27
9. Security Considerations . . . . . . . . . . . . . . . . . . . 28
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 30
11.1. Normative References . . . . . . . . . . . . . . . . . . . 30
11.2. Informative References . . . . . . . . . . . . . . . . . . 30
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33
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1. Introduction
The IPFIX architectural components in [RFC5470] consist of IPFIX
Devices and IPFIX Collectors communicating using the IPFIX protocol.
In case of sustained growth of IP traffic in heterogeneous network
environments, this Exporter-Collector architecture leads to the
following problems: a lack of measurement system scalability,
incompatibility of application requirements in a wide variety of
measurement application, etc. These problems are described in detail
in [IPFIX-MD-PS].
To acihive application requirements with limited system resources,
IPFIX architecture needs to introduce an intermediate device between
Exporters and Collectors. From a data manipulation point of view,
this intermediate device provides the aggregation, correlation,
filtering, and modification of Flow Records and/or PSAMP Packet
Reports to optimize measurement system resources as a pre-process for
the Collector. From a protocol conversion point of view, this
intermediate device provides conversion into IPFIX or conversion of
IPFIX transport protocols (e.g., from UDP to SCTP) to improve the
reliability of the transport protocol.
This document introduces a generalized concept for such intermediate
devices for IPFIX and describes the high-level architecture of IPFIX
Mediation, key IPFIX Mediation architectural components, and
characteristics of IPFIX Mediation.
This document is structured as follows: section 2 describes the
terminology used in this document, section 3 gives an IPFIX/PSAMP
document overview, section 4 describes a high-level reference model,
section 5 describes functional features related to IPFIX Mediation,
section 6 describes combinations of components along with some
application examples, section 7 describes consideration points of the
encoding for IPFIX Message Headers, and section 8 describes the
Information Elements used in an IPFIX Mediator.
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2. Terminology and Definitions
The IPFIX-specific and PSAMP-specific terminology used in this
document is defined in [RFC5101] and [RFC5476], respectively. The
IPFIX Mediation-specific terminology used in this document is defined
in [IPFIX-MD-PS]. However, as reading the problem statements
document is not a prerequisite to reading this framework document,
the definitions have been reproduced here along with additional
definitions. In this document, as in [RFC5101] and [RFC5476], the
first letter of each IPFIX-specific and PSAMP-specific term is
capitalized along with the IPFIX Mediation-specific term defined
here. The use of the terms "must", "should", and "may" in this
document are informational only.
In this document, we use the generic term "record stream" to denote a
set of flow- or packet-based data records with their additional
information that flows from data sources, whether encoded in IPFIX
protocol as IPFIX Data Records, or non-IPFIX protocols. In IPFIX
protocol, we use the generic term Data Records for IPFIX Flow
Records, PSAMP Packet Reports, and Data Records defined by Options
Templates, unless an explicit distinction is required.
Transport Session Information
The Transport Session is specified in [RFC5101]. In SCTP, the
Transport Session Information is the SCTP association. In TCP and
UDP, the Transport Session Information corresponds to a 5-tuple
{Exporter IP address, Collector IP address, Exporter transport
port, Collector transport port, transport protocol}.
Original Exporter
An Original Exporter is an IPFIX Device that hosts the Observation
Points where the metered IP packets are observed.
IPFIX Mediation
IPFIX Mediation is the manipulation and conversion of a record
stream for subsequent export using the IPFIX protocol.
The following terms are used in this document to describe the
architectural entities used by IPFIX Mediation.
Intermediate Process
An Intermediate Process takes a record stream as its input from
Collecting Processes, Metering Processes, IPFIX File Readers,
other Intermediate Processes, or other record sources; performs
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some transformations on this stream, based upon the content of
each record, states maintained across multiple records, or other
data sources; and passes the transformed record stream as its
output to Exporting Processes, IPFIX File Writers, or other
Intermediate Processes, in order to perform IPFIX Mediation.
Typically, an Intermediate Process is hosted by an IPFIX Mediator.
Alternatively, an Intermediate Process may be hosted by an
Original Exporter.
Specific Intermediate Processes are described below. However, this
is not an exhaustive list.
Intermediate Conversion Process
An Intermediate Conversion Process is an Intermediate Process that
transforms non IPFIX into IPFIX, or manages the relation among
Templates and states of incoming/outgoing transport sessions in
the case of transport protocol conversion (e.g., from UDP to
SCTP).
Intermediate Aggregation Process
An Intermediate Aggregation Process is an Intermediate Process
that aggregates records based upon a set of Flow Keys or functions
applied to fields from the record (e.g., binning and subnet
aggregation).
Intermediate Correlation Process
An Intermediate Correlation Process is an Intermediate Process
that adds information to records, noting correlations among them,
or generates new records with correlated data from multiple
records (e.g., the production of bidirectional flow records from
unidirectional flow records).
Intermediate Selection Process
An Intermediate Selection Process is an Intermediate Process that
selects records from a sequence based upon criteria-evaluated
record values and passes only those records that match the
criteria (e.g., filtering only records from a given network to a
given Collector).
Intermediate Anonymization Process
An Intermediate Anonymization Process is an Intermediate Process
that transforms records in order to anonymize them, to protect the
identity of the entities described by the records (e.g., by
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applying prefix-preserving pseudonymization of IP addresses).
IPFIX Mediator
An IPFIX Mediator is an IPFIX Device that provides IPFIX Mediation
by receiving a record stream from some data sources, hosting one
or more Intermediate Processes to transform that stream, and
exporting the transformed record stream into IPFIX Messages via an
Exporting Process. In the common case, an IPFIX Mediator receives
a record stream from a Collecting Process, but it could also
receive a record stream from data sources not encoded using IPFIX,
e.g., in the case of conversion from the NetFlow V9 protocol
[RFC3954] to IPFIX protocol.
Specific types of IPFIX Mediators are defined below.
IPFIX Proxy
An IPFIX Proxy is an IPFIX Mediator that converts a record stream
for the purpose of protocol conversion.
IPFIX Concentrator
An IPFIX Concentrator is an IPFIX Mediator that receives a record
stream from one or more Exporters and performs correlation,
aggregation, and/or modification.
IPFIX Distributor
An IPFIX Distributor is an IPFIX Mediator that receives a record
stream from one or more Exporters and exports each record to one
or more Collectors, deciding to which Collector(s) to export each
record depending on the decision of an Intermediate Process.
IPFIX Masquerading Proxy
An IPFIX Masquerading Proxy is an IPFIX Mediator that receives a
record stream from one or more Exporters to screen out parts of
records according to configured policies in order to protect the
privacy of the network's end users or to retain sensitive data of
the exporting organization.
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The following is a summary table for specific IPFIX Mediator types.
The abbreviation "IP" stands for Intermediate Process.
Table A: IPFIX Mediator Type Summary Table.
+-------------------+------------+---------------------------------+
IPFIX Mediator Number of Intermediate Process Type
Type hosted IPs
+===================+============+=================================+
IPFIX Proxy one or more Intermediate Conversion Process
+-------------------+------------+---------------------------------+
IPFIX Distributor one or more Intermediate Selection Process
+-------------------+------------+---------------------------------+
IPFIX Concentrator one or more Intermediate Aggregation Process
Intermediate Correlation Process
+-------------------+------------+---------------------------------+
IPFIX Masquerading one or more Intermediate Anonymization
Proxy Process
+-------------------+------------+---------------------------------+
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3. IPFIX/PSAMP Documents Overview
3.1. IPFIX Documents Overview
The IPFIX protocol [RFC5101] provides network administrators with
access to IP flow information. The architecture for the export of
measured IP flow information from an IPFIX Exporting Process to a
Collecting Process is defined in [RFC5470], per the requirements
defined in [RFC3917]. The IPFIX protocol [RFC5101] specifies how
IPFIX Data Records and Templates are carried via a number of
transport protocols from IPFIX Exporting Processes to IPFIX
Collecting Processes. IPFIX has a formal description of IPFIX
Information Elements, their names, types, and additional semantic
information, as specified in [RFC5102]. [IPFIX-MIB] specifies the
IPFIX Management Information Base. Finally, [RFC5472] describes what
types of applications can use the IPFIX protocol and how they can use
the information provided. It furthermore shows how the IPFIX
framework relates to other architectures and frameworks. The storage
of IPFIX Messages in a file is specified in [IPFIX-FILE].
3.2. PSAMP Documents Overview
The framework for packet selection and reporting [RFC5474] enables
network elements to select subsets of packets by statistical and
other methods and to export a stream of reports on the selected
packets to a Collector. The set of packet selection techniques
(sampling and filtering) standardized by PSAMP is described in
[RFC5475]. The PSAMP protocol [RFC5476] specifies the export of
packet information from a PSAMP Exporting Process to a Collector.
Like IPFIX, PSAMP has a formal description of its Information
Elements, their names, types, and additional semantic information.
The PSAMP information model is defined in [RFC5477]. [PSAMP-MIB]
describes the PSAMP Management Information Base.
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4. IPFIX Mediation Reference Model
The figure below shows the high-level IPFIX Mediation reference model
based on [RFC5470]. This figure covers the various possible
scenarios that can exist in an IPFIX measurement system.
+----------------+ +---------------+ +---------------+
| Collector 1 | | Collector 2 | | Collector N |
|[Collecting | |[Collecting | |[Collecting |
| Process(es)] | | Process(es)] |... | Process(es)] |
+----^-----------+ +---^--------^--+ +--------^------+
| / \ |
| / \ |
Flow Records Flow Records Flow Records Flow Records
| / \ |
+------+-------------+------+ +------+-----------+--------+
|IPFIX Mediator M | |IPFIX Mediator Z |
|[Exporting Process(es)] | |[Exporting Process(es)] |
|[Intermediate Process(es)] | |[Intermediate Process(es)] |
|[Collecting Process(es)] |... |[Collecting Process(es)] |
+----^----------------^-----+ +------^----------------^---+
| | | |
Flow Records Flow Records Packet Reports record stream
| | | |
+------+------+ +------+-------+ +------+-------+ +-----+-----+
|IPFIX | |IPFIX Original| |PSAMP Original| |Other |
| Mediator 1 | | Exporter 1 | | Exporter 1 | | Source 1 |
|+-------------+ |+--------------+ |+--------------+ |+-----------+
+|IPFIX | +|IPFIX Original| +|PSAMP Original| +|Other |
| Mediator N | | Exporter N | | Exporter N | | Source N |
|[Exporting | |[Exporting | |[Exporting | | |
| Process(es)]| | Process(es)]| | Process(es)]| | |
|[Intermediate| |[Metering | |[Metering | | |
| Process(es)]| | Process(es)]| | Process(es)]| | |
|[Collecting | |[Observation | |[Observation | | |
| Process(es)]| | Point(s)]| | Point(s)]| | |
+------^------+ +-----^-^------+ +-----^-^------+ +-----------+
| | | | |
Flow Records Packets coming Packets coming
into Observation into Observation
Points Points
Figure A: IPFIX Mediation Reference Model Overview.
The functional components within each device are indicated within
brackets []. An IPFIX Mediator receives IPFIX Flow Records or PSAMP
Packet Records from other IPFIX Mediators, IPFIX Flow Records from
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IPFIX Original Exporters, PSAMP Packet Reports from PSAMP Original
Exporters, and/or a record stream from other sources. The IPFIX
Mediator then exports IPFIX Flow Records and/or PSAMP Packet Reports
to multiple Collectors and/or other IPFIX Mediators.
The figure below shows the basic IPFIX Mediator component model.
Basically, an IPFIX Mediator, i.e., an IPFIX Proxy, IPFIX
Masquerading Proxy, IPFIX Distributor, or IPFIX Concentrator, is
composed of these components. An IPFIX Mediator contains one or more
Intermediate Processes and one or more Exporting Processes. In
typical case, it contains a Collecting Process, as described in the
next figure.
IPFIX (Data Records)
^
^ |
+------------------------|-|---------------------+
| IPFIX Mediator | | |
| | | |
| .---------------------|-+-------------------. |
| .----------------------+--------------------.| |
| | Exporting Process(es) |' |
| '----------------------^--------------------' |
| | | |
| .---------------------|-+-------------------. |
| .----------------------+--------------------.| |
| | Intermediate Process(es) |' |
| '----------------------^--------------------' |
| | | |
| .---------------------|-+-------------------. |
| .----------------------+--------------------.| |
| | Collecting Process(es) |' |
| '----------------------^--------------------' |
+------------------------|-|---------------------+
|
IPFIX (Data Records)
Figure B: Basic IPFIX Mediator Component Model.
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However, other data sources are also possible: an IPFIX Mediator,
i.e., IPFIX Proxy, can receive a record stream from non-IPFIX
protocols such as NetFlow [RFC3954] exporter(s). This document does
not make any particular assumption on how a record stream is
transferred to an IPFIX Mediator. The figure below shows the IPFIX
Mediator component model in the case of IPFIX protocol conversion
from non-IPFIX exporters, so receiving a record stream.
IPFIX (Data Records)
^
^ |
+------------------------|-|---------------------+
| IPFIX Mediator | | |
| .---------------------|-+-------------------. |
| .----------------------+--------------------.| |
| | Exporting Process(es) |' |
| '----------------------^--------------------' |
| .---------------------|-+-------------------. |
| .----------------------+--------------------.| |
| | Intermediate Process(es) |' |
| '----------------------^--------------------' |
+------------------------|-----------------------+
| record stream
+------------------------|-----------------------+
| +-------------+----------+ |
|.---------+-----------. .---------+-----------.|
|| Observation point 1 |..| Observation point N ||
|'---------^-----------' '---------^-----------'|
+----------|------------------------|------------+
| |
Packets coming into Observation Points
Figure C: IPFIX Mediator Component Model in IPFIX Protocol
Conversion.
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Alternatively, an Original Exporter may provide IPFIX Mediation by
hosting one or more Intermediate Processes. The component model
(Figure D) is composed by adding Intermediate Process(es) to the
IPFIX Device model illustrated in [RFC5470]. In comparison with
Figure 1 or 2 in [RFC5470], the Intermediate Process is located
between IPFIX Metering Process(es), or PSAMP Metering Process(es) and
Exporting Process(es).
IPFIX (Data Records)
^ ^
+---------------------------|-|------------------------+
| Original Exporter | | |
| | | |
| .---------------------|-+-------------------. |
| .----------------------+--------------------.| |
| | Exporting Process(es) |' |
| '----------------------^--------------------' |
| | | |
| .---------------------|-+-------------------. |
| .----------------------+--------------------.| |
| | Intermediate Process(es) |' |
| '---------^-----------------------^---------' |
| | Data Records | |
| .----------+---------. .---------+----------. |
| | Metering Process 1 |...| Metering Process N | |
| '----------^---------' '---------^----------' |
| | | |
| .-----------+---------. .---------+-----------. |
| | Observation Point 1 |...| Observation Point N | |
| '-----------^---------' '---------^-----------' |
+--------------|-----------------------|---------------+
| |
Packets coming into Observation Points
Figure D: IPFIX Mediation Component Model at Original Exporter.
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In addition, an Intermediate Process may be collocated with an IPFIX
File Reader and/or Writer. The following figure shows an IPFIX
Mediation component model with an IPFIX File Writer and/or Reader.
IPFIX (Data Records)
^
^ |
.----------------------|-+--------------------.
.-----------------------+---------------------.|
| Exporting Process(es) / IPFIX File Writer |'
'-----------------------^---------------------'
| |
.----------------------|-+--------------------.
.-----------------------+---------------------.|
| Intermediate Process(es) |'
'-----------------------^---------------------'
| |
.----------------------|-+--------------------.
.-----------------------+---------------------.|
| Collecting Process(es) / IPFIX File Reader |'
'-----------------------^---------------------'
|
IPFIX (Data Records)
Figure E: IPFIX Mediation Component Model collocated with IPFIX File
Writer/Reader.
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5. IPFIX Mediation Functional Blocks
The following figure shows a functional block diagram of IPFIX
Mediation in an IPFIX Mediator, having different Intermediate Process
types.
IPFIX IPFIX IPFIX
^ ^ ^
| | |
.------------. .-----+-------. .-----+-------. .------+------.
| IPFIX File | | Exporting | | Exporting | | Exporting |
| Writer | | Process 1 | | Process 2 |....| Process N |
'-----^-^----' '-----^-------' '-----^-------' '------^------'
| | | | |
| +-------------+ | |
: Flow Records / Packet Reports :
.------+-------. .-----+--------. .----+---------. |
| Intermediate | | Intermediate | | Intermediate | |
| Anonymization| | Correlation | | Aggregation | |
| Process N | | Process N | | Process N | |
'------|-------' '------|-------' '-----|-|------' |
| +---------------+ | |
: : : :
.------+-------. .------+-------. .-------+------. |
| Intermediate | | Intermediate | | Intermediate | |
| Selection | | Selection | | Selection | |
| Process 1 | | Process 2 | | Process 3 | |
'------|-|-----' '------|-------' '-----|--------' |
| +--------------+ | +----------------+
| | | | |
: Flow Records / Packet Reports :
.------+------. .-------+-----. .-----+-+-----. .-----+------.
| Collecting | | Collecting | | Collecting | | IPFIX File |
| Process 1 | | Process 2 |...| Process N | | Reader |
'------^------' '------^------' '------^------' '------------'
| | |
Flow Records Flow Records Flow Records
Figure F: IPFIX Mediation Functional Block.
5.1. Collecting Process
A Collecting Process in an IPFIX Mediator is not different than the
Collecting Process described in [RFC5101]. Additional functions in
an IPFIX Mediator include transmitting the set of Data Records and
Control Information to one or more components, i.e., Intermediate
Processes and other applications. In other words, a Collecting
Process may duplicate the set and transmit it to one or more
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components in sequence or in parallel. In the case of an IPFIX
Mediator, the Control Information described in [RFC5470] includes
IPFIX Message header information and Transport Session Information
along with information about the Metering Process and the Exporting
Process in an Original Exporter, e.g., sampling parameters.
5.2. Exporting Process
An Exporting Process in an IPFIX Mediator is not different than the
Exporting Process described in [RFC5101]. Additional functions in an
IPFIX Mediator may include the following.
o Receiving the trigger to transmit the Template Withdrawal Messages
from Intermediate Process(es) when relevant Templates become
invalid due to, for example, incoming session failure.
o Transmitting the measured data origins (e.g., Observation Point,
Observation Domain ID, Original Exporter IP address, etc.) by
encoding them to IPFIX. This function must be configurable.
5.3. Intermediate Process
An Intermediate Process is a key functional block for IPFIX
Mediation. Its typical functions include the following:
o Generating a new record stream from an input record stream
including context information (e.g., "Export Time", "Observation
Domain ID", and Transport Session Information), and transmitting
it to other components.
o Reporting statistics and interpretations for IPFIX Metering
Processes, PSAMP Metering Processes, and Exporting Processes from
an Original Exporter. See section 4 of [RFC5101] and section 6 of
[RFC5476] for relevant statistics data structures and
interpretations, respectively. This function must be
configurable.
o Maintaining the configurable relation between Collecting
Process(es)/Metering Process(es) and Exporting Process(es)/other
Intermediate Process(es).
A Collecting Process or Metering Process participating in IPFIX
Mediation is associated with at least one Intermediate Process.
Furthermore, an Intermediate Process is associated with at least
one Exporting Process or another Intermediate Process. This
relation can be configurable.
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o Maintaining database(s) of all the Data Records in the case of an
Intermediate Aggregation Process and an Intermediate Correlation
Process. The function has the Data Record expiration rules
described in the next subsection.
o Maintaining statistics on the Intermediate Process itself, such as
the number of input/output Data Records, etc.
o Maintaining additional information about output record streams,
which includes information related to Original Exporter, and some
configuration parameters related to each function.
In the case of an Intermediate Aggregation Process, Intermediate
Anonymization Process, and Intermediate Correlation Process, the
value of the "flowKeyIndicator" needs to be modified when
modifying the data structure defined by an original Template.
5.3.1. Data Record Expiration
An Intermediate Aggregation Process and Intermediate Correlation
Process need to have expiration conditions to export cached Data
Records. In the case of the Metering Process in an Original
Exporter, these conditions are described in [RFC5470]. In the case
of the Intermediate Process, these conditions are as follows:
o If there are no input Data Records belonging to a cached Flow for
a certain time period, aggregated Flow Records will expire. This
time period should be configurable at the Intermediate Process.
o If the Intermediate Process experiences resource constraints,
aggregated Flow Records may prematurely expire (e.g., lack of
memory to store Flow Records).
o For long-running Flows, the Intermediate Process should cause the
Flow to expire on a regular basis or on the basis of an expiration
policy. This periodicity or expiration policy should be
configurable at the Intermediate Process.
In the case of an Intermediate Correlation Process, a cached Data
Record may be prematurely expired (and discarded) when no correlation
can be computed with newly received Data Records. For example, an
Intermediate Correlation Process computing one way delay may discard
the cached Packet Report when no other matching packet Report are
observed within a certain time period.
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5.3.2. Specific Intermediate Processes
This section shows the functional blocks of specific Intermediate
Processes.
5.3.2.1. Intermediate Conversion Process
When receiving a non IPFIX record stream, the Intermediate Conversion
Process covers the following functions:
o Retrieving the value for each Information Element from each
record, and converting the Information Element IDs (e.g., from
NetFlow V9 protocol [RFC3954] to IPFIX Information Model
[RFC5102]).
o Transforming a record stream into Data Records, (Options) Template
Records, and/or Data Records defined by Options Templates.
o Transforming additional information (e.g., Sampling rate, Sampling
algorithm, and observation information) into Data Records or Data
Records defined by Options Templates.
In the case of IPFIX transport protocol conversion, the Intermediate
Conversion Process covers the following functions.
o Relaying Data Records, (Options) Template Records, and Data
Records defined by Options Templates.
o Setting the trigger for the Exporting Process in order to export
IPFIX Template Withdrawal Messages relevant to the Templates when
Templates becomes invalid due to, for example, incoming session
failure.
o Maintaining the mapping information about Transport Sessions,
Observation Domain IDs, and Template IDs on the incoming/outgoing
sides to confirm the appropriateness of the scope field values in
Data Records defined by Options Templates and of IPFIX Template
Withdrawal Messages.
5.3.2.2. Intermediate Selection Process
An Intermediate Selection Process has analogous functions to the
PSAMP Selection Process described in [RFC5475]. The difference is
that the Intermediate Selection Process takes a record stream, e.g.,
Flow Records or Packet Reports, rather than observed packets.
The typical function is property match filtering that retrieves a
record stream of interest. The function selects a Data Record if the
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value of a specific field in the Data Record equals a configured
value or falls within a configured range.
5.3.2.3. Intermediate Aggregation Process
An Intermediate Aggregation Process covers the following typical
functions:
o Merging a set of Data Records within a certain time period into
one Flow Record by adding up the counters.
o Maintaining statistic and additional information about aggregated
Flow Records.
The statistics for an aggregated Flow Record may include the
number of original Data Records and the maximum and minimum values
of per-flow counters. Additional information may include a
certain time period, a new set of Flow Keys, and observation
location information involved in the Flow aggregation.
Observation location information can be tuples of (Observation
Point, Observation Domain ID, Original Exporter IP address) or
another identifier indicating an area.
o Data Records aggregation, which can be done in the following ways:
* Spatial composition
With spatial composition, Data Records sharing common
properties are merged into one Flow Record within a certain
time period. One typical aggregation can be based on a new set
of Flow Keys. Generally, a shorter set of common properties
than an original set of Flow Keys creates more aggregated Flow
Records. Another aggregation can be based on a set of
Observation Points within an Observation Domain, on a set of
Observation Domains within an Exporter, or on a set of
Exporters.
If some fields do not serve as Flow Keys, the Intermediate
Aggregation Process determines these values by the first
received Data Record, a specific Exporter IP address, or other
arbitrary decision. The Intermediate Aggregation Process
should be consistent in its decision method in an Intermediate
Aggregation Process.
Furthermore, a new identifier indicating a group of observation
locations can be introduced, for example, to indicate an area
on a large network or a link aggregation interface composed of
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physical interfaces, or a set of values of a specified field in
the original Data Records.
* Temporal composition
With temporal composition, Flow Records on one Observation
Point are merged into one Flow Record within a certain time
period. For example, short-period Flow Records, e.g., 1
minute, are merged into a long-period Flow Record, e.g., 30
minutes. In case of a long-running Flow, The temporal
composition provides some advantages:
+ Reducing the number of Flow Records for long-running Flows,
reducing the export bandwidth requirements.
+ Computing the real active time period for long-running Flows
by summing up the short-period Flow Records.
+ Producing more precise maximum and minimum values without
increasing the number of Flow Records on a Collector.
For example, short-period Flow Records created at a Metering
Process by configuring a short active time, e.g., 1 or 10
sec, are merged within a certain time period, e.g., 60 or
300 sec at an Intermediate Aggregation Process. While
merging, new counters, such as the maximum and minimum, can
be created.
When some traffic requires timely traffic monitoring and
other traffic does not, a combination of the Intermediate
Selection Process and Intermediate Aggregation Process is
useful, as described in section 6.
5.3.2.4. Intermediate Anonymization Process
An Intermediate Anonymization Process covers the following typical
functions.
o Deleting specified fields
The function deletes existing fields in accordance with some
instruction rules. Examples include hiding network topology
information and private information. In the case of feeding Data
Records to end customers, disclosing vulnerabilities is avoided by
deleting fields, e.g., "ipNextHopIP{v4|v6}Address",
"bgpNextHopIP{v4|v6}Address", "bgp{Next|Prev}AdjacentAsNumber",
and "mplsLabelStackSection", described in [RFC5102].
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o Anonymizing value of specified fields
The function modifies the value of specified fields. Examples
include anonymizing customers' private information, such as IP
address and port number, in accordance with a privacy protection
policy. The Intermediate Anonymization Process may also report
anonymized fields and the anonymization method as additional
information.
5.3.2.5. Intermediate Correlation Process
An Intermediate Correlation Process can be viewed as a special case
of the Intermediate Aggregation Process, covering the following
typical functions:
o Producing new information including metrics, counters, attributes,
or packet property parameters by evaluating the correlation among
sets of Data Records or among Data Records and other meta data
after gathering sets of Data Records within a certain time period.
o Adding new fields into a Data Record or creating a new Data
Record.
A correlation for Data Records can be done in the following ways.
o One-to-one correlation between Data Records, with the following
examples:
* One-way delay, Packet delay variation in [RFC5481]
The metrics follow from the correlation of the timestamp value
on a pair of Packet Reports indicating an identical packet from
different Exporters.
* Packet inter-arrival time or jitter
The metrics follow from the correlation of the timestamp value
on consecutive Packet Reports from a single Exporter.
* Rate-limiting ratio, compression ratio, optimization ratio,
etc.
The data values follow from the correlation of Data Records
indicating identical a Flow observed on the incoming/outgoing
points of a WAN interface.
o Correlation amongst Data Records, with the following examples:
* Bidirectional Flow composition
The method of exporting and representing a bidirectional flow
(Biflow) is described in [RFC5103]. The bidirectional flow
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composition is a special case of Flow Key aggregation. The
Flow Records are merged into one Flow Record as Biflow, if Non-
directional Key Fields matches and the Directional Key Field
matches their reverse direction counterparts. The direction
assignment method to assign the Biflow Source and Destination
as additional information may be reported. In the case of an
Intermediate Aggregation Process, the direction may be assigned
as "arbitrary".
* Average/maximum/minimum for packets, bytes, one-way delay,
packet loss, etc.
The data values follow from the correlation of multiple Data
Records while the Intermediate Aggregation Process executes.
o Correlation between Data Record and other meta data
Typical examples are derived packet property parameters described
in [RFC5102]. The parameters are retrieved based on the value of
the specified field in an input Data Record, compensating for
traditional exporting devices or probes that are unable to add
packet property parameters. Therefore, Collectors do not need to
recognize the differences among implementations of routers from
several vendors or among Exporter types, such as router, switch,
or probe. Typical derived packet property parameters are as
follows:
* "bgpNextHop{IPv4|IPv6}Address" described in [RFC5102], which
indicates the egress router of a network domain. It is useful
for making a traffic matrix that covers the whole network
domain.
* BGP Communities attribute
This attribute indicates tagging for routes of geographical and
topological information and source types (e.g., transit, peer,
or customer) as described in [RFC4384]. Therefore, network
administrators can monitor the geographically-based or source
type-based traffic volume by correlating the attribute.
* "mplsVpnRouteDistinguisher" described in [RFC5102]
This value indicates the VPN customer's identification, which
cannot be extracted from the core router in MPLS networks.
Therefore, network administrators can monitor the customer-
based traffic volume on even core routers.
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6. Component Combination
An IPFIX Mediator should be able to simultaneously support more than
one Intermediate Process. Each of the Intermediate Processes should
be independent. Multiple Intermediate Processes generally are
configured in the following ways.
o Parallel Intermediate Processes
To feed a record stream to different applications having different
requirements, the Intermediate Processes are located in parallel.
o Serial Intermediate Processes
To execute flexible manipulation of a record stream, the
Intermediate Processes are connected serially. In that case, an
output record stream from one Intermediate Process forms an input
record stream for a succeeding Intermediate Process.
In consideration of resource contention, the series of Intermediate
Processes and associated Exporting Processes has preferably the same
priority value determined based on application requirements.
In addition to the combination of Intermediate Processes, the
combination of some components (Exporting Process, Collecting
Process, IPFIX File Writer and Reader) can be applied to provide
various data reduction techniques. This section shows some
combinations along with examples.
6.1. Data-based Collector Selection
The combination of one or more Intermediate Selection Processes and
Exporting Processes can determine to which Collector input Data
Records are exported. Applicable examples include exporting Data
Records to a dedicated Collector on the basis of customer or
organization. For example, an Intermediate Selection Process selects
Data Records from record stream duplicated in a Collecting Process on
the basis of the peering autonomous system number, and an Exporting
Process sends them to a dedicated Collector, as shown in the
following figure.
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.----------------------. .------------.
| Intermediate | | Exporting |
| Selection Process 1 | | Process 1 |
+--+--- Peering AS #10 ---+-->| +--> Collector 1
| '----------------------' '------------'
| .----------------------. .------------.
record | | Intermediate | | Exporting |
stream | | Selection Process 2 | | Process 2 |
-------+--+--- Peering AS #20 ---+-->| +--> Collector 2
| '----------------------' '------------'
| .----------------------. .------------.
| | Intermediate | | Exporting |
| | Selection Process 3 | | Process 3 |
+--+--- Peering AS #30 ---+-->| +--> Collector 3
'----------------------' '------------'
Figure G: Data-based Collector Selection.
6.2. Flow Selection and Aggregation
The combination of one or more Intermediate Selection Processes and
Intermediate Aggregation Processes can efficiently reduce the amount
of Flow Records. The combination structure is similar to the concept
of the Composite Selector described in [RFC5474]. For example, an
Intermediate Selection Process selects Flows consisting of a small
number of packets and then transmits them to an Intermediate
Aggregation Process. Another Intermediate Selection Process selects
other Flow Records and then transmits them to an Exporting Process,
as shown in the following figure. This results in aggregation on the
basis of the distribution of the number of packets per Flow.
.------------------. .--------------. .------------.
| Intermediate | | Intermediate | | Exporting |
| Selection | | Aggregation | | Process |
| Process 1 | | Process | | |
+-+ packetDeltaCount +->| +->| |
| | <= 5 | | | | |
record | '------------------' '--------------' | |
stream | .------------------. | |
-------+ | Intermediate | | |
| | Selection | | |
| | Process 2 | | |
+-+ packetDeltaCount +------------------->| |
| > 5 | | |
'------------------' '------------'
Figure H: Flow Selection and Aggregation Example.
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6.3. IPFIX File Writer/Reader
The IPFIX File Writer/Reader on an IPFIX Mediator complies with
[IPFIX-FILE]. The IPFIX File Writer stores Data Records in a file
system. When Data Records include problematic Information Elements,
an Intermediate Anonymization Process can delete these fields before
the IPFIX File Writer handles them, as shown in the following figure.
.---------------. .---------------. .-------------.
| Collecting | | Intermediate | | IPFIX |
IPFIX | Process | | Anonymization | | File |
----->| +->| Process +->| Writer |
'---------------' '---------------' '-------------'
Figure I: IPFIX Mediation Example with IPFIX File Writer.
In contrast, the IPFIX File Reader retrieves stored Data Records when
administrators want to retrieve past Data Records from a given time
period. If the data structure of the Data Records from the IPFIX
File Reader is different from what administrators want, an
Intermediate Anonymization Process and Intermediate Correlation
Process can modify the data structure, as shown in the following
figure.
.-------------. .---------------. .---------------. .-----------.
| IPFIX | | Intermediate | | Intermediate | | Exporting |
| File | | Anonymization | | Correlation | | Process |
| Reader +->| Process +->| Process +->| |
'-------------' '---------------' '---------------' '-----------'
Figure J: IPFIX Mediation Example with IPFIX File Reader.
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7. Encoding for IPFIX Message Header
The IPFIX Message Header [RFC5101] includes Export Time, Sequence
Number, and Observation Domain ID fields. This section describes
some consideration points for the IPFIX Message Header encoding.
Export Time
An IPFIX Mediator can set the Export Time in two ways.
* Case 1: keeping the field value of incoming Transport Sessions
* Case 2: setting the time at which an IPFIX Message leaves the
IPFIX Mediator
In case 2, the IPFIX Mediator needs to handle any delta time stamp
fields, such as "flowStartDeltaMicroseconds" and
"flowEndDeltaMicroseconds", described in [RFC5102].
Sequence Number
In the case of an IPFIX Proxy relaying a one-to-one Transport
Session, the IPFIX Proxy needs to handle the Sequence Number value
when the incoming Transport Session shuts down and starts.
Observation Domain ID
An IPFIX Mediator can set the Observation Domain ID independently
of the incoming Observation Domain ID. There are two
consideration points.
* Case 1: relaying an IPFIX Message after replacing each incoming
Observation Domain ID with a new value in the case of an IPFIX
Proxy and an IPFIX Concentrator
* Case 2: aggregating incoming Flow Records in the case of an
IPFIX Concentrator
In case 1, an IPFIX Proxy needs to set the appropriate scope
fields in Data Records defined in Options Template Records when
the incoming Observation Domain IDs are used as the scope fields.
In case 2, according to the description in [RFC5101], an IPFIX
Concentrator needs to set a value of 0 for the Observation Domain
ID. In that case, the IPFIX Concentrator can add a new field to
the Flow Record instead of the Observation Domain ID. The field
indicates the largest set of Observation Points for an aggregated
Flow Record.
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8. Information Model
IPFIX Mediation reuses the general information models from [RFC5102]
and [RFC5477]. However, several Intermediate Processes would
potentially require additional Information Elements as follows:
o Number of original Data Records belonging to output aggregated
Flow Records as described in section 5.3.2.3. Something similar
to the "Flow" Information Element, id 3 in NetFlow version 9
[RFC3954].
o New observation domain information instead of Observation Domain
ID in IPFIX Concentrator as described in section 7.
o Maximum and minimum values for packet count and octet count as
described in the "time composition" paragraph in section 5.3.2.3.
o Some metrics related to network performance, e.g., one-way delay,
packet inter-arrival time, etc., as described in section 5.3.2.5.
o Anonymization method and report on the anonymized fields as
described in section 5.3.2.4.
o Report on the applied treatment items in IPFIX Mediation.
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9. Security Considerations
An IPFIX measurement system must also prevent the security threats
related to IPFIX Mediation that follow as well as the security
threats described in the security consideration section in [RFC5101].
o Attacks against IPFIX Mediators
IPFIX Mediators need to prevent unauthorized access or denial-of-
service (DoS) attacks. One solution is for IPFIX Mediators to
host the packet filter function to reject malicious packets at an
outside interface.
o Man-in-the-middle attacks by untrusted IPFIX Mediators
The Exporter-Mediator-Collector structure model would increase the
risk of man-in-the-middle attacks. One solution is that IPFIX
Collectors and Exporters must verify trusted IPFIX Mediators to
prevent connection to untrusted IPFIX Mediators.
o Configuration of IPFIX Mediation
In the case of IPFIX Distributors and IPFIX Masquerading Proxies,
an accidental misconfiguration and unauthorized access to
configuration data could lead to the crucial problem of disclosure
of confidential traffic data.
To eliminate these risks, IPFIX Mediators must provide the
authentication function for authorized administrators and the
facilities to help in tracing configuration changes to their
origins.
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10. IANA Considerations
This document has no actions for IANA.
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11. References
11.1. Normative References
[RFC5101] Claise, B., "Specification of the IP Flow Information
Export (IPFIX) Protocol for the Exchange of IP Traffic
Flow Information", January 2008.
[RFC5476] Claise, B., Quittek, J., and A. Johnson, "Packet Sampling
(PSAMP) Protocol Specifications", March 2009.
11.2. Informative References
[IPFIX-FILE]
Trammell, B., Boschi, E., Mark, L., Zseby, T., and A.
Wagner, "An IPFIX-Based File Format",
draft-ietf-ipfix-file-05 (work in progress) , August 2009.
[IPFIX-MD-PS]
Kobayashi, A., Claise, B., Nishida, H., Sommer, C.,
Dressler, F., and E. Stephan, "IPFIX Mediation: Problem
Statement",
draft-ietf-ipfix-mediation-problem-statement-05 (work in
progress) , July 2009.
[IPFIX-MIB]
Dietz, T., Claise, B., and A. Kobayashi, "Definitions of
Managed Objects for IP Flow Information Export",
draft-ietf-ipfix-mib-07 (work in progress) , July 2009.
[PSAMP-MIB]
Dietz, T. and B. Claise, "Definitions of Managed Objects
for Packet Sampling", draft-ietf-psamp-mib-06 (work in
progress) , June 2006.
[RFC3917] Quittek, J., Zseby, T., Claise, B., and S. Zander,
"Requirements for IP Flow Information Export (IPFIX)",
October 2004.
[RFC3954] Claise, B., "Cisco Systems NetFlow Services Export Version
9", October 2004.
[RFC4384] Meyer, D., "BGP Communities for Data Collection",
February 2006.
[RFC5102] Quittek, J., Bryant, S., Claise, B., Aitken, P., and J.
Meyer, "Information Model for IP Flow Information Export",
January 2008.
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[RFC5103] Trammell, B. and E. Boschi, "Bidirectional Flow Export
Using IP Flow Information Export (IPFIX)", January 2008.
[RFC5470] Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,
"Architecture for IP Flow Information Export", March 2009.
[RFC5472] Zseby, T., Boschi, E., Brownlee, N., and B. Claise, "IPFIX
Applicability", March 2009.
[RFC5474] Duffield, N., "A Framework for Packet Selection and
Reporting", March 2009.
[RFC5475] Zseby, T., Molina, M., Duffield, N., Niccolini, S., and F.
Raspall, "Sampling and Filtering Techniques for IP Packet
Selection", March 2009.
[RFC5477] Dietz, T., Claise, B., Aitken, P., Dressler, F., and G.
Carle, "Information Model for Packet Sampling Exports",
March 2009.
[RFC5481] Morton, A. and B. Claise, "Packet Delay Variation
Applicability Statement", March 2009.
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Appendix A. Acknowledgements
We would like to thank the following persons: Gerhard Muenz for the
thorough detail review and significant contribution regarding the
improvement of whole sections; Daisuke Matsubara, Tsuyoshi Kondoh,
Hiroshi Kurakami, Haruhiko Nishida for contribution during the
initial phases of the document; Brian Trammel for contribution
regarding the improvement of terminologies section; Nevil Brownlee,
Juergen Quittek for the technical reviews and feedback.
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Authors' Addresses
Atsushi Kobayashi
NTT Information Sharing Platform Laboratories
3-9-11 Midori-cho
Musashino-shi, Tokyo 180-8585
Japan
Phone: +81-422-59-3978
Email: akoba@nttv6.net
Benoit Claise
Cisco Systems, Inc.
De Kleetlaan 6a b1
Diegem 1831
Belgium
Phone: +32 2 704 5622
Email: bclaise@cisco.com
Keisuke Ishibashi
NTT Information Sharing Platform Laboratories
3-9-11 Midori-cho
Musashino-shi 180-8585
Japan
Phone: +81-422-59-3978
Email: ishibashi.keisuke@lab.ntt.co.jp
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