IPFIX Working Group E. Boschi
Internet-Draft B. Trammell
Intended status: Experimental Hitachi Europe
Expires: July 16, 2009 January 12, 2009
IP Flow Anonymisation Support
draft-boschi-ipfix-anon-02.txt
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Abstract
This document describes anonymisation techniques for IP flow data and
the export of anonymised data using the IPFIX protocol. It provides
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a categorization of common anonymisation schemes and defines the
parameters needed to describe them. It provides guidelines for the
implementation of anonymised data export and storage over IPFIX, and
describes an Options-based method for anonymization metadata export
within the IPFIX protocol, providing the basis for the definition of
information models for configuring anonymisation techniques within an
IPFIX Metering or Exporting Process, and for reporting the technique
in use to an IPFIX Collecting Process.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. IPFIX Protocol Overview . . . . . . . . . . . . . . . . . 3
1.2. IPFIX Documents Overview . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Categorisation of Anonymisation Techniques . . . . . . . . . . 4
4. Anonymisation of IP Flow Data . . . . . . . . . . . . . . . . 6
4.1. IP Address Anonymisation . . . . . . . . . . . . . . . . . 7
4.1.1. Truncation . . . . . . . . . . . . . . . . . . . . . . 7
4.1.2. Random Permutation . . . . . . . . . . . . . . . . . . 7
4.1.3. Prefix-preserving Pseudonymisation . . . . . . . . . . 7
4.2. Timestamp Anonymisation . . . . . . . . . . . . . . . . . 8
4.2.1. Precision Degradation . . . . . . . . . . . . . . . . 8
4.2.2. Enumeration . . . . . . . . . . . . . . . . . . . . . 8
4.2.3. Random Time Shifts . . . . . . . . . . . . . . . . . . 8
4.3. Counter Anonymisation . . . . . . . . . . . . . . . . . . 8
4.3.1. Precision Degradation . . . . . . . . . . . . . . . . 9
4.3.2. Binning . . . . . . . . . . . . . . . . . . . . . . . 9
4.3.3. Random Noise Addition . . . . . . . . . . . . . . . . 9
4.4. Anonymisation of Other Flow Fields . . . . . . . . . . . . 9
5. Applying Anonymisation Techniques to IPFIX Export and
Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. Arrangement of Processes in IPFIX Anonymisation . . . . . 10
5.2. IPFIX-Specific Anonymisation Guidelines . . . . . . . . . 11
5.2.1. Anonymisation of Header Data . . . . . . . . . . . . . 11
5.2.2. Anonymisation of Options Data . . . . . . . . . . . . 12
6. Parameters for the Description of Anonymisation Techniques . . 13
7. Anonymisation Metadata Support in IPFIX . . . . . . . . . . . 13
8. Security Considerations . . . . . . . . . . . . . . . . . . . 14
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
11.1. Normative References . . . . . . . . . . . . . . . . . . . 14
11.2. Informative References . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
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1. Introduction
The standardisation of an IP flow information export protocol
[RFC5101] and associated representations removes a technical barrier
to the sharing of IP flow data across organizational boundaries and
with network operations, security, and research communities for a
wide variety of purposes. However, with wider dissemination comes
greater risks to the privacy of the users of networks under
measurement, and to the security of those networks. While it is not
a complete solution to the issues posed by distribution of IP flow
information, anonymisation is an important tool for the protection of
privacy within network measurement infrastructures.
This document presents a mechanism for representing anonymised data
within IPFIX and guidelines for using it. It begins with a
categorization of anonymisation techniques. It then describes
applicability of each technique to commonly anonymisable fields of IP
flow data, organized by information element data type and semantics
as in [RFC5102]; enumerates the parameters required by each of the
applicable anonymisation techniques; and provides guidelines for the
use of each of these techniques in accordance with best practices in
data protection. Finally, it specifies a mechanism for exporting
anonymised data and binding anonymisation metadata to templates using
IPFIX Options.
1.1. IPFIX Protocol Overview
In the IPFIX protocol, { type, length, value } tuples are expressed
in templates containing { type, length } pairs, specifying which {
value } fields are present in data records conforming to the
Template, giving great flexibility as to what data is transmitted.
Since Templates are sent very infrequently compared with Data
Records, this results in significant bandwidth savings. Various
different data formats may be transmitted simply by sending new
Templates specifying the { type, length } pairs for the new data
format. See [RFC5101] for more information.
The IPFIX information model [RFC5102] defines a large number of
standard Information Elements which provide the necessary { type }
information for Templates. The use of standard elements enables
interoperability among different vendors' implementations.
Additionally, non-standard enterprise-specific elements may be
defined for private use.
1.2. IPFIX Documents Overview
"Specification of the IPFIX Protocol for the Exchange of IP Traffic
Flow Information" [RFC5101] and its associated documents define the
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IPFIX Protocol, which provides network engineers and administrators
with access to IP traffic flow information.
"Architecture for IP Flow Information Export"
[I-D.ietf-ipfix-architecture] defines the architecture for the export
of measured IP flow information out of an IPFIX Exporting Process to
an IPFIX Collecting Process, and the basic terminology used to
describe the elements of this architecture, per the requirements
defined in "Requirements for IP Flow Information Export" [RFC3917].
The IPFIX Protocol document [RFC5101] then covers the details of the
method for transporting IPFIX Data Records and Templates via a
congestion-aware transport protocol from an IPFIX Exporting Process
to an IPFIX Collecting Process.
"Information Model for IP Flow Information Export" [RFC5102]
describes the Information Elements used by IPFIX, including details
on Information Element naming, numbering, and data type encoding.
Finally, "IPFIX Applicability" [I-D.ietf-ipfix-as] describes the
various applications of the IPFIX protocol and their use of
information exported via IPFIX, and relates the IPFIX architecture to
other measurement architectures and frameworks.
Additionally, the "Specification of the IPFIX File Format"
[I-D.ietf-ipfix-file] describes a file format based upon the IPFIX
Protocol for the storage of flow data.
This document references the Protocol and Architecture documents for
terminology, and extends the IPFIX Information Model to provide new
Information Elements for anonymisation metadata. The anonymisation
techniques described herein are equally applicable to the IPFIX
Protocol and data stored in IPFIX Files.
2. Terminology
Terms used in this document that are defined in the Terminology
section of the IPFIX Protocol [RFC5101] document are to be
interpreted as defined there.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
3. Categorisation of Anonymisation Techniques
Anonymisation modifies a data set in order to protect the identity of
the people or entities described by the data set from disclosure.
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With respect to network traffic data, anonymisation generally
attempts to preserve some set of properties of the network traffic
useful for a given application or applications, while ensuring the
data cannot be traced back to the specific networks, hosts, or users
generating the traffic.
Anonymisation may be broadly classified according to two properties:
recoverability and countability. All anonymisation techniques map
the real space of identifiers or values into a separate, anonymised
space, according to some function. A technique is said to be
recoverable when the function used is invertible or can otherwise be
reversed and a real identifier can be recovered from a given
replacement identifier.
Countability compares the dimension of the anonymised space (N) to
the dimension of the real space (M), and denotes how the count of
unique values is preserved by the anonymisation function. If the
anonymised space is smaller than the real space, then the function is
said to generalise the input, mapping more than one input point to
each anonymous value (e.g., as with aggregation). By definition,
generalisation is not recoverable.
If the dimensions of the anonymised and real spaces are the same,
such that the count of unique values is preserved, then the function
is said to be a direct substitution function. If the dimension of
the anonymised space is larger, such that each real value maps to a
set of anonymised values, then the function is said to be a set
substitution function. Note that with set substitution functions,
the sets of anonymised values are not necessarily disjoint. Either
direct or set substitution functions are said to be one-way if there
exists no method for recovering the real data point from an
anonymised one.
This classification is summarised in the table below.
+------------------------+-----------------+------------------------+
| Recoverability / | Recoverable | Non-recoverable |
| Countability | | |
+------------------------+-----------------+------------------------+
| N < M | N.A. | Generalisation |
| N = M | Direct | One-way Direct |
| | Substitution | Substitution |
| N > M | Set | One-way Set |
| | Substitution | Substitution |
+------------------------+-----------------+------------------------+
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4. Anonymisation of IP Flow Data
Due to the restricted semantics of IP flow data, there are a
relatively limited set of specific anonymisation techniques available
on flow data, though each falls into the broad categories above.
Each type of field that may commonly appear in a flow record may have
its own applicable specific techniques.
While anonymisation is generally applied at the resolution of single
fields within a flow record, attacks against anonymisation use entire
flows and relationships between hosts and flows within a given data
set. Therefore, fields which may not necessarily be identifying by
themselves may be anonymised in order to increase the anonymity of
the data set as a whole.
Of all the fields in an IP flow record, only IP addresses directly
identify entities in the real world. Each IP address is associated
with an interface on a network host, and can potentially be
identified with a single user. Additionally, IP addresses are
structured identifiers; that is, partial IP address prefixes may be
used to identify networks just as full IP addresses identify hosts.
This makes anonymisation of IP addresses particularly important.
Port numbers identify abstract entities (applications) as opposed to
real-world entities, but they can be used to classify hosts and user
behavior. Passive port fingerprinting, both of well-known and
ephemeral ports, can be used to determine the operating system
running on a host. Relative data volumes by port can also be used to
determine the host's function (workstation, web server, etc.); this
information can be used to identify hosts and users.
While not identifiers in and of themselves, timestamps and counters
can reveal the behavior of the hosts and users on a network. Any
given network activity is recognizable by a pattern of relative time
differences and data volumes in the associated sequence of flows,
even without host address information. They can therefore be used to
identify hosts and users. Timestamps and counters are also
vulnerable to traffic injection attacks, where traffic with a known
pattern is injected into a network under measurement, and this
pattern is later identified in the anonymised data set.
The simplest and most extreme form of anonymisation, which can be
applied to any field of a flow record, is black-marker anonymisation,
or complete deletion of a given field. Note that black-marker
anonymisation is equivalent to simply not exporting the field(s) in
question.
While black-marker anonymisation completely protects the data in the
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deleted fields from the risk of disclosure, it also reduces the
utility of the anonymised data set as a whole. Techniques that
retain some information while reducing (though not eliminating) the
disclosure risk will be extensively discussed in the following
sections; note that the techniques specifically applicable to IP
addresses, timestamps, and counters will be discussed in separate
sections.
4.1. IP Address Anonymisation
The following table gives an overview of the schemes for IP address
anonymization described in this document and their categorization.
+-------------------------------+-------------------+---------------+
| Scheme | Action | Reversibility |
+-------------------------------+-------------------+---------------+
| Truncation | Generalisation | N |
| Random Permutation | Direct | Y/N |
| | Substitution | |
| Prefix-preserving | Direct | Y |
| Pseudonymisation | Substitution | |
+-------------------------------+-------------------+---------------+
Note that random permutations might be either reversible or not,
depending on the function used.
4.1.1. Truncation
Truncation removes "n" of the least significant bits from an IP
address. Note that truncating 8 bits would replace an IP address
with the corresponding class C network address.
4.1.2. Random Permutation
Random permutation replaces each IP address with a unique address
randomply selected from the set of possible IP addresses. The
permutation function is implementable using a hash table to ensure
uniqueness.
4.1.3. Prefix-preserving Pseudonymisation
Prefix-preserving pseudonymisation preserves the structure of subnets
at each level while anonymising IP addresses. If two real IP
addresses match on a prefix of "n" bits, the two anonymised IP
addresses will match on a prefix of "n" bits as well.
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4.2. Timestamp Anonymisation
[TODO: introductory text]
+-----------------------+---------------------------+---------------+
| Scheme | Action | Reversibility |
+-----------------------+---------------------------+---------------+
| Precision Degradation | Generalisation | N |
| Enumeration | Direct or Set | Y |
| | Substitution | |
| Random Shifts | Direct Substitution | Y |
+-----------------------+---------------------------+---------------+
4.2.1. Precision Degradation
Precision Degradation removes the most precise components of a
timestamp, accounting all events occurring in each given interval
(e.g. one millisecond for millisecond level degradation) as
simultaneous. This has the effect of potentially collapsing many
timestamps into one. With this technique time precision is reduced,
and sequencing may be lost, but the information at which time the
event occurred is preserved.
4.2.2. Enumeration
Enumeration keeps the chronological order in which events occurred
while eliminating time information. Timestamps are substituted by
equidistant timestamps (or numbers) starting from an randomly chosen
start value.
4.2.3. Random Time Shifts
Random Time Shifts keep the information on how far apart two events
are from each other. This is achieved by shifting all timestamps by
the same random number. Note that random time shifts also preserve
chronological order.
4.3. Counter Anonymisation
Counters (such as packet and octet volumes per flow) are subject to
fingerprinting and injection attacks against anonymisation, as
timestamps are, but relative magnitudes of activity can be useful for
certain analysis tasks. [TODO: more intro text]
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+-----------------------+---------------------------+---------------+
| Scheme | Action | Reversibility |
+-----------------------+---------------------------+---------------+
| Precision Degradation | Generalisation | N |
| Binning | Generalisation | N |
| Random noise addition | Direct or Set | N |
| | Substitution | |
+-----------------------+---------------------------+---------------+
4.3.1. Precision Degradation
As with precision degradation in timestamps, precision degradation of
counters removes lower-order bits of the counters, treating all the
counters in a given range as having the same value. Depending on the
precision reduction, this loses information about the relationships
between sizes of similarly-sized flows, but keeps relative magnitude
information.
4.3.2. Binning
Binning can be seen as a special case of precision degradation; the
operation is identical, except for in precision degradation the
counter ranges are uniform, and in binning they need not be. For
example, a common counter binning scheme for packet counters could be
to bin values 1-2 together, and 3-infinity together, thereby
separating potentially completely-opened TCP connections from
unopened ones. Binning schemes are generally chosen to keep
precisely the amount of information required in a counter for a given
analysis task
4.3.3. Random Noise Addition
Random noise addition adds a random amount to a counter in each flow;
this is used to keep relative magnitude information and minimize the
disruption to size relationship information while avoiding
fingerprinting attacks against anonymization.
4.4. Anonymisation of Other Flow Fields
[TODO: as section 4.1]
5. Applying Anonymisation Techniques to IPFIX Export and Storage
When exporting or storing anonymised flow data using IPFIX, certain
interactions between the IPFIX Protocol and the anonymisation
techniques in use must be considered; these are treated in the
subsections below.
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5.1. Arrangement of Processes in IPFIX Anonymisation
Anonymisation may be applied to IPFIX data at three stages within a
the collection infrastructure: on initial export, at a mediator, or
after collection, as shown in Figure 1. Each of these locations has
specific considerations and applicability.
+--------------------+
| IPFIX File Storage |
+--------------------+
^
| (Anonymised after collection)
|
+=======================================+
| Collecting Process |
+=======================================+
^ ^
| (Anonymised at mediator) |
| |
+=============================+ |
| Mediator | |
+=============================+ |
^ |
| (Anonymised on initial export) |
| |
+=======================================+
| Exporting Process |
+=======================================+
Figure 1: Potential Anonymisation Locations
Anonymisation is generally performed before the wider dissemination
or repurposing of a flow data set, e.g., adapting operational
measurement data for research. Therefore, direct anonymisation of
flow data on initial export is only applicable in certain restricted
circumstances: when the Exporting Process is "publishing" data to a
Collecting Process directly, and the Exporting Process and Collecting
Process are operated by different entities. Note that certain
guidelines in Section 5.2.1 with respect to timestamp anonymisation
may not apply in this case, as the Collecting Process may be able to
deduce certain timing information from the time at which each Message
is received.
A much more flexible arrangement is to anonymise data within a
Mediator [I-D.ietf-ipfix-mediators-framework]. Here, original data
is sent to a Mediator, which performs the anonymisation function and
re-exports the anonymised data. Such a Mediator could be located at
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the administrative domain boundary of the initial Exporting Process
operator, exporting anonymised data to other consumers outside the
organisation. In this case, the original Exporter SHOULD use TLS as
specified in [RFC5101] to secure the channel to the Mediator, and the
Mediator should follow the guidelines in Section 5.2, to mitigate the
risk of original data disclosure.
When data is to be published as an anonymised data set in an IPFIX
File [I-D.ietf-ipfix-file], the anonymisation may be done at the
final Collecting Process before storage and dissemination, as well.
In this case, the Collector should follow the guidelines in
Section 5.2, especially as regards File-specific Options in
Section 5.2.2
Note that anonymisation may occur at more than one location within a
given collection infrastructure, to provide varying levels of
anonymisation reversal risk and utility for specific purposes.
5.2. IPFIX-Specific Anonymisation Guidelines
In implementing and deploying the anonymisation techniques described
in this document, care must be taken that data structures supporting
the operation of the protocol itself do not leak data that could be
used to reverse the anonymisation applied to the flow data. Such
data structures may appear in the header, or within the data stream
itself, especially as options data. Each of these and their impact
on specific anonymisation techniques is noted in a separate
subsection below.
5.2.1. Anonymisation of Header Data
Each IPFIX Message contains a Message Header; within this Message
Header are contained two fields which may be used to break certain
anonymisation techniques: the Export Time, and the Observation Domain
ID
Export of IPFIX Messages containing anonymised timestamp data where
the original Export Time Message header has some relationship to the
anonymised timestamps SHOULD anonymise the Export Time header field
using an equivalent technique, if possible. Otherwise, relationships
between export and flow time could be used to partially or totally
reverse timestamp anonymisation.
The similarity in size between an Observation Domain ID and an IPv4
address (32 bits) may lead to a temptation to use an IPv4 interface
address on the Metering or Exporting Process as the Observation
Domain ID. If this address bears some relation to the IP addresses
in the flow data (e.g., shares a network prefix with internal
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addresses) and the IP addresses in the flow data are anonymised in a
structure-preserving way, then the Observation Domain ID may be used
to break the IP address anonymisation. Use of an IPv4 interface
address on the Metering or Exporting Process as the Observation
Domain ID is NOT RECOMMENDED in this case.
[EDITOR'S NOTE: We might want to see if anyone is actually doing this
with IPFIX. The example comes from other network measurement tools
(e.g. Argus) which default to using an IPv4 address as a sensor ID.]
5.2.2. Anonymisation of Options Data
IPFIX uses the Options mechanism to export, among other things,
metadata about exported flows and the flow collection infrastructure.
As with the IPFIX Message Header, certain Options recommended in
[RFC5101] and the IPFIX File Format [I-D.ietf-ipfix-file] containing
flow timestamps and network addresses of Exporting and Collecting
Processes may be used to break certain anonymisation techniques; care
should be taken while using them with anonymised data export and
storage.
The Exporting Process Reliability Statistics Options Template,
recommended in [RFC5101], contains an Exporting Process ID field,
which may be an exportingProcessIPv4Address Information Element or an
exportingProcessIPv6Address Information Element. If the Exporting
Process address bears some relation to the IP addresses in the flow
data (e.g., shares a network prefix with internal addresses) and the
IP addresses in the flow data are anonymised in a structure-
preserving way, then the Exporting Process address may be used to
break the IP address anonymisation. Exporting Processes exporting
anonymised data in this situation SHOULD mitigate the risk of attack
either by omitting Options described by the Exporting Process
Reliability Statistics Options Template, or by anonymising the
Exporting Process address using a similar technique to that used to
anonymise the IP addresses in the exported data.
Similarly, the Export Session Details Options Template and Message
Details Options Template specified for the IPFIX File Format
[I-D.ietf-ipfix-file] may contain the exportingProcessIPv4Address
Information Element or the exportingProcessIPv6Address Information
Element to identify an Exporting Process from which a flow record was
received, and the collectingProcessIPv4Address Information Element or
the collectingProcessIPv6Address Information Element to identify the
Collecting Process which received it. If the Exporting Process or
Collecting Process address bears some relation to the IP addresses in
the flow data (e.g., shares a network prefix with internal addresses)
and the IP addresses in the flow data are anonymised in a structure-
preserving way, then the Exporting Process or Collecting Process
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address may be used to break the IP address anonymisation. Since
these Options Templates are primarily intended for storing IPFIX
Transport Session data for auditing, replay, and testing purposes, it
is NOT RECOMMENDED that storage of anonymised data include these
Options Templates in order to mitigate the risk of attack.
The Message Details Options Template specified for the IPFIX File
Format [I-D.ietf-ipfix-file] also contains the
collectionTimeMilliseconds Information Element. As with the Export
Time Message Header field, if the exported flow data contains
anonymised timestamp information, and the collectionTimeMilliseconds
Information Element in a given Message has some relationship to the
anonymised timestamp information, then this relationship can be
exploited to reverse the timestamp anonymisation. Since this Options
Template is primarily intended for storing IPFIX Transport Session
data for auditing, replay, and testing purposes, it is NOT
RECOMMENDED that storage of anonymised data include this Options
Template in order to mitigate the risk of attack.
Since the Time Window Options Template specified for the IPFIX File
Format [I-D.ietf-ipfix-file] refers to the timestamps within the flow
data to provide partial table of contents information for an IPFIX
File, care must be taken to ensure that Options described by this
template are written using the anonymised timestamps instead of the
original ones.
6. Parameters for the Description of Anonymisation Techniques
[TODO: see corresponding section of draft-ietf-psamp-sample-tech for
the proposed structure of this section.]
7. Anonymisation Metadata Support in IPFIX
[TODO: Here we'll describe how the information specified above can be
transmitted on the wire using an option template. The idea is to
scope the option to the Template ID and for each field specify which
are anonymised, providing info on the output characteristics of the
technique, and which ones aren't.]
[EDITOR'S NOTE: Multiple anon. techniques applied on an IE at the
same time is indicated with multiple elements of the same type (in
application order as in PSAMP)]
[EDITOR'S NOTE: for blackmarking we'll recommend not to export the
information at all following the data protection law principle that
only necessary information should be exported.]
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8. Security Considerations
[TODO: write this section.]
9. IANA Considerations
This document contains no actions for IANA.
10. Acknowledgments
We thank Paul Aitken for his comments and insight, and the PRISM
project for its support of this work.
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", RFC 5101, January 2008.
[RFC5102] Quittek, J., Bryant, S., Claise, B., Aitken, P., and J.
Meyer, "Information Model for IP Flow Information Export",
RFC 5102, January 2008.
11.2. Informative References
[I-D.ietf-ipfix-as]
Zseby, T., "IPFIX Applicability", draft-ietf-ipfix-as-12
(work in progress), July 2007.
[I-D.ietf-ipfix-architecture]
Sadasivan, G., "Architecture for IP Flow Information
Export", draft-ietf-ipfix-architecture-12 (work in
progress), September 2006.
[I-D.ietf-ipfix-file]
Trammell, B., Boschi, E., Mark, L., Zseby, T., and A.
Wagner, "Specification of the IPFIX File Format",
draft-ietf-ipfix-file-03 (work in progress), October 2008.
[I-D.ietf-ipfix-mediators-framework]
Kobayashi, A., Nishida, H., and B. Claise, "IPFIX
Mediation: Framework",
draft-ietf-ipfix-mediators-framework-01 (work in
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Internet-Draft IP Flow Anonymisation Support January 2009
progress), November 2008.
[RFC3917] Quittek, J., Zseby, T., Claise, B., and S. Zander,
"Requirements for IP Flow Information Export (IPFIX)",
RFC 3917, October 2004.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Authors' Addresses
Elisa Boschi
Hitachi Europe
c/o ETH Zurich
Gloriastrasse 35
8092 Zurich
Switzerland
Phone: +41 44 632 70 57
Email: elisa.boschi@hitachi-eu.com
Brian Trammell
Hitachi Europe
c/o ETH Zurich
Gloriastrasse 35
8092 Zurich
Switzerland
Phone: +41 44 632 70 13
Email: brian.trammell@hitachi-eu.com
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