IPFIX Working Group B. Trammell
Internet-Draft CERT/NetSA
Intended status: Standards Track E. Boschi
Expires: August 24, 2008 Hitachi Europe
L. Mark
T. Zseby
Fraunhofer FOKUS
A. Wagner
ETH Zurich
February 21, 2008
An IPFIX-Based File Format
draft-ietf-ipfix-file-01.txt
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Abstract
This document describes a file format for the storage of flow data
based upon the IPFIX Message format. It proposes a set of
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requirements for flat-file, binary flow data file formats, then
applies the IPFIX message format to these requirements to build a new
file format. This IPFIX-based file format is designed to facilitate
interoperability and reusability among a wide variety of flow
storage, processing, and analysis tools.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. IPFIX Documents Overview . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Design Overview . . . . . . . . . . . . . . . . . . . . . . . 5
4. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. Record Format Flexibility . . . . . . . . . . . . . . . . 9
5.2. Self Description . . . . . . . . . . . . . . . . . . . . . 9
5.3. Data Compression . . . . . . . . . . . . . . . . . . . . . 10
5.4. Indexing and Searching . . . . . . . . . . . . . . . . . . 10
5.5. Data Integrity . . . . . . . . . . . . . . . . . . . . . . 11
5.6. Creator Authentication and Confidentiality . . . . . . . . 12
5.7. Anonymization and Obfuscation . . . . . . . . . . . . . . 12
5.8. Session Auditability and Replayability . . . . . . . . . . 13
5.9. Performance Characteristics . . . . . . . . . . . . . . . 13
6. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 13
6.1. Testing IPFIX Collecting Processes . . . . . . . . . . . . 14
6.2. Storage of IPFIX-collected Flow Data . . . . . . . . . . . 14
6.3. Storage of NetFlow V9-collected Flow Data . . . . . . . . 15
7. Detailed Description . . . . . . . . . . . . . . . . . . . . . 15
7.1. Recommended Options Templates for IPFIX Files . . . . . . 18
7.1.1. Message Checksum Options Template . . . . . . . . . . 18
7.1.2. File Time Window Options Template . . . . . . . . . . 19
7.1.3. Export Session Details Options Template . . . . . . . 19
7.1.4. Message Details Options Template . . . . . . . . . . . 21
7.2. Recommended Information Elements for IPFIX Files . . . . . 23
7.2.1. collectionTimeMilliseconds . . . . . . . . . . . . . . 24
7.2.2. maxExportSeconds . . . . . . . . . . . . . . . . . . . 24
7.2.3. maxFlowEndSeconds . . . . . . . . . . . . . . . . . . 24
7.2.4. messageMD5Checksum . . . . . . . . . . . . . . . . . . 25
7.2.5. messageScope . . . . . . . . . . . . . . . . . . . . . 25
7.2.6. minExportSeconds . . . . . . . . . . . . . . . . . . . 26
7.2.7. minFlowStartSeconds . . . . . . . . . . . . . . . . . 26
7.2.8. opaqueOctets . . . . . . . . . . . . . . . . . . . . . 26
7.2.9. sessionScope . . . . . . . . . . . . . . . . . . . . . 27
7.3. Recommended Compression Error Resilience Strategy . . . . 27
7.4. Recommended Encryption Error Resilience Strategy . . . . . 28
7.5. Encapsulation of Non-IPFIX Data . . . . . . . . . . . . . 29
8. Security Considerations . . . . . . . . . . . . . . . . . . . 30
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9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 31
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31
11.1. Normative References . . . . . . . . . . . . . . . . . . . 31
11.2. Informative References . . . . . . . . . . . . . . . . . . 32
Appendix A. Example IPFIX File . . . . . . . . . . . . . . . . . 32
A.1. Example Options Templates . . . . . . . . . . . . . . . . 34
A.2. Example Supplemental Options Data . . . . . . . . . . . . 36
A.3. Example Message Checksum . . . . . . . . . . . . . . . . . 38
A.4. File Example Data Set . . . . . . . . . . . . . . . . . . 39
A.5. Complete File Example . . . . . . . . . . . . . . . . . . 39
Appendix B. Applicability of IPFIX Files to NetFlow V9 flow
storage . . . . . . . . . . . . . . . . . . . . . . . 41
B.1. Comparing NetFlow V9 to IPFIX . . . . . . . . . . . . . . 41
B.1.1. Message Header Format . . . . . . . . . . . . . . . . 41
B.1.2. Set Header Format . . . . . . . . . . . . . . . . . . 42
B.1.3. Template Format . . . . . . . . . . . . . . . . . . . 43
B.1.4. Information Model . . . . . . . . . . . . . . . . . . 43
B.1.5. Template Management . . . . . . . . . . . . . . . . . 43
B.1.6. Transport . . . . . . . . . . . . . . . . . . . . . . 43
B.2. A Method for Transforming NetFlow V9 messages to IPFIX . . 44
B.3. NetFlow V9 Transformation Example . . . . . . . . . . . . 45
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 47
Intellectual Property and Copyright Statements . . . . . . . . . . 49
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1. Introduction
This document proposes a file format based upon IPFIX. It begins
with an overview of the IPFIX File format, as a quick summary of how
IPFIX Files work. It then explores the motivation for proposing a
standardized flow file format and using IPFIX as the basis for this
new file format. Section 4 describes the applicability of this file
format to various specific applications. The document then closes by
specifying the details of new file format, and Section 5 defines a
set of requirements for this file format, and describes either how
the IPFIX Message format meets each requirement, or how a file format
based upon it could meet the requirement. Examples of IPFIX Files
meeting this specification appear in Appendix A This format makes use
of the IPFIX Options mechanism for additional file metadata, in order
to avoid requiring any protocol or message format extensions, and to
minimize the effort required to adapt IPFIX implementations to use
the file format.
1.1. IPFIX Documents Overview
"Specification of the IPFIX Protocol for the Exchange of IP Traffic
Flow Information" [RFC5101] (informally, the IPFIX Protocol document)
and its associated documents define the 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-arch]
(the IPFIX Architecture document) 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]
(informally, the IPFIX Information Model document) 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.
In addition, "Exporting Type Information for IPFIX Information
Elements" [I-D.ietf-ipfix-exporting-type] (informally, the IPFIX
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Exporting Type document) specifies a method for encoding Information
Model properties within an IPFIX Message stream.
This document references the Protocol and Architecture documents for
terminology, defines IPFIX File Writer and IPFIX File Reader in terms
of the IPFIX Exporting Processes and IPFIX Collecting Process
definitions from the Protocol, and extends the IPFIX Information
Model to provide new Information Elements for IPFIX File metadata.
It uses the method described in the IPFIX Exporting Type document to
support the self-description of IPFIX Files containing enterprise-
specific Information Elements.
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.
IPFIX File: An IPFIX File is a serialized stream of IPFIX Messages
stored on a filesystem. Any IPFIX Message stream that would be
considered valid when transported one or more of the specified
IPFIX transports (SCTP, TCP, or UDP) as defined in the IPFIX
Protocol [RFC5101] is considered an IPFIX File for purposes of
this document; however, this document extends that definition with
recommendations on the construction of IPFIX Files that meet the
requirements identified herein.
IPFIX File Reader: An IPFIX File Reader is a Process which reads
IPFIX Files from a filesystem, and is analogous to an IPFIX
Collecting Process. An IPFIX File Reader MUST behave as an IPFIX
Collecting Process as outlined in the IPFIX Protocol [RFC5101],
except as modified by this document.
IPFIX File Writer: An IPFIX File Writer is a process which writes
IPFIX Files to a filesystem, and is analogous to an IPFIX
Exporting Process. An IPFIX File Writer MUST behave as an IPFIX
Exporting Process as outlined in the IPFIX Protocol [RFC5101],
except as modified by this document.
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. Design Overview
An IPFIX File, as defined by this document, is simply a stream
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containing one or more IPFIX Messages serialized to some filesystem.
Though any set of valid IPFIX Messages can be serialized into an
IPFIX File, the specification proposes guidelines designed to ease
storage and retrieval of flow data using the format.
IPFIX Files contain only IPFIX Messages; any file metadata such as
checksums or export session details are stored using Options within
the IPFIX Message. This design has several advantages, including
complete compatibility with the IPFIX Protocol on the wire and free
manipulability of IPFIX Files through concatenation, appending, and
splitting (on IPFIX Message boundaries). A schematic of a typical
file is shown below:
+=======================================+
| IPFIX File |
| +===================================+ |
| | IPFIX Message | |
| | +-------------------------------+ | |
| | | Options Template Set | | |
| | | Options Template Record | | |
| | | . . . | | |
| | +-------------------------------+ | |
| | +-------------------------------+ | |
| | | Template Set | | |
| | | Template Record | | |
| | | . . . | | |
| | +-------------------------------+ | |
| +===================================+ |
| | IPFIX Message | |
| | +-------------------------------+ | |
| | | Data Set | | |
| | | Data Record | | |
| | | . . . | | |
| | +-------------------------------+ | |
| | +-------------------------------+ | |
| | | Data Set | | |
| | | Data Record | | |
| | | . . . | | |
| | +-------------------------------+ | |
| | . . . | |
| +===================================+ |
| . . . |
+=======================================+
Figure 1: Typical File Structure
See Section 7 for details of the implementation of this design,
including specific requirements and guidelines for File Readers and
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File Writers, and Information Elements and Options Templates used for
file metadata.
4. Motivation
There are a wide variety of applications for the file-based storage
of IP flow data, across a continuum of time scales. Tools used in
the analysis of flow data and creation of analysis products often use
files as a convenient unit of work, with an ephemeral lifetime. A
set of flows relevant to a security investigation may be stored in a
file for the duration of that investigation, and further exchanged
among incident handlers via email or within an external incident
handling workflow application. Sets of flow data relevant to
Internet measurement research may be published as files, much as
libpcap packet trace files are, to provide common data sets for the
repeatability of research efforts; these files would have lifetimes
measured in months or years. Operational flow measurement systems
also have a need for long-term, archival storage of flow data, either
as a primary flow data repository, or as a backing tier for online
storage in a relational database management system (RDBMS).
The variety of applications of flow data, and the variety of
presently deployed storage approaches, would seem to indicate the
need for a standard approach to flow storage with applicability
across the continuum of time scales over which flow data is stored.
A storage format based around flat files would best address the
variety of storage requirements. While much work has been done on
structured storage via RDBMS, relational database systems are not a
good basis for format standardization owing to the fact that their
internal data structures are generally private to a single
implementation and subject to change for internal reasons. Also,
there are a wide variety of operations available on flat files, and
external tools and standards can be leveraged to meet file-based flow
storage requirements. Further, flow data is often not very
semantically complicated, and is managed in very high volume;
therefore, an RDBMS-based flow storage system would not benefit much
from the advantages of relational database technology.
The simplest way to create a new file format is simply to serialize
some internal data model to disk, with either textual or binary
representation of data elements, and some framing strategy for
delimiting fields and records. "Ad-hoc" file formats such as this
have several important disadvantages. They impose the semantics of
the data model from which they are derived on the file format, and as
such, they are difficult to extend, describe, and standardize.
Indeed, one de facto standard for the storage of flow data is one of
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these ad-hoc formats. A common method of storing data collected via
Cisco NetFlow V5 or V7 is to serialize a stream of raw NetFlow
datagrams into files. These NetFlow PDU files consist of a
collection of header-prefixed blocks (corresponding to the datagrams
as received on the wire) containing fixed-length binary flow records.
NetFlow V5 and V7 data may be mixed within a given file, as the
header on each datagram defines the NetFlow version of the records
following; there is indeed very little difference between the two
record formats. While this NetFlow PDU file format has all the
disadvantages of an ad-hoc format, and is not extensible to data
models other than that defined by Cisco NetFlow, it is at least
reasonably well-understood due to its ubiquity.
Over the past decade XML markup has emerged as a new "universal"
representation format for structured data. It is intended to be
human-readable; indeed, that is one reason for its rapid adoption.
However XML has limited usefulness for representing network flow
data. Network flow data has a simple, repetitive, non-hierarchical
structure that does not benefit much from XML. An XML representation
of flow data would be an essentially flat list of the attributes and
their values for each flow record.
The XML approach to data encoding is very heavyweight when compared
to binary flow encoding. XML's use of start- and end-tags, and
plain-text encoding of the actual values, leads to significant
inefficiency in encoding size. Typical network flow datasets can
contain millions or billions of flows per hour of traffic
represented. Any increase in storage size per record can have
dramatic impact on flow data storage and transfer sizes. While data
compression algorithms can partially remove the redundancy introduced
by XML encoding, they introduce additional overhead of their own.
A further problem is that XML processing tools require a full XML
parser. XML parsers are fully general and therefore complex,
resource-intensive and relatively slow, introducing significant
processing time overhead for large network-flow datasets. In
contrast, parsers for typical binary flow data encodings are simply
structured, since they only need to parse a very small header and
then have complete knowledge of all following fields for the
particular flow. These can then be read in a very efficient linear
fashion.
This leads us to propose the IPFIX Message format as the basis for a
new flow data file format. The IPFIX working group, in defining the
IPFIX protocol, has already defined an information model and data
formatting rules for representation of flow data. Especially at
shorter time scales, when a file is a unit of data interchange, the
filesystem may be viewed as simply another IPFIX Message transport
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between processes. This format is especially well suited to
representing flow data, as it was designed specifically for flow data
export; it is easily extensible unlike ad-hoc serialization, and
compact unlike XML. In addition, IPFIX is an IETF standard for the
export and collection of flow data; using a common format for storage
and analysis at the collection side allows implementors to use
substantially the same information model and data formatting
implementation for transport as well as storage.
5. Requirements
In this section, we outline a proposed set of requirements
[SAINT2007] for any persistent storage format for flow data. First
and foremost, a flow data file format should support storage across
the continuum of time scales important to flow storage applications.
Each of the requirements enumerated in the sections below is broadly
applicable to flow storage applications, though each may be more
important at certain time scales. For each, we first identify the
requirement, then explain how the IPFIX Message format addresses it,
or briefly outline the changes that must be made in order for an
IPFIX-based file format to meet the requirement.
5.1. Record Format Flexibility
Due to the wide variety of flow attributes collected by different
network flow attribute measurement systems, the ideal flow storage
format will not impose a single data model or a specific record type
on the flows it stores. The file format must be flexible and
extensible; that is, it must support the definition of multiple
record types within the file itself, and must be able to support new
field types for data within the records in a graceful way.
IPFIX provides extensibility through the use of Templates to describe
each Data Record, through the use of an IANA Registry to define its
Information Elements, and through the use of enterprise-specific
Information Elements.
5.2. Self Description
Archived data may be read at a time in the future where any external
reference to the meaning of the data may be lost. The ideal flow
storage format should be self-describing; that is, a process reading
flow data from storage should be able to properly interpret the
stored flows without reference to anything other than standard
sources (e.g., the standards document describing the file format) and
the stored flow data itself.
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The IPFIX Message format is partially self-describing; that is, IPFIX
Templates containing only IANA-assigned Information Elements can be
completely interpreted according to the IPFIX Information Model
without additional external data.
However, Templates containing private information elements lack
detailed type and semantic information; a Collecting Process
receiving data described by a template containing private Information
Elements it does not understand can only treat the data contained
within those Information Elements as octet arrays. To be fully self-
describing, enterprise-specific Information Elements must be
additionally described via IPFIX Options according to the Information
Element Type Options Template defined in "Exporting Type Information
for IPFIX Information Elements" [I-D.ietf-ipfix-exporting-type].
5.3. Data Compression
Regardless of the representation format, flow data describing traffic
on real networks tends to be highly compressible. Compression tends
to improve the scalability of flow collection systems, by reducing
the disk storage and I/O bandwidth requirement for a given workload.
The ideal flow storage format should support applications which wish
to leverage this fact by supporting compression of stored data.
The IPFIX Message format has no support for data compression, as the
IPFIX protocol was designed for speed and simplicity of export. Of
course, any flat file is readily compressible using a wide variety of
external data compression tools, formats, and algorithms; therefore,
this requirement can be met externally.
However, a couple of simple optimizations can be made by File Writers
to increase the integrity and usability of compressed IPFIX data;
these are outlined in Section 7.3.
5.4. Indexing and Searching
Binary, record stream oriented file formats natively support only one
form of searching, sequential scan in file order. By choosing the
order of records in a file carefully (e.g., by flow start or flow end
time), a file can be indexed by a single key.
Beyond this, properly addressing indexing is an application-specific
problem, as it inherently involves tradeoffs between storage
complexity and retrieval speed, and requirements vary widely based on
time scales and the types of queries used from site to site.
However, a generic standard flow storage format may provide limited
direct support for indexing and searching.
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The ideal flow storage format will support a limited table of
contents facility noting that the records in a file contain data
relating only to certain keys or values of keys, in order to keep
multi-file search implementations from having to scan a file for data
it does not contain.
The IPFIX Message format has no direct support for indexing.
However, its template mechanism and the technique described in
"Reducing Redundancy in IPFIX and PSAMP Reports"
[I-D.ietf-ipfix-reducing-redundancy] can be used to describe the
contents of a file in a limited way. Additionally, as flow data is
often sorted and divided by time, the start and end time of the flows
in a file may be declared using the File Time Window Options Template
defined in Section 7.1.2.
5.5. Data Integrity
When storing flow data over long time scales, especially for archival
purposes, it is important to ensure that hardware or software faults
do not introduce errors into the data over time. The ideal flow
storage format will support the detection and correction of encoding-
level errors in the data.
Note that more advanced error correction is almost certainly best
handled at a layer below that addressed by this document. Error
correction is a topic well addressed by the storage industry in
general (e.g. by RAID and other technologies), and by specifying a
flow storage format based upon files, we can leverage these features
to meet this requirement.
However, the ideal flow storage format will be resilient against
errors, providing an internal facility for the detection of errors
and the ability to isolate errors to as few data records as possible.
Note that this requirement interacts with the choice of data
compression or encryption algorithm. The use of block compression
algorithms can serve to isolate errors to a single compression block,
unlike stream compressors, which may fail to resynchronize after a
single bit error, invalidating the entire message stream. Similarly,
the use of a stream cipher can serve to isolate errors in the
plaintext without amplifying them as, for example, a cipher in CBC
mode can. See the "Recommended Compression Error Resilience
Strategy" and "Recommended Encryption Error Resilience Strategy"
sections below for more on this interaction.
The IPFIX Message format does not support data integrity assurance.
It is assumed that advanced error correction will be provided
externally. For simple error detection support, checksums may be
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attached to messages via IPFIX Options according to the Message
Checksum Options Template defined in Section 7.1.1.
5.6. Creator Authentication and Confidentiality
Storage of flow data across long time scales may also require
assurance that no unauthorized entity can read or modify the stored
data. Asymmetric-key cryptography can be applied to this problem, by
signing flow data with the private key of the creator, and encrypting
it with the public keys of those authorized to read it. The ideal
flow storage format will support the encryption and signing of flow
data.
As with error correction, this problem has been addressed well at a
layer below that addressed by this document. Instead of specifying a
particular choice of encryption technology, we can leverage the fact
that existing cryptographic technologies work quite well on data
stored in files to meet this requirement.
Beyond support for the use of TLS for transport over TCP or DTLS for
transport over SCTP or UDP, both of which provide transient
authentication and confidentiality, the IPFIX protocol does not
support this requirement directly. It is assumed that this
requirement will be met externally.
5.7. Anonymization and Obfuscation
To ensure the privacy of individuals and organizations at the
endpoints of communications represented by flow records, it is often
necessary to obfuscate or anonymize stored and exported flow data.
The ideal flow storage format will provide for a notation that a
given information element on a given record type represents
anonymized, rather than real, data.
The IPFIX Message format presently has no support for anonymization
notation. It should be noted that anonymization is one of the
requirements given for IPFIX in RFC 3917 [RFC3917]. The decision to
qualify this requirement with 'MAY' and not 'MUST' in the
requirements document, and its subsequent lack of specification in
the current version of the IPFIX protocol, is due to the fact that
anonymization algorithms are still an open area of research, and that
there currently exist no standardized methods for anonymization.
No support is presently defined in the IPFIX Protocol or this IPFIX-
based File Format for anonymization, as anonymization notation is an
area of open work for the IPFIX working group.
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5.8. Session Auditability and Replayability
Certain use cases for archival flow storage require the storage of
collection infrastructure details alongside the data itself. These
details include information about how and when data was received, and
where it was received from, and are useful for auditing as well as
for the replaying received data for testing purposes.
The IPFIX Message format contains no direct support for auditability
and replayability, though the IPFIX Information Model does define
various Information Elements required to represent collection
infrastructure details. These details may be stored in IPFIX Files
using the Export Session Details Options Template defined in
Section 7.1.3 and the Message Details Options Template defined in
Section 7.1.4.
5.9. Performance Characteristics
The ideal standard flow storage format will not have a significant
negative impact on the performance of the application generating or
processing flow data stored in the format. This is a non-functional
requirement, but it is important to note that a standard that implies
a significant performance penalty is unlikely to be widely
implemented and adopted.
A static analysis of the IPFIX Message format would seem to suggest
that implementations of it are not particularly prone to slowness;
indeed, a template-based data representation is more easily subject
to optimization for common cases than representations that embed
structural information directly in the data stream (e.g. XML).
However, a full analysis of the impact of using IPFIX Messages as a
basis for flow data storage on read/write performance will require
more implementation experience and performance measurement.
6. Applicability
This section describes the specific applicability of IPFIX Files to
various use cases. IPFIX Files are particularly useful in a flow
collection and processing infrastructure using IPFIX for flow export.
We explore the applicability and provide guidelines for using IPFIX
files for the testing of IPFIX Collecting Processes, and the storage
of flow data collected by IPFIX Collecting Processes and NetFlow V9
collectors.
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6.1. Testing IPFIX Collecting Processes
IPFIX Files can be used to store IPFIX Messages for the testing of
IPFIX Collecting Processes. A variety of test cases may be stored in
IPFIX Files. First, IPFIX data sets collected in real network
environments and stored in an IPFIX File can be used as input to
check the behavior of new or extended implementations of IPFIX
Collectors. Furthermore, IPFIX Files could be used to validate the
operation of a given IPFIX Collecting Process in a new environment,
i.e., to test with recorded IPFIX data from the target network before
installing the Collecting Process in the network.
The IPFIX File format can also be used to store artificial, non-
compliant reference messages for specific Collecting Process test
cases. Examples for such test cases are sets of IPFIX records with
undefined Information Elements, Data Records described by missing
Templates, or incorrectly framed messages or data sets.
Representative error handling test cases are defined in "IPFIX
Testing" [I-D.ietf-ipfix-testing].
Furthermore, fast replay of IPFIX records stored in a file can be
used for stress/load tests (e.g., high rate of incoming Data Records,
large Templates with high Information Element counts), as described
in "IPFIX Testing" [I-D.ietf-ipfix-testing]. The provisioning and
use of a set of reference files for testing simplifies the
performance of tests and increases the comparability of test results.
Note that an extremely simple IPFIX Exporting Process may be crafted
for testing purposes by simply reading an IPFIX File and transmitting
it directly to a Collecting Process. Similarly, an extremely simple
Collecting Process may be crafted for testing purposes by simply
accepting connections and/or IPFIX Messages from Exporting Processes
and writing the session's message stream to an IPFIX File.
6.2. Storage of IPFIX-collected Flow Data
IPFIX Files can also, naturally, be used to store flow data collected
by an IPFIX Collecting Process; indeed, this was one of the primary
initial motivations behind the file format described within this
document. Using IPFIX Files as such allows IPFIX implementations to
leverage substantially the same code for flow export and flow
storage. In addition, the storage of single Transport Sessions in
IPFIX Files is particularly important for network measurement
research, allowing repeatability of experiments by providing a format
for the storage and exchange of IPFIX flow trace data much as the
libpcap format is used for experiments on packet trace data.
As noted in the section above, the simplest way for a Collecting
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Process to store the data collected in a single Transport Session is
to simply write the incoming IPFIX Messages to a file as they are
read. However, while the resulting files are valid IPFIX Files, they
are lacking information about the IPFIX Transport Session used to
export them, such as the network addresses of the Exporting and
Collecting Processes and the protocols used to transport them. An
IPFIX File Writer MAY store a single IPFIX Transport Session in an
IPFIX File and record information about the Transport Session using
the Export Session Details Options Template described above.
Additional per-Message information MAY be recorded by the File Writer
using the Message Details Options Template described above. Per-
message information includes the time at which each IPFIX Message was
received at the Collecting Process, and can be used to resend IPFIX
Messages while keeping the original measurement plane traffic
profile. This Options Template also allows the storage of the export
session metainformation provided the Export Session Details Options
Template, for storing information from multiple Transport Sessions in
the same IPFIX File.
6.3. Storage of NetFlow V9-collected Flow Data
Although the IPFIX protocol is based on the Cisco Netflow Services,
Version 9 (NetFlow V9) protocol [RFC3954], the two have diverged
since work began on IPFIX. However, since the NetFlow V9 information
model is a compatible subset of the IPFIX information model, it is
possible to use IPFIX files to store collected NetFlow V9 flow data.
This approach may be particularly useful in multi-vendor, multi-
protocol collection infrastructures using both NetFlow V9 and IPFIX
to export flow data.
The applicability of IPFIX Files to this use case is outlined in
Appendix B.
7. Detailed Description
An IPFIX File, as introduced in Section 3 and elaborated below, is at
its core simply an IPFIX Message stream serialized to some
filesystem. Any valid serialized IPFIX Message stream MUST be
accepted by a File Reader as a valid IPFIX file. In this way, the
filesystem is simply treated as another IPFIX Transport alongside
SCTP, TCP, and UDP. In contrast to normal IPFIX operation, the time
between a File Writer writing an IPFIX Message stream to a File and a
File Reader reading it can be extremely variable. In other words,
this notional file transport has unusually high latency, as the File
Reader and File Writer do not necessarily run at the same time.
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An IPFIX File Reader MUST accept as valid any IPFIX Message stream
that would be considered valid by one or more of the other defined
IPFIX transport layers. Practically, this means that the union of
template management features supported by SCTP, TCP, and UDP MUST be
supported in IPFIX Files. The following requirements apply to IPFIX
File Readers:
o File Readers MUST accept IPFIX Messages containing Template Sets,
Options Template Sets, and Data Sets within the same message, as
with IPFIX over TCP or UDP.
o File Readers MUST accept Template Sets that define templates
already defined within the file, as may occur with template
retransmission when using IPFIX over UDP as described in section
10.3.6 of the IPFIX Protocol document [RFC5101]. In the event of
a conflict between a resent definition and a previous definition,
the File Reader MUST assume that the new template replaces the
old, as consistent with UDP template expiration and ID reuse.
o File Readers MUST accept Template Withdrawals as described in
section 8 of the IPFIX Protocol document [RFC5101], provided that
the Template to be withdrawn is defined, as is the case with IPFIX
over TCP and SCTP.
However, for representation simplicity and read performance, File
Writers may choose to use the following template and scope management
strategy:
o File Writers SHOULD emit each Template Set or Options Template Set
before any Data Set described by the Templates within that Set, to
ensure the File Reader can decode every Data Set without waiting
to process subsequent Templates or Options Templates.
o If possible, File Writers MAY emit all Template Sets and Options
Template Sets to appear at the beginning of the file, before any
Data Sets, to ensure all Templates are available and can be
inspected before any data is read.
o File Writers SHOULD emit special Data Records described by Options
Templates at the beginning of the file after Template Sets and
Options Template Sets as above, but before any other Data Records,
in the following order:
* Time Window records described by the File Time Window Options
Template as defined in Section 7.1.2 below; followed by
* commonPropertiesId definitions as described in "Reducing
Redundancy in IPFIX and PSAMP Reports"
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[I-D.ietf-ipfix-reducing-redundancy]; followed by
* Information Element Type Records as described in "Exporting
Type Information for IPFIX Information Elements"
[I-D.ietf-ipfix-exporting-type]; followed by
* Export Session details records described by the Export Session
Details Options Template as defined in Section 7.1.3 below.
o File Writers SHOULD emit Data Records described by Options
Templates to appear in the file before any Data Records which
depend on the scopes defined by those options.
o File Writers SHOULD use Template Withdrawals to withdraw Templates
if template IDs need to be reused. In this case, the new
Templates reusing those IDs SHOULD appear directly in the file
after the Template Withdrawals making the IDs available for reuse.
Template Withdrawals SHOULD NOT be used unless necessary to reuse
template IDs.
Note that Message Checksum records described by the Message Checksum
Options Template as defined in Section 7.1.1 below and Message Detail
records described by the Message Details Options Template as defined
in Section 7.1.4 below MAY appear anywhere in an IPFIX Message.
Each IPFIX File is generally synonymous with a single Transport
Session. File Writers SHOULD store the Templates and Options
required to decode the data within the File in the File itself, and
File Readers SHOULD NOT use Templates or Options defined in one file
to decode or interpret Data Sets in another.
However, some applications, particularly those storing large
collections of data over long periods of time, may benefit from the
ability to treat a collection of IPFIX Files as a single Transport
Session. A File Reader MAY be configurable to treat a collection of
Files (e.g., all the files in a directory) as a single Transport
Session. However, a File Reader MUST NOT treat a single IPFIX File
as containing multiple Transport Sessions.
File Writers SHOULD write IPFIX Messages within an IPFIX File in
ascending Export Time order. If a File Writer is writing data
collected from an IPFIX Collecting Process, the Export Time SHOULD be
the export time as reported by the remote IPFIX Exporting Process;
otherwise, the Export Time SHOULD be the time at which the message
was written to the file.
Note that File Writers storing IPFIX data collected from an IPFIX
Collecting Process using SCTP as the transport protocol SHOULD
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interleave messages from multiple streams in order to preserve Export
Time order, and SHOULD reorder the written messages as necessary to
ensure that each Template Set or Options Template Set appears in the
file before any Data Set described by the Templates within that Set.
File Writers MAY write records to an IPFIX File in any order.
However, File Writers that write flow records to an IPFIX File in
flowStartTime or flowEndTime order SHOULD be consistent in this
ordering within each File.
If an IPFIX File uses the technique described in "Reducing Redundancy
in IPFIX and PSAMP Reports" [I-D.ietf-ipfix-reducing-redundancy] AND
all of the non-Options Templates in the File contain the
commonPropertiesId Information Element, a File Reader MAY assume the
set of commonPropertiesId definitions provides a complete table of
contents for the File for searching purposes.
7.1. Recommended Options Templates for IPFIX Files
The following Options Templates allow IPFIX Message streams to meet
the requirements outlined above without extension to the message
format or protocol. They are defined in terms of existing
Information Elements defined in the IPFIX Information Model
[RFC5102], the Information Elements defined in "Exporting Type
Information for IPFIX Information Elements"
[I-D.ietf-ipfix-exporting-type], as well as Information Elements
defined in Section 7.2. IPFIX File Readers and Writers SHOULD
support these options templates as defined below.
In addition, IPFIX File Readers and Writers SHOULD support the
Options Templates defined in "Exporting Type Information for IPFIX
Information Elements" [I-D.ietf-ipfix-exporting-type] in order to
support self-description of enterprise-specific Information Elements.
7.1.1. Message Checksum Options Template
The Message Checksum Options Template specifies the structure of a
Data Record for attaching an MD5 message checksum to an IPFIX
Message. An MD5 message checksum as described MAY be used if long-
term data integrity is important to the application. The described
Data Record MUST appear only once per IPFIX Message.
The template SHOULD contain the following Information Elements:
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+--------------------+----------------------------------------------+
| IE | Description |
+--------------------+----------------------------------------------+
| messageScope | A marker denoting this Option applies to the |
| [scope] | whole IPFIX Message; content is ignored. |
| | This Information Element MUST be defined as |
| | a Scope Field. |
| messageMD5Checksum | The MD5 checksum of the containing IPFIX |
| | Message. |
+--------------------+----------------------------------------------+
7.1.2. File Time Window Options Template
The File Time Window Options Template specifies the structure of a
Data Record for attaching a time window to an IPFIX File; this Data
Record is referred to as a time window record. A time window record
defines the earliest flow start time and the latest flow end time of
the flow records within a File. One and only one time window record
MAY appear within an IPFIX File if the time window information is
available; a File Writer MUST NOT write more than one time window
record to an IPFIX File. A File Writer that writes a time window
record to a File MUST NOT write any Flow with a start time before the
beginning of the window or an end time after the end of the window to
that File.
The template SHOULD contain the following Information Elements:
+---------------------+---------------------------------------------+
| IE | Description |
+---------------------+---------------------------------------------+
| sessionScope | A marker denoting this Option applies to |
| [scope] | the whole IPFIX Transport Session (i.e., |
| | IPFIX File); content is ignored. This |
| | Information Element MUST be defined as a |
| | Scope Field. |
| minFlowStartSeconds | The start time of the earliest flow in the |
| | Transport Session (i.e., File) in epoch |
| | seconds. |
| maxFlowEndSeconds | The end time of the latest flow in the |
| | Transport Session (i.e., File) in epoch |
| | seconds. |
+---------------------+---------------------------------------------+
7.1.3. Export Session Details Options Template
The Export Session Details Options Template specifies the structure
of a Data Record for recording the details of an IPFIX Transport
Session in an IPFIX File. It is intended for use in storing a single
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complete IPFIX Transport Session in a single IPFIX File. The
described Data Record SHOULD appear only once in a given IPFIX File.
The template SHOULD contain the following Information Elements,
subject to applicability as noted on each Information Element:
+----------------------------+--------------------------------------+
| IE | Description |
+----------------------------+--------------------------------------+
| sessionScope [scope] | A marker denoting this Option |
| | applies to the whole IPFIX Transport |
| | Session (i.e., IPFIX File); content |
| | is ignored. This Information |
| | Element MUST be defined as a Scope |
| | Field. |
| exporterIPv4Address | IPv4 address of the IPFIX Exporting |
| | Process from which the Messages in |
| | this Transport Session were |
| | received. Present only for |
| | Exporting Processes with an IPv4 |
| | interface. For multi-homed SCTP |
| | associations, this SHOULD be the |
| | primary path endpoint address of the |
| | Exporting Process. |
| exporterIPv6Address | IPv6 address of the IPFIX Exporting |
| | Process from which the Messages in |
| | this Transport Session were |
| | received. Present only for |
| | Exporting Processes with an IPv6 |
| | interface. For multi-homed SCTP |
| | associations, this SHOULD be the |
| | primary path endpoint address of the |
| | Exporting Process. |
| exporterTransportPort | The source port from which the |
| | Messages in this Transport Session |
| | were received. |
| collectorIPv4Address | IPv4 address of the IPFIX Collecting |
| | Process which received the Messages |
| | in this Transport Session. Present |
| | only for Collecting Processes with |
| | an IPv4 interface. For multi-homed |
| | SCTP associations, this SHOULD be |
| | the primary path endpoint address of |
| | the Collecting Process. |
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| collectorIPv6Address | IPv6 address of the IPFIX Collecting |
| | Process which received the Messages |
| | in this Transport Session. Present |
| | only for Collecting Processes with |
| | an IPv6 interface. For multi-homed |
| | SCTP associations, this SHOULD be |
| | the primary path endpoint address of |
| | the Collecting Process. |
| collectorTransportPort | The destination port on which the |
| | Messages in this Transport Session |
| | were received. |
| collectorTransportProtocol | The IP Protocol Identifier of the |
| | transport protocol used to transport |
| | Messages within this Transport |
| | Session. |
| collectorProtocolVersion | The version of the IPFIX Protocol |
| | used to transport Messages within |
| | this Transport Session. |
| minExportSeconds | The Export Time of the first Message |
| | in the Transport Session. |
| maxExportSeconds | The Export Time of the last Message |
| | in the Transport Session. |
+----------------------------+--------------------------------------+
7.1.4. Message Details Options Template
The Message Details Options Template specifies the structure of a
Data Record for attaching additional export details to an IPFIX
Message. These details include the time at which a message was
received and information about the export and collection
infrastructure used to transport the Message.
The template SHOULD contain the following Information Elements,
subject to applicability as noted for each Information Element. Note
that when used in conjunction with the Export Session Details Options
Template, when storing a single complete IPFIX Transport Session in
an IPFIX File, this template SHOULD contain only the messageScope and
collectionTimeMilliseconds Information Elements.
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+----------------------------+--------------------------------------+
| IE | Description |
+----------------------------+--------------------------------------+
| messageScope [scope] | A marker denoting this Option |
| | applies to the whole IPFIX message; |
| | content is ignored. This |
| | Information Element MUST be defined |
| | as a Scope Field. |
| collectionTimeMilliseconds | The absolute time at which this |
| | Message was received by the IPFIX |
| | Collecting Process. |
| exporterIPv4Address | IPv4 address of the IPFIX Exporting |
| | Process from which the Messages in |
| | this Transport Session were |
| | received. Present only for |
| | Exporting Processes with an IPv4 |
| | interface, and if this information |
| | is not available via the Export |
| | Session Details Options Template. |
| | For multi-homed SCTP associations, |
| | this SHOULD be the primary path |
| | endpoint address of the Exporting |
| | Process. |
| exporterIPv6Address | IPv6 address of the IPFIX Exporting |
| | Process from which the Messages in |
| | this Transport Session were |
| | received. Present only for |
| | Exporting Processes with an IPv6 |
| | interface, and if this information |
| | is not available via the Export |
| | Session Details Options Template. |
| | For multi-homed SCTP associations, |
| | this SHOULD be the primary path |
| | endpoint address of the Exporting |
| | Process. |
| exporterTransportPort | The source port from which the |
| | Messages in this Transport Session |
| | were received. Present only if this |
| | information is not available via the |
| | Export Session Details Options |
| | Template. |
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| collectorIPv4Address | IPv4 address of the IPFIX Collecting |
| | Process which received the Messages |
| | in this Transport Session. Present |
| | only for Collecting Processes with |
| | an IPv4 interface, and if this |
| | information is not available via the |
| | Export Session Details Options |
| | Template. For multi-homed SCTP |
| | associations, this SHOULD be the |
| | primary path endpoint address of the |
| | Collecting Process. |
| collectorIPv6Address | IPv6 address of the IPFIX Collecting |
| | Process which received the Messages |
| | in this Transport Session. Present |
| | only for Collecting Processes with |
| | an IPv6 interface, and if this |
| | information is not available via the |
| | Export Session Details Options |
| | Template. For multi-homed SCTP |
| | associations, this SHOULD be the |
| | primary path endpoint address of the |
| | Collecting Process. |
| collectorTransportPort | The destination port on which the |
| | Messages in this Transport Session |
| | were received. Present only if this |
| | information is not available via the |
| | Export Session Details Options |
| | Template. |
| collectorTransportProtocol | The IP Protocol Identifier of the |
| | transport protocol used to transport |
| | Messages within this Transport |
| | Session. Present only if this |
| | information is not available via the |
| | Export Session Details Options |
| | Template. |
| collectorProtocolVersion | The version of the IPFIX Protocol |
| | used to transport Messages within |
| | this Transport Session. Present |
| | only if this information is not |
| | available via the Export Session |
| | Details Options Template. |
+----------------------------+--------------------------------------+
7.2. Recommended Information Elements for IPFIX Files
The following Information Elements are used by the options templates
in Section 7.1 to allow IPFIX Message streams to meet the
requirements outlined above without extension of the message format
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or protocol. IPFIX File Readers and Writers SHOULD support these
Information Elements as defined below.
In addition, IPFIX File Readers and Writers SHOULD support the
Information Elements defined in "Exporting Type Information for IPFIX
Information Elements" [I-D.ietf-ipfix-exporting-type] in order to
support full self-description of Information Elements.
7.2.1. collectionTimeMilliseconds
Description: The absolute timestamp at which the data within the
scope containing this Information Element was received by a
Collecting Process. This Information Element SHOULD be bound to
its containing IPFIX Message via an options record and the
messageScope Information Element, as defined below.
Abstract Data Type: dateTimeMilliseconds
ElementId: TBD1
Status: Proposed
7.2.2. maxExportSeconds
Description: The absolute Export Time of the latest IPFIX Message
within the scope containing this Information Element. This
Information Element SHOULD be bound to its containing IPFIX
Transport Session (i.e., File) via an options record and the
sessionScope Information Element, as defined below, and SHOULD
appear only once in a given IPFIX File.
Abstract Data Type: dateTimeSeconds
ElementId: TBD3
Status: Proposed
Units: seconds
7.2.3. maxFlowEndSeconds
Description: The latest absolute timestamp of the last packet
within any Flow within the scope containing this Information
Element, rounded up to the second. This Information Element
SHOULD be bound to its containing IPFIX Transport Session (i.e.,
File) via an options record and the sessionScope Information
Element, as defined below, and SHOULD appear only once in a given
IPFIX File.
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Abstract Data Type: dateTimeSeconds
ElementId: TBD4
Status: Proposed
Units: seconds
7.2.4. messageMD5Checksum
Description: The MD5 checksum of the IPFIX Message containing this
record. This Information Element SHOULD be bound to its
containing IPFIX Message via an options record and the
messageScope Information Element, as defined below, and SHOULD
appear only once in a given IPFIX Message. To calculate the value
of this Information Element, first buffer the containing IPFIX
Message, setting the value of this Information Element to all
zeroes. Then caluclate the MD5 checksum of the resulting buffer
as defined in RFC 1321 [RFC1321], place the resulting value in
this Information Element, and export the buffered message.
Abstract Data Type: octetArray (16 bytes)
ElementId: TBD5
Status: Proposed
Reference: RFC 1321, The MD5 Message-Digest Algorithm [RFC1321]
7.2.5. messageScope
Description: The presence of this Information Element as scope in
an Options Template signifies that the options described by the
Template apply to the IPFIX Message that contains them. It is
defined for general purpose message scoping of options, and
proposed specifically to allow the attachment a checksum to a
message via IPFIX Options. The value of this Information Element
MUST be written as 0 by the File Writer or Exporting Process. The
value of this Information Element MUST be ignored by the File
Reader or the Collecting Process.
Abstract Data Type: octet
ElementId: TBD6
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Status: Proposed
7.2.6. minExportSeconds
Description: The absolute Export Time of the earliest IPFIX Message
within the scope containing this Information Element. This
Information Element SHOULD be bound to its containing IPFIX
Transport Session (i.e., File) via an options record and the
sessionScope Information Element, as defined below, and SHOULD
appear only once in a given IPFIX File.
Abstract Data Type: dateTimeSeconds
ElementId: TBD7
Status: Proposed
Units: seconds
7.2.7. minFlowStartSeconds
Description: The earliest absolute timestamp of the first packet
within any Flow within the scope containing this Information
Element, rounded down to the second. This Information Element
SHOULD be bound to its containing IPFIX Transport Session (i.e.,
File) via an options record and the sessionScope Information
Element, as defined below, and SHOULD appear only once in a given
IPFIX File.
Abstract Data Type: dateTimeSeconds
ElementId: TBD8
Status: Proposed
Units: seconds
7.2.8. opaqueOctets
Description: This Information Element is used to encapsulate non-
IPFIX data into an IPFIX Message stream, for the purpose of
allowing a non-IPFIX data processor to store a data stream inline
within an IPFIX file. A Collecting Process or File Writer MUST
NOT try to interpret this binary data. This Information Element
differs from paddingOctets as its contents are meaningful in some
non-IPFIX context, while the contents of paddingOctets MUST be
0x00 and are intended only for Information Element alignment.
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Abstract Data Type: octet
ElementId: TBD9
Status: Proposed
7.2.9. sessionScope
Description: The presence of this Information Element as scope in
an Options Template signifies that the options described by the
Template apply to the IPFIX Transport Session that contains them.
Note that as all options are implicitly scoped to Transport
Session and Observation Domain, this Information Element is
equivalent to a "null" scope. It is defined for general purpose
session scoping of options, and proposed specifically to allow the
attachment of time window to a file via IPFIX Options. The value
of this Information Element MUST be written as 0 by the File
Writer or Exporting Process. The value of this Information
Element MUST be ignored by the File Reader or the Collecting
Process.
Abstract Data Type: octet
ElementId: TBD10
Status: Proposed
7.3. Recommended Compression Error Resilience Strategy
Note that, since any file may be compressed and decompressed with a
variety of widely available tools implementing a variety of
compression standards (both specified and de facto), compression of
IPFIX File data can be accomplished externally. However, compression
at the file level is not particularly resilient to errors; in the
worst case, a single bit error in a stream-compressed file may result
in the loss of the entire file.
To limit the impact of errors on the recoverability of compressed
data, we recommend the use of block compression where possible.
Ideally, the block compression algorithm should support the
identification and isolation of blocks containing errors; bzip2 is an
example of such a block compressor.
Since the block boundary of a block-compressed IPFIX File may fall in
the middle of an IPFIX Message, resynchronization of an IPFIX Message
stream by a File Reader after a compression error requires some care.
The beginning of an IPFIX Message may be identified by its header
signature (the Version field of the Message Header, 0x00 0x0A,
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followed by a 16-bit Message Length), but simply searching for the
first occurance of the Version field is insufficient, since these two
bytes may occur in valid IPFIX Template or Data Sets.
Therefore, we propose the following algorithm for File Readers to
resynchronize an IPFIX Message Stream after skipping a compressed
block containing errors:
1. Search after the error for the first occurrence of the octet
string 0x00, 0x0A (the IPFIX Message Header Version field.)
2. Treat this field as the beginning of a candidate IPFIX Message.
Read the two bytes following the Version field as a Message
Length, and seek to that offset from the beginning of the
candidate IPFIX Message.
3. If the first two octets after the candidate IPFIX Message are
0x00, 0x0A (i.e., the IPFIX Message Header Version field of the
next message in the stream), or if the end of the file is reached
precisely at the end of the candidate IPFIX Message, presume that
the candidate IPFIX Message is valid, and begin reading the IPFIX
File from the start of the candidate IPFIX Message.
4. If not, or if the seek reaches end-of-file or another block
containing errors before finding the end of the candidate
message, go back to step 1, starting the search two bytes from
the start of the candidate IPFIX Message.
The algorithm above will improperly identify a non-message as a
message approximately 1 in 2^32 times, assuming random IPFIX data.
It may be expanded to consider multiple candidate IPFIX Messages in
order to increase reliability.
In applications (e.g. archival storage) in which error resilience is
very important, File Writers SHOULD use block compression algorithms,
and MAY attempt to align IPFIX Messages within compression blocks to
ease resynchronization after errors, if such is supported by the
chosen block compressor. File Readers SHOULD use the
resynchronization algorithm above to minimize data loss due to
compression errors.
7.4. Recommended Encryption Error Resilience Strategy
File-level encryption has error resilience issues similar to file-
level compression. Single bit errors in the encrypted data stream
can result in unreadability of the entire remaining file, dependent
on the encryption method used. The use of CBC (Cipher Block
Chaining) mode, which suffers from this low error resilience, is
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relatively common.
In applications (e.g. archival storage) in which error resilience is
very important, File Writers SHOULD use a stream cipher, for example
a block cipher in OFB (Output Feedback) mode (often referred to as
stream mode) instead of modes like CBC when encrypting, since errors
are not amplified by stream ciphers: A single-bit error in the
ciphertext results in a single bit error in the plaintext.
Alternatively File Writers SHOULD use any other cipher which can
resynchronize after bit errors. An example is a block cipher in CBC
mode that is reinitialized after a specific amount of data has been
encrypted. The maximum data loss per bit-error is then up to the
next reinitialization point. In this case, File Writers SHOULD also
use the Message Checksum Options Template to attach a checksum to
each IPFIX Message in the IPFIX File, in order to support the
recognition of errors in the decrypted data.
7.5. Encapsulation of Non-IPFIX Data
At times it may be useful to export or store non-IPFIX data inline in
an IPFIX File or Message stream. To do this cleanly, this data must
be encapsulated into IPFIX Messages so that an IPFIX File Reader or
Collecting Process can handle it without any need to interpret it.
At the same time, this data must not be changed during transmission
or storage. The opaqueOctets Information Element as defined in
Section 7.2.8 is provided foe this encapsulation.
Processing the encapsulated non-IPFIX data is left to a separate
processing mechanisms that can identify encapsulated non-IPFIX data
in an IPFIX message stream, but need not have any other IPFIX
handling capability, except the ability to skip over all IPFIX
messages that do not encapsulate non-IPFIX data.
The Message Checksum Options Template, described in Section 7.1.1 may
be used as a uniform mechanism to identify errors within encapsulated
data.
Note that this mechanism can only encapsulate data objects up to
65,515 octets in length. If the space available in one IPFIX Message
is not enough for the amount of data to be encapsulated, then the
data must be broken into smaller segments that are encapsulated into
consecutive IPFIX Messages. Any additional structuring or semantics
of the raw data is outside the scope of IPFIX and must be implemented
within the encapsulated binary data itself. Furthermore, the raw
encapsulated data can not be assumed to have any specific format.
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8. Security Considerations
The IPFIX-based file format itself does not directly introduce
security issues. Rather it is used to store information which may
for privacy or business issues be considered sensitive. The file
format must therefore provide appropriate procedures to guarantee the
integrity and confidentiality of the stored information.
The underlying protocol used to exchange the information that will be
stored using the format proposed in this document must as well apply
appropriate procedures to guarantee the integrity and confidentiality
of the exported information. Such issues are addressed in separate
documents, specifically in the IPFIX Protocol [RFC5101].
Implementors of IPFIX File Writers which store data taken from an
IPFIX Collecting Process using TLS or DTLS for transport security
should note that IPFIX Files may present a potential breach of
confidentiality if IPFIX data collected using TLS or DTLS is stored
in unencrypted files, and should consider providing an external file
encryption option to mitigate this risk.
9. IANA Considerations
This document specifies the creation of several new IPFIX Information
Elements in the IPFIX Information Element registry located at
http://www.iana.org/assignments/ipfix, as defined in Section 7.2
above. IANA has assigned the following Information Element numbers
for their respective Information Elements as specified below:
o Information Element number TBD1 for the collectionTimeMilliseconds
Information Element.
o Information Element number TBD3 for the maxExportSeconds
Information Element.
o Information Element number TBD4 for the maxFlowEndSeconds
Information Element.
o Information Element number TBD5 for the messageMD5Checksum
Information Element.
o Information Element number TBD6 for the messageScope Information
Element.
o Information Element number TBD7 for the minExportSeconds
Information Element.
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o Information Element number TBD8 for the minFlowStartSeconds
Information Element.
o Information Element number TBD9 for the opaqueOctets Information
Element.
o Information Element number TBD10 for the sessionScope Information
Element.
[NOTE for IANA: The text TBDn should be replaced with the respective
assigned Information Element numbers where they appear in this
document.]
10. Acknowledgements
Thanks to Maurizio Molina, Tom Kosnar, and Andreas Kind for technical
assistance with the requirements for a standard flow storage format.
Thanks to Benoit Claise, Paul Aitken, and Andrew Johnson for their
reviews and feedback.
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.
[I-D.ietf-ipfix-reducing-redundancy]
Boschi, E., "Reducing Redundancy in IP Flow Information
Export (IPFIX) and Packet Sampling (PSAMP) Reports",
draft-ietf-ipfix-reducing-redundancy-04 (work in
progress), May 2007.
[I-D.ietf-ipfix-exporting-type]
Boschi, E., Trammell, B., Mark, L., and T. Zseby,
"Exporting Type Information for IPFIX Information
Elements", draft-ietf-ipfix-exporting-type-00 (work in
progress), January 2008.
[RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
April 1992.
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11.2. Informative References
[I-D.ietf-ipfix-arch]
Sadasivan, G. and N. Brownlee, "Architecture Model for IP
Flow Information Export", draft-ietf-ipfix-arch-02 (work
in progress), October 2003.
[I-D.ietf-ipfix-as]
Zseby, T., "IPFIX Applicability", draft-ietf-ipfix-as-12
(work in progress), July 2007.
[RFC5103] Trammell, B. and E. Boschi, "Bidirectional Flow Export
Using IP Flow Information Export (IPFIX)", RFC 5103,
January 2008.
[I-D.ietf-ipfix-testing]
Schmoll, C., Aitken, P., and B. Claise, "Guidelines for IP
Flow Information eXport (IPFIX) Testing",
draft-ietf-ipfix-testing-04 (work in progress),
February 2008.
[RFC3954] Claise, B., "Cisco Systems NetFlow Services Export Version
9", RFC 3954, October 2004.
[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.
[SAINT2007]
Trammell, B., Boschi, E., Mark, L., and T. Zseby,
"Requirements for a standardized flow storage solution",
in Proceedings of the SAINT 2007 workshop on Internet
Measurement Technology, Hiroshima, Japan, January 2007.
Appendix A. Example IPFIX File
In this section we will explore an example IPFIX File which
demonstrates the various features of the IPFIX File format. This
file contains flow records described by a single Template. This file
also contains a File Time Window record to note the start and end
time of the data, and an Export Session Details record to record
collection infrastructure information. Each Message within this File
also contains a Message Checksum record, as this file may be
externally encrypted and/or stored as an archive. The structure of
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this file is shown in Figure 2.
+=================================================+
| IPFIX Message seq. 0 |
| +---------------------------------------------+ |
| | Template Set (id 2) 1 rec | |
| | Data Tmpl. id 256 | |
| +---------------------------------------------+ |
| | Options Template Set (id 3) 3 recs | |
| | File Time Window Opt. Tmpl. id 257 | |
| | Message Checksum Opt. Tmpl. id 259 | |
| | Export Session Details Opt. Tmpl. id 258 | |
| +---------------------------------------------+ |
| | Data Set (id 259) [Message Checksum] 1 rec | |
| +---------------------------------------------+ |
+=================================================+
| IPFIX Message seq. 1 |
| +---------------------------------------------+ |
| | Data Set (id 257) [File Time Window] 1 rec | |
| +---------------------------------------------+ |
| | Data Set (id 258) [Export Session] 1 rec | |
| +---------------------------------------------+ |
| | Data Set (id 259) [Message Checksum] 1 rec | |
| +---------------------------------------------+ |
+=================================================+
| IPFIX Message seq. 6 |
| +---------------------------------------------+ |
| | Data Set (id 256) 50 recs | |
| | contains flow data | |
| +---------------------------------------------+ |
| | Data Set (id 259) [Message Checksum] 1 rec | |
| +---------------------------------------------+ |
+=================================================+
| IPFIX Message seq. 57 |
| . . . |
Figure 2: File Example Structure
The template describing the data records contains a flow start
timestamp, an IPv4 5-tuple, and packet and octet total counts. The
data described by this Template contains anonymized source and
destination IPv4 addresses. The Template Set defining this is as
shown in Figure 3 below:
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1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 2 | Length = 40 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID = 256 | Field Count = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| flowStartSeconds = 150 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| sourceIPv4Address = 8 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| dest.IPv4Address = 12 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| sourceTransportPort = 7 | Field Length = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| dest.TransportPort = 11 | Field Length = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| protocolIdentifier = 4 | Field Length = 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| octetTotalCount = 85 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| packetTotalCount = 86 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: File Example Data Template
A.1. Example Options Templates
This is followed by an Options Template Set containing the options
templates required to read the File: the File Time Window Options
Template defined in Section 7.1.2 above, the Export Session Details
Options Template defined in Section 7.1.3 above, and the Message
Checksum Options Template defined in Section 7.1.1 above. This
Options Template Set is shown in Figure 4 and Figure 5 below:
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1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 3 | Length = 78 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID = 257 | Field Count = 3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope Field Count = 1 |0| sessionScope = TBD10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 1 |0| minFlowStartSeconds = TBD8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| maxFlowEndSeconds = TBD4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 | Template ID = 259 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Count = 2 | Scope Field Count = 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| messageScope = TBD6 | Field Length = 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| messageMD5Checksum = TBD5 | Field Length = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: File Example Options Templates (Time Window and Checksum)
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1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID = 258 | Field Count = 9 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope Field Count = 1 |0| sessionScope = TBD10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 1 |0| exporterIPv4Address = 130 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| collectorIPv4Address = 211 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| exporterTransportPort = 217 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 2 |0| col.TransportPort = 216 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 2 |0| col.TransportProtocol = 215 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 1 |0| col.ProtocolVersion = 214 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 1 |0| minExportSeconds = TBD7 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| maxExportSeconds = TBD3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: File Example Options Templates, Continued (Session Details)
A.2. Example Supplemental Options Data
Following the templates required to decode the file is the
supplemental options information used to describe the file's contents
and type information. First comes the File Time Window record; it
notes that the file contains data from 9 October 2007 between
00:01:13 and 23:56:27 UTC, and appears within its Data Set as in
Figure 6:
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1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 257 | Length = 13 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sessionScope | minFlowStartSeconds
| 0 | 2007-10-09 00:01:13 UTC . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| maxFlowEndSeconds
. . . | 2007-10-09 23:56:27 UTC . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
. . . |
+-+-+-+-+-+-+-+-+
Figure 6: File Example Time Window
This is followed by information about how the data in the file was
collected, in the Export Session Details record. This record notes
that the session stored in this file was sent via SCTP from an
exporter at 192.0.2.30 port 32769 to an collector at 192.0.2.40 port
4739, and contains messages exported between 00:01:57 and 23:57:12
UTC on 9 October 2007; it is represented in its Data Set as in
Figure 7:
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1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 258 | Length = 27 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sessionScope | exporterIPv4Address
| 0 | 192.0.2.30 . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| collectorIPv4Address
. . . | 192.0.2.31 . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| exporterTransportPort | cTPort
. . . | 32769 | 4739 . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| cTProtocol | cPVersion |
. . . | 132 | 10 | . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
minExportSeconds |
. . . 2007-10-09 00:01:57 UTC | . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
maxExportSeconds |
. . . 2007-10-09 23:57:12 UTC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: File Example Export Session Details
A.3. Example Message Checksum
Each IPFIX Message within the file is completed with a Message
Checksum record; the structure of this record within its Data Set is
as in Figure 8:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 259 | Length = 21 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| messageScope | |
| 0 | |
+-+-+-+-+-+-+-+-+ |
| messageMD5Checksum |
| (16 byte MD5 checksum of options message) |
| |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+
Figure 8: File Example Message Checksum
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A.4. File Example Data Set
After the templates and supplemental options information comes the
data itself. The first record of an example Data Set is shown with
its message and set headers in Figure 9:
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version = 10 | Length = 1296 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Export Time = 2007-10-09 00:01:57 UTC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number = 6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Observation Domain ID = 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 256 | Length = 1254 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| flowStartSeconds |
| 2007-10-09 00:01:13 UTC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sourceIPv4Address |
| 192.0.2.2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| destinationIPv4Address |
| 192.0.2.3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sourceTransportPort | destinationTransportPort |
| 32770 | 80 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| protocolId | totalOctetCount
| 6 | 18000 . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| totalPacketCount
. . . | 65 . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (49 more records)
. . . |
+-+-+-+-+-+-+-+-+
Figure 9: File Example Data Set
A.5. Complete File Example
Bringing together the examples above and adding message headers as
appropriate, a hex dump of the first 317 bytes of the example file
constructed above would appear as in the annotated Figure 10 below.
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[EDITOR'S NOTE: In this figure, xx refers to unassigned IANA IE
numbers as in the IANA Considerations section above; cs refers to
message checksum bytes that depend on the rest of the message
contents. These will have to be replaced if we keep this example
once the IE numbers are assigned.]
0:|00 0A 00 A0 47 0A B6 E5 00 00 00 00 00 00 00 01
[^ first message header (length 160 bytes) -->
16:|00 02 00 28 01 00 00 08 00 96 00 04 00 08 00 04
[^ data template set -->
32: 00 0C 00 04 00 07 00 02 00 0B 00 02 00 04 00 01
48: 00 55 00 04 00 56 00 04|00 03 00 4E 01 01 00 03
[^ opt template set -->
64: 00 01 xx xx 00 01 xx xx 00 04 xx xx 00 04 01 03
80: 00 02 00 01 xx xx 00 01 xx xx 00 10 01 02 00 09
96: 00 01 xx xx 00 01 00 82 00 04 00 D3 00 04 00 D9
112: 00 02 00 D8 00 02 00 D7 00 01 00 D0 00 01 xx xx
128: 00 04 xx xx 00 04|01 03 00 18 00 cs cs cs cs cs
[^ message checksum record -->
144: cs cs cs cs cs cs cs cs cs cs cs|00 00 00 00 00
[^ set padding ]
176:|00 0A 00 50 47 0A B6 E5 00 00 00 01 00 00 00 01
[^ second message header (length 80 bytes) -->
192:|01 01 00 0E 00 47 0A B6 B9 47 0C 07 1B 00|01 02
[^ time window rec -> [ session detail rec ^ -->
208: 00 1C 00 C0 00 02 1E 0C 00 02 1F 80 01 12 83 84
224: 0A 47 0A B6 E5 47 0C 07 48 00|01 03 00 18 00 cs
[ message checksum rec ^ -->
240: cs cs cs cs cs cs cs cs cs cs cs cs cs cs cs|00
[ set padding ^]
256:|00 0A 05 10 47 0A B6 E5 00 00 00 06 00 00 00 01
[^ third message header (length 1296 bytes) -->
272:|01 00 04 E6|47 0A B6 B9 C0 00 02 02 C0 00 02 03
[^ set hdr ][^ first data rec -->
288: 80 02 00 50 06 00 00 46 50 00 00 00 41
Figure 10: File Example Hex Dump
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Appendix B. Applicability of IPFIX Files to NetFlow V9 flow storage
As the IPFIX Message format is nearly a superset of the NetFlow V9
packet format, IPFIX Files can be used for store NetFlow V9 data
relatively easily. This section describes a method for doing so.
The differences between the two protocols are outlined in
Appendix B.1 below. A simple, lightweight, message-for-message
translation method for transforming V9 Packets into IPFIX Messages
for storage within IPFIX Files is described in Appendix B.2. An
example of this translation method is given in Appendix B.3.
B.1. Comparing NetFlow V9 to IPFIX
With a few caveats, the IPFIX Protocol is a superset of the NetFlow
V9 protocol, having evolved from it largely through a process of
feature addition to bring it into compliance with the IPFIX
Requirements and the needs of stakeholders within the IPFIX Working
Group. This appendix outlines the differences between the two
protocols. It is informative only, and presented as an exploration
of the two protocols to motivate the usage of IPFIX Files to store
V9-collected flow data.
B.1.1. Message Header Format
Both NetFlow V9 and IPFIX use streams of messages prefixed by a
message header, though the message header differs significantly
between the two. Note that in NetFlow V9 terminology, these messages
are called packets, and messages must be delimited by datagram
boundaries. IPFIX does not have this constraint. The header formats
are detailed below:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version Number | Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sysUpTime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UNIX Secs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: NetFlow V9 Packet Header Format
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version Number | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Export Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Observation Domain ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: IPFIX Message Header Format
Version Number: The IPFIX Version Number MUST be 10, while the
NetFlow V9 Version Number MUST be 9.
Length vs. Count: The Count field in the NetFlow V9 packet header
counts records in the message (including data and template
records), while the Length field in the IPFIX Message Header
counts octets in the message. Note that this implies that NetFlow
V9 collectors must rely on datagram boundaries or some other
external delimeter; or otherwise must completely consume a message
before finding its end.
System Uptime: System uptime in milliseconds is exported in the
NetFlow V9 packet header. This field is not present in the IPFIX
Message Header, and must be exported using an IPFIX Option if
required.
Export Time: Aside from being called UNIX Secs in the NetFlow V9
packet header specification, the export time in seconds since 1
January 1970 at 0000 UTC appears in both NetFlow V9 and IPFIX
message headers.
Sequence Number: The NetFlow V9 Sequence Number counts packets,
while the IPFIX Sequence Number counts records in Data Sets. Both
are scoped to Observation Domain.
Observation Domain ID: Similarly, the NetFlow V9 sourceID has
become the IPFIX Observation Domain ID.
B.1.2. Set Header Format
Set headers are identical between NetFlow V9 and IPFIX; that is, each
Set (FlowSet in NetFlow V9 terminology) is prefixed by a 4-byte set
header containing the Set ID and the length of the set in octets.
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Note that the special Set IDs are different between IPFIX and NetFlow
V9. IPFIX Template Sets are identified by Set ID 2, while NetFlow V9
Template FlowSets are identified by Set ID 0. Similarly, IPFIX
Options Template Sets are identified by Set ID 3, while NetFlow V9
Options Template FlowSets are identified by Set ID 1.
Both protocols reserve Set IDs 0-255, and use Set IDs 256-65535 for
Date Sets (or FlowSets, in NetFlow V9 terminology).
B.1.3. Template Format
Template FlowSets in NetFlow V9 support a subset of functionality of
those in IPFIX. Specifically, NetFlow V9 does not have any support
for vendor-specific Information Elements as IPFIX does, so there is
no enterprise bit or facility for associating a private enterprise
number with an information element.
Options Template FlowSets in NetFlow V9 are similar to Options
Template Sets in IPFIX in the same way.
B.1.4. Information Model
The NetFlow V9 field type definitions are a compatible subset of, and
have evolved in concert with, the IPFIX Information Model. IPFIX
Information Element numbers in the range 1-127 are defined by the
IPFIX Information Model [RFC5102] to be compatible with the
corresponding NetFlow V9 field types.
B.1.5. Template Management
NetFlow V9 has no concept of a Transport Session as in IPFIX, as
NetFlow V9 was designed with a connectionless transport in mind.
Template IDs are therefore scoped to an Exporting Process lifetime
(i.e., an Exporting Process instance between restarts). There is no
facility in NetFlow V9 as in IPFIX for Template withdrawal or
Template ID reuse. Template retransmission at the Exporter works as
in UDP-based IPFIX Exporting Processes.
B.1.6. Transport
In practice, though NetFlow V9 is designed to be transport-
independent, it is transported only over UDP. There is no facility
as in IPFIX for full connection-oriented transport without datagram
boundaries, due to the use of a record count field as opposed to a
message length field in the packet header. There is no support in
NetFlow V9 for transport layer security via TLS or DTLS.
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B.2. A Method for Transforming NetFlow V9 messages to IPFIX
This appendix describes a method for transforming NetFlow V9 Packets
into IPFIX Messages, which can be used to store NetFlow V9 data in
IPFIX Files. A process transforming NetFlow V9 Packets into IPFIX
Messages must handle the fact that NetFlow V9 Packets and IPFIX
Messages are framed differently, that sequence numbering works
differently, and that the NetFlow V9 field type definitions are only
compatible with the IPFIX Information Model field and/or information
element numbers below Information Element number 128.
For each incoming NetFlow V9 packet, the transformation process must:
1. Verify that the Version field of the packet header is 9.
2. Verify that the Sequence Number field of the packet header is
valid.
3. Scan the packet to:
1. verify that it contains no Templates with field numbers
outside the range 1-127;
2. verify that it contains no FlowSets with Set IDs between 2
and 255 inclusive;
3. verify that it contains the number of records in FlowSets,
Template FlowSets, and Options Template FlowSets declared in
the Count field of the packet header; and
4. count the number of records in FlowSets for calculating the
IPFIX Sequence number.
4. Calculate a Sequence Number for each IPFIX Observation Domain by
storing the last Sequence Number sent for each Observation Domain
plus the count of records in FlowSets in the previous step to be
sent as the Sequence Number for the IPFIX Message within that
Observation Domain following this one.
5. Generate a new IPFIX Message Header with:
1. a Version field of 10;
2. a Length field with the number of octets in the IPFIX
Message, generally available by subtracting 4 from the length
of the NetFlow V9 packet as returned from the transport layer
(accounting for the difference in message header lengths);
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3. the Sequence Number calculated for this message by the
Sequence Number calculation step; and
4. Export Time and Observation Domain ID taken from the UNIX
secs and Source ID fields of the NetFlow V9 packet header,
respectively.
6. Copy each FlowSet from the Netflow V9 packet to the IPFIX Message
after the header. Replace Set ID 0 with Set ID 2 for Template
Sets, and Set ID 1 with Set ID 3 for Options Template Sets.
Note that this process loses system uptime information; if such
information is required, the transformation process will have to
export that information using IPFIX Options. This may require a more
sophisticated transformation process structure.
B.3. NetFlow V9 Transformation Example
The following two figures show a single NetFlow V9 packet with
templates and the corresponding IPFIX Message, exporting a single
flow record representing 60,303 octets sent from 192.0.2.2 to
192.0.2.3. This would be the 3rd packet exported in Observation
Domain 33 from the NetFlow V9 exporter, containing records starting
with the 12th record (packet and record sequence numbers count from
0).
The ** symbol in the IPFIX example shows those fields that required
modification from the NetFlow V9 packet by the transformation
process.
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1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version = 9 | Count = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Uptime = 3750405 ms (1:02:30.405) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Export Time = 1171557627 epoch sec (2007-02-15 16:40:27) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Observation Domain ID = 33 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 0 | Set Length = 20 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID = 256 | Field Count = 3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPV4_SRC_ADDR = 8 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPV4_DST_ADDR = 12 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IN_BYTES = 1 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 256 | Set Length = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPV4_SRC_ADDR |
| 192.0.2.2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPV4_DST_ADDR |
| 192.0.2.3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IN_BYTES |
| 60303 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 13: Example NetFlow V9 Packet
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1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ** Version = 10 | ** Length = 52 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Export Time = 1171557627 epoch sec (2007-02-15 16:40:27) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ** Sequence Number = 11 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Observation Domain ID = 33 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ** Set ID = 2 | Set Length = 20 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID = 256 | Field Count = 3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| sourceIPv4Address = 8 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| destinationIPv4Address = 12 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| octetDeltaCount = 1 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 256 | Set Length = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sourceIPv4Address |
| 192.0.2.2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| destinationIPv4Address |
| 192.0.2.3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| octetDeltaCount |
| 60303 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14: Corresponding Example IPFIX Message
Authors' Addresses
Brian H. Trammell
CERT Network Situational Awareness
Software Engineering Institute
4500 Fifth Avenue
Pittsburgh, Pennsylvania 15213
United States
Phone: +1 412 268 9748
Email: bht@cert.org
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Elisa Boschi
Hitachi Europe
c/o ETH Zurich
Gloriastrasse 35
8092 Zurich
Switzerland
Phone: +41 44 6327057
Email: elisa.boschi@hitachi-eu.com
Lutz Mark
Fraunhofer Institute for Open Communication Systems
Kaiserin-Augusta-Allee 31
10589 Berlin
Germany
Phone: +49 30 3463 7306
Email: lutz.mark@fokus.fraunhofer.de
Tanja Zseby
Fraunhofer Institute for Open Communication Systems
Kaiserin-Augusta-Allee 31
10589 Berlin
Germany
Phone: +49 30 3463 7153
Email: tanja.zseby@fokus.fraunhofer.de
Arno Wagner
Swiss Federal Institute of Technology Zurich
Gloriastrasse 35
8092 Zurich
Switzerland
Phone: +41 44 632 70 04
Email: arno@wagner.name
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