Specification of the IP Flow Information Export (IPFIX) File Format
draft-ietf-ipfix-file-05
The information below is for an old version of the document that is already published as an RFC.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 5655.
|
|
|---|---|---|---|
| Authors | Lutz Mark , Arno Wagner , Elisa Boschi , Tanja Zseby , Brian Trammell | ||
| Last updated | 2020-01-21 (Latest revision 2009-08-06) | ||
| Replaces | draft-trammell-ipfix-file | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Proposed Standard | ||
| Formats | |||
| Reviews | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | (None) | |
| Document shepherd | (None) | ||
| IESG | IESG state | Became RFC 5655 (Proposed Standard) | |
| Action Holders |
(None)
|
||
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | Dan Romascanu | ||
| Send notices to | (None) |
draft-ietf-ipfix-file-05
IPFIX Working Group B. Trammell
Internet-Draft E. Boschi
Intended status: Standards Track Hitachi Europe
Expires: February 7, 2010 L. Mark
Fraunhofer IFAM
T. Zseby
Fraunhofer FOKUS
A. Wagner
ETH Zurich
August 6, 2009
Specification of the IPFIX File Format
draft-ietf-ipfix-file-05.txt
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Abstract
This document describes a file format for the storage of flow data
based upon the IPFIX Protocol. It proposes a set of requirements for
flat-file, binary flow data file formats, then specifies the IPFIX
File format to meet these requirements based upon IPFIX Messages.
This IPFIX 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 . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. IPFIX Documents Overview . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Design Overview . . . . . . . . . . . . . . . . . . . . . . . 7
4. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.1. Record Format Flexibility . . . . . . . . . . . . . . . . 11
5.2. Self Description . . . . . . . . . . . . . . . . . . . . . 11
5.3. Data Compression . . . . . . . . . . . . . . . . . . . . . 12
5.4. Indexing and Searching . . . . . . . . . . . . . . . . . . 12
5.5. Error Recovery . . . . . . . . . . . . . . . . . . . . . . 13
5.6. Authentication, Confidentiality, and Integrity . . . . . . 13
5.7. Anonymization and Obfuscation . . . . . . . . . . . . . . 14
5.8. Session Auditability and Replayability . . . . . . . . . . 14
5.9. Performance Characteristics . . . . . . . . . . . . . . . 15
6. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 15
6.1. Storage of IPFIX-collected Flow Data . . . . . . . . . . . 15
6.2. Storage of NetFlow V9-collected Flow Data . . . . . . . . 15
6.3. Testing IPFIX Collecting Processes . . . . . . . . . . . . 16
6.4. IPFIX Device Diagnostics . . . . . . . . . . . . . . . . . 16
7. Detailed File Format Specification . . . . . . . . . . . . . . 17
7.1. File Reader Specification . . . . . . . . . . . . . . . . 17
7.2. File Writer Specification . . . . . . . . . . . . . . . . 18
7.3. Specific File Writer Use Cases . . . . . . . . . . . . . . 19
7.3.1. Collocating a File Writer with a Collecting Process . 19
7.3.2. Collocating a File Writer with a Metering Process . . 20
7.3.3. Using IPFIX Files for Archival Storage . . . . . . . . 21
7.3.4. Using IPFIX Files as Documents . . . . . . . . . . . . 21
7.3.5. Using IPFIX Files for Testing . . . . . . . . . . . . 22
7.3.6. Writing IPFIX Files for Device Diagnostics . . . . . . 22
7.3.7. IPFIX File Manipulation . . . . . . . . . . . . . . . 22
7.4. Media type of IPFIX Files . . . . . . . . . . . . . . . . 23
8. File Format Metadata Specification . . . . . . . . . . . . . . 23
8.1. Recommended Options Templates for IPFIX Files . . . . . . 23
8.1.1. Message Checksum Options Template . . . . . . . . . . 23
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8.1.2. File Time Window Options Template . . . . . . . . . . 24
8.1.3. Export Session Details Options Template . . . . . . . 25
8.1.4. Message Details Options Template . . . . . . . . . . . 27
8.2. Recommended Information Elements for IPFIX Files . . . . . 29
8.2.1. collectionTimeMilliseconds . . . . . . . . . . . . . . 30
8.2.2. collectorCertificate . . . . . . . . . . . . . . . . . 30
8.2.3. exporterCertificate . . . . . . . . . . . . . . . . . 30
8.2.4. exportSctpStreamId . . . . . . . . . . . . . . . . . . 31
8.2.5. maxExportSeconds . . . . . . . . . . . . . . . . . . . 31
8.2.6. maxFlowEndMicroseconds . . . . . . . . . . . . . . . . 31
8.2.7. maxFlowEndMilliseconds . . . . . . . . . . . . . . . . 32
8.2.8. maxFlowEndNanoseconds . . . . . . . . . . . . . . . . 32
8.2.9. maxFlowEndSeconds . . . . . . . . . . . . . . . . . . 32
8.2.10. messageMD5Checksum . . . . . . . . . . . . . . . . . . 33
8.2.11. messageScope . . . . . . . . . . . . . . . . . . . . . 33
8.2.12. minExportSeconds . . . . . . . . . . . . . . . . . . . 34
8.2.13. minFlowStartMicroseconds . . . . . . . . . . . . . . . 34
8.2.14. minFlowStartMilliseconds . . . . . . . . . . . . . . . 34
8.2.15. minFlowStartNanoseconds . . . . . . . . . . . . . . . 35
8.2.16. minFlowStartSeconds . . . . . . . . . . . . . . . . . 35
8.2.17. opaqueOctets . . . . . . . . . . . . . . . . . . . . . 36
8.2.18. sessionScope . . . . . . . . . . . . . . . . . . . . . 36
9. Signing and Encryption of IPFIX Files . . . . . . . . . . . . 37
9.1. CMS Detached Signatures . . . . . . . . . . . . . . . . . 37
9.1.1. ContentInfo . . . . . . . . . . . . . . . . . . . . . 38
9.1.2. SignedData . . . . . . . . . . . . . . . . . . . . . . 39
9.1.3. SignerInfo . . . . . . . . . . . . . . . . . . . . . . 39
9.1.4. EncapsulatedContentInfo . . . . . . . . . . . . . . . 40
9.2. Encryption Error Resilience . . . . . . . . . . . . . . . 40
10. Compression of IPFIX Files . . . . . . . . . . . . . . . . . . 40
10.1. Supported Compression Formats . . . . . . . . . . . . . . 41
10.2. Compression Recognition at the File Reader . . . . . . . . 41
10.3. Compression Error Resilience . . . . . . . . . . . . . . . 41
11. Recommended File Integration Strategies . . . . . . . . . . . 42
11.1. Encapsulation of Non-IPFIX Data in IPFIX Files . . . . . . 43
11.2. Encapsulation of IPFIX Files within Other File Formats . . 43
12. Security Considerations . . . . . . . . . . . . . . . . . . . 43
12.1. Relationship between IPFIX File and Transport
Encryption . . . . . . . . . . . . . . . . . . . . . . . . 44
12.2. End-to-End Assertions for IPFIX Files . . . . . . . . . . 44
12.3. Recommendations for Strength of Cryptography for IPFIX
Files . . . . . . . . . . . . . . . . . . . . . . . . . . 45
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 45
14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 48
15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 48
15.1. Normative References . . . . . . . . . . . . . . . . . . . 48
15.2. Informative References . . . . . . . . . . . . . . . . . . 49
Appendix A. Example IPFIX File . . . . . . . . . . . . . . . . . 50
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A.1. Example Options Templates . . . . . . . . . . . . . . . . 52
A.2. Example Supplemental Options Data . . . . . . . . . . . . 54
A.3. Example Message Checksum . . . . . . . . . . . . . . . . . 56
A.4. File Example Data Set . . . . . . . . . . . . . . . . . . 57
A.5. Complete File Example . . . . . . . . . . . . . . . . . . 57
Appendix B. Applicability of IPFIX Files to NetFlow V9 flow
storage . . . . . . . . . . . . . . . . . . . . . . . 59
B.1. Comparing NetFlow V9 to IPFIX . . . . . . . . . . . . . . 59
B.1.1. Message Header Format . . . . . . . . . . . . . . . . 59
B.1.2. Set Header Format . . . . . . . . . . . . . . . . . . 60
B.1.3. Template Format . . . . . . . . . . . . . . . . . . . 61
B.1.4. Information Model . . . . . . . . . . . . . . . . . . 61
B.1.5. Template Management . . . . . . . . . . . . . . . . . 61
B.1.6. Transport . . . . . . . . . . . . . . . . . . . . . . 61
B.2. A Method for Transforming NetFlow V9 messages to IPFIX . . 62
B.3. NetFlow V9 Transformation Example . . . . . . . . . . . . 63
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 65
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1. Introduction
This document specifies a file format based upon IPFIX, designed to
facilitate interoperability and reusability among a wide variety of
flow storage, processing, and analysis tools. It begins with an
overview of the IPFIX File format, and a quick summary of how IPFIX
Files work in Section 3. The detailed specification of the IPFIX
File format appears in Section 7; this section includes general
specifications for IPFIX File Readers and IPFIX File Writers and
specific recommendations for common situations in which they are
used. The format makes use of the IPFIX Options mechanism for
additional file metadata, in order to avoid requiring any protocol
extensions, and to minimize the effort required to adapt IPFIX
implementations to use the file format; a detailed definition of the
Options Templates used for storage metadata appears in Section 8.
Appendix A contains a detailed example IPFIX File.
An advantage of file-based storage is that files can be readily
encapsulated within each other and other data storage and
transmission formats. The IPFIX File Format leverages this to
provide encryption, described in Section 9 and compression, described
in Section 10. Section 11 provides specific recommendations for
integration of IPFIX File data with other formats.
The IPFIX File format was designed to be applicable to a wide variety
of flow storage situations; the motivation behind its creation is
described in Section 4. The document outlines of the set of
requirements the format is designed to meet in Section 5, and
explores the applicability of such a format to various specific
application areas in Section 6. These sections are intended to give
background on the development of IPFIX Files.
1.1. IPFIX Documents Overview
"Specification of the IPFIX Protocol for the Exchange of IP Traffic
Flow Information" [RFC5101] 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" [RFC5470] 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]. [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.
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"Information Model for IP Flow Information Export" [RFC5102]
describes the Information Elements used by IPFIX, including details
on Information Element naming, numbering, and data type encoding.
"IPFIX Applicability" [RFC5472] 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" [RFC5610] specifies a method for encoding Information Model
properties within an IPFIX Message stream.
This document references [RFC5101] and the architecture document for
terminology, defines IPFIX File Writer and IPFIX File Reader in terms
of the IPFIX Exporting Processes and IPFIX Collecting Process
definitions from [RFC5101], and extends the IPFIX Information Model
defined in [RFC5102] to provide new Information Elements for IPFIX
File metadata. It uses the method described in "Exporting Type
Information for IPFIX Information Elements" [RFC5610] document to
support the self-description of IPFIX Files containing enterprise-
specific Information Elements.
2. Terminology
This section defines terminology related to the IPFIX File Format.
In addition, terms used in this document that are defined in the
Terminology section of [RFC5101] are to be interpreted as defined
there.
IPFIX File: An IPFIX File is a serialized stream of IPFIX Messages;
this stream may be stored on a filesystem or transported using any
technique customarily used for files. 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
[RFC5101] is considered an IPFIX File. However, this document
extends that definition with recommendations on the construction
of IPFIX Files that meet the requirements identified in Section 5.
IPFIX File Reader: An IPFIX File Reader is a process which reads
IPFIX Files from a filesystem. An IPFIX File Reader operates as
an IPFIX Collecting Process as specified in [RFC5101], except as
modified by this document.
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IPFIX File Writer: An IPFIX File Writer is a process which writes
IPFIX Files to a filesystem. An IPFIX File Writer operates as an
IPFIX Exporting Process as specified in [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 [RFC2119].
3. Design Overview
An IPFIX File is simply a data stream 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 includes guidelines designed to ease storage and
retrieval of flow data using the IPFIX File 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 is completely compatible with the
IPFIX protocol on the wire. A schematic of a typical IPFIX File is
shown below:
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+=======================================+
| IPFIX File |
| +===================================+ |
| | IPFIX Message | |
| | +-------------------------------+ | |
| | | IPFIX Message Header | | |
| | +-------------------------------+ | |
| | +-------------------------------+ | |
| | | Options Template Set | | |
| | | Options Template Record | | |
| | | . . . | | |
| | +-------------------------------+ | |
| | +-------------------------------+ | |
| | | Template Set | | |
| | | Template Record | | |
| | | . . . | | |
| | +-------------------------------+ | |
| +===================================+ |
| | IPFIX Message | |
| | +-------------------------------+ | |
| | | IPFIX Message Header | | |
| | +-------------------------------+ | |
| | +-------------------------------+ | |
| | | Data Set | | |
| | | Data Record | | |
| | | . . . | | |
| | +-------------------------------+ | |
| | +-------------------------------+ | |
| | | Data Set | | |
| | | Data Record | | |
| | | . . . | | |
| | +-------------------------------+ | |
| | . . . | |
| +===================================+ |
| . . . |
+=======================================+
Figure 1: Typical File Structure
4. Motivation
There is 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
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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 datasets 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, indicates 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
these ad-hoc formats. A common method of storing data collected via
Cisco NetFlow 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, V7,
and V8 data may be mixed within a given file, as the header on each
datagram defines the NetFlow version of the records following. 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.
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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 traffic 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
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
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[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 record format flexibility 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.
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 Records described by a Template containing enterprise-
specific 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
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Information for IPFIX Information Elements" [RFC5610].
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 via enapsulation in one of these formats.
Section 10 specifies an encapsulation based on bzip2 or gzip, to
maximize interoperability.
A few simple optimizations can be made by File Writers to increase
the integrity and usability of compressed IPFIX data; these are
outlined in Section 10.3.
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 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.
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, the technique described in "Reducing Redundancy in IPFIX and
PSAMP Reports" [RFC5473] 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
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may be declared using the File Time Window Options Template defined
in Section 8.1.2.
5.5. Error Recovery
When storing flow data 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 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. For example, 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.
The IPFIX Message format does not support data integrity assurance.
It is assumed that advanced error correction will be provided
externally. Compression and encryption, if used, provide some
allowance for detection, if not correction, of errors. For simple
error detection support in the absence of compression or encryption,
checksums may be attached to messages via IPFIX Options according to
the Message Checksum Options Template defined in Section 8.1.1.
5.6. Authentication, Confidentiality, and Integrity
Archival storage of flow data may also require assurance that no
unauthorized entity can read or modify the stored data. Cryptography
can be applied to this problem to ensure integrity and
confidentiality by signing and encryption.
As with error correction, this problem has been addressed well at a
layer below that addressed by this document. 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
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transport over SCTP or UDP, both of which provide transient
authentication and confidentiality, the IPFIX protocol does not
support this requirement directly. The IETF has specified the
Cryptographic Message Syntax (CMS) [RFC3852] for creating detached
signatures for integrity and authentication; Section 9 specifies a
CMS-based method for signing IPFIX Files. Confidentiality protection
is assumed to be met by methods external to this specification,
leveraging one of the many such technologies for encrypting files to
meet specific application and process requirements; however, notes on
improving archival integrity of encrypted IPFIX Files are given in
Section 9.2.
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 Protocol presently has no support for anonymization
notation. It should be noted that anonymization is one of the
requirements given for IPFIX in [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 [RFC5101] or this IPFIX-based File
Format for anonymization, as anonymization notation is an area of
open work for the IPFIX working group.
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 Protocol 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 8.1.3 and the
Message Details Options Template defined in Section 8.1.4.
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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.
An examination of the IPFIX Protocol 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 storage of flow data collected by IPFIX Collecting
Processes and NetFlow V9 collectors, the testing of IPFIX Collecting
Processes, and diagnostics of IPFIX Devices.
6.1. Storage of IPFIX-collected Flow Data
IPFIX Files can 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 provides a single, standard, well-
understood encoding to be used for flow data on disk and on the wire,
and 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.
6.2. 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
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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.
6.3. 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 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 can 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" [RFC5471].
Furthermore, fast replay of IPFIX Messages 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" [RFC5471]. The provisioning and use of a set of
reference files for testing simplifies the performance of tests and
increases the comparability of test results.
6.4. IPFIX Device Diagnostics
As an IPFIX File can be used to store any collection of flows, the
format may also be used for dumping and storing various types of flow
data for IPFIX Device diagnostics (e.g., the open flow cache of a
Metering Process or the flow backlog of an Exporting or Collecting
Process at the time of a process reset or crash). File-based storage
is preferable to remote transmission in such error-recovery
situations.
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7. Detailed File Format Specification
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,
albeit a potentially high-latency transport, as the File Reader and
File Writer do not necessarily run at the same time.
This section specifies the detailed actions of File Readers and File
Writers in handling IPFIX Files, and further specifies actions of
File Writers in specific use cases. Unless otherwise specified
herein, IPFIX File Writers MUST behave as IPFIX Exporting Processes,
and IPFIX File Readers MUST behave as IPFIX Collecting Processes,
where appropriate.
7.1. File Reader Specification
An IPFIX File Reader MUST act as an IPFIX Collecting Process as
specified in [RFC5101], except as modified by this document.
An IPFIX File Reader MUST accept as valid any serialized 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 IPFIX Template management features supported by SCTP,
TCP, and UDP MUST be supported in IPFIX Files. File Readers MUST:
o accept IPFIX Messages containing Template Sets, Options Template
Sets, and Data Sets within the same message, as with IPFIX over
TCP or UDP;
o accept Template Sets that define Templates already defined within
the File, as may occur with retransmission of Templates when using
IPFIX over UDP as described in section 10.3.6 of [RFC5101];
o resolve any conflict between a resent definition and a previous
definition by assuming that the new Template replaces the old, as
consistent with Template expiration and ID reuse when using UDP at
the IPFIX transport protocol; and
o accept Template Withdrawals as described in section 8 of
[RFC5101], provided that the Template to be withdrawn is defined,
as is the case with IPFIX over TCP and SCTP.
Considering the filesystem-as-transport view, in the general case an
IPFIX File SHOULD be treated as containing a single Transport Session
as defined by [RFC5101]. However, some applications may benefit from
the ability to treat a collection of IPFIX Files as a single
Transport Session; see especially Section 7.3.3 below. A File Reader
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MAY be configurable to treat a collection of Files as a single
Transport Session. However, a File Reader MUST NOT treat a single
IPFIX File as containing multiple Transport Sessions.
If an IPFIX File uses the technique described in "Reducing Redundancy
in IPFIX and PSAMP Reports" [RFC5473] 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.
7.2. File Writer Specification
An IPFIX File Writer MUST act as an IPFIX Exporting Process as
specified in [RFC5101], except as modified by this document. This
section contains specifications for IPFIX File Writers in all
situations; specifications and recommendations for specific File
Writer use cases are found in below.
File Writers SHOULD store the Templates and Options required to
decode the data within the File in the File itself, unless modified
by the requirements of a specific use case in a subsection of
Section 7.3. In this way, a single IPFIX File generally contains a
single notional Transport Session as defined by [RFC5101].
File Writers SHOULD emit each Template Set or Options Template Set to
appear in the File 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.
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.
File Writers SHOULD use Template Withdrawals to withdraw Templates if
Template IDs need to be reused. Template Withdrawals SHOULD NOT be
used unless necessary to reuse Template IDs.
File Writers SHOULD write IPFIX Messages within an IPFIX File in
ascending Export Time order.
File Writers MAY write Data 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.
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7.3. Specific File Writer Use Cases
The specifications in this section apply to specific situations.
Each section below extends or modifies the base File Writer
specification in Section 7.2. Considerations for collocation of a
File Writer with IPFIX Collecting Processes and Metering Processes
are given, as are specific guidelines for using IPFIX Files for
archival storage, or as documents. Also covered are the use of IPFIX
Files in the testing and diagnostics of IPFIX Devices.
7.3.1. Collocating a File Writer with a Collecting Process
When collocating a File Writer with an IPFIX Collecting Process for
archival storage of collected data in IPFIX Files as described in
Section 6.1, the following recommendations may improve the usefulness
of the stored data.
The simplest way for a File Writer to store the data collected in a
single Transport Session is to simply write the incoming IPFIX
Messages to an IPFIX File as they are collected. This approach has
several drawbacks. First, if the original Exporting Process did not
conform to the recommendations in Section 7.2 with respect to
Template and Data Record ordering, the written file can be difficult
to use later; in this case, File Writers MAY reorder records as
received in order to ensure that Templates appear before the Data
Records they describe.
A File Writer collocated with a Collecting Process that starts
writing data from a running Transport Session SHOULD write all the
Templates currently active within that Transport Session before
writing any Data Records described by them.
Also, the resulting IPFIX Files will lack 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. In this case, if information about the Transport
Session is required, the File Writer SHOULD store a single IPFIX
Transport Session in an IPFIX File and SHOULD record information
about the Transport Session using the Export Session Details Options
Template described in Section 8.1.3.
Additional per-Message information MAY be recorded by the File Writer
using the Message Details Options Template described in
Section 8.1.4. 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.
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When collocating a File Writer with a Collecting Process, the Export
Time of each Message SHOULD be the Export Time of the Message
received by the Collecting Process containing the first Data Record
in the Message. Note that File Writers storing IPFIX data collected
from an IPFIX Collecting Process using SCTP as the transport protocol
SHOULD 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. Template reordering MUST preserve the sequence of
Template Sets with Template Withdrawals in order to ensure
consistency of Templates.
Note that when adding additional information to IPFIX Messages
received from Collecting Processes (e.g. Message Checksum Options,
Message Detail Options), the File Writer SHOULD extend the length of
the Message for the additional data if possible; otherwise, the
Message SHOULD be split into two approximately equal-size Messages
aligned on a Data Set or Template Set boundary from the original
Message if possible; otherwise, the Message SHOULD be split into
approximately two equal size Messages aligned on a Data Record
boundary. Note that, since the MSS or MTU of most network links
(1500-9000 for common Ethernets) is smaller than the maximum IPFIX
Message size (65536) within an IPFIX File, it is expected that
message length extension will suffice in most circumstances.
A File Writer collocated with a Collecting Process SHOULD NOT sign a
File as specified in Section 9.1 unless the Transport Session over
which the data was exported was protected via TLS or DTLS, and the
Collecting Process positively identified the Exporting Process by its
certificate. See Section 12.2 for more information on this issue.
7.3.2. Collocating a File Writer with a Metering Process
Note that File Writers may also be collocated directly with IPFIX
Metering Processes, for writing measured information directly to disk
without intermediate IPFIX Exporting or Collecting Processes. This
arrangement may be particularly useful when providing data to an
analysis environment with an IPFIX File based workflow, when testing
Metering Processes during development, or when the authentication of
a Metering Process is important.
When collocating a File Writer with a Metering Process, note that
Information Elements associated with Exporting or Collecting
Processes are meaningless, and SHOULD NOT appear in the Export
Session Details Options Template described in Section 8.1.3 or the
Message Details Options Template described in Section 8.1.4.
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When collocating a File Writer with an Metering Process, the Export
Time of each Message SHOULD be the time at which the first Data
Record in the Message was received from the Metering Process.
Note that collocating a File Writer with a Metering Process is the
only way to provide positive authentication of a Metering Process
through signatures as in Section 9.1. See Section 12.2 for more
information on this issue.
7.3.3. Using IPFIX Files for Archival Storage
While in the general case File Writers should store one Transport
Session per IPFIX File, some applications 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 Writer MAY be configurable to write data from a single Transport
Session into multiple IPFIX Files; however, File Writers supporting
such a configuration option MUST provide a configuration option to
support one-file-per-session behavior for interoperability purposes.
File Writers using IPFIX Files for archival storage SHOULD support
compression as in Section 10.
7.3.4. Using IPFIX Files as Documents
When IPFIX Files are used as documents, to store a set of flows
relevant to query, investigation, or other common context, or for the
publication of traffic datasets relevant to network research, each
File MUST be readable as a single Transport Session, self-contained
and making no reference to metadata stored in separate Files, in
order to ensure interoperability.
When writing Files to be used as documents, File Writers MAY emit the
special Data Records described by Options Templates before any other
Data Records in the File in the following order to ease the
inspection and use of documents by File Readers:
o Time Window records described by the File Time Window Options
Template as defined in Section 8.1.2 below; followed by
o Information Element Type Records as described in "Exporting Type
Information for IPFIX Information Elements" [RFC5610]; followed by
o commonPropertiesId definitions as described in "Reducing
Redundancy in IPFIX and PSAMP Reports" [RFC5473]; followed by
o Export Session details records described by the Export Session
Details Options Template as defined in Section 8.1.3 below.
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The Export Time of each Message within a File used as a document
SHOULD be the time at which the Message was written by the File
Writer.
If an IPFIX File used as a document uses the technique described in
"Reducing Redundancy in IPFIX and PSAMP Reports" [RFC5473] 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.
7.3.5. Using IPFIX Files for Testing
IPFIX Files can be used for testing IPFIX Collecting Processes in two
ways. First, IPFIX Files can be used to store specific flow data for
regression and stress testing of Collectors; there are no special
considerations for IPFIX Files used in this way.
Second, IPFIX Files are useful for storing reference messages which
do not comply to the IPFIX Protocol in order to test the error
handling and recovery behavior of Collectors. Of course, IPFIX Files
intended to be used in this application necessarily MAY violate any
of the specifications in this document or in [RFC5101], and such
Files MUST NOT be transmitted to Collecting Processes or given as
input to File Readers not under test.
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.
7.3.6. Writing IPFIX Files for Device Diagnostics
IPFIX Files can be used in the debugging of devices which use flow
data as internal state, as a common format for the representation of
flow tables. In such situations, the opaqueOctets information
element can be used to store additional non-IPFIX encoded, non-flow
information (e.g., stack backtraces, process state, etc.) within the
IPFIX File as in Section 11.1; the IPFIX flow table information could
also be embedded in a larger proprietary diagnostic format using
delimiters as in Section 11.2
7.3.7. IPFIX File Manipulation
For many applications, it may prove useful for implementations to
provide functionality for the manipulation of IPFIX Files; for
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example, to select data from a File, to change the Templates used
within a File, or to split or join data in Files. Any such utility
should take special care to ensure that its output remains a valid
IPFIX File, specifically with respect to Templates and Options, which
are scoped to Transport Sessions.
Any operation which splits one File into multiple Files SHOULD write
all necessary Templates and Options to each resulting File, and
ensure that written Options are valid for each resulting File (e.g.,
the Time Window Options Template in Section 8.1.2). Any operation
which joins multiple Files into a single File should do the same,
additionally ensuring that Template IDs do not collide, through the
use of different Observation Domain IDs or Template ID rewrition.
Combining operations may also want to ensure any desired ordering of
flow records is maintained.
7.4. Media type of IPFIX Files
The media type for IPFIX Files is application/ipfix. The
registration information [RFC4288] for this media type is given in
the IANA Considerations section.
8. File Format Metadata Specification
This section defines the Options Templates used for IPFIX File
metadata, and the Information Elements they require.
8.1. 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 [RFC5102], the Information Elements
defined in "Exporting Type Information for IPFIX Information
Elements" [RFC5610], as well as Information Elements defined in
Section 8.2. 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" [RFC5610] in order to support self-description
of enterprise-specific Information Elements.
8.1.1. 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
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Message. An MD5 message checksum as described MAY be used if data
integrity is important to the application but file signing is not
available or desired. The described Data Record MUST appear only
once per IPFIX Message, but MAY appear anywhere within the Message.
This Options Template SHOULD contain the following Information
Elements:
+--------------------+----------------------------------------------+
| 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. |
+--------------------+----------------------------------------------+
8.1.2. 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.
This Options Template SHOULD contain the following Information
Elements:
+---------------+---------------------------------------------------+
| IE | Description |
+---------------+---------------------------------------------------+
| sessionScope | A marker denoting this Option applies to the |
| [scope] | whole IPFIX Transport Session (i.e., the IPFIX |
| | File in the common case); content is ignored. |
| | This Information Element MUST be defined as a |
| | Scope Field. |
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| minFlowStart* | Exactly one of minFlowStartSeconds, |
| | minFlowStartMilliseconds, |
| | minFlowStartMicroseconds, or |
| | minFlowStartNanoseconds; SHOULD match the |
| | precision of the accompanying maxFlowEnd* |
| | Information Element. The start time of the |
| | earliest flow in the Transport Session (i.e., |
| | File). |
| maxFlowEnd* | Exactly one of maxFlowEndSeconds, |
| | maxFlowEndMilliseconds, maxFlowEndMicroseconds, |
| | or maxFlowEndNanoseconds; SHOULD match the |
| | precision of the accompanying minFlowStart* |
| | Information Element. The end time of the latest |
| | flow in the Transport Session (i.e., File). |
+---------------+---------------------------------------------------+
8.1.3. 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
complete IPFIX Transport Session in a single IPFIX File. The
described Data Record SHOULD appear only once in a given IPFIX File.
This Options Template SHOULD contain at least 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., the IPFIX File in the |
| | common case); 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. |
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| 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. |
| exporterCertificate | The certificate used by the IPFIX |
| | Exporting Process from which the |
| | Messages in this Transport Session |
| | were received. Present only for |
| | Transport Sessions protected by TLS |
| | or DTLS. |
| 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. |
| 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 export protocol |
| | used to transport Messages within |
| | this Transport Session. Applicable |
| | only in mixed NetFlow V9-IPFIX |
| | collection environments when storing |
| | NetFlow V9 data in IPFIX Messages, |
| | as in Appendix B |
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| collectorCertificate | The certificate used by the IPFIX |
| | Collecting Process which received |
| | the Messages in this Transport |
| | Session. Present only for Transport |
| | Sessions protected by TLS or DTLS. |
| minExportSeconds | The Export Time of the first Message |
| | in the Transport Session. |
| maxExportSeconds | The Export Time of the last Message |
| | in the Transport Session. |
+----------------------------+--------------------------------------+
8.1.4. 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. This Options Template
also allows the storage of the export session metadata provided the
Export Session Details Options Template, for storing information from
multiple Transport Sessions in the same IPFIX File.
This Options Template SHOULD contain at least 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 Options
Template SHOULD contain only the messageScope and
collectionTimeMilliseconds Information Elements, and the
exportSctpStreamId Information Element for Messages transported via
SCTP.
+----------------------------+--------------------------------------+
| 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. |
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| exporterIPv4Address | IPv4 address of the IPFIX Exporting |
| | Process from which this Message was |
| | 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 this Message was 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 this |
| | Message received. Present only if |
| | this information is not available |
| | via the Export Session Details |
| | Options Template. |
| exporterCertificate | The certificate used by the IPFIX |
| | Exporting Process from which this |
| | Message was received. Present only |
| | for Transport Sessions protected by |
| | TLS or DTLS. |
| collectorIPv4Address | IPv4 address of the IPFIX Collecting |
| | Process which received this Message. |
| | 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. |
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| collectorIPv6Address | IPv6 address of the IPFIX Collecting |
| | Process which received this Message. |
| | 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 this |
| | Message was 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 |
| | this Message. Present only if this |
| | information is not available via the |
| | Export Session Details Options |
| | Template. |
| collectorProtocolVersion | The version of the export protocol |
| | used to transport this Message. |
| | Present only if necessary and if |
| | this information is not available |
| | via the Export Session Details |
| | Options Template. |
| collectorCertificate | The certificate used by the IPFIX |
| | Collecting Process which received |
| | this Message. Present only for |
| | Transport Sessions protected by TLS |
| | or DTLS. |
| exportSctpStreamId | The SCTP stream used to transport |
| | this Message. Present only if the |
| | Message was transported via SCTP. |
+----------------------------+--------------------------------------+
8.2. Recommended Information Elements for IPFIX Files
The following Information Elements are used by the Options Templates
in Section 8.1 to allow IPFIX Message streams to meet the
requirements outlined above without extension of the 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" [RFC5610] in order to support full self-
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description of Information Elements.
8.2.1. 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 IPFIX Options and the
messageScope Information Element, as defined below.
Abstract Data Type: dateTimeMilliseconds
ElementId: TBD1
Status: current
8.2.2. collectorCertificate
Description: The full X.509 certificate, encoded in ASN.1 DER
format, used by the collector when IPFIX Messages were transmitted
using TLS or DTLS. This Information Element SHOULD be bound to
its containing IPFIX Transport Session via an options record and
the sessionScope Information Element, or to its containing IPFIX
Message via an options record and the messageScope Information
Element.
Abstract Data Type: octetArray
ElementId: TBD17
Status: current
8.2.3. exporterCertificate
Description: The full X.509 certificate, encoded in ASN.1 DER
format, used by the collector when IPFIX Messages were transmitted
using TLS or DTLS. This Information Element SHOULD be bound to
its containing IPFIX Transport Session via an options record and
the sessionScope Information Element, or to its containing IPFIX
Message via an options record and the messageScope Information
Element.
Abstract Data Type: octetArray
ElementId: TBD18
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Status: current
8.2.4. exportSctpStreamId
Description: The value of the SCTP Stream Identifier used by the
Exporting Process for exporting IPFIX Message data. This is
carried in the Stream Identifier field of the header of the SCTP
DATA chunk containing the IPFIX Message(s).
Abstract Data Type: unsigned16
Data Type Semantics: identifier
ElementId: TBD2
Status: current
8.2.5. 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 via IPFIX Options and the sessionScope
Information Element.
Abstract Data Type: dateTimeSeconds
ElementId: TBD3
Status: current
Units: seconds
8.2.6. maxFlowEndMicroseconds
Description: The latest absolute timestamp of the last packet
within any Flow within the scope containing this Information
Element, rounded up to the microsecond if necessary. This
Information Element SHOULD be bound to its containing IPFIX
Transport Session via IPFIX Options and the sessionScope
Information Element. This Information Element SHOULD be used only
in Transport Sessions containing Flow Records with microsecond-
precision (or better) timestamp Information Elements.
Abstract Data Type: dateTimeMicroseconds
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ElementId: TBD11
Status: current
Units: microseconds
8.2.7. maxFlowEndMilliseconds
Description: The latest absolute timestamp of the last packet
within any Flow within the scope containing this Information
Element, rounded up to the millisecond if necessary. This
Information Element SHOULD be bound to its containing IPFIX
Transport Session via IPFIX Options and the sessionScope
Information Element. This Information Element SHOULD be used only
in Transport Sessions containing Flow Records with millisecond-
precision (or better) timestamp Information Elements.
Abstract Data Type: dateTimeMilliseconds
ElementId: TBD12
Status: current
Units: milliseconds
8.2.8. maxFlowEndNanoseconds
Description: The latest absolute timestamp of the last packet
within any Flow within the scope containing this Information
Element. This Information Element SHOULD be bound to its
containing IPFIX Transport Session via IPFIX Options and the
sessionScope Information Element. This Information Element SHOULD
be used only in Transport Sessions containing Flow Records with
nanosecond-precision timestamp Information Elements.
Abstract Data Type: dateTimeNanoseconds
ElementId: TBD13
Status: current
Units: nanoseconds
8.2.9. maxFlowEndSeconds
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Description: The latest absolute timestamp of the last packet
within any Flow within the scope containing this Information
Element, rounded up to the second if necessary. This Information
Element SHOULD be bound to its containing IPFIX Transport Session
via IPFIX Options and the sessionScope Information Element.
Abstract Data Type: dateTimeSeconds
ElementId: TBD4
Status: current
Units: seconds
8.2.10. 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 calculate the MD5 checksum of the resulting buffer
as defined in [RFC1321], place the resulting value in this
Information Element, and export the buffered message. This
Information Element is intended as a simple checksum only;
therefore collision resistance and algorithm agility are not
required, and MD5 is an appropriate message digest.
Abstract Data Type: octetArray (16 bytes)
ElementId: TBD5
Status: current
Reference: RFC 1321, The MD5 Message-Digest Algorithm [RFC1321]
8.2.11. 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
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Reader or the Collecting Process.
Abstract Data Type: octet
ElementId: TBD6
Status: current
8.2.12. 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 via an options record and the sessionScope
Information Element.
Abstract Data Type: dateTimeSeconds
ElementId: TBD7
Status: current
Units: seconds
8.2.13. minFlowStartMicroseconds
Description: The earliest absolute timestamp of the first packet
within any Flow within the scope containing this Information
Element, rounded down to the microsecond if necessary. This
Information Element SHOULD be bound to its containing IPFIX
Transport Session via an options record and the sessionScope
Information Element. This Information Element SHOULD be used only
in Transport Sessions containing Flow Records with microsecond-
precision (or better) timestamp Information Elements.
Abstract Data Type: dateTimeMicroseconds
ElementId: TBD14
Status: current
Units: microseconds
8.2.14. minFlowStartMilliseconds
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Description: The earliest absolute timestamp of the first packet
within any Flow within the scope containing this Information
Element, rounded down to the millisecond if necessary. This
Information Element SHOULD be bound to its containing IPFIX
Transport Session via an options record and the sessionScope
Information Element. This Information Element SHOULD be used only
in Transport Sessions containing Flow Records with millisecond-
precision (or better) timestamp Information Elements.
Abstract Data Type: dateTimeMilliseconds
ElementId: TBD15
Status: current
Units: milliseconds
8.2.15. minFlowStartNanoseconds
Description: The earliest absolute timestamp of the first packet
within any Flow within the scope containing this Information
Element. This Information Element SHOULD be bound to its
containing IPFIX Transport Session via an options record and the
sessionScope Information Element. This Information Element SHOULD
be used only in Transport Sessions containing Flow Records with
nanosecond-precision timestamp Information Elements.
Abstract Data Type: dateTimeNanoseconds
ElementId: TBD16
Status: current
Units: nanoseconds
8.2.16. 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 if necessary. This
Information Element SHOULD be bound to its containing IPFIX
Transport Session via an options record and the sessionScope
Information Element.
Abstract Data Type: dateTimeSeconds
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ElementId: TBD8
Status: current
Units: seconds
8.2.17. 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.
Abstract Data Type: octet
ElementId: TBD9
Status: current
8.2.18. 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 an IPFIX 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: current
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9. Signing and Encryption of IPFIX Files
In order to ensure the integrity of IPFIX Files and the identity of
IPFIX File Writers, File Writers and File Readers SHOULD provide for
an interoperable and easily-implemented method for signing IPFIX
Files, and verifying those signatures. This section specifies method
via CMS detached signatures.
Note that while CMS specifies an encapsulation format which can be
used for encryption as well as signing, no method is specified for
encapsulation for confidentiality protection. It is assumed that
application-specific or process-specific requirements outweigh the
need for interoperability for encrypted files.
9.1. CMS Detached Signatures
The Cryptographic Message Syntax (CMS) [RFC3852] defines an
encapsulation syntax for data protection, used to digitally sign,
authenticate, or encrypt arbitrary message content. CMS can also be
used to create detached signatures, in which the signature is stored
in a separate file. This arrangement maximizes interoperability, as
File Readers which are not aware of CMS detached signatures and have
no requirement for them can simply ignore them; the content of the
IPFIX File itself is unchanged by the signature.
The detached signature file for an IPFIX File SHOULD be stored,
transported, or otherwise made available (e.g., by FTP or HTTP)
alongside the signed IPFIX File, with the same filename as the IPFIX
File, except that the file extension ".p7s" is added to the end,
conforming to the naming convention in [RFC3851].
Within the detached signature, the CMS ContentInfo type MUST always
be present, and it MUST encapsulate the CMS SignedData content type,
which in turn MUST NOT encapsulate the signed IPFIX File content.
The CMS detached signature is summarized as follows:
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ContentInfo {
contentType id-signedData, -- (1.2.840.113549.1.7.2)
content SignedData
}
SignedData {
version CMSVersion, -- Always set to 3
digestAlgorithms DigestAlgorithmIdentifiers,
encapContentInfo EncapsulatedContentInfo,
certificates CertificateSet, -- File Writer certificate(s)
crls CertificateRevocationLists, -- Optional
signerInfos SET OF SignerInfo -- Only one signer
}
SignerInfo {
version CMSVersion, -- Always set to 3
sid SignerIdentifier,
digestAlgorithm DigestAlgorithmIdentifier,
signedAttrs SignedAttributes,
signatureAlgorithm SignatureAlgorithmIdentifier,
signature SignatureValue,
unsignedAttrs UnsignedAttributes
}
EncapsulatedContentInfo {
eContentType id-ct-anyContentType, -- (1.2.840.113549.1.9.16.1.0)
eContent OCTET STRING -- Always absent
}
The details of the contents of each CMS encapsulation are detailed in
the subsections below.
9.1.1. ContentInfo
[RFC3852] requires the outer-most encapsulation to be ContentInfo;
the fields of ContentInfo are as follows:
contentType indicates the type of the associated content. For the
detached signature file, the encapsulated type is always
SignedData, so the id-signedData (1.2.840.113549.1.7.2) object
identifier MUST be present in this field.
content contains a SignedData content, detailed in Section 9.1.2.
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9.1.2. SignedData
The SignedData content type contains the signature of the IPFIX File
and information to aid in validation; the fields of SignedData are as
follows:
version MUST be 3.
digestAlgorithms is a collection of one-way hash function
identifiers. It MUST contain the identifier used by the File
Writer to generate the digital signature.
encapContentInfo is the signed content, including a content type
identifier. Since a detached signature is being created, it does
not encapsulate the IPFIX File. The EncapsulatedContentInfo is
detailed in Section 9.1.4.
certificates is a collection of certificates. It SHOULD include the
X.509 certificate needed to validate the digital signature file.
Certification Authority (CA) and File Writer certificates MUST
conform to the certificate profile specified in [RFC5280].
crls is an optional collection of certificate revocation lists
(CRLs). It SHOULD NOT contain any CRLs; any CRLs which are
present MUST conform to the certificate profile specified in
[RFC5280].
signerInfos is a collection of per-signer information; this
identifies the File Writer. More than one SignerInfo MAY appear
to facilitate transitions between keys or algorithms. The
SignerInfo type is detailed in Section 9.1.3.
9.1.3. SignerInfo
The SignerInfo type identifies the File Writer; the fields of
SignerInfo are as follows:
version MUST be 3.
sid identifies the File Writer's public key. This identifier MUST
match the value included in the subjectKeyIdentifier certificate
extension on the File Writer's X.509 certificate.
digestAlgorithm identifies the one-way hash function and associated
parameters used to generate the signature.
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signedAttrs is an optional set of attributes that are signed along
with the content.
digestAlgorithm identifies the digital signature algorithm and
associated parameters used to generate the signature.
signature is the digital signature of the associated file.
unsignedAttrs is an optional of attributes that are not signed.
9.1.4. EncapsulatedContentInfo
The EncapsulatedContentInfo structure contains a content type
identifier. Since a detached signature is being created, it does not
encapsulate the Internet-Draft. The fields of
EncapsulatedContentInfo are as follows:
eContentType is an object identifier that uniquely specifies the
content type. The content type associated with the plain text
file MUST be id-ct-anyContentType (1.2.840.113549.1.9.16.1.0).
eContent is an optional field containing the signed content. Since
this is a detached signature, eContent MUST be absent.
9.2. Encryption Error Resilience
File-level encryption has error resilience issues similar to file-
level compression. Single bit errors in the encrypted data stream
can result in larger errors in the decrypted stream, depending on the
encryption scheme used.
In applications (e.g. archival storage) in which error resilience is
very important, File Writers SHOULD use an encryption scheme which
can resynchronize after bit errors. An common example is a block
cipher in CBC (Cipher Block Chaining) mode. In this case, File
Writers MAY 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.
10. Compression of IPFIX Files
Network traffic measurement data is also generally highly
compressible. IPFIX Templates tend to increase the information
content per record by not requiring the export of irrelevant or non-
present fields in records, and the technique described in [RFC5473]
also reduces the export of redundant information. However, even with
these techniques, generalized compression can decrease storage
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requirements significantly; therefore, IPFIX File Writers and File
Readers SHOULD support compression as described in this section.
10.1. Supported Compression Formats
IPFIX files support two compression encapsulation formats: bzip2
[bzip2] and gzip [RFC1952]. bzip2 provides better compression than
gzip and, as a block compression algorithm, better error recovery
characteristics, at the expense of slower compression. gzip is
potentially a better choice when compression time is an issue. These
two algorithms and encapsulation formats were chosen for ubiquity and
ease of implementation.
IPFIX File Readers and Writers supporting compression MUST support
bzip2, and SHOULD support gzip.
10.2. Compression Recognition at the File Reader
bzip2, gzip, and uncompressed IPFIX Files have distinct magic
numbers. IPFIX File Readers SHOULD use these magic numbers to
determine what compression, if any, is in use for an IPFIX File, and
invoke the proper decompression. bzip2 files are identified by the
initial three-octet string 0x42, 0x5A, 0x68 ("BZh"). gzip files are
identified by the initial two-octet string 0x1F, 0x8B. IPFIX Files
are identified by the initial two-octet string 0x00, 0x0A; these are
the version bytes of the first IPFIX Message header in the File.
10.3. Compression Error Resilience
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.
Since block compression algorithms that support the identification
and isolation of blocks containing errors limit the impact of errors
on the recoverability of compressed data, the use of bzip2 in
applications where error resilience is important is RECOMMENDED.
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,
followed by a 16-bit Message Length), but simply searching for the
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first occurance of the Version field is insufficient, since these two
bytes may occur in valid IPFIX Template or Data Sets.
Therefore, we specify 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 end-of-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.
11. Recommended File Integration Strategies
This section describes methods for integrating IPFIX File data with
other file formats.
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11.1. Encapsulation of Non-IPFIX Data in IPFIX Files
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 8.2.17 is provided for 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 8.1.1 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 cannot be assumed by an IPFIX File Reader to have
any specific format.
11.2. Encapsulation of IPFIX Files within Other File Formats
Consequently, it may also be useful to reverse the encapsulation,
that is, to export or store IPFIX data inline within a non-IPFIX file
or data stream. This makes sense when the other file format is not
compatible with the encapsulation described above in Section 11.1.
Generally speaking, the encapsulation here will be specific to the
format of the containing file. For example, IPFIX Files may be
embedded in XML elements using hex or Base64 encoding, or in raw
binary files using start and end delimiters or some form of run-
length encoding. As there are as many potential encapsulations here
as there are potential file formats, the specifics of each are out of
scope for this specification.
12. Security Considerations
The security considerations section of [RFC5101], on which the IPFIX
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File format is based, is largely concerned with the proper
application of TLS and DTLS to ensure confidentiality and integrity
when exporting IPFIX Messages. By analogy, this document specifies
the use of CMS [RFC3852] detached signatures to provide equivalent
integrity protection to TLS and DTLS in Section 9.1. However, aside
from merely applying CMS for signatures, there are several security
issues which much be considered in certain circumstances; these are
covered in the subsections below.
12.1. Relationship between IPFIX File and Transport Encryption
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 [RFC5101].
Specifically, IPFIX Files which store data taken from an IPFIX
Collecting Process using TLS or DTLS for transport security SHOULD be
signed as in Section 9.1 and SHOULD be encrypted out of band; storage
of such flow data without encryption may present a potential breach
of confidentiality. Conversely, flow data considered sensitive
enough to require encryption in storage that is later transmitted
using IPFIX SHOULD be transmitted using TLS or DTLS for transport
security.
12.2. End-to-End Assertions for IPFIX Files
Note that while both TLS and CMS provide the ability to sign an IPFIX
Transport Session or an IPFIX File, there exists no method for
protecting data integrity end-to-end in the case in which a
Collecting Process is collocated with a File Writer. The channel
between the Exporting Process to Collecting Process using IPFIX is
signed by the Exporting Process key and protected via TLS and DTLS,
while the File is signed by the File Writer key and protected via
CMS. The identity of the Exporting Process is not asserted in the
file, and the records may be modified between the Collecting Process
and the File Writer.
There are two potential ways to address this issue. The first is by
fiat, and is appropriate only when the application allows the
Collecting Process to File Writer channel to be trusted. In this
case, the File Writer's signature is an implicit assertion that the
channel to the Exporting Process was protected, that the Exporting
Process's signature was verified, and that the data was not changed
after collection. For this to work, a File Writer collocated with a
Collecting Process SHOULD NOT sign a File as specified in Section 9.1
unless the Transport Session over which the data was exported was
protected via TLS or DTLS, and the Collecting Process positively
identified the Exporting Process by its certificate. The File Writer
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SHOULD include the Exporting Process and Collecting Process
certificates within the File using the Export Session Detail Options
Template in Section 8.1.3 or the Message Detail Options Template in
Section 8.1.4 to allow for later verification.
In situations in which the Collecting Process and/or File Writer
cannot be trusted, end-to-end integrity can then be approximated by
collocating the File Writer with the Metering Process, and removing
the IPFIX Protocol completely from the chain. In this case, the File
Writer's signature is an implicit assertion that the Metering Process
is identified and is not tampering with the information as observed
on the wire.
Verification of these trust relationships is out of scope for this
document, and should be considered on a per-implementation basis.
12.3. Recommendations for Strength of Cryptography for IPFIX Files
Note that when encrypting files for archival storage, the
cryptographic strength is dependent on the length of time over which
archival data is expected to be kept. Long term storage may require
re-application of cryptographic protection, periodically resigning
and reencrypting files with stronger keys. In this case, it is
recommended that the existing signed and/or encypted data be
encapsulated within newer, stronger protection. See [RFC4810] for a
discussion of this issue.
13. 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 8.2
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 TBD17 for the collectorCertificate
Information Element.
o Information Element number TBD18 for the exporterCertificate
Information Element.
o Information Element number TBD2 for the exportSctpStreamId
Information Element.
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o Information Element number TBD3 for the maxExportSeconds
Information Element.
o Information Element number TBD11 for the maxFlowEndMicroseconds
Information Element.
o Information Element number TBD12 for the maxFlowEndMilliseconds
Information Element.
o Information Element number TBD13 for the maxFlowEndNanoseconds
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.
o Information Element number TBD14 for the minFlowStartMicroseconds
Information Element.
o Information Element number TBD15 for the minFlowStartMilliseconds
Information Element.
o Information Element number TBD16 for the minFlowStartNanoseconds
Information Element.
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.]
IANA has created the media type application/ipfix for IPFIX data, as
described by the following registration information:
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Type name: application
Subtype name: ipfix
Required parameters: none
Optional parameters: none
Encoding considerations: IPFIX files are binary, and therefore must
be encoded in non-binary contexts.
Security considerations: See the Security Considerations section
(Section 12) of this document, and the Security Considerations
section of [RFC5101].
Interoperability considerations: See the Detailed Specification
section (Section 7) of this document. The format is designed to
be broadly interoperable, as any valid stream of IPFIX Messages
over any transport specified in [RFC5101] MUST be recognizable as
a valid IPFIX File.
Published specification: This document, especially Section 7, and
[RFC5101].
Applications that use this media type: Various IPFIX
implementations (see [RFC5153]) support the construction of IPFIX
File Readers and Writers.
Additional information: none
Magic number(s): None, although the first two bytes of any IPFIX
file are the first two bytes of a message header, the Version
field, which as of [RFC5101] are always 10 in network byte order:
0x00, 0x0A.
File extension(s): .ipfix
Macintosh file type code(s): none
For further information: Authors of this document, IETF IPFIX
Working Group
Intended usage: LIMITED USE
Restrictions on usage: none
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Change controller: Authors of this document, IETF IPFIX Working
Group
14. 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, Andrew Johnson, Gerhard Muenz,
and Nevil Brownlee for their reviews and feedback. Thanks to Pasi
Eronen for pointing out [RFC5485], and Russ Housley for writing it;
it specifies a detached signature format, from which Section 9.1 is
largely drawn. Thanks to the PRISM project for its support of this
work.
15. References
15.1. 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.
[RFC5610] Boschi, E., Trammell, B., Mark, L., and T. Zseby,
"Exporting Type Information for IP Flow Information Export
(IPFIX) Information Elements", RFC 5610, July 2009.
[RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
April 1992.
[RFC1952] Deutsch, P., Gailly, J-L., Adler, M., Deutsch, L., and G.
Randers-Pehrson, "GZIP file format specification version
4.3", RFC 1952, May 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3852] Housley, R., "Cryptographic Message Syntax (CMS)",
RFC 3852, July 2004.
[RFC4810] Wallace, C., Pordesch, U., and R. Brandner, "Long-Term
Archive Service Requirements", RFC 4810, March 2007.
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[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008.
[bzip2] Seward, J., "bzip2 (http://www.bzip.org/)", March 2008.
15.2. Informative References
[RFC3917] Quittek, J., Zseby, T., Claise, B., and S. Zander,
"Requirements for IP Flow Information Export (IPFIX)",
RFC 3917, October 2004.
[RFC3954] Claise, B., "Cisco Systems NetFlow Services Export Version
9", RFC 3954, October 2004.
[RFC5153] Boschi, E., Mark, L., Quittek, J., Stiemerling, M., and P.
Aitken, "IP Flow Information Export (IPFIX) Implementation
Guidelines", RFC 5153, April 2008.
[RFC5470] Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,
"Architecture for IP Flow Information Export", RFC 5470,
March 2009.
[RFC5471] Schmoll, C., Aitken, P., and B. Claise, "Guidelines for IP
Flow Information Export (IPFIX) Testing", RFC 5471,
March 2009.
[RFC5472] Zseby, T., Boschi, E., Brownlee, N., and B. Claise, "IP
Flow Information Export (IPFIX) Applicability", RFC 5472,
March 2009.
[RFC5473] Boschi, E., Mark, L., and B. Claise, "Reducing Redundancy
in IP Flow Information Export (IPFIX) and Packet Sampling
(PSAMP) Reports", RFC 5473, March 2009.
[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.
[RFC3851] Ramsdell, B., "Secure/Multipurpose Internet Mail
Extensions (S/MIME) Version 3.1 Message Specification",
RFC 3851, July 2004.
[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and
Registration Procedures", BCP 13, RFC 4288, December 2005.
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[RFC5485] Housley, R., "Digital Signatures on Internet-Draft
Documents", RFC 5485, March 2009.
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
this File is shown in Figure 2.
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+=================================================+
| 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. 4 |
| +---------------------------------------------+ |
| | Data Set (id 256) 50 recs | |
| | contains flow data | |
| +---------------------------------------------+ |
| | Data Set (id 259) [Message Checksum] 1 rec | |
| +---------------------------------------------+ |
+=================================================+
| IPFIX Message seq. 55 |
| . . . |
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
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 8.1.2 above, the Export Session Details
Options Template defined in Section 8.1.3 above, and the Message
Checksum Options Template defined in Section 8.1.1 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 = 80 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 | set padding (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 IPFIX 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 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 = 24 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| messageScope | |
| 0 | |
+-+-+-+-+-+-+-+-+ |
| messageMD5Checksum |
| (16 byte MD5 checksum of options message) |
| |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | set padding (3 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 Gile
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 50 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 00 00|01 03 00 18 00 cs cs cs
[^ checksum record -->
144: cs cs cs cs cs cs cs cs cs cs cs cs cs 00 00 00
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
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
Data 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. NetFlow V9 also does not support
variable-length fields.
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 identifiers 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 below Information Element
identifier 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 types 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 Data 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 Data FlowSets in the previous step
to be sent as the Sequence Number for the IPFIX Message following
this one within that Observation Domain.
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 Trammell
Hitachi Europe
c/o ETH Zurich
Gloriastrasse 35
8092 Zurich
Switzerland
Phone: +41 44 632 70 13
Email: brian.trammell@hitachi-eu.com
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Elisa Boschi
Hitachi Europe
c/o ETH Zurich
Gloriastrasse 35
8092 Zurich
Switzerland
Phone: +41 44 632 70 57
Email: elisa.boschi@hitachi-eu.com
Lutz Mark
Fraunhofer IFAM
Wiener Str. 12
28359 Bremen
Germany
Phone: +49 421 2246206
Email: lutz.mark@ifam.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
ETH Zurich
Gloriastrasse 35
8092 Zurich
Switzerland
Phone: +41 44 632 70 04
Email: arno@wagner.name
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