Internet Engineering Task Force (IETF) B. Trammell
Request for Comments: 7373 ETH Zurich
Category: Standards Track September 2014
ISSN: 2070-1721
Textual Representation of IP Flow Information Export (IPFIX)
Abstract Data Types
Abstract
This document defines UTF-8 representations for IP Flow Information
Export (IPFIX) abstract data types (ADTs) to support interoperable
usage of the IPFIX Information Elements with protocols based on
textual encodings.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7373.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Identifying Information Elements . . . . . . . . . . . . . . 3
4. Data Type Encodings . . . . . . . . . . . . . . . . . . . . . 3
4.1. octetArray . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. unsigned8, unsigned16, unsigned32, and unsigned64 . . . . 4
4.3. signed8, signed16, signed32, and signed64 . . . . . . . . 5
4.4. float32 and float64 . . . . . . . . . . . . . . . . . . . 6
4.5. boolean . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.6. macAddress . . . . . . . . . . . . . . . . . . . . . . . 7
4.7. string . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.8. The dateTime ADTs . . . . . . . . . . . . . . . . . . . . 8
4.9. ipv4Address . . . . . . . . . . . . . . . . . . . . . . . 8
4.10. ipv6Address . . . . . . . . . . . . . . . . . . . . . . . 9
4.11. basicList, subTemplateList, and subTemplateMultiList . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.1. Normative References . . . . . . . . . . . . . . . . . . 10
6.2. Informative References . . . . . . . . . . . . . . . . . 11
Appendix A. Example . . . . . . . . . . . . . . . . . . . . . . 13
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 14
Author's Address . . . . . . . . . . . . . . . . . . . . . . . .
1. Introduction
The IP Flow Information Export (IPFIX) Information Model [RFC7012]
provides a set of abstract data types (ADTs) for the IANA "IPFIX
Information Elements" registry [IANA-IPFIX], which contains a rich
set of Information Elements for description of information about
network entities and network traffic data, and abstract data types
for these Information Elements. The IPFIX Protocol Specification
[RFC7011], in turn, defines a big-endian binary encoding for these
abstract data types suitable for use with the IPFIX protocol.
However, present and future operations and management protocols and
applications may use textual encodings, and generic framing and
structure, as in JSON [RFC7159] or XML. A definition of canonical
textual encodings for the IPFIX abstract data types would allow this
set of Information Elements to be used for such applications and for
these applications to interoperate with IPFIX applications at the
Information Element definition level.
Note that templating or other mechanisms used for data description
for such applications and protocols are application specific and,
therefore, out of scope for this document: only Information Element
identification and value representation are defined here.
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In most cases where a textual representation will be used, an
explicit tradeoff is made for human readability or manipulability
over compactness; this assumption is used in defining standard
representations of IPFIX ADTs.
2. Terminology
Capitalized terms defined in the IPFIX Protocol Specification
[RFC7011] and the IPFIX Information Model [RFC7012] are used in this
document as defined in those documents. 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]. In addition, this document
defines the following terminology for its own use:
Enclosing Context
A textual representation of Information Element values is applied
to use the IPFIX Information Model within some existing textual
format (e.g., XML [W3C-XML] and JSON [RFC7159]). This outer
format is referred to as the Enclosing Context within this
document. Enclosing Contexts define escaping and quoting rules
for represented values.
3. Identifying Information Elements
The "IPFIX Information Elements" registry [IANA-IPFIX] defines a set
of Information Elements numbered by Information Element identifiers
and named for human readability. These Information Element
identifiers are meant for use with the IPFIX protocol and have little
meaning when applying the "IPFIX Information Elements" registry to
textual representations.
Instead, applications using textual representations of Information
Elements use Information Element names to identify them; see
Appendix A for examples illustrating this principle.
4. Data Type Encodings
Each subsection of this section defines a textual encoding for the
abstract data types defined in [RFC7012]. This section uses ABNF,
including the Core Rules in Appendix B of [RFC5234], to describe the
format of textual representations of IPFIX abstract data types.
If future documents update [RFC7012] to add new abstract data types
to the IPFIX Information Model, and those abstract data types are
generally useful, this document will also need to be updated in order
to define textual encodings for those abstract data types.
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4.1. octetArray
If the Enclosing Context defines a representation for binary objects,
that representation SHOULD be used.
Otherwise, since the goal of textual representation of Information
Elements is human readability over compactness, the values of
Information Elements of the octetArray data type are represented as a
string of pairs of hexadecimal digits, one pair per byte, in the
order the bytes would appear on the wire were the octetArray encoded
directly in IPFIX per [RFC7011]. Whitespace may occur between any
pair of digits to assist in human readability of the string but is
not necessary. In ABNF:
hex-octet = 2HEXDIG
octetarray = hex-octet *([WSP] hex-octet)
4.2. unsigned8, unsigned16, unsigned32, and unsigned64
If the Enclosing Context defines a representation for unsigned
integers, that representation SHOULD be used.
In the special case where the unsigned Information Element has
identifier semantics and refers to a set of codepoints either in an
external registry, in a sub-registry, or directly in the description
of the Information Element, then the name or short description for
that codepoint as a string MAY be used to improve readability.
Otherwise, the values of Information Elements of an unsigned integer
type may be represented as either unprefixed base-10 (decimal)
strings, base-16 (hexadecimal) strings prefixed by "0x", or base-2
(binary) strings prefixed by "0b". In ABNF:
unsigned = 1*DIGIT / "0x" 1*HEXDIG / "0b" 1*BIT
Leading zeroes are allowed in any representation and do not signify
base-8 (octal) representation. Binary representation is intended for
use with Information Elements with flag semantics, but it can be used
in any case.
The encoded value MUST be in range for the corresponding abstract
data type or Information Element. Values that are out of range are
interpreted as clipped to the implicit range for the Information
Element as defined by the abstract data type or to the explicit range
of the Information Element if defined. Minimum and maximum values
for abstract data types are shown in Table 1 below.
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+------------+---------+----------------------+
| type | minimum | maximum |
+------------+---------+----------------------+
| unsigned8 | 0 | 255 |
| unsigned16 | 0 | 65535 |
| unsigned32 | 0 | 4294967295 |
| unsigned64 | 0 | 18446744073709551615 |
+------------+---------+----------------------+
Table 1: Ranges for Unsigned Abstract Data Types (in Decimal)
4.3. signed8, signed16, signed32, and signed64
If the Enclosing Context defines a representation for signed
integers, that representation SHOULD be used.
Otherwise, the values of Information Elements of signed integer types
are represented as optionally prefixed base-10 (decimal) strings. In
ABNF:
sign = "+" / "-"
signed = [sign] 1*DIGIT
If the sign is omitted, it is assumed to be positive. Leading zeroes
are allowed and do not signify base-8 (octal) encoding. The
representation "-0" is explicitly allowed and is equal to zero.
The encoded value MUST be in range for the corresponding abstract
data type or Information Element. Values that are out of range are
to be interpreted as clipped to the implicit range for the
Information Element as defined by the abstract data type or to the
explicit range of the Information Element if defined. Minimum and
maximum values for abstract data types are shown in Table 2 below.
+----------+----------------------+----------------------+
| type | minimum | maximum |
+----------+----------------------+----------------------+
| signed8 | -128 | +127 |
| signed16 | -32768 | +32767 |
| signed32 | -2147483648 | +2147483647 |
| signed64 | -9223372036854775808 | +9223372036854775807 |
+----------+----------------------+----------------------+
Table 2: Ranges for Signed Abstract Data Types (in Decimal)
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4.4. float32 and float64
If the Enclosing Context defines a representation for floating-point
numbers, that representation SHOULD be used.
Otherwise, the values of Information Elements of float32 or float64
types are represented as optionally sign-prefixed, optionally base-10
exponent-suffixed, floating-point decimal numbers, as in
[IEEE.754.2008]. The special strings "NaN", "+inf", and "-inf"
represent "not a number", "positive infinity", and "negative
infinity", respectively.
In ABNF:
sign = "+" / "-"
exponent = "e" [sign] 1*3DIGIT
right-decimal = "." 1*DIGIT
mantissa = 1*DIGIT [right-decimal]
num = [sign] mantissa [exponent]
naninf = "NaN" / (sign "inf")
float = num / naninf
The expressed value is ( mantissa * 10 ^ exponent ). If the sign is
omitted, it is assumed to be positive. If the exponent is omitted,
it is assumed to be zero. Leading zeroes may appear in the mantissa
and/or the exponent. Values MUST be within range for single- or
double-precision numbers as defined in [IEEE.754.2008]; finite values
outside the appropriate range are to be interpreted as clamped to be
within the range. Note that no more than three digits are required
or allowed for exponents in this encoding due to these ranges.
Note that since this representation is meant for human readability,
writers MAY sacrifice precision to use a more human-readable
representation of a given value, at the expense of the ability to
recover the exact bit pattern at the reader. Therefore, decoders
MUST NOT assume that the represented values are exactly comparable
for equality.
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4.5. boolean
If the Enclosing Context defines a representation for boolean values,
that representation SHOULD be used.
Otherwise, a true boolean value is represented by the literal string
"true" and a false boolean value by the literal string "false". In
ABNF:
boolean-true = "true"
boolean-false = "false"
boolean = boolean-true / boolean-false
4.6. macAddress
Media Access Control (MAC) addresses are represented as IEEE 802
MAC-48 addresses, hexadecimal bytes with the most significant byte
first, separated by colons. In ABNF:
hex-octet = 2HEXDIG
macaddress = hex-octet 5( ":" hex-octet )
4.7. string
As Information Elements of the string type are simply Unicode strings
(encoded as UTF-8 when appearing in Data Sets in IPFIX Messages
[RFC7011]), they are represented directly, using the Unicode encoding
rules and quoting and escaping rules of the Enclosing Context.
If the Enclosing Context cannot natively represent Unicode
characters, the escaping facility provided by the Enclosing Context
MUST be used for nonrepresentable characters. Additionally, strings
containing characters reserved in the Enclosing Context (e.g.,
control characters, markup characters, and quotes) MUST be escaped or
quoted according to the rules of the Enclosing Context.
It is presumed that the Enclosing Context has sufficient restrictions
on the use of Unicode to prevent the unsafe use of nonprinting and
control characters. As there is no accepted solution for the
processing and safe display of mixed-direction strings, mixed-
direction strings should be avoided using this encoding. Note also
that since this document presents no additional requirements for the
normalization of Unicode strings, care must be taken when comparing
strings using this encoding; direct byte-pattern comparisons are not
sufficient for determining whether two strings are equivalent. See
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[RFC6885] and [PRECIS] for more on possible unexpected results and
related risks in comparing Unicode strings.
4.8. The dateTime ADTs
Timestamp abstract data types are represented generally as in
[RFC3339], with two important differences. First, all IPFIX
timestamps are expressed in terms of UTC, so textual representations
of these Information Elements are explicitly in UTC as well. Time
zone offsets are, therefore, not required or supported. Second,
there are four timestamp abstract data types, separated by the
precision that they can express. Fractional seconds are omitted in
dateTimeSeconds, expressed in milliseconds in dateTimeMilliseconds,
and so on.
In ABNF, taken from [RFC3339] and modified as follows:
date-fullyear = 4DIGIT
date-month = 2DIGIT ; 01-12
date-mday = 2DIGIT ; 01-28, 01-29, 01-30, 01-31
time-hour = 2DIGIT ; 00-23
time-minute = 2DIGIT ; 00-59
time-second = 2DIGIT ; 00-58, 00-59, 00-60
time-msec = "." 3DIGIT
time-usec = "." 6DIGIT
time-nsec = "." 9DIGIT
full-date = date-fullyear "-" date-month "-" date-mday
integer-time = time-hour ":" time-minute ":" time-second
datetimeseconds = full-date "T" integer-time
datetimemilliseconds = full-date "T" integer-time "." time-msec
datetimemicroseconds = full-date "T" integer-time "." time-usec
datetimenanoseconds = full-date "T" integer-time "." time-nsec
4.9. ipv4Address
IP version 4 addresses are represented in dotted-quad format, most
significant byte first, as it would be in a Uniform Resource
Identifier [RFC3986]; the ABNF for an IPv4 address is taken from
[RFC3986] and reproduced below:
dec-octet = DIGIT ; 0-9
/ %x31-39 DIGIT ; 10-99
/ "1" 2DIGIT ; 100-199
/ "2" %x30-34 DIGIT ; 200-249
/ "25" %x30-35 ; 250-255
ipv4address = dec-octet 3( "." dec-octet )
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4.10. ipv6Address
IP version 6 addresses are represented as in Section 2.2 of
[RFC4291], as updated by Section 4 of [RFC5952]. The ABNF for an
IPv6 address is taken from [RFC3986] and reproduced below, using the
ipv4address production from the previous section:
ls32 = ( h16 ":" h16 ) / ipv4address
; least significant 32 bits of address
h16 = 1*4HEXDIG
; 16 bits of address represented in hexadecimal
; zeroes to be suppressed as in RFC 5952
ipv6address = 6( h16 ":" ) ls32
/ "::" 5( h16 ":" ) ls32
/ [ h16 ] "::" 4( h16 ":" ) ls32
/ [ h16 ":" h16 ] "::" 3( h16 ":" ) ls32
/ [ *2( h16 ":" ) h16 ] "::" 2( h16 ":" ) ls32
/ [ *3( h16 ":" ) h16 ] "::" h16 ":" ls32
/ [ *4( h16 ":" ) h16 ] "::" ls32
/ [ *5( h16 ":" ) h16 ] "::" h16
/ [ *6( h16 ":" ) h16 ] "::"
4.11. basicList, subTemplateList, and subTemplateMultiList
These abstract data types, defined for IPFIX Structured Data
[RFC6313], do not represent actual data types; they are instead
designed to provide a mechanism by which complex structure can be
represented in IPFIX below the template level. It is assumed that
protocols using textual Information Element representation will
provide their own structure. Therefore, Information Elements of
these data types MUST NOT be used in textual representations.
5. Security Considerations
The security considerations for the IPFIX protocol [RFC7011] apply.
Implementations of decoders of Information Element values using these
representations must take care to correctly handle invalid input, but
the encodings presented here are not special in that respect.
The encoding specified in this document, and representations that may
be built upon it, are specifically not intended for the storage of
data. However, since storage of data in the format in which it is
exchanged is a very common practice, and the ubiquity of tools for
indexing and searching text significantly increases the ease of
searching and the risk of privacy-sensitive data being accidentally
indexed or searched, the privacy considerations in Section 11.8 of
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[RFC7011] are especially important to observe when storing data using
the encoding specified in this document that was derived from the
measurement of network traffic.
When using representations based on this encoding to transmit or
store network traffic data, consider omitting especially privacy-
sensitive values by not representing the columns or keys containing
those values, as in black-marker anonymization as discussed in
Section 4 of [RFC6235]. Other anonymization techniques described in
[RFC6235] may also be useful in these situations.
The encodings for all abstract data types other than 'string' are
defined in such a way as to be representable in the US-ASCII
character set and, therefore, should be unproblematic for all
Enclosing Contexts. However, the 'string' abstract data type may be
vulnerable to problems with ill-formed UTF-8 strings as discussed in
Section 6.1.6 of [RFC7011]; see [UTF8-EXPLOIT] for background.
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3339] Klyne, G., Ed. and C. Newman, "Date and Time on the
Internet: Timestamps", RFC 3339, July 2002,
<http://www.rfc-editor.org/info/rfc3986>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, RFC
3986, January 2005,
<http://www.rfc-editor.org/info/rfc3986>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006,
<http://www.rfc-editor.org/info/rfc4291>.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>.
[RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
Address Text Representation", RFC 5952, August 2010,
<http://www.rfc-editor.org/info/rfc5952>.
Trammell Standards Track [Page 10]RFC 7373 IPFIX Text Types September 2014
[RFC7011] Claise, B., Trammell, B., and P. Aitken, "Specification of
the IP Flow Information Export (IPFIX) Protocol for the
Exchange of Flow Information", STD 77, RFC 7011, September
2013, <http://www.rfc-editor.org/info/rfc7011>.
6.2. Informative References
[IANA-IPFIX]
IANA, "IPFIX Information Elements",
<http://www.iana.org/assignments/ipfix/>.
[IEEE.754.2008]
Institute of Electrical and Electronics Engineers, "IEEE
Standard for Floating-Point Arithmetic", IEEE Standard
754, August 2008.
[PRECIS] Saint-Andre, P. and M. Blanchet, "PRECIS Framework:
Preparation and Comparison of Internationalized Strings in
Application Protocols", Work in Progress, draft-ietf-
precis-framework-18, September 2014.
[RFC6235] Boschi, E. and B. Trammell, "IP Flow Anonymization
Support", RFC 6235, May 2011,
<http://www.rfc-editor.org/info/rfc6235>.
[RFC6313] Claise, B., Dhandapani, G., Aitken, P., and S. Yates,
"Export of Structured Data in IP Flow Information Export
(IPFIX)", RFC 6313, July 2011,
<http://www.rfc-editor.org/info/rfc6313>.
[RFC6885] Blanchet, M. and A. Sullivan, "Stringprep Revision and
Problem Statement for the Preparation and Comparison of
Internationalized Strings (PRECIS)", RFC 6885, March 2013,
<http://www.rfc-editor.org/info/rfc6885>.
[RFC7012] Claise, B. and B. Trammell, "Information Model for IP Flow
Information Export (IPFIX)", RFC 7012, September 2013,
<http://www.rfc-editor.org/info/rfc7012>.
[RFC7013] Trammell, B. and B. Claise, "Guidelines for Authors and
Reviewers of IP Flow Information Export (IPFIX)
Information Elements", BCP 184, RFC 7013, September 2013,
<http://www.rfc-editor.org/info/rfc7013>.
[RFC7159] Bray, T., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, March 2014,
<http://www.rfc-editor.org/info/rfc7159>.
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[UTF8-EXPLOIT]
Davis, M. and M. Suignard, "Unicode Technical Report #36:
Unicode Security Considerations", The Unicode Consortium,
November 2012.
[W3C-XML] Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E., and
F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fifth
Edition)", W3C Recommendation REC-xml, November 2008.
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Appendix A. Example
In this section, we examine an IPFIX Template and a Data Record
defined by that Template and show how that Data Record would be
represented in JSON according to the specification in this document.
Note that this is specifically NOT a recommendation for a particular
representation but merely an illustration of the encodings in this
document; the quoting and formatting in the example are JSON
specific.
Figure 1 shows a Template in Information Element Specifier (IESpec)
format as defined in Section 10.1 of [RFC7013]; a corresponding JSON
object representing a record defined by this template in the text
format specified in this document is shown in Figure 2.
flowStartMilliseconds(152)<dateTimeMilliseconds>[8]
flowEndMilliseconds(153)<dateTimeMilliseconds>[8]
octetDeltaCount(1)<unsigned64>[4]
packetDeltaCount(2)<unsigned64>[4]
sourceIPv6Address(27)<ipv6Address>[16]{key}
destinationIPv6Address(28)<ipv6Address>[16]{key}
sourceTransportPort(7)<unsigned16>[2]{key}
destinationTransportPort(11)<unsigned16>[2]{key}
protocolIdentifier(4)<unsigned8>[1]{key}
tcpControlBits(6)<unsigned16>[2]
flowEndReason(136)<unsigned8>[1]
Figure 1: Sample Flow Template in IESpec Format
{
"flowStartMilliseconds": "2012-11-05T18:31:01.135",
"flowEndMilliseconds": "2012-11-05T18:31:02.880",
"octetDeltaCount": 195383,
"packetDeltaCount": 88,
"sourceIPv6Address": "2001:db8:c:1337::2",
"destinationIPv6Address": "2001:db8:c:1337::3",
"sourceTransportPort": 80,
"destinationTransportPort": 32991,
"protocolIdentifier": "tcp",
"tcpControlBits": 19,
"flowEndReason": 3
}
Figure 2: JSON Object Containing Sample Flow
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Acknowledgments
Thanks to Paul Aitken, Benoit Claise, Andrew Feren, Juergen Quittek,
David Black, and the IESG for their reviews and comments. Thanks to
Dave Thaler and Stephan Neuhaus for discussions that improved the
floating-point representation section. This work is materially
supported by the European Union Seventh Framework Programme under
grant agreement 318627 mPlane.
Author's Address
Brian Trammell
Swiss Federal Institute of Technology Zurich
Gloriastrasse 35
8092 Zurich
Switzerland
Phone: +41 44 632 70 13
EMail: ietf@trammell.ch
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