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rfc:rfc5610

Network Working Group E. Boschi Request for Comments: 5610 B. Trammell Category: Standards Track Hitachi Europe

                                                               L. Mark
                                                       Fraunhofer IFAM
                                                              T. Zseby
                                                      Fraunhofer FOKUS
                                                             July 2009
                  Exporting Type Information for
      IP Flow Information Export (IPFIX) Information Elements

Abstract

 This document describes an extension to the IP Flow Information
 Export (IPFIX) protocol, which is used to represent and transmit data
 from IP flow measurement devices for collection, storage, and
 analysis, to allow the encoding of IPFIX Information Model properties
 within an IPFIX Message stream.  This enables the export of extended
 type information for enterprise-specific Information Elements and the
 storage of such information within IPFIX Files, facilitating
 interoperability and reusability among a wide variety of applications
 and tools.

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (c) 2009 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 in effect on the date of
 publication of this document (http://trustee.ietf.org/license-info).
 Please review these documents carefully, as they describe your rights
 and restrictions with respect to this document.

Boschi, et al. Standards Track [Page 1] RFC 5610 IPFIX Type Information July 2009

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   1.1.  IPFIX Documents Overview . . . . . . . . . . . . . . . . .  4
 2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
 3.  Type Information Export  . . . . . . . . . . . . . . . . . . .  5
   3.1.  informationElementDataType . . . . . . . . . . . . . . . .  5
   3.2.  informationElementDescription  . . . . . . . . . . . . . .  6
   3.3.  informationElementName . . . . . . . . . . . . . . . . . .  7
   3.4.  informationElementRangeBegin . . . . . . . . . . . . . . .  7
   3.5.  informationElementRangeEnd . . . . . . . . . . . . . . . .  7
   3.6.  informationElementSemantics  . . . . . . . . . . . . . . .  8
   3.7.  informationElementUnits  . . . . . . . . . . . . . . . . .  9
   3.8.  privateEnterpriseNumber  . . . . . . . . . . . . . . . . .  9
   3.9.  Information Element Type Options Template  . . . . . . . . 10
   3.10. Data Type and Semantics Restrictions . . . . . . . . . . . 12
 4.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
 5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
 6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
 7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
   7.1.  Normative References . . . . . . . . . . . . . . . . . . . 15
   7.2.  Informative References . . . . . . . . . . . . . . . . . . 16
 Appendix A.  Examples  . . . . . . . . . . . . . . . . . . . . . . 17

Boschi, et al. Standards Track [Page 2] RFC 5610 IPFIX Type Information July 2009

1. Introduction

 IP Flow Information Export (IPFIX) provides a template mechanism for
 the flexible description of Data Records, by defining a record as a
 collection of Information Elements defined in an IANA registry,
 However, these Templates provide limited information about the type
 of described data; indeed, they encode only the size of the fields
 defined by these Information Elements.  There presently exists no
 mechanism to provide full type information for these Information
 Elements, as is defined for the Information Elements in the IPFIX
 Information Model [RFC5102].
 This especially limits the interoperability of enterprise-specific
 Information Elements.  It is not possible to use analysis tools on
 IPFIX records containing these partially defined Information Elements
 that have not been developed with a priori knowledge of their types,
 since such tools will not be able to decode them; these tools can
 only treat and store them as opaque octet arrays.  However, if richer
 information is available, additional operations such as efficient
 storage, display, and limited analysis of records containing
 enterprise-specific Information Elements become possible, even for
 Collecting Processes that have not been specifically developed to
 understand them.
 This document defines a general mechanism to encode the full set of
 properties available for the definition of Information Elements
 within the IPFIX Information Model inline within an IPFIX Message
 stream using IPFIX Options.  This mechanism may be used to fully
 define type information for Information Elements used within a
 message stream, without resorting to an external reference or
 reliance on out-of-band configuration, thereby improving the
 interoperability of enterprise-specific Information Elements.
 Note that the solution described in this document is not intended as
 a replacement for registration with IANA of generally useful
 Information Elements.  It introduces overhead and does not lead to
 real interoperability as provided by standardization.  Therefore, we
 highly recommend standardizing all new generally useful Information
 Elements by registering them with IANA.  Standardization is
 straightforward, and the type information that needs to be specified
 in order to support the proposed solution provides a perfect basis
 for the description required for standardizing the Information
 Element.
 It might happen that an Information Element previously described by
 the mechanism in this document later becomes an IANA-registered,
 standard Information Element.  In such environments, old and new
 versions of the Information Element can coexist.  A translation

Boschi, et al. Standards Track [Page 3] RFC 5610 IPFIX Type Information July 2009

 between Information Elements expressed by the described solution and
 standardized Information Elements is therefore not necessary and is
 out of scope for this document.

1.1. IPFIX Documents Overview

 "Specification of the IP Flow Information Export (IPFIX) Protocol for
 the Exchange of IP Traffic Flow Information" [RFC5101] (informally,
 the IPFIX Protocol document) and its associated documents define the
 IPFIX Protocol, which provides network engineers and administrators
 with access to IP traffic flow information.
 "Architecture for IP Flow Information Export" [RFC5470] (the IPFIX
 Architecture document) defines the architecture for the export of
 measured IP flow information out of an IPFIX Exporting Process to an
 IPFIX Collecting Process, and the basic terminology used to describe
 the elements of this architecture, per the requirements defined in
 "Requirements for IP Flow Information Export" [RFC3917].  The IPFIX
 Protocol document [RFC5101] then covers the details of the method for
 transporting IPFIX Data Records and Templates via a congestion-aware
 transport protocol from an IPFIX Exporting Process to an IPFIX
 Collecting Process.
 "Information Model for IP Flow Information Export" [RFC5102]
 (informally, the IPFIX Information Model document) describes the
 Information Elements used by IPFIX, including details on Information
 Element naming, numbering, and data type encoding.
 This document references the Protocol and Architecture documents for
 terminology and extends the IPFIX Information Model to provide new
 Information Elements for the representation of Information Element
 properties.  It draws data type definitions and data type semantics
 definitions from the Information Model; the encodings of these data
 types are defined in [RFC5101].

2. Terminology

 Terms used in this document that are defined in the Terminology
 section of the IPFIX Protocol [RFC5101] document are to be
 interpreted as defined there.
 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in RFC 2119 [RFC2119].

Boschi, et al. Standards Track [Page 4] RFC 5610 IPFIX Type Information July 2009

3. Type Information Export

 This section describes the mechanism used to encode Information
 Element type information within an IPFIX Message stream.  This
 mechanism consists of an Options Template Record used to define
 Information Element type records, and a set of Information Elements
 required by these type records.  We first specify the necessary
 Information Elements, followed by the structure of the Options
 Template describing the type records.
 Note that Information Element type records require one Information
 Element, informationElementId, that is defined in the Packet Sampling
 (PSAMP) Information Model [RFC5477].  This Information Element
 supports references only to IANA-defined Information Elements; the
 privateEnterpriseNumber Information Element is required alongside
 informationElementId to describe enterprise-specific Information
 Elements.

3.1. informationElementDataType

 Description:   A description of the abstract data type of an IPFIX
    information element.  These are taken from the abstract data types
    defined in Section 3.1 of the IPFIX Information Model [RFC5102];
    see that section for more information on the types described
    below.  This field may take the values defined in Table 1 below.

Boschi, et al. Standards Track [Page 5] RFC 5610 IPFIX Type Information July 2009

                   +-------+----------------------+
                   | Value | Description          |
                   +-------+----------------------+
                   | 0     | octetArray           |
                   | 1     | unsigned8            |
                   | 2     | unsigned16           |
                   | 3     | unsigned32           |
                   | 4     | unsigned64           |
                   | 5     | signed8              |
                   | 6     | signed16             |
                   | 7     | signed32             |
                   | 8     | signed64             |
                   | 9     | float32              |
                   | 10    | float64              |
                   | 11    | boolean              |
                   | 12    | macAddress           |
                   | 13    | string               |
                   | 14    | dateTimeSeconds      |
                   | 15    | dateTimeMilliseconds |
                   | 16    | dateTimeMicroseconds |
                   | 17    | dateTimeNanoseconds  |
                   | 18    | ipv4Address          |
                   | 19    | ipv6Address          |
                   +-------+----------------------+
                       Table 1: IE Data Type Values
    These types are registered in the IANA IPFIX Information Element
    Data Type subregistry.  This subregistry is intended to assign
    numbers for type names, not to provide a mechanism for adding data
    types to the IPFIX Protocol, and as such requires a Standards
    Action [RFC5226] to modify.
 Abstract Data Type:   unsigned8
 ElementId:   339
 Status:   current
 Reference:   Section 3.1 of the IPFIX Information Model [RFC5102]

3.2. informationElementDescription

 Description:   A UTF-8 [RFC3629] encoded Unicode string containing a
    human-readable description of an Information Element.  The content
    of the informationElementDescription MAY be annotated with one or
    more language tags [RFC4646], encoded in-line [RFC2482] within the
    UTF-8 string, in order to specify the language in which the

Boschi, et al. Standards Track [Page 6] RFC 5610 IPFIX Type Information July 2009

    description is written.  Description text in multiple languages
    MAY tag each section with its own language tag; in this case, the
    description information in each language SHOULD have equivalent
    meaning.  In the absence of any language tag, the "i-default"
    [RFC2277] language SHOULD be assumed.  See the Security
    Considerations (Section 4) for notes on string handling for
    Information Element type records.
 Abstract Data Type:   string
 ElementId:   340
 Status:   current

3.3. informationElementName

 Description:   A UTF-8 [RFC3629] encoded Unicode string containing
    the name of an Information Element, intended as a simple
    identifier.  See the Security Considerations (Section 4) for notes
    on string handling for Information Element type records.
 Abstract Data Type:   string
 ElementId:   341
 Status:   current

3.4. informationElementRangeBegin

 Description:   Contains the inclusive low end of the range of
    acceptable values for an Information Element.
 Abstract Data Type:   unsigned64
 Data Type Semantics:   quantity
 ElementId:   342
 Status:   current

3.5. informationElementRangeEnd

 Description:   Contains the inclusive high end of the range of
    acceptable values for an Information Element.

Boschi, et al. Standards Track [Page 7] RFC 5610 IPFIX Type Information July 2009

 Abstract Data Type:   unsigned64
 Data Type Semantics:   quantity
 ElementId:   343
 Status:   current

3.6. informationElementSemantics

 Description:   A description of the semantics of an IPFIX Information
    Element.  These are taken from the data type semantics defined in
    Section 3.2 of the IPFIX Information Model [RFC5102]; see that
    section for more information on the types described below.  This
    field may take the values in Table 2 below.  The special value
    0x00 (default) is used to note that no semantics apply to the
    field; it cannot be manipulated by a Collecting Process or File
    Reader that does not understand it a priori.
                       +-------+--------------+
                       | Value | Description  |
                       +-------+--------------+
                       | 0     | default      |
                       | 1     | quantity     |
                       | 2     | totalCounter |
                       | 3     | deltaCounter |
                       | 4     | identifier   |
                       | 5     | flags        |
                       +-------+--------------+
                       Table 2: IE Semantics Values
    These semantics are registered in the IANA IPFIX Information
    Element Semantics subregistry.  This subregistry is intended to
    assign numbers for semantics names, not to provide a mechanism for
    adding semantics to the IPFIX Protocol, and as such requires a
    Standards Action [RFC5226] to modify.
 Abstract Data Type:   unsigned8
 ElementId:   344
 Status:   current
 Reference:   Section 3.2 of the IPFIX Information Model [RFC5102]

Boschi, et al. Standards Track [Page 8] RFC 5610 IPFIX Type Information July 2009

3.7. informationElementUnits

 Description:   A description of the units of an IPFIX Information
    Element.  These correspond to the units implicitly defined in the
    Information Element definitions in Section 5 of the IPFIX
    Information Model [RFC5102]; see that section for more information
    on the types described below.  This field may take the values in
    Table 3 below; the special value 0x00 (none) is used to note that
    the field is unitless.
         +-------+---------------+---------------------------+
         | Value | Name          | Notes                     |
         +-------+---------------+---------------------------+
         | 0     | none          |                           |
         | 1     | bits          |                           |
         | 2     | octets        |                           |
         | 3     | packets       |                           |
         | 4     | flows         |                           |
         | 5     | seconds       |                           |
         | 6     | milliseconds  |                           |
         | 7     | microseconds  |                           |
         | 8     | nanoseconds   |                           |
         | 9     | 4-octet words | for IPv4 header length    |
         | 10    | messages      | for reliability reporting |
         | 11    | hops          | for TTL                   |
         | 12    | entries       | for MPLS label stack      |
         +-------+---------------+---------------------------+
                         Table 3: IE Units Values
    These types are registered in the IANA IPFIX Information Element
    Units subregistry; new types may be added on a First Come First
    Served [RFC5226] basis.
 Abstract Data Type:   unsigned16
 ElementId:   345
 Status:   current
 Reference:   Section 5 of the IPFIX Information Model [RFC5102]

3.8. privateEnterpriseNumber

 Description:   A private enterprise number, as assigned by IANA.
    Within the context of an Information Element Type record, this
    element can be used along with the informationElementId element to
    scope properties to a specific Information Element.  To export

Boschi, et al. Standards Track [Page 9] RFC 5610 IPFIX Type Information July 2009

    type information about an IANA-assigned Information Element, set
    the privateEnterpriseNumber to 0, or do not export the
    privateEnterpriseNumber in the type record.  To export type
    information about an enterprise-specific Information Element,
    export the enterprise number in privateEnterpriseNumber, and
    export the Information Element number with the Enterprise bit
    cleared in informationElementId.  The Enterprise bit in the
    associated informationElementId Information Element MUST be
    ignored by the Collecting Process.
 Abstract Data Type:   unsigned32
 Data Type Semantics:   identifier
 ElementId:   346
 Status:   current
 Reference:   Sections 3.2 and 3.4.1 of the IPFIX Protocol [RFC5101];
    Section 8.2.3 of the PSAMP Information Model [RFC5477].

3.9. Information Element Type Options Template

 The Information Element Type Options Template attaches type
 information to Information Elements used within Template Records, as
 scoped to an Observation Domain within a Transport Session.  This
 provides a mechanism for representing an IPFIX Information Model
 inline within an IPFIX Message stream.  Data Records described by
 this template are referred to as Information Element type records.
 In deployments in which interoperability across vendor
 implementations of IPFIX is important, an Exporting Process exporting
 data using Templates containing enterprise-specific Information
 Elements SHOULD export an Information Element type record for each
 enterprise-specific Information Element it exports.  Collecting
 Processes MAY use these type records to improve handling of unknown
 enterprise-specific Information Elements.  Exporting Processes using
 enterprise-specific Information Elements to implement proprietary
 features MAY omit type records for those Information Elements.
 Information Element type records MUST be handled by Collecting
 Processes as scoped to the Transport Session in which they are sent;
 this facility is not intended to provide a method for the permanent
 definition of Information Elements.
 Similarly, for security reasons, type information for a given
 Information Element MUST NOT be redefined by Information Element type
 records, and a Collecting Process MUST NOT allow an Information

Boschi, et al. Standards Track [Page 10] RFC 5610 IPFIX Type Information July 2009

 Element type record to replace its own internal definition of an
 Information Element.  Information Element type records SHOULD NOT be
 duplicated in a given Observation Domain within a Transport Session.
 Once an Information Element type record has been exported for a given
 Information Element within a given Transport Session, all subsequent
 type records for that Information Element MUST be identical.
 Information Elements for which a Collecting Process receives
 conflicting semantic or type information MUST be ignored.
 Note that while this template MAY be used to export information about
 any Information Element, including those registered with IANA,
 Exporting Processes SHOULD NOT export any type records that could be
 reasonably assumed to duplicate type information available at the
 Collecting Process.  This mechanism is not intended as a replacement
 for Exporting and Collecting Processes keeping up to date with
 changes to the IANA registry; such an update mechanism is out of
 scope for this document.
 The template SHOULD contain the Information Elements in Table 4,
 below, as defined in the PSAMP Information Model [RFC5477] and in
 this document, above.
 +-------------------------------+-----------------------------------+
 | IE                            | Description                       |
 +-------------------------------+-----------------------------------+
 | informationElementId [scope]  | The Information Element           |
 |                               | identifier of the Information     |
 |                               | Element described by this type    |
 |                               | record.  This Information Element |
 |                               | MUST be defined as a Scope Field. |
 |                               | See the PSAMP Information Model   |
 |                               | [RFC5477] for a definition of     |
 |                               | this field.                       |
 | privateEnterpriseNumber       | The Private Enterprise number of  |
 | [scope]                       | the Information Element described |
 |                               | by this type record.  This        |
 |                               | Information Element MUST be       |
 |                               | defined as a Scope Field.         |
 | informationElementDataType    | The storage type of the specified |
 |                               | Information Element.              |
 | informationElementSemantics   | The semantic type of the          |
 |                               | specified Information Element.    |
 | informationElementUnits       | The units of the specified        |
 |                               | Information Element.  This        |
 |                               | element SHOULD be omitted if the  |
 |                               | Information Element is a unitless |
 |                               | quantity, or a not a quantity or  |
 |                               | counter.                          |

Boschi, et al. Standards Track [Page 11] RFC 5610 IPFIX Type Information July 2009

 +-------------------------------+-----------------------------------+
 | IE (Continued)                | Description (Continued)           |
 +-------------------------------+-----------------------------------+
 | informationElementRangeBegin  | The low end of the range of       |
 |                               | acceptable values for the         |
 |                               | specified Information Element.    |
 |                               | This element SHOULD be omitted if |
 |                               | the beginning of the Information  |
 |                               | Element's acceptable range is     |
 |                               | defined by its data type.         |
 | informationElementRangeEnd    | The high end of the range of      |
 |                               | acceptable values for the         |
 |                               | specified Information Element.    |
 |                               | This element SHOULD be omitted if |
 |                               | the end Information Element's     |
 |                               | acceptable range is defined by    |
 |                               | its data type.                    |
 | informationElementName        | The name of the specified         |
 |                               | Information Element.              |
 | informationElementDescription | A human-readable description of   |
 |                               | the specified Information         |
 |                               | Element.  This element MAY be     |
 |                               | omitted in the interest of export |
 |                               | efficiency.                       |
 +-------------------------------+-----------------------------------+
                       Table 4: IE Type Options

3.10. Data Type and Semantics Restrictions

 Note that the informationElementSemantics values defined in Section
 3.2 of [RFC5102] are primarily intended to differentiate semantic
 interpretation of numeric values, and that not all combinations of
 the informationElementDataType and informationElementSemantics
 Information Elements are valid; e.g., a counter cannot be encoded as
 an IPv4 address.  The following are acceptable values of
 informationElementSemantics:
 o  Any value is valid for unsigned informationElementDataType values
    ("unsigned8", "unsigned16", "unsigned32", or "unsigned64").
 o  Any value except "flags" is valid for signed
    informationElementDataType values ("signed8", "signed16",
    "signed32", or "signed64").
 o  Any value except "identifier" or "flags" is valid for floating-
    point informationElementDataType values ("float32" or "float64").

Boschi, et al. Standards Track [Page 12] RFC 5610 IPFIX Type Information July 2009

 o  Only "default" is valid for all other informationElementDataType
    values ("octetArray", "boolean", "macAddress", "string",
    "dateTimeSeconds", "dateTimeMilliseconds", "dateTimeMicroseconds",
    "dateTimeNanoseconds", "ipv4Address", or "ipv6Address").
 Information Element type records containing invalid combinations of
 informationElementSemantics and informationElementDataType MUST NOT
 be sent by Exporting Processes, and MUST be ignored by Collecting
 Processes.
 Future Standards Actions that modify the Information Element Data
 Type subregistry or the Information Element Semantics subregistry
 should contain a Data Type and Semantics Restrictions section such as
 this one to define allowable combinations of type and semantics
 information.

4. Security Considerations

 The same security considerations as for the IPFIX Protocol [RFC5101]
 apply.
 In addition, attention must be paid to the handling of Information
 Element type records at the Collecting Process.  Type information
 precedence rules defined above (a Collecting Process' current
 knowledge overrides type records; types are not redefinable during a
 session) are designed to minimize the opportunity for an attacker to
 maliciously redefine the data model.
 Note that Information Element type records may contain two strings
 describing Information Elements: informationElementName and
 informationElementDescription.  IPFIX strings on the wire are length-
 prefixed and UTF-8 [RFC3629] encoded, most often within an IPFIX
 variable-length Information Element, which mitigates the risk of
 unterminated-string attacks against IPFIX Collecting Processes.
 However, care should still be taken when handling strings within the
 type system of the Collecting Process.
 First, Collecting Processes should pay particular attention to buffer
 sizes converting between length-prefixed and null-terminated strings.
 Exporting Processes MUST NOT export, and Collecting Processes MUST
 ignore, any informationElementName or informationElementDescription
 content that contains null characters (U+0000) in order to ensure
 buffer and string lengths are consistent.
 Also, note that there is no limit to IPFIX string length beyond that
 inherent in the protocol.  The maximum IPFIX string length is 65512
 octets (maximum message length (65535), minus message header (16),
 minus set header (4), minus long variable length field (3)).

Boschi, et al. Standards Track [Page 13] RFC 5610 IPFIX Type Information July 2009

 Specifically, although the informationElementName of all IANA
 Information Elements at the time of this writing is less than about
 40 octets, and the informationElementDescription is less than 4096
 octets, either of these Information Elements may contain strings up
 to 65512 octets long.

5. IANA Considerations

 This document specifies several new IPFIX Information Elements in the
 IPFIX Information Element registry as defined in Section 3 above.
 IANA has assigned the following Information Element numbers for their
 respective Information Elements as specified below:
 o  Information Element Number 339 for the informationElementDataType
    Information Element
 o  Information Element Number 340 for the
    informationElementDescription Information Element
 o  Information Element Number 341 for the informationElementName
    Information Element
 o  Information Element Number 342 for the
    informationElementRangeBegin Information Element
 o  Information Element Number 343 for the informationElementRangeEnd
    Information Element
 o  Information Element Number 344 for the informationElementSemantics
    Information Element
 o  Information Element Number 345 for the informationElementUnits
    Information Element
 o  Information Element Number 346 for the privateEnterpriseNumber
    Information Element
 IANA has created an Information Element Data Type subregistry for the
 values defined for the informationElementDataType Information
 Element.  Entries may be added to this subregistry subject to a
 Standards Action [RFC5226].
 IANA has created an Information Element Semantics subregistry for the
 values defined for the informationElementSemantics Information
 Element.  Entries may be added to this subregistry subject to a
 Standards Action [RFC5226].

Boschi, et al. Standards Track [Page 14] RFC 5610 IPFIX Type Information July 2009

 IANA has created an Information Element Units subregistry for the
 values defined for the informationElementUnits Information Element.
 Entries may be added to this subregistry on an Expert Review
 [RFC5226] basis.

6. Acknowledgements

 Thanks to Paul Aitken and Gerhard Muenz for the detailed reviews, and
 to David Moore for first raising this issue to the IPFIX mailing
 list.  Thanks to the PRISM project for its support of this work.

7. References

7.1. 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.
 [RFC5477]  Dietz, T., Claise, B., Aitken, P., Dressler, F., and G.
            Carle, "Information Model for Packet Sampling Exports",
            RFC 5477, March 2009.
 [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
            10646", STD 63, RFC 3629, November 2003.
 [RFC2277]  Alvestrand, H., "IETF Policy on Character Sets and
            Languages", BCP 18, RFC 2277, January 1998.
 [RFC2482]  Whistler, K. and G. Adams, "Language Tagging in Unicode
            Plain Text", RFC 2482, January 1999.
 [RFC4646]  Phillips, A. and M. Davis, "Tags for Identifying
            Languages", BCP 47, RFC 4646, September 2006.
 [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
            IANA Considerations Section in RFCs", BCP 26, RFC 5226,
            May 2008.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.

Boschi, et al. Standards Track [Page 15] RFC 5610 IPFIX Type Information July 2009

7.2. Informative References

 [RFC3917]  Quittek, J., Zseby, T., Claise, B., and S. Zander,
            "Requirements for IP Flow Information Export (IPFIX)",
            RFC 3917, October 2004.
 [RFC5470]  Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,
            "Architecture for IP Flow Information Export", RFC 5470,
            March 2009.

Boschi, et al. Standards Track [Page 16] RFC 5610 IPFIX Type Information July 2009

Appendix A. Examples

 The following example illustrates how the type information extension
 mechanism defined in this document may be used to describe the
 semantics of enterprise-specific Information Elements.  The
 Information Elements used in this example are as follows:
 o  initialTCPFlags, an example private IE 14, 1 octet, the TCP flags
    on the first TCP packet in the flow.
 o  unionTCPFlags, an example private IE 15, 1 octet, the union of the
    TCP flags on all packets after the first TCP packet in the flow.
 An Exporting Process exporting flows containing these Information
 Elements might use a Template like the following:
                      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 =  52         |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      Template ID = 256        |        Field Count = 9        |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |0| flowStartSeconds        150 |       Field Length =  4       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |0| sourceIPv4Address         8 |       Field Length =  4       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |0| destinationIPv4Address   12 |       Field Length =  4       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |0| sourceTransportPort       7 |       Field Length =  2       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |0| destinationTransportPort 11 |       Field Length =  2       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |0| octetTotalCount          85 |       Field Length =  4       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |1| (initialTCPFlags)        14 |       Field Length =  1       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                  Private Enterprise Number                    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |1| (unionTCPFlags)          15 |       Field Length =  1       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                  Private Enterprise Number                    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |0| protocolIdentifier        4 |       Field Length =  1       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            Figure 1: Template with Enterprise-Specific IEs

Boschi, et al. Standards Track [Page 17] RFC 5610 IPFIX Type Information July 2009

 However, a Collecting Process receiving Data Sets described by this
 Template can only treat the enterprise-specific Information Elements
 as opaque octets; specifically, there is no hint to the collector
 that they contain flag information.  To use the type information
 extension mechanism to address this problem, the Exporting Process
 would first export the Information Element Type Options Template
 described in Section 3.9 above:
                      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 =  26         |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      Template ID = 257        |        Field Count = 4        |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Scope Field Count = 2      |0| priv.EnterpriseNumber   346 |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |       Field Length = 4        |0| informationElementId    303 |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |       Field Length = 2        |0| inf.El.DataType         339 |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |       Field Length = 1        |0| inf.El.Semantics        344 |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |       Field Length = 1        |0| inf.El.Name             341 |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Field Length = 65536      |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      Figure 2: Example Information Element Type Options Template
 Then, the Exporting Process would export two records described by the
 Example Information Element Type Options Template to describe the
 enterprise-specific Information Elements:

Boschi, et al. Standards Track [Page 18] RFC 5610 IPFIX Type Information July 2009

                      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 =  50         |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                  Private Enterprise Number                    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |X|         IE 14               |0x01 unsigned8 |0x05 flags     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   15 length   |                                               |
 +-+-+-+-+-+-+-+-+                                               |
 |                      "initialTCPFlags"                        |
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                  Private Enterprise Number                    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |X|         IE 15               |0x01 unsigned8 |0x05 flags     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   13 length   |                                               |
 +-+-+-+-+-+-+-+-+        "unionTCPFlags"                        |
 |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                     Figure 3: Type Record Example

Boschi, et al. Standards Track [Page 19] RFC 5610 IPFIX Type Information July 2009

Authors' Addresses

 Elisa Boschi
 Hitachi Europe
 c/o ETH Zurich
 Gloriastrasse 35
 8092 Zurich
 Switzerland
 Phone: +41 44 632 70 57
 EMail: elisa.boschi@hitachi-eu.com
 Brian Trammell
 Hitachi Europe
 c/o ETH Zurich
 Gloriastrasse 35
 8092 Zurich
 Switzerland
 Phone: +41 44 632 70 13
 EMail: brian.trammell@hitachi-eu.com
 Lutz Mark
 Fraunhofer Institute for Manufacturing Technology
 and Applied Materials Research
 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

Boschi, et al. Standards Track [Page 20]

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