Network Working Group B. Claise, Ed.

Network Working Group B. Claise, Ed.
Request for Comments: 3954 Cisco Systems
Category: Informational October 2004

Cisco Systems NetFlow Services Export Version 9

Status of this Memo

This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (2004).

IESG Note

This RFC documents the NetFlow services export protocol Version 9 as
it was when submitted to the IETF as a basis for further work in the
IPFIX WG.

This RFC itself is not a candidate for any level of Internet
Standard. The IETF disclaims any knowledge of the fitness of this
RFC for any purpose, and in particular notes that it has not had
complete IETF review for such things as security, congestion control,
or inappropriate interaction with deployed protocols. The RFC Editor
has chosen to publish this document at its discretion.

Abstract

This document specifies the data export format for version 9 of Cisco
Systems' NetFlow services, for use by implementations on the network
elements and/or matching collector programs. The version 9 export
format uses templates to provide access to observations of IP packet
flows in a flexible and extensible manner. A template defines a
collection of fields, with corresponding descriptions of structure
and semantics.

Table of Contents

1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Terminology Summary Table . . . . . . . . . . . . . . . 6
3. NetFlow High-Level Picture on the Exporter. . . . . . . . . . 6
3.1. The NetFlow Process on the Exporter . . . . . . . . . . 6
3.2. Flow Expiration . . . . . . . . . . . . . . . . . . . . 7

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3.3. Transport Protocol. . . . . . . . . . . . . . . . . . . 7
4. Packet Layout . . . . . . . . . . . . . . . . . . . . . . . . 8
5. Export Packet Format. . . . . . . . . . . . . . . . . . . . . 9
5.1. Header Format . . . . . . . . . . . . . . . . . . . . . 9
5.2. Template FlowSet Format . . . . . . . . . . . . . . . . 11
5.3. Data FlowSet Format . . . . . . . . . . . . . . . . . . 13
6. Options . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.1. Options Template FlowSet Format . . . . . . . . . . . . 14
6.2. Options Data Record Format. . . . . . . . . . . . . . . 16
7. Template Management . . . . . . . . . . . . . . . . . . . . . 17
8. Field Type Definitions. . . . . . . . . . . . . . . . . . . . 18
9. The Collector Side. . . . . . . . . . . . . . . . . . . . . . 25
10. Security Considerations . . . . . . . . . . . . . . . . . . . 26
10.1. Disclosure of Flow Information Data . . . . . . . . . . 26
10.2. Forgery of Flow Records or Template Records . . . . . . 26
10.3. Attacks on the NetFlow Collector. . . . . . . . . . . . 27
11. Examples. . . . . . . . . . . . . . . . . . . . . . . . . . . 27
11.1. Packet Header Example . . . . . . . . . . . . . . . . . 28
11.2. Template FlowSet Example. . . . . . . . . . . . . . . . 28
11.3. Data FlowSet Example. . . . . . . . . . . . . . . . . . 29
11.4. Options Template FlowSet Example. . . . . . . . . . . . 30
11.5. Data FlowSet with Options Data Records Example. . . . . 30
12. References. . . . . . . . . . . . . . . . . . . . . . . . . . 31
12.1. Normative References. . . . . . . . . . . . . . . . . . 31
12.2. Informative References. . . . . . . . . . . . . . . . . 31
13. Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 31
15. Authors' Addresses. . . . . . . . . . . . . . . . . . . . . . 32
16. Full Copyright Statement. . . . . . . . . . . . . . . . . . . 33

1. Introduction

Cisco Systems' NetFlow services provide network administrators with
access to IP flow information from their data networks. Network
elements (routers and switches) gather flow data and export it to
collectors. The collected data provides fine-grained metering for
highly flexible and detailed resource usage accounting.

A flow is defined as a unidirectional sequence of packets with some
common properties that pass through a network device. These
collected flows are exported to an external device, the NetFlow
collector. Network flows are highly granular; for example, flow
records include details such as IP addresses, packet and byte counts,
timestamps, Type of Service (ToS), application ports, input and
output interfaces, etc.

Exported NetFlow data is used for a variety of purposes, including
enterprise accounting and departmental chargebacks, ISP billing, data

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warehousing, network monitoring, capacity planning, application
monitoring and profiling, user monitoring and profiling, security
analysis, and data mining for marketing purposes.

This document specifies NetFlow version 9. It describes the
implementation specifications both from network element and NetFlow
collector points of view. These specifications should help the
deployment of NetFlow version 9 across different platforms and
different vendors by limiting the interoperability risks. The
NetFlow export format version 9 uses templates to provide access to
observations of IP packet flows in a flexible and extensible manner.

A template defines a collection of fields, with corresponding
descriptions of structure and semantics.

The template-based approach provides the following advantages:

- New fields can be added to NetFlow flow records without
changing the structure of the export record format. With
previous NetFlow versions, adding a new field in the flow
record implied a new version of the export protocol format and
a new version of the NetFlow collector that supported the
parsing of the new export protocol format.

- Templates that are sent to the NetFlow collector contain the
structural information about the exported flow record fields;
therefore, if the NetFlow collector does not understand the
semantics of new fields, it can still interpret the flow
record.

- Because the template mechanism is flexible, it allows the
export of only the required fields from the flows to the
NetFlow collector. This helps to reduce the exported flow data
volume and provides possible memory savings for the exporter
and NetFlow collector. Sending only the required information
can also reduce network load.

The IETF IPFIX Working Group (IP Flow Information eXport) is
developing a new protocol, based on the version 9 of Cisco Systems'
NetFlow services. Some enhancements in different domains (congestion
aware transport protocol, built-in security, etc... ) have been
incorporated in this new IPFIX protocol. Refer to the IPFIX Working
Group documents for more details.

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 BCP 14, RFC 2119
[RFC2119].

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2. Terminology

Various terms used in this document are described in this section.
Note that the terminology summary table in Section 2.1 gives a quick
overview of the relationships between some of the different terms
defined.

Observation Point
An Observation Point is a location in the network where IP packets
can be observed; for example, one or a set of interfaces on a network
device like a router. Every Observation Point is associated with an
Observation Domain.

Observation Domain
The set of Observation Points that is the largest aggregatable set of
flow information at the network device with NetFlow services enabled
is termed an Observation Domain. For example, a router line card
composed of several interfaces with each interface being an
Observation Point.

IP Flow or Flow
An IP Flow, also called a Flow, is defined as a set of IP packets
passing an Observation Point in the network during a certain time
interval. All packets that belong to a particular Flow have a set of
common properties derived from the data contained in the packet and
from the packet treatment at the Observation Point.

Flow Record
A Flow Record provides information about an IP Flow observed at an
Observation Point. In this document, the Flow Data Records are also
referred to as NetFlow services data and NetFlow data.

Exporter
A device (for example, a router) with the NetFlow services enabled,
the Exporter monitors packets entering an Observation Point and
creates Flows from these packets. The information from these Flows
is exported in the form of Flow Records to the NetFlow Collector.

NetFlow Collector
The NetFlow Collector receives Flow Records from one or more
Exporters. It processes the received Export Packet(s); that is, it
parses and stores the Flow Record information. Flow Records can be
optionally aggregated before being stored on the hard disk. The
NetFlow Collector is also referred to as the Collector in this
document.

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Export Packet
An Export Packet is a packet originating at the Exporter that carries
the Flow Records of this Exporter and whose destination is the
NetFlow Collector.

Packet Header
The Packet Header is the first part of an Export Packet. The Packet
Header provides basic information about the packet such as the
NetFlow version, number of records contained within the packet, and
sequence numbering.

Template Record
A Template Record defines the structure and interpretation of fields
in a Flow Data Record.

Flow Data Record
A Flow Data Record is a data record that contains values of the Flow
parameters corresponding to a Template Record.

Options Template Record
An Options Template Record defines the structure and interpretation
of fields in an Options Data Record, including defining the scope
within which the Options Data Record is relevant.

Options Data Record
The data record that contains values and scope information of the
Flow measurement parameters, corresponding to an Options Template
Record.

FlowSet
FlowSet is a generic term for a collection of Flow Records that have
a similar structure. In an Export Packet, one or more FlowSets
follow the Packet Header. There are three different types of
FlowSets: Template FlowSet, Options Template FlowSet, and Data
FlowSet.

Template FlowSet
A Template FlowSet is one or more Template Records that have been
grouped together in an Export Packet.

Options Template FlowSet
An Options Template FlowSet is one or more Options Template Records
that have been grouped together in an Export Packet.

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Data FlowSet
A Data FlowSet is one or more records, of the same type, that are
grouped together in an Export Packet. Each record is either a Flow
Data Record or an Options Data Record previously defined by a
Template Record or an Options Template Record.

2.1. Terminology Summary Table

+------------------+---------------------------------------------+
| | Contents |
| +--------------------+------------------------+
| FlowSet | Template Record | Data Record |
+------------------+--------------------+------------------------+
| | | Flow Data Record(s) |
| Data FlowSet | / | or |
| | | Options Data Record(s) |
+------------------+--------------------+------------------------+
| Template FlowSet | Template Record(s) | / |
+------------------+--------------------+------------------------+
| Options Template | Options Template | / |
| FlowSet | Record(s) | |
+------------------+--------------------+------------------------+

A Data FlowSet is composed of an Options Data Record(s) or Flow Data
Record(s). No Template Record is included. A Template Record defines
the Flow Data Record, and an Options Template Record defines the
Options Data Record.

A Template FlowSet is composed of Template Record(s). No Flow or
Options Data Record is included.

An Options Template FlowSet is composed of Options Template
Record(s). No Flow or Options Data Record is included.

3. NetFlow High-Level Picture on the Exporter

3.1. The NetFlow Process on the Exporter

The NetFlow process on the Exporter is responsible for the creation
of Flows from the observed IP packets. The details of this process
are beyond the scope of this document.

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3.2. Flow Expiration

A Flow is considered to be inactive if no packets belonging to the
Flow have been observed at the Observation Point for a given timeout.
If any packet is seen within the timeout, the flow is considered an
active flow. A Flow can be exported under the following conditions:

1. If the Exporter can detect the end of a Flow. For example, if
the FIN or RST bit is detected in a TCP [RFC793] connection,
the Flow Record is exported.

2. If the Flow has been inactive for a certain period of time.
This inactivity timeout SHOULD be configurable at the Exporter,
with a minimum value of 0 for an immediate expiration.

3. For long-lasting Flows, the Exporter SHOULD export the Flow
Records on a regular basis. This timeout SHOULD be
configurable at the Exporter.

4. If the Exporter experiences internal constraints, a Flow MAY be
forced to expire prematurely; for example, counters wrapping or
low memory.

3.3. Transport Protocol

To achieve efficiency in terms of processing at the Exporter while
handling high volumes of Export Packets, the NetFlow Export Packets
are encapsulated into UDP [RFC768] datagrams for export to the
NetFlow Collector. However, NetFlow version 9 has been designed to
be transport protocol independent. Hence, it can also operate over
congestion-aware protocols such as SCTP [RFC2960].

Note that the Exporter can export to multiple Collectors, using
independent transport protocols.

UDP [RFC768] is a non congestion-aware protocol, so when deploying
NetFlow version 9 in a congestion-sensitive environment, make the
connection between Exporter and NetFlow Collector through a dedicated
link. This ensures that any burstiness in the NetFlow traffic
affects only this dedicated link. When the NetFlow Collector can not
be placed within a one-hop distance from the Exporter or when the
export path from the Exporter to the NetFlow Collector can not be
exclusively used for the NetFlow Export Packets, the export path
should be designed so that it can always sustain the maximum
burstiness of NetFlow traffic from the Exporter. Note that the
congestion can occur on the Exporter in case the export path speed is
too low.

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4. Packet Layout

An Export Packet consists of a Packet Header followed by one or more
FlowSets. The FlowSets can be any of the possible three types:
Template, Data, or Options Template.

+--------+-------------------------------------------+
| | +----------+ +---------+ +----------+ |
| Packet | | Template | | Data | | Options | |
| Header | | FlowSet | | FlowSet | | Template | ... |
| | | | | | | FlowSet | |
| | +----------+ +---------+ +----------+ |
+--------+-------------------------------------------+
Export Packet

A FlowSet ID is used to distinguish the different types of FlowSets.
FlowSet IDs lower than 256 are reserved for special FlowSets, such as
the Template FlowSet (ID 0) and the Options Template FlowSet (ID 1).
The Data FlowSets have a FlowSet ID greater than 255.

The format of the Template, Data, and Options Template FlowSets will
be discussed later in this document. The Exporter MUST code all
binary integers of the Packet Header and the different FlowSets in
network byte order (also known as the big-endian byte ordering).

Following are some examples of export packets:

1. An Export Packet consisting of interleaved Template, Data, and
Options Template FlowSets. Example: a newly created Template is
exported as soon as possible. So if there is already an Export
Packet with a Data FlowSet that is being prepared for export, the
Template and Option FlowSets are also interleaved with this
information, subject to availability of space.

Export Packet:
+--------+--------------------------------------------------------+
| | +----------+ +---------+ +-----------+ +---------+ |
| Packet | | Template | | Data | | Options | | Data | |
| Header | | FlowSet | | FlowSet | ... | Template | | FlowSet | |
| | | | | | | FlowSet | | | |
| | +----------+ +---------+ +-----------+ +---------+ |
+--------+--------------------------------------------------------+

2. An Export Packet consisting entirely of Data FlowSets. Example:
after the appropriate Template Records have been defined and
transmitted to the NetFlow Collector device, the majority of
Export Packets consists solely of Data FlowSets.

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Export Packet:
+--------+----------------------------------------------+
| | +---------+ +---------+ +---------+ |
| Packet | | Data | ... | Data | ... | Data | |
| Header | | FlowSet | ... | FlowSet | ... | FlowSet | |
| | +---------+ +---------+ +---------+ |
+--------+----------------------------------------------+

3. An Export Packet consisting entirely of Template and Options
Template FlowSets. Example: the Exporter MAY transmit a packet
containing Template and Options Template FlowSets periodically to
help ensure that the NetFlow Collector has the correct Template
Records and Options Template Records when the corresponding Flow
Data records are received.

Export Packet:
+--------+-------------------------------------------------+
| | +----------+ +----------+ +----------+ |
| Packet | | Template | | Template | | Options | |
| Header | | FlowSet | ... | FlowSet | ... | Template | |
| | | | | | | FlowSet | |
| | +----------+ +----------+ +----------+ |
+--------+-------------------------------------------------+

5. Export Packet Format

5.1. Header Format

The Packet Header format is specified as:

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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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Packet Header Field Descriptions

Version
Version of Flow Record format exported in this packet. The
value of this field is 9 for the current version.

Count
The total number of records in the Export Packet, which is the
sum of Options FlowSet records, Template FlowSet records, and
Data FlowSet records.

sysUpTime
Time in milliseconds since this device was first booted.

UNIX Secs
Time in seconds since 0000 UTC 1970, at which the Export Packet
leaves the Exporter.

Sequence Number
Incremental sequence counter of all Export Packets sent from
the current Observation Domain by the Exporter. This value
MUST be cumulative, and SHOULD be used by the Collector to
identify whether any Export Packets have been missed.

Source ID
A 32-bit value that identifies the Exporter Observation Domain.
NetFlow Collectors SHOULD use the combination of the source IP
address and the Source ID field to separate different export
streams originating from the same Exporter.

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5.2. Template FlowSet Format

One of the essential elements in the NetFlow format is the Template
FlowSet. Templates greatly enhance the flexibility of the Flow
Record format because they allow the NetFlow Collector to process
Flow Records without necessarily knowing the interpretation of all
the data in the Flow Record. The format of the Template FlowSet is
as follows:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FlowSet ID = 0 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID 256 | Field Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Type 1 | Field Length 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Type 2 | Field Length 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Type N | Field Length N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID 257 | Field Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Type 1 | Field Length 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Type 2 | Field Length 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Type M | Field Length M |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID K | Field Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Template FlowSet Field Descriptions

FlowSet ID
FlowSet ID value of 0 is reserved for the Template FlowSet.

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Length
Total length of this FlowSet. Because an individual Template
FlowSet MAY contain multiple Template Records, the Length value
MUST be used to determine the position of the next FlowSet
record, which could be any type of FlowSet. Length is the sum
of the lengths of the FlowSet ID, the Length itself, and all
Template Records within this FlowSet.

Template ID
Each of the newly generated Template Records is given a unique
Template ID. This uniqueness is local to the Observation
Domain that generated the Template ID. Template IDs 0-255 are
reserved for Template FlowSets, Options FlowSets, and other
reserved FlowSets yet to be created. Template IDs of Data
FlowSets are numbered from 256 to 65535.

Field Count
Number of fields in this Template Record. Because a Template
FlowSet usually contains multiple Template Records, this field
allows the Collector to determine the end of the current
Template Record and the start of the next.

Field Type
A numeric value that represents the type of the field. Refer
to the "Field Type Definitions" section.

Field Length
The length of the corresponding Field Type, in bytes. Refer to
the "Field Type Definitions" section.

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5.3. Data FlowSet Format

The format of the Data FlowSet is as follows:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FlowSet ID = Template ID | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record 1 - Field Value 1 | Record 1 - Field Value 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record 1 - Field Value 3 | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record 2 - Field Value 1 | Record 2 - Field Value 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record 2 - Field Value 3 | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record 3 - Field Value 1 | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Data FlowSet Field Descriptions

FlowSet ID = Template ID
Each Data FlowSet is associated with a FlowSet ID. The FlowSet
ID maps to a (previously generated) Template ID. The Collector
MUST use the FlowSet ID to find the corresponding Template
Record and decode the Flow Records from the FlowSet.

Length
The length of this FlowSet. Length is the sum of the lengths
of the FlowSet ID, Length itself, all Flow Records within this
FlowSet, and the padding bytes, if any.

Record N - Field Value M
The remainder of the Data FlowSet is a collection of Flow Data
Record(s), each containing a set of field values. The Type and
Length of the fields have been previously defined in the
Template Record referenced by the FlowSet ID or Template ID.

Padding
The Exporter SHOULD insert some padding bytes so that the
subsequent FlowSet starts at a 4-byte aligned boundary. It is
important to note that the Length field includes the padding
bytes. Padding SHOULD be using zeros.

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Interpretation of the Data FlowSet format can be done only if the
Template FlowSet corresponding to the Template ID is available at the
Collector.

6. Options

6.1. Options Template FlowSet Format

The Options Template Record (and its corresponding Options Data
Record) is used to supply information about the NetFlow process
configuration or NetFlow process specific data, rather than supplying
information about IP Flows.

For example, the Options Template FlowSet can report the sample rate
of a specific interface, if sampling is supported, along with the
sampling method used.

The format of the Options Template FlowSet follows.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FlowSet ID = 1 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID | Option Scope Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Length | Scope 1 Field Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope 1 Field Length | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope N Field Length | Option 1 Field Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option 1 Field Length | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option M Field Length | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Options Template FlowSet Field Definitions

FlowSet ID = 1
A FlowSet ID value of 1 is reserved for the Options Template.

Length
Total length of this FlowSet. Each Options Template FlowSet
MAY contain multiple Options Template Records. Thus, the
Length value MUST be used to determine the position of the next
FlowSet record, which could be either a Template FlowSet or
Data FlowSet.

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Length is the sum of the lengths of the FlowSet ID, the Length
itself, and all Options Template Records within this FlowSet
Template ID.

Template ID
Template ID of this Options Template. This value is greater
than 255.

Option Scope Length
The length in bytes of any Scope field definition contained in
the Options Template Record (The use of "Scope" is described
below).

Option Length
The length (in bytes) of any options field definitions
contained in this Options Template Record.

Scope 1 Field Type
The relevant portion of the Exporter/NetFlow process to which
the Options Template Record refers.
Currently defined values are:
1 System
2 Interface
3 Line Card
4 Cache
5 Template
For example, the NetFlow process can be implemented on a per-
interface basis, so if the Options Template Record were
reporting on how the NetFlow process is configured, the Scope
for the report would be 2 (interface). The associated
interface ID would then be carried in the associated Options
Data FlowSet. The Scope can be limited further by listing
multiple scopes that all must match at the same time. Note
that the Scope fields always precede the Option fields.

Scope 1 Field Length
The length (in bytes) of the Scope field, as it would appear in
an Options Data Record.

Option 1 Field Type
A numeric value that represents the type of field that would
appear in the Options Template Record. Refer to the Field Type
Definitions section.

Option 1 Field Length
The length (in bytes) of the Option field.

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Padding
The Exporter SHOULD insert some padding bytes so that the
subsequent FlowSet starts at a 4-byte aligned boundary. It is
important to note that the Length field includes the padding
bytes. Padding SHOULD be using zeros.

6.2. Options Data Record Format

The Options Data Records are sent in Data FlowSets, on a regular
basis, but not with every Flow Data Record. How frequently these
Options Data Records are exported is configurable. See the
"Templates Management" section for more details.

The format of the Data FlowSet containing Options Data Records
follows.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FlowSet ID = Template ID | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record 1 - Scope 1 Value |Record 1 - Option Field 1 Value|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Record 1 - Option Field 2 Value| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record 2 - Scope 1 Value |Record 2 - Option Field 1 Value|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Record 2 - Option Field 2 Value| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Record 3 - Scope 1 Value |Record 3 - Option Field 1 Value|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Record 3 - Option Field 2 Value| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Options Data Records of the Data FlowSet Field Descriptions

FlowSet ID = Template ID
A FlowSet ID precedes each group of Options Data Records within
a Data FlowSet. The FlowSet ID maps to a previously generated
Template ID corresponding to this Options Template Record. The
Collector MUST use the FlowSet ID to map the appropriate type
and length to any field values that follow.

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Length
The length of this FlowSet. Length is the sum of the lengths of
the FlowSet ID, Length itself, all the Options Data Records
within this FlowSet, and the padding bytes, if any.

Record N - Option Field M Value
The remainder of the Data FlowSet is a collection of Flow
Records, each containing a set of scope and field values. The
type and length of the fields were previously defined in the
Options Template Record referenced by the FlowSet ID or
Template ID.

Padding
The Exporter SHOULD insert some padding bytes so that the
subsequent FlowSet starts at a 4-byte aligned boundary. It is
important to note that the Length field includes the padding
bytes. Padding SHOULD be using zeros.

The Data FlowSet format can be interpreted only if the Options
Template FlowSet corresponding to the Template ID is available at the
Collector.

7. Template Management

Flow Data records that correspond to a Template Record MAY appear in
the same and/or subsequent Export Packets. The Template Record is
not necessarily carried in every Export Packet. As such, the NetFlow
Collector MUST store the Template Record to interpret the
corresponding Flow Data Records that are received in subsequent data
packets.

A NetFlow Collector that receives Export Packets from several
Observation Domains from the same Exporter MUST be aware that the
uniqueness of the Template ID is not guaranteed across Observation
Domains.

The Template IDs must remain constant for the life of the NetFlow
process on the Exporter. If the Exporter or the NetFlow process
restarts for any reason, all information about Templates will be lost
and new Template IDs will be created. Template IDs are thus not
guaranteed to be consistent across an Exporter or NetFlow process
restart.

A newly created Template record is assigned an unused Template ID
from the Exporter. If the template configuration is changed, the
current Template ID is abandoned and SHOULD NOT be reused until the

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RFC 3954 Cisco Systems NetFlow Services Export V9 October 2004

NetFlow process or Exporter restarts. If a Collector should receive
a new definition for an already existing Template ID, it MUST discard
the previous template definition and use the new one.

If a configured Template Record on the Exporter is deleted, and re-
configured with exactly the same parameters, the same Template ID
COULD be reused.

The Exporter sends the Template FlowSet and Options Template FlowSet
under the following conditions:

1. After a NetFlow process restarts, the Exporter MUST NOT send any
Data FlowSet without sending the corresponding Template FlowSet
and the required Options Template FlowSet in a previous packet or
including it in the same Export Packet. It MAY transmit the
Template FlowSet and Options Template FlowSet, without any Data
FlowSets, in advance to help ensure that the Collector will have
the correct Template Record before receiving the first Flow or
Options Data Record.

2. In the event of configuration changes, the Exporter SHOULD send
the new template definitions at an accelerated rate. In such a
case, it MAY transmit the changed Template Record(s) and Options
Template Record(s), without any data, in advance to help ensure
that the Collector will have the correct template information
before receiving the first data.

3. On a regular basis, the Exporter MUST send all the Template
Records and Options Template Records to refresh the Collector.
Template IDs have a limited lifetime at the Collector and MUST be
periodically refreshed. Two approaches are taken to make sure
that Templates get refreshed at the Collector:
* Every N number of Export Packets.
* On a time basis, so every N number of minutes.
Both options MUST be configurable by the user on the Exporter.
When one of these expiry conditions is met, the Exporter MUST send
the Template FlowSet and Options Template.

4. In the event of a clock configuration change on the Exporter, the
Exporter SHOULD send the template definitions at an accelerated
rate.

8. Field Type Definitions

The following table describes all the field type definitions that an
Exporter MAY support. The fields are a selection of Packet Header
fields, lookup results (for example, the autonomous system numbers or
the subnet masks), and properties of the packet such as length.

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Field Type Value Length Description
(bytes)

Incoming counter with
length N x 8 bits for the
IN_BYTES 1 N number of bytes associated
with an IP Flow. By default
N is 4

Incoming counter with
length N x 8 bits for the
IN_PKTS 2 N number of packets
associated with an IP Flow.
By default N is 4

FLOWS 3 N Number of Flows
that were aggregated;
by default N is 4

PROTOCOL 4 1 IP protocol byte

Type of service byte
TOS 5 1 setting when entering
the incoming interface

TCP flags; cumulative of
TCP_FLAGS 6 1 all the TCP flags seen in
this Flow

TCP/UDP source port number
L4_SRC_PORT 7 2 (for example, FTP, Telnet,
or equivalent)

IPV4_SRC_ADDR 8 4 IPv4 source address

The number of contiguous
bits in the source subnet
SRC_MASK 9 1 mask (i.e., the mask in
slash notation)

Input interface index.
INPUT_SNMP 10 N By default N is 2, but
higher values can be used

TCP/UDP destination port
L4_DST_PORT 11 2 number (for example, FTP,
Telnet, or equivalent)

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RFC 3954 Cisco Systems NetFlow Services Export V9 October 2004

IPV4_DST_ADDR 12 4 IPv4 destination address

The number of contiguous
bits in the destination
DST_MASK 13 1 subnet mask (i.e., the mask
in slash notation)

Output interface index.

OUTPUT_SNMP 14 N By default N is 2, but
higher values can be used

IPV4_NEXT_HOP 15 4 IPv4 address of the next-
hop router

Source BGP autonomous
SRC_AS 16 N system number where N could
be 2 or 4. By default N is
2

Destination BGP autonomous
DST_AS 17 N system number where N could
be 2 or 4. By default N is
2

BGP_IPV4_NEXT_HOP 18 4 Next-hop router's IP
address in the BGP domain

IP multicast outgoing
packet counter with length
MUL_DST_PKTS 19 N N x 8 bits for packets
associated with the IP
Flow. By default N is 4

IP multicast outgoing
Octet (byte) counter with
length N x 8 bits for the
MUL_DST_BYTES 20 N number of bytes associated
with the IP Flow. By
default N is 4

sysUptime in msec at which
LAST_SWITCHED 21 4 the last packet of this
Flow was switched

sysUptime in msec at which
FIRST_SWITCHED 22 4 the first packet of this
Flow was switched

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RFC 3954 Cisco Systems NetFlow Services Export V9 October 2004

Outgoing counter with
length N x 8 bits for the
OUT_BYTES 23 N number of bytes associated
with an IP Flow. By
default N is 4

Outgoing counter with
length N x 8 bits for the
OUT_PKTS 24 N number of packets
associated with an IP Flow.
By default N is 4

IPV6_SRC_ADDR 27 16 IPv6 source address

IPV6_DST_ADDR 28 16 IPv6 destination address

IPV6_SRC_MASK 29 1 Length of the IPv6 source
mask in contiguous bits

Length of the IPv6
IPV6_DST_MASK 30 1 destination mask in
contiguous bits

IPV6_FLOW_LABEL 31 3 IPv6 flow label as per
RFC 2460 definition

Internet Control Message
ICMP_TYPE 32 2 Protocol (ICMP) packet
type; reported as
ICMP Type * 256 + ICMP code

MUL_IGMP_TYPE 33 1 Internet Group Management
Protocol (IGMP) packet type

When using sampled NetFlow,
the rate at which packets
SAMPLING_INTERVAL 34 4 are sampled; for example, a
value of 100 indicates that
one of every hundred
packets is sampled

For sampled NetFlow
platform-wide:
SAMPLING_ALGORITHM 35 1 0x01 deterministic sampling
0x02 random sampling
Use in connection with
SAMPLING_INTERVAL

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Timeout value (in seconds)

FLOW_ACTIVE_TIMEOUT 36 2 for active flow entries
in the NetFlow cache

Timeout value (in seconds)
FLOW_INACTIVE_TIMEOUT 37 2 for inactive Flow entries
in the NetFlow cache

Type of Flow switching
ENGINE_TYPE 38 1 engine (route processor,
linecard, etc...)

ENGINE_ID 39 1 ID number of the Flow
switching engine

Counter with length
N x 8 bits for the number
TOTAL_BYTES_EXP 40 N of bytes exported by the
Observation Domain. By
default N is 4

Counter with length
N x 8 bits for the number
TOTAL_PKTS_EXP 41 N of packets exported by the
Observation Domain. By
default N is 4

Counter with length
N x 8 bits for the number
TOTAL_FLOWS_EXP 42 N of Flows exported by the
Observation Domain. By
default N is 4

MPLS_TOP_LABEL_TYPE 46 1 MPLS Top Label Type:
0x00 UNKNOWN
0x01 TE-MIDPT
0x02 ATOM
0x03 VPN
0x04 BGP
0x05 LDP

Forwarding Equivalent Class
MPLS_TOP_LABEL_IP_ADDR 47 4 corresponding to the MPLS
Top Label

FLOW_SAMPLER_ID 48 1 Identifier shown
in "show flow-sampler"

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The type of algorithm used
for sampling data:
FLOW_SAMPLER_MODE 49 1 0x02 random sampling
Use in connection with
FLOW_SAMPLER_MODE
Packet interval at which to
FLOW_SAMPLER_RANDOM_INTERVAL 50 4 sample. Use in connection
with FLOW_SAMPLER_MODE

Type of Service byte
DST_TOS 55 1 setting when exiting
outgoing interface

SRC_MAC 56 6 Source MAC Address

DST_MAC 57 6 Destination MAC Address

Virtual LAN identifier

SRC_VLAN 58 2 associated with ingress
interface

Virtual LAN identifier
DST_VLAN 59 2 associated with egress
interface

Internet Protocol Version
Set to 4 for IPv4, set to 6
IP_PROTOCOL_VERSION 60 1 for IPv6. If not present in
the template, then version
4 is assumed

Flow direction:
DIRECTION 61 1 0 - ingress flow
1 - egress flow

IPV6_NEXT_HOP 62 16 IPv6 address of the
next-hop router

BGP_IPV6_NEXT_HOP 63 16 Next-hop router in the BGP
domain

Bit-encoded field
IPV6_OPTION_HEADERS 64 4 identifying IPv6 option
headers found in the flow

MPLS_LABEL_1 70 3 MPLS label at position 1 in
the stack

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RFC 3954 Cisco Systems NetFlow Services Export V9 October 2004

MPLS_LABEL_2 71 3 MPLS label at position 2 in
the stack

MPLS_LABEL_3 72 3 MPLS label at position 3 in
the stack

MPLS_LABEL_4 73 3 MPLS label at position 4 in
the stack

MPLS_LABEL_5 74 3 MPLS label at position 5 in
the stack

MPLS_LABEL_6 75 3 MPLS label at position 6 in
the stack

MPLS_LABEL_7 76 3 MPLS label at position 7 in
the stack

MPLS_LABEL_8 77 3 MPLS label at position 8 in
the stack

MPLS_LABEL_9 78 3 MPLS label at position 9 in
the stack

MPLS_LABEL_10 79 3 MPLS label at position 10
in the stack

The value field is a numeric identifier for the field type. The
following value fields are reserved for proprietary field types: 25,
26, 43 to 45, 51 to 54, and 65 to 69.

When extensibility is required, the new field types will be added to
the list. The new field types have to be updated on the Exporter and
Collector but the NetFlow export format would remain unchanged.
Refer to the latest documentation at http://www.cisco.com for the
newly updated list.

In some cases the size of a field type is fixed by definition, for
example PROTOCOL, or IPV4_SRC_ADDR. However in other cases they are
defined as a variant type. This improves the memory efficiency in
the collector and reduces the network bandwidth requirement between
the Exporter and the Collector. As an example, in the case IN_BYTES,
on an access router it might be sufficient to use a 32 bit counter (N
= 4), whilst on a core router a 64 bit counter (N = 8) would be
required.

All counters and counter-like objects are unsigned integers of size N
* 8 bits.

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RFC 3954 Cisco Systems NetFlow Services Export V9 October 2004

9. The Collector Side

The Collector receives Template Records from the Exporter, normally
before receiving Flow Data Records (or Options Data Records). The
Flow Data Records (or Options Data Records) can then be decoded and
stored locally on the devices. If the Template Records have not been
received at the time Flow Data Records (or Options Data Records) are
received, the Collector SHOULD store the Flow Data Records (or
Options Data Records) and decode them after the Template Records are
received. A Collector device MUST NOT assume that the Data FlowSet
and the associated Template FlowSet (or Options Template FlowSet) are
exported in the same Export Packet.

The Collector MUST NOT assume that one and only one Template FlowSet
is present in an Export Packet.

The life of a template at the Collector is limited to a fixed refresh
timeout. Templates not refreshed from the Exporter within the
timeout are expired at the Collector. The Collector MUST NOT attempt
to decode the Flow or Options Data Records with an expired Template.
At any given time the Collector SHOULD maintain the following for all
the current Template Records and Options Template Records: Exporter,
Observation Domain, Template ID, Template Definition, Last Received.

Note that the Observation Domain is identified by the Source ID field
from the Export Packet.

In the event of a clock configuration change on the Exporter, the
Collector SHOULD discard all Template Records and Options Template
Records associated with that Exporter, in order for Collector to
learn the new set of fields: Exporter, Observation Domain, Template
ID, Template Definition, Last Received.

Template IDs are unique per Exporter and per Observation Domain.

If the Collector receives a new Template Record (for example, in the
case of an Exporter restart) it MUST immediately override the
existing Template Record.

Finally, note that the Collector MUST accept padding in the Data
FlowSet and Options Template FlowSet, which means for the Flow Data
Records, the Options Data Records and the Template Records. Refer to
the terminology summary table in Section 2.1.

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10. Security Considerations

The NetFlow version 9 protocol was designed with the expectation that
the Exporter and Collector would remain within a single private
network. However the NetFlow version 9 protocol might be used to
transport Flow Records over the public Internet which exposes the
Flow Records to a number of security risks. For example an attacker
might capture, modify or insert Export Packets. There is therefore a
risk that IP Flow information might be captured or forged, or that
attacks might be directed at the NetFlow Collector.

The designers of NetFlow Version 9 did not impose any
confidentiality, integrity or authentication requirements on the
protocol because this reduced the efficiency of the implementation
and it was believed at the time that the majority of deployments
would confine the Flow Records to private networks, with the
Collector(s) and Exporter(s) in close proximity.

The IPFIX protocol (IP Flow Information eXport), which has chosen the
NetFlow version 9 protocol as the base protocol, addresses the
security considerations discussed in this section. See the security
section of IPFIX requirement draft [RFC3917] for more information.

10.1. Disclosure of Flow Information Data

Because the NetFlow Version 9 Export Packets are not encrypted, the
observation of Flow Records can give an attacker information about
the active flows in the network, communication endpoints and traffic
patterns. This information can be used both to spy on user behavior
and to plan and conceal future attacks.

The information that an attacker could derive from the interception
of Flow Records depends on the Flow definition. For example, a Flow
Record containing the source and destination IP addresses might
reveal privacy sensitive information regarding the end user's
activities, whilst a Flow Record only containing the source and
destination IP network would be less revealing.

10.2. Forgery of Flow Records or Template Records

If Flow Records are used in accounting and/or security applications,
there may be a strong incentive to forge exported Flow Records (for
example to defraud the service provider, or to prevent the detection
of an attack). This can be done either by altering the Flow Records
on the path between the Observer and the Collector, or by injecting
forged Flow Records that pretend to be originated by the Exporter.

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RFC 3954 Cisco Systems NetFlow Services Export V9 October 2004

An attacker could forge Templates and/or Options Templates and
thereby try to confuse the NetFlow Collector, rendering it unable to
decode the Export Packets.

10.3. Attacks on the NetFlow Collector

Denial of service attacks on the NetFlow Collector can consume so
many resources from the machine that, the Collector is unable to
capture or decode some NetFlow Export Packets. Such hazards are not
explicitly addressed by the NetFlow Version 9 protocol, although the
normal methods used to protect a server from a DoS attack will
mitigate the problem.

11. Examples

Let us consider the example of an Export Packet composed of a
Template FlowSet, a Data FlowSet (which contains three Flow Data
Records), an Options Template FlowSet, and a Data FlowSet (which
contains two Options Data Records).

Export Packet:

+--------+---------------------------------------------. . .
| | +--------------+ +-----------------------+
| Packet | | Template | | Data |
| Header | | FlowSet | | FlowSet | . . .
| | | (1 Template) | | (3 Flow Data Records) |
| | +--------------+ +-----------------------+
+--------+---------------------------------------------. . .

. . .+-------------------------------------------------+
+------------------+ +--------------------------+ |
| Options | | Data | |
. . .| Template FlowSet | | FlowSet | |
| (1 Template) | | (2 Options Data Records) | |
+------------------+ +--------------------------+ |
. . .--------------------------------------------------+

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RFC 3954 Cisco Systems NetFlow Services Export V9 October 2004

11.1. Packet Header Example

The Packet Header is composed of:

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 = 9 | Count = 7 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sysUpTime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UNIX Secs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

11.2. Template FlowSet Example

We want to report the following Field Types:
- The source IP address (IPv4), so the length is 4
- The destination IP address (IPv4), so the length is 4
- The next-hop IP address (IPv4), so the length is 4
- The number of bytes of the Flow
- The number of packets of the Flow

Therefore, the Template FlowSet is composed of the following:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FlowSet ID = 0 | Length = 28 bytes |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID 256 | Field Count = 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP_SRC_ADDR = 8 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP_DST_ADDR = 12 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP_NEXT_HOP = 15 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IN_PKTS = 2 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IN_BYTES = 1 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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RFC 3954 Cisco Systems NetFlow Services Export V9 October 2004

11.3. Data FlowSet Example

In this example, we report the following three Flow Records:

Src IP addr. | Dst IP addr. | Next Hop addr. | Packet | Bytes
| | | Number | Number
---------------------------------------------------------------
198.168.1.12 | 10.5.12.254 | 192.168.1.1 | 5009 | 5344385
192.168.1.27 | 10.5.12.23 | 192.168.1.1 | 748 | 388934
192.168.1.56 | 10.5.12.65 | 192.168.1.1 | 5 | 6534

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FlowSet ID = 256 | Length = 64 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 198.168.1.12 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 10.5.12.254 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 192.168.1.1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5009 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5344385 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 192.168.1.27 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 10.5.12.23 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 192.168.1.1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 748 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 388934 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 192.168.1.56 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 10.5.12.65 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 192.168.1.1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 6534 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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RFC 3954 Cisco Systems NetFlow Services Export V9 October 2004

Note that padding was not necessary in this example.

11.4. Options Template FlowSet Example

Per line card (the Exporter is composed of two line cards), we want
to report the following Field Types:
- Total number of Export Packets
- Total number of exported Flows

The format of the Options Template FlowSet is as follows:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FlowSet ID = 1 | Length = 24 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID 257 | Option Scope Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Length = 8 | Scope 1 Field Type = 3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope 1 Field Length = 2 | TOTAL_EXP_PKTS_SENT = 41 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 2 | TOTAL_FLOWS_EXP = 42 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 2 | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

11.5. Data FlowSet with Options Data Records Example

In this example, we report the following two records:

Line Card ID | Export Packet| Export Flow
------------------------------------------
Line Card 1 | 345 | 10201
Line Card 2 | 690 | 20402

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RFC 3954 Cisco Systems NetFlow Services Export V9 October 2004

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FlowSet ID = 257 | Length = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 | 345 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 10201 | 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 690 | 20402 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

12. References

12.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

12.2. Informative References

[RFC768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.

[RFC793] Postel, J., "Transmission Control Protocol", STD 7, RFC
793, September 1981.

[RFC2960] Stewart, R., Xie, Q., Morneault, K., Sharp, C.,
Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M.,
Zhang, L., and V. Paxson, "Stream Control Transmission
Protocol", RFC 2960, October 2000.

[RFC3917] Quittek, J., Zseby, T., Claise, B., and S. Zander,
"Requirements for IP Flow Information Export (IPFIX)",
RFC 3917, October 2004.

13. Authors

This document was jointly written by Vamsidhar Valluri, Martin
Djernaes, Ganesh Sadasivan, and Benoit Claise.

14. Acknowledgments

I would like to thank Pritam Shah, Paul Kohler, Dmitri Bouianovski,
and Stewart Bryant for their valuable technical feedback.

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RFC 3954 Cisco Systems NetFlow Services Export V9 October 2004

15. Authors' Addresses

Benoit Claise (Editor)
Cisco Systems
De Kleetlaan 6a b1
1831 Diegem
Belgium

Phone: +32 2 704 5622
EMail: [email protected]

Ganesh Sadasivan
Cisco Systems, Inc.
3750 Cisco Way
San Jose, CA 95134
USA

Phone: +1 408 527-0251
EMail: [email protected]

Vamsi Valluri
Cisco Systems, Inc.
510 McCarthy Blvd.
San Jose, CA 95035
USA

Phone: +1 408 525-1835
EMail: [email protected]

Martin Djernaes
Cisco Systems, Inc.
510 McCarthy Blvd.
San Jose, CA 95035
USA

Phone: +1 408 853-1676
EMail: [email protected]

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RFC 3954 Cisco Systems NetFlow Services Export V9 October 2004

Full Copyright Statement

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Funding for the RFC Editor function is currently provided by the
Internet Society.

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