rfc5476
Network Working Group B. Claise, Ed.
Request for Comments: 5476 A. Johnson
Category: Standards Track Cisco Systems, Inc.
J. Quittek
NEC Europe Ltd.
March 2009
Packet Sampling (PSAMP) Protocol Specifications
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.
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Claise, et al. Standards Track [Page 1]
RFC 5476 PSAMP Protocol Specification March 2009
Abstract
This document specifies the export of packet information from a
Packet SAMPling (PSAMP) Exporting Process to a PSAMP Collecting
Process. For export of packet information, the IP Flow Information
eXport (IPFIX) protocol is used, as both the IPFIX and PSAMP
architecture match very well, and the means provided by the IPFIX
protocol are sufficient. The document specifies in detail how the
IPFIX protocol is used for PSAMP export of packet information.
Table of Contents
1. Introduction ....................................................3
1.1. Conventions Used in This Document ..........................3
2. PSAMP Documents Overview ........................................4
3. Terminology .....................................................4
3.1. IPFIX Terminology ..........................................4
3.2. PSAMP Terminology ..........................................5
3.2.1. Packet Streams and Packet Content ...................5
3.2.2. Selection Process ...................................6
3.2.3. Reporting ...........................................7
3.2.4. Metering Process ....................................8
3.2.5. Exporting Process ...................................8
3.2.6. PSAMP Device ........................................8
3.2.7. Collector ...........................................8
3.2.8. Selection Methods ...................................9
3.3. IPFIX and PSAMP Terminology Comparison ....................11
3.3.1. IPFIX and PSAMP Processes ..........................11
3.3.2. Packet Report, Packet Interpretation, and
Data Record ........................................12
4. Differences between PSAMP and IPFIX ............................12
4.1. Architecture Point of View ................................12
4.2. Protocol Point of View ....................................14
4.3. Information Model Point of View ...........................14
5. PSAMP Requirements versus the IPFIX Solution ...................14
5.1. High-Level View of the Integration ........................15
6. Using the IPFIX Protocol for PSAMP .............................16
6.1. Selector ID ...............................................17
6.2. The Selection Sequence ID .................................17
6.3. The Exporting Process .....................................17
6.4. Packet Report .............................................17
6.4.1. Basic Packet Report ................................17
6.4.2. Extended Packet Report .............................21
6.5. Report Interpretation .....................................22
6.5.1. Selection Sequence Report Interpretation ...........23
6.5.2. Selector Report Interpretation .....................25
6.5.2.1. Systematic Count-Based Sampling ...........25
6.5.2.2. Systematic Time-Based Sampling ............27
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6.5.2.3. Random n-out-of-N Sampling ................28
6.5.2.4. Uniform Probabilistic Sampling ............29
6.5.2.5. Property Match Filtering ..................31
6.5.2.6. Hash-Based Filtering ......................33
6.5.2.7. Other Selection Methods ...................36
6.5.3. Selection Sequence Statistics Report
Interpretation .....................................37
6.5.4. Accuracy Report Interpretation .....................39
7. Security Considerations ........................................43
8. IANA Considerations ............................................43
8.1. IPFIX-Related Considerations ..............................43
8.2. PSAMP-Related Considerations ..............................43
9. References .....................................................44
9.1. Normative References ......................................44
9.2. Informative References ....................................44
10. Acknowledgments ...............................................45
1. Introduction
The name PSAMP is a contraction of the phrase "Packet Sampling". The
word "Sampling" captures the idea that only a subset of all packets
passing a network element will be selected for reporting. PSAMP
selection operations include random selection, deterministic
selection, and deterministic approximations to random selection
(Hash-based Selection).
The IP Flow Information eXport (IPFIX) protocol specified in
[RFC5101] exports IP traffic information [RFC5102] observed at
network devices. This matches the general protocol requirements
outlined in the PSAMP framework [RFC5474]. However, there are some
architectural differences between IPFIX and PSAMP in the requirements
for an export protocol. While the IPFIX architecture [RFC5470] is
focused on gathering and exporting IP traffic flow information, the
focus of the PSAMP framework [RFC5474] is on exporting information on
individual packets. This basic difference and a set of derived
differences in protocol requirements are outlined in Section 4.
Despite these differences, the IPFIX protocol is well suited for the
PSAMP protocol. Section 5 specifies how the IPFIX protocol is used
for the export of packet samples. Required extensions of the IPFIX
information model are specified in the PSAMP information model
[RFC5477].
1.1. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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2. PSAMP Documents Overview
This document is one out of a series of documents from the PSAMP
group.
[RFC5474]: "A Framework for Packet Selection and Reporting" describes
the PSAMP framework for network elements to select subsets of packets
by statistical and other methods, and to export a stream of reports
on the selected packets to a Collector.
[RFC5475]: "Sampling and Filtering Techniques for IP Packet
Selection" describes the set of packet selection techniques supported
by PSAMP.
RFC 5476 (this document): "Packet Sampling (PSAMP) Protocol
Specifications" specifies the export of packet information from a
PSAMP Exporting Process to a PSAMP Collecting Process.
[RFC5477]: "Information Model for Packet Sampling Exports" defines an
information and data model for PSAMP.
3. Terminology
As the IPFIX export protocol is used to export the PSAMP information,
the relevant IPFIX terminology from [RFC5101] is copied over in this
document. All terms defined in this section have their first letter
capitalized when used in this document. The terminology summary
table in Section 3.1 gives a quick overview of the relationships
between the different IPFIX terms. The PSAMP terminology defined
here is fully consistent with all terms listed in [RFC5475] and
[RFC5474], but only definitions that are relevant to the PSAMP
protocol appear here. Section 3.3 applies the PSAMP terminology to
the IPFIX protocol terminology.
3.1. IPFIX Terminology
IPFIX-specific terminology used in this document is defined in
Section 2 of [RFC5101]. The only exceptions are the Metering
Process, Exporting Process, and the Collector terms, which are
defined more precisely in the PSAMP terminology section. In this
document, as in [RFC5101], the first letter of each IPFIX-specific
term is capitalized.
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+------------------+---------------------------------------------+
| | contents |
| +--------------------+------------------------+
| Set | Template | record |
+------------------+--------------------+------------------------+
| Data Set | / | Data Record(s) |
+------------------+--------------------+------------------------+
| Template Set | Template Record(s) | / |
+------------------+--------------------+------------------------+
| Options Template | Options Template | / |
| Set | Record(s) | |
+------------------+--------------------+------------------------+
Figure A: Terminology Summary Table
3.2. PSAMP Terminology
The PSAMP terminology section has been copied from [RFC5475].
3.2.1. Packet Streams and Packet Content
* Observed Packet Stream
The Observed Packet Stream is the set of all packets observed at
the Observation Point.
* Packet Stream
A Packet Stream denotes a set of packets from the Observed Packet
Stream that flows past some specified point within the Metering
Process. An example of a Packet Stream is the output of the
Selection Process. Note that packets selected from a stream,
e.g., by Sampling, do not necessarily possess a property by which
they can be distinguished from packets that have not been
selected. For this reason, the term "stream" is favored over
"flow", which is defined as a set of packets with common
properties [RFC3917].
* Packet Content
The Packet Content denotes the union of the packet header (which
includes link layer, network layer, and other encapsulation
headers) and the packet payload. Note that, depending on the
Observation Point, the link layer information might not be
available.
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3.2.2. Selection Process
* Selection Process
A Selection Process takes the Observed Packet Stream as its input
and selects a subset of that stream as its output.
* Selection State
A Selection Process may maintain state information for use by the
Selection Process. At a given time, the Selection State may
depend on packets observed at and before that time, and other
variables. Examples include:
(i) sequence numbers of packets at the input of Selectors;
(ii) a timestamp of observation of the packet at the Observation
Point;
(iii) iterators for pseudorandom number generators;
(iv) hash values calculated during selection;
(v) indicators of whether the packet was selected by a given
Selector.
Selection Processes may change portions of the Selection State as
a result of processing a packet. Selection state for a packet is
to reflect the state after processing the packet.
* Selector
A Selector defines the action of a Selection Process on a single
packet of its input. If selected, the packet becomes an element
of the output Packet Stream.
The Selector can make use of the following information in
determining whether a packet is selected:
(i) the Packet Content;
(ii) information derived from the packet's treatment at the
Observation Point;
(iii) any selection state that may be maintained by the Selection
Process.
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* Composite Selector
A Composite Selector is an ordered composition of Selectors, in
which the output Packet Stream issuing from one Selector forms the
input Packet Stream to the succeeding Selector.
* Primitive Selector
A Selector is primitive if it is not a Composite Selector.
* Selector ID
The Selector ID is the unique ID identifying a Primitive Selector.
The ID is unique within the Observation Domain.
* Selection Sequence
From all the packets observed at an Observation Point, only a few
packets are selected by one or more Selectors. The Selection
Sequence is a unique value per Observation Domain describing the
Observation Point and the Selector IDs through which the packets
are selected.
3.2.3. Reporting
* Packet Reports
Packet Reports comprise a configurable subset of a packet's input
to the Selection Process, including the Packet Content,
information relating to its treatment (for example, the output
interface), and its associated selection state (for example, a
hash of the Packet Content).
* Report Interpretation
Report Interpretation comprises subsidiary information, relating
to one or more packets, that is used for interpretation of their
Packet Reports. Examples include configuration parameters of the
Selection Process.
* Report Stream
The Report Stream is the output of a Metering Process, comprising
two distinguished types of information: Packet Reports and Report
Interpretation.
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3.2.4. Metering Process
* Metering Process
A Metering Process selects packets from the Observed Packet Stream
using a Selection Process, and produces as output a Report Stream
concerning the selected packets.
The PSAMP Metering Process can be viewed as analogous to the IPFIX
Metering Process [RFC5101], which produces Flow Records as its
output, with the difference that the PSAMP Metering Process always
contains a Selection Process. The relationship between PSAMP and
IPFIX is further described in [RFC5477] and [RFC5474].
3.2.5. Exporting Process
* Exporting Process
An Exporting Process sends, in the form of Export Packets, the
output of one or more Metering Processes to one or more
Collectors.
* Export Packet
An Export Packet is a combination of Report Interpretation(s)
and/or one or more Packet Reports that are bundled by the
Exporting Process into an Export Packet for exporting to a
Collector.
3.2.6. PSAMP Device
* PSAMP Device
A PSAMP Device is a device hosting at least an Observation Point,
a Selection Process, and an Exporting Process. Typically,
corresponding Observation Point(s), Selection Process(es), and
Exporting Process(es) are co-located at this device, for example,
at a router.
3.2.7. Collector
* Collector
A Collector receives a Report Stream exported by one or more
Exporting Processes. In some cases, the host of the Metering
and/or Exporting Processes may also serve as the Collector.
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3.2.8. Selection Methods
* Filtering
A filter is a Selector that selects a packet deterministically
based on the Packet Content, or its treatment, or functions of
these occurring in the Selection State. Two examples are:
(i) Property Match Filtering: A packet is selected if a
specific field in the packet equals a predefined value.
(ii) Hash-based Selection: A Hash Function is applied to the
Packet Content, and the packet is selected if the result
falls in a specified range.
* Sampling
A Selector that is not a filter is called a Sampling
operation. This reflects the intuitive notion that if the
selection of a packet cannot be determined from its content
alone, there must be some type of Sampling taking place.
* Content-Independent Sampling
A Sampling operation that does not use Packet Content (or
quantities derived from it) as the basis for selection is
called a Content-independent Sampling operation. Examples
include systematic Sampling, and uniform pseudorandom
Sampling driven by a pseudorandom number whose generation
is independent of Packet Content. Note that in Content-
independent Sampling, it is not necessary to access the
Packet Content in order to make the selection decision.
* Content-Dependent Sampling
A Sampling operation where selection is dependent on Packet
Content is called a Content-dependent Sampling operation.
An example is pseudorandom selection according to a
probability that depends on the contents of a packet field.
Note that this is not a filter, because the selection is
not deterministic.
* Hash Domain
A Hash Domain is a subset of the Packet Content and the
packet treatment, viewed as an N-bit string for some
positive integer N.
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* Hash Range
A Hash Range is a set of M-bit strings for some positive
integer M that define the range of values the result of the
hash operation can take.
* Hash Function
A Hash Function defines a deterministic map from the Hash
Domain into the Hash Range.
* Hash Selection Range
A Hash Selection Range is a subset of the Hash Range. The
packet is selected if the action of the Hash Function on
the Hash Domain for the packet yields a result in the Hash
Selection Range.
* Hash-based Selection
A Hash-based Selection is Filtering specified by a Hash
Domain, a Hash Function, a Hash Range, and a Hash Selection
Range.
* Approximative Selection
Selectors in any of the above categories may be
approximated by operations in the same or another category
for the purposes of implementation. For example, uniform
pseudorandom Sampling may be approximated by Hash-based
Selection, using a suitable Hash Function and Hash Domain.
In this case, the closeness of the approximation depends on
the choice of Hash Function and Hash Domain.
* Population
A Population is a Packet Stream, or a subset of a Packet
Stream. A Population can be considered as a base set from
which packets are selected. An example is all packets in
the Observed Packet Stream that are observed within some
specified time interval.
* Population Size
The Population Size is the number of all packets in the
Population.
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* Sample Size
The Sample Size is the number of packets selected from the
Population by a Selector.
* Configured Selection Fraction
The Configured Selection Fraction is the expected ratio of
the Sample Size to the Population Size, as based on the
configured selection parameters.
* Attained Selection Fraction
The Attained Selection Fraction is the ratio of the actual
Sample Size to the Population Size. For some Sampling
methods, the Attained Selection Fraction can differ from
the Configured Selection Fraction due to, for example, the
inherent statistical variability in Sampling decisions of
probabilistic Sampling and Hash-based Selection.
Nevertheless, for large Population Sizes and properly
configured Selectors, the Attained Selection Fraction
usually approaches the Configured Selection Fraction.
3.3. IPFIX and PSAMP Terminology Comparison
The PSAMP terminology has been specified with an IPFIX background, as
PSAMP and IPFIX have similar terms. However, this section clarifies
the terms between the IPFIX and PSAMP terminology.
3.3.1. IPFIX and PSAMP Processes
Figure B indicates the sequence of the IPFIX processes (Metering and
Exporting) within the PSAMP Device.
+------------------+
| Metering Process |
| +-----------+ | +-----------+
Observed | | Selection | | | Exporting |
Packet--->| | Process |--------->| Process |--->Collector
Stream | +-----------+ | +-----------+
+------------------+
Figure B: PSAMP Processes
The Selection Process, which takes an Observed Packet Stream as its
input, is an integral part of the Metering Process. The Selection
Process chooses which packets from its input Packet Stream will be
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reported on by the rest of the Metering Process. Note that a
"Process" is not necessarily implemented as a separate CPU thread.
3.3.2. Packet Report, Packet Interpretation, and Data Record
The PSAMP terminology speaks of Packet Report and Packet
Interpretation, while the IPFIX terminology speaks of Data Record and
(Options) Template Record. The PSAMP Packet Report, which comprises
information about the observed packet, can be viewed as analogous to
the IPFIX Data Record defined by a Template Record. The PSAMP Report
Interpretation, which comprises subsidiary information used for the
interpretation of the Packet Reports, can be viewed as analogous to
the IPFIX Data Record defined by an Options Template Record. This
Options Template Record contains subsidiary information, applicable
to the observed packet sent into the PSAMP Packet Report.
4. Differences between PSAMP and IPFIX
The output of the IPFIX working group relevant for this document is
structured into three documents:
- IP Flow information architecture [RFC5470]
- IPFIX protocol specifications [RFC5101]
- IP Flow information export information model [RFC5102]
In the following sections, we investigate the differences between
IPFIX and PSAMP for each of those aspects.
4.1. Architecture Point of View
Traffic Flow measurement as described in the IPFIX requirements
[RFC3917] and the IPFIX architecture [RFC5470] can be separated into
two stages: packet processing and Flow processing. Figure C
illustrates these stages.
In stage 1, all processing steps act on packets. Packets are
captured, timestamped, selected by one or more selection steps, and
finally forwarded to packet classification that maps packets to
Flows. The packets' selection steps may include Filtering and
Sampling functions.
In stage 2, all processing steps act on Flows. After packets are
classified (mapped to Flows), Flows are generated (or updated if they
exist already). Flow generation and update steps may be performed
repeatedly for aggregating Flows. Finally, Flows are exported.
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Packet Sampling as described in the PSAMP framework [RFC5474] covers
only stage 1 of the IPFIX architecture with the packet classification
replaced by Packet Report export, while IPFIX covers stage 2 also, as
it generates Flow Records out of the selected packets.
IPFIX architecture PSAMP framework
packet header packet header
capturing \ capturing
| | |
timestamping | timestamping
| | |
v | v
+------>+ | stage 1: +------>+
| | > packet | |
| packet | processing | packet
| selection | | selection
| | | | |
+-------+ | +-------+
| | |
v | v
packet / Packet Report
classification \ export
| |
v |
+------>+ |
| | |
| Flow generation |
| and update | stage 2:
| | > Flow
| v | processing
| Flow |
| selection |
| | |
+-------+ |
| |
v |
Flow Record /
export
Figure C: Comparison of IPFIX Architecture and PSAMP Framework
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4.2. Protocol Point of View
Concerning the protocol, the major difference between IPFIX and PSAMP
is that the IPFIX protocol exports Flow Records while the PSAMP
protocol exports Packet Reports. From a pure export point of view,
IPFIX will not distinguish a Flow Record composed of several packets
aggregated together from a Flow Record composed of a single packet.
So the PSAMP export can be seen as a special IPFIX Flow Record
containing information about a single packet.
All extensions of the IPFIX protocol that are required to satisfy the
PSAMP requirements have already been incorporated in the IPFIX
protocol [RFC5101], which was developed in parallel with the PSAMP
protocol. An example is the need for a data type for protocol fields
that have flexible length, such as an octet array. This was added to
the IPFIX protocol specification in order to meet the requirement of
the PSAMP protocol to report content of captured packets, for
example, the first octets of a packet.
4.3. Information Model Point of View
From the information model point of view, the overlap between both
the IPFIX and PSAMP protocols is quite large. Most of the
Information Elements in the IPFIX protocol are also relevant for
exporting packet information, for example, all fields reporting
packet header properties. Only a few Information Elements, such as
observedFlowTotalCount (whose value will always be 1 for PSAMP),
etc., cannot be used in a meaningful way by the PSAMP protocol.
Also, IPFIX protocol requirements concerning stage 2 of Figure C do
not apply to the PSAMP Metering Process.
Further required extensions apply to the information model. Even if
the IPFIX charter speaks of Sampling, no Sampling-related Information
Elements are specified in [RFC5102]. The task of specifying them was
intentionally left for the PSAMP information model [RFC5477]. A set
of several additional fields is required for satisfying the
requirements for the PSAMP information model [RFC5475].
Exploiting the extensibility of the IPFIX information model, the
required extension is covered by the PSAMP information model
specified in [RFC5477].
5. PSAMP Requirements versus the IPFIX Solution
The [RFC5474] contains PSAMP protocol requirements throughout the
document, with a special focus in Section 4, "Generic Requirements
for PSAMP", and its subsections.
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Section 4 of [RFC5474] describes one requirement that, if not
directly related to the export protocol, will put some constraints on
it. Parallel Measurements: multiple independent Selection Processes
at the same entity.
[RFC5474] also describes a series of requirements specifying the
different Information Elements that MUST and SHOULD be reported to
the Collector. Nevertheless, IPFIX, being a generic export protocol,
can export any Information Elements as long as they are described in
the information model. So these requirements are mainly targeted for
[RFC5477].
The PSAMP protocol specification meets almost all the protocol
requirements stated in the PSAMP framework document [RFC5474]:
* Extensibility
* Parallel selection processes
* Encrypted packets
* Indication of information loss
* Accuracy
* Privacy
* Timeliness
* Congestion avoidance
* Secure export
* Export rate limit
* Microsecond timestamp resolution
The only requirement that is not met is Export Packet compression.
With the choice of IPFIX as the PSAMP export protocol, the Export
Packet compression option mentioned in the Section 8.5 of the
framework document [RFC5474] is not addressed.
5.1. High-Level View of the Integration
The Template Record in the Template Set is used to describe the
different PSAMP Information Elements that will be exported to the
Collector. The Collector decodes the Template Record in the Template
Set and knows which Information Elements to expect when it receives
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the Data Records in the PSAMP Packet Report Data Set. Typically, in
the base level of the PSAMP functionality, the Template Set will
contain the input sequence number, the packet fragment (some number
of contiguous bytes from the start of the packet or from the start of
the payload), and the Selection Sequence.
The Options Template Record in the Options Template Set is used to
describe the different PSAMP Information Elements that concern the
Metering Process itself: Sampling and/or Filtering functions, and the
associated parameters. The Collector decodes the Options Template
Records in the Options Template Set and knows which Information
Elements to expect when it receives the Data Records in the PSAMP
Report Interpretation Data Set. Typically, the Options Template
would contain the Selection Sequence, the Sampling or Filtering
functions, and the Sampling or Filtering associated parameters.
PSAMP requires all the different possibilities of the IPFIX protocol
specifications [RFC5101], that is, the three types of Sets (Data Set,
Template Set, and Options Templates Set) with the two types of
Template Records (Template Record and Options Template Record), as
described in Figure A. As a consequence, PSAMP can't rely on a
subset of the IPFIX protocol specifications described in [RFC5101].
The entire IPFIX protocol specifications [RFC5101] MUST be
implemented for the PSAMP protocol.
6. Using the IPFIX Protocol for PSAMP
In this section, we describe the usage of the IPFIX protocol for
PSAMP. We describe the record formats and the additional
requirements that must be met. PSAMP uses two different types of
messages:
- Packet Reports
- Report Interpretation
The format of Packet Reports is defined in IPFIX Template Records.
The PSAMP data is transferred as Information Elements in IPFIX Data
Records as described by the Template Record. There are two different
types of Packet Reports. Basic Packet Reports contain only the basic
Information Elements required for PSAMP reporting. Extended Packet
Reports MAY contain other Information Elements, and do not
necessarily include Packet Content (See section 6.4.2).
The format of Report Interpretations is defined in the IPFIX Options
Template Record. The Information Elements are transferred in IPFIX
Data Records as described by the Options Template Record. There are
four different types of Report Interpretation messages:
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- Selection Sequence Report Interpretation
- Selector Report Interpretation
- Selection Sequence Statistics Report Interpretation
- Accuracy Report Interpretation
A description and examples about the usage of those reports are given
below.
6.1. Selector ID
The Selector ID is the unique ID identifying a Primitive Selector.
Each Primitive Selector MUST have a unique ID within the Observation
Domain. The Selector ID is represented by the selectorId Information
Element [RFC5477].
6.2. The Selection Sequence ID
From all the packets observed at an Observation Point, a subset of
packets is selected by one or more Selectors. The Selection Sequence
is the combination of an Observation Point and one or more
Selector(s) through which the packets are selected. The Selection
Sequence ID is a unique value representing that combination. The
Selection Sequence ID is represented by the selectionSequenceId
Information Element [RFC5477].
6.3. The Exporting Process
An Exporting Process MUST be able to limit the export rate according
to a configurable value. The Exporting Process MAY limit the export
rate on a per Collecting Process basis.
6.4. Packet Report
For each Selection Sequence, for each selected packet, a Packet
Report MUST be created. The format of the Packet Report is specified
in a Template Record contained in a Template Set.
There are two types of Packet Report, as described in [RFC5474]: the
basic Packet Report and the extended Packet Report.
6.4.1. Basic Packet Report
For each selected packet, the Packet Report MUST contain the
following information:
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- The selectionSequenceId Information Element
If there is a digest function in the Selection Sequence, the Packet
Report MUST contain the hash value (digestHashValue Information
Element) generated by the digest Hash Function for each selected
packet. If there is more than one digest function, then each hash
value MUST be included in the same order as they appear in the
Selection Sequence. If there are no digest functions in the
Selection Sequence, no element for the digest needs to be sent.
- Some number of contiguous bytes from the start of the packet,
including the packet header (which includes link layer, network
layer, and other encapsulation headers) and some subsequent bytes
of the packet payload. Alternatively, the number of contiguous
bytes may start at the beginning of the payload. The
dataLinkFrameSection, mplsLabelStackSection,
mplsPayloadPacketSection, ipPacketSection, and
ipPayloadPacketSection PSAMP Information Elements are available for
this use.
For each selected packet, the Packet Report SHOULD contain a time-
related Information Element that matches the Metering Process time
accuracy. Typically, the observationTimeMicroseconds Information
Element. Other possible Information Elements are the
observationTimeSeconds, the observationTimeMilliseconds, or the
observationTimeNanoseconds.
In the Packet Report, the PSAMP Device MUST be capable of exporting
the number of observed packets and the number of packets selected by
each instance of its Primitive Selectors (as described by the
non-scope Information Elements of the Selection Sequence Statistics
Report Interpretation), although it MAY be a configurable option not
to include them. If exported, the Attained Selection Fraction may be
calculated precisely for the Observed Packet Stream. The Packet
Report MAY include only the final selector packetSelected, to act as
an index for that Selection Sequence in the Selection Sequence
Statistics Report Interpretation, which also allows the calculation
of the Attained Selection Fraction.
The contiguous Information Elements (dataLinkFrameSection,
mplsLabelStackSection, mplsPayloadPacketSection, ipPacketSection, and
ipPayloadPacketSection) MAY be encoded with a fixed-length field or
with a variable-sized field. If one of these Information Elements is
encoded with a fixed-length field whose length is too long for the
number of contiguous bytes in the selected packet, padding MUST NOT
be used. In this case, the Exporting Process MUST export the
information either in a new Template Record with the correct fixed-
length field or in a new Template Record with a variable-length
field.
Claise, et al. Standards Track [Page 18]
RFC 5476 PSAMP Protocol Specification March 2009
Here is an example of a basic Packet Report, with a
SelectionSequenceId value of 9 and dataLinkFrameSection Information
Element of 12 bytes, 0x4500 005B A174 0000 FF11 832E, encoded with a
fixed-length field.
IPFIX Template Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 2 | Length = 24 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID = 260 | Field Count = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| selectionSequenceId = 301 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| digestHashValue = 326 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| dataLinkFrameSection = 315 | Field Length = 12 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|observationTimeMicroseconds=324| Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The associated IPFIX Data Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 260 | Length = 32 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 9 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x9123 0613 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x4500 005B |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xA174 0000 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF11 832E |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| observation time ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... encoded as dateTimeMicroSeconds [RFC5101] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure D: Example of a Basic Packet Report
Claise, et al. Standards Track [Page 19]
RFC 5476 PSAMP Protocol Specification March 2009
Here is an example of a basic Packet Report, with a
SelectionSequenceId value of 9 and ipHeaderPacketSection Information
Element of 12 bytes, 0x4500 005B A174 0000 FF11 832E, encoded with a
variable-sized field.
IPFIX Template Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 2 | Length = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID = 261 | Field Count = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| selectionSequenceId = 301 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ipHeaderPacketSection = 313 | Field Length = 65535 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The associated IPFIX Data Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 261 | Length = 21 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 9 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length = 12 | 0x4500 ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... 005B | 0xA174 ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... 0000 | 0xFF11 ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... 832E |
+-+-+-+-+-+-+-+-+
Figure E: Example of a Basic Packet Report
with a Variable-Sized Field
Claise, et al. Standards Track [Page 20]
RFC 5476 PSAMP Protocol Specification March 2009
6.4.2. Extended Packet Report
Alternatively to the basic Packet Report, the extended Packet Report
MAY contain other Information Elements related to the protocols used
in the packet (such as source and destination IP addresses), related
to the packet treatment (such as output interface, destination BGP
autonomous system [RFC4271]), or related to the Selection State
associated with the packet (such as timestamp, hash value).
It is envisaged that selection of fields for extended Packet Reports
may be used to reduce reporting bandwidth, in which case the option
to report some number of contiguous bytes from the start of the
packet, mandatory in the basic Packet Report, may not be exercised.
In this case, the Packet Content MAY be omitted. Note this
configuration is quite similar to an IPFIX Device for which a
Template Record containing information about a single packet is
reported.
Example of a detailed Extended Packet Report:
IPFIX Template Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 2 | Length = 32 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID = 261 | Field Count = 6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| selectionSequenceId = 301 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| sourceIPv4Address = 8 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| destinationIPv4Address = 12 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| totalLengthIPv4 = 190 | Field Length = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| tcpSourcePort = 182 | Field Length = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| tcpDestinationPort = 183 | Field Length = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Claise, et al. Standards Track [Page 21]
RFC 5476 PSAMP Protocol Specification March 2009
The associated IPFIX Data Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 261 | Length = 20 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 9 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 192.0.2.1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 192.0.2.106 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 72 | 1372 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 80 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure F: Example of an Extended Packet Report
6.5. Report Interpretation
To make full sense of the Packet Reports, there are a number of
additional pieces of information that must be communicated to the
Collector:
- The details about which Selectors and Observation Points are being
used within a Selection Sequence MUST be provided using the
Selection Sequence Report Interpretation.
- The configuration details of each Selector MUST be provided using
the Selector Report Interpretation.
- The Selector ID statistics MUST be provided using the Selection
Sequence Statistics Report Interpretation.
- The accuracies of the reported fields MUST be provided using the
Accuracy Report Interpretation.
Claise, et al. Standards Track [Page 22]
RFC 5476 PSAMP Protocol Specification March 2009
6.5.1. Selection Sequence Report Interpretation
Each Packet Report contains a selectionSequenceId Information Element
that identifies the particular combination of Observation Point and
Selector(s) used for its selection. For every selectionSequenceId
Information Element in use, the PSAMP Device MUST export a Selection
Sequence Report Interpretation using an Options Template with the
following Information Elements:
Scope: selectionSequenceId
Non-Scope: one Information Element mapping the Observation Point
selectorId (one or more)
An Information Element representing the Observation Point would
typically be taken from the ingressInterface, egressInterface,
lineCardId, exporterIPv4Address, or exporterIPv6Address Information
Elements (specified in [RFC5102]), but is not limited to those: any
Information Element specified in [RFC5102] or [RFC5477] can
potentially be used. In case of more complex Observation Points
(such as a list of interfaces, a bus, etc.), a new Information
Element describing the new type of Observation Point must be
specified, along with an Options Template Record describing it in
more detail (if necessary).
If the packets are selected by a Composite Selector, the Selection
Sequence is composed of several Primitive Selectors. In such a case,
the Selection Sequence Report Interpretation MUST contain the list of
all the Primitive Selector IDs in the Selection Sequence. If
multiple Selectors are contained in the Selection Sequence Report
Interpretation, the selectorId's MUST be identified in the order they
are used.
Example of two Selection Sequences:
Selection Sequence 7 (Filter->Sampling):
ingressInterface 5
selectorId 5 (Filter, match IPV4SourceAddress 192.0.2.1)
selectorId 10 (Sampler, Random 1 out-of ten)
Selection Sequence 9 (Sampling->Filtering):
ingressInterface 5
selectorId 10 (Sampler, Random 1 out-of ten)
selectorId 5 (Filter, match IPV4SourceAddress 192.0.2.1)
Claise, et al. Standards Track [Page 23]
RFC 5476 PSAMP Protocol Specification March 2009
IPFIX Options Template Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 3 | Length = 26 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID = 262 | Field Count = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope Field Count = 1 |0| selectionSequenceId = 301 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope 1 Length = 4 |0| ingressInterface = 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| selectorId = 302 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| selectorId = 302 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The associated IPFIX Data Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 262 | Length = 36 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 7 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 9 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure G: Example of a Selection Sequence Report Interpretation
Claise, et al. Standards Track [Page 24]
RFC 5476 PSAMP Protocol Specification March 2009
Notes:
* There are two Records here in the same Data Set. Each record
defines a different Selection Sequence.
* If, for example, a different Selection Sequence is composed of
three Selectors, then a different Options Template with three
selectorId Information Elements (instead of two) must be used.
6.5.2. Selector Report Interpretation
An IPFIX Data Record, defined by an Options Template Record, MUST be
used to send the configuration details of every Selector in use. The
Options Template Record MUST contain the selectorId Information
Element as the Scope field and the SelectorAlgorithm Information
Element followed by some specific configuration parameters:
Scope: selectorId
Non-scope: selectorAlgorithm
algorithm-specific Information Elements
The algorithm-specific Information Elements are specified in the
following subsections, depending on the selection method represented
by the value of the selectorAlgorithm [RFC5477].
6.5.2.1. Systematic Count-Based Sampling
In systematic count-based Sampling, the start and stop triggers for
the Sampling interval are defined in accordance with the spatial
packet position (packet count) [RFC5475].
The REQUIRED algorithm-specific Information Elements in the case of
systematic count-based Sampling are:
samplingPacketInterval: number of packets selected in a row
samplingPacketSpace: number of packets between selections
Example of a simple 1 out-of 10 systematic count-based Selector
definition, where the samplingPacketInterval is 1 and the
samplingPacketSpace is 9.
Claise, et al. Standards Track [Page 25]
RFC 5476 PSAMP Protocol Specification March 2009
IPFIX Options Template Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 3 | Length = 26 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID = 263 | Field Count = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope Field Count = 1 |0| selectorId = 302 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope 1 Length = 4 |0| selectorAlgorithm = 304 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 1 |0|samplingPacketInterval = 305 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 1 |0| samplingPacketSpace = 306 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Associated IPFIX Data Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 263 | Length = 11 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 15 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 | 1 | 9 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure H: Example of the Selector Report Interpretation
for Systematic Count-Based Sampling
Notes:
* A selectorAlgorithm value of 1 represents systematic count-based
Sampling.
* samplingPacketInterval and samplingPacketSpace are of type
unsigned32 but are compressed down to one octet here, as allowed by
the IPFIX protocol specifications [RFC5101].
Claise, et al. Standards Track [Page 26]
RFC 5476 PSAMP Protocol Specification March 2009
6.5.2.2. Systematic Time-Based Sampling
In systematic time-based Sampling, the start and stop triggers are
used to define the Sampling intervals [RFC5475]. The REQUIRED
algorithm-specific Information Elements in the case of systematic
time-based Sampling are:
samplingTimeInterval: time (in microseconds) when packets are
selected
samplingTimeSpace: time (in microseconds) between selections
Example of a 100 microsecond out-of 1000 microsecond systematic
time-based Selector definition, where the samplingTimeInterval is 100
and the samplingTimeSpace is 900.
IPFIX Options Template Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 3 | Length = 26 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID = 264 | Field Count = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope Field Count = 1 |0| selectorId = 302 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope 1 Length = 4 |0| selectorAlgorithm = 304 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 1 |0| samplingTimeInterval = 307 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 1 |0| samplingTimeSpace = 308 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Associated IPFIX Data Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 264 | Length = 12 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 2 | 100 | 900 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure I: Example of the Selector Report Interpretation
Claise, et al. Standards Track [Page 27]
RFC 5476 PSAMP Protocol Specification March 2009
for Systematic Time-Based Sampling
Notes:
* A selectorAlgorithm value of 2 represents systematic time-based
Sampling.
* samplingTimeInterval and samplingTimeSpace are of type unsigned32
but are compressed down here.
6.5.2.3. Random n-out-of-N Sampling
In random n-out-of-N Sampling, n elements are selected out of the
parent Population that consists of N elements [RFC5475]. The
REQUIRED algorithm-specific Information Elements in case of random
n-out-of-N Sampling are:
samplingSize: number of packets selected
samplingPopulation: number of packets in selection Population
Example of a 1 out-of 10 random n-out-of-N Sampling Selector:
IPFIX Options Template Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 3 | Length = 26 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID = 265 | Field Count = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope Field Count = 1 |0| selectorId = 302 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope 1 Length = 4 |0| selectorAlgorithm = 304 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 1 |0| samplingSize = 309 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 1 |0| samplingPopulation = 310 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Claise, et al. Standards Track [Page 28]
RFC 5476 PSAMP Protocol Specification March 2009
Associated IPFIX Data Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 265 | Length = 11 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 17 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 | 1 | 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure J: Example of the Selector Report Interpretation
for Random n-out-of-N Sampling
Notes:
* A selectorAlgorithm value of 3 represents Random n-out-of-N
Sampling.
* samplingSize and samplingPopulation are of type unsigned32 but are
compressed down to one octet here.
6.5.2.4. Uniform Probabilistic Sampling
In uniform probabilistic Sampling, each element has the same
probability p of being selected from the parent Population [RFC5475].
The algorithm-specific Information Element in case of uniform
probabilistic Sampling is:
samplingProbability: a floating point number for the Sampling
probability.
Claise, et al. Standards Track [Page 29]
RFC 5476 PSAMP Protocol Specification March 2009
Example of a 15% uniform probability Sampling Selector:
IPFIX Options Template Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 3 | Length = 22 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID = 271 | Field Count = 3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope Field Count = 1 |0| selectorId = 302 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| selectorAlgorithm = 304 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 1 |0| samplingProbability = 311 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Associated IPFIX Data Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 271 | Length = 11 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 20 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 4 | 0.15 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+
Figure K: Example of the Selector Report Interpretation
for Uniform Probabilistic Sampling
Notes:
* A selectorAlgorithm value of 4 represents Uniform Probabilistic
Sampling.
* samplingProbability is of type float64 but is compressed down to a
float32 here.
Claise, et al. Standards Track [Page 30]
RFC 5476 PSAMP Protocol Specification March 2009
6.5.2.5. Property Match Filtering
This classification includes match(es) on field(s) within a packet
and/or on properties of the router state. With this method, a packet
is selected if a specific field in the packet equals a predefined
value.
The algorithm-specific Information Elements defining configuration
parameters for Property Match Filtering are taken from the full range
of available Information Elements.
When multiple different Information Elements are defined, the filter
acts as a logical AND. Note that the logical OR is not covered by
these PSAMP specifications. The Property Match Filtering Options
Template Record MUST NOT have multiple identical Information
Elements. The result of the filter is independent from the order of
the Information Elements in the Options Template Record, but the
order may be important for implementation purposes, as the first
filter will have to work at a higher rate. In any case, an
implementation is not constrained to respect the filter ordering as
long as the result is the same, and it may even implement the
composite Filtering in one single step.
Since encryption alters the meaning of encrypted fields, when the
Property Match Filtering classification is based on the encrypted
field(s) in the packet, it MUST be able to recognize that the
field(s) are not available and MUST NOT select those packets unless
specifically directed by the Information Element description. Even
if they are ignored, the encrypted packets MUST be accounted for in
the Selector packetsObserved Information Element [RFC5477], part of
the Selection Sequence Statistics Report Interpretation.
Example of a match-based filter Selector, whose rules are:
IPv4 Source Address = 192.0.2.1
IPv4 Next-Hop Address = 192.0.2.129
Claise, et al. Standards Track [Page 31]
RFC 5476 PSAMP Protocol Specification March 2009
IPFIX Options Template Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 3 | Length = 26 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID = 266 | Field Count = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope Field Count = 1 |0| selectorId = 302 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope 1 Length = 4 |0| selectorAlgorithm = 304 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 1 |0| sourceIPv4Address = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| ipNextHopIPv4Address = 15 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Associated IPFIX Data Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 266 | Length = 11 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 21 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5 | 192.0.2 ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... .1 | 192.0.2 ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... .129 |
+-+-+-+-+-+-+-+-+
Figure L: Example of the Selector Report Interpretation
for Match-Based and Router State Filtering
Notes:
* A selectorAlgorithm value of 5 represents Property Match Filtering.
* In this filter, there is a mix of information from the packet and
information from the router.
Claise, et al. Standards Track [Page 32]
RFC 5476 PSAMP Protocol Specification March 2009
6.5.2.6. Hash-Based Filtering
In Hash-based Selection, a Hash Function is run on IPv4 traffic. The
following fields MUST be used as input to that Hash Function:
- IP identification field
- Flags field
- Fragment offset
- Source IP address
- Destination IP address
- A number of bytes from the IP payload. The number of bytes and
starting offset MUST be configurable if the Hash Function
supports it.
For the bytes taken from the IP payload, IPSX has a fixed offset of 0
bytes and a fixed size of 8 bytes. The number and offset of payload
bytes in the BOB function MUST be configurable.
The minimum configuration ranges MUST be as follows:
Number of bytes: from 8 to 32
Offset: from 0 to 64
If the selected payload bytes are not available and the Hash Function
can take a variable-sized input, then the Hash Function MUST be run
with the information that is available and a shorter size. Passing 0
as a substitute for missing payload bytes is only acceptable if the
Hash Function takes a fixed size as is the case with IPSX.
If the Hash Function can take an initialization value, then this
value MUST be configurable.
A Hash-based Selection function MAY be configurable as a digest
function. Any Selection Process that is configured as a digest
function MUST have the output value included in the basic Packet
Report for any selected packet.
Each Hash Function used as a Hash-based Selection Selector requires
its own value for the selectorAlgorithm. Currently, we have BOB (6),
IPSX (7), and CRC (8) defined and any MAY be used for either
Filtering or creating a Packet Digest. Only BOB is recommended
though and SHOULD be used.
Claise, et al. Standards Track [Page 33]
RFC 5476 PSAMP Protocol Specification March 2009
The REQUIRED algorithm-specific Information Elements in case of
Hash-based Selection are:
hashIPPayloadOffset - The payload offset used by a Hash-based
Selection Selector
hashIPPayloadSize - The payload size used by a Hash-based
Selection Selector
hashOutputRangeMin - One or more values for the beginning of each
potential output range.
hashOutputRangeMax - One or more values for the end of each
potential output range.
hashSelectedRangeMin - One or more values for the beginning of each
selected range.
hashSelectedRangeMax - One or more values for the end of each
selected range.
hashDigestOutput - A boolean value, TRUE if the output from this
Selector has been configured to be included
in the Packet Report as a packet digest.
Note: If more than one selection or output range needs to be sent,
then the minimum and maximum elements may be repeated as needed.
These MUST make one or more non-overlapping ranges. The elements
SHOULD be sent as pairs of minimum and maximum in ascending order;
however, if they are sent out of order, then there will only be one
way to interpret the ranges to produce a non-overlapping range and
the Collecting Process MUST be prepared to accept and decode this.
The following algorithm-specific Information Element MAY be sent, but
is optional for security considerations:
hashInitialiserValue - The initialiser value to the Hash Function.
Since encryption alters the meaning of encrypted fields, when the
Hash-based Filtering classification is based on the encrypted
field(s) in the packet, it MUST be able to recognize that the
field(s) are not available and MUST NOT select those packets. Even
if they are ignored, the encrypted packets MUST be accounted for in
the Selector packetsObserved Information Element [RFC5477], which is
part of the Selection Sequence Statistics Report Interpretation.
Claise, et al. Standards Track [Page 34]
RFC 5476 PSAMP Protocol Specification March 2009
Example of a Hash-based Filter Selector, whose configuration is:
Hash Function = BOB
Hash IP Payload Offset = 0
Hash IP Payload Size = 16
Hash Initialiser Value = 0x9A3F9A3F
Hash Output Range = 0 to 0xFFFFFFFF
Hash Selected Range = 100 to 200 and 400 to 500
IPFIX Options Template Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 3 | Length = 50 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID = 269 | Field Count = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope Field Count = 1 |0| selectorId = 302 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope 1 Length = 4 |0| selectorAlgorithm = 302 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 1 |0| hashIPpayloadOffset = 327 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| hashIPpayloadSize = 328 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| hashInitialiserValue = 329 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| hashOutputRangeMin = 330 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| hashOutputRangeMax = 331 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| hashSeletionRangeMin = 332 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| hashSeletionRangeMax = 333 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| hashSeletionRangeMin = 332 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| hashSeletionRangeMax = 333 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Claise, et al. Standards Track [Page 35]
RFC 5476 PSAMP Protocol Specification March 2009
Associated IPFIX Data Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 266 | Length = 45 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 22 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 6 | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... 0 | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... 16 | 0x9A3F9A ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... 3F | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... 0 | 0xFFFFFF ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... FF | ... 100 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | ... 200 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | ... 400 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | ... 500 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+
Figure M: Example of the Selector Report Interpretation
for Hash-based Filtering
Notes:
* A selectorAlgorithm value of 6 represents Hash-based Filtering
using the BOB algorithm.
6.5.2.7. Other Selection Methods
Some potential new selection methods MAY be added. Some of the new
selection methods, such as non-uniform probabilistic Sampling and
flow-state-dependent Sampling, are described in [RFC5475], with
further references.
Claise, et al. Standards Track [Page 36]
RFC 5476 PSAMP Protocol Specification March 2009
Each new selection method MUST be assigned a unique value for the
selectorAlgorithm Information Element. Its configuration
parameter(s), along with the way to report it/them with an Options
Template, MUST be clearly specified.
6.5.3. Selection Sequence Statistics Report Interpretation
A Selector MAY be used in multiple Selection Sequences. However,
each use of a Selector must be independent, so each separate logical
instance of a Selector MUST maintain its own individual Selection
State and statistics.
The Selection Sequence Statistics Report Interpretation MUST include
the number of observed packets (Population Size) and the number of
packets selected (Sample Size) by each instance of its Primitive
Selectors.
Within a Selection Sequence composed of several Primitive Selectors,
the number of packets selected for one Selector is equal to the
number of packets seen by the next Selector. The order of the
Selectors in the Selection Sequence Statistics Report Interpretation
MUST match the order of the Selectors in the Selection Sequence.
If the full set of statistics is not sent as part of the Basic Packet
Reports, the PSAMP Device MUST export a Selection Sequence Statistics
Report Interpretation for every Selection Sequence, using an Options
Template containing the following Information Elements:
Scope: selectionSequenceId
Non-scope: packetsObserved
packetsSelected (first Selector)
...
packetsSelected (last Selector)
The packetsObserved Information Element [RFC5477] MUST contain the
number of packets seen at the Observation Point, and as a consequence
passed to the first Selector in the Selection Sequence. The
packetsSelected Information Element [RFC5477] contains the number of
packets selected by a Selector in the Selection Sequence.
The Attained Selection Fraction for the Selection Sequence is
calculated by dividing the number of selected packets
(packetsSelected Information Element) for the last Selector by the
number of observed packets (packetsObserved Information Element).
The Attained Selection Fraction can be calculated for each Selector
by dividing the number of packets selected for that Selector by the
value for the previous Selector.
Claise, et al. Standards Track [Page 37]
RFC 5476 PSAMP Protocol Specification March 2009
The statistics for the whole sequence SHOULD be taken at a single
logical point in time; the input value for a Selector MUST equal the
output value of the previous Selector.
The Selection Sequence Statistics Report Interpretation MUST be
exported periodically.
Example of Selection Sequence Statistics Report Interpretation:
Selection Sequence 7 (Filter->Sampling):
Observed 100 (observationPointId 1, Interface 5)
Selected 50 (selectorId 5, match IPV4SourceAddress 192.0.2.1)
Selected 6 (selectorId 10, Sampler: Random one out-of ten)
Selection Sequence 9 (Sampling->Filtering):
Observed 100 (observationPointId 1, Interface 5)
Selected 10 (selectorId 10, Sampler: Random one out-of ten)
Selected 3 (selectorId 5, match IPV4SourceAddress 192.0.2.1)
IPFIX Options Template Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 3 | Length = 26 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID = 267 | Field Count = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope Field Count = 1 |0| selectionSequenceId = 301 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope 1 Length = 4 |0| packetsObserved = 318 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| packetsSelected = 319 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| packetsSelected = 319 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Claise, et al. Standards Track [Page 38]
RFC 5476 PSAMP Protocol Specification March 2009
The associated IPFIX Data Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 267 | Length = 36 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 7 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 100 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 50 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 9 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 100 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure N: Example of the Selection Sequence Statistics
Report Interpretation
Notes:
* The Attained Selection Fractions for Selection Sequence 7 are:
Filter 10: 50/100
Sampler 5: 6/50
Number of samples selected: 6
* The Attained Selection Fractions for Selection Sequence 9 are:
Sampler 5: 10/100
Filter 10: 3/10
Number of samples selected: 3
6.5.4. Accuracy Report Interpretation
In order for the Collecting Process to determine the inherent
accuracy of the reported quantities (for example, timestamps), the
PSAMP Device SHOULD send an Accuracy Report Interpretation.
The Accuracy Report Interpretation MUST be exported by an Options
Template Record with a scope that contains the Information Element
for which the accuracy is required. In case the accuracy is specific
Claise, et al. Standards Track [Page 39]
RFC 5476 PSAMP Protocol Specification March 2009
to a template, a second scope containing the templateId value MUST be
added to the Options Template Record. The accuracy SHOULD be
reported either with the absoluteError Information Element [RFC5477]
or with the relativeError Information Element [RFC5477].
Accuracy Report Interpretation using the absoluteError Information
Element:
Scope: informationElementId
Non-scope: absoluteError
Accuracy Report Interpretation using the absoluteError Information
Element and a double scope:
Scope: templateId
informationElementId
Non-scope: absoluteError
Accuracy Report Interpretation using the relativeError Information
Element:
Scope: informationElementId
Non-scope: relativeError
Accuracy Report Interpretation using the relativeError Information
Element and a double scope:
Scope: templateId
informationElementId
Non-scope: relativeError
For example, the accuracy of an Information Element whose Abstract
Data Type is dateTimeMilliseconds [RFC5102], for which the unit is
specified as milliseconds, can be specified with the absoluteError
Information Element with the milliseconds units. In this case, the
error interval is the Information Element value +/- the value
reported in the absoluteError.
For example, the accuracy of an Information Element to estimate the
accuracy of a sampled flow, for which the unit would be specified in
octets, can be specified with the relativeError Information Element
with the octet units. In this case, the error interval is the
Information Element value +/- the value reported in the relativeError
times the reported Information Element value.
An alternative to reporting either the absoluteError Information
Element or the relativeError Information Element in the Accuracy
Report Interpretation, is to report both. For this case whatever is
least accurate for the reported value should be used.
If the accuracy of a reported quantity changes on the Metering
Process, a new Accuracy Report Interpretation MUST be generated. The
Claise, et al. Standards Track [Page 40]
RFC 5476 PSAMP Protocol Specification March 2009
Collecting Process MUST keep the accuracy of the latest Accuracy
Report Interpretation.
Example of an Accuracy Report Interpretation using the absoluteError
Information Element and a double scope: the timeMicroseconds
contained in the Template 5 has an accuracy of +/- 2 ms, represented
by the absoluteError Information Element.
Scope: templateId = 6
informationElementId = timeMicroseconds
Non-scope: absoluteError = 2 ms
IPFIX Options Template Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 3 | Length = 22 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID = 267 | Field Count = 3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope Field Count = 2 |0| templateId = 145 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope 1 Length = 2 |0| InformationElementId = 303 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope 2 Length = 2 |0| absoluteError = 320 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The associated IPFIX Data Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 267 | Length = 12 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5 | 324 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 2 (encoded as a float32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure O: Example of the Selection Sequence
Statistics Report Interpretation
Claise, et al. Standards Track [Page 41]
RFC 5476 PSAMP Protocol Specification March 2009
Notes:
* absoluteError is of type float64 but is compressed down to a
float32 here.
The second example displays an Accuracy Report Interpretation using
the relativeError Information Element and a single scope: the
timeMicroseconds has an error of 5%, represented by the
proportionalAccuracy Information Element.
Scope: informationElementId = timeMicroseconds
Non-scope: relativeError = 0.05
IPFIX Options Template Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 3 | Length = 18 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Template ID = 268 | Field Count = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope Field Count = 1 |0| InformationElementId = 303 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope 1 Length = 2 |0| relativeError= 321 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The associated IPFIX Data Record:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set ID = 267 | Length = 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 324 | 0.05 ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...(encoded as a float32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure P: Example of the Selection Sequence
Statistics Report Interpretation
Notes:
* relativeError is of type float64 but is compressed down to a
float32 here.
Claise, et al. Standards Track [Page 42]
RFC 5476 PSAMP Protocol Specification March 2009
7. Security Considerations
As IPFIX has been selected as the PSAMP export protocol and as the
PSAMP security requirements are not stricter than the IPFIX security
requirements, refer to the IPFIX export protocol [RFC5101] for the
security considerations.
In the basic Packet Report, a PSAMP Device exports some number of
contiguous bytes from the start of the packet, including the packet
header (which includes link layer, network layer, and other
encapsulation headers) and some subsequent bytes of the packet
payload. The PSAMP Device SHOULD NOT export the full payload of
conversations, as this would mean wiretapping [RFC2804]. The PSAMP
Device MUST respect local privacy laws.
8. IANA Considerations
The PSAMP protocol, as set out in this document, has two sets of
assigned numbers. Considerations for assigning them are discussed in
this section, using the example policies as set out in [RFC5226],
"Guidelines for IANA Considerations".
8.1. IPFIX-Related Considerations
As the PSAMP protocol uses the IPFIX protocol, refer to the IANA
considerations section in [RFC5101] for the assignments of numbers
used in the protocol and for the numbers used in the information
model.
8.2. PSAMP-Related Considerations
Each new selection method MUST be assigned a unique value for the
selectorAlgorithm Information Element [RFC5477]. Initial contents of
this registry are found in Section 8.2.1 in [RFC5477]. Its
configuration parameter(s), along with the way to report them with an
Options Template, MUST be clearly specified.
New assignments for the PSAMP selection method will be administered
by IANA, on a First Come First Served basis [RFC5226], subject to
Expert Review [RFC5226]. The group of experts must double check the
Information Elements definitions with already defined Information
Elements for completeness, accuracy, and redundancy. These experts
will initially be drawn from the Working Group Chairs and document
editors of the IPFIX and PSAMP Working Groups.
Claise, et al. Standards Track [Page 43]
RFC 5476 PSAMP Protocol Specification March 2009
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5101] Claise, B., Ed., "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.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, May
2008.
[RFC5475] Zseby, T., Molina, M., Duffield, N., Niccolini, S., and F.
Raspall, "Sampling and Filtering Techniques for IP Packet
Selection", RFC 5475, March 2009.
[RFC5477] Dietz, T., Claise, B., Aitken, P., Dressler, F., and G.
Carle, "Information Model for Packet Sampling Exports", RFC
5477, March 2009.
9.2. Informative References
[RFC2804] IAB and IESG, "IETF Policy on Wiretapping", RFC 2804, May
2000.
[RFC3917] Quittek, J., Zseby, T., Claise, B., and S. Zander,
"Requirements for IP Flow Information Export (IPFIX)", RFC
3917, October 2004.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border
Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC5470] Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,
"Architecture for IP Flow Information Export" RFC 5470,
March 2009.
[RFC5474] Duffield, N., Ed., "A Framework for Packet Selection and
Reporting", RFC 5474, March 2009.
Claise, et al. Standards Track [Page 44]
RFC 5476 PSAMP Protocol Specification March 2009
10. Acknowledgments
The authors would like to thank the PSAMP group, especially Paul
Aitken for fruitful discussions and for proofreading the document
several times.
Authors' Addresses
Benoit Claise
Cisco Systems
De Kleetlaan 6a b1
1831 Diegem
Belgium
Phone: +32 2 704 5622
EMail: bclaise@cisco.com
Juergen Quittek
NEC Europe Ltd.
Network Laboratories
Kurfuersten-Anlage 36
69115 Heidelberg
Germany
Phone: +49 6221 90511-15
EMail: quittek@nw.neclab.eu
Andrew Johnson
Cisco Systems
96 Commercial Quay
Edinburgh EH6 6LX
Scotland
Phone: +44 131 561 3641
EMail: andrjohn@cisco.com
Claise, et al. Standards Track [Page 45]
ERRATA
