PSAMP working group
Internet Draft EDITOR: B. Claise
draft-ietf-psamp-protocol-04.txt Cisco Systems
Expires: September 2006 March 2006
Packet Sampling (PSAMP) Protocol Specifications
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Abstract
This document specifies the export of packet information from a
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
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sufficient. The document specifies in detail how the IPFIX protocol
is used for PSAMP export of packet information.
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].
Table of Contents
1. Introduction................................................3
2. PSAMP Documents Overview....................................3
3. Terminology.................................................4
3.1 IPFIX Terminology..........................................4
3.2 PSAMP Terminology..........................................8
3.2.1 Packet Streams and Packet Content.....................8
3.2.2 Selection Process.....................................9
3.2.3 Reporting............................................10
3.2.4 Exporting Process....................................11
3.2.5 PSAMP Device.........................................11
3.2.6 Selection Methods....................................11
3.3 IPFIX and PSMAP Terminology Comparison....................13
3.3.1 PSAMP and IPFIX Processes............................13
3.3.2 Packet Report, Packet Interpretation, and Data Record14
4. Differences between PSAMP and IPFIX........................14
4.1 Architecture Point of View................................14
4.2 Protocol Point of View....................................16
4.3 Information Model Point of View...........................16
5. PSAMP Requirements versus the IPFIX Solution...............16
5.1 High Level View of the Integration........................17
6. Using the IPFIX Protocol for PSAMP.........................18
6.1 Selector ID...............................................18
6.2 The Selection Sequence....................................18
6.3 The Exporting Process.....................................18
6.4 Packet Report.............................................18
6.4.1 Basic Packet Report..................................19
6.4.2 Extended Packet Report...............................21
6.5 Report Interpretation.....................................23
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
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.............................30
6.5.2.6 Hash-Based Filtering.................................32
6.5.2.7 Other Selection Methods..............................35
6.5.3 Selection Sequence Statistics Report Interpretation..35
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6.5.4 Accuracy Report Interpretation.......................38
7. Security Considerations....................................41
8. IANA Considerations........................................41
8.1 IPFIX Related Considerations..............................41
8.2 PSAMP Related Considerations..............................41
9. References.................................................42
9.1 Normative References......................................42
9.2 Informative References....................................42
10. Acknowledgments...........................................43
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 (filtering), and deterministic approximations to random
selection (hash-based selection).
The IP Flow information export (IPFIX) protocol specified in [IPFIX-
PROTO] exports IP traffic information [IPFIX-INFO] observed at
network devices. This matches the general protocol requirements
outlined in the PSAMP framework [PSAMP-FMWK]. However, there are
some architectural differences between IPFIX and PSAMP in the
requirements for an export protocol. While the IPFIX architecture
[IPFIX-ARCH] is focused on gathering and exporting IP traffic flow
information, the focus of the PSAMP framework [PSAMP-FMWK] 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 as 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 [PSAMP-INFO].
2.
PSAMP Documents Overview
[PSAMP-FMWK]: "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.
[PSAMP-TECH]: "Sampling and Filtering Techniques for IP Packet
Selection", describes the set of packet selection techniques
supported by PSAMP.
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[PSAMP-PROTO]: "Packet Sampling (PSAMP) Protocol Specifications"
(this document), specifies the export of packet information from a
PSAMP Exporting Process to a PSAMP Collecting Process.
[PSAMP-INFO]: "Information Model for Packet Sampling Exports" defines
an information and data model for PSAMP.
[PSAMP-MIB]: "Definitions of Managed Objects for Packet Sampling"
describes the PSAMP Management Information Base.
3.
Terminology
As the IPFIX export protocol is used to export the PSAMP information,
the relevant IPFIX terminology from [IPFIX-PROTO] is copied over in
this document. The terminology summary table in section 4.1 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 [PSAMP-TECH] and [PSAMP-FMWK] but only
definitions that are only relevant to the PSAMP protocol appear here.
Section 5.4 applies the PSAMP terminology to the IPFIX protocol
terminology.
3.1
IPFIX Terminology
The IPFIX terminology section has been entirely copied over from
[IPFIX-PROTO], except for the IPFIX Exporting Process term, which is
defined more precisely in the PSAMP terminology section.
Observation Point
An Observation Point is a location in the network where IP packets
can be observed. Examples include: a line to which a probe is
attached, a shared medium, such as an Ethernet-based LAN, a single
port of a router, or a set of interfaces (physical or logical) of a
router.
Note that every Observation Point is associated with an Observation
Domain (defined below), and that one Observation Point may be a
superset of several other Observation Points. For example one
Observation Point can be an entire line card. That would be the
superset of the individual Observation Points at the line card's
interfaces.
Observation Domain
An Observation Domain is the largest set of Observation Points for
which Flow information can be aggregated by a Metering Process.
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Each Observation Domain presents itself using a unique ID to the
Collecting Process to identify the IPFIX Messages it generates. For
example, a router line card may be an observation domain if it is
composed of several interfaces, each of which is an Observation
Point. Every Observation Point is associated with an Observation
Domain.
IP Traffic Flow or Flow
There are several definitions of the term 'flow' being used by the
Internet community. Within the context of IPFIX we use the following
definition:
A Flow is defined as a set of IP packets passing an Observation Point
in the network during a certain time interval. All packets belonging
to a particular Flow have a set of common properties. Each property
is defined as the result of applying a function to the values of:
1. one or more packet header field (e.g. destination IP address),
transport header field (e.g. destination port number), or
application header field (e.g. RTP header fields [RFC1889])
2. one or more characteristics of the packet itself (e.g. number
of MPLS labels, etc...)
3. one or more of fields derived from packet treatment (e.g. next
hop IP address, the output interface, etc...)
A packet is defined to belong to a Flow if it completely satisfies
all the defined properties of the Flow.
This definition covers the range from a Flow containing all packets
observed at a network interface to a Flow consisting of just a single
packet between two applications. It includes packets selected by a
sampling mechanism.
Flow Key
Each of the fields which
1. Belong to the packet header (e.g. destination IP address)
2. Are a property of the packet itself (e.g. packet length)
3. Are derived from packet treatment (e.g. AS number)
and which are used to define a Flow are termed Flow Keys.
Flow Record
A Flow Record contains information about a specific Flow that was
observed at an Observation Point. A Flow Record contains measured
properties of the Flow (e.g. the total number of bytes for all the
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Flow's packets) and usually characteristic properties of the Flow
(e.g. source IP address).
Metering Process
The Metering Process generates Flow Records. Inputs to the process
are packet headers and characteristics observed at an Observation
Point, and packet treatment at the Observation Point (for example the
selected output interface).
The Metering Process consists of a set of functions that includes
packet header capturing, timestamping, sampling, classifying, and
maintaining Flow Records.
The maintenance of Flow Records may include creating new records,
updating existing ones, computing Flow statistics, deriving further
Flow properties, detecting Flow expiration, passing Flow Records to
the Exporting Process, and deleting Flow Records.
Exporter
A device which hosts one or more Exporting Processes is termed an
Exporter.
IPFIX Device
An IPFIX Device hosts at least one Observation Point, a Metering
Process and an Exporting Process.
Collecting Process
A Collecting Process receives Flow Records from one or more
Exporting Processes. The Collecting Process might process or store
received Flow Records, but such actions are out of scope for this
document.
Collector
A device which hosts one or more Collecting Processes is termed a
Collector.
Template
Template is an ordered sequence of <type, length> pairs, used to
completely specify the structure and semantics of a particular set of
information that needs to be communicated from an IPFIX Device to a
Collector. Each Template is uniquely identifiable by means of a
Template ID.
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IPFIX Message
An IPFIX Message is a message originating at the Exporting Process
that carries the IPFIX records of this Exporting Process and whose
destination is a Collecting Process. An IPFIX Message is
encapsulated at the transport layer.
Message Header
The Message Header is the first part of an IPFIX Message, which
provides basic information about the message such as the IPFIX
version, length of the message, message sequence number, etc.
Template Record
A Template Record defines the structure and interpretation of fields
in a Data Record.
Data Record
A Data Record is a record that contains values of the parameters
corresponding to a Template Record.
Options Template Record
An Options Template Record is a Template Record that defines the
structure and interpretation of fields in a Data Record, including
defining how to scope the applicability of the Data Record.
Set
Set is a generic term for a collection of records that have a similar
structure. In an IPFIX Message, one or more Sets follow the Message
Header.
There are three different types of Sets: Template Set, Options
Template Set, and Data Set.
Template Set
A Template Set is a collection of one or more Template Records that
have been grouped together in an IPFIX Message.
Options Template Set
An Options Template Set is a collection of one or more Options
Template Records that have been grouped together in an IPFIX Message.
Data Set
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A Data Set is one or more Data Records, of the same type, that are
grouped together in an IPFIX Message. Each Data Record is previously
defined by a Template Record or an Options Template Record.
Information Element
An Information Element is a protocol and encoding independent
description of an attribute which may appear in an IPFIX Record. The
IPFIX information model [IPFIX-INFO] defines the base set of
Information Elements for IPFIX. The type associated with an
Information Element indicates constraints on what it may contain and
also determines the valid encoding mechanisms for use in IPFIX.
+------------------+---------------------------------------------+
| | 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 over from [PSAMP-TECH].
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 that flows past some
specified point within the Selection 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
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not been selected. For this reason the term "stream" is favored over
"flow", which is defined as set of packets with common properties
[IPFIX-REQ].
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.
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.
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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.
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
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Report Interpretation comprises subsidiary information, relating to
one or more packets, that are 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 Selection Process, comprising
two distinguished types of information: Packet Reports, and Report
Interpretation.
3.2.4 Exporting Process
Exporting Process
An Exporting Process sends, in the form of Export Packets, the output
of one or more Selection 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 a Export Packet for exporting to a Collector.
3.2.5 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.
3.2.6 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. Examples include field match
Filtering, and Hash-based Selection.
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
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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. Examples include
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 subset of the Packet Content and the packet treatment, viewed as an
N-bit string for some positive integer N.
Hash Range
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 deterministic map from the Hash Domain into the Hash Range.
Hash Selection Range
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
Filtering specified by a Hash Domain, a Hash Function, a Hash Range
and a Hash Selection Range.
Approximative Selection
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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.
Sample Size
The number of packets selected from the Population by a Selector.
Configured Selection Fraction
The Configured Selection Fraction is the ratio of the number of
packets selected by a Selector from an input Population, to the
Population Size, as based on the configured selection parameters.
Attained Selection Fraction
The Attained Selection Fraction is the actual ratio of the
number of packets selected by a Selector from an input
Population, 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 PSMAP Terminology Comparison
The PSAMP terminology has been specified with an IPFIX background, as
PSAMP and IPFIX have similar terms. However, this section explains
the non compatible terms between IPFIX and PSAMP.
3.3.1 PSAMP and IPFIX Processes
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The figure B indicates the sequence of the processes (selection and
exporting) within the PSAMP Device.
+----------+ +-----------+
Observed | Metering | | Exporting |
Packet--->| Process |----->| Process |--->Collector
Stream +----------+ +-----------+
Figure B: PSAMP Processes
The Selection Process, which takes an Observed Packet Stream as its
input and produces Packet Reports as its output, is an integral part
of the Metering Process, which by its definition produces Flow
Records as its output.
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
(Option) 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 Packet
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 Option Template Record.
4.
Differences between PSAMP and IPFIX
The output of the IPFIX working group relevant for this draft is
structured into three documents:
- IP Flow information architecture [IPFIX-ARCH]
- IPFIX protocol specifications [IPFIX-PROTO]
- IP Flow information export information model [IPFIX-INFO]
4.1
Architecture Point of View
Traffic Flow measurement as described in the IPFIX requirements
[RFC3917] and the IPFIX architecture [IPFIX-ARCH] 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, time stamped, 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.
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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.
Packet Sampling as described in the PSAMP framework [PSAMP-FMWK]
covers only stage 1 of the IPFIX architecture with the packet
classification replaced by packet record export.
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 record
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 Records. 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 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 [IPFIX-PROTO], 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
flowCount, packetCount (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 [IPFIX-INFO]. The task of specifying them
was intentionally left for the PSAMP information model [PSAMP-INFO].
A set of several additional fields is required for satisfying the
requirements for the PSAMP information model [PSAMP-TECH].
Exploiting the extensibility of the IPFIX information model, the
required extension is covered by the PSAMP information model
specified in [PSAMP-INFO].
5.
PSAMP Requirements versus the IPFIX Solution
In the "Generic Requirements for PSAMP" section, [PSAMP-FMWK]
describes some requirements that affect directly the PSAMP export
protocol.
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In the "Generic Selection Process Requirements" section, [PSAMP-FMWK]
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.
Finally, [PSAMP-FMWK] 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 there are
described in the information model. So these requirements are mainly
targeted for the [PSAMP-INFO] document.
The PSAMP protocol specifications meets almost all the protocol
requirements stated in the PSAMP framework document [PSAMP-FMWK]:
* Extensibility
* Parallel measurement 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 PSAMP export protocol, the export packet
compression option mentioned in the section 8.5 of the framework
document [PSAMP-FMWK] 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
the Data Records in the Data Set, i.e. the PSAMP Packet Reports.
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
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Records in the Option Template Set and knows which Information
Elements to expect when it receives the Data Records in the Data Set,
i.e. the PSAMP Report Interpretation. 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 [IPFIX-PROTO]. That is the 3 types of Set (Data Set,
Template Set and Options Templates Set) with the 2 types of Templates
Records (Template Record and Options Template Record), as described
in the figure A. As a consequence, PSAMP can't rely on a subset of
the IPFIX protocol specifications are described in [IPFIX-PROTO].
The entire IPFIX protocol specifications [IPFIX-PROTO] MUST be
implemented for the PSAMP protocol.
6.
Using the IPFIX Protocol for PSAMP
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 [PSAMP-INFO].
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 [PSAMP-INFO].
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 Sequences, 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 [PSAMP-FWMK]:
the basic Packet Report and the extended Packet Report.
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PSAMP Protocol Specifications March 2006
6.4.1 Basic Packet Report
For each selected packet, the Packet Report MUST contain the
following information:
- The selectionSequenceId Information Element
- The hash value (digestHashValue) generated by the digest hash
function. If there are no digest functions in the selection
sequence then no element needs to be sent. 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.
- 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 the
following information:
- the observationTimeMicroSeconds Information Element
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 either in a new Template Record with
a variable length field.
Here is an example of a basic Packet Report, with a
SelectionSequenceId value of 9 and ipHeaderPacketSection Information
Claise, et. al Standard Track [Page 19]
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ipHeaderPacketSection = 313 | 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 = 28 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 9 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x9123 0613 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x4500 005B |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xA174 0000 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF11 832E |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| observation time encoded as dateTimeSeconds [IPFIX-PROTO] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure D: Example of a Basic Packet Report
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.
Claise, et. al Standard Track [Page 20]
PSAMP Protocol Specifications March 2006
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
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), 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
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PSAMP Protocol Specifications March 2006
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 = 44 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| destinationIPv4Address = 45 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| totalLengthIPv4 = 190 | Field Length = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| tcpSourcePort = 182 | Field Length = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| tcpDestinationPort = 183 | Field Length = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 10.0.0.1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 10.0.1.106 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 72 | 1372 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 80 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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PSAMP Protocol Specifications March 2006
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 Sequences 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.
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 representing
the Observation Point
selectorId (one or more)
An Information Element representing the Observation Point would
typically be taken from the ingressInterface, egressInterface,
lineCardId, exporterIPv4Address, exporterIPv6Address Information
Elements (specified in [IPFIX-INFO]), but not limited to those: any
Information Element specified in [IFPIX-INFO] or [PSAMP-INFO] 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 option template record describing it in more
details (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
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PSAMP Protocol Specifications March 2006
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 10.0.0.1)
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 10.0.0.1)
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 = 262 | Field Count = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope Field Count = 1 |0| selectionSequenceId = 301 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope 1 Length = 4 |0| ingressInterface = 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| selectorId = 300 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |0| selectorId = 300 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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PSAMP Protocol Specifications March 2006
| 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 9 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure G: Example of a Selection Sequence Report Interpretation
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 Option Template Record, MUST be
used to send the configuration details of every Selector in use. The
Option 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.
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) [PSAMP-TECH].
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
Claise, et. al Standard Track [Page 25]
PSAMP Protocol Specifications March 2006
Example of a simple 1 out-of 10 systematic count-based Selector
definition, where the samplingPacketInterval is 1 and the
samplingPacketSpace is 9.
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 [IPFIX-PROTO].
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PSAMP Protocol Specifications March 2006
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 [PSAMP-TECH]. The REQUIRED
algorithm specific Information Elements in the case of systematic
time-based Sampling are:
samplingTimeInterval: time (in us) when packets are selected
samplingTimeSpace: time (in us) between selections
Example of a 100 us out-of 1000 us 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,
For Systematic Time-Based Sampling
Claise, et. al Standard Track [Page 27]
PSAMP Protocol Specifications March 2006
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 [PSAMP-TECH]. 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 |
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PSAMP Protocol Specifications March 2006
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 [PSAMP-
TECH]. The algorithm specific Information Element in case of uniform
probabilistic Sampling is:
samplingProbablility: a floating point number for the Sampling
probability.
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| samplingProbabilility = 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
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PSAMP Protocol Specifications March 2006
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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.
* samplingProbablility is of type float64 but is compressed down to a
float32 here.
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 Option 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 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.
Even if they are ignored, the encrypted packets MUST be accounted for
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PSAMP Protocol Specifications March 2006
in the Selector packetsObserved Information Element [PSAMP-INFO],
part of the Selection Sequence Statistics Report Interpretation.
Example of a match based filter Selector, whose rules are:
IPv4 Source Address = 10.0.0.1
IPv4 Next-Hop Address = 10.0.1.1
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 = 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 | 10.0.0 ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... .1 | 10.0.1 ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... .1 |
+-+-+-+-+-+-+-+-+
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.
Claise, et. al Standard Track [Page 31]
PSAMP Protocol Specifications March 2006
* In this filter there is a mix of information from the packet and
information from the router.
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. If any
of the configured set of bytes from the IP payload are unavailable
then 0 MUST be used, which may result in a different value than
if the hash function is run on a subset of the input.
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 which 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 which 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 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.
The REQUIRED algorithm specific Information Elements in case of hash
Claise, et. al Standard Track [Page 32]
PSAMP Protocol Specifications March 2006
based selection are:
hashIPPayloadOffset - The payload offset used by a hash based
Selector
hashIPPayloadSize - The payload size used by a hash based
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 select
those packets. Even if they are ignored, the encrypted packets MUST
be accounted in the Selector packetsObserved Information Element
[PSAMP-INFO], part of the Selection Sequence Statistics Report
Interpretation.
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:
Claise, et. al Standard Track [Page 33]
PSAMP Protocol Specifications March 2006
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 = 300 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 | ... |
Claise, et. al Standard Track [Page 34]
PSAMP Protocol Specifications March 2006
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... 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 [PSAMP-TECH], with
further references.
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
Claise, et. al Standard Track [Page 35]
PSAMP Protocol Specifications March 2006
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 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)
...
packetsSelected (last)
The packetsObserved Information Element [PSAMP-INFO] 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 [PSAMP-INFO] 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 observed packets
(packetsObserved Information Element) by the value of selected
packets (packetsSelected Information Element) for the last Selector.
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.
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 10.0.0.1)
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 10.0.0.1)
Claise, et. al Standard Track [Page 36]
PSAMP Protocol Specifications March 2006
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
Claise, et. al Standard Track [Page 37]
PSAMP Protocol Specifications March 2006
Notes:
* The Attained Sampling Fractions for Selection Sequence 7 are:
Filter 10: 50/100
Sampler 5: 6/50
Number of samples selected: 6
* The Attained Sampling 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 Option
Template Record with a scope that contains the Information Element
for which the accuracy is required. In case the accuracy is specific
to a template, a second scope containing the templateId value MUST be
added to the Option Template Record. The accuracy SHOULD be reported
either with the fixedError Information Element [PSAMP-INFO], or with
the relativeError Information Element [PSAMP-INFO].
Accuracy Report Interpretation using the fixedError Information
Element:
Scope: informationElementId
Non-scope: fixedError
Accuracy Report Interpretation using the fixedError Information
Element and a double scope:
Scope: templateId
informationElementId
Non-scope: fixedError
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
Claise, et. al Standard Track [Page 38]
PSAMP Protocol Specifications March 2006
Data Type is dateTimeMilliSeconds [IPFIX-INFO], for which the unit is
specified as milliseconds, can be specified with the fixedError
Information Element with the milliseconds units. In this case, the
error interval is the Information Element value +/- the value
reported in the fixedError.
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
time the reported Information Element value.
Alternatively to reporting either the fixedError Information Element
or the relativeError Information Element in the Accuracy Report
Interpretation, both Information Elements MAY be present. This
scenario could help in more complex situations where the system clock
drifts, on the top of having its own accuracy, during the duration of
a measurement.
If the accuracy of a reported quantity changes on the Metering
Process, a new Accuracy Report Interpretation MUST be generated. The
Collecting Process MUST keep the accuracy of the latest Accuracy
Report Interpretation.
Example of an Accuracy Report Interpretation using the fixedError
Information Element and a double scope: the timeMicroSeconds
contained in the Template 5 has an accuracy of +/- 2 ms, represented
by the fixedError Information Element.
Scope: templateId = 6
informationElementId = timeMicroSeconds
Non-scope: fixedError = 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| fixedError = 320 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Field Length = 4 |
Claise, et. al Standard Track [Page 39]
PSAMP Protocol Specifications March 2006
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
Notes:
* fixedError 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 percents, 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
Claise, et. al Standard Track [Page 40]
PSAMP Protocol Specifications March 2006
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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.
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 [IPFIX-PROTO] 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].
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 the
"Guidelines for IANA Considerations" document IANA-RFC [RFC2434].
8.1
IPFIX Related Considerations
As the PSAMP protocol uses the IPFIX protocol, refer to the IANA
considerations section in [IPFIX-PROTO] 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. Its configuration
Claise, et. al Standard Track [Page 41]
PSAMP Protocol Specifications March 2006
parameter(s), along with the way to report it/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 [RFC 2434], subject to
Expert Review [RFC 2434], i.e. review by one of a group of experts
designated by an IETF Operations and Management Area Director. The
group of experts must double check the Information Elements
definitions with already defined Information Elements for
completeness, accuracy and redundancy. Those experts will initially
be drawn from the Working Group Chairs and document editors of the
IPFIX and PSAMP Working Groups.
9.
References
9.1
Normative References
[RFC1771] Y. Rekhter, T. Li, "A Border Gateway Protocol 4 (BGP-4)",
RFC 1771, March 1995
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997
[RFC2434] H. Alvestrand, T. Narten, "Guidelines for Writing an IANA
Considerations Section in RFCs", RFC 2434, October 1998
[PSAMP-TECH] T. Zseby, M. Molina, N. Duffield, S. Niccolini, F.
Raspall, "Sampling and Filtering Techniques for IP Packet Selection"
draft-ietf-psamp-sample-tech-07.txt
[PSAMP-INFO] T. Dietz, F. Dressler, G. Carle, B. Claise, "Information
Model for Packet Sampling Exports", draft-ietf-psamp-info-03.txt
[IPFIX-ARCH] G. Sadasivan, N. Brownlee, B. Claise, J. Quittek,
"Architecture Model for IP Flow Information Export" draft-ietf-ipfix-
arch-09.txt"
[IPFIX-INFO] J. Quittek, S. Bryant, B. Claise, J. Meyer, "Information
Model for IP Flow Information Export" draft-ietf-ipfix-info-11.txt
[IPFIX-PROTO] B. Claise (Editor) "IPFIX Protocol Specifications",
draft-ietf-ipfix-protocol-19.txt
9.2
Informative References
[PSAMP-MIB] T. Dietz, B. Claise "Definitions of Managed Objects for
Packet Sampling" draft-ietf-psamp-mib-05.txt
Claise, et. al Standard Track [Page 42]
PSAMP Protocol Specifications March 2006
[PSAMP-FMWK] D. Chiou, B. Claise, N. Duffield, A. Greenberg, M.
Grossglauser, P. Marimuthu, J. Rexford, G. Sadasivan, "A Framework
for Passive Packet Measurement" draft-ietf-psamp-framework-10.txt
[RFC3917] J. Quittek, T. Zseby, B. Claise, S. Zander, "Requirements
for IP Flow Information Export", RFC 3917, October 2004
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
E-mail: bclaise@cisco.com
Juergen Quittek
NEC Europe Ltd.
Network Laboratories
Kurfuersten-Anlage 36
69115 Heidelberg
Germany
Phone: +49 6221 90511-15
Email: quittek@ccrle.nec.de
Andrew Johnson
Cisco Systems
96 Commercial Quay
Edinburgh EH6 6LX
Scotland
Phone: +44 131 561 3641
Email: andrjohn@cisco.com
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Claise, et. al Standard Track [Page 43]
PSAMP Protocol Specifications March 2006
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Claise, et. al Standard Track [Page 44]