draft-ietf-ippm-duplicate-08.txt   rfc5560.txt 
Network Working Group H. Uijterwaal Network Working Group H. Uijterwaal
Internet-Draft RIPE NCC Request for Comments: 5560 RIPE NCC
Intended status: Standards Track April 17, 2009
Expires: October 19, 2009
A One-Way Packet Duplication Metric A One-Way Packet Duplication Metric
draft-ietf-ippm-duplicate-08.txt
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Abstract Abstract
When a packet is sent from one host to the other, one normally When a packet is sent from one host to the other, one normally
expects that exactly one copy of the packet that was sent arrives at expects that exactly one copy of the packet that was sent arrives at
the destination. It is, however, possible that a packet is either the destination. It is, however, possible that a packet is either
lost or that multiple copies arrive. lost or that multiple copies arrive.
In earlier work a metric for packet loss has been defined. This In earlier work, a metric for packet loss was defined. This metric
metric quantifies the case where a packet that is sent, does not quantifies the case where a packet that is sent does not arrive at
arrive at its destination within a reasonable time. In this memo, a its destination within a reasonable time. In this memo, a metric for
metric for another case is defined: a packet is sent, but multiple another case is defined: a packet is sent, but multiple copies
copies arrive. The document also discusses streams and methods to arrive. The document also discusses streams and methods to summarize
summarize the results of streams. the results of streams.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction ....................................................3
1.1. Requirements notation . . . . . . . . . . . . . . . . . . 4 1.1. Requirements Notation ......................................3
1.2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Motivation .................................................4
2. A Singleton Definition for one-way packet arrival count . . . 5 2. A Singleton Definition for One-Way Packet Arrival Count .........4
2.1. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Metric Name ................................................4
2.2. Metrics Parameters . . . . . . . . . . . . . . . . . . . . 5 2.2. Metrics Parameters .........................................4
2.3. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 5 2.3. Metric Units ...............................................4
2.4. Definition . . . . . . . . . . . . . . . . . . . . . . . . 5 2.4. Definition .................................................4
2.5. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 6 2.5. Discussion .................................................5
2.6. Methodology . . . . . . . . . . . . . . . . . . . . . . . 7 2.6. Methodology ................................................6
2.7. Errors and uncertainties . . . . . . . . . . . . . . . . . 7 2.7. Errors and Uncertainties ...................................6
2.8. Reporting the metric . . . . . . . . . . . . . . . . . . . 7 2.8. Reporting the Metric .......................................6
3. A Singleton Definition for one-way packet duplication . . . . 7 3. A Singleton Definition for One-Way Packet Duplication ...........6
3.1. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 7 3.1. Metric Name ................................................6
3.2. Metrics Parameters . . . . . . . . . . . . . . . . . . . . 7 3.2. Metrics Parameters .........................................7
3.3. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 7 3.3. Metric Units ...............................................7
3.4. Definition . . . . . . . . . . . . . . . . . . . . . . . . 7 3.4. Definition .................................................7
3.5. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 8 3.5. Discussion .................................................7
4. Definition for samples for one-way Packet Duplication . . . . 8 4. Definition for Samples for One-Way Packet Duplication ...........7
4.1. Poisson Streams . . . . . . . . . . . . . . . . . . . . . 8 4.1. Poisson Streams ............................................7
4.1.1. Metric Name . . . . . . . . . . . . . . . . . . . . . 8 4.1.1. Metric Name .........................................7
4.1.2. Metric Parameters . . . . . . . . . . . . . . . . . . 8 4.1.2. Metric Parameters ...................................8
4.1.3. Metric Units . . . . . . . . . . . . . . . . . . . . . 8 4.1.3. Metric Units ........................................8
4.1.4. Definition . . . . . . . . . . . . . . . . . . . . . . 8 4.1.4. Definition ..........................................8
4.1.5. Methodology . . . . . . . . . . . . . . . . . . . . . 9 4.1.5. Methodology .........................................8
4.1.6. Errors and uncertainties . . . . . . . . . . . . . . . 9 4.1.6. Errors and Uncertainties ............................8
4.1.7. Reporting the metric . . . . . . . . . . . . . . . . . 9 4.1.7. Reporting the Metric ................................8
4.2. Periodic Streams . . . . . . . . . . . . . . . . . . . . . 9 4.2. Periodic Streams ...........................................9
4.2.1. Metric Name . . . . . . . . . . . . . . . . . . . . . 9 4.2.1. Metric Name .........................................9
4.2.2. Metric Parameters . . . . . . . . . . . . . . . . . . 9 4.2.2. Metric Parameters ...................................9
4.2.3. Metric Units . . . . . . . . . . . . . . . . . . . . . 9 4.2.3. Metric Units ........................................9
4.2.4. Definition . . . . . . . . . . . . . . . . . . . . . . 9 4.2.4. Definition ..........................................9
4.2.5. Methodology . . . . . . . . . . . . . . . . . . . . . 10 4.2.5. Methodology .........................................9
4.2.6. Errors and uncertainties . . . . . . . . . . . . . . . 10 4.2.6. Errors and uncertainties ............................9
4.2.7. Reporting the metric . . . . . . . . . . . . . . . . . 10 4.2.7. Reporting the metric ...............................10
5. Some statistics definitions for one-way Duplication . . . . . 10 5. Some Statistics Definitions for One-Way Duplication ............10
5.1. Type-P-one-way-packet-duplication-fraction . . . . . . . . 10 5.1. Type-P-one-way-packet-duplication-fraction ................10
5.2. Type-P-one-way-replicated-packet-rate . . . . . . . . . . 10 5.2. Type-P-one-way-replicated-packet-rate .....................10
5.3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 11 5.3. Examples ..................................................11
6. Security Considerations . . . . . . . . . . . . . . . . . . . 12 6. Security Considerations ........................................12
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 7. IANA Considerations ............................................12
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 8. Acknowledgements ...............................................13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 9. References .....................................................13
9.1. Normative References . . . . . . . . . . . . . . . . . . . 13 9.1. Normative References ......................................13
9.2. Informative References . . . . . . . . . . . . . . . . . . 13 9.2. Informative References ....................................13
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction 1. Introduction
This document defines a metric for one-way packet duplication across This document defines a metric for one-way packet duplication across
Internet paths. It builds on the IPPM Framework document [RFC2330]; Internet paths. It builds on the IP Performance Metrics (IPPM)
the reader is assumed to be familiar with that document. Framework document [RFC2330]; the reader is assumed to be familiar
with that document.
This document follows the same structure as the document for one-way This document follows the same structure as the document for one-way
Packet Loss [RFC2680]; the reader is assumed to be familiar with that packet loss [RFC2680]; the reader is assumed to be familiar with that
document as well. document as well.
The structure of this memo is as follows: The structure of this memo is as follows:
o First, a singleton metric, called Type-P-one-way-packet-arrival- o First, a singleton metric, called Type-P-one-way-packet-arrival-
count, is introduced to measure the number of arriving packets for count, is introduced to measure the number of arriving packets for
each packet sent. each packet sent.
o Then, a singleton metric, called Type-P-one-way-packet- o Then, a singleton metric, called Type-P-one-way-packet-
duplication, is defined to describe a single instance of packet duplication, is defined to describe a single instance of packet
duplication. duplication.
o Next, this singleton metric is used to define samples, Type-P-one- o Next, this singleton metric is used to define samples, Type-P-one-
way-Packet-Duplication-Poisson-Stream and Type-P-one-way-Packet- way-Packet-Duplication-Poisson-Stream and Type-P-one-way-Packet-
Duplication-Periodic-Stream. These are introduced to measure Duplication-Periodic-Stream. These are introduced to measure
duplication in a series of packets sent with either Poisson- duplication in a series of packets sent with either Poisson-
distributed [RFC2680] or periodic [RFC3432] intervals between the distributed [RFC2680] or periodic [RFC3432] intervals between the
packets. packets.
o Finally, statistics that summarize the properties of these samples o Finally, statistics that summarize the properties of these samples
are introduced. are introduced.
1.1. Requirements notation 1.1. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
Although RFC 2119 was written with protocols in mind, the key words Although RFC 2119 was written with protocols in mind, the key words
are used in this document for similar reasons. They are used to are used in this document for similar reasons. They are used to
ensure the results of measurements from two different implementations ensure the results of measurements from two different implementations
are comparable, and to note instances when an implementation could are comparable and to note instances when an implementation could
perturb the network. perturb the network.
1.2. Motivation 1.2. Motivation
When a packet is sent from one host to the other, one normally When a packet is sent from one host to the other, one normally
expects that exactly one copy of the packet that was sent arrives at expects that exactly one copy of the packet that was sent arrives at
the destination. It is, however, possible that a packet is either the destination. It is, however, possible that a packet is either
lost or that multiple copies arrive. lost or that multiple copies arrive.
In earlier work a metric for packet loss has been defined [RFC2680]. In earlier work, a metric for packet loss was defined [RFC2680].
This metric distinguishes between cases where the packet arrives and This metric distinguishes between cases where the packet arrives and
where the packet does not arrive within a reasonable time. In this where the packet does not arrive within a reasonable time. In this
memo, a metric for a third outcome is defined: a single packet is memo, a metric for a third outcome is defined: a single packet is
sent but multiple copies arrive. sent, but multiple copies arrive.
As this document describes a case similar to the one discussed in As this document describes a case similar to the one discussed in
[RFC2680], all considerations from that document on timing and [RFC2680], all considerations from that document on timing and
accuracy apply. accuracy apply.
2. A Singleton Definition for one-way packet arrival count 2. A Singleton Definition for One-Way Packet Arrival Count
2.1. Metric Name 2.1. Metric Name
Type-P-one-way-packet-arrival-count Type-P-one-way-packet-arrival-count
2.2. Metrics Parameters 2.2. Metrics Parameters
o Src, the IP address of a host o src, the IP address of a host
o Dst, the IP address of a host
o dst, the IP address of a host
o T, the wire time of a packet at the source o T, the wire time of a packet at the source
o T0, the maximum waiting time for a packet to arrive at the o T0, the maximum waiting time for a packet to arrive at the
destination. destination.
2.3. Metric Units 2.3. Metric Units
An integer number An integer number.
2.4. Definition 2.4. Definition
Two packets are considered identical if and only if: Two packets are considered identical if and only if:
o Both contain identical information fields (see section 2.5). The o Both contain identical information fields (see Section 2.5). The
recipient thus could take either packet and use the data in an recipient thus could take either packet and use the data in an
application. The other packet does not contain any additional application. The other packet does not contain any additional
information. information.
o Both packets appear to have been sent by one and the same host, to o Both packets appear to have been sent by one and the same host, to
one and the same destination. Host are identified by their IP one and the same destination. Hosts are identified by their IP
addresses. addresses.
The value of a Type-P-one-way-packet-arrival-count is a positive The value of a Type-P-one-way-packet-arrival-count is a positive
integer number indicating the number of (uncorrupted and identical) integer number indicating the number of (uncorrupted and identical)
copies received by dst in the interval [T, T+T0] for a packet sent by copies received by dst in the interval [T, T+T0] for a packet sent by
src at time T. src at time T.
If a packet is sent, but it is lost or does not arrive in the If a packet is sent, but it is lost or does not arrive in the
interval [T, T+T0], then the metric is undefined. Applications MAY interval [T, T+T0], then the metric is undefined. Applications MAY
report an "impossible" value (for example, -1) to indicate this report an "impossible" value (for example, -1) to indicate this
condition instead of undefined. condition instead of undefined.
If a packet is fragmented during transport and if, for whatever If a packet is fragmented during transport and if, for whatever
reason, re-assembly does not occur, then the packet will be deemed reason, reassembly does not occur, then the packet will be deemed
lost. It is thus not included in the Type-P-one-way-packet-arrival- lost. It is thus not included in the Type-P-one-way-packet-arrival-
count. count.
2.5. Discussion 2.5. Discussion
This metric counts the number of packets arriving for each packet This metric counts the number of packets arriving for each packet
sent. The time-out value T0 SHOULD be set to a value when the sent. The time-out value T0 SHOULD be set to a value when the
application could potentially still use the packet and would not application could potentially still use the packet and would not
discard it automatically. discard it automatically.
If this metrics is used in parallel with the Packet Loss Metric If this metric is used in parallel with the Packet Loss Metric
[RFC2680], the value of T0 MUST be the same for both cases in order [RFC2680], the value of T0 MUST be the same for both cases in order
to keep the results comparable. to keep the results comparable.
The metric only counts packets that are not corrupted during The metric only counts packets that are not corrupted during
transmission and may have been resent automatically by lower layers transmission and may have been resent automatically by lower layers
or intermediate devices. Packets that were corrupted during or intermediate devices. Packets that were corrupted during
transmission but nevertheless still arrived at dst are not counted. transmission but, nevertheless, still arrived at dst are not counted.
Clocks do have to be synchronized between src and dst such that it is Clocks do have to be synchronized between src and dst such that it is
possible to uniquely and accurately determine the interval [T, T+T0] possible to uniquely and accurately determine the interval [T, T+T0]
at both sides. at both sides.
If this metric is used in an active measurement system, the system If this metric is used in an active measurement system, the system
MUST NOT send multiple packets with identical information fields, in MUST NOT send multiple packets with identical information fields in
order to avoid that all packets will be declared duplicates. This order to avoid that all packets will be declared duplicates. This
metric can be used inside a passive measurement system as well, using metric can be used inside a passive measurement system as well, using
packets generated by another source. However, if the source can send packets generated by another source. However, if the source can send
two identical packets within the interval [T, T+T0], this will be two identical packets within the interval [T, T+T0], this will be
incorrectly labelled as a duplicate, resulting in a false positive. incorrectly labeled as a duplicate, resulting in a false positive.
It is up to the implementor to estimate if this scenario is likely to It is up to the implementor to estimate if this scenario is likely to
happen and the rate of false positives is acceptable. happen and the rate of false positives that is acceptable.
The definition of identical information fields is such that two The definition of identical information fields is such that two
packets are considered to be identical if they are sent from the same packets are considered to be identical if they are sent from the same
source and contain the same information. This does not necessarily source and contain the same information. This does not necessarily
mean that all bits in the packet are the same. For example, when a mean that all bits in the packet are the same. For example, when a
packet is replicated and the copies are transferred along different packet is replicated and the copies are transferred along different
paths, the TTL may be different. The implementation MUST specify paths, the Time to Live (TTL) may be different. The implementation
which fields are compared when deciding if two packets are identical MUST specify which fields are compared when deciding whether or not
or not. two packets are identical.
In case of IPv4, these will usually be: version, ihl, identification, In the case of IPv4, these will usually be: version, ihl,
src, dst, protocol, some or all upper layer protocol data identification, src, dst, protocol, some or all upper-layer protocol
data.
In IPv6, these will usually be: version, next header, source, In IPv6, these will usually be: version, next header, source,
destination, some or all upper layer protocol data destination, some or all upper-layer protocol data
Note that the use of the identification field is not present in non- Note that the use of the identification field is not present in non-
fragmented IPv6 packets and may not be sufficient to distinguish fragmented IPv6 packets and may not be sufficient to distinguish
packets from each even in IPv4, particularly at higher transmission packets from each even in IPv4, particularly at higher transmission
speeds speeds
2.6. Methodology 2.6. Methodology
The basic technique to measure this metrics follows the methodology The basic technique to measure this metric follows the methodology
described in [RFC2680], section 2.6, with one exception. described in Section 2.6 of [RFC2680] with one exception.
[RFC2680] does not specify that the receiving host should be able to [RFC2680] does not specify that the receiving host should be able to
receive multiple copies of a single packet, as it only needs one copy receive multiple copies of a single packet, as it only needs one copy
to determine the metrics. Implementations for this metric should to determine the metrics. Implementations for this metric should
obviously be capable to receive multiple copies. obviously be capable of receiving multiple copies.
2.7. Errors and uncertainties 2.7. Errors and Uncertainties
Refer to section 2.7 of [RFC2680] Refer to Section 2.7 of [RFC2680].
2.8. Reporting the metric 2.8. Reporting the Metric
Refer to section 2.8 of [RFC2680] Refer to Section 2.8 of [RFC2680].
3. A Singleton Definition for one-way packet duplication 3. A Singleton Definition for One-Way Packet Duplication
3.1. Metric Name 3.1. Metric Name
Type-P-one-way-packet-duplication Type-P-one-way-packet-duplication
3.2. Metrics Parameters 3.2. Metrics Parameters
o Src, the IP address of a host o src, the IP address of a host
o Dst, the IP address of a host
o dst, the IP address of a host
o T, the wire time of a packet at the source o T, the wire time of a packet at the source
o T0, the maximum waiting time for a packet to arrive at the o T0, the maximum waiting time for a packet to arrive at the
destination. destination.
3.3. Metric Units 3.3. Metric Units
An integer number. An integer number.
3.4. Definition 3.4. Definition
The value of a Type-P-one-way-packet-duplication is a positive The value of a Type-P-one-way-packet-duplication is a positive
skipping to change at page 8, line 5 skipping to change at page 7, line 25
3.3. Metric Units 3.3. Metric Units
An integer number. An integer number.
3.4. Definition 3.4. Definition
The value of a Type-P-one-way-packet-duplication is a positive The value of a Type-P-one-way-packet-duplication is a positive
integer number indicating the number of (uncorrupted and identical) integer number indicating the number of (uncorrupted and identical)
additional copies of an individual packet received by dst in the additional copies of an individual packet received by dst in the
interval [T, T+T0] sent by src at time T. interval [T, T+T0] as sent by src at time T.
If a packet is sent and only one copy arrives in the interval [T, If a packet is sent and only one copy arrives in the interval [T,
T+T0], then the metric is 0. If no copy arrives in this interval, T+T0], then the metric is 0. If no copy arrives in this interval,
then the metric is undefined. Applications MAY report an then the metric is undefined. Applications MAY report an
"impossible" value (for example, -1) to indicate this condition. "impossible" value (for example, -1) to indicate this condition.
3.5. Discussion 3.5. Discussion
This metric is equal to This metric is equal to:
Type-P-one-way-packet-arrival-count - 1 Type-P-one-way-packet-arrival-count - 1
This metric is expected to be used for applications that need to know This metric is expected to be used for applications that need to know
duplication for an individual packet. All considerations regarding duplication for an individual packet. All considerations regarding
methodology, errors and reporting from the previous section apply. methodology, errors, and reporting from the previous section apply.
4. Definition for samples for one-way Packet Duplication 4. Definition for Samples for One-Way Packet Duplication
4.1. Poisson Streams 4.1. Poisson Streams
4.1.1. Metric Name 4.1.1. Metric Name
Type-P-one-way-Packet-Duplication-Poisson-Stream Type-P-one-way-Packet-Duplication-Poisson-Stream
4.1.2. Metric Parameters 4.1.2. Metric Parameters
o Src, the IP address of a host o src, the IP address of a host.
o Dst, the IP address of a host
o Ts, a time o dst, the IP address of a host.
o Ts, a time.
o Tf, a time. Ts and Tf specify the time interval when packets can o Tf, a time. Ts and Tf specify the time interval when packets can
be sent for this stream. be sent for this stream.
o T0, the maximum waiting time for a packet to arrive at the o T0, the maximum waiting time for a packet to arrive at the
destination. destination.
o lambda, a rate in reciprocal seconds
o lambda, a rate in reciprocal seconds.
4.1.3. Metric Units 4.1.3. Metric Units
A sequence of pairs; the elements of each pair are: A sequence of pairs; the elements of each pair are:
o T, a time o T, a time
o Type-P-one-way-packet-arrival-count for the packet sent at T. o Type-P-one-way-packet-arrival-count for the packet sent at T.
4.1.4. Definition 4.1.4. Definition
Given Ts, Tf and lambda, we compute a pseudo-random Poisson process Given Ts, Tf, and lambda, we compute a pseudo-random Poisson process
beginning at or before Ts, with average rate lambda and ending at or beginning at or before Ts, with average-rate lambda, and ending at or
after Tf. Those time values greater than or equal to Ts, and less after Tf. Those time values greater than or equal to Ts, and less
than or equal to Tf are then selected. At each of the times in this than or equal to Tf are then selected. At each of the times in this
process, we obtain the value of Type-P-one-way-packet-arrival-count. process, we obtain the value of Type-P-one-way-packet-arrival-count.
The value of the sample is the sequence made up of the resulting The value of the sample is the sequence made up of the resulting
{time, duplication} pairs. If there are no such pairs, the sequence {time, duplication} pairs. If there are no such pairs, the sequence
is of length zero and the sample is said to be empty. is of length zero, and the sample is said to be empty.
4.1.5. Methodology 4.1.5. Methodology
Refer to [RFC2680], section 3.6. Refer to Section 3.6 of [RFC2680].
4.1.6. Errors and uncertainties 4.1.6. Errors and Uncertainties
Refer to [RFC2680], section 3.7. Refer to Section 3.7 of [RFC2680].
4.1.7. Reporting the metric 4.1.7. Reporting the Metric
Refer to [RFC2680], section 3.8. Refer to Section 3.8 of [RFC2680].
4.2. Periodic Streams 4.2. Periodic Streams
4.2.1. Metric Name 4.2.1. Metric Name
Type-P-one-way-Packet-Duplication-Periodic-Stream Type-P-one-way-Packet-Duplication-Periodic-Stream
4.2.2. Metric Parameters 4.2.2. Metric Parameters
o Src, the IP address of a host o src, the IP address of a host.
o Dst, the IP address of a host
o Ts, a time o dst, the IP address of a host.
o Ts, a time.
o Tf, a time. Ts and Tf specify the time interval when packets can o Tf, a time. Ts and Tf specify the time interval when packets can
be sent for this stream. be sent for this stream.
o T0, the maximum waiting time for a packet to arrive at the o T0, the maximum waiting time for a packet to arrive at the
destination. destination.
o lambda, a rate in reciprocal seconds
o lambda, a rate in reciprocal seconds.
4.2.3. Metric Units 4.2.3. Metric Units
A sequence of pairs; the elements of each pair are: A sequence of pairs; the elements of each pair are:
o T, a time o T, a time
o Type-P-one-way-packet-arrival-count for the packet sent at T. o Type-P-one-way-packet-arrival-count for the packet sent at T.
4.2.4. Definition 4.2.4. Definition
At time Ts, we start sending packets with a constant rate lambda, At time Ts, we start sending packets with a constant-rate lambda,
until time Tf. For each packet sent, we obtain the value of Type-P- until time Tf. For each packet sent, we obtain the value of Type-P-
one-way-packet-arrival-count. The value of the sample is the one-way-packet-arrival-count. The value of the sample is the
sequence made up of the resulting {time, duplication} pairs. If sequence made up of the resulting {time, duplication} pairs. If
there are no such pairs, the sequence is of length zero and the there are no such pairs, the sequence is of length zero and the
sample is said to be empty. sample is said to be empty.
4.2.5. Methodology 4.2.5. Methodology
Refer to [RFC3432], section 4.5. Refer to Section 4.5 of [RFC3432].
4.2.6. Errors and uncertainties 4.2.6. Errors and uncertainties
Refer to [RFC3432], section 4.6. Refer to Section 4.6 of [RFC3432].
4.2.7. Reporting the metric 4.2.7. Reporting the metric
Refer to [RFC3432], section 4.7. Refer to Section 4.7 of [RFC3432].
5. Some statistics definitions for one-way Duplication 5. Some Statistics Definitions for One-Way Duplication
Note: the statistics described in this section can be used for both Note: the statistics described in this section can be used for both
Type-P-one-way-Packet-Duplication-Poisson-Stream and Type-P-one-way- Type-P-one-way-Packet-Duplication-Poisson-Stream and Type-P-one-way-
Packet-Duplication-Periodic-Stream. The application SHOULD report Packet-Duplication-Periodic-Stream. The application SHOULD report
which sample was used as input. which sample was used as input.
5.1. Type-P-one-way-packet-duplication-fraction 5.1. Type-P-one-way-packet-duplication-fraction
This statistic gives the fraction of additional packets that arrived This statistic gives the fraction of additional packets that arrived
in a stream. in a stream.
Given a Type-P-one-way-Packet-Duplication-Poisson-Stream, one first Given a Type-P-one-way-Packet-Duplication-Poisson-Stream, one first
removes all values of Type-P-one-way-Packet-Duplication which are removes all values of Type-P-one-way-Packet-Duplication that are
undefined. For the remaining pairs in the stream, one calculates: undefined. For the remaining pairs in the stream, one calculates:
(Sum Type-P-one-Way-packet-arrival-count/Number of pairs left) - 1 (Sum Type-P-one-way-packet-arrival-count/Number of pairs left) - 1
(In other words, (number of packets received)/(number of packets sent (In other words, (number of packets received)/(number of packets sent
and not lost).) and not lost).)
The number can be expressed as a percentage. The number can be expressed as a percentage.
Note: this statistic is the equivalent of the Y.1540 IPDR [Y1540] Note: this statistic is the equivalent to the Y.1540 IPDR [Y1540].
5.2. Type-P-one-way-replicated-packet-rate 5.2. Type-P-one-way-replicated-packet-rate
This statistic gives the fraction of packets that was duplicated (one This statistic gives the fraction of packets that was duplicated (one
or more times) in a stream. or more times) in a stream.
Given a Type-P-one-way-Packet-Duplication-Poisson-Stream, one first Given a Type-P-one-way-Packet-Duplication-Poisson-Stream, one first
removes all values of Type-P-one-way-packet-arrival-count which are removes all values of Type-P-one-way-packet-arrival-count that are
undefined. For the remaining pairs in the stream, one counts the undefined. For the remaining pairs in the stream, one counts the
number of pairs with Type-P-one-Way-packet-arrival-count greater than number of pairs with Type-P-one-way-packet-arrival-count greater than
1. Then one calculates the fraction of packets that meet this 1. Then, one calculates the fraction of packets that meet this
criterion as a fraction of the total. (In other words: (number of criterion as a fraction of the total. (In other words: (number of
duplicated packets)/(number of packets sent and not lost).). duplicated packets)/(number of packets sent and not lost).)
The number can be expressed as a percentage. The number can be expressed as a percentage.
Note: this statistic is the equivalent of the Y.1540 RIPR [Y1540] Note: this statistic is the equivalent of the Y.1540 RIPR [Y1540].
5.3. Examples 5.3. Examples
Consider a stream of 4 packets, sent as: Consider a stream of 4 packets, sent as:
(1, 2, 3, 4) (1, 2, 3, 4)
and arriving as: and arriving as:
o Case 1: (1, 2, 3, 4) o Case 1: (1, 2, 3, 4)
o Case 2: (1, 1, 2, 2, 3, 3, 4, 4) o Case 2: (1, 1, 2, 2, 3, 3, 4, 4)
o Case 3: (1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4) o Case 3: (1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4)
o Case 4: (1, 1, 1, 2, 3, 3, 3, 4) o Case 4: (1, 1, 1, 2, 3, 3, 3, 4)
Case 1: No packets are duplicated in a stream and both the Type-P- Case 1: No packets are duplicated in a stream, and both the Type-P-
one-way-packet-duplication-fraction and the type-P-one-way-packet- one-way-packet-duplication-fraction and the Type-P-one-way-packet-
replicated-packet-rate are 0. replicated-packet-rate are 0.
Case 2: Every packet is duplicated once and the Type-P-one-way- Case 2: Every packet is duplicated once, and the Type-P-one-way-
packet-duplication-fraction is 100%. The type-P-one-way-replicated- packet-duplication-fraction is 100%. The Type-P-one-way-replicated-
packet-rate is 100% too. packet-rate is 100%, too.
Case 3: Every packet is duplicated twice, so the Type-P-one-way- Case 3: Every packet is duplicated twice, so the Type-P-one-way-
packet-duplication-fraction is 200%. The type-P-one-way-replicated- packet-duplication-fraction is 200%. The Type-P-one-way-replicated-
packet-rate is still 100%. packet-rate is still 100%.
Case 4: Half the packets are duplicated twice and the other half are Case 4: Half the packets are duplicated twice and the other half are
not duplicated. The Type-P-one-way-packet-duplication-fraction is not duplicated. The Type-P-one-way-packet-duplication-fraction is
again 100% and this number does not show the difference with case 2. again 100%, and this number does not show the difference with case 2.
However, the type-P-one-way-packet-replicated-packet-rate is 50% in However, the Type-P-one-way-packet-replicated-packet-rate is 50% in
this case and 100% in case 2. this case and 100% in case 2.
However, the type-P-one-way-packet-duplication-rate will not show the However, the Type-P-one-way-packet-duplication-rate will not show the
difference between case 2 and 3. For this, one has to look at the difference between cases 2 and 3. For this, one has to look at the
Type-P-one-way-packet-duplication-fraction. Type-P-one-way-packet-duplication-fraction.
Finally, note that the order in which the packets arrived, do not Finally, note that the order in which the packets arrived does not
affect the results. For example, these variations of case 2: affect the results. For example, these variations of case 2:
o Case 2a: (1, 1, 2, 2, 3, 3, 4, 4) o Case 2a: (1, 1, 2, 2, 3, 3, 4, 4)
o Case 2b: (1, 2, 3, 4, 1, 2, 3, 4) o Case 2b: (1, 2, 3, 4, 1, 2, 3, 4)
o Case 2c: (1, 2, 3, 4, 4, 3, 2, 1) o Case 2c: (1, 2, 3, 4, 4, 3, 2, 1)
(as well as any other permutation) all yield the same results for (as well as any other permutation) all yield the same results for
Type-P-one-way-packet-duplication-fraction and the type-P-one-way- Type-P-one-way-packet-duplication-fraction and the Type-P-one-way-
replicated-packet-rate. replicated-packet-rate.
6. Security Considerations 6. Security Considerations
Conducting Internet measurements raises both security and privacy Conducting Internet measurements raises both security and privacy
concerns. This memo does not specify an implementation of the concerns. This memo does not specify an implementation of the
metrics, so it does not directly affect the security of the Internet metrics, so it does not directly affect the security of the Internet
nor of applications which run on the Internet. However, nor of applications that run on the Internet. However,
implementations of these metrics must be mindful of security and implementations of these metrics must be mindful of security and
privacy concerns. privacy concerns.
There are two types of security concerns: potential harm caused by There are two types of security concerns: potential harm caused by
the measurements, and potential harm to the measurements. The the measurements and potential harm to the measurements. The
measurements could cause harm because they are active, and inject measurements could cause harm because they are active, and they
packets into the network. The measurement parameters MUST be inject packets into the network. The measurement parameters MUST be
carefully selected so that the measurements inject trivial amounts of carefully selected so that the measurements inject trivial amounts of
additional traffic into the networks they measure. If they inject additional traffic into the networks they measure. If they inject
"too much" traffic, they can skew the results of the measurement, and "too much" traffic, they can skew the results of the measurement, and
in extreme cases cause congestion and denial of service. in extreme cases, cause congestion and denial of service.
The measurements themselves could be harmed by routers giving The measurements themselves could be harmed by routers giving
measurement traffic a different priority than "normal" traffic, or by measurement traffic a different priority than "normal" traffic or by
an attacker injecting artificial measurement traffic. If routers can an attacker injecting artificial measurement traffic. If routers can
recognize measurement traffic and treat it separately, the recognize measurement traffic and treat it separately, the
measurements will not reflect actual user traffic. If an attacker measurements will not reflect actual user traffic. If an attacker
injects artificial traffic that is accepted as legitimate, the loss injects artificial traffic that is accepted as legitimate, the loss
rate will be artificially lowered. Therefore, the measurement rate will be artificially lowered. Therefore, the measurement
methodologies SHOULD include appropriate techniques to reduce the methodologies SHOULD include appropriate techniques to reduce the
probability measurement traffic can be distinguished from "normal" probability that measurement traffic can be distinguished from
traffic. Authentication techniques, such as digital signatures, may "normal" traffic. Authentication techniques, such as digital
be used where appropriate to guard against injected traffic attacks. signatures, may be used where appropriate to guard against injected
traffic attacks.
The privacy concerns of network measurement are limited by the active The privacy concerns of network measurement are limited by the active
measurements described in this memo. Unlike passive measurements, measurements described in this memo. Unlike passive measurements,
there can be no release of existing user data. there can be no release of existing user data.
7. IANA Considerations 7. IANA Considerations
IANA is asked to add this metrics to the IANA IP Performance Metrics IANA has registered the metrics defined in this document in the IP
(IPPM) Metrics Registry, see [RFC4148]. This section can be removed Performance Metrics (IPPM) Metrics Registry, see [RFC4148].
after this has been done and upon publication as a RFC.
8. Acknowledgements 8. Acknowledgements
The idea to write this draft came up in a meeting with Al Morton, The idea to write this document came up in a meeting with Al Morton,
Stanislav Shalunov, Emile Stephan and the author, on the IPPM Stanislav Shalunov, Emile Stephan, and the author on the IPPM
reporting draft. reporting document.
This document relies heavily on [RFC2680] and the author likes to This document relies heavily on [RFC2680], and the author would like
thank the authors of that document for writing it. to thank the authors of that document for writing it.
Finally, thanks are due to Lars Eggert, Al Morton, Martin Swany and Finally, thanks are due to Lars Eggert, Al Morton, Martin Swany, and
Matt Zekauskas for their comments. Matt Zekauskas for their comments.
9. References 9. References
9.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2680] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way [RFC2680] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
skipping to change at page 13, line 41 skipping to change at page 13, line 41
9.2. Informative References 9.2. Informative References
[RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis, [RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
"Framework for IP Performance Metrics", RFC 2330, "Framework for IP Performance Metrics", RFC 2330,
May 1998. May 1998.
[RFC4148] Stephan, E., "IP Performance Metrics (IPPM) Metrics [RFC4148] Stephan, E., "IP Performance Metrics (IPPM) Metrics
Registry", BCP 108, RFC 4148, August 2005. Registry", BCP 108, RFC 4148, August 2005.
[Y1540] "Y.1540 ITU-T Recommendation Y.1540 (2007), Internet [Y1540] "Y.1540 ITU-T Recommendation Y.1540 (2007), Internet
protocol data communication service IP packet transfer protocol data communication service IP packet transfer and
and availability performance parameters.", 2007. availability performance parameters.", 2007.
Author's Address Author's Address
Henk Uijterwaal Henk Uijterwaal
RIPE NCC RIPE NCC
Singel 258 Singel 258
1016 AB Amsterdam 1016 AB Amsterdam
The Netherlands The Netherlands
Phone: +31 20 535 4444 Phone: +31 20 535 4444
Email: henk@ripe.net EMail: henk@ripe.net
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