Network Working Group H. Uijterwaal
Internet-Draft RIPE NCC
Expires: July 7, 2006 January 3, 2006
Overview of Implementation reports relating to IETF work on IP
Performance Measurements (IPPM, RFC 2678 - 2681)
draft-ietf-ippm-implement-02.txt
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Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This document contains a summary of the implementation reports
submitted for RFC's 2678 to 2681 during the second half of 2004.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Requirements notation . . . . . . . . . . . . . . . . . . . . 4
3. General Information . . . . . . . . . . . . . . . . . . . . . 5
3.1. BrixWorx . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1.1. General . . . . . . . . . . . . . . . . . . . . . . . 5
3.1.2. Other, related RFC's implemented . . . . . . . . . . . 6
3.2. NetWarrior . . . . . . . . . . . . . . . . . . . . . . . . 6
3.3. Surveyor . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.4. Test Traffic Measurements . . . . . . . . . . . . . . . . 7
3.4.1. General . . . . . . . . . . . . . . . . . . . . . . . 7
3.4.2. Other, related RFC's implemented . . . . . . . . . . . 8
3.5. WIPM . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.5.1. General . . . . . . . . . . . . . . . . . . . . . . . 8
3.5.2. Other, related RFC's implemented . . . . . . . . . . . 9
3.5.3. Common features . . . . . . . . . . . . . . . . . . . 9
4. RFC2678 metrics . . . . . . . . . . . . . . . . . . . . . . . 10
4.1. BrixWorx . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.2. NetWarrior . . . . . . . . . . . . . . . . . . . . . . . . 10
4.3. Surveyor . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.4. TTM . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.5. WIPM . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . 11
5. RFC2679 metrics . . . . . . . . . . . . . . . . . . . . . . . 12
5.1. BrixWorx . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.2. NetWarrior . . . . . . . . . . . . . . . . . . . . . . . . 12
5.3. Surveyor . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.4. TTM . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.5. WIPM . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.6. Delay of lost packets . . . . . . . . . . . . . . . . . . 16
5.7. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . 17
6. RFC2680 metrics . . . . . . . . . . . . . . . . . . . . . . . 17
6.1. BrixWorx . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.2. NetWarrior . . . . . . . . . . . . . . . . . . . . . . . . 17
6.3. Surveyor . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.4. TTM . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.5. WIPM . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . 20
7. RFC2681 metrics . . . . . . . . . . . . . . . . . . . . . . . 20
7.1. BrixWorx . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.2. NetWarrior . . . . . . . . . . . . . . . . . . . . . . . . 20
7.3. Surveyor . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.4. TTM . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.5. WIPM . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . 21
8. Security Considerations . . . . . . . . . . . . . . . . . . . 21
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
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10. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 21
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 23
Intellectual Property and Copyright Statements . . . . . . . . . . 24
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1. Introduction
Over the last years, the IPPM Working Group has developed metrics for
various quantities that can be measured on the Internet: Connectivity
[RFC2678], One way delay [RFC2679], One way packet loss [RFC2680] and
round trip delay [RFC2681]. These metrics are all based on the IPPM
Metrics framework [RFC2330]. All metrics have the state of proposed
standard. It is, however, the goal of the working group to move
these documents to Internet draft standards. In order to accomplish
these, one must have (at least) 2 interoperable implementations of
these RFC's.
During 2004, the chairs of the IPPM WG asked the participants to
report any implementations of these metrics. Five reports were
submitted. This document contains a summary of these reports.
It should be noted that interoperability for metrics is not a well
defined term. All implementations send packets to determine the
metrics and each packet will be treated differently by the network
elements in its path. Thus, two subsequent measurements of the same
metric by two implementations will not yield the same result,
However, a large number of measurements of the same quantity with two
implementations should produce samples that are statistically similar
to each other.
Even though the topic has been discussed in the past, there is
currently no accepted Internet standard to determine when two sets of
measurements are statistically different from each other or not. We
therefor only show what has been implemented but do not (in general)
present results to show that two implementations measuring along the
same path will yield the same result. Some studies have been done
though and these are mentioned where appropriate.
The outline of this document is as follows: Section 3 discusses
general details of the 5 implementations. It also lists features
that are common to all metrics implemented by a specific
implementation. Section 4 through Section 7 then discuss the
implementation of a particular RFC.
2. Requirements notation
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 [RFC2119].
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3. General Information
This section contains general information on the implementations as
well as information that applies to all metrics implemented by an
organization.
All information is taken from contributions by the person listed in
the contact details below. No attempt has been made to verify its
accuracy. The implementations are listed in alphabetical order.
3.1. BrixWorx
3.1.1. General
+--------------------+----------------------------------------------+
| Parameter | Value |
+--------------------+----------------------------------------------+
| Name of | BrixWorx Performance Management System |
| Implementation | |
| | BrixMon Performance Monitoring System |
| Mnemonic | BrixWorx |
| Organization | Brix Networks, Inc. |
| Contact details | 285 Mill Road, Chelmsford MA 01824, USA |
| | URL: http://www.brixnet.com |
| Report submitted | Kaynam Hedayat |
| by: | |
| Origin of code | Written from scratch |
| Platform | Brix Verifier, Brix Verifier agent for Linux |
| | or Windows |
+--------------------+----------------------------------------------+
The Brix system is a highly scalable and distributed system comprised
of hardware and software probes (Brix Verifiers) managed by a central
management system (BrixWorx). The Brix Verifiers are responsible for
performing tests and collection of performance metrics. BrixWorx is
responsible for provisioning and management of Brix Verifiers, data
storage, data sampling, user applications, and interfacing with third
party systems.
Brix Verifiers are available as hardware appliances or software
agents for Linux and Windows. The Brix Verifiers provide wire-time
hardware timestamping with microsecond accuracy that excludes any
host specific uncertainties. Time synchronization is available with
NTP, CDMA, or GPS for one-way measurements in both direciton during a
single test run. The testing can be performed between Verifiers or
between Verifiers and other network components.
Sun Solaris or Windows based BrixWorx central management servers
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provides a single point of management for all Verifiers in the
network. All measurements are collected by BrixWorx and stored in a
central database. The data is used for various applications
including SLA, reporting, and root cause analysis.
The platform offers flexible testing with multiple configuration
parameters including:
o Src, the IP address of a host
o Dst, the IP address of a host
o TOS/DSCP
o VLAN tag
o TTL
o Payload length
o Random scheduling of tests
o ICMP, UDP, TCP packet types
o Periodic and random sampling of tests
3.1.2. Other, related RFC's implemented
Brix has also implemented the RFC's on One-Way Loss Patterns
[RFC3357] and IP Delay Variations [RFC3393].
3.2. NetWarrior
+-----------------+-------------------------------------------------+
| Parameter | Value |
+-----------------+-------------------------------------------------+
| Name of | Netwarrior |
| Implementation | |
| Organization | QosMetrics, SA. |
| Contact details | Joe Ovanesian VP Engineering, 802 Calle Plano, |
| | Camarillo, CA 93012, USA |
| | Email: joe_ovanesian@qosmetrics.com |
| | URL: http://www.qosmetrics.com |
| Report | Yves Cognet, yves@qosmetrics.com, August 25, |
| submitted by: | 2004. |
| Origin of code | Written from scratch |
| Platform | Linux 2.4.22. |
+-----------------+-------------------------------------------------+
Hardware timestamping engine TSE (tx and rx) with built in GPS and
TXC0. This platform is running IPv4 and IPv6, PPPoE with both
static, dynamic and NAT'ed addresses. All tests have been done in
both the IPv4 and IPv6 environment (except for PPPoE).
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3.3. Surveyor
+---------------------+---------------------------------------------+
| Parameter | Value |
+---------------------+---------------------------------------------+
| Name of | Surveyor |
| Implementation | |
| Organization | Advanced Network & Services, Inc. |
| Contact details | 200 Business Park DR, Armonk, NY 10504, USA |
| (original) | |
| Contact details | Wisconsin Advanced Internet Lab |
| (current) | |
| | Email: pb@cs.wisc.edu |
| Report submitted | Matthew Zekauskas, August 1, 2004, |
| by: | matt@internet2.edu |
| Origin of code | Written from scratch |
| Platform | BSDI/OS 3.2+, TrueTime GPS-PC card, with |
| | custom device driver |
+---------------------+---------------------------------------------+
Advanced is essentially defunct as of this writing (30-Jul-2004); The
Surveyor code and data from 1997-2002 were donated to the Wisconsin
Advanced Internet Lab. For details on the implementation see the
INET'99 paper [inet99].
This platform is IPv4-only; while the code should be IP-address
independent, this was never verified, and would likely require some
tweaking.
3.4. Test Traffic Measurements
3.4.1. General
+----------------------+--------------------------------------------+
| Parameter | Value |
+----------------------+--------------------------------------------+
| Name of | RIPE NCC Test Traffic Measurements |
| Implementation | |
| Mnemonic | TTM |
| Organization | RIPE NCC |
| Contact details | P.O.Box 10096, 1001 EB Amsterdam, the |
| | Netherlands |
| | Email: ttm@ripe.net |
| | URL: http://www.ripe.net/ttm |
| | Phone: +31.20.5354444 |
| Report submitted by: | Henk Uijterwaal, henk@ripe.net, July 27, |
| | 2004 |
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| Origin of code | Written from scratch, uses NTP [RFC1305] |
| | and BPF. |
| Platform | FreeBSD (version 2.2.8, 4.5 and higher) |
+----------------------+--------------------------------------------+
3.4.2. Other, related RFC's implemented
RIPE NCC has also implemented the RFC on IP Delay Variations
[RFC3393].
3.5. WIPM
3.5.1. General
+----------------+--------------------------------------------------+
| Parameter | Value |
+----------------+--------------------------------------------------+
| Name of | World-wide IP Performance Measurement System |
| Implementation | |
| Mnemonic | WIPM |
| Organization | AT&T Labs |
| Contact | Len Ciavattone (lencia@att.com), Ron Kulper |
| details | (rkulper@att.com), Al Morton (acmorton@att.com) |
| | and Gomathi Ramachandran (gomathi@att.com). |
| Report | Al Morton, December 13, 2004. |
| submitted by: | |
| Origin of code | Written from scratch |
| Platform | Production platform is Sun Nextra T4 (2x |
| | UltraSPARC III+), 150 MHz, 2GB memory, Solaris 6 |
| | and 8. |
| | Measurement components also run on Intel with |
| | Red Hat 8+, Fedora Core 1 & 2, Knoppix 3.3. |
+----------------+--------------------------------------------------+
Measurement paths are determined by performing a traceroute at the
start time of each measurement stream. The return path is also
determined from traceroute from destination to source.
Measurement servers are located in major network nodes. Results are
combined at a single server dedicated to collection, data-feeds,
reporting, display, and alarm generation. All servers use two
stratum 1 NTP servers in AT&T's network for time-of-day
synchronization at the time of this writing. A subset of the results
are published continuously at http://www.att.com/ipnetwork.
WIPM measures the characteristics of both the Src-Dst and Dst-Src
paths in the same test interval by implementing a responder function
at the Destination. Today, there is very limited reporting of 1-way
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measurements due to time-of-day accuracy limitations, making round-
trip delay and loss measurements the most reliable from an accuracy
perspective.
WIPM results are stored in Daytona database format, in addition to
test-specific files with summary and per-packet (singleton) results.
For further details on the WIPM deployment and measurements see
[cia03].
3.5.2. Other, related RFC's implemented
AT&T Labs has also implemented the RFC on Network measurements with
periodic streams [RFC3432], portions of the RFC on IP Loss Patterns
[RFC3357] and portions of the RFC on IP Packet Delay Variation
[RFC3393].
3.5.3. Common features
For all metrics in WIMP, the following parameters are implemented:
o Src, the IP address of a host
o Dst, the IP address of a host
o T, a time (singleton)
o dT, or Th, a time threshold (for declaring loss)
o T0, a time (stream start)
o Tf, a time (stream finish)
o lambda, a rate in reciprocal seconds
The following parameters implemented for RFC 3432 [RFC3432] periodic
sampling are:
o T, the beginning of a time interval where a periodic sample is
desired.
o dT, the duration of the interval for allowed sample start times.
o T0, a time that MUST be selected at random from the interval [T,
T+dT] to start generating packets and taking measurements.
o Tf, a time, greater than T0, for stopping generation of packets
for a sample (Tf may be relative to T0 if desired).
o incT, the nominal duration of inter-packet interval, first bit to
first bit.
Type P capabilities: UDP packets are used. Source Port numbers are
variable. Payload length is variable. TOS field or Diffserv Code
Points can be set.
Reporting: The parameters above and the measurement path (traceroute)
are reported.
Resolution: The time stamp resolution currently in use is 1 ms.
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Duplicate Packets: Ignored, first to arrive is used.
Corrupted/Errored Packets: Treated as lost. They will fail either a
hardware, IP or UDP checksum verification, and do not reach the
measurement app.
Fragmented Packets: Included only if all fragments arrive.
Payload Padding bits: A bit pattern is used instead of random bits.
Errors and Uncertainties (pertaining to clock accuracy): The NTP
loopstats and peerstats are logged.
Tests done on the implementation:
o Verification of results with passive methods: comparison with
Packet Sniffer.
o Error estimation, clock source: Resolution dominates the error.
4. RFC2678 metrics
4.1. BrixWorx
The following metrics have been implemented:
o Type-P-Instantaneous-Unidirectional-Connectivity
o Type-P-Instantaneous-Bidirectional-Connectivity
o Type-P-Interval-Unidirectional-Connectivity
o Type-P-Interval-Bidirectional-Connectivity
The following metrics has not been implemented due to a lack of
market demand:
o Type-P-Interval-Temporal-Connectivity
4.2. NetWarrior
Implemented is: Type-P-Instantaneous-Bidirectional-Connectivity.
Parameters recorded:
o Src, the IP address of a host
o Dst, the IP address of a host
o T, a time
o TTL
o payload length
o TOS/DSCP
o VLAN
o Units: dT
Methodology: + According to section 3.1 of RFC 2678, time
synchronization is done by the TSE card, timestamping is done in
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hardware on the TSE card.
Comments: TCP packets are being used over ipv4 and ipv6. The TCP
checksum is over written when the frame is sent and when the TSE is
appending the time stamp. The port numbers for test traffic can be
specified. User data length is user defined. Access to special IP
bits (TOS/DSCP values) is available. If a packet is duplicated, any
duplicates are counted (the delay of the first packet to arrives is
used). Corrupted packets are counted as lost; they will fail either
a hardware CRC check, or IP or UDP checksum verification.
Features included: path variation (TTL variation) is being recorded.
Reporting the metric: all results are recorded in an SQL database,
good and bad records (lost of synchronization), all timestamps are
rpeorted in UTC. No aggregation is done by default, but this can be
done locally.
4.3. Surveyor
Has not implemented this RFC.
4.4. TTM
Has not implemented this RFC due to a lack of demand from its
customers. TTM does measure packet loss and assumes that when packet
loss is 100%, there is no connectivity.
4.5. WIPM
Implemented is: Type-P-Instantaneous-Bidirectional-Connectivity.
At the outset of all WIPM tests, there is a packet exchange between
the source and destination hosts (1 packet in each direction). If
this exchange is successful, the test will continue. These packets
assess Bidirectional Connectivity for A1-A2 at time T, and A2-A1 at
time T+dT, and are not included in the sample for any other metrics.
The commencement of the test stream is proof of this connectivity
(and the availability of test resources, which is seldom at issue).
The remaining metrics in this RFC have not been implemented. Other
metrics were deemed more useful.
4.6. Conclusion
Only the Type-P-Instantaneous-Bidirectional-Connectivity metric has
been implemented by 2 vendors.
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5. RFC2679 metrics
5.1. BrixWorx
o Type-P-One-way-Delay: implemented.
o Type-P-One-Way-Delay-Poisson-Stream: implemented.
o Type-P-One-Way-Delay-Percentile: Implemented, configurable.
o Type-P-One-Way-Delay-Median: implemented.
o Type-P-One-Way-Delay-Minimum: implemented.
o Type-P-One-Way-Delay-Inverse-Percentile: Not implemented due to
lack of interest from customers.
Hardware timestamp provides wire-time. CDMA, GPS or NTP is used for
time synchronization.
5.2. NetWarrior
o Implemented: Type-P-One-way-Delay.
* Parameters:
+ Src, the IP address of a host
+ Dst, the IP address of a host
+ T, a time
+ Payload
+ VLAN ID
+ Units: dt
* Methodology: According to section 3.6 of RFC 2679,
Synchronization via TSE card, Timestamping in hardware via TSE
card
* Comments: UDP and TCP packets are being used over ipv4 and
ipv6. TCP checksum is over written when the frame is sent and
when the TSE is appending the time stamp. The port numbers for
test traffic can be specified among sessions, although for any
given session port numbers were fixed. User data length was 12
bytes (32 bit sequence number, 64 bit time value). Access to
special IP bits ( TOS/DSCP values ) is available. If a packet
is duplicated, any duplicates are counted (the delay of the
first packet to arrives is used). Corrupted packets are
counted as lost; they will fail either a hardware CRC check, or
IP or UDP checksum verification.
* Features included: If either end lost synchronization (as
reported by the TSE timing card) the session is kept but
results are marked invalid. Path variation (TTL variation) is
recorded.
* Reporting the metric: All results are recorded in an SQL
database, good and bad records (lost of synchronization). The
loss threshold is 1 received packets for UPD traffic. All
timestamps are reported in UTC Local aggregation can be done.
TTL variation are being recorded.
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* Tests performed: calibration, measured time uncertainty is in
the 450 ns range end to end once TSE cards are in sync.
o Type-P-One-way-Delay-Percentile: By default, the 50th percentile
(median) and 90th percentile are calculated and reported for x
minute intervals (user setup).
o Type-P-One-way-Delay-Median: This value can be calculated and
reported from the database.
o Type-P-One-way-Delay-Minimum: This value is reported for x minute
intervals (user setup).
o Type-P-One-way-Delay-Poisson-Stream: Not implemented.
o RFC2679/Type-P-One-way-Delay-Inverse-Percentile.
5.3. Surveyor
o Type-P-One-way-Delay
* Parameters:
+ Src, the IP address of a host.
+ Dst, the IP address of a host.
+ T, a time.
+ Units: dt.
* Methodology: According to section 3.6 of RFC 2679.
Synchronization via GPS time cards. Timestamping in software
(and not in the network driver, although we did have an
experimental version that did this).
* Comments (Type-P): UDP packets are being used. The port
numbers for test traffic varied (and could not be specified)
among sessions, although for any given session port numbers
were fixed. User data length was 12 bytes (32 bit sequence
number, 64 bit time value). In general, no special IP bits are
set, but there was a version of the code which allowed the user
to set the TOS/DSCP values. If a packet is duplicated, any
duplicates are ignored (the delay of the first packet to
arrives is used). Corrupted packets are generally counted as
lost; they will fail either a hardware CRC check, or IP or UDP
checksum verification.
* Features included: If either end lost synchronization with GPS
(as reported by the timing card) the session was broken and
measurement ceased.
* Reporting the metric: Because measurements ceased when GPS
synchronization was lost, and the errors (typically 50 to 100
microseconds with our densest measurement mesh) were much
smaller than instrumented paths, negative values were not
reported, but flagged as a possible software error. The loss
threshold was 400 received packets in our implementation. For
typical paths where two packets per second (on average) were
sent, the loss threshold was about 200 seconds, or 3 1/3
minutes. In our implementation the distinguished value
10,000,000 was used to signify infinite delay (a loss). (10
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seconds -- although in practice I do not believe we saw
anything greater than ~3 sec.) All systematic errors are
removed from the timestamps before reporting the metrics.
Paths are being determined by running the well-known traceroute
tool approximately 6 times an hour (on a Poisson schedule with
average 10 seconds, but also clamped to 10 seconds maximum).
Paths were stored independent of delays, but displayed along
with delays in our graphical displays.
* Tests performed: Back-to-back tests of typical machines in the
field was performed for calibration. For our worst-case fan-
out (due to the software implementation, error became worse the
more paths that were measured), 80 paths, the calibration error
was 100 microseconds. Cross check of measurements against the
RIPE-TTM implementation (reported at the 44th IETF IPPM WG
meeting by Henk Uijterwaal).
o Type-P-One-way-Delay-Poisson-Stream
* Parameters:
+ Src, the IP address of a host.
+ Dst, the IP address of a host.
+ T0, a time.
+ Tf, a time.
+ lambda, a rate in reciprocal seconds. (packets per second).
* Units:
+ T, a time.
+ dT, either a real number or an undefined number of seconds.
* Report consists of series of measurements for Type-P-One-Way-
Delay. All the Type-P-One-Way-Delay features and comments
above apply here.
* Features: The receiver knew the send schedule (passed as a seed
to the random number generated used for the Poisson schedule)
so it could independently determine if packets were lost. As
with the singleton metrics, the loss threshold was 400 received
packets in our implementation. For typical paths where two
packets per second (on average) were sent, the loss threshold
was about 200 seconds, or 3 1/3 minutes. This 400 packet
window was also used to correct for reordering. All delay
values were kept to allow computation of arbitrary percentiles
on demand.
o Type-P-One-way-Delay-Percentile: By default, the 50th percentile
(median) and 90th percentile are calculated and reported for one
minute intervals. A separate Java-based UI could ask for
arbitrary percentiles over arbitrary intervals (provided the raw
data was on-line) -- typically 6 months of raw data were on-line.
o Type-P-One-way-Delay-Median: This value is calculated and reported
for one minute intervals, although we did have a separate Java-
based UI that could vary the reporting period.
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o Type-P-One-way-Delay-Minimum: This value is calculated and
reported for one minute intervals, although we did have a separate
Java-based UI that could vary the reporting period.
o Type-P-One-way-Delay-Inverse-Percentile: Not implemented. Our
implementation did not calculate any inverse percentiles. One
could ask for the raw data and calculate the inverse percentile
yourself. Our implementation did, however, provide a histogram of
delay values, by default ranging from 0 to 300mS in 10mS buckets.
5.4. TTM
o Type-P-One-way-Delay
* Parameters:
+ Src, the IP address of a host.
+ Dst, the IP address of a host.
+ T, a time.
* Units: dT.
* Methodology: According to section 3.6 of RFC 2679.
* Comments: UDP packets are being used. No special IP bits are
set.
* Features included: A bit to record if the src thinks its clock
is synchronized or not (based on NTP). Measurements with
unsynchronized clocks are not used in higher level statistics.
A bit to record if the dst thinks its clock is synchronized or
not. Experimental error estimate for src clock. Experimental
error estimate for dst clock. Experimental error estimate for
the measurement. Ports used at source and destination.
* Features not implemented: No special IP bits can be set.
* Reporting the metric: Negative delay values are reported.
Small negative values can occur when the experimental errors on
the clocks are large and the delays are small. Maximum delay
is 255 seconds, packets with higher delays are considered lost.
Packet size is being reported. All systematic errors are
removed from the timestamps before reporting the metrics.
Paths are being determined by running the well-known traceroute
tool approximately 10 times an hour, with the most recent path
reported.
* Tests performed: Cross check of measurements against the
surveyor implementation (Reported at the IETF44, IPPM WG
meeting). Cross check of measurements with passive
measurements (Reported at PAM2001).
o Type-P-One-way-Delay-Poisson-Stream
* Parameters:
+ Src, the IP address of a host.
+ Dst, the IP address of a host.
+ T0, a time.
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+ Tf, a time.
+ lambda, a rate in reciprocal seconds, reported as packets
per minute.
* Units:
+ T, a time.
+ dT, either a real number or an undefined number of seconds.
* Report consists of series of measurements for Type-P-One-Way-
Delay.
o Type-P-One-way-Delay-Median: This value is being calculated and
reported, for 15 minutes (or longer) intervals. 15 minutes came
from user feedback.
o Type-P-One-way-Delay-Minimum: Not implemented. We do, however,
report the 2.5% and 97.5% of the distribution for 15 minutes (or
longer) intervals. All individual measurements are available to
calculate arbitrary percentiles on request.
5.5. WIPM
o Type-P-One-way-Delay (singleton). Metric Units: dT and T are
recorded. The delay of lost packets is undefined, so our
implementation of this metric is more accurately described as
Type-P-Finite-One-way-Delay. Methodology is as described in
Section 3.6.
o Type-P-One-way-Delay-Poisson-Stream. Metric Units: dT and T are
recorded. Methodology is as described in section 4.6, including
the correct handling of out-of-order packets.
o Type-P-One-way-Delay-Periodic-Stream: implemented, see previous
item.
o Type-P-(Finite-)One-way-Delay-Percentile: Computation and report
of 0.1, 1.0, 50, 95, 99, and 99.9 percentiles.
o Type-P-(Finite-)One-way-Delay-Median: implemented.
o Type-P-(Finite-)One-way-Delay-Minimum: Computation and report of
minimum delay (dT) of the sample.
o Type-P-(Finite-)One-way-Delay-Inverse-Percentile: The fraction of
finite dT values greater than a threshold are reported.
Also reported in summary file: Mean, Standard Deviation, and Sum.
Metrics and features not implemented, and why not: We do not treat
lost packets as having infinite delay, as it would prevent the
calculation of Means. This approach is consistent with ITU-T Rec.
Y.1540.
5.6. Delay of lost packets
The RFC specifies that packets that are lost during transmission, are
assigned a value for the delay of "infinite", and should be included
when calculating statistics over a sample of packets (such as, for
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example, the median delay).
This approach suffers from two problems: First, infinite is not a
number and thus prevents one from calculating the average delay or
any other parameter involving the values of sample of packets.
Infinite is also not a number that can be assigned to a variable in
most programming languages. Second, including lost packets when
reporting the metric, essentially results in report of a metric that
combines two parameters (loss and delay), while the user is usually
interested in values for the individual metrics.
To circumvent this problem, all implementations assign a special but
numeric value to the delay of lost packets. (For example, -1.0
seconds). Lost packets are excluded when calculating statistics over
the sample of packets.
5.7. Conclusion
The basic metric (Type-P-One-way-Delay) has been implemented by all
implementations. The statistics that are reported vary from
implementation to implementation and depend on the feedback from the
users of a particular product. However, as the raw data is
available, one can always calculate the missing parameters after the
measurement. When advancing this, the paragraph on delays of lost
packets should be revisited and possibly reworded.
6. RFC2680 metrics
6.1. BrixWorx
o Type-P-One-way-Packet-Loss: implemented.
o Type-P-One-way-Packet-Poisson-Stream: implemented.
o Type-P-One-way-Packet-Loss-Average: implemented.
GPS, CDMA or NTP is used for time synchronization, time-outs are
configurable.
6.2. NetWarrior
o Type-P-One-way-Packet-Loss.
* Metric Parameters:
+ Src, the IP address of a host.
+ Dst, the IP address of a host.
+ T, a time.
* Comments: The time is the time the packet was sent, 40 nano
second ticks. Packets that arrive at the machine corrupted are
dropped (CRC failure or by IP or UDP checksum failure). If a
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packet is duplicated, any duplicates are ignored.
o Type-P-One-way-Packet-Loss-Poisson-Stream: Not implemented.
o Type-P-One-way-Packet-Loss-Average: Not implemented.
6.3. Surveyor
o Type-P-One-way-Packet-Loss
* Metric Parameters:
+ Src, the IP address of a host.
+ Dst, the IP address of a host.
+ T, a time.
* Metric Units: Type-P-One-way-Packet-Loss = [0,1]
* Comments: The time is the time the packet was sent, rounded to
the nearest microsecond. Packets that arrive at the machine
corrupted are generally dropped either by the hardware CRC
failure, or by IP or UDP checksum failure. Hence, corrupted
packets are counted as lost. If a packet is duplicated, any
duplicates are ignored.
* Further comments: This metric has been implemented in
combination with RFC2679/Type-P-One-way-Delay. All comments
made there apply. If a packet arrives, it's Type-P-One-way-
Packet-Loss is 0. If a packet does not arrive in the specified
window (200 seconds by default) the delay is infinite
(undefined), and the Type-P-One-way-Packet-Loss is 1.
o Type-P-One-way-Packet-Loss-Poisson-Stream: This has been
implemented as part of RFC2679/Type-P-OWD-Poisson-Stream. Results
consists of a series of measurements for the One Way Delay, with
values of 10,000,000 for packets that were sent but did not
arrive.
o Type-P-One-way-Packet-Loss-Average: By default, the Surveyor
reporting mechanisms calculate this on one-minute intervals. A
Java UI allows calculations on different intervals.
6.4. TTM
o Type-P-One-way-Packet-Loss.
* Metric Parameters:
+ Src, the IP address of a host.
+ Dst, the IP address of a host.
+ T, a time.
* Metric Units: Type-P-One-way-Packet-Loss.
* Comments: UDP packets are being used. No special IP bits are
set. A packet is considered lost if it has not arrived after
255 seconds. There is no distinction between packets that do
arrive but take longer than 255 seconds, or that never arrive
at all. The time is the time the packet was sent, rounded to
the nearest full second.
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* Further comments: This metric has been implemented in
combination with RFC2679/Type-P-OWD. All comments made there
apply.
o Type-P-One-way-Packet-Loss-Poisson-Stream: This has been
implemented as part of RFC2679/Type-P-OWD-Poisson-Stream. Results
consists of a series of measurements for the One Way Delay, with
values of -1 for packets that were sent but did not arrive.
o Type-P-One-way-Packet-Loss-Average: This is being calculated for
15 minute (or longer) intervals.
6.5. WIPM
o Type-P-One-way-Packet-Loss.
* Metric Units: Successful transmission and Loss are indicated,
but not with the values 0 and 1.
* In general, the methodology of section 2.6 is followed. All
packets are allowed at least Th=3 seconds to arrive (see the
Stream section).
* Errors and Uncertainties: Measurement system "health metrics"
are periodically checked to ensure that resource limits are not
exceeded.
o Type-P-One-way-Loss-Periodic-Stream
* Metric Units: T and a finite delay are recorded for successful
packets. At present, T is not recorded for lost packets,
though it can be bounded using the sequence numbers applied to
successful packets. T will be reported for lost packets in a
future release.
* Methodology is as described in section 3.6, including the
correct handling of out-of-order packets. The threshold for
lost packets is Th=3 seconds for the LAST packet in the stream.
In other words, a sample with Tf-T0=900 seconds allows Th=903
seconds for the first packet in the sample. A constant Th
setting can be enforced by post-processing the finite delays.
Th is enforced on the Src-Dst-Src RTT in the WIPM responder
architecture.
o Type-P-One-way-Loss-Poisson-Stream: Implemented, see above.
o Type-P-One-way-Loss-Average: This and many RFC 3357 Loss patterns
metrics are reported.
Metrics and features not implemented, and why not: The degree of
synchronization between source and destination clocks can be derived
with limited accuracy, but it is not directly reported.
The Anderson-Darling test results for the Poisson Process are not
available at the time of this memo, however other tests assure the
similarity of our Poisson implementation to ideal.
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6.6. Conclusion
As was the case for delay, the basic metric Type-P-One-way-Packet-
Loss has been implemented by all implementations. Which statistics
are reported varies but, again, all statistics can be calculated
offline after the measurement.
7. RFC2681 metrics
7.1. BrixWorx
Implemented metrics are:
o Singleton: Type-P-Round-Trip-Delay.
o Sample: Type-P-Round-Trip-Delay-Poisson-Stream.
o Statistical: Type-P-Round-Trip-Delay-Percentile, configurable.
o Statistical: Type-P-Round-Trip-Delay-Median.
o Statistical: Type-P-Round-Trip-Delay-Minimum.
Not implemented is:
o Statistical: Type-P-Round-Trip-Delay-Inverse-Percentile, no market
demand.
7.2. NetWarrior
Has not implemented this RFC, if round trip results are needed, they
are created by adding one-way delays.
7.3. Surveyor
Has not implemented this RFC.
7.4. TTM
Has not implemented this RFC due to a lack of demand from its
customers
7.5. WIPM
Implemented metrics are:
o Type-P-Round-trip-Delay. Metric Units: T and Round trip time are
recorded. The delay of lost packets is undefined, so our
implementation of this metric is more accurately described as
Type-P-Finite-Round-trip-Delay. Methodology is as described in
Section 2.6, in general. If the packet return transmission is
delayed at the destination, the processing time is recorded and
inserted in the packet.
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o Type-P-Round-trip-Delay-Poisson-Stream and
o Type-P-Round-trip-Delay-Periodic-Stream. Metric Units: T and
Round trip Time, dT, are recorded. Methodology is as described in
Section 3.6, in general including the correct handling of out-of-
order packets.
o Type-P-(Finite-)Round-trip-Delay-Percentile and
o Type-P-(Finite-)Round-trip-Delay-Median. Computation and report
of the 0.1, 1.0, 50, 95, 99, and 99.9 percentiles.
o Type-P-(Finite-)Round-trip-Delay-Minimum: Computation and report
of minimum round-trip delay (dT) of the sample.
o Type-P-(Finite-)Round-trip-Delay-Inverse-Percentile: The fraction
of finite dT values greater than a threshold are reported.
Also calculated and reported are: Mean, Standard Deviation, and Sum.
Note: We do not treat lost packets as having infinite delay, as it
would prevent the calculation of Means.
7.6. Conclusion
This metric has been implemented by 2 vendors.
8. Security Considerations
All security concerns raised in the specification of the various
metrics apply to this report.
9. IANA Considerations
None.
10. Conclusion
All metrics have been implemented by multiple vendors and can be
moved to draft standard.
11. Acknowledgements
The authors would like to thank all implementors who submitted an
implementation report: Yves Cognet (QosMetrics) for Netwarrior,
Kaynam Hedayat (Brix) for BrixWorx, Al Morton (AT&T) for WIPM, Henk
Uijterwaal (RIPE NCC) for TTM and Matt Zekauskas (Internet2) for
Surveyor.
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12. References
[RFC1305] Mills, D., "Network Time Protocol (Version 3)
Specification, Implementation", RFC 1305, March 1992.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
"Framework for IP Performance Metrics", RFC 2330,
May 1998.
[RFC2678] Mahdavi, J. and V. Paxson, "IPPM Metrics for Measuring
Connectivity", RFC 2678, September 1999.
[RFC2679] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
Delay Metric for IPPM", RFC 2679, September 1999.
[RFC2680] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
Packet Loss Metric for IPPM", RFC 2680, September 1999.
[RFC2681] Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip
Delay Metric for IPPM", RFC 2681, September 1999.
[RFC3357] Koodli, R. and R. Ravikanth, "One-way Loss Pattern Sample
Metrics", RFC 3357, August 2002.
[RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation
Metric for IP Performance Metrics (IPPM)", RFC 3393,
November 2002.
[RFC3432] Raisanen, V., Grotefeld, G., and A. Morton, "Network
performance measurement with periodic streams", RFC 3432,
November 2002.
[cia03] L. Ciavattone, A. Morton and G. Ramachandran,
""Standardized Active Measurements on a Tier 1 IP
Backbone", IEEE Communications Magazine, pp 90-97",
July 2003.
[inet99] Sunil Kalidindi and Matthew Zekauskas, "Surveyor: An
Infrastructure for Internet Performance Measurements, in
proceedings of INET'99", 1999.
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Author's Address
Henk Uijterwaal
RIPE NCC
Singel 258
1016 AB Amsterdam
NL
Phone: +31 20 535 4444
Email: henk@ripe.net
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