Internet DRAFT - draft-akhter-opsawg-perfmon-ipfix
draft-akhter-opsawg-perfmon-ipfix
Network Working Group A. Akhter
Internet-Draft Cisco Systems
Intended status: Standards Track H. Scholz
Expires: January 31, 2013 VOIPFUTURE GmbH
July 30, 2012
IPFIX Information Elements for RTP Flow Performance Measurement
draft-akhter-opsawg-perfmon-ipfix-03.txt
Abstract
There is a need to be able to quantify and report the performance of
RTP based applications. This performance data provides information
essential in validating service level agreements, fault isolation as
well as early warnings of greater problems. This document describes
IPFIX Information Elements related to RTP performance measurement of
network based applications. In addition, to the performance
information several non-metric information elements are also included
to provide greater context to the reports. The measurements use
audio/video applications as a base but are not restricted to these
class of applications. These new IPFIX Information Elements can
describe the entire duration of an RTP stream or a smaller time slice
of it.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 31, 2013.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Provisions Relating to IETF Documents
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publication of this document. Please review these documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. General Usage . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Quality of Service (QoS) Monitoring . . . . . . . . . . . 6
3.2. Fault Isolation and Troubleshooting . . . . . . . . . . . 6
4. New Information Elements . . . . . . . . . . . . . . . . . . . 7
4.1. Transport Layer . . . . . . . . . . . . . . . . . . . . . 7
4.1.1. perfObservationType . . . . . . . . . . . . . . . . . 7
4.1.2. perfIntervalStartMilliseconds . . . . . . . . . . . . 8
4.1.3. perfIntervalEndMilliseconds . . . . . . . . . . . . . 9
4.1.4. perfSampleOffsetMilliseconds . . . . . . . . . . . . . 10
4.1.5. perfSampleTimeMilliseconds . . . . . . . . . . . . . . 11
4.1.6. perfStreamState . . . . . . . . . . . . . . . . . . . 12
4.1.7. perfPacketLoss . . . . . . . . . . . . . . . . . . . . 13
4.1.8. perfPacketExpected . . . . . . . . . . . . . . . . . . 13
4.1.9. perfPacketLossRate . . . . . . . . . . . . . . . . . . 14
4.1.10. perfPacketLossEvent . . . . . . . . . . . . . . . . . 14
4.1.11. perfPacketInterArrivalJitterAvg . . . . . . . . . . . 15
4.1.12. perfPacketInterArrivalJitterMin . . . . . . . . . . . 15
4.1.13. perfPacketInterArrivalJitterMax . . . . . . . . . . . 16
4.1.14. rtpPacketizationTime . . . . . . . . . . . . . . . . . 17
4.1.15. rtpPacketizationChange . . . . . . . . . . . . . . . . 17
4.1.16. perfDuplicates . . . . . . . . . . . . . . . . . . . . 18
4.1.17. rtpPacketOrder . . . . . . . . . . . . . . . . . . . . 19
4.1.18. rtpSequenceError . . . . . . . . . . . . . . . . . . . 19
4.1.19. perfRoundTripNetworkDelay . . . . . . . . . . . . . . 19
4.2. User and Application Layer . . . . . . . . . . . . . . . . 20
4.2.1. perfSessionSetupDelay . . . . . . . . . . . . . . . . 20
4.3. RTP Header . . . . . . . . . . . . . . . . . . . . . . . . 20
4.3.1. rtpProtocolVersion . . . . . . . . . . . . . . . . . . 20
4.3.2. rtpSSRC . . . . . . . . . . . . . . . . . . . . . . . 21
4.3.3. rtpPayloadType . . . . . . . . . . . . . . . . . . . . 22
4.3.4. rtpMediaType . . . . . . . . . . . . . . . . . . . . . 23
4.3.5. rtpMediaSubType . . . . . . . . . . . . . . . . . . . 23
4.3.6. RTP Payload . . . . . . . . . . . . . . . . . . . . . 24
4.3.7. rtpMediaType . . . . . . . . . . . . . . . . . . . . . 26
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4.3.8. rtpMediaSubType . . . . . . . . . . . . . . . . . . . 26
4.3.9. rtpDelayType . . . . . . . . . . . . . . . . . . . . . 26
4.3.10. rtpDelayOneWay . . . . . . . . . . . . . . . . . . . . 26
4.3.11. rtpIsSRTP . . . . . . . . . . . . . . . . . . . . . . 27
4.3.12. rtpTimestamp . . . . . . . . . . . . . . . . . . . . . 27
4.3.13. rtpCodecChange . . . . . . . . . . . . . . . . . . . . 27
4.3.14. rtpMarkerBit . . . . . . . . . . . . . . . . . . . . . 27
4.3.15. rtpComfortNoise . . . . . . . . . . . . . . . . . . . 27
4.3.16. rtpDSCPChange . . . . . . . . . . . . . . . . . . . . 27
5. Security Considerations . . . . . . . . . . . . . . . . . . . 27
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 27
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
8.1. Normative References . . . . . . . . . . . . . . . . . . . 27
8.2. Informative References . . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29
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1. Introduction
Today's networks support a multitude of highly demanding and
sensitive network applications. Network issues are readily apparent
by the users of these applications due to the sensitivity of these
applications to impaired network conditions. Examples of these
network applications include applications making use of IP based
audio, video, database transactions, virtual desktop interface (VDI),
online gaming, cloud services and many more. In some cases, the
impaired application translates directly to loss of revenue. In
other cases, there may be regulatory or contractual service level
agreements that motivate the network operator. Due to the
sensitivity of these types of applications to impaired service it
leaves a poor impression of the service on the user-- regardless of
the actual performance of the network itself. In the case of an
actual problem within the network service, monitoring the performance
may yield a early indicator of a much more serious problem.
Due to the demanding and sensitive nature of these applications,
network operators have tried to engineer their networks towards
wringing better and differentiated performance. However, that same
differentiated design prevents network operators from extrapolating
observational data from one application to another, or from one set
of synthetic (active test) test traffic to actual application
performance. This gap highlights the importance of generic
measurements as well as the reliance on user traffic measurements--
rather than synthetic tests.
Performance measurements on user data provide greater visibility not
only into the quality of experience of the end users but also
visibility into network health. With regards to network health, as
flow performance is being measured, there will be visibility into the
end to end performance which means that not only visibility into
local network health, but also viability into remote network health.
If these measurements are made at multiple points within the network
(or between the network and end device) then there is not only
identification that there might be an issue, but a span of area can
be established where the issue might be. The resolution of the fault
increases with the number of measurement points along the flow path.
IP based applications, esp. those with real-time requirements, may
suffer temporarily from impairments such as bandwidth bottlenecks or
packet loss. Performance measurement with average values is not able
to record and highlight these issues. Due to this the measurement
interval must be configurable to a short time slice in order to
indicate such temporary impairments. Aggregation of measurements
shall be possible to aggregate multiple measurements of the same
application stream or multiple streams of the same type but
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potentially generated by different users.
The IP Flow Information Export Protocol (IPFIX) [RFC5101] provides
new levels of flexibility in reporting from measurement points across
the life cycle of a network based application. IPFIX can provide
granular results in terms of flow specificity as well as time
granularity. At the same time, IPFIX allows for summarization of
data along different types of boundaries for operators that are
unconcerned about specific sessions but about health of a service or
a portion of the network. This document details the expression of
IPFIX Information Elements whose calculation is defined in an
accompanying document.
As this document covers the reporting of these metrics via IPFIX,
consideration is taken with mapping the metric's capabilities and
context with the IPFIX information and data representation model.
The guidelines outlined in [I-D.trammell-ipfix-ie-doctors] are used
to ensure proper IPFIX information element definition.
There has been related work in this area such as [RFC2321].
[I-D.huici-ipfix-sipfix], and [VoIP-monitor].
2. Terminology
Terms used in this document that are defined in the Terminology
section of the IPFIX Protocol [RFC5101] document are to be
interpreted as defined there.
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].
In addition, the information element definitions use the following
terms:
Name: Name of the information element per the IPFIX rules defined in
Section 2.3 of [RFC5102]
Description: Short description of what the information element is
trying to convey.
Observation Point: Where the measurement is meant to be performed.
Either at an intermediate point (for example, a router) or end
system.
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Element Data Type: The IPFIX informationElementDataType as defined
in Section 3.1 of [RFC5610]
Element Semantics: The IPFIX informationElementSemantics as defined
in section Section 3.6 of [RFC5610]
Element Units: The IPFIX informationElementUnits as defined in
section Section 3.7 of [RFC5610]
Element Range Begin: The IPFIX informationElementRangeBegin as
defined in section Section 3.7 of [RFC5610]
Element Range End: The IPFIX informationElementRangeEnd as defined
in section Section 3.7 of [RFC5610]
Element Id: The IPFIX global unique element ID as defined in Section
3.2 of [RFC5101]
Status: The status of the specification of this IPFIX Information
Element.
3. General Usage
3.1. Quality of Service (QoS) Monitoring
For QoS monitoring, it is important to be able to capture the
application context. For example, in the case of interactive audio
flows, the codec and the fact that the application is interactive
should be captured. The codec type can be used to determine loss
thresholds affecting end user quality and the interactive nature
would suggest thresholds over one way delay. The IPFIX reporting
would need to keep this information organized together for operator
to be able to perform correlated analysis.
3.2. Fault Isolation and Troubleshooting
It has been generally easier to troubleshoot and fix problems that
are binary in nature: it either works or does not work. The host is
pingable or not pingable. However, the much more difficult to
resolve issues that are transitory in nature, move from location to
location, more complicated that simple ICMP reachability and many
times unverifiable reports by the users themselves. It is these
intermittent and seemingly inconsistent network impairments that
performance metrics can be extremely helpful with. Just the basic
timely detection that there is a problem (or an impending problem)
can give the provider the confidence that there is a real problem
that needs to be resolved. The next step would be to assist the
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operator in a speedy resolution by providing information regarding
the network location and nature of the problem.
Transient problems which affect a user only for a short time of this
session can be made visible with measurements taken in short fixed
time slices, e.g. every 10 seconds. While a traditional measurement
on a per session basis may not show an intermittent impairment (e.g.
packet loss) the short measurement interval highlights these.
4. New Information Elements
The information elements are organized into two main groups:
Transport Layer: Metrics that might be calculated from observations
at higher layers but essentially provide information about the
network transport of user date. For example, the metrics related
to packet loss, latency and jitter would be defined here.
RTP Header: Information Elements that describe the RTP stream
properties based on RTP header information but not the RTP payload
itself.
RTP Payload: Information Elements that describe the RTP payload.
For example, packet count and media type.
User and Application Layer: Metrics that are might be affected by
the network indirectly, but are ultimately related to user, end-
system and session states. For example, session setup time,
transaction rate and session duration would be defined here.
4.1. Transport Layer
4.1.1. perfObservationType
Name: perfObservationType
Description: The observation type is analog to sipObservationType
defined in [trammel sip-msg]. It defines the place of the
metering process in the network path.
Observation Point: The observation can be made anywhere along the
media path or on the endpoints themselves. The observation is
only relevant in a unidirectional sense.
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Element Data Type: unsigned8
Element Semantics: identifier
Element Units: n/a
Element Range Begin: 0
Element Range End: 0xFF
Element Id: TBDperfObservationType
Status: current
Use and Applications
0: unknown: The Metering Process does not specify the observation
type
1: receiver: The Metering Process is, or is co-located with, the
receiver of the RTP stream.
2: sender: The Metering Process is, or is co-located with, the
sender of the RTP stream.
3: passive: The Metering Process passively observed the RTP
stream.
4: rtcp: The Metering Process obtains the data conveyed in the
IPFIX message for one or more RTCP reports.
Calculation Method:
Units of Measurement: n/a
Measurement Timing
4.1.2. perfIntervalStartMilliseconds
Name: perfIntervalStartMilliseconds
Description: Start time of the monitoring interval in milliseconds
since 0000 UTC Jan 1, 1970. The time is taken from the local
clock which SHOULD be NTP synchronized. If a flow only covers
part of the monitoring interval (for example, the flow started
after the interval start time), start time MUST be set to the
start time of the monitoring interval.
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Observation Point:
Element Data Type: dateTimeMilliseconds
Element Semantics: identifier
Element Units: n/a
Element Range Begin: 0
Element Range End: ???
Element Id: TBDperfIntervalStartMilliseconds
Status: current
Use and Applications
Calculation Method:
Units of Measurement: n/a
Measurement Timing
4.1.3. perfIntervalEndMilliseconds
Name: perfIntervalEndMilliseconds
Description: End time of the flow's monitoring interval in
milliseconds since 0000 UTC Jan 1, 1970. The time is taken from
the local clock which SHOULD be NTP synchronized. If the flow
covers part of the monitoring interval (for example, the flow
ended before the interval end time), the
perfIntervalEndMilliseconds MUST be set to the end of observation
interval.
Observation Point:
Element Data Type: datetimeMilliseconds
Element Semantics: identifier
Element Units: n/a
Element Range Begin: 0
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Element Range End: 0xFF
Element Id: TBDperfObservationType
Status: current
Use and Applications
0: unknown: The Metering Process does not specify the observation
type
1: receiver: The Metering Process is, or is co-located with, the
receiver of the RTP stream.
2: sender: The Metering Process is, or is co-located with, the
sender of the RTP stream.
3: passive: The Metering Process passively observed the RTP
stream.
4: rtcp: TBD
Calculation Method:
Units of Measurement: n/a
Measurement Timing
4.1.4. perfSampleOffsetMilliseconds
Name: perfSampleOffsetMilliseconds
Description: Offset of the observation interval contained in this
flow record. The value is measured in milliseconds and contains
the offset of the beginning of the flow record from the beginning
of the RTP stream.
Observation Point:
Element Data Type: unsigned32
Element Semantics: identifier
Element Units: milliseconds
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Element Range Begin: 0
Element Range End: 0xFFFFFFFF
Element Id: TBDperfSampleOffsetMilliseconds
Status: current
Use and Applications
Calculation Method:
Measurement Timing
4.1.5. perfSampleTimeMilliseconds
Name: perfSampleTimeMilliseconds
Description: An IPFIX observer may generate and export a flow record
for the entire duration of an RTP stream or for a specific part,
e.g. a fixed time slice of 10 seconds. In case a single flow
record is created the rtpSampleTime equals the RTP stream duration
in milliseconds. In either case the rtpStreamState IE should be
set to true if this flow record describes an ended RTP stream.
Observation Point:
Element Data Type: unsigned32
Element Semantics: DeltaCounter
Element Units: milliseconds
Element Range Begin: 0
Element Range End: 0xFFFFFFFF
Element Id: TBDperfSampleTimeMilliseconds
Status: current
Use and Applications
Calculation Method:
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Units of Measurement: milliseconds
Measurement Timing
4.1.6. perfStreamState
Name: perfStreamState
Description: Using the rtpSampleOffset and rtpSampleTime IEs flow
entries may be generated which describe only part of an RTP
stream. This IE is used to describe the state of the observed
stream, e.g. to indicate the reception of the last flow record
belonging to a single RTP stream.
Observation Point:
Element Data Type: unsigned8
Element Semantics: identifier
Element Units: n/a
Element Range Begin: 0
Element Range End: 0xFF
Element Id: TBDperfObservationType
Status: current
Use and Applications
0: undefined: The state of the stream is not known.
1: running: The Metering Process expects more RTP packets or has
already received packets for this RTP stream which are outside
the scope of this flow record.
2: ended: The Metering Process determined that the RTP stream
ended. Information sources could be signaling information or
the fact that no RTP media has been received for a longer
period of time.
3: no packets: The Metering Process has not received any RTP
packets for this RTP stream in the observation interval but the
stream has not ended. A VoIP endpoint may have requested the
media stream to be suspended, i.e. put 'on hold' (tbd:reference
to sendonly ..)
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Calculation Method:
Units of Measurement: n/a
Measurement Timing
4.1.7. perfPacketLoss
Name: perfPacketLoss
Description: The packet loss metric reports the number of individual
packets that were lost in the reporting interval.
Observation Point: The observation can be made anywhere along the
media path or on the endpoints them selves. The observation is
only relevant in a unidirectional sense.
Element Data Type: unsigned32
Element Semantics: deltaCounter
Element Units: packets
Element Range Begin: 0
Element Range End: 0xFFFFFFFE
Element Id: TBDperfPacketLoss
Status: current
4.1.8. perfPacketExpected
Name: perfPacketExpected
Description: The number of packets there were expected within a
monitoring interval.
Observation Point: The observation can be made anywhere along the
media path or on the endpoints them selves. The observation is
only relevant in a unidirectional sense.
Element Data Type: unsigned32
Element Semantics: deltaCounter
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Element Units: packets
Element Range Begin: 0
Element Range End: 0xFFFFFFFE
Element Id: TBDperfPacketExpected
Status: current
4.1.9. perfPacketLossRate
Name: perfPacketLossRate
Description: Percentage of number of packets lost out of the total
set of packets sent.
Observation Point: The observation can be made anywhere along the
media path or on the endpoints them selves. The observation is
only relevant in a unidirectional sense.
Element Data Type: unsigned16
Element Semantics: quantity
Element Units: float16 (IPFIX has not defined float16 yet)
Element Range Begin: 0
Element Range End: 0x64
Element Id: TBDperfPacketLossRate
Status: current
4.1.10. perfPacketLossEvent
Name: perfPacketLossEvent
Description: The packet loss event metric reports the number of
continuous sets of packets that were lost in the reporting
interval.
Observation Point: The observation can be made anywhere along the
media path or on the endpoints them selves. The observation is
only relevant in a unidirectional sense.
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Element Data Type: unsigned32
Element Semantics: deltaCounter
Element Units: event
Element Range Begin: 0
Element Range End: 0xFFFFFFFE
Element Id: TBDperfPacketExpected
Status: current
4.1.11. perfPacketInterArrivalJitterAvg
Name: perfPacketInterArrivalJitterAvg
Description: This metric measures the absolute deviation of the
difference in packet spacing at the measurement point compared to
the packet spacing at the sender.
Observation Point: The observation can be made anywhere along the
media path or on the receiver. The observation is only relevant
in a unidirectional sense.
Element Data Type: unsigned32
Element Semantics: quantity
Element Units: microseconds
Element Range Begin: 0
Element Range End: 0xFFFFFFFE
Element Id: TBDperfPacketInterArrivalJitterAvg
Status: current
4.1.12. perfPacketInterArrivalJitterMin
Name: perfPacketInterArrivalJitterMin
Description: This metric measures the minimum value the calculation
used for perfPacketInterArrivalJitterAvg within the monitoring
interval.
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Observation Point: The observation can be made anywhere along the
media path or on the receiver. The observation is only relevant
in a unidirectional sense.
Element Data Type: unsigned32
Element Semantics: quantity
Element Units: microseconds
Element Range Begin: 0
Element Range End: 0xFFFFFFFE
Element Id: TBDperfPacketInterArrivalJitterMin
Status: current
4.1.13. perfPacketInterArrivalJitterMax
Name: perfPacketInterArrivalJitterMax
Description: This metric measures the maximum value the calculation
used for perfPacketInterArrivalJitterAvg within the monitoring
interval.
Observation Point: The observation can be made anywhere along the
media path or on the receiver. The observation is only relevant
in a unidirectional sense.
Element Data Type: unsigned32
Element Semantics: quantity
Element Units: microseconds
Element Range Begin: 0
Element Range End: 0xFFFFFFFE
Element Id: TBDperfPacketInterArrivalJitterMax
Status: current
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4.1.14. rtpPacketizationTime
Name: rtpPacketizationTime
Description: The RTP audio packetization time defines the amount of
audio contained in the individual RTP packet. This packetization
is typically fixed for the duration of an RTP stream but may be
changed. The allowed values depend on the codec. Values
typically observed are 10, 20 or 30ms.
Depending on the codec the amount of data contained in each RTP
packet can be derived from RTP time stamp information or RTP
payload size.
If the packetization time changes during an IPFIX monitoring
interval this value should indicate the most common value
monitored. Optionally the rtpPacketizationChange Information
Element may be updated accordingly.
Observation Point: The observation can be made anywhere along the
media path or on the receiver. The observation is only relevant
in a unidirectional sense.
Element Data Type: unsigned8
Element Semantics: quantity
Element Units: milliseconds
Element Range Begin: 0
Element Range End: 0xFF
Element Id: TBDrtpPacketizationTime
Status: current
4.1.15. rtpPacketizationChange
Name: rtpPacketizationChange
Description: Each time the packetization time of the observed RTP
stream changes during the monitoring interval this IE is
incremented.
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Observation Point: The observation can be made anywhere along the
media path or on the receiver. The observation is only relevant
in a unidirectional sense.
Element Data Type: unsigned32
Element Semantics: deltaCounter
Element Units: n/a
Element Range Begin: 0
Element Range End: 0xFFFFFFFF
Element Id: TBDrtpPacketizationChange
Status: current
4.1.16. perfDuplicates
Name: perfDuplicates
Description: Packets belonging to an observed stream or session may
be duplicated. The reason or source of duplication (e.g. the
generator or entities on the network path) is out of scope of this
IE. This IE describes the number of protocol specific duplicate
packets observed in the monitoring interval.
Observation Point: anywhere
Element Data Type: unsigned32
Element Semantics: deltaCounter
Element Units: packets
Element Range Begin: 0
Element Range End: 0xFFFFFFFE
Element Id: TBDperfDuplicates
Status: current
Use and Applications
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Calculation Method: The calculation method for duplicate packets
depends on the transport and application protocol used.
Duplicates on the application layer SHALL be counted if possible.
For [RFC3550] style RTP streams the RTP sequence numbers MUST be
used to identify duplicate packets. If a packet with the same
sequence number is observed twice or more in the monitoring
interval it is counted as duplicate. The perfDuplicates IE
describes the number of duplicate packets received, not counting
the first packet with each sequence number.
Units of Measurement: packets
Measurement Timing n/a
4.1.17. rtpPacketOrder
4.1.18. rtpSequenceError
4.1.19. perfRoundTripNetworkDelay
Name: perfRoundTripNetworkDelay
Description: This metric measures the network round trip time
between end stations for a flow.
Observation Point: The observation can be made anywhere along the
flow path as long as the bidirectional network delay is accounted
for.
Element Data Type: unsigned32
Element Semantics: quantity
Element Units: microseconds
Element Range Begin: 0
Element Range End: 0xFFFFFFFE
Element Id: TBDperfRoundTripNetworkDelay
Status: current
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4.2. User and Application Layer
4.2.1. perfSessionSetupDelay
Name: perfSessionSetupDelay
Description: The Session Setup Delay metric reports the time taken
from a request being initiated by a host/endpoint to the response
(or request indicator) to the request being observed. This metric
is defined in [RFC4710], however the units have been updated to
microseconds.
Observation Point: This metric needs to be calculated where both
request and response can be observed. This could be at network
choke points, application proxies, or within the end systems
themselves.
Element Data Type: unsigned32
Element Semantics: quantity
Element Units: microseconds
Element Range Begin: 0
Element Range End: 0xFFFFFFFE
Element Id: TBDperfSessionSetupDelay
Status: current
4.3. RTP Header
4.3.1. rtpProtocolVersion
Name: rtpProtocolVersion
Description: Value of the RTP version taken from the RTP header.
For [RFC3550] RTP packets this will typically be set to 2.
Observation Point: anywhere
Element Data Type: unsigned8
Element Semantics: identifier
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Element Units: none
Element Range Begin: 0
Element Range End: 0x02
Element Id: TBDrtpProtocolVersion
Status: current
Use and Applications The RTP protocol version is taken directly from
the RTP header information. It can be used to identify RTP
packets and differ between different RTP versions once they become
available.
Calculation Method: The value is obtained from the RTP header. For
[RFC3550] RTP this two bit field must always be set to two (2).
In case different values are observed in a single monitoring
interval the IE shall carry the value identified in the first RTP
packet of the monitoring interval.
Units of Measurement: none
Measurement Timing does not apply.
4.3.2. rtpSSRC
Name: rtpSSRC
Description: Value of the synchronization source (SSRC) field in the
RTP header of the flow. This field is defined in [RFC3550].
Observation Point: This metric can be gleaned from the RTP packets
directly, so the observation point can be either on the any RTP
endpoints or on the flow path in between the endpoints. It is
possible for the SSRC to change for a media flow without notice.
In these cases the IE would represent the value seen in the
packet-- the new SSRC and this would be treated as a new 'flow'
per configured flow record definitions.
Element Data Type: unsigned32
Element Semantics: identifier
Element Units: none
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Element Range Begin: 0
Element Range End: 0xFFFFFFFE
Element Id: TBDrtpSSRC
Status: current
Use and Applications The RTP SSRC value denotes a specific media
stream. As such when trying to differentiate media stream
problems between session participants the SSRC field is needed.
Calculation Method: Copy from RTP header's SSRC field as defined in
[RFC3550]. In the case of a non-RTP flow, or the time period in
which the flow has not been verified to be a RTP flow the value
0xFFFFFFFE MUST be reported.
Units of Measurement: identifier
Measurement Timing It is possible that the SSRC may have be
renegotiated mid-session due to collisions with other RTP senders.
4.3.3. rtpPayloadType
Name: rtpPayloadType
Description: The value of the RTP Payload Type Field as observed in
the RTP header of the flow. This field is defined in [RFC3550]
Observation Point: This metric can be gleaned from the RTP packets
directly, so the observation point needs to on the flow path or
within the endpoints.
Element Data Type: unsigned8
Element Semantics: identifier
Element Units: none
Element Range Begin: 0
Element Range End: 0xFF
Element Id: TBDrtpPayloadType
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Status: current
4.3.4. rtpMediaType
Name: rtpMediaType
Description: The rtpMediaType field carries the verbatim media type
name (e.g. Audio) as defined by [RFC4855].
Observation Point: anywhere
Element Data Type: string
Element Semantics: tbd
Element Units: n/a
Element Range Begin: n/a
Element Range End: n/a
Element Id: TBDrtpMediaType
Status: current
4.3.5. rtpMediaSubType
Name: rtpMediaSubType
Description: The rtpMediaSubType field carries the verbatim media
type name (e.g. PCMA) as defined by [RFC4855].
Observation Point: anywhere
Element Data Type: string
Element Semantics: tbd
Element Units: n/a
Element Range Begin: n/a
Element Range End: n/a
Element Id: TBDrtpMediaSubType
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Status: current
4.3.6. RTP Payload
This section defines additional Information Elements which describe
RTP stream payload and characteristics beyond the transport
information. Complicated metrics may be subject to different
measurement methods. In order to prevent data from being unusable
due to incompatible formats or measurement methods most Information
Elements are counter values which allow calculation of metrics on
mediator or collector systems. Additionally this allows matching
flow records to be aggregated by addition, e.g. addition of the
rtpPacketCount values of multiple observation intervals.
4.3.6.1. rtpPacketCount
Name: rtpPacketCount
Description: Number of RTP packets covered in this flow record.
This includes observed duplicate packets.
Observation Point: anywhere
Element Data Type: unsigned32
Element Semantics: deltaCounter
Element Units: packets
Element Range Begin: 0
Element Range End: 0xFFFFFFFE
Element Id: TBDrtpPacketCount
Status: current
Use and Applications The packet count may be used in conjunction
with the rtpPacketCountLoss and rtpPacketCountDiscard information
elements to calculate a packet loss rate per monitoring interval.
The benefit of transporting absolute numbers versus percentiles is
that an IPFIX mediator or collector may merge multiple IPFIX
records of the same or different RTP streams into a single record
for aggregation purposes.
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Calculation Method: The IPFIX observer counts all packets belonging
to the respective flow. Lost packets as identified by skipped RTP
sequence numbers MUST not be counted. Duplicate packets MUST be
counted. The packet order is not observed and does not impact the
packet count.
Units of Measurement: packets
Measurement Timing
4.3.6.2. rtpPacketCountLoss
Name: rtpPacketCountLoss
Description: Number of RTP packets lost in the duration covered by
this flow record. The number of lost packets SHOULD be calculated
using the RTP sequence numbers.
Observation Point: anywhere
Element Data Type: unsigned32
Element Semantics: deltaCounter
Element Units: packets
Element Range Begin: 0
Element Range End: 0xFFFFFFFE
Element Id: TBDrtpPacketCountLoss
Status: current
Use and Applications
Calculation Method: The IPFIX observer tracks the RTP sequence
numbers of each RTP stream and at the end of the monitoring
interval counts the number of packets not received based on the
missing sequence numbers.
Units of Measurement: packets
Measurement Timing
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4.3.6.3. rtpPacketCountDiscard
Name: rtpPacketCountDiscard
Description: Passive monitoring equipment shall assume a fixed 40
millisecond jitter buffer (TODO: add reference to TM Forum/ITU).
A packet observed later than the expected packet inter-arrival
time plus the 40ms is assumed to be received by the RTP receiver
too late to be played out. Even though the packet may be received
by the RTP receiver it will be discarded which has the same effect
as packet loss.
Observation Point: anywhere
Element Data Type: unsigned32
Element Semantics: deltaCounter
Element Units: packets
Element Range Begin: 0
Element Range End: 0xFFFFFFFE
Element Id: TBDrtpPacketCountDiscard
Status: current
Use and Applications
Calculation Method: The IPFIX observer implements a 40ms jitter
buffer per RTP stream observing sequence numbers as an RTP
endpoint would do. Packets received 40ms after their scheduled
playout time are considered discarded. Lost packets MUST not be
counted as discarded.
Units of Measurement: packets
Measurement Timing
4.3.7. rtpMediaType
4.3.8. rtpMediaSubType
4.3.9. rtpDelayType
4.3.10. rtpDelayOneWay
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4.3.11. rtpIsSRTP
4.3.12. rtpTimestamp
4.3.13. rtpCodecChange
4.3.14. rtpMarkerBit
4.3.15. rtpComfortNoise
4.3.16. rtpDSCPChange
5. Security Considerations
The recommendations in this document do not introduce any additional
security issues to those already mentioned in [RFC5101] and [RFC5477]
6. IANA Considerations
This document requires an elements assignment to be made by IANA.
7. Acknowledgements
The authors would like to thank Shingo Kashima, Jan Novak and Al
Morton for their invaluable review and comments. Thank-you.
8. References
8.1. Normative References
[RFC5101] Claise, B., "Specification of the IP Flow Information
Export (IPFIX) Protocol for the Exchange of IP Traffic
Flow Information", RFC 5101, January 2008.
[RFC5610] Boschi, E., Trammell, B., Mark, L., and T. Zseby,
"Exporting Type Information for IP Flow Information Export
(IPFIX) Information Elements", RFC 5610, July 2009.
[RFC4710] Siddiqui, A., Romascanu, D., and E. Golovinsky, "Real-time
Application Quality-of-Service Monitoring (RAQMON)
Framework", RFC 4710, October 2006.
[RFC5102] Quittek, J., Bryant, S., Claise, B., Aitken, P., and J.
Meyer, "Information Model for IP Flow Information Export",
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RFC 5102, January 2008.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003.
[RFC3497] Gharai, L., Perkins, C., Goncher, G., and A. Mankin, "RTP
Payload Format for Society of Motion Picture and
Television Engineers (SMPTE) 292M Video", RFC 3497,
March 2003.
[RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
"Session Traversal Utilities for NAT (STUN)", RFC 5389,
October 2008.
[RFC4855] Casner, S., "Media Type Registration of RTP Payload
Formats", RFC 4855, February 2007.
[RFC6076] Malas, D. and A. Morton, "Basic Telephony SIP End-to-End
Performance Metrics", RFC 6076, January 2011.
[iana-ipfix-assignments]
Internet Assigned Numbers Authority, "IP Flow Information
Export Information Elements
(http://www.iana.org/assignments/ipfix/ipfix.xml)".
8.2. Informative References
[I-D.trammell-ipfix-ie-doctors]
Trammell, B. and B. Claise, "Guidelines for Authors and
Reviewers of IPFIX Information Elements",
draft-trammell-ipfix-ie-doctors-03 (work in progress),
October 2011.
[RFC2508] Casner, S. and V. Jacobson, "Compressing IP/UDP/RTP
Headers for Low-Speed Serial Links", RFC 2508,
February 1999.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, March 2004.
[RFC2250] Hoffman, D., Fernando, G., Goyal, V., and M. Civanlar,
"RTP Payload Format for MPEG1/MPEG2 Video", RFC 2250,
January 1998.
[RFC2890] Dommety, G., "Key and Sequence Number Extensions to GRE",
RFC 2890, September 2000.
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[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, December 2005.
[RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and
Control Packets on a Single Port", RFC 5761, April 2010.
[I-D.huici-ipfix-sipfix]
Huici, F., Niccolini, S., and S. Anderson, "SIPFIX: Use
Cases and Problem Statement for VoIP Monitoring and
Exporting", draft-huici-ipfix-sipfix-00 (work in
progress), June 2009.
[RFC2321] Bressen, A., "RITA -- The Reliable Internetwork
Troubleshooting Agent", RFC 2321, April 1998.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5477] Dietz, T., Claise, B., Aitken, P., Dressler, F., and G.
Carle, "Information Model for Packet Sampling Exports",
RFC 5477, March 2009.
[VoIP-monitor]
L. Chang-Yong, H. Kim, K. Ko, J. Jim, and H. Jeong, "A
VoIP Traffic Monitoring System based on NetFlow v9,
International Journal of Advanced Science and Technology,
vol. 4, Mar. 2009".
Authors' Addresses
Aamer Akhter
Cisco Systems, Inc.
7025 Kit Creek Road
RTP, NC 27709
USA
Email: aakhter@cisco.com
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Hendrik Scholz
VOIPFUTURE GmbH
Wendenstrasse 4
Hamburg 20097
Germany
Phone: +49 40 688 900 100
Email: hscholz@voipfuture.com
URI: http://www.voipfuture.com/
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