wdiff draft-akhter-opsawg-perfmon-ipfix-02.txt draft-akhter-opsawg-perfmon-ipfix-03.txt

Network Working Group A. Akhter
Internet-Draft Cisco Systems
Intended status: Standards Track March 27, 2012 H. Scholz
Expires: September 28, January 31, 2013 VOIPFUTURE GmbH
July 30, 2012

IPFIX Information Elements for RTP Flow Performance Measurement
draft-akhter-opsawg-perfmon-ipfix-02.txt
draft-akhter-opsawg-perfmon-ipfix-03.txt

Abstract

There is a need to be able to quantify and report the performance of
network applications and the network service in handling user data.
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
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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
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This Internet-Draft will expire on September 28, 2012. January 31, 2013.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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described in the Simplified BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 5
3. General Usage . . . . . . . . . . . . . . . . . . . . . . . . 5 6
3.1. Quality of Service (QoS) Monitoring . . . . . . . . . . . 5 6
3.2. Service Level Agreemnt (SLA) Validation . . . . . . . . . 5
3.3. Fault Isolation and Troubleshooting . . . . . . . . . . . 6
4. New Information Elements . . . . . . . . . . . . . . . . . . . 6 7
4.1. Transport Layer . . . . . . . . . . . . . . . . . . . . . 6 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 . . . . . . . . . . . . . . . . . . . . 6
4.1.2. 13
4.1.8. perfPacketExpected . . . . . . . . . . . . . . . . . . 7
4.1.3. 13
4.1.9. perfPacketLossRate . . . . . . . . . . . . . . . . . . 8
4.1.4. 14
4.1.10. perfPacketLossEvent . . . . . . . . . . . . . . . . . 8
4.1.5. 14
4.1.11. perfPacketInterArrivalJitterAvg . . . . . . . . . . . 9
4.1.6. 15
4.1.12. perfPacketInterArrivalJitterMin . . . . . . . . . . . 9
4.1.7. 15
4.1.13. perfPacketInterArrivalJitterMax . . . . . . . . . . . 10
4.1.8. 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 . . . . . . . . . . . . . . 10 19
4.2. User and Application Layer . . . . . . . . . . . . . . . . 11 20
4.2.1. perfSessionSetupDelay . . . . . . . . . . . . . . . . 11 20
4.3. Contextual Elements RTP Header . . . . . . . . . . . . . . . . . . . 12
4.3.1. mediaRTPSSRC . . . . . 20
4.3.1. rtpProtocolVersion . . . . . . . . . . . . . . . . 12 . . 20
4.3.2. mediaRTPPayloadType rtpSSRC . . . . . . . . . . . . . . . . . 12 . . . . . . 21
4.3.3. mediaCodec rtpPayloadType . . . . . . . . . . . . . . . . . . . . 22
4.3.4. rtpMediaType . . 13 . . . . . . . . . . . . . . . . . . . 23
4.3.5. rtpMediaSubType . . . . . . . . . . . . . . . . . . . 23
4.3.6. RTP Payload . . . . . . . . . . . . . . . . . . . . . 24
4.3.7. rtpMediaType . . . . . . . . . . . . . . . . . . . . . 26
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 . . . . . . . . . . . . . . . . . . . 13 27
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 27
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 27
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 27
8.1. Normative References . . . . . . . . . . . . . . . . . . . 14 27
8.2. Informative References . . . . . . . . . . . . . . . . . . 14
Author's Address . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 29

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 measurents-- 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
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 documet document details the expresison 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]. This document is also
an attempt to generalize as well as standardize the reporting formats
and measurement methodology.

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.

Element Data Type: The IPFIX informationElementDataTypeas 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

The network operator needs to be able to gauge the end user's
satisfaction with the network service. While there are many
components of the satisfaction such as pricing, packaging, offering,
etc., a major component of satisfaction is delivering a consistent
service. The user builds trust on this consistency of the network
service and is then to be able to run network applications-- which is
of course the end goal. Without the ability to deliver a consistent
service for end user network applications network operator will be
left dealing with price sensitive disgruntled users with very low
expectations (if they don't have choice of operator) or abandonment
(if they have choice).

For QoS monitoring, it is importnat important to be able to capture the
applicaiton
application context. For example, in the case of interactive audio
flows, the codec and the fact that the application is interactive
shoudl
should be captured. The codec type can be used to determine loss
thresholds affecting end user quality and the interactive nature
would suggest threshodlds thresholds over one way delay. The IPFIX reporting
would need to keep this information organized together for opeartor operator
to be able to perform correlated analysis.

3.2. Service Level Agreemnt (SLA) Validation

Similar to QoS and QoE validation, there might be contractual or
regulatory requirements that need to be met by the network operator.
Monitoring the performance of the flows allows the application
operator, network operator as well as the end user to validate of the
target service is being delivered. While there is quite a diversity
in the codification of network SLAs they may eventually involve some
measurement of network uptime, end to end latency, end to end jitter
and perhaps service response time. In the case violation of the SLA,
the start and end times, nature and network scope of the violation
needs to be captured to allow for the most accurate settling of the
SLA.

3.3. 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
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.

Contextual Elements Information elements that provide further
context

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 metrics. For example,
media type, codec type, path or on the endpoints themselves. The observation is
only relevant in a unidirectional sense.

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 application would 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 defined here.

4.1. Transport Layer

4.1.1. 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.

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
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
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:

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 ..)

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

4.1.2.

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
Element Units: none packets

Element Range Begin: 0

Element Range End: 0xFFFFFFFE

Element Id: TBDperfPacketExpected

Status: current

4.1.3.

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: none float16 (IPFIX has not defined float16 yet)

Element Range Begin: 0

Element Range End: 0xFFFE 0x64

Element Id: TBDperfPacketLossRate

Status: current

4.1.4.

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.

Element Data Type: unsigned32

Element Semantics: deltaCounter

Element Units: none event

Element Range Begin: 0

Element Range End: 0xFFFFFFFE

Element Id: TBDperfPacketExpected

Status: current

4.1.5.

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

4.1.6.

4.1.12. perfPacketInterArrivalJitterMin

Name: perfPacketInterArrivalJitterMin

Description: This metric measures the minimum 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: TBDperfPacketInterArrivalJitterMin

Status: current

4.1.7.

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

4.1.8.

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.

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
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

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. Contextual Elements RTP Header

4.3.1. mediaRTPSSRC rtpProtocolVersion

Name: mediaRTPSSRC 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
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] [RFC3550].

Observation Point: This metric can be gleaned from the RTP packets
directly, so the observation point needs to can be either on the any RTP
endpoints or on the flow path or
within 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: octets none
Element Range Begin: 0

Element Range End: 0xFFFFFFFE

Element Id: TBDmediaRTPSSRC TBDrtpSSRC

Status: current

4.3.2. mediaRTPPayloadType

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: mediaRTPPayloadType rtpPayloadType

Description: The value of the RTP Payload Type Field as seen 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: octets none

Element Range Begin: 0

Element Range End: 0xFF

Element Id: TBDmediaRTPPayloadType TBDrtpPayloadType
Status: current

4.3.3. mediaCodec

4.3.4. rtpMediaType

Name: mediaCodec rtpMediaType

Description: The rtpMediaType field carries the verbatim media codec 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
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.

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 ideal location IPFIX observer tracks the RTP sequence
numbers of this metric is each RTP stream and at the end of the monitoring
interval counts the number of packets not received based on the media
generators and consumers. However, given application inspection
or static configuration it
missing sequence numbers.

Units of Measurement: packets

Measurement Timing

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 possible that intermediate nodes are
able assumed to generate codec information. 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: string unsigned32

Element Semantics: identifier deltaCounter

Element Units: octets packets

Element Range Begin: 0

Element Range End: 0xFFFFFFFE

Element Id: TBDmediaCodec 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
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 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",
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.

[I-D.ietf-pmol-sip-perf-metrics]

[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", draft-ietf-pmol-sip-perf-metrics-07
(work in progress), September 2010. 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.ietf-pmol-metrics-framework]
Clark, A. and B. Claise, "Guidelines for Considering New
Performance Metric Development",
draft-ietf-pmol-metrics-framework-12 (work in progress),
July 2011.

[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.

[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.

[nProbe] "nProbe - NetFlow/IPFIX Network Probe
(http://www.ntop.org/nProbe.html)".

[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".

Author's Address

Authors' Addresses

Aamer Akhter
Cisco Systems, Inc.
7025 Kit Creek Road
RTP, NC 27709
USA

Email: aakhter@cisco.com
Hendrik Scholz
VOIPFUTURE GmbH
Wendenstrasse 4
Hamburg 20097
Germany

Phone: +49 40 688 900 100
Email: hscholz@voipfuture.com
URI: http://www.voipfuture.com/