Internet Engineering Task Force R.Kumar
Internet Draft D.Auerbach
Document: draft-auerbach-mgcp-rtcpxr-07 C. Sivachelvan
Category: Informational Cisco Systems
Expires: May 1, 2008 D. Hancock
CableLabs
B. Hare
Arris
Nov. 1, 2007
RTCP XR VoIP Metrics Package for the Media Gateway Control Protocol
draft-auerbach-mgcp-rtcpxr-07
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Abstract
The main intent of this document is to define a Media Gateway Control
Protocol (MGCP) package to control the reporting of metrics supported
by the VoIP metrics block in RTCP Extended Reports as specified in [RFC
3611]. It also allows the call agent to control whether or not the
gateway will request a peer device via SDP to send the VoIP metrics
block in RTCP Extended Reports and whether it will respond positively
to such requests from the peer device. Besides this primary focus, this
MGCP RTCP-XR Package 4/12/2007
package also allows the reporting of metrics defined for RTCP Sender
Reports and Receiver Reports [RFC 3550] and the reporting of session
description parameters (based on the ones defined in RFC 2327, RFC 2198
etc.).
Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC 2119.
Table of Contents
1. Introduction
2. VoIP Metrics Package Definition
2.1 Local Connection Options
2.1.1 Responses to the xrm/mcr local connection option
2.1.1.1 Response to a value of "off"
2.1.1.2 Response to a value of "on"
2.1.1.3 Response to a value of "negotiate"
2.1.2 Impact of the xrm/mcr LCO on VoIP metrics block exchange
2.2 MGCP Protocol Procedures
2.2.1 DeleteConnection Procedures
2.2.2 AuditConnection Procedures
2.2.3 ModifyConnection Procedures
2.3 The LVM and RVM Lines for reporting Local And Remote Metrics
2.3.1 Inclusion/Omission of XRM/LVM and XRM/RVM parameters
2.3.2 XRM/LVM and XRM/RVM parameter values
2.3.3 Procedures for the resetting of metrics
2.3.4 Impact redundancy and FEC on packet loss computations
2.3.5 Parameter Extension Mechanism
2.3.6 Formal Syntax of VoIP Metrics Package
2.3.7 Impact of media state changes on VoIP metrics
2.3.8 Applicability of VoIP metrics to Voice Band Data
2.3.9 Applicability of VoIP metrics to Fax Relay and Text Relay
3. Call Flow Examples
3.1 Metrics Reporting during Call agent-initiated Delete Connection
3.2 Metrics Reporting during Gateway-initiated Delete Connection
3.3 Metrics Reporting during Audit Connection
3.4 Metrics Reporting during Modify Connection
4. Security Considerations
5. IANA Considerations
5.1 Package Registration
5.2 Extension Registration
6. Changes from earlier drafts
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6.1 Changes from the -00 version to the -01 version
6.2 Changes from the -01 version to the -02 version
6.3 Changes from the -02 version to the -03 version
6.4 Changes from the -03 version to the -04 version
6.5 Changes from the -04 version to the -05 version
6.6 Changes from the -05 version to the -06 version
6.7 Potential future updates
7. Normative References
8. Acknowledgments
9. Copyright Statement
1. Introduction
This document defines a Media Gateway Control Protocol (MGCP) [RFC
3435] package that enables the collection and reporting of metrics that
measure the quality of traffic on two-way VoIP connections. This
capability is based on and utilizes the VoIP Metrics Block of the RTCP
Extended Report as specified in [RFC 3611].
In accordance with [RFC 3435], the term "gateway" is used to denote the
device controlled via MGCP. This is not intended to preclude the use of
MGCP or of this package to control devices that are not, in the
strictest terms, media gateways. For the purposes of this package, the
terms "media gateway", "gateway" and "endpoint" are used
interchangeably. Also, the terms "media gateway controller" and "call
agent" are used interchangeably.
In addition to the parameters in the RTCP XR VoIP metrics block, this
package allows the collection of statistics defined for RTCP Sender
Reports and Receiver Reports [RFC 3550]. The ConnectionParameters
structure [RFC 3435] allows the reporting of the local, but not the
remote, version of statistics defined for RTCP Sender Reports and
Receiver Reports [RFC 3550]. To report both the local and remote
versions of these RTP statistics, this package MAY be used. Note that
this package does not affect the collection or reporting of connection
parameters defined in the base MGCP specification (RFC 3435). Nor does
it affect the sending of RTCP Sender Reports (SR) and Receiver Reports
(RR).
This package also includes session description parameters (based on the
ones defined in RFC 2327, RFC 2198 etc.). These MAY be reported via
this package to obviate the need for call agents to snoop SDP session
descriptors.
This package makes a distinction between collecting, responding and
reporting. The term "collecting" refers to the process of calculating
and accumulating local metric data and accumulating remote metric data
received in RTCP Sender, Receiver and Extended Reports from the remote
device. The term "responding" in the context of this package is
limited to the sending of accumulated local metric data via RTCP
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Extended Reports to the remote device as specified in [RFC 3611]. Note
that this package does not control the communication of session
statistics via RTCP Sender Reports (SR) and Receiver Reports (RR).
These reports MUST be sent in the manner REQUIRED of all RTP endpoints
[RFC 3550]. The term "reporting" refers to the process of reporting the
accumulated local and remote metric data for the connection to the Call
Agent in either a DeleteConnection, ModifyConnection or AuditConnection
command sequence.
An endpoint will "collect" local session metrics for several reasons:
- To report metrics in the "northbound" direction via the XRM/LVM
and XRM/RVM parameters specified in this package.
- To communicate metrics in the "east-west" direction via RTCP
extended reports,
- To report metrics in the "northbound" direction via other
mechanisms such as connection parameters [RFC 3435] and log
transfers not addressed in this document,
- To communicate metrics in the "east-west" direction via RTCP
Sender Reports and Receiver Reports.
The sets of metrics collected for these purposes are not the same. This
package is limited to defining the metrics that MAY be reported via the
XRM/LVM and XRM/RVM lines. This MAY or MAY not be a superset of the
metrics that MAY be communicated via the VoIP metrics block in RTCP
extended reports.
The Call Agent can ask an endpoint to enable or disable the reporting
of metrics via this package. Enabling this reporting also enables the
"east-west" communication of metrics via the RTCP XR VoIP metrics block
from the local endpoint's perspective. Whether this "east-west"
communication actually takes place also depends on the peer endpoint's
capabilities. When it disables "northbound" reporting via this package,
the call agent MAY either disable the "east-west" communication of
metrics via the RTCP XR VoIP metrics block, or it MAY require the
endpoint to communicate the VoIP metrics block in the "east-west"
direction if the remote end requests it. Disabling "northbound"
reporting via this package has no impact on the use of RTCP Sender
Reports or Receiver Reports.
Like RTCP-XR [RFC 3611], this package focuses on voice metrics.
However, it does examine the relevance of these metrics to other media
modes such as voice band data [ITU V.152], fax relay [ITU T.38] and
text relay [ITU V.151]. The MGGCP-based reporting of metrics that are
unique to the voice band data, fax relay and text relay will need to be
defined in other MGCP packages.
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The metric data reported to the Call Agent via this package when a
connection is deleted, modified or audited represents the data that was
accumulated/averaged over a computation interval. This package allows
this interval to be selected in a flexible manner. This interval MAY
encompass the time since the last metrics reset, if any, or since the
start of the session (in the absence of resets). Alternately, this
interval MAY consist of a relatively short period (e.g. 5 seconds)
prior to metrics capture and reporting. The metrics reset is commanded
by the call agent in the case of feature invocations such as call
transfer or call pick-up.
In the case of media mode shifts (such as voice to voice band data),
this package allows the resetting of metrics or their seamless
continuation in to the new mode. In the case of call agent-controlled
media mode shifts, this resetting is controlled by the call agent. In
the case of autonomous, endpoint-controlled media mode shifts, this
resetting is also under endpoint control. The preferred behavior,
which might not be followed by all endpoints, is for the metrics to be
reset.
Note that, in some implementations, metrics are not reset during media
mode shifts. Instead, metrics that are applicable in the new mode
continue to be accumulated/averaged as before. Also, for metrics that
are not applicable in the new mode, further computation is suspended
until when another media mode shift renders these metrics relevant
again.
The VoIP Metrics package definition is provided in Section 2. This
includes a detailed description of relevant MGCP protocol procedures, a
list of parameters that can be reported via this package, and an
analysis of the applicability of these parameters to voice band data,
fax relay and text relay. In Section 3, we provide four call flow
examples showing how to use the package. Security considerations are
found in Section 4, followed by the IANA considerations and references.
Table 1 lists the metrics based on the VoIP metrics block in RTCP
Extended Reports [RFC 3611]. It also includes parameters that address
the metrics computation interval and the occurrence of metrics resets
since session start. Table 2 lists the metrics based on RTCP Sender
Reports and Receiver Reports [RFC 3550]. Note that Table 2 uses the
metrics definitions in [RFC 3550] and [RFC 3435] as is, without
attempting to improve them by specifying, for instance, a better
method for handling duplicates. Table 3 lists session parameters, most
of which are from RFCs which define SDP constructs (e.g. RFC 2327, RFC
2198, RFC 2733). Tables 4, 5 and 6 list the applicability of the
metrics and session parameters in Tables 1, 2 and 3 respectively to fax
relay. Tables 7, 8 and 9 do the same for text relay.
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2. VoIP Session Metrics Package Definition
A package is defined for VoIP session metrics.
Package Name: XRM
Package Version: 0
This package defines the following parameters:
- A new local connections option, "mcr" (Metrics Reporting) for
enabling and disabling metrics reporting via this package. Note
that metrics collection via MGCP might use other mechanisms (e.g.
the connection parameters in the base MGCP specification, RFC
3435) that are not impacted by this local connection option.
- A new parameter line, "MMO" (Media Metrics Option) that allows
the call agent to request local and remote metrics in a modify
connection response, and/or to reset the local and remote
metrics.
- A new parameter line, "LVM" (Local VoIP Metrics), for reporting
locally collected metrics.
- A new parameter line, "RVM" (Remote VoIP Metrics), for reporting
remotely collected metrics communicated to the reporting endpoint
via RTCP Extended Reports, Sender Reports and Receiver Reports.
2.1 Local Connection Options
The local connection option (LCO) parameter, "xrm/mcr", is an OPTIONAL
parameter with one of the following three values:
- "off": Disables the reporting of metrics via this package AND the
"east-west" communication of metrics via the RTCP XR VoIP metrics
block
- "on": Enables the reporting of metrics via this package AND the
"east-west" communication of metrics via the RTCP XR VoIP metrics
block. Whether this "east-west" communication actually takes
place also depends on the peer endpoint's capabilities.
- "negotiate": Disables the reporting of metrics via this package.
However, the endpoint is REQUIRED to communicate the VoIP metrics
block in the "east-west" direction if the remote end requests it.
For example,
L: a:PCMU, xrm/mcr: on
assigns a value of "on" to the "mcr" LCO.
In CreateConnection commands, the xrm/mcr LCO value defaults to
"negotiate". In ModifyConnection commands, the xrm/mcr LCO value
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defaults to its current value for the connection. Thus, if
LocalConnectionOptions are either omitted or the xrm/mcr LCO is not
included in a ModifyConnection command, the previous xrm/mcr LCO value
for the connection is retained.
An MGCP endpoint supporting this package SHALL always use SDP to
request the VoIP metrics block from the remote device if the value of
the "xrm/mcr" LCO is set to "on". However, even if the value of value
of the "xrm/mcr" LCO is "on" or "negotiate", the endpoint SHALL NOT
send the VoIP metrics block in RTCP Extended Reports (XR) unless the
remote device has requested this block via SDP signaling. Thus, for
MGCP endpoints supporting this package, the permission in [RFC 3611] to
send RTCP XR blocks in the absence of the "rtcp-xr" SDP attribute is
revoked.
Note that the value of the "xrm/mcr" LCO does not affect the collection
or reporting of connection parameters in the connection parameters line
(P: line) as defined in the base MGCP specification [RFC 3435]. Nor
does it affect the sending of RTCP Sender Reports (SR) and Receiver
Reports (RR). An endpoint supporting this package MUST continue to
include the connection parameters (P:) line in an audit connection
response where this data is requested, in a delete connection response
and in a gateway-initiated delete connection. There can be overlap if
equivalent parameters are also reported via this package in procedures
for the deletion and audit of connections. There is no overlap in the
case of modify connection responses since these do not include the
connection parameters line.
2.1.1 Responses to the xrm/mcr local connection option
This section details the endpoint's response to each of the xrm/mcr LCO
values.
2.1.1.1 Response to a value of "off"
On receiving this value, the endpoint MUST erase any local or remote
VoIP metric data previously collected for the connection, and MUST
instruct the far-end device to stop sending RTCP XR VoIP Metrics Report
Blocks. The endpoint MUST ignore an SDP request for metrics and MUST
NOT transmit local metrics to the peer device. The local endpoint
MUST NOT report XR metrics upon receiving or initiating a
DeleteConnection sequence and MUST NOT report XR metrics when
responding to a ModifyConnection command or an AuditConnection
command.
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2.1.1.2 Response to a value of "on"
On receiving this value in a CreateConnection or ModifyConnection
command, if not already doing so, the endpoint MUST:
- Start collecting/calculating the metrics which it will expose to
the Call Agent via this package.
- Instruct the far-end device to start sending the VoIP Metrics
block in RTCP Extended Reports by including an "rtcp-xr"
attribute with a value of "voip-metrics" in the SDP.
- Report local and remote metrics via the XRM/LVM and XRM/RVM lines
defined below in the response to DeleteConnection that targets a
single connection, in the response to a ModifyConnection when
these metrics are requested, in the response to an
AuditConnection when these metrics are audited, and when sending
a DeleteConnection command for a single connection.
2.1.1.3 Response to a value of "negotiate"
On receiving this value, the endpoint disables the "northbound"
reporting of metrics, via this package, to the call agent. Also, it
sets an internal flag to indicate that it will respond positively to
SDP requests by the remote peer device to send the VoIP metrics block
in RTCP Extended Reports.
2.1.2 Impact of the xrm/mcr LCO on VoIP metrics block exchange
This section details the concepts introduced in the previous section
regarding the use of the xrm/mcr local connection option to govern the
endpoint's behavior regarding the negotiation, via SDP, of the VoIP
metrics block in RTCP extended reports [RFC 3611].
RFC 3611 adds a new SDP attribute called "rtcp-xr" that can be used by
an endpoint to ask the remote device to send RTCP Extended Reports.
This attribute is encoded as follows:
rtcp-xr:<xr-format>
This rtcp-xr attribute can be used as either a session-level or media-
level attribute. See [RFC 3611] for more information. Only one of the
xr-format values, voip-metrics, is within the scope of this package.
For an endpoint supporting this package, the inclusion of the voip-
metrics value in an rtcp-xr attribute line in its SDP local session
descriptions SHALL be per the following rules:
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- The voip-metrics value SHALL be included if the xrm/mcr LCO is
set to "on".
- The voip-metrics value SHALL NOT be included if the xrm/mcr LCO
is set to "off" or "negotiate".
The inclusion or exclusion of any other xr-format values (denoting
other RTCP XR blocks) in the rtcp-xr SDP attribute line is independent
of the xrm/mcr LCO. This is not addressed by this package.
The response of an endpoint supporting this package to the receipt from
a remote peer of an SDP remote session description with an rtcp-xr
attribute line that has voip-metrics as one of its values (or its only
value) SHALL be as follows:
- The endpoint MUST send RTCP Extended Reports with the VoIP
metrics block to the remote peer if the xrm/mcr LCO is "on" or
"negotiate".
- The endpoint SHALL NOT send RTCP Extended Reports with the VoIP
metrics block to the remote peer if the xrm/mcr LCO is "off".
Regardless of the value of the xrm/mcr LCO, an endpoint supporting this
package SHALL NOT send RTCP Extended Reports with the VoIP metrics
block to the remote peer if any of the following is true:
- The rtcp-xr attribute is not included in the SDP remote session
description.
- The rtcp-xr attribute is included in the SDP remote session
description but "voip-metrics" is not one of its values. This
includes the case in which the attribute has an empty parameter
list.
[RFC 3611] allows endpoints that uses SDP (e.g. MGCP endpoints) to
exchange RTCP Extended Reports without prior SDP signaling, which is
OPTIONAL. This allowance is rescinded for endpoints supporting this
package which MUST implement the SDP signalling specified in this
section.
2.2 MGCP Protocol Procedures
2.2.1 DeleteConnection Procedures
These procedures refer to call agent-initiated delete connection
commands that are targeted at a specific connection ID and to gateway-
initiated delete connection commands. They do not apply to call agent-
initiated delete connection commands that are targeted at all
connections associated with a call, an endpoint, an endpoint group or a
gateway. In the latter case, the XRM/LVM and XRM/RVM lines (described
in detail below) SHALL NOT be returned.
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Endpoints supporting this package MUST report local metrics in the
XRM/LVM parameter line in delete connection responses and in gateway-
initiated delete connection commands if and only if the local
connection option xrm/mcr is set to "on".
Endpoints supporting this package MUST report remote metrics, if
available, in the XRM/RVM parameter line in delete connection responses
and in gateway-initiated delete connection commands if and only if the
local connection option xrm/mcr is set to "on".
We do not define a mechanism for suppressing metrics reporting in
response to a delete connection command that is targeted at a specific
connection ID. In situations (such as a switchover)where the call agent
needs to delete connections without retaining any records of the
connections, it can use the version of the delete connection procedure
that targets all connections associated with a call, an endpoint, an
endpoint group or a gateway [RFC 3435]. No metrics are returned in
response to this version of the delete connection command.
2.2.2 AuditConnection Procedures
This package defines two new RequestedInfo values to be used with an
AuditConnection (AUCX). These allow a call agent to explicitly request
that the endpoint return the current values of either the local or
remote metrics. The request does not reset the values. When one or
both of these RequestedInfo values are included in an AUCX command, the
endpoint MUST return the appropriate metric values if available. The
two new RequestedInfo values are:
XRM/LVM Return the local voice metric values.
XRM/RVM Return the remote voice metric values.
The call agent MAY audit the local and remote voice metrics at any
time. Some example uses of this capability are:
- Audits in response to a "quality alert" event notification
[RFC 3660],
- Audits in response to an event notification that MAY lead to
a media transition e.g. a fax tone event ('ft') or a modem tone
event ('mt') [RFC 3660].
- Audits in response to an event notification of a media transition
e.g. the start of a gateway-controlled fax procedure
{fxr/gwfax(start)} [FAX PKG].
A quality alert event notification MAY be sent in response to a metrics
threshold crossing by an endpoint supporting the RTP package defined in
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RFC 3660. When audited within a time window T1 after sending a quality
alert, the endpoint SHOULD respond with metrics captured at the time of
the threshold crossing rather than metrics captured in response to the
associated metrics audit request.
In the case of events that MAY lead to a media state transition (e.g.
voice to voice band data or fax relay), the endpoint SHOULD respond to
a metrics audit received within a time window of T1 with metrics
captured just prior to the event notification rather than at the time
of the audit. In the case of events that report a media state
transition, the endpoint SHOULD respond to a metrics audit received
within a time window of T1 with metrics captured just prior to the
state transition rather than at the time of the audit. Naturally, the
reported values are captured prior to any parameter reset ensuing from
the media state change.
A value of five seconds is RECOMMENDED for the time window, T1, used to
associate an event notification with a metrics audit. However, the
value of this window depends on the application. Although not
RECOMMENDED, an endpoint MAY automatically associate a metrics audit
request with a prior relevant event notification, if any, regardless of
the time-lag between the two.
The rules in the MGCP base specification [RFC 3435] for handling audits
of unsupported parameters and parameters for which an endpoint has no
values MUST be followed. As a result:
- If an endpoint that does not understand the XRM/LVM or XRM/RVM
parameter is audited for that parameter, it MUST NOT generate an
error. Instead, the parameter MUST be omitted from the audit
response. Since this rule is based on the MGCP base
specification, it also applies to endpoints that do not support
this package.
- If an endpoint that does not have values for the XRM/LVM or
XRM/RVM parameter is audited for that parameter, it MUST NOT
generate an error. Instead, the parameter MUST be included in the
audit response with an empty value.
2.2.3 ModifyConnection Procedures
This package defines a new MGCP parameter, the MediaMetricsOption
("MMO") that MAY be OPTIONALly included in a ModifyConnection command
on an "XRM/MMO" line. This parameter is forbidden in all other MGCP
commands and responses. It can have one of the following four values:
- "REP" (report). This option commands the endpoint to report local
and remote metrics via this package. Local and remote session
parameters MAY also be reported.
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- "RES" (reset). This option commands the endpoint to reset the
local and remote metrics.
- "RR" (report and reset). Local and remote metrics are first
reported and then reset. Local and remote session parameters MAY also
be reported.
- "NULL". No metrics (local or remote) are reset or reported. This
value is equivalent to omitting the "XRM/MMO" line in the
ModifyConnection command. Of course, it is more efficient and,
therefore, preferable to omit the XRM/MMO line than to use it with an
explicit value of "NULL".
Note that the XRM/MMO parameter is specific to a ModifyConnection
command and its value does not persist following the end of a
ModifyConnection procedure. Therefore, this package does not define a
RequestedInfo value for auditing the XRM/MMO parameter.
Also note that metrics are not reported in response to a "REP" or "RR"
value of the XRM/MMO parameter if the value of the XRM/MCR local
connection option is "off" or "negotiate".
When the value of the XRM/MMO parameter is REP or RR, then the
available metrics are reported, as applicable, in the XRM/LVM and
XRM/RVM lines defined below. In order to comply with the ABNF rules in
[RFC 3435], the connection parameters line (the P: line) SHALL NOT be
included in a ModifyConnection response. However, metrics equivalent to
the connection parameters (Table 2) can be included in the XRM/LVM and
XRM/RVM lines.
The metrics that are reset and/or reported in response to the XRM/MMO
parameter include metrics associated with RTCP extended reports (Table
1) and metrics associated with RTCP sender reports and receiver reports
(Table 2).
See the section titled "Procedures for the resetting of metrics" for
the values assigned to metrics on reset.
The MMO parameter is needed to handle situations in which the call
agent invokes a feature that alters the media stream in a manner that
renders previous metrics values inapplicable to the new situation.
Examples are call transfer and call pick-up. It is also useful in
situations in which the call agent choreographs a media state
transition such as from voice to voice band data [ITU V.152] or fax
relay [ITU T.38].
2.3 The LVM and RVM Lines for reporting Local And Remote Metrics
The "XRM/LVM" and "XRM/RVM" lines are for the reporting of local and
remote metrics respectively. For example, an endpoint that is recording
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local metrics and has received remote metrics returns the following
lines in a DLCX response:
XRM/LVM: PLC=1, JBA=2, JBR=7 ...
XRM/RVM: PLC=0, JBA=0, JBR=3 ...
The parameters that MAY be reported in an XRM/LVM or XRM/RVM line fall
into the following categories:
- Parameters that define the metrics computation interval and
indicate whether any metrics resets have occurred since session
start. These are listed in Table 1.
- Parameters based on the VoIP metrics block [RFC 3611]. These are
listed in Table 1.
- Parameters based on Sender Reports and Receiver Reports [RFC
3550]. These are listed in Table 2.
- Parameters that describe the session. These are listed in Table
3. Many of these are based on SDP parameters such as those
specified in RFC 2327, RFC 2198, RFC 2733 etc.
Although Tables 1-3 include top-level definitions of these parameters,
some of their technical details MAY need to gleaned from the
references. For instance, the meaning of "standard" vs. "enhanced"
packet loss concealment must be obtained from [RFC 3611].
Note that the rationale for allowing the reporting of parameters based
on RTCP Sender Reports and Receiver Reports (Table 2) in the XRM/LVM
and XRM/RVM lines is two-fold:
- The connection parameters line (the P: line) in the MGCP base
protocol [RFC 3435] does not address remote metrics,
- The ABNF for packet loss in RFC 3435 is inconsistent with its RFC
3550-based textual definition of packet loss.
Note that the latency metric in the connection parameters line (the P:
line) is not included in Table 2 since it is already included in the
RTCP XR VoIP metrics block as the round trip delay. RTCP XR [RFC 3611]
allows any method for its computation, including methods based on [RFC
3550] or on the DLRR report block in [RFC 3611].
2.3.1 Inclusion/Omission of XRM/LVM and XRM/RVM parameters
In general, the inclusion of a parameter from Tables 1-3 in the
XRM/LVM or XRM/RVM lines is subject to:
- The availability of the parameter.
- Local policy regarding its inclusion.
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The following rules apply only to endpoints supporting this package:
DLCX/MDCX/AUCX rule for XRM/LVM: This rule applies to: (i) Endpoint
responses to call agent-initiated delete connection commands that are
targeted at a specific connection ID, (ii) Endpoint-initiated delete
connection commands, (iii) Endpoint responses to modify connection
commands that request session metrics via the XRM/MMO line, (iv)
Endpoint responses to audit connection commands that include "XRM/LVM"
in the RequestedInfo list. In each of these contexts, the XRM/LVM line
MUST be included by an endpoint supporting this package. Further, this
endpoint MUST compute at least one metric from the VoIP metrics block
(Table 1) and report it in the XRM/LVM line. All other parameters
(Tables 2 and 3) are completely OPTIONAL. Their inclusion depends on
local policy. The endpoint MUST omit all parameters that are not
computed locally rather than include them with dummy values (e.g. 127
for the various MOS parameters).
DLCX/MDCX rule for XRM/RVM: This rule applies to: (i) Endpoint
responses to call agent-initiated delete connection commands that are
targeted at a specific connection ID, (ii) Endpoint-initiated delete
connection commands, (iii) Endpoint responses to modify connection
commands that request session metrics via the XRM/MMO line. In each of
these contexts, the XRM/RVM line MUST be included if the remote peer
sends VoIP metrics blocks [RFC 3611] in RTCP Extended Reports. If the
remote device indicates that a particular VoIP metrics block parameter
is unavailable by sending a dummy value, then the dummy value MUST be
reported or the parameter MUST be omitted from the XRM/RVM: line. For
example, the dummy value of 127, if used, indicates that the signal
level, noise level, residual echo return loss, the various R-factors
and MOS estimates are unavailable. If the VoIP metrics block is not
received from the remote device, the endpoint MAY omit the XRM/RVM line
even if it has non-VoIP metrics block parameters to report in the
XRM/RVM line, such as metrics communicated via RTCP Sender Reports (SR)
and Receiver Reports (RR). The endpoint MAY, of course, include the
XRM/RVM line with known non-VoIP metrics block parameters (Tables 2 and
3) when the VoIP metrics block is not communicated by the remote end.
If the remote device indicates that a particular Sender/Receiver Report
parameter is unavailable by assigning it a dummy value (such as an
inter-arrival jitter of 0), the endpoint MAY either omit it in the
XRM/RVM line or assign it a dummy value.
AUCX rule for XRM/RVM: This rule applies to endpoint responses to audit
connection commands that include "XRM/RVM" in the RequestedInfo list.
In this context, the XRM/RVM line MUST be included even if no VoIP
metrics blocks are received in RTCP extended reports from the remote
device. This line MAY, however, be empty if no data pertaining to RTCP
XR VoIP metrics block (Table 1) is provided by the remote device.
Alternately, the local endpoint MAY include other known remote
Kumar et al Informational Page 14
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parameters (Tables 2 and 3) in the XRM/RVM line. If the remote device
sends the VoIP metrics block in RTCP Extended Reports and indicates
that a particular parameter is unavailable by sending a dummy value,
then the dummy value MUST be reported or the parameter MUST be omitted
from the XRM/RVM: line. If the remote device indicates that a
particular Sender/Receiver Report parameter is unavailable by assigning
it a dummy value (such as an inter-arrival jitter of 0), the endpoint
MAY either omit it in the XRM/RVM line or assign it a dummy value.
Rule for disallowed values: An endpoint receiving a disallowed value in
the VoIP metrics block MAY omit it in the XRM/RVM line. For example,
RFC 3611 does not allow a value of 60 in the 8-bit MOS-LQ field in the
VoIP metrics block.
2.3.2 XRM/LVM and XRM/RVM parameter values
The metrics used in the XRM/LVM and XRM/RVM lines (Tables 1-3) are,
except when otherwise noted, cumulative/average values over a
computation interval. This interval MAY be indicated via the OPTIONAL
computation interval (CMPI) parameter in Table 1. The CMPI parameter
indicates the period of time over which the XRM/LVM and XRM/RVM
parameters are computed. When the CMPI parameter is omitted, the
computation interval SHALL be defined as the period from the last
metrics reset (if any) up to the time of metrics reporting. If the CMPI
parameter is omitted and there has been no metrics reset, then the
computation interval SHALL be defined as the period from the start of
the session up to the time of metrics reporting.
The procedures for communicating voice quality metrics in the XRM/LVM
and XRM/RVM lines are invoked at one of the following instances:
- the DeleteConnection procedures are invoked end of a session,
- the ModifyConnection procedures are invoked end of a call phase,
such as when a call transfer is invoked or when the call agent
effects a media state transition (e.g. voice to voice band data)
- the AuditConnection procedures MAY be invoked whenever the call
agent needs a snapshot of the metrics. For instance, these
procedures MAY be invoked in response to event notifications from
the endpoint. Examples from RFC 3660 of such event notifications
are tone events ('ft' and 'mt') and quality alerts ('qa').
The general use is to not use the CMPI parameter for these procedures
and to reports metrics accumulated/averaged from the start of the
session or from the time of the last metrics reset, as applicable. One
exception where an explicit computation interval, conveyed via CMPI, is
RECOMMENDED is when the XRM/RVM lines are communicated in response to
Kumar et al Informational Page 15
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an audit connection that is associated per Section 2.2.2 with a quality
alert ('qa') event. In this case, the metrics values of interest are
those that pertain to some short interval (e.g. 1-5 seconds)
immediately before the threshold crossing occurrence.
The OPTIONAL Reset Occurrences ("ROC") parameter is useful in
indicating whether a prior reset of metrics has occurred. Although some
resets are commanded by the call agent via ModifyConnection procedures,
the endpoint is not precluded from autonomously resetting its VoIP
metrics. For example, the endpoint MAY reset its metrics when it
changes the mode of a media stream (e.g. from voice to voice band
data). Since such autonomous resets are not universally implemented, it
is beneficial to explicitly indicate their occurrence. For example,
ROC=1 in conjunction with an omitted CMPI parameter indicates that the
reported metrics have been accumulated/averaged for just the current
call phase and not for the entire call duration.
It is RECOMMENDED that the unstable or indeterminate periods at the
start and end of a call or call phase be factored out of metrics
computation. The duration of these guard bands is left to the
implementation.
Note that the metrics formats used by the call agent to store and
report metrics might be different from the formats used in this
package. For instance, the media gateway controller can convert the
binary representation [RFC 3611] of network packet loss into a fixed-
point percentage. Thus, an NLR value of 20 (Table 1) might be stored or
displayed as 7.81%.
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TABLE 1: PARAMETERS BASED ON THE RTCP XR VOIP METRICS BLOCK
---------------------------------------------------------
| Parameter | Code | Value |
| | | |
---------------------------------------------------------
|Computation | CMPI |The period, in milliseconds, from |
|Interval | |the start of metrics computation to|
| | |the time of metrics capture for |
| | |reporting purposes. This parameter |
| | |MAY be omitted. A value of 0 is |
| | |equivalent to its omission. |
| | |Expressed as an integer number. |
---------------------------------------------------------
|Reset | ROC |Whether the metrics have been |
|Occurrences | |one or more times since session |
| | |start. Expressed as a boolean with |
| | |"1" indicating one or more resets |
| | |and "0" indicating the absence of |
| | |of resets. These resets MAY be |
| | |commanded by the call agent, or |
| | |autonomously triggered by the |
| | |endpoint. This parameter is |
| | |OPTIONAL and MAY be omitted. Its |
| | |omission does not imply anything |
| | |regarding the occurrence of |
| | |metrics resets. |
---------------------------------------------------------
|Network | NLR |The proportion of packets lost |
|packet loss | |since the start of metrics |
|rate | |computation expressed as an 8-bit |
| | |binary fraction obtained by |
| | |dividing the number of packets lost|
| | |in the transmission path by the |
| | |total number of packets expected by|
| | |the receiver, multiplying this |
| | |value by 256 and taking the integer|
| | |portion of the result. Computed |
| | |after taking any loss mitigation |
| | |due to FEC and/or redundancy into |
| | |account. The numbers of duplicated |
| | |packets and discarded packets do |
| | |not enter into this calculation. |
---------------------------------------------------------
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---------------------------------------------------------
| Parameter | Code | Value |
| | | |
---------------------------------------------------------
|Jitter |JDR |The proportion of the packets |
|buffer | |discarded by the receiving |
|discard | |jitter buffer since the start of |
|rate | |metrics computation expressed as an|
| | |8-bit binary fraction obtained by |
| | |dividing the number of packets |
| | |discarded by the jitter buffer |
| | |by the total number of packets |
| | |expected by the receiver, |
| | |multiplying this value by 256 |
| | |and taking the integer portion |
| | |of the result. Computed |
| | |after taking any loss mitigation |
| | |due to FEC and/or redundancy into |
| | |account. The number of duplicate |
| | |packet discards does not enter |
| | |into this calculation. |
---------------------------------------------------------
|Burst loss | BLD |The average proportion (since the |
|density | |start of metrics computation) of |
| | |lost and discarded packets |
| | |occurring during burst periods |
| | |expressed as an 8 bit |
| | |binary fraction obtained by |
| | |dividing the sum of the number of |
| | |packets detected as lost during |
| | |burst periods and the number of |
| | |packets discarded by the jitter |
| | |buffer during burst periods by |
| | |the total number of packets |
| | |expected by the receiver, |
| | |multiplying this value by 256 |
| | |and taking the integer portion |
| | |of the result. Computed |
| | |after taking any loss mitigation |
| | |due to FEC and/or redundancy into |
| | |account. Duplicate packet discards |
| | |are excluded from this computation.|
---------------------------------------------------------
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---------------------------------------------------------
| Parameter | Code | Value |
| | | |
---------------------------------------------------------
|Gap loss | GLD |The average proportion (since the |
|density | |start of metrics computation) of |
| | |lost and discarded packets |
| | |occurring during gap periods |
| | |expressed as an 8 bit binary |
| | |fraction obtained by |
| | |dividing the sum of the number of |
| | |packets detected as lost during |
| | |gap periods and the number of |
| | |packets discarded by the jitter |
| | |buffer during gap periods by |
| | |the total number of packets |
| | |expected by the receiver, |
| | |multiplying this value by 256 |
| | |and taking the integer portion |
| | |of the result. Computed |
| | |after taking any loss mitigation |
| | |due to FEC and/or redundancy into |
| | |account. Duplicate packet discards |
| | |are excluded from this computation.|
---------------------------------------------------------
|Burst |BD |The average duration of the burst |
|duration | |periods, in milliseconds. Computed |
| | |from the start of metrics |
| | |computation. Bursts are determined |
| | |after taking any loss mitigation |
| | |due to FEC and/or redundancy into |
| | |account. |
---------------------------------------------------------
|Gap |GD |The average duration of the gap |
|duration | |periods, in milliseconds. Computed |
| | |from the start of metrics |
| | |computation. Bursts are determined |
| | |after taking any loss mitigation |
| | |due to FEC and/or redundancy into |
| | |account. |
---------------------------------------------------------
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---------------------------------------------------------
| Parameter | Code | Value |
| | | |
---------------------------------------------------------
|Round trip |RTD |The round trip delay, in |
|network | |milliseconds, between the RTP |
|delay | |interfaces of the local and |
| | |remote call endpoints. Valid |
| | |values MUST be greater than or |
| | |equal to 0 milliseconds. This |
| | |could be computed on the basis of |
| | |RFC 3550, or the DLRR report |
| | |block in [RFC 3611] or any other |
| | |valid method. The average of all |
| | |measurements since the start of |
| | |metrics computation SHOULD be used.|
---------------------------------------------------------
|End system |ESD |The end system (endpoint) delay, in|
|delay | |milliseconds, comprising the |
| | |encode, decode and jitter buffer |
| | |delay. Valid values MUST be |
| | |greater than or equal to 0 |
| | |milliseconds. The average of all |
| | |measurements since the start |
| | |metrics computation SHOULD be used.|
---------------------------------------------------------
|Signal |SL |The ratio of the average signal |
|level | |level to a 0 dBm0 reference, |
| | |expressed in dB. This is |
| | |expressed as an integer with an |
| | |OPTIONAL negative ("-") sign. |
| | |When the sign is omitted, a |
| | |positive value is assumed. |
| | |Typical values SHOULD generally |
| | |be between -15 and -20. |
| | |This metric SHALL be averaged |
| | |from the start of metrics |
| | |computation. A value of 127 |
| | |indicates that the parameter is |
| | |unavailable. |
---------------------------------------------------------
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---------------------------------------------------------
| Parameter | Code | Value |
| | | |
---------------------------------------------------------
|Noise |NL |The ratio of the silent period |
|level | |average background noise level to |
| | |a 0 dBm0 reference, in dB. This |
| | |is expressed as an integer without |
| | |a +ve or -ve sign. No sign is |
| | |necessary since this value MUST be |
| | |equal to or less than 0 dB. A value|
| | |of 127 indicates that the parameter|
| | |is unavailable. A +ve or -ve sign, |
| | |if used, SHALL be ignored. |
| | |The metric SHALL be averaged from |
| | |the start of metrics computation. |
---------------------------------------------------------
|Residual |RERL |The echo return loss after the |
|echo return | |effects of echo cancellation, in |
|loss | |dB. This value is expressed as |
| | |a positive integer without a |
| | |negative sign. A value of 127 |
| | |indicates that the parameter is |
| | |unavailable. Thus, RERL=23 |
| | |indicates an echo loss of 23 dB |
| | |after factoring in any echo |
| | |cancellation. This metric SHALL be |
| | |averaged from the start of metrics |
| | |computation. |
---------------------------------------------------------
|Minimum gap |GMN | The gap/burst transition |
|threshold | | threshold; the RECOMMENDED value |
| | | is 16. Values in the range 1 - - |
| | | 255 are permitted. |
---------------------------------------------------------
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---------------------------------------------------------
| Parameter | Code | Value |
| | | |
---------------------------------------------------------
|R-factor |NSR | Conversational quality |
|(Conversat- | | R-factor for the "inner segment", |
|-ional | | of the call, which is the VoIP |
|quality) | | session on which |
| | | the endpoint resides. This value |
| | | represents the conversational |
| | | quality of the RTP session |
| | | calculated per ITU G.107. Valid |
| | | values are greater than 0 and |
| | | less than or equal to 120. A |
| | | value of 127 indicates that the |
| | | parameter is unavailable. This |
| | | parameter is computed from the |
| | | start of metrics computation. |
| | | When the term 'R-factor' is used |
| | | without further qualification, |
| | | this parameter is implied. |
---------------------------------------------------------
|R-factor |RLQ | A value representing the |
|(Listening | | listening quality of |
|quality) | | the RTP session; |
| | | calculated as per ITU-T |
| | | Recommendation G.107. Valid |
| | | values are greater than 0 and |
| | | less than or equal to 120. A |
| | | value of 127 indicates that the |
| | | parameter is unavailable. This |
| | | parameter is computed from the |
| | | start of metrics computation. |
---------------------------------------------------------
|External |XSR | Listening quality R-factor for an |
|R-factor | | "external segment" which is any |
| | | call segment external to the VoIP |
| | | session on which the endpoint |
| | | resides. This value is |
| | | calculated per ITU-T |
| | | Recommendation G.107. Valid |
| | | values are greater than 0 and |
| | | less than or equal to 120. A |
| | | value of 127 indicates that the |
| | | parameter is unavailable. This |
| | | parameter is computed from the |
| | | start of metrics computation. |
---------------------------------------------------------
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---------------------------------------------------------
| Parameter | Code | Value |
| | | |
---------------------------------------------------------
|Estimated |MLQ | An estimated receiving end |
|MOS-LQ | | listening quality MOS. The |
| | | nominal range of MOS scores is |
| | | 1-5. Before being expressed in |
| | | MGCP, the MOS score is |
| | | multiplied by 10 and any |
| | | fractional part is truncated. |
| | | This results in an integer with |
| | | valid values in the range 10 - 50.|
| | | A value of 127 indicates that |
| | | the parameter is unavailable. |
| | | This parameter is computed from |
| | | the start of metrics computation. |
---------------------------------------------------------
|Estimated |MCQ | An estimated receiving end |
|MOS-CQ | | conversational quality MOS. The |
| | | nominal range of MOS scores is |
| | | 1-5. Before being expressed in |
| | | MGCP, the MOS score is |
| | | multiplied by 10 and any |
| | | fractional part is truncated. |
| | | This results in an integer with |
| | | valid values in the range 10 - 50.|
| | | A value of 127 indicates that |
| | | the parameter is unavailable. |
| | | This parameter is averaged from |
| | | the start of metrics computation. |
---------------------------------------------------------
|Packet loss |PLC | The type of packet loss |
|concealment | | concealment algorithm in use; |
|type | | SHOULD be one of the following |
| | | enumeration values: |
| | | 0 - Unspecified |
| | | 1 - Disabled |
| | | 2 - Enhanced |
| | | 3 - Standard |
---------------------------------------------------------
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---------------------------------------------------------
| Parameter | Code | Value |
| | | |
---------------------------------------------------------
|Jitter |JBA | The adaptability of the jitter |
|Buffer | | buffer. Should be one of the |
|Adaptability| | following enumeration values: |
| | | 0 - Unknown |
| | | 1 - Reserved |
| | | 2 - Non-adaptive |
| | | 3 - Adaptive |
---------------------------------------------------------
|Jitter |JBR | The jitter buffer adjustment |
|Buffer | | rate. Value is between 0 and |
|Rate | | 15. |
---------------------------------------------------------
|Nominal |JBN | Current nominal delay in |
|jitter | | milliseconds that corresponds to |
|buffer | | the nominal jitter buffer delay |
|delay | | for packets that arrive exactly |
| | | on time. The last computed value |
| | | is used. |
---------------------------------------------------------
|Maximum |JBM | Current maximum delay in |
|jitter | | milliseconds that corresponds to |
|buffer | | the earliest arriving packet |
|delay | | that would not be discarded. In |
| | | simple queue implementations, |
| | | this MAY correspond to the |
| | | nominal jitter buffer delay. In |
| | | adaptive jitter buffer |
| | | implementations, this value MAY |
| | | dynamically vary up to the |
| | | absolute maximum jitter buffer |
| | | delay (see below). The last |
| | | computed value is used. |
---------------------------------------------------------
|Absolute |JBS | Absolute maximum delay in |
|maximum | | milliseconds that an adaptive |
|jitter | | jitter buffer can reach under |
|buffer | | worst case conditions. This is |
|delay | | a configured parameter. For fixed |
| | | jitter buffers, this must be set |
| | | to the maximum jitter buffer |
| | | delay. |
---------------------------------------------------------
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---------------------------------------------------------
| Parameter | Code | Value |
| | | |
---------------------------------------------------------
|MOS-LQ |MLES | Algorithm used to estimate the |
|Estimation | | the MOS-LQ metric, MLQ. This |
|Algorithm | | is expressed as a human-readable |
| | | character string with an |
| | | unrestricted set of values. |
---------------------------------------------------------
|MOS-CQ |MCES | Algorithm used to estimate the |
|Estimation | | the MOS-CQ metric, MCQ. This |
|Algorithm | | is expressed as a human-readable |
| | | character string with an |
| | | unrestricted set of values. |
---------------------------------------------------------
|R-factor |RFES | Algorithm(s) used to estimate |
|Estimation | | the one or more R-factors |
|Algorithm(s)| | reported. This is expressed as a |
| | | human-readable character string |
| | | with an unrestricted set of |
| | | values. This string MAY contain |
| | | separate descriptions for the |
| | | algorithms pertaining to the |
| | | R-factors NSR, MLQ and XSR |
| | | described above. |
---------------------------------------------------------
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TABLE 2: PARAMETERS BASED ON RTCP SENDER AND RECEIVER REPORTS
---------------------------------------------------------
| Parameter | Code | Value |
| | | |
---------------------------------------------------------
|Packets sent |PS | The number of packets that were |
| | | were sent on the connection since|
| | | the start of metrics computation.|
| | | Does not include any FEC packets |
| | | sent on a different SSRC or port.|
---------------------------------------------------------
|Octets sent |OS | The number of payload octets that|
| | | were sent out on the connection |
| | | since the start of metrics |
| | | computation. Header and padding |
| | | octets are not included. Nor are |
| | | octets in redundant or FEC |
| | | payloads/packets. |
---------------------------------------------------------
|Packets |PR | The number of packets that were |
|received | | were received on the connection |
| | | since the start of metrics |
| | | computation. Does not include any|
| | | FEC packets received on a |
| | | different SSRC or port. |
---------------------------------------------------------
|Octets |OR | The number of payload octets that|
|received | | were received on the |
| | | connection since the start of |
| | | metrics computation. Header and |
| | | padding octets are not included. |
| | | Nor are octets in redundant or |
| | | FEC payloads/packets. |
---------------------------------------------------------
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---------------------------------------------------------
| Parameter | Code | Value |
| | | |
---------------------------------------------------------
|Packets |PL | The total number of media packets|
|lost | | that have been lost since the |
| | | beginning of metrics computation.|
| | | This is defined to be the number |
| | | of packets expected less the |
| | | number of packets actually |
| | | received, where the number of |
| | | packets received includes any |
| | | which are late or duplicates. |
| | | Thus packets that arrive late are|
| | | not counted as lost, and the loss|
| | | MAY be negative if there are |
| | | duplicates. This metric does not |
| | | take any loss mitigation due to |
| | | redundancy or FEC into account. |
---------------------------------------------------------
|Inter- |IAJ | Per [RFC 3550], the inter-arrival|
|arrival | | jitter is defined to be |
|jitter | | the mean deviation (smoothed |
| | | absolute value) of the difference|
| | | in packet spacing at the |
| | | the receiver compared to the |
| | | sender for a pair of packets. |
| | | This metric is averaged from the |
| | | start of computation and is |
| | | expressed in milliseconds. |
| | | The corresponding connection |
| | | parameter in [RFC 3435] is JI. |
---------------------------------------------------------
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TABLE 3: SESSION DESCRIPTION PARAMETERS
---------------------------------------------------------
| Parameter | Code | Value |
| | | |
---------------------------------------------------------
|SSRC |SSRC | SSRC of the measured stream. |
| | | If it changes due to a collision,|
| | | the last value is used. |
| | | Represented as the decimal |
| | | equivalent of a 32-bit word. |
---------------------------------------------------------
|Source IP |IPAS | The source IP address for |
|address | | the stream under measurement |
---------------------------------------------------------
|Source IP |IPTS | This indicates whether the source|
|address type | | IP address is IP version 4 or 6. |
---------------------------------------------------------
|Destination |IPAD | The destination IP address for |
|IP address | | the stream under measurement. |
---------------------------------------------------------
|Destination |IPTD | This indicates whether the |
|IP address | | destination IP address is |
|type | | IP version 4 or 6. |
---------------------------------------------------------
|Source |RTUS | The source RTP/UDPTL port for |
|RTP/UDPTL | | the stream under measurement. |
|port | | |
---------------------------------------------------------
|Destination |RTUD | The destination RTP/UDPTL port |
|RTP/UDPTL | | for the stream under measurement|
|port | | |
---------------------------------------------------------
|Source |RTCS | The source RTCP port for |
|RTCP port | | the stream under measurement. |
---------------------------------------------------------
|Destination |RTCD | The destination RTCP port for |
|RTCP port | | the stream under measurement. |
---------------------------------------------------------
|Codec |VCD | The last voice or voice band data|
|(voice or | | codec used. This is expressed |
|voice band | | as a character string |
|data) | | corresponding to a MIME subtype |
| | | from [IANA RTP] (e.g. " G726-40")|
| | | or as an experimental codec name |
| | | starting with "X-". |
---------------------------------------------------------
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---------------------------------------------------------
| Parameter | Code | Value |
| | | |
---------------------------------------------------------
|Secondary |VCDS | In the case of RFC 2198 |
|codec | | redundancy, the secondary codec |
|(voice or | | used. Semantics identical to |
|voice band | | primary codec. (See VCD parameter|
|data) | | above.) |
---------------------------------------------------------
|Media |MMOD | This indicates whether the |
|Mode | | the media carried by the session |
| | | is audio ("a"), voice band data |
| | | ("v"), fax relay ("f"), modem |
| | | relay ("m") or text relay ("t"). |
| | | The last mode is indicated by |
| | | this parameter. Audio and text |
| | | relay packets MAY be interleaved |
| | | in the text relay mode. |
| | | Voice band data, fax relay, modem|
| | | relay and text relay are defined |
| | | in [ITU V.152], [ITU T.38], |
| | | [ITU V.150.1] and [ITU V.151] |
| | | respectively. All of these media,|
| | | with the exception of modem |
| | | relay, can be transported via |
| | | RTP. |
---------------------------------------------------------
|Sample rate |SMPL | The rate at which media is |
|(voice or | | is sampled (samples per second) |
|voice band | | for the last voice or voice band |
|data) | | data codec used. |
---------------------------------------------------------
|Codec frame |FRSZ | The number of octets in a codec |
|size | | frame for the last voice or |
|(voice or | | voice band data codec. |
|voice band | | |
|data) | | |
---------------------------------------------------------
|RTP payload |PLSZ | The number of octets in a the RTP|
|size | | packet payload for the |
|(voice or | | last voice or voice band data |
|voice band | | codec used. |
|data) | | |
---------------------------------------------------------
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---------------------------------------------------------
| Parameter | Code | Value |
| | | |
---------------------------------------------------------
|Packetization|PKRT | The number of RTP packets per |
|rate | | second for the last voice or |
|(voice or | | voice band data codec used. |
|voice band | | |
|data) | | |
---------------------------------------------------------
|Silence |SSUP | This indicates whether silence |
|Suppression | | suppression, also known as Voice |
|State | | Activity Detection (VAD)is |
| | | enabled. The last value is used. |
| | | It is assumed that silence |
| | | suppression is accompanied by |
| | | comfort noise generation. |
---------------------------------------------------------
|Echo |ECAN | This indicates whether echo |
|Cancellation | | cancellation is enabled. The last|
|State | | value is used. |
---------------------------------------------------------
|Redundancy |VRED | This indicates whether |
|State | | redundancy [RFC 2198] was used |
|(voice or | | for the last voice or voice band |
|voice band | | data codec. |
|data). | | |
---------------------------------------------------------
|FEC State |VFEC | This indicates whether |
|(voice or | | Forward Error Correction |
|voice band | | [RFC 2733] was used for the last |
|data). | | voice or voice band data codec. |
| | | RFC 2733 FEC MAY be used in |
| | | conjunction with RFC 2198 |
| | | redundancy. |
---------------------------------------------------------
|SSRC of the |FSRC | SSRC of the received FEC stream, |
|received FEC | | if any. If it changes due to a |
|stream | | collision, the last value is |
| | | used. Represented as the decimal |
| | | equivalent of a 32-bit word. |
---------------------------------------------------------
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---------------------------------------------------------
| Parameter | Code | Value |
| | | |
---------------------------------------------------------
|Destination |IPAF | The destination IP address for |
|IP address | | the FEC stream received with the |
|for FEC | | RTP media stream. Identical to |
| | | IPAD (above) if the FEC stream |
| | | is sent to the same |
| | | IP address as the media |
| | | stream under measurement. In |
| | | either case, the IP address type |
| | | is per the IPTD parameter above. |
---------------------------------------------------------
|Destination |RTFD | The destination RTP port for any |
|RTP port | | FEC stream received with the RTP |
|for FEC | | media stream. Identical to |
| | | RTUD (above) if the FEC stream |
| | | is sent to the same |
| | | RTP port as the media |
| | | stream under measurement. |
---------------------------------------------------------
2.3.3 Procedures for the resetting of metrics
The metrics associated with the XRM/LVM and XRM/RVM lines MAY be
reset/reinitialized in response to the XRM/MMO parameter in a
ModifyConnection command from the call agent, or autonomously by the
endpoint when a media state transition (e.g. from voice to voice band
data) occurs. Also, as a rule an SSRC change SHOULD NOT reset VQ
metrics. This is consistent with the base MGCP protocol [RFC 3435].
SSRC can occur due to rare collision events [RFC 3550].
The impact of reset depends on the semantics of each individual
parameter. In general, the following actions are taken during metrics
reset:
- All counters are set to 0.
- Measurements that are not counts are set to an unknown value.
For example, 127 indicates an unknown value for the signal level,
noise level, RERL, the various R-factors and MOS estimates.
Further, any computations of the average, minimum and maximum
values associated with these measurements are restarted.
- The Reset Occurrences (ROC) parameter is not changed.
- Configuration parameters such as the absolute maximum jitter
buffer delay and session-related parameters (Table 3) reflect current
values.
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2.3.4 Impact redundancy and FEC on packet loss computations
The packet loss and discard parameters based on the RTCP XR VoIP
metrics block [RFC 3611] are computed after taking redundancy and FEC
into account. Thus, the following parameters from Table 1 SHALL be
computed after taking the effect of redundancy (e.g. RFC 2198) and/or
FEC (e.g. RFC 2733) into account:
- Network packet loss rate, NLR
- Jitter buffer discard rate, JDR
- Burst loss density, BLD, and burst duration, BD
- Gap loss density, GLD, and gap duration, GD
By contrast, the packet receipt and packet loss parameters based on
RTCP Sender Reports (SR) and Receiver Reports (RR) do not take
redundancy or FEC into account. They are meant to be indicative of
impairments "on the wire" than in end-to-end service. Thus, the packets
lost (PL) parameter in Table 2 does not take into account any loss
mitigation due to redundancy (e.g. RFC 2198) or FEC (e.g. RFC 2733)
into account.
2.3.5 Parameter Extension Mechanism
The XRM/LVM and XRM/RVM lines MAY include vendor extension parameters
that begin with an "X-". An MGCP entity that receives an extension
parameter in these lines MUST ignore it if it cannot understand it.
Since these parameters introduce an unmanaged name space, there is a
potential for name clashing. Vendors are consequently encouraged to
include some vendor specific string, e.g. vendor name or stock ticker
symbol, in their vendor extensions. For example, if Acme Widgets, a
fictional company, wishes to use metric "ABC", it is preferable to use
the name "X-acmewidgets-ABC" rather than "X-ABC".
Vendors MAY register new metrics in an IANA registry of MGCP names of
VoIP metrics. The "X-" prefix is not germane to a metric following
registration.
2.3.6 Formal Syntax of VoIP Metrics Package
The following describes the ABNF encoding [RFC 2234] for the parameters
defined in this package. Per MGCP conventions, all parameters defined
in this package are case-insensitive.
The standard tokens SP, WSP, ALPHA, DIGIT, HEXDIG etc. are per RFC
2234.
MediaMetricsOption = "XRM/MMO:" *WSP ("REP"/"RES"/"RR")
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RemoteVoIPMetrics = "XRM/LVM:" *WSP [VoIPMetric *("," *WSP
VoIPMetric)]
; zero or more local metrics
; zero metrics are permitted in AUCX responses
RemoteVoIPMetrics = "XRM/RVM:" *WSP [VoIPMetric *("," *WSP
VoIPMetric)]
; zero or more remote metrics
VoIPMetric = ComputationInterval
/ ResetOccurrences
/ NetworkPacketLossRate
/ JitterBufferDiscardRate
/ BurstLossDensity
/ GapLossDensity
/ BurstDuration
/ GapDuration
/ RoundTripNetworkDelay
/ EndSystemDelay
/ SignalLevel
/ NoiseLevel
/ ResidualEchoReturnLoss
/ MinimumGapThreshold
/ RFactor-CQ
/ RFactor-LQ
/ ExternalRFactor
/ EstimatedMOS-LQ
/ EstimatedMOS-CQ
/ PacketLossConcealmentType
/ JitterBufferAdaptability
/ JitterBufferRate
/ JitterBufferNominal
/ JitterBufferMax
/ JitterBufferAbsMax
/ MOSLQEstimationAlgorithm
/ MOSLQEstimationAlgorithm
/ RfacorEstimationAlgorithms
/ InterArrivalJitter
/ PacketsSent
/ OctetsSent
/ PacketsReceived
/ OctetsReceived
/ PacketsLost
/ SSRC
/ SourceIPAddress
/ SourceIPAddressType
/ DestinationIPAddress
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/ DestinationIPAddressType
/ SourceRTPPort
/ DestinationRTPPort
/ SourceRTCPPort
/ DestinationRTCPPort
/ VoiceOrVBDprimaryCodec
/ VoiceOrVBDsecondaryCodec
/ MaxCharacterRate
/ MediaMode
/ SampleRate
/ CodecFrameSize
/ RTPpayloadSize
/ PacketizationRate
/ SilenceSuppression
/ EchoCancellation
/ RFC2198RedundancyForVoiceOrVBD
/ RFC2733FECforVoiceOrVBD
/ FECstreamSSRC
/ FECDestinationIPAddress
/ FECDestinationRTPPort
/ UnregisteredExtension
/ RegisteredExtension
ComputationInterval = "CMPI" = 1*20(DIGIT);
ResetOccurrences = "ROC" = "0"/"1";
NetworkPacketLossRate = "NLR=" 1*3(DIGIT) ;0-255
JitterBufferDiscardRate = "JDR=" 1*3(DIGIT) ;0-255
BurstLossDensity = "BLD=" 1*3(DIGIT) ; 0-255
GapLossDensity = "GLD=" 1*3(DIGIT) ; 0-255
BurstDuration = "BD=" 1*5(DIGIT) ; 0-65535
GapDuration = "GD=" 1*5(DIGIT) ; 0-65535
MinimumGapThreshold = "GMN=" 1*3(DIGIT) ; 1-255
RoundTripNetworkDelay = "RTD=" 1*4(DIGIT) ;
EndSystemDelay = "ESD=" 1*4(DIGIT) ;
SignalLevel = "SL=" ["-"] 1*3(DIGIT) ;-128 to 127
NoiseLevel = "NL=" 1*3(DIGIT)
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; 0 to 127, indicates dB below 0 dBm0
ResidualEchoReturnLoss = "RERL=" 1*3(DIGIT) ;0-127
RFactor-CQ = "NSR=" 1*3(DIGIT)
;0-120, or 127
RFactor-LQ = "RLQ=" 1*3(DIGIT)
;0-120, or 127
ExternalRFactor = "XRF=" 1*3(DIGIT) ;0-120, or 127
EstimatedMOS-LQ = "MLQ=" 1*3(DIGIT) ; 10-50, or 127
EstimatedMOS-CQ = "MCQ=" 1*3(DIGIT) ; 10-50, or 127
PacketLossConcealmentType= "PLC=" ("0" / "1" / "2" / "3")
JitterBufferAdaptability = "JBA=" ("0" / "1" / "2" / "3")
JitterBufferRate = "JBR=" 1*2(DIGIT) ;0-15
JitterBufferNominal = "JBN=" 1*5(DIGIT) ;0-65535
JitterBufferMax = "JBM=" 1*5(DIGIT) ;0-65535
JitterBufferAbsMax = "JBS=" 1*5(DIGIT) ;0-65535
MOSLQEstimationAlgorithm = "MLES=" ALPHA 1*127 (permittedchar)
;first character must be alphabetic
MOSCQEstimationAlgorithm = "MCES=" ALPHA 1*127 (permittedchar)
;first character must be alphabetic
RfactorAlgorithms = "RFES=" ALPHA 1*127 (permittedchar)
;first character must be alphabetic
InterArrivalJitter = "IAJ=" 1*3(DIGIT) ;
PacketsSent = "PS=" 1*9(DIGIT);
OctetsSent = "OS=" 1*9(DIGIT);
PacketsReceived = "PR=" 1*9(DIGIT);
OctetsReceived = "OR=" 1*9(DIGIT);
PacketsLost = "PL=" ["-"] 1*9(DIGIT);
SSRC = "SSRC=" 1*10 (DIGIT); 0-4,294,967,296
SourceIPAddressType = "IPTS=" ("IPv4" / "IPv6")
DestinationIPAddressType = "IPTD=" ("IPv4" / "IPv6")
SourceIPAddress = "IPAS=" (IPv4address / IPv6address)
; IPv4address and IPv6address defined in RFC 3261
DestinationIPAddress = "IPAD=" (IPv4address / IPv6address)
; IPv4address and IPv6address defined in RFC 3261
SourceRTPPort = "RTUS=" 1*5(DIGIT) ;1024-65535 inclusive
DestinationRTPPort = "RTUD=" 1*5(DIGIT)
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;1024-65535 inclusive
SourceRTCPPort = "RTCS=" 1*5(DIGIT) ;1024-65535 inclusive
DestinationRTCPPort = "RTCD=" 1*5(DIGIT)
;1024-65535 inclusive
VoiceOrVBDprimaryCodec = "VCD=" ALPHA 1*31 (permittedchar)
;first character must be alphabetic
VoiceOrVBDsecondaryCodec = "VCDS=" ALPHA 1*31 (permittedchar)
;first character must be alphabetic
MaxCharacterRate = "CPS=" 1*2 (DIGIT)
MediaMode = "MMOD=" "a" / "v" / "f" / "m" / "t" / ALPHA
; audio, voice band data, fax relay, modem relay, text relay
; the token ALPHA is to permit additional future definitions
SampleRate = "SMPL=" 1*7 (DIGIT)
CodecFrameSize = "FRSZ=" 1*3 (DIGIT)
RTPpayloadSize = "PLSZ=" 1*3 (DIGIT)
PacketizationRate = "PKRT=" 1*5 (DIGIT)
SilenceSuppression = "SSUP=" ("on" / "off")
EchoCancellation = "ECAN=" ("on" / "off")
RFC2198RedundancyForVoiceOrVBD = "VRED=" ("on" / "off")
RFC2733FECforVoiceOrVBD = "VFEC=" ("on" / "off")
FECstreamSSRC = "FSRC=" 1*10 (DIGIT); 0-4,294,967,296
FECDestinationIPAddress = "IPAF=" (IPv4address / IPv6address)
; IPv4address and IPv6address defined in RFC 3261
FECDestinationRTPPort = "RTFD=" 1*5(DIGIT)
;1024-65535 inclusive
UnregisteredExtension = "X-" ExtensionName "=" ExtensionVal
RegisteredExtension = ExtensionName "=" ExtensionVal
ExtensionName = 1*32 (ALPHA)
ExtensionVal = 1*32 (alphanum)
;More precise definition in extension specifications
alphanum = ALPHA / DIGIT
permittedchar = alphanum / permittedspecialchar
permittedspecialchar = "-" / "_" / "." / "!" / "~" / "*" /
"'" / "(" / ")" / SP
2.3.7 Impact of media state changes on VoIP metrics
The RECOMMENDED endpoint behavior when the media state changes (e.g.
from voice to voice band data or vice versa) is to reset/reinitialize
the parameters in Tables 1, 2 and 3. Section 2.3.3 describes the
procedures for this resetting/reinitialization.
However, it is recognized that some endpoints MAY continue to
accumulate or average parameters across media state changes. For
example, an endpoint MAY continue to accumulate parameters such as
packet loss rate (NLR) and to average parameters such as round trip
delay (RTD)across transitions between voice and voice band data. If
metrics computation is carried over from one media state to another,
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then metrics and parameters that do not apply to the new state (such as
MOS-LQ in the case of fax relay)SHOULD be placed in a suspended state
until another state transition (such as fax relay to voice in the case
of MOS-LQ) renders them applicable again. If any reporting activity
occurs during their suspension, the last applicable value SHOULD be
conveyed.
If the session is initially established in a mode for which some of the
metrics and parameters in Tables 1-3 do not apply, then these
parameters MUST be omitted or dummied out (per the rules in Section
2.3.1) for any reporting while they are inapplicable. For example, if
an endpoint uses this package to convey the metrics for a session that
is currently in the T.38 fax relay mode in which it was initially
established, then the MOS-LQ parameter MUST be omitted or dummied out
(by setting it to 127).
2.3.8 Applicability of VoIP metrics to Voice Band Data
For the definition of voice band data, see [ITU V.152]. Voice band data
sessions are RTP sessions. RTCP is REQUIRED in conjunction with any RTP
session [RFC 3550]. However, the various blocks in RTCP-XR, such as the
VoIP metrics block, are not. They must be negotiated at session
establishment.
Also note that, since this document is focused on voice, it lacks key
voice band data metrics.
The parameters from the RTCP XR VoIP metrics block (Table 1) and the
RTCP Sender/Receiver Reports (Table 2) MAY be applied to voice band
data. The session description parameters (Table 3) are also applicable
to voice band data.
Note that the utility of the various MOS scores and R-factors might be
limited for voice band data since there is no correlation of the
various MOS scores and R-factors with the end-users' perspective of the
quality of the modem or fax transmission. Notwithstanding, some
implementations MAY elect to use the MLQ metric as an indicator of the
transmission quality of voice band data channel.
For some voice band data sessions, echo cancellation is turned off. For
others, it is turned on. If echo cancellation is off, then RERL reverts
to the Echo Return Loss of the hybrid transformer or acoustic coupling
path. However, some implementations might not measure this parameter in
the absence of an active echo canceller. In such cases, this parameter
will be omitted in the XRM/LVM and XRM/RVM lines, or set to a dummy
value (127) in the XRM/RVM line.
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Many voice band data sessions [ITU V.152] use fixed-length jitter
buffers. If this is the case, then this will be reflected in the JBA
parameter (set to "non-adaptive"), the JBR parameter (set to 0) and the
JBS parameter (set to JBM).
2.3.9 Applicability of VoIP metrics to Fax Relay and Text Relay
Since this document is focused on voice, it lacks key metrics related
to fax [ITU T.38], text [ITU V.151] and modem [ITU V.150.1] relay.
Other specifications such as [FAX PKG] will address in a
comprehensive manner the reporting via MGCP of the metrics
that pertain to the various relay modes.
However, it is instructive to examine how the parameters defined in
this document apply to various relay mechanisms. Tables 4, 5 and 6
examine the relevance of the metrics and session parameters listed in
Tables 1, 2 and 3 to fax relay [ITU T.38]. Tables 7, 8 and 9 examine
the relevance of the metrics and session parameters listed in Tables 1,
2 and 3 to text relay [ITU V.151].
Note that the basic definitions of parameters from Tables 1, 2, and 3
are not repeated in Tables 4 through 9. All that these tables address
is the applicability of these parameters to fax relay and text relay.
Parameters from Tables 1, 2 and 3 that are not relevant to fax relay
are not listed in Tables 4, 5 and 6. Similarly, parameters from Tables
1, 2 and 3 that are not relevant to text relay are not listed in Tables
7, 8 and 9.
Relay sessions (fax or text) get established in two ways. In the first
case, the session is established as a fax or text relay session during
call set-up. In the second case, it is established as an audio session
which is transitioned, at media gateways, to fax relay or text relay
on the receipt of certain tones or stimuli. A variant of this second
case involves a transition from audio to voice band data and
subsequently to fax relay or text relay.
RTCP is REQUIRED in conjunction with any RTP session [RFC 3550]. This
includes RTP-based fax relay and RTP-based text relay. However, the
various blocks in RTCP-XR, such as the VoIP metrics block, are not.
They must be negotiated at session establishment. Note that, in
contrast to RTP-based relay sessions, RTCP is not applicable to non-RTP
relay such as UDTPL-based fax relay [ITU T.38].
Note that burst parameters (burst loss density, gap loss density, burst
duration, gap duration and the minimum gap threshold) are not germane
to relay mechanisms (such as fax relay or text relay) since such relay
streams are not continuous for significant periods of time. Any burst
characterization is, therefore, likely to be deceptive.
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Also note that the various R-factors and MOS scores in Table 1 are not
applicable to baseband data transmission such as fax relay or data
relay.
TABLE 4: PARAMETERS FROM TABLE 1 THAT ARE APPLICABLE TO FAX RELAY
+-----------------+-----------------------------------------------+
| PARAMETER | APPLICABILITY TO FAX RELAY |
| from Table 1 | |
+-----------------+-----------------------------------------------+
|Network packet |Loss refers to fax relay packets which MAY be |
|loss rate(NLR) |UDPTL or RTP [ITU T.38]. Computed after FEC |
| |and/or redundancy processing. As described |
| |in [ITU T.38], the FEC and redundancy |
| |schemes applicable to UDPTL fax relay and RTP |
| |fax relay are different. |
+-----------------+-----------------------------------------------+
|Jitter buffer |Discards refer to fax relay packets which MAY |
|discard rate |be UDPTL or RTP [ITU T.38]. Computed after FEC |
|(JDR) |and/or redundancy processing. As described |
| |in [ITU T.38], the FEC and redundancy |
| |schemes applicable to UDPTL fax relay and RTP |
| |fax relay are different. |
+-----------------+-----------------------------------------------+
|Round trip |Not very useful for fax relay sessions. Can be |
|network delay |computed using RTCP for RTP-based fax relay. |
|(RTD) |There is no standard mechanism for round-trip |
| |delay computation in the case of UDPTL-based |
| |fax relay. |
-------------------------------------------------------------------
|End system delay | Not very useful for fax relay sessions. |
|(ESD) | |
+-----------------+-----------------------------------------------+
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TABLE 5: PARAMETERS FROM TABLE 2 THAT ARE APPLICABLE TO FAX RELAY
+-----------------+-----------------------------------------------+
| PARAMETER | APPLICABILITY TO FAX RELAY |
| from Table 2 | |
+-----------------+-----------------------------------------------+
|Packets sent |Refers to fax relay packets, which MAY be UDPTL|
|(PS) |or RTP. Does not include any RTP FEC packets |
| |sent on a different SSRC or port. |
+-----------------+-----------------------------------------------+
|Octets sent |Refers only to T.4 image octets in |
|(OS) |primary UDPTL/RTP payloads/packets. Octets in |
| |redundant/FEC payloads/packets are not counted.|
+-----------------+-----------------------------------------------+
|Packets |Refers to fax relay packets, which MAY be UDPTL|
|Received |or RTP. Does not include any RTP FEC packets |
|(PR) |received on a different SSRC or port. |
+-----------------+-----------------------------------------------+
|Octets received |Refers only to T.4 image octets in |
|(OR) |primary UDPTL/RTP payloads/packets. Octets in |
| |redundant/FEC payloads/packets are not |
| |counted. |
+-----------------+-----------------------------------------------+
|Packets lost |Refers to lost UDPTL/RTP fax relay packets |
|(PL) |without taking into account any loss mitigation|
| |due to redundancy or FEC. As described |
| |in [ITU T.38], the FEC and redundancy |
| |schemes applicable to UDPTL fax relay and RTP |
| |fax relay are different. |
+-----------------+-----------------------------------------------+
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TABLE 6: PARAMETERS FROM TABLE 3 THAT ARE APPLICABLE TO FAX RELAY
+-----------------+-----------------------------------------------+
| PARAMETER | APPLICABILITY TO FAX RELAY |
| from Table 3 | |
+-----------------+-----------------------------------------------+
|SSRC |Not applicable to UDPTL-based fax relay. For |
|(SSRC) |RTP-based fax relay, this is the SSRC of the |
| |RTP fax relay stream. |
+-----------------+-----------------------------------------------+
|Source IP address| Applicable to fax relay sessions. |
|(IPAS) | |
+-----------------+-----------------------------------------------+
|Source IP address| Applicable to fax relay sessions. |
|type (IPTS) | |
+-----------------+-----------------------------------------------+
|Destination IP | Applicable to fax relay sessions. |
|address (IPAD) | |
+-----------------+-----------------------------------------------+
|Destination IP | Applicable to fax relay sessions. |
|address type | |
|(IPTD) | |
+-----------------+-----------------------------------------------+
|Source RTP/UDPTL | Applicable to fax relay sessions. |
|port (RTUS) | |
+-----------------+-----------------------------------------------+
|Destination | Applicable to fax relay sessions. |
|RTP/UDPTL port | |
|(RTUD) | |
+-----------------+-----------------------------------------------+
|Source RTCP | Applicable to RTP-based fax relay sessions. |
|port (RTCS) | |
+-----------------+-----------------------------------------------+
|Destination RTCP | Applicable to RTP-based fax relay sessions. |
|port (RTCD) | |
+-----------------+-----------------------------------------------+
|Media Mode (MMOD)| Applicable to fax relay sessions. |
+-----------------+-----------------------------------------------+
|SSRC of received |Applicable to RTP-based fax relay if FEC is |
|FEC stream |used in conjunction with it. |
|(FSRC) | |
+-----------------+-----------------------------------------------+
|Destination IP |Applicable to RTP-based fax relay if FEC is |
|address for FEC |used in conjunction with it. |
|(IPAF) | |
+-----------------+-----------------------------------------------+
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+-----------------+-----------------------------------------------+
| PARAMETER | APPLICABILITY TO FAX RELAY |
| from Table 3 | |
+-----------------+-----------------------------------------------+
|Destination RTP |Applicable to RTP-based fax relay if FEC is |
|port for FEC |used in conjunction with it. |
|(RTFD) | |
+-----------------+-----------------------------------------------+
TABLE 7: PARAMETERS FROM TABLE 1 THAT ARE APPLICABLE TO TEXT RELAY
+-----------------+-----------------------------------------------+
| PARAMETER | APPLICABILITY TO TEXT RELAY |
| from Table 1 | |
+-----------------+-----------------------------------------------+
|Network packet |Packet loss is computed for a stream of packets|
|loss rate(NLR) |sharing an SSRC and, therefore, the same |
| |sequence number space. This is either a |
| |stream of RTP-based text relay packets or an |
| |interleaved stream of audio and text relay |
| |packets. This loss rate is computed after FEC |
| |and/or redundancy processing. |
+-----------------+-----------------------------------------------+
|Jitter buffer |The discard rate is computed for a stream of |
|discard rate |packets sharing an SSRC and, therefore, the |
|(JDR) |same sequence number space. This is either a |
| |stream of RTP-based text relay packets or an |
| |interleaved stream of audio and text relay |
| |packets. This loss rate is computed after FEC |
| |and/or redundancy processing. |
+-----------------+-----------------------------------------------+
|Round trip |Applicable to text relay sessions. |
|network delay | |
|(RTD) | |
+-----------------+-----------------------------------------------+
|End system delay |Applicable to text relay sessions. |
|(ESD) | |
+-----------------+-----------------------------------------------+
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TABLE 8: PARAMETERS FROM TABLE 2 THAT ARE APPLICABLE TO TEXT RELAY
+-----------------+-----------------------------------------------+
| PARAMETER | APPLICABILITY TO TEXT RELAY |
| from Table 2 | |
+-----------------+-----------------------------------------------+
|Packets sent |Refers to text relay packets. If these packets |
|(PS) |share an SSRC with an interleaved audio stream,|
| |it refers to the composite stream. Does not |
| |include any FEC packets sent on a different |
| |SSRC or port. |
+-----------------+-----------------------------------------------+
|Octets sent |Refers only to payload octets in primary RTP |
|(OS) |payloads/packets. Payload octets include text |
| |octets and audio octets sent with the same |
| |SSRC. Octets in redundant or FEC |
| |payloads/packets are not counted. |
+-----------------+-----------------------------------------------+
|Packets received |Refers to text relay packets. If these packets |
|(PR) |share an SSRC with an interleaved audio stream,|
| |it refers to the composite stream. Does not |
| |include any FEC packets received on a different|
| |SSRC or port. |
+-----------------+-----------------------------------------------+
|Octets received |Refers only to payload octets in primary RTP |
|(OR) |payloads/packets. Payload octets include text |
| |octets and audio octets received with the same |
| |SSRC. Octets in redundant or FEC |
| |payloads/packets are not counted. |
+-----------------+-----------------------------------------------+
|Packets lost |Refers to text relay packets. If these packets |
|(PL) |share an SSRC with an interleaved audio stream,|
| |it refers to the composite stream. Does not |
| |take into account any loss mitigation due to |
| |due to redundancy or FEC. |
+-----------------+-----------------------------------------------+
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TABLE 9: PARAMETERS FROM TABLE 3 THAT ARE APPLICABLE TO TEXT RELAY
+-----------------+-----------------------------------------------+
| PARAMETER | APPLICABILITY TO TEXT RELAY |
| from Table 3 | |
+-----------------+-----------------------------------------------+
|SSRC |Applicable to text relay sessions and sessions |
|(SSRC) |with interleaved text relay and audio packets. |
+-----------------+-----------------------------------------------+
|Source IP |Applicable to text relay sessions and sessions |
|address (IPAS) |with interleaved text relay and audio packets. |
+-----------------+-----------------------------------------------+
|Source IP address|Applicable to text relay sessions and sessions |
|type (IPTS) |with interleaved text relay and audio packets. |
+-----------------+-----------------------------------------------+
|Destination IP |Applicable to text relay sessions and sessions |
|address (IPAD) |with interleaved text relay and audio packets. |
+-----------------+-----------------------------------------------+
|Destination IP |Applicable to text relay sessions and sessions |
|address type |with interleaved text relay and audio packets. |
|(IPTD) | |
+-----------------+-----------------------------------------------+
|Source RTP/UDPTL |Applicable to text relay sessions and sessions |
|port(RTUS) |with interleaved text relay and audio packets. |
+-----------------+-----------------------------------------------+
|Destination |Applicable to text relay sessions and sessions |
|RTP/UDPTL port |with interleaved text relay and audio packets. |
|(RTUD) | |
+-----------------+-----------------------------------------------+
|Source RTCP |Applicable to text relay sessions and sessions |
|port (RTCS) |with interleaved text relay and audio packets. |
+-----------------+-----------------------------------------------+
|Destination RTCP |Applicable to text relay sessions and sessions |
|port (RTCD) |with interleaved text relay and audio packets. |
+-----------------+-----------------------------------------------+
|Media Mode |Applicable to text relay sessions and sessions |
|(MMOD) |with interleaved text relay and audio packets. |
+-----------------+-----------------------------------------------+
|SSRC of received |Applicable if FEC is used. |
|FEC stream (FSRC)| |
+-----------------+-----------------------------------------------+
|Destination IP |Applicable if FEC is used. |
|address for FEC | |
|(IPAF) | |
+-----------------+-----------------------------------------------+
|Destination RTP |Applicable if FEC is used. |
|port for FEC | |
|(RTFD) | |
+-----------------+-----------------------------------------------+
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3. Call Flow Examples
The following examples are partial call flows for the case where the
XRM/mcr local connection option is set to "on". Only one endpoint's
perspective is shown. In this example, the remote endpoint sends voice
metrics to this endpoint via RTCP Extended Reports, Sender Reports and
Receiver Reports.
Note that these are call flow examples and not examples of typical
metrics values. These values have not been derived from real-world
situations and, therefore, do not necessarily have the right numeric
relationship between themselves.
3.1 Metrics Reporting during Call agent-initiated Delete Connection
Step 1:
The Call Agent issues a CreateConnection command to the endpoint
instructing it to use PCMU media encoding and to invoke RTCP XR metric
collection, responding and reporting:
CRCX 1000 ds/ds1-1/1@gw-o.example.net MGCP 1.0
C: 1
L: a:PCMU, xrm/mcr: on
M: recvonly
Step 2:
The endpoint acknowledges the command and includes the rtxp-xr
attribute set to "voip-metrics":
200 1000 OK
I:1
v=0
o=- 25678 753849 IN IP4 128.96.41.1
s=-
c=IN IP4 128.96.41.1
t=0 0
m=audio 3456 RTP/AVP 0
a=rtcp-xr:voip-metrics
Step 3:
The endpoint receives a ModifyConnection command containing an LCO with
no xrm/mcr parameter, which indicates that the endpoint SHOULD continue
to use the previously received value of "on". Since the received SDP
also contains the rtcp-xr attribute with a value of "voip-metrics", it
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is safe to assume that both ends will exchange the VoIP metrics block
in RTCP Extended Reports (XR).
MDCX 1001 ds/ds1-1/1@gw-o.example.net MGCP 1.0
C: 1
I: 1
L: a:PCMU;G728
M: sendrecv
I:1
v=0
o=- 4723891 7428910 IN IP4 128.96.63.25
s=-
c=IN IP4 128.96.63.25
t=0 0
m=audio 4082 RTP/AVP 0
a=rtcp-xr:voip-metrics
Step 4:
The endpoint acknowledges the command and, since VoIP metrics
collection/reporting is still "on", includes the rtxp-xr attribute set
to "voip-metrics":
200 1001 OK
v=0
o=- 25678 753849 IN IP4 128.96.41.1
s=-
c=IN IP4 128.96.41.1
t=0 0
m=audio 3456 RTP/AVP 0
a=rtcp-xr:voip-metrics
Step 5:
The Call Agent eventually issues a DeleteConnection:
DLCX 1100 ds/ds1-1/1@gw-o.example.net MGCP 1.0
C: 1
I: 1
Step 6:
The endpoint acknowledges the command and returns the standard MGCP
connection parameters along with the XRM/LVM line and the XRM/RVM line.
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This endpoint elects to include the remote equivalents of the
connection parameters on XRM/RVM line. Note that the remote end has
indicated that the ITU G.107 specification has been used to compute the
R-factors and that a proprietary algorithm, "Acme Widgets 233", has
been used to compute MOS-LQ. The remote end has not indicated the
algorithm used to compute MOS-CQ, which is on of the metrics that it
has communicated via an RTCP extended report. Also note that new lines
shown here are for document formatting reasons only.
250 1100 OK
P: PS=5000, OS=200000, PR=6000, OR=340000, PL=800,
JI=27, LA=180
XRM/LVM: NLR=28, JDR=14, BLD=128, GLD=10,
BD=55, GD=1000, RTD=180,ESD=30, SL=-15, NL=20,
RERL=23, GMN=16, NSR=63, RLQ=61, XSR=65, MLQ=33, MCQ=31, PLC=3,
JBA=3, JBR=8, JBN=40, JBM=80, JBS=120, SSRC=27513888,
IPAD=128.96.41.1, RTPD=3456, VCD=PCMU, VPT=0, MMOD=a, SMPL=8000,
PKRT=200, SSUP=on, ECAN=on, VRED=off, VFEC=off
XRM/RVM: NLR=6, JDR=2, BLD=50, GLD=3, BD=20, GD=6000, RTD=180,
ESD=23, SL=-16, NL=25, RERL=23, GMN=16, NSR=80, RLQ=82, XSR=77,
MLQ=37, MCQ=35, PLC=3, JBA=3, JBR=8, JBN=30, JBM=60, JBS=100,
MLES=Acme widgets 233, RFES=ITU G.107,PS=6800, OS=272000,
PR=4900, OR=196000, IAJ=15, SSRC=832829, IPAD=128.96.63.25,
RTPD=4082, VCD=PCMU, VPT=0, MMOD=a, SMPL=8000, PKRT=200, SSUP=on,
ECAN=on, VRED=off, VFEC=off
3.2 Metrics Reporting during Gateway-initiated Delete Connection
Step 1:
The Call Agent issues a CreateConnection command to the endpoint
instructing it to use PCMU media encoding and to invoke RTCP XR metric
collection and reporting:
CRCX 1000 ds/ds1-1/1@gw-o.example.net MGCP 1.0
C: 1
L: a:PCMU, xrm/mcr: on
M: recvonly
Step 2:
The endpoint acknowledges the command and includes the rtxp-xr
attribute set to "voip-metrics":
200 1000 OK
I:1
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v=0
o=- 25678 753849 IN IP4 128.96.41.1
s=-
c=IN IP4 128.96.41.1
t=0 0
m=audio 3456 RTP/AVP 0
a=rtcp-xr:voip-metrics
Step 3:
The Endpoint issues a DeleteConnection command including the connection
parameters along with the XRM/LVM line and the XRM/RVM line:
DLCX 1100 ds/ds1-1/1@gw-o.example.net MGCP 1.0
C: 1
I: 1
E: 900 - - Hardware error
P: PS=5000, OS=200000, PR=6000, OR=340000, PL=800,
JI=27, LA=180
XRM/LVM: NLR=28, JDR=14, BLD=128, GLD=10,
BD=55, GD=1000, RTD=180,ESD=30, SL=-15, NL=20,
RERL=23, GMN=16, NSR=63, XSR=65, MLQ=33, MCQ=31, PLC=3, JBA=3,
JBR=8, JBN=40, JBM=80, JBS=120, SSRC=27513888, IPAD=128.96.41.1,
RTPD=3456, VCD=PCMU, VPT=0, SMPL=8000,
PKRT=200, SSUP=on, ECAN=on, VRED=off, VFEC=off
XRM/RVM: NLR=6, JDR=2, BLD=50, GLD=3, BD=20, GD=6000, RTD=180,
ESD=23, SL=-16, NL=25, RERL=23, GMN=16, NSR=80, XSR=77, MLQ=37,
MCQ=35, PLC=3, JBA=3, JBR=8, JBN=30, JBM=60, JBS=100, PS=6800,
OS=272000, PR=4900, OR=196000, IAJ=15, SSRC=832829,
IPAD=128.96.63.25, RTPD=4082, VCD=PCMU, VPT=0, SMPL=8000,
PKRT=200, SSUP=on, ECAN=on, VRED=off, VFEC=off
Note that the RLQ parameter is not included in the XRM/LVM or the
XRM/RVM lines. This is just an example of allowed parameter omission.
This example could have very well been constructed with the RLQ
parameter.
Step 4:
The Call Agent acknowledges the command:
200 1100 OK
3.3 Metrics Reporting during Audit Connection
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Step 1:
The Call Agent issues a CreateConnection command to the endpoint
instructing it to use PCMU media encoding and to invoke RTCP XR metric
collection, responding and reporting:
CRCX 1000 ds/ds1-1/1@gw-o.example.net MGCP 1.0
C: 1
L: a:PCMU, xrm/mcr: on
M: recvonly
Step 2:
The endpoint acknowledges the command and includes the rtxp-xr
attribute set to "voip-metrics":
200 1000 OK
I:1
v=0
o=- 25678 753849 IN IP4 128.96.41.1
s=-
c=IN IP4 128.96.41.1
t=0 0
m=audio 3456 RTP/AVP 0
a=rtcp-xr:voip-metrics
Step 3:
The endpoint receives a ModifyConnection command containing an LCO with
no xrm/mcr parameter, which indicates that the endpoint SHOULD continue
to use the previously received value of "on". Since the received SDP
also contains the rtcp-xr attribute with a value of "voip-metrics", it
is safe to assume that both ends will exchange the VoIP metrics block
in RTCP Extended Reports (XR).
MDCX 1001 ds/ds1-1/1@gw-o.example.net MGCP 1.0
C: 1
I: 1
L: a:PCMU;G728
M: sendrecv
v=0
o=- 4723891 7428910 IN IP4 128.96.63.25
s=-
c=IN IP4 128.96.63.25
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t=0 0
m=audio 4082 RTP/AVP 0
a=rtcp-xr:voip-metrics
Step 4:
The endpoint acknowledges the command and, since VoIP metrics
collection/reporting is still "on", includes the rtxp-xr attribute set
to "voip-metrics":
200 1001 OK
I:1
v=0
o=- 25678 753849 IN IP4 128.96.41.1
s=-
c=IN IP4 128.96.41.1
t=0 0
m=audio 3456 RTP/AVP 0
a=rtcp-xr:voip-metrics
Step 5:
The Call Agent eventually issues a AuditConnection that requests the
XRM/LVM and XRM/RVM lines but not the P (connection parameters) line:
AUCX 1100 ds/ds1-1/1@gw-o.example.net MGCP 1.0
C: 1
I: 1
F: XRM/LVM, XRM/RVM
Step 6:
The endpoint acknowledges the command and returns the XRM/LVM line and
the XRM/RVM line. This endpoint elects to include the local and remote
equivalents of the connection parameters in the XRM/LVM and XRM/RVM
line. Also note that new lines shown here are for document formatting
reasons only.
200 1100 OK
XRM/LVM: NLR=28, JDR=14, BLD=128, GLD=10,
BD=55, GD=1000, RTD=180,ESD=30, SL=-15, NL=20,
RERL=23, GMN=16, NSR=63, RLQ=61, XSR=65, MLQ=33, MCQ=31, PLC=3,
JBA=3, JBR=8, JBN=40, JBM=80, JBS=120, PS=5000, OS=200000,
PR=6000, OR=340000, PL=800, IAJ=27, SSRC=27513888,
IPAD=128.96.41.1, RTPD=3456, VCD=PCMU, VPT=0, MMOD=a, SMPL=8000,
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PKRT=200, SSUP=on, ECAN=on, VRED=off, VFEC=off
XRM/RVM: NLR=6, JDR=2, BLD=50, GLD=3, BD=20, GD=6000, RTD=180,
ESD=23, SL=-16, NL=25, RERL=23, GMN=16, NSR=80, RLQ=82, XSR=77,
MLQ=37, MCQ=35, PLC=3, JBA=3, JBR=8, JBN=30, JBM=60, JBS=100,
PS=6800, OS=272000, PR=4900, OR=196000, IAJ=15, SSRC=832829,
IPAD=128.96.63.25, RTPD=4082, VCD=PCMU, VPT=0, MMOD=a, SMPL=8000,
PKRT=200, SSUP=on, ECAN=on, VRED=off, VFEC=off
3.4 Metrics Reporting during Modify Connection
Step 1:
The Call Agent issues a CreateConnection command to the endpoint
instructing it to use PCMU media encoding and to invoke RTCP XR metric
collection, responding and reporting:
CRCX 1000 ds/ds1-1/1@gw-o.example.net MGCP 1.0
C: 1
L: a:PCMU, xrm/mcr: on
M: recvonly
Step 2:
The endpoint acknowledges the command and includes the rtxp-xr
attribute set to "voip-metrics":
200 1000 OK
I:1
v=0
o=- 25678 753849 IN IP4 128.96.41.1
s=-
c=IN IP4 128.96.41.1
t=0 0
m=audio 3456 RTP/AVP 0
a=rtcp-xr:voip-metrics
Step 3:
The endpoint receives a ModifyConnection command containing an LCO with
no xrm/mcr parameter, which indicates that the endpoint SHOULD continue
to use the previously received value of "on". Since the received SDP
also contains the rtcp-xr attribute with a value of "voip-metrics", it
is safe to assume that both ends will exchange the VoIP metrics block
in RTCP Extended Reports (XR).
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MGCP RTCP-XR Package 4/12/2007
MDCX 1001 ds/ds1-1/1@gw-o.example.net MGCP 1.0
C: 1
I: 1
L: a:PCMU;G728
M: sendrecv
v=0
o=- 4723891 7428910 IN IP4 128.96.63.25
s=-
c=IN IP4 128.96.63.25
t=0 0
m=audio 4082 RTP/AVP 0
a=rtcp-xr:voip-metrics
Step 4:
The endpoint acknowledges the command and, since VoIP metrics
collection/reporting is still "on", includes the rtxp-xr attribute set
to "voip-metrics":
200 1001 OK
I:1
v=0
o=- 25678 753849 IN IP4 128.96.41.1
s=-
c=IN IP4 128.96.41.1
t=0 0
m=audio 3456 RTP/AVP 0
a=rtcp-xr:voip-metrics
Step 5:
The Call Agent eventually issues a ModifyConnection with the XRM/MMO
line requesting that local and remote metrics be reset and reported.
MDCX 1001 ds/ds1-1/1@gw-o.example.net MGCP 1.0
C: 1
I: 1
L: a:PCMU;G728
M: sendrecv
XRM/MMO: RR
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Step 6:
The endpoint acknowledges the command and returns the XRM/LVM line and
the XRM/RVM line. The endpoint does not include the connection
parameters line since this would violate [RFC 3435]. Instead, it
includes the local and remote equivalents of the connection parameters
in the XRM/LVM and XRM/RVM line. Also note that new lines shown here
are for document formatting reasons only.
200 1001 OK
XRM/LVM: NLR=28, JDR=14, BLD=128, GLD=10,
BD=55, GD=1000, RTD=180,ESD=30, SL=-15, NL=20,
RERL=23, GMN=16, NSR=63, RLQ=61, XSR=65, MLQ=33, MCQ=31, PLC=3,
JBA=3, JBR=8, JBN=40, JBM=80, JBS=120, PS=5000, OS=200000,
PR=6000, OR=340000, PL=800, IAJ=27, SSRC=27513888,
IPAD=128.96.41.1, RTPD=3456, VCD=PCMU, VPT=0, MMOD=a, SMPL=8000,
PKRT=200, SSUP=on, ECAN=on, VRED=off, VFEC=off
XRM/RVM: NLR=6, JDR=2, BLD=50, GLD=3, BD=20, GD=6000, RTD=180,
ESD=23, SL=-16, NL=25, RERL=23, GMN=16, NSR=80, RLQ=82, XSR=77,
MLQ=37, MCQ=35, PLC=3, JBA=3, JBR=8, JBN=30, JBM=60, JBS=100,
PS=6800, OS=272000, PR=4900, OR=196000, IAJ=15, SSRC=832829,
IPAD=128.96.63.25, RTPD=4082, VCD=PCMU, VPT=0, MMOD=a, SMPL=8000,
PKRT=200, SSUP=on, ECAN=on, VRED=off, VFEC=off
4. Security Considerations
This package inherits the security considerations of the base MGCP
protocol. A possible new security issue involves a remote device
placing extra burden on a local endpoint by requesting metric
collection on that local endpoint. This threat can be mitigated by the
call agent specifically prohibiting the generation of local metrics
using the local connection option: xrm/mcr: off.
5. IANA Considerations
5.1 Package Registration
The IANA is hereby requested to register the following MGCP package:
Package Title Name Version
------------- ---- -------
RTCP XR metrics XRM 0
5.2. Extension Registration
The IANA is requested to create a registry of MGCP names of vendor-
specified VoIP metrics. These metrics MAY be used in the XRM/LVM and
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XRM/RVM lines defined in this package. Such a metric SHALL be described
in a specification ("source document") approved by an accredited
standards organization such as the IETF or ITU. This document MAY be
informative and MAY address more than one metric. It MUST include:
- Contact name, email address and telephone number.
- Metric name, as an alphabetic character string
- Description of and ABNF notation for the permitted
range of values,
- A functional description of the metric i.e. what it
measures and how it is to be used,
- Optionally, the measurement algorithm and any IPR statements
associated with it.
6. Changes from earlier drafts
6.1 Changes from the -00 version to the -01 version
All changes from the -00 version to the -01 version of this draft are
backwards compatible. All new features in the 01 version are OPTIONAL.
Note that the -00 version was incorporated into the PacketCable 1.5
specifications.
Changes from the -00 version to the -01 version are:
- Inclusion of statistics from the RTCP sender and receiver reports,
with the exception of latency which is already present in the RTCP XR
VoIP metrics block. The reporting of these statistics via this package
is OPTIONAL.
- Inclusion of session description parameters based on the ones defined
in RFC 2327, RFC 2198 etc. This included media description parameters
such as codec type.
- Inclusion of a modify connection procedure for the reporting and
resetting of voice quality metrics.
- Clarification of cumulative vs. interval metrics. For the SR/RR
metrics, these rules are inherited from connection parameters in [RFC
3435].
- Inclusion of a new G.107-based parameter, RLQ, for indicating the
listening quality of a VoIP session.
- Inclusion of a new parameter, MLES, for indicating the algorithm used
to estimate the MOS-LQ metric.
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- ABNF correction for requiring at least one metric in the XRM/LVM
line.
- Inclusion of a mechanism for defining vendor extension metrics that
can be used in this package, and a mechanism for OPTIONALly registering
these metrics with the IANA.
6.2 Changes from the -01 version to the -02 version
All changes from the -01 version of this draft to the -02 version are
backwards compatible. These are:
- Included the impact of redundancy (e.g. RFC 2198) and FEC (e.g.
RFC 2733) on packet loss computation.
- Corrections of errors and typos in the ABNF.
6.3 Changes from the -02 version to the -03 version
All changes from the -02 version of this draft to the -03 version are
backwards compatible. These are:
- Added the parameters FSRC, IPAF and RTFD to Table 3 to fully
cover the case in which an RFC 2733 FEC is used.
- Added section 2.3.9 on the applicability to fax relay and text
relay of the VoIP metrics and session parameters reported via
this package.
6.4 Changes from the -03 version to the -04 version
All changes from the -03 version of this draft to the -04 version are
backwards compatible. These are:
- Clarification that metrics MAY be reset during media mode shifts,
and that this is the preferred behavior.
- Clarified how an audit connection MAY be associated with a
preceding event notification. This is based on temporal
proximity. Included recommendation to report the metrics captured
just prior to the event.
- Included two new parameters that MAY be OPTIONALly reported: the
computation interval (CMPI) and the number of reset occurrences
(ROC).
- Included section 2.3.7 describing the impact of media state
changes on VoIP metrics.
6.5 Changes from the -04 version to the -05 version
Spelling errors.
6.6 Changes from the -05 version to the -06 version
Formatting.
6.7 Changes from the -06 version to the -07 version
Formatting.
6.8 Potential future updates
- Add list of acronyms
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7. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, March 1997.
[RFC 3435] F. Andreasen, B. Foster, "Media Gateway Control Protocol
(MGCP) Version 1.0", January 2003.
[RFC 3611] T. Friedman, R. Caceres, A. Clark, "RTP Control Protocol
Extended Reports (RTCP XR)", November 2003.
[RFC 3550] H. Schulzrinne, S. Casner, R. Frederick and V. Jacobson,
"RTP: A Transport Protocol for Real-Time Applications", July 2003.
[RFC 2327] M.Handley and V. Jacobson, "SDP: Session Description
Protocol", April 1998.
[RFC 3660] B.Foster and F.Andreasen, "Basic Media Gateway Control
Protocol (MGCP) Packages", December 2003.
[RFC 2234] D.Crocker and P.Overell, "Augmented BNF for Syntax
Specifications: ABNF", November 1997.
[RFC 3261] J.Rosenberg, H.Schulzrinne, G.Camarillo, A.Johnston,
J.Peterson, R.Sparks, M.Handley, E.Schooler, "SIP: Session Initiation
Protocol", June 2002.
[RFC 2198] C.Perkins, I.Kouvelas, O.Hodson, V.Hardman, M.Handley,
J.C.Balot, A.Vega-Garcia and S. Fosse-Parisis, "RTP Payload for
Redundant Audio Data", September 1997.
[RFC 2733] J.Rosenberg, H.Schulzrinne, "An RTP Payload format for
Generic Forward Error Correction", December 1999.
[IANA RTP] http://www.iana.org/assignments/media-types/audio/.
[US-ASCII] Coded Character Set--7-Bit American Standard Code for
Information Interchange, ANSI X3.4-1986.
[ITU V.152] Procedures for supporting Voice-Band Data over IP Networks,
ITU V.152, January 2005.
[FAX PKG] draft-andreasen-mgcp-fax-04.txt, Media Gateway Control
Protocol Fax Package, F. Andreasen.
[RFC 4103] RTP Payload for Text Conversation, Gunnar Hellstrom and Paul
Jones.
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[ITU V.150.1] Modem-over-IP networks: Procedures for the end-to-end
connection of V-series DCEs, ITU V.150.1, January 2003.
[ITU V.151] Procedures for the end-to-end connection of analogue PSTN
text telephones over an IP network utilizing Text Relay,
Telecommunications Industries Association (TIA) Technical Draft TR-
30.1/05-03-006, Tampa, FL, Feb 28 - March4, 2005.
[ITU T.140] Protocol for multimedia application text conversation,
February 1998. Also, addendum 1, February 2000.
[RFC 2793] G. Hellstrom, RTP Payload for Text Conversation. Also, its
upcoming successor documents: G. Hellstrom and P. Jones, draft-ietf-
avt-rfc2793bis-09, and G. Hellstrom and P. Jones, draft-ietf-avt-audio-
t140c-00.
[ITU T.35] Procedure for the allocation of ITU-T defined codes for non-
standard facilities, February 2000.
[ITU T.38] Procedures for real-time Group 3 facsimile communication
over IP networks, September 2005.
[ITU P.VTQ] Add a reference when ITU P.VTQ becomes a standard for MOS-
LQ.
8. Acknowledgments
Contributors to this document include Alan Clark, Joe Stone, Flemming
Andreasen, Robert Biskner, Michael Ramalho, Paul Jones, Steve White,
Kevin Connor, Jim Frauenthal, Tom Hock, Prakash Bhat, David Ensign and
the PacketCable NCS Specification Team.
9. Copyright Statement
Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors retain
all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Kumar et al Informational Page 57