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Network Working Group D. Cromwell
Request for Comments: 2897 Nortel Networks
Category: Informational August 2000
Proposal for an MGCP Advanced Audio Package
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2000). All Rights Reserved.
Abstract
This document is a proposal to add a new event/signal package to the
MGCP (Media Gateway Control Protocol) protocol to control an ARF
(Audio Resource Function) which may reside on a Media Gateway or
specialized Audio Server.
This event package provides support for the standard IVR (Interactive
Voice Response) operations of PlayAnnouncement, PlayCollect, and
PlayRecord. It supports direct references to simple audio as well as
indirect references to simple and complex audio. It provides audio
variables, control of audio interruptibility, digit buffer control,
special key sequences, and support for reprompting during data
collection. It also provides an arbitrary number of user defined
qualifiers to be used in resolving complex audio structures. For
example, the user could define qualifiers for any or all of the
following: language, accent, audio file format, gender, speaker, or
customer.
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RFC 2897 MGCP Advanced Audio Package August 2000
Table of Contents
1. Introduction ................................................ 2
1.1. Audio Segments ............................................ 3
1.1.1. Sequences And Sets ...................................... 3
1.1.2. Segment Types ........................................... 4
2. Advanced Audio Package ...................................... 5
3. Events ...................................................... 5
4. Event Parameters ............................................ 7
5. Return Parameters ........................................... 7
6. Variables ................................................... 14
7. Selectors ................................................... 17
8. Aliases ..................................................... 18
9. Examples .................................................... 21
10. Formal Syntax Description .................................. 22
11. References ................................................. 22
12. Formal Syntax Description .................................. 25
13. References ................................................. 32
14. Author's Address ........................................... 33
15. Full Copyright Statement ................................... 34
1. Introduction
The following syntax supports both simple and complex audio
structures. A simple audio structure might be a single announcement
such as "Welcome to Bell South's Automated Directory Assistance
Service". A more complex audio structure might consist of an
announcement followed by voice variable followed by another
announcement, for example "There are thirty seven minutes remaining
on your prepaid calling card," where "There are" is a prompt, the
number of minutes is a voice variable, and "minutes remaining on your
prepaid calling card" is another prompt.
It is also possible to define complex audio structures that are
qualified by user defined selectors such as language, audio file
format, gender, accent, customer, or voice talent. For instance, if
the above example were qualified by language and accent selectors, it
would be possible to play "There are thirty seven minutes remaining
on your prepaid calling card" in English spoken with a southern
accent or in English spoken with a mid-western accent, providing that
the audio to support this had been provisioned.
There are two methods of specifying complex audio. The first is to
directly reference the individual components. This requires a
complete description of each component to be specified via the
protocol. The second method is to provision the components on the
Audio Server as a single entity and to export a reference to that
entity to the call agent. In this case, only the reference (plus any
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RFC 2897 MGCP Advanced Audio Package August 2000
dynamic data required, such as a variable data) is passed via the
protocol, and no specification of individual components is necessary.
The Audio Server Package provides significant functionality most of
which is controlled via protocol parameters. Most parameters are
optional, and where ever possible default to reasonable values. An
audio application that references to provisioned, complex audio
structures, and which takes advantage of parameter optionality and
defaults, can specify audio events using a minimum of syntax.
1.1. Background
The next two sections contain background information which may be
helpful in understanding the syntax.
1.1.1. Sequence And Sets
The syntax supports abstractions of set and sequence for storing and
referencing audio data.
A sequence is a provisioned sequence of one or more audio segments.
Component segments are not necessarily all of the same type. Every
sequence is assigned a unique segment id. On playback, a sequence id
reference is deconstructed into its individual parts, each of which
is played in order.
A set is a provisioned collection of audio segments with an
associated selector. On playback, the selector value is resolved to
a particular set element. Selector types are supported by the
syntax, but individual selector types are not defined in the syntax
except for the pre-defined language selector; they are instead
defined by the user (i.e. provisioner). A user could define one or
more of the following selector types: language, accent, audio file
format, gender, accent, customer, or day of the week. For each
selector type, the user must define a range of valid values. The
user may also choose to define a default value. At runtime if a
selector value is not supplied the default value is used.
For example, to support an application which plays a particular piece
of audio in either English, French, or Russian, a provisioner would
define a set with the pre-defined selector, "Lang", and would define
three possible values for that selector, "eng", "fra", and "rus".
The provisioner would then provision three recordings of the prompt,
one in each language, and would associate the French recording with
the "fra" selector value, etc. The provisioner also could define a
default value of the selector when no selector value is supplied,
"eng" for instance. The entire set would be assigned a unique
segment id.
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RFC 2897 MGCP Advanced Audio Package August 2000
At runtime a reference to the set with the selector set to "rus"
would result in the Russian version of the prompt being played. A
reference to the set with no selector would result in the English
version of the prompt being played since English has been set as the
default selector value.
Nested definition of both sets and sequences is allowed, i.e. it
legal to define a set of sets or a sequence of sequences. In
addition, audio structures may also be specified by intermixing sets
and sequences, and it is possible to specify a set of sequences or a
sequence containing one or more set elements. Direct or transitive
definition of a set or segment in terms of itself is not allowed.
1.1.2. Segment Types
The syntax supports the following segment types:
RECORDING: A reference by unique id to a single piece of recorded
audio.
RECORDINGs may be provisioned or they may be made during the
course of a call. A RECORDING made during the course of a call
can be temporary or persistent. A temporary RECORDING lasts only
for the life of the call during which it was recorded. A
persistent RECORDING lasts beyond the live of the call during
which it was recorded.
A provisioned RECORDING may be replaced (or overridden) by a
persistent RECORDING. A reference to the id of the provisioned
RECORDING will then resolve to the persistent RECORDING. The
overriding persistent audio can subsequently be deleted and the
original provisioned audio can be restored.
A provisioned RECORDING may be overridden more than once. In this
case, the id of the provisioned RECORDING refers to the latest
overriding RECORDING. When the overriding RECORDING is deleted,
the original provisioned RECORDING is restored, even if the
segment has been overridden multiple times.
TEXT: A reference to a block of text to be converted to speech or
to be displayed on a device. Reference may be by unique id to a
block of provisioned text or by direct specification of text in a
parameter.
SILENCE: A specification of a length of silence to be played in
units of 100 milliseconds.
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RFC 2897 MGCP Advanced Audio Package August 2000
TONE: The specification of a tone to be played by algorithmic
generation. Most tones however will probably be recorded, not
generated. Exact specification of this segment type is tbd.
VARIABLE: The specification of a voice variable by the parameters
of type, subtype, and value. Specification of variables is
considered in more detail in a subsequent section of this
document.
SEQUENCE: A reference by unique id to a provisioned sequence of
mixed RECORDING, TEXT, SILENCE, TONE, VARIABLE, SET, or SEQUENCE
segments. Nested definition of SEQUENCE segments is allowed.
Direct or transitive definition of a SEQUENCE segment in terms of
itself is not allowed.
SET: A reference by unique id to a provisioned set of segments.
The intended and recommended use of the SET type is that all
segments in the set should be semantically equivalent, however
there is no real way of enforcing this restriction either in the
protocol or in provisioning. Every set has an associated selector
which is used at runtime to resolve the set reference to a
specific element of the set. The elements of a set may one of the
following segment types: RECORDING, TEXT, TONE, SILENCE,
SEQUENCE, or SET. Specific selector types are not specified by
the protocol and must be defined by the user. Nested definition
of SET segments is allowed. Direct or transitive definition of a
SET segment in terms of itself is not allowed.
2. Advanced Audio Package
Package Name: AU
This package defines events and signals for an ARF package for an
Audio Server Media Gateway.
3. Events
______________________________________________________________________
| Symbol | Definition | R | S Duration |
|______________|________________________|______|______________________|
| pa(parms) | PlayAnnouncement | | TO variable |
| pc(parms) | PlayCollect | | TO variable |
| pr(parms) | PlayRecord | | TO variable |
| es(parm) | EndSignal | | BR |
| oc(parms) | OperationComplete | x | |
| of(parms) | OperationFailed | x | |
|______________|________________________|______|______________________|
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RFC 2897 MGCP Advanced Audio Package August 2000
The events provided by the AS Package are defined as follows:
PlayAnnouncement:
Plays an announcement in situations where there is no need for
interaction with the user. Because there is no need to monitor
the incoming media stream this event is an efficient mechanism for
treatments, informational announcements, etc.
PlayCollect:
Plays a prompt and collects DTMF digits entered by a user. If no
digits are entered or an invalid digit pattern is entered, the
user may be reprompted and given another chance to enter a correct
pattern of digits. The following digits are supported: 0-9, *,
#, A, B, C, D. By default PlayCollect does not play an initial
prompt, makes only one attempt to collect digits, and therefore
functions as a simple Collect operation. Various special purpose
keys, key sequences, and key sets can be defined for use during
the PlayCollect operation.
PlayRecord:
Plays a prompt and records user speech. If the user does not
speak, the user may be reprompted and given another chance to
record. By default PlayRecord does not play an initial prompt,
makes only one attempt to record, and therefore functions as a
simple Record operation.
OperationComplete:
Detected upon the successful completion of a Play, PlayRecord, or
Play Collect signal.
OperationFailed:
Detected upon the failure of a Play, PlayRecord, or PlayCollect
signal.
EndSignal:
Gracefully terminates a Play, PlayCollect, or PlayRecord signal.
For each of these signals, if the signal is terminated with the
EndSignal signal the resulting OperationComplete event or
OperationFailed event will contain all the parameters it would
normally, including any collected digits or the recording id of
the recording that was in progress when the EndSignal signal was
received.
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4. Signal Interactions
If an Advanced Audio Package signal is active on an endpoint and
another signal of the same type is applied, the two signals including
parameters and parameter values will compared If the signals are
identical, the signal in progress will be allowed to continue and the
new signal will be discarded. Because of this behavior the Advanced
Audio Package may not interoperate well with some other packages such
as the Line and Trunk packages.
5. Parameters
The PlayAnnouncement, PlayRecord, and PlayCollect events may each be
qualified by a string of parameters, most of which are optional.
Where appropriate, parameters default to reasonable values. The
only event with a required parameter is PlayAnnouncement. If a
Play-Announcement event is not provided with a parameter specifying
some form of playable audio an error is returned to the application.
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These parameters are shown in the following table:
_______________________________________________________________________
| Parameters |
|______________________________________________________________________|
| Symbol | Definition | pl | pc | pr |
|___________|_________________________________|________|________|______|
| an | announcement | x | | |
| ip | initial prompt | | x | x |
| rp | reprompt | | x | x |
| nd | no digits reprompt | | x | |
| ns | no speech reprompt | | | x |
| fa | failure announcement | | x | x |
| sa | success announcement | | x | x |
| ni | non-interruptible play | | x | x |
| it | iterations | x | | |
| iv | interval | x | | |
| du | duration | x | | |
| sp | speed | x | x | x |
| vl | volume | x | x | x |
| cb | clear digit buffer | | x | x |
| mx | maximum # of digits | | x | |
| mn | minimum # of digits | | x | |
| dp | digit pattern | | x | |
| fdt | first digit timer | | x | |
| idt | inter digit timer | | x | |
| edt | extra digit timer | | x | |
| prt | pre-speech timer | | | x |
| pst | post-speech timer | | | x |
| rlt | total recording length timer | | | x |
| rsk | restart key | | x | x |
| rik | reinput key | | x | x |
| rtk | return key | | x | x |
| psk | position key | | x | x |
| stk | stop key | | x | x |
| sik | start input key | | x | |
| eik | end input key | | x | x |
| iek | include end input key | | x | |
| na | number of attempts | | x | x |
|___________|_________________________________|________|________|______|
Parameters to the Advanced Audio Package events are defined as
follows:
Announcement:
An announcement to be played. Consists of one or more audio
segments.
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RFC 2897 MGCP Advanced Audio Package August 2000
Initial Prompt:
The initial announcement prompting the user to either enter DTMF
digits or to speak. Consists of one or more audio segments. If
not specified (the default), the event immediately begins digit
collection or recording.
Reprompt:
Played after the user has made an error such as entering an
invalid digit pattern or not speaking. Consists of one or more
audio segments. Defaults to the Initial Prompt.
No Digits Reprompt:
Played after the user has failed to enter a valid digit pattern
during a PlayCollect event. Consists of one or more audio
segments. Defaults to the Reprompt.
No Speech Reprompt:
Played after the user has failed to speak during a PlayRecord
event. Consists of one or more audio segments. Defaults to the
Reprompt.
Failure Announcement:
Played when all data entry attempts have failed. Consists of one
or more audio segments. No default.
Success Announcement:
Played when data collection has succeeded. Consists of one or
more audio segments. No default.
Non-Interruptible Play:
If set to true, initial prompt is not interruptible by either
voice or digits. Defaults to false. Valid values are the text
strings "true" and "false".
Iterations:
The maximum number of times an announcement is to be played. A
value of minus one (-1) indicates the announcement is to be
repeated forever. Defaults to one (1).
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Interval:
The interval of silence to be inserted between iterative plays.
Specified in units of 100 milliseconds. Defaults to 10 (1
second).
Duration:
The maximum amount of time to play and possibly replay an
announcement. Takes precedence over iteration and interval.
Specified in units of 100 milliseconds. No default.
Speed:
The relative playback speed of announcement specifiable as a
positive or negative percentage of the original playback speed.
Volume:
The relative playback volume of announcement specifiable as a
positive or negative decibel variation from the original play-back
volume.
Clear Digit Buffer:
If set to true, clears the digit buffer before playing the initial
prompt. Defaults to false. Valid values are the text strings
"true" and "false".
Maximum # Of Digits:
The maximum number of digits to collect. Defaults to one. This
parameter should not be specified if the Digit Pattern parameter
is present.
Minimum # Of Digits:
The minimum number of digits to collect. Defaults to one. This
parameter should not be specified if the Digit Pattern parameter
is present.
Digit Pattern:
A legal digit map as described in section 7.1.14 of the Megaco
protocol [6] using the DTMF mappings associated with the Megaco
DTMF Detection Package described in the Megaco protocol document
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RFC 2897 MGCP Advanced Audio Package August 2000
[6]. This parameter should not be specified if one or both of the
Minimum # Of Digits parameter and the Maximum Number Of Digits
parameter is present.
First Digit Timer:
The amount of time allowed for the user to enter the first digit.
Specified in units of 100 milliseconds. 50 (5 seconds).
Inter Digit Timer:
The amount of time allowed for the user to enter each subsequent
digit. Specified units of 100 milliseconds seconds. Defaults to
30 (3 seconds).
Extra Digit Timer:
The amount of time to wait for a user to enter a final digit once
the maximum expected amount of digits have been entered.
Typically this timer is used to wait for a terminating key in
applications where a specific key has been defined to terminate
input. Specified in units of 100 milliseconds. If not specified,
this timer is not activated.
Pre-speech Timer:
The amount of time to wait for the user to initially speak.
Specified in units of 100 milliseconds. Defaults to 30 (3
seconds).
Post-speech Timer:
The amount of silence necessary after the end of the last speech
segment for the recording to be considered complete. Specified in
units of 100 milliseconds. Defaults to 20 (2 seconds).
Recording Length Timer:
The maximum allowable length of the recording, not including pre
or post speech silence. Specified in units of 100 milliseconds.
This parameter is mandatory.
Restart Key:
Defines a key sequence consisting of a command key optionally
followed by zero or more keys. This key sequence has the
following action: discard any digits collected or recording in
progress, replay the prompt, and resume digit collection or
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RFC 2897 MGCP Advanced Audio Package August 2000
recording. No default. An application that defines more than one
command key sequence, will typically use the same command key for
all command key sequences. If more than one command key sequence
is defined, then all key sequences must consist of a command key
plus at least one other key.
Reinput Key:
Defines a key sequence consisting of a command key optionally
followed by zero or more keys. This key sequence has the
following action: discard any digits collected or recordings in
progress and resume digit collection or recording. No default. An
application that defines more than one command key sequence, will
typically use the same command key for all command key sequences.
If more than one command key sequence is defined, then all key
sequences must consist of a command key plus at least one other
key.
Return Key:
Defines a key sequence consisting of a command key optionally
followed by zero or more keys. This key sequence has the
following action: terminate the current event and any queued
event and return the terminating key sequence to the call
processing agent. No default. An application that defines more
than one command key sequence, will typically use the same command
key for all command key sequences. If more than one command key
sequence is defined, then all key sequences must consist of a
command key plus at least one other key.
Position Key:
Defines a key with the following action. Stop playing the current
announcement and resume playing at the beginning of the first,
last, previous, next, or the current segment of the announcement.
No default. The actions for the position key are fst, lst, prv,
nxt, and cur.
Stop Key:
Defines a key with the following action. Terminate playback of
the announcement. No default.
Start Input Keys:
Defines a set of keys that are acceptable as the first digit
collected. This set of keys can be specified to interrupt a
playing announcement or to not interrupt a playing announcement.
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RFC 2897 MGCP Advanced Audio Package August 2000
The default key set is 0-9. The default behavior is to interrupt a
playing announcement when a Start Input Key is pressed. This
behavior can be overidden for the initial prompt only by using the
ni (Non-Interruptible Play) parameter. Specification is a list of
keys with no separators, e.g. 123456789#.
End Input Key:
Specifies a key that signals the end of digit collection or voice
recording. The default end input key is the # key. To specify that
no End Input Key be used the parameter is set to the string
"null". The default behavior not to return the End Input Key in
the digits returned to the call agent. This behavior can be
overidden by the Include End Input Key (eik) parameter.
Include End Input Key:
By default the End Input Key is not included in the collected
digits returned to the call agent. If this parameter is set to
"true" then the End Input Key will be returned with the collected
digits returned to the call agent. Default is "false".
Number Of Attempts:
The number of attempts the user needed to enter a valid digit
pattern or to make a recording. Defaults to 1. Also used as a
return parameter to indicate the number of attempts the user made.
Record Persistent Audio:
If set to true, the recording that is made is persistent instead
of temporary. Defaults to false. Valid values are the text
strings "true" and "false".
Delete Persistent Audio
Indicates that the specified persistent audio segment is to be
deleted. This parameter is carried by the PlayRecord event,
although nothing is either played or recorded in this case.
Override Audio:
Indicates that the specified provisioned audio segment is to be
overridden with a persistent audio segment to be recorded in the
PlayRecord operation that carries this parameter.
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RFC 2897 MGCP Advanced Audio Package August 2000
Restore Audio:
Indicates that the provisioned audio segment originally associated
with the specified segment id is to be restored and that the
overriding persistent audio is to be deleted. This parameter is
carried by the PlayRecord event, although nothing is either played
or recorded in this case.
6. Return Parameters
Each event has an associated set of possible return parameters which
are listed in the following tables.
________________________________________________________________________
| Return Parameters |
|_______________________________________________________________________|
| Symbol | Definition | pl | pc | pr |
|___________|________________________________|________|_________|_______|
| vi | voice interrupt | | | x |
| ik | interrupting key sequence | | x | |
| ap | amount played | | x | x |
| na | number of attempts | | x | x |
| dc | digits collected | | x | |
| ri | recording id | | | x |
| rc | return code | x | x | x |
|___________|________________________________|________|_________|_______|
Voice Interrupted:
Set to "true" if the initial prompt of a PlayRecord operation was
interrupted by voice. Defaults to "false".
Interrupting Key Sequence:
The key or key sequence that interrupted the initial prompt of a
PlayCollect specified using the digit map characters "0" through
"9" and "A" through "F" as defined in the DTMF Detection Package
in the Megaco protocol document [6].
Amount Played:
The length played of an initial prompt if the prompt was
interrupted, in 100 ms units.
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Number Of Attempts:
The number of attempts the user needed to enter a valid digit
pattern or to make a recording. Defaults to 1. Also used as an
input parameter to specify the number of attempts the user will be
allowed to enter a valid digit pattern or make a recording.
Digits Collected:
The DTMF digits that were collected during a PlayCollect operation
specified using the digit map characters "0" through "9" and "A"
through "F" as defined in the DTMF Detection Package in the Megaco
protocol document [6].
Recording ID:
A 32 bit binary integer assigned to audio recorded during the Play
Record operation.
Return Code:
A return code giving the final status of the operation. Two
ranges are defined:
_________________________________
| Range | Meaning |
|________|_______________________|
|100-199 | successful completion |
|300-399 | error |
|________|_______________________|
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The following return codes are define:
________________________________________________________________________
|Return Code | Meaning |
|____________|__________________________________________________________|
| 100 | Success |
| 300 | Unspecified failure |
| 301 | Bad audio ID |
| 302 | Bad selector type |
| 303 | Bad selector value |
| 304 | Variable type not supported |
| 305 | Variable subtype not supported |
| 306 | Invalid variable name |
| 307 | Variable value out of range |
| 308 | Inconsistent variable specification |
| 309 | Alias not found |
| 310 | Extra sequence data |
| 311 | Missing sequence data |
| 312 | Mismatch between play specification and provisioned data |
| 313 | Language not set |
| 314 | Remove override error |
| 315 | Override error |
| 316 | Delete audio error |
| 317 | Unable to record temporary audio |
| 318 | Unable to delete temporary audio |
| 319 | Unable to record persistent audio |
| 320 | Unable to delete persistent audio |
| 321 | Unable to override non-existent segment id |
| 322 | Unable to remove override from non-existent segment id |
| 323 | Provisioning error |
| 324 | Unspecified hardware failure |
| 325 | Syntax error |
| 326 | No digits |
| 327 | No speech |
| 328 | Spoke too long |
| 329 | Digit pattern not matched |
| 330 | Max attempts exceeded |
|____________|__________________________________________________________|
Here are some examples of how the return parameters are used:
The PlayAnnouncement event completed successfully:
O: AU/oc(rc=100)
The PlayAnnouncement event failed because an alias was not found:
O: AU/of(rc=309)
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The PlayCollect event completed successfully on the user's second
attempt when the user entered the digits 04375182:
O: AU/oc(rc=100 na=2 dc=04375182)
The PlayRecord event was successful on the user's first attempt; the
id of the recording made by the user is 983:
O: AU/oc(rc=100 na=1 ri=983)
7. Segment Descriptors
Segment descriptors are used with the an, ip, rp, nd, ns, fa, and sa
parameters to define the segments that make up an announcement.
________________________________________________________________________
| Segment Descriptors |
|_______________________________________________________________________|
| Symbol | Definition |
|____________________________________|__________________________________|
| 32 bit binary number | segment identifier |
| ts | text to speech |
| dt | display text |
| si | silence |
| to | tone |
| vb | variable |
|____________________________________|__________________________________|
Segment Identifier:
A 32 bit binary integer identifying a provisioned entity such as a
recording, set, sequence, etc.
Text To Speech:
Specifies a text string to be converted to speech.
Display Text:
Specifies a text string to be displayed on a device.
Silence:
Specifies a length of silence to be played in units of 100
milliseconds.
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Tone:
Specifies a tone to be played by algorithmic generation. Exact
specification of this parameter is tbd. Most tones will likely be
recorded, not generated.
Variable:
Specifies a voice variable by type, subtype, and value. Variables
are more completely defined in a subsequent section of the
document.
8. Variables
The syntax supports two kinds of variables. Embedded embedded
variables are variables that have been provisioned as part of a
segment. Standalone variables are completely specified in the
protocol message.
Typically embedded variables are provisioned along with recorded
speech, e.g. "A representative will be with you in approximately 5
minutes. If you would prefer to leave a voice message, press 1 now".
where the variable is the number of minutes. This kind of variable is
often referred to as an embedded variable.
Variables are specified by the following parameters: type, subtype,
and value. Variable types include Date, Money, Number, Time, etc.
Subtype is a refinement of type. For example the variable type Money
might have an associated range of subtypes such as Dollar, Rupee,
Dinar, etc. Not all variables require a subtype, and for these
variables the subtype parameter should be set to null.
For embedded variables, the type and subtype must be provisioned.
The value may be provisioned. If it is not provisioned it must be
specified as part of the variable reference. In a list of segments,
an embedded variable value specification applies only to the segment
that directly precedes it. If a segment has multiple embedded
variables, the values must be given in the order in which the
variables are encountered when the segment is played.
Some examples follow below:
A standalone variable:
S: pa(an=vb(mny,usd,1153))
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An embedded variable:
S: pa(an=37<1153>)
Not all variables, such as the date variable shown in the next
example, require a subtype. In that case, the subtype is encoded
with the value "null":
S: pa(an=vb(dat,null,101598))
In some cases it may be desirable to play an announcement that
contains an embedded variable without playing the variable itself.
To do this a single "null" is provided for the value:
S: pa(an=37<null>)
________________________________________________________________________
| Variables Qualifiers |
|_______________________________________________________________________|
| Symbol | Definition | Type | Subtype | Subtype Of |
|_________|__________________________|________|___________|_____________|
| dat | date | x | | |
| dig | digits | x | | |
| gen | generic | | x | dig |
| ndn | North American DN | | x | dig |
| dur | duration | x | | |
| mth | month | x | | |
| mny | money | x | | |
| num | number | x | | |
| crd | cardinal | | x | nm |
| ord | ordinal | | x | nm |
| sil | silence | x | | |
| str | string | x | | |
| txt | text | x | | |
| dsp | display text | | x | txt |
| spk | text to speech | | x | txt |
| tme | time | x | | |
| t12 | twelve hour format | | x | tme |
| t24 | twenty four hour format | | x | tme |
| ton | tone | x | | |
| wkd | weekday | x | | |
|_________|__________________________|________|___________|_____________|
Date:
Speaks a date specified as YYYYMMDD (per ISO 8601, International
Date and Time Notation [7]). For example "19981015" is spoken as
"October fifteenth nineteen ninety eight".
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RFC 2897 MGCP Advanced Audio Package August 2000
Digits:
Speaks a string of digits one at a time. If the subtype is North
American DN, the format of which is NPA-NXX-XXXX, the digits are
spoken with appropriate pauses between the NPA and NXX and between
the NXX and XXXX. If the subtype is generic, the digits are
spoken no pauses.
Duration:
Duration is specified in seconds and is spoken in one or more
units of time as appropriate, e.g. "3661" is spoken as "One hour,
one minute, and one second".
Money:
Money is specified in the smallest units of a given currency and
is spoken in one or more units of currency as appropriate, e.g.
"110" in U.S. Dollars would be spoken "one dollar and ten cents".
The three letter codes defined in ISO 4217, Currency And Funds
Code List [5] are used to specify the currency subtype. A small
excerpt from ISO 4217 follows:
__________________________________________________________
|Alpha-code | Numeric-code | Currency | Entity |
|___________|______________|__________|___________________|
|GQE | 226 | Ekwele | Equatorial Guinea |
|GRD | 300 | Drachma | Greece |
|GTQ | 320 | Quetzal | Guatemala |
|___________|______________|__________|___________________|
Money can be specified in negative or positive units of currency.
In the above example "-110" would be spoken as "minus one dollar
and ten cents".
Month:
Speaks the specified month, e.g. "10" is spoken as "October".
Specification is in MM format with "01" denoting January, "02"
denoting February, etc.
Number:
Speaks a number in cardinal form or in ordinal form. For example,
"100" is spoken as "one hundred" in cardinal form and "one
hundredth" in ordinal form. Cardinal numbers can be specified as
negative or positive.
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RFC 2897 MGCP Advanced Audio Package August 2000
Silence:
Plays a specified period of silence. Specification is in 100
millisecond units.
String:
Speaks each character of a string, e.g. "a34bc" is spoken "A,
three, four, b, c". Valid characters are a-z, A-Z, 0-9, #, and *.
Text:
Produces the specified text as speech or displays it on a device.
Time:
Speaks a time in either twelve hour format or twenty four hour
format depending on the specified subtype. For example "1700" is
spoken as "Five pm" in twelve hour format or as "Seventeen hundred
hours" in twenty four hour format. Specification is in HHMM
format per ISO 8601, International Data and Time Notation [7].
Tone:
Plays an algorithmically generated tone, specification of which is
tbd. Probably most applications will use prerecorded tones.
Weekday:
Speaks the day of the week, e.g. "Monday". Weekdays are specified
as single digits, with "1" denoting Sunday, "2" denoting Monday,
etc.
9. Selectors
Selector types, except for the pre-defined "Lang" (language)
selector, are definable by the user and may be applied to an
individual segment within an operation or to all the segments in an
operation. For each selector type, the user must also define a range
of values that the selector can assume.
For example, if the user defines a selector of type "phase-of-the-
moon", he might also define the legal values for that selector to be
"new", "half", "full", "harvest", and "blue". For the selector to
actually work at runtime, audio associated with each of the selector
values must be provisioned.
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RFC 2897 MGCP Advanced Audio Package August 2000
Although not required, it is suggested that the three letter codes
defined in ISO standard 639-2, Code For The Representation Of Names
Of Languages [4] be used as values for user defined language
selectors. A small excerpt from ISO 639-2 follows:
_________________
|Code | Language |
|_____|__________|
|cze | Czech |
|cym | Welsh |
|dan | Danish |
|_____|__________|
Selectors can apply to entire operations or to a segment within an
operation. If an operation contains multiple segments, each segment
may have its own set of selectors. If selectors for an individual
segment and selectors for the entire operation are present, the
selector for the individual segment takes precedence for that
segment. The selectors for the operation apply to all segments
within that operation that do not have individual segment selectors.
If a selector set is not specified, provisioned defaults are used.
Selectors are applied to variables only after the variable has been
resolved. For instance if a date variable resolved to "October 15th,
1998" the voice with which the variable is spoken could resolve to
either male or female if a gender selector had been defined.
10. Aliases
Aliasing of audio segments is supported. The alias to segment id
mapping is provisioned and at runtime the alias is resolved to its
associated segment id. The syntax for an alias is inclusion of the
alias between two forward slashes, e.g.:
S: pa(an=/not-in-service/)
11. Examples
This section presents a number of examples of how the syntax is used.
Note that arguments to an event are separated by a one or more
whitespace characters, which can be either an ASCII space character
or an ASCII tabulation character.
Play an announcement that consists of a single segment:
S: pa(an=39)
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RFC 2897 MGCP Advanced Audio Package August 2000
Play an announcement that consists of multiple segments:
S: pa(an=39,40,47)
Play an announcement that consists of a recording followed by silence
followed by text to speech followed by a standalone voice variable:
S: pa(an=39 si(30) ts(hello) vb(my,usd,3999))
Play an announcement with an embedded variable. If the first three
segments of the previous announcement were provisioned as segment 40,
the following would be exactly equivalent to the play in the
preceding example:
S: pa(an=40<3999>)
Play an announcement with two embedded variables:
S: pa(an=113<3999,10151998>)
Play a prompt and collect a single digit. If need be, play a
reprompt, a no digits prompt, and a success or failure announcement.
Give the user three attempts to enter a digit:
S: pc(ip=21 rp=109 nd=102 fa=81 sa=72 na=3)
Play a prompt and collect a single digit. If the user does not enter
a digit replay the initial prompt. Give the user three attempts to
enter a digit:
S: pc(ip=21 na=3)
Play a prompt and record voice. If the user does not speak play a no
speech prompt. Give the user two attempts to record:
S: pr(ip=22 ns=42 na=2)
Play an announcement at ninety percent of its original speed and five
decibels softer than its original volume. Play the announcement
three times with two seconds of silence between plays.
S: pa(an=27 sp=90 vl=-5 it=3 iv=20)
Give the user two attempts to enter a three digit pattern. Clear the
digit buffer before playing the prompt. The user can signal end of
input using the # key, which is not returned to the call agent with
the collected digits.
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RFC 2897 MGCP Advanced Audio Package August 2000
S: pc(ip=43 cb=true mn=3 mx=3 na=2)
Give the user three attempts to enter a three digit pattern. If the
user enters one digits or two digits on the first or second attempts
a reprompt is played. If the user enters no digits on the first or
second attempts a no digits reprompt is played. If all three
attempts fail, a failure announcement is played. If one of the
attempts is successful, a success announcement is played and the
collected digits are returned to the call agent. The user can signal
end of input using the # key. If the # key terminates a successful
input attempt, the collected digits, but not the # key, are returned
to the call agent.
S: pc(ip=87 rp=5 nd=409 fa=9 sa=18 mx=3 na=3)
Give the user a single attempt to enter a a 1 to 4 digit pattern,
allow 8 seconds for the user to enter the first digit, and allow 6
seconds for the user to enter each subsequent digit. If the
subsequent digit timer expires after the user has less than four
digits, the digits collected are returned to the call agent. The
user can signal end of input using the # key which is not returned to
the call agent with the collected digits.
S: pc(ip=4 fdt=80 idt=60 mx=4)
Give the user three chances to enter an 11 digit number that begins
with 0 or 1. If the user makes a mistake while entering digits, he
can press the * key to discard any digits already collected, replay
the prompt, and resume collection.
S: pc(ip=33 mn=11 mx=11 sik=01 rsk=* na=3)
Give the user three chances to enter an 11 digit number that begins
with 0 or 1. If the user makes a mistake while entering digits, he
can press the key sequence *11 to discard any digits already
collected, replay the prompt, and resume collection. If the user
enters the key sequence *12 the play collect is terminated along with
any queued events, and the terminating key sequence is returned to
the call agent for processing.
S: pc(ip=33 mn=11 mx=11 sik=01 rsk=*11 rtk=*12 na=3)
Give the user two chances to make a recording. After playing the
prompt, wait 5 seconds for the user to speak, otherwise replay the
initial prompt and try again. If the user does speak, wait for seven
seconds after speech stops to make sure the user is finished. If the
recording is successful, return a reference to the recording to the
call agent.
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RFC 2897 MGCP Advanced Audio Package August 2000
S: pr(ip=6 prt=50 pst=70 na=2)
Play an announcement in the default language:
S: pa(an=5)
Play the same announcement the English. In the first example, the
selector applies to the an segment; in the second it applies to the
pa operation. For these particular examples, the net effect is the
same.
S: pa(an=5[Lang=eng]) or S: pa(an=5)[Lang=eng]
Play an announcement in Danish using a female voice with a Cajun
accent.
S: pa(an=6)[Lang=dan,gender=female,accent=cajun]
Play the first part of an announcement in English, the second part in
the default language, and the third part in French.
S: pa(an=5[Lang=eng],6,7[Language=fra])
Play an announcement with an embedded variable in English:
S: pa(an=5<101599>)[Lang=eng]
12. Formal Syntax Description
AudPkgEvent = PlayAnnouncement / PlayCollect / PlayRecord /
OperationComplete / OperationFailed / EndSignal
PlayAnnouncement = [ AdvAudioPkgToken SLASH ] PlayAnnToken
LPAREN PlayAnnParmList RPAREN [ OpSelectorList ]
PlayCollect = [ AdvAudioPkgToken SLASH ] PlayColToken
LPAREN [ PlayColParmList ] RPAREN [ OpSelectorList ]
PlayRecord = [ AdvAudioPkgToken SLASH ] PlayRecToken
LPAREN [ PlayRecParmList ] RPAREN [ OpSelectorList ]
OperationComplete = [ AdvAudioPkgToken SLASH ] OpCompleteToken
LPAREN OpCompleteParmList RPAREN
OperationFailed = [ AdvAudioPkgToken SLASH ] OpFailedToken
LPAREN ReturnCodeParm RPAREN
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RFC 2897 MGCP Advanced Audio Package August 2000
EndSignal = [ AdvAudioPkgToken SLASH ] EndSignalToken
LPAREN SignalParm RPAREN
OpSelectorList = LSQUARE OpSelector *( COMMA OpSelector ) RSQUARE
OpSelector = NAME EQUALS NAME
PlayAnnParmList = PlayAnnParm *( WSP PlayAnnParm )
PlayColParmList = PlayColParm *( WSP PlayColParm )
PlayRecParmList = PlayRecParm *( WSP PlayRecParm )
OpCompleteParmList = OpCompleteParm *( WSP OpCompleteParm )
PlayAnnParm = ( AnnouncementParm / IterationsParm / IntervalParm /
DurationParm / SpeedParm / VolumeParm )
PlayColParm = ( InitPromptParm / RepromptParm / NoDigitsParm /
FailAnnParm / SuccessAnnParm / NoInterruptParm /
SpeedParm / VolumeParm / ClearBufferParm /
MaxDigitsParm / MinDigitsParm / DigitPatternParm /
FirstDigitParm / InterDigitParm / ExtraDigitParm /
RestartKeyParm / ReinputKeyParm / ReturnKeyParm /
PosKeyParm / StopKeyParm / StartInputKeyParm /
EndInputKeyParm / IncludeEndInputKey /
NumAttemptsParm )
PlayRecParm = ( InitPromptParm / RepromptParm / NoSpeechParm /
FailAnnParm / SuccessAnnParm / NoInterruptParm /
SpeedParm / VolumeParm / ClearBufferParm /
PreSpeechParm / PostSpeechParm / RecordLenParm /
RestartKeyParm / ReinputKeyParm / ReturnKeyParm /
PosKeyParm / StopKeyParm / EndInputKeyParm /
RecPersistParm / OverrideAudioParm /
RestoreAudioParm / DeletePersistParm /
NumAttemptsParm )
OpCompleteParm = ( VoiceInterruptParm / IntKeySeqParm /
NumAttemptsParm / AmtPlayedParm / DigitsColParm /
RecordingIdParm / ReturnCodeParm )
AnnouncementParm = AnParmToken EQUALS Segmentlist
InitPromptParm = IpParmToken EQUALS Segmentlist
RepromptParm = RpParmToken EQUALS Segmentlist
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RFC 2897 MGCP Advanced Audio Package August 2000
NoDigitsParm = NdParmToken EQUALS Segmentlist
NoSpeechParm = NsParmToken EQUALS Segmentlist
FailAnnParm = FaParmToken EQUALS Segmentlist
SuccessAnnParm = SaParmToken EQUALS Segmentlist
DurationParm = DuParmToken EQUALS NUMBER
IterationsParm = ItParmToken EQUALS ( NUMBER / "-1" )
IntervalParm = IvParmToken EQUALS NUMBER
SpeedParm = SpParmToken EQUALS SIGNEDINT
VolumeParm = VlParmToken EQUALS SIGNEDINT
NoInterruptParm = NiParmToken EQUALS BOOLSTR
ClearBufferParm = CbParmToken EQUALS BOOLSTR
MaxDigitsParm = MxParmToken EQUALS NUMBER
MinDigitsParm = MnParmToken EQUALS NUMBER
DigitPatternParm = DpParmToken EQUALS DIGITPATTERN
FirstDigitParm = FdtParmToken EQUALS NUMBER
InterDigitParm = IdtParmToken EQUALS NUMBER
ExtraDigitParm = EdtParmToken EQUALS NUMBER
PreSpeechParm = PrtParmToken EQUALS NUMBER
PostSpeechParm = PstParmToken EQUALS NUMBER
RecordLenParm = RltParmToken EQUALS NUMBER
RestartKeyParm = RskParmToken EQUALS CommandKeySequence
ReinputKeyParm = RikParmToken EQUALS CommandKeySequence
ReturnKeyParm = RtkParmToken EQUALS CommandKeySequence
PosKeyParm = PskParmToken EQUALS KeyPadKey COMMA PosKeyAction
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RFC 2897 MGCP Advanced Audio Package August 2000
PosKeyAction = FirstSegmentToken / LastSegmentToken /
PreviousSegmentToken / NextSegmentToken /
CurrentSegmentToken
StopKeyParm = StkParmToken EQUALS KeyPadKey
StartInputKeyParm = SikParmToken EQUALS KeySet
EndInputKeyParm = EikParmToken EQUALS KeyPadKey
IncludeEndinputKey = IekParmToken EQUALS BOOLSTR
RecPersistParm = RpaParmToken EQUALS BOOLSTR
OverrideAudioParm = OaParmToken EQUALS SEGID
RestoreAudioParm = RaParmToken EQUALS SEGID
DeletePersistParm = DpaParmToken EQUALS SEGID
NumAttemptsParm = NaParmToken EQUALS NUMBER
VoiceInterruptParm = ViParmToken EQUALS BOOLSTR
IntKeySeqParm = IkParmToken EQUALS CommandKeySequence
AmtPlayedParm = ApParmToken EQUALS NUMBER
DigitsColParm = DcParmToken EQUALS KeySequence
RecordingIdParm = RiParmToken EQUALS NUMBER
ReturnCodeParm = RcParmToken EQUALS 3*3(DIGIT)
KeyPadKey = "1" / "2" / "3" / "4" / "5" / "6" / "7" / "8" / "9" /
"*" / "#"
CommandKeySequence = 1*3(KeyPadKey)
KeySequence = 1*64(KeyPadKey)
KeySet = 1*11(KeyPadKey)
SignalParm = SgParmToken EQUALS ( PlayAnnToken / PlayColToken /
PlayRecToken ) RPAREN
Segmentlist = SegmentDescriptor *( COMMA SegmentDescriptor )
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RFC 2897 MGCP Advanced Audio Package August 2000
SegmentDescriptor = ( ( SegmentId [ EmbedVarList ]
[ SegSelectorList ] ) /
( TextToSpeechSeg [ SegSelectorList ] ) /
( DisplayTextSeg [ SegSelectorList ] ) /
( VariableSeg [ SegSelectorList ] ) /
SilenceSeg )
SegmentId = ( Segid / Alias )
TextToSpeechSeg = TextToSpeechSegToken LPAREN NAME RPAREN
DisplayTextSeg = DisplayTextSegToken LPAREN NAME RPAREN
SilenceSeg = SilenceSegToken LPAREN NAME RPAREN
VariableSeg = VariableSegToken LPAREN FullSpecVar RPAREN
Segid = NUMBER
Alias = SLASH NAME SLASH
EmbedVarList = LANGLE NAME *( COMMA NAME ) RANGLE
SegSelectorList = LSQUARE SegSelector *( COMMA SegSelector ) RSQUARE
SegSelector = NAME EQUALS NAME
FullSpecVar = ( DateVariable / DigitsVariable / DurationVariable /
MonthVariable / MoneyVariable / NumberVariable /
SilenceVariable / StringVariable / TextVariable /
TimeVariable / WeekdayVariable )
DateVariable = DateVarToken COMMA NullStrToken COMMA Date
Date = 8*8(DIGIT)
DigitsVariable = DigitsVarToken COMMA (NorthAmericanDnToken /
GenericDigitsToken) COMMA NUMBER
DurationVariable = DurationVarToken COMMA NullStrToken COMMA NUMBER
MoneyVariable = MoneyVarToken COMMA 3*3(ALPHA) COMMA OPTSIGNEDINT
MonthVariable = MonthVarToken COMMA NullStrToken COMMA Month
Month = "01" / "02" / "03" / "04" / "05" / "06" / "07" / "08" / "09" /
"10" / "11" / "12"
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RFC 2897 MGCP Advanced Audio Package August 2000
NumberVariable = (NumberVarToken COMMA CardinalNumberToken COMMA
OPTSIGNEDINT) / (NumberVarToken COMMA
OrdinalNumberToken COMMA NUMBER)
SilenceVariable = SilenceVarToken COMMA NullStrToken COMMA NUMBER
StringVariable = StringVarToken COMMA NullStrToken COMMA *(KeyPadKey)
OrdinalNumberToken) COMMA NUMBER
SilenceVariable = SilenceVarToken COMMA NullStrToken COMMA NUMBER
StringVariable = StringVarToken COMMA NullStrToken COMMA
*(KeyPadKey)
TextVariable = TextVarToken COMMA (DisplayTextToken /
TextToSpeechToken) COMMA NAME
TimeVariable = TimeVarToken COMMA (TwelveHourFormatToken /
TwentyFourHourFormatToken) COMMA 4*4(DIGIT)
WeekdayVariable = WeekdayVarToken COMMA NullStrToken COMMA NAME
AdvAudioPkgToken = "A"
PlayAnnToken = "pa"
PlayColToken = "pc"
PlayRecToken = "pr"
OpCompleteToken = "oc"
OpFailedToken = "of"
EndSignalToken = "es"
TextToSpeechSegToken = "ts"
DisplayTextSegToken = "dt"
SilenceSegToken = "si"
VariableSegToken = "vb"
AnParmToken = "an"
IpParmToken = "ip"
RpParmToken = "rp"
NdParmToken = "nd"
NsParmToken = "ns"
FaParmToken = "fa"
SaParmToken = "sa"
NiParmToken = "ni"
ItParmToken = "it"
IvParmToken = "iv"
DuParmToken = "du"
SpParmToken = "sp"
VlParmToken = "vl"
CbParmToken = "cb"
MxParmToken = "mx"
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RFC 2897 MGCP Advanced Audio Package August 2000
MnParmToken = "mn"
DpParmToken = "dp"
FdtParmToken = "fdt"
IdtParmToken = "idt"
EdtParmToken = "edt"
PrtParmToken = "prt"
PstParmToken = "pst"
RltParmToken = "rlt"
RskParmToken = "rsk"
RikParmToken = "rik"
RtkParmToken = "rtk"
PskParmToken = "psk"
StkParmToken = "stk"
SikParmToken = "sik"
EikParmToken = "eik"
IekParmToken = "iek"
RpaParmToken = "rpa"
DpaParmToken = "dpa"
OaParmToken = "oa"
RaParmToken = "ra"
NaParmToken = "na"
RidParmToken = "rid"
ViParmToken = "vi"
IkParmToken = "ik"
ApParmToken = "ap"
DcParmToken = "dc"
RiParmToken = "ri"
RcParmToken = "rc"
SgParmToken = "sg"
DateVarToken = "dat"
DigitsVarToken = "dig"
DuratioNVarToken = "dur"
MoneyVarToken = "mny"
MonthVarToken = "mth"
NumberVarToken = "num"
SilenceVarToken = "sil"
StringVarToken = "str"
TextVarToken = "txt"
TimeVarToken = "tme"
WeekdayVarToken = "wkd"
GenericDigitsToken = "gen"
NorthAmericanDnSToken = "ndn"
CardinalNumberToken = "crd"
OrdinalNumberToken = "ord"
DisplayTextToken = "dsp"
TextToSpeechToken = "spk"
TwelveHourFormatToken = "t12"
TwentyFourHourFormatToken = "t24"
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RFC 2897 MGCP Advanced Audio Package August 2000
NullStrToken = "null"
FirstSegmentToken = "fst"
LastSegmentToken = "lst"
PreviousSegmentToken = "prv"
NextSegmentToken = "nxt"
CurrentSegmentToken = "cur"
BOOLSTR = "true" / "false"
NAMECHAR = ALPHA / DIGIT / "_" / "-"
NAME = 1*64(NAMECHAR)
NUMBER = DIGIT *31(DIGIT)
SIGNEDINT = ("+" / "-") DIGIT *31(DIGIT)
OPTSIGNEDINT = ["+" / "-"] DIGIT *31(DIGIT)
EQUALS = "="
COMMA = ","
LSQUARE = "["
RSQUARE = "]"
LANGLE = "<"
RANGLE = ">"
LPAREN = "("
RPAREN = ")"
SLASH = "/"
WSP = SP / HTAB
13. References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Arango, M., Dugan, A., Elliott, I., Huitema, C. and S. Pickett,
"Media Gateway Control Protocol (MGCP) Version 0.1", RFC 2705,
October 1999.
[3] Cromwell, D. and M. Durling, "Requirements For Control Of A Media
Services Function", Version 0.0, Work in Progres..
[4] ISO 639-2, "Code For The Representation Of Names Of Languages",
1998.
[5] ISO 4217, "Currency And Funds Code List", 1981.
[6] Cuervo, F., Hill, B., Greene, N., Huitema, C., Rayhan, A., Rosen,
B. and J. Segers, "Megaco Protocol", RFC 2885, August 2000.
[7] ISO 8601, "International Date and Time Notation", 1998.
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RFC 2897 MGCP Advanced Audio Package August 2000
14. Author's Address
David Cromwell
Nortel Networks
Box 13478
35 Davis Drive
Research Triangle Park, NC 27709
Phone: 919-991-8870
EMail: cromwell@nortelnetworks.com
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RFC 2897 MGCP Advanced Audio Package August 2000
15. Full Copyright Statement
Copyright (C) The Internet Society (2000). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS 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.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
Cromwell Informational [Page 34]