SIPPING E. Burger
Internet-Draft SnowShore Networks, Inc.
Expires: April 25, 2004 M. Dolly
AT&T Labs
October 26, 2003
Keypad Stimulus Protocol (KPML)
draft-ietf-sipping-kpml-01
Status of this Memo
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all provisions of Section 10 of RFC2026.
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
The Key Press Stimulus Protocol uses the SIP SUBSCRIBE/NOTIFY
mechanism and Keypad Markup Language (KPML) to provide instructions
to SIP User Agents for the reporting of user key presses.
Conventions used in this document
RFC2119 [1] provides the interpretations for the key words "MUST",
"MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", and "OPTIONAL" found in this document.
In the narrative discussion, the "user device" is a User Agent that
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will report stimulus. it could be, for example, a SIP phone, edge
media processor, or media gateway. An "application" is a User Agent
requesting the user device to report stimulus. The "user" is an
entity that stimulates the user device. In English, the user device
is a phone, the application is an application server or proxy server,
and the user presses keys to generate stimulus.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Keypress Stimulus Protocol . . . . . . . . . . . . . . . . . 5
2.1 Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Operation . . . . . . . . . . . . . . . . . . . . . . . . . 7
3. Protocol Machinery . . . . . . . . . . . . . . . . . . . . . 8
3.1 Event Package Name . . . . . . . . . . . . . . . . . . . . . 8
3.2 Event Package Parameters . . . . . . . . . . . . . . . . . . 8
3.3 SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . . . . 10
3.4 Subscription Duration . . . . . . . . . . . . . . . . . . . 10
3.5 NOTIFY Bodies . . . . . . . . . . . . . . . . . . . . . . . 10
3.6 Notifier Generation of NOTIFY Messages . . . . . . . . . . . 10
3.6.1 SIP Protocol-Generated . . . . . . . . . . . . . . . . . . . 10
3.6.2 KPML-Generated . . . . . . . . . . . . . . . . . . . . . . . 10
3.6.3 One-Shot vs. Persistant Requests . . . . . . . . . . . . . . 10
4. Message Format - KPML . . . . . . . . . . . . . . . . . . . 11
4.1 KPML Request . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1.1 Digit Suppression . . . . . . . . . . . . . . . . . . . . . 12
4.1.2 One-Shot and Persistant Triggers . . . . . . . . . . . . . . 14
4.1.3 Multiple Patterns . . . . . . . . . . . . . . . . . . . . . 14
4.1.4 Multiple, Simultaneous Subscriptions . . . . . . . . . . . . 14
4.2 KPML Reports . . . . . . . . . . . . . . . . . . . . . . . . 15
4.2.1 Pattern Match Reports . . . . . . . . . . . . . . . . . . . 15
4.2.2 KPML No Match Reports . . . . . . . . . . . . . . . . . . . 16
5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.1 Monitoring for Octorhorpe . . . . . . . . . . . . . . . . . 17
5.2 Dial String Collection . . . . . . . . . . . . . . . . . . . 17
5.3 Interactive Digit Collection . . . . . . . . . . . . . . . . 18
6. Call Flow Example . . . . . . . . . . . . . . . . . . . . . 19
6.1 INVITE-Initiated Dialog . . . . . . . . . . . . . . . . . . 19
6.2 Third-Party Subscription . . . . . . . . . . . . . . . . . . 24
6.3 Remote-End Monitoring . . . . . . . . . . . . . . . . . . . 24
7. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . 24
8. Enumeration of KPML Failure Codes . . . . . . . . . . . . . 26
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . 26
9.1 IANA Registration of MIME media type application/kpml+xml . 26
10. Security Considerations . . . . . . . . . . . . . . . . . . 26
Normative References . . . . . . . . . . . . . . . . . . . . 27
Informative References . . . . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 28
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A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 28
B. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 29
Intellectual Property and Copyright Statements . . . . . . . 30
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1. Introduction
This document describes the Key Press Stimulus Protocol. The Key
Press Stimulus Protocol exchanges messages using the SUBSCIBE and
NOTIFY methods of SIP [2] with message bodies formed from the Keypad
Markup Language, KPML. KPML is a markup [12] that enables "dumb
phones" to report user key-press events. Colloquially, this
mechanism provides for "digit reporting" or "DTMF reporting."
We strongly discourage the use of non-validating XML parsers, as one
can expect problems with future versions of KPML. That said, one
could envision user devices that only accept SIP reporting and have a
fixed parser, rather than a full XML parser. This means that a goal
of KPML is to fit in an extremely small memory and processing
footprint. Note KPML has a corresponding lack of functionality. For
those applications that require more functionality, please refer to
VoiceXML [13] and MSCML [3].
The name of the markup, KPML, reflects its legacy support role. The
public switched telephony network (PSTN) accomplished end-to-end
signaling by transporting Dual-Tone, Multi-Frequency (DTMF) tones in
the bearer channel. This is in-band signaling.
From the point of view of an application being signaled, what is
important is the fact the stimulus occurred, not the tones used to
transport the stimulus. For example, an application may ask the
caller to press the "1" key. What the application cares about is the
key press, not that there were two cosine waves of 697 Hz and 1209 Hz
transmitted.
A SIP-signaled [4] network transports end-to-end signaling with
RFC2833 [14] packets. In RFC2833, the signaling application inserts
RFC2833 named signal packets as well as or instead of generating
tones in the media path. The receiving application gets the signal
information, which is what it wanted in the first place.
RFC2833 is the only method that can correlate the time the end user
pressed a digit with the user's media. However, out-of-band
signaling methods, as are appropriate for user device to application
signaling, do not need millisecond accuracy. On the other hand, they
do need reliability, which RFC2833 does not provide.
An interested application could request notifications of every key
press. However, many of the use cases for such signaling has the
application interested in only one or a few keystrokes. Thus we need
a mechanism for specifying to the user device what stimulus the
application would like notification of.
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2. Keypress Stimulus Protocol
2.1 Model
There are two usage models for the protocol. Functionally, they are
both equivalent. However, it is useful to understand the use cases
driving the signaling.
The first model is that of a SIP User Agent (UA) that directly
interacts, on a given dialog, with the end device. Figure 1 shows a
two-party SIP dialog. In this scenario, the SIP UA requests the End
Point to report on key press events that would normally eminate from
End Point port B.
In this case, the requesting User Agent requests digit notification
on the same dialog established for the call, between SIP ports A and
X.
+-------+ SIP +-----+
| A--------------------X |
| End | | SIP |
| Point | RTP | UA |
| B--------------------Y |
+-------+ +-----+
Figure 1: Endpoint Model
The second model is that of a third-party application that is
interested in entered key presses. Figure 2 shows an established
two-party SIP dialog between the End Point and the SIP UA. The
requesting application addresses the particular media stream either
by referencing the established dialog identifier refering to the
dialog between SIP ports A and X or by referencing the SDP, either of
port B or port Y.
Specifying the SDP for port Y monitors the key presses at the SIP UA,
as received by the End Point. Specifying the SDP for port B monitors
the key presses at the End Point.
Not all End Point devices are able to monitor the remote media
stream. However, the End Point MUST be able to report on local (End
Point-generated) key press events.
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+-------------+
| Requesting |
/---| Application |
/ +-------------+
/
SIP / (SUBSCRIBE/NOTIFY)
/
/
+---M---+ SIP (INVITE) +-----+
| A--------------------X |
| End | | SIP |
| Point | RTP | UA |
| B--------------------Y |
+-------+ +-----+
Figure 2: Third-Party Model
The third model is that of a media proxy. A media proxy is a media
relay in the terminology of RFC1889 [15]. However, in addition to
the RTP forwarding capability of a RFC1889 media relay, the media
proxy can also do light media processing, such as tone detection,
tone transcoding (tones to RFC2833 [14], and so on.
If the Requesting Application uses dialog identifiers to identify the
stream to monitor, the default is to monitor the media entering the
End Point. For example, if the Requesting Applciation in Figure 3
usess the dialog represented by SIP ports V-C, then the media coming
from SIP UAa RTP port W gets monitored. Likewise, the dialog
represented by A-X directs the End Point to monitor the media coming
from SIP UAb RTP Port Y.
To monitor the reverse direction, from the End Point to one of the
User Agents, the Requesting Application MUST specify the SDP of the
End Point RTP port to monitor, as in the first example above.
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+-------------+
| Requesting |
/---| Application |
/ +-------------+
/
SIP / (SUBSCRIBE/NOTIFY)
/
/
+-----+ SIP +---M---+ SIP +-----+
| V--------------------C A--------------------X |
| SIP | | End | | SIP |
| UAa | RTP | Point | RTP | UAb |
| W--------------------D B--------------------Y |
+-----+ +-------+ +-----+
Figure 3: Media Proxy Model
2.2 Operation
The key press stimulus protocol uses explicit subscription requests
and notification requests, using the semantics of SUBSCRIBE/NOTIFY
[2].
Following the semantics of SUBSCRIBE, if the user device receives a
second subscription on the same dialog, the user device MUST
terminate the existing KPML request (if any) and replace it with the
new request.
If the user device supports multiple, simultaneous KPML requests, the
application registers the separate requests on different
SUBSCRIBE-initiated dialogs. An application may register multiple
digit patterns in a single KPML request.
If the user device does not support multiple, simultaneous KPML
requests, it responds with an error response code. See Section 4.1.4
for more information.
A KPML request can be persistent or one-shot. Persistent requests
are active until either the dialog terminates, the client replaces
them, or the client deletes them by sending a null document on the
user instance. One-shot requests terminate themselves once a match
occurs. The persist KPML element specifies whether the subscription
remains registered for the duration specified in the SUBSCRIBE
message or if it automatically terminates after a pattern matches.
KPML requests route to the user device using standard SIP request
routing. A KPML request identifies the leg in question in one of two
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ways. The first method is to send the request on an existing,
INVITE-initiated dialog. The second method is to explicitly identify
the call leg by its transport-layer identifiers, such as RTP port
number and IP address.
Response messages are KPML documents (messages). If the user device
matched a digit map, the response indicates the digits detected and
whether the user device suppressed digits. If the user device had an
error, such as a timeout, it will indicate that, instead.
3. Protocol Machinery
The Key Press Stimulus Protocol uses the SIP [4]SUBSCRIBE/NOTIFY [2]
mechanism.
The registration of a digit map is simply setting a digit event
notification filter. When the device detects the digits, it sends an
event notification to the application.
The following sub-sections are the formal specification of the KPML
SIP-specific event notification package.
3.1 Event Package Name
The name for the Key Press Stimulus Protocol package is "kpml".
3.2 Event Package Parameters
The "leg" parameter identifies the call leg being monitored.
If the "leg" parameter is not present, the SUBSCRIBE MUST be on an
established INVITE-initiated SIP dialog. In this case, the leg the
end device monitors is the call leg associated with the established
dialog. If there is no corresponding dialog or call leg, the end
device will send a 481 result code in a KPML notification.
NOTE: The SUBSCRIBE will presumably succeed, resulting in a 200
OK. However, the "current state" will be the KPML 481 result, and
the subscription state will be "terminated."
If the application is using SIP-level identifiers, the value of the
"leg" parameter is "SIP". If the application is using SDP-level
parameters, the value of the "leg" parameter is "SDP".
SIP identifies call legs by their dialog identifier. The dialog
identifier is the to:, from:, and call-id: entities.
To identify a specific dialog, all three of these parameters MUST be
present. The to-tag matches the local address including tag, the
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from-tag matches the remote address including tag, and the call-id
matches the Call-ID.
Note there may be ambiguity in specifying only the SIP dialog to
monitor. The dialog may specify multiple SDP streams that could
carry key press events. For example, a dialog may have multiple
audio streams. Wherever possible, the End Point MAY apply local
policy to diambiguate which stream or streams to monitor. However,
if the Application desires to specify exactly which stream to
monitor, it MUST use the SDP method of specifying which stream to
monitor.
For most situations, such as a mono point-to-point call with a single
codec, the stream to monitor is obvious. In such situations the
Application need not specify which stream to monitor.
The BNF for these parameters is as follows. The definitions of
callid, token, EQUAL, SWS, and DQUOTE are from RFC3261 [4].
call-id = "call-id" EQUAL DQUOTE callid DQUOTE
from-tag = "from-tag" EQUAL token
to-tag = "to-tag" EQUAL token
The call-id parameter is a quoted string. This is because the BNF for
word (which is used by callid) allows for characters not allowed
within token. One usually just copies these elements from the
Call-Id, to, and from fields of the SIP INVITE.
One can use any method of determining the dialog identifier. One
method available, particularly for third-party applications, is to
use the SIP Dialog Package [16].
SDP identifies call legs by transport connection information (e.g.,
IPv6 IP address) and media address. The identifiers are the c-line
and m-line from SDP.
The BNF for these parameters is as follows. The definitions of
nettype, addrtype, connection-address, media, port, integer, space,
proto, and fmt are from RFC2327 [5] as updated by RFC3266 [6].
address = "c" EQUAL DQUOTE nettype space addrtype space
connection-address DQUOTE
media = "m" EQUAL DQUOTE media space port ["/" integer]
[space [proto [1*(space fmt)]]] DQUOTE
All of the c-line attributes are significant. However, for the
m-line, only the port (and optional pair mark) is significant.
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Note the c-line might not be on the End Point. In this case, the End
Point monitors the stream from the specified host. Note there is no
quirement on an End Point to be able to monitor remote streams.
3.3 SUBSCRIBE Bodies
Key press filtering requests uses KPML, as described in Section 4.1.
The MIME type for KPML is application/kpml+xml.
3.4 Subscription Duration
The subscription lifetime should be longer than the expected call
time. The default subscription lifetime (Expires value) MUST be 7200
seconds. This two-hour subscription time is entirely arbitrary.
Please contact the editor if you have a better suggestion, and why.
3.5 NOTIFY Bodies
The key press notification uses KPML, as described in Section 4.2.
The MIME type for KPML is application/kpml+xml. The default MIME
type for the kpml event package is application/kpml+xml.
3.6 Notifier Generation of NOTIFY Messages
3.6.1 SIP Protocol-Generated
The end device (notifier in SUBSCRIBE/NOTIFY parlance) generates
NOTIFY requests based on the requirements of RFC3265 [2].
Specifically, unless a SUBSCRIBE request is not valid, all SUBSCRIBE
requests will result in an immediate NOTIFY.
The KPML payload distinguishes between a NOTIFY that RFC3265 mandates
and a NOTIFY informing of key presses. If there are no digits
quarantined at the time of the SUBSCRIBE (see Section 4.1 below),
then the immediate NOTIFY MUST return a valid KPML document with a
KPML result code of 100. If there are digits quarantined, then the
NOTIFY MUST return the appropriate KPML document.
3.6.2 KPML-Generated
During the subscription lifetime, the end device may detect a key
press stimulus that triggers a KPML event. In this case, the end
device (notifier) MUST return the appropriate KPML document.
3.6.3 One-Shot vs. Persistant Requests
A one-shot kpml subscription is one that the KPML document does not
mark as persistent. If the end device detects a key press stimulus
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that triggers a one-shot KPML event, then the end device (notifier)
MUST set the "Subscription-State" in the NOTIFY message to
"terminated". At this point the end device MUST consider the
subscription destroyed. This means that further SUBSCRIBE requests
on the same dialog MUST result in SIP 481 SUBSCRIPTION DOES NOT EXIST
response.
For persistent kpml subscriptions, the KPML document remains active
for the lifetime of the SUBSCRIPTION.
NOTE: If the subscription uses the leg="SDP" method of
determining the call leg to monitor, be aware that if the call
ends, it is the responsibility of the application to unsubscribe
the kpml subscription.
4. Message Format - KPML
The Key Press Stimulus Protocol exchanges KPML messages. There are
two, mutually exclusive elements to KPML: the request and response.
4.1 KPML Request
A KPML document (message) contains a <pattern> tag with a series of
<regex> tags. The <regex> element specifies a digit pattern for the
device to report on. KPML supports three modes of digit map
specification: MSCML [3] regular expressions, MGCP [7] digit maps,
and H.248.1 [8] digit maps. The type attribute indicates what kind
of digit map appears in the expression.
regex The default; use regular expression matching.
mgcpdigitmap Use digit maps as specified in MGCP [7].
megacodigitmap Use digit maps as specified in H.248.1 [8].
Interface attributes, such as what constitutes a long key press, are
implementation matters beyond the scope of this document.
Some devices can buffer entered digits. Subsequent KPML requests
first apply their patterns against the buffered digits. Some
applications use modal interfaces where the first few key presses
determine what the following digits mean. For a novice user, the
application may play a prompt describing what mode the application is
in. However, "power users" often barge through the prompt.
The protocol provides a flush attribute to the <pattern> tag. The
default is "flush=no". Flushing digits means that the user device
flushes any buffered digits. This has the effect of ignoring entered
digits before the KPML request.
NOTE: Protocol action like this imposes an infinite buffer
requirement on the End Device. Options are to make buffer depth
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purely an implementation issue; have a buffer size attribute on
the request (and fail if cannot honor request); NOTIFY if the
buffer fills; others?
If the user presses a key not matched by the <regex> tags, the user
device MUST discard the key press from consideration against the
current or future KPML messages. However, as described above, once
there is a match, the user device quarantines any keys the user
enters subsequent to the match.
The end device MAY support an inter-digit timeout value. This is the
amount of time the end device will wait for user input before
returning a timeout error result on a partially matched pattern. The
application can specify the inter-digit timeout as an integer number
of milliseconds by using the interdigittimer attribute to the
<pattern> tag. The default is 1000ms. If the end device does not
support the specification of an inter-digit timeout, the end device
MUST silently ignore the specification. If the end device supports
the specification of an inter-digit timeout, but not to the
granularity specified by the value presented, the end device MUST
round the requested value to the closest value it can support.
KPML messages are independent. Thus it is not possible for the
current document to know if a following document will enable barging
or want the digits flushed. Therefore, the user device MUST
quarantine all digits detected between the time of the report and the
interpretation of the next script, if any. If the next script has
"flush=yes", then the interpreter MUST flush all collected digits.
If the next script has "flush=no", then the interpreter MUST apply
the collected digits (if possible) against the digit maps presented
by the script's <regex> tags. If there is a match, the interpreter
MUST quarantine the remaining digits. If there is no match, the
interpreter MUST flush all of the collected digits.
Unless there is a suppress indicator in the digit map, it is not
possible to know if the signaled digits are for local KPML processing
or for other recipients of the media stream. Thus, in the absence of
a digit suppression indicator, the user device transmits the digits
to the far end in real time, using either RFC2833, generating the
appropriate tones, or both.
The section Digit Suppression (Section 4.1.1) describes the operation
of the suppress indicator.
4.1.1 Digit Suppression
Under basic operation, a KPML endpoint will transmit in-band tones
(RFC2833 [14] or actual tone) in parallel with digit reporting.
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NOTE: If KPML did not have this behavior, then a user device
executing KPML could easily break called applications. For
example, take a personal assistant that uses "*9" for attention.
If the user presses the "*" key, KPML will hold the digit, looking
for the "9". What if the user just enters a "*" key, possibly
because they accessed an IVR system that looks for "*"? In this
case, the "*" would get held by the user device, because it is
looking for the "*9" pattern. The user would probably press the
"*" key again, hoping that the called IVR system just did not hear
the key press. At that point, the user device would send both "*"
entries, as "**" does not match "*9". However, that would not
have the effect the user intended when they pressed "*".
On the other hand, there are situations where passing through tones
in-band is not desirable. Such situations include call centers that
use in-band tone spills to effect a transfer.
For those situations, KPML adds a digit suppression attribute, "pre",
to the <regex> tag. There MUST NOT be more than one pre in any given
<regex>.
If there is only a single <pattern> and a single <regex>, the
suppression processing is straightforward. The end-point passes
digits until the stream matches the regular expression pre. At that
point, the endpoint will continue collecting digits, but will
suppress the generation or pass-through of any in-band digits.
If the endpoint suppresses digits, it MUST indicate this by including
the attribute "suppressed" with a value of "yes" in the digit report.
A KPML endpoint MAY perform digit suppression. If it is not capable
of digit suppression, it ignores the digit suppression attribute and
will never send a suppressed indication in the digit report. In this
case, it will match concatenated patterns of pre+value.
At some point in time, the endpoint will collect enough digits to the
point it hits a pre pattern. The interdigittimer attribute indicates
how long to wait once the user enters digits before reporting a
time-out error. If the interdigittimer expires, the endpoint MUST
issue a time-out report and transmit the suppressed digits on the
media stream.
After digit suppression begins, it may become clear that a match will
not occur. For example, take the expression <regex pre="*8"
value="xxx[2-9]xxxxxx"/>. At the point the endpoint receives "*8",
it will stop forwarding digits. Let us say that the next three
digits are "408". If the next digit is a zero or one, the pattern
will not match.
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NOTE: It is critically important for the endpoint to have a
sensible inter-digit timer. This is because an errant dot (".")
may suppress digit sending forever. See Section 4.1 for setting
the inter-digit timer.
Applications should be very careful to indicate suppression only when
they are fairly sure the user will enter a digit string that will
match the regular expression. In addition, applications should deal
with situations such as no-match or time-out. This is because the
endpoint will hold digits, which will have obvious user interface
issues in the case of a failure.
4.1.2 One-Shot and Persistant Triggers
The KPML document specifies if the patterns are to be persistent by
setting the persistent attribute to the <pattern> tag to "true".
Otherwise, the request will be a one-shot subscription. If the end
device does not support persistent subscriptions, it returns a KPML
document with the KPML result code set to 531.
4.1.3 Multiple Patterns
Some end devices may support multiple regular expressions in a given
pattern request. In this situation, the application may wish to know
which pattern triggered the event.
KPML provides a "tag" attribute to the <regex> tag. The "tag" is an
opaque string that the end device sends back in the notification
report upon a match in the digit map. In the case of multiple
matches, the end device MUST chose the longest match in the KPML
document. If multiple matches match the same length, the end device
MUST chose the first expression listed in the subscription KPML
document based on KPML document order.
If the end device does not support multiple regular expressions in a
pattern request, the end device MUST return a KPML document with the
KPML result code set to 532.
4.1.4 Multiple, Simultaneous Subscriptions
Some end devices may support multiple key press event notification
subscriptions at the same time. In this situation, the end device
honors each subscription individually and independently.
If the end device does not support multiple, simultaneous
subscriptions, the end device MUST return a KPML document with the
KPML result code set to 533.
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4.2 KPML Reports
When the user enters key press(es) that match a <regex> tag, the end
device will issue a report.
After reporting, the interpreter terminates the KPML session unless
the subscription has a persistence indicator. If the subscription
does not have a persistence indicator, the end device MUST set the
state of the subscription to "terminated" in the NOTIFY report.
If the subscription does not have a persistence indicator, to collect
more digits the requestor must issue a new request.
NOTE: This highlights the "one shot" nature of KPML, reflecting
the balance of features and ease of implementing an interpreter.
If your goal is to build an IVR session, we strongly suggest you
investigate more appropriate technologies such as VoiceXML [13] or
MSCML [3].
KPML reports have two mandatory attributes, code and text. These
attributes describe the state of the KPML interpreter on the end
device. Note the KPML code is not necessarily related to the SIP
result code. An important example of this is where a legal SIP
subscription request gets a normal SIP 200 OK followed by a NOTIFY,
but there is something wrong with the KPML request. In this case,
the NOTIFY would include the KPML failure code in the KPML report.
Note that from a SIP perspective, the SUBSCRIBE and NOTIFY were
successful. Also, if the KPML failure is not recoverable, the end
device will most likely set the Subscription-Sate to terminated.
This lets the SIP machinery know the subscription is no longer
active.
4.2.1 Pattern Match Reports
If a pattern matches, the end device will emit a KPML report. Since
this is a success report, the code is "200" and the text is "OK".
The KPML report includes the actual digits matched in the digit
attribute. The digit string uses the conventional characters '*' and
'#' for star and octothorpe respectively. The KPML report also
includes the tag attribute if the regex that matched the digits had a
tag attribute.
If the subscription requested digit suppression (Section 4.1.1) and
the end device suppressed digits, the suppressed attribute indicates
"true". The default value of suppressed is "false".
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NOTE: KPML does not include a timestamp. There are a number of
reasons for this. First, what timestamp would in include? Would
it be the time of the first detected key press? The time the
interpreter collected the entire string? A range? Second, if the
RTP timestamp is a datum of interest, why not simply get RTP in
the first place? That all said, if it is really compelling to
have the timestamp in the response, it could be an attribute to
the <response> tag.
4.2.2 KPML No Match Reports
There are a few circumstances in which the end device will emit a no
match report. They are an immediate NOTIFY in response to SUBSCRIBE
request (no digits detected yet), a request for service not supported
by end device, or a failure of a digit map to match a string
(timeout).
4.2.2.1 Immediate NOTIFY
The NOTIFY in response to a SUBSCRIBE request results in a KPML code
of 100. An example of this is in Figure 6.
NOTIFY sip:application@example.com SIP/2.0
Via: SIP/2.0/UDP proxy.example.com
Max-Forwards: 70
To: <sip:application@example.com>
From: <sip:endpoint@example.net>
Call-Id: 439hu409h4h09903fj0ioij
CSeq: 49851 NOTIFY
Content-Type: application/kpml+xml
Content-Length: 79
Event: kpml
<?xml version="1.0"?>
<kpml>
<response code="100" text="TRYING"/>
</kpml>
Figure 6: Immediate NOTIFY Example
NOTE: We should give serious thought to just having an empty body
mean this message was protocol generated. Since the Section
4.2.2.3 section describes all the message bodies on match failure,
including time-out, which has no digits returned, an empty body is
probably a much better route to go.
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4.2.2.2 Unsupported Service
See discussion above on 5xx errors.
4.2.2.3 Match Failure
Discuss timeouts here. Timeouts result in a NOTIFY with a
descriptive code and text.
5. Examples
5.1 Monitoring for Octorhorpe
A common need for pre-paid and personal assistant applications is to
monitor a conversation for a signal indicating a change in user focus
from the party they called through the application to the application
itself. For example, if you call a party using a pre-paid calling
card and the party you call redirects you to voice mail, digits you
press are for the voice mail system. However, many applications have
a special key sequence, such as the octothorpe (#, or pound sign) or
*9 that terminate the called party leg and shift the user's focus to
the application.
Figure 7 shows the KPML for long octothorpe. Note that the href is
really on one line, but divided for clarity.
<?xml version="1.0">
<kpml version="1.0">
<request>
<pattern>
<regex type="megacodigitmap" value="ZF"/>
</pattern>
</request>
</kpml>
Figure 7: Long Octothorpe Example
The regex value Z indicates the following digit needs to be a
long-duration key press. F, from the H.248.1 DTMF package, is the
octothorpe key. In fact, KPML supports all digits, 1-9, *, #, A-D
from the H.248.1 DTMF package.
5.2 Dial String Collection
In this example, the user device collects a dial string. The
application uses KPML to quickly determine when the user enters a
target number. In addition, KPML indicates what type of number the
user entered.
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<?xml version="1.0">
<kpml version="1.0">
<request>
<pattern>
<regex value="0" tag="local-operator"/>
<regex value="00" tag="ld-operator"/>
<regex type="mgcpdigitmap" value="7[x][x][x]"
tag="vpn"/>
<regex type="megacodigitmap" value="9xxxxxxx"
tag="local-number7"/>
<regex type="megacodigitmap" value="9401xxxxxxx"
tag="RI-number"/>
<regex type="megacodigitmap" value="9xxxxxxxxxx"
tag="local-number10"/>
<regex type="megacodigitmap" value="91xxxxxxxxxx"
tag="ddd"/>
<regex type="megacodigitmap" value="011x."
tag="iddd"/>
</pattern>
</request>
</kpml>
Figure 8: Dial String KPML Example Code
Note the use of the "tag" attribute to indicate which regex matched
the dialed string. The interesting case here is if the user entered
"94015551212". This string matches both the "9401xxxxxxx" and
"9xxxxxxxxxx" regular expressions. By following the rules described
in Section 4.1.3, the KPML interpreter will pick the "9401xxxxxxx"
string, as it occurs first in document order (both expressions match
the same length). Figure 9 shows the response.
<?xml version="1.0"?>
<kpml version="1.0">
<response code="200" text="OK"
digits="94015551212" tag="RI-number"/>
</kpml>
Figure 9: Dial String KPML Response
5.3 Interactive Digit Collection
This is an example where one would probably be better off using a
full scripting language such as VoiceXML [13] or MSCML [3] or a
device control language such as H.248.1 [8].
In this example, an application requests the user device to send the
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user's signaling directly to the platform in HTTP, rather than
monitoring the entire RTP stream. Figure 10 shows a voice mail menu,
where presumably the application played a "Press K to keep the
message, R to replay the message, and D to delete the message"
prompt. In addition, the application does not want the user to be
able to barge the prompt.
<?xml version="1.0">
<kpml version="1.0">
<request>
<pattern flush="yes">
<regex value="5" tag="keep" />
<regex value="7" tag="replay" />
<regex value="3" tag="delete" />
</pattern>
</request>
</kpml>
Figure 10: IVR KPML Example Code
NOTE: This usage of KPML is clearly inferior to using a device
control protocol like H.248.1. From the application's point of
view, it has to do the low-level prompt-collect logic. Granted,
it is relatively easy to change the key mappings for a given menu.
However, often more of the call flow than a given menu mapping
gets changed. Thus there would be little value in such a mapping
to KPML. We STRONGLY suggest using a real scripting language such
as VoiceXML or MSCML for this purpose.
6. Call Flow Example
6.1 INVITE-Initiated Dialog
This section describes a successful subscription and notification
from an Application with an End Device ("User A") in an
INVITE-Initiated dialog. Note the Application can be a Record-Route
Proxy, a B2BUA, or another end device.
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User A Application
| |
| INVITE F1 |
|--------------->|
| 100 F2|
|<---------------|
| 180 F3 |
|<---------------|
| 200 OK F4 |
|<---------------|
| ACK F5 |
|--------------->|
| Media Session |
|<==============>|
| SUBSCRIBE F6 | Application Subscribes to "***" from User A
|<---------------|
| 200 OK F7 |
|--------------->|
| NOTIFY F8 | Immediate Notify indicating moinitoring
|--------------->|
| 200 OK F9 |
|<---------------|
| . |
| : |
| NOTIFY F10 |
|--------------->| Notification of detection of "***"
| 200 OK F11 |
|<---------------|
| |
Connection setup between User A and an Application subscribing to a
DTMF event of "***" at User A.
F1 INVITE User A --> Application
INVITE sip:UserB@subB.example.com SIP/2.0
Via: SIP/2.0/UDP client.subA.example.com:5060;branch=z9hG4bK74
Max-Forwards: 70
From: <sip:UserA@subA.example.com>;tag=1234567
To: <sip:UserB@subB.example.com>
Call-ID: 12345601@subA.example.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.subA.example.com>
Route: <sip:application.subA.example.com;lr>
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, SUBCRIBE, NOTIFY
Allow-Events: kpml
Supported: replaces
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Content-Type: application/sdp
Content-Length: ...
v=0
o=UserA 2890844526 2890844526 IN IP4 client.subA.example.com
s=Session SDP
c=IN IP4 client.subA.example.com
t=3034423619 0
m=audio 49170 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F2 100 Trying Application --> User A
SIP/2.0 100 Trying
Via: SIP/2.0/UDP client.subA.example.com:5060;branch=z9hG4bK74
;received=192.168.12.22
From: <sip:UserA@subA.example.com>;tag=1234567
To: <sip:UserB@subB.example.com>
Call-ID: 12345601@subA.example.com
CSeq: 1 INVITE
Content-Length: 0
F3 180 Ringing Application --> User A
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP client.subA.example.com:5060;branch=z9hG4bK74
;received=192.168.12.22
Record-Route: <sip:application.subA.example.com;lr>
From: <sip:UserA@subA.example.com>;tag=1234567
To: <sip:UserB@subB.example.com>;tag=567890
Call-ID: 12345601@subA.example.com
CSeq: 1 INVITE
Contact: <sip:UserB@client.subB.example.com>
Content Length: 0
F4 200 OK Application --> User A
SIP/2.0 200 OK
Via: SIP/2.0/UDP client.subA.example.com:5060;branch=z9hG4bK74
;received=192.168.12.22
Record-Route: <sip:application.subA.example.com;lr>
From: <sip:UserA@subA.example.com>;tag=1234567
To: <sip:UserB@subB.example.com>;tag=567890
Call-ID: 12345601@subA.example.com
CSeq: 1 INVITE
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Contact: <sip:UserB@client.subB.example.com>
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, SUBSCRIBE, NOTIFY
Supported: replaces
Content-Type: application/sdp
Content-Length: ...
v=0
o=UserB 2890844527 2890844527 IN IP4 client.subB.example.com
s=Session SDP
c=IN IP4 client.subB.example.com
t=3034423619 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F5 ACK User A --> Application
ACK sip:UserB@subB.example.com SIP/2.0
Via: SIP/2.0/UDP client.subA.example.com:5060;branch=z9hG4bK74
Max-Forwards: 70
Route: <sip:application.subA.example.com;lr>
From: <sip:UserA@subA.example.com>;tag=1234567
To: <sip:UserB@subB.example.com>;tag=567890
Call-ID: 12345601@subA.example.com
CSeq: 1 ACK
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
Supported: replaces
Content-Length: 0
F6 SUBSCRIBE Application --> User A
SUBSCRIBE sip:UserA@subA.example.com SIP/2.0
Max-Forwards: 70
JVD: Swap To: and From: for new request
From: <sip:UserB@subB.example.com>;tag=567890
To: <sip:UserA@subA.example.com>;tag=1234567
Call-ID: 12345601@subA.example.com
CSeq: 1 SUBSCRIBE
Contact: <sip:UserB@client.subB.example.com>
Event: kpml
Subscription-State: active;expires=3600
Accept: application/kpml+xml
Content-Type: application/kmpl+xml
Content-Length: ...
<?xml version="1.0">
<kpml version="1.0">
<request>
<pattern>
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<regex value="***"/>
</pattern>
</request>
</kpml>
F7 200 OK User A --> Application
SIP/2.0 200 OK
To: <sip:UserA@subA.example.com>;tag=1234567
From: <sip:UserB@subB.example.com>;tag=567890
Call-ID: 12345601@subA.example.com
CSeq: 1 SUBSCRIBE
Contact: <sip:UserB@client.subB.example.com>
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, SUBSCRIBE, NOTIFY
Supported: replaces
Content-Length: 0
F8 NOTIFY User A --> Application
NOTIFY sip:UserB@subB.example.com SIP/2.0
Max-Forwards: 70
From: <sip:UserA@subA.example.com>;tag=1234567
To: <sip:UserB@subB.example.com>;tag=567890
Call-ID: 12345601@subA.example.com
CSeq: 2 NOTIFY
Content-Type: application/kpml+xml
Content-Length: ...
Event: kpml
<?xml version="1.0"?>
<kpml>
<response code="100" text="TRYING"/>
</kpml>
F9 200 OK Application --> User A
SIP/2.0 200 OK
From: <sip:UserA@subA.example.com>;tag=1234567
To: <sip:UserB@subB.example.com>;tag=567890
Call-ID: 12345601@subA.example.com
CSeq: 2 NOTIFY
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, SUBSCRIBE, NOTIFY
Supported: replaces
Content-Type: application/sdp
Content-Length: 0
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F10 NOTIFY User A --> Application
NOTIFY sip:UserB@subB.example.com SIP/2.0
Max-Forwards: 70
From: <sip:UserA@subA.example.com>;tag=1234567
To: <sip:UserB@Application.example.com>;tag=567890
Call-ID: 12345601@subA.example.com
Increment CSeq
CSeq: 3 NOTIFY
Content-Type: application/kpml+xml
Content-Length: ...
Event: kpml
<?xml version="1.0"?>
<kpml>
<response code="200" text="OK"
digits="***"/>
</kpml>
F11 200 OK Application --> User A
SIP/2.0 200 OK
From: <sips:UserA@subA.net>;tag=1234567
To: <sips:UserB@Application.example.com>
Call-ID: 12345601@subA.com
JVD: CSeq: 3 NOTIFY
Contact: <sips:UserB@Application.example.com>
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, SUBSCRIBE, NOTIFY
Supported: replaces
Content-Type: application/sdp
Content-Length: 0
6.2 Third-Party Subscription
Coming soon!
6.3 Remote-End Monitoring
Coming soon!
7. Formal Syntax
The following syntax in Figure 13 uses the XML Schema [9].
<?xml version="1.0" encoding="UTF-8"?>
<!-- edited with XMLSPY v2004 rel. 2 U (http://www.xmlspy.com)
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by Eric Burger (Snowshore Networks Inc.) -->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified"
attributeFormDefault="unqualified">
<xs:element name="kpml">
<xs:annotation>
<xs:documentation>IETF Keypad Markup Language</xs:documentation>
</xs:annotation>
<xs:complexType>
<xs:choice>
<xs:element name="request">
<xs:complexType>
<xs:sequence>
<xs:element name="pattern">
<xs:complexType>
<xs:sequence>
<xs:element name="regex" maxOccurs="unbounded">
<xs:complexType>
<xs:attribute name="type" use="optional">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="regex"/>
<xs:enumeration value="mgcpdigitmap"/>
<xs:enumeration value="megacodigitmap"/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
<xs:attribute name="pre" type="xs:string"
use="optional"/>
<xs:attribute name="value" type="xs:string"
use="required"/>
<xs:attribute name="tag" type="xs:string"
use="optional"/>
</xs:complexType>
</xs:element>
</xs:sequence>
<xs:attribute name="flush" type="xs:boolean"
use="optional" default="true"/>
<xs:attribute name="persistent" type="xs:boolean"
use="optional" default="false"/>
<xs:attribute name="interdigittimer" type="xs:integer"
use="optional" default="1000"/>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="response">
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<xs:complexType>
<xs:attribute name="code" type="xs:string" use="required"/>
<xs:attribute name="text" type="xs:string" use="required"/>
<xs:attribute name="suppressed" type="xs:boolean"
use="optional"/>
<xs:attribute name="digits" type="xs:string" use="optional"/>
<xs:attribute name="tag" type="xs:string" use="optional"/>
</xs:complexType>
</xs:element>
</xs:choice>
</xs:complexType>
</xs:element>
</xs:schema>
Figure 13: XML Schema for KPML
8. Enumeration of KPML Failure Codes
Coming soon.
9. IANA Considerations
9.1 IANA Registration of MIME media type application/kpml+xml
MIME media type name: application
MIME subtype name: kpml+xml
Required parameters: none
Optional parameters: charset
charset This parameter has identical semantics to the charset
parameter of the "application/xml" media type as specified in
XML Media Types [10].
Encoding considerations: See RFC3023 [10].
Interoperability considerations: See RFC2023 [10] and this document.
Published specification: This document.
Applications which use this media type: Session-oriented applications
that have primitive user interfaces.
Intended usage: COMMON
10. Security Considerations
KPML presents no further security issues beyond the startup issues
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addressed in the companion documents to this document.
As an XML markup, all of the security considerations of RFC3023 [10]
apply.
Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Roach, A., "Session Initiation Protocol (SIP)-Specific Event
Notification", RFC 3265, June 2002.
[3] Burger, E., Van Dyke, J. and A. Spitzer, "Media Server Control
Markup Language (MSCML) and Protocol", draft-vandyke-mscml-02
(work in progress), June 2003.
[4] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002.
[5] Handley, M. and V. Jacobson, "SDP: Session Description
Protocol", RFC 2327, April 1998.
[6] Olson, S., Camarillo, G. and A. Roach, "Support for IPv6 in
Session Description Protocol (SDP)", RFC 3266, June 2002.
[7] Andreasen, F. and B. Foster, "Media Gateway Control Protocol
(MGCP) Version 1.0", RFC 3435, January 2003.
[8] Groves, C., Pantaleo, M., Anderson, T. and T. Taylor, "Gateway
Control Protocol Version 1", RFC 3525, June 2003.
[9] Thompson, H., Beech, D., Maloney, M. and N. Mendelsohn, "XML
Schema Part 1: Structures", W3C REC REC-xmlschema-1-20010502,
May 2001.
[10] Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC
3023, January 2001.
[11] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., Masinter, L.,
Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol --
HTTP/1.1", RFC 2616, June 1999.
Informative References
[12] Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler,
"Extensible Markup Language (XML) 1.0 (Second Edition)", W3C
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REC REC-xml-20001006, October 2000.
[13] World Wide Web Consortium, "Voice Extensible Markup Language
(VoiceXML) Version 2.0", W3C Working Draft , April 2002,
<http://www.w3.org/TR/voicexml20/>.
[14] Schulzrinne, H. and S. Petrack, "RTP Payload for DTMF Digits,
Telephony Tones and Telephony Signals", RFC 2833, May 2000.
[15] Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson,
"RTP: A Transport Protocol for Real-Time Applications", RFC
1889, January 1996.
[16] Rosenberg, J. and H. Schulzrinne, "An INVITE Inititiated Dialog
Event Package for the Session Initiation Protocol (SIP",
draft-ietf-sipping-dialog-package-02 (work in progress), June
2003.
[17] Burger (Ed.), E., Van Dyke, J. and A. Spitzer, "Basic Network
Media Services with SIP", draft-burger-sipping-netann-07 (work
in progress), September 2003.
[18] Hunt, A. and S. McGlashan, "Speech Recognition Grammar
Specification Version 1.0", W3C CR CR-speech-grammar-20020626,
June 2002.
Authors' Addresses
Eric Burger
SnowShore Networks, Inc.
285 Billerica Rd.
Chelmsford, MA 01824-4120
USA
EMail: e.burger@ieee.org
Martin Dolly
AT&T Labs
EMail: mdolly@att.com
Appendix A. Contributors
Jeff Van Dyke worked enough hours and wrote enough text to be
considered an author under the old rules.
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Robert Fairlie-Cuninghame, Cullen Jennings, Jonathan Rosenberg, and I
were the members of the Application Stimulus Signaling Design Team.
All members of the team contributed to this work. In addition,
Jonathan Rosenberg postulated DML in his "A Framework for Stimulus
Signaling in SIP Using Markup" draft.
This version of KPML has significant influence from MSCML, the
SnowShore Media Server Control Markup Language. Jeff Van Dyke and
Andy Spitzer were the primary contributors to that effort.
That said, any errors, misinterpretation, or fouls in this document
are my own.
Appendix B. Acknowledgements
Hal Purdy and Eric Cheung of AT&T Laboratories helped immensely
through many conversations and challenges.
Steve Fisher of AT&T Laboratories helped with the digit suppression
logic and syntax.
Terence Lobo of SnowShore Networks made it all work.
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HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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Burger & Dolly Expires April 25, 2004 [Page 31]
