SIPPING E. Burger
Internet-Draft SnowShore Networks, Inc.
Expires: August 2, 2004 M. Dolly
AT&T Labs
February 2, 2004
Keypad Stimulus Protocol (KPML)
draft-ietf-sipping-kpml-02
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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Copyright Notice
Copyright (C) The Internet Society (2004). 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. Key Press Stimulus Protocol . . . . . . . . . . . . . . . . 5
2.1 Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Monitoring Leg . . . . . . . . . . . . . . . . . . . . . . . 7
2.3 Operation . . . . . . . . . . . . . . . . . . . . . . . . . 7
3. Protocol Machinery . . . . . . . . . . . . . . . . . . . . . 8
3.1 Event Package Name . . . . . . . . . . . . . . . . . . . . . 9
3.2 Event Package Parameters . . . . . . . . . . . . . . . . . . 9
3.3 SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . . . . 10
3.4 Subscription Duration . . . . . . . . . . . . . . . . . . . 10
3.5 NOTIFY Bodies . . . . . . . . . . . . . . . . . . . . . . . 10
3.6 Notifier Processing of SUBSCRIBE Requests . . . . . . . . . 10
3.7 Notifier Generation of NOTIFY Requests . . . . . . . . . . . 12
3.7.1 SIP Protocol-Generated . . . . . . . . . . . . . . . . . . . 12
3.7.2 Match . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.7.3 Inter-Digit Timeout No Match . . . . . . . . . . . . . . . . 12
3.7.4 Dialog Terminated . . . . . . . . . . . . . . . . . . . . . 13
3.7.5 No Call Leg . . . . . . . . . . . . . . . . . . . . . . . . 14
3.7.6 Bad Document . . . . . . . . . . . . . . . . . . . . . . . . 14
3.7.7 One-Shot vs. Persistent Requests . . . . . . . . . . . . . . 14
3.8 Subscriber Processing of NOTIFY Requests . . . . . . . . . . 15
3.8.1 No KPML Body . . . . . . . . . . . . . . . . . . . . . . . . 15
3.8.2 KPML Body . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.9 Handling of Forked Requests . . . . . . . . . . . . . . . . 15
3.10 Rate of Notifications . . . . . . . . . . . . . . . . . . . 15
3.11 State Agents . . . . . . . . . . . . . . . . . . . . . . . . 16
4. Message Format - KPML . . . . . . . . . . . . . . . . . . . 16
4.1 KPML Request . . . . . . . . . . . . . . . . . . . . . . . . 16
4.1.1 Pattern Matching . . . . . . . . . . . . . . . . . . . . . . 18
4.1.2 Digit Suppression . . . . . . . . . . . . . . . . . . . . . 20
4.1.3 One-Shot and Persistent Triggers . . . . . . . . . . . . . . 22
4.1.4 Multiple Patterns . . . . . . . . . . . . . . . . . . . . . 22
4.1.5 Monitoring Direction . . . . . . . . . . . . . . . . . . . . 22
4.1.6 Multiple, Simultaneous Subscriptions . . . . . . . . . . . . 23
4.2 KPML Reports . . . . . . . . . . . . . . . . . . . . . . . . 23
4.2.1 Pattern Match Reports . . . . . . . . . . . . . . . . . . . 24
4.2.2 KPML No Match Reports . . . . . . . . . . . . . . . . . . . 24
5. DRegex Syntax . . . . . . . . . . . . . . . . . . . . . . . 25
6. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . 26
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7. Enumeration of KPML Status Codes . . . . . . . . . . . . . . 27
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . 28
8.1 MIME Media Type application/kpml+xml . . . . . . . . . . . . 28
8.2 URN Sub-Namespace Registration for urn:ietf:xml:ns:kpml . . 29
8.3 KPML Schema Registration . . . . . . . . . . . . . . . . . . 29
9. Security Considerations . . . . . . . . . . . . . . . . . . 29
10. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 30
10.1 Monitoring for Octothorpe . . . . . . . . . . . . . . . . . 30
10.2 Dial String Collection . . . . . . . . . . . . . . . . . . . 30
10.3 Interactive Digit Collection . . . . . . . . . . . . . . . . 31
11. Call Flow Example . . . . . . . . . . . . . . . . . . . . . 32
11.1 INVITE-Initiated Dialog . . . . . . . . . . . . . . . . . . 32
11.2 Third-Party Subscription . . . . . . . . . . . . . . . . . . 37
11.3 Remote-End Monitoring . . . . . . . . . . . . . . . . . . . 38
Normative References . . . . . . . . . . . . . . . . . . . . 38
Informative References . . . . . . . . . . . . . . . . . . . 38
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 39
A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 40
B. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 40
Intellectual Property and Copyright Statements . . . . . . . 41
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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 [7] that enables "dumb
phones" to report user key-press events. Colloquially, this
mechanism provides for "digit reporting" or "DTMF reporting."
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 [8] and MSCML [9].
We strongly discourage the use of non-validating XML parsers, as one
can expect problems with future versions of KPML.
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 [3] network transports end-to-end signaling with
RFC2833 [10] 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 correlates 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. Key Press 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.
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 emanate from
End Point port B. This could represent, for example, a toll by-pass
scenario where the End Point is an ingress gateway and the SIP UA is
an egress gateway.
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 by
referencing the established dialog identifier referring to the dialog
between SIP ports A and X.
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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 [11]. 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 [10], and so on.
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 Application in Figure 3
uses 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.
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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 Monitoring Leg
The default leg to monitor is the leg represented by the local tag of
the SIP dialog at the monitoring End Point. A requesting application
MAY request monitoring of the leg represented by the remote tag of
the SIP dialog at the monitoring 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.
If the requesting application wishes to monitor both legs at a given
End Point, the application will establish two subscriptions, one for
each leg.
Section 4.1.5 describes how to specify to the End Point which leg of
the dialog to monitor.
2.3 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.
An application may register multiple digit patterns in a single KPML
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request.
If the user device supports multiple, simultaneous KPML requests, the
application registers the separate requests either in a new
SUBSCRIBE-initiated dialog or on an existing SUBSCRIBE-initiated
dialog with a new event id tag.
If the user device does not support multiple, simultaneous KPML
requests, it responds with an error response code. See Section 4.1.6
for more information.
A KPML request can be persistent or one-shot. Persistent requests
are active until either the dialog terminates, including normal
subscription expiration, the client replaces them, the client deletes
them by sending a null document on the dialog, or the client deletes
the subscription by sending a SUBCRIBE with an expires of zero (0).
Standard SUBSCRIBE processing dictates the end point sends a NOTIFY
response if it receives a SUBSCRIBE with an expires of zero.
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
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 dialog identifiers.
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 [3]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.
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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 may succeed, resulting in a SIP 200 OK.
However, the "current state" will be the KPML 481 result, and the
subscription state will be "terminated."
SIP identifies call legs by their dialog identifier. The dialog
identifier is the remote-tag, local-tag, and Call-ID entities.
To identify a specific dialog, all three of these parameters MUST be
present. Usually, the local-tag is the To: entity with the To tag,
the remote-tag is the From: entity including tag, and the call-id
matches the Call-ID. Although semantically different, the important
entities are the To: and From: tags.
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 disambiguate which stream or streams to monitor. In order
to have an extensible mechanism for identifying streams, the
mechanism for specifying streams is as an element content to the
<stream> tag. The only content defined today is the <reverse/> tag.
For most situations, such as a monaural 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 [3].
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
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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 the
SIP Dialog Package [12].
3.3 SUBSCRIBE Bodies
Key press filtering requests use KPML, as described in Section 4.1.
The MIME type for KPML is application/kpml+xml.
Because of the potentially sensitive nature of the information
reported by KPML, subscribers SHOULD use sips: and SHOULD consider
the use of S/MIME on the content.
Subscribers MUST be prepared for the notifier to insist on
authentication at a minimum and encryption as a likelihood.
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.
Subscribers MUST be able to handle the end device returning an
Expires value smaller than the requested value. Per RFC3265 [2], the
subscription duration is the value returned by the end device in the
200 OK response Expires entity.
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.
If the requestor is not using a secure transport protocol such as TLS
(e.g., by using a sips: URI), the end device SHOULD use S/MIME to
protect the user information in responses.
3.6 Notifier Processing of SUBSCRIBE Requests
The user information transported by KPML is potentially sensitive.
For example, it could include calling card or credit card numbers.
Thus the first action of the end device (notifier) SHOULD be to
authenticate the requesting party.
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End devices MUST support digest authentication at a minimum.
End devices MUST support the sips: scheme and TLS.
Upon authenticating the requesting party, the end device determines
if the requesting party has authorization to monitor the user's key
presses. Determining authorization policies and procedures is beyond
the scope of this specification.
NOTE: While it would be good to require both authorization and
user notification for KPML, some uses, such as lawful intercept
pen registers, have very strict authorization requirements yet
have a requirement of no user notification. Conversely, pre-paid
applications running on a private network may have no
authorization requirements and already have implicit user
acceptance of key press monitoring. Thus we cannot give any
guidelines here.
After authorizing the request (RECOMMENDED), the end device checks to
see if the request is to terminate a subscription. If the request
will terminate the subscription, the end device does the appropriate
processing, including the procedures described in Section 3.7.4.
If the request has no KPML body, than any KPML document running on
that dialog, and addressed by the event id, if present, immediately
terminates. This is a mechanism for unloading a KPML document while
keeping the SUBSCRIBE-initiated dialog active. This can be important
for secure sessions that have high costs for session establishment,
such as TLS. The end device follows the procedures described in
Section 3.7.1.
If the SUBSCRIBE request arrived on an INVITE-initiated dialog, and
there is no "leg" parameter to the kpml subscription, then the KPML
document acts upon the call legs created by the INVITE-initiated
dialog.
If the SUBSCRIBE request has a "leg" parameter to the kpml
subscription, then the KPML document acts upon the call leg referred
to by the "leg" parameter. If appropriate, the end device SHOULD
validate the requestor has authorization to monitor a given leg.
If the SUBSCRIBE request has a "leg" parameter to the kpml
subscription, but the referenced leg does not exist, the end device
follows the procedures in Section 3.7.5 Note the end device MUST
issue a 200 OK before issuing the NOTIFY, as the SUBSCRIBE itself is
well-formed.
If the request has a KPML body, the end device parses the KPML
document. The end device SHOULD validate the XML document against
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the schema presented in Section 6. If the document is not valid, the
end device performs the procedures described in Section 3.7.6. If
there is a loaded KPML document on the dialog (and given event id, if
present), the end device unloads the document.
If the KPML document is valid, and the end device is capable of
performing the monitoring, the end device performs the filtering
specified by the KPML document. See Section 4 for the specification
of KPML.
3.7 Notifier Generation of NOTIFY Requests
3.7.1 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) or
the quarantined digits do not match the new KPML document, then the
immediate NOTIFY MUST NOT contain a KPML body. If end device has
digits quarantined that result in a digit match using the new KPML
document, then the NOTIFY MUST return the appropriate KPML document.
3.7.2 Match
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.
3.7.3 Inter-Digit Timeout No Match
Once a user starts to enter digits, it is highly likely they will
enter all of the digits of interest within a specific time period.
There is a temporal locality of reference for key presses. It is
possible for users to accidentally press a key, however. Moreover,
users may start pressing a key and then be lost as to what to do
next. For applications to handle this situation, KPML allows
applications to request notification if the user starts to enter
digits but then stops before a digit map matches.
Once the end point detects a key press that matches the first
character of a digit map, the end point starts the interdigit timer
specified in the <pattern> tag. Every subsequent key press detected
restarts the interdigit timer. If the interdigit timer expires, the
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end point generates a KPML report with the KPML status code 423,
Timer Expired. The report also includes the digits collected up to
the time the timer expired. This could be the null string. After
sending the NOTIFY, the end point will resume quarantining additional
detected digits.
Applications may have different requirements for the interdigit
timer. For example, applications targeted to user populations that
tend to key in information slowly may require longer interdigit
timers. The specification of the interdigit timer is in
milliseconds. The default value is 4000, for 4 seconds. A value of
zero indicates disabling the interdigit timer. The End Device MUST
round up the requested interdigit timer to the nearest time increment
it is capable of detecting.
3.7.4 Dialog Terminated
It is possible for a dialog to terminate during key press collection.
The cases enumerated here are explicit SUBSCRIPTION termination,
automatic SUBSCRIPTION termination, and underlying (INVITE-initiated)
dialog termination.
If a SUBSCRIBE request has an expires of zero (explicit SUBSCRIBE
termination), includes a KPML request, and there are quarantined
digits, then the end device attempts to process the quarantined
digits against the document. If there is a match, the end device
generates the appropriate KPML report with the KPML status code of
200. The SIP NOTIFY body terminates the subscription by setting the
subscription state to "terminated" and a reason of "timeout". If the
subscription was on a SUBSCRIBE-initiated dialog, and there are no
more active event id's associated with the dialog, then the end point
MUST consider the dialog terminated. If the subscription was on an
INVITE-initiated dialog, then the end point MAY release KPML-specific
resources related to the dialog, but it MUST NOT alter the state of
the INVITE-initiated dialog.
If the requesting party issues a SUBSCRIBE with an expires of zero
and no KPML body or the expires timer on the SUBSCRIBE-initiated
dialog fires at the end device (notifier), then the end device issues
a KPML report with the KPML status code 487, Subscription Expired.
The report also includes the digits collected up to the time the
expires timer expired or when the subscription with expires equal to
zero was processed. This could be the null string. Also, note that
the digits in this case cannot match a digit map. If they did, the
end device would have generated a KPML match report if they did.
Again, per the mechanisms of RFC3265 [2], the end device will
terminate the SIP SUBSCRIBE dialog. The end device does this via the
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SIP NOTIFY body transporting the final report described in the
preceding paragraph. In particular, the subscription state will be
"terminated" and a reason of "timeout". If the subscription was on a
SUBSCRIBE-initiated dialog, then the end point MUST consider the
dialog terminated. If the subscription was on an INVITE-initiated
dialog, then the end point MAY release KPML-specific resources
related to the dialog, but it MUST NOT alter the state of the
INVITE-initiated dialog.
3.7.5 No Call Leg
If a SUBSCRIBE request references a dialog that is not present at the
endpoint, usually by specifying a dialog identifier through the leg
parameter to the kpml event package, the end point generates a KPML
report with the KPML status code 481, Dialog Not Found. The end
device terminates the subscription by setting the subscription state
to "terminated". If the subscription was on a SUBSCRIBE-initiated
dialog, and there are no more active event id's associated with the
dialog, then the end point MUST consider the dialog terminated. If
the subscription was on an INVITE-initiated dialog, then the end
point MAY release KPML-specific resources related to the dialog, but
it MUST NOT alter the state of the INVITE-initiated dialog.
IMPORTANT: The end device can invoke this procedure if the dialog
underlying a subscription terminates. For example, a
SUBSCRIBE-initiated dialog subscribes to the state of a different
dialog (call) via the leg kpml parameter. That different call may
terminate before the SUBSCRIBE-initiated dialog terminates. In this
case, the end device MUST terminate the SUBSCRIBE-initiated dialog.
This ensures reauthorization (if necessary) for attaching to
subsequent call legs.
3.7.6 Bad Document
If the KPML document is not valid, the end device generates a KPML
report with the KPML status code 501, Bad Document. The end device
terminates the subscription by setting the subscription state to
"terminated". If the subscription was on a SUBSCRIBE-initiated
dialog, and there are no more active event id's associated with the
dialog, then the end point MUST consider the dialog terminated. If
the subscription was on an INVITE-initiated dialog, then the end
point MAY release KPML-specific resources related to the dialog, but
it MUST NOT alter the state of the INVITE-initiated dialog.
3.7.7 One-Shot vs. Persistent 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. The end device MUST quarantine digits per
the controls specified in Section 4.1.
For persistent kpml subscriptions, the KPML document remains active
for the lifetime of the subscription.
3.8 Subscriber Processing of NOTIFY Requests
3.8.1 No KPML Body
If there is no KPML body, it means the SUBSCRIBE was successful.
This establishes the dialog if there are no quarantined digits to
report.
3.8.2 KPML Body
If there is a KPML document, and the KPML status code is 200, then a
match occurred.
If there is a KPML document, and the KPML status code is 4xx, then an
error occurred with digit collection. The most likely cause is a
timeout condition.
If there is a KPML document, and the KPML status code is 5xx, then an
error occurred with the subscription. See Section 7 for more on the
meaning of error codes.
The subscriber MUST be mindful of the subscription state. The end
device may terminate the subscription at any time.
3.9 Handling of Forked Requests
The SUBSCRIBE behavior described in Section 3.6 ensures that it is
only possible to have a subscription where there is an active (e.g.,
voice) dialog. Thus the case of multiple subscription installation
cannot occur.
3.10 Rate of Notifications
The end device MUST NOT generate messages faster than one message
every 40 milliseconds. This is the minimum time period for MF digit
spills. Even 30 millisecond DTMF, as one sometimes finds in Japan,
has a 20 millisecond off-time, resulting in a 50 millisecond
interdigit time. This document strongly RECOMMENDS AGAINST using
KPML for digit-by-digit messaging, such as would be the case if the
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only <regex> is "x".
Because there is no meaningful metric for throttling requests. In
addition, the end device MUST reliably deliver notifications. Thus
the end device SHOULD send NOTIFY messages over a
congestion-controlled transport, such as TCP or SCTP.
End devices MUST at a minimum implement SIP over TCP.
3.11 State Agents
Not applicable.
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 request document (message) contains a <request> entity
containing a <pattern> tag with a series of <regex> tags. The
<regex> element specifies a digit pattern for the device to report
on. Section 5 describes the DRegex, or digit regular expression,
language.
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> tag in the <pattern> element. The
default is not to flush digits. Flushing digits means the user
device flushes any buffered digits. This has the effect of ignoring
digits entered before the KPML request. To flush digits, the KPML
includes <flush>yes</flush>.
The End Device MUST be able to receive <flush>no</flush>. This
directive is effectively a no-op.
Other string values for <flush> may be defined in the future. If the
End Device receives a string it does not understand, it MUST treat
the string as a no-op.
If the user presses a key not matched by the <regex> tags, the user
device MUST discard the key press from consideration against the
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current or future KPML messages. However, as described above, once
there is a match, the user device quarantines any key presses the
user entered subsequent to the match.
NOTE: This behavior allows for applications to only receive
digits that interest them. For example, a pre-paid application
only wishes to monitor for a long pound. If the user enters other
digits, presumably for other systems, the pre-paid applicationd
does not want notification of those digits. This feature is
fundamentally different than the behavior of every system
receiving every digit that TDM-based equipment provides.
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 4000 milliseconds. 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 up 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
indicates a buffer flush, then the interpreter MUST flush all
collected digits from consideration from KPML documents received on
that dialog with the given event id. If the next script does not
indicate flushing the quarantine digits, 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 follow the procedures in Section 3.7.2 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 4.1.2) describes the operation
of the suppress indicator.
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4.1.1 Pattern Matching
4.1.1.1 Inter-Digit Timing
The pattern matching logic works as follows. KPML endpoints MUST
follow the logic presented in this section so that multiple
implementations will perform deterministically on the same KPML
document given the same key press input.
The pattern match algorithm matches the longest regular expression.
This is the same mode as H.248.1 [13] and not the mode presented by
MGCP [14]. The pattern match algorithm choice has an impact on
determining when a pattern matches. Consider the following KPML
document.
<?xml version="1.0" encoding="UTF-8"?>
<kpml xmlns="urn:ietf:params:xml:ns:kpml"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:ietf:params:xml:ns:kpml kpml.xsd"
version="1.0">
<request>
<pattern>
<regex>0</regex>
<regex>011</regex>
</pattern>
</request>
</kpml>
Figure 5: Greedy Matching
In Figure 5, if we were to match on the first found pattern, the
string "011" would never match. This happens because the "0" rule
would match first.
While this behavior is what most applications desire, it does come at
a cost. Consider the following KPML document snippet.
<regex>x{7}</regex>
<regex>x{10}</regex>
Figure 6: Timeout Matching
Figure 6 is a typical NANP dial plan. From an application
perspective, users expect a seven digit number to respond quickly,
not waiting the typical inter-digit critical timer (usually four
seconds). From a user's perspective, they do not want the system to
cut off their ten digit number at seven digits because they did not
enter the number fast enough.
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One approach to this problem is to have an explicit dial string
terminator. Typically, it is the pound key (#). Now, consider the
following snippet.
<regex>x{7}#</regex>
<regex>x{10}#</regex>
Figure 7: Timeout Matching with Enter
The problem with the approach in Figure 7 is that the digit collector
will still look for a digit after the "#" in the seven-digit case.
Worse yet, the "#" will appear in the returned dial string.
The approach used in KPML is to have an explicit "Enter Key", as
shown in the following snippet.
<request>
<pattern enterkey="#">
<regex>xxxxxxx</regex>
<regex>xxxxxxxxxx</regex>
</pattern>
</request>
Figure 8: Timeout Matching with Enter Key
In Figure 8 the enterkey parameter to the <pattern> tag specifies a
string that terminates a pattern. In this situation, if the user
enters seven digits followed by the "#" key, the pattern matches (or
fails) immediately. KPML indicates a terminated nomatch with a KPML
status code 402.
To address the various key press collection scenarios, we define
three timers. The timers are the critical timer (criticaltimer), the
inter-digit timer (interdigittimer), and the extra digit timer
(extradigittimer). The critical timer is the time to wait for
another digit if the collected digits can match a pattern. The extra
timer is the time to wait after the longest match has occurred
(presumably for the return key). The inter-digit timer inter-digit
timer is the time to wait between digits in all other cases. Note
there is no start timer, as that concept does not apply in the KPML
context.
All of these timers are parameters to the <pattern> tag.
4.1.1.2 Intra-Digit Timing
Some patterns look for long duration key presses. For example, some
applications look for long "#" or long "*".
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KPML uses the "L" modifier to <regex> characters to indicate long key
presses. The following KPML document looks for long pound.
<?xml version="1.0" encoding="UTF-8"?>
<kpml xmlns="urn:ietf:params:xml:ns:kpml"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:ietf:params:xml:ns:kpml kpml.xsd"
version="1.0">
<request>
<pattern>
<regex>L#</regex>
</pattern>
</request>
</kpml>
The request can specify what constitutes "long" by setting the long
attribute to the <pattern>. This attribute is an integer
representing the number of milliseconds. If the user presses a key
for longer than longtimer milliseconds, the Long modifier is true.
NOTE: It is a local matter at the end device to consider multiple
presses of the same key during the longtimer period to be
equivalent to the Long version of that key. This is to support
end devices that do not generate continuous key press tones.
4.1.2 Digit Suppression
Under basic operation, a KPML endpoint will transmit in-band tones
(RFC2833 [10] or actual tone) in parallel with digit reporting.
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 tag, "pre", to
the <regex> tag. There MUST NOT be more than one <pre> in any given
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<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 suppressed digits, it MUST indicate this by including
the attribute "suppressed" with a value of "yes" in the digit report.
Clearly, if the end device is processing the KPML document against
quarantined digits, it is too late to suppress digits, as the end
device has long sent the digits. This is a situation where there is
a <pre> specification, but the "suppressed" attribute is not "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, transmit the suppressed digits
on the media stream, and stop suppressing digit transmission.
Once the end device detects a match and it sends a NOTIFY request to
report the digit string, the end device MUST stop digit suppression.
Clearly, if subsequent digits match another <pre> expression, then
the end device MUST start digit suppression.
After digit suppression begins, it may become clear that a match will
not occur. For example, take the expression "<regex> <pre>*8</
pre>xxx[2-9]xxxxxx</regex>". 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.
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
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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.
4.1.3 One-Shot and Persistent 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. If there are digits
in the quarantine buffer and the digits match an expression in the
KPML document, the end device prepares the appropriate KPML document.
4.1.4 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.
4.1.5 Monitoring Direction
By default, the end device monitors key presses emanating from the
device. Given a dialog identifier of Call-ID, local-tag, and
remote-tag, the end device monitors the key presses associated with
the local-tag.
In the media proxy case, and potentially other cases, there is a need
to monitor the key presses arriving from the remote user agent. The
optional <stream> element to the >request> tag specifies which stream
to monitor. The only legal value is "reverse", which means to
monitor the stream associated with the remote-tag. The end point
MUST ignore other values.
NOTE: The reason this is a tag is so individual stream selection,
if needed can be addressed in a backwards-compatible way.
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4.1.6 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.
A SIP user agent may request multiple subscriptions on the same
SUBSCRIBE dialog, using the id parameter to the kpml event request.
One or more SIP user agents may request independent subscriptions on
different SIP dialogs. In the body of the SUBSCRIBE is a leg
parameter that indicates which leg to monitor. Section 3.2 describes
the dialog addressing mechanism in detail.
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 on the dialog that requested the second
subscription. The end device MUST NOT modify the state of the first
subscription on the account of the second subscription attempt.
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 [8] or
MSCML [9].
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
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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 4.1.2) and
the end device suppressed digits, the suppressed attribute indicates
"true". The default value of suppressed is "false".
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 has no KPML if there
are no matching quarantined digits. An example of this is in Figure
10.
If there are quarantined digits in the SUBSCRIBE request that match a
pattern, then the NOTIFY message in response to the SUBSCRIBE request
MUST include the appropriate KPML document.
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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
Subscription-State: active; expires=7200
CSeq: 49851 NOTIFY
Event: kpml
Figure 10: Immediate NOTIFY Example
5. DRegex Syntax
The Digit REGular EXpression (DRegex) syntax follows the Unix egrep
and Java Regular Expression syntax.
White space is removed before parsing DRegex. This enables sensible
pretty printing in XML without affecting the meaning of the DRegex
string.
The following rules describe the use of DRegex in KPML.
+---------------------------------+---------------------------------+
| Entity | Matches |
+---------------------------------+---------------------------------+
| digit | digit 0-9 and A-D |
| [digit selector] | Any digit in selector |
| [^digit selector] | Any digit NOT in selector |
| [digit-range] | Any digit in range |
| x | Any digit 0-9 |
| . | Zero or more repetitions of |
| | previous pattern |
| | | Alternation |
| {m} | m repetitions of previous |
| | pattern |
| {m,} | m or more repetitions of |
| | previous pattern |
| {,n} | At most n (including zero) |
| | repetitions of previous pattern |
| {m,n} | at least m and at most n |
| | repetitions of previous pattern |
| Ldigit | Match the digit if it is "long" |
+---------------------------------+---------------------------------+
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+------------+-----------------------------------------+
| Example | Description |
+------------+-----------------------------------------+
| 1 | Matches the digit 1 |
| [179] | Matches 1, 7, or 9 |
| [^01] | Matches 2, 3, 4, 5, 6, 7, 8, 9 |
| [2-9] | Matches 2, 3, 4, 5, 6, 7, 8, 9 |
| x | Any single digit |
| 2|3 | Matches 2 or 3; same as [23] |
| 00|011 | Matches the string 00 or 011 |
| 0. | Zero or more occurrences of 0 |
| [2-9]. | Zero or more occurrences of 2-9 |
| 011x{7,15} | 011 followed by seven to fifteen digits |
| L* | Long star |
+------------+-----------------------------------------+
6. Formal Syntax
The following syntax in Figure 11 uses the XML Schema [4].
<?xml version="1.0" encoding="UTF-8"?>
<!-- edited with XMLSPY v2004 rel. 3 U (http://www.xmlspy.com)
by Eric Burger (Snowshore Networks Inc.) -->
<xs:schema targetNamespace="urn:ietf:params:xml:ns:kpml"
xmlns="urn:ietf:params:xml:ns:kpml"
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="flush" type="xs:string" minOccurs="0"/>
<xs:element name="regex" maxOccurs="unbounded">
<xs:complexType mixed="true">
<xs:sequence>
<xs:element name="pre" type="xs:string" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="tag" type="xs:string"
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use="optional"/>
</xs:complexType>
</xs:element>
</xs:sequence>
<xs:attribute name="persistent" type="xs:boolean"
use="optional"/>
<xs:attribute name="enterkey" type="xs:string"
use="optional"/>
<xs:attribute name="interdigittimer" type="xs:integer"
use="optional"/>
<xs:attribute name="criticaldigittimer" type="xs:integer"
use="optional"/>
<xs:attribute name="extradigittimer" type="xs:integer"
use="optional"/>
<xs:attribute name="longtimer" type="xs:integer"
use="optional"/>
</xs:complexType>
</xs:element>
<xs:element name="stream" type="xs:string" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="response">
<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:attribute name="version" type="xs:string" use="required"/>
</xs:complexType>
</xs:element>
</xs:schema>
Figure 11: XML Schema for KPML
7. Enumeration of KPML Status Codes
KPML failure codes broadly follow their SIP counterparts. Codes that
start with a 2 indicate success. Codes that start with a 4 indicate
failure. Codes that start with a 5 indicate a server failure,
usually a failure to interpret the document or to support a requested
feature.
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KPML clients MUST be able to handle arbitrary status codes by
examining the first digit only.
Any text can be in a KPML report document. KPML clients MUST NOT
interpret the text field.
+------+---------------------------------------------------------+
| Code | Text |
+------+---------------------------------------------------------+
| 200 | Success |
| 402 | User Terminated Without Match |
| 423 | Timer Expired |
| 481 | Dialog (call leg) Not Found |
| 487 | Subscription Expired |
| 501 | Bad Document |
| 531 | Persistent Subscriptions Not Supported |
| 532 | Multiple or Alternate Regular Expressions Not Supported |
| 533 | Multiple Subscriptions on a Call Leg Not Supported |
+------+---------------------------------------------------------+
Table 3: KPML Failure Codes
8. IANA Considerations
8.1 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 [5].
Encoding considerations: See RFC3023 [5].
Interoperability considerations: See RFC2023 [5] and this document.
Published specification: This document.
Applications which use this media type: Session-oriented applications
that have primitive user interfaces.
Intended usage: COMMON
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8.2 URN Sub-Namespace Registration for urn:ietf:xml:ns:kpml
URI: urn:ietf:params:xml:ns:kpml
Registrant Contact: Eric Burger <eburger@ietf.org>
XML:
<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C/DTD XHTML Basic 1.0//EN"
"http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type"
content="text/html;charset=iso-8859-1"/>
<title>Key Press Markup Language</title>
</head>
<body>
<h1>Namespace for Key Press Markup Language</h1>
<h2>urn:ietf:params:xml:ns:kpml</h2>
<p>
<a href="ftp://ftp.rfc-editor.org/in-notes/rfcXXXX.txt">RFCXXXX</a>.
</p>
</body>
</html>
8.3 KPML Schema Registration
Please register the XML Schema for KPML as referenced in Section 6.
9. Security Considerations
As an XML markup, all of the security considerations of RFC3023 [5]
and RFC3406 [6] apply. Pay particular attention to the robustness
requirements of parsing XML.
Key press information is potentially sensitive. Hijacking sessions
allow unauthorized entities access to this sensitive information.
Therefore, signaling SHOULD be secure, e.g., use of TLS and sips:
SHOULD be used. Moreover, the information itself is sensitive. Thus
if TLS is not used, S/MIME or other appropriate mechanism SHOULD be
used.
End devices implementing this specification MUST implement TLS and
SHOULD implement S/MIME at a minimum.
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10. Examples
This section is informative in nature. If there is a discrepancy
between this section and the normative sections above, the normative
sections take precedence.
10.1 Monitoring for Octothorpe
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 13 shows the KPML for long octothorpe. Note that the href is
really on one line, but divided for clarity.
<?xml version="1.0">
<kpml xmlns="urn:ietf:params:xml:ns:kpml"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:ietf:params:xml:ns:kpml kpml.xsd"
version="1.0">
<request>
<pattern>
<regex>L#</regex>
</pattern>
</request>
</kpml>
Figure 13: Long Octothorpe Example
The regex value L indicates the following digit needs to be a
long-duration key press.
10.2 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 xmlns="urn:ietf:params:xml:ns:kpml"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:ietf:params:xml:ns:kpml kpml.xsd"
version="1.0">
<request>
<pattern>
<regex tag="local-operator">0</regex>
<regex tag="ld-operator"/>00</regex>
<regex tag="vpn">7[x][x][x]</regex>
<regex tag="local-number7">9xxxxxxx</regex>
<regex tag="RI-number">9401xxxxxxx</regex>
<regex tag="local-number10">9xxxxxxxxxx</regex>
<regex tag="ddd">91xxxxxxxxxx</regex>
<regex tag="iddd">011x.</regex>
</pattern>
</request>
</kpml>
Figure 14: 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 4.1.4, the KPML interpreter will pick the "9401xxxxxxx"
string, as it occurs first in document order (both expressions match
the same length). Figure 15 shows the response.
<?xml version="1.0"?>
<kpml xmlns="urn:ietf:params:xml:ns:kpml"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:ietf:params:xml:ns:kpml kpml.xsd"
version="1.0">
<response code="200" text="OK"
digits="94015551212" tag="RI-number"/>
</kpml>
Figure 15: Dial String KPML Response
10.3 Interactive Digit Collection
This is an example where one would probably be better off using a
full scripting language such as VoiceXML [8] or MSCML [9] or a device
control language such as H.248.1 [13].
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 16 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 xmlns="urn:ietf:params:xml:ns:kpml"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:ietf:params:xml:ns:kpml kpml.xsd"
version="1.0">
<request>
<pattern>
<flush>yes</flush>
<regex tag="keep">5</regex>
<regex tag="replay">7</regex>
<regex tag="delete">3</regex>
</pattern>
</request>
</kpml>
Figure 16: 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.
11. Call Flow Example
11.1 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 TRYING 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 monitoring
|--------------->|
| 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
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
Expires: 7200
Accept: application/kpml+xml
Content-Type: application/kmpl+xml
Content-Length: ...
<?xml version="1.0">
<kpml xmlns="urn:ietf:params:xml:ns:kpml"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:ietf:params:xml:ns:kpml kpml.xsd"
version="1.0">
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<request>
<pattern>
<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
Subscription-State: active;expires=3600
Content-Type: application/kpml+xml
Content-Length: ...
Event: kpml
<?xml version="1.0"?>
<kpml xmlns="urn:ietf:params:xml:ns:kpml"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:ietf:params:xml:ns:kpml kpml.xsd"
version="1.0">
<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
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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
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
CSeq: 3 NOTIFY
Subscription-State: active;expires=3125
Content-Type: application/kpml+xml
Content-Length: ...
Event: kpml
<?xml version="1.0"?>
<kpml xmlns="urn:ietf:params:xml:ns:kpml"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:ietf:params:xml:ns:kpml kpml.xsd"
version="1.0">
<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
11.2 Third-Party Subscription
Coming soon!
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11.3 Remote-End Monitoring
Coming soon!
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] 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.
[4] Thompson, H., Beech, D., Maloney, M. and N. Mendelsohn, "XML
Schema Part 1: Structures", W3C REC REC-xmlschema-1-20010502,
May 2001.
[5] Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC
3023, January 2001.
[6] Daigle, L., van Gulik, D., Iannella, R. and P. Faltstrom,
"Uniform Resource Names (URN) Namespace Definition Mechanisms",
BCP 66, RFC 3406, October 2002.
Informative References
[7] Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler,
"Extensible Markup Language (XML) 1.0 (Second Edition)", W3C
REC REC-xml-20001006, October 2000.
[8] World Wide Web Consortium, "Voice Extensible Markup Language
(VoiceXML) Version 2.0", W3C Working Draft , April 2002,
<http://www.w3.org/TR/voicexml20/>.
[9] 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.
[10] Schulzrinne, H. and S. Petrack, "RTP Payload for DTMF Digits,
Telephony Tones and Telephony Signals", RFC 2833, May 2000.
[11] Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson,
"RTP: A Transport Protocol for Real-Time Applications", RFC
1889, January 1996.
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[12] 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.
[13] Groves, C., Pantaleo, M., Anderson, T. and T. Taylor, "Gateway
Control Protocol Version 1", RFC 3525, June 2003.
[14] Andreasen, F. and B. Foster, "Media Gateway Control Protocol
(MGCP) Version 1.0", RFC 3435, January 2003.
[15] Handley, M. and V. Jacobson, "SDP: Session Description
Protocol", RFC 2327, April 1998.
[16] 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.
[17] Olson, S., Camarillo, G. and A. Roach, "Support for IPv6 in
Session Description Protocol (SDP)", RFC 3266, June 2002.
[18] Hunt, A. and S. McGlashan, "Speech Recognition Grammar
Specification Version 1.0", W3C CR CR-speech-grammar-20020626,
June 2002.
[19] 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.
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
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Appendix A. Contributors
Jeff Van Dyke worked enough hours and wrote enough text to be
considered an author under the old rules.
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 suggested the digit suppression
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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