SIPPING E. Burger
Internet-Draft SnowShore Networks, Inc.
Expires: November 15, 2004 M. Dolly
AT&T Labs
May 17, 2004
A Session Initiation Protocol (SIP) Event Package for Key Press
Stimulus (KPML)
draft-ietf-sipping-kpml-03
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 Event Package is a component of the
Applications Interaction Framework for the Session Initiation
Protocol (SIP). The event package defines a Key Press Markup
Language (KPML) that describes filter specifications for reporting
key presses entered at a presentation-free user interface SIP User
Agent (UA). The scope of this package is for collecting supplemental
key presses or mid-call key presses (triggers). We recommend using
VoiceXML or MSCML, as described in the Applications Interaction
Framework, for building interactive voice response applications.
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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.
The Application Interaction Framework [9] provides the
interpretations for the terms "User Device", "SIP Application", and
"User Input". This document uses the term "Application" and
"Requesting Application" interchangeably with "SIP Application".
The Application Interaction Framework discusses User Device Proxies.
A common instantiation of a User Device Proxy is a Public-Switched
Telephone Network (PSTN) gateway. Because the normative behavior of
a presentation-free user interface is identical for a
presentation-free SIP User Agent and a presentation-free User Device
Proxy, this document uses "User Device" for both cases.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Key Press Stimulus Operation . . . . . . . . . . . . . . . . . 5
2.1 Model . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Stream to Monitor . . . . . . . . . . . . . . . . . . . . 7
2.3 Operation . . . . . . . . . . . . . . . . . . . . . . . . 8
3. Event Package Operation . . . . . . . . . . . . . . . . . . . 9
3.1 Event Package Name . . . . . . . . . . . . . . . . . . . . 9
3.2 Event Package Parameters . . . . . . . . . . . . . . . . . 9
3.3 SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . . . 10
3.4 Subscription Duration . . . . . . . . . . . . . . . . . . 11
3.5 NOTIFY Bodies . . . . . . . . . . . . . . . . . . . . . . 11
3.6 Notifier Processing of SUBSCRIBE Requests . . . . . . . . 11
3.7 Notifier Generation of NOTIFY Requests . . . . . . . . . . 13
3.7.1 SIP Protocol-Generated . . . . . . . . . . . . . . . . 13
3.7.2 Match . . . . . . . . . . . . . . . . . . . . . . . . 13
3.7.3 Inter-Digit Timeout No Match . . . . . . . . . . . . . 13
3.7.4 Dialog Terminated . . . . . . . . . . . . . . . . . . 14
3.7.5 No Call Leg . . . . . . . . . . . . . . . . . . . . . 14
3.7.6 Bad Document . . . . . . . . . . . . . . . . . . . . . 14
3.7.7 One-Shot vs. Persistent Requests . . . . . . . . . . . 15
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 . . . . . . . . . . . . . . . 16
3.10 Rate of Notifications . . . . . . . . . . . . . . . . . . 16
3.11 State Agents . . . . . . . . . . . . . . . . . . . . . . . 16
4. Message Format - KPML . . . . . . . . . . . . . . . . . . . . 16
4.1 KPML Request . . . . . . . . . . . . . . . . . . . . . . . 16
4.1.1 User Input Buffer Behavior . . . . . . . . . . . . . . 17
4.1.2 Pattern Matching . . . . . . . . . . . . . . . . . . . 18
4.1.3 Digit Suppression . . . . . . . . . . . . . . . . . . 22
4.1.4 One-Shot and Persistent Triggers . . . . . . . . . . . 23
4.1.5 Multiple Patterns . . . . . . . . . . . . . . . . . . 24
4.1.6 Monitoring Direction . . . . . . . . . . . . . . . . . 24
4.1.7 Multiple, Simultaneous Subscriptions . . . . . . . . . 24
4.2 KPML Reports . . . . . . . . . . . . . . . . . . . . . . . 25
4.2.1 Pattern Match Reports . . . . . . . . . . . . . . . . 25
4.2.2 KPML No Match Reports . . . . . . . . . . . . . . . . 26
5. DRegex Syntax . . . . . . . . . . . . . . . . . . . . . . . . 27
6. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 29
6.1 DRegex . . . . . . . . . . . . . . . . . . . . . . . . . . 29
6.2 KPML . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
7. Enumeration of KPML Status Codes . . . . . . . . . . . . . . . 33
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34
8.1 MIME Media Type application/kpml+xml . . . . . . . . . . . 34
8.2 URN Sub-Namespace Registration for urn:ietf:xml:ns:kpml . 34
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8.3 KPML Schema Registration . . . . . . . . . . . . . . . . . 35
9. Security Considerations . . . . . . . . . . . . . . . . . . . 35
10. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 36
10.1 Monitoring for Octothorpe . . . . . . . . . . . . . . . . 36
10.2 Dial String Collection . . . . . . . . . . . . . . . . . . 36
10.3 Interactive Digit Collection . . . . . . . . . . . . . . . 37
11. Call Flow Example . . . . . . . . . . . . . . . . . . . . . 38
11.1 INVITE-Initiated Dialog . . . . . . . . . . . . . . . . . 38
11.2 Third-Party Subscription . . . . . . . . . . . . . . . . . 43
11.3 Remote-End Monitoring . . . . . . . . . . . . . . . . . . 44
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 44
12.1 Normative References . . . . . . . . . . . . . . . . . . . . 44
12.2 Informative References . . . . . . . . . . . . . . . . . . . 44
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 46
A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 46
B. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 46
Intellectual Property and Copyright Statements . . . . . . . . 48
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1. Introduction
This document describes the Key Press Stimulus Event Package. The
Key Press Stimulus Package is a SIP Event Notification Package [2]
that uses the SUBSCRIBE and NOTIFY methods of SIP. The subscription
filter and notification report bodies use the Keypad Markup Language,
KPML. KPML is a markup [10] that enables presentation-free user
interfaces as described in the Application Interaction Framework [9].
In particular, KPML enables "dumb phones" and gateways to dumb phones
to report user key-press events. Colloquially, this mechanism
provides for "digit reporting" or "Dual-Tone Multi-Frequency (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 [11] and MSCML [12].
The name of the markup, KPML, reflects its legacy support role. The
public switched telephony network (PSTN) accomplished end-to-end
signaling by transporting DTMF tones in the bearer channel. This is
in-band signaling.
Voice-over-IP networks transport in-band signaling with actual DTMF
waveforms or RFC2833 [13] 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 in the media stream.
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.
2. Key Press Stimulus Operation
2.1 Model
The Key Press Stimulus reporting model is that key presses, or
detected digits, are events at the User Device. The subscription
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installs an event filter. That event filter specifies the User Input
strings, which, if matched, the User Device sends a notification.
There are three usage models for the event package. Functionally,
they are equivalent. However, it is useful to understand the use
cases.
The first model is that of a third-party application that is
interested in the User Input. Figure 1 shows an established SIP
dialog between the User Device and the SIP UA. The Requesting
Application addresses the particular media stream (From RTP [14] port
B to RTP port Y) by referencing the dialog identifier referring to
the dialog between SIP ports A and X.
+-------------+
| Requesting |
/---| Application |
/ +-------------+
/
SIP / (SUBSCRIBE/NOTIFY)
/
/
+---M----+ SIP (INVITE) +-----+
| A--------------------X |
| User | | SIP |
| Device | RTP | UA |
| B--------------------Y |
+--------+ +-----+
Figure 1: Third-Party Model
The second model is that of a SIP User Agent (UA) that directly
interacts, on a given dialog, with the User Device. Figure 2 shows a
SIP dialog. In this scenario, the SIP UA takes on the role of the
Application. Thus it issues a SUBSCRIBE request to establish a new
dialog for the User Device to report on User Input (key press)
events. This could represent, for example, a toll by-pass scenario
where the User Device is an ingress gateway and the SIP UA is an
egress gateway.
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+--------+ SIP (INVITE) +-----+
| A--------------------X SIP |
| | SIP (SUBSCRIBE) | UA |
| User A'-------------------X' |
| Device | RTP |(App)|
| B--------------------Y |
+--------+ +-----+
Figure 2: Endpoint Model
The third model is that of a media proxy. A media proxy is a media
relay in the terminology of RFC1889 [14]. 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 [13]), and so on.
The Requesting Application uses dialog identifiers to identify the
stream to monitor. The default is to monitor the media entering the
User Device. For example, if the Requesting Application in Figure 3
refers to 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 User Device to monitor the media
coming from SIP UAb RTP Port Y.
+-------------+
| Requesting |
/---| Application |
/ +-------------+
/
SIP / (SUBSCRIBE/NOTIFY)
/
/
+-----+ SIP +---M----+ SIP +-----+
| V--------------------C A--------------------X |
| SIP | | User | | SIP |
| UAa | RTP | Device | RTP | UAb |
| W--------------------D B--------------------Y |
+-----+ +--------+ +-----+
Figure 3: Media Proxy Model
2.2 Stream to Monitor
The default media stream to monitor is the stream represented by the
local tag of the SIP dialog at the monitoring User Device. A
requesting application MAY request monitoring of the stream
represented by the remote tag of the SIP dialog at the User Device.
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Not all User Devices are able to monitor the remote media stream.
However, the User Device MUST be able to report on local User Input.
In the case where the User Device is a gateway, that is, it is a User
Device Proxy, local User Input is the media stream that emanates from
the User Device.
If the requesting application wishes to monitor both the ingress and
egress streams at a given User Device, the application MUST establish
two subscriptions, one for each leg.
Section 4.1.6 describes how to specify to the User Device which
stream direction of the dialog to monitor.
2.3 Operation
The Key Press Stimulus Event Package uses explicit subscription
notification requests, using the SUBSCRIBE/NOTIFY [2] mechanism.
The User Device MUST return a GRUU [15] in the Contact header of a
SIP INVITE, 1xx, or 2xx response.
NOTE: Generating and using a GRUU is in no way required for the
KPML mechanism to operate. For example, consider a restricted
deployment scenario, such as between a single service provider's
gateway (User Device) and application server (Application) without
any intervening proxies. Ignoring the obvious performance issues
of requesting GRUUs, the service provider probably does not want
the gateway to offer the first, principal feature of a GRUU.
Namely, the service provider may NOT want to offer a globally
routable Request-URI. All of the mechanisms in this document will
work in such deployment topologies without a GRUU. However, as
described in the GRUU document, there are scenarios where the
subscriber may not be able to find the User Device without a GRUU.
Thus, this document mandates the use of a GRUU as part of an
Internet standard. That is, mandating a GRUU means the mechanism
will work in all deployment scenarios. Likewise, an
implementation that did not use a GRUU is not fully compliant with
this specification.
Following the semantics of SUBSCRIBE, if the User Device receives a
second subscription on the same dialog, including id, if present, the
User Device MUST terminate the existing KPML subscription and replace
it with the new subscription.
An Application MAY register multiple User Input patterns in a single
KPML subscription.
If the User Device supports multiple, simultaneous KPML
subscriptions, the Application installs the subscriptions either in a
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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
subscriptions, the User Device MUST respond with an error response
code. See Section 4.1.7 for more information.
A KPML subscription can be persistent or one-shot. Persistent
requests are active until either the dialog terminates, including
normal subscription expiration, the Application replaces them, the
Application deletes them by sending a null document on the dialog, or
the Application deletes the subscription by sending a SUBCRIBE with
an expires of zero (0).
Standard SUBSCRIBE processing dictates the User Device 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
active for the duration specified in the SUBSCRIBE message or if it
automatically terminates after a pattern matches.
KPML subscriptions route to the User Device using standard SIP
request routing. A KPML subscription identifies the media stream by
referencing its dialog identifiers.
Notifications are KPML documents. If the User Device matched a digit
map, the response indicates the User Input detected and whether the
User Device suppressed User Input. If the User Device had an error,
such as a timeout, it will indicate that instead.
3. Event Package Operation
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 Event Package is "kpml".
3.2 Event Package Parameters
SIP identifies dialogs 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
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matches the Call-ID. Although semantically different, the important
entities are the To: and From: tags.
The "leg" parameter identifies the dialog to monitor. If there is no
corresponding dialog, the User Device MUST 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."
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 User Device 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, 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
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 [16].
3.3 SUBSCRIBE Bodies
Key press event notification filters use KPML, as described in
Section 4.1. The MIME type for KPML is application/kpml+xml.
The KPML document MUST be well-formed and SHOULD be valid. KPML
documents MUST conform to XML 1.0 [10] and MUST use UTF-8 encoding.
Because of the potentially sensitive nature of the information
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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 to expect encryption on the
documents.
3.4 Subscription Duration
The "persist" attribute to the <pattern> tag in the KPML subscription
body affects the lifetime of the subscription.
If the persist attribute is "one-shot", then once there is a match
(or no match is possible), the subscription ends after the User
Device notifies the Application.
If the persist attribute is "persistent" or "single-notify", then the
subscription ends when the Application explicitly ends it or the User
Device terminates the subscription.
The subscription lifetime MUST NOT be longer than the negotiated
expires time, per RFC3265 [2].
The subscription lifetime should be longer than the expected call
time. The default subscription lifetime (Expires value) MUST be 7200
seconds.
Subscribers MUST be able to handle the User Device returning an
Expires value smaller than the requested value. Per RFC3265 [2], the
subscription duration is the value returned by the User Device in the
200 OK 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 User 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 User Device (notifier) SHOULD be to
authenticate the requesting party.
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User Devices MUST support digest authentication at a minimum.
User Devices MUST support the sips: scheme and TLS.
Upon authenticating the requesting party, the User 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 User Device checks
to see if the request is to terminate a subscription. If the request
will terminate the subscription, the User Device does the appropriate
processing, including the procedures described in Section 3.7.4.
If the request has no KPML body, then 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 User Device follows the procedures described in
Section 3.7.1.
If the dialog referenced by the "leg" parameter to the kpml
subscription does not exist, the User Device follows the procedures
in Section 3.7.5 Note the User 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 User Device parses the KPML
document. The User Device SHOULD validate the XML document against
the schema presented in Section 6.2. If the document is not valid,
the User 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 User Device unloads the document.
If the KPML document is valid, and the User Device is capable of
performing the monitoring, the User Device performs the filtering
specified by the KPML document. See Section 4 for the specification
of KPML.
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3.7 Notifier Generation of NOTIFY Requests
3.7.1 SIP Protocol-Generated
The User 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 is no User Input
quarantined at the time of the SUBSCRIBE (see Section 4.1 below) or
the quarantined User Input does not match the new KPML document, then
the immediate NOTIFY MUST NOT contain a KPML body. If User Device
has User Input quarantined that result in a match using the new KPML
document, then the NOTIFY MUST return the appropriate KPML document.
3.7.2 Match
During the subscription lifetime, the User Device may detect a key
press stimulus that triggers a KPML event. In this case, the User
Device (notifier) MUST return the appropriate KPML document.
3.7.3 Inter-Digit Timeout No Match
Once a user starts to enter stimulus, it is highly likely they will
enter all of the key presses 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
stimulus but then stops before a match.
Once the User Device detects a key press that matches the first
character of a digit map, the User Device starts the interdigit timer
specified in the <pattern> tag. Every subsequent key press detected
restarts the interdigit timer. If the interdigit timer expires, the
User Device generates a KPML report with the KPML status code 423,
Timer Expired. The report also includes the User Input collected up
to the time the timer expired. This could be the null string. After
sending the NOTIFY, the User Device will resume quarantining
additional detected User Input.
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
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milliseconds. The default value is 4000, for 4 seconds. A value of
zero indicates disabling the interdigit timer. The User 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 document, and there is quarantined User
Input, then the User Device attempts to process the quarantined
digits against the document. If there is a match, the User Device
MUST generate 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 SUBSCRIBE request has an expires of zero and no KPML body or
the expires timer on the SUBSCRIBE-initiated dialog fires at the User
Device (notifier), then the User Device MUST issue a KPML report with
the KPML status code 487, Subscription Expired. The report also
includes the User Input 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.
Per the mechanisms of RFC3265 [2], the User Device MUST terminate the
SIP SUBSCRIBE dialog. The User Device does this via the 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".
Terminating the subscription when a dialog terminates ensures
reauthorization (if necessary) for attaching to subsequent call legs.
3.7.5 No Call Leg
If a SUBSCRIBE request references a dialog that is not present at the
User Device, the User Device MUST generate a KPML report with the
KPML status code 481, Dialog Not Found. The User Device terminates
the subscription by setting the subscription state to "terminated".
3.7.6 Bad Document
If the KPML document is not valid, the User Device generates a KPML
report with the KPML status code 501, Bad Document. The User Device
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terminates the subscription by setting the subscription state to
"terminated".
If the document is valid but the User Device does not support a
namespace in the document, the User Device MUST respond with a KPML
status code 502, Namespace Not Supported.
3.7.7 One-Shot vs. Persistent Requests
There are two types of subscriptions: one-shot and persistent.
Persistent subscriptions have two sub-types: continuous notify and
single-notify.
One-shot subscriptions terminate after a pattern match and report.
If the User Device detects a key press stimulus that triggers a
one-shot KPML event, then the User Device (notifier) MUST set the
"Subscription-State" in the NOTIFY message to "terminated". At this
point the User Device MUST consider the subscription destroyed. The
User Device MUST quarantine User Input per the controls specified in
Section 4.1.
Persistent subscriptions remain active at the User Device, even after
a match. For continuous notify persistent subscriptions, the User
Device will emit a notification whenever the User Input matches a
pattern. For single-notify persistent subscriptions, the User Device
will emit a notification at the first match, but will not emit
further notifications until the Application issues a new document on
the subscription dialog.
NOTE: The single-notify persistent subscription enables lock-step
(race-free) quarantining of User Input between different digit
maps.
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 is no quarantined User Input 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 User Input collection. The most likely cause is
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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 User
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 User 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
only <regex> is "x".
The User Device MUST reliably deliver notifications. Because there
is no meaningful metric for throttling requests, the User Device
SHOULD send NOTIFY messages over a congestion-controlled transport,
such as TCP or SCTP.
User Devices MUST at a minimum implement SIP over TCP.
3.11 State Agents
Not applicable.
4. Message Format - KPML
The Key Press Markup Language (KPML) has two, mutually exclusive
elements: the request and response.
4.1 KPML Request
A KPML request document contains a <request> entity containing a
<pattern> tag with a series of <regex> tags. The <regex> element
specifies a pattern for the User Device to report on. Section 5
describes the DRegex, or digit regular expression, language.
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4.1.1 User Input Buffer Behavior
User Devices MUST buffer User Input. Subsequent KPML documents apply
their patterns against the buffered User Input. Some applications
use modal interfaces where the first few key presses determine what
the following key presses 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 markup provides a <flush> tag in the <pattern> element. The
default is not to flush User Input. Flushing User Input has the
effect of ignoring key presses entered before the installation of the
KPML subscription. To flush User Input, include the tag <flush>yes</
flush> in the KPML subscription document. Note that this directive
affects only the current subscription dialog/id combination.
Lock-step processing of User Input is where the User Device issues a
notification, the Application processes the notification while the
User Device buffers additional User Input, the Application requests
more User Input, and only then does the User Device notify the
Application based on the collected User Input. To direct the User
Device to operate in lock-step mode, set the <pattern> attribute
persist="single-notify".
The User Device MUST be able to process <flush>no</flush>. This
directive is effectively a no-op.
Other string values for <flush> may be defined in the future. If the
User 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 a <regex> tag, the User
Device MUST discard the key press from consideration against the
current or future KPML documents on a given dialog. 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 User
Input that interest them. For example, a pre-paid application
only wishes to monitor for a long pound. If the user enters other
stimulus, presumably for other applications, the pre-paid
applicationd does not want notification of that User Input. This
feature is fundamentally different than the behavior of TDM-based
equipment where every application receives every key press.
To limit reports to only complete matches, set the "nopartial"
attribute to the <pattern> tag to "true". In this case, the User
Device attempts to match a rolling window over the collected User
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input.
KPML subscriptions are independent. Thus it is not possible for the
current document to know if a following document will enable barging
or want User Input flushed. Therefore, the User Device MUST buffer
all User Input.
On a given SUBSCRIBE dialog with a given id, the User Device MUST
quarantine all User Input detected between the time of the report and
the receipt of the next document, if any. If the next document
indicates a buffer flush, then the interpreter MUST flush all
collected User Input from consideration from KPML documents received
on that dialog with the given event id. If the next document does
not indicate flushing the quarantined User Input, then the
interpreter MUST apply the collected User Input (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
User Input.
Given the potential for the need for an infinite buffer for User
Input, the User Device MAY discard the oldest User Input from the
buffer. When the User Device issues a KPML notification, it MUST set
the forced_flush attribute of the <response> tag to "true". For
future use, the Application MUST consider any non-null value, other
than "false" that it does not understand, to be the same as "true".
NOTE: The requirement to buffer all User Input for the entire
length of the session is not really onerous under normal
operation. For example, if one has a gateway with 8,000 sessions,
and the gateway buffers 50 key presses on each session, the
requirement is only 400,000 bytes, assuming one byte per key
press.
Unless there is a suppress indicator in the digit map, it is not
possible to know if the User Input is for local KPML processing or
for other recipients of the media stream. Thus, in the absence of a
suppression indicator, the User Device transmits the User Input to
the far end in real time, using either RFC2833, generating the
appropriate tones, or both.
The section Digit Suppression (Section 4.1.3) describes the operation
of the suppress indicator.
4.1.2 Pattern Matching
4.1.2.1 Inter-Digit Timing
The pattern matching logic works as follows. KPML User Devices MUST
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follow the logic presented in this section so that different
implementations will perform deterministically on the same KPML
document given the same User Input.
The pattern match algorithm matches the longest regular expression.
This is the same mode as H.248.1 [17] and not the mode presented by
MGCP [18]. 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 North American 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). Conversely, the User does not want the system to cut off
their ten-digit number at seven digits because they did not enter the
number fast enough.
One approach to this problem is to have an explicit dial string
terminator. Typically, it is the pound key (#). Now, consider the
following snippet.
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<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>x{7}</regex>
<regex>x{10}</regex>
</pattern>
</request>
Figure 8: Timeout Matching with Enter Key
In Figure 8, the enterkey attribute 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.
NOTE: The enterkey is a string. The enterkey can be a sequence
of key presses.
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.
The User Device MAY support an inter-digit timeout value. This is
the amount of time the User 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 User Device
does not support the specification of an inter-digit timeout, the
User Device MUST silently ignore the specification. If the User
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Device supports the specification of an inter-digit timeout, but not
to the granularity specified by the value presented, the User Device
MUST round up the requested value to the closest value it can
support.
The User Device MAY support an extra-digit timeout value. This is
the amount of time the User Device will wait for another key press
when it already has a matched <regex>. The application can specify
the extra-digit timeout as an integer number of milliseconds by using
the "extradigittimer" attribute to the <pattern> tag. The default is
500 milliseconds.
The User Device MAY support a critical-digit timeout value. This is
the amount of time the User Device will wait for another key press
when it already has a matched <regex> but there is another, longer
<regex> that may also match the pattern. The application can specify
the extra-digit timeout as an integer number of milliseconds by using
the "extradigittimer" attribute to the <pattern> tag. The default is
1000 milliseconds.
4.1.2.2 Intra-Digit Timing
Some patterns look for long duration key presses. For example, some
applications look for long "#" or long "*".
KPML uses the "L" modifier to <regex> characters to indicate long key
presses. The following KPML document looks for a long pound of at
least 3 seconds.
<?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 long="3000">
<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.
The default length of the long attribute is 2500 milliseconds.
Some User Devices are unable to present long key presses. An example
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is an old private branch exchange (PBX) phone set that emits
fixed-length tones when the user presses a key. To address this
issue, the User Device MAY interpret a succession of a single key
press to be equivalent to a long key press of the same key. The
Application indicates it wants this behavior by setting the
"longrepeat" attribute tot he <pattern> to "true".
4.1.3 Digit Suppression
Under basic operation, a KPML User Device will transmit in-band tones
(RFC2833 [13] or actual tone) in parallel with User Input 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 suppression tag, "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>, suppression
processing is straightforward. The end-point passes User Input until
the stream matches the regular expression <pre>. At that point, the
User Device will continue collecting User Input, but will suppress
the generation or pass-through of any in-band User Input.
If the User Device suppressed stimulus, it MUST indicate this by
including the attribute "suppressed" with a value of "true" in the
notification.
Clearly, if the User Device is processing the KPML document against
quarantined User Input, it is too late to suppress the transmission
of the User Input, as the User Device has long sent the stimulus.
This is a situation where there is a <pre> specification, but the
"suppressed" attribute will not be "true" in the notification. If
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there is a <pre> tag that the User Device matched and the User Device
is unable to suppress the User Input, it MUST set the "suppressed"
attribute to "false".
A KPML User Device MAY perform suppression. If it is not capable of
suppression, it ignores the suppression attribute. It MUST set the
"suppressed" attribute to "false". In this case, the pattern to
match is the concatenated pattern of pre+value.
At some point in time, the User Device will collect enough User Input
to the point it hits a <pre> pattern. The interdigittimer attribute
indicates how long to wait once the user enters stimulus before
reporting a time-out error. If the interdigittimer expires, the User
Device MUST issue a time-out report, transmit the suppressed User
Input on the media stream, and stop suppression.
Once the User Device detects a match and it sends a NOTIFY request to
report the User Input, the User Device MUST stop suppression.
Clearly, if subsequent User Input matches another <pre> expression,
then the User Device MUST start suppression.
After 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 User Device receives
"*8", it will stop forwarding stimulus. 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 User Device 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
User Device will hold digits, which will have obvious user interface
issues in the case of a failure.
4.1.4 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 "persistent"
or "one-notify". Any other value, including "one-shot", indicates
the request is a one-shot subscription. If the User 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
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buffer and the digits match an expression in the KPML document, the
User Device prepares the appropriate KPML document.
Note the values of the persistent attribute are case sensitive.
4.1.5 Multiple Patterns
Some User 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 User Device sends back in the notification
report upon a match in the digit map. In the case of multiple
matches, the User Device MUST chose the longest match in the KPML
document. If multiple matches match the same length, the User Device
MUST chose the first expression listed in the subscription KPML
document based on KPML document order.
If the User Device does not support multiple regular expressions in a
pattern request, the User Device MUST return a KPML document with the
KPML result code set to 532.
4.1.6 Monitoring Direction
By default, the User Device monitors key presses emanating from the
User Device. Given a dialog identifier of Call-ID, local-tag, and
remote-tag, the User 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 User Device
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.
4.1.7 Multiple, Simultaneous Subscriptions
Some User Devices may support multiple key press event notification
subscriptions at the same time. In this situation, the User 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.
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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 User Device does not support multiple, simultaneous
subscriptions, the User Device MUST return a KPML document with the
KPML result code set to 533 on the dialog that requested the second
subscription. The User 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 User
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 User 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 [11] or
MSCML [12].
KPML reports have two mandatory attributes, code and text. These
attributes describe the state of the KPML interpreter on the User
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 User
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 User Device will emit a KPML report. Since
this is a success report, the code is "200" and the text is "OK".
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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 4.1.3) and
the User 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 User 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 User 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.
DRegex is a proper superset of RFC3435 [18] syntax. There are two
additions. The first is Digit Not in Range ([^digits]). This syntax
comes directly from egrep. Not in Range enables the easy
specification of, for example, the North American Numbering Plan.
The second is the Java RegExp Repeat Indicator ({m,n}). The Java
RegExp Repeat Indicator solves a serious deficiency in both RFC3235
and H.248.1 [17] regular expressions. Namely, the dot rule does not
have any limit and could collect an infinite number of digits. With
the repeat indicator, one can specify the minimum and maximum number
of digits or a pattern will match.
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 demonstrate the use of DRegex in KPML. Section
6.1 describes the ABNF for DRegex.
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+---------------------------------+---------------------------------+
| Entity | Matches |
+---------------------------------+---------------------------------+
| character | digits 0-9 and A-D (case |
| | insensitive) |
| * | * |
| # | # |
| [character selector] | Any character in selector |
| [^digit selector] | Any digit (0-9) NOT in selector |
| [range1-range2] | Any digit (0-9) in range from |
| | range1 to range2, inclusive |
| 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 |
| Lc | Match the character c if it is |
| | "long"; c is a digit 0-9 and |
| | A-D, #, or *. |
+---------------------------------+---------------------------------+
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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 | Matches 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 |
| 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 |
| *6[179#] | Matches *61, *67, *69, or *6# |
| x{10} | Ten digits (0-9) |
| 011x{7,15} | 011 followed by seven to fifteen digits |
| L* | Long star |
+------------+-----------------------------------------+
6. Formal Syntax
6.1 DRegex
The following definition follows RFC2234 [4]. The definition of
DIGIT is from the CORE specification of RFC2234, namely the
characters "0" through "9". Note the DRegexCharacater is not a
HEXDIG from RFC2234. In particular, DRegexCharacter neither includes
"E" nor "F". Moreover DRegexCharacter is case insensitive, unlike
HEXDIG.
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DRegex = DRegexString *( "|" DRegexString )
DRegexString = 1*( DRegexPosition [ RepeatCount ] )
DRegexPosition = DRegexSymbol / DRegexSet
DRegexSet = ( "[" DRegexSetList "]" ) /
( "[^" DigitList "]" )
DRegexSetList = 1*( (DIGIT "-" DIGIT) / DRegexSymbol )
DigitList = 1*( (DIGIT "-" DIGIT) / DIGIT )
DRegexSymbol = DRegexCharacter / ( "L" DRegexCharacter )
RepeatCount = "." / "{" RepeatRange "}"
RepeatRange = Count / ( Count "," Count ) /
( Count "," ) / ( "," Count )
Count = 1*(DIGIT)
DRegexCharacter = DIGIT / "*" / "#" / "A" / "a" / "B" / "b" /
"x" / "X" / "C" / "c" / "D" / "d"
Note that future extensions to this document may introduce other
characters for DRegexCharacter, in the scheme of H.248.1 [17] or
possibly as named strings or XML namespaces.
6.2 KPML
The following syntax in Figure 12 uses the XML Schema [5].
<?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:xs="http://www.w3.org/2001/XMLSchema"
xmlns="urn:ietf:params:xml:ns:kpml"
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="stream" type="xs:string" minOccurs="0"/>
<xs:element name="pattern">
<xs:complexType>
<xs:sequence>
<xs:element name="flush" minOccurs="0">
<xs:annotation>
<xs:documentation>Default is to not flush buffer
</xs:documentation>
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</xs:annotation>
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:string"/>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:element name="enterkey" minOccurs="0">
<xs:annotation>
<xs:documentation>No default enter key
</xs:documentation>
</xs:annotation>
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:string"/>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:element name="regex" maxOccurs="unbounded">
<xs:annotation>
<xs:documentation>Key press notation is a string to
allow for future extension of non-16 digit keypads
or named keys
</xs:documentation>
</xs:annotation>
<xs:complexType mixed="true">
<xs:sequence>
<xs:element name="pre" minOccurs="0">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:string"/>
</xs:simpleContent>
</xs:complexType>
</xs:element>
</xs:sequence>
<xs:attribute name="tag" type="xs:string"
use="optional"/>
</xs:complexType>
</xs:element>
</xs:sequence>
<xs:attribute name="persistent" use="optional">
<xs:annotation>
<xs:documentation>Default is "one-shot"
</xs:documentation>
</xs:annotation>
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="one-shot"/>
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<xs:enumeration value="persistent"/>
<xs:enumeration value="single-notify"/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
<xs:attribute name="interdigittimer" type="xs:integer"
use="optional">
<xs:annotation>
<xs:documentation>Default is 4000 (ms)</xs:documentation>
</xs:annotation>
</xs:attribute>
<xs:attribute name="criticaldigittimer" type="xs:integer"
use="optional">
<xs:annotation>
<xs:documentation>Default is 1000 (ms)</xs:documentation>
</xs:annotation>
</xs:attribute>
<xs:attribute name="extradigittimer" type="xs:integer"
use="optional">
<xs:annotation>
<xs:documentation>Default is 500 (ms)</xs:documentation>
</xs:annotation>
</xs:attribute>
<xs:attribute name="longtimer" type="xs:integer"
use="optional"/>
<xs:attribute name="longrepeat" type="xs:boolean"
use="optional"/>
<xs:attribute name="nopartial" type="xs:boolean"
use="optional">
<xs:annotation>
<xs:documentation>Default is false</xs:documentation>
</xs:annotation>
</xs:attribute>
</xs:complexType>
</xs:element>
</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="forced_flush" type="xs:string"
use="optional">
<xs:annotation>
<xs:documentation>String for future use for e.g., number
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of digits lost.</xs:documentation>
</xs:annotation>
</xs:attribute>
<xs:attribute name="digits" type="xs:string" use="optional"/>
<xs:attribute name="tag" type="xs:string" use="optional">
<xs:annotation>
<xs:documentation>Matches tag from regex in request
</xs:documentation>
</xs:annotation>
</xs:attribute>
</xs:complexType>
</xs:element>
</xs:choice>
<xs:attribute name="version" type="xs:string" use="required"/>
</xs:complexType>
</xs:element>
</xs:schema>
Figure 12: 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.
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.
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+------+---------------------------------------------------------+
| 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 [6].
Encoding considerations: See RFC3023 [6].
Interoperability considerations: See RFC2023 [6] and this document.
Published specification: This document.
Applications which use this media type: Session-oriented applications
that have primitive user interfaces.
Intended usage: COMMON
8.2 URN Sub-Namespace Registration for urn:ietf:xml:ns:kpml
URI: urn:ietf:params:xml:ns:kpml
Registrant Contact: IETF, SIPPING Work Group <sipping@ietf.org>, Eric
Burger <eburger@ieee.org>.
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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
Per RFC3688 [7], please register the XML Schema for KPML as
referenced in Section 6.2.
URI: Please assign.
Registrant Contact: IETF, SIPPING Work Group <sipping@ietf.org>, Eric
Burger <eburger@ieee.org>.
9. Security Considerations
As an XML markup, all of the security considerations of RFC3023 [6]
and RFC3406 [8] 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.
User 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 14 shows the KPML for long octothorpe.
<?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 14: 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 15: 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 4.1.5, the KPML interpreter will pick the "9401xxxxxxx"
string, as it occurs first in document order (both expressions match
the same length). Figure 16 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 16: 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 [11] or MSCML [12] or a
device control language such as H.248.1 [17].
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 17 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 17: 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 User Device ("User A") in an
INVITE-Initiated dialog. Note the Application can be a Record-Route
Proxy, a B2BUA, or another User 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!
12. References
12.1 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] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[5] Thompson, H., Beech, D., Maloney, M. and N. Mendelsohn, "XML
Schema Part 1: Structures", W3C REC REC-xmlschema-1-20010502,
May 2001.
[6] Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC
3023, January 2001.
[7] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, January
2004.
[8] Daigle, L., van Gulik, D., Iannella, R. and P. Faltstrom,
"Uniform Resource Names (URN) Namespace Definition Mechanisms",
BCP 66, RFC 3406, October 2002.
12.2 Informative References
[9] Rosenberg, J., "A Framework for Application Interaction in the
Session Initiation Protocol (SIP)",
draft-ietf-sipping-app-interaction-framework-01 (work in
progress), February 2004.
[10] 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.
[11] World Wide Web Consortium, "Voice Extensible Markup Language
(VoiceXML) Version 2.0", W3C Working Draft , April 2002,
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<http://www.w3.org/TR/voicexml20/>.
[12] Burger, E., Van Dyke, J. and A. Spitzer, "Media Server Control
Markup Language (MSCML) and Protocol", draft-vandyke-mscml-04
(work in progress), March 2004.
[13] Schulzrinne, H. and S. Petrack, "RTP Payload for DTMF Digits,
Telephony Tones and Telephony Signals", RFC 2833, May 2000.
[14] Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson,
"RTP: A Transport Protocol for Real-Time Applications", RFC
1889, January 1996.
[15] Rosenberg, J., "Obtaining and Using Globally Routable User
Agent (UA) URIs (GRUU) in the Session Initiation Protocol
(SIP)", draft-ietf-sip-gruu-01 (work in progress), February
2004.
[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] Groves, C., Pantaleo, M., Anderson, T. and T. Taylor, "Gateway
Control Protocol Version 1", RFC 3525, June 2003.
[18] Andreasen, F. and B. Foster, "Media Gateway Control Protocol
(MGCP) Version 1.0", RFC 3435, January 2003.
[19] Handley, M. and V. Jacobson, "SDP: Session Description
Protocol", RFC 2327, April 1998.
[20] 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.
[21] Olson, S., Camarillo, G. and A. Roach, "Support for IPv6 in
Session Description Protocol (SDP)", RFC 3266, June 2002.
[22] Hunt, A. and S. McGlashan, "Speech Recognition Grammar
Specification Version 1.0", W3C CR CR-speech-grammar-20020626,
June 2002.
[23] Burger (Ed.), E., Van Dyke, J. and A. Spitzer, "Basic Network
Media Services with SIP", draft-burger-sipping-netann-08 (work
in progress), February 2004.
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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
Ophir Frieder of the Illinois Institute of Technology collaborated on
the development of the quarantine algorithm.
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 and provided excellent review of the document.
Terence Lobo of SnowShore Networks made it all work.
Jerry Kamitses, Swati Dhuleshia, Shaun Bharrat, Sunil Menon, and
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Bryan Hill helped with clarifying the quarantine behavior and DRegex
syntax.
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