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Versions: (draft-burger-sipping-kpml) 00 01 02 03 04 05 06 07 08 RFC 4730

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.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
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   The list of current Internet-Drafts can be accessed at http://
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   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on August 2, 2004.

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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