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rfc:rfc4730

Network Working Group E. Burger Request for Comments: 4730 Cantata Technology, Inc. Category: Standards Track M. Dolly

                                                             AT&T Labs
                                                         November 2006
         A Session Initiation Protocol (SIP) Event Package
                   for Key Press Stimulus (KPML)

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The IETF Trust (2006).

Abstract

 This document describes a SIP Event Package "kpml" that enables
 monitoring of Dual Tone Multi-Frequency (DTMF) signals and uses
 Extensible Markup Language (XML) documents referred to as Key Press
 Markup Language (KPML).  The kpml Event Package may be used to
 support applications consistent with the principles defined in the
 document titled "A Framework for Application Interaction in the
 Session Initiation Protocol (SIP)".  The event package uses SUBSCRIBE
 messages and allows for XML documents that define and describe filter
 specifications for capturing key presses (DTMF Tones) entered at a
 presentation-free User Interface SIP User Agent (UA).  The event
 package uses NOTIFY messages and allows for XML documents to report
 the captured key presses (DTMF tones), consistent with the filter
 specifications, to an Application Server.  The scope of this package
 is for collecting supplemental key presses or mid-call key presses
 (triggers).

Burger & Dolly Standards Track [Page 1] RFC 4730 KPML November 2006

Table of Contents

 1. Introduction ....................................................4
    1.1. Conventions Used in This Document ..........................5
 2. Protocol Overview ...............................................5
 3. Key Concepts ....................................................6
    3.1. Subscription Duration ......................................6
    3.2. Timers .....................................................7
    3.3. Pattern Matches ............................................8
    3.4. Digit Suppression .........................................12
    3.5. User Input Buffer Behavior ................................14
    3.6. DRegex ....................................................16
         3.6.1. Overview ...........................................16
         3.6.2. Operation ..........................................18
    3.7. Monitoring Direction ......................................20
    3.8. Multiple Simultaneous Subscriptions .......................20
 4. Event Package Formal Definition ................................21
    4.1. Event Package Name ........................................21
    4.2. Event Package Parameters ..................................21
    4.3. SUBSCRIBE Bodies ..........................................22
    4.4. Subscription Duration .....................................22
    4.5. NOTIFY Bodies .............................................22
    4.6. Subscriber Generation of SUBSCRIBE Requests ...............22
    4.7. Notifier Processing of SUBSCRIBE Requests .................23
    4.8. Notifier Generation of NOTIFY Requests ....................25
    4.9. Subscriber Processing of NOTIFY Requests ..................27
    4.10. Handling of Forked Requests ..............................28
    4.11. Rate of Notifications ....................................28
    4.12. State Agents and Lists ...................................28
    4.13. Behavior of a Proxy Server ...............................29
 5. Formal Syntax ..................................................29
    5.1. DRegex ....................................................29
    5.2. KPML Request ..............................................30
    5.3. KPML Response .............................................33
 6. Enumeration of KPML Status Codes ...............................34
 7. IANA Considerations ............................................34
    7.1. SIP Event Package Registration ............................34
    7.2. MIME Media Type application/kpml-request+xml ..............35
    7.3. MIME Media Type application/kpml-response+xml .............35
    7.4. URN Sub-Namespace Registration for
         urn:ietf:xml:ns:kpml-request ..............................35
    7.5. URN Sub-Namespace Registration for
         urn:ietf:xml:ns:kpml-response .............................36
    7.6. KPML Request Schema Registration ..........................37
    7.7. KPML Response Schema Registration .........................37
 8. Security Considerations ........................................37
 9. Examples .......................................................38
    9.1. Monitoring for Octothorpe .................................38

Burger & Dolly Standards Track [Page 2] RFC 4730 KPML November 2006

    9.2. Dial String Collection ....................................39
 10. Call Flow Examples ............................................40
    10.1. Supplemental Digits ......................................40
    10.2. Multiple Applications ....................................45
 11. References ....................................................52
    11.1. Normative References .....................................52
    11.2. Informative References ...................................53
 Appendix A.  Contributors .........................................54
 Appendix B.  Acknowledgements .....................................54

Burger & Dolly Standards Track [Page 3] RFC 4730 KPML November 2006

1. Introduction

 This document describes a SIP Event Package "kpml" that enables
 monitoring of key presses and utilizes XML documents referred to as
 Key Press Markup Language (KPML).  KPML is a markup [14] that enables
 presentation-free User Interfaces as described in the Application
 Interaction Framework [15].  The Key Press Stimulus Package is a SIP
 Event Notification Package [5] that uses the SUBSCRIBE and NOTIFY
 methods of SIP.  The subscription filter and notification report
 bodies use the Keypad Markup Language, KPML.
 The "kpml" event package requires the definition of two new MIME
 types, two new URN sub-namespaces, and two schemas for the KPML
 Request and the KPML Response.  The scope of this package is for
 collecting supplemental key presses or mid-call key presses
 (triggers).  This capability allows an Application Server service
 provider to monitor (filter) for a set of DTMF patterns at a SIP User
 Agent located in either an end-user device or a gateway.
 In particular, the "kpml" event package enables "dumb phones" and
 "gateways" that receive signals from dumb phones to report user key-
 press events.  Colloquially, this mechanism provides for "digit
 reporting" or "Dual Tone Multi-Frequency (DTMF) reporting."  The
 capability eliminates the need for "hair-pinning" (routing media into
 and then out of the same device) through a Media Server or
 duplicating all the DTMF events, when an Application Server needs to
 trigger mid-call service processing on DTMF digit patterns.
 A goal of KPML is to fit in an extremely small memory and processing
 footprint.
 The name of the XML document, KPML, reflects its legacy support role.
 The public switched telephony network (PSTN) accomplished signaling
 by transporting DTMF tones in the bearer channel (in-band signaling)
 from the user terminal to the local exchange.
 Voice-over-IP networks transport in-band signals with actual DTMF
 waveforms or RFC 2833 [10] packets.  In RFC 2833, the signaling
 application inserts RFC 2833 named signal packets as well as, or
 instead of, generating tones in the media path.  The receiving
 application receives the signal information in the media stream.
 RFC 2833 tones are ideal for conveying telephone-events point-to-
 point in a Real-time Transport Protocol (RTP) stream, as in the
 context of straightforward sessions like a 2-party call or a simple,
 centrally mixed conference.  However, there are other environments
 where additional or alternative requirements are needed.  These other
 environments include protocol translation and complex call control.

Burger & Dolly Standards Track [Page 4] RFC 4730 KPML November 2006

 An interested application could request notifications of every key
 press.  However, many of the use cases for such signaling show that
 most applications are interested in only one or a few keystrokes.
 Thus a mechanism is needed for specifying to the user's interface
 what stimuli the application requires.

1.1. Conventions Used in This Document

 RFC 2119 [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 document [15] 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".
 Additionally, the Application Interaction Framework document
 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.

2. Protocol Overview

 The "kpml" event package uses explicit subscription notification
 requests using the SIP SUBSCRIBE and NOTIFY methods.  An Application
 that wants to collect digits creates an application/kpml-request+xml
 document with the digit patterns of interest to the Application and
 places this document in its SUBSCRIBE request.  SIP SUBSCRIBE
 messages are routed to the User Interface using standard SIP request
 routing.  KPML Subscriptions do not fork.  The KPML request contained
 in the SUBSCRIBE message identifies the target media stream by
 referencing the dialog identifiers corresponding to the session
 responsible for the media stream.  Once a subscription is
 established, the User Interface sends application/kpml-response+xml
 documents in NOTIFY requests when digits are collected or when
 timeouts or errors occur.
 A KPML subscription can be persistent or one-shot.  Persistent
 requests are active until the subscription terminates, the
 Application replaces the request, the Application deletes the request
 by sending a null document on the dialog, or the Application
 explicitly deletes the subscription by sending a SUBSCRIBE with an
 expires value of zero (0).

Burger & Dolly Standards Track [Page 5] RFC 4730 KPML November 2006

 One-shot requests terminate the subscription upon the receipt of DTMF
 values that provide a match.  The "persist" KPML element specifies
 whether the subscription remains active for the duration specified in
 the SUBSCRIBE message or if it automatically terminates upon a
 pattern match.
 NOTIFY messages can contain XML documents.  If the User Interface
 matches a digitmap, the NOTIFY message (response) contains an XML
 document that indicates the User Input detected and whether the User
 Interface suppressed the representation of User Input, such as tones,
 or RFC 2833, from the media streams.  If the User Interface
 encountered an error condition, such as a timeout, this will also be
 reported.

3. Key Concepts

3.1. Subscription Duration

 KPML recognizes 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 occurs and a
 report is issued in a NOTIFY message.  If the User Interface detects
 a key press stimulus that triggers a one-shot KPML event, then the
 User Interface (notifier) MUST set the "Subscription-State" in the
 NOTIFY message to "terminated".  At this point, the User Interface
 MUST consider the subscription expired.
 Persistent subscriptions remain active at the User Interface, even
 after a match.  For continuous-notify persistent subscriptions, the
 User Interface will emit a NOTIFY message whenever the User Input
 matches a subscribed pattern.  For single-notify persistent
 subscriptions, the user device will emit a NOTIFY message at the
 first match, but will not emit further NOTIFY messages until the
 Application issues a new subscription request on the subscription
 dialog.
    NOTE: The single-notify persistent subscription enables lock-step
    (race-free) quarantining of User Input between different digit
    maps.
 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
 Interface notifies the Application.

Burger & Dolly Standards Track [Page 6] RFC 4730 KPML November 2006

 If the "persist" attribute is "persist" or "single-notify", then the
 subscription ends when the Application explicitly ends it or the User
 Interface terminates the subscription.
 If the User Interface does not support persistent subscriptions, it
 returns a NOTIFY message with the KPML status code set to 531.  If
 there are digits in the buffer and the digits match an expression in
 the SUBSCRIBE filter, the User Interface prepares the appropriate
 NOTIFY response message.
 The values of the "persist" attribute are case sensitive.

3.2. Timers

 To address the various key press collection scenarios, three timers
 are defined.  They are the extra, critical, and inter-digit timers.
 o  The inter-digit timer is the maximum time to wait between digits.
    Note: unlike Media Gateway Control Protocol (MGCP) [11] or H.248
    [12], there is no start timer, as that concept does not apply in
    the KPML context.
 o  The critical timer is the time to wait for another digit if the
    collected digits can match more than one potential pattern.
 o  The extra timer is the time to wait for another digit if the
    collected digits can only match one potential pattern, but a
    longer match for this pattern is possible.
 The User Interface MAY support an inter-digit timeout value.  This is
 the amount of time the User Interface 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
 Interface does not support the specification of an inter-digit
 timeout, the User Interface MUST silently ignore the specification.
 If the User Interface supports the specification of an inter-digit
 timeout, but not to the granularity specified by the value presented,
 the User Interface MUST round up the requested value to the closest
 value it can support.
 The purpose of the inter-digit timeout is to protect applications
 from starting to match a pattern, yet never returning a result.  This
 can occur, for example, if the user accidentally enters a key that
 begins to match a pattern.  However, since the user accidentally
 entered the key, the rest of the pattern never comes.  Moreover, when
 the user does enter a pattern, since they have already entered a key,

Burger & Dolly Standards Track [Page 7] RFC 4730 KPML November 2006

 the pattern may not match or may not match as expected.  Likewise,
 consider the case where the user thinks they entered a key press, but
 the User Interface does not detect the key.  This could occur when
 collecting ten digits, but the device actually only receives 9.  In
 this case, the User Interface will wait forever for the tenth key
 press, while the user becomes frustrated wondering why the
 application is not responding.
 The User Interface MAY support a critical-digit timeout value.  This
 is the amount of time the User Interface 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 critical-digit timeout as an integer number of
 milliseconds by using the "criticaldigittimer" attribute to the
 <pattern> tag.  The default is 1000 milliseconds.
 The purpose of the critical-digit timeout is to allow the application
 to collect longer matches than the shortest presented.  This is
 unlike MGCP [11], where the shortest match gets returned.  For
 example, if the application registers for the patterns "0011", "011",
 "00", and "0", the critical-digit timeout enables the User Interface
 to distinguish between "0", "00", "011", and "0011".  Without this
 feature, the only value that the User Interface can detect is "0".
 The User Interface MAY support an extra-digit timeout value.  This is
 the amount of time the User Interface will wait for another key press
 when it already has matched the longest <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.  If there is no enterkey specified, then
 the User Interface MAY default the exteradigittimer to zero.
 The purpose of the extra-digit timeout is to allow the User Interface
 to collect the enterkey.  Without this feature, the User Interface
 would match the pattern, and the enterkey would be buffered and
 returned as the next pattern.

3.3. Pattern Matches

 During the subscription lifetime, the User Interface may detect a key
 press stimulus that triggers a KPML event.  In this case, the User
 Interface (notifier) MUST return the appropriate KPML document.
 The pattern matching logic works as follows.  KPML User Interfaces
 MUST follow the logic presented in this section so that different
 implementations will perform deterministically on the same KPML
 document given the same User Input.

Burger & Dolly Standards Track [Page 8] RFC 4730 KPML November 2006

 A kpml request document contains a <pattern> element with a series of
 <regex> tags.  Each <regex> element specifies a potential pattern for
 the User Interface to match.  The Section 5.1 describes the DRegex,
 or digit regular expression, language.
 The pattern match algorithm matches the longest regular expression.
 This is the same mode as H.248.1 [12] and not the mode presented by
 MGCP [11].  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-request xmlns="urn:ietf:params:xml:ns:kpml-request"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation=
         "urn:ietf:params:xml:ns:kpml-request kpml-request.xsd"
       version="1.0">
   <pattern>
     <regex>0</regex>
     <regex>011</regex>
   </pattern>
 </kpml-request>
                       Figure 1: Greedy Matching
 In Figure 1, 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 2: Timeout Matching
 Figure 2 shows 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.  Often, it is the pound key (#).  Now, consider the
 following snippet.

Burger & Dolly Standards Track [Page 9] RFC 4730 KPML November 2006

 <regex>x{7}#</regex>
 <regex>x{10}#</regex>
                 Figure 3: Timeout Matching with Enter
 The problem with the approach in Figure 3 is that the "#" will appear
 in the returned dial string.  Moreover, one often wants to allow the
 user to enter the string without the dial string termination key.  In
 addition, using explicit matching on the key means one has to double
 the number of patterns, e.g., "x{7}", "x{7}#", "x{10}", and "x{10}#".
 The approach used in KPML is to have an explicit "Enter Key", as
 shown in the following snippet.
 <pattern enterkey="#">
   <regex>x{7}</regex>
   <regex>x{10}</regex>
 </pattern>
               Figure 4: Timeout Matching with Enter Key
 In Figure 4, 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, such as "**".
 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.

Burger & Dolly Standards Track [Page 10] RFC 4730 KPML November 2006

 <?xml version="1.0" encoding="UTF-8"?>
 <kpml-request xmlns="urn:ietf:params:xml:ns:kpml-request"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation=
         "urn:ietf:params:xml:ns:kpml-request kpml-request.xsd"
       version="1.0">
   <pattern long="3000">
     <regex>L#</regex>
   </pattern>
 </kpml-request>
                              Long Pound
 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 "long" milliseconds, the Long modifier is true.  The
 default length of the long attribute is 2500 milliseconds.
 User Interfaces MUST distinguish between long and short input when
 the KPML document specifies both in a document.  However, if there is
 not a corresponding long key press pattern in a document, the User
 Interface MUST match the key press pattern irrespective of the length
 of time the user presses the key.
 As an example, in the following snippet in Figure 6, the User
 Interface discriminates between a long "*" and a normal "*", but any
 length "#" will match the pattern.
 <pattern>
   <regex tag="short_star">*</regex>
   <regex tag="long_star">L*</regex>
   <regex>#</regex>
 </pattern>
                   Figure 6: Long and Short Matching
 Some User Interfaces are unable to present long key presses.  An
 example 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 Interface MAY interpret a succession of presses of a
 single key to be equivalent to a long key press of the same key.  The
 Application indicates it wants this behavior by setting the
 "longrepeat" attribute to the <pattern> to "true".
 The KPML document specifies if the patterns are to be persistent by
 setting the "persist" attribute to the <pattern> tag to "persist" or
 "single-notify".  Any other value, including "one-shot", indicates

Burger & Dolly Standards Track [Page 11] RFC 4730 KPML November 2006

 the request is a one-shot subscription.  If the User Interface does
 not support persistent subscriptions, it returns a KPML document with
 the KPML status code set to 531.  If there are digits in the buffer
 and the digits match an expression in the KPML document, the User
 Interface emits the appropriate kpml notification.
 Note the values of the "persist" attribute are case sensitive.
 Some User Interfaces 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 Interface sends back in the notification
 report upon a match in the digit map.  In the case of multiple
 matches, the User Interface MUST choose the longest match in the KPML
 document.  If multiple matches match the same length, the User
 Interface MUST choose the first expression listed in the subscription
 KPML document based on KPML document order.
 If the User Interface cannot support multiple regular expressions in
 a pattern request, the User Interface MUST return a KPML document
 with the KPML status code set to 532.  If the User Interface cannot
 support the number of regular expressions in the pattern request, the
 User Interface MUST return a KPML document with the KPML status code
 set to 534.
    NOTE: We could mandate a minimum number of regular expressions
    that a User Interface must support per subscription request and
    globally.  However, such minimums tend to become designed-in,
    hard-coded limits.  For guidance, one should be able to easily
    handle tens of expressions per subscription and thousands
    globally.  A good implementation should have effectively no
    limits.  That said, to counter possible denial-of-service attacks,
    implementers of User Interfaces should be aware of the 534 and 501
    status codes and feel free to use them.

3.4. Digit Suppression

 Under basic operation, a KPML User Interface will transmit in-band
 tones (RFC 2833 [10] or actual tone) in parallel with User Input
 reporting.
    NOTE: If KPML did not have this behavior, then a User Interface
    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

Burger & Dolly Standards Track [Page 12] RFC 4730 KPML November 2006

    because they accessed an interactive voice response (IVR) system
    that looks for "*"?  In this case, the "*" would get held by the
    User Interface, 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 Interface 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 initiate a transfer.
 For those situations, KPML adds a suppression tag, "pre", to the
 <regex> tag.  There MUST NOT be more than one <pre> tag in any given
 <regex> tag.
 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 Interface will continue collecting User Input, but will suppress
 the generation or pass-through of any in-band User Input.
 If the User Interface suppressed stimulus, it MUST indicate this by
 including the attribute "suppressed" with a value of "true" in the
 notification.
 Clearly, if the User Interface is processing the KPML document
 against buffered User Input, it is too late to suppress the
 transmission of the User Input, as the User Interface 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 there is a <pre> tag that the User Interface
 matched and the User Interface is unable to suppress the User Input,
 it MUST set the "suppressed" attribute to "false".
 A KPML User Interface 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 Interface will collect enough User
 Input to the point it matches a <pre> pattern.  The interdigittimer
 attribute indicates how long to wait for the user to enter stimulus
 before reporting a time-out error.  If the interdigittimer expires,
 the User Interface MUST issue a time-out report, transmit the
 suppressed User Input on the media stream, and stop suppression.

Burger & Dolly Standards Track [Page 13] RFC 4730 KPML November 2006

 Once the User Interface detects a match and it sends a NOTIFY request
 to report the User Input, the User Interface MUST stop suppression.
 Clearly, if subsequent User Input matches another <pre> expression,
 then the User Interface 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 Interface 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 Interface to have a
    sensible inter-digit timer.  This is because an errant dot (".")
    may suppress digit sending forever.
 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 Interface will hold digits, which will have obvious User
 Interface issues in the case of a failure.

3.5. User Input Buffer Behavior

 User Interfaces MUST buffer User Input upon receipt of an
 authenticated and accepted subscription.  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.
 User Interfaces MUST NOT provide a subscriber with digits that were
 detected prior to the authentication and authorization of that
 subscriber.  Without prohibition, a subscriber might be able to gain
 access to calling card or other information that predated the
 subscriber's participation in the call.  Note that this prohibition
 MUST be applied on a per-subscription basis.
 KPML 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

Burger & Dolly Standards Track [Page 14] RFC 4730 KPML November 2006

 <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 Interface issues
 a notification, the Application processes the notification while the
 User Interface buffers additional User Input, the Application
 requests more User Input, and only then does the User Interface
 notify the Application based on the collected User Input.  To direct
 the User Interface to operate in lock-step mode, set the <pattern>
 attribute persist="single-notify".
 The User Interface 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 Interface receives a string it does not understand, it MUST
 treat the string as a no-op.
 If the user presses a key that cannot match any pattern within a
 <regex> tag, the User Interface MUST discard all buffered key presses
 up to and including the current 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 Interface buffers
 any key presses the user entered subsequent to the match.
    NOTE: This behavior allows applications to receive only User Input
    that is of interest to 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
    application does not want notification of that User Input.  This
    feature is fundamentally different than the behavior of Time
    Division Multiplexer (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
 Interface attempts to match a rolling window over the collected User
 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 Interface MUST
 buffer all User Input, subject to the forced_flush caveat described
 below.

Burger & Dolly Standards Track [Page 15] RFC 4730 KPML November 2006

 On a given SUBSCRIBE dialog with a given id, the User Interface MUST
 buffer 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 buffered 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 5.3.  If there is no match, the
 interpreter MUST flush all of the collected User Input.
 Given the potential for needing an infinite buffer for User Input,
 the User Interface MAY discard the oldest User Input from the buffer.
 If the User Interface discards digits, when the User Interface 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 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 Interface transmits the User Input to
 the far end in real time, using either RFC 2833, generating the
 appropriate tones, or both.

3.6. DRegex

3.6.1. Overview

 This subsection is informative in nature.
 The Digit REGular EXpression (DRegex) syntax is a telephony-oriented
 mapping of POSIX Extended Regular Expressions (ERE) [13].
 KPML does not use full POSIX ERE for the following reasons.
 o  KPML will often run on high density or extremely low power and
    memory footprint devices.

Burger & Dolly Standards Track [Page 16] RFC 4730 KPML November 2006

 o  Telephony application convention uses the star symbol ("*") for
    the star key and "x" for any digit 0-9.  Requiring the developer
    to escape the star ("\*") and expand the "x" ("[0-9]") is error
    prone.  This also leads DRegex to use the dot (".") to indicate
    repetition, which was the function of the unadorned star in POSIX
    ERE.
 o  Implementation experience with MGCP [11] and H.248.1 [12] has been
    that implementers and users have a hard time understanding the
    precedence of the alternation operator ("|").  This is due both to
    an under-specification of the operator in those documents and
    conceptual problems for users.  Thus, the SIPPING Working Group
    concluded that DRegex should not support alternation.  That said,
    each KPML <pattern> element may contain multiple regular
    expressions (<regex> elements).  Thus, it is straightforward to
    have pattern alternatives (use multiple <regex> elements) without
    the problems associated with the alternation operator ("|").
    Thus, DRegex does not support the POSIX alternation operator.
 o  DRegex includes character classes (characters enclosed in square
    brackets).  However, the negation operator inside a character
    class only operates on numbers.  That is, a negation class
    implicitly includes A-D, *, and #.  Including A-D, *, and # in a
    negation operator is a no-op.  Those familiar with POSIX would
    expect negation of the digits 4 and 5 (e.g., "[^45]") to include
    all other characters (including A-D, R, *, and #), while those
    familiar with telephony digit maps would expect negation to
    implicitly exclude non-digit characters.  Since the complete
    character set of DRegex is very small, constructing a negation
    class using A-D, R, *, and # requires the user to specify the
    positive inverse mapping.  For example, to specify all key
    presses, including A-D and *, except #, the specification would be
    "[0-9A-D*]" instead of "[^#R]".
 The following table shows the mapping from DRegex to POSIX ERE.
                        +--------+-----------+
                        | DRegex | POSIX ERE |
                        +--------+-----------+
                        | *      | \*        |
                        | .      | *         |
                        | x      | [0-9]     |
                        | [xc]   | [0-9c]    |
                        +--------+-----------+
                 Table 1: DRegex to POSIX ERE Mapping

Burger & Dolly Standards Track [Page 17] RFC 4730 KPML November 2006

 The first substitution, which replaces a star for an escaped star, is
 because telephony application designers are used to using the star
 for the (very common) star key.  Requiring an escape sequence for
 this common pattern would be error prone.  In addition, the usage
 found in DRegex is the same as found in MGCP [11] and H.248.1 [12].
 Likewise, the use of the dot instead of star is common usage from
 MGCP and H.248.1, and reusing the star in this context would also be
 confusing and error prone.
 The "x" character is a common indicator of the digits 0 through 9.
 We use it here, continuing the convention.  Clearly, for the case
 "[xc]", where c is any character, the substitution is not a blind
 replacement of "[0-9]" for "x", as that would result in "[[0-9]c]",
 which is not a legal POSIX ERE.  Rather, the substitution for "[xc]"
 is "[0-9c]".
    NOTE: "x" does not include the characters *, #, R, or A through D.
 Users need to take care not to confuse the DRegex syntax with POSIX
 EREs.  They are NOT identical.  In particular, there are many
 features of POSIX EREs that DRegex does not support.
 As an implementation note, if one makes the substitutions described
 in the above table, then a standard POSIX ERE engine can parse the
 digit string.  However, the mapping does not work in the reverse
 (POSIX ERE to DRegex) direction.  DRegex only implements the
 normative behavior described below.

3.6.2. Operation

 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.

Burger & Dolly Standards Track [Page 18] RFC 4730 KPML November 2006

 +---------+---------------------------------------------------------+
 | Entity  | Matches                                                 |
 +---------+---------------------------------------------------------+
 | c       | digits 0-9, *, #, R, and A-D (case insensitive)         |
 | *       | the * character                                         |
 | #       | the # character                                         |
 | R       | The R (Register Recall) key                             |
 | [c]     | Any character in selector                               |
 | [^d]    | Any digit (0-9) not in selector                         |
 | [r1-r2] | Any character in range from r1 to r2, inclusive         |
 | x       | Any digit 0-9                                           |
 | {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 *.                                       |
 +---------+---------------------------------------------------------+
                            DRegex Entities
 For ranges, the A-D characters are disjoint from the 0-9 characters.
 If the device does not have an "R" key, the device MAY report a hook
 flash as an R character.
     +--------------+--------------------------------------------+
     | Example      | Description                                |
     +--------------+--------------------------------------------+
     | 1            | Matches the digit 1                        |
     | [179]        | Matches 1, 7, or 9                         |
     | [2-9]        | Matches 2, 3, 4, 5, 6, 7, 8, 9             |
     | [^15]        | Matches 0, 2, 3, 4, 6, 7, 8, 9             |
     | [02-46-9A-D] | Matches 0, 2, 3, 4, 6, 7, 8, 9, A, B, C, D |
     | x            | Matches 0, 1, 2, 3, 4, 5, 6, 7, 8, 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                                  |
     +--------------+--------------------------------------------+
                            DRegex Examples

Burger & Dolly Standards Track [Page 19] RFC 4730 KPML November 2006

3.7. Monitoring Direction

 SIP identifies dialogs by their dialog identifier.  The dialog
 identifier is the remote-tag, local-tag, and Call-ID entities defined
 in RFC 3261 [4].
 One method of determining the dialog identifier, particularly for
 third-party applications, is the SIP Dialog Package [17].
 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.
 But 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 Interface 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
 <stream>reverse</stream> tag.
 By default, the User Interface monitors key presses emanating from
 the User Interface.  Given a dialog identifier of Call-ID, local-tag,
 and remote-tag, the User Interface 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
 Interface 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.
    Further specification of the stream to monitor is the subject of
    future standardization.

3.8. Multiple Simultaneous Subscriptions

 An Application MAY register multiple User Input patterns in a single
 KPML subscription.  If the User Interface supports multiple,
 simultaneous KPML subscriptions, the Application installs the
 subscriptions either in a new SUBSCRIBE-initiated dialog or on an
 existing SUBSCRIBE-initiated dialog with a new event id tag.  If the
 User Interface does not support multiple, simultaneous KPML

Burger & Dolly Standards Track [Page 20] RFC 4730 KPML November 2006

 subscriptions, the User Interface MUST respond with an appropriate
 KPML status code.
 Some User Interfaces may support multiple key press event
 notification subscriptions at the same time.  In this situation, the
 User Interface 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, although reusing the same dialog for multiple
 subscriptions is NOT RECOMMENDED.
 If the User Interface does not support multiple, simultaneous
 subscriptions, the User Interface MUST return a KPML document with
 the KPML status code set to 533 on the dialog that requested the
 second subscription.  The User Interface MUST NOT modify the state of
 the first subscription on account of the second subscription attempt.

4. Event Package Formal Definition

4.1. Event Package Name

 This document defines a SIP Event Package as defined in RFC 3265 [5].
 The event-package token name for this package is:
         "kpml"

4.2. Event Package Parameters

 This package defines three Event Package parameters: call-id, remote-
 tag, and local-tag.  These parameters MUST be present, to identify
 the subscription dialog.  The User Interface matches the local-tag
 against the to tag, the remote-tag against the from tag, and the
 call-id against the Call-ID.
 The ABNF for these parameters is below.  It refers to many
 constructions from the ABNF of RFC 3261, such as EQUAL, DQUOTE, and
 token.
 call-id     =  "call-id" EQUAL ( token / DQUOTE callid DQUOTE )
                  ;; NOTE: any DQUOTEs inside callid MUST be escaped!
 remote-tag  =  "remote-tag" EQUAL token
 local-tag   =  "local-tag" EQUAL token

Burger & Dolly Standards Track [Page 21] RFC 4730 KPML November 2006

 If any call-ids contain embedded double-quotes, those double-quotes
 MUST be escaped using the backslash-quoting mechanism.  Note that the
 call-id parameter may need to be expressed as a quoted string.  This
 is because the ABNF for the callid production and the word
 production, which is used by callid (both from RFC 3261 [1]), allow
 some characters (such as "@", "[", and ":") that are not allowed
 within a token.

4.3. SUBSCRIBE Bodies

 Applications using this event package include an application/
 kpml-request+xml body in SUBSCRIBE requests to indicate which digit
 patterns they are interested in.  The syntax of this body type is
 formally described in Section 5.2.

4.4. Subscription Duration

 The subscription lifetime should be longer than the expected call
 time.  Subscriptions to this event package MAY range from minutes to
 weeks.  Subscriptions in hours or days are more typical and are
 RECOMMENDED.  The default subscription duration for this event
 package is 7200 seconds.
    Subscribers MUST be able to handle the User Interface returning an
    Expires value smaller than the requested value.  Per RFC 3265 [5],
    the subscription duration is the value returned by the Notifier in
    the 200 OK Expires header.

4.5. NOTIFY Bodies

 NOTIFY requests can contain application/kpml-response+xml (KPML
 Response) bodies.  The syntax of this body type is formally described
 in Section 5.3.  NOTIFY requests in immediate response to a SUBSCRIBE
 request MUST NOT contain a body unless they are notifying the
 subscriber of an error condition or previously buffered digits.
 Notifiers MAY send notifications with any format acceptable to the
 subscriber (based on the subscriber's inclusion of these formats in
 an Accept header).  A future extension MAY define other NOTIFY
 bodies.  If no "Accept" header is present in the SUBSCRIBE, the body
 type defined in this document MUST be assumed.

4.6. Subscriber Generation of SUBSCRIBE Requests

 A kpml request document contains a <pattern> element with a series of
 <regex> tags.  Each <regex> element specifies a potential pattern for
 the User Interface to match.  Section 5.1 describes the DRegex, or
 digit regular expression, language.

Burger & Dolly Standards Track [Page 22] RFC 4730 KPML November 2006

 KPML specifies key press event notification filters.  The MIME type
 for KPML requests is application/kpml-request+xml.
 The KPML request document MUST be well formed and SHOULD be valid.
 KPML documents MUST conform to XML 1.0 [14] and MUST use UTF-8
 encoding.
 Because of the potentially sensitive nature of the information
 reported by KPML, subscribers SHOULD use sips: and MAY use S/MIME on
 the content.
 Subscribers MUST be prepared for the notifier to insist on
 authentication of the subscription request.  Subscribers MUST be
 prepared for the notifier to insist on using a secure communication
 channel.

4.7. 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 User Interface (notifier) MUST authenticate the requesting
 party in some way before accepting the subscription.
 User Interfaces MUST implement SIP Digest authentication as required
 by RFC 3261 [4] and MUST implement the sips: scheme and TLS.
 Upon authenticating the requesting party, the User Interface
 determines if the requesting party has authorization to monitor the
 user's key presses.  The default authorization policy is to allow a
 KPML subscriber who can authenticate with a specific identity to
 monitor key presses from SIP sessions in which the same or equivalent
 authenticated identity is a participant.  In addition, KPML will
 often be used, for example, between "application servers"
 (subscribers) and PSTN gateways (notifiers) operated by the same
 domain or federation of domains.  In this situation a notifier MAY be
 configured with a list of subscribers which are specifically trusted
 and authorized to subscribe to key press information related to all
 sessions in a particular context.
 The User Interface returns a Contact URI that may have GRUU [9]
 properties in the Contact header of a SIP INVITE, 1xx, or 2xx
 response.
 After authorizing the request, the User Interface checks to see if
 the request is to terminate a subscription.  If the request will
 terminate the subscription, the User Interface does the appropriate
 processing, including the procedures described in Section 5.2.

Burger & Dolly Standards Track [Page 23] RFC 4730 KPML November 2006

 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.
 The User Interface follows the procedures described in Section 5.2.
 If the dialog referenced by the kpml subscription does not exist, the
 User Interface follows the procedures in Section 5.3.  Note the User
 Interface MUST issue a 200 OK to the SUBSCRIBE request before issuing
 the NOTIFY, as the SUBSCRIBE itself is well formed.
 If the request has a KPML body, the User Interface parses the KPML
 document.  The User Interface SHOULD validate the XML document
 against the schema presented in Section 5.2.  If the document is not
 valid, the User Interface rejects the SUBSCRIBE request with an
 appropriate error response and terminates the subscription.  If there
 is a loaded KPML document on the subscription, the User Interface
 unloads the document.
 In addition, if there is a loaded KPML document on the subscription,
 the end device unloads the document.
 Following the semantics of SUBSCRIBE, if the User Interface receives
 a resubscription, the User Interface MUST terminate the existing KPML
 request and replace it with the new request.
 It is possible for the INVITE usage of the 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 buffered User
 Input, then the User Interface attempts to process the buffered
 digits against the document.  If there is a match, the User Interface
 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
 Interface (notifier), then the User Interface 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.

Burger & Dolly Standards Track [Page 24] RFC 4730 KPML November 2006

 Per the mechanisms of RFC 3265 [5], the User Interface MUST terminate
 the SIP SUBSCRIBE dialog.  The User Interface 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
 subscriptions.
 If a SUBSCRIBE request references a dialog that is not present at the
 User Interface, the User Interface MUST generate a KPML report with
 the KPML status code 481, Dialog Not Found.  The User Interface
 terminates the subscription by setting the subscription state to
 "terminated".
 If the KPML document is not valid, the User Interface generates a
 KPML report with the KPML status code 501, Bad Document.  The User
 Interface terminates the subscription by setting the subscription
 state to "terminated".
 If the document is valid but the User Interface does not support a
 namespace in the document, the User Interface MUST respond with a
 KPML status code 502, Namespace Not Supported.

4.8. Notifier Generation of NOTIFY Requests

 Immediately after a subscription is accepted, the Notifier MUST send
 a NOTIFY with the current location information as appropriate based
 on the identity of the subscriber.  This allows the Subscriber to
 resynchronize its state.
 The User Interface (notifier in SUBSCRIBE/NOTIFY parlance) generates
 NOTIFY requests based on the requirements of RFC 3265 [5].
 Specifically, if a SUBSCRIBE request is valid and authorized, it will
 result in an immediate NOTIFY.
 The KPML payload distinguishes between an initial NOTIFY and a NOTIFY
 informing of key presses.  If there is no User Input buffered at the
 time of the SUBSCRIBE (see below) or the buffered User Input does not
 match the new KPML document, then the immediate NOTIFY MUST NOT
 contain a KPML body.  If User Interface has User Input buffered that
 results in a match using the new KPML document, then the NOTIFY MUST
 return the appropriate KPML document.
 The NOTIFY in response to a SUBSCRIBE request has no KPML if there
 are no matching buffered digits.  An example of this is in Figure 10.

Burger & Dolly Standards Track [Page 25] RFC 4730 KPML November 2006

 If there are buffered 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.
 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
 All subscriptions MUST be authenticated, particularly those that
 match on buffered input.
 KPML specifies the key press notification report format.  The MIME
 type for KPML reports is application/kpml-response+xml.  The default
 MIME type for the kpml event package is application/
 kpml-response+xml.
 If the requestor is not using a secure transport protocol such as TLS
 for every hop (e.g., by using a sips: URI), the User Interface SHOULD
 use S/MIME to protect the user information in responses.
 When the user enters key presses that match a <regex> tag, the User
 Interface 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 Interface 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.
 KPML reports have two mandatory attributes, code and text.  These
 attributes describe the state of the KPML interpreter on the User
 Interface.  Note the KPML status 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

Burger & Dolly Standards Track [Page 26] RFC 4730 KPML November 2006

 case, the NOTIFY would include the KPML status 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 Interface will most likely set the Subscription-State to
 "terminated".  This lets the SIP machinery know the subscription is
 no longer active.
 If a pattern matches, the User Interface 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 and the User
 Interface 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 it 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.
 Note that if the monitored (INVITE-initiated) dialog terminates, the
 notifier still MUST explicitly terminate the KPML subscriptions
 monitoring that dialog.

4.9. Subscriber Processing of NOTIFY Requests

 If there is no KPML body, it means the SUBSCRIBE was successful.
 This establishes the dialog if there is no buffered User Input to
 report.
 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 between 400
 and 499, then an error occurred with User Input collection.  The most
 likely cause is a timeout condition.

Burger & Dolly Standards Track [Page 27] RFC 4730 KPML November 2006

 If there is a KPML document, and the KPML status code is between 500
 and 599, then an error occurred with the subscription.  See Section 6
 for more on the meaning of KPML status codes.
 The subscriber MUST be mindful of the subscription state.  The User
 Interface may terminate the subscription at any time.

4.10. Handling of Forked Requests

 Forked requests are NOT ALLOWED for this event type.  This can be
 ensured if the Subscriptions to this event package are sent to SIP
 URIs that have GRUU properties.

4.11. Rate of Notifications

 The User Interface MUST NOT generate messages faster than 25 messages
 per second, or 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 sustained rate of notification shall be no more than 100 Notifies
 per minute.
 The User Interface MUST reliably deliver notifications.  Because
 there is no meaningful metric for throttling requests, the User
 Interface SHOULD send NOTIFY messages over a congestion-controlled
 transport, such as TCP.
    Note that all SIP implementations are already required to
    implement SIP over TCP.

4.12. State Agents and Lists

 KPML requests are sent to a specific SIP URI, which may have GRUU
 properties, and they attempt to monitor a specific stream that
 corresponds with a specific target dialog.  Consequently,
 implementers MUST NOT define state agents for this event package or
 allow subscriptions for this event package to resource lists using
 the event list extension [18].

Burger & Dolly Standards Track [Page 28] RFC 4730 KPML November 2006

4.13. Behavior of a Proxy Server

 There are no additional requirements on a SIP Proxy, other than to
 transparently forward the SUBSCRIBE and NOTIFY methods as required in
 SIP.

5. Formal Syntax

5.1. DRegex

 The following definition follows RFC 4234 [2].  The definition of
 DIGIT is from RFC 4234, namely, the characters "0" through "9".  Note
 the DRegexCharacter is not a HEXDIG from RFC 4234.  In particular,
 DRegexCharacter includes neither "E" nor "F".  Note that
 DRegexCharacter is case insensitive.
 DRegex           = 1*( DRegexPosition [ RepeatCount ] )
 DRegexPosition   = DRegexSymbol / DRegexSet
 DRegexSymbol     = [ "L" ] DRegexCharacter
 DRegexSet        = "[" 1*DRegexSetList "]"
 DRegexSetList    = DRegexCharacter [ "-" DRegexCharacter ]
 DRegexCharacter  = DIGIT / "A" / "B" / "C" / "D" / "R" / "*" / "#" /
                          "a" / "b" / "c" / "d" / "r"
 RepeatCount      = "." / "{" RepeatRange "}"
 RepeatRange      = Count / ( Count "," Count ) /
                            ( Count "," ) / ( "," Count )
 Count            = 1*DIGIT
                            ABNF for DRegex
 Note that future extensions to this document may introduce other
 characters for DRegexCharacter, in the scheme of H.248.1 [12] or
 possibly as named strings or XML namespaces.

Burger & Dolly Standards Track [Page 29] RFC 4730 KPML November 2006

5.2. KPML Request

 The following syntax for KPML requests uses the XML Schema [8].
 <?xml version="1.0" encoding="UTF-8"?>
 <xs:schema targetNamespace="urn:ietf:params:xml:ns:kpml-request"
  xmlns="urn:ietf:params:xml:ns:kpml-request"
  xmlns:xs="http://www.w3.org/2001/XMLSchema"
  elementFormDefault="qualified"
  attributeFormDefault="unqualified">
   <xs:element name="kpml-request">
     <xs:annotation>
       <xs:documentation>IETF Keypad Markup Language Request
       </xs:documentation>
     </xs:annotation>
     <xs:complexType>
       <xs:sequence>
         <xs:element name="stream" minOccurs="0">
           <xs:complexType>
             <xs:choice>
               <xs:element name="reverse" minOccurs="0"/>
               <xs:any namespace="##other"/>
             </xs:choice>
           </xs:complexType>
         </xs:element>
         <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>
                 </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>

Burger & Dolly Standards Track [Page 30] RFC 4730 KPML November 2006

                 <xs:complexType mixed="true">
                   <xs:choice>
                     <xs:element name="pre" minOccurs="0">
                       <xs:complexType>
                         <xs:simpleContent>
                           <xs:extension base="xs:string"/>
                         </xs:simpleContent>
                       </xs:complexType>
                     </xs:element>
                     <xs:any namespace="##other"/>
                   </xs:choice>
                   <xs:attribute name="tag" type="xs:string"
                                 use="optional"/>
                 </xs:complexType>
               </xs:element>
             </xs:sequence>
             <xs:attribute name="persist" 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"/>
                   <xs:enumeration value="persist"/>
                   <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">

Burger & Dolly Standards Track [Page 31] RFC 4730 KPML November 2006

               <xs:annotation>
                 <xs:documentation>Default is 500 (ms)
                 </xs:documentation>
               </xs:annotation>
             </xs:attribute>
             <xs:attribute name="long" 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:attribute name="enterkey" type="xs:string"
                           use="optional">
               <xs:annotation>
                 <xs:documentation>No default enterkey
                 </xs:documentation>
               </xs:annotation>
             </xs:attribute>
           </xs:complexType>
         </xs:element>
       </xs:sequence>
       <xs:attribute name="version" type="xs:string"
                     use="required"/>
     </xs:complexType>
   </xs:element>
 </xs:schema>
                Figure 12: XML Schema for KPML Requests

Burger & Dolly Standards Track [Page 32] RFC 4730 KPML November 2006

5.3. KPML Response

 The following syntax for KPML responses uses the XML Schema [8].
 <?xml version="1.0" encoding="UTF-8"?>
 <xs:schema targetNamespace="urn:ietf:params:xml:ns:kpml-response"
  xmlns:xs="http://www.w3.org/2001/XMLSchema"
  xmlns="urn:ietf:params:xml:ns:kpml-response"
  elementFormDefault="qualified"
  attributeFormDefault="unqualified">
   <xs:element name="kpml-response">
     <xs:annotation>
       <xs:documentation>IETF Keypad Markup Language Response
       </xs:documentation>
     </xs:annotation>
     <xs:complexType>
       <xs:attribute name="version" type="xs:string"
                     use="required"/>
       <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 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:schema>
                     XML Schema for KPML Responses

Burger & Dolly Standards Track [Page 33] RFC 4730 KPML November 2006

6. Enumeration of KPML Status Codes

 KPML status 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.
      +------+--------------------------------------------------+
      | Code | Text                                             |
      +------+--------------------------------------------------+
      | 200  | Success                                          |
      | 402  | User Terminated without Match                    |
      | 423  | Timer Expired                                    |
      | 481  | Dialog Not Found                                 |
      | 487  | Subscription Expired                             |
      | 501  | Bad Document                                     |
      | 502  | Namespace Not Supported                          |
      | 531  | Persistent Subscriptions Not Supported           |
      | 532  | Multiple Regular Expressions Not Supported       |
      | 533  | Multiple Subscriptions on a Dialog Not Supported |
      | 534  | Too Many Regular Expressions                     |
      +------+--------------------------------------------------+
                      Table 4: KPML Status Codes

7. IANA Considerations

 This document registers a new SIP Event Package, two new MIME types,
 and two new XML namespaces.

7.1. SIP Event Package Registration

 Package name:  kpml
 Type:  package
 Contact:  Eric Burger, <e.burger@ieee.org>
 Change Controller:  SIPPING Working Group delegated from the IESG
 Published Specification:  RFC 4730

Burger & Dolly Standards Track [Page 34] RFC 4730 KPML November 2006

7.2. MIME Media Type application/kpml-request+xml

 MIME media type name:  application
 MIME subtype name:  kpml-request+xml
 Required parameters:  none
 Optional parameters:  Same as charset parameter application/xml as
    specified in XML Media Types [3]
 Encoding considerations:  See RFC 3023 [3].
 Security considerations:  See Section 10 of RFC 3023 [3] and
    Section 8 of RFC 4730
 Interoperability considerations:  See RFC 2023 [3] and RFC 4730
 Published specification:  RFC 4730
 Applications which use this media type:  Session-oriented
    applications that have primitive User Interfaces.
 Change controller:  SIPPING Working Group delegated from the IESG
 Personal and email address for further information:  Eric Burger
    <e.burger@ieee.org>
 Intended usage:  COMMON

7.3. MIME Media Type application/kpml-response+xml

 MIME media type name:  application
 MIME subtype name:  kpml-response+xml
 Required parameters:  none
 Optional parameters:  Same as charset parameter application/xml as
    specified in XML Media Types [3]
 Encoding considerations:  See RFC 3023 [3].
 Security considerations:  See Section 10 of RFC 3023 [3] and
    Section 8 of RFC 4730
 Interoperability considerations:  See RFC 2023 [3] and RFC 4730
 Published specification:  RFC 4730
 Applications which use this media type:  Session-oriented
    applications that have primitive User Interfaces.
 Change controller:  SIPPING Working Group delegated from the IESG
 Personal and email address for further information:  Eric Burger
    <e.burger@ieee.org>
 Intended usage:  COMMON

7.4. URN Sub-Namespace Registration for urn:ietf:xml:ns:kpml-request

 URI: urn:ietf:params:xml:ns:kpml-request
 Registrant Contact: The IESG <iesg@ietf.org>

Burger & Dolly Standards Track [Page 35] RFC 4730 KPML November 2006

 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 Request</title>
   </head>
   <body>
     <h1>Namespace for Key Press Markup Language Request</h1>
     <h2>urn:ietf:params:xml:ns:kpml-request</h2>
     <p>
 <a href="ftp://ftp.rfc-editor.org/in-notes/RFC4730.txt">RFC 4730</a>.
     </p>
   </body>
 </html>

7.5. URN Sub-Namespace Registration for urn:ietf:xml:ns:kpml-response

 URI: urn:ietf:params:xml:ns:kpml-response
 Registrant Contact: The IESG <iesg@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 Response</title>
   </head>
   <body>
     <h1>Namespace for Key Press Markup Language Response</h1>
     <h2>urn:ietf:params:xml:ns:kpml-response</h2>
     <p>
 <a href="ftp://ftp.rfc-editor.org/in-notes/rfc4730.txt">RFC 4730</a>.
     </p>
   </body>
 </html>

Burger & Dolly Standards Track [Page 36] RFC 4730 KPML November 2006

7.6. KPML Request Schema Registration

 Per RFC 3688 [7], IANA registered the XML Schema for KPML as
 referenced in Section 5.2 of RFC 4730.
 URI: urn:ietf:params:xml:schema:kpml-request
 Registrant Contact: <iesg@ietf.org>

7.7. KPML Response Schema Registration

 Per RFC 3688 [7], IANA registered the XML Schema for KPML as
 referenced in Section 5.3 of RFC 4730.
 URI: urn:ietf:params:xml:schema:kpml-response
 Registrant Contact: IETF, SIPPING Work Group <sipping@ietf.org>, Eric
 Burger <e.burger@ieee.org>.

8. Security Considerations

 The user information transported by KPML is potentially sensitive.
 For example, it could include calling card or credit card numbers.
 This potentially private information could be provided accidentally
 if the notifier does not properly authenticate or authorize a
 subscription.  Similarly private information (such as a credit card
 number or calling card number) could be revealed to an otherwise
 legitimate subscriber (one operating an IVR) if digits buffered
 earlier in the session are provided unintentionally to the new
 subscriber.
 Likewise, an eavesdropper could view KPML digit information if it is
 not encrypted, or an attacker could inject fraudulent notifications
 unless the messages or the SIP path over which they travel are
 integrity protected.
 Therefore, User Interfaces MUST NOT downgrade their own security
 policy.  That is, if a User Interface policy is to restrict
 notifications to authenticated and authorized subscribers over secure
 communications, then the User Interface must not accept an
 unauthenticated, unauthorized subscription over an insecure
 communication channel.
 As an XML markup, all of the security considerations of RFC 3023 [3]
 and RFC 3406 [6] MUST be met.  Pay particular attention to the
 robustness requirements of parsing XML.

Burger & Dolly Standards Track [Page 37] RFC 4730 KPML November 2006

 Key press information is potentially sensitive.  For example, it can
 represent credit card, calling card, or other personal information.
 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 so S/MIME or other appropriate mechanisms SHOULD
 be used.
 Subscriptions MUST be authenticated in some manner.  As required by
 the core SIP [4] specification, all SIP implementations MUST support
 digest authentication.  In addition, User Interfaces MUST implement
 support for the sips: scheme and SIP over TLS.  Subscribers MUST
 expect the User Interface to demand the use of an authentication
 scheme.  If the local policy of a User Interface is to use
 authentication or secure communication channels, the User Interface
 MUST reject subscription requests that do not meet that policy.
 User Interfaces MUST begin buffering User Input upon receipt of an
 authenticated and accepted subscription.  This buffering is done on a
 per-subscription basis.

9. 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.

9.1. 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 session and shift the user's
 focus to the application.

Burger & Dolly Standards Track [Page 38] RFC 4730 KPML November 2006

 Figure 16 shows the KPML for long octothorpe.
 <?xml version="1.0"?>
 <kpml-request xmlns="urn:ietf:params:xml:ns:kpml-request"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation=
         "urn:ietf:params:xml:ns:kpml-request kpml-request.xsd"
       version="1.0">
   <pattern>
     <regex>L#</regex>
   </pattern>
 </kpml-request>
                  Figure 16: Long Octothorpe Example
 The regex value L indicates the following digit needs to be a long-
 duration key press.

9.2. Dial String Collection

 In this example, the User Interface 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.
 <?xml version="1.0"?>
 <kpml-request xmlns="urn:ietf:params:xml:ns:kpml-request"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation=
         "urn:ietf:params:xml:ns:kpml-request kpml-request.xsd"
       version="1.0">
   <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>
 </kpml-request>
               Figure 17: 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

Burger & Dolly Standards Track [Page 39] RFC 4730 KPML November 2006

 "9xxxxxxxxxx" regular expressions.  Both expressions are the same
 length.  Thus the KPML interpreter will pick the "9401xxxxxxx"
 string, as it occurs first in document order.  Figure 18 shows the
 response.
 <?xml version="1.0"?>
 <kpml-response xmlns="urn:ietf:params:xml:ns:kpml-resposne"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation=
         "urn:ietf:params:xml:ns:kpml-response kpml-response.xsd"
       version="1.0"
       code="200" text="OK"
       digits="94015551212" tag="RI-number"/>
                 Figure 18: Dial String KPML Response

10. Call Flow Examples

10.1. Supplemental Digits

 This section gives a non-normative example of an application that
 collects supplemental digits.  Supplemental digit collection is where
 the network requests additional digits after the caller enters the
 destination address.  A typical supplemental dial string is four
 digits in length.

Burger & Dolly Standards Track [Page 40] RFC 4730 KPML November 2006

 Ingress Gateway      Application Server       Egress Gateway
        |                      |                      |
        |                      |                      |
        |                      |                      |
        |(1) INVITE            |                      |
        |-------------------------------------------->|
        |                      |                      |
        |                      |                      |
        |(2) 200 OK            |                      |
        |<--------------------------------------------|
        |                      |                      |
        |                      |                      |
        |(3) ACK               |                      |
        |-------------------------------------------->|
        |                      |                      |
        |                      |                      |
        |(4) SUBSCRIBE (one-shot)                     |
        |<---------------------|                      |
        |                      |                      |
        |                      |                      |
        |(5) 200 OK            |                      |
        |--------------------->|                      |
        |                      |                      |
        |                      |                      |
        |(6) NOTIFY            |                      |
        |--------------------->|                      |
        |                      |                      |
        |                      |                      |
        |(7) 200 OK            |                      |
        |<---------------------|                      |
        |                      |                      |
        |                      |                      |
        |(8)                   |                      |
        |......................|                      |
        |                      |                      |
        |                      |                      |
        |(9) NOTIFY (digits)   |                      |
        |--------------------->|                      |
        |                      |                      |
        |                      |                      |
        |(10) 200 OK           |                      |
        |<---------------------|                      |
        |                      |                      |
        |                      |                      |
        |                      |                      |
        |                      |                      |
               Figure 19: Supplemental Digits Call Flow

Burger & Dolly Standards Track [Page 41] RFC 4730 KPML November 2006

 In messages (1-3), the ingress gateway establishes a dialog with an
 egress gateway.  The application learns the dialog ID through out-of-
 band mechanisms, such as the Dialog Package or being co-resident with
 the egress gateway.  Part of the ACK message is below, to illustrate
 the dialog identifiers.
 ACK sip:gw@subA.example.com SIP/2.0
 Via: ...
 Max-Forwards: ...
 Route: ...
 From: <sip:phn@example.com>;tag=jfh21
 To: <sip:gw@subA.example.com>;tag=onjwe2
 Call-ID: 12345592@subA.example.com
 ...
 In message (4), the application the requests that gateway collect a
 string of four key presses.
 SUBSCRIBE sip:gw@subA.example.com SIP/2.0
 Via: SIP/2.0/TCP client.subB.example.com;branch=q4i9ufr4ui3
 From: <sip:ap@subB.example.com>;tag=567890
 To: <sip:gw@subA.example.com>
 Call-ID: 12345601@subA.example.com
 CSeq: 1 SUBSCRIBE
 Contact: <sip:ap@client.subB.example.com>
 Max-Forwards: 70
 Event: kpml ;remote-tag="sip:phn@example.com;tag=jfh21"
             ;local-tag="sip:gw@subA.example.com;tag=onjwe2"
             ;call-id="12345592@subA.example.com"
 Expires: 7200
 Accept: application/kpml-response+xml
 Content-Type: application/kpml-request+xml
 Content-Length: 292
 <?xml version="1.0" encoding="UTF-8"?>
 <kpml-request xmlns="urn:ietf:params:xml:ns:kpml-request"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation=
       "urn:ietf:params:xml:ns:kpml-request kpml-request.xsd"
     version="1.0">
   <pattern persist="one-shot">
     <regex>xxxx</regex>
   </pattern>
 </kpml-request>

Burger & Dolly Standards Track [Page 42] RFC 4730 KPML November 2006

 Message (5) is the acknowledgement of the subscription request.
 SIP/2.0 200 OK
 Via: SIP/2.0/TCP subB.example.com;branch=q4i9ufr4ui3;
      received=192.168.125.12
 From: <sip:ap@subB.example.com>;tag=567890
 To: <sip:gw@subA.example.com>;tag=1234567
 Call-ID: 12345601@subA.example.com
 CSeq: 1 SUBSCRIBE
 Contact: <sip:gw27@subA.example.com>
 Expires: 3600
 Event: kpml
 Message (6) is the immediate notification of the subscription.
 NOTIFY sip:ap@client.subB.example.com SIP/2.0
 Via: SIP/2.0/UDP subA.example.com;branch=gw27id4993
 To: <sip:ap@subB.example.com>;tag=567890
 From: <sip:gw@subA.example.com>;tag=1234567
 Call-ID: 12345601@subA.example.com
 CSeq: 1000 NOTIFY
 Contact: <sip:gw27@subA.example.com>
 Event: kpml
 Subscription-State: active;expires=3599
 Max-Forwards: 70
 Content-Length: 0
 Message (7) is the acknowledgement of the notification message.
 SIP/2.0 200 OK
 Via: SIP/2.0/TCP subA.example.com;branch=gw27id4993
 To: <sip:ap@subB.example.com>;tag=567890
 From: <sip:gw@subA.example.com>;tag=1234567
 Call-ID: 12345601@subA.example.com
 CSeq: 1000 NOTIFY
 Some time elapses (8).
 The user enters the input.  The device provides the notification of
 the collected digits in message (9).  Since this was a one-shot
 subscription, note the Subscription-State is "terminated".

Burger & Dolly Standards Track [Page 43] RFC 4730 KPML November 2006

 NOTIFY sip:ap@client.subB.example.com SIP/2.0
 Via: SIP/2.0/UDP subA.example.com;branch=gw27id4993
 To: <sip:ap@subB.example.com>;tag=567890
 From: <sip:gw@subA.example.com>;tag=1234567
 Call-ID: 12345601@subA.example.com
 CSeq: 1001 NOTIFY
 Contact: <sip:gw27@subA.example.com>
 Event: kpml
 Subscription-State: terminated
 Max-Forwards: 70
 Content-Type: application/kpml-response+xml
 Content-Length: 258
 <?xml version="1.0" encoding="UTF-8"?>
 <kpml-response xmlns="urn:ietf:params:xml:ns:kpml-response"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation=
         "urn:ietf:params:xml:ns:kpml-response kpml-response.xsd"
       version="1.0"
       code="200" text="OK"
       digits="4336"/>
 Message (10) is the acknowledgement of the notification.
 SIP/2.0 200 OK
 Via: SIP/2.0/TCP subA.example.com;branch=gw27id4993
 To: <sip:ap@subB.example.com>;tag=567890
 From: <sip:gw@subA.example.com>;tag=1234567
 Call-ID: 12345601@subA.example.com
 CSeq: 1001 NOTIFY

Burger & Dolly Standards Track [Page 44] RFC 4730 KPML November 2006

10.2. Multiple Applications

 This section gives a non-normative example of multiple applications.
 One application collects a destination number to call.  That
 application then waits for a "long pound."  During the call, the call
 goes to a personal assistant application, which interacts with the
 user.  In addition, the personal assistant application looks for a
 "short pound."
 For clarity, we do not show the INVITE dialogs.
 Gateway           Card Application      Personal Assistant
    |                      |                      |
    |                      |                      |
    |                      |                      |
    |(1) SUBSCRIBE (persistent)                   |
    |<---------------------|                      |
    |                      |                      |
    |                      |                      |
    |(2) 200 OK            |                      |
    |--------------------->|                      |
    |                      |                      |
    |                      |                      |
    |(3) NOTIFY            |                      |
    |--------------------->|                      |
    |                      |                      |
    |                      |                      |
    |(4) 200 OK            |                      |
    |<---------------------|                      |
    |                      |                      |
    |                      |                      |
    |(5)                   |                      |
    |......................|                      |
    |                      |                      |
    |                      |                      |
    |(6) NOTIFY (tag=card) |                      |
    |--------------------->|                      |
    |                      |                      |
    |                      |                      |
    |(7) 200 OK            |                      |
    |<---------------------|                      |
    |                      |                      |
    |                      |                      |
    |(8)                   |                      |
    |......................|                      |
    |                      |                      |
    |                      |                      |
    |(9) NOTIFY (tag=number)                      |

Burger & Dolly Standards Track [Page 45] RFC 4730 KPML November 2006

    |--------------------->|                      |
    |                      |                      |
    |                      |                      |
    |(10) 200 OK           |                      |
    |<---------------------|                      |
    |                      |                      |
    |                      |                      |
    |(11) SUBSCRIBE        |                      |
    |<--------------------------------------------|
    |                      |                      |
    |                      |                      |
    |(12) 200 OK           |                      |
    |-------------------------------------------->|
    |                      |                      |
    |                      |                      |
    |(13) NOTIFY           |                      |
    |-------------------------------------------->|
    |                      |                      |
    |                      |                      |
    |(14) 200 OK           |                      |
    |<--------------------------------------------|
    |                      |                      |
    |                      |                      |
    |(15)                  |                      |
    |.............................................|
    |                      |                      |
    |                      |                      |
    |(16) NOTIFY (tag=number)                     |
    |-------------------------------------------->|
    |                      |                      |
    |                      |                      |
    |(17) 200 OK           |                      |
    |<--------------------------------------------|
    |                      |                      |
    |                      |                      |
    |(18)                  |                      |
    |.............................................|
    |                      |                      |
    |                      |                      |
    |(19) NOTIFY (tag=#)   |                      |
    |-------------------------------------------->|
    |                      |                      |
    |                      |                      |
    |(20) 200 OK           |                      |
    |<--------------------------------------------|
    |                      |                      |
    |                      |                      |
    |(21)                  |                      |

Burger & Dolly Standards Track [Page 46] RFC 4730 KPML November 2006

    |.............................................|
    |                      |                      |
    |                      |                      |
    |(22) NOTIFY (tag=number)                     |
    |-------------------------------------------->|
    |                      |                      |
    |                      |                      |
    |(23) 200 OK           |                      |
    |<--------------------------------------------|
    |                      |                      |
    |                      |                      |
    |(24)                  |                      |
    |.............................................|
    |                      |                      |
    |                      |                      |
    |(25) NOTIFY (L#)      |                      |
    |--------------------->|                      |
    |                      |                      |
    |                      |                      |
    |(26) 200 OK           |                      |
    |<---------------------|                      |
    |                      |                      |
    |                      |                      |
    |                      |                      |
    |                      |                      |
               Figure 27: Multiple Application Call Flow
 Message (1) is the subscription request for the card number.
 SUBSCRIBE sip:gw@subA.example.com SIP/2.0
 Via: SIP/2.0/TCP client.subB.example.com;branch=3qo3j0ouq
 From: <sip:ap@subB.example.com>;tag=978675
 To: <sip:gw@subA.example.com>
 Call-ID: 12345601@subA.example.com
 CSeq: 20 SUBSCRIBE
 Contact: <sip:ap@client.subB.example.com>
 Max-Forwards: 70
 Event: kpml ;remote-tag="<sip:phn@example.com;tag=jfi23>"
             ;local-tag="sip:gw@subA.example.com;tag=oi43jfq"
             ;call-id="12345598@subA.example.com"
 Expires: 7200
 Accept: application/kpml-response+xml
 Content-Type: application/kpml-request+xml
 Content-Length: 339

Burger & Dolly Standards Track [Page 47] RFC 4730 KPML November 2006

 <?xml version="1.0" encoding="UTF-8"?>
 <kpml-request xmlns="urn:ietf:params:xml:ns:kpml-request"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation=
         "urn:ietf:params:xml:ns:kpml-request kpml-request.xsd"
       version="1.0">
   <pattern persist="persist">
     <regex tag="card">x{16}</regex>
     <regex tag="number">x{10}</regex>
   </pattern>
 </kpml-request>
 Messages (2-4) are not shown, for brevity.  Message (6) is the
 notification of the card number.
 NOTIFY sip:ap@client.subB.example.com SIP/2.0
 Via: SIP/2.0/UDP subA.example.com;branch=3qo3j0ouq
 To: <sip:ap@subB.example.com>;tag=978675
 From: <sip:gw@subA.example.com>;tag=9783453
 Call-ID: 12345601@subA.example.com
 CSeq: 3001 NOTIFY
 Contact: <sip:gw27@subA.example.com>
 Event: kpml
 Subscription-State: active;expires=3442
 Max-Forwards: 70
 Content-Type: application/kpml-response+xml
 Content-Length: 271
 <?xml version="1.0" encoding="UTF-8"?>
 <kpml-response xmlns="urn:ietf:params:xml:ns:kpml-response"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation=
         "urn:ietf:params:xml:ns:kpml-response kpml-response.xsd"
       version="1.0"
       code="200" text="OK"
       digits="9999888877776666"/>

Burger & Dolly Standards Track [Page 48] RFC 4730 KPML November 2006

 Message (7) is the acknowledgement of the notification.  Time goes by
 in (8).  Message (9) is the notification of the dialed number.
 NOTIFY sip:ap@client.subB.example.com SIP/2.0
 Via: SIP/2.0/UDP subA.example.com;branch=3qo3j0ouq
 To: <sip:ap@subB.example.com>;tag=978675
 From: <sip:gw@subA.example.com>;tag=9783453
 Call-ID: 12345601@subA.example.com
 CSeq: 3001 NOTIFY
 Contact: <sip:gw27@subA.example.com>
 Event: kpml
 Subscription-State: active;expires=3542
 Max-Forwards: 70
 Content-Type: application/kpml-response+xml
 Content-Length: 278
 <?xml version="1.0" encoding="UTF-8"?>
 <kpml-response xmlns="urn:ietf:params:xml:ns:kpml-response"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation=
         "urn:ietf:params:xml:ns:kpml-response kpml-response.xsd"
       version="1.0"
       code="200" text="OK"
       digits="2225551212" tag="number"/>
 Message (11) is the request for long-pound monitoring.
 SUBSCRIBE sip:gw@subA.example.com SIP/2.0
 Via: SIP/2.0/TCP client.subB.example.com;branch=3qo3j0ouq
 From: <sip:ap@subB.example.com>;tag=978675
 To: <sip:gw@subA.example.com>
 Call-ID: 12345601@subA.example.com
 CSeq: 21 SUBSCRIBE
 Contact: <sip:ap@client.subB.example.com>
 Max-Forwards: 70
 Event: kpml ;remote-tag="<sip:phn@example.com;tag=jfi23>"
             ;local-tag="sip:gw@subA.example.com;tag=oi43jfq"
             ;call-id="12345598@subA.example.com"
 Expires: 7200
 Accept: application/kpml-response+xml
 Content-Type: application/kpml-request+xml
 Content-Length: 295

Burger & Dolly Standards Track [Page 49] RFC 4730 KPML November 2006

 <?xml version="1.0" encoding="UTF-8"?>
 <kpml-request xmlns="urn:ietf:params:xml:ns:kpml-request"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation=
         "urn:ietf:params:xml:ns:kpml-request kpml-request.xsd"
       version="1.0">
   <pattern persist="single-notify">
     <regex>L#</regex>
   </pattern>
 </kpml-request>
 Message (13) is the request from the personal assistant application
 for number and pound sign monitoring.
 SUBSCRIBE sip:gw@subA.example.com SIP/2.0
 Via: SIP/2.0/TCP pahost.example.com;branch=xzvsadf
 From: <sip:pa@example.com>;tag=4rgj0f
 To: <sip:gw@subA.example.com>
 Call-ID: 93845@pahost.example.com
 CSeq: 21 SUBSCRIBE
 Contact: <sip:pa12@pahost.example.com>
 Max-Forwards: 70
 Event: kpml ;remote-tag="<sip:phn@example.com;tag=jfi23>"
             ;local-tag="sip:gw@subA.example.com;tag=oi43jfq"
             ;call-id="12345598@subA.example.com"
 Expires: 7200
 Accept: application/kpml-response+xml
 Content-Type: application/kpml-request+xml
 Content-Length: 332
 <?xml version="1.0" encoding="UTF-8"?>
 <kpml-request xmlns="urn:ietf:params:xml:ns:kpml-request"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation=
         "urn:ietf:params:xml:ns:kpml-request kpml-request.xsd"
       version="1.0">
   <pattern persist="persist">
     <regex tag="number">x{10}</regex>
     <regex tag="#">#</regex>
   </pattern>
 </kpml-request>

Burger & Dolly Standards Track [Page 50] RFC 4730 KPML November 2006

 Message (18) is the notification of the number collected.
 NOTIFY sip:pa@example.com SIP/2.0
 Via: SIP/2.0/UDP subA.example.com;branch=xzvsadf
 To: <sip:pa@example.com>;tag=4rgj0f
 From: <sip:gw@subA.example.com>;tag=9788823
 Call-ID: 93845@pahost.example.com
 CSeq: 3021 NOTIFY
 Contact: <sip:gw27@subA.example.com>
 Event: kpml
 Subscription-State: active;expires=3540
 Max-Forwards: 70
 Content-Type: application/kpml-response+xml
 Content-Length: 278
 <?xml version="1.0" encoding="UTF-8"?>
 <kpml-response xmlns="urn:ietf:params:xml:ns:kpml-response"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation=
         "urn:ietf:params:xml:ns:kpml-response kpml-response.xsd"
       version="1.0"
       code="200" text="OK" digits="3335551212" tag="number"/>
 Message (21) is the notification of pound sign detected.
 NOTIFY sip:pa@example.com SIP/2.0
 Via: SIP/2.0/UDP subA.example.com;branch=xzvsadf
 To: <sip:pa@example.com>;tag=4rgj0f
 From: <sip:gw@subA.example.com>;tag=9788823
 Call-ID: 93845@pahost.example.com
 CSeq: 3022 NOTIFY
 Contact: <sip:gw27@subA.example.com>
 Event: kpml
 Subscription-State: active;expires=3540
 Max-Forwards: 70
 Content-Type: application/kpml-response+xml
 Content-Length: 264
 <?xml version="1.0" encoding="UTF-8"?>
 <kpml-response xmlns="urn:ietf:params:xml:ns:kpml-response"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation=
         "urn:ietf:params:xml:ns:kpml-response kpml-response.xsd"
       version="1.0"
       code="200" text="OK"
       digits="#" tag="#"/>

Burger & Dolly Standards Track [Page 51] RFC 4730 KPML November 2006

 Message (27) is the notification of long pound to the card
 application.
 NOTIFY sip:ap@client.subB.example.com SIP/2.0
 Via: SIP/2.0/UDP subA.example.com;branch=3qo3j0ouq
 To: <sip:ap@subB.example.com>;tag=978675
 From: <sip:gw@subA.example.com>;tag=9783453
 Call-ID: 12345601@subA.example.com
 CSeq: 3037 NOTIFY
 Contact: <sip:gw27@subA.example.com>
 Event: kpml
 Subscription-State: active;expires=3216
 Max-Forwards: 70
 Content-Type: application/kpml-response+xml
 Content-Length: 256
 <?xml version="1.0" encoding="UTF-8"?>
 <kpml-response xmlns="urn:ietf:params:xml:ns:kpml-response"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation=
         "urn:ietf:params:xml:ns:kpml-response kpml-response.xsd"
       version="1.0"
       code="200" text="OK"
       digits="#"/>

11. References

11.1. Normative References

 [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
      Levels", BCP 14, RFC 2119, March 1997.
 [2]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
      Specifications: ABNF", RFC 4234, October 2005.
 [3]  Murata, M., St. Laurent, S., and D. Kohn, "XML Media Types",
      RFC 3023, January 2001.
 [4]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
      Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
      Session Initiation Protocol", RFC 3261, June 2002.
 [5]  Roach, A., "Session Initiation Protocol (SIP)-Specific Event
      Notification", RFC 3265, June 2002.
 [6]  Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom,
      "Uniform Resource Names (URN) Namespace Definition Mechanisms",
      BCP 66, RFC 3406, October 2002.

Burger & Dolly Standards Track [Page 52] RFC 4730 KPML November 2006

 [7]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
      January 2004.
 [8]  Thompson, H., Beech, D., Maloney, M., and N. Mendelsohn, "XML
      Schema Part 1: Structures", W3C REC REC-xmlschema-1-20010502,
      May 2001.

11.2. Informative References

 [9]   Rosenberg, J., "Obtaining and Using Globally Routable User
       Agent (UA) URIs (GRUU) in the  Session Initiation Protocol
       (SIP)", Work in Progress, June 2006.
 [10]  Schulzrinne, H. and S. Petrack, "RTP Payload for DTMF Digits,
       Telephony Tones and Telephony Signals", RFC 2833, May 2000.
 [11]  Andreasen, F. and B. Foster, "Media Gateway Control Protocol
       (MGCP) Version 1.0", RFC 3435, January 2003.
 [12]  Groves, C., Pantaleo, M., Anderson, T., and T. Taylor, "Gateway
       Control Protocol Version 1", RFC 3525, June 2003.
 [13]  Institute of Electrical and Electronics Engineers, "Information
       Technology - Portable Operating System Interface (POSIX) - Part
       1: Base Definitions, Chapter 9", IEEE Standard 1003.1,
       June 2001.
 [14]  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.
 [15]  Rosenberg, J., "A Framework for Application Interaction in the
       Session Initiation Protocol  (SIP)", Work in Progress,
       July 2005.
 [16]  Burger, E., Van Dyke, J., and A. Spitzer, "Media Server Control
       Markup Language (MSCML) and Protocol", RFC 4722, November 2006.
 [17]  Rosenberg, J., Schulzrinne, H., and R. Mahy, "An INVITE-
       Initiated Dialog Event Package for the Session Initiation
       Protocol (SIP)", RFC 4235, November 2005.
 [18]  Roach, A., Campbell, B., and J. Rosenberg, "A Session
       Initiation Protocol (SIP) Event Notification Extension for
       Resource Lists", RFC 4662, August 2006.

Burger & Dolly Standards Track [Page 53] RFC 4730 KPML November 2006

Appendix A. Contributors

 Ophir Frieder of the Illinois Institute of Technology collaborated on
 the development of the buffer 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
 we 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 [16], the
 SnowShore Media Server Control Markup Language.  Jeff Van Dyke and
 Andy Spitzer were the primary contributors to that effort.
 Rohan Mahy did a significant reorganization of the content, as well
 as providing considerable moral support in the production of this
 document.
 That said, any errors, misinterpretation, or fouls in this document
 are our 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
 Bryan Hill helped with clarifying the buffer behavior and DRegex
 syntax.
 Silvano Brewster and Bill Fenner of AT&T Laboratories and Joe Zebarth
 of Nortel helped considerably with making the text clear and DRegex
 tight.
 Bert Culpepper and Allison Mankin gave an early version of this
 document a good scouring.
 Scott Hollenbeck provided XML and MIME review.  Tim Bray pointed out
 the general issue of UTF-8 versus UTF-16 with XML.

Burger & Dolly Standards Track [Page 54] RFC 4730 KPML November 2006

Authors' Addresses

 Eric Burger
 Cantata Technology, Inc.
 18 Keewaydin Dr.
 Salem, NH  03079
 USA
 EMail: eburger@cantata.com
 Martin Dolly
 AT&T Labs
 EMail: mdolly@att.com

Burger & Dolly Standards Track [Page 55] RFC 4730 KPML November 2006

Full Copyright Statement

 Copyright (C) The IETF Trust (2006).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST,
 AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES,
 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT
 THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY
 IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
 PURPOSE.

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 The IETF takes no position regarding the validity or scope of any
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 might or might not be available; nor does it represent that it has
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 Copies of IPR disclosures made to the IETF Secretariat and any
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Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Burger & Dolly Standards Track [Page 56]

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