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rfc:rfc5022

Network Working Group J. Van Dyke Request for Comments: 5022 Cantata Technology, Inc. Obsoletes: 4722 E. Burger, Ed. Category: Informational BEA Systems, Inc.

                                                            A. Spitzer
                                                       Bluesocket Inc.
                                                        September 2007
     Media Server Control Markup Language (MSCML) and Protocol

Status of This Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

IESG Note

 This RFC is not a candidate for any level of Internet Standard.  The
 IETF disclaims any knowledge of the fitness of this RFC for any
 purpose and in particular notes that the decision to publish is not
 based on IETF review for such things as security, congestion control,
 or inappropriate interaction with deployed protocols.  The RFC Editor
 has chosen to publish this document at its discretion.  Readers of
 this document should exercise caution in evaluating its value for
 implementation and deployment.  See RFC 3932 for more information.

Abstract

 Media Server Control Markup Language (MSCML) is a markup language
 used in conjunction with SIP to provide advanced conferencing and
 interactive voice response (IVR) functions.  MSCML presents an
 application-level control model, as opposed to device-level control
 models.  One use of this protocol is for communications between a
 conference focus and mixer in the IETF SIP Conferencing Framework.

Van Dyke, et al. Informational [Page 1] RFC 5022 MSCML September 2007

Table of Contents

 1. Introduction ....................................................4
    1.1. Conventions Used in This Document ..........................5
 2. MSCML Approach ..................................................5
 3. Use of SIP Request Methods ......................................6
 4. MSCML Design ....................................................8
    4.1. Transaction Model ..........................................8
    4.2. XML Usage ..................................................9
         4.2.1. MSCML Time Values ...................................9
 5. Advanced Conferencing ..........................................10
    5.1. Conference Model ..........................................10
    5.2. Configure Conference Request <configure_conference> .......11
    5.3. Configure Leg Request <configure_leg> .....................13
    5.4. Terminating a Conference ..................................14
    5.5. Conference Manipulation ...................................15
    5.6. Video Conferencing ........................................16
    5.7. Conference Events .........................................17
    5.8. Conferencing with Personalized Mixes ......................18
         5.8.1. MSCML Elements and Attributes for
                Personalized Mixes .................................19
         5.8.2. Example Usage of Personalized Mixes ................20
 6. Interactive Voice Response (IVR) ...............................23
    6.1. Specifying Prompt Content .................................24
         6.1.1. Use of the Prompt Element ..........................24
    6.2. Multimedia Processing for IVR .............................30
    6.3. Playing Announcements <play> ..............................31
    6.4. Prompt and Collect <playcollect> ..........................32
         6.4.1. Control of Digit Buffering and Barge-In ............33
         6.4.2. Mapping DTMF Keys to Special Functions .............33
         6.4.3. Collection Timers ..................................35
         6.4.4. Logging Caller DTMF Input ..........................36
         6.4.5. Specifying DTMF Grammars ...........................36
         6.4.6. Playcollect Response ...............................37
         6.4.7. Playcollect Example ................................38
    6.5. Prompt and Record <playrecord> ............................38
         6.5.1. Prompt Phase .......................................38
         6.5.2. Record Phase .......................................39
         6.5.3. Playrecord Example .................................41
    6.6. Stop Request <stop> .......................................42
 7. Call Leg Events ................................................43
    7.1. Keypress Events ...........................................43
         7.1.1. Keypress Subscription Examples .....................45
         7.1.2. Keypress Notification Examples .....................45
    7.2. Signal Events .............................................46
         7.2.1. Signal Event Examples ..............................47
 8. Managing Content <managecontent> ...............................48
    8.1. Managecontent Example .....................................50

Van Dyke, et al. Informational [Page 2] RFC 5022 MSCML September 2007

 9. Fax Processing .................................................51
    9.1. Recording a Fax <faxrecord> ...............................51
    9.2. Sending a Fax <faxplay> ...................................53
 10. MSCML Response Attributes and Elements ........................56
    10.1. Mechanism ................................................56
    10.2. Base <response> Attributes ...............................56
    10.3. Response Attributes and Elements for <configure_leg> .....57
    10.4. Response Attributes and Elements for <play> ..............57
          10.4.1. Reporting Content Retrieval Errors ...............58
    10.5. Response Attributes and Elements for <playcollect> .......59
    10.6. Response Attributes and Elements for <playrecord> ........60
    10.7. Response Attributes and Elements for <managecontent> .....61
    10.8. Response Attributes and Elements for <faxplay>
          and <faxrecord> ..........................................61
 11. Formal Syntax .................................................62
    11.1. Schema ...................................................62
 12. IANA Considerations ...........................................73
    12.1. IANA Registration of MIME Media Type application/
          mediaservercontrol+xml ...................................73
 13. Security Considerations .......................................74
 14. References ....................................................75
    14.1. Normative References .....................................75
    14.2. Informative References ...................................76
 Appendix A.  Regex Grammar Syntax .................................78
 Appendix B.  Contributors .........................................79
 Appendix C.  Acknowledgements .....................................79

Van Dyke, et al. Informational [Page 3] RFC 5022 MSCML September 2007

1. Introduction

 This document describes the Media Server Control Markup Language
 (MSCML) and its usage.  It describes payloads that one can send to a
 media server using standard SIP INVITE and INFO methods and the
 capabilities these payloads implement.  RFC 4240 [2] describes media
 server SIP URI formats.
 Prior to MSCML, there was not a standard way to deliver SIP-based
 enhanced conferencing.  Basic SIP constructs, such as those described
 in RFC 4240 [2], serve simple n-way conferencing well.  The SIP URI
 provides a natural mechanism for identifying a specific SIP
 conference, while INVITE and BYE methods elegantly implement
 conference join and leave semantics.  However, enhanced conferencing
 applications also require features such as sizing and resizing, in-
 conference IVR operations (e.g., recording and playing participant
 names to the full conference), and conference event reporting.  MSCML
 payloads within standard SIP methods realize these features.
 The structure and approach of MSCML satisfy the requirements set out
 in RFC 4353 [10].  In particular, MSCML serves as the interface
 between the conference server or focus and a centralized conference
 mixer.  In this case, a media server has the role of the conference
 mixer.
 There are two broad classes of MSCML functionality.  The first class
 includes primitives for advanced conferencing, such as conference
 configuration, participant leg manipulation, and conference event
 reporting.  The second class comprises primitives for interactive
 voice response (IVR).  These include collecting DTMF digits and
 playing and recording multimedia content.
 MSCML fills the need for IVR and conference control with requests and
 responses over a SIP transport.  VoiceXML [11] fills the need for IVR
 with requests and responses over a HTTP transport.  This enables
 developers to use whatever model fits their needs best.
 In general, a media server offers services to SIP UACs, such as
 Application Servers, Feature Servers, and Media Gateway Controllers.
 See the IPCC Reference Architecture [12] for definitions of these
 terms.  It is unlikely, but not prohibited, for end-user SIP UACs to
 have a direct signaling relationship with a media server.  The term
 "client" is used in this document to refer generically to an entity
 that interacts with the media server using SIP and MSCML.

Van Dyke, et al. Informational [Page 4] RFC 5022 MSCML September 2007

 The media server fulfills the role of the Media Resource Function
 (MRF) in the IP Multimedia Subsystem (IMS) [13] as described by 3GPP.
 MSCML and RFC 4240 [2], upon which MSCML builds, are specifically
 focused on the Media resource (Mr) interface which supports
 interactions between application logic and the MRF.
 This document describes a working framework and protocol with which
 there is considerable implementation experience.  Application
 developers and service providers have created several MSCML-based
 services since the availability of the initial version in 2001.  This
 experience is highly relevant to the ongoing work of the IETF,
 particularly the SIP [26], SIPPING [27], MMUSIC [28], and XCON [29]
 work groups, the IMS [30] work in 3GPP, and the CCXML work in the
 Voice Browser Work Group of the W3C.

1.1. Conventions Used in This Document

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in RFC 2119 [1].

2. MSCML Approach

 It is critically important to emphasize that the goal of MSCML is to
 provide an application interface that follows the SIP, HTTP, and XML
 development paradigm to foster easier and more rapid application
 deployment.  This goal is reflected in MSCML in two ways.
 First, the programming model is that of peer to peer rather than
 master-slave.  Importantly, this allows the media server to be used
 simultaneously for multiple applications rather than be tied to a
 single point of control.  It also enables standard SIP mechanisms to
 be used for media server location and load balancing.
 Second, MSCML defines constructs and primitives that are meaningful
 at the application level to ensure that programmers are not
 distracted by unnecessary complexity.  For example, the mixing
 resource operates on constructs such as conferences and call
 participants rather than directly on individual media streams.
 The MSCML paradigm is important to the developer community, in that
 developers and operators conceptually write applications about calls,
 conferences, and call legs.  For the majority of developers and
 applications this approach significantly simplifies and speeds
 development.

Van Dyke, et al. Informational [Page 5] RFC 5022 MSCML September 2007

3. Use of SIP Request Methods

 As mentioned above, MSCML payloads may be carried in either SIP
 INVITE or INFO requests.  The initial INVITE, which creates an
 enhanced conference, MAY include an MSCML payload.  A subsequent
 INVITE to the same Request-URI joins a participant leg to the
 conference.  This INVITE MAY include an MSCML payload.  The initial
 INVITE that establishes an IVR session MUST NOT include an MSCML
 payload.  The client sends all mid-call MSCML payloads for
 conferencing and IVR via SIP INFO requests.
 SIP INVITE requests that contain both MSCML and Session Description
 Protocol (SDP) body parts are used frequently in conferencing
 scenarios.  Therefore, the media server MUST support message bodies
 with the MIME type "multipart/mixed" in SIP INVITE requests.
 The media server transports MSCML responses in the final response to
 the SIP INVITE containing the matching MSCML request or in a SIP INFO
 message.  The only allowable final response to a SIP INFO containing
 a message body is a 200 OK, per RFC 2976 [3].  Therefore, if the
 client sends the MSCML request via SIP INFO, the media server
 responds with the MSCML response in a separate INFO request.  In
 general, these responses are asynchronous in nature and require a
 separate transaction due to timing considerations.
 There has been considerable debate on the use of the SIP INFO method
 for any purpose.  Our experience is that MSCML would not have been
 possible without it.  At the time the first MSCML specification was
 published, the first SIP Event Notification draft had just been
 submitted as an individual submission.  At that time, there was no
 mechanism to link SUBSCRIBE/NOTIFY to an existing dialog.  This
 prevented its use in MSCML, since all events occurred in an INVITE-
 established dialog.  And while SUBSCRIBE/NOTIFY was well suited for
 reporting conference events, its semantics seemed inappropriate for
 modifying a participant leg or conference setting where the only
 "event" was the success or failure of the request.  Lastly, since SIP
 INFO was an established RFC, most SIP stack implementations supported
 it at that time.  We had few, if any, interoperability issues as a
 result.
 More recent developments have provided additional reasons why
 SUBSCRIBE/NOTIFY is not appropriate for use in MSCML.  Use of
 SUBSCRIBE presents two problems.  The first is semantic.  The purpose
 of SUBSCRIBE is to register interest in User Agent state.  However,
 using SUBSCRIBE for MSCML results in the SUBSCRIBE modifying the User
 Agent state.  The second reason SUBSCRIBE is not appropriate is
 because MSCML is inherently call based.  The association of a SIP
 dialog with a call leg means MSCML can be incredibly straightforward.

Van Dyke, et al. Informational [Page 6] RFC 5022 MSCML September 2007

 For example, if one used SUBSCRIBE or other SIP method to send
 commands about some context, one must identify that context somehow.
 Relating commands to the SIP dialog they arrive on defines the
 context for free.  Moreover, it is conceptually easy for the
 developer.  Using NOTIFY to transport MSCML responses is also not
 appropriate, as the NOTIFY would be in response to an implicit
 subscription.  The SIP and SIPPING lists have discussed the dangers
 of implicit subscription.
 In order to guarantee interoperability with this specification, as
 well as with SIP User Agents that are unaware of MSCML, SIP UACs that
 wish to use MSCML services MUST specify a service indicator that
 supports MSCML in the initial INVITE.  RFC 4240 [2] defines the
 service indicator "conf", which MUST be used for MSCML conferencing
 applications.  The service indicator "ivr" MUST be used for MSCML
 interactive voice response applications.  In this specification, only
 "conf" and "ivr" are described.
 The media server MUST support moving the call between services
 through sending the media server a BYE on the existing dialog and
 establishing a new dialog with an INVITE to the desired service.
 Media servers SHOULD support moving between services without
 requiring modification of the previously established SDP parameters.
 This is achieved by sending a re-INVITE on the existing dialog in
 which the Request-URI is modified to specify the new service desired
 by the client.  This eliminates the need for the client to send an
 INVITE to the caller or gateway to establish new SDP parameters.
 The media server, as a SIP UAS, MUST respond appropriately to an
 INVITE that contains an MSCML body.  If MSCML is not supported, the
 media server MUST generate a 415 final response and include a list of
 the supported content types in the response per RFC 3261 [4].  The
 media server MUST also advertise its support of MSCML in responses to
 OPTIONS requests, by including "application/mediaservercontrol+xml"
 as a supported content type in an Accept header.  This alleviates the
 major issues with using INFO for the transport of application data;
 namely, the User Agent's proper interpretation of what is, by design,
 an opaque message request.

Van Dyke, et al. Informational [Page 7] RFC 5022 MSCML September 2007

4. MSCML Design

4.1. Transaction Model

 To avoid undue complexity, MSCML establishes two rules regarding its
 usage.  The first is that only one MSCML body may be present in a SIP
 request.  The second is that each MSCML body may contain only one
 request or response.  This greatly simplifies transaction management.
 MSCML syntax does provide for the unique identification of multiple
 requests in a single body part.  However, this is not supported in
 this specification.
 Per the guidelines of RFC 3470 [14], MSCML bodies MUST be well formed
 and valid.
 MSCML is a direct request-response protocol.  There are no
 provisional responses, only final responses.  A request may, however,
 result in multiple notifications.  For example, a request for active
 talker reports will result in a notification for each speaker set.
 This maps to the three major element trees for MSCML: <request>,
 <response>, and <notification>.
 Figure 1 shows a request body.  Depending on the command, one can
 send the request in an INVITE or an INFO.  Figure 2 shows a response
 body.  The SIP INFO method transports response bodies.  Figure 3
 shows a notification body.  The SIP INFO method transports
 notifications.
 <?xml version="1.0" encoding="utf-8"?>
 <MediaServerControl version="1.0">
   <request>
     ... request body ...
   </request>
 </MediaServerControl>
 Figure 1: MSCML Request Format
 <?xml version="1.0" encoding="utf-8"?>
 <MediaServerControl version="1.0">
   <response>
     ... response body ...
   </response>
 </MediaServerControl>
 Figure 2: MSCML Response Format

Van Dyke, et al. Informational [Page 8] RFC 5022 MSCML September 2007

 <?xml version="1.0" encoding="utf-8"?>
 <MediaServerControl version="1.0">
   <notification>
     ... notification body ...
   </notification>
 </MediaServerControl>
 Figure 3: MSCML Notification Format
 MSCML requests MAY include a client-defined ID attribute for the
 purposes of matching requests and responses.  The values used for
 these IDs need only be unique within the scope of the dialog in which
 the requests are issued.

4.2. XML Usage

 In the philosophy of XML as a text-based description language, and
 not as a programming language, MSCML makes the choice of many
 attribute values for readability by a human.  Thus, many attributes
 that would often be "boolean" instead take "yes" or "no" values.  For
 example, what does 'report="false"' or 'report="1"' mean?  However,
 'report="yes"' is clearer: I want a report.  Some programmers prefer
 the precision of a boolean.  To satisfy both styles, MSCML defines an
 XML type, "yesnoType", that takes on the values "yes" and "no" as
 well as "true", "false", "1", and "0".
 Many attributes in the MSCML schema have default values.  In order to
 limit demands on the XML parser, MSCML applies these values at the
 protocol, not XML, level.  The MSCML schema documents these defaults
 as XML annotations to the appropriate attribute.

4.2.1. MSCML Time Values

 For clarity, time values in MSCML are based on the time designations
 described in the Cascading Style Sheets level 2 (CSS2) Specification
 [15].  Their format consists of a number immediately followed by an
 optional time unit identifier of the following form:
    ms: milliseconds (default)
    s: seconds
 If no time unit identifier is present, the value MUST be interpreted
 as being in milliseconds.  As extensions to [15] MSCML allows the
 string values "immediate" and "infinite", which have special meaning
 for certain timers.

Van Dyke, et al. Informational [Page 9] RFC 5022 MSCML September 2007

5. Advanced Conferencing

5.1. Conference Model

 The advanced conferencing model is a star controller model, with both
 signaling and media directed to a central location.  Figure 4 depicts
 a typical signaling relationship between end users' UACs, a
 conference application server, and a media server.
 RFC 4353 [10] describes this model.  The application server is an
 instantiation of the conference focus.  The media server is an
 instantiation of the media mixer.  Note that user-level constructs,
 such as event notifications, are in the purview of the application
 server.  This is why, for example, the media server sends active
 talker reports using MSCML notifications, while the application
 server would instead use the conference package [16] for individual
 notifications to SIP user agents.  Note that we do not recommend the
 use of the conference package for media server to application server
 notifications because none of the filtering and membership
 information is available at the media server.
    +-------+
    | UAC 1 |---\   Public URI  +-------------+
    +-------+    \ _____________| Application |
                  /    /        |   Server    |     Not shown:
    +-------+    /    /         +-------------+     RTP flows directly
    | UAC 2 |---/    /                 | Private    between UACs and
    +-------+       /                  |   URI      media server
        .          /            +--------------+
        :         /             |              |
    +-------+    /              | Media Server |
    | UAC n |---/               |              |
    +-------+                   +--------------+
                        Figure 4: Conference Model
 Each UAC sends an INVITE to a Public Conference URI.  Presumably, the
 client publishes this URI, or it is an ad hoc URI.  In any event, the
 client generates a Private URI, following the rules specified by RFC
 4240 [2].  That is, the URI is of the following form:
 sip:conf=UniqueID@ms.example.net
 where UniqueID is a unique conference identifier and ms.example.net
 is the host name or IP address of the media server.  There is nothing
 to prevent the UACs from contacting the media server directly.
 However, one would expect the owner of the media server to restrict
 who can use its resources.

Van Dyke, et al. Informational [Page 10] RFC 5022 MSCML September 2007

 As for basic conferencing, described by RFC 4240 [2], the first
 INVITE to the media server with a UniqueID creates a conference.
 However, in advanced conferencing, the first INVITE MAY include a
 MSCML <configure_conference> payload rather than the SDP of a
 conference participant.  The <configure_conference> payload conveys
 extended session parameters (e.g., number of participants) that SDP
 does not readily express, but the media server must know to allocate
 the appropriate resources.
 When the conference is created by sending an INVITE containing a
 MSCML <configure_conference> payload, the resulting SIP dialog is
 termed the "Conference Control Leg."  This leg has several useful
 properties.  The lifetime of the conference is the same as that of
 its control leg.  This ensures that the conference remains in
 existence even if all participant legs leave or have not yet arrived.
 In addition, when the client terminates the Conference Control Leg,
 the media server automatically terminates all participant legs.  The
 Conference Control Leg is also used for play or record operations
 to/from the entire conference and for active talker notifications.
 Full conference media operations and active talker report
 subscriptions MUST be executed on the Conference Control Leg.
 Creation of a Conference Control Leg is RECOMMENDED because full
 advanced conferencing capabilities are not available without it.
 Clients MUST establish the Conference Control Leg in the initial
 INVITE that creates the conference; it cannot be created later.
 Once the client has created the conference with or without the
 Conference Control Leg, participants can be joined to the conference.
 This is achieved by the client's directing an INVITE to the Private
 Conference URI for each participant.  Using the example conference
 URI given above, this would be sip:conf=UniqueID@ms.example.net.

5.2. Configure Conference Request <configure_conference>

 The <configure_conference> request has two attributes that control
 the resources the media server sets aside for the conference.  These
 are described in the list below.
 Attributes of <configure_conference>:
 o  reservedtalkers - optional (see note), no default value: The
    maximum number of talker legs allocated for the conference.  Note:
    required when establishing the Conference Control Leg but optional
    in subsequent <configure_conference> requests.

Van Dyke, et al. Informational [Page 11] RFC 5022 MSCML September 2007

 o  reserveconfmedia - optional, default value "yes": Controls
    allocation of resources to enable playing or recording to or from
    the entire conference.
 When the reservedtalkers+1st INVITE arrives at the media server, the
 media server SHOULD generate a 486 Busy Here response.  Failure to
 send a 486 response to this condition can cause the media server to
 oversubscribe its resources.
    NOTE: It would be symmetric to have a reservedlisteners parameter.
    However, the practical limitation on the media server is the
    number of talkers for a mixer to monitor.  In either case, the
    client regulates who gets into the conference by either proxying
    the INVITEs from the user agent clients or metering to whom it
    gives the conference URI.
 For example, to create a conference with up to 120 active talkers and
 the ability to play audio into the conference or record portions or
 all of the conference full mix, the client specifies both attributes,
 as shown in Figure 6.
 <?xml version="1.0" encoding="utf-8"?>
 <MediaServerControl version="1.0">
   <request>
     <configure_conference reservedtalkers="120"
       reserveconfmedia="yes"/>
   </request>
 </MediaServerControl>
 Figure 6: 120 Speaker MSCML Example
 In addition to these attributes, a <configure_conference> request MAY
 contain a child <subscribe> element.  The <subscribe> element is used
 to request notifications for conference-wide active talker events.
 Detailed information regarding active talker events is contained in
 Section 5.7.
 The client MUST include a <configure_conference> request in the
 initial INVITE which establishes the conference when creating the
 Conference Control Leg. The client server MUST issue asynchronous
 commands, such as <play>, separately (i.e., in INFO messages) to
 avoid ambiguous responses.
 Media operations on the Conference Control leg are performed
 internally, no external RTP streams are involved.  Accordingly, the
 media server does not expect RTP on the Conference Control Leg.
 Therefore, the client MUST send either no SDP or hold SDP in the
 INVITE request containing a <configure_conference> payload.  The

Van Dyke, et al. Informational [Page 12] RFC 5022 MSCML September 2007

 media server MUST treat SDP with all media lines set to "inactive" or
 with connection addresses set to 0.0.0.0 (for backwards
 compatibility) as hold SDP.
 The media server sends a response when it has finished processing the
 <configure_conference> request.  The format of the
 <configure_conference> response is detailed in Section 10.2.

5.3. Configure Leg Request <configure_leg>

 Conference legs have a number of properties the client can modify.
 These are set using the <configure_leg> request.  This request has
 the attributes described in the list below.
 Attributes of <configure_leg>:
 o  type - optional, default value "talker": Consider this leg's audio
    for inclusion in the output mix.  Alternative is "listener".
 o  dtmfclamp - optional, default value "yes": Remove detected DTMF
    digits from the input audio.
 o  toneclamp - optional, default value "yes": Remove tones from the
    input audio.  Tones include call progress tones and the like.
 o  mixmode - optional, default value "full": Be a candidate for the
    full mix.  Alternatives are "mute", to disallow media in the mix,
    "parked", to disconnect the leg's media streams from the
    conference for IVR operations, "preferred", to give this stream
    preferential selection in the mix (i.e., even if not loudest
    talker, include media, if present, from this leg in the mix), and
    "private", which enables personalized mixes.
 In addition to these attributes, there are four child elements
 defined for <configure_leg>.  These are <inputgain>, <outputgain>,
 <configure_team>, and <subscribe>.
 The first two, <inputgain> and <outputgain>, modify the gain applied
 to the input and output audio streams, respectively.  These may
 contain <auto>, to use automatic gain control (AGC) or <fixed>.  The
 <auto> element has the attributes "startlevel", "targetlevel", and
 "silencethreshold".  All the parameters are in dB.  The <fixed>
 element has the attribute "level", which is in dB.  The default for
 both <inputgain> and <outputgain> is <fixed>.  The media server MAY

Van Dyke, et al. Informational [Page 13] RFC 5022 MSCML September 2007

 silently cap <inputgain> or <outputgain> requests that exceed the
 gain limits imposed by the platform.
 Clients most commonly manipulate only the input gain for a conference
 leg and rely on the mixer to set an optimum output gain based on the
 inputs currently in the mix.  However, as described above, MSCML does
 allow for manipulation of the output gain as well.  Some of the IVR
 commands, such as <play>, enable control of the output gain for
 content playback operations.  The interaction of conference output
 gain and IVR playback gain controls is described in Section 6.1.1.
 Note that <inputgain> and <outputgain> settings apply only to
 conference legs and do not apply to IVR sessions.
 The <configure_team> element is used to create and manipulate groups
 for personalized mixes.  Details of personalized mixes are discussed
 in Section 5.8.
 The <subscribe> element is used to request notifications for call leg
 related events, such as asynchronous DTMF digit reports.  Detailed
 information regarding call leg events is discussed in Section 7.
 If the default parameters are acceptable for the leg the client
 wishes to enter into the conference, then a normal SIP INVITE, with
 no MSCML body, is sufficient.  However, if the client wishes to
 modify one or more of the parameters, the client can include a MSCML
 body in addition to the SDP body.
 The client can modify the conference leg parameters during the
 conference by issuing a SIP INFO on the dialog representing the
 conference leg.  Of course, the client cannot modify SDP in an INFO
 message.
 The media server sends a response when it has finished processing the
 <configure_leg> request.  The format of the <configure_leg> response
 is detailed in Section 10.3.

5.4. Terminating a Conference

 To remove a leg from the conference, the client issues a SIP BYE
 request on the selected dialog representing the conference leg.
 The client can terminate all legs in a conference by issuing a SIP
 BYE request on the Conference Control Leg.  If one or more
 participants are still in the conference when the media server
 receives a SIP BYE request on the Conference Control Leg, the media
 server issues SIP BYE requests on all remaining conference legs to
 ensure cleanup of the legs.

Van Dyke, et al. Informational [Page 14] RFC 5022 MSCML September 2007

 The media server returns a 200 OK to the SIP BYE request as it sends
 BYE requests to the other legs.  This is because we cannot issue a
 provisional response to a non-INVITE request, yet the teardown of the
 other legs may exceed the retransmission timer limits of the original
 request.  While the conference is being cleaned up, the media server
 MUST reject any new INVITEs to the terminated conference with a 486
 Busy Here response.  This response indicates that the specified
 conference cannot accept any new members, pending deletion.

5.5. Conference Manipulation

 Once the conference has begun, the client can manipulate the
 conference as a whole or a particular participant leg by issuing
 commands on the associated SIP dialog.  For example, by sending MSCML
 requests on the Conference Control Leg the client can request that
 the media server record the conference, play a prompt to the
 conference, or request reports on active talker events.  Similarly,
 the client may mute a participant leg, configure a personalized mix
 or request reports for call leg events, such as DTMF keypresses.
 Figure 7 shows an example of an MSCML command that plays a prompt to
 all conference participants.
 <?xml version="1.0" encoding="utf-8"?>
 <MediaServerControl version="1.0">
   <request>
     <play>
       <prompt>
         <audio url="http://prompts.example.net/en_US/welcome.au"/>
       </prompt>
     </play>
   </request>
 </MediaServerControl>
 Figure 7: Full Conference Audio Command - Play
 A client can modify a leg by issuing an INFO on the dialog associated
 with the participant leg.  For example, Figure 8 mutes a conference
 leg.
 <?xml version="1.0" encoding="utf-8"?>
 <MediaServerControl version="1.0">
   <request>
     <configure_leg mixmode="mute"/>
   </request>
 </MediaServerControl>
 Figure 8: Sample Change Leg Command

Van Dyke, et al. Informational [Page 15] RFC 5022 MSCML September 2007

 In Figure 7, we saw a request to play a prompt to the entire
 conference.  The client can also request to play a prompt to an
 individual call leg.  In that case, the MSCML request is issued
 within the SIP dialog of the desired conference participant.
 Section 6 describes the interactive voice response (IVR) services
 offered by MSCML.  If an IVR command arrives on the control channel,
 it takes effect on the whole conference.  This is a mechanism for
 playing prompts to the entire conference (e.g., announcing new
 participants).  If an IVR command arrives on an individual leg, it
 only affects that leg.  This is a mechanism for interacting with
 users, such as the creation of "waiting rooms", allowing a user to
 mute themselves using key presses, allowing a moderator to out-dial,
 etc.
 A participant leg MUST be configured with mixmode="parked" prior to
 the issuance of any IVR commands with prompt content ('prompturl'
 attribute or <prompt> element).  Parking the leg isolates the
 participant's input and output media from the conference and allows
 use of those streams for playing and recording purposes.  However,
 the mixmode has no effect if just digit collection or recording is
 desired. <playcollect> and <playrecord> requests without prompt
 content MAY be sent on participant legs without setting
 mixmode="parked".

5.6. Video Conferencing

 MSCML-controlled advanced conferences, as well as RFC 4240 [2]
 controlled basic conferences, implicitly support video conferencing
 in the form of video switching.  In video switching, the video stream
 of the loudest talker (with some hysteresis) is sent to all
 participants other than that talker.  The loudest talker receives the
 video stream from the immediately prior loudest talker.
 Media servers MUST ensure that participants receive video media
 compatible with their session.  For example, a participant who has
 established an H.263 video stream will not receive video from another
 participant employing H.264 media.  Media servers SHOULD implement
 video transcoding to minimize media incompatibilities between
 participants.
 The media server MUST switch video streams only when it receives a
 refresh video frame.  A refresh frame contains all the video
 information required to decode that frame (i.e., there is no
 dependency on data from previous video frames).

Van Dyke, et al. Informational [Page 16] RFC 5022 MSCML September 2007

 Refresh frames are large and generally sent infrequently to conserve
 network bandwidth.  The media server MUST implement standard
 mechanisms to request that the new loudest talker's video encoder
 transmits a refresh frame to ensure that video can be switched
 quickly.

5.7. Conference Events

 A client can subscribe for periodic active talker event reports that
 indicate which participants are included in the conference mix.  As
 these are conference-level events, the subscription and notifications
 are sent on the Conference Control Leg.
 Media servers MAY impose limits on the minimum interval for active
 talker reports for performance reasons.  If the client request is
 below the imposed minimum, the media server SHOULD set the interval
 to the minimum value supported.  To limit unnecessary notification
 traffic, the media server SHOULD NOT send a report if the active
 talker information for the conference has not changed during the
 reporting interval.
 A request for an active talker report is in Figure 9.  The active
 talker report enumerates the current call legs in the mix.
 <?xml version="1.0" encoding="utf-8"?>
 <MediaServerControl version="1.0">
   <request>
     <configure_conference>
       <subscribe>
         <events>
           <activetalkers report="yes" interval="60s"/>
         </events>
       </subscribe>
     </configure_conference>
   </request>
 </MediaServerControl>
 Figure 9: Active Talker Request
 Event notifications are sent in SIP INFO messages.  Figure 10 shows
 an example of a report.

Van Dyke, et al. Informational [Page 17] RFC 5022 MSCML September 2007

 <?xml version="1.0" encoding="utf-8"?>
 <MediaServerControl version="1.0">
   <notification>
     <conference uniqueid="ab34h76z" numtalkers="47">
       <activetalkers>
         <talker callid="myhost4sn123"/>
         <talker callid="myhost2sn456"/>
         <talker callid="myhost12sn78"/>
       </activetalkers>
     </conference>
   </notification>
 </MediaServerControl>
 Figure 10: Active Talker Event Example
 The value of the "callid" attribute in the <talker> element
 corresponds to the value of the SIP Call-ID header of the associated
 dialog.  This enables the client to associate the active talker with
 a specific participant leg.

5.8. Conferencing with Personalized Mixes

 MSCML enables clients to create personalized mixes through the
 <configure_team> element for scenarios where the standard mixmode
 settings do not provide sufficient control.  The <configure_team>
 element is a child of <configure_leg>.
 To create personalized mixes, the client has to identify the
 relationships among the participants.  This is accomplished by
 manipulating two MSCML objects.  These objects are:
 1.  The list of team members (<teammate> elements), set using
     <configure_team>
 2.  The mixmode attribute set through <configure_leg>
 The media server uses the values of these objects to determine which
 audio inputs to combine for output to the participant.  In a normal
 conference, each participant hears the conference mix minus their own
 input if they are part of the mixed output.  The team list enables
 the client to specify other participants that the leg can hear in
 addition to the normal mixed output.  Note that personalized mix
 settings apply only to audio media and do not affect video switching.
 Team relationships are implicitly symmetric.  If the client sets
 participant A as a team member of participant B, then the media
 server automatically sets participant B as a team member for A.

Van Dyke, et al. Informational [Page 18] RFC 5022 MSCML September 2007

 The id attribute set through <configure_leg> is used to identify the
 various participants.  A unique ID MUST be assigned to each
 participant included in a personalized mix.  The IDs used MUST be
 unique within the scope of the conference in which they appear.
 By itself, the team list only defines those participants that the leg
 can hear.  The mixmode attribute of each team member determines
 whether to include their audio input in the personalized mix.  If the
 client sets the teammate's mixmode to private, then it is part of the
 mix.  If the mixmode is set to any other value, it is not.

5.8.1. MSCML Elements and Attributes for Personalized Mixes

 Control of personalized mixes rely on two major MSCML elements:
 1.  <configure_leg>, using the mixmode attribute setting
     mixmode="private"
 2.  <configure_team>
 The <configure_team> element allows the user to make the participants
 members of a team within a specific conference.  It is a child of the
 <configure_leg> parent element.
 The client sends the <configure_team> element in a <configure_leg>
 request in either a SIP INVITE or SIP INFO.
 o  In an INVITE, to join a participant whose properties differ from
    the properties established for the conference as a whole.
 o  In an INFO, to change the properties for an existing leg.
 The two attributes of the configure_team element are "id" and
 "action".  The id attribute MUST contain the unique ID of the leg
 being modified, as set in the original <configure_leg> request.  The
 action attribute can take on the values "add", "delete", "query", and
 "set".  The default value is "query".  This attribute allows the user
 to modify the team list.  Table 1 describes the actions that can be
 performed on the team list.

Van Dyke, et al. Informational [Page 19] RFC 5022 MSCML September 2007

 +--------+----------------------------------------------------------+
 | Action | Description                                              |
 +--------+----------------------------------------------------------+
 | add    | Adds a teammate to the mix.                              |
 | delete | Deletes a teammate from the mix.                         |
 | query  | Returns the teammate list to the requestor.  This is the |
 |        | default value.                                           |
 | set    | Creates a team list when followed by <teammate id="n">   |
 |        | and also removes all the teammates from the team list    |
 |        | for example, when the creator (originator) of the team   |
 |        | list on that specific conference leg wants to remove all |
 |        | of the teammates from the team.  If the set operation    |
 |        | removes all teammates from a participant, that           |
 |        | participant hears the full conference mix.               |
 +--------+----------------------------------------------------------+
                    Table 1: Configure Team Actions

5.8.2. Example Usage of Personalized Mixes

 A common use of personalized mixing is to support coaching of one
 participant by another.  The coaching scenario includes three
 participants:
 1.  The Supervisor, who coaches the agent.
 2.  The Agent, who interacts with the customer.
 3.  The Customer, who interacts with the agent.
 Table 2 illustrates the details of the coached conference topology.
 +-------------+------------+------------+---------+-----------------+
 | Participant | ID         | Team       | Mixmode | Hears           |
 |             |            | Members    |         |                 |
 +-------------+------------+------------+---------+-----------------+
 | Supervisor  | supervisor | Agent      | Private | customer +      |
 |             |            |            |         | agent           |
 | Agent       | agent      | Supervisor | Full    | customer +      |
 |             |            |            |         | supervisor      |
 | Customer    | customer   | none       | Full    | agent           |
 +-------------+------------+------------+---------+-----------------+
                  Table 2: Coached Conference Example
 To create this topology, the client performs the following actions:
 1.  The client joins each leg to the conference, being certain to
     include a unique ID in the <configure_leg> request.  The leg ID
     needs to be unique only within the scope of the conference to
     which it belongs.

Van Dyke, et al. Informational [Page 20] RFC 5022 MSCML September 2007

 2.  The client configures the teammate list and mixmode of each
     participant, as required.
 Both actions (steps 1 and 2) may be combined in a single MSCML
 request.  The following sections detail these actions and their
 corresponding MSCML payloads.

5.8.2.1. Create the Conference

 Before joining any participants, the client must create the
 conference by sending a SIP INVITE that contains an MSCML
 <configure_conference> request with a unique conference identifier.

5.8.2.2. Joining and Configuring the Coach

 Join the coach leg to the conference and configure its desired
 properties by sending a SIP INVITE containing a <configure_leg>
 request.  The <configure_leg> element sets the leg's unique ID to
 supervisor and its mixmode to private.
 The corresponding MSCML request is as follows.
 <?xml version="1.0"?>
 <MediaServerControl version="1.0">
   <request>
     <configure_leg id="supervisor" mixmode="private"/>
   </request>
 </MediaServerControl>
 Figure 11: Join Coach Request
 Note that the client cannot configure the teammate list for the coach
 yet, as there are no other participants in the conference.  One must
 join a participant to the conference before one can add it as a
 teammate for another leg.

5.8.2.3. Joining and Configuring the Agent

 Join the agent leg to the conference and configure its desired
 properties by sending a SIP INVITE containing a <configure_leg>
 request.  The <configure_leg> element sets the leg's unique ID to
 "agent" and sets the supervisor as a team member of the agent.
 Because team member relationships are symmetric, this action also
 adds the agent as a team member for the coach.

Van Dyke, et al. Informational [Page 21] RFC 5022 MSCML September 2007

 The corresponding MSCML request is as follows.
 <?xml version="1.0"?>
 <MediaServerControl version="1.0">
  <request>
     <configure_leg id="agent">
       <configure_team action="set">
         <teammate id="supervisor"/>
       </configure_team>
     </configure_leg>
   </request>
 </MediaServerControl>
 Figure 12: Join Agent Request
 Because the desired mixmode for this leg is full, which is the
 default value, there is no need to set it explicitly.

5.8.2.4. Joining and Configuring the Client

 Join the client leg to the conference and configure its desired
 properties by sending a SIP INVITE containing a <configure_leg>
 request.  The <configure_leg> element simply sets the leg's unique ID
 to "customer".  The media server does not need further configuration
 because the desired mixmode, full, is the default and the customer
 has no team members.
 The corresponding MSCML request is as follows.
 <?xml version="1.0"?>
 <MediaServerControl version="1.0">
   <request>
     <configure_leg id="customer"/>
   </request>
 </MediaServerControl>
 Figure 13: Join Client Request
 Strictly speaking, it is not a requirement that the client give the
 customer leg a unique ID because it will not be a team member.
 However, when using coached conferencing, we RECOMMEND that one
 assign a unique ID to each leg in the initial INVITE request.
 Assigning a unique ID eliminates the need to set it later by sending
 a SIP INFO if one later desires personalized mixing for the customer
 leg.
 The conference is now in the desired configuration, shown previously
 in Table 2.

Van Dyke, et al. Informational [Page 22] RFC 5022 MSCML September 2007

6. Interactive Voice Response (IVR)

 In the IVR model, the media server acts as a media-processing proxy
 for the UAC.  This is particularly useful when the UAC is a media
 gateway or other device with limited media processing capability.
 The typical use case for MSCML is when there is an application server
 that is the MSCML client.  The client can use the SIP Service URI
 concept (RFC 3087) to initiate a service.  The client then uses RFC
 4240 [2] to initiate a MSCML session on a media server.  These
 relationships are shown in Figure 14.
                           SIP       +--------------+
                       Service URI   | Application  |
                    /----------------|    Server    |
                   /(e.g., RFC 3087) +--------------+
                  /                        |  MSCML
                 /                     SIP | Session
                /                    +--------------+
        +-----+/       RTP           |              |
        | UAC |======================| Media Server |
        +-----+                      |              |
                                     +--------------+
                             Figure 14: IVR Model
 The IVR service supports basic Interactive Voice Response functions,
 playing announcements, collecting DTMF digits, and recording, based
 on Media Server Control Markup Language (MSCML) directives added to
 the message body of a SIP request.  The major MSCML IVR requests are
 <play>, <playcollect>, and <playrecord>.
 Multifunction media servers MUST use the URI conventions described in
 RFC 4240 [2].  The service indicator for MSCML IVR MUST be set to
 "ivr", as shown in the following example:
 sip:ivr@ms.example.net
 The VoiceXML IVR service indicator is "dialog".  This service
 indicator MUST NOT be used for any other interactive voice response
 control mechanism.
 The media server MUST accept MSCML IVR payloads in INFO requests and
 MUST NOT accept MSCML IVR payloads in the initial or subsequent
 INVITEs.  The INFO method reduces certain timing issues that occur
 with INVITEs and requires less processing on both the client and
 media server.

Van Dyke, et al. Informational [Page 23] RFC 5022 MSCML September 2007

 The media server notifies the client that the command has completed
 through a <response> message containing final status information and
 associated data such as collected DTMF digits.
 The media server does not queue IVR requests.  If the media server
 receives a new IVR request while another is in progress, the media
 server stops the first operation and it carries out the new request.
 The media server generates a <response> message for the first request
 and returns any data collected up to that point.  If a client wishes
 to stop a request in progress but does not wish to initiate another
 operation, it issues a <stop> request.  This also causes the media
 server to generate a <response> message.
 The media server treats a SIP re-INVITE that modifies the established
 SDP parameters as an implicit <stop> request.  Examples of such SDP
 modifications include receiving hold SDP or removing an audio or
 video stream.  When this occurs, the media server immediately
 terminates the running <play>, <playcollect>, or <playrecord> request
 and sends a <response> indicating "reason=stopped".

6.1. Specifying Prompt Content

 The MSCML IVR requests support two methods of specifying content to
 be delivered to the user.  These are the <prompt> element and the
 prompturl attribute.  Clients MUST NOT utilize both methods in a
 single IVR request.  Clients SHOULD use the more flexible <prompt>
 mechanism.  Use of the prompturl attribute is deprecated and may not
 be supported in future MSCML versions.

6.1.1. Use of the Prompt Element

 The <prompt> element MAY be included in the body of a <play>,
 <playcollect>, or <playrecord> request to specify a prompt sequence
 to be delivered to the caller.  The prompt sequence consists of one
 or more references to physical content files, spoken variables, or
 dynamic URLs that return a sub-sequence of files or variables.  In
 addition, the <prompt> element has several attributes that control
 playback of the included content.  These are described in the list
 below.
 Attributes of <prompt>:
 o  baseurl - optional, no default value: For notational convenience,
    as well as reducing the MSCML payload size, the "baseurl"
    attribute is used to specify a base URL that is prepended to any
    other URLs in the sequence that are not fully qualified.

Van Dyke, et al. Informational [Page 24] RFC 5022 MSCML September 2007

 o  delay - optional, default value "0": The "delay" attribute to the
    prompt element specifies the time to pause between repetitions of
    the <prompt> sequence.  It has no effect on the first iteration of
    the sequence.  Expressed as a time value (Section 4.2.1) from 0
    onwards.
 o  duration - optional, default value "infinite": The "duration"
    attribute to the prompt element controls the maximum amount of
    time that may elapse while the media server repeats the sequence.
    This allows the client to set an upper bound on the length of
    play.  Expressed as a time value (Section 4.2.1) from 1ms onwards
    or the strings "immediate" and "infinite".  "Immediate" directs
    the media server to end play immediately, whereas "infinite"
    indicates that the media server imposes no limit.
 o  gain - optional, default value "0": Sets the absolute gain to be
    applied to the content contained in <prompt>.  The value of this
    attribute is specified in units of dB.  The media server MAY
    silently cap values that exceed the gain limits imposed by the
    platform.  The level reverts back to its original value when
    playback of the content contained in <prompt> has been completed.
 o  gaindelta - optional, default value "0": Sets the relative gain to
    be applied to the content contained in <prompt>.  The value of
    this attribute is specified in units of dB.  The media server MAY
    silently cap values which exceed the gain limits imposed by the
    platform.  The level reverts back to its original value when
    playback of the content contained in <prompt> has been completed.
 o  rate - optional, default value "0": Specifies the absolute
    playback rate of the content relative to normal as either a
    positive percentage (faster) or a negative percentage (slower).
    Any value that attempts to set the rate above the maximum allowed
    or below the minimum allowed silently sets the rate to the maximum
    or minimum.  The rate reverts back to its original value when
    playback of the content contained in <prompt> has been completed.
 o  ratedelta - optional, default value "0": Specifies the playback
    rate of the content relative to it's current rate as either a
    positive percentage (faster) or negative percentage (slower).  Any
    value that attempts to set the rate above the maximum allowed or
    below the minimum allowed silently sets the rate to the maximum or
    minimum.  The rate reverts back to its original value when
    playback of the content contained in <prompt> has completed.

Van Dyke, et al. Informational [Page 25] RFC 5022 MSCML September 2007

 o  locale - optional, no default value: Specifies the language and
    country variant used for resolving spoken variables.  The language
    is defined as a two-letter code per ISO 639.  The country variant
    is also defined as a two-letter code per ISO 3166.  These codes
    are concatenated with a single underscore (%x5F) character.
 o  offset - optional, default value "0": A time value (Section 4.2.1)
    which specifies the time from the beginning of the sequence at
    which play is to begin.  Offset only applies to the first
    repetition; subsequent repetitions begin play at offset 0.
    Allowable values are positive time values from 0 onwards.  When
    the sequence consists of multiple content files, the offset may
    select any point in the sequence.  If the offset value is greater
    than the total time of the sequence, it will "wrap" to the
    beginning and continue from there until the media server reaches
    the specified offset.
 o  repeat - optional, default value "1": The "repeat" attribute to
    the prompt element controls the number of times the media server
    plays the sequence in the <prompt> element.  Allowable values are
    integers from 0 on and the string "infinite", which indicates that
    repetition should occur indefinitely.  For example, "repeat=2"
    means that the sequence will be played twice, and "repeat=0",
    which is allowed, means that the sequence is not played.
 o  stoponerror - optional, default value "no": Controls media server
    handling and reporting of errors encountered when retrieving
    remote content.  If set to "yes", content play will end if a fetch
    error occurs, and the response will contain details regarding the
    failure.  If set to "no", the media server will silently move on
    to the next URL in the sequence if a fetch failure occurs.
 Clients MUST NOT include both 'gain' and 'gaindelta' attributes
 within a single <prompt> element.
 When the client explicitly controls the output gain on a conference
 leg, as described in Section 5.3, the 'gain' and 'gaindelta'
 attributes SHOULD interact with the conference leg output gain
 settings in the following manner.
 o  Conference leg output gain set to <fixed>: The operation of the
    'gain' and 'gaindelta' attributes are unchanged.  However, the
    baseline gain value before any playback changes are applied is the
    value specified for the conference leg.
 o  Conference leg output gain set to <auto>: When playback gain
    controls are used, the automatic gain control settings for the leg
    are suspended for the duration of the playback operation.  The

Van Dyke, et al. Informational [Page 26] RFC 5022 MSCML September 2007

    operation of the 'gain' and 'gaindelta' attributes are unchanged.
    The automatic gain control settings are reinstated when playback
    has finished.
 Media servers SHOULD support rate controls for content.  However,
 media servers MAY silently ignore rate change requests if content
 limitations do not allow the request to be honored.  Clients MUST NOT
 include both 'rate' and 'ratedelta' attributes within a single
 <prompt> element.
 Figure 16 shows a sample prompt block.
 <prompt stoponerror="yes"
   baseurl="file:////var/mediaserver/prompts/"
   locale="en_US" offset="0" gain="0" rate="0"
   delay="0" duration="infinite" repeat="1">
   <audio url="num_dialed.raw" encoding="ulaw"/>
   <variable type="dig" subtype="ndn" value="3014170700"/>
   <audio url="num_invalid.wav"/>
   <audio url="please_check.wav"/>
 </prompt>
 Figure 16: Prompt Block Example

6.1.1.1. <audio> and <variable> Elements

 Clients compose prompt sequences using the <audio> and <variable>
 elements.  An <audio> element MAY refer to content that contains
 audio, video, or both; the generic name is preserved for backwards
 compatibility.  The <audio> element has the attributes described in
 the list below.
 Attributes of <audio>:
 o  url - required, no default value: The URL of the content to be
    retrieved and played.  The target may be a local or remote (NFS)
    "file://" scheme URL or an "http://" or "https://" scheme URL.  If
    the URL is not fully qualified and a "baseurl" attribute was set,
    the value of the "baseurl" attribute will be prepended to this
    value to generate the target URL.
 o  encoding - optional, default value "ulaw": Specifies the content
    encoding for file formats that are not self-describing (e.g.,
    .WAV).  Allowable values are "ulaw", "alaw", and "msgsm".  This
    attribute only affects "file://" scheme URLs.
 o  gain - optional, default value "0": Sets the absolute gain to be
    applied to the content URL.  The value of this attribute is

Van Dyke, et al. Informational [Page 27] RFC 5022 MSCML September 2007

    specified in units of dB.  The media server MAY silently cap
    values that exceed the gain limits imposed by the platform.  The
    level reverts back to its original value when playback of the
    content URL has been completed.
 o  gaindelta - optional, default value "0": Sets the relative gain to
    be applied to the content URL.  The value of this attribute is
    specified in units of dB.  The media server MAY silently cap
    values that exceed the gain limits imposed by the platform.  The
    level reverts back to its original value when playback of the
    content URL has been completed.
 o  rate - optional, default value "0": Specifies the absolute
    playback rate of the content relative to normal as either a
    positive percentage (faster) or a negative percentage (slower).
    Any value that attempts to set the rate above the maximum allowed
    or below the minimum allowed silently sets the rate to the maximum
    or minimum.  The rate reverts back to its original value when
    playback of the content URL has been completed.
 o  ratedelta - optional, default value "0": Specifies the playback
    rate of the content relative to it's current rate as either a
    positive percentage (faster) or a negative percentage (slower).
    Any value that attempts to set the rate above the maximum allowed
    or below the minimum allowed silently sets the rate to the maximum
    or minimum.  The rate reverts back to its original value when
    playback of the content URL has been completed.
 Clients MUST NOT include both 'gain' and 'gaindelta' attributes
 within a single <audio> element.
 When the client explicitly controls the output gain on a conference
 leg, as described in Section 5.3, the 'gain' and 'gaindelta'
 attributes SHOULD interact with the conference leg output gain
 settings in the following manner.
 o  Conference leg output gain set to <fixed>: The operation of the
    'gain' and 'gaindelta' attributes are unchanged.  However, the
    baseline gain value before any playback changes are applied is the
    value specified for the conference leg.
 o  Conference leg output gain set to <auto>: When playback gain
    controls are used, the automatic gain control settings for the leg
    are suspended for the duration of the playback operation.  The
    operation of the 'gain' and 'gaindelta' attributes are unchanged.
    The automatic gain control settings are reinstated when playback
    has finished.

Van Dyke, et al. Informational [Page 28] RFC 5022 MSCML September 2007

 Media servers SHOULD support rate controls for content.  However,
 media servers MAY silently ignore rate change requests if content
 limitations do not allow the request to be honored.  Clients MUST NOT
 include both 'rate' and 'ratedelta' attributes within a single
 <audio> element.
 Media servers MUST support local and remote (NFS) "file://" scheme
 URLs and "http://" and "https://" scheme URLs for content retrieval.
    NOTE: The provisioning of NFS mount points and their mapping to
    the "file://" schema is purely a local matter at the media server.
 MSCML also supports "http://" and "https://" scheme URLS that return
 a list of physical URLs using the "text/uri-list" MIME type.  This
 facility provides flexibility for applications to dynamically
 generate prompt sequences at execution time and enables separation of
 this function from the client and media server.
 Spoken variables are specified using the <variable> element.  This
 element has the attributes described in the list below.  MSCML's
 spoken variables are based on those described in Audio Server
 Protocol [17].
 Attributes of <variable>:
 o  type - required, no default value: Specifies the major type format
    of the spoken variable to be played.  Allowable values are "dat"
    (date), "dig" (digit), "dur" (duration), "mth" (month), "mny"
    (money), "num" (number), "sil" (silence), "str" (string), "tme"
    (time), and "wkd" (weekday).
 o  subtype - optional, no default value: Specifies the minor type
    format of the spoken variable to be played.  Allowable values
    depend on the value of the corresponding "type" attribute.
    Possible values are "mdy", "ymd", and "dmy" for dates, "t12" and
    "t24" for times, "gen", "ndn", "crd", and "ord" for digits, and
    "USD" for money.
 o  value - required, no default value: A string that will be
    interpreted based on the formatting information specified in the
    "type" and "subtype" attributes and the "locale" attribute of the
    parent <prompt> element to render the spoken variable.
 If the "locale" attribute was not specified in <prompt>, the media
 server SHOULD make a selection based on platform configuration.  If
 the precise "locale" requested cannot be honored, the media server
 SHOULD select the closest match based on the available content.

Van Dyke, et al. Informational [Page 29] RFC 5022 MSCML September 2007

 IVR applications normally require specialized prompt content that is
 authored by the application provider.  To deliver a quality user
 interaction, the specialized prompts and spoken variables must be
 generated by the same speaker.  Since the media server inherently
 supports multiple simultaneous applications, it is extremely
 difficult to provision all the necessary application prompts and
 matching spoken variable content locally on the media server.
 Therefore, we STRONGLY RECOMMEND that clients employ the dynamic URL
 mechanism described earlier to generate spoken variables using an
 external web server that returns "text/uri-list" content.

6.2. Multimedia Processing for IVR

 MSCML IVR requests implicitly support multimedia content.  Multimedia
 capabilities are controlled by the audio and video media negotiated
 for the dialog and the content specified by the client for play and
 record operations.  If the content specified for delivery contains
 both audio and video tracks and the dialog has audio and video
 streams, both tracks are streamed to the caller.  Likewise, if the
 dialog has both audio and video streams and the content format
 specified supports both (e.g., .3gp files) the media server records
 both streams to the file.
 If there is a mismatch between the real time media and specified
 content, the media server MUST play or record the appropriate content
 tracks rather than failing the request.  For example, if the client
 has requested playback of content with audio and video tracks but
 only audio media has been established for the dialog, the media
 server should play the audio track.  If the dialog has both audio and
 video media but the content is audio-only, the media server MAY
 stream a pre-provisioned video track to the caller.  Media servers
 SHOULD implement video transcoding functions to minimize
 incompatibilities between real time media and content.
 The media server MUST begin recording video media only when it
 receives a refresh video frame.  A refresh frame contains all the
 video information required to decode that frame (i.e., there is no
 dependency on data from previous video frames).  Refresh frames are
 large and generally sent infrequently to conserve network bandwidth.
 The media server MUST implement standard mechanisms to request that
 the caller (video encoder) transmit a refresh frame to ensure video
 recording begins quickly.  The media server MUST begin recording the
 audio track immediately while waiting to receive the video refresh
 frame.

Van Dyke, et al. Informational [Page 30] RFC 5022 MSCML September 2007

6.3. Playing Announcements <play>

 The client issues a <play> request to play an announcement without
 interruption and with no digit collection.  One use, for example, is
 to announce the name of a new participant to the entire conference.
 The <play> request has the attributes described in the list below.
 Attributes of <play>:
 o  id - optional, no default value: Specifies a client-defined ID for
    purposes of matching requests and responses.
 o  offset - optional, default value "0": Specifies the time from the
    beginning of the URL specified in the 'prompturl' attribute at
    which play will begin.  Expressed as a time value (Section 4.2.1)
    from 0 onwards.  If the offset value is greater than the total
    time of the content, it will "wrap" to the beginning and continue
    from there until the media server reaches the specified offset.
    NOTE: Use of this attribute is deprecated.
 o  promptencoding - optional, no default value: Specifies the content
    encoding for file formats that are not self-describing (e.g.,
    .WAV).  Allowable values are "ulaw", "alaw", and "msgsm".  This
    attribute only affects "file://" scheme URLs.  NOTE: Use of this
    attribute is deprecated.
 o  prompturl - optional, no default value: The URL of the content to
    be retrieved and played.  The target may be a local or remote
    (NFS) "file://" scheme URL or an "http://" or "https://" scheme
    URL.  NOTE: Use of this attribute is deprecated.
 The <play> request has one child element defined, <prompt>.  Use of
 <prompt> is described in Section 6.1.1.
 The client MUST NOT use both the <prompt> element and "prompturl"
 attribute in a single request.  As previously discussed, the
 "prompturl" attribute is supported for backwards compatibility with
 older MSCML applications, but its use is deprecated.  The more
 flexible <prompt> element SHOULD be used instead.
 The following play request (Figure 17) example shows the delivery of
 a complex prompt sequence consisting of content accessed via NFS and
 spoken variables.

Van Dyke, et al. Informational [Page 31] RFC 5022 MSCML September 2007

 <?xml version="1.0"?>
 <MediaServerControl version="1.0">
   <request>
     <play id="332985001">
       <prompt stoponerror="yes"
         baseurl="file:////var/mediaserver/prompts/"
         locale="en_US" offset="0" gain="0" rate="0"
         delay="0" duration="infinite" repeat="1">
         <audio url="num_dialed.raw" encoding="ulaw"/>
         <variable type="dig" subtype="ndn" value="3014170700"/>
         <audio url="num_invalid.wav"/>
         <audio url="please_check.wav"/>
       </prompt>
     </play>
   </request>
 </MediaServerControl>
 Figure 17: <Play> Request Example
 When the announcement has finished playing, the media server sends a
 <response> payload to the client in a SIP INFO message.  Details
 regarding the format of <play> responses are provided in Section
 10.4.

6.4. Prompt and Collect <playcollect>

 The client issues a <playcollect> request to play an announcement
 (optional) and collect digits.  The <playcollect> request is executed
 in two phases, prompt and collect.  If the client specifies prompt
 content to be played, using the <prompt> element or prompturl
 attribute, the media server plays the content before starting the
 collection phase.  If no prompt content is specified, the collect
 phase begins immediately.
 The basic attributes of <playcollect> are the same as those of
 <play>, which were described in Section 6.3.  In addition to these
 basic attributes, <playcollect> defines others which control digit
 buffering and barge-in behavior, collection timers, special purpose
 DTMF key functions, and logging of user DTMF input.  Each functional
 category and its attributes are described below.

Van Dyke, et al. Informational [Page 32] RFC 5022 MSCML September 2007

6.4.1. Control of Digit Buffering and Barge-In

 Whenever the media server is processing a call that specifies an
 MSCML service (i.e., "conf" and "ivr"), the media server continuously
 looks for DTMF digits and places them in a quarantine buffer.  The
 quarantine buffer is examined when a <playcollect> request is
 received.  The media server compares any previously buffered digits
 for barge-in, and to look for matches with DTMF grammars or special
 purpose keys.  This provides the type-ahead behavior for menu
 traversal and other types of IVR interactions.
 Attributes for Control of Digit Buffering and Barge-In:
 o  cleardigits - optional, default value "no": Specifies whether
    previous user input should be considered or ignored for barge-in
    purposes and DTMF matching.  When it is set to "yes", any
    previously buffered digits are removed, so prior user input is
    ignored.  If it is set to "no", previously buffered digits will be
    considered.  If "cleardigits" is set to "no" and barge-in is
    enabled, previously buffered digits will immediately terminate the
    prompt phase.  In this case, the prompt is not played, and digit
    collection begins immediately.
 o  barge - optional, default value "yes": Specifies whether user
    input will barge the prompt and force transition to the collect
    phase.  When it is set to "yes", a DTMF input will barge the
    prompt.  When it is set to "no", the prompt phase cannot be
    barged, and any user input during the prompt is placed in the
    quarantine buffer for inspection during the collect phase.  Note
    that if the "barge" attribute is set to "no", the "cleardigits"
    attribute implicitly has a value of "yes".  This ensures that the
    media server does not leave DTMF input that occurred prior to the
    current collection in the quarantine buffer after the request is
    completed.

6.4.2. Mapping DTMF Keys to Special Functions

 The client can define mappings between DTMF digits and special
 functions.  The media server invokes the special function if the
 associated DTMF digit is detected.  MSCML has two attributes that
 define mappings that affect termination of the collect phase.  These
 attributes are described in the list below.

Van Dyke, et al. Informational [Page 33] RFC 5022 MSCML September 2007

 DTMF Key Mappings for <playcollect>:
 o  escapekey - optional, default value "*": Specifies a DTMF key that
    indicates that the user wishes to terminate the current operation
    without saving any input collected to that point.  Detection of
    the mapped DTMF key terminates the request immediately and
    generates a response.
 o  returnkey - optional, default value "#": Specifies a DTMF key that
    indicates that the user has completed input and wants to return
    all collected digits to the client.  When the media server detects
    the returnkey, it immediately terminates collection and returns
    the collected digits to the client in the <response> message.
 MSCML defines three additional mappings to enable video cassette
 recorder (VCR) type controls while playing a prompt sequence.  Media
 servers SHOULD support VCR controls.  However, if the media server
 does not support VCR controls, it MUST silently ignore DTMF inputs
 mapped to VCR functions and complete the <playcollect> request.  The
 VCR control attributes are described in the list below.
 Attributes for VCR Controls:
 o  skipinterval - optional, default value "6s": The "skipinterval"
    attribute indicates how far the media server should skip backwards
    or forwards when the rewind key (rwkey) or fast forward key
    (ffkey) is pressed, specified as a time value (Section 4.2.1).
 o  ffkey - optional, no default value: The "ffkey" attribute maps a
    DTMF key to a fast forward operation equal to the value of the
    "skipinterval" attribute.
 o  rwkey - optional, no default value: The "rwkey" attribute maps a
    DTMF key to a rewind action equal to the value of the
    "skipinterval" attribute.
 Clients MUST NOT map the same DTMF digit to both the "rwkey" and
 "ffkey" attributes in a single <playcollect> request.
 VCR control operations are bounded by the beginning and end of the
 prompt sequence.  A rewind action that moves the offset before the
 beginning of the sequence results in playback starting at the
 beginning of the sequence (i.e., offset=0).  A fast forward action
 that moves the offset past the end of the sequence results in the
 media server's treating the sequence as complete.

Van Dyke, et al. Informational [Page 34] RFC 5022 MSCML September 2007

6.4.3. Collection Timers

 MSCML defines several timer attributes that control how long the
 media server waits for digits in the input sequence.  All timer
 settings are time values (Section 4.2.1).  The list below describes
 these attributes and their use.
 Collection Timer Attributes:
 o  firstdigittimer - optional, default value "5000ms": Specifies how
    long the media server waits for the initial DTMF input before
    terminating the collection.  Expressed as a time value (Section
    4.2.1) from 1ms onwards or the strings "immediate" and "infinite."
    The value "immediate" indicates that the timer should fire
    immediately whereas "infinite" indicates that the timer will never
    fire.
 o  interdigittimer - optional, default value "2000ms": Specifies how
    long the media server waits between DTMF inputs.  Expressed as a
    time value (Section 4.2.1) from 1ms onwards or the strings
    "immediate" and "infinite."  The value "immediate" indicates that
    the timer should fire immediately, whereas "infinite" indicates
    that the timer will never fire.
 o  extradigittimer - optional, default value "1000ms": Specifies how
    long the media server waits for additional user input after the
    specified number of digits has been collected.  Expressed as a
    time value (Section 4.2.1) from 1ms onwards or the strings
    "immediate" and "infinite."  The value "immediate" indicates that
    the timer should fire immediately, whereas "infinite" indicates
    that the timer will never fire.
 o  interdigitcriticaltimer - optional, defaults to the value of the
    interdigittimer attribute: Specifies how long the media server
    waits after a grammar has been matched for a subsequent digit that
    may cause a longer match.  Expressed as a time value (Section
    4.2.1) from 1ms onwards or the strings "immediate" and "infinite."
    The value "immediate" results in "shortest match first" behavior,
    whereas "infinite" means to wait indefinitely for additional
    input.  If not explicitly specified otherwise, this attribute is
    set to the value of the 'interdigittimer' attribute.
 The extradigittimer setting enables the "returnkey" input to be
 associated with the current collection.  For example, if maxdigits is
 set to 3 and returnkey is set to #, the user may enter either "x#",
 "xx#", or "xxx#", where x represents a DTMF digit.

Van Dyke, et al. Informational [Page 35] RFC 5022 MSCML September 2007

 If the media server detects the "returnkey" pattern during the
 "extradigit" interval, the media server returns the collected digits
 to the client and removes the "returnkey" from the digit buffer.
 If this were not the case, the example would return "xxx" to the
 client and leave the terminating "#" in the digit buffer.  At the
 next <playcollect> request, the media server would process the '#'.
 This might result in the termination of the following prompt, which
 is clearly not what the user intended.
 The extradigittimer has no effect unless returnkey has been set.

6.4.4. Logging Caller DTMF Input

 Standard SIP mechanisms, such as those discussed in Security
 Considerations (Section 14), protect MSCML protocol exchanges and the
 information they contain.  These protections do not apply to data
 captured in media server log files.  In general, media server logging
 is platform specific and therefore is not covered by this
 specification.  However, one aspect of logging, the capture of
 sensitive information (such as personal identification numbers or
 credit card numbers), is relevant.  The media server has no means to
 determine whether the DTMF input it receives may be sensitive, as
 that is in the purview of the client.  Recognizing this, MSCML
 includes a per-request mechanism to suppress logging of captured DTMF
 to be enabled by clients as needed.
 The "maskdigits" attribute controls whether detected DTMF digits
 appear in the log output.  Clients use this attribute when the media
 server collects sensitive information that should not be accessible
 through the log files.
 Maskdigits Attribute:
 o  maskdigits - optional, default value "no": Controls whether user
    DTMF inputs are captured in media server log files.  The possible
    values for this attribute are "yes" and "no".

6.4.5. Specifying DTMF Grammars

 MSCML supports four methods for specifying DTMF grammars: the
 "maxdigits" attribute, which provides a simple mechanism for
 collecting any number of digits up to the maximum, regular
 expressions, MGCP [5] digit maps, and H.248.1 [6] digit maps.  A
 media server MUST support the maxdigits and regular expression
 methods for specifying DTMF grammars and SHOULD support MGCP and
 H.248.1 methods.  A client MUST NOT mix DTMF grammar types in a
 single <playcollect> request.

Van Dyke, et al. Informational [Page 36] RFC 5022 MSCML September 2007

 Following is a description of the "maxdigits" attribute.
 Maxdigits Attribute:
 o  maxdigits - optional, no default value: Specifies the maximum
    number of DTMF digits to be collected.
 The <pattern> element specifies a digit pattern or patterns for the
 media server to look for.  This element may contain three different
 child elements that specify the type of DTMF grammar used in the
 expression.  The <pattern> element has no attributes.
 <regex> Use regular expressions to define DTMF patterns to match.
    The complete regular expression syntax used in MSCML is described
    in Appendix A.
 <mgcpdigitmap> Use digit maps as specified in MGCP [5].
 <megacodigitmap> Use digit maps as specified in H.248.1 [6].
 At least one <regex> element MUST be present in <pattern> when regex
 grammars are used.  Multiple <regex> elements MAY be present.  When
 <mgcpdigitmap> or <megacodigitmap> grammars are used, <pattern> MUST
 contain only one grammar element.
 The DTMF grammar elements <regex>, <mgcpdigitmap>, and
 <megacodigitmap> have the attributes described in the list below.
 Attributes of DTMF Grammar Elements:
 o  value - required, no default value: Specifies a string
    representing a DTMF grammar matching the parent element type
    (e.g., regex).  Regex values represent a single DTMF grammar.
    MGCP and MEGACO digit maps allow multiple grammars to be described
    in a single string.
 o  name - optional, no default value: Associates a client defined
    name for the grammar that is sent back in the <playcollect>
    response.  This attribute is most useful with regex type grammars
    as each grammar element can have a unique name.

6.4.6. Playcollect Response

 When the <playcollect> has finished, the media server sends a
 <response> payload to the client in a SIP INFO message.
 Details of the <playcollect> response are described in Section 10.5.

Van Dyke, et al. Informational [Page 37] RFC 5022 MSCML September 2007

6.4.7. Playcollect Example

 The following <playcollect> request (Figure 18) example depicts use
 of the "maxdigits" attribute to control digit collection.
 <?xml version="1.0"?>
 <MediaServerControl version="1.0">
   <request>
     <playcollect id="332986004" maxdigits="6" firstdigittimer="10000"
       interdigittimer="5000" extradigittimer="1000"
       interdigitcriticaltimer="1000" returnkey="#" escapekey="*"
       cleardigits="no" barge="yes" maskdigits="no">
       <prompt baseurl="http://www.example.com/prompts/">
         <audio url="generic/en_US/enter_pin.wav"/>
       </prompt>
     </playcollect>
   </request>
 </MediaServerControl>
 Figure 18: <Playcollect> Request Example Using the Maxdigits
 Attribute

6.5. Prompt and Record <playrecord>

 The <playrecord> request directs the media server to convert and
 possibly to transcode the RTP payloads it receives and store them to
 the specified URL using the requested content codec(s) and file
 format.  This request proceeds in two phases; prompt and record.
 The <playrecord> request shares the basic attributes of <play> and
 <playcollect> as described in Section 6.3.  MSCML also defines other
 attributes that control the behavior of the prompt and recording
 phases.  These phases and the attributes that control them are
 described in the text and tables below.

6.5.1. Prompt Phase

 The presence or absence of a "prompturl" attribute or child <prompt>
 element controls whether a prompt is played before recording begins.
 As previously noted, use of the "prompturl" attribute is deprecated,
 and clients SHOULD use <prompt> instead.
 When the client requests that the media server prompt the caller
 before recording audio, <playrecord> has two stages.  The first is
 equivalent to a <playcollect> operation.  The client may set the
 prompt phase to be interruptible by DTMF input (barge) and may
 specify an escape key that will terminate the <playrecord> request
 before the recording phase begins.

Van Dyke, et al. Informational [Page 38] RFC 5022 MSCML September 2007

 The list below describes the attributes of <playrecord> that specify
 the behavior of the prompt phase of the request.
 Playrecord Attributes for the Prompt Phase:
 o  barge - optional, default value "yes": Specifies whether user
    input will barge the prompt and force transition to the record
    phase.  When it is set to "yes", a DTMF input will barge the
    prompt.  When it is set to "no", the prompt phase cannot be
    barged, and any user input during the prompt is placed in the
    quarantine buffer for inspection during the collect phase.  Note
    that if the "barge" attribute is set to "no", the "cleardigits"
    attribute implicitly has a value of "yes".  This ensures that the
    media server does not leave DTMF input that occurred prior to the
    current collection in the quarantine buffer after the request
    completes.
 o  cleardigits - optional, default value "no": Specifies whether
    previous user input should be considered or ignored for barge-in
    purposes.  When it is set to "yes", any previously buffered digits
    are removed, so prior user input is ignored.  If it is set to
    "no", previously buffered digits will be considered.  If
    "cleardigits" is set to "no" and barge-in is enabled, previously
    buffered digits will terminate the prompt phase immediately.  In
    this case, the prompt is not played, and recording begins
    immediately.
 o  escapekey - optional, default value "*": Specifies a DTMF key that
    indicates the user wishes to terminate the current operation
    without saving any input recorded to that point.  Detection of the
    mapped DTMF key terminates the request immediately and generates a
    response.
 Detection of the escape key generates a response message, and the
 operation returns immediately.  If the user presses any other keys
 and if the prompt is interruptible (barge="yes"), then the play stops
 immediately, and the recording phase begins.

6.5.2. Record Phase

 If the request proceeds to the recording phase, the media server
 discards any digits from the collect phase from the quarantine buffer
 to eliminate unintended termination of the recording.  The following
 attributes control recording behavior.
 Playrecord Attributes for the Record Phase:

Van Dyke, et al. Informational [Page 39] RFC 5022 MSCML September 2007

 o  recurl - required, no default value: Specifies the target URL for
    the recorded content.
 o  recencoding - optional, default value "ulaw": Specifies the
    encoding of the recorded content if it cannot be inferred from the
    recurl.  Possible values are "ulaw", "alaw", and "msgsm."
 o  mode - optional, default value "overwrite": Specifies whether the
    recording should overwrite or be appended to the target URL.
    Allowable values are "overwrite" and "append."
 o  duration - optional, default value "infinite": Specifies the
    maximum allowable duration for the recording.  Expressed as a time
    value (Section 4.2.1) from 1 onwards or the strings "immediate"
    and "infinite."  The value "immediate" indicates that recording
    will end immediately, whereas "infinite" indicates recording
    should continue indefinitely.  If the maximum duration is reached,
    the <playrecord> request will terminate and generate a response.
 o  beep - optional, default value "yes": Specifies whether a beep
    should be played to the caller immediately prior to the start of
    the recording phase.  Allowable values are "yes" and "no."
 o  initsilence - optional, default value "3000ms": Specifies how long
    to wait for initial speech input before terminating (canceling)
    the recording.  Expressed as a time value (Section 4.2.1) from 1ms
    onwards or the strings "immediate" and "infinite."  The value
    "immediate" indicates that the timer should fire immediately,
    whereas "infinite" directs the media server to wait indefinitely.
 o  endsilence - optional, default value "4000ms": Specifies how long
    the media server waits after speech has ended to stop the
    recording.  Expressed as a time value (Section 4.2.1) from 1ms
    onwards or the strings "immediate" and "infinite."  When set to
    "infinite", the recording will continue indefinitely after speech
    has ended and will only terminate due to a DTMF keypress or
    because the input has reached the maximum desired duration.
 o  recstopmask - optional, default value "0123456789ABCD#*":
    Specifies a list of individual DTMF characters that, if detected,
    will cause the recording to be terminated.  To ensure that the
    input of a specific key does not cause the recording to stop,
    remove the DTMF key from the list.
 Media servers MUST support local and remote (NFS) "file://" scheme
 URLs in the "recurl" attribute.  MSCML supports "http://" and
 "https://" scheme URLs indirectly through the <managecontent>
 (Section 8) request.

Van Dyke, et al. Informational [Page 40] RFC 5022 MSCML September 2007

 The media server buffers and returns any digits collected in the
 prompt phase, with the exception of those contained in the
 "recstopmask" attribute, in the response.
 The media server compares digits detected during the recording phase
 to the digits specified in the "recstopmask" to determine whether
 they indicate a recording termination request.
 The media server ignores digits not present in the recstopmask and
 passes them into the recording.  If DTMF input terminates the
 recording, the media server returns the collected digit to the client
 in the <response>.
 Once recording has begun, the media server writes the received media
 to the specified recurl URL no matter what DTMF events the media
 server detects.  It is the responsibility of the client to examine
 the DTMF input returned in the <response> message to determine
 whether the audio file should be saved or deleted and, potentially,
 re-recorded.
 If the endsilence timer expires, the media server trims the end of
 the recorded audio by an amount equal to the value of the
 "endsilence" attribute.
 When the recording is finished, the media server generates a
 <response> message and sends it to the client in a SIP INFO message.
 Details of the <playrecord> response are described in Section 10.6.

6.5.3. Playrecord Example

 The recording example (Figure 19) plays a prompt and records it to
 the destination specified in the "recurl" attribute encoded as MS-GSM
 in wave format.

Van Dyke, et al. Informational [Page 41] RFC 5022 MSCML September 2007

 <?xml version="1.0"?>
 <MediaServerControl version="1.0">
   <request>
     <playrecord id="5556123"
       recurl="file:////nfs.example.com/rec/name.wav"
       recencoding="msgsm"
       initsilence="5000" endsilence="3000" duration="30000"
       barge="yes"
       beep="yes"
       mode="overwrite"
       cleardigits="no"
       escapekey="*"
       recstopmask="0123456789#*">
       <prompt>
         <audio url="http://www.example.com/prompts/recordname.wav"/>
       </prompt>
     </playrecord>
   </request>
 </MediaServerControl>
 Figure 19: Recording Example

6.6. Stop Request <stop>

 The client issues a <stop> request when the objective is to stop a
 request in progress and not to initiate another operation.  This
 request generates a <response> message from the media server.
 The only attribute is id, which is optional.
 The client-defined request id correlates the asynchronous response
 with its original request and echoes back to the client in the media
 server's response.
 The following MSCML payload (Figure 20) depicts an example <stop>
 request.
 <?xml version="1.0"?>
 <MediaServerControl version="1.0">
   <request>
     <stop id="4578903"/>
   </request>
 </MediaServerControl>
 Figure 20: Stop Example
 The format of a response to a <stop> request is detailed in Section
 10.2.

Van Dyke, et al. Informational [Page 42] RFC 5022 MSCML September 2007

 As discussed previously, the media server treats a SIP re-INVITE that
 modifies the established SDP parameters as an implicit <stop>
 request.  Examples of such SDP modifications include receiving hold
 SDP or removing an audio or video stream.  When this occurs, the
 media server immediately terminates the running <play>,
 <playcollect>, or <playrecord> request and sends a <response>
 indicating "reason=stopped".

7. Call Leg Events

 MSCML defines event notifications that are scoped to a specific SIP
 dialog or call leg.  These events allow a client to be notified of
 individual, asynchronous DTMF keypresses, as well as of various call
 progress signals.  The subscription, event detection, and
 notifications for call leg events occur in the same SIP dialog.  This
 is different from the conference level active talker events described
 earlier.  The subscription and notifications for active talker events
 occur on the conference control leg, but the actual event detection
 occurs on one or more participant legs.
 Subscriptions for call leg events are made by sending an MSCML
 <configure_leg> request on the desired SIP dialog.  Call leg events
 may be used with the MSCML conferencing or IVR services.  When used
 with the IVR service, the <configure_leg> request SHOULD NOT include
 any conference-related attributes.  The media server MUST ignore
 these if present.  Call leg event subscriptions MUST NOT be made on
 the conference control leg, since it has no actual RTP media to
 process for event detection.  The media server MUST reject a
 <configure_leg> request sent on the conference control leg.
 The <configure_leg> request contains the child elements <subscribe>
 and <events>.  The <events> element may contain two child elements
 that control subscriptions to call leg events.  These are <keypress>
 and <signal>.  A <configure_leg> request MUST contain at most one
 <keypress> element but MAY contain multiple <signal> elements that
 request notification of different call progress events.

7.1. Keypress Events

 Keypress events are used when the client wishes to receive
 notifications of individual DTMF events that are not tied to a
 specific <playcollect> request.  One use of this facility is to
 monitor conference legs for DTMF inputs that require application
 intervention; for example, to notify the moderator that the caller
 wishes to speak.  Keypress events are also used when the application
 desires complete control of grammars and timing constraints.

Van Dyke, et al. Informational [Page 43] RFC 5022 MSCML September 2007

 When used in a subscription context, the <keypress> element has two
 attributes, 'report' and 'maskdigits', which are detailed in the list
 below.
 Keypress Subscription Attributes:
 o  report - required, no default value: Possible values are
    'standard', 'long', 'both', and 'none'.  'Standard' means that
    detected digits should be reported.  'Long' means that long digits
    should be reported.  'Long' digits are defined as a single key
    press held down for more than one second, or two distinct key
    presses (a "double") of the same digit that occur within two
    seconds of each other with no other intervening digits.  'Both'
    means that both 'standard' and 'long' digit events should be
    reported.  As a 'long' digit consists of one or more "normal"
    digits, a single long duration key press will generate one
    standard event and one 'long' event.  A "double" will produce two
    standard events and one 'long' event.  'None' means that no
    keypress events should be reported; it disables keypress event
    reporting if enabled.
 o  maskdigits - optional, default value "no": Controls whether user
    DTMF inputs are captured in media server log files.  The possible
    values for this attribute are "yes" and "no".
 The media server sends an MSCML response to the subscription
 immediately upon receiving the request.  Notifications are sent to
 the client when the specified events are detected.
 When used in a notification context, the <keypress> element has
 several attributes that are used to convey details of the event that
 was detected.  It also contains a child element, <status>, that
 provides information on any MSCML request that was in progress when
 the event occurred.  The details of these notification attributes are
 described in the list below.
 Keypress Notification Attributes:
 o  digit - required, no default value: Specifies the DTMF digit
    detected.  Possible values are [0-9], [A-D], '#', or '*'.
 o  length - required, no default value: Specifies the duration class
    of the DTMF input.  Possible values are 'standard' or 'long'.
 o  method - required, no default value: Specifies the keypress
    detection method that generated the notification.  Possible values
    are 'standard', 'long', and 'double'.

Van Dyke, et al. Informational [Page 44] RFC 5022 MSCML September 2007

 o  interdigittime - required, no default value: Specifies the elapsed
    time, as a time value (Section 4.2.1), between the current event
    detection and the previous one.

7.1.1. Keypress Subscription Examples

 The following examples of MSCML payloads depict a subscription for
 standard keypress events and disabling keypress reporting.
 Figure 21 shows a subscription for standard keypress events.
 <?xml version="1.0"?>
 <MediaServerControl version="1.0">
   <request>
     <configure_leg>
       <subscribe>
         <events>
           <keypress report="standard"/>
         </events>
       </subscribe>
     </configure_leg>
   </request>
 </MediaServerControl>
 Figure 21: Standard Digit Events Subscription
 Figure 22 shows a client disabling keypress event notifications.
 <?xml version="1.0"?>
 <MediaServerControl version="1.0">
   <request>
     <configure_leg>
       <subscribe>
         <events>
           <keypress report="none"/>
         </events>
       </subscribe>
     </configure_leg>
   </request>
 </MediaServerControl>
 Figure 22: Disabling Keypress Event Reporting

7.1.2. Keypress Notification Examples

 The following MSCML payloads depict keypress event notifications
 caused by various types of DTMF input.

Van Dyke, et al. Informational [Page 45] RFC 5022 MSCML September 2007

 Figure 23 shows a notification generated by the detection of a
 standard "4" DTMF digit.  In this example, this is the first digit
 detected.  Thus, the 'interdigittime' attribute has a value of '0'.
 <?xml version="1.0"?>
 <MediaServerControl version="1.0">
   <notification>
     <keypress digit="4" length="standard" method="standard"
       interdigittime="0">
       <status command="play" duration="10"/>
     </keypress>
   </notification>
 </MediaServerControl>
 Figure 23: Standard Keypress Notification
 Figure 24 shows a notification generated by detection of a long pound
 (#).
 <?xml version="1.0"?>
 <MediaServerControl version="1.0">
   <notification>
     <keypress digit="#" length="long" method="long"
       interdigittime="200">
       <status command="idle" duration="4"/>
     </keypress>
   </notification>
 </MediaServerControl>
 Figure 24: Long Keypress Notification

7.2. Signal Events

 MSCML supports notification of certain call progress tones through
 the <signal> element.  When used in a subscription context, the
 <signal> element has two attributes, 'type' and 'report', and no
 child elements.  These attributes are detailed in the list below.
 Signal Subscription Attributes:
 o  report - required, no default value: Controls whether the
    specified signal is reported.  Possible values are 'yes' and 'no'.
    When set to 'yes', the media server invokes the required signal
    detection code and reports detected events.  When it is set to
    'no', the media server disables the associated signal detection
    code and does not report events.

Van Dyke, et al. Informational [Page 46] RFC 5022 MSCML September 2007

 o  type - required, no default value: Specifies the type of call
    progress signal to detect.  Possible values are 'busy', 'ring',
    'CED', 'CNG', and '400', which correspond to busy tone, ring tone,
    fax CED, fax CNG, and 400 Hz tone, respectively.
    NOTE: The details of media server provisioning required to support
    country-specific variants of 'busy' and 'ring' is not covered by
    this specification.
 As stated previously, a single <configure_leg> request MAY contain
 multiple <signal> elements that request notification of different
 call progress tones.  A single <configure_leg> request SHOULD NOT
 contain multiple <signal> elements that have the same 'type'
 attribute value.  If the media server receives such a request, it
 SHOULD honor the last element specifying that type that appears in
 the request.
 The media server generates an immediate response to the
 <configure_leg> subscription request and sends notifications when the
 specified signals are detected.  A single notification is sent as
 soon as the specified signal has been reliably detected.  If the
 signal persists continuously, additional notifications will not be
 sent.  If the signal is interrupted and then resumes, additional
 notifications will be sent.
 Signal notifications have a single attribute, "type", as described in
 the list below.
 Signal Notification Attribute:
 o  type - required, no default value: Specifies the type of call
    progress signal that was detected.  Possible values are 'busy',
    'ring', 'CED', 'CNG', and '400', which correspond to busy tone,
    ring tone, fax CED, fax CNG, and 400 Hz tone, respectively.

7.2.1. Signal Event Examples

 The following MSCML payloads show a signal event subscription (Figure
 25) and notification (Figure 26).

Van Dyke, et al. Informational [Page 47] RFC 5022 MSCML September 2007

 <?xml version="1.0"?>
 <MediaServerControl version="1.0">
   <request>
     <configure_leg>
       <subscribe>
         <events>
           <signal type="busy" report="yes"/>
         </events>
       </subscribe>
     </configure_leg>
   </request>
 </MediaServerControl>
 Figure 25: Signal Event Subscription
 <?xml version="1.0"?>
 <MediaServerControl version="1.0">
   <notification>
     <signal type="busy"/>
   </notification>
 </MediaServerControl>
 Figure 26: Signal Event Notification

8. Managing Content <managecontent>

 MSCML uses the <managecontent> request to move recorded content from
 the media server to remote locations using the HTTP protocol.  This
 is a store-and-forward model, which requires the completion of local
 temporary recording before the media server can send it to the web
 server.  This facility is useful in applications such as voice
 messaging, where a message may be reviewed by the caller prior to
 being committed to persistent storage.
 The <managecontent> request contains no child elements and has the
 attributes described in the list below.
 Managecontent Attributes:
 o  src - required, no default value: Specifies the local source URL
    of the content.  The URL scheme MUST be "file://".
 o  dest - required (see note), no default value: Specifies the
    destination URL.  The URL scheme MUST be "http://".  Note: If the
    selected action is 'delete', this attribute is optional; otherwise
    it is required.

Van Dyke, et al. Informational [Page 48] RFC 5022 MSCML September 2007

 o  action - optional, default value "move": Specifies the operation
    for the media server to execute.  Values can be either 'move' or
    'delete'.  The 'delete' action operates on the local source file.
    After a successful move or delete, the media server deletes the
    source file from its local storage.  If the request is
    unsuccessful, the source file is not deleted, which gives the
    client complete control of the retry strategy.
 o  httpmethod - optional, default value "post": HTTP protocol method
    for the media server to use in the HTTP request.  The only values
    are 'post' or 'put'.
 o  name - required (see note), no default value: Specifies the field
    name for the content in the form when using the 'post' method.
    This is not to be confused with the "src" or "dest" attributes.
    Note: This attribute is required when the "htttpmethod" has the
    value "post" and is optional otherwise.
 o  fetchtimeout - optional, default value "10000ms": Specifies the
    maximum time allowed for the transfer to complete.  Expressed as a
    time value (Section 4.2.1) from 1ms onwards.
 o  mimetype - required (see note), no default value: Specifies the
    MIME type that the media server will use for the content transfer.
    If it is not provided, the media server MUST try to infer it from
    the content file extension based on a platform specific mapping
    table.  A non-normative, example mapping table is shown in Table
    3.  To avoid ambiguity, we RECOMMEND that clients explicitly set
    this attribute.  Note: If the MIME type of the content cannot be
    inferred from the file extension, this attribute is required.
 Table 3 shows common audio and video MIME types and possible file
 extension mappings.

Van Dyke, et al. Informational [Page 49] RFC 5022 MSCML September 2007

                  +-----------+--------------------+
                  | Extension | MIME Type          |
                  +-----------+--------------------+
                  | alaw      | audio/x-alaw-basic |
                  | ulaw      | audio/basic        |
                  | msgsm     | audio/ms-gsm       |
                  | wav       | audio/x-wav        |
                  | tif       | image/tiff         |
                  | tiff      | image/tiff         |
                  | mov       | video/quicktime    |
                  | qt        | video/quicktime    |
                  | 3gp       | video/3gpp         |
                  | 3gpp      | video/3gpp         |
                  +-----------+--------------------+
         Table 3: Example File Extension to MIME Type Mappings
 <Managecontent> is purely a transport operation; the underlying
 content is not changed by it.  Therefore clients MUST ensure that the
 source and destination file name extensions and MIME types are the
 same.  Failure to do so could result in content that is unreadable.
 The ability to move or delete any local file presents a potential
 risk to the security of the media server system.  For this reason, we
 STRONGLY RECOMMEND that implementers limit local file system access
 when using <managecontent>.  For example, we encourage limiting
 access as based on file ownership and/or specific directories.

8.1. Managecontent Example

 The following is an example (Figure 27) showing a local file on the
 media server being transferred to an HTTP URL using the "put" method.
 The client sends the following request.
 <?xml version="1.0"?>
 <MediaServerControl version="1.0">
   <request>
     <managecontent id="102"
     src="file:////var/mediaserver/rec/6A5GH49B.ulaw"
     dest="http://www.example.com/recordings/myrecording.ulaw"
     mimetype="audio/basic" action="move" httpmethod="put"
     fetchtimeout="5000"/>
   </request>
 </MediaServerControl>
 Figure 27: Managecontent Example

Van Dyke, et al. Informational [Page 50] RFC 5022 MSCML September 2007

 Note that the client can change the temporary file name assigned by
 the media server as part of this operation as shown.
 If the request is ambiguous, the media server MUST return a status
 code of "400" and text "Bad Request."  If the media server is unable
 to execute a syntactically correct and unambiguous request, it MUST
 return a "500" status code with the text "Server Error."  For
 example, the local file system access restrictions may prevent
 deletion of the specified file.  In this case, the "reason" attribute
 in the response conveys additional details on the server error that
 occurred.  If there is a network or remote server error, the media
 server provides detailed error information in the <error_info>
 element contained in the media server response.  Additional
 information regarding <managecontent> responses is provided in
 Section 10.7.

9. Fax Processing

9.1. Recording a Fax <faxrecord>

 The <faxrecord> request directs the media server to process a fax in
 answer mode.  The reason for a request separate from <playrecord> is
 that the media server needs to know to process the T.30 [18] or T.38
 [19] fax protocols.
 The <faxrecord> request has multiple attributes and one child
 element, <prompt>.  Its attributes are described in the list below.
 Attributes of <faxrecord>:
 o  lclid - optional, default value "" (the empty string): A string
    that identifies the called station.
 o  prompturl - optional, no default value: The URL of the fax content
    to be retrieved and played.  The target may be a local or remote
    (NFS) "file://" scheme URL or an "http://" or "https://" scheme
    URL.  NOTE: Use of this attribute is deprecated.
 o  promptencoding - optional, no default value: Specifies the content
    encoding for files that do not have a 'tif' or 'tiff' extension.
    The only allowable value is 'tiff'.  This attribute only affects
    "file://" scheme URLs.  NOTE: Use of this attribute is deprecated.
 o  recurl - optional, no default value: Specifies the target URL for
    the recorded content.
 o  rmtid - optional, no default value: Specifies the calling station
    identifier of the remote terminal.  If present, the media server

Van Dyke, et al. Informational [Page 51] RFC 5022 MSCML September 2007

    MUST reject transactions with the remote terminal if the remote
    terminal's identifier does not match the value of 'rmtid'.
 Clients SHOULD use the more flexible <prompt> mechanism for
 specifying fax content.  Use of the 'prompturl' attribute is
 deprecated and may not be supported in future MSCML versions.  The
 <prompt> element is described in Section 6.1.1.  A <prompt> element
 sent in a <faxrecord> request MUST NOT contain <variable> elements.
 Media servers MUST support local and remote (NFS) "file://" scheme
 URLs in the "recurl" attribute.  MSCML supports "http://" and
 "https://" scheme URLs indirectly through the <managecontent>
 (Section 8) request.
 The <faxrecord> request operates in one of three modes: receive,
 poll, and turnaround poll.  The combination of <prompt> or
 'prompturl' attribute and 'recurl' attribute define the mode.  Table
 4 describes these modes in detail.  The 'prompt' column in the table
 has the value 'yes' if the request has either a <prompt> element or a
 'prompturl' attribute.
 +--------+--------+---------+---------------------------------------+
 | prompt | recurl | Mode    | Operation                             |
 +--------+--------+---------+---------------------------------------+
 | no     | no     | Invalid | Request fails.                        |
 | no     | yes    | Receive | Record the fax to the target URL      |
 |        |        |         | specified in 'recurl'.                |
 | yes    | no     | Poll    | Send fax from source specified in the |
 |        |        |         | <prompt> element or 'prompturl'       |
 |        |        |         | attribute.  If there is a 'rmtid', it |
 |        |        |         | MUST match the remote terminal's      |
 |        |        |         | identifier, or the request will fail. |
 | yes    | yes    | TP      | Turnaround Poll (TP) mode. If the     |
 |        |        |         | remote terminal wishes to transmit,   |
 |        |        |         | the media server records the fax to   |
 |        |        |         | the target URL specified in 'recurl'. |
 |        |        |         | If the remote terminal wishes to      |
 |        |        |         | receive, the media server sends the   |
 |        |        |         | fax from the source URL contained in  |
 |        |        |         | <prompt> or 'prompturl'.  If there is |
 |        |        |         | a 'rmtid', it MUST match remote       |
 |        |        |         | terminal's identifier, or the send    |
 |        |        |         | request will fail.  A receive         |
 |        |        |         | operation will still succeed,         |
 |        |        |         | however.                              |
 +--------+--------+---------+---------------------------------------+
                      Table 4: Fax Receive Modes

Van Dyke, et al. Informational [Page 52] RFC 5022 MSCML September 2007

 In receive mode, the media server receives the fax and writes the fax
 data to the target URL specified by the 'recurl' attribute.
 In poll mode, the media server sends a fax, but as a polled (called)
 device.
 In turnaround poll mode, the media server will record a fax that the
 remote machine sends.  If the remote machine requests a transmission,
 then the media server will send the fax.
 When transmitting a fax, the media server will advertise that it can
 receive faxes in the DIS message.  Likewise, when receiving a fax,
 the media server will advertise that it can send faxes in the DIS
 message.
 The media server MUST flush any quarantined digits when it receives a
 <faxrecord> request.

9.2. Sending a Fax <faxplay>

 The <faxplay> request directs the media server to process a fax in
 originate mode.  The reason for a request separate from <play> is
 that the media server needs to know to process the T.30 [18] or T.38
 [19] fax protocols.
 The <faxplay> request has multiple attributes and one child element,
 <prompt>.  Its attributes are described in the list below.
 Attributes of <faxplay>:
 o  lclid - optional, default value "" (the empty string): A string
    that identifies the called station.
 o  prompturl - optional, no default value: The URL of the content to
    be retrieved and played.  The target may be a local or remote
    (NFS) "file://" scheme URL or an "http://" or "https://" scheme
    URL.  NOTE: Use of this attribute is deprecated.
 o  promptencoding - optional, no default value: Specifies the content
    encoding for files that do not have a 'tif' or 'tiff' extension.
    The only allowable value is 'tiff'.  This attribute only affects
    "file://" scheme URLs.  NOTE: Use of this attribute is deprecated.
 o  recurl - optional, no default value: Specifies the target URL for
    the recorded content.
 o  rmtid - optional, no default value: Specifies the calling station
    identifier of the remote terminal.  If present, the media server

Van Dyke, et al. Informational [Page 53] RFC 5022 MSCML September 2007

    MUST reject transactions with the remote terminal if the remote
    terminal's identifier does not match the value of 'rmtid'.
 Clients SHOULD use the more flexible <prompt> mechanism for
 specifying fax content.  Use of the 'prompturl' attribute is
 deprecated and may not be supported in future MSCML versions.  The
 <prompt> element is described in Section 6.1.1.  A <prompt> element
 sent in a <faxrecord> request MUST NOT contain <variable> elements.
 Media servers MUST support local and remote (NFS) "file://" scheme
 URLs in the "recurl" attribute.  MSCML supports "http://" and
 "https://" scheme URLs indirectly through the <managecontent>
 (Section 8) request.
 The <faxplay> request operates in one of three modes: send, remote
 poll, and turnaround poll.  The combination of <prompt> or
 'prompturl' attribute and 'recurl' attribute define the mode.  Table
 5 describes these modes in detail.  The 'prompt' column in the table
 has the value 'yes' if the request has either a <prompt> element or a
 'prompturl' attribute.

Van Dyke, et al. Informational [Page 54] RFC 5022 MSCML September 2007

 +--------+--------+---------+---------------------------------------+
 | prompt | recurl | Mode    | Operation                             |
 +--------+--------+---------+---------------------------------------+
 | no     | no     | Invalid | Request fails.                        |
 | yes    | no     | Send    | Send fax from source specified in the |
 |        |        |         | <prompt> element or 'prompturl'       |
 |        |        |         | attribute. If there is a 'rmtid', it  |
 |        |        |         | MUST match the remote terminal's      |
 |        |        |         | identifier, or the request will fail. |
 | no     | yes    | Poll    | Send fax from source specified in the |
 |        |        |         | <prompt> element or 'prompturl'       |
 |        |        |         | attribute, assuming the remote        |
 |        |        |         | terminal specifies it can receive a   |
 |        |        |         | fax in its DIS message. If the remote |
 |        |        |         | terminal does not support reverse     |
 |        |        |         | polling, the request will fail. If    |
 |        |        |         | 'rmtid' is specified, it MUST match   |
 |        |        |         | remote terminal's identifier, or the  |
 |        |        |         | request will fail.                    |
 | yes    | yes    | TP      | Turnaround Poll (TP) mode. If the     |
 |        |        |         | remote terminal wishes to transmit,   |
 |        |        |         | the media server records the fax to   |
 |        |        |         | the target URL specified in 'recurl'. |
 |        |        |         | If the remote terminal wishes to      |
 |        |        |         | receive, the media server sends the   |
 |        |        |         | fax from the source URL contained in  |
 |        |        |         | <prompt> or 'prompturl'. If there is  |
 |        |        |         | a 'rmtid', it MUST match remote       |
 |        |        |         | terminal's identifier, or the send    |
 |        |        |         | request will fail. A receive          |
 |        |        |         | operation will still succeed,         |
 |        |        |         | however.                              |
 +--------+--------+---------+---------------------------------------+
                        Table 5: Fax Send Modes
 In send mode, the media server sends the fax.
 In remote poll mode, the client places a call on behalf of the media
 server.  The media server requests a fax transmission from the remote
 fax terminal.
 In turnaround poll mode, the media server will record a fax that the
 remote machine sends.  If the remote machine requests a transmission,
 then the media server will send the fax.
 When transmitting a fax, the media server will advertise that it can
 receive faxes in the DIS message.  Likewise, when receiving a fax,

Van Dyke, et al. Informational [Page 55] RFC 5022 MSCML September 2007

 the media server will advertise that it can send faxes in the DIS
 message.
 The media server MUST flush any quarantined digits when it receives a
 <faxplay> request.

10. MSCML Response Attributes and Elements

10.1. Mechanism

 The media server acknowledges receipt of a client MSCML request sent
 in a SIP INVITE by sending a response of either 200 OK or 415 Bad
 Media Type.  The media server responds with 415 when the SIP request
 contains a content type other than "application/sdp" or "application/
 mediaservercontrol+xml".
 The media server acknowledges receipt of a client MSCML request sent
 in a SIP INFO with a 200 OK or 415 Bad Media Type.  The media server
 responds with 415 if the INFO request contains a content type other
 than "application/mediaservercontrol+xml".
 The media server transports the MSCML <response> message in a SIP
 INFO request.
 If there is an error in the request or the media server cannot
 complete the request, the media server sends the <response> message
 very shortly after receiving the request.  If the request is able to
 proceed, the <response> contains final status information as
 described below.

10.2. Base <response> Attributes

 All MSCML responses have the basic attributes defined in the list
 below.
 Basic MSCML Response Attributes:
 o  id - optional, no default value: Echoes the client-defined ID
    contained in the request.
 o  request - required, no default value: Specifies the MSCML request
    type that generated the response.  Allowable values are
    "configure_conference", "configure_leg", "play", "playcollect",
    "playrecord", "stop", "faxplay", "faxrecord", and "managecontent".

Van Dyke, et al. Informational [Page 56] RFC 5022 MSCML September 2007

 o  code - required, no default value: The final status code for the
    request.  MSCML uses a subset of the status classes defined in RFC
    3261 [4].  In MSCML, 2XX responses indicate success, 4XX responses
    indicate client error, and 5XX responses indicate an error on the
    media server.  There are no 1XX, 3XX, or 6XX status codes in
    MSCML.
 o  text - required, no default value: The human readable reason
    phrase associated with the status code.
 Responses to <configure_conference> and <stop> requests contain only
 the attributes above.  MSCML responses to other requests MAY contain
 additional request-specific attributes and elements.  These are
 described in the following sections.

10.3. Response Attributes and Elements for <configure_leg>

 Responses to <configure_leg> requests have only the base response
 attributes defined in Section 10.2.  However, when the request
 contains a <configure_team> element, the response includes a <team>
 element describing the teammate configuration for that leg.  The
 attributes of the <team> element are shown in the list below.
 Attributes of <team>:
 o  id - required, no default value: The client-defined unique
    identifier for the conference leg.
 o  numteam - required, no default value: The number of team members
    for the leg.
 Additional information on each team member is conveyed by child
 <teammate> elements contained within <team>.  Each teammate is
 represented by a single element in the list.  The <teammate> element
 has a single attribute, as described below.
 Attributes of <teammate>:
 o  id - required, no default value: The client-defined unique
    identifier for the teammate leg.

10.4. Response Attributes and Elements for <play>

 In addition to the base response attributes defined in Section 10.2,
 responses to <play> requests have the additional attributes described
 in the list below.

Van Dyke, et al. Informational [Page 57] RFC 5022 MSCML September 2007

 MSCML Response Attributes for <play>:
 o  reason - optional, no default value: For requests that are not
    completed immediately, the "reason" attribute conveys additional
    information regarding why the command was completed.  Possible
    values are "stopped", indicating that an explicit or implicit
    <stop> request was received, and "EOF", indicating that the end of
    the specified sequence of URLs was reached.
 o  playduration - required, no default value: A time value (Section
    4.2.1) that returns the duration of the associated content
    playout.
 o  playoffset - required, no default value: A time value (Section
    4.2.1) that returns the time offset into the specified content
    sequence where play was terminated.  If the initial "offset" value
    in the sequence was "0", then "playduration" and "playoffset" are
    equal.  However, if the initial offset had some other value,
    "playoffset" serves as a bookmark for the client to resume play in
    a subsequent request.

10.4.1. Reporting Content Retrieval Errors

 If the associated request set "stoponerror=yes" in <prompt> and an
 error occurred while retrieving the specified content the response
 will include an <error_info> element detailing the problem.  This
 element contains the response information received from the remote
 content server.  The <error_info> element has the attributes
 described in the list below.
 Attributes of <error_info>:
 o  code - required, no default value: The status code returned by the
    remote content server.  For example, a web server might return 404
    to indicate that the requested content was not found.
 o  text - required, no default value: The human-readable reason
    phrase returned by the remote content server.  For example, the
    reason phrase "Not Found" would be returned if the requested
    content was not found.
 o  context - required, no default value: Contains the content URL
    that was being fetched when the retrieval error occurred.  This
    enables the client to know precisely which URL in a sequence
    caused the problem.
 An <error_info> element MAY be present in the response to any request
 that contains a child <prompt> element.

Van Dyke, et al. Informational [Page 58] RFC 5022 MSCML September 2007

10.5. Response Attributes and Elements for <playcollect>

 In addition to the base response attributes defined in Section 10.2,
 responses to <playcollect> requests have the additional attributes
 described in the list below.
 MSCML Response Attributes for <playcollect>:
 o  reason - optional, no default value: For requests that are not
    completed immediately, the "reason" attribute conveys additional
    information regarding why the command was completed.  Possible
    values are "stopped", indicating that an explicit or implicit
    <stop> request was received; "match", meaning that a DTMF grammar
    was matched; "timeout", indicating that no DTMF input was received
    before one of the collection timers expired; and "returnkey" or
    "escapekey", meaning the DTMF digit mapped to that key was
    detected and the return key or escape key terminated the
    operation, respectively.
 o  playduration - required, no default value: A time value (Section
    4.2.1) that returns the duration of the associated content
    playout.  If the caller barged the prompt, this value will reflect
    the play duration up to that event.
 o  playoffset - required, no default value: A time value (Section
    4.2.1) that returns the time offset into the specified content
    sequence where play was terminated.  If the initial "offset" value
    in the sequence was "0", then "playduration" and "playoffset" are
    equal.  However, if the initial offset had some other value,
    "playoffset" serves as a bookmark for the client to resume play in
    a subsequent request.  If the caller barged the prompt this value
    will reflect the time offset at which barge-in occurred.
 o  digits - required, no default value: Contains the collected DTMF
    input characters.  If no DTMF input was collected, this attribute
    is set to the empty string ("").
 o  name - required (see note), no default value: The client-defined
    name of the DTMF grammar that was matched.  Note: This attribute
    is required if the "name" attribute was set in the matching DTMF
    grammar.
 Responses to <playcollect> requests MAY include an <error_info>
 element, as described in Section 10.4.1.

Van Dyke, et al. Informational [Page 59] RFC 5022 MSCML September 2007

10.6. Response Attributes and Elements for <playrecord>

 In addition to the base response attributes defined in Section 10.2,
 responses to <playrecord> requests have the additional attributes
 described in the list below.
 o  reason - optional, no default value: For requests that are not
    completed immediately, the "reason" attribute conveys additional
    information regarding why the command was completed.  Possible
    values are "stopped", indicating that an explicit or implicit
    <stop> request was received; "digit", meaning that a DTMF digit
    was detected and that the prompt phase was barged; "init_silence",
    meaning the recording terminated because of no input;
    "end_silence", meaning that the recording was terminated because
    the "endsilence" timer elapsed; "max_duration", indicating that
    the maximum time for the recording was reached; "escapekey",
    indicating that the DTMF input mapped to "escapekey" was detected,
    thus terminating the recording; and "error", indicating a general
    operation failure.
 o  playduration - required, no default value: A time value (Section
    4.2.1) that returns the duration of the associated content
    playout.  If the caller barged the prompt, this value will reflect
    the play duration up to that event.
 o  playoffset - required, no default value: A time value (Section
    4.2.1) that returns the time offset into the specified content
    sequence where play was terminated.  If the initial "offset" value
    in the sequence was "0", then "playduration" and "playoffset" are
    equal.  However, if the initial offset had some other value,
    "playoffset" serves as a bookmark for the client to resume play in
    a subsequent request.  If the caller barged the prompt this value
    will reflect the time offset at which barge-in occurred.
 o  digits - required, no default value: Contains the DTMF digit that
    terminated the recording.  If no DTMF input was detected, this
    attribute is set to the empty string ("").
 o  reclength - required, no default value: The length of the recorded
    content, in bytes.
 o  recduration - required, no default value: A time value (Section
    4.2.1) indicating the elapsed duration of the recording.
 Responses to <playrecord> requests MAY include an <error_info>
 element, as described in Section 10.4.1.

Van Dyke, et al. Informational [Page 60] RFC 5022 MSCML September 2007

10.7. Response Attributes and Elements for <managecontent>

 Responses to <managecontent> requests have only the base response
 attributes defined in Section 10.2.  If a content transfer error
 occurs while executing the request the response will also contain an
 <error_info> element as described in Section 10.4.1.

10.8. Response Attributes and Elements for <faxplay> and <faxrecord>

 In addition to the base response attributes defined in Section 10.2,
 responses to <faxplay> and <faxrecord> requests have the additional
 attributes described in the list below.
 o  reason - required, no default value: For requests that are not
    completed immediately, the "reason" attribute conveys additional
    information regarding why the command was completed.  Possible
    values are "stopped", indicating that an explicit or implicit
    <stop> request was received; "complete", indicating successful
    completion, even if there were bad lines or minor negotiation
    problems (e.g., a DCN was received); "disconnect", meaning that
    the session was disconnected; and "notfax", indicating that no DIS
    or DCS was received on the connection.
 o  pages_received - required (see note), no default value: Indicates
    the number of fax pages received.  Note: This attribute is
    required if any pages were received.
 o  pages_sent - required (see note), no default value: Indicates the
    number of fax pages sent.  Note: This attribute is required if any
    pages were sent.
 o  faxcode - required, no default value: The value of the "faxcode"
    attribute is the binary-or of the bit patterns defined in Table 6.

Van Dyke, et al. Informational [Page 61] RFC 5022 MSCML September 2007

            +------+--------------------------------------+
            | Mask | description                          |
            +------+--------------------------------------+
            | 0    | Operation Failed                     |
            | 1    | Operation Succeeded                  |
            | 2    | Partial Success                      |
            | 4    | Image received and placed in recurl  |
            | 8    | Image sent from specified source URL |
            | 16   | rmtid did not match                  |
            | 32   | Error reading source URL             |
            | 64   | Error writing recurl                 |
            | 128  | Negotiation failure on send phase    |
            | 256  | Negotiation failure on receive phase |
            | 512  | Reserved                             |
            | 1024 | Irrecoverable IP packet loss         |
            | 2048 | Line errors in received image        |
            +------+--------------------------------------+
                         Table 6: Faxcode Mask
 Responses to <faxplay> and <faxrecord> requests MAY include an
 <error_info> element, as described in Section 10.4.1.

11. Formal Syntax

 The following syntax specification uses XML Schema as described in
 XML [7].

11.1. Schema

 <?xml version="1.0" encoding="UTF-8"?>
 <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
   elementFormDefault="qualified">
   <xs:element name="MediaServerControl">
     <xs:complexType>
       <xs:choice>
         <xs:element name="request">
           <xs:complexType>
             <xs:choice>
               <xs:element name="configure_conference"
                 type="configure_conferenceRequestType"/>
               <xs:element name="configure_leg"
                 type="configure_legRequestType"/>
               <xs:element name="play" type="playRequestType"/>
               <xs:element name="playcollect"
                 type="playcollectRequestType"/>
               <xs:element name="playrecord"
                 type="playrecordRequestType"/>

Van Dyke, et al. Informational [Page 62] RFC 5022 MSCML September 2007

               <xs:element name="managecontent"
                 type="managecontentRequestType"/>
               <xs:element name="faxplay"
                 type="faxRequestType"/>
               <xs:element name="faxrecord"
                 type="faxRequestType"/>
               <xs:element name="stop" type="stopRequestType"/>
             </xs:choice>
           </xs:complexType>
         </xs:element>
         <xs:element name="response" type="responseType"/>
         <xs:element name="notification">
           <xs:complexType>
             <xs:choice>
               <xs:element name="conference"
                 type="conferenceNotificationType"/>
               <xs:element name="keypress"
                 type="keypressNotificationType"/>
               <xs:element name="signal"
                 type="signalNotificationType"/>
             </xs:choice>
           </xs:complexType>
         </xs:element>
       </xs:choice>
       <xs:attribute name="version" use="required"/>
     </xs:complexType>
   </xs:element>
   <!-- Definitions for base and concrete MSCML requests -->
   <!-- and embedded types. -->
   <xs:complexType name="base_requestType" abstract="true">
     <xs:attribute name="id" type="xs:string"/>
   </xs:complexType>
   <xs:complexType name="playRequestType">
     <xs:complexContent>
       <xs:extension base="base_requestType">
         <xs:sequence>
           <xs:element name="prompt" type="promptType"
             minOccurs="0"/>
         </xs:sequence>
         <xs:attribute name="prompturl" type="xs:string"/>
         <xs:attribute name="offset" type="xs:string"/>
         <xs:attribute name="promptencoding" type="xs:string"/>
       </xs:extension>
     </xs:complexContent>
   </xs:complexType>
   <xs:complexType name="configure_conferenceRequestType">
     <xs:complexContent>
       <xs:extension base="base_requestType">

Van Dyke, et al. Informational [Page 63] RFC 5022 MSCML September 2007

         <xs:sequence>
           <xs:element name="subscribe"
             type="conference_eventsubscriptionType" minOccurs="0"/>
         </xs:sequence>
         <xs:attribute name="reservedtalkers"
           type="xs:positiveInteger"/>
         <xs:attribute name="reserveconfmedia" type="yesnoType"
           default="yes"/>
       </xs:extension>
     </xs:complexContent>
   </xs:complexType>
   <xs:complexType name="configure_legRequestType">
     <xs:complexContent>
       <xs:extension base="base_requestType">
         <xs:sequence>
           <xs:element name="inputgain" type="gainType"
             minOccurs="0"/>
           <xs:element name="outputgain" type="gainType"
             minOccurs="0"/>
           <xs:element name="configure_team"
             type="configure_teamType" minOccurs="0"/>
           <xs:element name="subscribe"
             type="leg_eventsubscriptionType" minOccurs="0"/>
         </xs:sequence>
         <xs:attribute name="type">
           <xs:simpleType>
             <xs:restriction base="xs:NMTOKEN">
               <xs:enumeration value="talker"/>
               <xs:enumeration value="listener"/>
             </xs:restriction>
           </xs:simpleType>
         </xs:attribute>
         <xs:attribute name="mixmode">
           <xs:simpleType>
             <xs:restriction base="xs:NMTOKEN">
               <xs:enumeration value="full"/>
               <xs:enumeration value="mute"/>
               <xs:enumeration value="preferred"/>
               <xs:enumeration value="parked"/>
               <xs:enumeration value="private"/>
             </xs:restriction>
           </xs:simpleType>
         </xs:attribute>
         <xs:attribute name="dtmfclamp" type="yesnoType"/>
         <xs:attribute name="toneclamp" type="yesnoType"/>
       </xs:extension>
     </xs:complexContent>
   </xs:complexType>

Van Dyke, et al. Informational [Page 64] RFC 5022 MSCML September 2007

   <xs:complexType name="configure_teamType">
     <xs:sequence>
       <xs:element name="teammate" type="teammateType" minOccurs="0"
         maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:attribute name="id" type="xs:string"/>
     <xs:attribute name="action" use="required">
       <xs:simpleType>
         <xs:restriction base="xs:string">
           <xs:enumeration value="add"/>
           <xs:enumeration value="delete"/>
           <xs:enumeration value="query"/>
           <xs:enumeration value="set"/>
         </xs:restriction>
       </xs:simpleType>
     </xs:attribute>
   </xs:complexType>
   <xs:complexType name="teammateType">
     <xs:attribute name="id" type="xs:string" use="required"/>
   </xs:complexType>
   <xs:complexType name="playcollectRequestType">
     <xs:complexContent>
       <xs:extension base="base_requestType">
         <xs:sequence>
           <xs:element name="prompt" type="promptType"
             minOccurs="0"/>
           <xs:element name="pattern" type="dtmfGrammarType"
             minOccurs="0"/>
         </xs:sequence>
         <xs:attribute name="prompturl" type="xs:string"/>
         <xs:attribute name="offset" type="xs:string"/>
         <xs:attribute name="barge" type="yesnoType" default="yes"/>
         <xs:attribute name="promptencoding" type="xs:string"/>
         <xs:attribute name="cleardigits" type="yesnoType"
           default="no"/>
         <xs:attribute name="maxdigits" type="xs:string"/>
         <xs:attribute name="firstdigittimer" type="xs:string"
           default="5000ms"/>
         <xs:attribute name="interdigittimer" type="xs:string"
           default="2000ms"/>
         <xs:attribute name="extradigittimer" type="xs:string"
           default="1000ms"/>
         <xs:attribute name="interdigitcriticaltimer"
           type="xs:string"/>
         <xs:attribute name="skipinterval" type="xs:string"
           default="6s"/>
         <xs:attribute name="ffkey" type="DTMFkeyType"/>
         <xs:attribute name="rwkey" type="DTMFkeyType"/>

Van Dyke, et al. Informational [Page 65] RFC 5022 MSCML September 2007

         <xs:attribute name="returnkey" type="DTMFkeyType"
           default="#"/>
         <xs:attribute name="escapekey" type="DTMFkeyType"
           default="*"/>
         <xs:attribute name="maskdigits" type="yesnoType"
           default="no"/>
       </xs:extension>
     </xs:complexContent>
   </xs:complexType>
   <xs:complexType name="playrecordRequestType">
     <xs:complexContent>
       <xs:extension base="base_requestType">
         <xs:sequence>
           <xs:element name="prompt" type="promptType"
             minOccurs="0"/>
         </xs:sequence>
         <xs:attribute name="prompturl" type="xs:string"/>
         <xs:attribute name="promptencoding" type="xs:string"/>
         <xs:attribute name="offset" type="xs:string" default="0"/>
         <xs:attribute name="barge" type="yesnoType" default="yes"/>
         <xs:attribute name="cleardigits" type="yesnoType"
           default="no"/>
         <xs:attribute name="escapekey" type="xs:string" default="*"/>
         <xs:attribute name="recurl" type="xs:string" use="required"/>
         <xs:attribute name="mode" default="overwrite">
           <xs:simpleType>
             <xs:restriction base="xs:NMTOKEN">
               <xs:enumeration value="append"/>
               <xs:enumeration value="overwrite"/>
             </xs:restriction>
           </xs:simpleType>
         </xs:attribute>
         <xs:attribute name="recencoding" type="xs:string"/>
         <xs:attribute name="initsilence" type="xs:string"/>
         <xs:attribute name="endsilence" type="xs:string"/>
         <xs:attribute name="duration" type="xs:string"/>
         <xs:attribute name="beep" type="yesnoType" default="yes"/>
         <xs:attribute name="recstopmask" type="xs:string"
           default="01234567890*#"/>
       </xs:extension>
     </xs:complexContent>
   </xs:complexType>
   <xs:complexType name="managecontentRequestType">
     <xs:complexContent>
       <xs:extension base="base_requestType">
         <xs:attribute name="fetchtimeout" type="xs:string"
           default="10000"/>
         <xs:attribute name="mimetype" type="xs:string"/>

Van Dyke, et al. Informational [Page 66] RFC 5022 MSCML September 2007

         <xs:attribute name="name" type="xs:string"/>
         <xs:attribute name="httpmethod">
           <xs:simpleType>
             <xs:restriction base="xs:NMTOKEN">
               <xs:enumeration value="put"/>
               <xs:enumeration value="post"/>
             </xs:restriction>
           </xs:simpleType>
         </xs:attribute>
         <xs:attribute name="action">
           <xs:simpleType>
             <xs:restriction base="xs:NMTOKEN">
               <xs:enumeration value="move"/>
               <xs:enumeration value="delete"/>
             </xs:restriction>
           </xs:simpleType>
         </xs:attribute>
         <xs:attribute name="dest" type="xs:string"/>
         <xs:attribute name="src" type="xs:string" use="required"/>
       </xs:extension>
     </xs:complexContent>
   </xs:complexType>
   <xs:complexType name="stopRequestType">
     <xs:complexContent>
       <xs:extension base="base_requestType"/>
     </xs:complexContent>
   </xs:complexType>
   <xs:complexType name="faxRequestType">
     <xs:complexContent>
       <xs:extension base="base_requestType">
         <xs:sequence>
           <xs:element name="prompt" type="promptType" minOccurs="0"/>
         </xs:sequence>
         <xs:attribute name="lclid" type="xs:string"/>
         <xs:attribute name="prompturl" type="xs:string"/>
         <xs:attribute name="recurl" type="xs:string"/>
         <xs:attribute name="rmtid" type="xs:string"/>
       </xs:extension>
     </xs:complexContent>
   </xs:complexType>
   <xs:complexType name="dtmfGrammarType">
     <xs:choice>
       <xs:element name="regex" type="dtmfPatternType"
         maxOccurs="unbounded"/>
       <xs:element name="mgcpdigitmap" type="dtmfPatternType"/>
       <xs:element name="megacodigitmap" type="dtmfPatternType"/>
     </xs:choice>
   </xs:complexType>

Van Dyke, et al. Informational [Page 67] RFC 5022 MSCML September 2007

   <xs:complexType name="dtmfPatternType">
     <xs:attribute name="value" type="xs:string" use="required"/>
     <xs:attribute name="name" type="xs:string"/>
   </xs:complexType>
   <!-- Definitions for base and concrete MSCML responses -->
   <!-- and embedded types. -->
   <xs:complexType name="base_responseType" abstract="true">
     <xs:attribute name="request" use="required">
       <xs:simpleType>
         <xs:restriction base="xs:NMTOKEN">
           <xs:enumeration value="configure_conference"/>
           <xs:enumeration value="configure_leg"/>
           <xs:enumeration value="play"/>
           <xs:enumeration value="playcollect"/>
           <xs:enumeration value="playrecord"/>
           <xs:enumeration value="managecontent"/>
           <xs:enumeration value="faxplay"/>
           <xs:enumeration value="faxrecord"/>
           <xs:enumeration value="stop"/>
         </xs:restriction>
       </xs:simpleType>
     </xs:attribute>
     <xs:attribute name="id" type="xs:string"/>
     <xs:attribute name="code" type="xs:string" use="required"/>
     <xs:attribute name="text" type="xs:string" use="required"/>
   </xs:complexType>
   <xs:complexType name="responseType">
     <xs:complexContent>
       <xs:extension base="base_responseType">
         <xs:sequence>
           <xs:element name="error_info"
             type="stoponerrorResponseType" minOccurs="0"/>
           <xs:element name="team" type="configure_teamResponseType"
             minOccurs="0"/>
         </xs:sequence>
         <xs:attribute name="reason" type="xs:string"/>
         <xs:attribute name="reclength" type="xs:string"/>
         <xs:attribute name="recduration" type="xs:string"/>
         <xs:attribute name="digits" type="xs:string"/>
         <xs:attribute name="name" type="xs:string"/>
         <xs:attribute name="playduration" type="xs:string"/>
         <xs:attribute name="playoffset" type="xs:string"/>
         <xs:attribute name="faxcode" type="xs:string"/>
         <xs:attribute name="pages_sent" type="xs:string"/>
         <xs:attribute name="pages_recv" type="xs:string"/>
       </xs:extension>
     </xs:complexContent>
   </xs:complexType>

Van Dyke, et al. Informational [Page 68] RFC 5022 MSCML September 2007

   <xs:complexType name="stoponerrorResponseType">
     <xs:attribute name="code" type="xs:string" use="required"/>
     <xs:attribute name="text" type="xs:string" use="required"/>
     <xs:attribute name="context" type="xs:string" use="required"/>
   </xs:complexType>
   <xs:complexType name="configure_teamResponseType">
     <xs:sequence>
       <xs:element name="teammate" type="teammateType" minOccurs="0"
         maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:attribute name="id" type="xs:string" use="required"/>
     <xs:attribute name="numteam" type="xs:integer" use="required"/>
   </xs:complexType>
   <!-- Definitions for MSCML event subscriptions and -->
   <!-- embedded types -->
   <xs:complexType name="conference_eventsubscriptionType">
     <xs:sequence>
       <xs:element name="events">
         <xs:complexType>
           <xs:sequence>
             <xs:element name="activetalkers"
               type="activetalkersSubscriptionType"/>
           </xs:sequence>
         </xs:complexType>
       </xs:element>
     </xs:sequence>
   </xs:complexType>
   <xs:complexType name="activetalkersSubscriptionType">
     <xs:attribute name="report" type="yesnoType" use="required"/>
     <xs:attribute name="interval" type="xs:string" default="60s"/>
   </xs:complexType>
   <xs:complexType name="leg_eventsubscriptionType">
     <xs:sequence>
       <xs:element name="events">
         <xs:complexType>
           <xs:sequence>
             <xs:element name="keypress"
               type="keypressSubscriptionType" minOccurs="0"
                 maxOccurs="1"/>
             <xs:element name="signal" type="signalSubscriptionType"
               minOccurs="0" maxOccurs="unbounded"/>
           </xs:sequence>
         </xs:complexType>
       </xs:element>
     </xs:sequence>
   </xs:complexType>
   <xs:complexType name="keypressSubscriptionType">
     <xs:attribute name="report" use="required">

Van Dyke, et al. Informational [Page 69] RFC 5022 MSCML September 2007

       <xs:simpleType>
         <xs:restriction base="xs:NMTOKEN">
           <xs:enumeration value="standard"/>
           <xs:enumeration value="long"/>
           <xs:enumeration value="both"/>
           <xs:enumeration value="none"/>
         </xs:restriction>
       </xs:simpleType>
     </xs:attribute>
     <xs:attribute name="maskdigits" type="yesnoType" default="no"/>
   </xs:complexType>
   <xs:complexType name="signalSubscriptionType">
     <xs:attribute name="type" type="xs:NMTOKEN" use="required"/>
     <xs:attribute name="report" type="yesnoType" use="required"/>
   </xs:complexType>
   <!-- Definitions for MSCML event notifications and -->
   <!-- embedded types. -->
   <xs:complexType name="conferenceNotificationType">
     <xs:sequence>
       <xs:element name="activetalkers"
         type="activetalkersNotificationType" minOccurs="0"/>
     </xs:sequence>
     <xs:attribute name="uniqueid" type="xs:string" use="required"/>
     <xs:attribute name="numtalkers" type="xs:string"
       use="required"/>
   </xs:complexType>
   <xs:complexType name="activetalkersNotificationType">
     <xs:sequence minOccurs="0">
       <xs:element name="talker" maxOccurs="unbounded">
         <xs:complexType>
           <xs:attribute name="callid" type="xs:string"
            use="required"/>
         </xs:complexType>
       </xs:element>
     </xs:sequence>
   </xs:complexType>
   <xs:complexType name="keypressNotificationType">
     <xs:sequence>
       <xs:element name="status" type="statusType"/>
     </xs:sequence>
     <xs:attribute name="digit" type="DTMFkeyType" use="required"/>
     <xs:attribute name="length" use="required">
       <xs:simpleType>
         <xs:restriction base="xs:NMTOKEN">
           <xs:enumeration value="standard"/>
           <xs:enumeration value="long"/>
         </xs:restriction>
       </xs:simpleType>

Van Dyke, et al. Informational [Page 70] RFC 5022 MSCML September 2007

     </xs:attribute>
     <xs:attribute name="method" use="required">
       <xs:simpleType>
         <xs:restriction base="xs:NMTOKEN">
           <xs:enumeration value="standard"/>
           <xs:enumeration value="long"/>
           <xs:enumeration value="double"/>
         </xs:restriction>
       </xs:simpleType>
     </xs:attribute>
     <xs:attribute name="interdigittime" type="xs:string"
       use="required"/>
   </xs:complexType>
   <xs:complexType name="statusType">
     <xs:attribute name="command" use="required">
       <xs:simpleType>
         <xs:restriction base="xs:string">
           <xs:enumeration value="idle"/>
           <xs:enumeration value="play"/>
           <xs:enumeration value="collect"/>
           <xs:enumeration value="record"/>
         </xs:restriction>
       </xs:simpleType>
     </xs:attribute>
     <xs:attribute name="duration" type="xs:string" use="required"/>
   </xs:complexType>
   <xs:complexType name="signalNotificationType">
     <xs:attribute name="type" use="required" fixed="busy"/>
   </xs:complexType>
   <!-- Definitions for miscellaneous embedded, helper data types -->
   <xs:complexType name="promptType">
     <xs:choice maxOccurs="unbounded">
       <xs:element name="audio" type="promptcontentType"/>
       <xs:element name="variable" type="spokenvariableType"/>
     </xs:choice>
     <xs:attribute name="locale" type="xs:string"/>
     <xs:attribute name="baseurl" type="xs:string"/>
     <xs:attribute name="stoponerror" type="yesnoType" default="no"/>
     <xs:attribute name="gain" type="xs:string" default="0"/>
     <xs:attribute name="gaindelta" type="xs:string" default="0"/>
     <xs:attribute name="rate" type="xs:string" default="0"/>
     <xs:attribute name="ratedelta" type="xs:string" default="0"/>
     <xs:attribute name="repeat" type="xs:string" default="1"/>
     <xs:attribute name="duration" type="xs:string"
       default="infinite"/>
     <xs:attribute name="offset" type="xs:string" default="0"/>
     <xs:attribute name="delay" type="xs:string" default="0"/>
   </xs:complexType>

Van Dyke, et al. Informational [Page 71] RFC 5022 MSCML September 2007

   <xs:complexType name="promptcontentType">
     <xs:attribute name="url" type="xs:string" use="required"/>
     <xs:attribute name="encoding" type="xs:string"/>
     <xs:attribute name="gain" type="xs:string" default="0"/>
     <xs:attribute name="gaindelta" type="xs:string" default="0"/>
     <xs:attribute name="rate" type="xs:string" default="0"/>
     <xs:attribute name="ratedelta" type="xs:string" default="0"/>
   </xs:complexType>
   <xs:complexType name="spokenvariableType">
     <xs:attribute name="type" use="required">
       <xs:simpleType>
         <xs:restriction base="xs:NMTOKEN">
           <xs:enumeration value="dat"/>
           <xs:enumeration value="dig"/>
           <xs:enumeration value="dur"/>
           <xs:enumeration value="mth"/>
           <xs:enumeration value="mny"/>
           <xs:enumeration value="num"/>
           <xs:enumeration value="sil"/>
           <xs:enumeration value="str"/>
           <xs:enumeration value="tme"/>
           <xs:enumeration value="wkd"/>
         </xs:restriction>
       </xs:simpleType>
     </xs:attribute>
     <xs:attribute name="subtype">
       <xs:simpleType>
         <xs:restriction base="xs:NMTOKEN">
           <xs:enumeration value="mdy"/>
           <xs:enumeration value="dmy"/>
           <xs:enumeration value="ymd"/>
           <xs:enumeration value="ndn"/>
           <xs:enumeration value="t12"/>
           <xs:enumeration value="t24"/>
           <xs:enumeration value="USD"/>
           <xs:enumeration value="gen"/>
           <xs:enumeration value="ndn"/>
           <xs:enumeration value="crd"/>
           <xs:enumeration value="ord"/>
         </xs:restriction>
       </xs:simpleType>
     </xs:attribute>
     <xs:attribute name="value" type="xs:string" use="required"/>
   </xs:complexType>
   <xs:simpleType name="yesnoType">
     <xs:restriction base="xs:NMTOKEN">
       <xs:enumeration value="yes"/>
       <xs:enumeration value="no"/>

Van Dyke, et al. Informational [Page 72] RFC 5022 MSCML September 2007

       <xs:enumeration value="1"/>
       <xs:enumeration value="0"/>
       <xs:enumeration value="true"/>
       <xs:enumeration value="false"/>
     </xs:restriction>
   </xs:simpleType>
   <xs:simpleType name="DTMFkeyType">
     <xs:restriction base="xs:string">
       <xs:pattern value="[0-9]"/>
       <xs:pattern value="[A-D]"/>
       <xs:pattern value="[a-d]"/>
       <xs:pattern value="#"/>
       <xs:pattern value="\*"/>
     </xs:restriction>
   </xs:simpleType>
   <xs:complexType name="gainType">
     <xs:choice>
       <xs:element name="auto" type="autogainType"/>
       <xs:element name="fixed" type="fixedgainType"/>
     </xs:choice>
   </xs:complexType>
   <xs:complexType name="autogainType">
     <xs:attribute name="startlevel" type="xs:string"/>
     <xs:attribute name="targetlevel" type="xs:string"/>
     <xs:attribute name="silencethreshold" type="xs:string"/>
   </xs:complexType>
   <xs:complexType name="fixedgainType">
     <xs:attribute name="level" type="xs:string"/>
   </xs:complexType>
 </xs:schema>

12. IANA Considerations

12.1. IANA Registration of MIME Media Type application/

    mediaservercontrol+xml
    MIME media type name: application
    MIME subtype name: mediaservercontrol+xml
    Required parameters: none
    Optional parameters: charset
    charset This parameter has identical semantics to the charset
       parameter of the "application/xml" media type, as specified in
       XML Media Types [8].
 Encoding considerations: See RFC 3023 [8].
 Interoperability considerations: See RFC 2023 [8] and RFC 5022.
 Published specification: RFC 5022

Van Dyke, et al. Informational [Page 73] RFC 5022 MSCML September 2007

 Applications that use this media type: Multimedia, enhanced
    conferencing and interactive applications.
 Personal and email address for further
    information: eburger@cantata.com [31]
 Intended usage: COMMON

13. Security Considerations

 Because media flows through a media server in a conference, the media
 server itself MUST protect the integrity, confidentiality, and
 security of the sessions.  It should not be possible for a conference
 participant, on her own behalf, to be able to "tap in" to another
 conference without proper authorization.
 Because conferencing is a high-value application, the media server
 SHOULD implement appropriate security measures.  This includes, but
 is not limited to, access lists for application servers.  That is,
 the media server only allows a select list of application or proxy
 servers to create conferences, to invite participants to sessions,
 etc.  Note that the mechanisms for such security, like private
 networks, shared certificates, MAC white/black lists, are beyond the
 scope of this document.
 Security concerns are one important reason MSCML limits requests with
 conference scope to a separate control leg per conference.  MSCML
 uses the simple, proven, Internet-scale security model of SIP to
 determine if a client is who they say they are (authentication) and
 if they are allowed to create and manipulate a conference.  However,
 the security model to enable a control leg to manipulate arbitrary
 conferences on the media server is extremely difficult.  Not only
 would one need to authenticate and authorize the basic conference
 primitives, but privacy considerations require policies for one
 client to access another client's conferences, even if the two
 clients are on the same host.  For example, if the media server
 allowed any control leg to control any conference, an authorized but
 unrelated client could maliciously attach itself to an existing
 session and record or tap the conversation without the participant's
 knowledge or consent.
 Participants give implicit authorization to their applications by
 virtue of the INVITE to the application.  However, there is no trust,
 explicit or implicit, between the users of one service and a distinct
 client of another service.
 All MSCML messages are sent within an INVITE-created SIP dialog.  As
 a result, it would be difficult for an entity other than the original
 requestor to interfere with an established MSCML session, as this
 would require detailed information on the dialog state.  This allows

Van Dyke, et al. Informational [Page 74] RFC 5022 MSCML September 2007

 multiple applications to utilize the resources of a single media
 server simultaneously without interfering with one another.
 Because of the sensitive nature of collected data, such as credit
 card numbers or other identifying information, the media server MUST
 support sips: and TLS.  Clients, who presumably know the value of the
 information they collect, as well as the privacy expectations of
 their users, are free to use clear text signaling or encrypted secure
 signaling, depending on the application's needs.  Likewise, the media
 server SHOULD support Secure Realtime Transport Protocol (SRTP) [9].
 Again, the clients are free to negotiate the appropriate level of
 media security.
 The media management facilities of MSCML, such as the <managecontent>
 (Section 8) request, assume a trust relationship between the media
 server and file server.  This scenario is similar to the one
 addressed by URLAUTH [20].  Namely, the media server is acting on
 behalf of a given user, yet the media server does not have
 credentials for that user.  One might be tempted to use the user:pass
 facility of the HTTP URI to offer per-user security, but that also
 requires that the media server be secure, as the media server would
 need to know the user credentials in a form that is easily
 compromised (clear text passwords).
 The IETF is investigating methods for providing per-user or per-
 instance authorization of third-party http writing, as is needed for
 other protocols as well, such as WEBDAV [21].  However, until that
 work is completed, media server implementations MUST be prepared to
 authenticate themselves to file and web servers using appropriate
 authentication means.  At a minimum, the media server MUST support
 HTTPS basic authentication.  Implementers should note that the media
 server will need to respond appropriately to whatever authentication
 mechanism the file server requires.
 As this is an XML markup, all the security considerations of RFC 3023
 [8] apply.

14. References

14.1. Normative References

 [1]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
       Levels", BCP 14, RFC 2119, March 1997.
 [2]   Burger, E., Van Dyke, J., and A. Spitzer, "Basic Network Media
       Services with SIP", RFC 4240, December 2005.
 [3]   Donovan, S., "The SIP INFO Method", RFC 2976, October 2000.

Van Dyke, et al. Informational [Page 75] RFC 5022 MSCML September 2007

 [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]   "Network call signalling protocol for the delivery of time-
       critical services over cable television networks using cable
       modems", ITU-T J.162, March 2001.
 [6]   Groves, C., Pantaleo, M., Anderson, T., and T. Taylor, "Gateway
       Control Protocol Version 1", RFC 3525, June 2003.
 [7]   Thompson, H., Beech, D., Maloney, M., and N. Mendelsohn, "XML
       Schema Part 1: Structures", W3C REC REC-xmlschema-1-20010502,
       May 2001.
 [8]   Murata, M., St. Laurent, S., and D. Kohn, "XML Media Types",
       RFC 3023, January 2001.
 [9]   Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
       Norrman, "The Secure Real-time Transport Protocol (SRTP)", RFC
       3711, March 2004.

14.2. Informative References

 [10]  Rosenberg, J., "A Framework for Conferencing with the Session
       Initiation Protocol (SIP)", RFC 4353, February 2006.
 [11]  Carter, J., Danielsen, P., Hunt, A., Ferrans, J., Lucas, B.,
       Porter, B., Rehor, K., Tryphonas, S., McGlashan, S., and D.
       Burnett, "Voice Extensible Markup Language (VoiceXML) Version
       2.0", W3C REC REC-voicexml20-20040316, March 2004.
 [12]  International Packet Communications Consortium, "IPCC Reference
       Architecture V2", June 2002.
 [13]  European Telecommunications Standards Institute, "Digital
       cellular telecommunications system (Phase 2+); Universal Mobile
       Telecommunications System (UMTS); IP Multimedia Subsystem
       (IMS); Stage 2 (3GPP TS 23.228 version 7.2.0 Release 7)",
       December 2005.
 [14]  Hollenbeck, S., Rose, M., and L. Masinter, "Guidelines for the
       Use of Extensible Markup Language (XML) within IETF Protocols",
       BCP 70, RFC 3470, January 2003.
 [15]  Jacobs, I., Lie, H., Bos, B., and C. Lilley, "Cascading Style
       Sheets, level 2 (CSS2) Specification", W3C REC REC-CSS2-
       19980512, May 1998.

Van Dyke, et al. Informational [Page 76] RFC 5022 MSCML September 2007

 [16]  Rosenberg, J., Schulzrinne, H., and O. Levin, "A Session
       Initiation Protocol (SIP) Event Package for Conference State",
       RFC 4575, August 2006.
 [17]  Cable Television Laboratories, Inc., "Audio Server Protocol",
       January 2005.
 [18]  "Procedures for document facsimile transmission in the general
       switched telephone network", Recommendation T.30, April 1999.
 [19]  "Procedures for real-time Group 3 facsimile communication over
       IP networks", Recommendation T.38, March 2002.
 [20]  Crispin, M., "Internet Message Access Protocol (IMAP) - URLAUTH
       Extension", RFC 4467, May 2006.
 [21]  Dusseault, L., Ed., "HTTP Extensions for Web Distributed
       Authoring and Versioning (WebDAV)", RFC 4918, June 2007.
 [22]  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.
 [23]  Burger, E. and M. Dolly, "A Session Initiation Protocol (SIP)
       Event Package for Key Press Stimulus (KPML)", RFC 4730,
       November 2006.
 [24]  Klensin, J., "Simple Mail Transfer Protocol", RFC 2821, April
       2001.
 [25]  Campbell, B., Ed., Mahy, R., Ed., and C. Jennings, Ed., "The
       Message Session Relay Protocol", Work in Progress, February
       2007.

URIs

 [26]  <http://www.ietf.org/html.charters/sip-charter.html>
 [27]  <http://www.ietf.org/html.charters/sipping-charter.html>
 [28]  <http://www.ietf.org/html.charters/mmusic.html>
 [29]  <http://www.ietf.org/html.charters/xcon-charter.html>
 [30]  <http://www.3gpp.org/ftp/Specs/html-info/23228.htm>
 [31]  <mailto:eburger@cantata.com>

Van Dyke, et al. Informational [Page 77] RFC 5022 MSCML September 2007

Appendix A. Regex Grammar Syntax

 The regular expression syntax used in MSCML is a telephony-oriented
 subset of POSIX Extended Regular Expressions (ERE) [22] termed Digit
 REGular EXpression (DRegex).  This syntax was first described in KPML
 [23].
 DRegex includes ordinary characters, special characters, bracket
 expressions, and interval expressions.  These entities are defined in
 the list below.
 . matches digits 0-9, *, #, and A-D (case insensitive)
 *  matches the * character
 #  matches the # character
 [character selector] matches any character in selector
 [range1-range2] matches any character in range from range1 to range2,
    inclusive
 x  matches any digit 0-9
 {m} matches m repetitions of the previous pattern
 {m,} matches m or more repetitions of the previous pattern
 {,n} matches at most n (including zero) repetitions of the previous
    pattern
 {m,n} at least m and at most n repetitions of the previous pattern
 L  the presence of 'L' in any regex expression causes the media
    server to enable "long" digit detection mode.  See Section 7.1 for
    the definition of "long" digits.
 Table 7 illustrates DRegex usage through examples.
     +--------------+--------------------------------------------+
     | Example      | Description                                |
     +--------------+--------------------------------------------+
     | 1            | Matches the digit 1                        |
     | [179]        | Matches 1, 7, or 9                         |
     | [2-9]        | Matches 2, 3, 4, 5, 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       |
     | .            | Matches 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B,|
     |              | C, D, #, *                                 |
     | *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                                  |
     +--------------+--------------------------------------------+
                       Table 7: DRegex Examples

Van Dyke, et al. Informational [Page 78] RFC 5022 MSCML September 2007

Appendix B. Contributors

 Jeff Van Dyke and Andy Spitzer did the concept, development,
 documentation, and execution for MSCML at SnowShore Networks, Inc.,
 which is now part of Cantata Technology, Inc.  Andy Spitzer's
 original work at The Telephone Connection, Inc., influenced the IVR
 implementation.  Mary Ann Leekley implemented the personalized mix
 feature and several other enhancements.
 Cliff Schornak of Commetrex and Jeff Van Dyke developed the facsimile
 service.
 Jai Cauvet, Rolando Herrero, Srinivas Motamarri, and Ashish Patel
 contributed greatly by testing MSCML.

Appendix C. Acknowledgements

 The following individuals provided valuable assistance in the
 direction, development, or debugging of MSCML:
 o  Brian Badger and Phil Crable from Verizon Business
 o  Stephane Bastien from BroadSoft
 o  Peter Danielsen of Lucent Technologies
 o  Kevin Flemming, formerly of SnowShore Networks, Inc.
 o  Wesley Hicks and Ravindra Kabre, formerly from Sonus Networks
 o  Jon Hinckley from SkyWave/Sestro
 o  Terence Lobo, formerly of SnowShore Networks, Inc.
 o  Kunal Nawale, formerly of SnowShore Networks, Inc.
 o  Edwina Nowicki, formerly of SnowShore Networks, Inc.
 o  Diana Rawlins and Sharadha Vijay, formerly of WorldCom
 o  Gaurav Srivastva and Subhash Verma from BayPackets
 o  Kevin Summers from Sonus Networks
 o  Tim Wong from at&t
 The authors would like to thank Cullen Jennings and Dan Wing from
 Cisco Systems for their helpful review comments.
 The authors would also like to thank Scotty Farber for applying her
 technical writing expertise to the documentation of MSCML.

Van Dyke, et al. Informational [Page 79] RFC 5022 MSCML September 2007

Authors' Addresses

 Jeff Van Dyke
 Cantata Technology, Inc.
 18 Keewaydin Dr.
 Salem, NH  03079
 USA
 EMail: jvandyke@cantata.com
 Eric Burger (editor)
 BEA Systems, Inc.
 USA
 Email: eburger@standardstrack.com
 URI: http://www.standardstrack.com
 Andy Spitzer
 Bluesocket Inc.
 10 North Avenue
 Burlington, MA  01803
 USA
 EMail: woof@pingtel.com

Van Dyke, et al. Informational [Page 80] RFC 5022 MSCML September 2007

Full Copyright Statement

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 This document is subject to the rights, licenses and restrictions
 contained in BCP 78 and at www.rfc-editor.org/copyright.html, and
 except as set forth therein, the authors retain all their rights.
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Van Dyke, et al. Informational [Page 81]

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