tech-invite   World Map     

3GPP     Specs     Glossaries     Architecture     IMS     UICC       IETF     RFCs     Groups     SIP     ABNFs       Search

RFC 3660

 
 
 

Basic Media Gateway Control Protocol (MGCP) Packages

Part 3 of 3, p. 43 to 64
Prev RFC Part

 


prevText      Top      Up      ToC       Page 43 
2.10.  RTP Package

   Package Name: R
   Version: 1

    -------------------------------------------------------------
   | Symbol  |   Definition                 |   R |   S Duration |
   |-------------------------------------------------------------|
   | co1     |   Continuity Tone (single    |   C | TO,C 3 sec.  |
   |         |     or return tone)          |     |              |
   | co2     |   Continuity Test (go tone,  |   C | TO,C 3 sec.  |
   |         |     in dual tone procedures) |     |              |
   | iu(..)  |   ICMP Unreachable           |   C |              |
   |         |     Received                 |     |              |
   | ji(..)  |   Jitter Buffer Size Changed |   C |              |
   | ma      |   Media Start                |   C |              |
   | oc      |   Operation Complete         |   x |              |
   | of      |   Operation Failure          |   x |              |
   | pl(..)  |   Packet Loss Exceeded       |   C |              |
   | qa      |   Quality Alert              |   C |              |
   | rto(..) |   RTP/RTCP Timeout           |   C |              |
   | sr      |   Sampling Rate Changed      |   C |              |
   | uc      |   Used Codec Changed         |   C |              |
    -------------------------------------------------------------

   Changes in event types: "co1" and "co2" signals changed from OO to
   TO.

   New events added to this package from the previously unversioned
   package: "iu", "rto", "ma".

   Note that default time-out values may be over-ridden by the Call
   Agent for any Time-Out signal defined in this package by a "to"
   signal parameter.  Refer to section 2 of this document, as well as
   [1] for details.

   The events in this package all refer to media streams (connections),
   i.e., they cannot be detected on an endpoint.  Furthermore, with the
   exception of the "iu" event, which is defined for any type of media,
   all other events in this package are defined for RTP media streams
   only (i.e., if they are used on connections that do not use RTP, the
   behavior is not defined).

   Signals requested (e.g., "co1" and "co2") must indicate the
   connection ID (e.g., "S: r/co1@connectionID").  An event may be
   requested for all existing connections using the "*" wildcard for the
   connectionID as described in [1].

Top      Up      ToC       Page 44 
   Example:

      R: r/uc@*    (request to detect uc on all connections) or

      R: r/uc@connectionID   (request to detect uc only on a specific
      connection)

   An event detected on a connection will include the connectionID,
   e.g.:

      O: r/uc@connectionID(15)

   Continuity tones (co1 and co2):
      These are the same as the events defined in the Trunk package,
      except in this case, they are only played over a network
      connection and the connectionID MUST be supplied (e.g., "s:
      r/co1@connectionID").  They can be used in conjunction with the
      Network LoopBack (netwloop) or Network Continuity Test (netwtest)
      modes to test the continuity of an RTP circuit.  However, in the
      case of testing IP continuity, a one-tone test is sufficient i.e.,
      generating and detecting "co1" at one end, with connection mode in
      network loopback mode at the other end.  Note that the test can
      also be done using telephone events rather than tones, i.e., event
      167 in RFC 2833 [33] corresponds to "co1".  In this case,
      connection requests are made with local connection options such
      as:

         L: a:PCMU;telephone-event,fmtp:"telephone-event 167"

      in order to request support for telephone event 167.  If both ends
      support the event, then the network loopback proceeds as usual,
      except that telephone events corresponding to the co1 tone are
      sent, as opposed to the co1 tone itself.

   ICMP Unreachable Received (iu):
      This event indicates that some number of ICMP unreachable packets
      [19] was received for this connection since an RQNT was received
      requesting this event.  This notification indicates that packets
      that were sent by the gateway on this connection either did not
      arrive at their destination or were not accepted (e.g., the port
      was closed).  When this event is requested, a single parameter
      with a decimal number from 1 to 255 may be included to indicate
      the number of ICMP un-reachable packets that must occur before the
      event is notified.  If no parameter is supplied, with the request
      then a default value of 3 is assumed.  This is a one-shot event in
      that once the event occurs, a further request is required in order
      to re-initiate counting.

Top      Up      ToC       Page 45 
      The observed event is parameterized with two parameters:

         *  The first parameter is the number of ICMP unreachable
            packets received (i.e., the same value that was included in
            the request - or the value 3, if the requested event was not
            parameterized)

         *  The second parameter is the error code indicated in the ICMP
            unreachable packet, e.g.:

               0 = net unreachable;

               1 = host unreachable;

               2 = protocol unreachable;

               3 = port unreachable;

               4 = fragmentation needed and DF set;

               5 = source route failed.

               etc.

      An example of a request might be as follows:

         RQNT 2001 ds/ds1-3/6@gw-o.whatever.net MGCP 1.0
         X: 0123456789B0
         R: r/iu@364823(N)(5)

      In this case, a notify will occur if 5 ICMP port unreachable
      packets are received as a result of RTP and/or RTCP packets being
      sent from this gateway on the connection with connection ID
      364823.

      The resulting NTFY with observed events might be as follows:

         NTFY 3002 ds/ds1-3/6@gw-o.whatever.net MGCP 1.0
         X: 0123456789B0
         O: r/iu@364823(5,3)

      The first parameter indicates 5 ICMP unreachable packets were
      received since the RQNT with this request was sent.  The second
      parameter ("3") specifies the reason, which in this case, is "port
      unreachable".

Top      Up      ToC       Page 46 
   Jitter Buffer Size Changed (ji):
      This event is only included here to maintain compatibility with
      the previous version of this package.  This event is used to
      indicate that the gateway has made an adjustment to the depth of
      the jitter buffer.  The syntax for requesting notification is
      "ji", which tells the media gateway that the controller wants
      notification of any jitter buffer size changes.  The syntax for
      notification from the media gateway to the controller is
      "JI(####)", where the #### is a decimal number from 1 to 65536,
      indicating the new size of the jitter buffer in milliseconds.

   Media Start (ma):
      The media start event occurs on a connection when the first valid
      RTP media packet is received on the connection.  This event can be
      used to synchronize a local signal, e.g., ringback, with the
      arrival of media from the other party.

      The event is detected on a connection.  If no connection is
      specified, the event applies to all connections for the endpoint,
      regardless of when the connections are created (i.e., if a
      connection is not specified, the event will occur when the first
      valid RTP packet arrives on any one of the connections on that
      endpoint).

   Operation complete (oc):
      This is the standard definition of operation complete [1].

   Operation failure (of):
      This is the standard definition of operation failure [1].

   Packet Loss Exceeded (pl):
      Packet loss rate exceeds the threshold of the specified decimal
      number (with a range of 1 to 100,000) of packets per 100,000
      packets, where the packet loss number is indicated in parenthesis.
      For example, PL(10) is a drop rate of 10 in 100,000 packets.  This
      event is requested with a parameter indicating at what packet loss
      rate the Call Agent wishes to be reported.  If the packet loss
      exceeds that value, the event is reported with that same
      parameter.  The event is only reported once when the packet loss
      threshold is exceeded.  Once reported, a following request will
      re-initiate packet loss measurements and report when the threshold
      is exceeded again.

   Quality alert (qa):
      The packet loss rate or the combination of delay and jitter
      exceeding a quality threshold.  The quality thresholds for delay,
      jitter and packet loss rate are provisioned values.

Top      Up      ToC       Page 47 
   RTP/RTCP Timeout (rto(<timeout>,st=<start-time>)):
      This event indicates that neither RTP nor RTCP packets have been
      received on this connection for a period of time equal to the
      <timeout> value (in seconds).  The timeout value can be supplied
      as a decimal number from 1 to 65535 in the parameter when the
      request is made.  The <timeout> parameter will be supplied in
      ObservedEvents when the event is reported - it then simply repeats
      the value used.  If an RTP or RTCP packet is received before the
      timer expires, then the timer is reset and re-started.  The event
      will only be generated if the timer expires without an RTP or RTCP
      packet arriving on the specified connection during the specified
      period of time.  Note that if the event is requested without the
      <timeout> parameter, then a default timeout of 60 seconds is
      assumed.  The <timeout> value will still be reported in
      ObservedEvents, even if no timeout value was indicated in the
      request (the default value will be indicated in that case).  This
      is a one-shot event in that once the event occurs, a further
      request is required in order to re-initialize the timer.

      Another optional <start-time> parameter may also be included.
      This is used to indicate when the timer starts.  It can have one
      of the following values:

         *  "im" for immediate i.e., the timer starts as soon as the
            request is received.  This is the default.

         *  "ra" to indicate that the timer should start only after an
            RTCP packet has been received from the other end (i.e., the
            timer will be initiated when the first RTCP packet is
            received after the request is made).  Note that in the case
            where the other end does not support RTCP, the timer will
            never be initiated.

      Note that either the <timeout> or <start-time> may be included in
      the request, but only the <timeout> value is included in the
      report.

      An example of a request might be as follows:

         RQNT 2001 ds/ds1-3/6@gw-o.whatever.net MGCP 1.0
         X: 0123456789B0
         R: r/rto@364823(N)(120,st=im)

      In this case, a notify will occur if there is a period of time
      when no RTP or RTCP packets have been received on connection
      364823 for 120 seconds.

Top      Up      ToC       Page 48 
      The resulting NTFY with observed events would be as follows:

         NTFY 3002 ds/ds1-3/6@gw-o.whatever.net MGCP 1.0
         X: 0123456789B0
         O: r/rto@364823(120)

   Sampling Rate Changed (sr):
      This event is only included here to maintain compatibility with
      the previous version of this package.  This event indicates that
      the packetization period changed to some decimal number in
      milliseconds enclosed in parenthesis, as in SR(20).

   Used Codec Changed (uc):
      This event is only included here to maintain compatibility with
      the previous version of this package.  This event is requested
      without a parameter, but when reported, the hexadecimal payload
      type is enclosed in parenthesis, as in UC(8), to indicate the
      codec was changed to PCM A-law.  Codec Numbers are specified in
      RFC 3551 [26], or in a new definition of the audio profiles for
      RTP that replaces this RFC.

2.11.  Resource Reservation Package

   Package Name: RES
   Version: 0

2.11.1.  Description

   The "RES" package provides local connection option support for
   resource reservations as well as an event to indicate reservation
   loss.

   A number of LocalConnectionOption parameters are used in doing
   resource reservations: "reservation request", "reservation
   direction", "reservation confirmation" and "resource sharing".

   Reservation Request LocalConnectionOption: The gateways can be
   instructed to perform a reservation on a given connection using RSVP.
   When a reservation is needed, the Call Agent will specify the
   reservation profile that should be used, which is either "controlled
   load" or "guaranteed service".  The absence of reservation can be
   indicated by asking for the "best effort" service, which is the
   default value for this parameter.

   Whether or not RSVP will be done is dependent on whether the
   reservation request LocalConnectionOption parameter has been included
   in a connection request for this connection (with either "controlled
   load" or "guaranteed service" indicated).  If a modify connection

Top      Up      ToC       Page 49 
   (MDCX) request requires a change in the reservation and the
   "reservation request" parameter is not included in the
   LocalConnectionOptions, but was included in the
   LocalConnectionOptions for a previous connection request for that
   connection, then the "reservation request" value defaults to its
   previously saved value for that connection.  If a modify connection
   (MDCX) request explicitly contains a "reservation request",
   indicating a request for "best effort" for a connection that has an
   existing reservation, the existing reservation will be torn down.

   Reservation Direction LocalConnectionOption:
      When reservation has been requested on a connection, the gateway
      will examine the reservation direction LocalConnectionOption
      parameter to determine the direction that the reservations require
      and do the following:

         *  Start emitting RSVP "PATH" messages if the reservation
            direction LocalConnectionOptions parameter specified "send-
            only" or "send-receive".

         *  Start emitting RSVP "RESV" messages as soon as it receives
            "PATH" messages if the reservation direction parameter
            specified "receive-only" or "send-receive".

      If an RSVP reservation is requested, but the reservation direction
      LocalConnectionOption parameter is missing, the reservation
      direction defaults to the previously saved value of the
      reservation direction parameter for that connection.  If there was
      no previous reservation direction parameter for that connection,
      the value is deduced from the connection mode.  That is:

         *  Start emitting RSVP "PATH" messages if the connection is in
            "send-only", "send-receive", "conference", "network loop
            back" or "network continuity test" mode (if a remote
            connection descriptor has been received).

         *  Start emitting RSVP "RESV" messages as soon as it receives
            "PATH" messages if the connection is in "receive-only",
            "send-receive", "conference", "network loop back" or
            "network continuity test" mode.

   Reservation Confirmation LocalConnectionOption:
      Another LocalConnectionOption parameter for RSVP reservations is
      the reservation confirmation parameter, which determines what the
      resource reservation pre-condition (see [1]) is for acknowledging
      a successful connection request:

Top      Up      ToC       Page 50 
         *  If the reservation confirmation parameter is set to "none",
            the gateway will "Ack" the connection request without
            waiting for reservation completion.  This is the default
            behavior.

         *  If the "reservation confirmation" parameter is set to
            "send-only", the gateway will "Ack" when the PATH message
            has been sent and the corresponding RESV is received to
            indicate successful reservation in the send direction.

         *  If the "reservation confirmation" parameter is set to
            "receive-only", the gateway will "Ack" when reservation
            confirm for a reservation has been received.

         *  If the reservation confirmation parameter is set to "send-
            receive", the gateway will "Ack" only after the PATH message
            has been sent and the corresponding RESV has been received
            for send direction, and reservation confirm has been
            received for the receive direction.

   Note that:

      Values "receive-only" and "send-receive" are triggers for the
      gateway to request reservation confirm (RESVCONF) when it sends
      out the RESV.

      Pre-conditions SHOULD only be added for the direction(s) for which
      resource reservations have been requested.  If a direction is
      added as a pre-condition, and that direction was not requested in
      the resource reservation, the direction MUST simply be ignored as
      a pre-condition.

      In this approach, resource reservation success is the pre-
      condition to final acknowledgement of the connection request.  If
      the reservation fails, the connection request also fails (error
      code 404 - insufficient bandwidth) - as will any other part of the
      transaction, e.g., a notification request included as part of the
      connection request.  A typical example of this would be a request
      to ring the phone and look for off-hook, included with the
      connection request.  If the reservation fails, the phone will not
      ring.  Similarly, if the phone is already off-hook, the command
      fails and there will be no resource reservation.

      A provisional response SHOULD be provided if confirmation is
      expected to occur outside the normal retry timers and in fact a
      provisional response MUST be provided if the reservation
      confirmation parameter has value "send-receive" (without a
      provisional response, SDP information cannot be returned until the

Top      Up      ToC       Page 51 
      final "Ack" which will not occur until the reservation is
      complete.  This can result in a deadlock since the SDP information
      typically needs to be passed to the other end in order for it to
      initiate the RSVP PATH message in the other direction).  The SDP
      information and connectionID MUST be included in both the
      provisional response and the final response.  Note that in order
      to ensure rapid detection of a lost final response, final
      responses issued after provisional responses for a transaction
      SHALL be acknowledged, i.e., they SHALL include an empty
      "ResponseAck" parameter in the final response (see [1]).

      If the transaction time is outside the expected bounds (time
      T-HIST - see the section on provisional responses in [1]), error
      code 406 (transaction timeout) SHOULD be returned.

      Also note that if the reservation confirmation parameter is
      omitted, the value of the reservation confirmation parameter
      defaults to its previously saved value.  If there is no previously
      saved value for the reservation confirmation parameter, or the
      reservation confirmation parameter has the value "none", then
      successful resource reservation is not a pre-condition to
      providing an acknowledgement to the connection request (i.e., the
      gateway can "Ack" right away without waiting for the reservation
      to complete and a provisional response will not be necessary).

   Resource Sharing LocalConnectionOption:
      It may be possible to share network resources across multiple
      connections.  An example is a call-waiting scenario, where only
      one connection will ever be active at a time.  In a 3-way calling
      scenario with a similar set of connections, sharing is not
      possible.  Only the Call Agent knows what may be possible,
      depending on the feature that is being invoked.

      In order to allow the Call Agent to indicate that sharing is
      possible, a resource sharing LocalConnectionOption parameter is
      introduced.  This parameter can have one of the following values:

         *  A value "$" can be specified where $ refers to "this
            connection".  This value is used when doing a create
            connection and indicates the intent to share resources with
            this connection.

         *  A connection ID can be specified which indicates that this
            is a request to share resources with the connection having
            this connection ID (allowing multiple connections to share
            resources with the connection indicated).

Top      Up      ToC       Page 52 
         *  The value can be empty, which indicates a request to no
            longer share the resources of this connection with other
            connections.

      In the case of a CRCX, the default value for the resource sharing
      local connection option is empty, and for an MDCX, the default
      value is its current value.

   The RSVP filters will be deduced from the characteristics of the
   connection.  The RSVP resource profiles will be deduced from the
   connection's bandwidth and packetization period.

   Note that if RSVP is used with PacketCable Dynamic Quality of Service
   [35], then the parameters in NCS [36] would be used instead of the
   reservation direction, confirmation and reservation sharing
   parameters described here.

2.11.2.  Parameter Encoding

   The Local Connection Options for the "RES" package consist of the
   following:

      *  The resource reservation parameter, encoded as the keyword "r",
         followed by a colon and the value "g" (guaranteed service),
         "cl" (controlled load) or "be" (best effort).

      *  The reservation direction parameter, encoded as the keyword
         "r-dir" followed by a colon and the value "sendonly",
         "recvonly" or "sendrecv".

      *  The reservation confirmation parameter, encoded as the keyword
         "r-cnf" followed by a colon and the value "none", "sendonly",
         "recvonly" or "sendrecv".

      *  The resource sharing parameter, encoded as the keyword "r-sh"
         followed by a colon and either:

            *  The wild-card character "$" indicating this connection,
               indicating future plans to share resources with this
               connection, or

            *  A connection ID, indicating a request to share resources
               with the connection having the specified connection ID
               (and all other connections sharing resources with that
               connection), or

Top      Up      ToC       Page 53 
            *  An empty value (i.e., "r-sh:" with no value indicated),
               indicating a request to no longer share the resources of
               this connection with other connections

   Note that normally local connection options that are associated with
   a package have the package prefix included as per the package
   extension rules in [1].  The local connection options in the "RES"
   package are exceptions.  The package prefix is not included in the
   case of the "RES" package because it was created before the extension
   rules in [1] were defined.

2.11.3.  Events

   The following events are included as part of the resource reservation
   package:

    ------------------------------------------------------
   | Symbol  | Definition           |   R |   S  Duration |
   |------------------------------------------------------|
   |  re     | Resource Error       |   C |               |
   |  rl     | Resource Lost        |   C |               |
    ------------------------------------------------------

   Resource Error (re):
      This is an indication that an error in the resource reservation
      occurred during the life of the connection.  This event is not
      requested with a parameter, but is reported with a parameter (see
      possible values below).  This event may or may not indicate the
      permanent loss of the reservation (i.e., any error associated with
      the reservation whether permanent or temporary will be reported).
      If requested on an endpoint (without specifying the connection
      ID), the request refers to all present and future connections on
      that endpoint.  When reported, the connectionID is always supplied
      along with a reason for the error indicated as a parameter.  One
      of the following possible reasons for loss MUST be included as the
      parameter when the event is reported:

         -  "resverr" is used to indicate that a ResvErr message was
            received.

         -  "patherr" is used to indicate that a PathErr message was
            received.

         -  "other"

      In addition to a parameter indicating one of the reasons above,
      additional information on the type of error MAY be included as a
      second parameter in the form of a quoted string.

Top      Up      ToC       Page 54 
      Example report might include:

         O: res/rl@0A3F58(resverr)

      or

         O: res/rl@0A3F58(resverr, "some additional commentary")

      Note that this event will not be reported if an error occurs while
      a resource reservation is initially being set up (i.e., the event
      was only reported as a result of an error that occurred after the
      reservation was set up).

   Resource Lost (rl):
      Loss of reservation during the life of a connection can be
      reported by using the "rl" event.  This event is not requested
      with a parameter, but is reported with a parameter (see below for
      possible values).  If requested on an endpoint (without specifying
      the connection ID), the request refers to all present and future
      connections on that endpoint.

      When reported, the connectionID is always supplied along with a
      reason for the loss indicated as a parameter.  One of the
      following possible reasons for loss MUST be supplied as the
      parameter when the event is reported:

         -  "resvtear" indicating that the reservation loss was
            indicated by ResvTear message.

         -  "pathtear" indicating that the reservation loss was
            indicated by PathTear message.

         -  "other"

      In addition to a parameter indicating one of the reasons above,
      additional information on the type of error MAY be included as a
      second parameter in the form of a quoted string.

      Example report might include:

         O: res/rl@0A3F58(ResvTear)

      or

         O: res/rl@0A3F58(ResvTear, "some other commentary")

Top      Up      ToC       Page 55 
      Note that this event will not be reported if an error occurs while
      a resource reservation is initially being set up (i.e., the event
      is only reported if the reservation was lost after it was
      initially set up).

2.12.  Announcement Server Package

   Package Name: A
   Version: 1

    ---------------------------------------------------------------
   | Symbol         | Definition           |   R |  S     Duration |
   |---------------------------------------------------------------|
   | ann(url)       | Play an Announcement |     |  TO, C variable |
   | oc             | Operation Complete   |   x |                 |
   | of             | Operation Failure    |   x |                 |
    ---------------------------------------------------------------

   Changes from the previous version: change to conform to standard
   reporting of operation failure and operation complete events.

   The announcement signal is qualified by a URL name:

      S: ann(http://scripts.example.net/all-lines-busy.au)

   The URL name MAY be followed by a list of initial parameters,
   separated by commas.  However, standard parameters are not included
   as part of this package definition (Note: use of additional
   parameters is optional and would result in a proprietary interface).

   The gateway SHOULD support one or more standard URL schemes such as:

      *  file, http, ftp (RFC 1738 [28]), which indicate where the audio
         file is located (where to load the file from before playing the
         audio file on the gateway).

      *  RTSP URL (section 3.2 of RFC 2326 [29]), which in this case
         allows the media gateway to directly initiate playing of the
         announcement via an RTSP server.

   The pre-condition for a successful response (return code of "200") is
   correct syntax and capability (support is available for this
   request).  Standard MGCP return codes apply in the case of failure.
   Further indications of failure are provided in the operation failure
   event as a comment after the name of the failed event in the form of
   a quoted string.

Top      Up      ToC       Page 56 
   If the announcement cannot be played out for a reason determined
   after a successful response to the request has been provided, an
   operation failure event will be returned.  The failure MAY be
   explained by some commentary (in the form of a quoted string), as in:

      O: a/of(a/ann,"file not found")

   The "operation complete" event will be detected when the announcement
   is played out.

      O: a/oc(a/ann)

2.13.  Script Package

   Package Name: Script
   Version: 1

    -----------------------------------------------------------------
   | Symbol       |   Definition              | R |  S  |   Duration |
   |-----------------------------------------------------------------|
   | ir(..)        | Intermediate Results/Req.| x |  BR |            |
   | java(url,...) | Load & Run java script   |   |  TO |   variable |
   | oc            | operation complete       | x |     |            |
   | of            | operation failure        | x |     |            |
   | perl(url,...) | Load & Run perl script   |   |  TO |   variable |
   | tcl(url,...)  | Load & Run TCL script    |   |  TO |   variable |
   | vxml(url,...) | Load & Run VXML doc.     |   |  TO |   variable |
   | xml(url,...)  | Load & Run XML script    |   |  TO |   variable |
    -----------------------------------------------------------------

   Changes from the previous version of the package: "vxml" was added as
   a language type for loading and running VXML documents; change to
   conform with standard reporting of operation failure and operation
   complete events; addition of "ir" event.

   The current definition defines keywords for the most common
   languages.  More languages may be defined in later versions of this
   package.

   The "signal" specifying the scripting language is parameterized with
   a URL indicating the location of the script.  The URL parameter MAY
   be optionally followed by a comma-separated list of arguments as
   initial parameters to use in running the script.  URL schemes may
   include file ftp, or http schemes with syntax according to RFC 2396
   [30].  As an example:

      S: script/vxml(ftp://ftp.example.net/credit-card.vxml,arg1,arg2,
                                                              ...,argn)

Top      Up      ToC       Page 57 
   The argument list "arg1,arg2,...,argn" is passed to the
   script/document as a list of initial parameters.

   The pre-condition for a successful response (return code of "200") is
   correct syntax and capability (support is available for this
   request).  Standard MGCP return codes apply in the case of failure.
   Some further (non-application/script specific) failure indications
   MAY be provided in the operation failure event as a comment in the
   form of a quoted string following the name of the failed event.

   Example

      O: script/of(script/vxml,"file not found")

   The script produces an output, which consists of one or several text
   strings, separated by commas.  This provides the return-status of the
   script as well as return parameters (if there are any)

      O: script/oc(script/vxml,return-status=<status>,
                        name1=value1,name2=value2,...)

   where <status> can have one of the values "success" or "failure".
   This is then followed by output parameters as a comma-separated list
   of name-value pairs.

   Intermediate Result/Request (ir(<params>)):
      This provides a way for:

         *  The script to inform the Call Agent of intermediate results
            (e.g., a case where it is important because of timing
            concerns to inform the Call Agent prior to operation
            complete).

         *  The script to request some information from the Call Agent.

         *  The Call Agent to inform the script of some event or
            information that may be important for the operation of the
            script (in this case "ir" is used as a signal).

      Parameters (i.e., <params>) SHOULD be a comma-separated list of
      name-value pairs e.g., ir(name1=value1,name2=value2,..).  The Call
      Agent MAY include event parameters when it requests this event, in
      which case, the MGCP syntax requirements require that the action
      be specified (e.g., "R: ir(N)(nam1=value1,name2=value2,..)").

      If the Call Agent requests "ir" as a signal, at least one
      parameter MUST be provided.

Top      Up      ToC       Page 58 
      When requesting the "ir" signal, the Call Agent MUST also repeat
      the original script signal.  This is in order to be consistent
      with the semantics of TO signals in MGCP (i.e., if the original
      "script" signal is not included, then the signal/script will be
      stopped).  The only problem with this is that there is a possible
      race condition in which a request to send an "ir" signal could
      occur just as the script stopped.  In order to avoid this
      confusion, the following is RECOMMENDED: when the script signal is
      included with an "ir" signal, include a parameter (of the script
      signal) to indicate that this is not a new instance of the script
      i.e., if there is no script executing at the present time do not
      start executing a new one.

      The "ir" signal is only associated with an executing script.  If
      none are running when a request for the event/signal is made, or
      if a new script request is not included with the request, then the
      "ir" signal/event will not be executed (i.e., the "ir" event with
      its parameters is passed to an existing script for parsing and
      execution and is considered opaque as far as MGCP as concerned.
      If no such script exists, response code "800" will be returned,
      indicating that the script is not executing).

   The following response code is associated with this package:

      Code    Text                 Explanation

      800     Script not           Request for "ir" signal or event
              Executing            but no script is executing at the
                                   time the request was received.

      Note that package specific error codes include the package name
      following the error code.  For example, if error code 800 occurs
      in response to a request with a transaction ID of 1001, it would
      be sent as:

         800 1001 /SCRIPT

Top      Up      ToC       Page 59 
3.  IANA Considerations

   The following packages and their versions have been registered with
   IANA as per the instructions in [1].

      Package Title         Name     Version
      -------------         ----     -------
      Announcement           A        1
      DTMF                   D        1
      Digit Map Extension    DM1      0
      Media Format           FM       0
      Generic                G        1
      Handset                H        1
      Line                   L        1
      RTP                    R        1
      Resource Reservation   RES      0
      Script                 SCRIPT   1
      Supplementary Tones    SST      0
      Signal List            SL       0
      Trunk                  T        1

   The following extension digit map letter has been registered with
   IANA:

      Package Letter
      ------- ------
      DM1     P

   The following Local Connections have been registered with IANA:

      Field                       Name
      -------                     -----
      Media Format                fmtp
      Reservation Confirmation    r-cnf
      Reservation Direction       r-dir
      Resource Sharing            r-sh

4.  Security Considerations

   The MGCP packages contained in this document do not require any
   further security considerations beyond those indicated in the base
   MGCP specification [1].

5.  Acknowledgements

   Special thanks are due to the authors of the original MGCP 1.0
   specification: Mauricio Arango, Andrew Dugan, Isaac Elliott,
   Christian Huitema, and Scott Picket.

Top      Up      ToC       Page 60 
   Thanks also to the reviewers of this document, including but not
   limited to: Jerry Kamitses, Sonus Networks; Dave Auerbach, Dan Wing,
   Cisco Systems; Ed Guy, EMC Software; Martin Wakley, Nortel Networks.

6.  References

6.1.  Normative References

   [1]  Andreasen, F. and B. Foster, "Media Gateway Control Protocol
        (MGCP) Version 1.0", RFC 3435, January 2003.

   [2]  Bellcore, "LSSGR: Switching System Generic Requirements for Call
        Control Using the Integrated Services Digital Network User Part
        (ISDNUP)", GR-317-CORE, Issue 2, December 1997.

   [3]  ITU-T, "Telephone User Part Signaling Procedures", ITU-T Q.724,
        November 1988.

   [4]  ANSI, "OAM&P - Terminating Test Line Access and Capabilities",
        T1.207-2000.

   [5]  Bellcore, "Notes on the Network", Special Report SR-2275, Issue
        3, December 1997.

   [6]  Bellcore, "Call Processing" GR-505-CORE, Issue 1, December 1997.

   [7]  Bellcore, "LSSGR: Signaling for Analog Interfaces", GR-506-CORE,
        Issue 1, June 1996.

   [8]  ITU-T, "Technical Characteristics of Tones for the Telephone
        Service", ITU-T E.180, March 1998.

   [9]  ITU-T, "Various Tones Used in National Networks", ITU-T E.180,
        Supplement 2, January 1994.

   [10] ITU-T, "Applications of Tones and Recorded Announcements in
        Telephone Services", ITU-T E.182, March 1998.

   [11] Bellcore, "Call Forwarding Sub-Features FSD-01-02-1450, GR-586,
        Issue 1, June 2000.

   [12] Bellcore, "CPE Compatibility Considerations for the Voiceband
        Data Transmission Interface", SR-TSV-002476, December 1992.

   [13] Bellcore, "LSSGR: Visual Message Waiting Indicator Generic
        Requirements (FSD 01-02-2000)", GR-1401, Issue 01, June 2000.

Top      Up      ToC       Page 61 
   [14] Bellcore, "LSSGR Voiceband Data Transmission Interface", Section
        6.6, GR-30-CORE, Issue 02, December 1998.

   [15] Handley, M. and V. Jacobson, "SDP: Session Description
        Protocol", RFC 2327, April 1998.

   [16] Bellcore, "LSSGR: Call Waiting, FSD 01-02-1201", GR-571, Issue
        01, June 2000.

   [17] Bellcore, "LSSGR: Verification Connections FSD 25-05-0903", GR-
        531-CORE, Issue 1, June 2000.

   [18] Bellcore, " LSSGR: CLASS Feature: Calling Identity Delivery on
        Call Waiting, FSD 01-02-1090, GR-575, Issue 01, June 2000.

   [19] Postel, J., "Internet Control Message Protocol", STD 5, RFC 792,
        September 1981.

   [20] Bellcore, "Class Feature: Screen Editing (FSD 30-28-0000)", GR-
        220, Issue 2, April 2002.

   [21] ITU-T, "Procedure for document facsimile transmission in the
        general switched telephone network", ITU-T T.30, April 1999.

   [22] ITU-T, "300 bits per second duplex modem standardized for use in
        the general switched telephone network", ITU-T V.21, November
        1988.

   [23] Telcordia Technologies, "Telcordia Technologies Specification of
        Signaling System Number 7", GR-246-CORE, Issue 7, December 2002.

   [24] Telcordia Technologies, "LSSGR: CLASS Feature: Calling Name
        Delivery Generic Requirements (FSD 01-02-1070)", GR-1188, Issue
        02, December 2000.

   [25] Telcordia Technologies, "LSSGR: CLASS Feature: Calling Number
        Delivery (FSD 01-02-1051)", GR-31, Issue 01, June 2000.

   [26] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video
        Conferences with Minimal Control", RFC 3551, July 2003.

   [27] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S. and S. Jamin,
        "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional
        Specification", RFC 2205, September 1997.

   [28] Berners-Lee, T., Masinter, L. and M. McCahill, Eds., "Uniform
        Resource Locators (URL)", RFC 1738, December 1994.

Top      Up      ToC       Page 62 
   [29] Schulzrinne, H., Rao, A. and R. Lanphier, "Real Time Streaming
        Protocol (RTSP)", RFC 2326, April 1998.

   [30] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource
        Identifiers (URI): Generic Syntax", RFC 2396, August 1998.

   [31] Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

6.2.  Informative References

   [32] Perkins, C., Kouvelas, I., Hodson, O., Hardman, V., Handley, M.,
        Bolot, J.C., Vega-Garcia, A. and S. Fosse-Parisis, "RTP Payload
        for Redundant Audio Data", RFC 2198, September 1997.

   [33] Schulzrinne, H. and S. Petrack, "RTP Payload for DTMF Digits,
        Telephony Tones and Telephony Signals", RFC 2833, May 2000.

   [34] Foster, B., "MGCP CAS Packages", RFC 3064, February 2001.

   [35] PacketCableTM, Dynamic Quality if Service Specification,
        http://www.packetcable.com/downloads/specs/PKT-SP-DQOS-I07-
        030815.pdf

   [36] PacketCableTM Network-Based Call Signaling Protocol
        http://www.packetcable.com/downloads/specs/PKT-SP-EC-MGCP-I08-
        030728.pdf

   [37]  Groves, C., Pantaleo, M., Anderson, T. and T. Taylor, Eds.,
        "Gateway Control Protocol Version 1", RFC 3525, June 2003.

   [38] Arango, M., Dugan, A., Elliott, I., Huitema, C. and S. Pickett,
        "Media Gateway Control Protocol (MGCP) Version 1.0", RFC 2705,
        October 1999.

Top      Up      ToC       Page 63 
7.  Authors' Addresses

   Bill Foster
   Cisco Systems

   Phone: +1 250 758 9418
   EMail: bfoster@cisco.com


   Flemming Andreasen
   Cisco Systems
   Edison, NJ 08837

   EMail: fandreas@cisco.com

Top      Up      ToC       Page 64 
8.  Full Copyright Statement

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assignees.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

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