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Media Gateway Control (Megaco)                            Michael Brown
Internet Draft                                        Peter Blatherwick
Document: draft-ietf-megaco-h248g-00.txt                Nortel Networks
Category: Standards Track                                     July 2000


              H.248 Annex G (Pre-Decision White Document)


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026 [1].

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that
   other groups may also distribute working documents as Internet-
   Drafts. Internet-Drafts are draft documents valid for a maximum of
   six months and may be updated, replaced, or obsoleted by other
   documents at any time. It is inappropriate to use Internet- Drafts
   as reference material or to cite them other than as "work in
   progress."
   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt
   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.


1. Abstract

   This document reproduces the content of the ITU-T Study Group 16
   White Document draft of H.248 Annex G, which is scheduled for
   decision in Geneva in November 2000.  H.248 Annex G provides
   packages for "User Interface Elements and Actions".  Specifically,
   the packages in Annex G include:
        - Display
        - Key
        - Keypad
        - Label key
        - Function key
        - Indicator
        - Soft key
        - Ancillary input

   This document is submitted for IETF comment prior to ITU-T decision,
   in accordance with procedures currently being negotiated between
   ITU-T Study Group and ISOC on behalf of the IETF.







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2. 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 [2].


3. Introduction

   The following packages define a framework for specifying
   capabilities associated with user interface elements, such as text
   display, keys, dynamically labeled keys, indicators and alphanumeric
   input. In addition, specific extension packages for telephone
   keypads and telephone function keys are defined.

4. Proposed Packages

4.1 Display Package

   PackageID: dis, 0x0014
   Version: 1
   Extends: None

   This package defines properties and signals associated with text
   display user interface elements.  See Procedures for details of
   operation.

4.1.1 Properties

   Number of rows
        PropertyID: nrows (0x0001)
        Description: Maximum number of rows on the display
        Type: integer
        Defined in: TerminationState.
        Characteristics: read only.

   Number of columns
        PropertyID: ncols (0x0002)
        Description: Maximum number of columns on the display
        Type: integer
        Defined in: TerminationState.
        Characteristics: read only.

   Supported unicode code pages
        PropertyID: cdpgs (0x0003)
        Description: a list of supported unicode pages
        Type: list of enumerated type
        Defined in: TerminationState.
        Characteristics: read only.




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        Example: if the text display element supports U+2500 ->U+25ff,
        U+2600 ->U+26ff and U+2700 -> U+277f, this property would
        return "250, 258, 260, 268, 270" in cdpgs.
        Unicode page U+0000 -> U+00ff shall be supported in all
        implementations.

   Cursor row position
        PropertyID: cr (0x0004)
        Type: integer
        Defined in: TerminationState.
        Characteristics: read and write:

   Cursor column position
        PropertyID: cc (0x0005)
        Type: integer
        Defined in: TerminationState.
        Characteristics: read and write.

   Note: row and column numbering begin at 0.  A display's origin is
   row 0, column 0.  The origin is at the top left corner

4.1.2 Events

   None

4.1.3 Signals

4.1.3.1 Display

   SignalID: di (0x0001)
   Description: Display text.

   Parameters:

        Row

        ParameterID: r (0x0001)
        Type: Integer
        Insertion point row, relative to 0,0.  Default is current
        cursor position.

        Column

        ParameterID: c (0x0002)
        Type: Integer
        Insertion point column, relative to 0,0.  Default is current
        cursor position.

        String

        ParameterID: str (0x0003)
        Type: String

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        Default is empty string (moves cursor position).

        Attribute

        ParameterID: a (0x0004)
        Type: enumerated or list of enumerated
        Possible values: plain (0x0001), blink (0x0002), invert
        (0x0003), underline (0x0004)
        Default Value: Plain

4.1.3.2 Clear Display

   SignalID: cld, 0x0002

   Description:
   This signal clears the entire display and resets the current cursor
   position to the origin (row 0, column 0).

   Parameters: None

4.1.4 Statistics

   None

4.1.5 Procedures

   Unicode is supported to provide for multiple languages.  The Unicode
   Standard, Version 2.0 or ISO/IEC 10646-1:1993 [xxx] shall be the
   definitive standard intended when the term Unicode is used within
   the context of this document.  All text display elements shall at
   least support the Unicode pages U+0000 -> U+00ff as the basic
   character set.  All text strings shall be encoded using UTF-8 as
   defined in ISO/IEC 10646 AM1 [xxx].

   In the Display signal, text will be inserted beginning at the row
   and column given in the signal parameters, relative to 0,0.  If no
   row and column parameters are given, the text will be inserted
   starting at the current cursor position.  The current cursor
   position will always be advanced to the position immediately after
   the last character inserted.

   Carriage return <Unicode U+000D> is supported in-string, and moves
   the text input to the beginning of the next line, clearing the
   remainder (if any) of the current line.

   Text wrapping is not provided. A string will not word wrap to the
   next row.  If a string cannot fit into the current row, it will be
   truncated without warning.

   The attribute parameter applies to all characters contained in the
   current signal.  If no attribute is provided, plain text will be
   displayed.  For example, to turn on an attribute in the middle of a

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   string, one would send a signal with a beginning sub-string of plain
   text, follow by a signal with the desired attribute(s) for the
   middle sub-string, and finishing with the signal containing the
   remaining sub-string of plain text.


4.2 Key Package

   PackageID: key, 0x0015
   Version: 1
   Extends: none

   This package defines the basic behavior of key user interface
   elements. Specific key IDs are selected by name (keyid) from the
   list of keys.  This package does not specify parameter values for
   keys.

   Intended to be extended by other packages which have key behavior.

4.2.1 Properties

   None.

4.2.2 Events

4.2.2.1 keydown

   EventID: kd (0x0001)
   Detects key was pressed.

   EventDescriptor parameters: None.

   ObservedEventDescriptor parameters:

        Key name

        ParameterId: keyid (0x0001)
        Type: Enumeration
        Possible values: No values are specified in this package.
        Extensions to this package add possible values for keyid.

4.2.2.2 keyup

   EventID: ku (0x0002)
   Detects key up.

   EventDescriptor parameters: None.

   ObservedEventDescriptor parameters:

        Key name


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        ParameterId: keyid (0x0001)
        Type: Enumeration
        Possible values: No possible values are specified in this
        package. Extensions to this package would add possible values
        for keyid.

        Duration

        ParameterId: duration (0x0002)
        Type: Integer
        Units: miliseconds
        Description: Key press duration (key down to key up).

4.2.3 Signals

   None

4.2.4 Statistics

   None

4.2.5 Procedures

   None.


4.3 Keypad Package

   PackageID: kp, 0x0016
   Version: 1
   Extends: key version 1

   This package defines the keypad user interface element.  The keypad
   package is used to represent a standard 10 digit key pad plus the
   '*', '#', A, B, C, and D keys. Keypad may be used in conjunction
   with digit maps, similar to dtmf tone detection package.  Keypad
   entry can be directed to provide audio and/or display feedback to
   other user interface terminations, for example to automatically
   provide audible feedback of keypad touches to the user or to
   automatically update display.

   Additional Keyid values, and mapping to DigitMap symbols (as
   described in Megaco/H.248 Protocol, section 7.1.14):


         Name              Description       DigitMap Symbol

         k0 (0x0001)       Keypad digit 0    `0'
         k1 (0x0002)       Keypad digit 1    `1'
         k2 (0x0003)       Keypad digit 2    `2'
         k3 (0x0004)       Keypad digit 3    `3'
         k4 (0x0005)       Keypad digit 4    `4'

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         k5 (0x0006)       Keypad digit 5    `5'
         k6 (0x0007)       Keypad digit 6    `6'
         k7 (0x0008)       Keypad digit 7    `7'
         k8 (0x0009)       Keypad digit 8    `8'
         k9 (0x000a)       Keypad digit 9    `9'
         ks (0x000b)       Keypad digit *    `E' or `e'
         ko (0x000c)       Keypad digit #    `F' or `f'
         kA (0x000d)       Keypad digit A    `A' or `a'
         kB (0x000e)       Keypad digit B    `B' or `b'
         kC (0x000f)       Keypad digit C    `C' or  `c'
         kD (0x0010)       Keypad digit D    `D' or `d'

4.3.1 Properties

   None.

4.3.2 Events

4.3.2.1 DigitMap Completion Event

   EventID: ce (0x0001)
   Generated when a digit map completes as described in Megaco/H.248
   Protocol section 7.1.14.  Form of this event is identical to its
   definition in DTMF Detection Package (dd), Megaco/H.248 Protocol
   section E.6.2.

   EventsDescriptor parameters:

        Digit map processing is activated only if a digit map parameter
        is present, specifying a digit map by name or by value.  Other
        parameters such as a KeepActive flag or embedded Events or
        Signals Descriptors may be present.

   ObservedEventsDescriptor parameters:

        DigitString

        ParameterID: ds (0x0001)
        Type: String of digit map symbols (possibly empty) returned as
        a quotedString.
        Possible values: a sequence of the characters "0" through "9",
        "A" through "F", and the long duration modifier "Z".
        Description: the portion of the current dial string as
        described in Megaco/H.248 Protocol section 7.1.14 which matched
        part or all of an alternative event sequence specified in the
        digit map.

        Termination Method

        ParameterID: meth (0x0003)
        Type: enumeration

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        Possible values:
                "UM" (0x0001) Unambiguous match
                "PM"  (0x0002) Partial match, completion by timer
                expiry or unmatched event
                "FM"  (0x0003) Full match, completion by timer expiry
                or unmatched event
        Description: indicates the reason for generation of the event.
        See the procedures in Megaco/H.248 Protocol section 7.1.14.

4.3.3 Signals

   None.

4.3.4 Procedures

   None.


4.4 Label Key Package

   PackageID: labelkey, 0x0017
   Version: 1
   Extends: key version 1

   This package defines the basic behavior of labeled key user
   interface elements. Key labels may be used, for example, to provide
   information to the MGC regarding pre-configured telephone key
   assignments, allowing telephone moves and changes outside the
   initial administrative domain without requiring re-configuration of
   keys.  May also be used to provide static label information on the
   telephone user interface, identifying key function to the user
   without the need for manual labeling.

   Specific keys are addressed by name (keyid) from the list of keys.
   This package does not specify parameter values for keys.

   Intended to be extended by other packages which have key behavior.

4.4.1 Properties

   Key List
        Property ID: keylist (0x0001)
        Type: String, using the following format
                {{keyid, label, label_size}, ...}
        Description: Keylist property allows auditing and setting of
        keyid/label mapping.  Label size is also given. This package
        defines syntax only; no specific keys are defined.  See derived
        packages for the actual keyid lists.
        Defined in: TerminationState
        Characteristics: read and write



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4.4.2 Events

   None.

4.4.3 Signals

   None.

4.4.4 Procedures

   None.


4.5 Function Key Package

   PackageID: kf, 0x0018
   Version: 1
   Extends: labelkey version 1

   Common telephone function keys are defined in this package.  This
   allows, for example, line keys and other function keys to be
   implemented without specific knowledge of the physical layout of the
   telephone.

   Additional keyid values in keyup and keydown events and keylist
   property:

        Name                            Description

        kh (0x0011)                     Hookswitch
        kl (0x0012)                     Hold
        kc (0x0013)                     Conference
        kt (0x0014)                     Transfer
        l001 - l999 (0x0015-0x03fb)     Set of line keys

        f001 - f999 (0x03fc-0x07e2)     Set of assignable function keys

4.5.1 Procedures

   Function keys may have well known names (keyid) associated with
   function, for example "hookswitch", "hold", etc.  These well know
   names identify the purpose of the particular key on the actual
   device.  Function keys may also be assigned a label identifier by
   the MGC.  This approach avoids assumptions and/or the requirement
   for application level knowledge of device-specific configuration of
   the physical resources to derive intended function of keys.

   Function Keys can be co-related with physically associated
   Indicators using Function Key keyid and Indicator indid.  If the IDs
   are identical, the MGC application can safely assume that the key
   and indicator are physically (or otherwise) associated on the actual
   device.  Again, this avoids assumptions and/or the requirement for

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   application level knowledge of device-specific layout of the
   physical resources.  See also the Indicator package (ind).

   NOTE: The key sense of hookswitch (keyid=kh) is a special case.  Key
   up indicates the hookswitch is depressed (i.e. handset is nominally
   on hook).  Key down indicates the hookswitch is lifted (i.e. handset
   is nominally off hook).  This allows for sensible use of the
   duration parameter in the keyup event which will normally give the
   duration the handset was off-hook.


4.6 Indicator Package

   PackageID: ind, 0x0019
   Version: 1
   Extends: None

   This package defines the basic behavior of indicator user interface
   elements. Specific indicators are addressed by name (indid) from the
   list of indicators. Indicators may have well- known names (indid)
   associated with function, for example "message waiting", "hold",
   "line active", etc. This allows, for example, indicators to be
   implemented without specific knowledge of the physical layout of the
   telephone.

   Intended to be possible to extend by other packages which have
   indicator behavior.

4.6.1 Properties

   Indicator List
        Property ID: indlist (0x0001)
        Type: String, using the following format
                {{indid, label, label_size}, ...}
        Description: Indicator List property allows auditing and
        setting of indid/label mapping.  Label size is also given. This
        package defines syntax only; no specific indicators are
        defined.  See derived packages for the actual indid lists.
        Defined in: TerminationState.
        Characteristics: read and write.

4.6.2 Events

   None

4.6.3 Signals

4.6.3.1 SetIndactor

   SignalID: is (0x0001)
   Set indicator state.


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   Parameters:

        Indicator name

        ParameterId: Indid (0x0001)
        Type: Enumeration.
        Possible values:


            Name                    Description

            il (0x0001)             Hold
            ic (0x0002)             Conference
            l001-l999 (0x0003-      Set of line indicators
            0x03f9)
            f001-f999 (0x03fa-      Set of assignable
            0x07e0)                 function indicators
            ir (0x07e1)             Ringer/Alerter
                                    indication
            im (0x07e2)             Message waiting
                                    indicator

        Indicator state

        ParameterId: state (0x0002)
        Type: Enumeration.
        Possible values: On (0x0001), off (0x0002), blink (0x0003),
           fast_blink (0x0004), slow_blink (0x0005).
        Default is off.

4.6.4 Statistics

   None

4.6.5 Procedures

   Indicators can be co-related with physically associated Function
   Keys using Indicator indid and Function Key keyid.  If the IDs are
   identical, the MGC application can safely assume that the key and
   indicator are physically (or otherwise) associated on the actual
   device.  This avoids assumptions and/or the requirement for
   application level knowledge of device-specific layout of the
   physical resources.  See also the Function Keys package (kf).


4.7 Soft Key Package

   PackageID: ks, 0x001a
   Version: 1
   Extends: labelkey version 1



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   Softkeys are a combination of a function key and a display user
   interface element, sharing some behavior of each.  Softkeys are
   intended to be dynamically updated by the MGC, based on the current
   state and context of the application controlling the MG.  Since the
   display aspect and the key aspect are explicitely bound together,
   this avoids assumptions and/or the requirement for application level
   knowledge of device-specific layout of the physical resources.

   See Procedures for details.

4.7.1 Properties

   Number of softkeys
        PropertyID: nskeys (0x0001)
        PropertyType: Integer
        Characteristics: read only
        Defined in: TerminationState
        Description: Maximum number of individual soft keys.

   Display size
        PropertyID: sz (0x0002)
        Type: Integer
        Characteristics: read only
        Defined in: TerminationState
        Description: Maximum number of characters that can be displayed
        in each softkey.

   Supported unicode code pages
        PropertyID: cdpgs (0x0003)
        Description: a list of supported unicode pages
        Type: list of enumerated type
        Defined in: TerminationState.
        Characteristics: read only

4.7.2 Signals

4.7.2.1 SetDisplay

   SignalID: sd (0x0001)

   Description: Set softkey dynamic display content.

   Parameters:

        keyid

        Parameter ID: k (0x0001)
        Type: Enumeration
        Possible values: sk1-sk999 (0x0001-0x03e7)




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        displayContent

        Parameter ID: d (0x0002)
        Type: String

4.7.3 Procedures

   The display aspect is a subset of the Display (dis) package.
   Unicode is supported to provide for multiple languages [xxx], and
   all SoftKey elements shall at least support the Unicode pages U+0000
   -> U+00ff as the basic character set.  All text strings shall be
   encoded using UTF-8.  If a string cannot fit into the display area,
   it will be truncated without warning.

   The key aspect, including Events and labeling, derives directly from
   Label Key and Key packages. Softkey identifiers (keyid) are indexed
   1,2...N.  N (nskeys) is the maximum number of softkeys supported by
   the MG implementation.  Refer to the Label Key (labelkey) and Key
   (key) packages for further details.


4.8 Ancillary Input Package

   PackageID: anci, 0x001b
   Version: 1
   Extends: none

   The ancillary input package is used to enter user alphanumeric
   information such as text input or scan data, which is forwarded to
   the MGC for processing.  The information is presented as a Unicode
   character encoded in UTF-8 format [xxx].

4.8.1 Properties

   None.

4.8.2 Events

4.8.2.1 Character input

   EventID: ch (0x0001)
   Description: A character has been input.

   EventDescriptor parameters: None

   ObservedEventDescriptor parameters:
        Input character

        ParameterId: id (0x0001)
        Type: Character (UTF-8 character)



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4.8.3 Signals

   None.

4.8.4 Statistics

   None.

4.8.5 Procedures

   None.


5. Security Considerations

   Security considerations regarding media gateway control are
   discussed in section 10 of [3].


6. References


   1  Bradner, S., "The Internet Standards Process -- Revision 3", BCP
      9, RFC 2026, October 1996.

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

   3  ITU-T Recommendation H.248, "Gateway Control Protocol", Geneva,
      June 2000.  Also to appear as RFC xxxx (currently draft-ietf-
      megaco-merged-01.txt).


7.   Acknowledgments

   This document reflects the work of the TIA (Telecommunications
   Industry Association) TR-41.3.4 subcommittee under the leadership of
   Phil Holland.


8. Authors' Addresses


    C. Michael Brown (editor)           Peter Blatherwick (editor)
    Nortel Networks                     Nortel Networks
    4008 Chapel Hill Road               P.O. Box 3511, Stn C
    Research Triangle Park,             Ottawa, Ontario,
    NC USA 27709                        Canada K1Y 4H7
    Phone: (919) 991-7767               Phone: (613) 763-7539
    Email:                              Email:
    C.Michael.Brown@nortelnetworks.com  blather@nortelnetworks.com


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