rfc3525.txt

OTP是开放电信平台的简称

   in AuditValue as well as B, and event A/e1 would be available on a
   termination.  If the MG does not publish A, then only B/e1 would be
   available.  If published through AuditValue, A/e1 and B/e1 are the
   same event.





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   For improved interoperability and backward compatibility, an MG MAY
   publish all Packages supported by its Terminations, including base
   Packages from which extended Packages are derived.  An exception to
   this is in cases where the base packages are expressly "Designed to
   be extended only".

6.2.4 Termination properties and descriptors

   Terminations have properties.  The properties have unique
   PropertyIDs. Most properties have default values, which are
   explicitly defined in this protocol specification or in a package
   (see clause 12) or set by provisioning.  If not provisioned
   otherwise, the properties in all descriptors except TerminationState
   and LocalControl default to empty/"no value" when a Termination is
   first created or returned to the null Context.  The default contents
   of the two exceptions are described in 7.1.5 and 7.1.7.

   The provisioning of a property value in the MG will override any
   default value, be it supplied in this protocol specification or in a
   package.  Therefore if it is essential for the MGC to have full
   control over the property values of a Termination, it should supply
   explicit values when ADDing the Termination to a Context.
   Alternatively, for a physical Termination the MGC can determine any
   provisioned property values by auditing the Termination while it is
   in the NULL Context.

   There are a number of common properties for Terminations and
   properties specific to media streams.  The common properties are also
   called the Termination state properties.  For each media stream,
   there are local properties and properties of the received and
   transmitted flows.

   Properties not included in the base protocol are defined in Packages.
   These properties are referred to by a name consisting of the
   PackageName and a PropertyId.  Most properties have default values
   described in the Package description.  Properties may be read-only or
   read/write.  The possible values of a property may be audited, as can
   their current values.  For properties that are read/write, the MGC
   can set their values.  A property may be declared as "Global" which
   has a single value shared by all Terminations realizing the package.
   Related properties are grouped into descriptors for convenience.

   When a Termination is added to a Context, the value of its read/write
   properties can be set by including the appropriate descriptors as
   parameters to the Add command.  Similarly, a property of a
   Termination in a Context may have its value changed by the Modify
   command.




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   Properties may also have their values changed when a Termination is
   moved from one Context to another as a result of a Move command.  In
   some cases, descriptors are returned as output from a command.

   In general, if a Descriptor is completely omitted from one of the
   aforementioned Commands, the properties in that Descriptor retain
   their prior values for the Termination(s) upon which the Command
   acts.  On the other hand, if some read/write properties are omitted
   from a Descriptor in a Command (i.e., the Descriptor is only
   partially specified), those properties will be reset to their default
   values for the Termination(s) upon which the Command acts, unless the
   package specifies other behavior.  For more details, see clause 7.1
   dealing with the individual Descriptors.

   The following table lists all of the possible descriptors and their
   use.  Not all descriptors are legal as input or output parameters to
   every command.

   Descriptor name  Description

   Modem            Identifies modem type and properties when
                    applicable

   Mux              Describes multiplex type for multimedia
                    Terminations (e.g., H.221, H.223, H.225.0) and
                    Terminations forming the input mux

   Media            A list of media stream specifications (see 7.1.4)

   TerminationState Properties of a Termination (which can be defined
                    in Packages) that are not stream specific

   Stream           A list of remote/local/localControl descriptors for
                    a single stream

   Local            Contains properties that specify the media flows
                    that the MG receives from the remote entity.

   Remote           Contains properties that specify the media flows
                    that the MG sends to the remote entity.

   LocalControl     Contains properties (which can be defined in
                    packages) that are of interest between the MG and
                    the MGC.

   Events           Describes events to be detected by the MG and what
                    to do when an event is detected.




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   EventBuffer      Describes events to be detected by the MG when
                    Event Buffering is active.

   Signals          Describes signals (see 7.1.11) applied  to
                    Terminations.

   Audit            In Audit commands, identifies which information is
                    desired.

   Packages         In AuditValue, returns a list of Packages realized
                    by Termination.

   DigitMap         Defines patterns against which sequences of a
                    specified set of events are to be matched so they
                    can be reported as a group rather than singly.

   ServiceChange    In ServiceChange, what, why service change
                    occurred, etc.

   ObservedEvents   In Notify or AuditValue, report of events observed.

   Statistics       In Subtract and Audit, report of Statistics kept on
                    a Termination.

   Topology         Specifies flow directions between Terminations in a
                    Context.

   Error            Contains an error code and optionally error text;
                    it may occur in command replies and in Notify
                    requests.

6.2.5 Root Termination

   Occasionally, a command must refer to the entire gateway, rather than
   a Termination within it.  A special TerminationID, "Root" is reserved
   for this purpose.  Packages may be defined on Root.  Root thus may
   have properties, events and statistics (signals are not appropriate
   for root).  Accordingly, the root TerminationID may appear in:

   -  a Modify command - to change a property or set an event

   -  a Notify command - to report an event

   -  an AuditValue return - to examine the values of properties and
      statistics implemented on root

   -  an AuditCapability - to determine what properties of root are
      implemented



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   -  a ServiceChange - to declare the gateway in or out of service.

   Any other use of the root TerminationID is an error.  Error code
   410 - Incorrect identifier shall be returned in these cases.

7  Commands

   The protocol provides commands for manipulating the logical entities
   of the protocol connection model, Contexts and Terminations.
   Commands provide control at the finest level of granularity supported
   by the protocol.  For example, Commands exist to add Terminations to
   a Context, modify Terminations, subtract Terminations from a Context,
   and audit properties of Contexts or Terminations.  Commands provide
   for complete control of the properties of Contexts and Terminations.
   This includes specifying which events a Termination is to report,
   which signals/actions are to be applied to a Termination and
   specifying the topology of a Context (who hears/sees whom).

   Most commands are for the specific use of the Media Gateway
   Controller as command initiator in controlling Media Gateways as
   command responders.  The exceptions are the Notify and ServiceChange
   commands: Notify is sent from Media Gateway to Media Gateway
   Controller, and ServiceChange may be sent by either entity.  Below is
   an overview of the commands; they are explained in more detail in
   7.2.

   1) Add - The Add command adds a Termination to a Context.  The Add
      command on the first Termination in a Context is used to create a
      Context.

   2) Modify - The Modify command modifies the properties, events and
      signals of a Termination.

   3) Subtract - The Subtract command disconnects a Termination from its
      Context and returns statistics on the Termination's participation
      in the Context.  The Subtract command on the last Termination in a
      Context deletes the Context.

   4) Move - The Move command atomically moves a Termination to another
      Context.

   5) AuditValue - The AuditValue command returns the current state of
      properties, events, signals and statistics of Terminations.

   6) AuditCapabilities - The AuditCapabilities command returns all the
      possible values for Termination properties, events and signals
      allowed by the Media Gateway.




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   7) Notify - The Notify command allows the Media Gateway to inform the
      Media Gateway Controller of the occurrence of events in the Media
      Gateway.

   8) ServiceChange - The ServiceChange command allows the Media Gateway
      to notify the Media Gateway Controller that a Termination or group
      of Terminations is about to be taken out of service or has just
      been returned to service.  ServiceChange is also used by the MG to
      announce its availability to a MGC (registration), and to notify
      the MGC of impending or completed restart of the MG.  The MGC may
      announce a handover to the MG by sending it a ServiceChange
      command.  The MGC may also use ServiceChange to instruct the MG to
      take a Termination or group of Terminations in or out of service.

   These commands are detailed in 7.2.1 through 7.2.8.

7.1   Descriptors

   The parameters to a command are termed Descriptors.  A descriptor
   consists of a name and a list of items.  Some items may have values.
   Many Commands share common descriptors.  This subclause enumerates
   these descriptors.  Descriptors may be returned as output from a
   command.  In any such return of descriptor contents, an empty
   descriptor is represented by its name unaccompanied by any list.
   Parameters and parameter usage specific to a given Command type are
   described in the subclause that describes the Command.

7.1.1 Specifying parameters

   Command parameters are structured into a number of descriptors.  In
   general, the text format of descriptors is
   DescriptorName=<someID>{parm=value, parm=value, ...}.

   Parameters may be fully specified, overspecified or underspecified:

   1) Fully specified parameters have a single, unambiguous value that
      the command initiator is instructing the command responder to use
      for the specified parameter.

   2) Underspecified parameters, using the CHOOSE value, allow the
      command responder to choose any value it can support.

   3) Overspecified parameters have a list of potential values.  The
      list order specifies the command initiator's order of preference
      of selection.  The command responder chooses one value from
      the offered list and returns that value to the command initiator.





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   If a required descriptor other than the Audit descriptor is
   unspecified (i.e., entirely absent) from a command, the previous
   values set in that descriptor for that Termination, if any, are
   retained.  In commands other than Subtract, a missing Audit
   descriptor is equivalent to an empty Audit descriptor.  The Behaviour
   of the MG with respect to unspecified parameters within a descriptor
   varies with the descriptor concerned, as indicated in succeeding
   subcl