Internet Engineering Task Force Kushanava Laha Internet Draft Vikram Nair Document: draft-ietf-megaco-r2package-02.txt Hughes Software Systems Category: Informational June 2001 Megaco/H.248 R2 Package 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 obsolete 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 is work in progress and defines the R2 package in association with the Megaco/H.248 Protocol that can be used to control a Media Gateway (MG) from an external controller, called a Media Gateway controller (MGC). It is intended to satisfy the requirements in section 12 of the Megaco/H.248 requirement document [2]. 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 [3]. 3. Document Organization The subsequent portion of this draft is organized into the following major sections: * Introduction * Assumptions * Description of the R2 package * Procedures and Call Flows * References * Author's Address Laha, Nair Informational - Expires December, 2001 1 Megaco/H.248 R2 Package June 2001 4. Introduction Signaling System R2 is used for international/national signaling for both automatic and semiautomatic working. It allows for rapid call set-up by providing sufficient signals in both directions to permit the transmission of numerical and other information relating to the called and calling subscriber lines and to increase routing facilities. The R2 package presented in this draft shall be used to set up calls on R2 signaling trunks at one or both ends of the VoIP network. Terminations (signaling trunks) at the MG, implementing signaling system R2 are expected to realize this R2 package in conjunction with the basic CAS package (bcas) [4] It is to be noted that the R2 package, presented in this draft, is NOT an extension of the bcas package (as per definition of package extensions in [2]). It has been the intent to define the parameters in this R2 package as mutually exclusive from the ones defined in the bcas package. The bcas package defines the basic parameters that need to be supported by a termination in the MG, for it to be capable of implementing any form of CAS (including signaling System R2). A termination (signaling trunk at MG), in order to support signaling System R2, shall realize the package parameters defined in the bcas package as per guidelines described later in procedures section, in addition to all the parameters defined in the R2 package. The forward and backward compelled register signaling sequence for exchanging call setup control information shall be executed in the MG. Signaling System R2 defines several numbered (digit) and enumerated (non-digit) components of the call set-up control information. The numbered call setup-up control information components considered in this draft are the destination number, source number and country code. The enumerated call set-up control information components considered are echo suppression information, calling subscriber category, discriminating indicator, nature of circuit, subscriber line status and congestion information. Of these, the numbered components and the following enumerated components - echo suppression information, calling subscriber category, discriminating indicator and nature of circuit, are collectively termed as address parameters as they collectively convey the complete address information required for call set-up in Signaling system R2. They are also the components required at the minimum by the outgoing MG in order to start the compelling action. To gracefully handle time sensitive issues governing the compelling sequence and to keep the MGC transparent of implementation specific compelling at MG, the following simple guidelines have been observed while defining the package. o All numbered address parameters are exchanged as complete digit strings between the MG and MGC containing all the digits. Digit by digit reporting or signaling of numbered address parameters are not allowed between the MG and MGC. o It is necessary that the outgoing MG is equipped with all the address parameters before it can start with the outpulsing compelling sequence. Laha, Nair Informational - Expires December, 2001 2 Megaco/H.248 R2 Package June 2001 The MGC, therefore, sends the address parameters to the outgoing MG as additional parameters in one composite R2 Address signal. o The MG behaving as an incoming R2 end, shall compel and collect all the address parameters as per the provisioned compelling sequence. Flexibility is there in the package for the MGC to solicit each address parameter as separate events or as a single composite event - the R2 Address event, where the collected address parameters are Observed Events Descriptor parameters to the event. Signals and events related to only basic R2 signaling operation for automatic or semi-automatic working, have been considered in the R2 package. Variants of R2 signaling may define new supervisory (line) and call set-up control (register) signals to introduce features such as re-answering, trunk offering, re-ring, operator break-in etc, to name a few. As there is no single standard mechanism to implement such features (they vary from country to country), they have not been considered in this package. However it is possible to realize such features on the MEGACO interface, by defining additional signals and events in other packages that either extend this basic R2 package or are to be used in conjunction with this R2 package. 5. Assumptions a) As shown in the diagram below, MG shall be connected to R2 exchange for R2 compelled signaling, peer MG for media transport and MGC for exchanging R2 signaling information using MEGACO/H.248 with R2 package. +-----+ +-MEGACO-| MGC |-MEGACO-+ | +-----+ | | | (~~~~~~) +--+--+ +--+--+ (~~~~~~) ( PSTN )====R2=====| MG1 |------RTP--------| MG2 |====R2=====( PSTN ) (~~~~~~) +-----+ +-----+ (~~~~~~) [Call origination] [Incoming MG] [Outgoing MG] [Call Termination] Incoming - Outgoing convention ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This draft uses the following convention for incoming / outgoing MG o Incoming MG: R2 exchange initiates the call signaling towards MG. o Outgoing MG: MG initiates the call signaling towards R2 exchange. Hence as shown in the figure above, MG1 is an incoming MG and MG2 is an outgoing MG. b) Signaling system R2 can be used for analogue (one-way operation) or digital transmission systems (one-way or both-ways operations). The call agent (MGC) should be transparent of the transmission details at the physical layer. The MG is therefore assumed to be provisioned with the actual signaling frequencies for inter-register signaling (2-out-of-n in-band multi frequency code with forward and backward compelled signaling) along with their Laha, Nair Informational - Expires December, 2001 3 Megaco/H.248 R2 Package June 2001 properties such as amplitude, tone duration, cadence etc and also their logical significance. All timers that dictate the inter-register compelling actions are also assumed to be provisioned in the MG. The SF, E&M (for analog) and "abcd" bits (for digital) line signaling parameters generated at the physical layer, along with their logical significance, are also assumed to be provisioned at the MG. c) The MG, behaving as an incoming end, may not be provisioned to recognize the "end of pulsing" compelled forward register signal. It is assumed therefore that the incoming MG shall detect the end of digit information in called party number based on some digit map. This shall also take care of situations where identification of end of digit sequence is through length determination or timeout mechanisms. Calling party number shall be compelled till the occurrence of maximum length of calling party number or timeout, specified as package property or encountering end of pulsing. The MG is assumed to be provisioned with a list of possible country codes. The MG shall compel the country code digits based on this provisioned information. c) The VoIP Gateway (MG and MGC), supporting signaling System R2 on the PSTN side, forms the signaling and media interworking gateway between two very different types of signaling and network. It is therefore assumed that the MG shall either originate or terminate R2 signaling (acting as a true inter- working unit between the PSTN and packet network both in terms of signaling and media) depending on whether it emulates the outgoing or incoming end in the signal path. Under tandem operation, therefore, the MG converts end-to- end R2 signaling to link-by-link signaling and does not allow R2 register signals to pass through it as tones. Laha, Nair Informational - Expires December, 2001 4 Megaco/H.248 R2 Package June 2001 6. R2 Package 6.1 Package Package Name: R2 Package Package ID: r2 (To be allocated through IANA) Description: This package provides package parameters applicable to terminations supporting compelled R2-signalling between the Media Gateway and the PSTN network, in addition to the package parameters supplied in the bcas package. Version: 1 Extends: None 6.2 Properties The MG has a provisioned value for all the properties. If unmodified by MGC, the MG uses the provisioned value by default. Property Name: clear back signal validation time Property id: clrbtim (0x0001) Description: Specifies the minimum duration for which the MG, if behaving as an outgoing end, validates the "Clear-back" signal initiated by the other end (incoming end). Type: integer, in milliseconds Possible values: 0 and up Defined in: TerminationState Characteristics: Read/Write Property Name: source number length Property id: callen (0x0002) Description: Indicates that the calling party digits can be upto a maximum length as specified by the parameter value. Thus calling party digits are collected upto a maximum of this value or end of pulsing indicator. If this property is set to zero then MG should not report calling party number as ObservedEventsDescriptor in R2 Address event. Type: integer Possible values: 0 and up Defined in: TerminationState Characteristics: Read/Write Property Name: source number timeout Property id: caltout (0x0003) Description: Indicates that calling party digits are to be collected till timeout of this timer value. MG shall stop compelling source number and consider collection of source number to be complete either on expiry of this timer or when the source number length criterion is matched or on receipt of end of pulsing. Type: integer, in milliseconds Possible values: 0 and up Defined in: TerminationState Characteristics: Read/Write Laha, Nair Informational - Expires December, 2001 5 Megaco/H.248 R2 Package June 2001 Property Name: subscriber line status flag Property id: slsf (0x0004) Description: Specifies whether the MG, behaving as an incoming end, and after reporting all the address parameters to MGC, waits or does not wait for the called subscriber line status information to be signaled by MGC before terminating the compelling action. Type: enumeration Possible values: "WT" (0x0001) Wait "NW" (0x0002) Do not wait Defined in: TerminationState Characteristics: Read/Write Property Name: trunk direction Property id: trdir (0x0005) Description: Specifies whether the R2 termination is an incoming, outgoing or bothway trunk circuit. Type: enumeration Possible values: "IC" (0x0001) Incoming "OG" (0x0002) Outgoing "BW" (0x0003) Bothways Defined in: TerminationState Characteristics: Read 6.3 Events The line signaling condition that convey the line signaling events and the actual frequency, cadence, duration and amplitude values for the multi- frequency tones that convey the register signaling information on the physical interface are provisioned in the MG. 6.3.1 Event Name: Unblock EventID: ublk (0x0001) Description: Indicates an incoming line signal "Idle"/"Released" on a "Blocked" termination that removes the engaged condition. EventsDescriptor Parameters: none defined by this package ObservedEventsDescriptor Parameters: none defined by this package 6.3.2 Event Name: R2 Address EventID: r2addr (0x0002) Description: Reports the address parameter collected through compelled register signaling. The address parameter include the destination number, source number Laha, Nair Informational - Expires December, 2001 6 Megaco/H.248 R2 Package June 2001 identification, the calling subscriber category, controlling information for echo suppression, country code, nature of trunk circuit and discriminating digit information for international calls(whichever is applicable). EventsDescriptor Parameters: Digit map parameter activated for collection of destination number, specifying a digit map by name (previously configured) or by value. ObservedEventsDescriptor Parameters: Parameter Name: Destination number ParameterID: di (0x0001) Description: The called party number digit string that matched part or all of an alternative sequence specified in the digit map, collected through the compelled register signaling. Type: String of digits returned as a quoted string. Possible Values: A sequence of the characters "0" through "9" Parameter Name: Destination number Termination Method ParameterID: dimeth (0x0002) Description: Indicates the reason for the generation of the Destination number parameter. Type: enumeration Possible values: "UM" (0x0001) Unambiguous match "PM" (0x0002) Partial match, completion by timer expiry or "end of pulsing", or unmatched event. "FM" (0x0003) Full match, completion by timer expiry or "end of pulsing" Parameter Name: Source number ParameterID: si (0x0003) Description: The calling party number digit string, that is collected during compelled register signaling till the occurrence of any of the event mentioned below: o end of pulsing o maximum length of calling party digits (calllen) specified as package property. o timeout of calling party timer (caltout) specified as package property. Type: string of digits returned as a quoted string. Possible Values: a sequence of the characters "0" through "9" Parameter Name: Calling Subscriber Category ParameterID: sc (0x0004) Description: Calling Party subscriber's category, as collected through compelled register signaling. Type: enumeration Possible Values: "NNPS" (0x0001) Non-priority subscriber (National Working) "NPRS" (0x0002) Priority subscriber (National Working) "NMNT" (0x0003) Maintenance equipment (National working) Laha, Nair Informational - Expires December, 2001 7 Megaco/H.248 R2 Package June 2001 "NOPR" (0x0004) Operator call (National Working) "NDT" (0x0005) Data transmission (National working) "ISOPR" (0x0006) Subscriber or operator without forward transfer facility (International working) "IOPRF" (0x0007) Operator with forward transfer facility (International working) "IDT" (0x0008) Data transmission (International working) "IPRS" (0x0009) Priority subscriber (International working) "NSMTR" (0x000a) Subscriber with meter (National working) "SIDD" (0x000b) Subscriber with IDD Parameter Name: Echo Suppression Information ParameterID: es (0x0005) Description: Control Information on echo suppressors Type: enumeration Possible Values: "OGRQ" (0x0001) Call requires echo suppressors and outgoing half-echo suppressor has to be inserted "NRQ" (0x0002) Call may not require any echo suppressor "OGINS" (0x0003) Call requires echo suppressors and outgoing half-echo suppressor has already been inserted "ICRQ" (0x0004) Call requires incoming echo suppressors to be inserted Parameter Name: Country Code Information ParameterID: cc (0x0006) Description: Country code digit string collected as a part of the compelled register signaling in international working. MG shall be provisioned with the list of country codes in its local database, which can be referenced to collect country code digits. If present, conveys the country code (and possibly the area code as well) of the location of the outgoing international R2 register. Type: string of digits returned as a quoted string. Possible values: A sequence of the characters "0" through "9" Parameter Name: Discriminating Indicator ParameterID: disc (0x0007) Description: For automatic working this will specify that a discriminating digit is used. For semi-automatic working this will specify the service language (Language digit) to be used by the operator. For international working may serve as a test call indicator also. Type: enumeration Laha, Nair Informational - Expires December, 2001 8 Megaco/H.248 R2 Package June 2001 Possible Values: "DISC"(0x0001) Discriminating digit for automatic working "FR" (0x0002) Language digit French "EN" (0x0003) Language digit English "GR" (0x0004) Language digit German "RU" (0x0005) Language digit Russian "SP" (0x0006) Language digit Spanish "OT" (0x0007) Language digit Other "TCI" (0x0008) Call by automatic test equipment Parameter Name: Nature of circuit ParameterID: nac (0x0008) Description: Reports the nature of circuits involved in the connection so far viz. inclusion of satellite link. Type: enumeration Possible Values: "SATINC" (0x0001) Satellite link included "SATNOINC" (0x0002) Satellite link not included 6.3.3 Event Name: Subscriber Line Status EventID: sls (0x0003) Description: Reports the line status of the called subscriber, collected by the outgoing end through compelled register signaling. EventsDescriptor Parameters: none defined by this package ObservedEventsDescriptor Parameters: Parameter Name: Subscriber Line Condition ParameterID: lsts (0x0001) Description: Line conditions of the called subscriber Type: enumeration Possible Values: "UN" (0x0001) Unallocated number "SLB" (0x0002) Subscriber line busy "SLFC" (0x0003) Subscriber line free, charge "SLFNOC" (0x0004) Subscriber line free, no charge "SOO" (0x0005) Subscriber out of order "SIT" (0x0006) Send special information tone "NK" (0x0007) Subscriber status not known, set-up speech path 6.3.4 Event Name: R2 Failure EventID: r2f (0x0004) Description: Reports general failure or abnormal line and register signaling conditions associated specifically with this package. EventsDescriptor Parameters: none defined by this package Laha, Nair Informational - Expires December, 2001 9 Megaco/H.248 R2 Package June 2001 ObservedEventsDescriptor Parameters: Parameter Name: Error code ParameterID: ec (0x0001) Description: Describes the failure reason Type: enumeration Possible Values: "CNG" (0x0001) Congestion: Encountered Network congestion. "BLK" (0x0002) Blocked: Encountered engaged condition on an "idle" termination due to which the MGC should not attempt a call on this termination till the un-engaged ("unblocked") condition is restored. If reported on an already "seized" termination, indicates a failure condition for which the controlling MGC is expected to back-off and retry on a new termination, propagate the congestion condition backwards and/or clear the call on this termination (depending on the call state at MGC). "EADDR" (0x0003) Error in address specification: The address information specified by the MGC is incomplete or inappropriate with respect to the compelling sequence provisioned in the outgoing MG "BADR" (0x0004) Bad Signal Request: The package signal (supervisory line signal) requested by MGC for application is inappropriate with respect to the line signaling state at MG. The request is being dishonored by MG with no impact on the current signaling state. "DSEZ" (0x0005) Dual Seizure: Encountered dual seizure condition on the termination which MGC tried to seize 6.3.5 Event Name: Destination number EventID: di (0x0005) Description: Event to report destination number address parameter to MGC. EventsDescriptor Parameters: Digit map parameter activated for collection of destination number, specifying a digit map by name (previously configured) or by value. ObservedEventsDescriptor Parameters: Parameter Name: Destination number ParameterID: di (0x0001) Description: The called party number digit string that matched part or all of an alternative sequence specified in the digit map, collected through the compelled register signaling. Type: String of digits returned as a quoted string. Laha, Nair Informational - Expires December, 2001 10 Megaco/H.248 R2 Package June 2001 Possible Values: A sequence of the characters "0" through "9" Parameter Name: Destination number Termination Method ParameterID: dimeth (0x0002) Description: Indicates the reason for the generation of the Destination number parameter. Type: enumeration Possible values: "UM" (0x0001) Unambiguous match "PM" (0x0002) Partial match, completion by timer expiry or "end of pulsing", or unmatched event. "FM" (0x0003) Full match, completion by timer expiry or "end of pulsing" 6.3.6 Event Name: Source number EventID: si (0x0006) Description: Event to report source number address parameter to MGC. EventsDescriptor Parameters: none defined by this package ObservedEventsDescriptor Parameters: Parameter Name: Source number ParameterID: si (0x0001) Description: The calling party number digit string, that is collected during compelled register signaling till the occurrence of any of the event mentioned below: o end of pulsing o maximum length of calling party digits (calllen) specified as package property. o timeout of calling party timer (caltout) specified as package property. Type: String of digits returned as a quoted string. Possible Values: A sequence of the characters "0" through "9" 6.3.7 Event Name: Calling Subscriber Category EventID: sc (0x0007) Description: Event to report calling subscriber category parameter to MGC. EventsDescriptor Parameters: none defined by this package ObservedEventsDescriptor Parameters: Parameter Name: Subscriber Category ParameterID: sc (0x0001) Description: Calling Party's category, as collected through compelled register signaling. Type: enumeration Possible Values: "NNPS" (0x0001) Non-priority subscriber (National Working) "NPRS" (0x0002) Priority subscriber (National Working) Laha, Nair Informational - Expires December, 2001 11 Megaco/H.248 R2 Package June 2001 "NMNT" (0x0003) Maintenance equipment (National working) "NOPR" (0x0004) Operator call (National Working) "NDT" (0x0005) Data transmission (National working) "ISOPR" (0x0006) Subscriber or operator without forward transfer facility (International working) "IOPRF" (0x0007) Operator with forward transfer facility (International working) "IDT" (0x0008) Data transmission (International working) "IPRS" (0x0009) Priority subscriber (International working) "NSMTR" (0x000a) Subscriber with meter (National working) "SIDD" (0x000b) Subscriber with IDD 6.3.8 Event Name: Echo Suppression Information EventID: es (0x0008) Description: Event to report echo suppression information parameter to MGC. EventsDescriptor Parameters: none defined by this package ObservedEventsDescriptor Parameters: Parameter Name: Echo Suppression Information ParameterID: es (0x0001) Description: Control Information on echo suppressors Type: enumeration Possible Values: "OGRQ" (0x0001) Call requires echo suppressors and outgoing half-echo suppressor has to be inserted "NRQ" (0x0002) Call may not require any echo suppressor "OGINS" (0x0003) Call requires echo suppressors and outgoing half-echo suppressor has already been inserted "ICRQ" (0x0004) Call requires incoming echo suppressors to be inserted 6.3.9 Event Name: Country Code Information EventID: cc (0x0009) Description: Event to specify country code information parameter to MGC. EventsDescriptor Parameters: none defined by this package ObservedEventsDescriptor Parameters: Parameter Name: Country Code Information ParameterID: cc (0x0001) Description: Country code digit string collected as a part of the compelled register signaling in international working. MG shall be provisioned with the list of country codes in its local Laha, Nair Informational - Expires December, 2001 12 Megaco/H.248 R2 Package June 2001 database, which can be referenced to collect country code digits. If present, conveys the country code (and possibly the area code as well) of the location of the outgoing international R2 register.. Type: string of digits returned as a quoted string. Possible values: A sequence of the characters "0" through "9" 6.3.10 Event Name: Discriminating Indicator EventID: disc (0x000A) Description: Event to specify discriminating indicator parameter to MGC. EventsDescriptor Parameters: none defined by this package ObservedEventsDescriptor Parameters: Parameter Name: Discriminating Indicator ParameterID: disc (0x0001) Description: For automatic working this may specify that a discriminating digit is used. For semi-automatic working may specify the service language (Language digit) to be used by the operator. For international working may serve as a test call indicator. Type: enumeration Possible Values: "DISC"(0x0001) Discriminating digit for automatic working "FR" (0x0002) Language digit French "EN" (0x0003) Language digit English "GR" (0x0004) Language digit German "RU" (0x0005) Language digit Russian "SP" (0x0006) Language digit Spanish "OT" (0x0007) Language digit Other "TCI" (0x0008) Call by automatic test equipment 6.3.11 Event Name: Nature of circuit EventID: nac (0x000B) Description: Event to specify nature of circuit parameter to MGC. EventsDescriptor Parameters: none defined by this package ObservedEventsDescriptor Parameters: Parameter Name: Nature of circuit ParameterID: nac (0x0001) Description: Reports the nature of circuits involved in the connection so far viz. inclusion of satellite link. Type: enumeration Possible Values: "SATINC" (0x0001) Satellite link included "SATNOINC" (0x0002) Satellite link not included Laha, Nair Informational - Expires December, 2001 13 Megaco/H.248 R2 Package June 2001 6.4 Signals The line signals that are actually sent out on the physical interface and the actual frequency, cadence, duration and amplitude values for the multi- frequency tones that convey the register signaling information are provisioned in the MG. 6.4.1 Signal Name: Block SignalID: blk (0x0001) Description: Applies a "Blocked" signal on an "Idle" termination. Signal Type: (OO) On-off Duration: Not applicable Additional Parameters: None 6.4.2 Signal Name: Unblock SignalID: ublk (0x0002) Description: Applies an "Idle"/"Released" signal on a "Blocked" termination. Signal Type: (OO) On-off Duration: Not applicable Additional Parameters: None 6.4.3 Signal Name: R2 Address SignalID: r2addr (0x0003) Description: Composite signal that supplies all the necessary address parameters to start the compelling register signaling at the outgoing MG. All the parameter conveyed in this signal may not be actually applied on the termination by the outgoing MG. The MG shall transmit only those information that is relevant to the compelling action configured at the MG. Signal Type: (BR) Brief Duration: Provisioned Additional Parameters: Parameter Name: Destination number ParameterID: di (0x0001) Description: The called party number digits. This parameter shall be mandatorily present in the Address signal. Type: string of digits Possible Values: a sequence of the characters "0" through "9" Parameter Name: Source number ParameterID: si (0x0002) Description: The calling party number digits. If the source number is not available at the MGC, this parameter may be absent in the Address signal. Type: string of digits Laha, Nair Informational - Expires December, 2001 14 Megaco/H.248 R2 Package June 2001 Possible Values: a sequence of the characters "0" through "9" Parameter Name: Calling Subscriber Category ParameterID: sc (0x0003) Description: Calling party subscriber's category. If the calling subscriber category is not available at the MGC, this parameter may be absent in the signal. Type: enumeration Possible Values: "NNPS" (0x0001) Non-priority subscriber (National Working) "NPRS" (0x0002) Priority subscriber (National Working) "NMNT" (0x0003) Maintenance equipment (National working) "NOPR" (0x0004) Operator call (National Working) "NDT" (0x0005) Data transmission (National working) "ISOPR" (0x0006) Subscriber or operator without forward transfer facility (International working) "IOPRF" (0x0007) Operator with forward transfer facility (International working) "IDT" (0x0008) Data transmission (International working) "IPRS"(0x0009) Priority subscriber (International working) Parameter Name: Echo Suppression Information ParameterID: es (0x0004) Description: Control information on echo suppressors Type: enumeration Possible Values: "OGRQ" (0x0001) Call requires echo suppressors and outgoing half-echo suppressor has to be inserted "NRQ" (0x0002) Call may not require any echo suppressor "OGINS" (0x0003) Call requires echo suppressors and outgoing half-echo suppressor has already been inserted "ICRQ" (0x0003) Call requires incoming echo suppressors to be inserted Parameter Name: Country Code Information ParameterID: cc (0x0005) Description: Country code information. If present, conveys the country code (and possibly the area code as well) information digits. Type: string of digits Possible Values: a sequence of the characters "0" through "9" Parameter Name: Discriminating Indicator ParameterID: disc (0x0006) Description: For automatic working may specify that a discriminating digit is used. For semi-automatic working may specify the service language (Language digit) to be used by the operator. For international working may serve as a test call indicator. Laha, Nair Informational - Expires December, 2001 15 Megaco/H.248 R2 Package June 2001 Type: enumeration Possible Values: "DISC" (0x0001) Discriminating digit for automatic working "FR" (0x0002) Language digit French "EN" (0x0003) Language digit English "GR" (0x0004) Language digit German "RU" (0x0005) Language digit Russian "SP" (0x0006) Language digit Spanish "OT" (0x0007) Language digit Other "TCI" (0x0008) Call by automatic test equipment Parameter Name: Nature of Circuit ParameterID: nac (0x0007) Description: conveys the nature of circuits involved in the connection so far viz. inclusion of satellite link. Type: Enumeration Possible Values: "SATINC" (0x0001) Satellite link included "SATNOINC" (0x0002) Satellite link not included 6.4.4 Signal Name: Congestion SignalID: cng (0x0004) Description: This signal applies the network congestion compelled R2 signal on a termination in the incoming MG. It arises when at MGC the call setup attempt fails owing to unavailability of PDN resources or encounters network congestion while routing on PDN. Signal Type: (BR) Brief Duration: Provisioned Additional Parameters: None 6.4.5 Signal Name: Subscriber Line Status SignalID: sls (0x0005) Description: Applies the compelled R2 signal that translates to called subscriber line status information. Signal Type: (BR) Brief Duration: Provisioned Additional Parameters: Parameter Name: Subscriber Line Condition ParameterID: lsts (0x0001) Description: Line conditions of the called subscriber Type: enumeration Possible Values: "UN" (0x0001) Unallocated number "SLB" (0x0002) Subscriber line busy "SLFC" (0x0003) Subscriber line free, charge "SLFNOC" (0x0004) Subscriber line free, no charge Laha, Nair Informational - Expires December, 2001 16 Megaco/H.248 R2 Package June 2001 "SOO" (0x0005) Subscriber out of order "SIT" (0x0006) Send special information tone "NK" (0x0007) Subscriber status not known, set-up speech path 6.5 Statistics 6.5.1 Statistics Name: Call Duration StatisticsID: cd (0x0001) Description: Provides the cumulative duration the termination is in active call context i.e. from the point of applying/receiving "Answered" signal till the point of release ("Clear-forward" or "Clear-back") initiation. Units: Double, in seconds. Laha, Nair Informational - Expires December, 2001 17 Megaco/H.248 R2 Package June 2001 7. Procedures 7.1 Property parameters This section supplies the procedures for defining the property parameters in the bcas package, when using the bcas package in conjunction with the R2 package for realizing signaling System R2 on terminations (signaling trunks) at the MG. bcas/sztim ---------- If the signaling System R2 supported in the MG does not support "seize" signal validation feature, the property shall be provisioned with a default value 0 i.e. no validation required. bcas/sdto --------- On a digital interface, this property signifies the maximum duration within which the "seizure acknowledged" line signal is expected at the outgoing MG in response to the transmitted "Seizing" signal. The MG shall have default non-zero value provisioned for this property. On an analog interface, this property shall have a default zero value provisioned implying that the MG is required to report the "start dialing" event in bcas package to MGC immediately after it has successfully transmitted the "seizing" signal. bcas/ansto ---------- If the signaling System R2 supported in the MG does not provide a maximum time by which the "answer" signal should be received, the property shall be provisioned with a default value zero. bcas/anstim ----------- If the signaling System R2 supported in the MG does not support "answer" signal validation feature, the property shall be provisioned with a default value 0 i.e. no validation required. bcas/clrtim ----------- It specifies the minimum duration for which the MG, if behaving as an outgoing end, validates the "clear-forward" (digital operation) or "release" (analogue operation) signal. 7.2 Procedures for exchanging supervisory signals It has been the intention to optimize the inclusion of the additional supervisory signals in the R2 package, which are absent in the bcas package but are considered mandatory for the basic operation of signaling System R2. This section attempts to capture the procedures involved in using the package (R2 and bcas) signals and events for exchanging the supervisory signals in signaling System R2 between the MGC and MG under normal signaling operations. It is understood that the event parameters shall be Laha, Nair Informational - Expires December, 2001 18 Megaco/H.248 R2 Package June 2001 reported from the MG to MGC only if an events descriptor is activated by the MGC on the termination, requesting that event. Default behavior ---------------- When a termination in the MG is not involved in a call, it is in the "idle" state. The MGC configures an "idle" R2 termination to report bcas/sz event (for reporting incoming "seizing" signal) and bcas/casf, r2/r2f events (for reporting failure events such as Unexpected line signal, Protocol State machine malfunction and Blocked condition). Seizure (bcas/sz) ----------------- If an "idle" termination is selected for initiating an R2 call in an outgoing MG, the MGC shall send the bcas/sz signal to the MG and the MG shall transmit the "seizing" supervisory signal to the incoming end. The outgoing MG shall start the "start dialing timer" after transmitting the "seizing" signal. The MG, if behaving as an incoming end, shall report the bcas/sz event when it detects an incoming "seizing" signal on an "idle" R2 termination. Start Dialing (bcas/sd) ------------------------ This event notifies the MGC that the MG behaving as the outgoing end is ready to outpulse the call set-up control signals (address signals as compelled register signaling). In digital operation, the outgoing MG reports the bcas/sd event to the MGC, when it receives a "seizure acknowledged" supervisory signal from the incoming end in response to a "seizing" signal. In the event of "start dialing timeout", the outgoing MG shall report a failure condition to the MGC by filling up Start Dialing Timeout ("SDO") as the value of the Error Code (ec) parameter in the ObservedEvents Descriptor of the bcas/casf event. The behavior of the MGC is implementation specific. It may retry the "seizing" attempt on the same termination (after bringing back the termination to "idle" condition) or retry on some other termination. In analogue operations, Signaling System R2 does not define a "seizure acknowledged" supervisory signal. The "start dialing timeout" property shall be provisioned to default value zero. The outgoing MG shall report the bcas/sd event to the MGC immediately after it has successfully sent the "seizing" signal. This allows the MGC to experience an identical interface regardless of the termination (trunk) type (analogue or digital). It is to be noted that bcas/sd is only an event and not a signal, as it is not required in the incoming MG. The incoming MG is expected to respond to the incoming "seizing" signal on the physical interface depending on the termination type. For digital operations, the incoming MG shall respond with the "seizure acknowledged" line signal to the outgoing end. For analogue operations, the incoming MG shall maintain the line signal as "idle". Answer (bcas/ans) ----------------- bcas/ans is reported as an event from the outgoing MG to the MGC when the Laha, Nair Informational - Expires December, 2001 19 Megaco/H.248 R2 Package June 2001 "answer" line signal is detected from the incoming end. MGC uses bcas/ans as a signal to instruct the incoming MG to transmit the "answer" line signal to the outgoing end. Clearing (bcas/cf, bcas/cb) --------------------------- The bcas/cf and bcas/cb signal and event parameters defined in the bcas package shall be used to instruct and detect supervisory signals related to call clearing on an R2 termination. The MGC can configure the incoming interface by activating an events descriptor that requests the bcas/cf event, to detect and report the receipt of the "clear-forward" or "release" line signal. Similarly the MGC can instruct the MG to apply a bcas/cf signal to clear the call on an outgoing interface, anytime, subsequent to the transmission of the "seizing" signal. The MGC can configure the outgoing interface by activating an events descriptor that requests the bcas/cb event, to detect and report the receipt of the "clear-back" line signal. Similarly the MGC can instruct the MG to apply a bcas/cb signal to clear the call on an incoming interface, anytime, subsequent to the transmission of the "answer" signal. It is to be noted that the release and release-guard sequence defined by signaling System R2 shall be locally executed at the MG at the time of call clearing and the MGC shall be transparent of such procedures. The "clear signal validation time" and "clear back signal validation time" properties shall govern the release guard procedures. Blocking/Unblocking (r2/blk, r2/ublk) ------------------------------------- Signaling System R2 defines supervisory signals to render an "idle" R2 termination (trunk) to "blocked" state. The MGC applies the r2/blk signal to the MG on an incoming interface in "idle" state to prevent any incoming "seizure" of the circuit. The MG for which the same interface is an outgoing interface, shall report the blocking condition to its controlling MGC by filling up Blocked ("BLK") as the value of the Error Code (ec) parameter in the ObservedEvents Descriptor of the r2/r2f event. If the controlling MGC of the outgoing MG attempts to "seize" a "blocked" termination, the outgoing MG shall report a failure to the MGC (filling up "Bad Signal Request" as the value of Error code (ec) parameter in the ObservedEvents Descriptor of the bcas/casf event). Signaling System R2 similarly defines supervisory signals to render a "blocked" R2 termination (trunk) to "unblocked"/"idle" state. The MGC applies the r2/ublk signal to the MG on an incoming interface in "blocked" state to render it to "unblocked"/"idle" state and entertain subsequent "seizure" of the circuit. The MG for which the same interface is an outgoing interface, shall report the unblocking condition to its controlling MGC by reporting the r2/ublk event. This implies that when an MG reports the Blocked ("BLK") error code in the r2/r2f event, the controlling MGC is expected to configure the MG to detect and report the r2/ublk event. Subsequent "seizures" of the termination by the MGC shall be entertained by the MG for which the termination is an outgoing interface. Laha, Nair Informational - Expires December, 2001 20 Megaco/H.248 R2 Package June 2001 Glare Mitigation ---------------- The glare condition or more popularly known as Dual Seizure arises when the outgoing end detects simultaneous seizure of a both-way R2 trunk by both the ends i.e. when "seizing" signal has been transmitted and in response an incoming "Seizing" signal is detected. This glare condition in distributed MG-MGC architecture can occur in two possible scenarios: o MGC initially has applied bcas/sz event on a r2 termination. MG detects a bcas/sz on the termination and reports it to MGC. Meanwhile, MGC also initiates a call attempt by removing the bcas/sz event detection and applying bcas/sz signal on the same r2 termination. In such scenario MG gets a command to apply bcas/sz signal after reporting bcas/sz event and MGC gets a bcas/sz notification after applying bcas/sz signal on the same r2 termination. o MGC instructs MG to apply bcas/sz signal onto an r2 termination. MG, applies the bcas/sz signal on the r2 termination and subsequently receives an incoming "seizing" signal on the same r2 termination. For both of the scenarios MG shall detect the dual seizure condition and report the same to MGC by filling up Dual Seizure ("DSEZ") as the value of the Error Code (ec) parameter of the r2/r2f observed event. The following ladder diagrams illustrate the call flow diagrams for supervisory signal exchange on a digital interface involving an R2 outgoing end, MG behaving as an incoming end and its controlling MGC. These call flow diagrams demonstrate occurrence of dual seizure and handling of the same at MG. Dual seizure between MG and MGC ------------------------------- --------------------------------------------------------------- R2 MG MGC --------------------------------------------------------------- <---------- Modify [event = bcas/sz, bcas/casf, r2/r2f] -----------> "seizing" <----------- "seizure acknowledged" /*---------------------------------------------------------------- MG detecting a r2 trunk seize event from the peer r2 end reports the same to MGC. Meanwhile, MGC decides to use the same r2 trunk for another call and thus applies bcas/sz signal. This leads to a dual seizure scenario. MG shall notify r2 failure event to MGC with "DSEZ" as error code parameter. -----------------------------------------------------------------*/ Laha, Nair Informational - Expires December, 2001 21 Megaco/H.248 R2 Package June 2001 --------------------------------------------------------------- R2 MG MGC --------------------------------------------------------------- -----------> <----------- Notify Modify [bcas/sz] [signal = bcas/sz, event = bcas/cf, r2/r2f] -----------> Notify [r2/r2f {ec="DSEZ"}] Dual seizure between MG and network ------------------------------------ --------------------------------------------------------------- R2 MG MGC --------------------------------------------------------------- <---------- Modify [signal = bcas/sz, event = bcas/casf, r2/r2f] /*---------------------------------------------------------------- MG applies "seizing" signal onto r2 trunk. In response to "seizing" signal it detects seizure signal on the same trunk. This leads to a dual seizure scenario. MG shall notify r2 failure event to MGC with "DSEZ" as error code parameter. -----------------------------------------------------------------*/ -----------> <----------- "seizing" "seizing" -----------> Notify [r2/r2f {ec="DSEZ"}] Failure/Abnormal conditions (bcas/casf, r2/r2f) ----------------------------------------------- Failure or abnormal conditions at the MG (outgoing or incoming end) during supervisory signal exchange shall be reported through the bcas/casf or r2/r2f to the MGC. It is advised that the MGC at all times keeps an Events Descriptor activated on the termination (incoming or outgoing) that requests the bcas/casf and r2/r2f. 7.3 Procedures for exchanging call set-up control information The only signal that exists in the bcas package for carrying call set-up control information between the MGC and the MG, is the bcas/addr signal. It should be noted that the bcas/addr signal is incapable of conveying all the relevant call set-up control information which is required for complete R2 compelling action in the outgoing MG. There are no events defined in the bcas package for carrying the address information as events to MGC. Hence the requirement of introducing new signals and events in the R2 package. Laha, Nair Informational - Expires December, 2001 22 Megaco/H.248 R2 Package June 2001 Digit sequence termination at incoming MG ----------------------------------------- Address parameters calling party number, called party number and country code shall be compelled and the event completion criteria for each of the parameter shall be decided upon the conditions / procedures mentioned in the table below: Address Parameter Completion criteria ----------------- ------------------- Called Party Number MG shall collect called party number digits using the digit map specified by MGC. Now, if the MG is provisioned to recognize the "end of pulsing" register signal, this signal along with the digit map shall determine the termination condition of the accumulated digits. During called party number compelling if the "end of pulsing" signal is recognized when the MG also determines that an unambiguous match has been found with an alternative in the digit map, the MG shall report the collected digits of the relevant parameter with the completion method set to "Unambiguous Match". If the "end of pulsing" signal is recognized when an alternative in the digit map has partially matched, the MG shall report the collected digits of the relevant parameter with the completion method set to "Partial Match". Similarly, if the "end of pulsing" signal is recognized after one of the alternative in the digit map has fully matched and there are more digits available, the MG shall report all the collected digits of the relevant parameter with the completion method set to "Full Match". Calling Party Number MG shall collect calling party number digit string till the occurrence of any of the event mentioned below: o end of pulsing o maximum length of calling party digits (calllen) specified as package property. o timeout of calling party timer (caltout) specified as package property. "caltout" timer shall be started the moment calling party number compelling starts. Country Code MG shall collect country code digits based on provisioned list of country codes. Termination of Compelling Sequence ---------------------------------- After an incoming MG has reported the r2/addr event to its controlling MGC, the latter shall route the call based on the call set-up control information contained in the r2/addr event. Depending on the value of the property "subscriber line status flag", the incoming MG shall either terminate the compelled signaling sequence or wait for the outcome of the routing status to be signaled by the MGC. In the event of the second option, the MGC shall Laha, Nair Informational - Expires December, 2001 23 Megaco/H.248 R2 Package June 2001 indicate back to the incoming MG either the Called subscriber line status (r2/sls signal) or the r2/cng signal (if MGC encountered network congestion). Similarly the MG, if behaving as an outgoing end, shall wait for the called subscriber line status information from the incoming end. The same shall be reported as r2/sls event to its controlling MGC. If the outgoing MG receives congestion information instead, the same shall be reported as r2/r2f event to MGC with Error code parameter set to Congestion ("CNG"). Failure/Abnormal conditions (bcas/casf, r2/r2f) ----------------------------------------------- Failure or abnormal conditions at the MG (outgoing or incoming end) during call set-up control information exchange shall be reported through the bcas/casf or r2/r2f events to the MGC. It is advised that the MGC at all times keeps an Events Descriptor activated on the termination (incoming or outgoing) that requests the bcas/casf and r2/r2f. 7.4 Call flows for Incoming MG Digital trunk type is assumed at the physical interface level. The ladder diagrams attempt to capture the typical usage of the package signals and events and they are indicative in nature. Here MG is behaving as an incoming end and the MG and MGC are assumed to be placed such that they together form the last incoming R2 register (transit gateway) in the signaling path beyond which international interworking with PDN call signaling protocols start. There can be other legal combinations of packing the events and signals using the embedded descriptor capabilities of the MEGACO protocol. --------------------------------------------------------------- R2 MG MGC --------------------------------------------------------------- < --------- Modify [event = bcas/sz, bcas/casf, r2/r2f] -----------> "seizing" <----------- "seizure acknowledged" -----------> Notify [bcas/sz] /*---------------------------------------------------------------- Compelling action starts with the R2 outgoing end transmitting the country code indicator. The MG compels the country code digits and collects them till a match is found with one of the entries in its provisioned database. ----------------------------------------------------------------*/ Laha, Nair Informational - Expires December, 2001 24 Megaco/H.248 R2 Package June 2001 --------------------------------------------------------------- R2 MG MGC --------------------------------------------------------------- <---------- Modify [event = r2/addr,bcas/cf bcas/casf, r2/r2f] -----------> "Country Code Indicator, no echo suppressor required" <----------- "send next digit" -----------> "Country code (first digit)=9" <----------- "send next digit" -----------> "Country code (last digit)=1" /*------------------------------------------------------------------- MG solicits the language/discriminating digit information from the R2 end, as per compelling action defined in the MG. -------------------------------------------------------------------*/ <----------- "send language or discriminating digit" -----------> "discriminating digit=0" /*---------------------------------------------------------------- MGC has pre-configured the MG to report an r2/addr event by specifying a digit map in the digit map descriptor(plan or name reference to an already configured digit plan) for collecting called number. MG solicits the called party number information from the R2 end, as per compelling action defined in the MG. -------------------------------------------------------------------*/ <----------- "send next (called party number) digit" Laha, Nair Informational - Expires December, 2001 25 Megaco/H.248 R2 Package June 2001 --------------------------------------------------------------- R2 MG MGC --------------------------------------------------------------- -----------> "Called party no. (1st digit)=0" <----------- "send next digit" -----------> "Called party no. (next digit)=0" <----------- "send next digit" { Remaining Called party number exchanged through compelling } -----------> "Called party no. (last digit)=6" /*---------------------------------------------------------------- MG solicits the calling party category information from the R2 end, as per compelling action defined in the MG. ----------------------------------------------------------------*/ <----------- "send calling party category" -----------> "Calling party category = Non priority subscriber" /*---------------------------------------------------------------- Source number length and source number timeout properties for collecting calling number are as per provisioned values. MG solicits the calling party number information from the R2 end, as per compelling action defined in the MG. ----------------------------------------------------------------*/ <----------- "send calling party number " -----------> "Calling party no. (1st digit)=6" <----------- "send next (calling party number)digit" Laha, Nair Informational - Expires December, 2001 26 Megaco/H.248 R2 Package June 2001 --------------------------------------------------------------- R2 MG MGC --------------------------------------------------------------- -----------> "Calling party no. (next digit)=8" <----------- "send next (calling party number)digit" { Remaining Called party number exchanged through compelling } -----------> "Calling party no. (last digit)=7" /*---------------------------------------------------------------- MG has no further address parameters to compel. The r2addr event is reported to MGC with all collected address parameters as ObservedEvents Descriptor parameters ----------------------------------------------------------------*/ ------------> Notify [r2/addr {es = "NRQ", cc = "91", disc = "DISC" di = "00...6" dimeth = "UM" sc = "NP" si = "68...7"}] /*---------------------------------------------------------------- MGC has set the "subscriber line status flag" to "wait" so that MG waits for subscriber line status information signaled from the MGC, before terminating the compelling action. MG sends a dummy backward signal to complete the compelling sequence soliciting further digits. R2 outgoing end has no further digits to send. ----------------------------------------------------------------*/ <----------- "send next digit" /*---------------------------------------------------------------- Based on the received address information, MGC routes the call on PDN. However the subscriber line status is not known to MGC and the same information is signaled to MG. ----------------------------------------------------------------*/ <----------- Modify [signal = r2/sls {lsts = "NK"}] Laha, Nair Informational - Expires December, 2001 27 Megaco/H.248 R2 Package June 2001 --------------------------------------------------------------- R2 MG MGC --------------------------------------------------------------- /*---------------------------------------------------------------- MG terminates the compelling sequence by signaling the R2 end to set up the speech path (pulsed signal). R2 registers are deallocated at both ends} ----------------------------------------------------------------*/ <----------- "address complete, setup speechpath" /*---------------------------------------------------------------- Compelling action ends. Terminations successfully added to context. Called Subscriber answers. ----------------------------------------------------------------*/ <----------- Modify [signal = bcas/ans, <----------- "answer" ================================================================ Media ================================================================ /*---------------------------------------------------------------- Outgoing R2 end clears the call. ----------------------------------------------------------------*/ -----------> "clear forward" -----------> Notify [bcas/cf] /*---------------------------------------------------------------- MG executes the release guard sequence locally. ----------------------------------------------------------------*/ <----------- "released" /*---------------------------------------------------------------- MGC brings back the termination to default state. ----------------------------------------------------------------*/ <----------- Modify [ event = bcas/sz, bcas/casf, r2/r2f] Laha, Nair Informational - Expires December, 2001 28 Megaco/H.248 R2 Package June 2001 7.5 Call flows for Outgoing MG Digital trunk type is assumed at the physical interface level. The ladder diagrams attempt to capture the typical usage of the package signals and events and they are indicative in nature. Here MG is behaving as an outgoing end and the MG and MGC are assumed to be placed such that they together form the first outgoing R2 register in the signaling path beyond which R2 call signaling protocols start. There can be other legal combinations of packing the events and signals using the embedded descriptor capabilities of the MEGACO protocol. --------------------------------------------------------------- R2 MG MGC --------------------------------------------------------------- < --------- Modify [signal = bcas/sz, event = bcas/sd, bcas/casf, r2/r2f] <----------- "seizing" -----------> "seizure acknowledged" -----------> Notify [bcas/sd] /*---------------------------------------------------------------- MGC applies r2/addr signal to MG specifying address parameters required by MG for applying address signals while compelling. MGC waits for called destination status. ----------------------------------------------------------------*/ <---------- Modify [signal = r2/addr, event = bcas/casf, r2/r2f, r2/sls] /*---------------------------------------------------------------- Compelling action starts with outgoing MG transmitting the country Code indicator and the R2 end compelling the rest of the country code digits. ---------------------------------------------------------------*/ <----------- "Country Code Indicator, no echo suppressor required" -----------> "send next digit" Laha, Nair Informational - Expires December, 2001 29 Megaco/H.248 R2 Package June 2001 --------------------------------------------------------------- R2 MG MGC --------------------------------------------------------------- <----------- "Country code (first digit)=9" -----------> "send next digit" <----------- "Country code (last digit)=1" /*------------------------------------------------------------------- R2 end solicits the language/discriminating digit information from the MG. -------------------------------------------------------------------*/ -----------> "send language or discriminating digit" <----------- "discriminating digit=0" /*---------------------------------------------------------------- R2 end solicits the called party number information from the MG. ---------------------------------------------------------------*/ -----------> "send next (called party number) digit" <----------- "Called party no. (1st digit)=0" -----------> "send next digit" <----------- "Called party no. (next digit)=0" -----------> "send next digit" { Remaining Called party number exchanged through compelling } <----------- "Called party no. (last digit)=6" Laha, Nair Informational - Expires December, 2001 30 Megaco/H.248 R2 Package June 2001 --------------------------------------------------------------- R2 MG MGC --------------------------------------------------------------- /*---------------------------------------------------------------- R2 end solicits the calling party category information from the MG. ----------------------------------------------------------------*/ -----------> "send calling party category" <----------- "Calling party category = Non priority subscriber" /*---------------------------------------------------------------- R2 end solicits the calling party number information from the MG. ----------------------------------------------------------------*/ -----------> "send calling party number " <----------- "Calling party no. (1st digit)=6" -----------> "send next (calling party number)digit" <----------- "Calling party no. (next digit)=8" -----------> "send next (calling party number)digit" { Remaining Called party number exchanged through compelling } <----------- "Calling party no. (last digit)=7" /*---------------------------------------------------------------- R2 end terminates the compelling sequence by signaling the MG with the called destination status. R2 registers are deallocated at both ends. Terminations successfully added to context. ----------------------------------------------------------------*/ Laha, Nair Informational - Expires December, 2001 31 Megaco/H.248 R2 Package June 2001 --------------------------------------------------------------- R2 MG MGC --------------------------------------------------------------- ----------> "address complete, wait for called destination status" <----------- "Calling party category = Non priority subscriber" ----------> "subscriber line free, charge" -----------> Notify [r2/sls (lsts = {SLFC"}] /*---------------------------------------------------------------- MGC sets events for having answer reported. ----------------------------------------------------------------*/ <----------- Modify [event = bcas/ans, bcas/casf, r2/r2f, bcas/cb] /*---------------------------------------------------------------- R2 end sends answer signal to MG. MG reports answer event to MGC. ----------------------------------------------------------------*/ -----------> "answer" -----------> Notify [bcas/ans] ================================================================ Media ================================================================ /*---------------------------------------------------------------- Incoming R2 end clears the call. ----------------------------------------------------------------*/ -----------> "clear back" -----------> Notify [bcas/cb] Laha, Nair Informational - Expires December, 2001 32 Megaco/H.248 R2 Package June 2001 --------------------------------------------------------------- R2 MG MGC --------------------------------------------------------------- /*---------------------------------------------------------------- MGC brings the termination back to default handling. ----------------------------------------------------------------*/ <----------- Modify [signal = bcas/cf, event = bcas/sz, bcas/casf, r2/r2f] /*---------------------------------------------------------------- MG executes the release guard sequence locally. ----------------------------------------------------------------*/ <----------- "clear forward" -----------> "released" Laha, Nair Informational - Expires December, 2001 33 Megaco/H.248 R2 Package June 2001 8. References [1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996. [2] F. Cuervo, N. Greene, A. Rayhan, C. Huitema, B. Rosen, J. Segers, "Megaco Protocol Version 1.0", RFC 3015, November 2000. [3] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997 [4] V.Bajaj, K.Laha, Bill Foster, Michael Brown, Wendy Bothwell, "Megaco/H.248 Basic CAS Packages", Internet Draft, January 2001. [5] Specifications of Signaling System R2, Q.400 to Q.490, Blue Book, CCITT 9. Author's Addresses Kushanava Laha Hughes Software Systems, Ltd. Gurgaon,Haryana,India. 122015. Ph: (91)-11-6346666.Ext-2226 Email: klaha@hss.hns.com. Vikram Nair Hughes Software Systems, Ltd. Gurgaon,Haryana,India. 122015. Ph: (91)-11-6346666.Ex-2349 Email: vnair@hss.hns.com Laha, Nair Informational - Expires December, 2001 34 Megaco/H.248 R2 Package June 2001 Full Copyright Statement "Copyright (C) The Internet Society (June,2001). 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 Laha, Nair Informational - Expires December, 2001 35