One document matched: draft-ietf-megaco-r2package-03.txt
Differences from draft-ietf-megaco-r2package-02.txt
Internet Engineering Task Force Kushanava Laha
Internet Draft Vikram Nair
Document: draft-ietf-megaco-r2package-03.txt Hughes Software Systems
Category: Standards Track March 2003
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
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documents valid for a maximum of six months and may be updated, replaced, or
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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 for the
Megaco/H.248 Protocol that can be used to exchange call setup supervisory
and control information between a Media Gateway (MG) and a Media Gateway
Controller (MGC) to realize Signaling System R2 at a VoIP Gateway. It is
intended to satisfy the requirements in section 12 of the Megaco/H.248
protocol [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
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* R2 package
* Procedures
* References
* Author's Address
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.
Terminations (signaling trunks) at the MG, implementing signaling system R2
SHOULD realize the R2 package.
The R2 package presented in this draft extends the basic CAS package (bcas)
[4]. The bcas package defines the basic properties that need to be supported
by a termination in MG to realize any CAS protocol. It also specifies events
and signals required to be exchanged between the MGC and MG to execute basic
line signaling procedures for any CAS protocol (R2 Signaling System
inclusive). The R2 package adds the R2 address signaling parameters in the
form of additional properties, events and signals to complete the realization
of Signaling System R2 at a VoIP Gateway.
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 the R2 package 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. The R2 package defines a "r2addr"
signal and event used for exchanging address signaling parameters between MG
and MGC.
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 R2
package.
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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.
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
"r2addr" event, where the collected address parameters are ObservedEvents
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 can 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.
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Hence as shown in the figure above, MG1 is an incoming MG and MG2 is an
outgoing MG.
b) The call agent (MGC) is transparent of the transmission details at the
physical layer i.e. the R2 terminations at MG are analogue / digital,
one-way / both-ways etc. 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 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.
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.
d) 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.
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 register signaling
between the Media Gateway and the PSTN network.
Version: 1
Extends: bcas
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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: Source Number Length
Property id: snl (0x0001)
Description: Indicates that the calling party digits are to be collected
By the MG upto a maximum length as specified by this
parameter value.
Type: integer
Possible values: 0 and up
Defined in: TerminationState
Characteristics: Read/Write
Property Name: Compelling Sequence Keepalive Time
Property id: cskt (0x0002)
Description: Specifies the time duration for which the incoming MG MAY
keep alive the compelling sequence, waiting for the
subscriber line status information from MGC.
Type: integer
Possible Values: 0 and up in milliseconds
Defined In: TerminationState
Characteristics: Read
6.3 Events
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: R2 Address
EventID: r2addr (0x0001)
Description: Reports the address parameter collected through compelled
register signaling. The address parameter include the
destination number, source number 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 compelled and collected).
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)
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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. This is a
mandatory ObservedEventsDescriptor parameter.
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. This is a
mandatory ObservedEventsDescriptor parameter.
Type: enumeration
Possible values:
"UM" (0x0001) Unambiguous match
"PM" (0x0002) Partial match
"FM" (0x0003) Full match
Parameter Name: Source Number
ParameterID: si (0x0003)
Description: If present, reports the compelled calling party
number digit string.
Type: string of digits returned as a quoted string.
Possible Values: a sequence of the characters "0" through "9"
Parameter Name: Source Number Termination Method
ParameterID: simeth (0x0004)
Description: If Source Number parameter is reported,
indicates the reason for the generation of the
same.
Type: enumeration
Possible values:
"EP" (0x0001) End of Pulsing
"ML" (0x0002) Maximum Length
"TO" (0x0003) Timeout
Parameter Name: Calling Subscriber Category
ParameterID: sc (0x0005)
Description: If present, reports the compelled calling party
subscriber's category.
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)
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"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 (0x0006)
Description: If present, conveys the compelled 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 (0x0007)
Description: If present, conveys the country code (and
possibly the area code) digit string collected
as a part of the compelled register signaling
in international working.
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 (0x0008)
Description: If present, specifies the compelled information
on discriminating digit for automatic working.
For semi-automatic working this MAY 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
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
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"SP" (0x0006) Language digit Spanish
"OT" (0x0007) Language digit Other
"TCI" (0x0008) Call by automatic test equipment
Parameter Name: Nature of circuit
ParameterID: nac (0x0009)
Description: If present, reports the compelled information
on 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
6.3.2
Event Name: Called Party Reachability Status
EventID: cprs (0x0002)
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: Called Party Line Condition
ParameterID: cplc (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
6.3.3
Event Name: R2 Failure
EventID: r2f (0x0003)
Description: Reports abnormal R2 register signaling conditions to MGC
EventsDescriptor Parameters:
none defined by this package
ObservedEventsDescriptor Parameters:
Parameter Name: Error Code
ParameterID: ec (0x0001)
Description: Describes the failure reason
Type: enumeration
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Possible Values:
"ERR" (0x0001) Error in compelling sequence with
peer R2 register
"INC" (0x0002) Information signaled by the MGC is
incomplete to continue with the
compelling sequence at outgoing MG
"DISC" (0x0003) Information signaled by the MGC is
inappropriate at the compelling stage
at MG and hence discarded
6.3.4
Event Name: Destination number
EventID: di (0x0004)
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.
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
"FM" (0x0003) Full match
6.3.5
Event Name: Source number
EventID: si (0x0005)
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)
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Description: Reports the compelled calling party number
digit string.
Type: String of digits returned as a quoted string.
Possible Values: A sequence of the characters "0" through "9"
Parameter Name: Source Number Termination Method
ParameterID: simeth (0x0002)
Description: If Source Number parameter is reported,
indicates the reason for the generation of the
same.
Type: enumeration
Possible values:
"EP" (0x0001) End of Pulsing
"ML" (0x0002) Maximum Length
"TO" (0x0003) Timeout
6.3.6
Event Name: Calling Subscriber Category
EventID: sc (0x0006)
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)
"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
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6.3.7
Event Name: Echo Suppression Information
EventID: es (0x0007)
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
6.3.8
Event Name: Country Code Information
EventID: cc (0x0008)
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 (and possibly area code)digit
string collected as a part of the compelled
register signaling in international working.
Type: string of digits returned as a quoted string.
Possible values: A sequence of the characters "0" through "9"
6.3.9
Event Name: Discriminating Indicator
EventID: disc (0x0009)
Description: Event to specify discriminating indicator parameter to MGC.
EventsDescriptor Parameters:
none defined by this package
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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
6.3.10
Event Name: Nature of circuit
EventID: nac (0x000A)
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
6.3.11
Event Name: Congestion
EventID: cng (0x000B)
Description: Event to specify network congestion encountered.
EventsDescriptor Parameters:
none defined by this package
ObservedEventsDescriptor Parameters:
none defined by this package
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6.4 Signals
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: R2 Address
SignalID: r2addr (0x0001)
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
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)
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"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" (0x0004) 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.
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
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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
6.4.2
Signal Name: Congestion
SignalID: cng (0x0002)
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 resources or encounters network congestion while routing.
Signal Type: (BR) Brief
Duration: Provisioned
Additional Parameters: None
6.4.3
Signal Name: Called Party Reachability Status
SignalID: cprs (0x0003)
Description: This signal applies the compelled R2 signal that translates
to called subscriber line status information.
Signal Type: (BR) Brief
Duration: Provisioned
Additional Parameters:
Parameter Name: Called Party Line Condition
ParameterID: cplc (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
6.5 Statistics
none defined by this package
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7. Procedures
7.1 Termination of Called Party Number digit collection at incoming MG
MG SHALL collect called party number digits using the digit map specified by
MGC. If the MG is provisioned to recognize the "end of pulsing" register
signal, this signal together with the digit map SHALL determine the
termination condition of the accumulated digits.
During called party number compelling when the MG determines that an
unambiguous match has been found with an alternative in the digit map, the MG
SHALL report the collected digits with the Destination Number Termination
Method set to "Unambiguous Match". This matching criterion MAY also coincide
with the reception of the "end of pulsing" signal.
Digit collection MAY terminate due to completion by timer expiry or the
reception of "end of pulsing" signal when an alternative in the digit map has
partially matched. The MG SHALL then report the collected digits with the
Destination Number Termination Method set to "Partial Match".
Similarly, Digit collection MAY terminate due to completion by timer expiry
or the reception of "end of pulsing" signal 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 with the Destination Number Termination
Method set to "Full Match".
The action taken by the MGC based on the Destination Number Termination
Method is left implementation specific.
7.2 Termination of Calling Party Number collection at incoming MG
MG SHALL collect calling party number digit string till the occurrence of any
of the event mentioned below.
If MG is provisioned to recognize the end-of-pulsing signal, calling party
number collection MAY terminate due to reception of end-of-pulsing signal.
In such a case, MG SHALL report all the collected calling party digits with
the Source Number Termination Method set to "End of Pulsing".
If the "snl" property is set to a non-zero value, MG collects the calling
party number for this maximum number of digits. The MG SHALL report all the
collected calling party digits with the Source Number Termination Method set
to "Maximum Length".
MG MAY also implement a digit timeout mechanism. The timer value is
provisioned at the MG and started the moment calling party number compelling
starts. If the digit collection terminates due to this timeout, MG SHALL
report all the collected calling party digits with the Source Number
Termination Method set to "Timeout".
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The action taken by the MGC based on of the Source Number Termination Method
is implementation specific.
7.3 Termination of Country Code digit collection at incoming MG
MG maybe locally provisioned with the list of country codes corresponding
to location of the outgoing international R2 register based on which the MG
MAY terminate the compelling of the country code digits.
7.4 Termination of Compelling Sequence
R2 signaling imposes severe timing constraints on the compelling sequence
executed at the MG. The MGC MAY take a finite time to signal the Called Party
Reachability Status to the incoming MG after the necessary call setup address
information has been compelled and reported to MGC. At this point, the
incoming MG MAY
o Terminate the compelling sequence
o Keep the compelling sequence alive
If compelling timings are stringent, the incoming MG MAY terminate the
compelling sequence without waiting for the call routing status information
(Called Party Reachability Status or Congestion signal) being transmitted by
the MGC. The MG SHALL transmit a suitable backward register signal that
informs the peer R2 register to setup speech-path. The call routing status
cannot be therefore signaled through register signaling. In this case, the
MGC MAY instruct the MG to transmit the call routing status as inband call
progress tones (out of scope of this package), if call routing tones are not
already available inband at the MG.
If the compelling timings allow some room for the MG to wait for the call
routing status to be signaled, the incoming MG MAY alternately choose to keep
the compelling sequence alive within protocol limitations. The MG MAY
typically start a timer equal to the duration permitted by the R2 register
signaling protocol. If within this time, the MGC signals the Called Party
Reachability Status (or Congestion signal), the same is transmitted to the
peer R2 register as R2 register signals before completing the compelling
sequence. If timeout occurs at MG while waiting for the Called Party
Reachability Status or Congestion signal, the MG SHALL terminate the
compelling sequence by transmitting a suitable backward register signal that
informs the peer R2 register to setup speech path.
In either case, if the MGC signals the Called Party Reachability Status or
Congestion signal after the MG has terminated the compelling sequence, the MG
SHALL respond with an R2 Failure event with Error Code set as DISC. The MGC
MAY then choose to re-signal the call routing status as inband call progress
tones (out of scope of this package).
MGC MAY desire to audit the time window for which the incoming MG keeps
alive, before terminating, the compelling sequence; waiting for the call
routing status. Based on this time window, MGC MAY decide before hand as to
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how to send the routing status information to the MG - as Called Party
Reachability Status signal (or Congestion signal) or call routing tones. The
Compelling Sequence Keepalive Time property MAY be used for this purpose. A
value of zero indicates that the MG immediately terminates the compelling
sequence.
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, March 2002.
[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)-124-2346666. Ext-2226
Email: klaha@hss.hns.com.
Vikram Nair
Hughes Software Systems, Ltd.
Gurgaon,Haryana,India. 122015.
Ph: (91)-124-2346666. Ex-1632
Email: vnair@hss.hns.com
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Megaco/H.248 R2 Package
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