General Message Format & Information Element Coding

Overview

Protocol discriminator
Call reference
Message type
Message length

General Information Element (IE) format

ATM Adaptation Layer parameters

ATM Traffic Descriptor

Broadband Bearer Capability

Called Party Number

Calling Party Number

Cause

Connection Identifier

Quality of Service parameter

Overview

Within this protocol, every message shall consist of the following parts:

Protocol discriminator
Call reference
Message type
Message length

Variable length information elements, as required.(specific to each message type)

Protocol discriminator

To distinguish messages for user-network call control from other messages (to be defined) within this Recommendation (Q.2931).

Coding value: 0000 1001 Q.2931 user-network call control messages

Call reference

To identify the call at the local user-network interface to which the particular message applies.
Call reference values (CRV) are assigned by the originating side of the interface for a call. The call reference value is assigned at the beginning of a call and remains fixed for the lifetime of a call. After a call ends, the associated call reference value may be reassigned to a later call.

The originating side always sets the call reference flag to ‘0’. The destination side always sets the call reference flag to a ‘1’.

Message type

To identify the function of the message being sent and to allow the sender of a message to indicate explicitly the way the receiver should handle unrecognized messages.

Note: for this Implementation Agreement, the Flag field and Action Indicator Field shall be coded to zero.

Message length

To identify the length of the contents of a message. It has a fixed length of 2 octets.

General Information Element (IE) format

Note: The Flag field and Action Indicator Field shall be coded to zero.

ATM Adaptation Layer parameters

To indicate the requested AAL parameter values (end-to-end significance) for the AAL elements of procedures to be used for the call.

Note: In case of the absence of AAL parameters subfields, the following default values will apply:

multiplier: no default (mandatory for CBR Rate nx64 kbit/s & nx8 kbit/s)
clock frequency recovery : default = Null
error correction : default = Null
partially filled cells : default = 47 octets
forward max. CPCS-SDU : default = 65535 octets
backward max. CPCS-SDU : default = 65535 octets
SSCS-Type : default = Null

ATM Traffic Descriptor

To specify the set of traffic parameters which, together, specify a traffic control capability.
If Peak Cell Rate for CLP (Cell Loss Priority) = 0 is present, the network resource allocation shall assume that the difference between the indicated Peak Cell Rate for CLP = 0+1 and the Peak Cell Rate for CLP = 0 may be used for CLP = 1.

If only Peak Cell Rate for CLP = 0+1 is specified, the network resource allocation shall assume that the entire peak cell rate can be used for CLP = 0.

Note-All the parameters are position independent. The term "Forward" indicates the direction from calling user to the called user. The term "Backward" indicates the direction from the called user to the calling user.

Broadband Bearer Capability

To indicate a requested broadband connection oriented bearer service (see ITU-T Recommendation F.811) to be provided by the network.

BCOB-A (Broadband Connection Oriented Bearer, class A)
connection-oriented

constant bit rate service

timing requirements

BCOB-C (Broadband Connection Oriented Bearer, class C)

Connection-oriented
Variable bit rate traffic
Timing requirements

BCOB-X (Broadband Connection Oriented Bearer, class X)

Connection-oriented
Traffic type: defined by user
Timing requirements: defined by user
For native ATM devices (e.g. BCOB-X), a null AAL may be used (i.e. no AAL is used).

Note 1: This octet may only be present if Bearer Class X is indicated in Octet 5.

Called Party Number

To identify the called party of a call.

Note 1:Type of Number shall be coded as ‘International Number’ for E.164 Numbering Plan.

Note 2:Called Party Number

60 : Country code : Malaysia
05 : State code : Perak
8075611 : Local number : Taiping

Calling Party Number

To identify the origin of a call.

Note: Defaults are ‘presentation allowed’ and ‘User provided not screened’ if octet 6 is not included.

Cause

Describes the reason for generating certain messages, provides diagnostic information in the event of procedural errors, and indicates the location of the cause originator.

Connection Identifier

To identify the local ATM connection resources on the interface.

Note: When VP-associated signaling is indicated in octet 5, the VPCI field shall be ignored.

Quality of Service parameter

To request and indicate the Quality of Service Class for a connection.

QoS Class Forward(octet 5) & QoS Class Backward (octet 6)

Note: QoS Class 1 supports constant bit rate traffic with stringent timing requirements. So, it shall be chosen for AAL type 1.

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