ISDN Protocol Administrator's and Developer's Guide ... - Intervoice

DPNSS 1 Message StructureDPNSS 1 Message StructureThe DPNSS 1 protocol consists of a series of messages sent between theA and B sides of the interface. These messages consist of a one-octetheader followed by a variable-length information field containing astring of 8-bit ASCII characters.The characters in the information field make up one or moresupplementary information identifiers with either mandatory or optionalparameters. Each of these supplementary information identifiers beginswith an asterisk (*) and ends with the pound sign (#), with theparameters separated by additional asterisk characters. The very lastidentifier is known as the called party number and does not begin withan asterisk or end with a pound sign. It is always the very last identifierin the information field of the Initial Service Request Message Complete(ISRMC) message.An example of a standard message is shown below:HeaderISRMC SICThe Header contains the following components:• ISRMC (Initial Service Request Message Complete) is the messagetype.• SIC (Service Indicator Code) is the Service Indicator Code for thismessage. The SIC is a required component of the ISRMC messagebut is not contained in all message types.An example of an Information Field is shown below:Information Field*3#19*P#8000See Table 6-3 onpage 6-10 for moreinformation on theseSupplementaryInformation String (SIS)identifiers.The Information Field contains these three components:• *3# is the Supplementary Information String (SIS) identifier. Here,it is Calling /Called Line Category – Public ISDN. This identifierhas optional parameters that are not used in this example.• 19*P# is the Loop Avoidance SIS identifier. The P (parameter)indicates the Number of Further Transmits parameter.• 8000 is the Called Party Number. This identifier does not beginwith an asterisk or end with a pound sign.60001262, First Edition DPNSS 1 Protocol 6-9