You are here: CSP Developer’s Guide: Common Channel Signaling > 5 TUP, BT IUP & SSUTR2 > BT IUP Call Flows
Purpose
This section includes BT IUP outgoing and incoming call flows.
The PPL Event Request (SND) and PPL Event Indication (FAM/SAM) sequence may continue until a FAM is returned to the Host or the Host halts sending of PPL Event Requests (SND).
The following is a call flow diagram in which a successful call is originated from the host. All address digits are present in the Outseize Control message, therefore an IFAM is issued to the lower layers.
(1) The Outseize Control Message may be composed using either the IUP ICB or the Outpulse Stage N Address Data ICB and the Call Type ICB. When the IUP ICB is presented it is sent to lower layers unmodified. This example assumes that the HOST has built an IFAM message within the IUP ICB. When the Outpulse Stage N Address Data ICB format is chosen one or two BCD strings may be encoded in the ICB. When only one BCD string is encoded it will be interpreted as the called address. When two BCD strings are encoded the first one is interpreted as the calling address and the second as the called address. All other information required to format an IFAM will be extracted from the Config Bytes.
Successful Outgoing IAM Call Host Supplies Subsequent Digits
(2) The only way to cause an IAM is to encode an Outseize Control Message with a IUP ICB containing an IAM.
(3) This message may contain either a IUP ICB with the exact SAM or a generic Outpulse Stage N Address ICB.
(1) The Release reason is saved by L3P and is forwarded in the Clear Request to L4-CCP.
Successful Incoming Call for an LSU
This example assumes that the CSP is the Local Switching Unit (LSU) (that is, terminating switching functionality), since they only receive IFAM messages. When configured as an Intermediate Node (switching A Digital Main Switching Unit (DMSU)) IAM may begin the message exchange.
This message may contain either the received IUP ICB (i.e. containing the complete IFAM) from the IFAM or a BCD-Encoded Stages Data ICB. Which ICB type to attach to the Setup message is dependent upon a Config Byte defined above.
This message will be ignored by L3P IUP.
Incoming Call - Simple Telephone Call - Auto ACI Generation
This call flow depicts a situation where a Config Byte has been set to allow the automatic generation, via L3P, of Additional Call Information Requests (ACI) to the calling network.
Incoming Call - Simple Telephone Call - Host Control with ACI
This call flow depicts a situation where a config byte has been set to allow the host to control the requests for ACI data.
Successful Incoming Call Flows
For a DMSU where L3P IUP completes IAM Processing (AUTO SND)
A Digital Main Switching Unit (DMSU) must be able to process IAM and IFAM messages since this type of CSP may appear between two LSUs. The more complicated case is the reception of an IAM. L3P IUP analyzes the number of Address digits received. If the required number of digits has not been received within a configurable amount of time, as defined via Config Byte settings, the appropriate number of Send N Digit messages will be issued until the digit count is satisfied.
Successful Incoming Call - Host Control
For an DMSU where L3P IUP completes IAM Processing (Host Control
