C.2 TCAP segmentation

29.0023GPPMobile Application Part (MAP) specificationRelease 17TS

At the TCAP level the following segmentation mechanisms are available:

C.2.1 Empty Begin

In a dialogue with AC version >1 the first forward message (Begin) must contain a Dialogue Portion. Instead of sending the Dialogue Portion and the Component Portion in the first forward message, an empty Begin (i.e. without a Component Portion) is sent, followed (after successful dialogue establishment) by a Continue message which can carry a longer Component Portion since no Dialogue Portion is present in the second forward message.

C.2.2 Empty Continue

In a dialogue with AC version >1 the first backward message (Continue / End) must contain a Dialogue Portion. Instead of sending the Dialogue Portion and the Component Portion in the first backward message, an empty Continue (i.e. without a Component Portion) is sent, followed by a Continue/End message which can carry a longer Component Portion since no Dialogue Portion is present in the second backward message.

C.2.3 TC-Result-NL

A Result component may be segmented into one or several Result-Not-Last components followed by a Result-Last component. As specified in clause 15.6.3, the MAP user parameter shall be split so that each segment is compatible with the type defined for the parameter of the result of the associated operation.

Note that this segmentation mechanism runs the risk that the message carrying the Result-Last component arrives before the message carrying a Result-Not-Last component which results in failure. The use of SCCP class 1 "Sequence guaranteed", which raises the chance of in sequence delivery, is recommended.