The first step is to save the source and destination address in the IP decoder (IP.dec). The method used to save intraframe data is StoreIntraframeField, and it is used in a RETRIEVE clause on the field to be saved. The method name is followed by the intra-frame data name.
Here is a code fragment from the IP decoder, showing how the method is used to save the field values.
FIELD src_addr (Fixed 4 Byte)
RETRIEVE (StoreIntraframeField source_ip_address) (IPAddress) IN_SUMMARY Source 90 "Source Address"
FIELD dest_addr (Fixed 4 Byte)
RETRIEVE (StoreIntraframeField destination_ip_address) (IPAddress) IN_SUMMARY Destination 90 "Destination Address"