Collection communication involves both messaging and data transmission. The messaging part is illustrate below 
The details on alams are described under Alarm communication. Communication for getFileList can either be via the Get Data List client or be the same as for the Get Data List client (See Get File List Communications). Similar for the getChecksums communication, this can either be via the Get Checksums client or be the same as for the Get Checksums client (See Get Checksums Communication).
Each message is only sent to one pillar.