All software data are saved in the agentinstallersegments database (DB) table. The index of these data is saved in the agentinstaller DB table.
DSM provides the download URLs of these software to the Agents or ESXi using Tomcat servlets.SoftwareServlet. The download URL looks like the following:
https://DSM.example.domain:4119/vib/FilterDriver-ESX_5.0-9.0.0-854.x86_64.zip