Standalone Agent: Health update, job picking, status update and file download will happen directly against SapphireIMS server via HTTP/HTTPS protocol.
Slave Agent: Health update job picking, status update will happen against SapphireIMS server via HTTP/HTTPS protocol. But the file-download related jobs (such as software/script deployment, patch management jobs, agent upgrade) will be happening with help of mapped master agent via TCP protocol. This will reduce the load on the server and network bandwidth.
Please refer pictorial diagram in the article Explain conceptual diagram of Master & Slave Agent for patch/software file download