TCP: The TCP(transmission control protocol), manages the sending and receiving of all your data as packets. Like a guaranteed mail service. When you request a song on your device, Spotify sends a song broken up into many packets. When your packet arrives, TCP does a full inventory and sends back acknowledgements of each packet received. If all packets are there, TCP signs for your delivery and you’re done, but, if there are missing packets, it won’t sign. And for each missing or incomplete packet, Spotify will resend them. And again the procedure.