When you download music or movies it sue UDP or TCP/IP protocol?

When you download music or movies it sue UDP protocol only? Or when you download any datas like pdf file is use TCP/IP protocol?

That is correct, TCP requires each packet sent to be acknowledged before the next packet is sent to the client. TCP is used for data and webpages so that information can be recovered if packets are lost. To speed the process up the host will send more and more packets each time to the client reducing the amount of acknowledgements needed. If one packet is dropped then the packet count sent is reduced to maintain stability. This is known as 'Windowing'.

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UDP is another Transport protocol where no acknowledgement from the client is received. UDP is typically used for streaming services such as video or VoIP. This is because a packet that is resent would not be needed since the time has already passed when the packet was needed. This also reduces the bandwidth required for running a stream application since less packets are sent overall (No acknowledgments). The most noticeable applications which use UDP to transport packets are DNS requests, video and voice streaming and online multiplayer gaming.



A typical analogy would be:

TCP : "Tell me when you get there"

UDP: "I hope it gets there"

Hope This Helps,
Josh!