TCP is a stream oriented protocol, the bytes must arrive in the order they were sent. Packet loss will cause going back in the sliding window. For sending an e

TCP is a stream oriented protocol, the bytes must arrive in the order they were sent. Packet loss will cause going back in the sliding window. For sending an entire file over the network, you don't care which order the packets arrive. If a packet goes missing in the middle, there's no reason to stop transmitting and receiving later packets. Just re-transmit the missing piece from the middle at any point in the future. This is assuming that the entire file is stored on the sender's side. edit: the protocol design document (linked in this thread) also mentions multiplexing many "connections" using the same sockets in SPDY. With TCP, a lost packet in any of the mux'ed connections will slow down the others. Using UDP instead of TCP allows increasing bandwidth and decreasing latency. Website bloat is an orthogonal issue and should be addressed but QUIC can mitigate the problems a little.