Network edge:connection-oriented service Goal:data transfer TCP service_[RFC 793] between end systems reliable,in-order byte- ▣handshaking:setup stream data transfer (prepare for)data ÷loss:acknowledgements(确认 transfer ahead of time and retransmissions Hello,hello back human ▣flow control: protocol sender won't overwhelm *set up "state"in two 没)receiver communicating hosts ▣congestion control:. 口TCP-Transmission senders "slow down sending Control Protocol rate"when network *Internet's connection- congested(拥塞、拥挤、阻塞) oriented service Introduction 1-13 Introduction 1-13 Network edge: connection-oriented service Goal: data transfer between end systems ❑ handshaking: setup (prepare for) data transfer ahead of time ❖ Hello, hello back human protocol ❖ set up “state” in two communicating hosts ❑ TCP - Transmission Control Protocol ❖ Internet’s connection￾oriented service TCP service [RFC 793] ❑ reliable, in-order byte￾stream data transfer ❖ loss: acknowledgements（确认 ） and retransmissions ❑ flow control: ❖ sender won’t overwhelm（淹 没） receiver ❑ congestion control: ❖ senders “slow down sending rate” when network congested（拥塞、拥挤、阻塞）