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Chapter 5: Network Protocols
Figure 5-6
TCP Windowing
Windowing does not require that the sender stop sending in all cases, as is shown in Figure
5-6. If an acknowledgment is received before the window is exhausted, the sender continues to
send data until the current window is exhausted. With no errors or congestion, the sender can
send continually after the initially small window has been increased.
Connection Establishment and Termination
Connection establishment is the last TCP function reviewed in this section, but it occurs before
any of the other TCP features can begin their work. Connection establishment refers to the
process of initializing sequence and acknowledgment fields and agreeing to the port numbers
used. Figure 5-7 shows an example of connection establishment flow.
Figure 5-7
TCP Connection Establishment
Web Client
Web Server
SEQ=1000
SEQ=2000
SEQ=3000
SEQ=4000
SEQ=5000
SEQ=6000
ACK=4000
Windo
w=4000
ACK=1000
Windo
w=3000
SEQ=7000
Web
Client
Web
Server
SYN, DPORT=80, SPORT=1027
SYN, ACK, DPORT=1027, SPORT=80
ACK, DPORT=80, SPORT=1027
SEQ=200
SEQ=1450, ACK=201
SEQ=201, ACK=1451
ch05.fm Page 222 Monday, March 20, 2000 5:06 PM