Figure 2-4: General Message Organization, Continued Data Field Header Other Destination Message without Header Address a trailer Field Field Usually only data link layer messages have trailers 2-11
2-11 Figure 2-4: General Message Organization, Continued Data Field Header Other Header Field Destination Address Field Message without a trailer Usually only data link layer messages have trailers
Figure 2-4: General Message Organization, Continued Header Other Destination Message with Header Address only a header Field Field TCP supervisory messages are pure headers (there is no data field content to deliver) 2-12
2-12 Figure 2-4: General Message Organization, Continued Header Other Header Field Destination Address Field Message with only a header e.g. TCP supervisory messages are pure headers (there is no data field content to deliver)
Test Your Understanding ·P100 2-13
2-13 • Test Your Understanding • P 100
Reliability
2. Reliability
Figure 2-5: Reliable Transmission Control Protocol (TCP)Session The Transmission Control Protocol (TCP)is an important standard in Internet transmission TCP Receiver acknowledges each correctly-received TCP segment If an acknowledgments is not received by the sender the sender retransmits the TCP message(called a TCP segment) This gives reliability: error detection and error correction 2-15
2-15 Figure 2-5: Reliable Transmission Control Protocol (TCP) Session • The Transmission Control Protocol (TCP) is an important standard in Internet transmission • TCP – Receiver acknowledges each correctly-received TCP segment. – If an acknowledgments is not received by the sender, the sender retransmits the TCP message (called a TCP segment) – This gives reliability: error detection and error correction