The Internet Book

Chapter 16

3 A Packet Switching System Can Be Overrun Packet switching allows multiple computers to communicate without delay. –Requires that the computers divide data into small packets –Requires additional communication software to ensure

Figure 16.1 An example internet with four networks connected by routers. Figure 16.2 Cars from two roads merging onto another road are analogous to packets from two networks merging onto a third network.

5 TCP Helps IP Guarantee Delivery When hardware in a router or network system fails, other routers start sending datagrams. As a result, some datagrams: –Arrive in a different order than they were sent –Checked by TCP –Put in order –Checked for duplicates by TCP

6 TCP Provides A Connection Between Computer Programs TCP software makes it possible for two computer programs to communicate across the Internet. –Establishes a connection –Exchanges data –Terminates communication

7 The Magic Of Recovering Lost Datagrams TCP includes an identification of each datagram. –Ignores duplicate copies –Recovers lost datagrams Uses timers Sends an acknowledgement back to the source

8 TCP Retransmission Is Automatic TCP adapts to work everywhere on the Internet –Retransmits after a short time if destination computer is close –Retransmits after a longer period if destination computer is far –Measures delays –Adjusts the timeout factor automatically

9 TCP And IP Work Together TCP handles the problems that IP does not handle without duplicating the work that IP does. –Designed at the same time to work as a unified system –Engineered to: Cooperate with each other Compliment each other

10 Conclusion How does TCP detect and remove duplicate datagrams? How do TCP and IP work together to provide a reliable way to send data across the Internet?

12 Glossary Congestion –A problem in computer networks that occurs when too many packets arrive at a point in the network. Transmission Control Protocol –(TCP) One of the two major TCP/IP protocols. TCP handles the difficult task of ensuring that all data arrives at the destination in the correct order.