CCNA Cisco Certified Network Associate Study Guide - FTP Server

14 Chapter 1 � Internetworking
FIGURE 1.6 Windowing
Configured to a window size of 3, it’s allowed to transmit three data segments
before an acknowledgment is received. In our simplified example,
both the sending and receiving machines are workstations. Reality is rarely
that simple, and most often acknowledgments and packets will commingle
as they travel over the network and pass through routers. Routing complicates
things, but not to worry, you’ll learn about applied routing later in
the book.
Acknowledgments
Reliable data delivery ensures the integrity of a stream of data sent from one
machine to the other through a fully functional data link. It guarantees the
data won’t be duplicated or lost. The method that achieves this is known as
positive acknowledgment with retransmission. This technique requires a
receiving machine to communicate with the transmitting source by sending
an acknowledgment message back to the sender when it receives data. The
sender documents each segment it sends and waits for this acknowledgment