ccna previous year question papers pdf

ccna previous year question papers pdf.Figure 2.3 Data Segment Discard and RetransmissionOf course, if two data segments are lost, the first scheme is not feasible unless the target device sends a list of the lost data segments. With this in mind, most protocol stacks that use windowing techniques implement the second scheme. Given this behavior, the window size may affect performance. You might think that a window size of 100 would be very efficient, but some protocols will have to retransmit all 100 data segments if the first one is lost! As mentioned earlier, most protocol stacks pre-negotiate the window size and are able to renegotiate it at any time. Therefore, if the connection has a large number of errors, the window size can be reduced to improve efficiency. When the errors disappear or are less frequent, the window size can be increased to maximize the throughput of the connection.The window size can be different on the source and target devices, which further complicates the situation. For example, PC-A may have a window size of 3, while PC.B has a window size of 10. In this case, PC.A can send 10 data segments to PC.B before waiting for an acknowledgement; while PC-B must wait for an acknowledgement after sending 3 data segments to PC-A.Chapter 8 discusses TCP in more depth when it discusses how to use sequence numbers and acknowledgments to control traffic.Exam PointsReady/not-ready signaling and windowing techniques are used to implement traffic control at the transport layer. Ready/not-ready signaling is inefficient and can lead to unwanted traffic.inefficiencies can lead to unnecessary traffic drops and traffic transfer delays. Windowing solves these problems. When using windowing techniques, thewindow size will be determined, which specifies how many data segments must wait for an acknowledgement from the target device after transmission.2.2.5 Layer 3: Network LayerLayer 3 of the OSI reference model is the network layer, which provides a number of functions. First, it gives the network a logical topology using logical (layer 3) addresses. These addresses are used to group network components together; as you will see in Chapter 6, these addresses consist of two parts: a network part and a host part, where the network part is used to group devices together. Layer 3 addresses allow devices located in the same or different Layer 2 media (protocols) to communicate with each other.