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ccna 200 301 booksmart review roger.84Each segment is then sent to the network layer for processing, where it is responsible for network addressing and routing in the interconnected network. The logical address of each segment (e.g., IP) allows the segment to reach the correct network. The network layer protocol adds header control information to the data segments (delivered from the transport layer), and we refer to this new combination as a packet or datagram. Note that on the receiver host, the transport and network layers cooperate to be able to reconstruct the data stream; but within the local network segment, there is no need to interpret these two layers of PDUs-these PDUs only provide information about the router or host.The data link layer is responsible for processing the packets passed down from the network layer and placing them on the network medium (cable or wireless). The data link layer pairs each packet into a me basis; the header of the data frame contains the physical addresses of the source and destination hosts. If the destination device is located on a remote network, the data frame is sent to a router so that it can be routed through the interconnected network. When the data frame reaches the destination network, a new data frame is generated and this new data frame is responsible for delivering the packet to the destination host.In order to place a data frame into the network, it must first be converted into a digital signal. Since a data frame is actually a logical group of many 1s and 0s, it is the responsibility of the physical layer to encode these combinations of 1s and 0s into digital signals that can be read by devices in the same local network. The receiver device synchronizes these digital signals and decodes the logical combination of 1's and 0's from the digital signals. At this point, the receiver device reconstructs the data frame and then runs a CRC checksum and compares the result of the calculation with the data frame FCS field. If the two match, the receiver device extracts the packet from the data frame and discards the rest of the data frame, a process called liao-rolling This packet is handed off to the network layer where the network layer address is checked. If the address matches, the receiver device extracts the data segments from the packet and discards the rest of the packet. The data segmentation is then processed by the transport layer, which reconstructs the data stream and informs the transporting party device of each segment it received. After processing is complete, the transport layer submits the data stream to the upper layer application.On the sender device, the process of encapsulating the data is as follows.1. convert the user information into data so that it can be transmitted across the network.2. convert the data into data segments and establish a reliable connection between the sender host and the receiver host.3. Convert data segments into packets or datagrams, adding a logical address to the header of each packet so that the packet can be routed throughout the interconnected network. 4. Converting packets or datagrams into data frames for transmission within the local network. Within the local segment, a hardware (Ethernet) address is used to uniquely identify the hosts within the segment.5. converting data frames to bits while using digital encoding and clock synchronization mechanisms. For a clearer explanation of how addressing works at each layer. refer to Figure 3.13. keep in mind that the data stream is sent down from the upper layers to the transport layer. To a technical person, we don't care where the datastreams come from, because that's really for the programmer to consider. Our job is to efficiently reconstruct the data stream and hand it up to the upper layer application on the receiver's device.