ccna 200 301 booksmart review new york

ccna 200 301 booksmart review new york.Now that you know what the port number is used for and how it is used at the transport layer, go back and look at Figure 3.13 o After you add the transport layer header information to a small piece of data, that small piece of data becomes a data segment. This data segment is sent down to the network layer along with the destination IP address (the destination IP address is sent down to the transport layer along with the data stream from the upper layer, which is the destination IP address obtained through the domain name resolution mechanism - most likely DNS) .The network layer adds header information for each data segment, which contains logical addressing information (IP address). After header information is added to the data segment, the PDU becomes a packet. The packet carries a "protocol" field in the header that describes the source of the data segment it carries (whether TCP or UDP). The host can give the data segments to the correct protocol based on the information in the "Protocol" field.The network layer looks for the destination hardware address, which indicates which device on the local network the packet should be sent to. The network layer obtains the destination hardware address by using ARP (Address Resolution Protocol), more about which is described in Chapter 4. The network layer's IP protocol looks at the destination IP address of the packet and compares it to its own source IP address and subnet mask. If the packet's IP address is found to be on the local network, then the network layer will pass an ARP request to get the hardware address of the local host. If the packet is destined for a remote host, the network layer looks up the IP address of the default gateway (router).This packet is then sent down to the data link layer, along with the destination hardware address of the local host or default gateway. The data link layer adds a header to the front of the packet, thus forming it into a data frame (it is called a frame because the data link layer adds both a header and a tail to the front and back of the packet, which are like a bookend or a frame). The structure of a data frame is illustrated in Figure 3.13. The data frame uses the "Ethernet type" field to describe the network layer protocol to which the packet belongs. The data link layer performs a CRC (Cyclic Redundancy Check) algorithm on the data frame and adds the result of the calculation to the FCS (Frame Check Sequence) field at the end of the data frame.At this point the data frame is ready to continue to the physical layer, one lbit at a time, and the physical layer encodes the data into a digital signal using bit timing rules. All devices in the segment are clock synchronized and the 1s and 0s are extracted from the digital signal and used to recreate the data frame. After the data frame is reconstructed, the data link layer runs a CRC algorithm to ensure that the data frame is intact. If all goes well, the host then looks at the destination MAC and IP address of the data frame to determine if it was sent to itself.If the above description makes you do a double take and your head spin, never mind. In Chapter 9, we go into more detail about how data is encapsulated and routed across an interconnected network."Frame", as a technical term, translates to "frame". This phrase explains the rationale for using Frame to name this data structure. A translator's note3.4 SummaryIn this chapter, we learned about the basics of interconnecting Ethernet networks, how hosts communicate in a network, and how CSMA/CD works in an Ethernet half-duplex network. The chapter also covered the differences between half-duplex and full-duplex and discussed the conflict detection mechanism CSMA/CDoThis chapter then describes the common types of Ethernet cables used in today's networks. By the way, just a reminder that you must have a very good grasp of this section!