ccna question examples

ccna question examples.standard covers both physical layer and data link layer functionality. Initially, the main difference between the two standards was the framing approach; in addition, the IEEE divided the data link layer into two sublayers to simplify handling multiple Layer 2 and Layer 3 protocols.Another version of Ethernet was developed by the IEEE with the specification standards IEEE802.2 and 802.3. The IEEE divided the data link layer into two parts: medium access control (MAC) and logical link control (LLC), as shown in Table 3.1. The upper half of the data link layer is the LLC, whose functions are performed in software; the lower half is the MAC, whose functions are performed in hardware.The LLC uses the Service Access Point (SAP) identifier to perform multiplexing. When encapsulating a network layer packet in an 802.2 frame, the network layer protocol number is specified in the SAP field. Upon receipt of the frame, the target device looks at the SAP field to determine which network layer protocol the frame should be given to for processing. This allows the target network device to distinguish between TCP/IP, IPX, and other network layer protocols that transmit data over a data link layer connection. In addition, LLC alsocan provide sequencing and flow control functions, thus providing reliable service as TCP does at the transport layer, which is discussed in Chapter 8. However, most Ethernet data link layer implementations do not provide this functionality - if reliable connectivity is required, it can be provided by the transport or application layers.Table 3.1 Components of the IEEE Ethernet Data Link Layer Data Link Layer Component Name IEEE Standard Description !Upper Part Logical Link Control (LLC) 802.2 Defines how to multiplex network layer protocols in data link layer frames. where the data link layer is not required to be Ethernet. LLC functions are performed in softwareSecond half Media Access Control (MAC) 802.3 Defines how to transport information in an Ethernet environment and also defines how framing, MAC addressing, and Ethernet work. MAC functions are performed in hardware3.1.3 Framing MethodThe main difference between the IEEE implementation of Ethernet and the EthernetII implementation is the framing method. As described in Chapter 2, framing specifies the format of the information as it is transmitted through the data link layer medium, it specifies which fields the frame contains and the length of those fields, and it lets each device know how to read the contents of the frame. The next few subsections discuss the framing methods used by the positive EE standards 802.3 and 802.2, as well as EthernetII.1. IEEE802.3