ccna 200-301 network simulator ns2 serves next

ccna 200-301 network simulator ns2 serves next.. Error detection: an additional feature of data encapsulation is error detection. The end of each Ethernet frame contains a Cyclic Redundancy Check (CRC) of the frame contents. When a frame is received, the receiving node calculates a CRC and compares it with the received CRC. If the two CRCs match, the received frame has no errors and can be trusted.Media Access Control: The MAC sublayer controls the loading of frames onto and offloading of frames from the transport medium. As the name implies, it manages the access control of the media. This includes initializing frame transfers and recovering from transmission failures due to collisions.Logical Topology: The logical topology of Ethernet is a multiple access bus, which means that all nodes (devices) in that network share the transmission media. It further means that all nodes on this segment can receive frames transmitted by any node on this segment. Because all nodes can receive all frames, each node needs to determine whether it needs to receive and process a frame, which depends on the destination MAC address in the data frame. Ethernet provides a method for determining how nodes share access to media. The classic method for media access control is CSMA/CD (CarrierSenseMultipleAccess/Collision Detection), which will be described in a later section.3. Evolution of EthernetEthernet has its roots in the original Alohanet, a digital wireless network designed to transmit information between the Hawaiian Islands on a shared radio frequency. o Alohanet required all workstations to retransmit packets that did not receive an acknowledgement, and this technique of using shared media was later applied to the wired technology of today's Ethernet. The technology used in the first generation of Ethernet was CSMA/CDoEarly Ethernet used coaxial cables to connect computers in a bus topology, with each computer connected directly to the backbone. Early Ethernet consisted of thick cable (thicknet, 10base5) and thin cable (thinnet, 10base2). 10base5 allowed a transmission distance of 500m, 10base2 allowed a transmission distance of 185m. early deployments of Ethernet, in low bandwidth network environments, used the CSMA principle to access shared media, CSMA later CSMA later evolved into CSMA/CDo Ethernet using coaxial cables was a logical bus topology at the data link layer and a bus topology at the physical layer.Later, UTP cables replaced coaxial cables, which were easier to install, lighter and cheaper. Using hub interconnects, the physical topology was changed to a star topology. The hub was the equivalent of a hub, and other computers were connected to the hub via UTP, so that a failure of one computer's cable would not affect the entire network. When a computer sends data to the hub, the hub forwards the data to all ports except the receiving port, which is still logically a bus topologyk70Chapter 3 Ethernet*! 03flop structure. Because the media is shared and only one workstation can successfully transmit at the same time, this type of connection is described as half-duplex communication. As the number of devices in an Ethernet increases, the probability of collisions becomes greater and the communication becomes less efficient.