What is the purpose of a preamble in an Ethernet frame? It contains a description of the data that is to follow so the receiving NIC knows how to reassemble it. It provides the receiving NIC with the sending NIC's MAC address so communication can continue. It gives the receiving NIC time to realize a frame is coming and to know when the frame starts. It provides error-checking to ensure data integrity. What are in the Ethernet header The data directly from the application that generated the data The IP addresses 64 bytes The MAC addresses In Ethernet, if a node receives a frame and the calculated CRC does not match-detected an error, what action will the node take? O Disable the interface on which the frame arrives O Forward the frame as it is to the next host O Drop the frame O Reconstruct the frame from the CRC What is the purpose of the jam signal in CSMA/CD? To notify other nodes that a node is about to send To allow the media to recover To make sure that all sending nodes see the collision To identify the length of a frame