In a LAN packet-switched environment, such as with an Ethernet network, the transmission of the data packets relies on packet switches, routers, and LAN cables. In a LAN…, the switch establishes a connection between two segments only long enough to send the current packet. Incoming packets are saved to a temporary memory area or buffer in memory. In an Ethernet-based LAN, an Ethernet frame contains the payload or data portion of the packet and a special header that includes the media access control (MAC) address information for the source and destination of the packet. When the packets arrive at their destination, they are put back in order by a packet assembler. A packet assembler is needed because of the different routes that the packets may take. Bottom Line is a router breaks up a number of computers into segments. So the collision domain is all the computers in that segment. The router prevents data traveling to the other segment when it is not addressed to that segment.