To detect collisions, ethernet packets contain a checksum.Ĭhecking before transmitting is sometimes called "carrier sense (CS)" the fact that hosts can communicate without mastering the bus is sometimes called "multiple access (MA)". If the packet fails multiple times, it may be dropped. If a collision is detected, the sender may retransmit after a delay. Senders are responsible for listening to the network to ensure that the packets they sent were received. It is possible that there are collisions if two hosts on the same network try to send at the same time. If not, it places the packet on the wire. To send a packet, the sender first checks to see if the medium is in use. Ethernet is the most commonly used link-layer protocol.Įthernet is a broadcast protocol: many hosts are connected to all other hosts. On top of the physical layer, the link layer defines how packets of bits should be sent and received. The physical layer gives a mechanism for transmitting a packet of bits from one host to another. high voltage means 1) are referred to as the physical layer of the network. twisted pairs of wires, radio waves, fiber-optic cable, etc) along with the rules for interpreting those signals (e.g. The physical medium that is used to connect them (e.g. A network is a group of computers (which I will also call nodes, hosts, or machines) that are connected together.
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