Broadcast & Unicast with Ethernet & Wifi

Question

I feel confused about broadcast & unicast with Ethernet & Wifi protocols

When we talk about broadcast, the frame is destinated to any station compared to unicast where the frame is destinated to one station only.

What I want to know is concretely: when using Ethernet & Wifi, is the signal of the frame received by all nodes?

am I right, I feel confused after some readings stipulating that with Wifi the air frame is received by all nodes, but with Ethernet it's not the case

Thanks,

Answer 1

Boradcast is a transmission that is intended for all and will have ff:ff:ff:ff:ff:ff destination MAC address. a unicast is a transmission that is intended for a specific network adapter and it will have its specific MAC address as a destination.

In terms of who "hears" the transmission it depends, lets start with ethernet: All stations within the same LAN and behind the same switch interface as the sender or the destination will hear the transmission. In case the switch does not know where the destination is located it will flood (duplicate) the message to all interfaces (except the interface in), making all nodes connected to this switch hearing the message.

WiFi: a bit more complicated, since stations can be in power save mode. For the power save mode I'll just say that those nodes do not hear most of the unicasts. in wifi there are many channels and a network interface can only listen on one channel at a time. Stations that transmit on different channel cannot hear one another (not entirely true, but good enough for now). A node that is awake will hear all transmissions (with enough power) on the channel its listening on, even if the two nodes are connected to different access points.

That said, network interfaces will ignore the frames that do not have their MAC address or a broadcast address. (Unless you want to hear it in promiscuous or monitor mode)