Ethernet protocol
Ethernet is a broadcast protocol, operating on the datalink layer. Conceptually similar to radio. Every time a node communicates with another node, all nodes on the network receive the transmission, and each server's NIC, or DeviceDriver determines if this message was intended for it. Ethernet can be used in either wired, or wireless networks.
A collision occurs when two stations transmit at the same time. Information over the network is then corrupted, and retransmission is required. These retransmissions decrease the throughput of the entire network.
NOTE:
How does a network know retransmission is necessary? where does the request for retransmission come from?
Concepts
Ethernet Frame
Determines what a single unit of data passed over the network looks like. This is covered in great detail on wikipedia: https://en.wikipedia.org/wiki/Ethernet_frame
Broadcast Domain (LAN)
The section of a network where hosts talk directly to each other, without involving a router.
Hardware
Switches
Modern internet uses switches - either builtin to a router, or separately throughout the network. Switches receive a broadcast signal from one node, determine the target node's mac address, and fire it at just that one computer.
This results in an entirely collision free LAN. Wireless does not have switches, and it is frought with collisions.
Repeaters
Repeaters dumbly repeat any traffic they receive. The longer the cord, the more degraded the signal becomes. Repeaters continue to push traffic forwards, and extend the possible distance of a network
Bridges
Bridges function very similarly to repeaters, except that only well-formed packets are pushed forwards.
Testing
Testing ethernet can be done using ping. If a host was unreachable, you try checking:
- IPV4: arp table entry (address resolution protocol). (ipv4 > MAC)
- IPV6: nd table entry (neighbor discovery protocol). (ipv6 > MAC)
