The OSI Model

A hub in an network


A Switch in an network


Ethernet Networking

• Ethernet is a contention media access method that allows all hosts on a network to share the same bandwidth of a link.
• Ethernet is popular because it’s readily scalable, meaning that it’s comparatively easy to integrate new technologies, such as Fast Ethernet and Gigabit Ethernet, into an existing network infrastructure.
• It’s also relatively simple to implement in the first place, and with it, troubleshooting is reasonably straightforward.

Ethernet Collision Detection
CSMA/CD


Half and Full Duplex

Half-duplex Ethernet is defined in the original 802.3 Ethernet; Cisco says it uses only one wire pair with a digital signal running in both directions on the wire.

But full-duplex Ethernet uses two pairs of wires instead of one wire pair like half duplex. And full duplex uses a point-to-point connection between the transmitter of the transmitting device and the receiver of the receiving device.

Full-duplex Ethernet can be used in three situations:

• With a connection from a switch to a host
• With a connection from a switch to a switch
• With a connection from a host to a host using a crossover cable