2018/09/05
Before we get started, we need to know that there are many books that introduce old LAN technologies such as Token Ring, FDDI and ARCNET. However, I think Ethernet today dominates the Network world. We'd better focus only on how Ethernet works. All other old LAN technologies will get you into chaos and wasted time. After clarifying the content of Ethernet, it is time to learn other things.
Ethernet
A commonly used technologies in LAN.
A commonly used technologies in LAN.
UTP
Primary wire type for Ethernet.
Primary wire type for Ethernet.
Duplex
- Half Duplex is a type of communication that allows data to be sent and received using the same link, but only one direction can be used at the same time.
- Full Duplex is a type of communication that allows data to be sent and received using the same link and same time.
CSMA/CD
A media access control method used in early Ethernet (Half Duplex).
A media access control method used in early Ethernet (Half Duplex).
- Listen: Check if the medium is idle.
- Collision Detect: Check if the collision event occurs when transferring data.
- Backoff: Wait a random time (Binary Exponential Backoff Algorithm) if the medium is not idle in "listen" state or collision event occurs.
Modern Ethernet (Full Duplex)
Full duplex communication is achieved by using two links. One for transmitting and one for receiving. Modern Ethernet no longer needs to use "listening", "collision detection" and "backoff". Because it never hits a collision event.
Full duplex communication is achieved by using two links. One for transmitting and one for receiving. Modern Ethernet no longer needs to use "listening", "collision detection" and "backoff". Because it never hits a collision event.
Star Topology
Ethernet Frame Format
- Maximum Transmission Unit (MTU) of a standard Ethernet frame is 1518 octets (bytes). 14 octets of header, 4 octets of frame check sequence (FCS) and 1500 octets of data.
- MAC Address is a unique identifier in the world.
- Type is used to indicate which protocol is encapsulated in "Data" Column.
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