Specifications

Ethernet Features
2-4 Introduction
Frame Transmission
Ethernet stations encode their data into groups using a method known as
Manchester Encoding. These data groups, called frames, can be one of
four basic Ethernet frame types:
• 802.3 “raw” frame
• Ethernet II (DIX) frame
• Ethernet 802.2 frame
• Ethernet SNAP frame
The Ethernet 802.2 and Ethernet SNAP frames are extensions of the 802.3
“raw” frame format, while the Ethernet II frame is formatted differently.
More about Ethernet frame types and Manchester Encoding will be
discussed in Chapter 4,
Ethernet Data Frames.
Ethernet Topologies
The physical topology of the network defines its shape. Various network
topologies exist in the form of stars, trees, rings or buses. Complex
networks may employ several of the above topologies to form a hybrid
topology. A bus of stars or a ring of buses are two such examples.
Figure 2-1 shows some examples of several topology types. The boxes
indicate equipment of some type and the lines indicate cabling.
Figure 2-1. Various Network Topologies
Bus
Ring
Star
Tree
Hybrid
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