1 Ethernet as defined by IEEE-layered model (vis-? -vis the OSI model)
Application
Session
Presentation
Transport
Network
Data-Link
Physical
Seven-Layer OSI Model IEEE 802.3
Logical-Link
Control
Media Access Control
(MAC)
Physical
Media Support
(PHY)
6 Chapter 1
The Basic Ethernet Frame
The IEEE 802.39 has defined a basic Ethernet frame format, as shown in Figure 1.2.
The fields that comprise the basic Ethernet frame (which is also referred to as the
Protocol Data Unit or PDU10) are also shown and briefly described in the figure.
The maximum size of the Ethernet frame, referred to as the Maximum Transmission
Unit (MTU), in the standard case is 1526 Bytes (1 Byte = 8 bits), including the maximum
data payload of 1500 Bytes. If the data payload is larger than this, it is broken down
into smaller sizes and encapsulated within Ethernet frames. The maximum and minimum
frame size limits listed in the IEEE 802.3 do not include the preamble and start
of frame bytes. This makes the maximum untagged frame 1518 bytes and the minimum
untagged frame 64 bytes. Protocol analyzers and frame statistics probes normally report
frames in this manner.
Pages:
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97