| |
|
|
| |
Ethernet evolved from researchers at Xerox. The term Ethernet was
derived from the "mythical substance once assumed to permit light to
travel through space." The original specification for Ethernet was
established in September 1980, with a revised Ethernet II completed in
November 1982. Ethernet II and the IEEE 802.3 specification are
practically compatible. |
|
| |
|
|
| |
Ethernet uses a method called carrier sensing for transmitting data
over a network. This method allows multiple nodes (computers) to
access the network in an organized manner for data flow. Sometimes
simultaneous access occurs, resulting in a possible network collision.
If this happens, each node must attempt to resend its data with a
slightly modified time interval. A nominal amount of collision occurs
on any network. Any properly designed network will keep the collision
factor down to a minimum. |
|
| |
|
|
| |
An Ethernet data frame consists of six sections: 1. The preamble (8
bytes in size), 2. The destination address (6 bytes in size), 3. The
source address (6 bytes in size), 4. The type (2 bytes in size), 5.
The data (46 - 1500 bytes in size), and the FCS (4 bytes in size).
Sometimes the bytes of data in a frame are referred to octets. The
preamble indicates that a frame is beginning. The destination address
section is just that; it tells the network where the frame is going.
The same applies for the source address; it tell where the frame came
from. The type section indicates the data type (X.25, IP, ARP, etc.).
The data section is the area that actually contains a bit of data that
is being transferred from one node to another. The last section is
the FCS, or frame check sequence. It indicates any errors that have
occurred during the transferring of the frame. |
|
| |
|
|
| |
The node address, also known as the MAC address, is the physical
address that is permanently assigned to each individual node (in this
case, the Ethernet card). It is 48 bits in size, divided into 6 8-bit
sections. The first three sections determine the manufacturer of the
card. The last three sections are used by the manufacturer
themselves. There are no two MAC address alike for any Ethernet
adapter on the market. |
|