Computers as Components, 2nd Edition

8.3 Network-Based Design 413

Preamble

Start

frame

Destination

address

Source

address

Length Padding CRCData

FIGURE 8.17

Ethernet packet format.

Figure 8.17 shows the basic format of an Ethernet packet. It provides addresses

of both the destination and the source. It also provides for a variable-length data

payload.

The fact that it may take several attempts to successfully transmit a message and

that the waiting time includes a random factor makes Ethernet performance difficult

to analyze. It is possible to perform data streaming and other real-time activities on

Ethernets,particularly when the total network load is kept to a reasonable level,but

care must be ...