Like any type of LAN, 10BASE5 and 10BASE2 had limitations on the total length of a
cable. With 10BASE5, the limit was 500 m; with 10BASE2, it was 185 m. Interestingly, the
5 and 2 in the names 10BASE5 and 10BASE2 represent the maximum cable length—with
the 2 referring to 200 meters, which is pretty close to the actual maximum of 185 meters.
(Both of these types of Ethernet ran at 10 Mbps.)
In some cases, the maximum cable length was not enough, so a device called a repeater was developed. One of the problems that limited the length of a cable was that the signal sent by one device could attenuate too much if the cable was longer than 500 m or 185 m. Attenuation means that when electrical signals pass over a wire, the signal strength gets weaker the farther along the cable it travels. It’s the same concept behind why you can hear someone talking right next to you, but if that person speaks at the same volume and you are on the other side of a crowded room, you might not hear her because the sound waves have attenuated.
Repeaters connect to multiple cable segments, receive the electrical signal on one cable, interpret the bits as 1s and 0s, and generate a brand-new, clean, strong signal out the other cable. A repeater does not simply amplify the signal, because amplifying the signal might also amplify any noise picked up along the way.
NOTE :- Because the repeater does not interpret what the bits mean, but it does examine and generate electrical signals, a repeater is considered to operate at Layer 1
You should not expect to need to implement 10BASE5 or 10BASE2 Ethernet LANs today. However, for learning purposes, keep in mind several key points from this section as you move on to concepts that relate to today’s LANs:
The original Ethernet LANs created an electrical bus to which all devices connected.
Because collisions could occur on this bus, Ethernet defined the CSMA/CD algorithm, which defined a way to both avoid collisions and take action when collisions occurred.
Repeaters extended the length of LANs by cleaning up the electrical signal and repeating it—a Layer 1 function—but without interpreting the meaning of the electrical signal.
In some cases, the maximum cable length was not enough, so a device called a repeater was developed. One of the problems that limited the length of a cable was that the signal sent by one device could attenuate too much if the cable was longer than 500 m or 185 m. Attenuation means that when electrical signals pass over a wire, the signal strength gets weaker the farther along the cable it travels. It’s the same concept behind why you can hear someone talking right next to you, but if that person speaks at the same volume and you are on the other side of a crowded room, you might not hear her because the sound waves have attenuated.
Repeaters connect to multiple cable segments, receive the electrical signal on one cable, interpret the bits as 1s and 0s, and generate a brand-new, clean, strong signal out the other cable. A repeater does not simply amplify the signal, because amplifying the signal might also amplify any noise picked up along the way.
NOTE :- Because the repeater does not interpret what the bits mean, but it does examine and generate electrical signals, a repeater is considered to operate at Layer 1
You should not expect to need to implement 10BASE5 or 10BASE2 Ethernet LANs today. However, for learning purposes, keep in mind several key points from this section as you move on to concepts that relate to today’s LANs:
The original Ethernet LANs created an electrical bus to which all devices connected.
Because collisions could occur on this bus, Ethernet defined the CSMA/CD algorithm, which defined a way to both avoid collisions and take action when collisions occurred.
Repeaters extended the length of LANs by cleaning up the electrical signal and repeating it—a Layer 1 function—but without interpreting the meaning of the electrical signal.
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