Ethernet uses CSMA/CD (Carrier Sense Multiple Access with Collision Detection) as its media access control (MAC) system.
Understanding CSMA/CD in Ethernet
CSMA/CD is the original media access control protocol used by Ethernet networks. Here’s a more detailed look at how it works:
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Carrier Sense: Before transmitting data, a device listens to the network to check if it's already in use. This helps to avoid collisions by preventing multiple devices from transmitting at the same time.
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Multiple Access: Multiple devices on the network can access the transmission medium, sharing a common communication channel.
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Collision Detection: If two devices happen to start transmitting at nearly the same time, a collision occurs. When a collision is detected, the involved devices immediately stop transmitting, send a brief jamming signal to notify all other nodes, and wait for a random time interval before retransmitting. This is key to resolving conflicts effectively.
Why CSMA/CD?
The use of CSMA/CD aims to prevent and manage data collisions on the shared network medium, ensuring more efficient and orderly data transmission across the network. This protocol, while being a foundational technology, has become less common in modern, switched Ethernet networks where full-duplex communication and dedicated connections are the norm.
CSMA/CD in Today's Networks
While it was essential in older hub-based networks, modern Ethernet networks typically use switches. Switches greatly reduce the probability of collisions by creating point-to-point connections, making CSMA/CD less relevant in most current Ethernet environments. However, understanding CSMA/CD provides valuable context for the historical development and functionality of Ethernet.
| Feature | Description |
|---|---|
| Carrier Sense | Device listens before transmitting. |
| Multiple Access | Multiple devices can access the network. |
| Collision Detection | Detects and resolves collisions by stopping transmission and waiting before retransmitting. |
