7:36 PM Wednesday, April 23, 2014 (UTC)

Ethernet | Carrier Sense Multiple Access with Collision Detection

Introduction to Ethernet Networking

According to CCNA 640-802 Ethernet is a media access method. Ethernet permits hosts to share the same bandwidth on a network of a link. Ethernet easily join together new technologies like Fast Ethernet and Gigabit Ethernet into a productive network. Its deployment and troubleshooting is very easy and can utilize the specification of Data Link Layer and Physical layer.

Carrier Sense Multiple Access with Collision Detection (CSMA/CD)

Carrier Sense Multiple Access with Collision Detection (CSMA/CD) was introduced to sort out the issues of collisions those arise when packets are transmitted at the same time from multiple hosts. It is a protocol which facilitates hosts to share the same bandwidth of a link on a network. It employed by Ethernet Networking. Collision management is very important in a productive network because when a device transmits in a CSMA/CD network; all other devices on the network listen and observe that transmission. Routers and Bridges can avoid spreading of transmission on the network.

Carrier Sense Multiple Access with Collision Detection (CSMA-CD)

Let me tell you, how the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol work. Host A wants to transmit data to host D. First it makes sure the availability of digital signal on the wire. If no other host is transmitting and the wire is clear, then host A will go on to its transmission. But it does not stop there. Host A continuously watches the wire to confirm that no other hosts are transmitting. If host A perceives an additional signal on the wire it releases a jam or busy signal, which becomes reason to stop transmission of all hosts on the segment. All hosts must listen that jam or busy signal by waiting before trying to start transmitting again. Back-off algorithms decide when to retransmit. But if collisions stay taking place after 15 attempts, the transmitting hosts will then timeout.

The following conditions happen when collision occurs:

  • Jam or busy signal tells to all nodes that collision occurred.
  • The collision calls to backoff algorithm.
  • Every node stops the transmission until the timers expire.
  • After the expiration timers, each node has the same priority to transmit.

Carrier Sense Multiple Access with Collision Detection CSMA/CD causes the following:

  • Delay
  • Low throughput
  • Congestion

We have covered in this article that how to Carrier Sense Multiple Access with Collision Detection (CSMA/CD) works with Ethernet and how collision occur and jam the network segments according to the CCNA 640-802 Cisco Certified Network Associate’ course detail.

Filed in: HowTo's, Inter-Networking, Networking, Technology Updates

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