CSMA/CD is the multiple access protocol used by Ethernet. It uses carrier sensing to prevent transmissions when other nodes are transmitting. A node will send its frame if the channel is free. If a collision is detected during transmission, the detecting node aborts its transmission and sends a jam signal before waiting a random time to retry. The paper proposes a modified CSMA/CDNQ protocol to resolve weaknesses in the standard CSMA/CD protocol by prioritizing queues for transmission. Future work may include developing a prototype to test and analyze the performance of CSMA/CDNQ under different network conditions.

1. CSMA/CD
Name: Sherif Hesham – 20181161
Mina Nan - 20180220

2. Introduction
2
Carrier Sense Multiple Access with Collision Detection (CSMA/CD), also
referred to by IEEE (Institute of Electrical and Electronics Engineers)
standards as 802.3, is the currently used Ethernet multiple access
protocol. It uses carrier-sensing to hold transmissions until no other
stations are transmitting. The node detects a free channel, the frame is
sent. If another frame is detected on the channel during transmission
the collision detection element takes over. The first node that detects a
collision aborts frame transmission and begins transmitting a jam
signal instead and then waits for a random time interval before trying
to resend the frame.

3. Contents
• Introduction
• References
3

4. Conclusion
W. Al-Hanafy 4
The CSMA/CDNQ algorithm may appear complicated, but in fact is
simply a modified version of the CSMA/CD protocol that is currently in
use by the Ethernet. My research indicates weakness in the CSMA/CD
protocol that my CSMA/CDNQ resolves. A prototype may be developed
in the future to test and examine the CSMA/CDNQ under different
network situations to get an accurate analysis of the benefits and
performance statistics of the protocol.