Late Collisions on Ethernet Interfaces: Common Causes and Solutions

Reasons for Late Collisions on Ethernet Interfaces


What are two reasons that cause late collisions to increment on an Ethernet interface? (Choose two.)



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A. B. C. D. E.


A late collision is defined as any collision that occurs after the first 512 bits (or 64th byte) of the frame have been transmitted.

The usual possible causes are full- duplex/half-duplex mismatch, exceeded Ethernet cable length limits, or defective hardware such as incorrect cabling, non-compliant number of hubs in the network, or a bad NIC.

Late collisions should never occur in a properly designed Ethernet network.

They usually occur when Ethernet cables are too long or when there are too many repeaters in the network.

Late collisions occur when a device transmits a frame on an Ethernet network and detects that a collision has occurred after the 512th bit of the frame has been transmitted. This indicates that the collision occurred too late in the transmission process to be detected by the collision detection mechanism, which can result in a loss of data.

Two reasons that cause late collisions to increment on an Ethernet interface are:

B. When one side of the connection is configured for half-duplex: In a half-duplex connection, both devices cannot transmit and receive data simultaneously. Instead, they must take turns transmitting and receiving data. When a device that is configured for half-duplex mode tries to transmit while another device is still transmitting, a collision can occur. If the collision is detected early enough in the transmission process, the transmitting device can stop transmitting and retransmit the data. However, if the collision is detected too late in the transmission process, a late collision will occur.

E. When the cable length limits are exceeded: Ethernet networks have a maximum cable length limit, which is determined by the speed of the network and the type of cable being used. If the cable length limit is exceeded, the signal can become weak, resulting in errors and late collisions. When the signal travels too far, it may also be delayed and arrive too late to be detected by the collision detection mechanism. This can result in a late collision.

The other options are incorrect because:

A. Carrier Sense Multiple Access/Collision Detection (CSMA/CD) is a mechanism used by Ethernet networks to avoid and detect collisions. However, it does not cause late collisions to increment.

C. There is no standard time limit for retransmitting a frame after a collision. However, waiting 15 seconds before retransmitting a frame would not cause a late collision.

D. The 32nd byte of a frame is not significant in causing late collisions.