Multiple Copies of Unicast Frame Transmission

D

If we connect two switches via 2 or more links and do not enable STP on these switches then a loop (which creates multiple copies of the same unicast frame) will occur. It is an example of an improperly implemented redundant topology.

In a switched LAN, unicast frames are normally transmitted from the source to the destination without any duplication. However, there are certain circumstances where multiple copies of the same unicast frame may be transmitted.

A. During high traffic periods: During periods of high traffic, the switch may become congested and unable to transmit all the frames that are being sent. In such cases, the switch may resort to retransmitting the same frame multiple times to ensure that it reaches its destination.

B. After broken links are re-established: When a link between two switches or between a switch and a host is broken and then re-established, the switch may transmit multiple copies of the same frame to ensure that it is received by the destination device.

C. When upper-layer protocols require high reliability: Some upper-layer protocols, such as TCP, require reliable transmission of data. In such cases, the switch may transmit multiple copies of the same frame to ensure that the data is reliably delivered to the destination.

D. In an improperly implemented redundant topology: In a redundant topology, there may be multiple paths between a source and a destination. If the redundancy is not implemented correctly, there may be loops in the network that can cause multiple copies of the same frame to be transmitted.

E. When a dual ring topology is in use: In a dual ring topology, frames are transmitted in both directions around two separate rings. If there is a failure in one of the rings, frames may be transmitted on both rings, resulting in multiple copies of the same frame being sent.

In summary, multiple copies of the same unicast frame may be transmitted in a switched LAN during high traffic periods, after broken links are re-established, when upper-layer protocols require high reliability, in an improperly implemented redundant topology, and when a dual ring topology is in use.