Since 1 of the 5 links is connected to the processor and the other 4 links is connected to something else, you have a 4:1 oversubscription to the processor link. If all the links run at 100Mbps, then the max rate to the processor link can be 400Mbps. However, the processor link can only handle no more than 100Mbps. So the processor MAC will back pressure the switch by sending pause frames to the switch. The switch will have some built-in buffering to hold the data during the back pressure time. But eventually this buffer will not be enough due to the high oversubscription rate and packets will be dropped and the source will need to retransmit this packet again.
- Hung