|  | 5.5 |
Collisions and Collision Domains in Shared Layer Environments
| 5.5.9 | The four repeater rule
The four repeater rule in Ethernet states, that no more than four repeaters or repeating hubs can be between any two computers on the network. Each repeater adds latency or slows down the bits as their signal strength is boosted. Exceeding the four repeater rule can lead to violating the maximum delay limit. When this delay limit is exceeded, the number of late collisions dramatically increase. A late collision, is when a collision happens after the first 64 bytes of the frame are transmitted. The chipsets in NICs are not required to retransmit automatically when a late collision occurs. These late collision frames add delay referred to as consumption delay. As consumption delay and latency increase, network performance decreases. This Ethernet rule of thumb is also known as the 5-4-3-2-1 rule. Five sections of the network, four repeaters or hubs, three sections of the network are "mixing" segments (with hosts), two sections are link segments (for link purposes), and one large collision domain.