"No tiers or layers" in a flat network topology means:

1. _No hierarchical structure_: The network doesn't have a pyramid-like structure with higher and lower levels.

2. _All devices are peers_: Each device is equal and has the same status as others.

3. _No central backbone_: There is no central backbone or core network that controls the flow of data.

4. _No aggregation points_: Data is not aggregated or concentrated at specific points in the network.

5. _No dependency on specific devices_: The network doesn't rely on specific devices to function.

6. _Equal access to resources_: All devices have equal access to resources and data.

7. _Decentralized architecture_: The network is designed to be decentralized, with no single point of failure.

8. _Self-organizing network_: The network organizes itself without a central authority, with devices adapting to changes.

By eliminating tiers and layers, flat network topology enables a more decentralized, resilient, and democratic network, where devices can communicate and share resources on an equal basis.