Hubs and Switches
- Hubs and Switches perform a similar function.
- End hosts in a Local Area Network such as PCs, servers, and printers plug into them with an Ethernet cable.
- The end hosts can then communicate with each other through the hub or switch.
Hubs- Half-Duplex and Shared Collision Domain
- Hubs operate in half-duplex mode.
- Attached hosts cannot send and receive data at the same time, they can only do one or the other.
- All Hosts share the same collision domain – only one device can transmit at a time.
- If two hosts send at the same time a collision will occur.
- Hosts use Carrier_Sense Multiple Access with Collision Detection (CSMA/CD) to detect collisions and resend.
- Hubs operate at Layer 1 of the OSI model.
- They are not MAC address aware.
- Whenever a frame is received it is flooded out all ports apart from the one it was received on.
- All attached hosts must process all packets.
Switches – Full-Duplex and Separate Collision Domains
- Switches can operate in either full-duplex or half-duplex mode.
- In practice, they always operate as full-duplex.
- Attached hosts can both send and receive data at the same time.
- All hosts have their own dedicated collision domain.
- Collision Detection is not required.
- Switches operate at Layer 2 of the OSI model.
- They also operate at Layer 1.
- They are MAC address aware.