NIC (Network Interface Card):

• Amplifies electronic signals.
• Packages data for transmission.
• Physically connects computer to transmission media.
• Available in various speed (10 Mbps to 10 Gbps)
• Available in various variety (for Ethernet, Token Ring, FDDI)

Repeater:

• Receives signal from one point, regenerate it, and passes it from other point.
• Operates at physical layer (layer 1) of the OSI Model.

Hub:

• Broadcast the data packet.
  (Broadcast = one to all communication)
• Used as a central connecting point to connect multiple nodes in star topology.
• Layer 1 device.
• Have six or more ports.
• Work based on half duplex.
•  Also called multiport repeaters or repeating hub.
• Takes signal coming from one port, cleans it (eg. by filtering out noise), strengthen the signal and send the regenerated signal out to all other ports.
• It share the bandwidth among all connected nodes, as a result, it slow down the performance of network.
• Increasing the number of devices, decreases performance of network.

Types of Hub:
a) Active Hub:

• Regenerate / repeat the signals
• Require electrical power to run.

b) Passive Hub:

• Doesn’t amplify or regenerate the signal.
• Just work as a junction point to connect multiple nodes.
• Require no power / electricity.

Bridge:

• Divides a network into segments.
• Layer 2 device (work on Data Link Layer of OSI Model).
• Maintain Mac-Address table of connected nodes.
• Makes intelligent decision whether or not to pass the signal to another segment.
• Broadcast packets are forwarded to other segment as well.
• Ports upto 16.
  
  

  There are 3 basic types of Bridge:

• Local Bridges: It directly connect LANs
• Remote Bridges: It can be used to create a Wide Area Network (WAN) link between LANs. Remote bridges, where the connecting link is slower than the end networks, largely have been replaced with routers.
• Wireless Bridges: It can be used to join LANs or connect remote stations to LANs.

Switch:

• Unicast the data packets.
  (Unicast = one to one communication)
• Doesn’t share bandwidth like hub.
• We can call it a multiport bridge.
• Used in both LAN and WAN.
  (As it comes in Layer 2, 3, 4 and 7 varieties. Layer 2 switch work based on mac-address, Layer 3 based on IP address, Layer 4 based on port number, and Layer 7 based on application layer protocols)
• Various types available: Switch for Ethernet, Token Ring, ATM etc
• Ports upto 576.
• Provide full duplex communication.

Routers:

• Establish communication between two different networks.
• Work based on IP address (layer 3 device)
• Maintain Routing Table (Network Information, metric value, interface information etc)
• Know source and destination address of network.
• Find possible path and route the packets from the best path.
• Always unicast.
• It has multiple collision domains.