Computer Networks: Physical Topology

Physical Topology

• A multipoint connection is where more than two devices share a single link, with capacity shared spatially or temporally.
• In a mesh topology, every device has a dedicated point-to-point link to every other device, requiring n(n-1)/2 duplex-mode links for n nodes.

Advantages and Disadvantages of Mesh Topology

• Advantages: dedicated links, robustness, privacy or security, easy fault identification and isolation.
• Disadvantages: high cabling and I/O port requirements, difficult installation and reconnection, expensive hardware.

Physical Topology: Star

• In a star topology, each device has a dedicated point-to-point link only to a central controller (hub), with devices not directly linked to each other.

Advantages and Disadvantages of Star Topology

• Advantages: less expensive than mesh, easy to install and reconfigure, less cabling, robustness (if one link fails, only that link is affected).
• Disadvantages: dependency on the hub, if the hub fails, the whole system fails.

Physical Topology: Bus

• In a bus topology, one long cable acts as a backbone to link all devices in a network.

Advantages and Disadvantages of Bus Topology

• Advantages: easy installation, backbone cable can be laid along the most efficient path.
• Disadvantages: difficult reconnection and fault isolation, signal reflection at taps can cause signal degradation, a fault in the bus cable stops all transmission.

Physical Topology: Ring

• In a ring topology, each device has a dedicated point-to-point connection with only the two devices on either side of it, with a signal passed along the ring in one direction.

Advantages and Disadvantages of Ring Topology

• Advantages: easy to add or delete devices, fault isolation is simplified, a signal is circulating at all times.
• Disadvantages: unidirectional traffic, a break in the ring can disable the entire network (can be solved using a dual ring or switch).

Network Types

• Criteria for distinguishing network types include size, geographical coverage, and ownership.
• Two main types of networks: Local Area Network (LAN) and Wide Area Network (WAN).

Local Area Network (LAN)

• A LAN connects hosts in a single office, building, or campus, and is usually privately owned.
• Each host in a LAN has a unique identifier (address) that defines the host in the LAN.
• A packet sent by a host to another host carries both the source host's and destination host's addresses.

Wide Area Network (WAN)

• A WAN is an interconnection of devices capable of communication, with a wider geographical span than a LAN.
• A WAN interconnects connecting devices such as switches, routers, or modems, and is normally created and run by communication companies and leased by organizations.
• Two distinct examples of WANs: point-to-point WANs and switched WANs.