Network Communication Modes and Topologies
Communication Modes
Simplex Mode
The transmitter sends information to the receiver only.
Half-Duplex Mode
Both sender and receiver can transmit, but not at the same time.
Full-Duplex Mode
Simultaneous two-way communication is possible.
Network Types
Transmission Type
Peer-to-Peer Networks
Two devices connect directly via a link.
Multipoint Networks
Multiple devices share a single link.
Ownership
Private and public networks.
Network Categories
Local Area Networks (LANs)
Typically confined to a single building.
Metropolitan Area Networks (MANs)
Spanning entire cities or towns, connecting various public and private facilities.
Wide Area Networks (WANs)
Extending beyond the metropolitan scope, using large-scale communication networks.
Network Elements
Network Cards
Enable computer network access. Each card has a unique MAC address identifying it on the network. A computer on a network is called a node.
Repeater
Extends a physical connection’s range, often used to join two local area networks with similar technology.
Hub
Acts as a repeater, connecting multiple nodes. It receives a frame from one Ethernet port and repeats it to all others.
Bridge
Interconnects network segments, transferring frames between different networks based on a table mapping MAC addresses to segments. It receives a frame on one port and sends it to the specifically targeted port.
Switch
Interconnects multiple network segments at higher speeds and with more sophisticated functionality.
Network Topologies
Ring Topology
Devices connect in a closed circle via a shared cable. Signals circulate unidirectionally.
Evaluation Factors
- Application: Useful for fair network capacity allocation, high speeds over short distances, and a small number of nodes.
- Complexity: Physical implementation can be challenging.
- Response: Remains stable under high traffic, but average waiting time can be high.
- Vulnerability: A single station or channel failure can disrupt the entire system. Immediate repair is crucial.
Advantages
- Equal transmission capacity sharing.
- No reliance on a central node.
- Simplified message transmission.
- Easy broadcasting to all nodes.
- Acceptable access time.
- Low data transmission error rate.
- Potential for high transmission speeds.
Disadvantages
- Network reliability depends on repeaters.
- Complex installation.
Star Topology
Network segments converge at a central point, typically a hub. A single connection failure doesn’t affect the rest of the network unless the central hub fails.
Evaluation Factors
- Application: Suitable for integrating voice and data services.
- Complexity: Configuration can be complex, with each station potentially acting as a node for others.
- Response: Adequate for moderate loads, but hub performance significantly impacts response.
- Vulnerability: Central node failure disrupts the entire network. Single station failure has minimal impact.
- Expansion: Limited expansion capabilities.
Advantages
- Ideal for connecting many nodes to a single point.
- Supports diverse transmission speeds.
- Allows various transmission media.
- Potential for high security.
- Easy fault detection.
Disadvantages
- Susceptible to central node failures.
- High cost.
- Expensive wiring installation.
- Transmission speeds can be lower than other topologies due to server/node activity.
Bus Topology
All devices connect to a single, unterminated cable. A break in the cable disrupts the entire network.
Evaluation Factors
- Application: Suitable for small networks with low traffic.
- Complexity: Relatively simple.
- Response: Degrades rapidly under increasing load.
- Vulnerability: Single station failure doesn’t affect the network.
- Expansion: Simple expansion.
Advantages
- Passive transmission medium.
- Easy connection of new devices.
- Full utilization of available transmission capacity.
- Easy installation.
Disadvantages
- Requires intelligent devices for interfacing with the transmission medium.
- Potential for message interference.
- Unequal resource distribution.
- Limited transmission medium length (typically under 2km with few nodes).