Understanding Network Topologies
1. Definition
A network topology is the physical or logical arrangement of nodes and connections within a computer network. Networks can utilize a single topology or a combination, known as a mixed topology.
2. Common Topologies
2.1 Ring Network
In a ring network, stations are connected in a closed loop. Each station connects to its neighbors, with the last connecting back to the first. Data transmission occurs sequentially, with each station acting as a relay. This topology often employs a token-passing mechanism to prevent data collisions. However, a single node failure can disrupt the entire network.
2.2 Tree Network
A tree network arranges nodes hierarchically, resembling a tree structure. It can be viewed as interconnected star networks. This topology offers better fault tolerance than a bus network, as a single node failure doesn’t disrupt the entire network. However, it still relies on a shared communication channel.
2.3 Mesh Network
Mesh networks connect each node to one or more other nodes, providing multiple paths for data transmission. A fully connected mesh network offers the highest redundancy, as every server has a direct connection to every other server. This eliminates single points of failure.
2.4 Bus Network
A bus network connects all stations to a single communication channel via interface units and shunts. This shared channel facilitates direct communication between devices. However, a cable break can isolate segments of the network. While all devices can see all signals, this can lead to traffic congestion and collisions, often mitigated by network segmentation. This topology is common in small LANs using a hub or switch.
2.5 Star Network
In a star network, all stations connect directly to a central hub or server. All communication must pass through this central point. This simplifies network management and control but introduces a single point of failure. Individual node failures don’t affect the overall network, but a hub failure disrupts all communication. While reliable, the wiring costs can be high.
2.6 Wireless (Wi-Fi) Network
Wi-Fi, a trademark of the Wi-Fi Alliance, adheres to the IEEE 802.11 standards. It enables wireless connectivity to local networks, offering flexibility and mobility. Wi-Fi networks can be installed in public spaces for internet access. The IEEE 802.11b standard universalized this technology, allowing seamless integration with Ethernet and ADSL equipment. Security is a crucial aspect of Wi-Fi networks. Many networks are implemented without proper security measures, leaving them vulnerable. Encryption protocols like WEP and WPA, or IPSEC and 802.1x, are essential for securing Wi-Fi communications.
2.7 Cellular Network
Cellular networks divide a geographic area into cells, each with a central node. These networks rely on electromagnetic waves for communication, eliminating the need for physical links. This makes them suitable for wide-area coverage, including satellite communication. However, signals are susceptible to interference and security breaches. Cellular topologies are often integrated with other network types.
3. Bus Network: 802.3 “Ethernet”
The IEEE 802.3 standard, commonly known as Ethernet, defines how devices send and receive data over a shared physical medium that logically functions as a bus. Originally designed for 10 Mbps, Ethernet has evolved to support speeds up to 10 Gbps, with future versions targeting 40 Gbps and 100 Gbps. Ethernet utilizes the CSMA/CD (Carrier Sense Multiple Access/Collision Detection) protocol for media access. It’s the most widely used standard for local area networks (LANs). Developed at Xerox PARC, Ethernet initially used thick coaxial cable. Later versions incorporated thin coax, twisted-pair cabling (Category 3 and above), and fiber optic connections.
3.1 Common Ethernet Hardware
NIC (Network Interface Card): Enables a computer to connect to a network. Each NIC has a unique MAC address. A connected computer is called a node.
Repeater: Extends the range of a physical connection by reducing signal degradation.