Lec-6: Topologies in Computer Networks | Part-2 | All imp points of Mesh, Star, Hub, Bus, Hybrid

Summary

In this video, the presenter explains Bus and Ring topologies in networking. The key points covered include the structure and components of bus topology, such as the backbone cable and drop lines, highlighting its drawbacks like low reliability and security. The video also discusses the use of terminators and repeaters to extend network range. Moving on to Ring topology, the presenter compares it with bus topology, pointing out its unidirectional data flow and use of token rings to manage collisions. Overall, the video provides essential insights into the characteristics, advantages, and challenges of both topologies.

Takeaways

• 😀 Bus topology features a central backbone cable, also known as coaxial or thick Ethernet wire, to which multiple devices are connected using drop lines.
• 😀 In bus topology, the number of cables required is n+1, where n represents the number of devices, as it includes both the backbone cable and drop lines.
• 😀 Reliability in bus topology is low because if the backbone cable experiences failure, the entire network stops functioning.
• 😀 Security in bus topology is minimal since any message sent over the network can be received by all devices, not just the intended recipient.
• 😀 Bus topology is cost-effective compared to mesh topology because it requires fewer cables.
• 😀 Terminators or repeaters are used at the end of the backbone cable to prevent signal loss and extend the network’s reach (up to 1 km).
• 😀 In bus topology, a major issue is collision due to the multipoint nature of the network, where multiple devices share the same communication medium.
• 😀 Collisions can be minimized using techniques like token passing or CSMA/CD, but they still occur more often than in point-to-point topologies.
• 😀 Ring topology is formed by connecting the two ends of a bus topology, with devices connected in a circular manner and one acting as a monitor.
• 😀 Similar to bus topology, ring topology is less reliable because if any link is damaged, devices cannot communicate, and it also suffers from low security.
• 😀 In ring topology, messages travel unidirectionally, and a token system (token ring) is used to reduce collisions compared to bus topology.

Q & A

What is the main feature of Bus Topology?

In Bus Topology, there is a central backbone cable that connects multiple devices through drop lines. The backbone is typically a coaxial cable or thick Ethernet wire, and all devices share this single communication medium.

How many cables are required in Bus Topology for n devices?

In Bus Topology, for n devices, n+1 cables are required: n drop lines (one for each device) and 1 backbone cable.

What is a key drawback of Bus Topology regarding reliability?

The key drawback of Bus Topology is the 'single point of failure'. If the backbone cable fails, the entire network goes down, causing communication failure for all devices connected to it.

How does Bus Topology impact network security?

In Bus Topology, there is no inherent security. When a device sends a message, all other devices receive it, but only the intended recipient processes the message. Thus, other devices can 'see' the communication.

What role do repeaters play in Bus Topology?

Repeaters are used in Bus Topology to extend the range of the network. If the cable length exceeds the maximum distance for signal transmission (e.g., 500 meters), a repeater is added to boost the signal and extend the network further.

What causes collisions in Bus Topology, and how can they be managed?

Collisions in Bus Topology occur because multiple devices share the same communication channel. To manage collisions, methods like **CSMA/CD** (Carrier Sense Multiple Access with Collision Detection) or **token passing** can be employed.

How does Ring Topology differ from Bus Topology in terms of structure?

In Ring Topology, the devices are connected in a closed loop or ring, whereas in Bus Topology, devices are connected along a single central cable. Ring Topology is unidirectional, meaning data flows in one direction around the loop.

What happens if a link fails in Ring Topology?

If a link in Ring Topology fails, the communication is disrupted for devices that rely on that particular link. Since the network is a loop, the failure breaks the path for data transmission.

What is the function of a monitor device in Ring Topology?

In Ring Topology, one device acts as a monitor to oversee the network's operation. The monitor ensures that the data transmission is functioning properly and helps manage token passing to reduce collisions.

What are the advantages of using a token ring in Ring Topology?

Using a token ring in Ring Topology helps reduce collisions by allowing only the device holding the token to transmit data. This method ensures that only one device can send data at a time, minimizing the chances of simultaneous transmissions and collisions.