CN Quiz 1

Which of the following best describes the "network edge"?

• Central set of routers forwarding packets

• End-user devices and the networks they connect to

• Collection of all ISPs in the world

• The backbone links of the Internet

Answer explanation

The "network edge" refers to end-user devices and the networks they connect to, as it represents the point where users access the network, contrasting with core infrastructure like routers and backbone links.

What is the primary difference between DSL and Cable Internet access?

• DSL uses fiber; Cable uses copper

• DSL offers shared bandwidth; Cable does not

• Cable shares the access link among users; DSL does not

• Both use Wi-Fi access

Answer explanation

The primary difference is that Cable Internet shares the access link among multiple users, leading to potential slowdowns during peak times, while DSL provides a dedicated line, ensuring consistent speeds for individual users.

In which switching method do packets take independent paths to reach the destination?

• Circuit switching

• Packet switching

• TDM

• FDM

Answer explanation

In packet switching, data is divided into packets that can take different paths to reach the destination independently, optimizing network resource use. This contrasts with circuit switching, where a dedicated path is established.

A phone call uses a dedicated path throughout the call duration. This is an example of:

• Packet switching

• TCP flow

• Circuit switching

• Store-and-forward switching

Answer explanation

A phone call establishes a dedicated path for the entire duration, which is characteristic of circuit switching. In contrast, packet switching divides data into packets that travel independently, making circuit switching the correct choice.

Packet switching is more efficient for which type of traffic?

• Continuous voice calls

• Large video streams

• Bursty traffic like web browsing

• Satellite communication

Answer explanation

Packet switching is ideal for bursty traffic like web browsing because it allows data to be sent in small packets, efficiently utilizing network resources. This contrasts with continuous streams, which require a constant connection.

Which factor does not directly affect propagation delay?

• Distance

• Packet size

• Signal speed

• Medium type

Answer explanation

Packet size does not directly affect propagation delay, which is determined by distance, signal speed, and medium type. Propagation delay is the time it takes for a signal to travel through a medium, independent of the packet's size.

If a 1000-bit packet is transmitted over a 100 bps link, what is the transmission delay?

• 100 ms

• 10 seconds

• 1 second

• 0.1 second

Answer explanation

The transmission delay is calculated as packet size divided by link speed. Here, 1000 bits / 100 bps = 10 seconds. Therefore, the correct answer is 10 seconds.

What causes packet loss in a router?

• Slow propagation

• Empty buffers

• Full queues/buffers

• High bandwidth

Answer explanation

Packet loss in a router occurs primarily due to full queues/buffers. When these buffers reach capacity, incoming packets are dropped, leading to loss. Other options like slow propagation or high bandwidth do not directly cause packet loss.

What is the role of Tier-1 ISPs in Internet architecture?

• Provide home broadband

• Act as local DNS servers

• Connect regional and access ISPs globally

• Offer wireless LANs

Answer explanation

Tier-1 ISPs play a crucial role in connecting regional and access ISPs globally, forming the backbone of the Internet. They do not provide home broadband or act as local DNS servers, nor do they offer wireless LANs.

In which topology does failure of a central device bring down the entire network?

• Mesh

• Bus

• Star

• Ring

Answer explanation

In a star topology, all devices connect to a central hub or switch. If this central device fails, the entire network goes down, making it vulnerable to single points of failure. This is why the correct answer is Star.