Q1.Elaborate sliding window flow control mechanism with example. Also differentiate it with stop and wait method.

Answer:

check question no 4 of the given link: 

Elaborate sliding window flow control mechanism with example. Also differentiate it with stop and wait method.

Q2.Enlist the reasons for congestion occurrence in network?

Answer:

Unneeded traffic

Unneeded traffic is a common cause of network congestion. This will show up on networks in different ways. For example, someone streaming Netflix or YouTube videos at work would count as “unneeded” in a lot of situations, and causes congestion since video traffic uses a lot of bandwidth.

Poor Network Design/Mis-Configuration

A more serious cause of network congestion is poor design or device Mis-Configuration. Take for example a broadcast storm, where a large volume of broadcast and/or multicast traffic is seen on the network within a short time, resulting in severe performance degradation.

Since broadcasts are contained within subnets, the larger the subnet the more serious the effect of a broadcast storm. Therefore, a network that has been designed with large subnets without giving proper consideration to broadcast storms can result in network congestion.

Over-Utilized Devices

Devices such as routers, switches, and firewalls have been designed to handle certain network throughput. For example, the Juniper MX5 has a capacity of 20Gbps. Apart from the fact that this is a theoretical value (the capacity in the production environment will be slightly lower), this is also the maximum capacity.

Therefore, constantly pushing ~20Gbps of traffic through that device means that the device will be over-utilized and will likely result in high CPU utilization and packet drops, leading to congestion on the network.

Security Attack

Various security attacks can cause network congestion, including worms, viruses, and Denial of Service (DoS) attacks.

Q3.Discuss different techniques to control the congestion in the network.

Answer:

Monitor and Analyze Network Traffic

The starting point for solving most network congestion issues, especially for too many devices, over-utilized devices, or an insufficient network design, is monitoring and analyzing network traffic. This will help identify where congestion may exist and highlight under-utilized regions that are ripe for re-allocation to improve performance. With deeper insights into network traffic, it’s possible to take intelligent steps toward reducing network congestion.

Bandwidth

Speaking of bandwidth, network congestion is less likely when the network can transmit more data, making increasing bandwidth an obvious solution. However, a network, like a chain, is only as strong as the weakest—or in this case the slowest—component.

Segmenting and Prioritizing

Traffic monitoring produces an additional benefit: the capacity to design or re-design a bespoke, optimized network for any business. To do that, segment the network into smaller sub-networks to create space for practical priorities and increase efficiency. This permits more accurate monitoring as it produces a more viable network, increasing or reducing data traffic as needed to impact the areas most affected by network congestion.

Assess Your Devices

The number, type, and bandwidth usage of network devices affects the whole network’s data processing. In some cases, some network users might accidentally be incorrectly using devices, while other users could be using “legacy devices” that are not well-supported. Older and inefficient device usage both contribute to network congestion, so assess each device to reduce or even prevent network congestion.