Understand Congestion: It’s Effects on Modern Networks


Understand Congestion: It’s Effects on Modern Networks


Omotosho Olawale, Oyebode Aduragbemi* and Hinmikaiye Johnson

Department of Computer Science Babcock University, Nigeria


American Journal of Computer Engineering

As Internet, can be considered as a Queue of packets, where transmitting nodes are constantly adding packets and some of them (receiving nodes) are removing packets from the queue. So, consider a situation where too many packets are present in this queue (or internet or a part of internet), such that constantly transmitting nodes are pouring packets at a higher rate than receiving nodes are removing them (Cardwell, Cheng, Gunn, Yeganeh, & Jacobson, 2016). This degrades the performance, and such a situation is termed as Congestion. Main reason for congestion in a network system is a greater number of packets into the network than it can handle. So, the objective of congestion control can be summarized as to maintain the number of packets in the network below the level at which performance falls off dramatically (Faisal Shahzad1, Ullah, Siddique, Khurram, & Saher, 2015). The nature of a Packet switching network can be summarized in following points:
• A network of queues
• At each node, there is a queue of packets for each outgoing channel
• If packet arrival rate exceeds the packet transmission rate, the queue size grows without
bound
• When the line for which packets are, queuing becomes more than 80% utilized, the queue
length grows alarmingly
When the number of packets dumped into the network is within the carrying capacity, they all
are delivered, expect a few that have to be rejected due to transmission errors). And then the number delivered is proportional to the number of packets sent (Evans & Filsfils, 2007). However, as traffic increases too far, the routers are no longer able to cope, and they begin to lose packets. This tends to make matter worse. At very high traffic, performance collapse completely, and almost no packet is delivered.
Congestion is an important issue that can arise in packet switched network. Congestion is a situation in Communication Networks in which too many packets are present in a part of the subnet, performance degrades (Floyd & Fall, 1999). Congestion in a network may occur when the load on the network (i.e. the number of packets sent to the network) is greater than the capacity of the network (i.e. the number of packets a network can handle). In other words, when too much traffic is offered, congestion sets in and performance degrades sharply (Jayakumari & Senthilkumar, 2015). Congestion collapse occurs when the network is increasingly busy, but little useful work is getting done.
Congested network refers to the moment in network’s links when any new data entry to be sent to a destination will create instead a blocking effect into the transmission line. Thus, this may result primarily to throughput decrease with the data already admitted in process. Congestion occurs when the number of packets being transmitted through the network approaches the packet handling capacity of the network. It can be described is the reduced quality of service that occurs when a network node is carrying more data than it can handle.
Typical effects include queueing delay, packet loss or the blocking of new connections. A consequence of congestion is that an incremental increase in offered load leads either only to a small increase or even a decrease in network throughput.
Network protocols that use aggressive retransmissions to compensate for packet loss due to congestion can increase congestion, even after the initial load has been reduced to a level that would not normally have induced network congestion. Such networks exhibit two stable states under the same level of load. The stable state with low throughput is known as congestive collapse. Congestion collapse occurs when the network is increasingly busy, but little useful work is getting done.


Keywords: Congestion, Modern Networks

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How to cite this article:
Omotosho Olawale, Oyebode Aduragbemi and Hinmikaiye Johnson. Understand Congestion: It’s Effects on Modern Networks. American Journal of Computer Engineering, 2019; 2:5.


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