The four sentences (labelled 1, 2, 3 and 4) below, Arrange the following four sentences into a coherent paragraph:1. Computers and devices that transmit data over the internet break the data down into smaller packets and use a special algorithm to decide how fast to send those packets.2. But a team of MIT researchers has discovered that these algorithms can be deeply unfair. In a new study, they show there will always be a network scenario where at least one sender receives almost no bandwidth compared to other senders; that is, a problem known as "starvation" cannot be avoided.3. These congestion control algorithms seek to fully discover and utilize available network capacity while sharing it fairly with other users who may be sharing the same network.4. Over the past decade, researchers in industry and academia have developed several such algorithms that attempt to achieve high rates while controlling delays. Some of these, such as the BBR algorithm developed by Google, are now widely used by many websites and applications.

A node of a data communication network which can transmit data at 4 different rates r, 2r, 3r& 4r uses the mechanism described below to control congestion: At any given time the nodeis transmitting data at one of the above rates. It is assumed that data is always available fortransmission. There is a congestion indication flag which is assumed to be independent of thestate of the node but indicates congestion in the whole network. The data transmission rate isrevised in regular intervals keeping to following rules:1. If the congestion flag is on, the data rate is reduced by two steps or to the lowest step (i.e.rate r) whatever the higher.2. If the flag is off, the rate is increased by one step or remains in the highest step.a) Draw the Markov chain indicating the states and transitions assuming that the flag ison with probability p. [30 marks]b) What happens if p=0 and if p=1? [10 marks]c) Calculate the state probabilities for p=0.6. [30 marks]d) What is the average transmission rate? [20 marks]e) Comment on the validity of the results in c) & d) if p varies with time. [10 marks]Q2.a) Jobs arrive at the rate of 1 job per unit time into an M/M/1-FIFO queue. What is themean queue length if the mean service time is 0.55 time units? [20 marks]b) Another M/M/1-FIFO queue has a server identical to that in a) and the same arrivalrate, but a longer mean service time of 0.85 time units. What is the mean queue lengthof this queue? [10 marks]c) Now, both streams of jobs are diverted to a third queue of type M/H2/1-FIFO with asingle server working at double the rate of those in a) and b).a. What is the total arrival rate? [10 marks]b. What is the mean service time of the jobs in this queue? [10 marks]c. What is the mean queue length of this queue? [30 marks]d. Analyse the pros and cons of this queue against the combination of queues ina) and b). [20 marks]

Which of the following statements is true concerning TCP’s congestion control?Question 24AnswerIt is used by ISPs to control the traffic in the networkIt changes the sending rate dynamically according to indicators of the network’s traffic conditionsIt is a mechanism used by routers to reduce the network trafficIt allows the sender to slow down so that the receiver is not overwhelmed.

3. Explain the general principles of congestion control. Describe congestion control in datagram subnets '

Check all of the services below that are provided by the TCP protocol.Group of answer choicesA guarantee on the minimum amount of throughput that will be provided between sender and receiver.In-order data deliveryA byte stream abstraction, that does not preserve boundaries between message data sent in different socket send calls at the sender.A message abstraction, that preserves boundaries between message data sent in different socket send calls at the sender.A guarantee on the maximum amount of time needed to deliver data from sender to receiver.Reliable data delivery.A congestion control service to ensure that multiple senders do not overload network links.A flow-control service that ensures that a sender will not send at such a high rate so as to overflow receiving host buffers.

When an application uses a TCP socket, what transport services are provided to the application by TCP?  Check all that apply.Group of answer choicesThroughput guarantee. The socket can be configured to provide a minimum throughput guarantee between sender and receiver.Loss-free data transfer. The service will reliably transfer all data to the receiver, recovering from packets dropped in the network due to router buffer overflow.Congestion control.  The service will control senders so that the senders do not collectively send more data than links in the network can handle.Flow Control. The provided service will ensure that the sender does not send so fast as to overflow receiver buffers.Best effort service.  The service will make a best effort to deliver data to the destination but makes no guarantees that any particular segment of data will actually get there.Real-time delivery. The service will guarantee that data will be delivered to the receiver within a specified time bound.