3.6-3 Different approaches towards congestion control. Use the pulldown menu to match a congestion control approach to how the sender detects congestion.Group of answer choicesThe sender infers segment loss from the absence of an ACK from the receiver.Bits are set at a congested router in a sender-to-receiver datagram, and bits are in the returned to the sender in a receiver-to sender ACK, to indicate congestion to the sender.The sender measures RTTs and uses the current RTT measurement to infer the level of congestion.

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

tcp segment congestion control (transport layer)

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.

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]

3.1-4 Transport-layer services using UDP.   Check all of the services below that are provided by the UDP protocol.Group of answer choicesA message abstraction, that preserves boundaries between message data sent in different socket send calls at the sender.A congestion control service to ensure that multiple senders do not overload network links.In-order data deliveryA guarantee on the maximum amount of time needed to deliver data from sender to receiver.Reliable data delivery.A flow-control service that ensures that a sender will not send at such a high rate so as to overflow receiving host buffers.A byte stream abstraction, that does not preserve boundaries between message data sent in different socket send calls at the sender.A guarantee on the minimum amount of throughput that will be provided between sender and receiver.