What is Traffic Throttling in Computer Networks?

A network is made by connecting various devices either through ethernet or by connecting them wirelessly. When the performance of the network reduces due to the availability of so many packets in the subnet it is known as congestion. If the size of the router is small it leads to congestion and even if the size is large it takes more time for the packet to come to the front in the queue. Therefore to avoid the congestion traffic throttling technique is being used. The below article covers in detail about this strategy.

What is Traffic Throttling?

Traffic Throttling is an approach used to avoid congestion. In networks and the internet, the senders try to send as much traffic as possible as the network can readily deliver. In a network when congestion is approaching it should tell the senders of packets to slow down them. Traffic Throttling can be used in virtual circuit networks and datagram networks. Various approaches are used for throttling traffic. Each used approach must solve two problems. They are:

Problem 1. The router must be able to determine when the congestion is approaching. It must identify the congestion before it has arrived. For this, each router used in the network must continuously check for all the resources and their activities in the network. Router can continuously monitor using three possibilities. They are:

• Using output links
• To buffer the most useful and priority-based packets inside the router
• The total number of packets that are lost because of insufficient buffering

Problem 2. The second problem is that the router must send the feedback on time to the senders that are creating congestion. To deliver this feedback, the router must identify the senders properly. The router needs to send them warning efficiently without sending more packets in an already congested network. Different feedback mechanisms are used for solving this problem.

Feedback Mechanisms

1. Choke packets

Choke packets are a mechanism where the router directly sends the choked packet back to its sender or host. The header bit of the original packet is turned on so that it will not be able to generate any choke packet. At the time of congestion to decrease the load router will send back only the choked packets at a lower rate. In the case of datagram networks randomly, the packets are selected therefore it leads to more choked packets. The below diagram describes the choke packets approach.

Choke Packets Mechanism

2. Explicit Congestion Notification

In the explicit congestion notification approach the router does not send extra packets to the host but sets a bit of any one of the packet headers to inform that the network has approached with congestion. When any packet is delivered in the network the destination sends a reply packet to the sender informing that congestion has occurred. In the case of choke packets, the sender then throttles its transmission. The below diagram describes the explicit congestion notification.

Explicit Congestion Notification

3. Hop-by-Hop Backpressure

After the congestion has been signaled still due to a slow signal many packets are received from the long distances. The choke packets have an effect at every step and each router requires more buffers. The main aim of this Hop-by-Hop Backpressure technique is to provide faster relief at the point of congestion in the network. This technique propagates in the opposite direction of the data and is majorly used in virtual circuits. The below diagram describes Hop-by-Hop Backpressure in detail.

Hop-by-Hop Backpressure

FAQs on Traffic Throttling

Q1. What is meant by congestion control in TCP?

Answer:

TCP makes use of congestion control at the sender side to avoid congestion. The congestion window describes the maximum amount of data it can send.

Q2. Where the traffic throttling technique can be used?

Answer:

The traffic throttling technique can be used in virtual circuit networks and datagram networks to avoid congestion.

Q3. What is the difference between load shedding and traffic throttling?

Answer:

In load shedding the packets are directly discarded to avoid congestion whereas in traffic throttling the warning is sent to the sender of the packets.

Q4. Having a large size of buffer reduces the chances of congestion in the network?

Answer:

No, having a large size buffer does not reduce the chan of congestion because more time is required for the packets to come to the front of the queue. Within that time the use or importance of the packet might not be valid.