What happens if we do not use QoS in networking?

Not having a correctly configured QoS could result in one (or all) of the following issues:

• Latency:
  When the RTP packets haven’t been assigned their required priorities they will be delivered at the devices’ default speeds. In a congested network, the packets have to travel along with the rest of the non-urgent packets. While network latency itself won’t have an effect on the quality of the delivered audiovisual data per se, it will affect communication between end-users. At 100ms of latency, they will start talking on top of one another as the packets arrive out of sync, and at 300ms the conversation stops being comprehensible.
  
  

• Jitter:
  Real-time applications remove standard transport level buffering, so there is no mechanism to reassemble arriving packets in the correct order. Jitter is the irregular speed of packets on a network. It can result in packets arriving late and out of sequence. As the application does not wait for the stream to be assembled correctly, out of sequence packets get dropped resulting in distortion or gaps in the audio or video being delivered.
  
  
  
• Packet Loss:
  This is the worst-case scenario where we find that a number (or parts) of packets are lost due to too much congestion on the networking devices. When a switch or router’s output queue fills up, a tail drop occurs where the device discards any new incoming packets until space becomes available again.
  
  

In all the cases we have just seen, QoS can help by sorting the data out, managing the queues, and preventing data loss.

QoS in Networking FAQs

What is the difference between QoS and Network Throttling?

Throttling, which is also known as policing, involves setting an overall limit for traffic throughput and dropping excess traffic. QoS is a method that prioritizes some traffic over others and uses queuing, thus maximizing bandwidth for some traffic at the expense of others.

What's the main role of DSCP in QoS?

The Differentiated Services Code Point (DSCP) appears in packet headers. It is a packet-level opportunity to request a priority from QoS management software on network devices. Network managers can choose to turn DSCP detection on or off on the device, so this value can be ignored in favor of a different QoS queuing method.

Can you explain traffic shaping in QoS?

Traffic shaping is a method used by QoS to get the best value from network capacity. All networks experience surges in demand and traditional capacity planning demands bandwidth provision at the peak level plus a margin of safety. QoS traffic shaping introduces slight delays on certain traffic to enable a network with less capacity than peak demand to cater to all traffic.