Quality of Service (QoS) is an advanced feature that gives priority to certain network traffic depending on their application (Voice, Video, Streaming, Browsing, Downloading). In this case real-time audio and video traffic is being sent to Airtame.
Why do we need QoS?
Without QoS, all network traffic is considered equal, this means that if there is high demand for internet browsing traffic, Airtame's video stream may get held back until the browsing traffic has been transmitted, causing Airtame stream to disconnect or become delayed.
Since Airtame doesn't load content but rather shows real-time video, QoS is really important to get the audio and video to playback smoothly and without interruptions.
As you can see in the picture, Facebook browsing traffic will use the entire bandwidth during certain moments causing the Airtame to not receive any information for a certain amount of time, which can lead to a disconnect because of a time-out, i.e information has not been received for more than 5 seconds. And this only gets worse with more devices connected to the network or when certain devices are running a scheduled task that consumes a lot of traffic.
How do we identify types of traffic?
We identify the traffic based on classification. The most common way of identifying the traffic is by "Marking", "Addressing" or using "Application signatures".
For Airtame we use "Marking" and it is marked with value (AF41) "Interactive Video".
In each packet, there are four “Type of service” bits and three “Precedence” bits provided in each IP packet header. These bits are later re-defined as Differentiated services code points (DSCP).
The most common QoS design is that we will have 5 Queues for your network traffic and then we start Marking our network traffic depending on their classification as below:
Once you start configuring QoS, these markings will help us queue the traffic on the interface and serve the voice traffic first then the (Airtame) video traffic, then mission-critical traffic, then best effort, and finally scavenger traffic.
Most common issues without QoS:
On networks, the quality of service is affected by various factors. Many things can happen to packets as they travel from an origin (Computer) to destination (Airtame), resulting in the following problems:
-
Low throughput: Due to varying load from disparate users sharing the same network resources, the bit rate that can be provided to a certain data stream may be too low for real-time multimedia services if all data streams get the same scheduling priority like (Video or Voice).
-
Dropped packets: The routers might fail to deliver some packets if their data loads are corrupted, or the packets arrive when the router buffers are already full. The receiving application may ask for this information to be retransmitted if it is TCP, possibly causing severe delays in the overall transmission. In a case of UDP (voice and Video) the packet will be lost.
-
Errors: Sometimes packets are corrupted due to noise and interference, especially in wireless communications and long copper wires. The receiver has to detect this and, just as if the packet was dropped, may ask for this information to be retransmitted.
-
Latency: It might take a long time for each packet to reach its destination because it gets held up in long queues, or it takes a less direct route to avoid congestion. In some cases, excessive latency can render an application such as VoIP or online gaming unusable.
-
Jitter: Packets from the source will reach the destination with different delays. A packet's delay varies with its position in the queues of the routers along the path between source and destination and this position can vary unpredictably. It can seriously affect the quality of streaming audio and/or video.
-
Out-of-order delivery: When a collection of related packets is routed through a network, different packets may take different routes, each resulting in a different delay. The result is that the packets arrive in a different order than they were sent. This is especially important for video and VoIP streams where quality is dramatically affected by both latency and lack of sequence.
Configuring QoS:
Configuring QoS is different on every network brand, therefore we will not be able to guide you step by step but we can draw the basic outlined steps:
-
Identify what AP models and switch models you have.
-
Look for a guide to set up QoS on your AP model and do the same for the switches.
Comments
0 comments
Please sign in to leave a comment.