Today we will tell you how to configure QoS. What is this component, also described in detail below. We'll start with the definition, and then touch on the intricacies of the settings and the different approaches to applying the rules for processing traffic.
Definition
Quality of Service (QoS) is the technology for providing certain traffic classes with specified priorities for maintenance. This approach makes sense only when a queue occurs. The latter is formed in especially "narrow" places. And they often call it a "bottle neck". A typical example of a queue can be considered the Internet in the office, where computers are connected to the network at a speed of about 100 Mbps. At the same time, they all use a single channel. However, QoS technology can not be considered a panacea. If the "neck" is too narrow, the interface buffer is often full. It is in it that the data packets are placed.
Options
Next, the QoS setting will be discussed in detail. The change in the queue is to correct the classes. Next for them, you need to define the parameters for the bandwidth. Now you should apply the created structure to the interface. Further tuning QoS consists in sorting packets into classes. To do this, you can use different attributes. For example, based on the DSCP field, highlighting the corresponding specific protocol or specifying as an ACL template. Let's figure out where the router knows the entire band. Data comes from the bandwidth attribute in the interface. Even when it is clearly not configured, some value of it necessarily arises. It can be seen with the command sh int.
Principle of operation
When tuning QoS, it is important to note that by default, not all of the band is at our disposal, but only 75%. Packages that are not included in other classes come in class-default. Routers ensure that the administrator does not issue more bandwidth than is available. Such attempts are being stopped. It seems that politics intends to give classes no more than a given indicator. However, such a situation is created only if all the queues are full. In the case of the emptying of any, the band assigned to it proportionally divides the filled "neighbors". If the data comes from a class that has priority status, the router concentrates on the transfer of such packets. And there are several priority queues. In this case, the band between them is divided proportionally to the specified percentages. When the priority packets end, there is a queue for CBWFQ.
For each time count, the proportion of data is scooped from all the queues. It must be specified in the appropriate class configuration. If part of the queue for some reason is empty, their bandwidth is proportionally divided. Now let's look at what to do when it's necessary to severely cut data from a class that exceeds the specified speed. It is important to remember that specifying a bandwidth only distributes the bandwidth when the queues are fully loaded. You can specify the required average speed and maximum "ejection". The higher the last figure, the faster the transmission can deviate to the side. We briefly described which principles the QoS setting is based on.