QOS = Quality of Service ... it's a method for marking packets & frames (COS = Class of Service) such that, if the network infrastructure (all of it) is configured to watch for it, provides a mechanism to allow you to prioritize your traffic.
For example, VoIP& realtime video are sensitive to delay and variance of delay. By being able to mark VoIP and video traffic at a higher priority (and using a network that supports it), you provide a path that is likely to give better performance for those applications.
Most data traffic (web, database ...) is not time or delay sensitive, so it can be marked at a lower priority. Network infrastructure configured for QOS/COS will permit the higher priority traffic (voice, video) to pass ahead of lower priority (web, database) traffic.
Another part of it is which packets/frames are better to discard in the event that some congestion occurs. Along the path, if a congested queue is encountered, the infrasturcture device is given a clue as to which traffic is preferred to be lost ... saving the critical traffic.
Here's a link on the main Cisco site that discusses the various QOS types.
Remember that QoS, above all, does not give you any more bandwidth. In switching, you basically use a combination of queueing, scheduling, marking, policing, and congestion avoidance in order to give certain classes of traffic a higher or lower "quality" of service.
This is a very broad topic and is similar to asking what quality of life is. There are many factors, but you should start with what you want to accomplish, and sometimes QoS can get you there.
This is actually a pretty cool feature, i didn't even know it existed until I was looking for a solution to advertise a subnet (prefix in BGP talk), only if a certain condition existed. This is exactly what conditional advertisements does
j ai une question j ai achete un routeur cisco 887VA-k9 , je le configuré avec la configuration ci- dessous
si je le lier avec mon pc portable sur l un de ses ports directement ça marche toute est bien ( la connexion internet + m...
Attached policy provides CLI access to the Cisco 4G router over text messaging. Two files are in the attached .tar file:
2. PDF with instructions on how to load and use the .tcl file.