What is a QOS Module?

Answer 1

i know QOS
Short for Quality of Service, a networking term that specifies a guaranteed throughput level. One of the biggest advantages of ATM over competing technologies such as Frame Relay and Fast Ethernet, is that it supports QoS levels. This allows ATM providers to guarantee to their customers that end-to-end latency will not exceed a specified level.

but i know that QOS Module is for linux

Answer 2

End-to-end QoS is implemented on the end devices as well as all of the network devices in between - that's the only way to really ensure a certain Quality of Service.

There are several mechanisms and protocols used for QoS, but you can just think about it this way: Each packet gets transmitted with a certain bit set, that bit represents the QoS level to be applied to that packet. Each device has several different queues for packets, but lets just say there are 2 - high QoS and low QoS. If the bit in a packet is set (equals 1) then it is put in the high priority queue, if it's not set it's put in the low priority queue. The high priority queue is always emptied first, then when time permits, the low priority queue is emptied (there are actually a lot of different "fairness" algorithms that can be used here, and typically 4 or more queues).

So basically, based on a defined priority of service, a particular packet will be given or not given priority service. Above and beyond that basic concept there is rate limiting versus packet shaping, guaranteed bandwidth, etc. QoS is typically implemented to ensure that traffic that is either considered more important, due to being latency sensitive, simply considered more important, or simply due to a contractual agreement is given a higher priority than other traffic.

Answer 3

Quality of Service.

The widest application for QOS is to make sure that voice-over-IP (internet telephony) data has priority over computer data on a network. This ensures that telephone calls (using Voice-over-IP) are not dropped / have bad quality, when the telephone shares the same network with the computers.