# Introduction to QoS (Quality of Service) **URL:** \ **Category:** Lessons Discussion\ **Created:** [May 3, 2017, 11:38am UTC](https://forum.networklessons.com/t/introduction-to-qos-quality-of-service/1703 "2017-05-03T11:38:29Z")\ **Posts on this page:** 1\ **Showing post:** 71
**Author:** ![lagapidis](https://cdn-forum.networklessons.com/user_avatar/forum.networklessons.com/lagapidis/32/4949_2.png) [@lagapidis](https://forum.networklessons.com/u/lagapidis)\ **Post date:** [November 27, 2023, 5:42am UTC](https://forum.networklessons.com/t/introduction-to-qos-quality-of-service/1703/71 "2023-11-27T05:42:29Z")
Hello David > [@davidilles](#): > > - When it comes to QoS, I often see IP phones being represented as the originators of voice traffic. The question is, what if a computer is running an application like Discord, Skype or even Cisco Webex? How would we be able to classify and priotize voice traffic coming from such applications? Would NBAR also work here? When it comes to QoS, IP phones are typically easy to work with because they classify and mark voice traffic by default, and their traffic can be easily identified by other network devices due to the dedicated voice VLAN they use as well as the use of CDP or LLDP to identify the devices themselves. When voice traffic originates from applications like Discord, Skype, or Cisco Webex on a computer, the classification and prioritization become less automated, but it can still be achieved using several tactics: - Application-level marking can be performed by certain software applications (such as VoIP clients or videoconferencing software) to mark packets sent from these applications for QoS purposes. - Application recognition/deep packet inspection can be used by network devices to classify traffic coming from particular applications. This is where NBAR can be useful, inspecting packets deeply to recognize various applications, including voice services like Skype or Webex. This inspection goes beyond basic port numbers and can identify the application-specific signatures within the traffic. > [@davidilles](#): > > If we imagine a packet being sent between two routers → R1 and R2, these delays are all involved except for the queuing delay if there is **no congestion** , right? Yes, that is correct. Queuing delay is only experienced when there is congestion. All the other forms of delay mentioned occur always. I hope this has been helpful! Laz --- _[View the full topic](https://forum.networklessons.com/t/introduction-to-qos-quality-of-service/1703)._