DiffServ was designed to implement service provider quality of service (QoS) policies, where ingress and egress routers change the DiffServ Code Point (DSCP) in the IP header. However, nowadays, applications are beginning to directly set the DSCP themselves, in the hope that this will yield a more appropriate service for their respective video, audio and data streams. WebRTC is a prime example of such an application.
As a first step towards understanding whether "WebRTC QoS works", we measured, for both IPv4 and IPv6, what happens to DSCP values along Internet paths. Our study is based on end-to-end measurements from 160 IPv4 and 65 IPv6 geographically spread controlled probe clients to 34 IPv4 and 18 IPv6 servers respectively. Clearly, when the DSCP value is changed, the net result may not be what the application desired. We find that this happens often, and conclude with recommendations on how to improve WebRTC and other applications using the DSCP.