From various articles I gleaned that DSCP is a way to define packet priority or precedence- depending on the precedence set in the IP header the packet is put into a certain service class. My question is about use cases for DSCP- what sort of applications would use this and how (or who) controls injecting the service code into the the IP header? What info does ExtraHop expose about DSCP?
DSCP marking can be done via the application, but often the first hop router (gateway) will rewrite these to normalize all markings to an accepted profile… For example, highest priority is given to voice and voice signaling traffic (SIP and RTP). You wouldn’t want bulk traffic like FTP mixed into these same high priority queue’s, so traffic get’s remarked if it’s improperly marked at the router… Each hop along the path will look at a packets DSCP marking and place it in the proper Quality of Service Queue.
ExtraHop can look at DSCP values and tell you which traffic is in which queue. Our VoIP Bundle for instance will look at RTP packets by DSCP types (RTP is usually EF, AF11 or AF 22 or similar). This is to ensure that RTP packets don’t end up being marked as Best Effort. This is just an example as DSCP can be used within Dashboards and Triggers to look at DSCP in any way you wish.