The handling of scalable data streams by network entities is rendered less complex by, in the data stream, accompanying packets which actually carry data by packets of a different packet type which have a scalability axes descriptor defining the number of scalability axes and a semantic meaning thereof. In another aspect, the handling of scalable data streams by network entities is rendered more efficient by conveying level and/or profile descriptors using packets other than the data carrying packets, with profile and/or level descriptors being divided up into a first set explicitly signaling the definition of the available coding option set and/or available syntax element value range for a respective operation point, and a second set of profile and/or level descriptors which signal the definition of the available coding option set and/or available syntax element value range for their respective operation points by reference another profile and/or level descriptor.