Data is routed within a data network (8), for example a mobile ad hoc network (MANET), comprising at least one wireless network node (10), typically having a router (11). A processor (18) analyzes characteristics of a wireless link (12ab) between a pair of nodes (10a, 10b) within the network (8). Following such analysis, the processor (18) assigns a link class to the wireless link (12ab), the link class being chosen from a predefined set of link classes. A first link class represents that the link (for example link 12ab) is suitable for carrying one or more types of traffic (for example real-time audio and text), but not suitable for one or more other types of traffic (for example real-time video of a certain quality). A second link class represents that a link (for example link 12ac) is suitable for two or more types of traffic (for example real-time audio and real-time video) including at least one type of traffic (for example real-time video) not supported by the first link class. Data may then be routed across the network (8) while ensuring that only data of types consistent with the link classes assigned to respective links (12ab, 12ac, 12bd, etc) are transmitted via those links.