ocess facilitates the delivery of MAC SDUs with the appropriate QoS constraints. A clas- sification rule is a set of matching criteria applied to each packet entering the IEEE 802.16 entity. consists of some protocol-specific packet matching criteria (e.g., destination IP address), classifi- cation rule priority, and a reference to a CID (or, for an IEEE 802.16m BS or an MS, reference to a STID+FID combination). If a packet matches the specified packet matching criteria, it is then delivered to the SAP for delivery on the connection defined by the CID or STID+FID. Imple- mentation of each specific classification capability (e.g., IPv4 based classification) is optional. The service flow characteristics of the connection provide the QoS for that packet. This is illustrated in Figure 5-5. Several classification rules may each refer to the same service flow. The classification rule priority is used for prioritizing the mapping of classification rules to packets. Explicit ordering is necessary because the patterns used by classification rules may overlap. While the priority does not have to be unique, it must be ensured that there is no ambiguity in classification within a classification rule priority. The downlink classification rules are applied by the BS to packets it is transmitting, and the CHAPTER 5 The IEEE 802. 16m Convergence Sub-Layer SFID1 CIDi1: STID++ID1 SFID2 CIDi2: STIDj+FID2 SFID3 CIDi3: STID+IF3 Network Layer Packets SFID4 CIDi4: STID++IF4 SFID5 CIDi5: STIDj+FID5 SFID6 CIDk1 STID+FID SFID7 CIDk2: STID+FID2 SFID8 CIDk3: STIDk+FID3 Base Station Logical MAC Connections Air-Interface FIGURE 5-5 An illustration of service flow classification, SFID, STID, FID, and CID concepts [13] uplink classification rules are applied at the MS. It is possible for a packet to fail to match the set of defined classification rules. In this case, the CS discards the packet. Figure 5-5 shows the relationship between the classifier, SFID, STID, FID, and CID. Note that each mobile station is assigned a unique station identifie