# QoS Management and Flexible Traffic Detection Architecture for 5G Mobile Networks
## 2 General Architecture Considerations and Related Works
MPLS provides an excellent match between traffic flows and bearers with labels, improving the routing and increasing the traffic engineering possibilities [10]. However, the use of an MPLS data plane is not mandatory, and other alternatives can be used, such as 802.1Q or 802.1 ad [32; 33] without significant changes in the proposed architecture. It is important to note that the MPLS has 20 bits to identify labels, and 802.1 ad only uses 12 bits to identify the VLAN (Virtual Local Area Network); therefore, MPLS increases the number of available identifiers. Additionally, the MPLS protocol is thought to transport traffic through different Layer 2 technologies, which is a useful characteristic in heterogeneous networks. The use of an SDN data plane generates significant changes, as the use of the GPRS Tunneling Protocol User plane (GTP-U) inside the mobile domain to provide mobility management is no longer necessary [15; 32; 33; 34]. Figure 2 shows the changes in the protocol stack if the proposed SDN-MPLS data plane is combined with the LTE mobile access protocols. As shown, the radio-Bearer between the OF-NB and the UE remains unchanged, but the S1-Bearer and S5/S8-Bearer are unified in a new bearer called the OF-Bearer (managed and created by the Controller). The EPS-Bearer (in EPS terminology) or QoS-Flow(in 5 GS terminology [1]) is the concatenation of the Radio Bearer and the OF-Bearer, which is responsible for providing to the UE the appropriate end-to-end QoS communication through the mobile domain. For simplicity, this work references both terms, EPS-Bearer and QoS-Flow, as EPS-Bearer. Figure 2: Relationship between Evolved Packet System-Bearer/QoS-Flow with Radio Bearer and the proposed OF-Bearer. MPLS, Multiprotocol Label Switching; EPC, Evolved Packet Core; PDCP, Packet Data Convergence Control; RLC, Radio Link Control. Instead of adding a GTP-U header, with the appropriate Tunnel Endpoint Identifier (TEID), to reach the target UE and to identify the appropriate EPS-Bearer/QoS Flow, this work adds two MPLS labels to achieve the same objective. Routing through the EPS-Bearer is achieved by inspecting the two MPLS labels, where the inner MPLS label identifies the UE/Radio Bearer and the outer MPLS label identifies the appropriate OF-Bearer. Figure 3 shows the use of MPLS labels applied to a default EPS-Bearer (Default OF-Bearer 2). Current mobile networks propose the use of elements called Application Functions (AF) to detect traffic with specific QoS requirements. These elements must be placed in strategic sites, and the traffic to be analyzed must pass through them, thus reducing the solution flexibility; and the AF must be designed to detect the QoS requirement of a specific type of traffic. In the proposed logic, the QoS requirements detection functionality is distributed in the OF-NBs, and it is placed in a flexible and programmable way considering the different user profiles. When this policy detects traffic with QoS requirements, it is addressed to entities (located in central sites such as the data center) that extract the QoS requirements, increasing the traffic detection possibilities and the traffic engineering. Different from traditional SDN technologies that must wait for the Controller response to route the traffic or use per-configured flow entries to route the traffic, this work proposes a combined logic capable of immediately routing packets using general rules and, at the same time, sending the packets with QoS requirements in order to find the QoS characteristics. As will be described in the next sections, this method increases the routing speed and, at the same time, reduces the impact during the Controller high response times.