by using the pre-assigned STID obtained while in the LZone. On receiving the bandwidth request, the BS provides a UL grant to the MS to send its AAI_RNG-REQ message. After receiving the AAI_RNG-REQ message, the target BS responds with the AAI_RNG-RSP message. The MS also performs basic capability negotiation during network re-entry in the MZone by exchanging AAI_REG-REQ/RSP messages. The MS context mapping from LZone to MZone is performed by the BS. A new MS that is served by a legacy BS may scan and discover only a new BS, and may decide to directly perform handover to that BS. In this case, the MS performs legacy handover procedures with the serving legacy BS and then performs new network re-entry procedures with the target BS. 6.5 QUALITY OF SERVICE Quality of Service (QoS) for IP networks is an industry-wide set of standards and mechanisms for ensuring high-quality and performance for user applications. By using QoS mechanisms, network administrators or operators can use existing resources more efficiently and ensure the required level of service without reactively expanding or over-provisioning their networks. Traditionally, the concept of quality in computer networks meant that all network traffic was treated equally. The result was that all network traffic received the network's best effort, with no guarantees for reliability, delay, variation in delay, or other performance characteristics. With best-effort delivery service, a single bandwidth- intensive application can result in poor or unacceptable performance for all applications. The QoS is a concept in which the service requirements of some user applications are more critical than others, requiring preferential handling of the corresponding traffic. The goal of QoS is to provide preferential service delivery for the applications that need it by ensuring sufficient bandwidth, controlling latency and jitter, and reducing data loss. The Internet Engineering Task Force (IETF) defines two major models for QoS on IP networks: Integrated Services (Intserv) a