||With increased popularity and pervasiveness, mobile networking had become a definite trend for future networks. Users strongly demand the retaining of the connectivity and the QoS (Quality of Service) of ongoing services while roaming across different points of attachment. Efficient handover schemes and service paradigms are essential to the above vision. We will contribute to the QoS provisioning in mobile wireless networks from two complementary perspectives: one is the improved handover schemes at the client end for shorter latency and less packet loss, and the other is the service migration at server end for improved QoS.|
There are time-consuming procedures involved in the handover process. Various research works had devoted to the acceleration of movement detection and registration. However, a time-consuming operation, duplicate address detection, was overlooked by most studies. A novel scheme featuring anycast / multicast technique is developed and presented in this dissertation. The proposed approach switches to anycast / multicast addressing during handover and switches back to normal unicast addressing after all required operations are completed. By switching to anycast / multicast addressing, a mobile node can continue the reception of packets from its corresponding node before its new care-of address is actually validated. As a result, transmission disruption can be effectively minimized. In addition, simple but effective buffer control schemes are designed to reduce possible packet loss and to prevent the out-of-order problem. Analytical study reveals that improved performance can be guaranteed, as reflected in the simulation results.
The establishment of mobility-supported Internet protocols, such as IPv4 and IPv6, had made it possible that an ongoing service can be retained while a mobile node is roaming across different access domains. However, limited efforts had been paid to server sides if we consider the topological change due to node mobility. In the global network environment, the weighted network distance between a client and its server could change dramatically for reasons of topology change or node mobility. A new network service framework highlighting the concept of service migration is presented in this dissertation. The proposed framework take into account essential service quality factors, such as server loading, bandwidth, delay, and so on, and then dynamically migrates an ongoing service from a distant server to a new server with shorter “weighted network distance” to the client. As a result, the individual service connection, as well as the global network environment, will benefit from the service migration, in terms of improved service quality and bandwidth utilization.
This dissertation explains the general architecture of the proposed framework and focuses on the technical details of the core component - service migration module. Our experiences on the functional prototypes for service migration are also reported. The success of the prototyping system is an indication of the feasibility and effectiveness of the proposed scheme.