The Study of Packet Collision Avoidance and Bandwidth Allocation in All-optical Metro Networks

• Main Authors: Wen-ping chen, 陳文平
• Other Authors: Wen-Shyang Hwang
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/51410923493206108798

博士 === 國立高雄應用科技大學 === 電機工程系博碩士班 === 96 === Due to the numbers of multimedia applications in the Internet has grown enormously, and massive Internet protocol (IP) packets with variable-length are being made. There is a vast bandwidth requirement at the backbone networks, such as metropolitan area networks (MANs). For addressing the bottleneck in metro networks, in the metro core, a transmission medium with the bandwidth capabilities for handling such a vast amount of information is paramount. Therefore, the IP over wavelength division multiplexing (WDM) transport will replace conventional SONET/SDH transport in future all-optical metro core networks. Such networks require a novel MAC protocol to avoid packets collision and increase bandwidth utilization. This thesis proposes a new MAC protocol named carrier senses multiple access with idle detection (CSMA/ID) to handle variable-length packets over an all-optical metro ring network. For utilizing the channel bandwidth efficiently, this work studies packet scheduling based on three transmitting queue discipline (TQD) architectures and four idle space allocation (ISA) algorithms to realize the impact on performance for the protocol. For numerically evaluating performance, an analytical model was developed by pre-classification queue with weighted round robin (PCQ_WRR) architecture and random algorithm. Further, there are three kinds of different MAC protocols: multitoken, CSMA/CP, and CSMA/ID are also examined and compared. Besides, the recent explosive growth of multimedia has aggravated the lag of metro access networks. The “last mile” between LANs and metro core networks remains the main bottleneck. Ethernet passive optical networks (EPONs) technology is being considered as a promising solution for next-generation broadband access network due to the convergence of low-cost Ethernet equipment and fiber infrastructure. To prevent data collision and ensure efficient transmission, an EPON must employ a MAC protocol to allocate the shared resource of a common upstream transmission medium. Most researches have been focused on dynamic bandwidth allocation (DBA) algorithms to achieve good bandwidth utilization by polling schemes, but the idle time issue and overhead of REPORT messages under heavy load are still unsatisfactory to overcome. Therefore, this thesis proposes a Sort-DBA algorithm that sorts all REPORT messages by the request length at the next transmission cycle to fully utilize the idle time between cycles as long as at least one ONU requests a long enough transmission window; or some of ONUS requests be lain out together in the idle period to compensate for the idle time when without anyone grant length is not long enough. Besides, the proposed algorithm also includes a queue management scheme, which improves efficiency further by decreasing the number of REPORT messages when the ONU queues are long. Event-driven simulations show that Sort-DBA can significantly improve the network performance in terms of packet delay, average queue length and throughput, as compared with the well-known IPACT, DBA2, and scheduling control scheme DBA algorithms.