A Study on Total Ordering Message Delivery in Group Communication based on Communicating Sequencers

• Main Authors: Wen-Ray Chang, 張文瑞
• Other Authors: Ge-Ming Chiu
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/83035776664774808071

碩士 === 國立臺灣科技大學 === 電機工程系 === 90 === Group communication with total ordering message delivery has been highly demanded by many distributed applications. But yet existing methods still have many deficiencies. For instance, the single-sequencer technique may cause a bottleneck at the sequencer site, and in some cases, reqires normal operation to be blocked. Some other techniques depend on specific structures built on top of the participating sites. Maintaining these structures can be costly. In order to remedy these deficiencies we propse, in this thesis, an efficient group communication scheme that may achieve the property of global total ordering for message delivery. Our mechanism may be used in general open group communication systems in which groups may overlap. The proposed method is based on distributed coordination of multiple sequencers whereby each sequencer is designated for an individual group. A message destined to a group is first sent to the corresponding sequencer. The sequencer then requests for a relative order index from all the other sequencers whose corresponding groups overlap with the destination group. These order indices collectively provide for each destination process an order information for which it follows for message delivery. The relative index is decided by comparing the sequencer's local logical clock value with that associated with the message. Each sequencer need only maintain a small amount of information. In addition, the operation is completely asynchronous with no explicit blocking.