ASCEND is a collective research efforts to build scalable, affordable, and accessible peer-to-peer (P2P)-based 3D networked virtual environments (NVEs) where participants may share data (e.g. files, photos, blogs) and interact with one another in real-time. ASCEND is based on the highly scalable and topology-consistent Voronoi-based overlay network (VON) and we will investigate a number of important P2P-based NVE (P2P-NVE) research issues, including: 3D streaming for P2P-NVEs, state consistency in P2P-NVEs, persistent storage designed for P2P-NVEs, and suitable P2P overlays specifically for NVE applications. ASCEND's motivation is based on three important Internet trends: the rising popularity of Massively Multiplayer Online Games (MMOGs), the scalability potential of P2P networks, and the rapid growth of user-generated contents such as blog, file and photo sharing. We hope that ASCEND may bridge the transitions toward the next level of Internet communication that is 3D-based, highly interactive, and user-empowering. ASCEND covers three major research topics in the duration of three years:

1) 3D Streaming for P2P-NVE: We will investigate how real-time streaming delivery of 3D contents (geometric meshes and textures) may be done in a scalable manner by using P2P networks. We intend to devise distributed visibility determination and parallel streaming methods in order to relieve server load and to shorten client-side download time.

2) State Consistency Control in P2P-NVE: We will investigate how the synchronization of object states and event ordering may be supported in a distributed P2P environment by assigning ownerships for each object within a NVE. We intend to adopt a fully-distributed consensus-based voting mechanism for the efficient and correct determination of object owners. An update propagation mechanism that provides high availability of object states in the face of a dynamically changing environment will also be investigated.

3) Persistent Storage Design for P2P-NVE: We will investigate how persistent data may be supported in a P2P environment by using only a light-weight server for the eventual data backup. We intend to devise leader node election protocols and data aggregation techniques to support scheduled backups of object states without causing server overload.

        Implications of the ASCEND project include an improved understanding of how to construct NVE systems using the P2P paradigm, the creation of a set of open source programming libraries to support NVE developments, and the training of researchers and developers proficient in the new research field of P2P-based NVE systems. 

Related Sites: ASCEND.SourceForge  VAST  Plug

摘要

    ASCEND 計畫探討如何建構一個以同儕式 (Peer-to-Peer, P2P) 運算為基礎，具擴展性、建置成本低、且普遍易用的 3D 網路虛擬環境 (networked virtual environment, 簡稱 NVE)。在此環境中，使用者可共享檔案、相片或網誌 (blog) 等資料，及與其他使用者進行即時互動。ASCEND 以具高擴展性 (scalability) 及高拓樸一致性 (topology-consistent) 的範諾圖覆疊網路 (Voronoi-based overlay network) 為基礎，並將探討以P2P 建構 NVE 的相關議題，包括：在 P2P 環境中的3D資料串流 (3D streaming)、狀態一致性控管 (state consistency control)、永續性資料儲存 (persistent storage)，及適合支援大型 NVE 的 P2P 架構等等。ASCEND 的研究動機來自於三個重要的網際網路趨勢：多人線上遊戲 (Massively Multiplayer Online Games)的流行、P2P架構較佳之擴展性、及使用者自製內容的快速成長 (如網誌、檔案及相片之線上分享)。我們期許 ASCEND 成為跨入下一代 3D 導向、具高度互動性、且以使用者為主軸的網路溝通模式之橋樑。我們預計用三年的時間進行下列研究： 

1.    P2P-NVE中的3D資料串流：我們將探討如何以P2P支援高度擴展性的3D資料 (幾何模型及貼圖) 即時串流 (real-time streaming)。我們將設計平行串流傳輸的方法，及分散式的可視範圍判斷 (visibility determination) 機制，以減輕伺服器負擔並縮短使用者下載時間。

2.    P2P-NVE中的狀態一致性：我們將透過替每一物件指定擁有者 (owner) 的方式，探討如何解決分散式環境中，物件狀態與事件順序的同步問題。我們將提出完全分散的合議式投票法 (consensus-based voting)，以有效率地決定物件擁有者並保持物件狀態一致性，及更新傳播 (update propagation) 機制，使物件狀態在高度動態變化的狀況下仍具有高存取性 (availability)。

3.    P2P-NVE中的永續性儲存：為讓使用者每次上線皆能取得最新的狀態或場景資料，以感受情境的連貫，我們將研究如何在P2P環境中只用低成本的輕量伺服器即可達到永續性資料的儲存。為減輕伺服器負擔，我們將研究如何選出適當的領導節點 (leader node) 來匯集 (aggregate) 其他節點之資料，並讓伺服器選擇適合的時機進行資料備份。 

    ASCEND計畫將帶來下列的成果：增加對建構P2P-NVE相關議題的了解、發展一套可支援 NVE 開發的開放原始碼 (open source) 函式庫、及培訓 P2P-NVE 領域的研發人才。