分散式物件呼叫服務之架構環境的重要性日益增加，由於此軟體層架構在各種異質的網路環境之下是一種極為重要的設計模式。目前已經有許多知名的軟體廠商都已經注意到這個軟體層的重要性並推出了相關的解決方案，像是Java Remote Method Invocation (RMI)、.NET Remoting、與CCA remoting。

在這篇論文中提出了在軟體物件呼叫環境中，加入支援網路串流資料傳輸能力的新穎方法。本論文針對的架構是昇陽的Java RMI。我們為了支援在Java RMI上的網路串流能力，提出一些重要的機制，包含推送(pushing)機制讓伺服器以網路串流的方式將資料推送至客戶端；以及聚合(aggregation)機制讓客戶端能夠以單一的呼叫從許多不同的伺服端收集資料並將其聚合成完整的串流資料。另外，我們所設計的系統還包含了讓客戶端彼此之間能夠互相轉送(forwarding)資料的能力。我們的架構以標準的RMI為基礎，以插入元件的方式來修改RMI
stub，使得提供網路串流能力成為可能。所新增的元件包含了串流緩衝(streaming buffer)、串流控制器(streaming controller)；並以在傳輸層socket中插入續流緩衝(continuous
buffer)來達成在端點之間傳遞原始串流資料的能力。此一增強後的軟體架構使標準的RMI服務能夠輕易的整合網路串流能力。此外，我們還提出了針對靜態串流資料的聚合演算法。我們的實驗展現出此架構能夠產生不錯的效能。在實驗中，我們的串流RMI能夠產生85%的網路使用率，遠勝標準的RMI。另外，演算法的模擬也顯現出聚合演算法能夠大幅度的改進使用者的等待時間。

The increasing importance of distributed object-oriented
environments for use in parallel and distributed service frameworks has increased interest in efficiently supporting for remote-invocation frameworks, since this layer appears to be a promising paradigm for supporting ubiquitous component communications in heterogeneous network environments. This is also the layer where the well-known software layers such as Java Remote Method Invocation (RMI), .NET Remoting, and CCA remoting are located.

In this paper we present novel methodologies for enhancing the streaming capabilities of Java RMI. Our streaming support for Java RMI includes the pushing mechanism, which allows servers to push data in a streaming fashion to the client site, and the aggregation mechanism, which allows the client site to make a single remote invocation to gather data from multiple servers that keep replicas of data streams and aggregate partial data into a complete data stream. In addition, our system also allows the client
site to forward local data to other clients. Our framework is implemented by extending the Java RMI stub to allow custom designs for streaming buffers and controls, and by providing a continuous buffer for raw data in the transport layer socket. This enhanced framework allows standard Java RMI services to enjoy streaming capabilities. In addition, we propose aggregation algorithms as scheduling methods in such an environment. Preliminary experiments using our framework demonstrate its promising performance in the
provision of streaming services in Java RMI layers. Streaming RMI utilizes 85% of bandwith in Ethernet LAN, and reduces data overhead caused by standard RMI when it is deployed in a streaming application. The simulation indicates the average waiting time is improved when our aggregation policy is applied.

[1] G. K. Thiruvathukal, L. S. Thomas, and A. T. Korczynski. Re°ective
remote method invocation. Concurrency: Practice and Experience,
10(11{13):911{925, 1998.
[2] R. R. Raje, J. I. Williams, and M. Boyles. Asynchronous Remote
Method Invocation (ARMI) mechanism for Java. Concurrency: Prac-
tice and Experience, 9(11):1207{1211, 1997.
[3] J. Maassen, R. van Nieuwport, R. Veldema, H. E. Bal, and A. Plaat.
An e±cient implementation of Java remote method invocation. In:
The Proceedings of the 7th ACM SIGPLAN Symp. on Principles and
Practice of Parallel Programming, Atlanta, GA, pp. 173{182, May
1999.
[4] C. Nester, M. Philippsen, and B. Haumacher. A more e±cient RMI
for Java. In: Proceedings of the ACM Java Grande Conference, San
Francisco, CA, pp. 152{157, Jun. 1999.
[5] F. Breg, S. Diwan, J. Villacis, J. Balasubramanian, E. Akman, and
D. Gannon. Java RMI performance and object model interoperabil-
ity: experiments with Java/HPC++. Concurrency: Practice and
Experience, 10(11{13):941{956, 1998.
37

[6] P. C. Wey, J. S. Chen, C.-W. Chen, and J.-K. Lee. Support and
optimization of Java RMI over Bluetooth environments. In: Proceed-
ings of the ACM Java Grande - ISCOPE Conference, Seattle, WA,
17:967{989 , Nov. 2002.
[7] C.-W. Chen, C.-K. Chen, J.-C. Chen, C.-T. Ko, J.-K. Lee, H.-W.
Lin, and W.-J.Wu. E±cient support of Java RMI over heterogeneous
wireless networks. In: Proceedings of ICC, Paris, France, pp. 1391{
1395 , Jun. 2004.
[8] N. Narasimhan, L. E. Moser, and P. M. Melliar-Smith. Interception
in the Aroma system. In: Proceedings of the ACM Java Grande
Conference, San Francisco, CA, pp. 107{115, Jun. 2000.
[9] C.-K. Chen, C.-W. Chen, and J.-K. Lee. Speci‾cation and archi-
tecture supports for component adaptations on distributed environ-
ments. In: Proceedings of IPDPS, Santa Fe, NM, pp. 47a , Apr.
2004.
[10] C.-K. Chen, Y.-H. Chang, C.-W. Chen, Y.-T. Chen, C.-C. Yang, and
J.-K. Lee. E±cient switching supports of distributed .NET Remoting
with network processors. In: Proceedings of ICPP, Oslo , Norway,
pp. 350{357 , Jun. 2005.
[11] National Science Council (NSC). Research Excellence Project.
http://www.ccrc.nthu.edu.tw/PPAEUII/.
[12] T. Nguyen and A. Zakhor. Distributed video streaming over Internet.
In: Proceedings of SPIE/ACM MMCN, San Jones, CA , pp. , Jan.
2002.

[13] J. Jannotti, D. K. Gi®ord, and K. L. Johnson. Overcast: reliable
multicasting with an overlay network. In: Proceedings of the USENIX
Symposium on Operating System Design and Implementation, San
Diego, CA, pp. 209{301 , Oct. 2000.
[14] Object Management Group. Control and management of A/V
streams speci‾cation. OMG document telecom, 97-05-07 edn., Oct.
1997.
[15] Object Management Group. The common object request broker:
architecture and speci‾cation, edn. 2.2, Feb. 1998.
[16] S. Mungee, N. Surendran, D. C. Schmidt. The design and perfor-
mance of a CORBA audio/video streaming service. In: Proceedings
of the Hawaii International Conference on System Sciences, Maui,
Hawaii, pp. 8043 , Jan. 1999.
[17] T. Fitzpatrick, G. Blair, G. Coulson, N. Davies, and P. Robin. Sup-
porting adaptive multimedia applications through open bindings. In:
Proceedings of ICCDS, Annapolis, Maryland , pp. 128 , May 1998.