臺灣博碩士論文加值系統

在分散式計算環境中，RPC提供程式設計師在軟體開發與維護上較為節省人力的方式。然而在傳統端點對端點 (end-to-end) 的網路模式上，當使用者需求大量增加時，將造成遠端伺服器負載過重以及網路癱瘓等問題，不但使用者等待回應的時間拖長，網路服務也會因此而無法正常運作。此外，即使在正常情況下，若是遠端伺服器當機或網路中斷也都會造成RPC無法正常運作。這個問題雖然可利用多層計算模式 (multi-tier computation model) 的方式來解決，但程式設計師必須清楚知道兩端點間所加入的中間層部分，這反而增加了程式設計的複雜度。
主動式網路是一個新的網路架構，在其中有許多主動式路由器提供額外的計算能力，使得新的服務可以動態地佈建在網路中。在本論文中，我們討論在主動式網路的架構上，如何改進遠端方法呼叫的效能，並解決上述的問題。同時進一步在ANTS主動式網路架構上提出主動式遠端呼叫機制以改進Java RMI，稱之為ActiveRMI。以達成三個優點：第一，遠端伺服器的工作量可以由主動式網路之路由器共同分擔。第二，使用者到遠端伺服器之間的網路流量可因此而被分散開來。第三，使用者等待的時間（user response time）也會因此而明顯縮短。
我們將程式碼快取 (code cache) 在FreeBSD與ANTS上實作出來，並經過測試程式實際量測雛形系統的效能。雖然目前實驗結果僅是初步結果，但從實驗評估上，遠端的RMI服務確實可以移到近端主動式路由器上執行。進而降低遠端伺服器的工作負擔，使用者也有較快的回應時間，是原來的4%。
雖然有許多議題尚待進一步討論，但可看出主動式網路的動態佈建服務的特性，確實可用來改進網路服務效能，值得未來深入探討。

In distributed computing, Remote Method Invocation (RMI) provides an easy and transparent programming interface that simplifies programmers in designing distributed applications. However, based on the end-to-end network model, when a large amount of client requests bursts to the server, the server may become a centralized bottleneck if its workload is heavy. Another is that the network traffic is congested along the paths between the clients and the server. Therefore, not only the clients wait for the responses in a lengthy time, but also all network services on the paths are influenced. Furthermore, even in a formal situation, RMI services are fragile when server or network failures occur. Although introducing the extension of a multi-tier design can relieve these problematic situations, the clients still need to be aware of these explicitly added middle tiers. As a result, the complexity of RPC application design will be more increased.
Active networks provide a new network infrastructure in which intermediate active routers can provide extra computing power. In this thesis, how to improve RMI application performance on active networks and solve the foregoing problems are discussed. Furthermore, an active RMI running on ANTS active networks architecture to improve Java RMI is proposed, called ActiveRMI. Three advantages are achieved. First, the workload of the remote servers is shared with intermediate active routers. Second, the packet transmission is localized between the clients and the nearby intermediate active routers. As a result, the total amount of transmitted network packets is thus reduced. The service response time is also shortened.
We implement code cache in ANTS based on FreeBSD, and the RMI application performance is evaluated by testing programs. Although the conducted experimental results are preliminary, remote RMI services indeed can be migrated to proximate active routers. Therefore, the workload of the remote servers is alleviated and the user response time is improved approximately 4%.
Many issues still need to be further discussed, however, the feature of the dynamic service deployment of active networks indeed improves the performance of network services. It is worthy to be explored in the future.

1 Introduction 1
1.1 Background . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Motivations .. . . . . . . . . . . . . . . . . . . . . 3
1.3 The Objective . . . . . . .. . . . . . . . . . . . . . 5
1.4 Organization of the Thesis . . . . . . . . . . . . . . 6
2 RelatedWork 7
2.1 The RPC Paradigm . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 Research in Java RMI . . . . . . . . . . . . . . . . . 9
2.2.1 Java RMI Overview . . . . . . . . . . . . . . . . . 10
2.2.2 Object Caching Improvements . . . . . . . . . . . . 11
2.2.3 Summary in Java RMI . . . . . . . . . . . . . . . . 14
2.3 Active Networks . . . . . . . ... . . . . . . . . . . 15
2.3.1 ANTS . . . . . . . . . . . . .. . . . . . . . . . . 15
2.3.2 DAN . . . . . . . . . . . . . . . . . . . . . . . . 17
2.3.3 Active Network Calls . . . . . . . . . . . . . . . 18
2.3.4 Summary in Active Networks . . . . . . . . . . .. . 19
3 Code Cache Design 20
3.1 Architecture Overview . . . . . . . . . . . . . . . . 21
3.2 The ActiveRMI Protocol . . . . . . . . . . . . . . . 23
3.2.1 Protocol Design . . . . . . . . . . . . . . . . . . 23
3.2.2 Header Specifications . . . . . . . . . . . . . . . 26
3.3 Code Cache Design . . . . . . . . . . . . . . . . . . 26
3.3.1 RMI Code Cache . . . . . . . . . . . . . . . . . . 27
3.3.2 ActiveRMI Manager . . . . . . . . . . . . . . . . . 27
3.3.3 The Cache Table . . . . . . . . . . . . . . . . . . 29
3.3.4 Authentication . . . . . . . . . . . . . . . . . . 31
3.4 Consistency . . . . . . . . . . . . . . . . . . . . . 31
3.4.1 Sharing Attributes . . . . . . . . . . . . . . . . 32
3.4.2 The Consistency Protocol . . . . . . . . . . . . . 32
3.5 Summary . . . . . . . . . . . . . . . . . . . . . . . 37
4 Prototye Design and Performance Evaluation 38
4.1 The prototype . . . . . . . . . . . . . . . . . . . . 38
4.2 Experimental Environments . . . . . . . . . . . . . . 39
4.2.1 Matrix Multiplication without Code Caching . . . . 40
4.2.2 Matrix Multiplication with Code Caching . . . . . . 41
4.3 Performance Results . . . . . . . . . . . . . . . . . 42
4.4 Summary . . . . . . . . . . . . . . . . . . . . . . . 45
5 Conclusion 46

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