論文摘要

這篇文章我們提出了一個在叢集式網頁伺服器上以內容為分級的資源管理方式，我們所提出的資源管理方式和其他作法不同之處在於我們利用第七層繞送的基本作法，根據每一個網頁服務要求中的URL字串判斷該服務要求應該被轉送到哪一個伺服器節點或者其根本不應該被服務。

我們的系統提供了兩個重要的資源管理機制。當系統飽和或超載時，AdmissionControl 機制啟動以用來阻擋優先序較低的存取要求而盡量將資源保留給高優先序者以達到差異式網頁服務(Differentiated Web Service)；當系統在一般處理量時，我們提供一個更公平、更有效率的Load Balancing機制，其作法是將所有的網頁內容分為兩類，一類為靜態網頁，另一類則為動態網頁，靜態網頁考慮每一個要求所消耗的伺服器I/O資源，動態網頁則考慮每一個服務要求所消耗的CPU資源。後端的伺服器節點定時地將其所負擔的負載資訊傳給前端的分配器，負載資訊包含CPU的使用率和網路頻寬的使用率，分配器依據這些資訊將所有的伺服器排序，並得到CPU Light Load Set和I/O Light Load Set，表示一群較低CPU負載的伺服器節點和較低頻寬使用率的伺服器節點。在到下一次負載資訊更新的前，所有靜態網頁服務要求會由I/O Light Load Set的伺服器所服務，而動態網頁則由CPU Light Load Set負責。另外在Light Load Set中分配服務要求時，我們則考量每個節點分配到的服務要求所造成的系統資源消耗，平均地讓每個節點都能保有相同的處理能力和負載以符合負載平衡的要求。

我們透過實驗說明以內容為分級的資源管理機制將比一般叢集伺服器所採用的第四層繞送方式更能達到各個伺服器節點間的負載平衡。論文中將討論我們的系統與Linux Virtual Server(LVS)的效能比較並說明透過以Content-Based繞送機制可以比輪巡機制(Round Robin)與加權最少連線機制(Weighted Least Connection)更能達到負載平衡；另一方面透過實作與測量我們的系統也說明了在網頁服務上提供差異式服務的好處，同時我們也探討使用Content-Based繞送機制所帶來的額外負擔之大小及解決此問題的可能作法。

In this thesis we propose a Content-Based Differentiated Resource Management Mechanism for web cluster. The major difference of our system from other researches is that we used the URL string of content for request routing and admission control.

In the system we implemented two important mechanisms for resource management. The Content-Based Load Balancing is used to share the service requests of each server node and the admission control avoids overload and provides differentiated web service for high priority content. We separate the content into Static Content and Dynamic Content. For Static content, we consider the influence of I/O resource and for dynamic content we consider the influence of CPU resource. When system running server nodes send their load information to distributor periodically, and distributor sorts these server nodes according their load. The I/O load of server is its network bandwidth usage and CPU load information is its CPU Utilization. In the period that the system updates the load information, requests are be forwarded to Light Load Set. CPU light load set are the servers, which have lower CPU Utilization, and I/O light load set are servers having lower network bandwidth usage. And we use load index of each request recorded in URL table and bucket of each node to distribute the traffic evenly. When overload, admission control drops the lower priority request to protect the high priority requests. With priority and differentiated service, our system can provide more resource to important content.

Experiment results show that the proposed system has better performance than Linux Virtual Server(LVS) with Laver4 routing mechanism including RR(Round Robin) and WLC(Weight Least Connection).

一 研究動機與背景知識 ............................................1
1.1 研究動機 .................................................1
1.2 背景知識 .................................................2
二 相關研究探討 ..................................................5
2.1 QoS相關研究探討 .........................................5
2.2 Content-Aware Routing ...................................5
三 問題定義 ......................................................8
3.1 Sophisticated Load Balancing .............................8
3.2 在網頁伺服器上提供Differentiated Service .................9
3.3 研究目標 ................................................10
四 以內容為分級之資源管理機制 ...................................12
4.1 系統概觀 ................................................12
4.2 資源需求與負載識別 ......................................13
4.3 Content-Based Load Balancing ............................17
4.4 Differentiated Web Service ..............................18
五 效能量測 .....................................................25
5.1 測試環境 ................................................25
5.2 Content-Based Load Balancing與其他演算法的比較 ..........25
5.3 Admission Control .......................................26
5.4 Overhead ................................................27
六 結論 .........................................................29
七 參考文獻 .....................................................30

[1] 亞馬遜網路書店, http://www.amazon.com .

[2] 博客來網路書店, http://www.books.com.tw .

[3] 明?硅蘢蘅坁姿纀?, http://shop.acercm.com.tw/hot.htm .

[4] Ebay, http://www.ebay.com .

[5] Hinet, http://www.hinet.net .

[6] Seednet, http://www.seed.net.tw .

[7] F.Prefect, L.Doan, S.Gold, Th.Wicki, W.Wilicke, "Performance Limiting Factors in Http Server Operations," In COMPCON'96,IEEE.,1996 .

[8] H.Y. Yeom,J. Ha, and I.Kim, "IP multiplexing by transparent port-address translator" Proceedings of the 10th USENIX System Administration Conference Sep. 29 - Oct 4,1996 .

[9] C.S. Yang and M.Y. Luo, "Design and implementa of a environment for building scalable and highly available web server," Processing of 1998 International Symposium on Internet Technology, pp.124-131April 29 - May 1,1998 .

[10] IBM Corporation. The IBM Interactive Network Dispatcher 1998.

[11] CISCO. Local Director. http://www.cisco.com/ .

[12] Y.M. Wang, P.Y. Chung, C.M. Lin ,and Y. Huang, "HAWA: aclient-side approach to high-availability web access," Proceedings of 6th Internetional World Wide Web Conference, April 1997 .

[13] Dongeun Kim; Cheol Ho Park; Daeyeon Park,"Request rate adaptive dispatching architecture for scalable Internet server, "Cluster Computing, 2000. Proceedings. IEEE International Conference on , 2000 Page(s): 289 -296

[14] Colajanni, M.; Yu, P.S.; Cardellini, V. "Dynamic load balancing in geographically distributed heterogeneous Web servers ",Distributed Computing Systems, 1998. Proceedings. 18th International Conference on , 1998
[15] Narendran, B.; Rangarajan, S.; Yajnik, S. "Data distribution algorithms for load balanced fault-tolerant Web access," Reliable Distributed Systems, 1997. Proceedings., The Sixteenth Symposium on , 1997
Page(s): 97 -106

[16] R. Braden, D. Clark, S. Shenker "Integrated Services in the Internet Architecture :an overview" RFC1633, IETF IntServ Working Group, available at http://power2.nsysu.edu.tw/conference/INET2000/rfc/rfc1633.txt

[17] S. Blake, D. Black, M. Carlson, E. Davies, Z. Wang,W. Weiss "An Architecture for Differentiated Services" RFC2475, IETF IntServ Working Group, available at http://power2.nsysu.edu.tw/conference/INET2000/rfc/rfc2475.txt

[18] Lucent. PacketStar 6400 IP Switch. http://www.lucent.com/ .

[19] IBM. IBM 2210 Nways Multiprotocol Router. http://www.ibm.com/ .

[20] CISCO. Cisco 6000 Family. http://www.cisco.com/.

[21] Metz, C. "IP QOS: traveling in first class on the Internet " IEEE Internet Computing , Volume: 3 Issue: 2 , March-April 1999

[22] Fulu Li; Seddigh, N.; Nandy, B.; Matute, D. "An empirical study of today's Internet traffic for differentiated services IP QoS," Computers and Communications, 2000. Proceedings. ISCC 2000. Fifth IEEE Symposium on , 2000 Page(s): 207 -213

[23] Bhatti, N.; Friedrich, R. "Web server support for tiered services ,"
IEEE Network , Volume: 13 Issue: 5 , Sept.-Oct. 1999 Page(s): 64 -71

[24] HPWebQoS . http://www.hp.com/webqos/ .

[25] R. Pandey, J.F. Barnes ,and R. Olsson "Supporting quality of service in HTTP servers" ACM PODC'98 ,Puerto Vallarta Mexico , 1998 .

[26] Abdelzaher, T.F.; Bhatti, N. "Web server QoS management by adaptive content delivery," Quality of Service, 1999. IWQoS '99. 1999 Seventh International Workshop on , 1999 Page(s): 216 -225
[27] Chandra, S.; Ellis, C.S.; Vahdat, A. "Differentiated multimedia Web services using quality aware transcoding ," INFOCOM 2000. Nineteenth Annual Joint Conference of the IEEE Computer and Communications Societies. Proceedings. IEEE , Volume: 2 , 2000 Page(s): 961 -969 vol.2

[28] Chu-Sing Yang and Mon-Yen Luo. "Efficient Support for Content-Base Routing in Web Server Clusters, " In Proceeding of 2nd USENIX Symposium on Internet Technologies and System ,October 1999

[29] Kwan, T.T.; McGrath, R.E.; Reed, D.A. "NCSA's World Wide Web server: design and performance ,"Computer , Volume: 28 Issue: 11 , Nov. 1995
Page(s): 68 -74

[30] Mohit Aron, Peter Druschel and Willy Zwaenapoel. "Cluster Reserves:A mechanism for Resource Management in Cluster-based Network Servers,"

[31] M. Aron, P Druschel, and W Zwaenapoel. "Efficient Support for P-HTTP in Clustered-based Web Server," In Proceedings of the USENIX 1999 Annual Technical Conference, Monterey, CA ,June 1999.

[32] S. Chandra, C.S. Ellis and A. Vahdat. "Differentiated multimedia Web services using quality aware transcoding," INFOCOM 2000. Nineteenth Annual Joint Conference of the IEEE Computer and Communications Societies. Proceedings. IEEE , Volume: 2 , 2000 Page(s): 961 -969 vol.2

[33] M.Y. Luo and C.S. Yang ."System Support for scalabl, Reliable and Highly Manageable Web Hosting Service," In Proceedings of the USENIX 2001 Annual Technical Conference .

[34] PC Home online 網路家庭：http://www.pchome.com.tw