在LISP協定下一個基於貝氏網路之快取生命週期決定方法

A Bayesian Network Based Cache Lifetime Determination Scheme for Locator/ID Separation Protocol

林胤斈(Yin-Hsueh Lin)

指導教授 ： 周立德

國立中央大學/資訊電機學院/資訊工程學系/碩士(2014年)

摘要

現今使用的IP Address遽增，導致開發新型網路應用程式與網路服務有著極大困難。學者們提出了Locator/ID Separation Protocol（LISP）來解決此困境。LISP協定令IP address僅剩identifier功能，使用Ingress Tunnel Router（ITR）與Egress Tunnel Router（ETR）來代替locator 功能，並採用Mapping System將locator與identifier 做映射轉換。為了避免Mapping System負擔過重，ITR 上擁有快取（cache）設備。快取生命周期的長短將會影響ITR 對Mapping System 所發出的詢問次數。因此決定一個合適的cache lifetime 會使得Mapping System 的負擔得到舒緩，並減少mapping 所耗費的時間。

　　本論文在LISP 協定下，提出了基於貝氏網路之快取生命週期決定方法（BNCLD）來計算合適的cache lifetime方法。貝氏網路在處理具有不確定性的相關知識時具有相當優勢，因為貝氏網路可以經由觀測到的證據或已知的背景知識對未知或具有不確定性的狀態進行推論。BNCLD透過資料萃取模組抓取可以從網路上觀測到的資料，並將觀測資料交由運算模組。以貝氏網路為核心進行運算，最後推得出合適的cache lifetime。模擬結果顯示BNCLD 的效能比Fixed Time Method（FTM）優異。BNCLD 在average ITR delay較之使用FTM減少可達32.57%，packet loss ratio減少可達35.24%，control overhead上減少可達33.58%。

關鍵字

定位/標識分離協議 ； 貝氏網路 ； 快取生命週期

並列摘要

Due to the usage of IP addresses rises rapidly, researchers proposed Locator/ID Separation Protocol (LISP) to solve the routing scalability problem. LISP reserves the “identifier” function of IP address. LISP uses Ingress Tunnel Router (ITR) and Egress Tunnel Router (ETR) to represent the “locator” function. LISP uses mapping system to map identifier and locator. To ease the heavy burden of mapping system, ITR has the cache equipment. The value of cache lifetime will influence the times that ITR queries mapping system. Therefore, deciding an appropriate cache lifetime can reduce the load of mapping system.

A Bayesian Network Based Cache Lifetime Determination scheme (BNCLD) for LISP is proposed in this thesis. According to the observed quantities or domain knowledge, Bayesian network can solve problems under uncertainty. BNCLD uses the Information Retrieve Module (IRM) to collect parameters from the Internet. BNCLD uses Computation Module (CM) which is based on Bayesian network to infer an appropriate cache lifetime. According to simulation experimental results, BNCLD outperforms than Fixed Time Method (FTM). BNCLD has shorter average ITR delay than FTM up to 32.57%. BNCLD improves the packet loss ratio up to 35.24%. BNCLD can reduce the control overhead up to 33.58%.

並列關鍵字

Locator/ID Separation Protocol ； Bayesian Network ； Cache Lifetime

參考文獻

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