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    Please use this identifier to cite or link to this item: http://ccur.lib.ccu.edu.tw/handle/A095B0000Q/89


    Title: 具軟體定義網路之邊緣佈署重構EPC;SDN-enabled Edge-based Refactored EPC
    Authors: 楊凱翔;Yang, Kai-Hsiang
    Contributors: 資訊工程研究所
    Date: 2018
    Issue Date: 2019-05-23 10:30:26 (UTC+8)
    Publisher: 資訊工程研究所
    Abstract: 隨著網際網路、行動裝置和物聯網不斷的發展,網路上傳送的資料量快速的增加、傳送資料要求的品質上升,導致目前的行動網路服務技術漸漸無法支援如此大量的資料量。電信營運商為了使電信網路更有效率得處理龐大的資料量,增加許多的網路元件來提升網路服務的品質,為了降低管理網路元件的難度,能夠透過SDN技術來管理整體網路的狀態,及時應付網路元件的異常狀況。在這篇論文當中,我們提出一個SDN-enabled edge-based EPC架構稱為SDN-enabled Edge-based Refactored EPC (abbreviated to S-E-R EPC)。首先我們針對每個網路元件進行拆解與分析後得到所有的functions,再以functions產生七種procedures的corresponding string,再來利用三個指標MER (Message exchange reduction)、MHN (Message handling number)和SSE (Scaling side effect)來評估各種functions merging後的效能,藉以提出一個新的架構Refactoring EPC (R-EPC)。但是在傳統的架構中,所有的封包都需要傳送至在核心網路中的網路元件,才能夠將封包傳送至目的地。所以我們考慮將部分網路元件移動至離UE較近的edge network中,藉以縮短UE與傳統EPC網路元件之間封包傳送的距離。我們在edge network中加入SDN以及MPLS的技術,在edge network中透過SDN Controller為封包預設MPLS傳送路徑,藉以提升封包的傳輸效率。在我們設計的網路中,SDN Controller會分別透過OpenFlow protocol與Label Distribution Protocol (LDP)來向OpenFlow switches與MPLS switches溝通,取代了傳統EPC使用GPRS Tunnelling Protocol (GTP)傳送封包的方式。在我們的edge network中,所有封包藉由OpenFlow switches進入edge network,同時藉由OpenFlow switches封裝(encapsulate)上SDN Controller為該封包所規劃在edge network中繞送時的MPLS最佳路徑。比起過去使用GTP傳送方式,我們採用MPLS的方式,封包只須要在OSI第二層(資料鏈結層)進行遶送,取代GTP使用第三層(網路層)的routing方式,使封包傳送的延遲時間減短,增加網路傳輸的速度,更適合多媒體訊息的傳送。此外由於我們將標準EPC中的S/P-GW移動至edge network中,所以會導致UE會有更換Session Anchor Point的問題。為了解決以上的問題,我們設計了當UE移動至另一個edge network的範圍後,UE能夠持續接收原本session的封包的機制,以達到session不中斷的問題。在理論分析上透過signaling cost與M/M/1 queuing model來評估S-E-R EPC的效能。數值的結果呈現S-E-R EPC比起SDN enabled Full edge EPC與SDN enabled Partial edge EPC兩個架構,S-E-R EPC的signaling cost和在七個procedure中的queuing delay time都是最小,效能是最高的,另外還比較了S-E-R EPC與E-R-EPC兩者在user plane的latency的比較,證明加入了SDN架構以及透過MPLS方式傳送封包會提升user plane封包傳輸效率。
    As the Internet, mobile devices, and the Internet of Things develop, the number of Internet data transmitted rapidly rises, and the demand for high-quality data transmission increases. Current mobile network service technology is no longer able to support an increasing number of network packet. In order to make the telecommunication network more efficient in handling the huge amount of data, telecom operators have increased many network components to improve the quality of network services. However, in order to reduce the difficulty of managing network components, it is possible to manage the state of the overall network through SDN technology, which can deal with the abnormal conditions of the network components in time.In this thesis, we proposed a Software-Defined Networking (SDN)-enabled edge-based EPC structure called the "SDN-enabled edge-based refactored EPC" (S-E-R EPC). Firstly, we separated and analyzed each network component to obtain all the functions, and then used the functions to produce the corresponding strings of the seven procedures. Secondly, we used three indicators (i.e., Message Exchange Reduction (MER), Message Handling Number (MHN), and Scaling Side Effect (SSE)) to evaluate the performance of the various functions merging, on the basis of which a novel structure (i.e., refactoring EPC) was derived. Because all packets in a traditional architecture must be transmitted to CN components to enable the packets to be sent to their destinations. In this thesis we moved some network components to edge networks closer to user equipment (UE) to shorten the packet transmission distance between UEs and standard EPC network components. Additionally, we applied SDN and MPLS technology to edge networks, SDN Controller to configure MPLS routing path of packets in the edge networks to further elevate packet transmission speed. For the network architecture designed in this thesis, SDN Controllers communicated with OpenFlow switches and multiprotocol label switching (MPLS) switches through OpenFlow protocols and a Label Distribution Protocol (LDP), replacing the GPRS Tunnelling Protocol (GTP) used by standard EPC to transmit packets. In the edge networks, all packets entered edge networks through OpenFlow switches, and OpenFlow switches encapsulate the optimal MPLS routing paths on packets when the SDN Controller was plan the routing paths in the edge networks. Contrary to previous GTP transmission methods, where packets transmitted needed to route in the third layer (i.e., network layer) of internet, packets transmitted using the MPLS method only needed to route in the second layer (i.e., data link layer). This decreased packet transmission delay, increased network transmission speed, and was more suitable for transmitting multimedia information. Because moving the S/PGW of standard EPC to edge networks caused the session anchor points of UEs to change, this study design a mechanism that enabled UEs to continue to receive packets from the original sessions when UEs moved to other edge networks. This mechanism solved the problem of session interruption.In the theoretical analysis, we evaluate the performance of the S-E-R EPC by using signaling cost and the M/M/1 queuing model, where the numerical results showed that compared with SDN enabled Full edge EPC and SDN enabled Partial edge EPC, the signaling cost and queuing delay times of the seven procedures were the lowest, and the performance is the highest, confirming that the S-E-R EPC showed the most favorable performance.In addition, the comparison between the S-E-R EPC and the E-R-EPC in the user plane is compared. It is proved that the addition of the SDN architecture and the transmission of packets through the MPLS method will improve the packet transmission efficiency of the user plane.
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