Diagnosing performance and security problems in cellular networks with global measurements글로벌 데이터 분석을 통한 이동통신 네트워크의 성능과 보안 문제 진단

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over 60% of the operators suffer from problems related to mobility, access to LTE networks, and key management, and (2) performance degradation results from six major problems that include timing mismatch related to mobility management, misconfiguration of frequency information or security context, and delay due to redundant procedures. Five of these problems were discovered by our study. One problem had been introduced in a previous study, but the root cause analysis was different. Three problems were caused by misconfiguration and the other three were caused by inefficient combinations of normal procedures. The misconfiguration problems could have been discovered through manual in-depth analysis, as in previous studies. The latter case, however, could not have been found through the traffic analysis of a single operator. Examples of cases that are difficult to detect include: (1) 88.7% of the calls in a German operator suffer 0.79 s median delay, and (2) 100% of the calls in a Spanish operator suffers 0.44 s median delay. We believe that our analysis method is simple, and that it will be effective enough to detect many performance bugs including the cases that are hard to find. Lastly, we propose a location tracking method with changing temporary identifiers. To keep the confidentiality of subscribers' identity, cellular network operator must use temporary identifier instead of the permanent one according to the 3GPP standard. The temporary identifiers are Temporary Mobile Subscriber Identity (TMSI) and Globally Unique Temporary Identifier (GUTI) for GSM/3G and LTE, respectively. Unfortunately, recent studies have shown that carriers fail to protect subscribers in both GSM/3G and LTE, mainly because the temporary identifiers have static and persistent value. These identifiers can be used to track subscribers' location. These studies have suggested that temporary identifiers must be frequently reallocated to solve this privacy problem. The only mechanism to update the temporary identifier in current LTE implementation is called GUTI reallocation. We investigate if the current implementation of GUTI reallocation mechanism can provide enough security to protect subscribers' privacy. To do this, we collect data by invoking GUTI reallocation more than 30K times on 28 carriers over 11 countries using 78 SIM cards. We, then, investigate if 1) these reallocated GUTIs on each carrier have noticeable patterns, and 2) if they do, these patterns are consistent among different SIM cards within each carrier. Among 28 carriers, 19 carriers have easily predictable and consistent patterns in their GUTI reallocation mechanisms. Among the rest of 9 carriers, we revisit 4 carriers to investigate more deeply. For all these 4 carriers, in the end, we could find interesting yet predictable patterns, after invoking GUTI reallocation multiple times within a short time period. Using this predictability, we show that an adversary can track subscribers' location as in the previous work. Finally, we present a lightweight and unpredictable GUTI reallocation mechanism as a solution.; A cellular network is a closed system, and each carrier has built a unique system by combining different operation policies, network configurations, and implementation optimizations. Unfortunately, some of these combinations might lead to performance degradation due to misconfiguration or because of unnecessary procedures. In order to detect such degradations, a thorough understanding of even the minor details of the standards and carrier-specific implementations is important. However, it is difficult to detect such problems, as the control-plane is complicated by numerous procedures. Firstly, we introduce a simple yet powerful method that diagnoses these problems, by exploiting the carrier-specific implementations of cellular networks. We developed the signaling collection and analysis tool (SCAT), a tool that collects the control-plane messages from operators and finds problems through comparative analysis. The analysis process consists of three different control-plane comparison procedures that can find such problems, effectively. These procedures use a time threshold, control flow sequence, and signaling failure, respectively, as the basis for comparison. We analyzed the circuit-switched fallback technology that triggers a generation crossover between the 3G and LTE, as a case study. Our major findings are: (1) performance degradation is widespread in cellular networks
Advisors
Kim, Yong Daeresearcher김용대researcher
Description
한국과학기술원 :정보보호대학원,
Publisher
한국과학기술원
Issue Date
2018
Identifier
325007
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 정보보호대학원, 2018.2,[v, 72 p. :]

Keywords

Cellular network▼aLTE▼aID management▼aLocation tracking▼aCSFB▼aVoLTE▼aPerformance degradation▼aControl-plane; 이동통신▼aLTE▼aID 관리▼a위치 추적▼aCSFB▼aVoLTE▼a성능 저하▼a제어 영역

URI
http://hdl.handle.net/10203/265365
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=734428&flag=dissertation
Appears in Collection
IS-Theses_Ph.D.(박사논문)
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