Microsoft PowerPoint 권태경교수님Network-Research-CSE

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1 TCP/IP Introduction & Network 권태경 1

2 outline Internet IP TCP Network Research Wireless Network Social Network Content-centric Network Sensor Network, Internet of Things Data Center Network Video Delivery 2

3 Internet Protocol (IP) IP address is a 32 bit integer Every host has a unique IP address billion Written as 4 octets/bytes in decimal format Eg E.g , DNS:

4 IP performs routing How do packets get from A to B in the Internet? A Internet B 4

5 A Simplified Example Connectionless forwarding Each router (switch) makes a LOCAL decision to forward the packet towards B R1 R4 R7 R6 A R2 R8 B R3 R5 5

6 Internet structure Original Practice Tier 1 ISP Tier 2 ISP Large corporation Tier 2 ISP Small corporation Tier 3 ISP Tier 3 ISP Small Small Small corporation corporation corporation ISP: Internet Service Provider 6

7 Internet structure The reality is Source: Arbor Networks * Why peering and multi-homing? IXP: Internet exchange Point 7

8 What IP provides to application Best effort service it may lose packets it may reorder packets it may duplicate packets 8

9 The Transport Layer Two transport layer protocols supported by the Internet: Reliable: Transport Control Protocol (TCP) Unreliable Unreliable Datagram Protocol (UDP) 9

10 UDP UDP is an unreliable transport protocol UDP does not provide: connection management flow or error control guaranteed in-order packet delivery UDP is almost a null transport layer 10

11 TCP TCP provides the end-to-end d reliable connection that IP alone cannot support The protocol Frame format Connection management Retransmission Flow control Congestion control 11

12 Reliability: error detection and recovery A packet may be: corrupted completely lost TCP is based on explicit acknowledgements (ACK) When a data packet is received, the receiver generates an ACK packet 12

13 TCP Connection Establishment Three-way Handshake Host A Host B 13

14 Bottleneck Bandwidth one router, finite buffers sender retransmission of lost packet Host A in : original data out ' in : original data, plus retransmitted data Host B finite shared output link buffers 14

15 TCP Congestion Control Goal: achieve self-clocking state Even if don t know bandwidth dt of bottleneck botte ec Bottleneck may change over time Two phases to keep bottleneck busy: Slow-start ramps up to the bottleneck limit Packet loss signals we passed bandwidth of bottleneck Congestion Avoidance tries to maintain self clocking mode once established 15

16 TCP Slow Start (cont d) Congestion window Timed out Transmissions 1 Maximum Segment Size Transmission Number 16

17 TCP Linear Increase Threshold Phase Example: Maximum segment size = 1K Assume SSthresh=32K Congestion window 40K 32K 20K Timeout occurs when MIN(sliding window, congestion window) = 40K Thresholds 1K 17 Transmission Number

18 Resulting TCP Sawtooth In steady state, window oscillates around the bottleneck s capacity (I.e. number of outstanding bytes in transit) Congestion window 40K 32K Slow Start Linear Mode Sawtooth Bottleneck Capacity 20K 1K Transmission Number 18

19 Denial of Service (DoS) attack A: valid sender B: valid receiver SYN SYN + ACK ACK SYN Cache 19

20 DOS attack! X: attacker A: valid sender B: valid receiver SYN SYN SYN Cache Full Packet Dropped SYN Cache 20

21 Distributed DOS (DDOS) attack! Master Daemon Daemon Daemon Daemon Daemon Victim Real Attacker 21

22 Multicasting problems Open-Loop Transmission (No feedback such as ACK) Fixed/Low Tx Rate Efficiency issue Other STAs performance is degraded Similar to Performance Anomaly Problem 11 Mbps AP AP 1 Mbps Always 1 Mbps transmission even if 11 Mbps is possible 1 Mbps Unicast (Rate Adaptation) Multicast (No Rate Adaptation) 22

23 SCONE Lab Social and Computer Network Lab ( 소셜정보망연구실 ) Professor : 김종권 (Chong-Kwon Kim) Members Research Areas Ph. D Course: 7 Wireless Networking MS Course: 3 Data Center Networks Alumni: Ph. D(18), MS(55) Social Networks Network Security 23

24 Wireless Networking IEEE (Wi-Fi) PHY/MAC Layer Protocols Multiple-Input Multiple-Output (MIMO) Communications ZigBee, Bluetooth, LTE (4G) Smartphone-based Indoor Localization Data Center Networks Flow Load Balancing DCN traffic analysis DCN Routing and scheduling 24

25 Social Networks Information Diffusion and Cascades Influence Maximization Recommender system with social relation Network Security Distributed Denial of Service (DDoS) Social Network Threats Internet Traffic Classification & Measurements 25

26 이동컴퓨팅및통신연구실 Mobile Computing and Communications Lab. 이동컴퓨팅및통신연구실은유비쿼터스통신환경을위한차세대핵심기술인이동컴퓨팅기술및무선네트워킹기술에관한연구를진행하고있습니다. 지도교수 : 전화숙교수 연락처 : 이메일 : wsjeon@snu.ac.kr 학력 : 서울대학교공과대학컴퓨터공학과학사,1983 서울대학교공과대학컴퓨터공학과석사, 1985 서울대학교공과대학컴퓨터공학과박사, 1989 구성원 박사후과정 : 1 박사과정 : 3 석사과정 : 4 졸업생 : 박사 3 명, 석사 : 22 명 연구분야 Cognitive Radio Radio Resource Management Green Communication Relay-based Communication Wireless Mesh Network Network Performance Evaluation 현재진행중인프로젝트중첩 Super-WiFi/LTE 셀룰라네트워크에서통합무선자원관리기법설계 ( 한국연구재단, ~ ) 기지국 / 단말협력 (Cooperative) 무선전송기술 (ITRC, ~ ) 헬스갤럭시 (Health Galaxy) 를위한핵심기반기술개발 ( 삼성전자, ~ ) 26

27 이동컴퓨팅및통신연구실 -주요연구주제 인지라디오 (CR: Cognitive Radio) : 주파수스펙트럼환경을측정하고측정된정보를기반으로파악된빈주파수스펙트럼을이용하여통신하는기술 선순위사용자를효율적으로검출하는스펙트럼센싱기법연구 다중채널 CR ad-hoc 네트워크를위한무선접속기술연구및라우팅알고리즘개발 무선자원관리 Homepage: 멀티미디어트래픽의서비스품질을보장하면서셀처리량을최대화하기위한주파수및전력할당기법연구 이종 (heterogeneous) 네트워크에서의종단간서비스품질을보장하고시스템성능을최적화하는자원할당알고리즘개발 그린커뮤니케이션 (Green Communication) :CO 2 절감을위해에너지효율을고려하는무선통신및네트워크기술이종네트워크에서에너지효율적인무선자원할당알고리즘개발트래픽상황에따른셀최적화기술연구 27

28 Multimedia and Mobile communications Laboratory (MMLAB) mmlab.snu.ac.kr Members Yanghee Choi, Taekyoung Kwon 10 PhD students, 10 MS students Research Areas Content-centric t ti Networking (CCN) Mobile/Wireless Networking Adaptive Video Delivery P2P Networking 28

29 IP networking vs. CCN Network prefix Content name Destination Next thop Content t Name Next thop /16 Router C /a.com/b.jpg Router C /a.com/b.jpg 29

30 Q&A 30

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°í¼®ÁÖ Ãâ·Â Performance Optimization of SCTP in Wireless Internet Environments The existing works on Stream Control Transmission Protocol (SCTP) was focused on the fixed network environment. However, the number of