Energy Informatics 3-1 Introduction to Computer Networking - PowerPoint PPT Presentation

Energy Informatics 3-1 Introduction to Computer Networking Christian Schindelhauer Technical Faculty Computer-Networks and Telematics University of Freiburg

Overview § Challenges of Computer Networks - Size, complexity, technology § Fundamental concepts in Computer Networks - Layers - Protocols - Distributed Systems § Network Layers - Physical - Data link - Network - Transport - Application 2

Types of Networks (Tanenbaum) 3

The Internet § global system of interconnected WANs and LANs § open, system-independent, no global control [Tanenbaum, Computer Networks] 4

ARPANET ARPANET (a) December 1969 (b) July 1970 (c) March 1971 (d) April 1972 (e) September 1972 5

Internet Traffic 200 150 100 50 0 1990 1991 1992 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 Source: CISCO VNI 2009,2010,2012,2014,2016 6

Internet Traffic 1Pb/s 1000000000 100000000 10000000 1 Tb/s 1000000 100000 10000 1Gb/s 1000 100 10 Mb/s 1 1990 1991 1992 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 Source: CISCO VNI 2009,2010,2012,2014,2016 7

From Kilo To Yotta § Data - 1 Byte = 1 B = 8 Bit = 8b - 1 kilobyte = 1 kB = 1000 Bytes - 1 megabyte = 1 MB = 1000 kB = 10 6 Bytes - 1 gigabyte = 1 GB = 1000 MB = 10 9 Bytes - 1 terabyte = 1 TB = 1000 GB = 10 12 Bytes - 1 petabyte = 1 PB = 1000 TB = 10 15 Bytes - 1 exabyte = 1 EB = 1000 PB = 10 18 Bytes - 1 zettabyte = 1 ZB = 1000 EB = 10 21 Bytes - 1 yottabyte = 1 YB = 1000 ZB = 10 24 Bytes § Storage - 1 Byte = 1 B = 8 Bit = 8b - 1 kibibyte = 1 kB = 1024 Bytes - 1 mebibyte = 1 MiB = 1024 kiB = 1.04 10 6 Byte - 1 gibibyte = 1 GiB = 1024 MiB = 1.07 10 9 Bytes - 1 tebibyte = 1 TiB = 1024 GiB = 1.10 10 12 Bytes - 1 pebibyte = 1 PiB = 1024 TiB = 1.12 10 15 Bytes - 1 exbibyte = 1 EiB = 1024 PiB = 1.15 10 18 Bytes - 1 zebibyte = 1 ZiB = 1024 EiB = 1.18 10 21 Bytes - 1 yobibyte = 1 YiB = 1024 ZiB = 1.21 10 24 Bytes 8

An Open Network Architecture § Concept of Robert Kahn (DARPA 1972) - Local networks are autonomous • independent • no WAN configuration - packet-based communication - “best effort” communication • if a packet cannot reach the destination, it will be deleted • the application will re-transmit - black-box approach to connections • black boxes: gateways and routers • packet information is not stored • no flow control - no global control § Basic principles of the Internet 9


 Protocols of the Internet Application Telnet, FTP , HTTP , SMTP (E-Mail), ... TCP (Transmission Control Protocol) 
 Transport UDP (User Datagram Protocol) IP (Internet Protocol) IPv4 + IPv6 
 Network + ICMP (Internet Control Message Protocol) 
 + IGMP (Internet Group Management Protoccol) Host-to-Network LAN (e.g. Ethernet, W-LAN) 10

TCP/IP Layers § 1. Host-to-Network - Not specified, depends on the local networ,k e.g. Ethernet, WLAN 802.11, PPP, DSL § 2. Routing Layer/Network Layer (IP - Internet Protocol) - Defined packet format and protocol - Routing - Forwarding § 3. Transport Layer - TCP (Transmission Control Protocol) • Reliable, connection-oriented transmission • Fragmentation, Flow Control, Multiplexing - UDP (User Datagram Protocol) • hands packets over to IP • unreliable, no flow control § 4. Application Layer - Services such as e-mail, file transfer, Web, DNS, Games … 11

Example: Routing between LANs client server HTTP HTTP HTTP protocol Client Server TCP TCP protocol TCP router IP protocol IP protocol IP IP IP wireless Ethernet protocol protocol WLAN WLAN Ethernet Ethernet driver driver driver driver radio radio Ethernet Ethernet device device device device 12

ISO/OSI Reference model § 7. Application - Data transmission, e-mail, terminal, remote login Application Application Anwendung Anwendung § 6. Presentation Presentation Presentation - System-dependent presentation Präsentation Präsentation of the data (EBCDIC / ASCII) Session Session § 5. Session Sitzung Sitzung - start, end, restart Transport Transport Router § 4. Transport Network Network Network Network - Segmentation, congestion Vermittlung Vermittlung Vermittlung Vermittlung § 3. Network Data link Data link Data link Data link Sicherung Sicherung Sicherung Sicherung - Routing § 2. Data Link Physical Physical Physical Physical Bitübertragung Bitübertragung Bitübertragung Bitübertragung - Checksums, flow control § 1. Physical - Mechanics, electrics 13

Reference Models: OSI versus TCP/IP (Aus Tanenbaum) 14

Data/Packet Encapsulation user data application Appl. user data header TCP TCP application data header IP TCP segment IP TCP application data header header Ethernet IP datagram driver Ethernet IP TCP Ethernet application data header header header trailer 14 20 20 4 Ethernet Frame 46 to 1500 bytes 15

Smart Grids http://www.cisco.com/c/dam/en_us/solutions/industries/docs/energy/ip_arch_sg_wp.pdf 16

Physics – Background § Moving particles with electric charge cause electromagnetic waves - frequency • f : number of oscillations per second - unit: Hertz - bandwidth • difference between the upper and lower frequencies in a continuous set of frequencies - wavelength • λ : distance (in meters) between two wave maxima - antennas can create and receive electromagnetic waves - the transmission speed of electromagnetic waves in vacuum is constant • speed of light c ≈ 3 ⋅ 10 8 m/s § Relation between wavelength, frequency and speed of light: 
 λ ⋅ f = c 17

Electromagnetic Spectrum guided media coaxial cable optical twisted pair waveguide fibre Hz 10 3 10 5 10 7 10 9 10 11 10 13 10 15 low 
 high infrared micro wave medium frequency frequency visible frequency radio TV light unguided media 18

Bands § LF Low Frequency § MF Medium Frequency § HF High Frequency § VHF Very High Frequency § UHF Ultra High Frequency § UV Ultra Violet light Picture under creative commons license 19 http://creativecommons.org/licenses/by-sa/2.5/

Attenuation for Different Frequentes § Attenuation in earth’s atmosphere http://www.geographie.uni-muenchen.de/iggf/Multimedia/Klimatologie/physik_arbeit.htm 20

Noise and Interference § Noise - inaccuracies and heat development in electrical components - modeled by normal distribution § Interference from other transmitters - in the same spectrum - or in neighbored spectrum • e.g. because of bad filters § Effect - Signal is disrupted 21

Signal Interference Noise Ratio § reception energy = transmission energy ⋅ path loss - path loss ~ 1/d γ • γ ∈ [2,5] § Signal to Interference and Noise Ratio = SINR - S = (desired) Signal energy - I = energy of Interfering signals - N = Noise § Necessary condition for reception S SINR = I + N ≥ T hreshold 22

Fourier Analysis n a 0 X lim 2 + a k cos kx + b k sin kx = f ( x ) n →∞ k =1 π a k = 1 Z f ( x ) cos kx dx π − π π b k = 1 Z 6 f ( x ) sin kx dx 5 π 4 − π 3 2 1 2 4 6 8 6 5 4 3 2 1 2 4 6 8 23


 Fourier Analysis for Frequency f § Theorem of Fourier for period T=1/f: - The coefficients c, a n , b n are then obtained as follows 
 § The sum of squares of the k-th terms is proportional to the energy consumed in this frequency: 24

Measure how often? Fourier decomposition with 8 coefficients § How many 1.2 measurements are 1 necessary 0.8 - to determine a Fourier Voltage transform to the k-th 0.6 component, exactly? 0.4 § Nyquist-Shannon 0.2 sampling theorem 0 - To reconstruct a continuous band-limited -0.2 8 0 1 2 3 4 5 6 7 signal with a maximum Time frequency f max you need 0 1 1 0 0 0 1 0 at least a sampling frequency of 2 f max . 25

Symbols and Bits § For data transmission instead of bits can also be used symbols - E.g. 4 Symbols: A, B, C, D with • A = 00, B = 01, C = 10, D = 11 § Symbols - Measured in baud - Number of symbols per second § Data rate 0 1 1 0 0 0 1 0 - Measured in bits per second (bit / s) - Number of bits per second § Example - 2400 bit/s modem is 600 baud (uses 16 symbols) 26

Structure of a Baseband Digital Transmission § Source Coding • removing redundant or irrelevant information • e.g. with lossy compression (MP3, MPEG 4) • or with lossless compression (Huffman code) ‣ Channel Coding • Mapping of source bits to channel symbols • Possibly adding redundancy adapted to the channel characteristics • physical transmission ‣ Conversion into physical events physical source channel transmission coding coding data source channel source bits Medium symbols data target physical channel source reception decoding decoding 27

Structure of a Broadband Digital transmission § MOdulation/DEModulation - Translation of the channel symbols by • amplitude modulation • phase modulation • frequency modulation • or a combination thereof source channel physical Modulation coding coding transmission data source finite set of 
 channel source bits Medium waveforms symbols data target physical channel source Demodulation reception decoding decoding 28