Computer Networks 1. What is Internet? and the Internet 2. Network Edge: Access Networks and Media 3. Network Core: Packet vs. Circuit Switching Server 4. Delay, Loss, and Throughput Raj Jain 5. Protocol Layers Washington University in Saint Louis 6. Network Security Saint Louis, MO 63130 7. History of Internet [email protected] Audio/Video recordings of this lecture are available on-line at: http://www.cse.wustl.edu/~jain/cse473-16/ Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain 1-1 1-2 What is a Network? T Network: Enables data transfer among nodes Overview T Generally heterogeneous nodes T More than 2 nodes T E.g., Your home or office network 1. What is Internet? 2. Switching: Circuit vs. Packet Server 3. Edge vs. Core 4. Network Performance Measures: Delay, Loss, Throughput 5. Protocol Layers 6. Network Security T Communication: Two nodes. 7. History T Link level electrical issues. Note: This class lecture is based on Chapter 1 of the textbook (Kurose and Ross) and the slides provided by the authors. Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain 1-3 1-4 Key Concepts What is Internet? Server Net 1 Net 3 T End Systems: Systems that are sinks or sources of data, e.g., Desktops, Laptops, Servers, Printers, Cell Phones, etc. Net 2 T Intermediate Systems: Systems that forward/switch data from one link to another, e.g., routers, switches T Internet = Inter-Network = Network connecting networks T Hosts: End Systems T Approximately 1.05B hosts on Internet in 2016. T Gateways: Routers T ISP: Internet Service Provider. T Servers: End Systems that provide service, e.g., print server, storage server, Mail server, etc. T Provide access to Internet. T Clients: End systems that request service T Telecommunications (Telephone) Companies, AT&T, Verizon, Comcast, ... T Links: Connect the systems. Characterized by transmission rate, propagation delay T Coffee Shops (Wi-Fi) Ref: http://www.statista.com/statistics/264473/number-of-internet-hosts-in-the-domain-name-system/ Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain 1-5 1-6 Types of Networks Multiplexing T Point to point vs. Broadcast Point-to-Point Bus T How multiple users can share a link? T Time Division Multiplexing (TDM) Frequency 1 2 3 4 5 6 7 8 T Circuit switched vs. packet switched Star Time T Circuit: A path (circuit) is setup before transmission. T Frequency Division Multiplexing (FDM) 1 All bits follow the same path, e.g., Phone 2 3 4 T Packet: Packets of bits are forwarded individually Frequency 5 6 7 8 Time T Other multiplexing methods will be covered as needed. Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain 1-7 1-8 Types of Networks (Cont) Structure of the Internet T Local Area Networks (LAN): 0-2 km, Single Ownership Company A Metropolitan Area Networks (MAN) 2-50 km, Enterprise Networks Core Networks Wide Area Networks (WAN) 50+ km T Originally LAN/MAN/WAN technologies were different Company B Access Networks T Now they are all same T Telecom Networks: T Access: Between subscriber and the service provider T Enterprise/Home Networks: Stub Networks. Privately owned Not owned by ISP T Metro: Covering a city e.g., WUSTL network: Ethernet and WiFi T Core: Between cities T Access Network: Enterprise/Users to ISP (in the city) WiFi, 3G/4G, DSL T Core Network: ISP's network (between city): Optical Fiber Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain 1-9 1-10 Types of ISPs Transmission Media T Guided: Tier 1 Tier 1 T Twisted Pair T Coaxial cable Tier 2 …… Tier 2 Tier 2 T Optical fiber Tier 3 … Tier 3 Tier 3 … Tier 3 Tier 3 … Tier 3 T Unguided: T Microwave T Tier 1: Global or National, e.g., AT&T, Verizon, … T Satellite T Tier 2: Regional T Wireless T Tier 3: Local Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain 1-11 1-12 Twisted Pair (TP) Shielded and Unshielded TP T Shielded Twisted Pair (STP) T Metal braid or sheathing that reduces interference T More expensive T Harder to handle (thick, heavy) T Used in token rings T Unshielded Twisted Pair (UTP) T Twists decrease the cross-talk T Ordinary telephone wire T Cheap, Flexible T Neighboring pairs have different twist length Easiest to install T Most of telephone and network wiring in homes and T No shielding offices is TP. Suffers from external interference T Used in Telephone and Ethernet Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain 1-13 1-14 UTP Categories Optical Fiber T Cat 3 T Up to 16MHz T Voice grade found in most offices T Twist length of 7.5 cm to 10 cm T Cat 4 T Up to 20 MHz. Not used much in practice. T Cat 5 T Up to 100MHz T A cylindrical mirror is formed by the cladding T Used in 10 Mbps and 100 Mbps Ethernet T The light wave propagate by continuous reflection in the fiber T Twist length 0.6 cm to 0.85 cm T Not affected by external interference low bit error rate T Cat 5E (Enhanced), Cat 6, Cat 7, … T Fiber is used in all long-haul or high-speed communication T Infrared light is used in communication Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain 1-15 1-16 Optical Communication…History Electromagnetic Spectrum Fireflies use pulse-width modulation. T Infrared light is used for optical communication Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain 1-17 1-18 Homework 1A Network Edge: Enterprise Networks T Which networking media will you use for the 1. Ethernet following applications and why? 2. Wi-Fi 1. Very large file transfer at home 2. High-speed multiple channel video transmission at office 3. News reading while traveling in a car Note: Do not write the name of the protocol. Write the name of the media and justify. Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain 1-19 1-20 Ethernet Wi-Fi T Uses UTP (Unshielded Twisted Pair) T IEEE 802.11 T 10 Mbps, 100 Mbps, 1 Gbps, 10 Gbps T Uses 2.4 GHz and 5.8 GHz T Originally bus, now point-to-point (Star) topology Switch Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain 1-21 1-22 Access Networks DSL 1. DSL T Digital Subscriber Line (DSL) T Can transmit very high data rates on phone wire using special 2. Cable equipment at the phone company allowing higher frequency 3. Fiber-To-The-Home signals 4. Wi-Fi High-Speed ISP’s 5. LTE Network Network Home PC DSL DSLAM Phone Modem Company T DSL Access Multiplexer (DSLAM) T 100 kbps - 100 Mbps Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain 1-23 1-24 Cable Fiber-To-The-Home (FTTH) Optical T Cable companies have a very-high speed Services Distribution medium (for video transmission) Internet/Ethernet Network T Phone wire = 4kHz for voice Leased Line T1/E1 Optical Video Cable = 500 MHz for video Frame/Cell Relay Line ONU One TV Channel = 6 MHz Telephone Terminal T 30 Mbps down/1 Mbps up Interactive Video T Fiber in the main line + Coax in tributaries Cable Splitter Hybrid Fiber Coax (HFC) Modem T 100+ Mbps per home. Multiple services. T No electronic components in the distribution system Home 1 Home 2 Home 3 Home 4 Passive Reliable Cable T Passive Optical Network (PON) Company Fiber Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain 1-25 1-26 Wireless Access Networks Network Performance Measures T Wi-Fi hot spots T Delay T Cellular access: 2G/3G/4G (LTE) T Throughput T Loss Rate Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain Washington University in St.