Computer Networks and the Internet

Home , Packet switching, Throughput

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/

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.

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.

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

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

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

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

Fireflies use pulse-width modulation. T Infrared light is used for optical communication

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.

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

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

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

T Measured in Bits/Sec T Queuing Buffer overflow T Capacity: Nominal Throughput T Bit Error Rate on the link T Throughput: Realistic T Bottleneck determines the end-to-end throughput T Lost packets are retransmitted by the previous node or the source 100Mbps 1Gbps 10Mbps buffer packet being transmitted A (waiting area) Net end-to-end capacity = 10 Mbps Actual throughput will be less due to sharing and overhead. B packet arriving to full buffer is lost

Packet Switching Delay Packet Switching Delay: Example

1. Processing Delay: Check packets, decide where to send, etc. T 1500 Byte packets on 10 Mbps Ethernet, 1km segment 2. Queuing Delay: Wait behind other packets T Transmission Delay = 1500×8/10×106 = 1200 Ps = 1.2ms 3. Transmission Delay: First-bit out to last-bit out on the wire T Propagation delay = 1000 m/2×108 =5 Ps = Packet Length/bit rate 4. Propagation Delay: Time for a bit to travel from in to out = Distance/speed of signal Light speed = 3×108 m/s in vacuum, 2×108 m/s in fiber transmission A propagation

B nodal processing queueing 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 1-31 1-32 Delay Example (CBR Circuits) Homework 1B

T P5: Consider two hosts, A and B, connected by a single link of rate R bps. How long would it take to send a file of 640,000 bits Suppose that the two hosts are separated by m meters, and suppose the from host A to host B over a circuit-switched propagation speed along the link is s meters/sec. Host A is to send a packet network? of size L bits to Host B. A. Express the propagation delay, dprop in terms of m and s T All links are 1.536 Mbps B. Determine the transmission time of the packet dtrans in terms of L and R. C. Ignoring processing queuing delays, obtain an expression for the end-to-end T Each link is shared by 24 users delay T 500 ms to establish end-to-end circuit D. Suppose Host A begins to transmit the packet at time t=0. At time t=dtrans where is the last bit of the packet?

T Per User Rate = 1536/24 = 64 kbps E. Suppose dprop is greater than dtrans. At time t=dtrans, where is the first bit of the packet? T Time to transfer = 640kb/64kb = 10 s F. Suppose dprop is less than dtrans, at time t=dtrans, where is the first bit of the T Total time = .5 s + 10 s = 10.5 s packet G. Suppose s=2.5x108 m/s, L=240 bits, and R=56 kbps,. Find the distance m so that dprop equals dtrans.

Protocol Layers What is a Networking Protocol?

T Problem: Philosophers in different countries speak different T Network protocols define the format of messages, languages. The Telex system works only with English. their meanings, sequence, and actions I believe there is a God! Philosopher’s Protocol Philosopher

Please send me Translator’s Protocol www.google.com Translator Here is www.google.com Got it. Thank You. Telex Protocol Telex

Application File transfer, Email, Remote Login 5 Presentation ASCII Text, Sound Application 1 Application 2 Application 1 Application 2 Session Establish/manage connection 4 Transport End-to-end communication: TCP SDU 3 Network Routing, Addressing: IP Transport Transport 2 Datalink Two party communication: Ethernet PDU 1 Physical How to transmit signal: Coding Network Network Access Access T Service Access Points (SAPs) T Service Data Units (SDUs) T Protocol Data Units (PDUs)

Service Data Unit (SDU) Protocol Data Unit (PDU) Application APDU, Message PSDU Application Application Presentation PPDU Presentation Presentation SSDU SPDU Session Session Session TSDU TPDU Transport Transport Transport NPDU, Packet NSDU Network Network DPDU, Frame Network Datalink Datalink DSDU PhPDU, Frame Datalink Physical Physical PhSDU Physical

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 1-39 1-40 TCP/IP Reference Model OSI vs TCP/IP T TCP = Transport Control Protocol T IP = Internet Protocol (Routing) TCP/IP Ref Model TCP/IP Protocols Application FTP Telnet HTTP

Transport TCP UDP

Internetwork IP Host to Ether Point-to- Packet Network net Point Radio

Physical Coax Fiber Wireless

Washington University in St. Louis http://www.cse.wustl.edu/~jain/cse473-16/ ©2016 Raj Jain Washington University in St. Louis htthttp://www.cse.wustl.edu/~jain/cse473-16/ // tl d / j i / 473 16/ ©2016 Raj Jain 1-41 1-42

OSI vs TCP Reference Models PDUs in TCP/IP Architecture T OSI introduced concept of services, interface, protocols. These were force-fitted to TCP later It is not easy to replace protocols in TCP. User Data Application Byte Stream T In OSI, reference model was done before protocols. In TCP, protocols were done before the model TCP T OSI: Standardize first, build later TCP Header User Data Segment TCP: Build first, standardize later IP T OSI took too long to standardize. IP Header TCP Header User Data TCP/IP was already in wide use by the time. Datagram T OSI became too complex. Subnetwork Sub-network Header IP Header TCP Header User Data T TCP/IP is not general. Ad hoc. Packet

T Security Components T Types of Malware T Types of Attacks T Buffer Overflows T Distributed DoS Attacks

Security Components Types of Malware

T Confidentiality: Need access control, Cryptography, T Viruses: Code that attaches itself to programs, disks, or Existence of data memory to propagate itself. T Worms: Installs copies of itself on other machines on a T Integrity: No change, content, source, prevention network, e.g., by finding user names and passwords mechanisms, detection mechanisms T Trojan horses: Pretend to be a utility. Convince users to install on PC. T Availability: Denial of service attacks, T Spyware: Collect personal information T Confidentiality, Integrity and Availability (CIA) This is not a complete list.

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 1-47 1-48 Types of Attacks Distributed DoS Attacks T Tribe Flood Network (TFN) clients are installed on T Denial of Service (DoS): Flooding with compromised hosts. traffic/requests T All clients start a simultaneous DoS attack on a victim on a T Buffer Overflows: Error in system programs. Allows trigger from the attacker. hacker to insert his code in to a program. T Trinoo attack works similarly. Use UDP packets. Trinoo client report to Trinoo master when the system comes up. T Malware T Stacheldraht uses handlers on compromised hosts to receive T Brute Force: Try all passwords. encrypted commands from the attacker. T Port Scanning: Disable unnecessary services and close ports T Network Mapping

History of Internet History of Internet (Cont)

T 1961: Kleinrock developed queueing T Early 1990s: HTML, HTTP: Berners-Lee theory. Showed effectiveness of packet-switching T 1994: Mosaic, later Netscape T 1964: Baran’s report on packet- T 2007: switching T ~500 million hosts in military nets T Voice, Video over IP T 1967: ARPAnet conceived by Advanced Research Projects Agency T P2P applications: BitTorrent (file sharing) Skype (VoIP), PPLive (video) T 1969: First ARPAnet node operational First Request for Comment (RFC) T Video applications: YouTube, gaming www.ietf.org T Wireless, Mobility

T Internet Protocol (IP): Protocol T Address: All systems have an IP address, for example, 125.36.47.23 T Name: All systems have a human readable name, e.g., scorpio.cec.wustl.edu, ibm.com. T Technically called DNS (domain name systems) name. 1. Most common medium is UTP, wireless, fiber Details will be introduced later. 2. Internet is a network of networks T IETF: Internet Engineering Task Force. Make standards for Internet. IETF.org 3. Enterprise, access, and core networks T RFC: Request for comments. Documents that describe Internet 4. Performance Measures: Delay, Throughput, Loss Rate protocols. 5. Protocol Layers: ISO and TCP/IP reference models

Lab 1 Lab 1 (Cont)

1. Find the IP address of your computer (ipconfig, 4. Download Wireshark, ifconfig) https://www.wireshark.org/download.html T Install it on your laptop. 2. Find the IP address of www.wustl.edu (ping) T Start wireshark and start logging 3. Measure delay from your computer to T Tracert to www.google.com www.wustl.edu (ping or tracert) T Stop logging. Capture the current screen and submit. For all cases submit the screen snapshot showing the Do not worry about the part of the trace that is no longer command used and the output. (Use Alt-Print-screen on the screen. to capture a window to clipboard and then paste to T Q1: List 3 protocols that you see in the packet trace. word) T Q2: What is the internet address of www.google.com from the trace?

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 1-55 1-56 Scan This to Download These Slides Related Modules CSE 473s: Introduction to Computer Networks (Course Overview), http://www.cse.wustl.edu/~jain/cse473-16/ftp/i_0int.pdf CSE473S: Introduction to Computer Networks (Fall 2016), http://www.cse.wustl.edu/~jain/cse473-16/index.html Wireless and Mobile Networking (Spring 2016), Raj Jain http://www.cse.wustl.edu/~jain/cse574-16/index.html http://rajjain.com CSE571S: Network Security (Fall 2014), http://www.cse.wustl.edu/~jain/cse571-14/index.html Audio/Video Recordings and Podcasts of Professor Raj Jain's Lectures, https://www.youtube.com/channel/UCN4-5wzNP9-ruOzQMs-8NUw 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 1-57 1-58