Wireless Communicating Networks PDF

Wireless Communicating Networks Network Fundamental Dr. Yousef Hamouda Lecturer ◼ Dr Yousef Hamouda  Email: [email protected]  Meeting: At Computer Department and by appointment only (use the email)  Discussion: Could be in the meeting or after l...

Wireless Communicating Networks Network Fundamental Dr. Yousef Hamouda Lecturer ◼ Dr Yousef Hamouda  Email: [email protected]  Meeting: At Computer Department and by appointment only (use the email)  Discussion: Could be in the meeting or after lectures 2 Do and Don’t ◼ Don’t  No mobile phones in class  No noises and talking in class, unless you are asked to contribute  No late attendees (>10 minutes)  No eating or drinking during lectures ◼ Do  Study and concentrate in class  Ask for repeat  Ask questions 3 Supporting Information ◼ Source of Information  Lecture Notes  Test Books  additional resources – web links, paper, etc.  and more… 4 Text Books Behrouz A. Forouzan, “DATA COMMUNICATIONS AND NETWORKING”, Fourth Edition, 2007. Others 1- Kurose, James F, Ross, Keith W., "Computer networking: a top down approach featuring the Internet", Addison-Wesley. 2 Douglas E. Comer, “Internetworking with TCP/IP”, Prentice Hall 3- Halsall, Fred "Data communications, computer networks, and open systems", Addison-Wesley Pub. Co. 4- Haykin, S. S, "Communication systems", Wiley Relevant Internet Drafts and RFC’s 5- D. Comer, “Internetworking with TCP/IP, Vol 1: Principles, Protocols and Architecture”, 5th Edition; Prentice Hall 2006 6- Fred Halsall, “Computer Networking and the Internet”, (5th Edition). 5 Assessment ◼ Final Examination: 50% ◼ Written Coursework (individual): 50% Written Two Research Papers (6 pages each) Paper (1) Written: 15% Paper (2) Written : 15% Paper (1) Recorded Presentation: 10% Paper (2) Recorded Presentation: 10% 6 Research Topic ◼ Wireless Sensor Networks (WSN) ◼ Zigbee ◼ Bluetooth and Bluetooth Low Energy (BLE) ◼ Low Power Wide Area Networks (LPWAN) ◼ Narrowband IoT (NB-IoT) ◼ WiFi ◼ WiMax ◼ Machine Learning ◼ LoRa ◼ AI ◼ Wireless M-Bus ◼ Security ◼ Free Space Optical (FSO) ◼ Satellite Communication ◼ Near Field Communication (NFC) ◼ Radio Frequency Identification (RFID) ◼ Infrared (IR) 7 Computer Network ◼ A computer Network: Computers connected together. ◼ A computer network consists of:  Fixed Devices: Desktops (PC), Workstations.  Portable Devices: Laptops, Personal Digital Assistant (PDA), mobile phones, smart phones.  Network Devices: Hubs, switches, routers, printers.  Wireless Access Points: WLAN AP, Bluetooth AP 8 Simple Computer Network Node Link Node ◼ Node:  End Host: General-purpose computer, cell phone, PDA.  Network Node: Switch or Router. ◼ Link: Physical medium connecting nodes  Twisted Pair: The wire that connects to telephones  Coaxial Cable: The wire that connects to TV sets  Optical Fiber: High-bandwidth and long-distance links  Free Space: Propagation of radio waves or microwaves 9 Network Components Links Interfaces Network devices Large router Fibers Ethernet card Coaxial Cable Wireless card Computers 10 Multi-Access vs. Point-to-Point Link ◼ Multi-Access Link: means shared medium  Many nodes share the same physical link (wire, frequency, free space,...)  There must be some arbitration mechanism  Example: Ethernet, Wireless  Limitations: on the number of adapters per node How can we send data to only 1 computer and not all? ◼ Point-to-Point Link:  Only two nodes involved  Separate link per pair of nodes  no doubt about where data came from!  Limitations: On the number of adapters per node 11 Simplex vs Duplex ◼ Simplex:  One-way communication (One direction)  Example: TV ◼ Half Duplex:  Two-way communication (Either direction) BUT only one way at a time  Example: Police Radio ◼ Full Duplex:  Simultaneous two-way communication (Both directions at the same time)  Example: Telephone 12 Types of Networks 13 LAN Topologies ◼ Four Network Topologies: Tree, Bus, Ring and Star 14 Growth of the Internet ◼ The Internet has grown exponentially in the last decade  Increase in applications  Increase in users connected ◼ We cannot really live without this Internet  I check my email first thing when I wake up  We want to be connected all the time 15 The Internet ◼ All computers router workstation connected together server mobile ◼ Large networks local ISP ◼ Network of Networks regional ISP company network 16 The Internet ◼ All millions of connected router computing devices called workstation hosts (i.e., end systems ) server mobile ◼ Running network applications local ISP such as Internet Explorer. ◼ connected by communication links regional ISP  fiber, copper, radio, satellite  transmission rate = bandwidth company network 17 The Internet ◼ Routers: forward packets (chunks of data) ◼ Protocols control sending, receiving of messages  e.g., TCP, IP, HTTP, FTP ◼ Internet: “network of networks”  loosely hierarchical  public Internet versus private intranet 18 The Internet ◼ Many Different Internet Service Providers ◼ Each network is independent ◼ Interoperability requires using Internet standards: IP, TCP  the Internet is global and must run these standards  your private intranet can do whatever you want it to do 19 Who Defines the Protocols? ◼ IETF: Internet Engineering Task Force  http://www.ietf.org/ ◼ IETF standardises all networking protocols ◼ These standards are called: RFC – Request for Comments ◼ Over 5000 RFCs 20 Network Structure ◼ Network Edge  applications and hosts ◼ Network Core  routers  network of networks ◼ Access Networks  communication links 21 Network Edge ◼ End Systems (Hosts):  run application programs  e.g. Web, email ◼ Client/Server Model  client host requests, receives service from always-on server  e.g. Web browser/Web server; Email client/Email server ◼ Peer-to-Peer Model:  minimal (or no) use of dedicated servers. 22 Network Core ◼ Mesh of interconnected routers ◼ How is data transferred through network?  Circuit Switching: ◼ Telephone Network ◼ Dedicated circuit per call  Packet Switching: ◼ Data sent through the network in discrete “chunks” of data called “Packets” 23 Circuit Switching ◼ End-to-End resources reserved for “call”  Link bandwidth, Switch capacity ◼ Dedicated resources: No sharing ◼ Circuit-like (guaranteed) performance ◼ Call setup required 24 Advantages of Circuit Switching ◼ Guaranteed Bandwidth  Predictable communication performance  Not “best-effort” delivery with no real guarantees  Information transmitted at fixed data rate with only propagation delay ◼ Simple Abstraction  Reliable communication channel between hosts  No worries about lost or out-of-order packets ◼ Simple forwarding  Forwarding based on time slot or frequency  No need to inspect a packet header ◼ Low per-packet overhead  Forwarding based on time slot or frequency  No IP (and TCP/UDP) header on each packet 25 Disadvantages of Circuit Switching ◼ Wasted Bandwidth:  Channel capacity dedicated for duration of connection  Bursty traffic leads to idle connection during silent period  Unable to achieve gains from statistical multiplexing ◼ Delay prior to signal transfer for establishment ◼ Blocked connections  Connection refused when resources are not sufficient  Unable to offer “okay” service to everybody ◼ Connection set-up delay  No communication until the connection is set up  Unable to avoid extra latency for small data transfers ◼ Network state  Network nodes must store per-connection information  Unable to avoid per-connection storage and state 26 Packet Switching (1) ◼ Data traffic divided into packets  Each packet contains a header (with address) ◼ User packets share network resources  Each packet uses full link bandwidth  Resources used as needed ◼ Packets travel separately through network  Packet forwarding based on the header ◼ Destination reconstructs the message 27 Packet Switching (2) ◼ Best-effort Delivery:  Packets may be lost  Packets may be corrupted  Packets may be delivered out of order ◼ Aggregate resource demand can exceed amount available ◼ Congestion: packets queue, wait for link use ◼ Store and Forward: packets move one hop at a time  Node receives complete packet before forwarding 28 Disadvantages of Packet Switching ◼ Each packet switching node introduces a delay ◼ Overall packet delay can vary substantially  Caused by differing packet sizes, routes taken and varying delay in the switches ◼ Each packet requires overhead information  Includes destination and sequencing information  Reduces communication capacity ◼ More processing required at each node 29 Access Networks ◼ How to connect end systems to edge router? ◼ Residential access networks ◼ Home Network ◼ Institutional access networks (school, company) ◼ Mobile & Wireless access networks 30 Access Networks 31 Protocol Layers - Why layering? ◼ Divide a task into pieces and then solve each piece independently (or nearly so). ◼ Establishing a well defined interface between layers makes porting easier. ◼ Dealing with complex systems:  explicit structure allows identification, relationship of complex system’s pieces ◼ Specify different functionalities – achieved by different layers  modularization eases maintenance, updating of system ◼ e.g., change of implementation of layer’s service transparent to rest of system 32 OSI Model ◼ Open Systems Interconnection (OSI) High level protocols  Developed by International Standards Organization (ISO)  Has seven layers  Defines a networking model for implementing protocols in seven layers.  Designed to reduce complexity Low level  Each Layer has a separate function protocols  Each layer can only interact with the layer directly above or below it.  Each Layer receives the data from the previous layer, process it and forwards it to the next layer. 33 OSI Model Application (Layer 7) Application-specific protocols and services Examples: FTP, HTTP Presentation (Layer 6) Data representation (ASCII / EBCDIC) Transforming data from application to network format Session (Layer 5) Establishes, manage and terminates connections (sessions) between cooperating applications Transport (Layer 4) Provides reliable and transparent transfer of data between end-systems Provide end-to-end error recovery, data integrity and flow control Network (Layer 3) Switching and routing technologies to connect systems Data Link Layer (Layer 2) Control Access to data and synchronisation Manage communication between adjacent nodes Physical Layer (Layer 1) Transmit data as a Bit stream(0’s and 1’s) over the physical medium such as electrical pulse, light or radio signal 34 TCP/IP Protocol Stack 35 TCP/IP Physical Layer ◼ The physical interface between a data transmission devices (NIC on Computer) and a transmission medium (Network) ◼ Responsibility:  Transmission of raw bits over a communication channel ◼ Physical layer specifies:  Characteristics of the transmission medium  The nature of the signals  The data rate  Distances  Other related matters 36 TCP/IP Network Access Layer ◼ It is called TCP/IP Link Layer ◼ Concerned with the exchange of data between an end system and the network to which it's attached ◼ Responsibility:  Provide an error-free communication link ◼ Issues:  Framing (dividing data into chunks) ◼ header & trailer bits  Addressing ◼ Software used depends on type of network  Circuit switching/Packet switching  LANs (e.g., Ethernet), WLAN, Synchronous Optical Networking (SONET), Asynchronous Transfer Mode (ATM) 37 TCP/IP Internet Layer (IP) ◼ Uses Internet Protocol (IP) ◼ Provides routing functions to allow data to traverse multiple interconnected networks ◼ Implemented in end systems and routers ◼ Routers connect two networks and relays data between them 38 TCP/IP Transport Layer ◼ Common layer shared by all applications ◼ Provides services for host-to-host communication ◼ Provides reliable/unreliable delivery of data ◼ Provides packet ordering service ◼ Commonly uses:  Transmission Control Protocol (TCP)  User Datagram Protocol (UDP)  Real-time Transport Protocol (RTP) 39 TCP/IP Application Layer ◼ Provide support for user applications ◼ Need a separate module for each type of application ◼ Examples:  File Transfer protocol (FTP).  Hypertext Transfer Protocol (HTTP)  Domain Name System (DNS)  Dynamic Host Configuration Protocol (DHCP)  Simple Mail Transfer Protocol (SMTP)  BitTorrent: A peer-to-peer file sharing protocol used for distributing large amounts of data over the Internet. 40 TCP/IP Stack: Protocols 41 Layering & Headers ◼ Each layer needs to add some control information to the data in order to do it’s job. ◼ This information is typically prepended to the data before being given to the lower layer. ◼ Once the lower layers deliver the data and control information - the peer layer uses the control information. 42 Headers Application DATA Application Transport H DATA Transport Network H H DATA Network Data Link H H H DATA Data Link Layer N header and trailer added DATA Layer N-1 DATA header and trailer added continues though all the layers & can add significant overhead 43  source Encapsulation message M application segment Ht M transport datagram Hn Ht M network frame Hl Hn Ht M link physical Hl Hn Ht M link Hl Hn Ht M physical switch destination Hn Ht M network Hn Ht M M application Hl Hn Ht M link Hl Hn Ht M Ht M transport physical Hn Ht M network Hl Hn Ht M link router physical 44 Example: HTTP Service ◼ Host – all layers ◼ Hubs – Layer 1 ◼ Servers – all Layers ◼ Switches – Layer 2 ◼ Routers – Layer 3 45 Delays in Packet-Switched Networks ◼ Processing delay ◼ Transmission delay:  check bit errors  R=link bandwidth (bps)  determine output link  L=packet length (bits) ◼ Queuing delay  time to send bits into link = L/R  Time waiting at output ◼ Propagation delay: link for transmission  d = length of physical link  Depends on congestion  s = Medium propagation speed level of router  propagation delay = d/s transmission A propagation B 46 nodal processing queueing Delays in Packet-Switched Networks d nodal = d proc + d queue + d trans + d prop ◼ dproc = processing delay  typically a few microsecs or less ◼ dqueue = queuing delay  depends on congestion ◼ dtrans = transmission delay  = L/R, significant for low-speed links ◼ dprop = propagation delay  a few microsecs to hundreds of msecs “Real” Internet delays and routes traceroute: gaia.cs.umass.edu to www.eurecom.fr Three delay measurements from gaia.cs.umass.edu to cs-gw.cs.umass.edu 1 cs-gw (128.119.240.254) 1 ms 1 ms 2 ms 2 border1-rt-fa5-1-0.gw.umass.edu (128.119.3.145) 1 ms 1 ms 2 ms 3 cht-vbns.gw.umass.edu (128.119.3.130) 6 ms 5 ms 5 ms 4 jn1-at1-0-0-19.wor.vbns.net (204.147.132.129) 16 ms 11 ms 13 ms 5 jn1-so7-0-0-0.wae.vbns.net (204.147.136.136) 21 ms 18 ms 18 ms 6 abilene-vbns.abilene.ucaid.edu (198.32.11.9) 22 ms 18 ms 22 ms 7 nycm-wash.abilene.ucaid.edu (198.32.8.46) 22 ms 22 ms 22 ms 8 62.40.103.253 (62.40.103.253) 104 ms 109 ms 106 ms trans-oceanic 9 de2-1.de1.de.geant.net (62.40.96.129) 109 ms 102 ms 104 ms 10 de.fr1.fr.geant.net (62.40.96.50) 113 ms 121 ms 114 ms link 11 renater-gw.fr1.fr.geant.net (62.40.103.54) 112 ms 114 ms 112 ms 12 nio-n2.cssi.renater.fr (193.51.206.13) 111 ms 114 ms 116 ms 13 nice.cssi.renater.fr (195.220.98.102) 123 ms 125 ms 124 ms 14 r3t2-nice.cssi.renater.fr (195.220.98.110) 126 ms 126 ms 124 ms 15 eurecom-valbonne.r3t2.ft.net (193.48.50.54) 135 ms 128 ms 133 ms 16 194.214.211.25 (194.214.211.25) 126 ms 128 ms 126 ms 17 * * * 18 * * * 19 fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms 136 ms * means no reponse (probe lost, router not replying)