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Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
Lec 2 and_3
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Lec 2 and_3

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  • 1. Network Edge Access Networks and Physical Media Engr. Abbas Abbasi
  • 2. Important Terms Review  Host or End System  Communication Link  Transmission rate  Packet  Packet Switching  Route or Path  Router  Link Layer Switch  ISP  Protocol  TCP  IP  RFC  Distributed Application  API
  • 3. Chapter 1: roadmap 1.1 What is the Internet? 1.2 Network edge 1.3 Network core Network access and physical media Internet structure and ISPs 1.4 Delay & loss in packet-switched networks 1.5 Protocol layers, service models 1.6 Networks under attack: security (covered in Chap. 8) 1.7 History
  • 4. A closer look at network structure:  network edge: applications and hosts  network core:  routers  network of networks  access networks, physical media: communication links
  • 5. End Systems or Hosts  PCs  Game Consoles (Xbox, Playstation)  Internet Ready TVs (Google TV)  Home Appliances  IP enabled phones  Cyber-Physical Systems  Industrial Systems (ECS)  Biomedical Devices (Body Area Network: BAN)  GPS Device
  • 6. Hosts  They are called hosts because they host (run) applications  Client  Servers  Data Centers  Content Distribution Networks (CDNs)  Write down five ways to connect to the Internet
  • 7. The network edge:  end systems (hosts):  run application programs  e.g. Web, email  at “edge of network”  client/server model  client host requests, receives service from always-on server  e.g. Web browser/server; email client/server  peer-peer model:  minimal (or no) use of dedicated servers  e.g. Skype, BitTorrent, KaZaA
  • 8. Access Networks  network—the network that physically connects an end system to the first router (Edge Router) Home Network  WAN Mobile Network  Enterprise Network           DSL (Digital Subscriber Line) Cable FTTH (Fiber to the home) Dial-Up Satellite Ethernet WiFi (Wireless Fidelity) 3G (Third generation) LTE (Long Term Evolution)
  • 9. Network edge: connection-oriented service Goal: data transfer between end systems  handshaking: setup (prepare for) data transfer ahead of time  Hello, hello back -human protocol  set up “state” in two communicating hosts TCP service [RFC 793]  reliable, in-order byte-stream data transfer  loss: acknowledgements and retransmissions  flow control:  sender won’t overwhelm receiver  TCP - Transmission Control  congestion control:  senders “slow down sending rate” Protocol when network congested  Internet’s connection-oriented service
  • 10. Network edge: connectionless service Goal: data transfer between end systems  same as before!  UDP - User Datagram Protocol [RFC 768]: connectionless unreliable data transfer no flow control no congestion control App’s using TCP:  HTTP (Web), FTP (file transfer), Telnet (remote login), SMTP (email) App’s using UDP:  streaming media, teleconferencing, DNS, Internet telephony, Domain Name lookup, Time lookup.
  • 11. Access networks and physical media Q: How to connect end systems to edge router?  residential access nets  institutional access networks (school, company)  mobile access networks Keep in mind:  bandwidth (bits per second) of access network?  shared or dedicated?
  • 12. Residential access  Dialup via modem  up to 56Kbps direct access to router (often less)  Can not surf and phone at same time: can’t be “always on”  DSL: digital subscriber line  up to 1 Mbps upstream (today typically 500 kbps)  up to 20 Mbps downstream (today typically 8 Mbps)  FDM: 50 kHz - 1 MHz for downstream 4 kHz - 50 kHz for upstream 0 kHz - 4 kHz for ordinary telephone
  • 13. DSL Structure DSLAM: DSL Access Multiplexer
  • 14. Cable Access CMTS: Cable Modem Termination System
  • 15. Cable Network Architecture: Overview Typically 500 to 5,000 homes cable headend cable distribution network (simplified) home
  • 16. Cable Network Architecture: Overview FDM: V I D E O V I D E O V I D E O V I D E O V I D E O V I D E O D A T A D A T A C O N T R O L 1 2 3 4 5 6 7 8 9 Channels cable headend cable distribution network home
  • 17. Cable Network Architecture: Overview server(s) Fiber Coax cable headend cable distribution network home
  • 18. Cable Network Architecture: Overview cable headend cable distribution network (simplified) home
  • 19. Fiber to the home (FTTH)  Active Optical Network (AON) equivalent to Ethernet  Passive Optical Network (PON)
  • 20. PON Downstream: 20Mbps ONT: Optical Network Terminator Splitter supports <100 ONT OLT: Optical Line Terminator converts optical signals to electrical signals Shared Fiber
  • 21. Ethernet LAN
  • 22. Wireless access networks  shared wireless access network connects end system to router  via base station aka “access point”  wireless LANs:  802.11b/g (WiFi): 11 or 54 Mbps, @2.4 GHZ (range 100 m),  802.11a 54 Mbps @ 5 GHz  wider-area wireless access  provided by telco operator  3G ~ 384 kbps  GPRS in Europe/US  WiMax in US router base station mobile hosts
  • 23. Physical Media  Bit: propagates between transmitter/rcvr pairs  physical link: what lies between transmitter & receiver  guided media:  signals propagate in solid media: copper, fiber, coax  unguided media:  signals propagate freely, e.g., radio Twisted Pair (TP)  two insulated copper wires  Category 3: traditional phone wires, 10 (CAT-5) Mbps Ethernet  Category 5: 100 Mbps Ethernet  Category 7 1 Gbps and 10 Gbps E'net
  • 24. Physical Media: coax, fiber Coaxial cable:  two concentric copper conductors  bidirectional  baseband:  single channel on cable  legacy Ethernet  broadband:  multiple channels on cable  CATV HFC Fiber-Coax Optical Fiber cable:  glass fiber carrying light pulses, each pulse a bit  high-speed operation:  high-speed point-to-point transmission (e.g., 10’s-100’s Gps)  low error rate: repeaters spaced far apart ; immune to electromagnetic noise Lighted Fiber
  • 25. Physical media: radio  signal carried in electromagnetic spectrum  no physical “wire”  bidirectional  propagation environment effects:  reflection  obstruction by objects  interference Radio link types:  terrestrial microwave  e.g. up to 45 Mbps channels  LAN (e.g., WiFi)  11Mbps, 54 Mbps  wide-area (e.g., cellular)  e.g. 4G: several Mbps  satellite  Kbps to 45 Mbps channel (or multiple smaller channels)  270 msec end-end delay  geosynchronous versus low altitude
  • 26. Important Terms  DSL  LAN  DSLAM  3G  HFC  LTE  CMTS  WiFi  FTTH  Physical Medium Types  AON  UTP  PON  Shared Medium  ONT  OC (Optical Carrier)  OLT  Geostationary Satellite  LEO Satellite

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