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UNESCO PROJECT Advanced Course on Networking Professor Khalid Al-Begain UNESCO/CISM SECOND ADVANCED SCHOOL OF INFORMATICS University of Damascus, Syria, 06 - 15 April 2004. I am. Khalid Al-Begain School of Computing, University of Glamorgan, Wales, UK Professor in Mobile Networking

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  1. UNESCO PROJECT Advanced Course on Networking Professor Khalid Al-BegainUNESCO/CISM SECOND ADVANCED SCHOOL OF INFORMATICSUniversity of Damascus, Syria, 06 - 15 April 2004

  2. I am • Khalid Al-Begain • School of Computing, University of Glamorgan, Wales, UK • Professor in Mobile Networking • Head of the Mobile Computing and Networking Research Group • Performance evaluation Modelling, simulation and analysis • QoS Routing and Multicast Routing • Resource Management and Call admission Control • Traffic Engineering • Mobile Services for next generation mobile and wireless networks

  3. Course Content • Four Lectures • A combination of essential and advanced topics • New compared with last year : WIRELESS • The Course covers • LANs and WLAN standards • TCP/IP Theory : Protocols and Applications • Wireless and Cellular Networks: Channel Allocation Schemes

  4. LAN versus WAN -Revisited

  5. LANs: Major medium access techniques

  6. LANs: Major medium access techniques CD: Collision Detection Ethernet, Fast Ethernet

  7. LANs: Major medium access techniques CA: Collision Avoidance WLAN, Bluetooth

  8. IEEE 802 :LANs

  9. The Data Link Layer Logical Link Control Sublayer Medium Access Sublayer

  10. IEEE 802 Important The future will tell!

  11. IEEE 802.3 • Classic Ethernet (10 Mbps) (First Founded by Xerox in 1976) • Fast Ethernet (100Mbps) (IEEE 802.3u) • Gigabit Ethernet (1Gbps) (IEEE 802.3z)

  12. Classical Ethernet • The most common cabling methods

  13. Classical Ethernet • The most common cabling methods

  14. Manchester Encoding Used in Classical Ethernet

  15. Ethernet : Frame Formats • Two versions exist: (a) DIX (Digital, Intel, Xerox) (b) IEEE 802.3

  16. Ethernet Medium Access CSMA • All stations are connected to the cable • When a station wishes to transmit, it “listens” to the cable - if there is no signal it starts to transmit, otherwise it tries again later. (Non-Persistent, 1-Persistent, p-Persistent) • Whilst a station is transmitting it compares the signal on the coax with the signal it is transmitting - if they are different it stops and tries again later • CD: Collision Detection means when detects collision then stop transmission  wait random time  try again • The time to wait is calculated using the Binary Exponential Backoff algorithm.

  17. Collision Detection Cause: Signals need time to propagate!

  18. Binary Exponential Backoff Time slot = 51.2μs • Binary Exponential Backoff: • After 1st collision each participating station waits randomly 0 or 1 slot • After 2nd collision each participating station waits 0,1,2, or 3 slots • After n-th collision each participating station waits between 0 .. 2n-1 slots • Maximum Backoff = 1023 slots

  19. Beyond the 10Mbps • The early1980s luxury: • 8 MHz PC • 256 KByte RAM • 10 MByte Hard Disk • Connected to the Dream 10Mbps LAN But Parkinson’s Law is valid here too: “Work Expands to fill the time available for its Completion” In other words: “Data expands to fill the bandwidth available for their transmission”

  20. The 100Mbps LAN • Many proposals came to have faster LANs or MANs • FDDI : Fibre Distributed Data Interface • DQDB : Dual Queue Dual Bus • Fibre Channel • Common Feature : • Very complex • High Cost  However for a technology to work, it must be follow the KISS Law: “Keep It Simple, Stupid”

  21. Fast Ethernet • 1992 : the IEEE 802.3 committee again. • Task: make faster LAN. • Results: Fast Ethernet (IEEE 802.3u) which is in principle identical to Ethernet except that bit time is 10ns instead of 100ns.

  22. Fast Ethernet Cabling • Fast Ethernet uses either HUBs or Switches • No Manchester Encoding

  23. Gigabit Ethernet • 1995: the same idea: make Ethernet 10 time faster.

  24. The Ethernet real Competitor: Let us Go Wireless

  25. Who is interested? • Desktop and laptop systems • Handheld devices • PCs, scanners, data collection devices • PDAs • Palmtops • etc

  26. WLAN implications • Multiple propagation pathways • Signal interference • Lifetime of battery • Security • Path loss • Installation and connectivity • Health

  27. IEEE 802.11 • 1997 standard • 2.4GHz • 1Mbit/s and 2Mbit/s • FHSS and DSSS • 1999 standard • 802.11a 5 GHz - Orthogonal FDM up to 54 Mbit/s • 802.11b 2.4 GHz - DSSS up to 11 Mbit/s Logical Link Control (LLC) Data Link layer Media Access Control (MAC) Frequency Hopping Direct Sequence Infrared light PhysicalLayer

  28. IEEE 802.11a,b Pros & Cons! • IEEE 802.11a + Very high data rates - 5 GHz licensing problem • Competition with ETSI HiperLAN 2 • Illegal in Europe • Higher cost • IEEE 802.11b + Works in the Unlicensed band of 2.4 GHz ~ Data rates comparable with LANs • Interference with Cordless phones and Microwave ovens + Cheaper devices

  29. WLAN • Two modes of operation • Centralised • Ad hoc

  30. A multicel 802.11 network

  31. IEEE 802.11 MAC • The hidden Station problem:

  32. Distributed Coordination Function (DCF) • To solve the problem of Hidden station Use DCF: • Uses CSMA/CA (Collision Avoidance) • It is based on virtual channel sensing All WLANs must support DCF. For centralised WLANs, there is also PCF (Point Coordination Function)

  33. Virtual Channel Sensing using CSMA/CA • Example: A, B, C, and D stations (D out of the range of A) Request To Send Clear To Send Due to unreliable medium Network Allocation Vector

  34. Frame Fragmentation • Because the radio link is unreliable short frames are needed  long frames has to be fragmented.

  35. Interframe Spacing in 802.11

  36. IEEE802.11 Frame Structure

  37. IEEE802.11 MAC Services • Distribution system services • Association • Disassociation • Re-association • Distribution • Integration • Station services • Authentication • De-authentication • Privacy • Data Delivery

  38. What else in Wireless • Bluetooth (IEEE 802.15) • Broadband Wireless (IEEE 802.16) • And the Cellular Wireless Technologies • GSM, GPRS, and UMTS

  39. What else in Wireless • Bluetooth (IEEE 802.15) • Broadband Wireless (IEEE 802.16) (will follow but very briefly) • And the Cellular Wireless Technologies • GSM, GPRS, and UMTS

  40. Bluetooth • 1994: Ericsson SIG started (with IBM, Intel, Nokia and Toshiba) • Named after Viking King Harald Blaatand (Bluetooth) who unified Denmark and Norway without wires!! • Goal: Short-range, inexpensive (<$5) method to connect devices without wires (E.g., mobile-PDA) • July 1999, PAN (Personal Area Network) standard IEEE 802.15

  41. Bluetooth Characteristics • Works in the 2.4 GHz band (together with WLANs and microwave ovens) • Low range (< 10m) • 79 channels each with 1MHz 1Mbps • Organised into pico-cells (1 Master and 7 slaves) • Uses FHSS (Frequency Hopping) controlled by Master (1600 hops/sec) • Uses same Frequency band and hoping as WLAN (problem!!!)

  42. Bluetooth Architecture Scatternet, 255 parked slaves, Ad hoc

  43. Bluetooth Services

  44. Broadband Wireless IEEE802.16 • Wireless MAN or Wireless Local Loop • High data rates to Buildings • Can be seen as Wireless Cable TV network. • Uses bandwidth between 10-66 GHz • Uses sophisticated modulation to achieve high rates

  45. IEEE 802.16 Transmission Environment For example: with 25MHz spectrum rates are : 150, 100, 50 Mbps

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