html5-img
1 / 45

I am

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

hadassah-duke
Télécharger la présentation

I am

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related