Chapter 8 Wide Are Networking (WAN)

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Chapter 8 Wide Are Networking (WAN)

  1. 1. Chapter 8 Wide Are Networking (WAN) <ul><li>Concepts </li></ul><ul><ul><li>Packetizing </li></ul></ul><ul><ul><li>Multiplexing </li></ul></ul><ul><li>Switching </li></ul><ul><li>Transmissions </li></ul><ul><li>Services </li></ul><ul><li>Selection </li></ul>
  2. 2. Packetizing <ul><li>Organize a group of bits in a predetermined & structure format </li></ul><ul><li>Include user’s data, overhead or management information for error-free transmission </li></ul><ul><li>Packets, frames, cells, blocks, data units </li></ul>
  3. 3. Multiplexing <ul><li>Frequency division multiplexing (FDM) </li></ul><ul><li>Time division multiplexing (TDM) </li></ul><ul><li>Statistical time division multiplexing (STDM) </li></ul><ul><li>Wavelength division multiplexing (WDM) </li></ul><ul><li>No interoperation between different manufacturers </li></ul>
  4. 4. Frequency Division Multiplexing <ul><li>Use different frequencies for multiple input signals </li></ul><ul><li>Use guardbands (take space, not efficiency) </li></ul><ul><li>Transmit data and voice simultaneously over phone line </li></ul><ul><li>Data over voice (DOV) unit with PBX for college campus, not for PSTN </li></ul>
  5. 5. Time Division Multiplexing <ul><li>100% bandwidth available for a portion of the time </li></ul><ul><li>Use buffer memory & central clock for flow control (polling) </li></ul><ul><li>Composite message frame </li></ul><ul><li>Simple, not efficiency </li></ul>
  6. 6. Statistical Time Division Multiplexing <ul><li>Efficiency </li></ul><ul><ul><li>No idle time </li></ul></ul><ul><ul><li>No padded blanks or null characters in composite message blocks </li></ul></ul><ul><ul><li>Dynamically allocating time to terminals </li></ul></ul><ul><li>Higher cost </li></ul><ul><ul><li>Buffer </li></ul></ul><ul><ul><li>Processing power for control information (source terminal, bytes of data, & data compression) </li></ul></ul>
  7. 7. Wavelength Division Multiplexing <ul><li>Use different wavelengths of light </li></ul><ul><li>Long-distance fiber optic network </li></ul>
  8. 8. WAN Switching <ul><li>Packet switching network </li></ul><ul><li>Circuit switching network </li></ul>
  9. 9. Packet Switching <ul><li>Packet-switched network </li></ul><ul><li>Public data network (PDN) </li></ul><ul><li>Packet assembler/disassembler (PAD) </li></ul><ul><ul><li>Stand-alone devices </li></ul></ul><ul><ul><li>Combined with modems or multiplexers </li></ul></ul><ul><ul><li>Location: end-user or entry point of packet switched data network </li></ul></ul><ul><li>Equipment: DSEs (data-switching exchanges) or PSEs (packet-switching exchanges) </li></ul><ul><li>Every user having the same transmission rate </li></ul>
  10. 10. Packet Switched Services <ul><li>Connectionless </li></ul><ul><ul><li>Global address (source & destination) </li></ul></ul><ul><ul><li>Datagram (address with user data) </li></ul></ul><ul><ul><li>Unreliable (no error detection or flow control) </li></ul></ul><ul><li>Connection-oriented: virtual circuits </li></ul><ul><ul><li>Reliable packet network (ACK/NAK) </li></ul></ul><ul><ul><li>Call set-up packets, message-bearing packets, & clear request packet </li></ul></ul>
  11. 11. Circuit Switching <ul><li>Circuit switched network </li></ul><ul><li>Use circuit without source & destination address </li></ul>
  12. 12. WAN Networking Transmission <ul><li>Local Loop </li></ul><ul><ul><li>Plain old telephone service (POTS) </li></ul></ul><ul><ul><li>Integrated service digital network (ISDN) </li></ul></ul><ul><ul><li>Asymmetric digital subscriber line (ADSL) </li></ul></ul><ul><ul><li>Cable TV </li></ul></ul><ul><li>Boradband </li></ul><ul><ul><li>T1 </li></ul></ul><ul><ul><li>SONET </li></ul></ul>
  13. 13. ISDN <ul><li>A switched digital services for delivering voice, video, and data at same time </li></ul><ul><li>Types </li></ul><ul><ul><li>Basic rate interface (BRI): 2B+D ( 2 Bearer channels of 64 kbps & 1 Delta or Data channel of 16 kbps) </li></ul></ul><ul><ul><li>Primary rate interface (PRI): 23B+D </li></ul></ul><ul><li>Applications use ISDN terminal adapter </li></ul><ul><ul><li>Single user-to-office or Internet connection </li></ul></ul><ul><ul><li>Office-to-office connection </li></ul></ul>
  14. 14. ADSL <ul><li>Use POTS at higher frequencies </li></ul><ul><li>Use frequency division multiplexing: (upstream & downstream) </li></ul><ul><li>Internet & voice at same time </li></ul><ul><li>Types </li></ul><ul><ul><li>Very high speed digital subscriber line (VDSL) </li></ul></ul><ul><ul><li>Rate-adaptive digital subscriber line (RADSL) </li></ul></ul><ul><ul><li>Symmetric digital subscriber line (SDSL) </li></ul></ul><ul><li>Application: access Internet using POTS & ADSL units </li></ul>
  15. 15. Cable TV Problems for WAN <ul><li>Downstream only infrastructure </li></ul><ul><li>Remedy methods </li></ul><ul><ul><li>Upstream using POTS </li></ul></ul><ul><ul><li>Modify cable architecture to upstream & downstream </li></ul></ul>
  16. 16. T-1 <ul><li>High-capacity digital transmission over voice channel </li></ul><ul><li>1.544 Mbps bandwidth </li></ul><ul><li>24 64-Kbps channels (DS-0 circuit) </li></ul><ul><li>T1 multiplexers </li></ul><ul><li>Application </li></ul><ul><ul><li>Leased line or private line for business </li></ul></ul>
  17. 17. T-1 Digital Services <ul><li>Digital service hierarchy or DS standards </li></ul><ul><li>DS-0 : 64Kbps </li></ul><ul><li>DS-1: T-1uses four copper wires (two twisted pair) </li></ul><ul><li>DS-2: T-2 </li></ul><ul><li>DS-3: T-3 uses optical fiber media </li></ul><ul><li>DS-4: T-4 </li></ul>
  18. 18. SONET <ul><li>Optical transmission services: </li></ul><ul><ul><li>For failure tolerance & reliable data delivery </li></ul></ul><ul><ul><li>Metropolitan area only </li></ul></ul><ul><ul><li>Expensive </li></ul></ul><ul><li>Applications </li></ul><ul><ul><li>Broadband ISDN </li></ul></ul><ul><ul><li>High-definition television </li></ul></ul>
  19. 19. WAN Services <ul><li>X.25 </li></ul><ul><li>Frame relay </li></ul><ul><li>Switched multimegabit data service (SMDS) </li></ul><ul><li>Cell relay - ATM </li></ul><ul><li>Broadband ISDN </li></ul>
  20. 20. X.25 <ul><li>CCITT standard for the interface between DTE and packet-switched network </li></ul><ul><li>Point-to-point error checking or hop-by-hop error checking </li></ul><ul><li>Technology </li></ul><ul><ul><li>Packet assembler/disassembler (PAD) </li></ul></ul><ul><ul><li>X.25 switches </li></ul></ul>
  21. 21. Frame Relay <ul><li>Error detection & correction </li></ul><ul><ul><li>Point-to-point error detection (discard ) </li></ul></ul><ul><ul><li>End-to-end error correction </li></ul></ul><ul><li>Frame: variable length </li></ul><ul><li>Pro: high through put with low delay for data only </li></ul><ul><li>Con: no guaranteed time delivery (not for voice & video) </li></ul>
  22. 22. Frame Relay <ul><li>Technology </li></ul><ul><ul><li>Frame relay or frame assembler/disassembler (FRAD or FAD) or frame relay access devices </li></ul></ul><ul><ul><li>Frame relay switch </li></ul></ul><ul><li>Application: inter-LAN traffic </li></ul>
  23. 23. Switched Multimegabit Data Service - SMDS <ul><li>Connectionless network service </li></ul><ul><li>Use SONET (T-3) </li></ul><ul><li>Fixed-length cells of data </li></ul><ul><li>Broadcast </li></ul><ul><li>Only MCI for long distance </li></ul>
  24. 24. Cell Relay - ATM <ul><li>Cell </li></ul><ul><ul><li>fixed length (53 octects) </li></ul></ul><ul><ul><li>48 for data and 5 for control information </li></ul></ul><ul><li>Predictable delivery time for voice and video </li></ul><ul><li>Technology </li></ul><ul><ul><li>ATM network interface cards </li></ul></ul><ul><ul><li>ATM hub </li></ul></ul><ul><ul><li>ATM enterprise switch </li></ul></ul><ul><ul><li>ATM gateway switches or ATM access switches </li></ul></ul><ul><ul><li>ATM LAM emulation </li></ul></ul>
  25. 25. WAN Selection Criteria <ul><li>Data traffic patterns </li></ul><ul><li>Business objectives </li></ul>
  26. 26. Assignment <ul><li>Review chapter 8 </li></ul><ul><li>Read chapter 9 </li></ul>

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