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Homework

Homework. Term Paper due 12 April 2000 Readings: [15] “Voice over the Internet: Advantages & Pitfalls”. North American Digital Hierarchy. Obsolete... ... except for ‘last mile’ connectivity T1 byte interleaved, > T1 bit interleaved T1 Frame (Format for 1/8000th second)

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Homework

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  1. Homework • Term Paper due 12 April 2000 • Readings:[15] “Voice over the Internet: Advantages & Pitfalls”

  2. North American Digital Hierarchy • Obsolete... ...except for ‘last mile’ connectivity • T1 byte interleaved, > T1 bit interleaved • T1 Frame (Format for 1/8000th second) • A 4 Wire T1 Connection: • is Full Duplex (1.544 Mbps in two directions) • Carriers often sell bandwidth in T1 & T3 chunks (& fractions thereof)

  3. Switching • Crosspoint Switches Used for Space Division Switching Key component of CO switches • Time Slot Interchange Used for Time Division Switching • CO switches perform Space Division Switching • Any POTS switch handling TDM lines (such as a Tandem) performs Time & Space Division Switching

  4. Switching • Large Switches Have multiple Crosspoint & TSI stages • Packet Switches Handle Statistically Multiplexed traffic Require Buffers May use Crosspoints or Busses to switch between input/output lines • Cross Connects Under Network Control Long Term Trunk Switching

  5. Circuit Switched TDMNetwork POP Cable, RF Fiber Cable, RF Fiber Mux Mux Cross Connects Leased Lines CO Trunks POTS TimeSpaceSwitch ‘80’s Network Model. Evolved to Hybrid.

  6. Hybrid POP SONET, WDM Fiber SONET, WDM Fiber Mux Mux Cross Connects Leased Lines CO Trunks Frame Relay Best Potential Carrying Capacity of any switched network. POTS TimeSpaceSwitch

  7. Hybrid POP offers best potentialCarrying Capacity... Hybrid Carrying Capacity Cell Switch StatMux Packet Switch StatMux Circuit Switch TDM 0% Data 100% Data 100% TST 0% TST Offered Load

  8. ...but only if traffic is properly groomed.Real World systems tend to lay betweenthe extremes below. Hybrid Carrying Capacity if all data traffic is aggregated onto packet switches. Carrying Capacity Hybrid Carrying Capacity if no data traffic is aggregated onto packet switches. 0% Data 100% Data 100% TST 0% TST Offered Load

  9. A Typical Hybrid POP • Mixes all sorts of traffic onto the fiber... • ...using Cross Connects & multiplexers Circuit SwitchingTime Division Multiplexing • May have other switches (Voice, Frame Relay, ATM, or Routers) • POP doesn’t have switch needed?Traffic is back-hauled to nearest switch.Trade-off: Fiber Bandwidth vs. Cost of more Switches

  10. Backhauling... Tulsa POP StillwaterPOP If a Stillwater Customer wants a FR connection & the nearest switch is in Tulsa, the carrier will cross connect the leased line to the Tulsa switch. Carrier FR Switch Customer FRAD Frame Relay Trunk Backhauled Line OKC POP Fiber in the ground Leased Line

  11. Backhauling... Tulsa POP StillwaterPOP If a Stillwater Customer wants a FR connection & the nearest switch is in Tulsa, the carrier will cross connect the leased line to the Tulsa switch. Carrier FR Switch Customer FRAD Frame Relay Trunk Backhauled Line OKC POP Fiber in the ground Leased Line

  12. Cell Switched StatMux Network POP SONET, WDM Fiber SONET, WDM Fiber Mux Mux ATM Switch Leased Lines CO Trunks Frame Relay POTS TimeSpaceSwitch ATM Model

  13. ATM Carrying Capacity vs.Real World Hybrid Carrying Capacity Cell Switch StatMux Real World Hybrid 0% Data 100% Data 100% TST 0% TST Offered Load

  14. An ATM Backbone POP • Mixes all sorts of traffic onto the fiber... • ...using ATM Switches and multiplexers Cell SwitchingStatistical Multiplexing • Virtual Paths perform role of Hybrid’s Cross Connects • May have other switches (Voice, Frame Relay, Cross-Connects, or Routers) • POP doesn’t have switch needed?Traffic is back-hauled to nearest switch.

  15. Packet Switched StatMux Network POP SONET, WDM Fiber SONET, WDM Fiber Mux Mux Routers Leased Lines Local Connections VoiceSwitch 100% Internet Model Local Loops

  16. Carrying CapacityReal World Hybrid vs ATM vs Packet Carrying Capacity Packet Switch StatMux Cell Switch StatMux Real World Hybrid 0% Data 100% Data 100% TST 0% TST Offered Load

  17. A Packet-over-SONET POP • Mixes all sorts of traffic onto the fiber... • ...using Routers and multiplexers Packet SwitchingStatistical Multiplexing • May have other switches (Voice, Cross-Connects)

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