ECSE6660: Broadband Networks Exam 3: Comprehensive

1
ECSE-6660 Broadband Networks Exam 3
Comprehensive

• Time 120 min (strictly enforced)
• Points 100
• YOUR NAME
• Be brief, but DO NOT omit necessary detail
• Note Simply copying text directly from the
  slides or notes will not earn (partial) credit.
  Brief, clear and consistent explanation will.

2

• I. Quick True/False Questions (16 points)
• Tick True or False (1 pt each). Add a 1 line
  explanation JUSTIFYING your choice (1 pt each)
• T F
• ????Long-period and short-period fiber gratings
  both behave as Bragg gratings
• ????1R regeneration performs the same function as
  all-optical amplification
• ????Lasers work on the principle of spontaneous
  emission of radiation
• ????Spectral width of lasers is the same as its
  line width

3

• Tick True or False (1 pt each). Add a 1 line
  explanation JUSTIFYING your choice (1 pt each)
• T F
• ????NHRP is intended for making ATM run over
  Ethernet
• ????Diff-serv is a connectionless and stateless
  QoS architecture
• ????Delta modulation is an example of a vocoder
• ????SIP uses a gatekeeper to make phone calls to
  email addresses

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• II. (12 pts) Explain the economic and technical
  rationales for the following technology
  transitions
• a) T-carrier hierarchy to Survivable SONET/SDH 4
  pts
• b) SONET to (D)WDM 4 pts
• c) WDM to Optical Transport Networks (OTNs) 4
  pts

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• III. (12 pts)
• A. (6 pts) Define the meaning of the following
  terms
• a) Modal dispersion,
• b) Chromatic Dispersion
• c) Four Wave Mixing
• B. (6 pts) Describe the ways and exactly how (eg
  optical components, fiber innovations) the above
  technical problems were solved in optical
  communication

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• IV. (12 pts) What are the fundamental technical
  (not functional!) differences between
• a) Optical amplifiers (eg EDFA)
• b) Lasers
• c) LEDs
• d) Fabry-Perot etalons used for filtering
• e) P-I-N Photodetectors

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• V. (12 pts) What are the key differences between
  the following survivability techniques Linear
  APS, UPSR, 2-fiber BLSR and 4-fiber BLSR 6 pts.
  Where are these techniques typically deployed in
  todays broadband networks 2 pts? Why are these
  techniques deployed in these places 2 pts?
  Describe how mesh-based survivability differs
  from these methods in terms of techniques and
  objectives? 2 pts?

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• VI. (12 pts) Describe the differences between the
  following forms of QoS scheduling priority,
  round-robin, GPS, bit-by-bit round-robin, and
  weighted fair queuing scheduling

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• VII. (12 pts) Describe the key differences
  between QoS routing (eg PNNI), traffic
  engineering (eg MPLS, BANANAS) and regular IP
  routing (eg OSPF, BGP)

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• VII. (12 pts) SONET OC-48 line cards cost 25K
  ea, whereas IP/SONET OC-48 line-cards cost 100K
  ea. The primary reason is the complexity of IP
  lookup and scheduling/buffer management
  implemented in ASIC/FPGA/network processors.
• Describe WHY IP lookup and scheduling/buffer
  management are so complex 8 pts.
• Also describe the key tradeoffs in the choice of
  ASICs vs network processors 4 pts.