Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 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.}

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 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

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 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 addresses

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 4 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]

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 5 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:

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 6 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

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 7 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 today’s 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]?

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 8 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

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 9 VII. (12 pts) Describe the key differences between QoS routing (eg: PNNI), traffic engineering (eg: MPLS, BANANAS) and regular IP routing (eg: OSPF, BGP)

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 10 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].