Transcript [2 pts]? - ECSE - Rensselaer Polytechnic Institute

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
1
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
2
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
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
3
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
4
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
5
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
6
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
7
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
8
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
9
VII. (12 pts) SONET OC-48 line cards cost $25K ea, whereas IP/SONET OC-48 linecards 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].
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
10