Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 1 ECSE-6660: Broadband Networks Exam 2 Time: 75 min (strictly enforced) Points: 50 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: (8 points) Tick True or False (1 pt each). Add a 1 line explanation JUSTIFYING your choice (1 pt each) T F  PNNI is a distance-vector routing protocol used by each ATM cell  MPLS protocol is the result of the IP-over-ATM overlay mapping  IP forwarding in high-speed routers is done using hash-based address lookup  A signaled protocol (like ATM or MPLS) uses a global consistency condition to ensure routing convergence

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 3 II. Below, you are given a true or false statement and asked a follow up question. 1. [4 pts] False statement: Virtual Tributary in SONET is the same as Concatenated mode Explain how multiplexing is done in SONET, featuring the differences between the concepts of “virtual tributaries” and concatenated mode

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 4 2. (14 pts) True statement: IP-over-ATM internetworking ran into complexities both in the control-plane and data-plane mappings. (6 pts) Discuss what were the primary IP-over-ATM and Ethernet-over-ATM internetworking approaches? What were the fundamental differences between them? (2 pts) What were the unresolved data-plane mapping issues? Explain briefly. (3 pts) What were the unresolved control-plane mapping issues? Explain briefly. (3 pts) How did IP switching and MPLS provide a solution and/or side-step these internetworking issues ?

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 5

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 6 II. [12 pts] Traffic Engineering: Explain (4 pts) What are the differences between the goals of regular routing and traffic engineering? (4 pts) WHY does traffic engineering benefit from a signaled approach (eg: ATM or MPLS)? Why do current connectionless routing protocols fall short of providing sophisticated traffic engineering features. (4 pts) How does the BANANAS overcome some of these difficulties in a connectionless routing context? What are the features of MPLS it DOES NOT provide?

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 7

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 8 III. [12 pts] High-Speed Routing: a) The key parts of high-speed routers are the lookup algorithm, switching fabric and buffering/scheduling (QoS support). Explain what are the central issues in each case, and how modern routers are able to meet the design requirements. (9 pts) b) How does design of telephone switch fabrics differ from that of packet switches ? (3 pts)

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