1. Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 1 ECSE-6600: Internet Protocols Exam 3 Time: 90 min (strictly enforced) [Hint: spend time roughly in proportion to the points allocated to questions] 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.}

2. Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 2 I. [Basics] Consider the enterprise inter-network which uses VLSMs. A) (2 pts) Consider two hosts H1 and H2 configured with addresses 128.31.30.45 and 128.15.198.6. Which network if any, can they be placed on (among A,B,C,D), and what would their subnet mask be ? A A B B C C D D Addr: 128.13.15.7 Mask: 255.255.255.0 Addr: 128.15.20.10 Mask: 255.255.0.0 Addr: 128.15.6.13 Mask: 255.255.0.0 R2 Addr: 128.31.208.5 Mask: 255.255.192.0 Addr: 128.31.208.15 Mask: 255.255.192.0 Addr: 128.31.225.18 Mask: 255.255.224.0

3. Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 3 B) (3 pts) Fill up the routing table at router R2. One example entry is filled up for you. DestinationMaskNext Hop 128.13.15.0255.255.255.0128.15.6.13 ? ? ? ??? ? ? ?

4. Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 4 II [Congestion Control Models] I. [5 pts] Explain briefly what performance benefit an AQM scheme (eg: RED or REM) and ECN marking adds to end-to-end TCP congestion control (eg: TCP SACK) ? II. [5 pts] How do the Accumulation-based and Explicit Rate congestion control models materially differ from the TCP congestion control model? Briefly describe their advantages and potential disadvantages.

5. Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 5

6. Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 6 III. [5 pts] [QoS] Why do we not get QoS capabilities in simple packet-switched networks with FIFO queues? What information do the arrival-curve and service-curve give a QoS designer?

7. Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 7 IV. (High Speed Routing) [3 pts] Describe why high-speed lookup and high-speed switching of packets (at 10-100 Gbps) are hard problems. [2 pts] Describe why “tries” form a part of the solution for high-speed forwarding lookup. [2 pts] Mention some key differences between using network processors vs ASICs as building blocks for high speed routers.

8. Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 8 V. (IPv6) [5 pts] Describe how ICMPv6, Neighbor Discovery and Stateless methods consolidate and simplify auto-configuration in IPv6. [2 pts] Mention some advantages of having multiple IPv6 "addresses" for each interface.

9. Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 9 VI. (OAM & Configuration protocols) [5 pts] Briefly describe and contrast BOOTP with RARP. Why is the latter protocol (RARP) far more complex, and yet provides less functionality than BOOTP?

10. Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 10 VII. (Multicast) [5 pts] Explain why the ARP-equivalent function in multicast is simpler than unicast, but the multicast routing protocols (both intra- and inter-domain routing) are far more complex than unicast.

11. Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 11 VIII.(Transport layer: unicast vs multicast) [6 pts] Transport layer reliability is offered through a combination of temporal (transmission/status-report/retransmission) and spatial redundancy (FEC). TCP chooses byte- stream reliability, cumulative acks and no FEC while reliable multicast protocols choose packet- level reliability, possibly FEC, NAKs or bitmaps, elaborate control of status report/retransmission traffic. Explain the rationale behind these choices.