Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 1 ECSE-6600: Internet Protocols Exam 3 Time: 90 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. Below, you are given a true or false statement and asked a follow up question. Topic: ARP and Multicast 1. [5 pts] True statement: the address resolution problem (equivalent of ARP) in multicast is very easy Explain why multicast uses a very simple address resolution technique. Discuss why a technique like ARP would severely conflict with the multicast model.

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 3 Topic: QoS vs Congestion Control 2. (5 pts) True statement: The fundamental problems in QoS include the fact that FIFO does not provide isolation; and differentiation in terms of delay or bandwidth leads to zero-sum games with fixed resources. Explain how the problem of QoS differs from the problem of congestion control (both of them manage resources!).

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 4 Topic: OAM functions 3. (5 pts) True statement: DHCP solves a variety of IP configuration problems elegantly. Explain why RARP and ICMP together were insufficient for solving the IP configuration problems? What are the new features that DHCP adds compared to RARP & ICMP?

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 5 Topic: IPv6 vs ARP, DHCP 4. (5 pts) True statement: IPv6 provides powerful auto-configuration features Explain what new features IPv6 adds over-and-above DHCP. Explain why the neighbor discovery procedure (unlike ARP) also has a destination cache, prefix cache and router cache?

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 6 II. [5 pts] QoS architecture (1 pts) State briefly why the decision to de-couple end-to-end QoS techniques from network-based QoS techniques was an important architectural decision? (4 pts) Discuss the tradeoffs between stateful, reduced state and stateless architectures (eg: Intserv, Diffserv, DPS, Edge-based Closed-loop architectures).

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 7 III. [5 pts] Routing (Unicast vs Multicast) (3 pts) Explain the key differences between unicast and multicast routing paradigms. (2 pts) Explain briefly how the source-specific multicast (SSM) model helps resolve some of the problems with the original IP multicast model.

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 8 IV. [20 pts] Big Picture Revisited: Scalability and Heterogeneity a) (7 pts) The first goal of internetworking was “scalability.” Explain how IP forwarding, intra- and inter-domain routing split, congestion control schemes, IPv6’ larger address space, auto- configuration features, fast links and fast router designs contribute to the overall scalability of the Internet system. b) (7 pts) The second goal was “heterogeneity”: in terms of the disparate networks and applications supported. Explain how the overlay paradigm, simple packet format, best-effort service design, fragmentation/reassembly, QoS architectures, multicast techniques contribute to the support of heterogeneity in the Internet system. c) (3 pts) What does scalability mean for a network-box-designer (eg: Cisco)? What does scalability mean for a network operator/service provider? d) (3 pts) Explain why some aspects like address space shortage, NAT, QoS architectures, multicast routing, open group model of multicast, large BGP tables/update complexity/routing stability still pose problems in terms of scalability and heterogeneity?

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 9

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 10

Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 11