CS 6250 STUDY GUIDE WITH ACCURATE QUESTIONS AND COMPLETE SOLUTIONS GUARANTEED PASS 100%

1. Basic Components of a Router ANSWER Input ports: Receive packets, perform lookup; 2. Switching fabric: Moves packets from input to output ports; 3. Output ports: Store and transmit packets; 4. Control plane: Runs routing protocols and management. 2. Router's Control Plane ANSWER The part of the router that runs routing protocols and management. 3. Routing Protocols ANSWER Runs routing protocols, maintains routing tables, handles network management, and programs the data plane forwarding tables. 4. Memory-based Switching ANSWER Single packet at a time. 5. Bus-based Switching ANSWER Single packet at a time (shared bus). 6. Crossbar/Interconnection Network Switching ANSWER Multiple packets in parallel. 7. Head-of-line Blocking ANSWER Packets at front of queue block others. 8. Packet Classification ANSWER: determining which flow/class a packet belongs to. 9. CIDR ANSWER Classless Inter-Domain Routing. Introduced to address IP address exhaustion and routing table growth by allowing variable-length subnet masks and route aggregation. 10. Unibit Tries ANSWER Require too many memory accesses (up to 32 for IPv4). 11. Multibit Tries ANSWER Reduce the number of lookups by examining multiple bits at once. 12. Prefix Expansion ANSWER The process of expanding shorter prefixes to longer ones in multibit tries to ensure all possible bit combinations have valid entries. 13. Variable-stride Multibit Tries ANSWER More memory efficient, adapts to actual prefix distribution. 14. Fixed-stride Multibit Tries ANSWER Simpler implementation, predictable performance. 15. Quality of Service (QoS) ANSWER To differentiate traffic for QoS, security policies, billing, and traffic engineering, routers need to treat different types of packets differently based on multiple header fields. 16. Exact Match Classification ANSWER All header fields must match exactly. 17. Longest Prefix Match ANSWER Match on destination IP with longest prefix. 18. Best Effort Match ANSWER Find best match across multiple fields with wildcards. 19. Head-of-line Problem ANSWER When the packet at the front of an input queue is blocked (can't be forwarded), it prevents other packets behind it from being forwarded, even if their output ports are available. 20. Knockout Scheme ANSWER Uses multiple smaller queues at each input port and randomly drops packets when conflicts occur, rather than blocking entire queues. 21. FIFO with Tail Drop ANSWER A simple queue management where packets are served in first-in-first-out order, and when the queue is full, newly arriving packets are dropped. 22. Bit-by-bit Round Robin Scheduling ANSWER Idealized fair queuing where each active flow gets exactly equal bandwidth by serving one bit at a time from each queue in round-robin fashion. 23. Deficit Round Robin (DRR) ANSWER A practical fair queuing algorithm where each queue gets a quantum of bytes to send per round. Unused quota carries over as a 'deficit' to the next round. 24. Token Bucket Shaping ANSWER A traffic shaping mechanism using tokens generated at a constant rate. Packets can only be sent when tokens are available, smoothing bursty traffic. 25. Policing in Traffic Scheduling ANSWER Drops or marks packets that exceed rate limits. 26. Shaping in Traffic Scheduling ANSWER Buffers excess packets and sends them later to conform to rate limits. 27. End-to-end (e2e) principle ANSWER Network functions should be implemented at the endpoints (hosts) rather than in the network core, unless there's a compelling performance reason to do otherwise. 28. Example of a violation of the e2e principle ANSWER NAT (Network Address Translation), firewalls, or caching - these involve the network examining and modifying application data. 29. Evo arch model ANSWER An evolutionary model of Internet architecture. 30. Round in Evo arch model ANSWER A time period during which the network evolves - new nodes/technologies are introduced, compete, and some survive while others die out.