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Midterm Review

Midterm Review. These slides contain 90% recycled content. Problem 1: Network Address Translation. Could the packet leaving A have the wrong source address? Wrong destination address?. Src : 192.168.4.56:2410. Dst : 4.3.2.1:80. ?. Src : 128.32.131.210:80. Dst : 74.125.224.50:2500.

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Midterm Review

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  1. Midterm Review These slides contain 90% recycled content.

  2. Problem 1: Network Address Translation • Could the packet leaving A have the wrong source address? • Wrong destination address? Src: 192.168.4.56:2410 Dst: 4.3.2.1:80 ? Src: 128.32.131.210:80 Dst: 74.125.224.50:2500

  3. Problem 1: Network Address Translation 192.168.4.56:2410 74.125.224.50 4.3.2.1 Packet leaving B NAT 1 NAT 2 Packet leaving A Packet leaving NAT 2? Packet leaving NAT 1? 128.32.131.210:80 Packet leaving A Packet leaving B Src: 192.168.4.56:2410 Src: 128.32.131.210:80 Dst: 4.3.2.1:80 Dst: 74.125.224.50:2500

  4. Problem 3: Learning Switch B C→A C→B C E P1 E→A B→E E→B E A P2 A→B D P3 D→A D→A P4 5

  5. Problem 4ii: Routing [option 1] 3 3 A A F F 3 3 1 1 7 7 E E 1 1 D D 4 4 5 5 3 3 B B 1 1 C C

  6. Problem 4ii: Routing [option 2] 3 3 A A F F 3 3 1 1 7 7 E E 1 1 D D 4 4 5 5 3 3 B B 1 1 C C

  7. Problem 5: Packet Transmission THIS QUESTION IS GOING TO BE – WAIT FOR IT – • FTP: 1 bit per 10 seconds • Apartment is 300 meters away • RTP: 256GB flash drive, 5 minutes each way END-TO-END DELAYS

  8. Topics • Following slides list some points for discussion, taken from lecture slides. • Not deliberately mid-term related • Haven’t written new questions • Want your questions!

  9. 10. IP Addressing and Forwarding • Fragmentation • IPv4 and IPv6 Header Comparison • Security analysis: sender • Addressing: Layer 2 vs. 3 • Scalability (State, Churn): aggregation • Hierarchical addressing (network:host) [S6 P1] • Classful • CIDR [S6 P1]

  10. IP Header: Security analysis 4-bit Header Length 8-bit Type of Service (TOS) 4-bit Version 16-bit Total Length (Bytes) Evasion Ambiguity Datagram limit State-holding 3-bit Flags 16-bit Identification 13-bit Fragment Offset 8-bit Time to Live (TTL) 8-bit Protocol 16-bit Header Checksum 32-bit Source IP Address 32-bit Destination IP Address Options (if any) Payload Slide 49, Lecture 9; Slides 19-31, Lecture 10

  11. 11. Forwarding • Dealing with address scarcity • Dynamic Host Configuration Protocol [S6 P2] • Network Address Translation[S6 P2, S7 P1] • Address aggregation[S6 P1] • Longest prefix match[S6 P1]

  12. 12. Transport and TCP • Role of transport layer • Sliding window • TCP Header • Three-Way Handshake • Normal Termination, One Side At A Time • Abrupt Termination • Retransmission Timeout (RTO)

  13. Role of transport layer • De-multiplexing • Corruption • Translating between byte-streams and packets • Reliability • Not overloading receiver • Not overloading network • “Connection” set-up & tear-down Slide 20, Lecture 12

  14. TCP Header Source port Destination port Sequence number Flags: SYN ACK FIN RST PSH URG Acknowledgment Advertised window HdrLen Flags 0 Checksum Urgent pointer Options (variable) Data Slide 72, Lecture 12

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