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Lecture 11

Lecture 11. Routing in Virtual Circuit Networks Internet Addressing. Projects and midterm. Progress report Monday February 25, 8 AM from all individuals or groups. Midterm: Tuesday, February 26, 7-7:30 PM. Material – Chapters 1,2, and 4 up to the last lecture. Open book.

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Lecture 11

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  1. Lecture 11 • Routing in Virtual Circuit Networks • Internet Addressing

  2. Projects and midterm • Progress report Monday February 25, 8 AM from all individuals or groups. • Midterm: Tuesday, February 26, 7-7:30 PM. • Material – Chapters 1,2, and 4 up to the last lecture. • Open book. • 3 questions: 30 minutes

  3. Scalability issues with VCs • Assume a router with • n input and n output lines of b Gbps • average packet size l bytes • determine the size of the routing table

  4. Message delivery to processes

  5. Addressing • Address spaces • Flat • Hierarchical • Addressing Modes • Unicast • Multicast • Broadcast • Anycast

  6. Internet addressing • IPv4 address encoding – classes • Problems and solutions • Subnetting • Classless address encoding • Address resolution protocol (ARP) • Dynamic host reconfiguration protocol (DHCP) • Tunneling • Mobile IP

  7. IPv4 packet format

  8. IPv4 address encoding

  9. Problems with IPv4 address encoding • The size of the IP address space is: 232 • Class C addresses not very useful… • Class B addresses wasteful… • We would like to group network addresses to reduce the size of forwarding tables.

  10. Subnetting • Define a subnet mask and a subnet number. • Obtain the subnet number: (IP address) AND (subnet mask) • The whole idea is to allocate a single network number to a collection of networks. • All hosts in a subnet have the same subnet number. • Routing: given a destination IP address the router ANDs this address with the masks of all entries to determine the subnet number of the destination. Example.

  11. Subnetting

  12. Classless interdomain routing - CIDR • A block of class C addresses are aggregated to have a common prefix. • Example: 195.2.32.xx  11000101 00000010 00100000 xxxxxxxx 195.2.63.yy  11000101 00000010 00111111 yyyyyyyy Have a common 18 bit prefix 11000101 00000010 001

  13. Classless interdomain routing - CIDR • In this bloc we have 214 addresses (32-18=14). • If • all potential 16,384 hosts in this block are connected to LANs connected to the same router and • Allrouters know to use an 18 bit prefix for the lookup phase of forwarding we are in business.

  14. Address Resolution Protocol

  15. Tunneling

  16. Dynamic host reconfiguration protocol - DHCP

  17. Mobile IP

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