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Lecture, November 20, 2002. Message Delivery to Processes Internet Addressing Address resolution protocol (ARP) Dynamic host reconfiguration protocol (DHCP) Tunneling Mobile IP Routing in Virtual Circuit Networks. Message delivery to processes. Addressing. Address spaces Flat
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Lecture, November 20, 2002 • Message Delivery to Processes • Internet Addressing • Address resolution protocol (ARP) • Dynamic host reconfiguration protocol (DHCP) • Tunneling • Mobile IP • Routing in Virtual Circuit Networks
Addressing • Address spaces • Flat • Hierarchical • Addressing Modes • Unicast • Multicast • Broadcast • Anycast
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
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.
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.
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
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 • All routers know to use an 18 bit prefix for the lookup phase of forwarding we are in business.