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Published byBeverly Crawford Modified over 8 years ago
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1 Lecture 11 Routing in Virtual Circuit Networks Internet Addressing
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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
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4 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
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5 Message delivery to processes
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6 Addressing Address spaces Flat Hierarchical Addressing Modes Unicast Multicast Broadcast Anycast
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7 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
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8 IPv4 packet format
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9 IPv4 address encoding
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10 Problems with IPv4 address encoding The size of the IP address space is: 2 32 Class C addresses not very useful… Class B addresses wasteful… We would like to group network addresses to reduce the size of forwarding tables.
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11 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.
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12 Subnetting
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14 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
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15 Classless interdomain routing - CIDR In this bloc we have 2 14 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.
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16 Address Resolution Protocol
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17 Tunneling
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18 Dynamic host reconfiguration protocol - DHCP
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19 Mobile IP
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