ip.pdf - CS4344 – Computer Networks and Distributed Systems IP Dr Padmaraj Nair Host A Host B App X App Y App Y App X Port 1 2 3 2 Logical

ip.pdf - CS4344 – Computer Networks and Distributed...

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CS4344 – Computer Networks and Distributed Systems IP Dr. Padmaraj Nair
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Router J TCP IP Physical Physical IP NAP 1 NAP 2 Physical Physical Network Access Protocol #1 Host A App X App Y TCP IP Network Access Protocol #2 Host B App Y App X Network 1 Network 2 Global internet address 1 2 2 4 6 3 Subnetwork attachment point address Logical connection (e.g., virtual circuit) Logical connection (TCP connection) Port
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Connectionless Operation Internetworking involves connectionless operation at the level of the Internet Protocol (IP) IP Initially developed for the DARPA internet project Protocol is needed to access a particular network
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LAN 1 Frame relay WAN LAN 2 End system (A) End system (B) Router (X) Router (Y) IP LLC MAC TCP Physical Physical Physical Physical Physical TCP IP LLC MAC Physical LLC MAC IP IP LLC MAC LAPF LAPF t 1 t 2 t 3 t 6 t 5 t 4 t 11 t 12 t 13 t 16 t 15 t 14 t 7 t 8 t 10 t 9 t 1 , t 6 , t 7 , t 10 , t 11 , t 16 t 2 , t 5 t 3 , t 4 t 8 , t 9 t 12 , t 15 t 13 , t 14 TCP-H = TCP header IP-H = IP header LLCi-H = LLC header MACi-H = MAC header MACi-T = MAC trailer FR-H = Frame relay header FR-T = Frame relay trailer MAC1-H LLC1-H IP-H TCP-H Data LLC2-H IP-H TCP-H Data LLC1-H IP-H TCP-H Data IP-H TCP-H Data MAC1-T FR-H IP-H TCP-H Data FR-T MAC2-H LLC2-H IP-H TCP-H Data MAC2-T
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Connectionless Internetworking Connectionless internet facility is flexible IP provides a connectionless service between end systems Advantages: Is flexible Can be made robust Does not impose unnecessary overhead
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IP Design Issues Routing Datagram lifetime Fragmentation and reassembly Error control Flow control
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P2 P1 S1 S2 T1 T2 T3 (a) Packet-switching network architecture P3 R2 R1 S1 S2 N1 N2 N3 (b) Internetwork architecture Figure 14.3 The Internet as a Network R3 P P P P P P P P P
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Routing Routing table indicates next router to which datagram is sent Can be static or dynamic Routers maintain routing tables Source specifies route to be followed Can be useful for security and priority Source routing Each router appends its internet address to a list of addresses in the datagram Useful for testing and debugging purposes Route recording The routing table may be static or dynamic. A static table, however, could contain alternate routes if a particular router is unavailable. A dynamic table is more flexible in responding to both error and congestion conditions. For example, when a router goes down, all of its neighbors will send out a status report, allowing other routers and stations to update their routing tables. Congestion control is particularly important because of the mismatch in capacity between local and wide area networks.
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Datagram Lifetime If dynamic or alternate routing is used the potential exists for a datagram to loop indefinitely Consumes resources Transport protocol may need upper bound on lifetime of a datagram Can mark datagram with lifetime When lifetime expires, datagram is discarded
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Fragmentation and Re-assembly
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