Lect-08 - Internetworking and the Internet Protocol ECE/CS 438 Fall 2011 Slides from Peterson Davies CS/ECE 438 1 Internetworking n What is

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CS/ECE 438 1 Internetworking and the Internet Protocol ECE/CS 438 Fall 2011 Slides from Peterson & Davies
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Internetworking n What is internetwork ¡ An arbitrary collection of networks interconnected to provide some sort of host-host to packet delivery service A simple internetwork where H represents hosts and R represents routers
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Internetworking n What is IP ¡ IP stands for Internet Protocol ¡ Key tool used today to build scalable, heterogeneous internetworks ¡ It runs on all the nodes in a collection of networks and defines the infrastructure that allows these nodes and networks to function as a single logical internetwork A simple internetwork showing the protocol layers
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IP Service Model n Packet Delivery Model ¡ Connectionless model for data delivery ¡ Best-effort delivery (unreliable service) n packets are lost n packets are delivered out of order n duplicate copies of a packet are delivered n packets can be delayed for a long time n Global Addressing Scheme ¡ Provides a way to identify all hosts in the network
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Packet Format ¡ Version (4): currently 4 ¡ Hlen (4): number of 32-bit words in header ¡ TOS (8): type of service (not widely used) ¡ Length (16): number of bytes in this datagram ¡ Ident (16): used by fragmentation ¡ Flags/Offset (16): used by fragmentation ¡ TTL (8): number of hops this datagram has traveled ¡ Protocol (8): demux key (TCP=6, UDP=17) ¡ Checksum (16): of the header only ¡ DestAddr & SrcAddr (32)
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IP Fragmentation and Reassembly n Each network has some MTU (Maximum Transmission Unit) ¡ Ethernet (1500 bytes), FDDI (4500 bytes) n Strategy ¡ Fragmentation occurs in a router when it receives a datagram that it wants to forward over a network which has (MTU < datagram) ¡ Reassembly is done at the receiving host ¡ All the fragments carry the same identifier in the Ident field ¡ Fragments are self-contained datagrams ¡ IP does not recover from missing fragments
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IP Fragmentation and Reassembly IP datagrams traversing the sequence of physical networks
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IP Fragmentation and Reassembly Header fields used in IP fragmentation. (a) Unfragmented packet; (b) fragmented packets.
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Global Addresses n Properties ¡ globally unique ¡ hierarchical: network + host ¡ 4 Billion IP address, half are A type, ¼ is B type, and 1/8 is C type n Format n Dot notation ¡ 10.3.2.4 ¡ 128.96.33.81 ¡ 192.12.69.77
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n Strategy ¡ every datagram contains destination's address ¡ if directly connected to destination network, then forward to host ¡ if not directly connected to destination network, then forward to some router ¡ forwarding table maps network number into next hop
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This note was uploaded on 02/08/2012 for the course ECE 438 taught by Professor Luo during the Fall '08 term at University of Illinois, Urbana Champaign.

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Lect-08 - Internetworking and the Internet Protocol ECE/CS 438 Fall 2011 Slides from Peterson Davies CS/ECE 438 1 Internetworking n What is

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