Datagram Fragmentation, ICMP & IPv6 IP Datagram Encapsulation Network Maximum Transmission Unit...

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Transcript of Datagram Fragmentation, ICMP & IPv6 IP Datagram Encapsulation Network Maximum Transmission Unit...

  • Slide 1
  • Datagram Fragmentation, ICMP & IPv6 IP Datagram Encapsulation Network Maximum Transmission Unit (MTU) IP Datagram Fragmentation ICMP (Internet Control Message Protocol) - Error Report Mechanism - Information Query Mechanism - ICMP Message format and Transmission - ping and traceroute Utilities IPv6 - IPv6 Features - IPv6 Header and Format - IPv6 Address IP Datagram Encapsulation Network Maximum Transmission Unit (MTU) IP Datagram Fragmentation ICMP (Internet Control Message Protocol) - Error Report Mechanism - Information Query Mechanism - ICMP Message format and Transmission - ping and traceroute Utilities IPv6 - IPv6 Features - IPv6 Header and Format - IPv6 Address Lecture 10
  • Slide 2
  • Internet Transmission Paradigm Source host - Forms datagram with destination address - Sends to nearest router Intermediate routers - Forward datagram to next router Final router - Delivers to destination host Note: Datagram must be passed to network interface & sent across physical network. Network hardware does not recognize IP datagram format and IP address !! How is datagram transmitted across physical network ?? Address Resolution (ARP) and Encapsulation !! network router Source host Destination host IP D Routing Table --------- ## *** Routing Table --------- ## *** Routing Table --------- ## *** Routing Table --------- ## *** Routing Table --------- ## ***
  • Slide 3
  • IP Datagram Encapsulation Lecture 10 Frame Header Frame Data IP Header IP Data Area Entire datagram treated like data encapsulated in a frame for transmission Frame type (0800 for Ethernet) identifies contents as IP datagram Frame destination address gives next hop Next hop Frame/Hardware Address is obtained by address resolution protocol (ARP) IP address will not be changed while frame address is different in different network IP Datagram/Packet Hardware Network Frame/Packet Ethernet Frame Encapsulated into a frame/packet in lower layer
  • Slide 4
  • Lecture 10 Encapsulation Across Multiple Hops Each router extracts datagram, discard frame, determines next hop via ARP, encapsulates datagram in outgoing frame Frame headers may differ depended upon network types Datagram survives in entire trip, but frame only survives one hop Animation
  • Slide 5
  • Lecture 10 Maximum Transmission Unit (MTU) Every hardware technology specification includes the definition of the maximum size of the frame data area - called maximum transmission unit (MTU) IP datagrams can be larger than most hardware MTUs - IP: (2 16 1) bytes = 64K bytes - Ethernet: 1500 bytes - Token ring: 4464 bytes - FDDI: 4352 bytes - X.25: 576 bytes - PPP: 296 bytes (Point-to-Point Protocol) Any datagram encapsulated in a hardware frame must be smaller than the MTU for that hardware An internet may have networks with different MTUs Ethernet Frame
  • Slide 6
  • Lecture 10 Datagram Fragmentation Fragmentation: a technique to limit datagram size to smallest MTU of any network IP uses fragmentation split datagrams into pieces to fit in network with small MTU Router detects datagram larger than network MTU - Splits into pieces called fragments - Each piece smaller than output network MTU Each fragment has datagram header and is sent separately Ultimate destination reassembles fragments Fragmentation No-fragmentation Assemble fragments No-assemble > MTU Each