Meta InternetProtocolZ. Things MIPZ has to do: - ICMP-like functions () -- Packet could not be delivered - ARP-like functions (; IARP/RARP is ) -- Where do i send this packet? - DHCP-like functions (, ; BootP is , ) -- Who am i? What is my address? Where is the gateway/DNS server/etc? - negotiating IPZ header compression - no padding, MTF coding of addresses -> 1 byte each - IPSec-like functions ( etc) -- exchange of private keys -- indicating that a payload is encrypted - arranging an encapsulation tunnel -- specifying whether the tunnel is for local delivery or onward routing Hosts should never generate packet-loss messages in response to loss of MIPZ packets (or, under the new regime, packets with protocol 0). ICMP often includes the start of the offending packet, so that the recipient can work out which packet was lost. ICMP messages (numbered entries are coded subtypes, generally with codes off by one): - Destination Unreachable -# net unreachable -# host unreachable -# protocol unreachable -# port unreachable -# fragmentation needed and DF set -# source route failed CategoryNetwork