Chapter 20. Network Layer: IP Internetworking IPv4 IPv6 Transition from v4 to v6 Spring 2010 Communication Networks, KWU

Communication Networks, KWU IP Network layer protocol for the Internet Unreliable datagram protocol: Best-effort service Packets in the IP layer is also called datagrams No error control or flow control Only an error detection mechanism Delivery of a packet with no guarantees Connectionless protocol Each datagram (packet) is handled independently Each packet can follow different route to the destination Spring 2010 Communication Networks, KWU

Communication Networks, KWU IP Datagram Spring 2010 Communication Networks, KWU

Communication Networks, KWU IP: Multiplexing Spring 2010 Communication Networks, KWU

Communication Networks, KWU IP: Fragmentation MTU (Maximum Transfer Unit) Identification Flags (3 bits) DF: the 2nd bit, Do not Fragment bit MF: the 3rd bit, More Fragment bit Fragmentation offset: the value of the offset if measured in units of 8 bytes Spring 2010 Communication Networks, KWU

IP Fragmentation: Example Original packet length = packet header (20 bytes) + payload (4000 bytes) MTU of the link = 1420 bytes Spring 2010 Communication Networks, KWU

Communication Networks, KWU Spring 2010 Communication Networks, KWU

Communication Networks, KWU IP: Header Checksum Spring 2010 Communication Networks, KWU

Communication Networks, KWU IPv6 Larger address space – hexadecimal colon notation Better header format New options Allowance for extension Support for resource allocation Support for more security Spring 2010 Communication Networks, KWU

IPv6: Abbreviated Address Spring 2010 Communication Networks, KWU

IPv6: Transition from IPv4 Huge number of systems on the Internet The transition from IPv4 to IPv6 cannot happen suddenly Three strategies devised by the IETF Spring 2010 Communication Networks, KWU

Transition Strategies: Dual Stack It is recommended that all hosts have a dual stack before migrating completely to version 6 The source host queries the DNS to determine which version to use Spring 2010 Communication Networks, KWU

Transition Strategies: Tunneling Spring 2010 Communication Networks, KWU

Transition Strategies: Header Translation When the majority of the Internet has moved to IPv6 IPv6 sender and IPv4 receiver Spring 2010 Communication Networks, KWU