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Slide 1: IPv6 Refs: Chapter 10, Appendix A Netprog: IPv6 1
Slide 2: IPv6 availability • Generally available with (new) versions of most operating systems. – BSD, Linux 2.2 Solaris 8 • An option with Windows 2000/NT • Most routers can support IPV6 Netprog: IPv6 2
Slide 3: IPv6 Design Issues • Overcome IPv4 scaling problem – lack of address space. • • • • • Flexible transition mechanism. New routing capabilities. Quality of service. Security. Ability to add features in the future. Netprog: IPv6 3
Slide 4: IPv6 Headers • Simpler header - faster processing by routers. – No optional fields - fixed size (40 bytes) – No fragmentation fields. – No checksum • Support for multiple headers – more flexible than simple “protocol” field. Netprog: IPv6 4
Slide 5: 4 for IPv4 1 byte VERS IPv4 Header 1 byte 1 byte 1 byte HL Service Fragment Length Datagram ID FLAG Fragment Offset TTL Protocol Header Checksum Source Address Destination Address Options (if any) Data Netprog: IPv6 5
Slide 6: 6 for IPv6 1 byte IPv6 Header 1 byte 1 byte Flow Label Next Header 1 byte Hop Limit VERS PRIO Payload Length Source Address (128 bits - 16 bytes) Dest. Address (128 bits - 16 bytes) Netprog: IPv6 6
Slide 7: IPv6 Header Fields • VERS: 6 (IP version number) • Priority: will be used in congestion control • Flow Label: experimental - sender can label a sequence of packets as being in the same flow. • Payload Length: number of bytes in everything following the 40 byte header, or 0 for a Jumbogram. Netprog: IPv6 7
Slide 8: IPv6 Header Fields • Next Header is similar to the IPv4 “protocol” field - indicates what type of header follows the IPv6 header. • Hop Limit is similar to the IPv4 TTL field (but now it really means hops, not time). Netprog: IPv6 8
Slide 9: Extension Headers • Routing Header - source routing • Fragmentation Header - supports fragmentation of IPv6 datagrams. • Authentication Header • Encapsulating Security Payload Header Netprog: IPv6 9
Slide 10: IPv6 Addresses • 128 bits - written as eight 16-bit hex numbers. 5f1b:df00:ce3e:e200:0020:0800:2078:e3e3 • High order bits determine the type of address. The book shows the breakdown of address types. Netprog: IPv6 10
Slide 11: IPv6 Aggregate Global Unicast Address 3 13 32 NLA ID 16 SLA ID 64 Interface ID 001 TLA ID TLA: top-level aggregation NLA: next-level SLA: site-level Interface ID is (typically) based on hardware MAC address Netprog: IPv6 11
Slide 12: IPv4-Mapped IPv6 Address • IPv4-Mapped addresses allow a host that support both IPv4 and IPv6 to communicate with a host that supports only IPv4. • The IPv6 address is based completely on the IPv4 address. Netprog: IPv6 12
Slide 13: IPv4-Mapped IPv6 Address • 80 bits of 0s followed by 16 bits of ones, followed by a 32 bit IPv4 Address: 0000 . . . 0000 80 bits FFFF 16 bits IPv4 Address 32 bits Netprog: IPv6 13
Slide 14: Works with DNS • An IPv6 application asks DNS for the address of a host, but the host only has an IPv4 address. • DNS creates the IPv4-Mapped IPv6 address automatically. • Kernel understands this is a special address and really uses IPv4 communication. Netprog: IPv6 14
Slide 15: IPv4-Compatible IPv6 Address • An IPv4 compatible address allows a host supporting IPv6 to talk IPv6 even if the local router(s) don’t talk IPv6. • IPv4 compatible addresses tell endpoint software to create a tunnel by encapsulating the IPv6 packet in an IPv4 packet. Netprog: IPv6 15
Slide 16: IPv4-Compatible IPv6 Address • 80 bits of 0s followed by 16 bits of 0s, followed by a 32 bit IPv4 Address: 0000 . . . 0000 80 bits 0000 16 bits IPv4 Address 32 bits Netprog: IPv6 16
Slide 17: Tunneling (done automatically by kernel when IPv4-Compatible IPv6 addresses used) IPv6 Host IPv4 Routers IPv4 Datagram IPv6 Datagram IPv6 Host Netprog: IPv6 17
Slide 18: IPv6 Sockets programming • New address family: AF_INET6 • New address data type: in6_addr • New address structure: sockaddr_in6 Netprog: IPv6 18
Slide 19: in6_addr struct in6_addr { uint8_t s6_addr[16]; }; Netprog: IPv6 19
Slide 20: sockaddr_in6 struct sockaddr_in6 { uint8_t sin6_len; sa_family_t sin6_family; in_port_t sin6_port; uint32_t sin6_flowinfo; struct in6_addr sin6_addr; }; Netprog: IPv6 20
Slide 21: Dual Server • In the future it will be important to create servers that handle both IPv4 and IPv6. • The work is handled by the O.S. (which contains protocol stacks for both v4 and v6): – automatic creation of IPv6 address from an IPv4 client (IPv4-mapped IPv6 address). Netprog: IPv6 21
Slide 22: IPv4 client TCP IPv4 Datalink IPv6 client TCP IPv6 Datalink IPv4-mapped IPv6 address IPv4 IPv6 server TCP IPv6 Datalink Netprog: IPv6 22
Slide 23: IPv6 Clients • If an IPv6 client specifies an IPv4 address for the server, the kernel detects and talks IPv4 to the server. • DNS support for IPv6 addresses can make everything work. – getaddrinfo() returns an IPv4 mapped IPv6 address for hosts that only support IPv4. Netprog: IPv6 23
Slide 24: IPv6 - IPv4 Programming • The kernel does the work, we can assume we are talking IPv6 to everyone! • In case we really want to know, there are some macros that determine the type of an IPv6 address. – We can find out if we are talking to an IPv4 client or server by checking whether the address is an IPv4 mapped address. Netprog: IPv6 24