Socket Programming with IPv6

Why IPv6? Addressing and routing scalability Address space exhaustion Host autoconfiguration QoS of flow using flowlabel Mobile IP Multicast routing IP Security End to end semantics

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.

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.

5 IPv4 Header VERSHL Fragment Offset Fragment LengthService Datagram IDFLAG TTLProtocolHeader Checksum Source Address Destination Address Options (if any) Data 1 byte

6 IPv6 Header VERSPRIO Hop Limit Flow Label Payload LengthNext Header 1 byte Source Address (128 bits - 16 bytes) Dest. Address (128 bits - 16 bytes)

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: IPv68 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.

9 Extension Headers Routing Header - source routing Fragmentation Header - supports fragmentation of IPv6 datagrams. Authentication Header Encapsulating Security Payload Header

Netprog: IPv610 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.

11 IPv6 Addressing The following address classes are defined  Unspecified: ::  Loopback::1  Multicast:FF0x:  Link-local:FE80:  Site-local:FE40:  Rest are Unicast and anycast addresses Unicast address composed of prefix and MAC address

12 IPv6 Addressing

13 IPv6 Aggregate Global Unicast Address 001TLA IDNLA IDSLA IDInterface ID TLA: top-level aggregation NLA: next-level SLA: site-level Interface ID is (typically) based on hardware MAC address

Netprog: IPv614 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: IPv615 IPv4-Mapped IPv6 Address 80 bits of 0s followed by 16 bits of ones, followed by a 32 bit IPv4 Address: IPv4 AddressFFFF 80 bits32 bits16 bits

Netprog: IPv616 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: IPv617 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. No longer in use. Deprecated.

Netprog: IPv618 IPv4-Compatible IPv6 Address IPv4 Address bits32 bits16 bits 80 bits of 0s followed by 16 bits of 0s, followed by a 32 bit IPv4 Address:

19 Tunneling (done automatically by kernel when IPv4-Compatible IPv6 addresses used) IPv6 Host IPv6 Host IPv4 Routers IPv6 Datagram IPv4 Datagram

20 IPv6 Sockets programming New address family: AF_INET6 New address data type: in6_addr New address structure: sockaddr_in6 DNS lookup: getaddrinfo()

Netprog: IPv621 in6_addr struct in6_addr { uint8_t s6_addr[16]; };

Netprog: IPv622 sockaddr_in6 struct sockaddr_in6 { uint8_tsin6_len; sa_family_tsin6_family; in_port_tsin6_port; uint32_tsin6_flowinfo; struct in6_addrsin6_addr; };

Netprog: IPv623 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: IPv624 IPv4 client IPv4 client TCP IPv4 Datalink IPv6 client IPv6 client TCP IPv6 Datalink IPv6 server IPv6 server TCP Datalink IPv4 IPv6 IPv4-mapped IPv6 address

25 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.

26 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.

Ipv4, Ipv6 Compatibility Introduction IPv4 Client, IPv6 Server IPv6 Client, IPv4 Server

Introduction Server and client combination  IPv4 IPv4(most server and client)  IPv4 IPv6  IPv6 IPv4  IPv6 IPv6 How IPv4 application and IPv6 application can communicate with each other. Host are running dual stacks, both an IPv4 protocol stack and IPv6 protocol stack

IPv4 Client, IPv6 Server IPv6 dual stack server can handle both IPv4 and IPv6 clients. This is done using IPv4-mapped IPv6 address server create an IPv6 listening socket that is bound to the IPv6 wildcard address

IPv6 client IPv6 server TCP IPv6 Data link Data link IPv4 TCP IPv4 client TCP IPv4IPv6 Data link Enet hdr IPv4 hdr TCP hdr TCP data Enet hdr IPv4 hdr TCP hdr TCP data Type080 0 Dport IPv4 mapped IPv6 address IPv6 listening socket, bound to 0::0, port 8888 IPv6 address 5flb:df00:ce 3e:e200:20: 800:2b37:64 26

IPv4 datagramIPv6 datagram AF_INET SOCK_STREAM sockaddr_in AF_INET SOCK_DGRAM sockaddr_in AF_INET6 SOCK_DGRAM sockaddr_in6 AF_INET6 SOCK_DGRAM sockaddr_in6 TCP IPv4 IPv6 UDP IPv4 sockets IPv6 sockets Address returned by accept or recvfrom IPv6 IPv4 IPv4 mapped

IPv6 client, IPv4 server IPv4 server start on an IPv4 only host and create an IPv4 listening socket IPv6 client start, call gethostbyname. IPv4 mapped IPv6 address is returned. Using IPv4 datagram

IPv4 datagramIPv6 datagram AF_INET SOCK_STREAM sockaddr_in AF_INET SOCK_DGRAM sockaddr_in AF_INET6 SOCK_DGRAM sockaddr_in6 AF_INET6 SOCK_DGRAM sockaddr_in6 TCP IPv4 IPv6 UDP IPv4 sockets IPv6 sockets Address for connect or sendto IPv6 IPv4 IPv4 mapped IPv6

Summary of interoperability between IPv4 and IPv6 clients and servers.