Despre IPv6 pe scurt…
Increased Address Space
In retrospect, the 32-bit structure that IPv4 uses was not sufficient for an addressing structure. IPv6 offers 128 bits. This gives enough addresses for every device that requires one to have a unique public IPv6 address. In addition, the 64-bit host portion (interface ID) of an IPv6 address can be automatically generated from the network adapter hardware.
Automatic Address Configuration
Typically, IPv4 is configured either manually or by using DHCP. Automatic configuration (autoconfiguration) through APIPA is available for isolated subnets that are not routed to other networks. IPv6 deals with the need for simpler and more automatic address configuration by supporting both stateful and stateless address configuration. Stateful configuration uses DHCPv6. If stateless address configuration is used, hosts on a link automatically configure themselves with IPv6 addresses for the link and (optionally) with addresses that are derived from prefixes advertised by local routers. You can also configure a stateless DHCPv6 configuration that does not assign addresses to hosts but can assign settings to (for example) DNS servers, the domain names of which are not included in the router advertisements.
Private communication over the Internet requires encryption to protect data from being viewed or modified in transit. IPsec provides this facility, but its use is optional in IPv4. IPv6 makes IPsec mandatory. This provides a standards-based solution for network security needs and improves interoperability among different IPv6 implementations.
Real-Time Data Delivery
Quality of service (QoS) exists in IPv4, and bandwidth can be guaranteed for real-time traffic (such as video and audio transmissions) over a network. However, IPv4 real-time traffic support relies on the Type of Service (ToS) field and the identification of the payload, typically using a User Datagram Protocol (UDP) or Transmission Control Protocol (TCP) port. The IPv4 ToS field has limited functionality, and payload identification using a TCP port and a UDP port is not possible when an IPv4 packet payload is encrypted. Payload identification is included in the Flow Label field of the IPv6 header, so payload encryption does not affect QoS operation.
Removal of Broadcast Traffic
IPv4 relies on Address Resolution Protocol (ARP) broadcasts to resolve IP addresses to the MAC addresses of network interface cards (NICs). Broadcasts increase network traffic and are inefficient because every host processes them. The ND protocol for IPv6 uses a series of Internet Control Message Protocol for IPv6 (ICMPv6) messages that manage the interaction of nodes on the same link (neighboring nodes). ND replaces ARP broadcasts, ICMPv4 router discovery, and ICMPv4 Redirect messages with efficient multicast and unicast ND messages.
Solutii de compatibilitate
Teredo is an IPv6-within-IPv4 tunneling protocol. It is intended to tunnel the IPv6 packets within IPv4 to allow IPv6 systems to communicate with other IPv6 systems through a NAT server. In Windows Server 2008 R2 and Windows 7, the Teredo client is enabled but inactive by default and must be configured for proper functionality. A Teredo address consists of a 32-bit Teredo prefix. In Windows Server 2008 R2 (as well as Windows Vista and Windows 7), this is 2001::/32. The prefix is followed by the IPv4 (32-bit) public address of the Teredo server that assisted in the configuration of the address. The next 16 bits are reserved for Teredo flags. Currently, only the highest-ordered flag bit is defined. This is the cone flag and is set when the NAT device connected to the Internet is a cone NAT. A cone NAT stores the mapping between an internal address and port number and the public address and port number.
IPv6 can use an Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) address to communicate between two nodes over an IPv4 intranet. An ISATAP address starts with a 64-bit unicast link-local, site-local, global, or 6to4 global prefix. The next 32 bits are the ISATAP identifier 0:5efe. The final 32 bits hold the IPv4 address in either dotted decimal or hexadecimal notation. An ISATAP address can incorporate either a public or a private IPv4 address. For example, the ISATAP fe80::5efe:w.x.y.z address has a link-local prefix; the fec0::1111:0:5efe:w.x.y.z address has a site-local prefix; the 3ffe:1a05:510:1111:0:5efe:w.x.y.z address has a global prefix; and the 2002:9d36:1:2:0:5efe:w.x.y.z address has a 6to4 global prefix. In all cases, w.x.y.z represents an IPv4 address. By default, Windows Server 2008 automatically configures the ISATAP address fe80::5efe:w.x.y.z for each IPv4 address that is assigned to a node. This link-local ISATAP address enables two hosts to communicate over an IPv4 network by using each other’s ISATAP address. You can implement IPv6-to-IPv4 configuration by using the netsh interface ipv6 6to4, netsh interface ipv6 isatap, and netsh interface ipv6 add v6v4tunnel IPv6 commands. For example, to create an IPv6-in-IPv4 tunnel between the local address 10.0.0.11 and the remote address 192.168.123.116 on an interface named Remote, you would type netsh interface ipv6 add v6v4tunnel “Remote” 10.0.0.11 192.168.123.116. You can also configure the appropriate compatibility addresses manually by using the netsh interface ipv6 set address command or the Internet Protocol Version 6 (TCP/IPv6) GUI as described in the next section of this lesson.