Introduction to Windows Networking - MCTS Guide to Microsoft Windows Server 2008 Active Directory Configuration - page 344

Windows Server 2008 and Vista use dual-IP layer architecture , which means the IP protocol
is the only component of the TCP/IP suite that's different in IPv6. IPv4 and IPv6 share the
common components of the suite (see Figure 8-14). This architecture results in improved relia-
bility and performance in TCP/IP.

Dual-stack architecture

Client for Microsoft Networks, File and Printer Sharing, HTTP, DNS, DHCP, and so on

TCP and UDP TCP and UDP

IPv4 IPv6

LAN or WAN drivers (such as Ethernet) LAN or WAN drivers (such as Ethernet)

Dual-IP layer architecture

Client for Microsoft Networks, File and
Printer Sharing, HTTP, DNS, DHCP, and so on

TCP and UDP

IPv4 IPv6

LAN or WAN architecture
(such as Ethernet)

Figure 8-14 Dual-stack versus dual-IP layer architecture

IPv6 Overview
The Internet Engineering Task Force (IETF) developed IPng (IP next generation) in 1994, which
was later named IPv6. IPv6 was developed to address IPv4's shortcomings. Some improvements
and changes in IPv6 include the following:
• Larger address space —Recall that IPv4 addresses are 32 bits, which provide a theoretical
four billion addresses. IPv6 addresses are 128 bits, so the number of possible addresses can
be expressed as 34 followed by 37 zeros, or 340 trillion trillion trillion. It's probably safe
to say that running out of IPv6 addresses is unlikely.
• Hierarchical address space —Unlike IPv4, in which numbers in the IP address have little
meaning other than the address class and the network and host IDs, IPv6 addresses have a
more defined structure. For example, the first part of an address can indicate the ISP.
• Autoconfiguration —IPv6 can be self-configuring or autoconfigured from a router running
IPv6 or through DHCPv6.
• Built-in Quality of Service (QoS) support —IPv6 includes built-in fields in packet headers
to support QoS strategies without requiring the installation of additional protocol compo-
nents, as IPv4 does.
• Built-in security —In designing IPv6, security was considered from the beginning, whereas
to achieve secure communication in IPv4, add-on protocols are required.