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Changes to TCP/IP in Windows Vista

Unless you've been living under a rock, you no doubt know by now that Microsoft is currently working toward releasing the next version of the Windows operating system, Windows Vista. As you would probably expect, Windows Vista will be loaded with new features. One thing that caught me by surprise though was that Microsoft has made some major changes to the way that TCP/IP is implemented.

About ten years ago, I remember listening to an instructor in an MCSE class explaining that the world was about to run out of IP addresses. He went on to explain that soon there would be no choice but to adopt a different addressing scheme. The process, he explained, would be painful because having everyone switch to a different addressing scheme would be comparable to having everyone in the world simultaneously change phone numbers. Since that time, I have heard a few other people express similar concerns. At the time, making a switch to the IP Version 6 (IPv6) was touted as a solution to the problem. What actually ended up happening though was that the world adopted NAT as a method for conserving IP addresses.

Although almost nobody uses IPv6, it has never really gone away. Several Windows releases have supported IPv6, but Windows Vista will be the first Windows release to enable IPv6 by default.

Before you start panicking and assuming that you will have to relearn the inner workings of TCP/IP, I should explain that Microsoft has not abandoned the current version of TCP/IP, IPv4.

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Microsoft was in a tough spot when they had to decide how TCP/IP would be supported in Vista. On the one hand, IPv4 was invented in the 1970s, and although it has been extended numerous times, it is ridiculously outdated. On the other hand, pretty much everybody in the world uses IPv4, so Microsoft couldn't just stop supporting it. What they chose to do instead was to create a dual IP layer architecture. In English this means that Vista will support IPv4 and IPv6 simultaneously. In fact, both protocols share common transport and framing layers.

Since Microsoft is placing a greater emphasis on IPv6 by enabling it by default, you might be wondering what the advantages are of using IPv6. As I alluded to earlier, the primary advantage is a large address space. IPv6 provides a 128 bit address space, compared to IPv4's 32 bit address space. If the world were to adopt IPv6, there would no longer be a shortage of publicly accessible IP addresses.

Another benefit of IPv6 is that it is a whole lot faster than IPv4. The IPv6 packet header is more streamlined than the one used by IPv4, and IPv6 supports hierarchical routing which means that routers can forward IPv6 packets much more quickly than IPv4 packets.

Additionally, IPv6 is designed to address some of the security problems found in IPv4. One enhancement is that IPv6 has built in support for the IPsec protocol. Sure, Windows XP and Windows Server 2003 allow you to run IPsec over IPv6, but you are very limited in doing so. If you want to use IPv6 and IPsec together in Windows XP or in Windows Server 2003, you have to configure the various policies and keys through text files and then activate the configuration by running IPSEC6.EXE. In Vista, support for IPsec over IPv6 will be implemented in exactly the same way as it is for IPv4. Vista will even support Internet Key Exchange and data encryption for IPsec over IPv6, unlike the current Windows operating systems.

Initially, I don't expect Vista's IPv6 support to receive much fanfare. Over time though, I believe that IPv6 will become much more heavily used than it is today. If you would like to read more about the way that Microsoft is implementing IPv6 in Windows Vista, there is an interesting article about it on Microsoft's Web site.


Brien M. Posey, MCSE, is a Microsoft Most Valuable Professional for his work with Windows 2000 Server and IIS. Brien has served as CIO for a nationwide chain of hospitals and was once in charge of IT security for Fort Knox. As a freelance technical writer he has written for Microsoft, CNET, ZDNet, TechTarget, MSD2D, Relevant Technologies and other technology companies. You can visit Brien's personal Web site at www.brienposey.com.

This was first published in November 2005

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