Internet protocol version 6 (IPv6) promises to deliver connectivity features in Windows Vista not possible with today's Internet protocol version 4 (IPv4).

Microsoft Corp.'s "community technology preview" was issued in December. The second version ships in February. Both versions already support IPv6-enabled file-sharing and remote-access features.

Driving Microsoft to adopt the IPv6 protocol in Vista is the ability to enable "new application experiences." It meant being able to incorporate "richer collaboration," multiplayer gaming, or voice and video into applications. Sinead O'Donovan, product unit manger for networking at Microsoft, said "When we looked at key applications such as MSN Messenger, we learned that developers needed to do too many tricks to get them to work over NAT."

Network Address Translation, or NAT, is a technology commonly used in the United States in which several devises can connect to the Internet on one IP address. It was developed as a temporary patch for the lack of IP connection points as more devices link to the Web.

As for the cost, software developers who are designing these applications for Windows in IPv4 were finding it too expensive. "If you had to route all the file-sharing traffic in MSN Messenger through your server it's very expensive to build that application because they must have a lot of servers to support the application," O'Donovan said. "IPv6 allows them take advantage of end-to-end connectivity, so if it makes sense for the traffic to go between two peers they can."

O'Donovan said it's important for applications with both voice and video traffic to travel directly between two piers because latency is an issue and users will notice any delay.

O'Donovan believes IPv6 offers securer data transmissions through longer IP addresses. The header length for IPv6 is 40-bytes and address 128-bits, compared with IPv4's 20-byte to 24-byte header and 32-bit address, Dale Geesey, vice president of consulting, v6 transition at UPIPv6 Summit Inc, confirmed in an e-mail.

IPv6 has inherent security features. Risks, such as worms, that quickly scan a range of addresses to find a vulnerable machine for an attack will need to scan more address, which requires increased computing power. Alex Lightman, chief executive officer and president of IPv6 Summit Inc., said "IPv6 has 2¹²⁸ [or 3.4 10³⁸] addresses," a number so large it's incomprehensible, "compared with IPv4, which has 2³² addresses, or roughly 4 billion addresses."

Other security features exist, too. There is IPsec encryption, and a new technology called Secure Neighbor Discovery (SEND) protocol, a way to prevent IP address spoofing through cryptographically generating addresses.