PNRP uses multiple clouds, in which a cloud is a grouping of computers that are able to find each other. PNRP provides two clouds:

■The global cloud corresponds to the global IPv6 address scope and global addresses and represents all the computers on the entire IPv6 Internet. There is only a single global cloud.

■The link-local cloud corresponds to the link-local IPv6 address scope and link-local addresses. A link-local cloud is for a specific link, which is typically the same as the locally attached subnet. There can be multiple link-local clouds.

In Windows Server 2008 and Windows Vista, Windows Peer-to-Peer Networking applications can access PNRP name publication and resolution functions through a simplified PNRP application programming interface (API). With the simplified PNRP publication API, you do not have to specify the clouds with which to register the name and addresses. The PNRP component will automatically determine the appropriate clouds to join and the addresses to publish within the clouds.

For highly simplified PNRP name resolution, PNRP names are now integrated into the Getaddrinfo() Windows Sockets function. To use PNRP to resolve a name to an IPv6 address, applications can use the Getaddrinfo() function to resolve the FQDN name.prnp.net, in which name is the peer name being resolved. The pnrp.net domain is a reserved domain in Windows Server 2008 and Windows Vista for PNRP name resolution.

The details of how PNRP works to resolve names is beyond the scope of this book. For more information, see the Peer Name Resolution Protocol article at http://technet.microsoft.com/enus/library/bb726971.aspx.

References

The following references were cited in this chapter:

■RFC 1035 — “Domain Names - Implementation and Specification”

■RFC 1886 — “DNS Extensions to support IP version 6”

■RFC 3484 — “Default Address Selection for Internet Protocol version 6 (IPv6)”

■RFC 3646 — “DNS Configuration options for Dynamic Host Configuration Protocol for IPv6 (DHCPv6)”

■RFC 4795 — “Link-local Multicast Name Resolution (LLMNR)”

You can obtain these RFCs from the \RFCs_and_Drafts folder on the companion CD-ROM or from http://www.ietf.org/rfc.html.

230 Understanding IPv6, Second Edition

Testing for Understanding

To test your understanding of IPv6 name resolution, answer the following questions. See Appendix D, “Testing for Understanding Answers,” to check your answers.

1.Why is the DNS record for IPv6 name resolution named the “AAAA” record?

2.A host computer running Windows Vista is assigned the IPv4 address 172.30.90.65 on its single LAN interface. IPv6 on this computer receives a Router Advertisement message on its ISATAP tunneling interface that contains both a unique local prefix (FD3A:47A1:2CB9:C140::/64) and a global prefix (2001:DB8:A3:C140::/64). List the IPv6 addresses for the AAAA records registered with DNS by this host.

3.Describe the importance of address selection rules for a node running both IPv4 and IPv6 that is using a DNS infrastructure containing both A and AAAA records.

4.Describe how LLMNR messages are the same as and different from DNS messages.