Applications that include IP addresses in the data they transmit over TCP/IP require changes when enabling for IPv6, as the IPv6 addresses have a different format from IPv4 addresses. The following options can be considered in dealing with these changes:

• Determine whether IP addresses are needed in the data exchanged by the applications.
• Change the partner applications processing to always send IP addresses encoded using IPv6 format. In the case where IPv4 addresses are being used, they can be represented as IPv4-mapped IPv6 addresses.
• Include a version identifier that describes the format of the IP address being sent (IPv4 or IPv6).
• Modify applications to use host names instead of IP addresses in the data stream. This approach requires that the partner receiving the host name is able to resolve it to an IP address. Also note that a single IP host can have multiple IP addresses.
• In many cases, you might not be able to change all partner applications in your network at the same time. As a result, determining the type of IP address to send is a key consideration. Consider the following options when making this decision:
  • Determine the level of support when the connection is established by exchanging version or supported functions.
  • Encode the IPv6 addresses using new options. If the option is rejected by the peer, then it does not support IPv6.
  • Base the decision on the partner application's IP address. If the partner's source IP address is an IPv4 address, use only IPv4 addresses; otherwise, use an IPv6 address. This option can cause an IPv6-enabled partner application to be treated as an IPv4 partner if that application uses an IPv4-mapped IPv6 address to connect.