Web site domain - 1.2 1.2 t 5 www.example.com. IN A 10.1.1.1
1.2 1.2 t 5 www.example.com. IN A 10.1.1.1 If www.example.com resolves to an IPv6 address, connect to the IPv6 address. www.example.com. IN AAAA 3ffe:501:ffff::1234 If www.example.com resolves to multiple IPv4/v6 addresses, IPv6 addresses will be tried first, and then IPv4 addresses will be tried. For example, with the following DNS records, we will try connecting to 3ffe:501:ffff::1234, then 3ffe:501:ffff::5678, and finally 10.1.1.1. www.example.com. IN AAAA 3ffe:501:ffff::1234 www.example.com. IN AAAA 3ffe:501:ffff::5678 www.example.com. IN A 10.1.1.1 Since we assume that IPv6 nodes will be able to use IPv4 as well, the Internet will be filled with IPv4/v6 dual stack nodes in the near future, and the use of IPv6 will become dominant. 1.2.2 Tunneling Even when we have IPv4/v6 dual stack nodes at two locations (e.g., home and office), it may be possible that the intermediate network (ISPs) are not IPv6-ready yet. To circumvent this situation, RFC 2893 defines ways to encapsulate an IPv6 packet into an IPv4 packet. The encapsulated packet will travel IPv4 Internet with no trouble, and then decapsulate at the other end. We call this technology IPv6-over-IPv4 tunneling. For example, imagine the following situation (see Figure 1.1): We have two networks: home and office. We have an IPv4/v6 dual stack host and router at both locations. However, we have IPv4-only connectivity to the upstream ISP. In this case, we can configure an IPv6-over-IPv4 tunnel between X and Y. An IPv6 packet from A to B will be routed as follows (see Figure 1.2): The IPv6 packet will be transmitted from A to X, as is. X will encapsulate the packet into an IPv4 packet. The IPv4 packet will travel the IPv4 Internet, to Y. Y will decapsulate the packet and recover the original IPv6 packet. The packet will reach B. Chapter
Check our reliable web hosting section. Most often, a reliable protocol is also connection-oriented. However, this is not always so. For example, TCP/IP is a connection-oriented protocol, with the virtual circuit ID consisting of source and destination IP addresses and port numbers. However, there are also unreliable protocols that are connection-oriented as well. These include ATM and Frame Relay, on which 90% or more of all Internet traffic is passed.