Introduction to IPv6 ISATAP Transition Technology

The transition from IPv4 to IPv6 is the trend of the times. However, due to the success and widespread use of IPv4, many researchers are actively exploring the technology of transition from IPv4 to IPv6. The existing technologies can be divided into three types: Dual-stack, translation, and tunnel. They can be divided into core network, enterprise network, and host at the network level.

ISATAP: Intra-Site Automatic Tunnel Addressing Protocol ISATAP: Intra-Site tunic Tunnel Addressing Protocol. ISATAP embeds the IPv4 address into the IPv6 address. When two ISATAP hosts communicate, the IPv4 address is automatically extracted to establish a tunnel, and no other special network device is required, you only need to maintain a smooth IPv4 network between each other. This technology does not require that the tunnel end node have a unique IPv4 address in the world, as long as the dual stack has an IPv4 unicast address, both the public address and the private address are allowed ).

1. IPv6 ISATAP Technical Principles

A dual-stack host obtains an ISATAP address before communicating with other hosts or routers. The dual-stack host sends a routing request to the ISATAP server to obtain a 64-bit IPv6 address prefix, and then adds the 64-bit interface identifier: 0: 5EFE: x. x. x. x here x. x. x. x is the IPv4 unicast address of the dual-stack host. After the ISATAP address is configured on the dual-stack host, it becomes an ISATAP client and can communicate with other ISATAP clients in the IPv4 domain. Generally, the ISATAP address configuration supports both automatic and manual configuration of stateless addresses.

1.1 Communication Between Two ISATAP clients in the same IPv4 domain is as follows:

① After obtaining the ISATAP address of the double stack host 2, send the data packet to the ISATAP interface for sending;

② ISATAP extracts the corresponding IPv4 address and destination address from the IPv6 source address and destination address of the data packet, and encapsulates the data packet with the IPv4 header;

③ The encapsulated data packet is sent to the dual-stack host 2 according to its IPv4 destination address;

④ The dual-stack host 2 unpacks the packet after receiving it and obtains the original IPv6 packet;

⑤ Double stack host 2 returns the response data to double stack HOST 1 through a process similar to the above.

From the above communication process we can see that ISATAP is actually IPv4 network as a bearer platform, through the establishment of a IPv6-in-IPv4 automatic tunnel on it to complete IPv6 communication.

1.2 communications between ISATAP clients and other networks

In addition to communicating with other ISATAP hosts in the ISATAP domain, the ISATAP host can also communicate with other networks through the ISATAP router. For example, an ISATAP host can communicate with an IPv6 server in an IPv6 network through an ISATAP router,

① The ISATAP host obtains the local address of the ISATAP address site), and sets the next hop to the local address of the ISATAP address site of the ISATAP router );

② When the ISATAP host sends an IPv4 packet to an address other than the sub-network, the ISATAP first encapsulates the IPv6 packet and then sends it to the IPv4 address of the ISATAP router through a tunnel;

③ After the ISATAP router removes the IPv4 packet header, it forwards the IPv6 packet to the destination IPv6 server in the IPv6 network;

④ The IPv6 server directly sends the IPv6 packet to the ISATAP network;

⑤ When an IPv6 packet is received by the ISATAP router, The ISATAP router first encapsulates the IPv6 packet and then forwards it to the ISATAP host;

⑥ After receiving the response packet, the ISATAP host removes the IPv4 packet header and restores it to the original IPv6 packet.

Through the above steps, the ISATAP host and the IPv6 server in the IPv6 network have completed a complete data communication process.

2. IPv6 ISATAP Address Resolution Mechanism

ISATAP transition technology uses the IPv6 Neighbor Discovery Mechanism (see ietf rfc 2461) to achieve route redirection, neighbor inaccessibility detection (NUD), and next hop selection.

The ISATAP address is obtained through static computing at the link layer IPv4 address. After obtaining the ISATAP address, the host sends a neighbor request and receives a neighbor message to check whether the neighbor is reachable. In addition, the host must perform neighbor inaccessibility detection. Because it is implemented in an ISATAP domain, it assumes that the IPv4 address is unique, so that the ISATAP address does not need to be checked repeatedly.

In addition to the data structure prefix list and default vro list, the ISATAP link also adds a new data structure-the list of potential routers (PSS) and a new configuration variable PrlRefreshInterval. The list of potential vrouters lists the potential vrouters available for ISATAP nodes. The PrlRefreshInterval variable is used to set the interval (in seconds) between two consecutive refresh BPS after initialization.

3. Advantages of IPv6 ISATAP Technology

The ISATAP transition technology has the following advantages:

① The IPv6 address prefix used by ISATAP transition technology can be any valid IPv6 single-point propagation 64-bit prefix, including the Global Address prefix starting with 2001:, 2002:, 3ffe) the local link prefix starts with fe80:) and the local site prefix starts with fec0:). This makes this technology easy to work with other transitional technologies, in combination with the 6to4 tunnel technology, the dual-stack hosts on the Intranet can easily access the IPv6 backbone network;

② The ISATAP transition technology does not require the tunnel end node to have the only IPv4 address in the world. As long as the dual-stack host has an IPv4 unicast address, it can be either public or private. This effectively avoids IPv4 address insufficiency;

③ ISATAP transition technology does not require sites to provide special IPv4 services, such as Multicast), so it is easy to implement;

④ When ISATAP transition technology is used, a new IPv6 host can be deployed on an IPv4 site without affecting the aggregation scope on the Border Gateway, therefore, it can be used for IPv6 communication between two-stack hosts in the internal private network.