Duplex Communication difference between IPv6 and IPv4 protocol networks

We all know the essential differences between IPv6 and IPv4 protocol networks. So what are the differences between the two in the two-way session communication process? The following describes the content in detail. The NAT-PT can only be used for applications that initiate a session by a terminal in the Ipv6 network, and the NAT-PT cannot be implemented if an application needs to initiate a session by a terminal in the IPv4 protocol network, because the terminal in the IPv4 protocol network cannot use an IPv4 address to bind a terminal in the IPv6 network.

If you want to implement a session initiated by a terminal in the IPv4 protocol network, you need to use static NAT, that is, configure the ing between the static IPv4 address and the IPv6 address in Router R3.

If Terminal C wants to access the DNS server IPv6 DNS in the IPv6 network, an IPv4 group with 10.1.1.1 as the source address and 193.1.1.5 as the destination address is constructed. After the IPv4 group arrives at router R3, vror3 R3 converts the destination address to 2001: 2E0: FCFF: FE00: 9 by configuring static address ing.

However, if static address ing is also applied to other terminals in IPv6, it is obviously impossible to statically allocate IPv4 addresses to all terminals that may communicate with IPv4 networks.

Router R3 is not only an address and Protocol converter, but also a DNS Application Layer Gateway. DNS is used to resolve a fully qualified domain name to an IP address. If it is an IPv6 network, it is resolved to an IPv6 address. If it is an IPv4 network, it is resolved to an IPv4 address.

The DNS server provides A fully qualified ing between the domain name and the corresponding IP address, for example, Terminal A 2001: 2E0: FCFF: FE00: 7. When Terminal C wants to initiate A session with terminal A, Terminal C resolves the IPv4 address corresponding to Terminal A through Terminal A's fully qualified domain name: Terminal.

Because the IPv6 address of the DNS server in the IPv6 network has been statically configured in Router R3: 2001: 2E0: FCFF: FE00: 9 and IPv4 address: 193.1.1.5, terminal C sends a request packet to the DNS server whose IPv4 address is 193.1.1.5. The request packet is encapsulated into an IPv4 group, then enters the IPv4 network, and is routed to the router R3 by the IPv4 protocol network. Vror3 R3 converts IPv4 DNS request packets to IPv6 DNS request packets, encapsulates the request packets into a source address of 2: 10.1.1.1, with 2001: 2E0: FCFF: FE00: 9 refers to the IPv6 Group of the destination address. The IPv6 group is transmitted to the DNS server of the IPv6 network through the IPv6 network.

The DNS server of the IPv6 network resolves the IPv6 address: 2001: 2E0: FCFF: FE00: 7 According to the Fully Qualified Domain Name: Terminal, and send this address back to Terminal C whose source address is 2: 10.1.1.1 through the DNS response packet ). The response packet is routed to router R3 by the IPv6 network. Router R3 selects an IPv4 address in the IPv4 address pool, which is assumed to be 193.1.1.1) and assigns the packet to Terminal A. At the same time, 2001 is created in the session table :: ing between 2E0: FCFF: FE00: 7 And 193.1.1.1.

Vror3 R3 converts IPv6 DNS response packets to IPv4 DNS response packets, and encapsulates IPv4 DNS response packets into IPv4 groups with the IP address 10.1.1.1, the IPv4 packet is transmitted to Terminal C through the IPv4 protocol network. Terminal C then communicates with terminal A through IPv4 address: 193.1.1.1. It should be noted that in the above communication process, the terminal in the IPv4 protocol Network creates a session through the DNS address resolution process and binds the address ing with the session, all IPv6 groups whose source address is 2001: 2E0: FCFF: FE00: 7 or IPv4 groups whose destination address is 193.1.1.1 belong to this session. The address conversion is completed based on the address ing given in the session table. This type of session can only be ended by an IP group that does not belong to the session for a specified period of time.

The IPv6 addresses of all terminals and servers in the IPv4 protocol network are fixed. terminals in the IPv6 network can obtain the IPv6 addresses of all terminals and servers in the Pv4 network. Therefore, A terminal in an IPv6 network can communicate with a terminal in an IPv4 protocol network by providing an IPv6 address directly.

Of course, it is easier to remember a fully qualified domain name than to remember a-bit IPv6 address. Therefore, terminals in an IPv6 network may pass a fully qualified domain name such as terminal C) initiate a session with a terminal in an IPv4 protocol network. In this case, the IPv6 terminal sends a DNS request packet to the DNS server of the IPv4 protocol. The router R3 converts the IPv6 DNS request packet to the IPv4 DNS request packet. When vror3 R3 receives the DNS response packet sent back by the DNS server in the IPv4 protocol network, it converts the resolved IPv4 address to an IPv6 address by adding the network prefix 2, on the other hand, it completes the conversion from IPv4 DNS response packets to IPv6 DNS response packets.