IPv6 multicast in Network Interconnection (1)

In the network overuse phase, we will use the dual-stack technology to connect the two networks. In the double stack technology, IPv6 multicast provides powerful functions. It can run on both the router and host, and can write v4 and v6 to form a convergence point. In transition technology, IPv6 multicast is very important. We will discuss this in depth.

IPv6 multicast Transition Technology

1 double stack Technology

The dual-stack multicast transition solution is actually a combination of pure IPv4 multicast networks and pure IPv6 multicast networks. In unicast, servers can be configured as dual-stack, so that only IPv4 and IPv6 hosts can easily access it. Likewise, multicast sources can be configured as dual-stack, and data streams can be sent to IPv4 and IPv6 groups at the same time, this allows all hosts running different protocol stacks to receive multicast packets ｡

Both IPv4 and IPv6 Multicast can be deployed on a dual-stack network. IPv4 and IPv6 Multicast can run on both the router and host, and can exist on the same network link at the same time; the router can also be the convergence point (RP) of the IPv4 and IPv6 groups at the same time )｡

For simple single-source scenarios, if the data stream only exists in one closed environment, all potential receivers support the same IP protocol, the source only needs to use this IP protocol. In more open environments, potential receivers and Their supported IP protocols are unknown. To ensure that all receivers can receive, there must be an IPv4 source and an IPv6 source. At this time, both sources must use the same source data ｡

When there are only a few sources, you can use the dual-stack technology to configure all sources into a dual-stack, and send packets to IPv4 and IPv6 groups at the same time. However, in a video conference, almost everyone needs to receive and send data at the same time, and some participants use pure IPv4, while others use pure IPv6. In this case, the dual-stack technology will be powerless, when the dual-stack technology is used, the bandwidth consumption will be twice the original ｡

The dual-stack technology does not require additional devices or additional conversions to multicast data. Therefore, it is the easiest solution to implement. It is applicable to scenarios where communication between IPv4 hosts and IPv6 hosts is not required in the application environment, such as content distribution ｡

2 protocol conversion technology

Protocol conversion technology allows IPv6 hosts to communicate with IPv6 multicast groups without changing the infrastructure, the common IPv6 multicast protocol is used to communicate with any IPv4 multicast groups. The core idea is: place one or more conversion devices on the path between the IP protocol and the IP protocol. In rare cases, the conversion is also completed on the sending or receiving host, which is mainly for applications that run on a dual-stack host but only support one IP protocol. Common conversion methods include:

(1) Forwarder

In IPv4, Reflector is often used when global multicast fails. Virtual Room Video Conferencing System (VRVS) is a typical example, it uses pure Multicast on the core network, and sets the forwarder as the multicast proxy in this region directly through the multicast area, you can use pure multicast or unicast between the forwarder and the terminal system ｡

The IPv4-IPv6 multicast forwarder converts between IPv4 and IPv6 multicast (Reflect ), instead of converting between unicast and multicast. Given the IPv4 group address and port, as well as the IPv6 group address and port, the forwarder will join both groups and listen to the corresponding port at the same time, all data received from one group is resent to another group ｡

According to the IPv6 transition process, the forwarder can have two deployment schemes: when the protocol used by the content provider is not widely supported and the host or application does not support the dual protocol, the forwarder is located near the source. When the receiver uses another protocol different from the source protocol, it is very effective to place the forwarder near the receiver ｡

The main defect of the repeater solution is that it has low performance and cannot support large-scale multicast applications. In addition, it must enable an instance for each session, even if there is no receiver, it still executes the process of receiving and resending ｡

Due to the limitations above, the forwarder can be used to work for Multiple Multicast Groups, but the number of sessions that work at the same time is limited. If you use the forwarder to provide services on the network, You must contact the administrator, apply to allocate a session within a limited period of time; or use Web Authentication and other auxiliary measures like Tunnel Broker to automate the session allocation process ｡