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Method to use Dynamic Source Routing with Multihomed Servers Disclosure Number: IPCOM000016482D
Original Publication Date: 2003-Jun-24
Included in the Prior Art Database: 2003-Jun-24
Document File: 1 page(s) / 40K

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In the client-server model, clients usually connect to servers using an IP address that is obtained by doing a DNS lookup on the server hostname. It may happen that the route to that server then fails for some reason (e.g. a router along the way goes down). Most applications today will simply log a communication failure to the server and the connection will either hang or terminate. Now, let us consider the case of a multi-homed server i.e. it has multiple interfaces (with multiple IP addresses). This means that there are possibly a number of alternate routes to the server that could be used. Applications can make use of these other routes to the server.

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Method to use Dynamic Source Routing with Multihomed Servers

During the client's initial connection to the server, the client asks the server for information about all its IP addresses. One of these addresses is then used by the client as the main address for all further communication.

If the client now detects that the network path to this main IP address (and corresponding network interface) has failed, it will take the following steps to use the alternate routes to the server: Insert a source routing option in all future network packets being sent to the server. This routing option will cause the packets to first be delivered to the alternate network interfaces of the server. When the server receives the packet, it will realize that the final destination address is one of its own, and will accept the packet.

The application may periodically attempt communication directly to the original IP address (i.e. without source routing) to check if the path has recovered. If the original path has recovered, the application will then stop using the alternate IP addresses.

Advantages of our invention:

- This invention will work very efficiently with IPv6-enabled applications. The extended sockets API for IPv6 (see RFC2292) provides an extremely simple way for applications to dynamically change the source route to a destination.

- This technique may also be used for performance reasons instead of just for failure recovery. For example, if the current path to the server is...