Dynamic routing method for packet switched satellite communications

[0002] The invention relates to network communications and, more particularly, to a method of routing data packets within a satellite communications network.

[0003] In a full mesh network such as a satellite network, it is possible for a source node to communicate with a destination node in a single hop. Single hop communications are possible when the source node has knowledge of both the network address of the destination node and the physical address of the destination node. Existing methods of distributing address information to the nodes within a network make use of dynamic routing protocols and address resolution protocols. These protocols can generally be classified as either broadcast-based or server- based protocols.

[0004] Broadcast based protocols transmit routing and address resolution information to all nodes within the network on a periodic basis. Because all routing information is distributed throughout the entire network on a periodic basis, broadcast-based implementations tend to be very bandwidth intensive.

[0005] Server-based protocols are based on the concept of an intelligent server having all routing and address resolution information for the entire network. To send information from a source node to a destination node, the source node requests routing information from the intelligent server. In response, the server transmits routing information back to the source node. Once the source node receives the address resolution information for the destination node, it transmits the data directly to the destination node. The process is then repeated for each subsequent communication. Such server-based communication methods increase the number of protocol exchanges, thereby increasing delays within the system.

[0006] The bandwidth usage associated with broadcast-based systems and the communications delay associated with server-based systems are both undesirable in a bandwidth-sensitive and delay-sensitive wireless environment such as a geostationary satellite network.

[0007] The present invention overcomes the drawbacks of these prior art systems through the provision of one or more intelligent routing nodes which maintains routing and address resolution information for all nodes within the routing node's domain. When the intelligent routing node detects that a source node is transmitting a data packet using a sub-optimal communication path, the routing node communicates updated routing information to the source node to improve the communication path.

[0008] When a source node transmits a data packet to the routing node, the routing node senses the network address of the destination node, retransmits the data packet to the destination node at the physical address associated with the destination node, and redirects the destination node physical address to the source node. The source node then stores this information such that subsequent data packets containing the same network address can be transmitted directly by the source node to the destination node.

[0009] The present invention provides an improved network communications system and method. The present invention also minimizes bandwidth usage and communications delay within a network.

[0010] For a more complete understanding of the invention, reference should now be had to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention.

[0011] In the drawings:

[0012] FIG. 1 is a block diagram of a communications network according to the present invention.

[0013] FIG. 2 illustrates a full mesh interconnected satellite system according to the present invention.

[0014] FIG. 3 is a block diagram of a source node transmitting data to a routing node within the communications network of FIG. 1.

[0015] FIG. 4 is a block diagram illustrating the routing node data transmissions for the communications network of FIG. 3.

[0016] FIG. 5 is a block diagram depicting inter-domain data transmission according to the present invention.

[0017] FIGS. 6A and 6B are block diagrams depicting alternate methods of redirecting address resolution information to a source node according to the present invention.

[0018] FIGS. 7A and 7B are block diagrams showing the optimum communications pathway from a source node to a destination node within a network according to the present invention.

[0019] FIG. 8 shows the routing logic of the present invention in flowchart form.

[0020] While the invention will be described in connection with one or more embodiments, it will be understood that the invention is not limited to those embodiments. On the contrary, the invention covers all alternatives, modifications, and equivalents as may be included within the spirit and scope of the appended claims.

[0021] The communications network of the present invention groups communication nodes by network addresses into routing domains where a single node serves as the routing node for all other nodes in the domain. The routing node is designated as the default routing node for all the nodes in the domain.

[0022] Referring to FIG. 1, a routing domain 10 is shown including a routing node 12 and a plurality of communication nodes 14a, 14b, 14ceach having associated memory. Although only one routing domain 10 is shown in FIG. 1, there may be multiple routing domains within the network, wherein each routing domain includes an associated routing node. The role of the routing node 12 is to distribute optimal routing information to the communication nodes 14a, 14b, 14cin the network when sub-optimal communication pathways are detected. A redirecting message containing updated address information for the optimal route is transmitted by the routing node 12 to the source node when the optimal communication pathway is unknown to the source node. This routing logic is illustrated in FIGS. 3 and 4.

[0023] Routing the optimal communications pathway to the source nodes allows for subsequent single-hop communications, thus providing the performance of a full-mesh interconnected network without the associated delays of a server-based network or bandwidth requirements of a broadcast-based network.

[0024] FIG. 2 illustrates an example of a full-mesh interconnected satellite communication system wherein a network of satellites 16 are in operative communication with each other in orbit about the earth 18.

[0025] In FIG. 3, there is shown a routing domain 20, including a source node 22, destination node 24, and routing node 26, each having associated memory. Each data packet to be transmitted within the network comprises data and the network address of the destination node that is to receive the data packet. The memory associated with each node allows the nodes to store network address and physical address resolution information. When a data packet is received by the source node 22, it is processed to retrieve the network address of the destination node 24 where the data packet is to be sent. Given the network address, the source node searches its memory to determine whether is has a route, i.e., a physical address, to the destination node 24 associated with the data packet information. If the route to the network address is unknown, the source node 22 forwards the data packet to its default routing node 26.

[0026] Routing node 26 performs address management tasks and maintains routing information for all nodes within the routing domain 20. If the destination node 24 is within the routing domain 20 of the default routing node 26, the data packet is forwarded to the destination node 24 as shown in FIG. 4. Because a non-optimal communication pathway is being used between the source node 22 and the destination node 24, the routing node 26 also transmits a redirect message to the source node 22. The redirect message contains updating routing and physical address information for the destination node 24. The source node 22 stores this information in its memory, such that subsequent data packets having the same network address can be transmitted directly to the destination node 24 at the physical address associated with the network address contained in the data packet.

[0027] FIGS. 5, 6a, and 6billustrate the routing logic when the destination node is outside of the default routing node's domain. In FIG. 5, when the source node 22 receives a data packet containing a destination node network address and the source node memory does not have an associated physical address, the data packet is forwarded to the default routing node 26 as before. The routing node 26 then processes the network address to determine whether the destination node associated with the physical address is located within the domain 20 of the routing node 26. If the routing node 26 does not know the physical address for the desired destination node, it forwards the data packet to the routing node 36 within the routing domain 30 where the destination node 34 resides. Thereafter, the routing node 36 retransmits the data packet to the destination node 34 within the routing domain 30.

[0028] FIGS. 6aand 6billustrate two alternatives for the redirect messaging related to the data packet transmission shown in FIG. 5. As before, the redirecting message is sent to the source node 22, however the redirecting message can be sent by either the routing node 36 associated with the destination node domain 30 or the routing node 26 associated with the source node domain 20. Once the updated routing information is processed by the source node 22, data packets can be transmitted directly from the source node 22 to the desired destination node as shown in FIGS. 7aand 7b.

[0029] FIG. 8 depicts the routing logic of the present invention in flow-chart form. The logic enclosed in box 40 describes the processes undertaken within the source node 22 to transmit a received data packet, and the logic within box 50 describes the processes undertaken within the routing node 26 to transmit the data packet received at the source node.

[0030] From the foregoing, it will be seen that there has been brought to the art a new and improved network communications system and method which minimizes bandwidth usage and latency associated with broadcast and server-based communications systems.

[0031] While particular embodiments of the invention have been shown, it will be understood, of course, that the invention is not limited thereto since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. For example, although the invention has been described with reference to a satellite communications system, the network routing logic of the present invention is equally applicable to a computer network. The invention, therefore, includes all alternatives, modifications, and equivalents as may be included within the spirit and scope of the appended claims.