Mobile IP for mobile Ad Hoc networks

• US 20010024443A1
• Filed: 12/20/2000
• Published: 09/27/2001
• Est. Priority Date: 12/20/1999
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Jonsson, Ulf, Alriksson, Fredrik, Purser, Kevin
• Granted Patent: US 6,977,938 B2
• Time in Patent Office: Days
• US Class Current: 370/401
• CPC Class Codes: H04L 45/00 Routing or path finding of packets in data switching networks routing or path finding in wireless networks H04W40/00
• CPC Class Codes: H04W 40/22 using selective relaying for reaching a BTS [Base Transceiver Station] or an access point
• CPC Class Codes: H04W 40/246 Connectivity information discovery
• CPC Class Codes: H04W 40/248 Connectivity information update
• CPC Class Codes: H04W 40/28 for reactive routing
• CPC Class Codes: H04W 60/00 Affiliation to network, e.g. registration; Terminating affiliation with the network, e.g. de-registration
• CPC Class Codes: H04W 8/26 Network addressing or numbering for mobility support
• CPC Class Codes: H04W 80/04 Network layer protocols, e.g. mobile IP [Internet Protocol]
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks
• CPC Class Codes: H04W 88/16 Gateway arrangements
• CPC Class Codes: H04W 92/02 Inter-networking arrangements

Abstract

In a wireless or mobile ad hoc network the routing intetworks with the ordinary Internet routing using the Mobile IP. Mobile IP foreign agents are used as gateways between the ad hoc network and the Internet. The nodes in the ad hoc network use their s home addresses for all communication and register with a foreign agent in the network. To send packets to hosts on the Internet either tunnelling or proxying is used. To receive packets from the Internet the packets are routed to the foreign agent using the Mobile IP. The foreign agent then routes the packets to the destination in the ad hoc network. Since the ordinary Mobile IP requires link-layer connectivity between the foreign agent and a visiting node which is not guaranteed on the ad hoc network, modifications are accordingly made to the procedures of the Mobile IP.

Claims

1. A method for communicating information between nodes in a mobile ad hoc network and the Internet, the mobile network including at least one first mobile node and a second node, the at least one first mobile node having a home address and using the home address for communicating with the Internet, the second node acting as a gateway for communicating information between the first mobile node and the Internet, wherein in sending information from the at least one of the mobile nodes first default routes and network routes using either tunnelling or proxying are incorporated.

41. A computer program product directly loadable into the internal memory of a digital computer, comprising software code portions for performing steps of the methods of or the methods performed by any block or device according to any of the preceding claims when the product is run on a computer.

42. A computer program product stored on a computer usable medium, comprising readable program means for causing a computer to control the execution of steps of the methods performed by any block or device according to any of the preceding claims.

2. A method for route discovery in a mobile ad hoc network which is interworking with the Internet, the ad hoc network comprising a first mobile node having a home address, the first node using its home address for communicating with the Internet, and further comprising a second node acting as a gateway for communicating information packets between the first node in the ad hoc network and the Internet, the gateway being a Mobile IP foreign agent, the method comprising the steps of:

sending a route request at initiation of communication with a destination using the gateway;

forwarding from the gateway the route request comprising a sequence number, the destination being external to the ad hoc network;

sending a check to the destination;

receiving an indication from the destination, the indication being positive or negative;

sending a proxy route reply after receiving a positive indication from the destination; and

adding a route table entry for the external destination comprising a sequence number equal to or higher than the sequence number in the route request.

3. A mobile ad hoc network comprising a plurality of nodes including at least one first mobile node and a second node, the at least one first mobile node having a home address and using the home address for communicating with the Internet, the second node acting as a gateway for communicating information between the first mobile node and the Internet, wherein at least one of the nodes in the mobile ad hoc network comprises means for incorporating default routes and network routes using either tunnelling or proxying, in order to be capable of sending information from the at least one first mobile node to the Internet.

4. The mobile ad hoc network of

claim 3

, wherein the gateway acts as a foreign agent according to the Mobile IP, and that means are provided for routing information to the foreign agent by the Mobile IP in order to allow information from hosts on the Internet to be received by the at least one node.

5. The mobile ad hoc network of

claim 3

, wherein communication using the gateway is initiated by sending a route request;

in the case of a destination in the ad hoc network, forwarding the request;

in the case of a destination external to the ad hoc network, sending a check to the destination;

after receiving a positive indication from the destination, sending a proxy route reply; and

adding a route table entry for the external destination with a sequence number at least equal to the sequence number in the route request.

6. The mobile ad hoc network of

claim 5

, wherein the check sent to an external destination is an ICMP ECHO_REQUEST.

7. The mobile ad hoc network of

claim 5

, wherein the positive indication is an ICMP ECHO_RESPONSE.

8. The mobile ad hoc network of

claim 5

, wherein in the case where a node initiates a route discovering procedure to another node in the network, the network having at least one route to the destination involving a gateway and at least one direct route to the destination;

and that nodes intermediate between the node initiating the discovering procedure and the destination node replace an incorrect proxy route with either a better proxy route, if such a route is available, or with a direct route, and will send a route error message to intermediate nodes using the incorrect proxy route.

9. The mobile ad hoc network of

claim 5

, wherein in the case where the route request is sent by a mobile node initiating route discovery and there are a plurality of gateways, each gateway receiving a route reply performs the following steps:

checking if the gateway has a stored route to the destination;

if there is no stored route then accept the route reply;

if there is a stored route, check if the stored route is a proxy route;

if the stored route is a proxy route, check if the route reply sequence number is more recent, else check if the route reply is a proxy reply;

if the route reply is a proxy reply, discard the route reply else check if the route reply sequence number is more recent;

if the route reply sequence number is more recent, accept the route reply, else check if the route reply sequence number is equivalent to the stored route sequence number;

if the route reply sequence number is equivalent to the stored route sequence number, check if the route reply hop count is lower than that of the stored route, else discard the route reply;

if the route reply hop count is lower than that of the stored route, accept the route reply.

10. The mobile ad hoc network of

claim 3

, wherein

each node has a routing table, the node initiating communication by first looking for an entry in its routing table that matches the complete address of the destination and using that address if found;

if no entry was found in the routing table, invoking the routing protocol of the ad hoc network to find a host route within the ad hoc network by using route discovery mechanisms and using that route, if found;

if no route is found then tunnel the packet to the gateway, if a gateway can be found;

if no gateway can be found the consider the destination unreachable.

11. The mobile ad hoc network of

claim 10

, wherein information that a gateway is available is sent to the at least one node using Mobile IP agent advertisements.

12. The mobile ad hoc network of

claim 10

, wherein information that a gateway is available is sent to the at least one node using a route discovery mechanism.

13. The mobile ad hoc network of

claim 10

, wherein information that a gateway is available is sent to the at least one node using ICMP router advertisements.

14. The mobile ad hoc network of

claim 10

, wherein the tunnelling is accomplished using encapsulation.

15. The mobile ad hoc network of

claim 10

, wherein the tunnelling is accomplished using source routing.

16. The mobile ad hoc network of

claim 15

, wherein the source routing is strict.

17. The mobile ad hoc network of

claim 15

, wherein the source routing is loose.

18. The mobile ad hoc network of

claim 4

, wherein

when a node registers as a visiting node with a foreign agent, it informs the network routing protocol that it can tunnel packets out of the ad hoc network;

if the registered visiting node cannot find a host using a route discovery mechanism it creates a host route for the destination and stores it on its routing table;

this host route should direct packets to a virtual interface where they will be encapsulated with the foreign agent as a destination address.

22. The mobile ad hoc network of

claim 18

, wherein nodes solicit foreign agents, the agents responding by unicasting an agent advertisement to nodes registered as visiting nodes.

28. The mobile ad hoc network of

claim 4

, wherein the network has a plurality of foreign agents;

in selecting the best agent, a visiting node that is not registered selects the agent which has the best metric;

in selecting the best agent, a visiting node that is registered with a foreign agent, switches to another agent only if the metric of the other agent is a predetermined quantity better than the metric of the agent with which the visiting node is registered and is better for a predetermined number of consecutive agent advertisements.

29. The mobile ad hoc network of

claim 28

, wherein the metric is the hop count and the metric is better when the hop count is lower.

30. The mobile ad hoc network of

claim 4

, wherein the network has a plurality of foreign agents periodically broadcasting agent advertisements and each node that receives an advertisement only forwards the best quality advertisement received.

31. The mobile ad hoc network of

claim 30

, wherein the quality of agent advertisements is determined based on the number of hops that the advertisement has travelled.

32. The mobile ad hoc network of

claim 4

, wherein

the network has a plurality of foreign agents periodically broadcasting agent advertisements and each node that receives an advertisement stores it;

and

each node having a stored advertisement that receives an agent solicitation responds with the stored advertisement instead of forwarding the solicitation to the agent.

33. The mobile ad hoc network of

claim 32

, wherein a stored advertisement has a lifetime for which it is valid, the stored advertisement being discarded after the lifetime has expired.

34. The mobile ad hoc network of

claim 4

, wherein agent advertisements and agent solicitations are sent using IP multicast.

35. The mobile ad hoc network of

claim 34

, wherein there are a plurality of multicast groups, one group being dedicated to agent solicitations and agent advertisements, with all visiting nodes and foreign agents listening to the one dedicated multicast group.

36. The mobile ad hoc network of

claim 3

, wherein the network has an Interworking Unit (IWU) located between the node using the Mobile IP and the network, to allow the use of multihop routing of Mobile IP messages in the network.

37. The mobile ad hoc network of

claim 36

, wherein the IWU and the foreign agent are located on the same link.

38. The mobile ad hoc network of

claim 37

, wherein the IWU and the foreign agent are located in the same node.

39. The mobile ad hoc network of

claim 36

, wherein if agent solicitations are to be replied to with broadcast agent advertisements, the IWU changes all incoming agent advertisements to broadcast and forwards them to the ad hoc network, else if the agent solicitations are to be responded to with unicast agent advertisements, the IWU only forwards the unmodified advertisements to the ad hoc network.

40. The mobile ad hoc network of

claim 36

, wherein if periodic agent advertisements are unicast to registered nodes only, the IWU ensures that all incoming broadcast agent advertisements are copied and unicast to every registered visiting node, else if periodic agent advertisements are broadcast, the IWU forwards the agent advertisements to the ad hoc network.

19. The mobile ad hoc network of

claim 19

, wherein agents periodically broadcast an agent advertisement to all nodes in the network, and when nodes solicit foreign agents, the agents respond by broadcasting an agent advertisement to all the nodes in the network.

20. The mobile ad hoc network of

claim 19

, wherein the nodes soliciting foreign agents cooperate so that a plurality of visiting nodes will send only one solicitation for the group.

21. The mobile ad hoc network of

claim 20

, wherein a plurality of nodes are prevented from simultaneously soliciting foreign agents by forcing them to wait a time t before being allowed to solicit, the time in particular being equal to t=t_hop*(n_hop−

1+random (0,0.5)), where t hop is the time that it takes for a packet to traverse one hop and n_hop is the distance, in hops, i.e. the number of hops, between a node and the foreign agent with which it was previously registered.

23. The mobile ad hoc network of

claim 19

, wherein the foreign agent adaptively selects between unicasting and broadcasting advertisements based on the number of nodes registered as visitors to the network.

24. The mobile ad hoc network of

claim 23

, wherein the foreign agent periodically unicasts agent advertisements while the number of visiting nodes is below a set threshold;

when the number of visiting nodes goes above the threshold the foreign agent will begin broadcasting agent advertisements.

25. The mobile ad hoc network of

claim 24

, wherein the foreign agent reverts to unicasting when a number of agent registrations expires, bringing the total number of agents registered below a second set threshold.

26. The mobile ad hoc network of

claim 25

, wherein the foreign agent periodically unicasts agent advertisements while the ratio of visiting nodes to total nodes in the network is below a threshold;

when the number of visiting nodes exceeds the threshold the foreign agent begins broadcasting agent advertisements.

27. The mobile ad hoc network of

claim 26

, wherein the ratio is guessed by estimating the diameter of the network using the number of hops to the visiting nodes.