DHCP over mobile IP

• US 7,539,770 B2
• Filed: 08/22/2006
• Issued: 05/26/2009
• Est. Priority Date: 04/25/2001
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Meier, Robert C.
• Primary Examiner(s): Follansbee; John
• Assistant Examiner(s): Tran; Nghi V
• Application Number:
  US11/466,286
• Publication Number:
  US 20060280179A1
• Time in Patent Office: 1,008 Days
• Field of Search: 709/220, 709/222, 709/230, 709/236
• US Class Current: 709/236
• CPC Class Codes: H04L 61/5014 using dynamic host configuration protocol [DHCP] or bootstrap protocol [BOOTP]
• 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]

Abstract

A protocol that enables an 802 mobile host to obtain a “home IP address,” and other configuration parameters via DHCP or BOOTP, while attached to either its home subnet or a foreign subnet. Inner and outer encapsulation headers are used to forward DHCP messages from a DHCP server outbound through a “forward tunnel,” to a mobile host on a foreign subnet and are also used to forward DHCP messages from a mobile host on a foreign subnet inbound through a “reverse tunnel” to the home subnet. A mobile host adds an inner encapsulation header to inbound DHCP packets with the source IP address set to 0 to indicate that the packet is from a mobile host that does not have a registered home IP address. Outer encapsulation headers contain the home address and the care-of address for the mobile host.

Claims

1. An apparatus comprising:

a Dynamic Host Configuration Protocol (DHCP) client in an Internet Protocol (IP) host; and

a mobile host communicatively coupled to the DHCP client;

wherein the DHCP client is responsive to submit a DHCP request from a foreign agent by generating a DHCP request comprising a protocol field, a source IP address and a gateway IP address (giaddr), wherein the protocol field is set to the Media Access Control (MAC) address of the Mobile Host, the source IP address is set to a predefined value indicative that a source IP address has not been assigned and the gateway IP address is set to a predefined value indicative that a gateway IP address has not been assigned;

wherein the mobile host is configured to be responsive to receiving the DHCP request with the protocol field is set to the Media Access Control (MAC) address of the Mobile Host, the source IP address is set to predefined value indicative that a source IP address has not been assigned and the gateway IP address is set to a predefined value indicative that a gateway IP address has not been assigned to add an IP in IP encapsulation header with a source address and a destination address to the DHCP request;

wherein the predefined value indicative that a source IP address has not been assigned is zero, the predefined value indicative that a gateway IP address has not been assigned is zero, and the predetermined address indicative that the source address is undefined is zero;

wherein the mobile host sets the destination address of the IP in IP encapsulation header to an unicast address of the foreign agent; and

wherein the mobile host sets the source address of the IP in IP encapsulation header to a predetermined address indicative that the source address is undefined.

2. An apparatus according to claim 1, further comprising:

a foreign agent communicatively coupled to the mobile host;

wherein the foreign agent is responsive to receiving the DHCP request from the mobile host to determine the source IP address in the IP in IP encapsulation header;

wherein the foreign agent is responsive to discard the DHCP request responsive to determining the source IP address of the IP in IP encapsulation header is a value indicative of an assigned IP address; and

wherein the foreign agent is responsive to use the MAC address to locate mobility bindings for the mobile host responsive to determining the source IP address of the IP in IP encapsulation is a value is undefined.

3. An apparatus according to claim 2, wherein the foreign agent is responsive to determining the source IP address of the IP in IP encapsulation is a value is undefined to add a second IP in IP encapsulation header to the DHCP request.

4. An apparatus according to claim 3, wherein the second IP in IP encapsulation header comprises a source address and a destination address;

wherein the foreign agent is responsive to set the source address of the second IP in IP encapsulation header to an address for the foreign agent; and

wherein the foreign agent is responsive to set the destination address of the second IP in IP encapsulation header to an address for a home agent.

5. A apparatus comprising:

a mobile host communicatively coupled to the DHCP client in an Internet Protocol (IP) host;

a home agent;

a Bootstrap Protocol (BOOTP) relay agent communicatively coupled to the home agent;

wherein the BOOTP relay agent is responsive to receiving the DHCP request to insert a home agent address for a home subnet into the gateway IP address (giaddr) of the DHCP request;

wherein the BOOTP relay agent is configured to forward the DHCP request to a DHCP server communicatively coupled to the BOOTP relay agent;

wherein the BOOTP relay agent is responsive to receiving a DHCP reply to add on of a group consisting of an unicast destination IP address and a broadcast destination IP address to the DHCP reply;

wherein the BOOTP relay agent is responsive to receiving the DHCP reply to add an inner IP in IP header to the DHCP reply;

wherein the home agent is responsive to receiving a dynamic host control protocol (DHCP) request comprising a protocol field, a source IP address and a gateway IP address (giaddr) encapsulated with an inner IP in IP encapsulation header and an outer IP in IP encapsulation header to remove the out IP in IP encapsulation header from the request;

wherein the home agent is configured to examine a source IP address in the inner IP in IP encapsulation header;

wherein the home agent is responsive to the source IP address not being an unassigned IP address to discard the DHCP request responsive;

wherein the inner IP in IP header comprises a source address and a destination address;

wherein the BOOTP relay agent is configured to insert a home agent address into the source field and setting the destination address to a value indicating the destination address has no IP address;

wherein the home agent is responsive to the source IP address being an unassigned IP address to obtain a media access control (MAC) address of a mobile host associated with the DHCP request from the protocol field and forwards the DHCP request to the BOOTP relay agent.

6. An apparatus according to claim 5, further comprising:

the BOOTP relay agent is configured to send the DHCP reply with inner IP in IP encapsulation header to the home agent; and

the home agent is responsive to receiving the DHCP reply with inner IP in IP encapsulation header to add an outer IP in IP encapsulation header to the DHCP reply.

7. An apparatus according to claim 6, wherein the outer IP in IP encapsulation header of the DHCP reply comprises a source address and a destination address, the home agent is configured to insert a home agent address into the source address of the outer IP in IP encapsulation header of the DHCP reply and to insert a care of address for a foreign agent into the destination address of the outer IP in IP encapsulation header of the DHCP reply.

8. An apparatus according to claim 7, wherein the home agent is configured to forward the DHCP reply with the inner IP in IP encapsulation header and outer IP in IP encapsulation header to the foreign agent.

9. A system comprising:

a mobile host communicatively coupled to the DHCP client in an Internet Protocol (IP) host;

means for sending a mobile registration request having a MAC address as a mobile host identifier;

means for generating a DHCP request by a DHCP client, the DHCP request having a protocol field, a source IP address field and a gateway IP address (giaddr) field, wherein the protocol field being set to the MAC address of the mobile host, the source IP address field is set to 0, and the giaddr field is set to 0;

means for adding a first inner IP encapsulation header to the DHCP request;

means for adding a first outer IP encapsulation header to the DHCP request;

means for sending the DHCP request to a home subnet;

means for removing the first inner IP encapsulation header a first outer IP encapsulation header from the DHCP request;

means for forwarding the request to a DHCP server;

means for generating a reply to the DHCP request;

means for adding a second inner IP encapsulation and a second outer IP encapsulation header to the reply;

wherein the second inner IP encapsulation header having a source IP address and a destination IP address, the mean for adding a second inner IP encapsulation and a second outer IP encapsulation header to the reply further comprises means for setting the second inner IP encapsulation header destination IP address to indicate that the source mobile host does not have an IP address;

means for sending the reply to a foreigh subnet;

means for removing the second outer encapsulation header and the second inner encapsulation header from the reply; and

means for forwarding the reply to the DHCP client;

wherein the DHCP server is on the home subnet and the DHCP client obtains an IP address from the reply sent by the DHCP server.

10. A system according to claim 9, wherein the first inner IP encapsulation header comprise a source address and a destination, the means for adding a first inner IP encapsulation header further comprises means for setting the first inner IP encapsulation header destination IP address to indicate that the DHCP client does not have an IP address.

11. A system according to claim 9, wherein the first outer IP encapsulation header has a source address and a destination address, the means for adding a first inner IP encapsulation header further comprises means for setting the first outer IP encapsulation header source address to the foreign agent care of address and the first outer IP encapsulation header destination address to the home agent address.

12. A system according to claim 9, wherein the DHCP request comprises a giaddr field and a chaddr field, the means for removing the first inner IP encapsulation header and first outer IP encapsulation header from the DHCP request further comprises:

means for obtaining the MAC address of the DHCP client from the chaddr field; and

means for inserting the BOOTP relay agent IP address into the giaddr field.

13. A system according to claim 9, the second outer IP encapsulation header having a source IP address and a destination IP address, the means for adding a second inner IP encapsulation and a second outer IP encapsulation header to the reply further comprises means for setting the second outer IP encapsulation header source address to the home agent IP address, and setting the second outer IP encapsulation header destination IP address to the foreign agent care of IP address.