Title of Invention

METHOD OF FAST HANDOFF PROCEDURE WHEN A MOBILE NODE RETURNS TO ITS HOME NETWORK

Abstract

The present invention proposes a method of fast handoff procedure when FMIPv6-MN returns to its home network. According to the present invention a new flag is introduced in the Fast Binding Update (FBU) message and in the Handover Initiate (HI) message of the existing FMIPv6 protocol. With the present invention the step of checking for the Next Care of Address (NCoA) at the Next Access Router (NAR) is skipped improving the efficiency of the protocol. This allows a Mobile Node (MN) to use its home address as its NCoA when returning back to its home network in the FMIPv6 protocol operation.

Full Text

FIELD OF THE INVENTION The present invention, in general, relates to the field of mobile communications. In particular, the present invention relates to the changes required in Fast handovers for Mobile IP v6 (FMIPv6) protocol when a mobile node is moving back to its Home network from a foreign network. More particularly, the present invention relates to a method of fast handoff procedure when FMIPv6-MN returns to its home network. DESCRIPTION OF THE RELATED ART In Fast handovers for Mobile IP v6 (FMIPv6) protocol, when a Mobile Node (MN) is moving towards another network, the MN sends Router Solicitation for Proxy Advertisement (RtSolPr) message to Previous Access Router (PAR) asking for the prefix information of the Next Access Point (NAP). The Previous Access Router (PAR) replies with Proxy Router Advertisement (PrRtAdv) message to MN. In case the MN decides to do handoff, it forms New Care of Address (NCoA) using the prefix information and the link identifier. MN now sends Fast Binding Update (FBU) message to PAR with this address. PAR forwards the NCoA message in Handover Initiate (HI) message for NAR to verify that MN can use that address. If NAR finds that the address is already in use, it suggests a new address. If the address is not in use, then NAR accepts the same address and start defending for MN till it associates with it. NAR also includes this address in the Fast Binding Acknowledgement (FBAck) message. On reception of FBAck MN configures an address when it does the handoff. It happens quite often that a MN returns back to its home network. When the Home Agent (HA) and NAR are two different nodes providing this functionality or a single node which have these functionalities but run as independent applications, if the MN proposes HA as its NCoA, NAR does not allow setting this address and gives a new address. As MN is away from the home network, HA defends its address and NAR detects it as address collision. This leads to the MN having two addresses configured in the home network. However if the MN is aware that it is returning back to its home network, then it can convey the information to NAR so that NAR can skip the check for address collision. The basic secured FMIPv6 message exchanges can be illustrated with respect to figure 1 and figure 2 as follows. Figure 1 depicts FBU message format defined in FMIPv6 protocol, RFC 4068. A FBU message contains a sequence number field, a lifetime field specifying the lifetime of the binding. FBU message also defines the following flags A flag: Acknowledge flag, must be set to one to request that PAR sends a Fast Binding Acknowledgment (FBAck) message H flag: Home Registration, must be set to one. L flag: Link-Local Address Compatibility K flag: Key Management Mobility Capability Mobility options contain an alternate Care of Address (CoA) option set to the NCoA (the prospective care of address on the new link) Figure 2 depicts HI message format defined in FMIPv6 Protocol, RFC 4068. HI message contain the fields Type, Code and Checksum. HI message also defines flags as follows S flag: Assigned address configuration flag. When set, this flag requests a new CoA to be returned by the destination. May be set when Code = 0. Must be 0 when Code = 1. U flag: Buffer flag. When set, the destination should buffer any packets moving towards the node indicated in the options of this message. Used when Code =0, Should be set to 0 when Code = 1. Reserved field must be set to zero by the sender and ignored by the receiver. Options contain an alternate CoA option set to the NCoA (the prospective care of address on the new link). SUMMARY OF THE INVENTION It is therefore the primary object of the invention to provide a method to assist a Mobile Node (MN) to use its home address as its Next Care of Address (NCoA), when returning back to its home network in the Fast handovers for Mobile IP v6 (FMIPv6) protocol operation. It is another object of the invention to configure the Fast Binding Update (FBU) message and Handover Initiate (HI) message with an N flag so as to indicate the NAR that the NCoA included in the mobility options contains the home address of the Mobile Node (MN). It is yet another object of the invention to make the NAR skip the checking of NCoA if it contains the home address, thereby letting FMIPV6 protocol work more efficiently. It is a further object of the invention to have a handoff procedure that works well for predictive and reactive handoff procedures of the FMIPv6 protocol. It is another object of the invention to relieve NAR from having to act as proxy to MN if the Home Agent is already doing that job. Accordingly, the present invention proposes a method to improve the efficiency of FMIPv6 protocol, when the mobile node (MN) is moving back to its home network, by reconfiguring the Fast Binding Update (FBU) message format in the existing FMIPv6 protocol to include an N flag to tell the PAR that the New Care of Address (NCoA) included in mobility options is indeed the home address of the MN, the method comprising, • Sending the FBU message to PAR by MN with its home address as its NCoA and the N flag set (indicating that it is the home address). • Forwarding the NCoA by PAR in a Handover Initiate (HI) message, whose N flag status is set according to the same in the FBU by PAR, to NAR. • Skipping the check for address collision by the NAR if the flag is set. • Returning the same NCoA in a Hack Message back to PAR. • Sending the Fast Binding Acknowledgement (FBAck) message to MN by the PAR indicating that the MN can use its home address as NCoA when it moves to its home network. These and other objects, features and advantages of the present invention will become more apparent from the ensuing detailed description of the present invention taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Figure 1 depicts a Fast Binding Update (FBU) message as per RFC 4068; Figure 2 depicts a Handover Initiate (HI) message as per RFC 4068; Figure 3 depicts the scenario of a FMIPv6 MN returning to its home network; Figure 4 depicts Fast Binding Update (FBU) message with the new flag; Figure 5 depicts Handover Initiate (HI) message with the new flag; Figure 6 depicts the sequence of messages exchanged in Predictive Fast Handover, and Figure 7 depicts the sequence of messages exchanged in Reactive Fast Handover DETAILED DESCRIPTION OF THE INVENTION The preferred embodiments of the present invention will now be explained with reference to the accompanying drawings. It should be understood however that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. The following description is not to be construed as limiting the invention and numerous specific details are described to provide a thorough understanding of the present invention, as the basis for the claims and as a basis for teaching one skilled in the art how to make and/or use the invention. However, in certain instances, well-known or conventional details are not described in order not to unnecessarily obscure the present invention in detail. The present invention proposes a method to assist a Mobile Node (MN) to use its home address as its Next Care of Address (NCoA) when returning back to its home network in the Fast handovers for Mobile IP v6 (FMIPv6) protocol operation. According to the present invention, the MN sends Router Solicitation for Proxy Advertisement (RtSolPr) message to the Previous Access Router (PAR) and gets the reply with Proxy Router Advertisement (PrRtAdv) message. This message contains the subnet information about the neighboring access points/ routers. The MN on getting the subnet information of the neighboring access points/ routers, it identifies the network to whom it is going to do the handoff is its home network. MN takes this decision based on the prefix information of home network and the prefix information of the network where it is planning to do the handoff. MN configures the NCoA for FMIPv6 operation same as its home address. MN includes this address in the Fast Binding Update (FBU) message sent to the PAR. Further the MN also sets a flag 'N' to specify that the address formed by MN is its home address. In a similar way, the MN sets an N flag in the Handover Initiate (HI) message indicating that NCoA included in mobility options is the home address of the MN. When Next Access Router (NAR) receives the HI message with the N flag set, it skips checking whether the NCoA is acceptable or not and returns the same NCoA in the Handover acknowledgement (Hack) message. In this case since Home Agent is already acting as proxy for MN, NAR will not act as proxy for MN. Figure 3 depicts the scenario of an FMIPv6 MN returning to its home network. PAR represents the Previous Access Router in the foreign network and NAR represents the Next Access Router in the home network. CN is the correspondent node. MN represents mobile node moving from the foreign network to the home network. HA represents the Home Agent. Home Agent and the NAR are two separate entities on same home network. NAP is the next access point with respect to the home network and PAP is the previous access point with respect to the foreign network respectively. NAP and PAP are optional entities and access router can also be directly connected as end point to the mobile node. Figure 4 depicts Fast Binding Update (FBU) message with the new flag. Newly added (N' flag indicates that the NCoA included in mobility options is the home address of the mobile node. When the MN is moving to its home network from a foreign network, it sends FBU message to the PAR including its home address as its prospective NCoA and also sets the 'N' flag to indicate the same in the message. PAR on receiving the FBU message with 'N' flag set, it will send HI message to NAR setting the 'N' flag. Newly added flag can be defined to any bit in the reserved field. Actual bit for the flag can be finalized as per (Internet Assigned Numbers Authority (I AN A) allocation Figure 5 depicts Handover Initiate (HI) message with the new flag. Newly added 'N' flag indicates that NCoA included in Options is the home address of the mobile node. PAR sets the 'N' flag on receiving FBU message with the 'N' flag set. NAR on receiving HI with 'N' flag set, skips checking whether NCoA is acceptable and returns the same NCoA in Hack message. On receipt of the Hack from the NAR, PAR sends the Fast Binding Acknowledgement (FBAck) message to MN. MN starts using its home address as NCoA when it moves to its home network. The Newly added flag 'N' can be defined to any bit in the reserved field. Actual bit for the flag can be finalized as per IANA allocation. FMIPv6 handoff operations work in both reactive and the predictive cases. These can be explained in detail with reference to figure 6 and figure 7 as follows. Figure 6 depicts the sequence of messages exchanged in Predictive Fast Handover. The following steps explain the sequence of events in Predictive Fast Handover. 1. MN sends Router Solicitation for Proxy Advertisement (RtSolPr) to PAR to get the neighboring subnet information 2. PAR sends the prefix information in Proxy Router Advertisement (PrRtAdv) message to MN 3. If the prefix of the neighboring subnet matches with the home address of MN, MN sends FBU to PAR with its home address as the prospective NCoA and sets the 'N' flag 4. PAR sends HI message to NAR setting 'N' flag 5. NAR on receiving HI with 'N' flag set returns the same home address in the Hack message saying it as valid 6. As Home Agent (HA) is already acting as proxy for the MN's home address, NAR will not act as proxy for MN. 7. PAR returns the same home address to MN in FBAck message and starts tunneling packets to MN's home address 8. MN immediately starts configuring home address in its home network and starts fmipv6 and mipv6 communication in the new link with its home address Figure 7 depicts the sequence of messages exchanged in Reactive Fast Handover. The following steps explain the sequence of events in Reactive Fast Handover. 1. MN encapsulates FBU in the Fast Neighbor Advertisement (FNA) message as soon as it attaches to new link. N' flag is set in the FBU if MN attaches to its home network and configures its home address. MN can also send a FNA with the 'N' flag set to avoid checking the address collision at NAR. 2. If 'N' flag is set in the encapsulated FBU message or in FNA flag, NAR will not check whether NCoA is acceptable and simply forwards FBU to PAR. 3. PAR sends FBAck to MN and starts tunneling of packets to MN's home address as specified in FMIPv6 protocol. Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are possible and are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart there from. GLOSSARY OF TERMS AND DEFINITIONS THEREOF BU : Binding Update CN : Correspondent Node CoA : Care of Address FBU : Fast Binding Update FBAck : Fast Binding Acknowledgement FNA : Fast Neighbor Advertisement. HA : Home Agent Hack : Handover Acknowledge HI : Handover Initiate MN : Mobile Node NAP : Next Access Point NAR : Next Access Router NCoA : New Care of Address PAP : Previous Access Point PAR : Previous Access Router PrRtAdv : Proxy Router Advertisement. RtSolPr : Router Solicitation for Proxy Advertisement We Claim 1. A method to improve the efficiency of FMIPv6 protocol, when the mobile node (MN) is moving back to its home network from a foreign network, by reconfiguring the Fast Binding Update (FBU) message format in the existing FMIPv6 protocol to include an N flag to tell the PAR that the New Care of Address (NCoA) included in mobility options is indeed the home address of the MN, the method comprising, • Sending the FBU message to PAR by MN with its home address as its NCoA and the N flag set (indicating that it is the home address); • Forwarding the NCoA by PAR in a Handover Initiate (HI) message, whose N flag status is set on the basis of the same in the FBU by PAR, to NAR; • Skipping the check for address collision by the NAR if the flag is set; • Returning the same NCoA in a Hack Message back to PAR; • Sending the Fast Binding Acknowledgement (FBAck) message to MN by the PAR indicating that the MN can use its home address as NCoA when it moves to its home network. 2. The method according to claim 1, wherein the new addition flag does not add new security concerns to the existing FMIPv6 operation. 3. The method according to claim 1, wherein the new flag can be assigned to any bit in the reserve field of FBU and HI. 4. The method according to claim 3, wherein the actual bit for the flag is finalized as per (Internet Assigned Numbers Authority (IANA) allocation. 5. The method according to claim 1, wherein it works for both the predictive and reactive handoff procedures of the FMIPv6 protocol. 6. The method as claimed in claim 1, wherein the NAR does not act as a proxy for MN since the Home Agent is already donning that role. 7. A method to improve the efficiency of FMIPv6 protocol, when the mobile node (MN) is moving back to its home network from a foreign network, by reconfiguring the Fast Binding Update (FBU) message format in the existing FMIPv6 protocol to include an N flag to tell the PAR that the New Care of Address (NCoA) included in mobility options is indeed the home address of the MN, substantially as herein described with reference to the accompanying drawings.

Documents:

2464-CHE-2006 FORM-1 12-08-2013.pdf

2464-CHE-2006 OTHER PATENT DOCUMENT 12-08-2013.pdf

2464-CHE-2006 AMENDED CLAIMS 12-08-2013.pdf

2464-CHE-2006 AMENDED PAGES OF SPECIFICATION 12-08-2013.pdf

2464-CHE-2006 POWER OF ATTORNEY 12-08-2013.pdf

2464-CHE-2006 AMENDED PAGES OF SPECIFICATION 07-11-2014..pdf

2464-CHE-2006 EXAMINATION REPORT REPLY RECEIVED 12-08-2013.pdf

2464-CHE-2006 EXAMINATION REPORT REPLY RECIEVED 07-11-2014..pdf

2464-CHE-2006 FORM-1 07-11-2014..pdf

2464-CHE-2006 FORM-13 12-08-2013.pdf

2464-CHE-2006 FORM-13 12-12-2013.pdf

2464-CHE-2006 POWER OF ATTORNEY 07-11-2014..pdf

2464-CHE-2006 ABSTRACT.pdf

2464-CHE-2006 CLAIMS.pdf

2464-CHE-2006 CORRESPONDENCE OTHERS.pdf

2464-CHE-2006 DESCRIPTION (COMPLETE).pdf

2464-CHE-2006 DRAWINGS.pdf

2464-CHE-2006 FORM 1.pdf

2464-CHE-2006 FORM 18.pdf

2464-CHE-2006 FORM 5.pdf

2464-CHE-2006 FORM-13 16-12-2013.pdf

2464-che-2006-correspondnece-others.pdf

2464-che-2006-description(provisional).pdf

2464-che-2006-drawings.pdf

2464-che-2006-form 1.pdf

2464-che-2006-form 26.pdf