Title of Invention

METHOD FOR QUICK DETECTION OF LAYER 3 LINK IDENTITY IN A COMMUNICATION SYSTEM

Abstract

A method for "link identification" during mobility of a host device where in the Detecting Network Attachment (DNA) in particular link identity detection with single router solicitation- router advertisement exchange, is disclosed. The host device checks the DNA prefix list and selects a prefix, which has highest lifetime. The host device identifies change in the IP connectivity by exchanging RS (with DNAPrefix), RA with the router(s). The router verifies with its prefix list and responds with "router advertisement" (RA) message. If router locates the prefix, it responds back with a message "YES". A "YES" message implies that the host device need not change its IP configuration, and assumes to be in the same subnet. If the prefix does not match the router list, the RA would be a "NO" message along with the new link information. If the message is 'NO', then the host device assumes the link change and configures the new link information. If the host device moves to a non-DNA link then it relies on the complete prefix list (CPL). Thus, the present invention optimizes the hand-over process and establishes connection with single RS-RA message.

Full Text

FIELD OF INVENTION The present invention in general relates to communication technology. In particular the present invention relates to Detecting Network Attachment (DNA) in particular link identity detection with single router solicitation- router advertisement exchange which is applicable for hosts and routers supporting DNA.. More specifically the present invention relates to a method for quick detection of layer 3 link identity. DESCRIPTION OF RELATED ART Link Identification (LinkID) specifies a protocol for link identity detection with prefix based link identifier. This method selects a prefix (called LinkID prefix) among the prefixes advertised in the link and uses this prefix for link identification. Routers advertise the LinkID in each router advertisement. Hosts compares the LinkID received in RA with the LinkID that they stored. In the case of mismatch, hosts will assume the link change. However, the system necessitates the RA to carry the LinkID prefix information, even in those cases, where it is not required. In order to synchronize the LinkID, additional mechanisms are used, which adds to the complexity. If the link change occurs, host may not get all the information in one RA to configure in new link and it requires a fast RA mechanism. DNAv6 identifies the link by a set of prefixes that are assigned to the link. In this method, host chooses one of the prefixes as landmark prefix, and includes this option to know the link change. Host includes the landmark option in router solicitation to know the link identity asking if it is still attached to same link. Router(s) will reply with "Yes" or "No" in router advertisement. In the case of "No", routers try to include as much information as possible. However the method involves difficulty in synchronization of prefixes. Because of lack of synchronization, host may receive incorrect answers. In this system, host needs to compare all the prefixes in the RA with CPL maintained in the host side, even in the case of "No" answer from router. This method also requires fast RA mechanism. In US patent number 20040203596 titled," Mobile unit attachment / update to cellular communication network", for reducing IP level signaling and radio resource load during the attachment or update, e.g. L3 or IP attachment/update, of a mobile unit to a cellular wireless communication network, preferably an IPv6 based network, wherein access network elements and routing network elements are provided, an identification element is transmitted from the mobile unit to one of the access network elements. The identification element indicates a current attachment of the mobile unit to one of the routing network elements. The transmitted identification element is checked so as to determine whether the access network element is provided with a connection to the one routing network element. Furthermore, it is checked whether a network status still allows the usage of this routing network element by the mobile unit. If both of these criteria are fulfilled, the attachment or update procedure between the mobile unit and the access network element is completed while the attachment of the mobile unit to the routing network element is retained unaffected. This attachment is executable when the mobile unit moves from one cell area to another cell area, or when a network status concerning the attachment of the mobile unit has changed, or when a predetermined period of time is expired while the mobile unit remains in the same cell area. However, this patent publication does not specifically describe the use of DNA prefix list. Another US Patent numbered 6959009 and titled," Address acquisition", describes a method for a mobile station to acquire a IP network address from a gateway in GPRS system. First the mobile station generates a link identifier. Next the mobile requests a network address by sending a link identifier over a wireless to a gateway along with a request for the gateway to check to see if the link identifier is unique. Upon receiving the network address request the gateway checks to see if the link identifier is unique. The gateway responses by either confirming that the network link identifier is unique or by sending a different unique link identifier to the mobile station. The gateway also has the ability to respond by sending a network prefix to the mobile station. Upon receiving the network prefix the mobile station combines the network prefix with the interface identifier to generate an IP network address. However, the patent publication describes configuration of IP address based on the generated link identifier and received network prefix from the gateway. Moreover, the mobile station randomly generates link identifier, which may not be based on the DNA prefix list. In yet another US 20050041634 titled," Verifying location of a mobile node", the patent publication describes a method for updating the address of a mobile node. The mobile node sends HoA (home address) to the AR (access router) via router solicitation (RS) message. The AR authenticates the HoA and returns with a signature to the mobile node via router advertisement (RA) message. The mobile node sends a binding update message incorporating both HoA and received AR signature to the correspondent node (CN). The correspondent node verifies the signature and confirms whether AR is an authorized one. If it is an authorized router, the connection is continued and if not, AR sends a request to the mobile node to update with a new address and establish a new connection with the network. SUMMARY OF THE INVENTION The basic object of the present invention is to provide a link identity method to identify the link in less time, which is noval. The invention proposes a method for link identification using single router solicitation - router advertisement exchange. This method uses prefix for link identification. In this method, routers do not require routers to synchronize the prefixes on the link. • Synchronization: - Since this method does not rely on learned prefixes > Unlike, LinkID method, this method does not required additional mechanisms there by adding complexity to synchronize prefixes. > Unlike, Landmark method, this method always gives the correct answer. • Processing Complexity > Since RS is unicast message, all the routers in the link need not process RS unlike multicast RS. > While processing RS at router, router needs to compare only PIOs. No Fast Router Advertisement mechanism is required. Accordingly this invention explains a method for quick detection of layer 3 link identity in a communication system comprising the steps of: maintaining the router(s) address(es) by Host corresponding to DNA Prefix; maintaining the router(s) address (es) by host corresponding to other prefixes; sending unicast RS(s) with DNAPrefix by the host whenever a link change trigger comes; sending unicast RA by router with "YES" or "NO" answer in response to unicast RS by comparing with only a subset of total prefixes; and assuming link change by the host if it does not receive RA. Host selects one of the prefixes advertised in the link as a DNAPrefix based on the following criteria: a. Prefix is used to configure the address on that interface; and b. Prefix has highest life time among such prefixes. Host stores the address of the router that has sent the DNAPrefix in PIO (Prefix Information Option) of the router advertisement. If the DNAPrefix is advertised in PIO by more than one router, host stores all such routers' addresses. Host is adapted to maintain router addresses corresponding to more than one prefix. If DNAPrefix becomes invalid, host selects the new DNAPrefix. When host needs to identify the link host sends a router solicitation with DNAPrefix which is a unicast message, destined to router (s) corresponding to DNAPrefix. Router that receives RS with DNAPrefix, checks if DNAPrefix is present in the prefixes that it is advertising. If prefix is present, the router sends RA with "YES" answer and if prefix is not present, the router sends RA with "NO" answer. After receiving RA, host checks for link identify and if the answer in RA is "YES", host assumes that IP connectivity is changed. After receiving RA, host checks for link identify and if the answer in RA is "NO", host assumes that IP connectivity is not changed. These and other objects, features and advantages of the present invention will become more apparent from the ensuing detailed description of the invention taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Figure 1 depicts the present invention. 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 and drawings are 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. Referring to figure 1 it shows a possible scenario where this invented method is applicable. AP1 and AR1 are the access point and access router with which host is previously associated with. AP2 and AR2 are the access point and access router with which host is currently associated with. Host will perform the procedures described in this invention to detect if its Iayer3 connection is changed or not after attaching to AP2. IP protocol is used in many of the existing wired and wireless networks and expanding to different wireless networks. Future networks will rely on packet switching and will be based on IP, both in wireless and wired parts of the network. To support the mobility in these networks, nodes shall detect the change in the IP connectivity, so that it can modify its configuration as per new subnet. Nodes can not assume the change in IP connectivity based on the change in the layer-2 association, since IP subnet can span more than one layer-2 link. So when a mobile node gets the hint of change in IP connectivity (Ex: - layer-2 association change), node has to verify if its IP subnet is changed. Node shall check the change in connectivity as soon as possible so that handoff latency will be small there by service disruption can be minimized. To detect the IP connectivity, an identifier shall be there and node has to be provided with identifier to detect the IP connectivity. Router Solicitation and Router Advertisement is used to communicate the identifier. The operation of the proposed invention is described herein: 1) Host selects one of the prefixes advertised in the link as a DNAPrefix based on the following criteria a. Prefix is used to configure the address on that interface. b. Prefix has highest life time among such prefixes. 2) Host stores the address of the router that has sent the DNAPrefix in PIO (Prefix Information Option) of the router advertisement. In case the DNAPrefix is advertised (in PIO) by more than one router, host stores all such routers' addresses. 3) For robustness, host can maintain router addresses corresponding to more than one prefix. 4) If DNAPrefix becomes invalid, host has to select the new DNAPrefix based on the method specified in 1. 5) Whenever host needs to identify the link (Ex: - Node wants to identify the change in the link to perform mobility procedures), host will send a router solicitation with DNAPrefix. a. This RS is a unicast message, destined to router (s) corresponding to DNAPrefix. b. Landmark option format defined in [DNAv6] draft can be used to send DNAPrefix in RS. 6) A router that receives RS with DNAPrefix, a. Checks if DNAPrefix is present in the prefixes that it is advertising. b. If prefix is present, the router sends RA with "YES" answer. c. If prefix is not present, the router sends RA with "NO" answer. d. Landmark option format defined in [DNAv6] draft can be used to send the "YES" or "NO" answers in RA. 7) After receiving RA, host checks for link identify as follows a. If the answer in RA is "YES", host assumes that IP connectivity is not changed. b. If the answer in RA is "NO", host assumes that IP connectivity is changed. 8) If the host does not receive RA, it will assume the link change. It will also be obvious to those skilled in the art that other control methods and apparatuses can be derived from the combinations of the various methods and apparatuses of the present invention as taught by the description and the accompanying drawings and these shall also be considered within the scope of the present invention. Further, description of such combinations and variations is therefore omitted above. It should also be noted that the host for storing the applications include but not limited to a microchip, microprocessor, handheld communication device. 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 therefrom. GLOSSARY OF TERMS AND DEFINITIONS THEREOF AR - Access Router DNA - Detecting Network Attachment MN - Mobile Node PIO - Prefix Information Option RA - Router Advertisement RS - Router Solicitation REFERENCES [LinkID] Choi & Madanapalli DNA Solution: Link Identifier based approach, draft-jinchoi-dna-protocol2-01.txt, June 2005 [DNAv6] Kempf, et al. Detecting Network Attachment in IPv6 Networks (DNAv6), draft-pentland-dna-protocol-01.txt, July 2005

Documents:

2472-CHE-2006 CORRESPONDENCE OTHERS 14-05-2013.pdf

2472-CHE-2006 EXAMINATION REPORT REPLY RECEIVED 27-03-2013.pdf

2472-CHE-2006 POWER OF ATTORNEY 14-05-2013.pdf

2472-CHE-2006 POWER OF ATTORNEY 27-03-2013.pdf

2472-CHE-2006 AMENDED CLAIMS 27-03-2013.pdf

2472-CHE-2006 AMENDED PAGES OF SPECIFICATION 27-03-2013.pdf

2472-CHE-2006 FORM-1 27-03-2013.pdf

2472-CHE-2006 FORM-13 27-03-2013.pdf

2472-CHE-2006 FORM-5 27-03-2013.pdf

2472-CHE-2006 OTHER PATENT DOCUMENT 27-03-2013.pdf

2472-CHE-2006 FORM 18.pdf

2472-che-2006-abstract.pdf

2472-che-2006-claims.pdf

2472-che-2006-correspondnece-others.pdf

2472-che-2006-description(complete).pdf

2472-che-2006-drawings.pdf

2472-che-2006-form 1.pdf

2472-che-2006-form 26.pdf