Title of Invention

METHOD OF ROUTING AN INTERNET PROTOCOL VERSION 6 DATA PACKET IN AN INTERNET PROTOCOL VERSION 4 BASED NETWORK ENVIRONMENT

Abstract

The present invention relates to IPv6 technology and particularly to a method for IPv6 cloud discovery over IPV4 backbone. This invention explains a method for IPv6 cloud discovery over ipv4 backbone in a network system comprising plurality of Dual-Stack Border Routers connected through IPv4 for providing IPv6 connectivity, the said method comprising the steps of: at the Dual-Stack Border Router/Host: Joining a multicast group/using shared-unicast for sharing IPv6 reachability information; Triggering Route Reachability Info request using ICMPv6 if no match to an IPv6 destination is found in the IPv6 routing table; Constructing ICMPv6 IPV6_R0UTEJNF0 Request/Reply message; Encapsulating ICMPv6 IPV6_R0UTEJNF0 Request message in an IPv4 packet and transmitting it to a multicast/shared-unicast destination; Decapsulating IPv4 packet containing ICMPV6 IPv6_R0UTEJNF0 REQUEST/REPLY message after receiving it and processing ; Triggering route lookup for IPv6 host/network address on processing IPv6_R0UTEJNF0 REQUEST message; Constructing ICMPv6 IPV6_R0UTEJNF0 REPLY message in response to IPV6_R0UTEJNF0 Request; and Encapsulating ICMPv6 IPV6_R0UTEJNF0 REPLY message in an IPv4 packet and transmitting it.

Full Text

FIELD OF TECHNOLOGY The present invention relates to IPv6 technology. More particularly the present invention relates to a method for ipv6 cloud discovery over IPV4 backbone. DESCRIPTION OF THE RELATED ART Manual configuration:- Using manual configuration, bi-directional IPv6-in-IPv4 tunnels have to be configured on the border routers that separated by v4 Network. No other method is available to discover the reachability to IPv6 networks if no default route is present in IPv6 routing table at the Dual-Stack border router. However the Manual Configuration method is tedious and if no route to reach IPv6 destination is available, then packets are discarded by Dual-Stack Border Router. SUMMARY OF THE INVENTION Currently IPv4 to IPv6 transition is in initial stage of development. Hence, many IPv6 networks are coming up and there is need for connectivity between these clouds through IPv4 back bone. For this IPv6-in-IPv4 tunnels between the clouds establish the IPv6 connectivity transparently to the IPv6 nodes in the clouds over IPv4 backbone/infrastructure. The primary object of this invention is to provide a method for discovering the route to isolated IPv6 clouds over IPv4 backbone/infrastructure in case no route is available. This method can be used to discover the route to a destination IPv6 host/network over IPv4 backbone. This method uses new ICMPv6 messages for obtaining route reachability information. The dual-stack (IPv4/IPv6) border routers exchange the ICMPv6 messages to obtain reachability of a destination IPv6 host/network if and only if the default route is not available in the IPv6 routing table in the dual-stack border router. It may also use any administrator-defined trigger mechanism to initiate the discovery process. The method uses IPv6-in-IPv4 encapsulation/decapsulation to send/receive the ICMPv6 messages defined in this invention. This method automates the process of identifying the IPv4 address of the tunnel-end point on the Dual-Stack Router/Host which can reach the destination IPv6 host. This method is very easy to implement and requires very minimal implementation changes to existing equipments. In case the Dual-Stack Border Router/Host implementing this method is unable to get any replies for the requests, it returns ICMPv6 Host/Network Unreachable message to IPv6 Source as per current RFC standards/implementations. This method automates the process of identifying the IPv4 address of the tunnel-end point on the Dual-Stack Router/Host which can reach the destination IPv6 host. Accordingly the present invention relates to a network system comprising two or more Dual-Stack Border Routers connected through IPv4 for providing IPv6 connectivity for their network IPv6 nodes or isolated Dual-Stack hosts with only IPv4 connectivity, a method comprising the steps of: • At the Dual-Stack Border Router/Host: i. Joining a multicast group/using shared-unicast for sharing IPv6 reachability information. ii. Triggering Route Reachability Info request using ICMPv6 if no match to an IPv6 destination is found in the IPv6 routing table. iii. Constructing ICMPv6 IPV6_ROUTE_INFO Request/Reply message. iv. Encapsulating ICMPv6 IPV6_ROUTE_INFO Request message in an IPv4 packet and transmitting it to a multicast/shared-unicast destination. v. Decapsulating IPv4 packet containing ICMPV6 I Pv6_ROUTE_l N FO REQUEST/REPLY message after receiving it and processing of the same. vi. Triggering route lookup for IPv6 host/network address on processing IPv6_ROUTE_INFO REQUEST message. vii. Constructing ICMPv6 IPV6_ROUTE_INFO REPLY message in response to IPV6_ROUTE_INFO Request. viii. Encapsulating ICMPv6 IPV6_ROUTE_INFO REPLY message in an IPv4 packet and transmitting it Accordingly the present invention relates to a method comprising, ICMPv6 instructing the data link layer abstraction to create IPv6-in-IPv4 tunnel with the pair Accordingly the present invention relates to a method further comprising, addition of route entry for an IPv6 host/network after creating the tunnel by using this invention. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Figure 1 depicts the new ICMPv6 message used for carrying the IPv4 address of the border router/host which will be used for the creation of IPv6-in-IPv4 tunnel. Figure 2 depicts an example scenario of two IPv6 clouds separated by v4 network, where this method is helpful. BRIEF DESCRIPTION OF THE INVENTION A number of IPv4 to IPv6 Transition mechanisms like Tunneling, Translation and Dual-Stack Transition Mechanisms are currently being used to enable IPv4 and IPv6 to co-exist and co-work during the transition phase. Tunneling is the most common transition mechanism deployed world-wide. There is a growing awareness among the standards committees like IETF, 3GPP and 3GPP2 to make efforts to develop and deploy methods to automate the process of establishing IPv6-in-IPv4 tunnels so that isolated IPv6 networks or hosts can obtain connectivity to other such IPv6 networks or hosts over IPv4 backbone networks with very minimal changes to existing protocols and equipments. In this invention a method to automate the discovery of IPv6 networks or hosts over IPv4 backbone is proposed. This method provides an almost zero-configuration solution. For this method, we assume the presence of Border Routers with Dual-Stack (supports both IPv4 and IPv6) capability. These border routers will act as default/gateway routers for one or more IPv6 networks connected to its downstream links. The upstream links from these border routers are connected to IPv4 backbone networks. The proposed method will be implemented in these Dual-Stack Border Routers or in any isolated Dual-Stack host with only IPv4 connectivity. All the Dual-Stack nodes which want to send/receive and process the messages shall a multicast group address or a shared-unicast address as applicable depending on whether IPv4 multicasting is supported or not. This method will be triggered: 1. If there is a no network specific match for the destination IPv6 network/host address in the routing table and also no default entry in the routing table. 2. Administrator-defined triggers or other events like attachment of new IPv6 cloud. New ICMP messages are being proposed and will be used by this invention. The following are the description of various fields in the message: The first 4-bytes are part of any standard ICMPv6 message. TYPE-1 PV6_RO UTE_I N FO (The value of this ICMPv6 message will be requested and obtained from IANA after PATENT filing.) CODE - REQUEST or REPLY (The value of thess ICMPv6 message codes will be requested and obtained from IANA after PATENT filing.) CHECKSUM - As per ICMPv6 standards specification. RESERVED - Always set to 0 (ZERO). ICMPv6 message code is set to REQUEST, the sender (Dual-Stack Border Router's IPv6 Address belonging to same network as IPv6 Source Host) is the one transmitting the message and the target is the actual IPv6 destination whose reachability information is being checked. ICMPv6 message code is set to REQUEST, the sender is the one which has IPv6 destination reachiability information and the target is the Dual-Stack Border Router which sent the REQUEST. When the CODE is set to REQUEST, the following fields are filled as mentioned by the Host/router sending this message: SENDER PREFIX LENGTH - Prefix Length of the Sender's IPv6 Address. SENDER IPv6 ADDRESS - Sender's IPv6 host/network address. SENDER IPv4 ADDRESS - Sender's IPv4 Address. TARGET PREFIX LENGTH - Always set to 128. TARGET IPv6 ADDRESS - Target IPv6 Address for which we are trying to discover the reachability. TARGET IPv4 ADDRESS - Always set to 0. When the CODE is set to REPLY, the following fields are filled as mentioned by the Host/router sending this message: RESERVED - Always set to 0 (ZERO). SENDER PREFIX LENGTH - Prefix Length of the Sender's IPv6 Address. SENDER IPv6 ADDRESS - Sender's IPv6 host/network address. SENDER IPv4 ADDRESS - Sender's IPv4 Address. TARGET PREFIX LENGTH - Set to 128 by default. TARGET IPv6 ADDRESS - Value same as SENDER IPv6 ADDRESS as in ICMPv6 message code set to REQUEST. TARGET IPv4 ADDRESS - Value same as SENDER IPv4 ADDRESS as in ICMPv6 message code set to REQUEST. The brief description about the steps involved in the invention is described herein : 1. Any IPv6 packet from IPv6 Source Host and destined to another IPv6 host is routed to its Dual-Stack Border Router (designated DSBR-1). 2. Route lookup is done at the DSBR-1 for the destination IPv6 host. 3. If the Route lookup fails at DSBR-1, it triggers ICMPv6 Route Reachability Request. 4. The DSBR-1 then forms an ICMPv6 with a TYPE_ROUTE_INFO (with REQUEST code) message for destination IPv6 address reachability. (Prefix information and IPv4 of DSBR-1) 5. This ICMPv6 message in an IPv6 packet is then tunneled in an IPv4 packet (source address in IPv4 packet - DSBR1-IPv4 unicast address, destination address in IPv4 packet - Multicast group address [TBD] or Shared-Unicast address). 6. Other Dual-Stack Router(s) receive this packet from DSBR-1. 7. If member of multicast group or shared-unicast address, then the DSBR decapsulates the tunneled packet. 8. The ICMPv6 processes this TYPE_REQUEST_INFO message (with REQUEST code). 9. The DSBR then looks up in its IPv6 routing table for a match to the destination IPv6 (TARGET IPv6 ADDRESS information in ICMPv6 message). 10. If the route lookup is successful then DSBR (identified as DSBR-n) forms an ICMPv6 TYPE_REQUESTJNFO message (with REPLY code). 11. The DSBR-n then sends this ICMPv6 message in an IPv6 packet is then tunneled in an IPv4 packet (source address in IPv4 packet - DSBR-n, destination address in IPv4 packet-DSBR-1). 12. DSBR-1 selects from the multiple replies, the route satisfying longest prefix match and creates a tunnel to that DSBR.(DSBR-n) 13. DSBR-1 also adds an route entry in the IPv6 routing table destination IPv6 host/network address, prefix length, outgoing interface is the tunnel interface created in the above step>. 14. DSBR-1 then sends the currently held IPv6 packet or any further packets destined to destination IPv6 tunneled in an IPv4 unicast packet, (source address in IPv4 packet - DSBR-1, destination address in IPv4 - DSBR-n). 15. DSBR-n then decapsulates the tunneled packet and routes the IPv6 packet to destination IPv6. 16. If DSBR-1 does not get any replies, it then sends an ICMPv6 Host/Network unreachable to the IPv6 source. The Operation described above is applicable to cases wherein Dual-Stack Border Router might also be the source/destination of the IPv6 packet. It is also applicable to cases wherein Dual-Stack Border Router might be the source/destination of the IPv6 packet and there is no IPv6 network in its downlink. In such cases the Dual-Stack Border Router acts like a Dual-Stack host with only IPv4 connectivity. Glossary of Terms and their definitions: IPv4 :- Internet Protocol Version 4 IPv6 :- Internet Protocol Version 6 DSBR :- Dual-Stack Border Router which support both IPv4 and IPv6 capability. ICMPv6 :- Internet Control Messages for IPv6. IPv6-in-IPv4:- IPv6 packets encapsulated in an IPv4 packet. Dated this 7th day of October 2004 R. JEEVANANDHAM Patent Agent Agent for the Applicant References Application No. Total No. of Pages 2 Samsung Electronics Co. Ltd., India Software Operations Page 1 TYPE CODE CHECKSUM RESERVED SENDER PREFIX LENGTH 128-bits SENDER IPv6 ADDRESS 32-bKs SENDER IPv4 ADDRESS RESERVED TARGET PREFIX LENGTH Signature R. JEEVANANDHAM 128-btts TARGET IPv6 ADDRESS 32-bits TARGET IPv4 ADDRESS Figure 1 Patent Agent Agent for the Applicant Application No. Total No. of Pages 2 Page 2 Samsung Electronics Co. Ltd., India Software Operations Dual-stack bd Dual-stack bd rder Router 2 irder Router 1 IfWlRtjMpBt Figure 2 FORM 2 THE PATENTS ACT, 1970 [39 of 1970] COMPLETE SPECIFICATION (Section 10; Rule 13) A METHOD FOR IPV6 CLOUD DISCOVERY OVER IPV4 BACKBONE SAMSUNG INDIA SOFTWARE OPERATIONS PRIVATE Ltd. BAGMANE LAKEVIEW, BLOCK 'B\ No. 66/1, BAGMANE TECH PARK, C V RAMAN NAGAR, BYRASANDRA , BANGALORE - 560093 A wholly owned subsidiary of Samsung Electronics Company Limited, Korea, [an Indian Company] The following Specification particularly describes the nature of the invention and the manner in which it is to be performed FIELD OF TECHNOLOGY The present invention relates to IPv6 technology. Further, this invention relates to cloud discovery in IPv6 technology. More particularly, the present invention relates to a method for IPv6 cloud discovery over IPv4 backbone. DESCRIPTION OF RELATED ART Manual configuration: Using manual configuration, bi-directional IPv6-in-IPv4 tunnels have to be configured on the border routers that separated by v4 Network. No other method is available to discover the reachability to IPv6 networks if no default route is present in IPv6 routing table at the Dual-Stack border router. However the Manual Configuration method is tedious and if no route to reach IPv6 destination is available, then packets are discarded by Dual-Stack Border Router. SUMMARY OF THE INVENTION Currently IPv4 to IPv6 transition is in initial stage of development. Hence, many IPv6 networks are coming up and there is need for connectivity between these clouds through IPv4 backbone. For this IPv6-in-IPv4 tunnels between the clouds establish the IPv6 connectivity transparently to the IPv6 nodes in the clouds over IPv4 backbone/infrastructure. The primary object of this invention is to provide a method for discovering the route to isolated IPv6 clouds over IPv4 backbone/infrastructure in case no route is available. This method can be used to discover the route to a destination IPv6 host/network over IPv4 backbone. This method uses new ICMPv6 messages for obtaining route reachability information. The dual-stack (IPv4/IPv6) border routers exchange the ICMPv6 messages to obtain reachability of a destination IPv6 host/network if and only if the default route is not available in the IPv6 routing table in the dual-stack border router. It may also use any administrator-defined trigger mechanism to initiate the discovery process. The method uses IPv6-in-IPv4 encapsulation/decapsulation to send/receive the ICMPv6 messages defined in this invention. This method automates the process of identifying the IPv4 address of the tunnel-end point on the Dual-Stack Router/Host which can reach the destination IPv6 host. This method is very easy to implement and requires very minimal implementation changes to existing equipments. In case the Dual-Stack Border Router/Host implementing this method is unable to get any replies for the requests, it returns ICMPv6 Host/Network Unreachable message to IPv6 Source as per current RFC standards/implementations. This method automates the process of identifying the IPv4 address of the tunnel-end point on the Dual-Stack Router/Host which can reach the destination IPv6 host. Accordingly the present invention relates to a network system comprising two or more Dual-Stack Border Routers connected through IPv4 for providing IPv6 connectivity for their network IPv6 nodes or isolated Dual-Stack hosts with only IPv4 connectivity, a method comprising the steps of: • At the Dual-Stack Border Router/Host: i. Joining a multicast group/using shared-unicast for sharing IPv6 reachability information. ii. Triggering Route Reachability Info request using ICMPv6 if no match to an IPv6 destination is found in the IPv6 routing table. iii. Constructing ICMPv6 IPV6_ROUTE_INFO Request/Reply message. iv. Encapsulating ICMPv6 IPV6_ROUTE_INFO Request message in an IPv4 packet and transmitting it to a multicast/shared-unicast destination. v. Decapsulating IPv4 packet containing ICMPV6 I Pv6_ROUTEJ NFO REQUEST/REPLY message after receiving it and processing of the same. vi. Triggering route lookup for IPv6 host/network address on processing IPv6_ROUTE_INFO REQUEST message. vii. Constructing ICMPv6 IPV6_ROUTE_INFO REPLY message in response to IPV6_ROUTE_INFO Request. viii. Encapsulating ICMPv6 IPV6_ROUTE_INFO REPLY message in an IPv4 packet and transmitting it Accordingly the present invention relates to a method comprising, ICMPv6 instructing the data link layer abstraction to create IPv6-in-IPv4 tunnel with the pair The said method is triggered if there is a no network specific match for the destination IPv6 network/host address in the routing table and also no default entry in the routing table. The said method is triggered by administrator-defined triggers or other events like attachment of new IPv6 cloud. Any IPv6 packet from IPv6 Source Host and destined to another IPv6 host is routed to a first DSBR. The Route lookup is done at the said first DSBR for the destination IPv6 host. If the Route lookup fails at the said first DSBR , it triggers ICMPv6 Route Reachability Request. The first DSBR forms an ICMPv6 with a TYPE_ROUTE_INFO message for destination IPv6 address reachability. The ICMPv6 message in an IPv6 packet is tunneled in an IPv4 packet where the source address in IPv4 packet is first DSBR, IPv4 unicast address and destination address in IPv4 packet is Multicast group address or Shared-Unicast address. The Other Dual-Stack Routers receive the said packet from first DSBR and if it is a member of multicast group or shared-unicast address, then the DSBR decapsulates the tunneled packet. The ICMPv6 processes the TYPE_REQUEST_I NFO message with REQUEST code. The DSBR looks up in its IPv6 routing table for a match to the destination IPv6. If the route lookup is successful then DSBR-n forms an ICMPv6 TYPE_REQUEST_INFO message with REPLY code. The DSBR-n then sends the ICMPv6 message in an IPv6 packet and tunnels it in an IPv4 packet having source address in IPv4 packet as DSBR-n, and destination address in IPv4 packet as first DSBR. First DSBR selects from the multiple replies, the route satisfying longest prefix match and creates a tunnel to the DSBR-n. First DSBR adds a route entry in the IPv6 routing table. Then first DSBR sends the currently held IPv6 packet or any further packets destined to destination IPv6 tunneled in an IPv4 unicast packet having source address in IPv4 packet as first DSBR, and destination address in IPv4 as DSBR-n. Then DSBR-n decapsulates the tunneled packet and routes the IPv6 packet to destination IPv6. If first DSBR does not get any replies, it then sends an ICMPv6 Host/Network unreachable to the IPv6 source. Accordingly, the present invention relates to a method further comprising, addition of route entry for an IPv6 host/network after creating the tunnel by using this invention. The other objects, features and advantages of the present invention will be apparent from ensuing the detailed description of the invention taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Figure 1 depicts the new ICMPv6 message used for carrying the IPv4 address of the border router/host which will be used for the creation of IPv6-in-IPv4 tunnel. Figure 2 depicts an example scenario of two IPv6 clouds separated by v4 network, where this method is helpful. 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. A number of IPv4 to IPv6 Transition mechanisms like Tunneling, Translation and Dual-Stack Transition Mechanisms are currently being used to enable IPv4 and IPv6 to co-exist and co-work during the transition phase. Tunneling is the most common transition mechanism deployed world-wide. There is a growing awareness among the standards committees like IETF, 3GPP and 3GPP2 to make efforts to develop and deploy methods to automate the process of establishing IPv6-in-IPv4 tunnels so that isolated IPv6 networks or hosts can obtain connectivity to other such IPv6 networks or hosts over IPv4 backbone networks with very minimal changes to existing protocols and equipments. In this invention a method to automate the discovery of IPv6 networks or hosts over IPv4 backbone is proposed. This method provides an almost zero-configuration solution. Figure 1 depicts the new ICMPv6 message used for carrying the IPv4 address of the border router/host which will be used for the creation of IPv6-in-IPv4 tunnel. The following is the description of various fields in the message: TYPE -1PV6_ROUTE_lNFO (The value of this ICMPv6 message will be requested and obtained from IANA for public use.) CODE - REQUEST or REPLY (The value of these ICMPv6 message codes will be requested and obtained from IANA after PATENT filing.) CHECKSUM - As per ICMPv6 standards specification. RESERVED - Always set to 0 (ZERO). ICMPv6 message code is set to REQUEST, the sender (Dual-Stack Border Router's IPv6 Address belonging to same network as IPv6 Source Host) is the one transmitting the message and the target is the actual IPv6 destination whose reachability information is being checked. ICMPv6 message code is set to REQUEST, the sender is the one which has IPv6 destination reachability information and the target is the Dual-Stack Border Router which sent the REQUEST. When the CODE is set to REQUEST, the following fields are filled as mentioned by the node/router sending this message: SENDER PREFIX LENGTH - Prefix Length of the Sender's IPv6 Address. SENDER IPv6 ADDRESS - Sender's I Pv6 host/network address. SENDER IPv4 ADDRESS - Sender's IPv4 Address. TARGET PREFIX LENGTH - Always set to 128. TARGET IPv6 ADDRESS - Target I Pv6 Address for which we are trying to discover the reachability. TARGET IPv4 ADDRESS - Always set to 0. When the CODE is set to REPLY, the following fields are filled as mentioned by the node/router sending this message: RESERVED - Always set to 0 (ZERO). SENDER PREFIX LENGTH - Prefix Length of the Sender's IPv6 Address. SENDER IPv6 ADDRESS - Sender's IPv6 host/network address. SENDER IPv4 ADDRESS - Sender's I Pv4 Address. TARGET PREFIX LENGTH - Set to 128 by default. TARGET IPv6 ADDRESS - Value same as SENDER IPv6 ADDRESS as in ICMPv6 message code set to REQUEST. TARGET IPv4 ADDRESS - Value same as SENDER IPv4 ADDRESS as in ICMPv6 message code set to REQUEST Figure 2 depicts an example scenario of two IPv6 clouds separated by v4 network, where this method is helpful. More precisely the figure shows two IPv6-only hosts which are behind the Dual Stack Border routers separated by IPv4-only Internet. For the two hosts (IPv6 Host 1 & 2) to communicate to each other, the border routers tunnels the IPv6 packets through the IPv4-only Internet. For this method, we assume the presence of Border Routers with Dual-Stack (supports both IPv4 and IPv6) capability. These border routers will act as default/gateway routers for one or more IPv6 networks connected to its downstream links. The upstream links from these border routers are connected to IPv4 backbone networks. The proposed method will be implemented in these Dual-Stack Border Routers or in any isolated Dual-Stack host with only IPv4 connectivity. All the Dual-Stack nodes which want to send/receive and process the messages shall a multicast group address or a shared-unicast address as applicable depending on whether IPv4 multicasting is supported or not. This method will be triggered: 1. If there is a no network specific match for the destination IPv6 network/host address in the routing table and also no default entry in the routing table. 2. Administrator-defined triggers or other events like attachment of new IPv6 cloud. New ICMP messages are being proposed and will be used by this invention. The following are the description of various fields in the message: The first 4-bytes are part of any standard ICMPv6 message. TYPE -1PV6_ROUTE_lNFO (The value of this ICMPv6 message will be requested and obtained from IANA after PATENT filing.) CODE - REQUEST or REPLY (The value of thess ICMPv6 message codes will be requested and obtained from IANA after PATENT filing.) CHECKSUM - As per ICMPv6 standards specification. RESERVED - Always set to 0 (ZERO). ICMPv6 message code is set to REQUEST, the sender (Dual-Stack Border Router's IPv6 Address belonging to same network as IPv6 Source Host) is the one transmitting the message and the target is the actual IPv6 destination whose reachability information is being checked. ICMPv6 message code is set to REQUEST, the sender is the one which has IPv6 destination reachability information and the target is the Dual-Stack Border Router which sent the REQUEST. When the CODE is set to REQUEST, the following fields are filled as mentioned by the Host/router sending this message: SENDER PREFIX LENGTH - Prefix Length of the Sender's IPv6 Address. SENDER IPv6 ADDRESS - Sender's IPv6 host/network address. SENDER IPv4 ADDRESS - Sender's IPv4 Address. TARGET PREFIX LENGTH - Always set to 128. TARGET IPv6 ADDRESS - Target I Pv6 Address for which we are trying to discover the reachability. TARGET IPv4 ADDRESS - Always set to 0. When the CODE is set to REPLY, the following fields are filled as mentioned by the Host/router sending this message: RESERVED - Always set to 0 (ZERO). SENDER PREFIX LENGTH - Prefix Length of the Sender's IPv6 Address. SENDER IPv6 ADDRESS - Sender's IPv6 host/network address. SENDER IPv4 ADDRESS - Sender's IPv4 Address. TARGET PREFIX LENGTH - Set to 128 by default. TARGET IPv6 ADDRESS - Value same as SENDER IPv6 ADDRESS as in ICMPv6 message code set to REQUEST. TARGET IPv4 ADDRESS - Value same as SENDER IPv4 ADDRESS as in ICMPv6 message code set to REQUEST. The brief description about the steps involved in the invention is described herein : 1. Any IPv6 packet from IPv6 Source Host and destined to another IPv6 host is routed to its Dual-Stack Border Router (designated DSBR-1). 2. Route lookup is done at the DSBR-1 for the destination IPv6 host. 3. If the Route lookup fails at DSBR-1, it triggers ICMPv6 Route Reachability Request. 4. The DSBR-1 then forms an ICMPv6 with a TYPE_ROUTE_INFO (with REQUEST code) message for destination IPv6 address reachability. (Prefix information and IPv4 of DSBR-1) 5. This ICMPv6 message in an IPv6 packet is then tunneled in an IPv4 packet (source address in IPv4 packet - DSBR1-IPv4 unicast address, destination address in IPv4 packet - Multicast group address [TBD] or Shared-Unicast address). 6. Other Dual-Stack Router(s) receive this packet from DSBR-1. 7. If member of multicast group or shared-unicast address, then the DSBR decapsulates the tunneled packet. 8. The ICMPv6 processes this TYPE_REQUEST_INFO message (with REQUEST code). 9. The DSBR then looks up in its IPv6 routing table for a match to the destination IPv6 (TARGET IPv6 ADDRESS information in ICMPv6 message). 10. If the route lookup is successful then DSBR (identified as DSBR-n) forms an ICMPv6 TYPE_REQUEST_INFO message (with REPLY code). 11. The DSBR-n then sends this ICMPv6 message in an IPv6 packet is then tunneled in an IPv4 packet (source address in IPv4 packet - DSBR-n, destination address in IPv4 packet - DSBR-1). 12. DSBR-1 selects from the multiple replies, the route satisfying longest prefix match and creates a tunnel to that DSBR.(DSBR-n) 13. DSBR-1 also adds an route entry in the IPv6 routing table . 14. DSBR-1 then sends the currently held IPv6 packet or any further packets destined to destination IPv6 tunneled in an IPv4 unicast packet, (source address in IPv4 packet - DSBR-1, destination address in IPv4 - DSBR-n). 15. DSBR-n then decapsulates the tunneled packet and routes the IPv6 packet to destination IPv6. 16. If DSBR-1 does not get any replies, it then sends an ICMPv6 Host/Network unreachable to the IPv6 source. The Operation described above is applicable to cases wherein Dual-Stack Border Router might also be the source/destination of the IPv6 packet. It is also applicable to cases wherein Dual-Stack Border Router might be the source/destination of the IPv6 packet and there is no IPv6 network in its downlink. In such cases the Dual-Stack Border Router acts like a Dual-Stack host with only IPv4 connectivity. The above-presented description is of the best mode contemplated for carrying out the present invention. The manner and process of making and using it is in such a full, clear, concise and exact terms as to enable to any person skilled in the art to which it pertains to make and use this invention. New embodiments in particular, which also lie within the scope of the invention can be created, in which different details of the different examples can in a purposeful way be combined with one another. This invention is however, susceptible to modifications and alternate constructions from that disclosed above which are fully equivalent. Consequently, it is not the intention to limit this invention to the particular embodiment disclosed. On the contrary, the intention is to cover all modifications and alternate constructions coming within the spirit and scope of the invention as generally expressed by the following claims which particularly point out and distinctly claim the subject matter of the invention. GLOSSARY OF TERMS AND THEIR DEFINITIONS IPv4 :- Internet Protocol Version 4 IPv6 :- Internet Protocol Version 6 DSBR :- Dual-Stack Border Router which support both IPv4 and IPv6 capability. ICMPv6 :- Internet Control Messages for IPv6. IPv6-in-IPv4:- IPv6 packets encapsulated in an IPv4 packet. i RFC 2463 - ICMPv6 2 RFC 2460 - IPv6 3 RFC 791 - IPv4 WE CLAIM 1. A method for IPv6 cloud discovery over ipv4 backbone in a network system comprising plurality of Dual-Stack Border Routers connected through IPv4 for providing IPv6 connectivity, the said method comprising the steps of: • At the Dual-Stack Border Router/Host: i. Joining a multicast group/using shared-unicast for sharing IPv6 reachability information; ii. Triggering Route Reachability Info request using ICMPv6 if no match to an IPv6 destination is found in the IPv6 routing table; iii. Constructing ICMPv6 IPV6_ROUTE_INFO Request/Reply message; iv. Encapsulating ICMPv6 IPV6_ROUTE_INFO Request message in an IPv4 packet and transmitting it to a multicast / shared-unicast destination; v. Decapsulating IPv4 packet containing ICMPV6 I Pv6_ROUTE J N FO REQUEST/REPLY message after receiving it and processing; vi. Triggering route lookup for IPv6 host/network address on processing IPv6_ROUTE_INFO REQUEST message; vii. Constructing ICMPv6 IPV6_ROUTE_INFO REPLY message in response to IPV6_ROUTE_INFO Request; and viii. Encapsulating ICMPv6 IPV6_ROUTE_INFO REPLY message in an IPv4 packet and transmitting it. 2. A method as claimed in claim 1 wherein the said method is triggered if there is a no network specific match for the destination IPv6 network/host address in the routing table and also no default entry in the routing table. 3. A method as claimed in claim 1 wherein the said method is triggered by administrator-defined triggers or other events like attachment of new IPv6 cloud. 4. A method as claimed in claim 1 wherein any IPv6 packet from IPv6 Source Host and destined to another IPv6 host is routed to a first DSBR. 5. A method as claimed in claim 4 wherein the Route lookup is done at the said first DSBR for the destination IPv6 host. 6. A method as claimed in claim 5 wherein if the Route lookup fails at the said first DSBR, it triggers ICMPv6 Route Reachability Request. 7. A method as claimed in claim 6 wherein the first DSBR forms an ICMPv6 with a TYPE_ROUTE_INFO message for destination IPv6 address reachability. 8. A method as claimed in claim 7 wherein the ICMPv6 message in an IPv6 packet is tunneled in an IPv4 packet where the source address in IPv4 packet is first DSBR, IPv4 unicast address, and destination address in IPv4 packet is Multicast group address or Shared-Unicast address. 9. A method as claimed in claim 8 wherein the Other Dual-Stack Routers receive the said packet from first DSBR and if it is a member of multicast group or shared-unicast address, then the DSBR decapsulates the tunneled packet. 10. A method as claimed in claim 9 wherein the ICMPv6 processes the TYPE_REQUEST_INFO message with REQUEST code. 11. A method as claimed in claim 10 wherein the DSBR looks up in its IPv6 routing table for a match to the destination IPv6. 12. A method as claimed in claim 11 wherein if the route lookup is successful then DSBR-n forms an ICMPv6 TYPE_REQUEST_INFO message with REPLY code. 13. A method as claimed in claim 12 wherein the DSBR-n then sends the ICMPv6 message in an IPv6 packet and tunnels it in an IPv4 packet having source address in IPv4 packet as DSBR-n, and destination address in IPv4 packet as first DSBR. 14. A method as claimed in claim 13 wherein first DSBR selects from the multiple replies, the route satisfying longest prefix match and creates a tunnel to the DSBR-n. 15. A method as claimed in claim 14 wherein first DSBR adds a route entry in the IPv6 routing table. 16. A method as claimed in claim 15 wherein first DSBR sends the currently held IPv6 packet or any further packets destined to destination IPv6 tunneled in an IPv4 unicast packet having source address in IPv4 packet as first DSBR, and destination address in IPv4 as DSBR-n. 17. A method as claimed in claim 16 wherein DSBR-n decapsulates the tunneled packet and routes the IPv6 packet to destination IPv6. 18. A method as claimed in claim 17 wherein if first DSBR does not get any replies, it then sends an ICMPv6 Host/Network unreachable to the IPv6 source. 19. A method for IPv6 cloud discovery over ipv4 backbone substantially described particularly with reference to the accompanying drawings.

Documents:

1034-CHE-2004 AMENDED CLAIMS 22-02-2012.pdf

1034-CHE-2004 AMENDED PAGES OF SPECIFICATION 22-02-2012.pdf

1034-CHE-2004 CORRESPONDENCE OTHERS. 06-12-2012.pdf

1034-CHE-2004 EXAMINATION REPORT REPLY RECEIVED 09-10-2012.pdf

1034-CHE-2004 EXAMINATION REPORT REPLY RECEIVED 22-02-2012.pdf

1034-che-2004 form-13 19-06-2006.pdf

1034-CHE-2004 POWER OF ATTORNEY 22-02-2012.pdf

1034-CHE-2004 AMENDED CLAIMS 18-07-2012.pdf

1034-CHE-2004 AMENDED PAGES OF SPECIFICATION 18-07-2012.pdf

1034-CHE-2004 CORRESPONDENCE OTHERS 18-07-2012.pdf

1034-CHE-2004 FORM-1 18-07-2012.pdf

1034-che-2004 form-1 19-06-2006.pdf

1034-CHE-2004 FORM-13 18-07-2012.pdf

1034-che-2004 form-18.pdf

1034-che-2004-abstract.pdf

1034-che-2004-claims.pdf

1034-che-2004-correspondnece-others.pdf

1034-che-2004-description(complete).pdf

1034-che-2004-description(provisional).pdf

1034-che-2004-drawings.pdf

1034-che-2004-form 1.pdf

1034-che-2004-form 13.pdf

1034-che-2004-form 5.pdf