Title of Invention

A METHOD FOR IPV6 2-HOP NEIGHBOUR DISCOVERY

Abstract

The invention relates to a method for 2-Hop Neighbor Discovery for a host with the help of Router Advertisement messages. The proposed invention hereafter will be referred to as IPV6 2-HOP neighbor discovery. The invention explains explains a method for IPV6 2-HOP neighbor discovery in a network of router systems connected to the host network comprising the steps of: including the off-link prefixes in router advertisement message by the router; including the MTU of links con-esponding to off-link prefixes in router advertisement message by the router; including the off-link prefixes in a database and using the prefixes while sending out data packets by the host; and calculating the path-MTU for 2-hop neighbors based on off-link MTU information received in router advertisements by the host.

Full Text

FIELD OF INVENTION The proposed invention applies to the IPv6 technology. Specifically this invention relates to the Router Discovery mechanism under IPv6. The RFC 2461 - Neighbor Discovery protocol describes the basic Neighbor & Router Discovery mechanism. The RFC 2461 shall be used for all details on existing art. Further, the proposed invention relates to a method for 2-Hop Neighbor Discovery for a host with the help of Router Advertisement messages. The proposed invention hereafter will be referred to as IPV6 2-HOP neighbor discovery. DESCRIPTION OF RELATED ART The 2-hop neighbor discovery relates to a host acquiring knowledge of its 2-hop neighbors with the help of IPv6 Router Discovery mechanism. The IPv6 Router Discovery mechanism is already well established under RFC 2461 and referred to as existing art. Under Router Discovery mechanism, a host builds a router list, with the routers connected to the hosts on its attached links. The Router Discovery mechanism helps a host to achieve the following: Router discovery - hosts builds a list of default routers. Prefix discovery - hosts discover the set of address prefixes that define which destinations are on-link for an attached link. Link parameter discovery - a node discovers the link parameters, such as the link MTU. Configuration parameter discovery - this relates to address auto configuration for a node. In the existing art, a host carries out the following operation to send out a data packet: ? Check Neighbor Cache for existing next-hop entry for particular destination ? Check whether destination is on-link or off-link ? On-link: Sent directly to destination ? Off-link: Sent to default router ? Identify link-layer address of next-hop Thus in the existing art, the Router Discovery mechanism helps a host to reach only the on-link prefixes (i.e. 1-hop or which are directly reachable). All the traffic destined to off-link nodes (i.e. reachable only via a router) are sent to a default router, from the router list, without any intelligence. The proposed invention as explained in subsequent paragraphs, helps a host to reach 2-hop networks (i.e. networks which are connected to the router or off-link). The existing art is confined to on-link neighbor discovery, A host learns Its on-link neighbors with the help of Router Discovery mechanism. It does not say anything about how to discover 2-hop neighbors for a multihomed host. Any traffic to off-link nodes are send to a default router which shall not work for a multihomed host. SUMMARY OF THE INVENTION The objective of the invention is to enable a host know its neighbors in a 2-hop diameter. This when coupled with the Path-MTU mechanism, lets a host send out an off-link packet without the need of Path-MTU discovery for Its 2-hop neighbors. The invention makes use of the existing Router Discovery mechanism to provide 2-hop neighbor Information to the host. The Router Discovery Mechanism is explained in RFC 2461 Under existing art (i.e. RFC 2461), Router Solicitation & Router Advertisement messages are used. The Router Advertisement message is responsible for Router Discovery. Host sends Router Solicitations in order to prompt Routers to generate Router Advertisement messages quickly. Router sends Router Advertisement messages periodically or In response to a Router Solicitation message. On receiving a Router Advertisement message, a host becomes aware of the Routers on the connected links. This enables a host to maintain a database of the routers, to be used, when it wants to forward a packet which is not directly reachable to it The list of Routers which are directly reachable from the host can also be called as 1-hop router list as these can be reached directly. The host in the existing art, chooses a default router (no intelligence applied in the existing art) from the list of routers available, to fonward the packet. The default router in tum takes care of forwarding the data packet to appropriate network node. If the default router was wrongly chosen to reach 2-hop neighbors, it in tum forwards the packet to the conf^ect router This additional packet forwarding can be omitted with the help of the proposed invention. Now as per the proposed art, a router will also include the off-link information in the Router Advertisement message (by setting the appropriate bit in the Router advertisement message and including the off-link networic information). The hosts upon receiving the Router Advertisement messages will be aware of the nodes connected to the other side (off-link) of the router. This helps the host to build a 2-hop neighbor database which contains the following: a) the router list directly reachable in 1-hop (as explained above with respect to existing art) b) the networks which are reachable via the routers in router list in 2-hop. A host then uses its 2-hop neighbor database to send traffic to off-link nodes through an appropriate router, instead of choosing a default router. The 2-hop database shall contain the list of networks reachable via a directly connected router. The hosts while sending out a data packet to off-link nodes, always consults the 2-hop neighbor database. If this node's networi A host uses Prefix discovery' under Router discovery mechanism, to create a 2-hop neighbor database for better reachability. If 2-hop neighbor information is available, a multihomed host may be able to choose the correct outgoing interface when sending traffic to Its 2-hop neighbor. Similarly, a host connected to 2 or more routers on a single subnet may be able to choose the correct outgoing interface when sending packet to its 2-hop neighbor. With the link infOmiation, e.g. MTU supplied with the off-link prefix, a host shall be able to avoid path MTU discovery for its 2-hop neighbors. Accordingly, this invention explains a method for IPV6 2-HOP neighbor discovery in a network of router systems connected to the host network comprising the steps of: (a) including the off-link prefixes in router advertisement message by the router; (b) including the MTU of links corresponding to off-link prefixes in router advertisement message by the router; (c) including the off-link prefixes in a database and using the prefixes while sending out data packets by the host; and (d) calculating the path-MTU for 2-hop neighbors based on off-link MTU information received in router advertisements by the host. The "prefix" option in router advertisement message is reused as an off-link prefix infonnation. The V bit in "prefix" option signify an on-link or off-link prefix. The "MTU" option is reused to signify the off-link MTU information. All off-link "prefixes" options coH'esponding to a link succeeds the "MTU" option for the link. A node considers an address to be on-link if It is covered by one of the link's prefixes, A node considers an address to be on-link if a neighboring router specifies the address as the target of a redirect message. A node considers an address to be on-link if a neighbor advertisement message is received for the address. A node considers an address to be on-link if any neighbor discovery message is received from the address. Any address that is not assigned to any interfaces on the specified link is considered to be off-link. The hosts use the advertised on-link prefixes to build and maintain a list that is used in deciding when a packet's destination is on-Jink or beyond a router. The host uses Prefix discovery' under Router discovery mechanism, to create a 2-hop neighbor database. The router includes the off-link information in the Router Advertisement message and the hosts upon receiving the Router Advertisement messages gets aware of the nodes connected to the off-link of the router. The database contains the router list directly reachable in 1-hop and the networks which are reachable via the routers in router list in 2-hop. The host uses its 2-hop neighbor database to send traffic to off-link nodes through an appropriate router. The 2-hop database contains the list of networks reachable via a directly connected router. The hosts while sending out a data packet to off-link nodes, consults the 2-hop neighbor database and if this node's network is present in the 2-hop database, the concerned router from the database is selected to send the data packets. 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 represents the existing art related to Router Discovery Mechanism. Figure 2 is a block diagram representing the 2-Hop Neighbor Discovery Functionality. Figure 3 explains the Path-MTU mechanism with respect to 2-Hop Neighbor Discovery. Figure 4 gives the message format for the Router Advertisement message which is reused under 2-hop neighbor discovery mechanism. Figure 5 provides the message format for the Prefix Information option under Router Advertisement message. DETAILED DESCRIPTION OF THE INVENTION The prefen^ed 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. The existing art provides a host a list of default routers with the help of 'Router Discovery' mechanism. This default router list may cause the following issues: Implementations may randomly select a default router. Implementations may cycle through default list in a round-robin. What happens when default router is the wrong router? To avoid choosing a default router in case of multihomed host, the 2-Hop Neighbor Discovery mechanism Is used. This when deployed within IPv6 implementation shall help a host to automatically configure itself in multihomed environment without requiring any manual configuration. Figure 1 represents the existing art related to Router Discovery Mechanism. This figure explains a router list (i.e. Default GW-list) being build for a host. The up arrow represents 'Router Solicitation' message and down an'ow represents 'Router Advertisment' message. The host chooses a default router (among A, B, C) to foHA^ard off-link packets. Figure 2 is a block diagram representing the 2-Hop Neighbor Discovery Functionality. ? The Host 1 does not have any infomnation on how to reach Host 2. ? It should select Router A as the default gateway to reach Host 2, ? It can do so if it has the off-link prefix information from Router A through Router Advertisement message. Router Advertisement message Is a periodic message. Figure 3 explains the Path-MTU mechanism with respect to 2-Hop Neighbor Discovery. The host receives Router advertisement message from both Routers. For an example, FEC0:18::1 (off-link prefix) is advertised by the top router in the Router Advertisement message. And for FEC0:18::1, the host knows the total Path-MTU as advertised in Router advertisement message. This helps the host not to run the path-mtu discovery mechanism for FEC0:18::1 as it is already known to the host. Figure 4 gives the message format for the Router Advertisement message which is reused under 2-hop neighbor discovery mechanism. Figure 5 provides the message fonnat for the Prefix Information option under Router Advertisement message. The Prefix information option provides the off-link information under 2-hop neighbor discovery mechanism. To enable 2-Hop Neighbor discovery, the Router Advertisement message shall be reused. The following points describes the updates in the Router Advertisement message, [Refer Figure 4] There will be no addition of any new option to the existing router advertisement message. The "prefix" option [Refer Figure 5] in router advertisement message will be reused as an off-link prefix information. The *L* bit in "prefix" option [Refer Figure 5] shall signify an on-link or off-link prefix. The "MTU" optlon_shall be reused to signify the off-link MTU information. All off-link "prefixes" options [Refer Figure 5] con^esponding to a link shall succeed the "MTU" option for that link. A node considers an address to be on-link if: - It is covered by one of the link's prefixes, or - a neighboring router specifies the address as the target of a Redirect message - a Neighbor Advertisement message is received for the (target) address - any Neighbor Discovery message is received from the address Similariy, any address that is not assigned to any interfaces on the specified link Is considered to be off-link. Hosts use the advertised on-link prefixes to build and maintain a list that is used In deciding when a packet's destination is on-link or beyond a router. The following steps shall be canied out by hosts and routers with respect to 2-Hop Neighbor discovery mechanism: A router will include the off-link prefixes in router advertisement message. ? A router will also include the MTU of links con-esponding to off-link prefixes in Router advertisement message. ? A host shall Include the off-link prefixes in its database and shall use those while sending out data packets. ? A host shall calculate the path-MTU for 2-hop neighbors based on off-link MTU information received in router advertisements. The invention has the following advantages With the help of IPv6 2-Hop Neighbor Discovery mechanism a host shall be able to create a 2-hop neighbor database under IPv6 Router Discovery mechanism. This 2-Hop table helps a host (e.g. multihomed host) to reach out to the off-link nodes in a diameter of 2-hops. Similarly with the help of Path MTU for 2-hop neighbors, a host can avoid using Path-MTU discovery for its 2-hop neighbors. With this invention no manual configuration is required on a multihomed host to reach its 2-hop neighbors. In its absence, a static route needs to be added to the host routing table. The proposed invention is applicable for Router systems In core network. These Router systems connect the host network on one side^ to the Internet Service Provider (ISP) on the other side. The Router systems can make use of the proposed invention to advertise the networks on the ISP side to the networks on the host side. Using this proposed invention therefore^ the hosts connected to the Core Router can make intelligent decision to forward packets which are at a 2-hop reach (i.e. networks connected towards the ISP side). This way packet forwarding will be much faster for 2-hop networks, as a correct router will be chosen, instead of choosing a default router. In the existing art but it's the default router which again fonwards the data packet to the correct router^ If the 2-hop network is not reachable to it. The proposed invention is not dependent to any particular hardware but is applicable to any router system which supports the IPv6 forwarding mechanism & runs neighbor discover protocol. 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, computer, rendering device or a multi function device. Although the present invention has been fully described in connection with the prefen-ed 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 NDP IPv6 ICMP Node Router itself Host Neighbor Discovery Protocol Intemet Protocol Version 6 internet Message Control Protocol a device that implements IP a node that fonwards IP packets not explicitly addressed to : any node that is not a router Interface : a node's attachment to a link Neighbors : nodes attached to the same link Address : an IP-layer identifier for an interface Prefix : a bit string that consists of some number of initial bits of an address On-link : an address that is assigned to an interface on a specified link. Off-link : the opposite of on-link. The off-link nodes can be reached only via a router. MTU : maximum transmission unit. ISP : Intemet Service Provider WE CLAIM 1. A method for IPV6 2-HOP neighbor discovery in a network of router systems connected to the host network comprising the steps of: (a) including the off-link prefixes in router advertisement message by the router; (b) including the MTU of links corresponding to off-link prefixes in router advertisement message by the router; (c) including the off-link prefixes in a database and using the prefixes while sending out data packets by the host; and (d) calculating the path-MTU for 2-hop neighbors based on off-link MTU information received in router advertisements by the host. 2. A method as claimed in claim 1 wherein the "prefix" option in router advertisement message is reused as an off-link prefix information. 3. A method as claimed in claim 1 wherein the 'L' bit In "prefix" option signify an on-link or off-link prefix. 4. A method as claimed in claim 1 wherein the "MTU" option is reused to signify the off-link MTU information. 5. A method as claimed in claim 1 wherein all off-link "prefixes" options coresponding to a link succeeds the "MTU" option for the link. 6. A method as claimed in claim 1 wherein a node considers an address to be on-link if it is covered by one of the link's prefixes. 7. A method as claimed in claim 1 wherein a node considers an address to be on-link if a neighboring router specifies the address as the target of a redirect message, 8. A method as claimed in claim 1 wherein a node considers an address to be on-link if a neighbor advertisement message is received for the address. 9. A method as claimed in claim 1 wherein a node considers an address to be on-link if any neighbor discovery message is received from the address. 10. A method as claimed in claim 1 wherein any address that is not assigned to any interfaces on the specified link is considered to be off-link. 11. A method as claimed in claim 1 wherein the hosts use the advertised on-link prefixes to build and maintain a list that is used in deciding when a packet's destination is on-link or beyond a router. 12. A method as claimed in claim 1 wherein the host uses Prefix discovery' under Router discovery mechanism, to create a 2-hop neighbor database. 13. A method as claimed in claim 1 wherein the router includes the off-link information in the Router Advertisement message and the hosts upon receiving the Router Advertisement messages gets aware of the nodes connected to the off-link of the router. 14. A method as claimed in claim 1 wherein the database contains the router list directly reachable in 1-hop and the networks which are reachable via the routers in router list in 2-hop. 15. A method as claimed in claim 1 wherein the host uses its 2-hop neighbor database to send traffic to off-link nodes through an appropriate router. 16. A method as claimed in claim 1 wherein the 2-hop database contains the list of networks reachable via a directly connected router. 17. A method as claimed in claim 1 wherein the hosts while sending out a data packet to off-link nodes, consults the 2-hop neighbor database and if this node's network is present in the 2-hop database, the concerned router from the database is selected to send the data packets. 18, A method for IPV6 2-HOP neighbor discovery in a network of router systems connected to the host network substantially described particularly with reference to the accompanying drawings.

Documents:

1464-che-2004-abstract.pdf

1464-che-2004-assignement.pdf

1464-che-2004-claims.pdf

1464-che-2004-correspondnece-others.pdf

1464-che-2004-correspondnece-po.pdf

1464-che-2004-description(complete).pdf

1464-che-2004-description(provisional).pdf

1464-che-2004-drawings.pdf

1464-che-2004-form 1.pdf

1464-che-2004-form 26.pdf

1464-che-2004-form 3.pdf

1464-che-2004-form 5.pdf

1464-che-2004-form 9.pdf