Title of Invention

METHOD FOR FAST DISCOVERY OF EXISTENCE OF A NEIGHBOURING ROUTER

Abstract

This invention relates to Router Discovery based on IPv6 Router Advertisements. This will be useful in Detecting Network Attachment. More particularly, this invention relates to a method and System for Fast Router Discovery. This invention explains a system and method for fast router discovery in a communication system, comprising a mobile node MN, Access point AP that provides wireless services to the MNs in its coverage area or cell, Access router AR that acts as subnet router for MN and is connected to internet.

Full Text

FIELD OF TECHNOLOGY The present invention, in general, relates to the field of IPv6 technology. Further, this invention relates to Router Discovery based on IPv6 Router Advertisements. This will be useful for Detecting Network Attachment. More particularly, this invention relates to a method and System for Fast Router Discovery. DESCRIPTION OF RELATED ART The following references and explanations therefore clearly describe the present state of art and the limitations and weaknesses therein. [1] RFC 2461 - Neighbor Discovery Router Discovery operation in [1] involves sending solicited as well as unsolicited Router Advertisements. A router sends unsolicited Router Advertisements periodically to all-nodes multicast address. Thus host can discover the neighboring routers as well as learn prefixes on its link. But host may be unwilling to wait for the next unsolicited Router Advertisement. To obtain Router Advertisements quickly, host shall send a Router Solicitation message to the All-Routers multicast address. But before it sends an initial solicitation, it should delay the transmission for a random amount of time between 0 and 1 second to alleviate congestion when many hosts start up on a link at the same time. Routers shall send advertisements in response to valid solicitations. A solicited Router Advertisement should have a random delay between 0 and 500 milliseconds, to avoid the advertisements from all the routers colliding on the link causing congestion and higher probability of packet loss. In addition, it suggests that the RAs be multicast, and multicast RAs are rate limited to one message every 3 seconds. This implies that the response to a RS might be delayed up to 3.5 seconds. Figure 1 depicts the Router Discovery operation for this method when a MN associates to a new link. MN is the mobile node, AP is the link layer point of attachment and AR is the subnet router. LIMITATIONS The technology described above has inherent delay because of the Random Timer delay in sending RS and RA. Changing this behavior (reducing the random delay) may affect other scenarios. [2] FRD-I - A patent from SAIT by JinHyeock Choi (http://www.ietf.orq/internet-drafts/draft-dnadt-dna-discussion-OQ.txt) Access Points cache the most recent RA(s) and forward it (them) to a host upon detection of its association. This is very simple and potentially very fast and places no requirements on hosts or routers. Figure.2 depicts the Router Discovery operation for this method when MN associates to a new link. ? AP needs to process all packets to capture the RAs and cache them. ? AP needs to o Maintain the database of the RAs o Maintain the State (valid or stale) of the RA. o Validating the database with the received RA, each time an RA is received. o To have latest RAs, AP needs to maintain the timers, when expires, should solicit for the latest RA ? If the AP is not having the latest RA and its state in AP indicates that RA is Stale, AP then needs to solicit RA, process it then send it to MN. ? This is link-specific and raises some security concerns since it is, by definition, a "man in the middle". ? Where there are multiple routers on a link it needs to be determined which RA(s) will be forwarded, and how to time out old cache entries. ? Sometimes it may give stale/invalid RAs [3] Fast RA from DNA WG Routers on a link listen for advertisements from other routers and form tokens for them from the source addresses. When an RS is received by a router, some function of the source of the RS and each of the router tokens is used to create a ranking. One or more of the routers then respond in order with fixed delays starting from zero. The advantage here is that it doesn't have a single point of failure and will result in multiple (if there are multiple routers) RAs quickly. One Router among the routers on the link responds with RA without Random Delay ? This method avoids the delay on the router side only ? The host side random delay is still a problem for seamless mobility for mobile nodes SUMMARY OF THE INVENTION The system and method proposed herein (which may be termed as FRD-II) encompasses a way for getting the fast Router Advertisement from the routers when an MN is associating with an AP on new link. AP sends an RS on the link upon successful association of an IPv6 node (MN) without any random delay on behalf of the MN. As different hosts associate with AP at different times, RS on the link will be sent at different times and hence congestion problems will not occur. Accordingly, this invention explains a method for fast router discovery in a communication system, comprising a mobile node MN, Access point AP that provides wireless services to the MNs in its coverage area or cell, Access router AR that acts as subnet router for MN and is connected to internet, the said method comprising the steps of: On AP side, (a) receiving Assoc/Re-assoc request from MN; (b) sending RS message on behalf of MN on its link, before the association response is sent to MN if the association of MN is successful; (c) sending a unicast RS to all the routers on the link sequentially if the IP addresses of all on-link routers are available; (d) sending RS to all-routers multicast address if the IP addresses of all on-link routers are not available; On Router side: (e) responding with an RA message by the router; (f) responding with an RA without any random delay by the router if unicast RS is received; and (g) router using any of the FastRA mechanism to avoid the random delay if multicast RS is received; On AP side, the RS message includes TSLLA option which contains the MAC address of the MN that is getting associated and is obtained from the Assoc/Re-assoc request sent by MN. If multicast RA is preferred on the link, TSLLA option shall not be included. The IP source address of the RS message shall be unspecified address. On Router side, if TSLLA option is received in the RS message, RA is sent directly to the MN's MAC address and to achieve this, destination address in the IP header is set to the all-nodes multicast address and destination address in L2 header is set to MAC address of MN. If TSLLA option is not present in the RS message, Router shall multicast RA to all nodes. Accordingly, this invention further explains a system for fast router discovery in a communication system, comprising a mobile node MN, Access point AP that provides wireless services to the MNs in its coverage area or cell, Access router AR that acts as subnet router for MN and is connected to internet, the said system comprising: On AP side, (a) means for receiving Assoc/Re-assoc request from MN; (b) means for sending RS message on behalf of MN on its link, before the association response is sent to MN if the association of MN is successful; (c) means for sending a unicast RS to all the routers on the link sequentially if the IP addresses of all on-link routers are available; (d) means for sending RS to all-routers multicast address if the IP addresses of all on-link routers are not available; On Router side; (e) means for responding with an RA message by the router; (f) means for responding with an RA without any random delay by the router if unicast RS is received; and (g) means for router using any of the FastRA mechanism to avoid the random delay if multicast RS is received. Upon reception of an RS the routers respond to RS with RA. Routers can send RA without random delay if the RS was unicast RS. Routers may use Fast RA described in [3] or other mechanism to avoid the Random Delay in case AP sends RS to all-routers link local multicast address. Thus random delay is nullified on both the host and router while sending RS and RA. AP need not process any received packets, maintain any RA cache, timers etc. Thus not much processing is involved in AP except for sending RS on association of any MN. 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 Router Discovery operation for this method when a MN associates to a new link. Figure 2 depicts the Router Discovery operation for this method when MN associates to a new link. Figure 3 depicts the example scenario where the proposed method is applicable. Figure 4 shows the message sequence chart of the proposed system where AP sends RS with TSLLA option. 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. Figure 3 depicts the example scenario where the proposed method is applicable. It consists of an Access Router AR, Access Point AP and a mobile node MN. AR is the subnet router and is connected to the internet. AP provides wireless services to the mobile nodes in its geographical region referred to as cell. It acts as bridge between AR and MN. Whenever MN moves into AP's coverage area, it will send an Association/Re-association request to the AP to establish association with it. AP sends an association response indicating whether the association is successful. AP after receiving an association request from MN, if the association is successful, before sending association response, it will send RS on the link on behalf of MN to aid in getting fast RA without any random delay. ? If AP has IP addresses of all on-link routers, it can send a unicast RS to all the routers on the link sequentially. ? If AP does not have addresses of on-link routers, it can send RS to the all-routers multicast address. ? Since different MNs will associate at different times, no congestion problems will occur and hence random delay is not required. ? The RS message sent by AP should include TSLLA option which contains the MAC address of the MN. It can be obtained from the Assoc/Re-assoc request sent by MN. This option is used to indicate the Routers that RA can be sent directly to MN's MAC address. If multicast RA is preferred on the link, this option shall not be included. ? The IP source address of the RS message should be unspecified address i.e. ? The RS message should not contain any SLLA option. Routers, on receiving RS message, will respond with an RA message as follows; ? If unicast RS is received, Router shall respond with an RA without any random delay ? If multicast RS is received, Router shall use any of the FastRA mechanism described in [3] to avoid the random delay. ? If TSLLA option is received in the RS message, RA will be sent directly to the MN's MAC address. To achieve this, destination address in the IP header shall be set to the all-nodes multicast address and destination address in l_2 header shall be set to MAC address of MN. If TSLLA option is not present in the RS message, Router shall multicast RA to all nodes. rigure 4 shows the message sequence chart of the proposed system where AP sends RS with TSLLA option. AR sends RA directly to MN using MAC address in the TSLLA option present in RS message. No random delay is present while sending RS or RA. To send unicast RS messages to all on-link routers, AP needs to know the addresses of all on-link routers. This information can be configured statically in AP or it can get dynamically learn the adresses of all on-link routers by observing the RA messages passing through it. ADVANTAGES 1. This method reduces the delay in obtaining RA by host when it associates with a new link. 2. Does not introduce any changes on host implementation which are in larger number. 3. Very minimal implementation changes are required on AP. 4. The MN always gets the latest Router Advertisement. 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 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 THEIR DEFINITIONS RA - Router Advertisement MN -Mobile Node RS - Router Solicitation CN - Correspondent Node AP - Access Point AR - Access Router DNA- Detecting Network Attachment MAC - Media Access Control TSLLAO - Tentative Source Link-Layer Address ---------------------■■■■■■■■■■■■■■■■■■■■■■■•■•■■■•■■■■■■■•■■■■■■■■i WE CLAIM 1. A method for fast router discovery in a communication system, comprising a mobile node MN, Access point AP that provides wireless services to the MNs in its coverage area or cell, Access router AR that acts as subnet router for MN and is connected to internet, the said method comprising the steps of: On AP side, (a) receiving Assoc/Re-assoc request from MN; (b) sending RS message on behalf of MN on its link, before the association response is sent to MN if the association of MN is successful; (c) sending a unicast RS to all the routers on the link sequentially if the IP addresses of all on-link routers are available; (d) sending RS to all-routers multicast address if the IP addresses of all on-link routers are not available; On Router side: (e) responding with an RA message by the router; (f) responding with an RA without any random delay by the router if unicast RS is received; and (g) router using any of the FastRA mechanism to avoid the random delay if multicast RS is received; 2. A method as claimed in claim 1 wherein on AP side, the RS message includes TSLLA option which contains the MAC address of the MN that is getting associated and is obtained from the Assoc/Re-assoc request sent by MN. 3. A method as claimed in claim 2 wherein if multicast RA is preferred on the link, TSLLA option shall not be included. 4. A method as claimed in claim 2 wherein the IP source address of the RS message shall be unspecified address. 5. A method as claimed in claim 1 wherein On Router side, if TSLLA option is received in the RS message, RA is sent directly to the MN's MAC address and to achieve this, destination address in the IP header is set to the all-nodes multicast address and destination address in L2 header is set to MAC address of MINI. 6. A method as claimed in claim 1 wherein if TSLLA option is not present in the RS message, Router shall multicast RA to all nodes. 7. A system for fast router discovery in a communication system, comprising a mobile node MN, Access point AP that provides wireless services to the MNs in its coverage area or cell, Access router AR that acts as subnet router for MN and is connected to internet, the said system comprising: On AP side, (a) means for receiving Assoc/Re-assoc request from MN; (b) means for sending RS message on behalf of MN on its link, before the association response is sent to MN if the association of MN is successful; (c) means for sending a unicast RS to all the routers on the link sequentially if the IP addresses of all on-link routers are available; (d) means for sending RS to all-routers multicast address if the IP addresses of all on-link routers are not available; On Router side: (e) means for responding with an RA message by the router; (f) means for responding with an RA without any random delay by the router if unicast RS is received; and (g) means for router using any of the FastRA mechanism to avoid the random delay if multicast RS is received. 8. A system as claimed in claim 7 wherein on AP side, the RS message includes TSLLA option which contains the MAC address of the MN that is getting associated and is obtained from the Assoc/Re-assoc request sent by MN. 9. A system as claimed in claim 8 wherein if multicast RA is preferred on the link, TSLLA option shall not be included. 10.A system as claimed in claim 8 wherein the IP source address of the RS message shall be unspecified address. 11. A system as claimed in claim 7 wherein On Router side, if TSLLA option is received in the RS message, RA is sent directly to the MN's MAC address and to achieve this, destination address in the IP header is set to the all-nodes multicast address and destination address in L2 header is set to MAC address of MN. 12. A system as claimed in claim 7 wherein if TSLLA option is not present in the RS message, Router shall multicast RA to all nodes. 13. A method for fast router discovery in a communication system substantially described particularly with reference to the accompanying drawings. 14. A system for fast router discovery in a communication system substantially described particularly with reference to the accompanying drawings.

Documents:

1018-CHE-2005 EXAMINATION REPORT REPLY RECEIVED 26-02-2013.pdf

1018-CHE-2005 FORM-1 26-02-2013.pdf

1018-CHE-2005 FORM-13 26-02-2013.pdf

1018-CHE-2005 OTHER PATENT DOCUMENT 26-02-2013.pdf

1018-CHE-2005 POWER OF ATTORNEY 19-04-2013.pdf

1018-CHE-2005 POWER OF ATTORNEY 26-02-2013.pdf

1018-CHE-2005 AMENDED PAGES OF SPECIFICATION 26-02-2013.pdf

1018-CHE-2005 AMENDED CLAIMS 26-02-2013.pdf

1018-CHE-2005 CORRESPONDENCE OTHERS 19-04-2013.pdf

1018-CHE-2005 FORM-13 19-06-2006.pdf

1018-che-2005-abstract.pdf

1018-che-2005-claims.pdf

1018-che-2005-correspondnece-others.pdf

1018-che-2005-description(complete).pdf

1018-che-2005-description(provisional).pdf

1018-che-2005-drawings.pdf

1018-che-2005-form 1.pdf

1018-che-2005-form 13.pdf

1018-che-2005-form 26.pdf

1018-che-2005-form 5.pdf