FIELD OF INVENTION
This invention relates to service discovery using DHCPv6. Further, this invention relates to the field of IPv6 technology and DHCP for IPv6. More particularly, this invention encompasses an efficient method for service discovery using DHCPv6. DHCPv6 is the application layer protocol and is meant for IPv6 nodes.
DESCRIPTION OF RELATED ART
DHCPv6 is a protocol used to automate the process of address configuration dynamically with out any manual intervention amid. In its evolution, it also has been used for getting the configuration information required for different protocols such as DNS Server address for DNS Client and NTP Server address for NTP Client.
An IPv6 Anycast address is an address that is assigned to more than one interface (typically belonging to different nodes), with the property that a packet sent to an Anycast address is routed to the "nearest" interface having that address, according to the routing protocols' measure of distance. Also, unicast and multicast addresses are not associated with any specific application. On the other hand, anycast addresses are generally associated with a specific service class.
In the existing art there are not any anycast address assignment methods in DHCPV6.
Further there are no specific requirements from client side in current unicast address assignment in DHCPv6. Where as, anycast addresses need to be assigned depending the service class specified by the client.
Further DHCPv6 currently does not have any way to discover the services.

SUMMARY OF INVENTION
The primary object of this invention is therefore to introducing anycast address assignment methods in DHCPv6.
It is another object of this invention to invent an Anycast address assignment for a requested service class Service / Service Provider address Discovery using DHCPv6.
Anycast Communication is one of the features that IPv6 supports better than its predecessor IPv4. In IPv6, an Anycast Address is assigned to more than one interface (typically belonging to different nodes), with the property that a packet sent to an Anycast address is routed to the "nearest" Anycast Member, according to the routing protocols' measure of distance.
DHCPv6 is a protocol used to automate the process of address configuration dynamically with out any manual intervention amid. In its evolution, it also has been used for getting the configuration information required for different protocols such as DNS Server address for DNS Client and NTP Server address for NTP Client. Currently, DHCPv6 supports the address assignment of unicast and multicast. However, the address assignment for unicast and multicast addresses is very different from address assignment for anycast address in a way that the anycast addresses are assigned to the service class requested by the client. Also, currently DHCPv6 does not provide any method to discovery service provider information given the service required.
Accordingly, the invention relates to a communication method comprising DHCPv6 Client and DHCPv6 Server for providing Automatic Anycast/Shared UnicastAA/ell"known Address Assignment and Service Discovery, the method comprising the steps of:
(a) Administrator configuring the DHCPv6 Server with the Addresses (Anycast/Shared Unicast/Well-known/Administrator defined Addresses) and

corresponding services in DHCPv6 Server
(b) A server obtaining an address for a particular Service from DHCPv6 Server
(c) DHCPv6 Clients discovering the Server's address from the DHCPv6 Server.
Accordingly, this invention relates to a wherein DHCPv6 Server is configured with all addresses and service types by the administrator.
Accordingly this invention further relates to a method wherein a new DHCPv6 Option (IA_SA) for Service Address assignment is used.
Accordingly this invention further relates to a method wherein a flag is used to convey if the address being assigned is an Anycast Address.
Accordingly this invention further relates to a method wherein a new DHCPv6 Option (OPTION_SRVC_DSCVRY) is used for DHCPv6 Clients to discover the addresses where a particular service can be obtained.
Accordingly, this invention explains a method for service discovery using DHCPV6 in a communication system comprising DHCPv6 Client and DHCPv6 Server, the said method comprising the steps of:
(a) configuring the DHCPv6 Server with the Anycast / Shared Unicast / Well-known / Administrator defined Addresses and corresponding services in DHCPv6 Server by the administrator;
(b) obtaining an address by the server for a particular Service from DHCPv6 Server; and
(c) discovering the Server's address from the DHCPv6 Server by DHCPv6 Clients.
A new DHCPv6 Option IA_SA for Service Address assignment is used where the IA_SA option fields comprises an Option Type, Option Length, lAID, Service Type, Anycast flag, T1, T2 and Sub-options. The Option Type is given by IA_SA having an Option Length obtained by adding 20 to the Length of the options in IA_SA

sub-options field. The said lAID is an identifier for the lA and it is chosen in the same way as I AID for any other I A. The said Service Type is the Service type of the application that requests the anycast address. The renew time for this IA_SA and T2 is the rebind time for this IA_SA.
The addresses to be filled by the server in reply is given by the sub-options. The said system uses Service Discovery option fields comprising Option Type, Option Length, Service Type, and Sub-options. The said option type is Service Discovery and the said option length is obtained by adding eight with the Length of the options in Service Discovery sub-options field. The said Service Type is the Service type of the application that requested the anycast address. The addresses to be filled by the server in reply is given by the sub-option. In an anycast Address assignment message exchange the DHCPv6 client sends a solicit message with IA_SA option. The DHCPv6 server receives solicit message and sends back the advertisement with anycast/shared unicast address for the requested service class. The DHCPv6 client then waits for the advertisements from different servers and selects a suitable server.
The DHCPv6 client sends a request message with IA_SA option and said client receives request message and sends back the reply with anycast/shared unicast address for the requested service class. When the Service user application requests DHCPv6 client to get anycast/shared-unicast for providing the services with its service type the DHCPv6 client forms a solicit message with the Service Address Assignment option specifying the service type for which the service is going to be provided at the address to be leased. The DHCPv6 server after receiving the solicit message sends back the advertisement and the DHCPv6 client after collecting the advertisements from multiple servers selects one and then the DHCPv6 client forms a request message with the Service Address Assignment option specifying the service type for which the service is going to be provided at the address to be leased. The DHCPv6 server after receiving the request message sends back the reply with anycast/shared-unicast address and also adds an entry in the service provider records for the service type with the leased anycast /

shared-unicast address for future service discovery requests to that service type to be served using the said record. The DHCPv6 client that wants to get an anycast address for a particular service provision/usage sends out a DHCPvS message with IA_SA option. The DHCPv6 server after receiving the client's interested service class leases an anycast or shared unicast address. In a Service Discovery message exchange the DHCPv6 client sends a info-request message with SD option. The DHCPvS server receives info-request message and sends back the reply with service provider's information for the service requested by the client in the information-request message. The DHCPv6 client after receiving the reply from server hands over the service provider address to the service user application. The service user application then sends out a service request message to service provider/server address where the Service provider / server sends back the reply related to the service.
The Service user application requests DHCPv6 client to get service provider's information for using the services with its service type and the DHCPv6 client forms a information-request message with the SD option specifying the service type for which the service provider information is required. The DHCPv6 server after receiving the information-request message looks into its service provider database and sends back the service provider information in SD option of reply message. The DHCPv6 client upon receiving the reply with SD option conveys the same to the service user application which has initiated the current message exchange and the service user application contacts the service provider and gets the required services. To know the service provider information the DHCPv6 client sends out a DHCPv6 message with Service Discovery option. The DHCPv6 server after receiving the client's interested service type returns back the service discovery option with the service provider information.
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 describe an IA_SA option fields which contains
Figure 2 illustrates Service Discovery option fields.
Figure 3 illustrates Anycast Address assignment message exchange.
Figure 4 illustrates Service Discovery message exchange.
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 1 describe an IA_SA option fields which contains
Option Type = IA_SA
Option Length = 20 + Length of the options in IA_SA sub-options field
lAID = Identifier for this lA to be chosen much in the same way as lAID for any other
lA.
Service Type = Service type of the application that requested the anycast address
Anycast flag (A): Anycast = 1, Shared Unicast = 0
T1: Renew time for this lA SA

T2: Rebind time for this IA_SA
Sub-options: Addresses to be filled by the server in reply
Figure 2 describes Service Discovery option fields which contains
Option Type = Service Discovery
Option Length = 8 + Length of the options in Service Discovery sub-options field Service Type = Service type of the application that requested the anycast address Sub-options: Addresses to be filled by the server in reply
Figure 3 explains Anycast Address assignment message exchange
1) DHCPv6 client sends a solicit message with IA_SA option
2) DHCPv6 server receives solicit message and sends back the advertisement with anycast/shared unicast address for the requested service class
3) DHCPv6 client meanwhile waits for the advertisements from different servers
4) DHCPv6 client selects the suitable server
5) DHCPv6 client sends a request message with IA_SA option
6) DHCPv6 server receives request message and sends back the reply with anycast/shared unicast address for the requested service class
Figure 4 explains Service Discovery message exchange
1) DHCPv6 client sends a info-request message with SD option
2) DHCPv6 server receives info-request message and sends back the reply with service providers information for the service requested by the client in the information-request message
3) DHCPv6 client after receiving the reply from server hands over the service provider address to the service user application
4) Service user application then sends out a service request message to service provider/server address
5) Service provider / server then sends back the reply related to the service

Anycast address assignment
Service user application requests DHCPv6 client to get anycast/shared-unicast for providing the services with its service type. Then DHCPv6 client forms a solicit message with the SAA (Service Address Assignment) option specifying the service type for which the service is going to be provided at the address to be leased. DHCPv6 server after receiving the solicit message sends back the advertisement. DHCPv6 client after collecting the advertisements from multiple servers selects one. Then DHCPv6 client forms a request message with the SAA (Service Address Assignment) option specifying the service type for which the service is going to be provided at the address to be leased. DHCPv6 server after receiving the request message sends back the reply with anycast/shared-unicast address and also adds an entry in the service provider records for this service type with the leased anycast/shared-unicast address so that the future service discovery requests to that service type can be served using this record.
A DHCPv6 client that wants to get an anycast address for a particular service provision/usage sends out a DHCPv6 message with IA_SA option in the same way as of IA_NA or IA_TA. The option format for IA_SA is depicted in figure 1.
The DHCPv6 server after receiving the client's interested service class leases an anycast or shared unicast address. Note that the address assigned, here to this client, need not be assigned to this client alone. The typical message sequence for this anycast address assignment is depicted in figure 3.
Service Discovery
Service user application requests DHCPv6 client to get service provider's information for using the services with its service type. Then DHCPv6 client forms a information-request message with the SD (Service Discovery) option specifying the service type for which the service provider information is required. DHCPv6 server after receiving the information-request message looks into its service provider database and sends back the service provider information in SD option of reply

message. DHCPv6 client upon receiving the reply with SD option conveys the same to the service user application which has initiated the current message exchange. Then, the service user application typically contacts the service provider and gets the required services.
A DHCPv6 client that wants to get a particular service will typically need to know the service provider information such as the service provider's address, etc. This can be done using DHCPv6 much like the way discovering the service using DNS Service Records. In this case the DHCPv6 client typically sends out a DHCPv6 message with Service Discovery option. The option format is depicted in figure-2. Also, the message exchange for the service discovery is depicted in figure 4.
The DHCPv6 server after receiving the client's interested service type returns back the service discovery option with the service provider information.
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.

REFERENCES
[IPV6]
Deering, S, and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998.
[ADDR-ARCH]
Hinden, R., and Deering, S., "Internet Protocol, Version 6 (IPv6) Addressing Architecture", RFC 3513, April 2003.
GLOSSARY OF TERMS AND THEIR DEFINITIONS
Anycasting
Sending out the packet to Anycast Address (i.e. with Destination Address as Anycast Address)
Anycast Address
An IPv6 Anycast address is an address that is assigned to more than one interface (typically belonging to different nodes), with the property that a packet sent to an Anycast address is routed to the "nearest" interface / host having that address, according to the routing protocols' measure of distance.

WE CLAIM
1. A method for service discovery using DHCPV6 in a communication system
comprising DHCPv6 Client and DHCPv6 Server, the said method comprising
the steps of:
(a) configuring the DHCPv6 Server with the Anycast / Shared Unicast / Well-known / Administrator defined Addresses and corresponding services in DHCPv6 Server by the administrator;
(b) obtaining an address by the server for a particular Service from DHCPv6 Server; and
(c) discovering the Server's address from the DHCPv6 Server by DHCPv6 Clients.

2. A method as claimed in claim 1 wherein a new DHCPv6 Option IA_SA for Service Address assignment is used where the IA_SA option fields comprises an Option Type, Option Length, lAID, Service Type, Anycast flag, T1, T2 and Sub-options.
3. A method as claimed in claim 2 wherein the Option Type is given by IA__SA having an Option Length obtained by adding 20 to the Length of the options In IA_SA sub-options field.
4. A method as claimed in claim 2 wherein the said lAID is an identifier for the lA and it is chosen in the same way as lAID for any other lA.
5. A method as claimed in claim 2 wherein the said Service Type is the Service type of the application that requests the anycast address.
6. A method as claimed in claim 2 wherein T1 is the renew time for this IA_SA and T2 is the rebind time for this IA_SA.

7. A method as claimed in claim 2 wherein addresses to be filled by the server in reply is given by the sub-options.
8. A method as claimed in claim 2 wherein the said system uses Service Discovery option fields comprising Option Type, Option Length, Service Type, and Sub-options.
9. A method as claimed in claim 8 wherein the said option type is Service Discovery and the said option length is obtained by adding eight with the Length of the options in Service Discovery sub-options field.
10. A method as claimed in claim 8 wherein the said Service Type is the Service type of the application that requested the anycast address.
11. A method as claimed in claim 8 wherein the addresses to be filled by the server in reply is given by the sub-option.
12. A method as claimed in claim 1 wherein in an anycast Address assignment message exchange the DHCPv6 client sends a solicit message with IA_SA option.
13. A method as claimed in claim 12 wherein DHCPv6 server receives solicit message and sends back the advertisement with anycast/shared unicast address for the requested service class.
14. A method as claimed in claim 13 wherein DHCPvS client then waits for the advertisements from different servers and selects a suitable server.
15.A method as claimed in claim 14 wherein DHCPv6 client sends a request message with IA_SA option and said client receives request message and sends back the reply with anycast/shared unicast address for the requested service class.

16. A method as claimed in claim 12 wherein when the Service user application requests DHCPv6 client to get anycast/shared-unicast for providing the services with its service type the DHCPv6 client forms a solicit message with the Service Address Assignment option specifying the service type for which the service is going to be provided at the address to be leased.
17. A method as claimed in claim 16 wherein the DHCPv6 server after receiving the solicit message sends back the advertisement and the DHCPv6 client after collecting the advertisements from multiple servers selects one and then the DHCPv6 client forms a request message with the Service Address Assignment option specifying the service type for which the service is going to be provided at the address to be leased.
18. A method as claimed in claim 17 wherein DHCPv6 server after receiving the request message sends back the reply with anycast/shared-unicast address and also adds an entry in the service provider records for the service type with the leased anycast/shared-unicast address for future service discovery requests to that service type to be served using the said record.
19. A method as claimed in claim 18 wherein the DHCPv6 client that wants to get an anycast address for a particular service provision/usage sends out a DHCPv6 message with IA_SA option.
20. A method as claimed in claim 18 wherein the DHCPv6 server after receiving the client's interested service class leases an anycast or shared unicast address.
21. A method as claimed in claim 1 wherein in a Service Discovery message exchange the DHCPv6 client sends an info-request message with SD option.

22. A method as claimed in claim 21 wherein DHCPv6 server receives info-request message and sends back the reply with service provider's information for the service requested by the client in the information-request message.
23. A method as claimed in claim 22 wherein DHCPv6 client after receiving the reply from server hands over the service provider address to the service user application.
24. A method as claimed in claim 23 wherein the service user application then sends out a service request message to service provider/server address where the Service provider / server sends back the reply related to the service.
25. A method as claimed in claim 21 wherein Service user application requests DHCPv6 client to get service provider's information for using the services with its service type and the DHCPv6 client forms a information-request message with the SD option specifying the service type for which the service provider information is required.
26. A method as claimed in claim 25 wherein DHCPv6 server after receiving the information-request message looks into its service provider database and sends back the service provider information in SD option of reply message.
27. A method as claimed in claim 26 wherein DHCPv6 client upon receiving the reply with SD option conveys the same to the service user application which has initiated the current message exchange and the service user application contacts the service provider and gets the required services.
28. A method as claimed in claim 27 wherein to know the service provider information the DHCPv6 client sends out a DHCPv6 message with Service Discovery option.

29. A method as claimed in claim 28 wherein the DHCPv6 server after receiving the client's interested service type returns back the service discovery option with the service provider information.
30.A method for service discovery using DHCPV6 substantially described particularly with reference to the accompanying drawings.