Dynamic address assignment and resolution technique

• US 5,835,725 A
• Filed: 10/21/1996
• Issued: 11/10/1998
• Est. Priority Date: 10/21/1996
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Lee, Joseph S., Chiang, Steve Tsowen
• Primary Examiner(s): Lim, Krisna
• Assistant Examiner(s): Coulter, Kenneth R.
• Application Number:
  US08/734,496
• Time in Patent Office: 750 Days
• Field of Search: 395/200.16, 395/200.75, 395/200.58
• US Class Current: 709/228
• CPC Class Codes: H04L 2101/622 Layer-2 addresses, e.g. medium access control [MAC] addresses
• CPC Class Codes: H04L 61/10 of different types
• CPC Class Codes: H04L 61/5007 Internet protocol [IP] addresses
• CPC Class Codes: H04L 61/5061 Pools of addresses
• CPC Class Codes: H04L 67/01 Protocols
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

An address resolution protocol technique enables an intermediate station of a heterogeneous network to dynamically assign an address to an end station for use in a communication session between the end station and other stations of the network. The end station initiates the session by issuing a novel address assignment request to the intermediate station. In response to the request, the intermediate station assigns the end station an address chosen from a pool of addresses allocated to the intermediate station. If the assigned address is unacceptable, the end station reissues the address assignment request to which the intermediate station allocates another address from the pool.

Claims

1. Apparatus for dynamically assigning addresses to stations of a computer network, said addresses being for identifying said stations to each other in said network the apparatus comprising:

an end station coupled to the computer network, the end station comprising means for generating an address assignment request and means for issuing the address assignment request over the network to initiate a communication session; and

an intermediate station coupled to the computer network and having a pool of addresses allocated thereto, the intermediate station comprising means for assigning the end station an address chosen from the pool in response to the request, such that if the assigned address is unacceptable, the end station reissues the address assignment request to which the intermediate station allocates another address from the pool.

2. The apparatus of claim 1 wherein the end station is a workstation, and wherein the means for generating the address assignment request is an address resolution client module of the workstation.

3. The apparatus of claim 2 wherein the means for issuing the address assignment request comprises the address resolution client module cooperating with a communications architecture of the workstation.

4. The apparatus of claim 3 wherein the communications architecture comprises a transmission control protocol/Internet protocol (TCP/IP) protocol stack.

5. The apparatus of claim 4 wherein the intermediate station is a router, and wherein the means for assigning the address is an address resolution server module of the router.

6. The apparatus of claim 5 wherein the address is a media access control address and wherein the address assignment request is a capability exchange request used to exchange information between the workstation and router.

7. The apparatus of claim 6 wherein the communication session is a connection-oriented session.

8. The apparatus of claim 7 wherein the connection-oriented session is a TCP session.

9. A method for dynamically assigning a media access control (MAC) address from a router to a workstation of a computer network, said MAC address being for uniquely identifying said workstation to said router in said network the method comprising the steps of:

(A) issuing a capability exchange request message from the workstation to the router, the request having a null value loaded into an address field thereof;

(B) at the router, (i) assigning the workstation a MAC address chosen from a pool of addresses allocated to the router, (ii) loading the assigned MAC address into the address field of the capability exchange message and (iii) transmitting the message to the workstation; and

one of,

(C) reissuing the capability exchange request message from the workstation to the router with the null value loaded into the address field if the assigned MAC address is unacceptable to the workstation; and

(D) acknowledging receipt and acceptance of the assigned MAC address by issuing a capability exchange response message from the workstation to the router with the assigned MAC address loaded into the address field.

10. A system for dynamically assigning a media access control (MAC) address to a workstation of a heterogeneous computer network for use in a communications session between the workstation and a host station of the network, the system comprising:

a plurality of first stations coupled to first network, the first stations including the host station;

a plurality of second stations coupled to a second network, the second stations including the workstation configured as a client for issuing a capability exchange request over the second network; and

a router interconnecting the first and the second networks, the router being configured as a server having a pool of allocated MAC addresses for assigning the workstation a specific MAC address in response to the capability exchange request said specific MAC address being for uniquely identifying said workstation in said heterogeneous computer network;

wherein said workstation is configured to issue another capability exchange request if said specific MAC address is unacceptable and said router is configured to assign to the workstation another specific MAC address in response to said another capability exchange request.

11. The system of claim 10 wherein the first network is a Systems Network Architecture network and wherein communication among the first stations is determined on the basis of Synchronous Data Link Control addresses.

12. The system of claim 10 wherein the first network is a Systems Network Architecture network and wherein communication among the first stations is determined on the basis of MAC addresses.

13. The system of claim 12 wherein the second network is an Internet protocol (IP) network comprising one of a local area network, a wide area network and an asynchronous communications link.

14. The system of claim 13 wherein the asynchronous communications link is a dial-up line and wherein communication between the workstation and router is determined on the basis of one of a MAC address or IP address.

15. A method of dynamically assigning an address to an end station of a computer network so as to permit unique identification of said end station using said address, the method comprising the steps of:

receiving from the end station an address assignment message containing an ads address field from the end station over the computer network and providing a received address assignment messaged indicative thereof;

checking said address field of said received address assignment message to determine if an address value loaded in said address field is unique;

if said address value is not unique

(1) selecting a unique address value from plurality of available unique address values; and

(2) loading said selected unique address into an address field of a response message and transmitting said response message to the end station over the computer network.

16. The method of claim 15 further comprising the step of again receiving said address assignment message from the end station with a null value loaded into said address field if said selected unique address is unacceptable to the end station.

17. The method of claim 16 further comprising the step of acknowledging receipt and acceptance of the assigned address by receiving said address assignment message with said selected unique address loaded into the address field.

18. A method for dynamically assigning an address from an intermediate station to an end station of a computer network, the method comprising the steps of:

(A) generating an address assignment message at the end station;

(B) determining whether an address has been previously assigned to the end station;

(C) issuing the address assignment message from the end station to the intermediate station and one of (i) if an address has not been previously assigned, loading a null value into an address field of the message and (ii) if an address has been previously assigned, loading the address value into the address field of the message;

(D) at the intermediate station, one of (iii) assigning the end station an address chosen from a pool of addresses allocated to the intermediate station if the address field contains the null value, and (iv) determining whether the previously assigned address is unique if the address field contains the assigned address; and

(E) loading the assigned address value into the address field of the address assignment message and transmitting the message to the end station if the address is assigned and unique.

19. The method of claim 18 further comprising the step of (F) reissuing the address assignment message from the end station to the intermediate station with the null value loaded into the address field if the assigned address is unacceptable to the end station.

20. The method of claim 19 further comprising the step of (G) acknowledging receipt and acceptance of the assigned address by issuing the address assignment message from the end station to the intermediate station with the assigned address loaded into the address field.

21. The method of claim 20 wherein the address is at media access control address.

22. The method of claim 21 wherein the address assignment message of step (C) is a capability exchange request message.

23. The method of claim 22 wherein the address assignment message of step (E) is a capability exchange response message.