Redundancy mechanisms for classical internet protocol over asynchronous transfer mode networks

• US 5,936,936 A
• Filed: 04/11/1997
• Issued: 08/10/1999
• Est. Priority Date: 04/11/1997
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: International Business Machines Corporation
• Inventors: Yedavalli, Rama Mohan, Smith, Timothy James, Verrilli, Colin Beaton, Alexander, Cedell Adam Jr.
• Primary Examiner(s): VU, HUY DUY
• Application Number:
  US08/826,988
• Time in Patent Office: 851 Days
• Field of Search: 370/395, 370/396, 370/397, 370/398, 370/399, 370/216, 370/217, 370/218, 370/219, 370/220, 370/241, 370/242, 370/244, 370/245, 370/250, 370/252, 370/401, 370/402, 395/200.75
• US Class Current: 370/216
• CPC Class Codes: H04L 2012/5618 Bridges, gateways [GW] or interworking units [IWU]
• CPC Class Codes: H04L 2012/562 Routing
• CPC Class Codes: H04L 2012/5627 Fault tolerance and recovery
• CPC Class Codes: H04L 2012/5667 IP over ATM
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections

Abstract

A primary ARP server and a backup ARP server are connected to an ATM communications network. The primary and backup ARP servers each have associated ATM addresses. Also, a LIS is connected to the ATM communications network. Either the primary or backup ARP server is the active ARP server and resolves IP addresses to ATM addresses for the LIS. When the backup ARP server recognizes the removal of a redundancy virtual channel connection (VCC) between the backup ARP server and the primary ARP server, the backup ARP server registers using the ATM address associated with the primary ARP server. This allows the backup ARP server to take over for the primary ARP server to become the active ARP server.

In addition, a primary default gateway and a backup default gateway are connected to the ATM communications network. These default gateways have associated ATM addresses. One of the primary and backup default gateways is active at a time. The active default gateway provides routing services for hosts that do not run routing topology protocols. When the backup default gateway recognizes the removal of a redundancy virtual channel connection (VCC) between the backup default gateway and the primary default gateway, the backup default gateway registers a mapping between the ATM address associated with the backup default gateway and an IP address of the default gateway. In this manner the backup default gateway takes over for the primary default gateway to become the active default gateway.

Claims

1. An asynchronous transfer mode (ATM) communications network with redundant address resolution protocol (ARP) servers, comprising:

a primary ARP server and a backup ARP server, wherein both the primary and backup ARP servers are connected to the ATM communications network and wherein the primary and backup ARP servers have associated ATM addresses;

a logical internet protocol subnet (LIS), wherein the LIS is connected to the ATM communications network, and wherein an active ARP server resolves internet protocol (IP) addresses to ATM addresses for the LIS;

the primary and backup ARP servers being operable in a first switchover mode of operation, wherein

the backup ARP server recognizes a removal of a redundancy virtual channel connection (VCC) between the backup ARP server and the primary ARP server; and

the backup ARP server registers using the ATM address associated with the primary ARP server, wherein the backup ARP server takes over for the primary ARP server to become the active ARP server.

2. The communications network as defined in claim 1, with the primary and backup ARP servers being operable in a second switchover mode of operation, wherein

the primary ARP server reestablishes the redundancy VCC to the backup ARP server, where the backup ARP server is active;

the backup ARP server deregisters its ATM address from the ATM communications network; and

the primary ARP server registers its ATM address and becomes the active ARP server.

3. The communications network as defined in claim 1, wherein the primary and backup ARP servers have ATM addresses which are used to establish the redundancy VCC.

4. The communications network as defined in claim 1, further comprising a plurality of clients connected to the LIS which utilize the active ARP server to resolve IP addresses to ATM addresses.

5. The communications network as recited in claim 1, wherein the ATM addresses associated with the primary and backup ARP servers have identical end system identifiers and selectors.

6. An asynchronous transfer mode (ATM) communications network with redundant default gateways, comprising:

a primary default gateway and a backup default gateway, wherein both the primary and backup default gateways are connected to the ATM communications network and wherein ATM addresses are associated with the primary and backup default gateways;

a logical internet protocol subnet (LIS), wherein the LIS is connected to the ATM communications network; and

an active default gateway for providing routing services for hosts that do not run routing topology protocols;

the primary and backup default gateways being operable in a first switchover mode of operation, wherein

the backup default gateway recognizes the removal of a redundancy virtual channel connection (VCC) between the backup default gateway and the primary default gateway; and

the backup default gateway registers a mapping between the ATM address associated with the backup default gateway and an IP address of the default gateway, wherein the backup default gateway takes over for the primary default gateway to become the active default gateway.

7. The communications network as defined in claim 6, with the primary and backup default gateways being operable in a second switchover mode of operation, wherein

the primary default gateway reestablishes the redundancy VCC to the backup default gateway, where the backup default gateway is active;

the backup default gateway releases VCCs associated with itself; and

the primary default gateway registers a mapping between the ATM address associated with the primary default gateway and the IP address of the default gateway.

8. The communications network as defined in claim 6, wherein the primary and backup default gateways have ATM addresses which are used to establish the redundancy VCC.

9. The communications network as defined in claim 6, further comprising a plurality of clients connected to the LIS which utilize the active default gateway to provide routing services.

10. The communications network as defined in claim 6, wherein the ATM communications network includes a first and a second interconnected ATM switches, where the primary default gateway is connected to the first ATM switch and the backup default gateway is connected to the second ATM switch.

11. A method of communicating using an asynchronous transfer mode (ATM) communications network with redundant address resolution protocol (ARP) servers, comprising:

providing a primary ARP server and a backup ARP server, wherein both the primary and backup ARP servers are connected to the ATM communications network and wherein the primary and backup ARP servers have associated ATM addresses;

providing a logical internet protocol subnet (LIS), wherein the LIS is connected to the ATM communications network, and wherein an active ARP server resolves internet protocol (IP) addresses to ATM addresses for the LIS;

removing a redundancy virtual channel connection (VCC) between the backup ARP server and the primary ARP server;

detecting the removal of the redundancy VCC using the backup ARP server; and

registering the ATM address associated with the primary ARP server using the backup ARP server, wherein the backup ARP server takes over for the primary ARP server to become the active ARP server.

12. The method as defined in claim 11, further comprising:

reestablishing the redundancy VCC between the primary ARP server and the backup ARP server, where the backup ARP server is active;

deregistering the ATM address associated with the primary ARP server; and

registering the address associated with the primary ARP server using the primary ARP server where the primary ARP server becomes the active ARP server.

13. The method as defined in claim 11, wherein the primary and backup ARP servers have ATM addresses which are used to establish the redundancy VCC.

14. The method as defined in claim 11, further comprising:

providing a plurality of clients connected to the LIS which utilize the active ARP server to resolve IP addresses to ATM addresses.

15. The communications network as recited in claim 11, wherein the ATM addresses associated with the primary and backup ARP servers have identical end system identifiers and selectors.

16. An method of communicating using an asynchronous transfer mode (ATM) communications network with redundant default gateways, comprising:

providing a primary default gateway and a backup default gateway, wherein both the primary and backup default gateways are connected to the ATM communications network and wherein ATM addresses are associated with the primary and backup default gateways;

providing a logical internet protocol subnet (LIS), wherein the LIS is connected to the ATM communications network, and an active default gateway which provides routing services for hosts that do not run routing topology protocols;

removing a redundancy virtual channel connection (VCC) between the backup default gateway and the primary default gateway;

recognizing the removal of the redundancy VCC using the backup default gateway; and

registering a mapping between the ATM address associated with the backup default gateway and an IP address of the default gateway, wherein the backup default gateway takes over for the primary default gateway to become the active default gateway.

17. The method as defined in claim 16, further comprising:

reestablishing the redundancy VCC between the primary default gateway and the backup default gateway, where the backup default gateway is active;

releasing VCCs associated with the backup default gateway; and

registering a mapping between the ATM address associated with the primary default gateway and the IP address of the default gateway, wherein the primary default gateway takes over for the backup default gateway.

18. The method as defined in claim 16, wherein the primary and backup default gateways have ATM addresses which are used to establish the redundancy VCC.

19. The method as defined in claim 16, further comprising:

providing a plurality of clients connected to the LIS which utilize the active default gateway to provide routing services.

20. The method as defined in claim 16, wherein the ATM communications network includes a first and a second interconnected ATM switches, where the primary default gateway is connected to the first ATM switch and the backup default gateway is connected to the second ATM switch.