Method and apparatus for switching routable frames between disparate media

• US 6,061,356 A
• Filed: 11/25/1996
• Issued: 05/09/2000
• Est. Priority Date: 11/25/1996
• Status: Expired due to Term

• Current Assignee: Alcatel SA (Nokia Corporation)
• Original Assignee: Alcatel Internetworking Incorporated (Nokia Corporation)
• Inventors: Terry, Philip Frank
• Primary Examiner(s): Vu, Huy D.
• Assistant Examiner(s): KWOH, JASPER C
• Application Number:
  US08/756,284
• Time in Patent Office: 1,261 Days
• Field of Search: 370/466, 370/467, 370/351, 370/401, 370/445
• US Class Current: 370/401
• CPC Class Codes: H04L 12/4625 Single bridge functionality, e.g. connection of two networks over a single bridge

Abstract

A method and apparatus for switching/bridging frames between a heterogeneous media is disclosed. Bridges and/or switches normally bit-swap a MAC header of a frame when switching the frame between heterogeneous media. However, this practice introduces errors in address formats in certain situations. Such problems are resolved by investigating whether a frame to be switched includes local address components, and if so, these address components in the frame are manipulated to ensure that the address formats are proper for a media onto which the frame is being switched.

Claims

1. A method for switching frames between a medium operating according to a first protocol and a medium operating according to a second protocol, the method comprising the steps of:

receiving a frame;

determining whether a first address in the frame is a local address, including comparing a second address in the frame with the first address, wherein the second address is a Data Link layer address and the first address is not a Data Link layer address; and

formatting the first address in accordance with expectations of a station on the medium onto which the frame is being switched if the first address is determined to be a local address.

2. The method of claim 1 wherein the step of determining if the first address is a local address comprises the step of:

comparing a source address in a media access control (MAC) header of the frame with a source node address in an Internet Packet Exchange (IPX) header of the frame, wherein a match in the comparison identifies the first address as a local address.

3. The method of claim 1 wherein the step of determining if the first address is a local address comprises the step of:

comparing a destination address in a MAC header of the frame with a destination node address in an IPX header of the frame, wherein a match in the comparison identifies the first address as a local address.

4. The method of claim 1 wherein the step of formatting the first address, in the case where the second protocol is Token ring, comprises the steps of:

converting an address in an IPX header of the frame to noncanonical format if not already in noncanonical format.

5. The method of claim 1 wherein the step of formatting the first address, in the case where the second protocol is carrier sense multiple access with collision detection (CSMA/CD), comprises the steps of:

converting an address in an IPX header of the frame to canonical format if not already in canonical format.

6. The method of claim 1 wherein the step of formatting the first address, in the case where the second protocol is fiber distributed data interface (FDDI), comprises the steps of:

converting an address in an IPX header of the frame to canonical format if not already in canonical format.

7. The method of claim 1 wherein the step of determining if the first address is a local address comprises the step of:

examining a socket number in a User Datagram Protocol (UDP) header of the frame; and

comparing a source address in a MAC header of the frame with an address in a Dynamic Host Configuration Protocol (DHCP) message field of the frame, wherein a match in the comparison identifies the first address as a local address.

8. The method of claim 1 wherein the step of determining if the first address is a local address comprises the step of:

examining a socket number in a UDP header of the frame; and

comparing a destination address in a MAC header of the frame with an address stored in a DHCP message field of the frame, wherein a match in the comparison identifies the first address as a local address.

9. The method of claim 1 wherein the step of formatting the first address, in the case where the second protocol is Token ring, comprises the steps of:

converting an address in a DHCP message field of the frame to noncanonical format if not already in noncanonical format.

10. The method of claim 1 wherein the step of formatting the first address, in the case where the second protocol is CSMA/CD, comprises the steps of:

converting an address in a DHCP message field of the frame to canonical format if not already in canonical format.

11. The method of claim 1 wherein the step of formatting the first address, in the second protocol is FDDI, comprises the steps of:

converting an address in a DHCP message field of the frame to canonical format if not already in canonical format.

12. The method of claim 1, wherein the step of determining whether the first address is a local address comprises identifying the first and second protocols according to which the media are operating.

13. An apparatus for switching frames between a medium operating according to a first protocol and a medium operating according to a second protocol, the apparatus comprising:

means for receiving a frame;

means for determining whether a first address in the frame is a local address, including comparing a second address in the frame with the first address, wherein the second address is a Data Link layer address and the first address is not a Data Link layer address; and

means for formatting the first address in accordance with expectations of a station on the medium onto which the frame is being switched if the first address is determined to be a local address.

14. The apparatus of claim 13 wherein the means for determining if the first address is a local address compares a source address in a MAC header of the frame with a source node address in an IPX header of the frame, wherein a match identifies the first address as a local address.

15. The apparatus of claim 13 wherein the means for determining if the first address is a local address compares a destination address in a MAC header of the frame with a destination node address in an IPX header of the frame, wherein a match in the comparison identifies the first address as a local address.

16. The apparatus of claim 13 wherein, in the case where the second protocol is Token ring, the means for formatting the first address converts an address in an IPX header of the frame to noncanonical format if not already in noncanonical format.

17. The apparatus of claim 13 wherein, in the case where the second protocol is CSMA/CD, the means for formatting the first address converts an address in an IPX header of the frame to canonical format if not already in canonical format.

18. The apparatus of claim 13 wherein, in the case where the second protocol is FDDI, the means for formatting the first address converts an address in an IPX header of the frame to canonical format if not already in canonical format.

19. The apparatus of claim 13, wherein the means for determining if the first address is a local address comprises:

means for examining a socket number carried in a UDP header of the frame; and

means for comparing a source address in a MAC header of the frame with an address in a DHCP message field of the frame, wherein a match in the comparison identifies the first address as a local address.

20. The apparatus of claim 13, wherein the means for determining if the first address is a local address comprises:

means for examining a socket number carried in a UDP header of the frame; and

means for comparing a destination address in a MAC header of the frame with an address in a DHCP message field of the frame, wherein a match in the comparison identifies the first address as a local address.

21. The apparatus of claim 13, wherein the means for determining whether the second address is a local address comprises identifying the first and second protocols according to which the media are operating.

22. A method for switching frames between a medium operating according to a first protocol and a medium operating according to a second protocol, wherein the first and second protocols are different, the method comprising the steps of:

receiving a frame;

comparing a Data Link layer address in the frame with a Network layer address in the frame for a match; and

formatting the Network layer address in accordance with expectations of a station on the medium onto which the frame is being switched.

23. The method of claim 22 wherein the first layer is the Data Link layer and the second layer is the Network layer.

24. The method of claim 22 wherein the comparing step comprises:

comparing a source address in a MAC header of the frame with a source node address in an IPX header of the frame.

25. The method of claim 22 wherein the comparing step comprises:

comparing a destination address in a MAC header of the frame with a destination node address in an IPX header of the frame.

26. The method of claim 22 wherein the formatting step, in the case where the second protocol is Token ring, comprises converting the Network layer address to noncanonical format if not already in noncanonical format.

27. The method of claim 22 wherein the formatting step, in the case where the second protocol is CSMA/CD, comprises converting the Network layer address to canonical format if not already in canonical format.

28. The method of claim 22 wherein the formatting step, in the case where the second protocol is FDDI, comprises converting the Network layer address to canonical format if not already in canonical format.

29. The method of claim 22 wherein the comparing step comprises identifying the first and second protocols operating at the first layer.

30. An apparatus for switching frames between a medium operating according to a first protocol and a medium operating according to a second protocol, wherein the first and second protocols are different, the apparatus comprising means for receiving a frame;

means for comparing a Data Link layer address in the frame with a Network layer address in the frame for a match; and

means for formatting the Network layer address in accordance with expectations of a station on the medium onto which the frame is being switched.