Method and apparatus for encoding bridging/switching information within a routing information filed in a token ring environment

• US 6,714,541 B1
• Filed: 08/10/1999
• Issued: 03/30/2004
• Est. Priority Date: 08/10/1999
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Iyer, Jayaraman, Patel, Kushal A.
• Primary Examiner(s): Jung, Min
• Application Number:
  US09/371,672
• Time in Patent Office: 1,694 Days
• Field of Search: 370/389, 370/392, 370/395.3, 370/395.31, 370/395.5, 370/395.53, 370/395.54, 370/395.7, 370/401, 370/465, 370/466, 709/238, 709/242
• US Class Current: 370/392
• CPC Class Codes: H04L 45/00 Routing or path finding of packets in data switching networks routing or path finding in wireless networks H04W40/00

Abstract

A technique increases the efficiency of functions performed by an intermediate device of a computer network by encoding a portion of a routing information field (RIF) of a token ring frame transported over the network with information for use by the device. The maximum number of route descriptor (RD) hops in the network is altered to provide a predetermined portion of the RIF for storing encoded information. Each intermediate device configured in accordance with the technique identifies this predetermined portion as that portion of the RIF immediately following its matching RD.

Claims

1. A method for operating an intermediate device of a computer network, the method comprising the steps of:

receiving a token ring (TR) frame transported over the computer network at the intermediate device, the TR frame transmitted by a source host, the TR frame including a routing information field (RIF), the RIF including a plurality of route descriptors (RDs);

using a RD to designate the intermediate device;

modifying a predetermined portion of the RIF of the TR frame; and

transmitting a second TR frame to the source host to enable the modified RIF to be incorporated into a plurality of subsequent data frames of a session, the predetermined portion of the RIF used by the intermediate device in processing the subsequent data frames.

2. The method of claim 1 wherein the step of encoding comprises the step of:

altering a maximum number of RDs capable of being stored in the RIF to provide the predetermined portion of the RIF of the second TR frame.

3. The method of claim 2 further comprising the step of:

locating the predetermined portion as that portion of the RIF immediately following the RD that designates the intermediate device.

4. The method of claim 3 wherein the intermediate device is a Data Link Switching (DLSw) switch and wherein the step of encoding further comprises the step of:

configuring the DLSw switch to encode a first part of the predetermined portion of the RIF with a value that enables efficient searching of a DLSw table.

5. The method of claim 4 further comprising the step of:

wherein the value is a session index, accessing information stored on the DLSw table using the session index when correlating logical link control type 2 frames with switch-to-switch protocol frames transmitted over transmission control protocol (TCP) connection sessions through a TCP/IP cloud of the network.

6. The method of claim 5 wherein the step of configuring the DLSw switch to encode a first part of the predetermined portion of the RIF with the session index further comprises the step of:

using a small value rather than a large address to access the DLSw table to thereby increase efficiency of table searching.

7. The method of claim 6 wherein the step of encoding further comprises the step of:

encoding a second part of the predetermined portion of the RIF to provide prioritization information associated with TR frames transmitted over the TCP sessions.

8. The method of claim 7 wherein the step of encoding the second part of the predetermined portion of the RIF comprises the step of:

prioritizing the TR frames in an order specified by transmission priority information available at the DLSw switch.

9. The method of claim 3 wherein the intermediate device is a TR switch having a plurality of Concentrator Relay Functions (CRF) coupled to a Bridge Relay Function (BRF) and wherein the step of encoding further comprises the step of:

configuring the TR switch to encode a predetermined portion of the RIF with information that enables efficient rendering of forwarding decision operations with respect to subsequent frames received at and transmitted from ports associated with the CRFs.

10. The method of claim 9 wherein the step of identifying the predetermined portion comprises the step of:

scanning the RIF at port circuitry of an inbound port of the TR switch to find the matching RD.

11. The method of claim 10 further comprising the step of:

wherein the information is an identifier, accessing entries of a forwarding table using the identifier when rendering forwarding decisions for the subsequent frames.

27. A computer readable media, comprising:

said computer readable media containing instructions for execution in a processor of the method of claim 1 or 21.

28. Electromagnetic signals propagating on a computer network, comprising:

said electromagnetic signals carrying instructions for execution on a processor for the practice of the method of claim 1 or 21.

12. An intermediate device of a computer network, comprising:

means for receiving a token ring (TR) frame transported over the computer network at the intermediate device, the TR frame transmitted by a source host, the TR frame including a routing information field (RIF), the RIF including a plurality of route descriptors (RDs);

means for using a RD to designate the intermediate device;

means for modifying a predetermined portion of the RIF of the TR frame; and

means for transmitting a second TR frame to the source host to enable the modified RIF to be incorporated into a plurality of subsequent data frames of a session, the predetermined portion of the RIF used by the intermediate device in processing the subsequent data frames.

13. The apparatus of claim 12 wherein the means for encoding comprises:

means for altering a maximum number of RDs capable of being stored in the RIF to provide the predetermined portion of the RIF of the second TR frame.

14. The apparatus of claim 13 wherein the intermediate device is a Data Link Switching (DLSw) switch and wherein the means for encoding further comprises:

means for encoding a first part of the predetermined portion of the RIF with a value that enables efficient searching of a DLSw table coupled to the DLSw switch.

15. The apparatus of claim 14, further comprising:

the value is a session index.

16. The apparatus of claim 15 further comprising:

means for accessing information stored on the DLSw table using the session index when correlating logical link control type 2 frames with switch-to-switch protocol frames transmitted over transmission control protocol (TCP) connection sessions through a TCP/IP cloud of the network.

17. The apparatus of claim 16 wherein the means for encoding further comprises:

means for encoding a second part of the predetermined portion of the RIF to provide prioritization information associated with TR frames transmitted over the TCP sessions.

18. The apparatus of claim 17 wherein the means for encoding the second part of the predetermined portion of the RIF comprises:

means for prioritizing the TR frames in an order specified by transmission priority information available at the DLSw switch.

19. The apparatus of claim 13 wherein the intermediate device is a TR switch having a plurality of Concentrator Relay Functions (CRF) coupled to a Bridge Relay Function (BRF) and wherein the means for encoding further comprises:

means for encoding a predetermined portion of the RIF with information that enables efficient rendering of forwarding decision operations with respect to subsequent frames received at and transmitted from ports associated with the CRFs.

20. The apparatus of claim 19, further comprising:

the information is an identifier.

21. A method for operating an intermediate device of a computer network, the method comprising the steps of:

receiving an I-can-reach explorer frame (ICR_ex) at the intermediate device, the ICR_ex frame transmitted by a peer intermediate device in response to a can-u-reach explorer frame (CUR_ex) transmitted by the intermediate device, the CUR_ex frame transmitted in response to the intermediate device receiving a first token ring (TR) frame from a host;

the first TR frame including a routing information field (RIF), the RIF including a plurality of route descriptors (RDs);

incorporating into a RIF of a second TR frame a RD corresponding to the intermediate device and an INFO field, the INFO field storing an index into a switching table of the intermediate device; and

transmitting, in response to receiving the ICR_ex frame, the second TR frame to the host to enable the host to transmit a further TR frame incorporating the INFO field in a RIF field of the further TR frame.

22. The method of claim 21 further comprising the step of:

receiving a data frame from the host, the data frame having a RIF including a RD corresponding to the intermediate device and an INFO field storing an index following the RD; and

using the index to perform a lookup operation on the switching table of the intermediate device.

23. The method of claim 22 wherein the step of incorporating further comprises the step of:

storing priority information in the INFO field to thereby specify transmission priority.

24. An intermediate device of a computer network, the apparatus comprising:

means for receiving an I-can-reach explorer frame (ICR_ex) at the intermediate device, the ICR_ex frame transmitted by a peer intermediate device in response to a can-u-reach explorer frame (CUR_ex) transmitted by the intermediate device, the CUR_ex frame transmitted in response to the intermediate device receiving a first token ring (TR) frame from a host;

the first TR frame including a routing information field (RIF), the RIF including a plurality of route descriptors (RDs);

means for incorporating into a RIF of a second TR frame a RD corresponding to the intermediate device and an INFO field, the INFO field storing an index into a switching table of the intermediate device; and

means for transmitting, in response to receiving the ICR_ex frame, the second TR frame to the host to enable the host to transmit a further TR frame incorporating the INFO field in a RIF field of the further TR frame.

25. The apparatus of claim 24 further comprising:

means for receiving a data frame from the host, the data frame having a RIF including a RD corresponding to the intermediate device and an INFO field storing an index following the RD; and

means for using the index to perform a lookup operation on a switching table in the intermediate device.

26. The apparatus of claim 24, further comprising:

means for storing priority information in the INFO field to thereby specify transmission priority.