Network protocol header alignment

• US 8,599,855 B2
• Filed: 11/16/2010
• Issued: 12/03/2013
• Est. Priority Date: 11/15/2004
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Lee, William, Wright, Michael, Chowdhury, Joydeep, Haridas, Sriram, Hughes, Martin
• Primary Examiner(s): TOWFIGHI, AFSHAWN M
• Application Number:
  US12/947,535
• Publication Number:
  US 20110064081A1
• Time in Patent Office: 1,113 Days
• Field of Search: 370/392, 370/401, 370/389, 370/258
• 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
• CPC Class Codes: H04L 45/60 Router architectures
• CPC Class Codes: H04L 49/602 Multilayer or multiprotocol switching, e.g. IP switching

Abstract

Techniques for routing a payload of a first network protocol, which includes header information for a second network protocol, include communicating a packet. In a circuit block, a first type for the first network protocol and a second type for the second network protocol are determined. The circuit block stores a classification that indicates a unique combination of the first type and the second type. A general purpose processor routes the packet based on the classification. Processor clock cycles are saved that would be consumed in determining the types. Furthermore, based on the classification, the processor can store an offset value for aligning the header relative to a cache line. The circuit block can store the packet shifted by the offset value. The processor can then retrieve from memory a single cache line to receive the header, thereby saving excess loading and ejecting of cache.

Claims

1. A method comprising:

receiving a packet;

identifying a type of a first network protocol and a type of a second network protocol, the first network protocol and the second network protocol used by the packet;

determining a classification of the packet based on the type of the first network protocol combined with the type of the second network protocol;

receiving an offset value associated with the classification; and

aligning a header for the second network protocol relative to a boundary of a cache line by shifting the packet based on the offset value.

2. The method of claim 1, further comprising:

routing the packet based at least in part on the second network protocol.

3. The method of claim 1, wherein the offset value is a number of bits.

4. The method of claim 1, wherein

determining the classification comprises selecting a classification code for the packet based on the type of the first network protocol combined with the type of the second network protocol;

and

receiving the offset values comprises accessing a table to retrieve the offset value associated with the classification code.

5. The method of claim 4, wherein the table comprises a plurality of registers and at least one multiplexer.

6. The method of claim 4, wherein the first network protocol is one of a first plurality of protocols indexed in rows of the table and the second network protocol is one of a second plurality of protocols indexed in columns of the table.

7. The method of claim 6, wherein the second plurality of protocols includes multi-protocol layer switch (MPLS).

8. The method of claim 1, wherein the first network protocol is an Open Systems Interconnection (OSI) data link layer or layer 2 protocol and the second network protocol is an OSI layer other than data link layer or layer 2 and included in a payload of the first network protocol.

9. The method of claim 1, further comprising:

padding a start of the packet with an arbitrary value until the packet is shifted by a number of bits indicated by the offset value.

10. An apparatus comprising:

a network interface configured to receive a packet;

a controller in communication with the network interface and configured to identify a first network protocol and a second network protocol used by the packet, the controller further configured to determine an offset value based on a combination of the identities of the first network protocol and the second network protocol; and

a memory configured to store the packet according to the offset value through alignment of a header for the second network protocol relative to a boundary of a cache line.

11. The apparatus of claim 10, further comprising:

a central processing unit (CPU) configured to read the cache line from the memory and route the packet according to the cache line.

12. The apparatus of claim 11, further comprising:

a device bus configured to facilitate communication between the CPU and the network interface in communication with the controller.

13. The apparatus of claim 10, wherein the offset value is a number of bits defined by a size of headers of the first network protocol.

14. The apparatus of claim 10, wherein the controller is further configured to select a classification code for the packet based the combination of the identities of the first network protocol and the second network protocol and access a table to retrieve the offset value associated with the classification code.

15. The apparatus of claim 14, wherein the first network protocol is one of a first plurality of protocols indexed in rows of the table and the second network protocol is one of a second plurality of protocols indexed in columns of the table.

16. The apparatus of claim 10, further comprising:

a plurality of registers each configured to store one of a plurality of offset values; and

a multiplexer configured to select one of the plurality of registers based on a classification code associated with a unique combination of network protocols and output the offset value.

17. The apparatus of claim 10, wherein the first network protocol is an Open Systems Interconnection (OSI) data link layer or layer 2 protocol and the second network protocol is an OSI layer other than data link layer or layer 2 and included in a payload of the first network protocol.

18. The apparatus of claim 10, wherein the controller is further configured to pad a start of the packet with an arbitrary value until the packet is shifted by a number of bits indicated by the offset value.

19. A computer readable storage medium encoded with computer executable instructions operable to:

receive a packet at a network interface including a controller;

identify types of a first network protocol and a second network protocol used by the packet;

select a classification code based on a combination of the types of the first network protocol and the second network protocol;

associate an offset value with the combination of the types of the first network protocol and the second network protocol using the classification code;

store a header for the second network protocol relative to a boundary of a cache line by shifting the packet based on the offset value; and

send an interrupt to a central processing unit (CPU) to initiate processing of the second network protocol.

20. The computer readable storage medium of claim 19, wherein a network link facilitates communication between the controller and the CPU.