Offloaded neighbor cache entry synchronization

• US 20070083638A1
• Filed: 08/31/2005
• Published: 04/12/2007
• Est. Priority Date: 08/31/2005
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Kaniyar, Sanjay, Pinkerton, James
• Granted Patent: US 7,886,083 B2
• Time in Patent Office: Days
• US Class Current: 709/224
• CPC Class Codes: H04L 69/12 Protocol engines
• CPC Class Codes: H04L 69/161 Implementation details of TCP/IP or UDP/IP stack architecture; Specification of modified or new header fields
• CPC Class Codes: H04L 69/32 Architecture of open systems interconnection [OSI] 7-layer type protocol stacks, e.g. the interfaces between the data link level and the physical level
• CPC Class Codes: H04L 69/321 Interlayer communication protocols or service data unit [SDU] definitions; Interfaces between layers

Abstract

A method for the synchronization of network neighbor reachability between a host networking stack and a peripheral device, which offloads one or more network protocols is provided. The network neighbor reachability represents the reachability of another computer on the network. This invention enables conventional neighbor reachability to be extended to seamlessly support some network connections to a specific remote host to be offloaded to a peripheral device, while other network connections are not.

Claims

1. At least one computer-readable medium having thereon computer-executable instructions for offloaded neighbor cache entry synchronization comprising:

determining a host reachability delta;

if the host reachability delta is greater than a threshold, querying an offload target for a device reachability delta; and

re-determining the host reachability delta.

2. Said at least one computer-readable medium of claim 1, wherein:

the computer-executable instructions further comprise retrieving a host reachability time from a neighbor state object; and

determining the host reachability delta comprises determining the host reachability delta as a function of, at least, the host reachability time.

3. Said at least one computer-readable medium of claim 2, wherein:

the neighbor state object is a host neighbor state object maintained by a host;

a device neighbor state object corresponding to the host neighbor state object is maintained by the offload target; and

each neighbor state object references a corresponding neighbor cache entry.

4. Said at least one computer-readable medium of claim 1, wherein:

the computer-executable instructions further comprise;

receiving the device reachability delta from the offload target; and

updating a host reachability time as a function of, at least, the device reachability delta; and

re-determining the host reachability delta comprises re-determining the host reachability delta as a function of, at least, the updated host reachability time.

5. Said at least one computer-readable medium of claim 4, wherein updating the host reachability time as a function of, at least, the device reachability delta comprises setting the host reachability time to a maximum of a set of values comprising:

a current host reachability time; and

a difference between a current time and the device reachability delta.

6. At least one computer-readable medium having thereon computer-executable instructions for offloaded neighbor cache entry synchronization comprising:

determining a device reachability delta;

if the device reachability delta is greater than a threshold, querying a host for a host reachability delta; and

receiving the host reachability delta from the host.

7. Said at least one computer-readable medium of claim 6, wherein:

the computer-executable instructions further comprise retrieving a device reachability time from a neighbor state object; and

determining the device reachability delta comprises determining the device reachability delta as a function of, at least, the device reachability time.

8. Said at least one computer-readable medium of claim 7, wherein determining the device reachability delta comprises:

determining a difference between a current time and the device reachability time; and

applying a scaling function to compensate for clock differences.

9. Said at least one computer-readable medium of claim 7, wherein:

the neighbor state object is a device neighbor state object maintained by an offload target;

a host neighbor state object corresponding to the device neighbor state object is maintained by the host; and

each neighbor state object references a corresponding neighbor cache entry.

10. Said at least one computer-readable medium of claim 6, wherein querying the host comprises providing the device reachability delta to the host.

11. Said at least one computer-readable medium of claim 10, wherein the computer-executable instructions further comprise:

updating a host reachability time as a function of, at least, the device reachability delta provided by the query; and

determining the host reachability delta as a function of, at least, the updated host reachability time.

12. Said at least one computer-readable medium of claim 11, wherein updating the host reachability time as a function of, at least, the device reachability delta provided by the query comprises setting the host reachability time to a maximum of a set of values comprising:

a current host reachability time; and

a difference between a current time and the device reachability delta provided by the query.

13. Said at least one computer-readable medium of claim 11, wherein the computer-executable instructions further comprise updating a neighbor cache entry state if the device reachability delta is greater than a threshold.

14. Said at least one computer-readable medium of claim 6, wherein the computer-executable instructions further comprise:

determining the host reachability delta;

determining a neighbor cache entry state;

if the neighbor cache entry state is REACHABLE, responding to the query with the determined host reachability delta; and

otherwise, at least;

setting an invalidate timer; and

responding to the query with a nonstandard host reachability delta value.

15. Said at least one computer-readable medium of claim 14, wherein the computer-executable instructions further comprise querying an offload target for the device reachability delta in response to a triggering of the invalidate timer.

16. Said at least one computer-readable medium of claim 15, wherein the computer-executable instructions further comprise:

receiving the device reachability delta from the offload target;

updating a host reachability time as a function of, at least, the device reachability delta;

re-determining the host reachability delta as a function of, at least, the host reachability time;

if the re-determined host reachability delta exceeds the threshold, updating a neighbor cache entry state in accordance with a threshold exceeded event; and

otherwise, updating the neighbor cache entry state in accordance with a beneath threshold event.

17. Said at least one computer-readable medium of claim 16, wherein the computer-executable instructions further comprise:

sending a Neighbor Solicitation probe if the neighbor cache entry state is PROBE; and

if no response is received to the Neighbor Solicitation probe and a maximum number of Neighbor Solicitation probes has been sent, invalidating the neighbor cache entry.

18. At least one computer-readable medium having thereon computer-executable instructions for offloaded neighbor cache entry synchronization comprising:

offloading at least part of a communication protocol stack from a host to an offload target;

maintaining at least one neighbor cache entry at the host; and

minimizing neighbor cache entry synchronization traffic between the host and the offload target by delaying reachability delta queries until required for neighbor cache entry state transition correctness.

19. Said at least one computer-readable medium of claim 18, wherein delaying reachability delta queries until required for neighbor cache entry state transition correctness comprises querying the offload target for a device reachability delta if a host reachability delta exceeds a threshold.

20. Said at least one computer-readable medium of claim 18, wherein delaying reachability delta queries until required for neighbor cache entry state transition correctness comprises querying the host for a host reachability delta if a device reachability delta exceeds a threshold.