NETWORK COMMUNICATION WITH PATH MTU SIZE DISCOVERY

• US 20080298376A1
• Filed: 05/30/2007
• Published: 12/04/2008
• Est. Priority Date: 05/30/2007
• Status: Active Grant

• Current Assignee: Sony Interactive Entertainment Inc. (Sony Group Corp.)
• Original Assignee: Sony Computer Entertainment Incorporated (Sony Group Corp.)
• Inventors: Marr, James E., Takeda, Yutaka, White, Payton R.
• Granted Patent: US 7,995,478 B2
• Time in Patent Office: Days
• US Class Current: 370/400
• CPC Class Codes: H04L 43/50 Testing arrangements
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/36 by determining packet size, e.g. maximum transfer unit [MTU]

Abstract

A method for network communication and an apparatus for discovery of a maximum transmission unit (MTU) size in a path between two nodes of a network are disclosed. A plurality of test packets of varying transmission unit (TU) size may be sent from the first host to the second host. A “do not fragment” (DF) flag for the test packets is not set. It is determined whether one or more of the test packets were received by the second host. An estimated path MTU for a network path between the first and second hosts size may then be calculated based on one or more patterns of receipt of the test packets by the second host. Once the estimated Path MTU size has been determined, message packets of a size less than or equal to the Path MTU size may be sent over the network path.

Claims

1. A method for network communication between a first host and a second host connected by a network, the method comprising:

a) sending a plurality of test packets of varying transmission unit (TU) size from the first host to the second host, wherein a “

do not fragment”

(DF) flag for the test packets is not set;

b) determining whether one or more of the test packets were received by the second host;

c) calculating an estimated path MTU size for a network path between the first and second hosts based on one or more patterns of receipt of the test packets by the second host; and

d) sending one or more message packets of a size less than or equal to the estimated path MTU size over the network path.

2. The method of claim 1 wherein a) comprises sending a first test packet of an initial TU size and subsequently sending a second packet of a size which is greater than the initial TU size by about 50% or less.

3. The method of claim 2 wherein the initial TU size is about 576 bytes.

4. The method of claim 1 wherein c) comprises:

determining whether a network path between the first and second hosts is bit-rate limited or packet rate limited based on the one or more patterns.

5. The method of claim 4, wherein a) comprises sending one or more test packets of increasing size compared to an initial TU size from the first host to the second host.

6. The method of claim 5 wherein an increase in size of the test packets is characterized by a TU size increase that is less than or equal to about 50% of the initial TU size.

7. The method of claim 5 wherein the initial TU size is about 576 bytes.

8. The method of claim 4, wherein c) further comprises determining a data transfer rate of test packets received by the second host.

9. The method of claim 8 wherein determining the data transfer rate comprises including in the test packets a request for the second host to send a reply containing the data transfer rate and receiving the reply at the first host.

10. The method of claim 8, further comprising determining a behavior of the data transfer rate of the packets received by the second host as a function of TU size.

11. The method of claim 10, further comprising determining whether a drop in data transfer rate exhibits occurs above a particular TU size.

12. The method of claim 10, further comprising determining whether the data transfer rate tends to flatten out with increasing TU size.

13. The method of claim 1 wherein the plurality of test packets comprise a plurality of User Datagram Protocol (UDP) packets.

14. The method of claim 1, further comprising repetitively testing the path between the first and second host with packets of varying size to verify a previous result.

15. The method of claim 1 wherein a) comprises, sending one or more packets at an initial bandwidth and gradually increasing the bandwidth for subsequent packets until bandwidth saturation is detected.

16. The method of claim 1 wherein d) takes place by peer-to-peer connection between an application layer of a protocol stack on the first host and an application layer of a protocol stack on the second host.

17. The method of claim 1 wherein d) takes place by peer-to-peer connection between a transport layer of a protocol stack on the first host and a transport layer of a protocol stack on the second host.

18. An apparatus for discovery of a maximum transmission unit (MTU) size in a path between two nodes of a network, comprising:

a first host having a computer with a computer readable program stored in a memory the wherein the program is configured to implement a method for discovery of a path MTU size between the two nodes, the method comprising;

sending a plurality of test packets of varying transmission unit (TU) size from the first host to the second host;

determining whether one or more of the test packets were received by the second host; and

calculating an estimated path MTU size for a network path between the first and second hosts based on one or more patterns of receipt of the test packets by the second host.

19. The apparatus of claim 18 wherein the first host includes a protocol stack having an application layer, wherein the program is configured to be implemented at the application layer.

20. A computer readable medium encoded with a computer readable program configured to implement a method for discovery of a maximum transmission unit (MTU) size in a path between a first host and a second host connected by a network, the computer readable program comprising:

a) an instruction that when executed causes the first host to send a plurality of test packets of varying transmission unit (TU) size from the first host to the second host;

b) an instruction that when executed causes the first host to determine whether one or more of the test packets were received by the second host; and

c) an instruction that when executed causes the first host to calculate an estimated path MTU size for a network path between the first and second hosts based on one or more patterns of receipt of the test packets by the second host.