Hardware Time Stamping and Synchronized Data Transmission

• US 20090257354A1
• Filed: 06/19/2009
• Published: 10/15/2009
• Est. Priority Date: 03/30/2005
• Status: Active Grant

• Current Assignee: Keysight Technologies Singapore Sales Pte Ltd (Keysight Technologies, Inc.)
• Original Assignee: Ixia (Keysight Technologies, Inc.)
• Inventors: Hannel, Clifford, Olderdissen, Jan, Standridge, Roger, Schafer, Doug
• Granted Patent: US 8,159,957 B2
• Time in Patent Office: Days
• US Class Current: 370/241
• CPC Class Codes: H04J 3/0697 Synchronisation in a packet node
• CPC Class Codes: H04L 43/0858 One way delays
• CPC Class Codes: H04L 43/0864 Round trip delays
• CPC Class Codes: H04L 43/087 Jitter
• CPC Class Codes: H04L 43/106 using time related information in packets, e.g. by adding timestamps
• CPC Class Codes: H04L 43/50 Testing arrangements

Abstract

Hardware time stamping and synchronized data transmission disclosed. In a method, a reference time stamp and a local time stamp are obtained. A synchronization offset is prepared based on the local time stamp and the reference time stamp. Instructions are received to send a plurality of data units at a specified time. The plurality of data units are sent at the specified time based on referring to a local time obtained from a local clock and the synchronization offset to simultaneously send a packet storm comprising the plurality of data units. The method may be achieved by a network communications unit on a plurality of network cards included in a network testing system.

Claims

1. A method performed by a plurality of network cards in one or more network testing systems, each network card including a network communications unit, the method comprising:

each of the network communications units of the plurality of network cards obtaining a reference time stamp;

each of the network communications units of the plurality of network cards obtaining a local time stamp;

each of the network communications units of the plurality of network cards preparing a synchronization offset based on the local time stamp and the reference time stamp;

each of the plurality of network cards receiving instructions to send a plurality of data units at a specified time;

each of the plurality of network cards sending the plurality of data units at the specified time based on the network communications units of the plurality of network cards referring to a local time obtained from a local clock and the synchronization offset to simultaneously send a packet storm comprising the plurality of data units.

2. The method of claim 1 wherein the obtaining a reference time stamp comprises:

making a software call to an external time source, wherein the external time source is one of a satellite broadcast clock signal, a cellular telephone clock signal, and a global positioning system (GPS) signal.

3. The method of claim 1 wherein obtaining a reference time stamp comprises:

making a software call to a local crystal oscillator which is set by referring to an external time source, wherein the external time source is one of a satellite broadcast clock signal, a cellular telephone clock signal, and a global positioning system (GPS) signal.

4. The method of claim 1 wherein obtaining a local time stamp comprises:

obtaining the local time from a counter included in the network communications unit.

5. The method of claim 1 wherein preparing a synchronization offset comprises:

subtracting the local time stamp from the reference time stamp.

6. The method of claim 1 wherein the packet storm is directed to one of a network device, a network segment or a network application.

7. A network testing system comprising:

a plurality of network cards, each network card comprising;

a processor,

a memory coupled with the processor,

a network communications unit coupled with the processor,

a PHY unit coupled with the network communications unit and to a network,

the network communications unit having instructions stored thereon which when executed cause the network communications unit to perform actions comprising;

obtaining a reference time stamp;

obtaining a local time stamp;

preparing a synchronization offset based on the local time stamp and the reference time stamp;

receiving instructions to send a plurality of data units at a specified time;

sending the plurality of data units at the specified time based on referring to a local time obtained from a local clock and the synchronization offset to simultaneously send a packet storm comprising the plurality of data units.

8. The network testing system of claim 7 wherein the obtaining a reference time stamp comprises:

making a software call to an external time source, wherein the external time source is one of a satellite broadcast clock signal, a cellular telephone clock signal, and a global positioning system (GPS) signal.

9. The network testing system of claim 7 wherein obtaining a reference time stamp comprises:

making a software call to a local crystal oscillator which is set by referring to an external time source, wherein the external time source is one of a satellite broadcast clock signal, a cellular telephone clock signal, and a global positioning system (GPS) signal.

10. The network testing system of claim 7 wherein obtaining a local time stamp comprises:

obtaining the local time from a counter included in the network communications unit.

11. The network testing system of claim 7 wherein preparing a synchronization offset comprises:

subtracting the local time stamp from the reference time stamp.

12. The network testing system of claim 7 wherein the packet storm is directed to one of a network device, a network segment or a network application.

13. A system comprising a plurality of the network testing systems of claim 7.