Synchronized Transmit on Time Stamp on Multiple SmartNICs

Napatech Link-Capture™ Software Features

Intel® PAC
Napatech SmartNIC
Content Type
Feature Description
Capture Software Version
Link™ Capture Software 12.11

The offset-based scheme also supports synchronized transmit of frames on multiple ports on multiple SmartNICs.

Synchronizing SmartNICs for transmit on time stamp

If the transmission time is to be synchronized across ports on multiple SmartNICs, the SmartNICs must be time-synchronized to ensure a common notion of time.

Also, time stamps in the sequences of frames to be transmitted on different ports must be based on a common notion of time. If this is not the case, frames will be transmitted with the correct relative distance on each port, however, asynchronously across ports.

Example configuration

The following figure shows a configuration in which a host application is transmitting frames on two SmartNICs.

tx_on_ts_multiple_nics Rectangle.112 Rectangle.113 Transmit frame processing Transmit frame processing Dynamic connector.114 Rectangle.115 Host application Host application Dynamic connector.116 Rectangle.137 0 0 Rectangle.13 1 1 Rectangle.15 Rectangle.16 Transmit frame processing Transmit frame processing Rectangle.17 0 0 Rectangle.18 1 1 Dynamic connector.19 Dynamic connector.20 Sheet.14 Circle Sheet.16 Dynamic connector.24 Dynamic connector.25 Rectangle.43 Δ Δ Rectangle.44 Δ Δ Rectangle.45 Δ Δ Rectangle.46 Δ Δ Sheet.23 Circle Sheet.25 Dynamic connector Sheet.27 Time synchronized Time synchronized

Calculating the offset

The synchronized start is obtained by writing a common constant offset ∆ to the offset register for each port used. The time stamp of the first frame is used as the reference for calculating the common offset value, similarly to the calculation for transmit on time stamp on a single port. The additional offset TD part of ∆ must be large enough to allow all the ports to be initialized and for allowing the frames scheduled for transmission to be placed in the transmit buffer system of all the SmartNICs, so that all ports are ready for transmission when the transmit time for the first frame occurs, as illustrated in the following figure.

tx_on_ts_multiple_ports Rectangle.50 Frame 0A Frame 0A Sheet.2 Port 0 Port 0 Rectangle.52 Frame 1A Frame 1A Sheet.4 Port 1 Port 1 Rectangle.54 Frame 2A Frame 2A Sheet.6 Port 2 Port 2 Rectangle.56 Frame 3A Frame 3A Sheet.8 Port 3 Port 3 Sheet.9 First frame is transmitted First frame is transmitted Rectangle.59 Δ Δ Rectangle.62 Δ Δ Rectangle.63 Δ Δ Rectangle.64 Δ Δ Rectangle.66 Frame 0B Frame 0B Rectangle.67 Frame 0C Frame 0C Rectangle.68 Frame 1B Frame 1B Rectangle.69 Frame 1C Frame 1C Rectangle.70 Frame 2B Frame 2B Rectangle.71 Frame 3B Frame 3B Rectangle.72 Rectangle.73 Rectangle.74 Rectangle.75 Rectangle.76 Rectangle.77 Rectangle.78 Rectangle.79 Rectangle.80 Rectangle.81 Rectangle.82 Rectangle.83 Sheet.34 Initialization time Initialization time