Time Stamping is part of VSS Monitoring's Packet Optimization™* feature set. It allows users to append a time stamp to each packet as it enters a network ingress port.
The time stamp is inserted as an 8-byte stamp after the payload and before the CRC. The first 4 bytes indicate seconds, the second 4 bytes indicate nanoseconds. After applying the stamp, the CRC is recalculated and forwarded to the monitor ports as a standard Ethernet frame. Time Stamping only affects monitor traffic - inline network traffic is always unaffected. Application of the time stamp can be enabled or disabled by the user at any time.
Selective Aggregation, Hardware-Based Filtering, and Session-Aware Load Balancing are significant value creating features that are available in VSS' current generation of traffic capture devices. High-performance networks, however, traditionally have not been able to take advantage of these features because they introduce some minimal latency to each packet and may affect the accuracy of monitoring tool time stamps. With VSS Monitoring's Time Stamping feature, these concerns are eliminated, and users of high-performance networks can realize the full power of Distributed Traffic Capture.
The application of a time stamp on the network ingress ports before any Aggregation, Hardware-Based Filtering, or Session-Aware Load Balancing occurs allows users to take advantage of the scalability and value enhancement offered by such features. Because of this, Time Stamping is ideal for latency-sensitive monitoring applications as well as latency monitoring itself.
*Hardware-based modification of a packet by adding or stripping from it. Does not affect inline network traffic and can be enabled or disabled at will.