Capturing in Time-Sensitive Networking Environments with Profishark

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Time-Sensitive Networking (TSN) is a set of standards defining mechanisms for the time-sensitive transmission of data over Ethernet networks. Deterministic communication is critical to multiple industries (Audio Video Bridging, Automotive, Industrial and Power automation, Mobile Fronthaul Networks). The purpose of this feature brief is to demonstrate the benefit of ProfiShark in TSN environments and to describe its usage. In order to support TSN, a TAP has special requirements in terms of latency, jitter and capture capability.

Like all Profitap’s in-line TAPs, the ProfiShark is protocol agnostic and L1 passthrough for all frames, tags, and encapsulations. This includes preempted frames (IEEE 802.1Qbu/802.3br), fragmented and CRC-invalid frames.

Device Latency Jitter L1 pass-through
ProfiShark 100M 2 ns 100 μs Yes
ProfiShark 1G/1G+ 400 ns 32 ns Yes
ProfiShark 10G/10G+ 300 ns 40 ns Yes

The in-line latency and the jitter introduced by the in-line circuit is minimal, making it suitable for IEEE 802.1AS and 1588 v2.

preempted frames (IEEE 802.1Qbu/802.3br), fragmented and CRC-invalid frames

Moreover, the ProfiShark Manager offers an option to capture the entire L1 Ethernet frame in direct capture. When ‘capture full frames’ option is enabled, the frames are captured with the preamble (0x55), the SMD and the CRC.

Frame Type Preamble count SMD FCS
Standard / Express 7 0xD5 CRC
SMD-Ix Premptable frame start 7 0xE6, 0x4C, 0x7F or 0xB3 CRC
SMD-Cx Non-initial fragment 6 0x61, 0x52, 0x9E or 0xAD CRC 0xFFFF0000

With ‘capture full frames’ option enabled, the PCAP-NG Link-Layer Header is set to LINKTYPE_ ETHERNET_MPACKET. This Link-Layer type is fully supported by Wireshark since 2.6.0 and allows proper dissection of L1 frames (see Wireshark view below). Once dissected, the additional L1 data is displayed in the Packet detail view and doesn’t conflict with higher protocols. Additionally, fragmented preempted frames can be reassembled in Wireshark.

The ProfiShark Manager offers different capture options. The different capture options and their effect are listed below.

  • Last modified: August 13, 2021