Data Path Overview

The following diagram describes each port within the PXIe-8521.
Figure 4. PXIe-8521 Block Diagram

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Each port has three data paths: XNET monitor, XNET endpoint, and OS stack. All three data paths can be used simultaneously depending on port mode. The monitor path reads and inspects all Ethernet frames that are received or transmitted on the port. The endpoint path transmits and receives Ethernet frames on the port. The endpoint path is typically used if you need it to act as an AVB endpoint. The OS stack path transmits and receives data using standard network sockets via the operating system's network stack. The OS stack is typically used with applications designed to use traditional TCP- or UDP-based protocols for its network communication.

Note The PXIe-8521 does not support jumbo frames.

For Ethernet interfaces, the suffix "/monitor" indicates the use of a monitor path when it is appended to the interface name. For example, "ENET1" specifies use of the endpoint path, and "ENET1/ monitor" specifies use of the monitor path. The monitor path is used to read Ethernet frames that are received or transmitted on each port. When Tap is enabled, data received via the monitor path by a Tap pair will be identical on each port in the pair.

The IEEE 802.1AS protocol is implemented by the firmware running on the PXIe-8521, and packet timestamps are taken near the device's physical layer. This helps guarantee a high degree of synchronization accuracy for each port's network time.