56.6.23.3 IEEE 802.3br: Interspersing Express Traffic

IEEE 802.3br “Interspersing Express Traffic” is one of the TSN standards, which defines a mechanism to transmit an express frame with a minimum delay at the expense of delaying completion of normal priority frames.

This standard is implemented by instantiating two separate MAC modules with related DMA, an MMSL (MAC Merge Sub Layer) and a system bus arbiter. One MAC is termed the express or eMAC and the other is a pre-emptable or pMAC.

The eMAC is designed to carry time sensitive traffic which must be delivered within a known time.

A conceptual view of this structure is shown in the following figure.