Remote Loopback In the loopback mode, every Ethernet frame received is transmitted
back on that same port except for OAMPDUs and pause frames, which provide
flow control and OAM functionality. This particular functionality helps network administrators
assure and measure link quality during installation or troubleshooting
stages, when no standard data exchange occurs and the given links are subject to testing
and quality evaluation. The remote loopback session requires a periodic exchange
of OAMPDUs messages; otherwise, the OAM session is interrupted and all link peer
stations transit into the standard transmission mode. It is interesting to note that any
OAM-enabled station with a link in active mode (as opposed to passive mode) can force
its link peer station into the remote loopback mode simply by sending a loopback control
OAMPDU. The loopback command is acknowledged by responding with an Information
OAMPDU, with the loopback state indicated in the state field.
OAM remote loopback sessions are, therefore, used to evaluate particular network
segments in terms of their transmission quality, SLA compliance, end-to-end packet
delay, jitter, and average/peak line throughputs.
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