S/UNI-IMA-4 Telecom Standard Product Data Sheet
Released
IMA Frame Synchronization Mechanism (IFSM)
For IMA links, the RDAT performs the IFSM. The IFSM is based upon the cell delineation
mechanism in I.432. The details of the IFSM can be found in AF-PHY-0086.001 “Inverse
Multiplexing for ATM (IMA) Specification Version 1.1”, March 1999. The state Machine is
shown in Figure 12.
Figure 12 IFSM State Machine
Valid ICP at unexpected position or OCD(with cell by cell hunting)
Missing ICP Cell
Starting
State
consecutive
ꢀꢁ
invalid ICP cells
consecutive
ꢂꢁ
errored ICP cells
IMA SYNC
IMA HUNT
(frame by frame)
(cell by cell)
One invalid or
errored/missing
ICP cell
One valid
ICP cells
consecutive
ꢃꢁ
valid ICP cells
Valid ICP at unexpected position
(with cell by cell hunting)
IMA PRESYNC
(frame by frame)
During group start-up, the fields in the ICP cells are validated by the RX IMA Protocol
Processor (RIPP) block and the validated information is used to determine whether the ICP cells
are valid or not. Validation by the RIPP checks the group fields of the ICP cell to ensure that
they match the rest of the group and checks the LID to ensure that it is unique in the group. An
ICP cell is invalid if either the IMA OAM Label, the LID, the IMA_ID, M, IFSN or the offset is
not the same as the validated values. If the ICP cell cannot be validated by the RIPP (. i.e. the
IMA_ID is different from the rest of the group or the LID is a duplicate), the IFSM will remain
in the starting state.
Once the ICP cells are validated by the RIPP, the IFSM will enter the IMA Hunt state. In this
state, each cell will be examined to see if it is a valid ICP cell. When a single valid ICP cell has
been received, the IFSM will enter the IMA Presync state.
Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC-2020889, Issue 2
58
PMC [ PMC-SIERRA, INC ]
