I think you have tagged it by mistake to LTE. Up to my knowledge CFN concept was in UMTS.
CFN Connection Frame Number (counter):. CFN is the frame counter used for the L2/transport channel synchronization between UE and UTRAN. A CFN value is associated to each TBS and it is passed together with it through the MAC-L1 SAP. CFN provides a common frame reference (at L2) to be used e.g. for synchronized transport channel reconfiguration. The duration of the CFN cycle is longer than the maximum allowed transport delay between MAC and L1 (in UTRAN side, between SRNC and Node B, because the L1 functions that handle the transport channel synchronization are in the Node B). Range: 0 to 255 frames, 8 bits. When used for PCH the range is 0 to 4095 frames, 12 bits.
It is just a counter and if you say failure it means the counter has been expired.
Time of Arrival (ToA): ToA is the time difference between the end point of the DL arrival window (ToAWE) and the actual arrival time of DL frame for a specific CFN. A positive ToA means that the frame is received before the ToAWE, a negative ToA means that the frame is received after the ToAWE.
