On a trunk in a TDM-based network, almost every frame slip causes data to be lost, since there is likely to be data contained in at least one timeslot of every frame. On a trunk in a FastPacket or ATM network, many idle packets or cells transmit every second. All IGX and BPX trunk cards discard idle cells from the network before they are buffered and processed. This prevents the error condition of input buffer overflow from occurring. Because of the fundamental characteristic of cell-based networking, a network with a plesiochronous synchronization plan can usually operate free of error.
Frame slips can occur on either or both ends of the line.
Both the PBX and the switch may record frame slips. To help resolve frame slips, configure the external equipment to receive clock from the network. If the external equipment can't accept network clock, configure the circuit line interface for loop clock. If configuring one end of the circuit line for loop clock does not eliminate frame slips, evaluate the clocking architecture of the network and external equipment. Clocking problems typically cause Packet Errors, HEC errors, PLCP errors, or frame-sync errors.