The Point to Point Interface MIB module.
This MIB manages the generic objects for
Serial link or SONET/SDH like point to point network 
interfaces with the encapsulations of PPP 
(Point to Point Protocol), HDLC (High Level Data Link Control)
or cHDLC (CIsco extension to High Level Data Link Control) 
framing.
Acronyms and terms:
FCS - Frame Check Sequence. The frame check sequence is 
      used to ensure that the data received is actually 
      the data sent.
CRC - Cyclic Redundancy Check. The transmitting system 
      processes the frame check sequence portion of the 
      frame through an algorithm called a CRC (Cyclic 
      Redundancy Check).

One of the usages of CRC is in the following 
PPP/HLDC over SONET/SDH example.
+----+
| PPP|   FCS           Bit                      SONET/SDH
|HDLC|=> Generation => Stuffing => Scrambling => Framing
+----+   CRC 16,32