Can controllers come in various packages and in various forms.
1. Some of CAN Controllers are integrated into microcontrollers such as AT89C51CC03
2. Some of the CAN Controller devices come as separate chip such as MCP2515 (from Microchip). MCP2515 is a SPI to CAN bridge IC which comes in various packages such as
A. 20 pin QFN
B. 18 pin SOIC
C. 18 pin DIP
CAN protocol is a communication scheme that is more related with number of bytes to send and receive, message IDs etc. Whereas CAN controller is a physical device which implements the CAN protocol.
You may look at datasheet of MCP2515 device to understand more about internal architecture of CAN controller
MCP2515 DATASHEET:
**broken link removed**
and I would suggest you to read following topic on CAN from: