- Synchronous Data Link Control (SDLC)
- Created by: IBM for mainframes.
- Function: Connects mainframes to remote offices using a polling media access method.
- Characteristics: Works with dedicated leased lines that are permanently active.
- OSI Layer: Operates at the Data Link Layer.
- High-level Data Link Control (HDLC)
- Extension of: SDLC, also designed for mainframes.
- Function: Uses data encapsulation on synchronous serial links with frame characters and checksums.
- OSI Layer: Operates at the Data Link Layer.
- High Speed Serial Interface (HSSI)
- Function: Defines the electrical and physical interfaces used for DTE/DCE communications.
- OSI Layer: Operates at the Physical Layer.
These protocols are key in facilitating reliable and efficient communication in various network environments, particularly in mainframe and high-speed serial communication setups.