WAN Data link Layer protocols describe how frames are transmitted in the Data Link Layer.
Several common Data Link Layer standards [only for reference]:
High Level Data Link Control (HDLC)
Point to Point Protocol (PPP)
Integrated Service Digital Network (ISDN)
Simple Data Link Control Protocol (SDLC)
Serial Line Interface Protocol (SLIP)
Link Access Procedure Balance (LAPB)
Link Access Procedure D-channel (LAPD)
Link Access Procedure Frame (LAPF)
Asynchronous Transfer Mode (ATM)
We will study The star-marked topics
WAN Data Link Layer: PPP (Point-to-Point Protocol)
IETF took the initiative to design PPP as the data link layer protocol for point-to-point lines. Their goal was to use it as the official Internet Standard.
Q: What’s Point-to-Point? A: A point-to-point network may consist of more than one connection between two machines: source and destination. A packet sent from source to destination may have to visit one or more intermediate machines. But the source and destination will think that they are connected by a single wire.
In future all the ISP’s (Internet Service Provider) will support PPP.
PPP Frame Format 01111110 11111111 00000011 variable 01111110
History: For more than 100 years, the international telecommunication infrastructure has been public circuit-switched telephone system. It can support only analog voice transmission. Hence it is not enough for modern communication. So the telephone companies of the world decided to design a new, fully digital telephone system. The main goal was to integrate voice and non-voice service . This new system is called ISDN .
Features of ISDN: 1. Voice (the main service) 2. Intercom button for calling secretaries instantly 3. Multiple hotkeys for instantly calling (no delay for call setup) anywhere in the world 4. Caller ID display 5. Telephone can be connected to computer so that caller’s tel. no + name + address can be displayed from database 6. Call forwarding 7. Conferencing worldwide. There are more…