Advanced Computer Networking Graduate Course from Electrical Engineering School A. Beheshti Communication Group Iran University of Science and Technology Chapter 5 Link Layer Text Book: Computer Networking: A Top Down Approach 6th edition Jim Kurose, Keith Ross Addison-Wesley March 2012 All material copyright 1996-2012 J.F Kurose and K.W. Ross, All Rights Reserved Link Layer
Point to Point link protocols High level Data link control (HDLC) History IBM: SDLC (synchronous data link control) ANSI: ADCP (advanced data communication control prcedure) ISO: HDLC CCITT: adopted as a part of X25 link access procedure (LAP) then modified to LAPB specification Bit oriented Bit stuffing for data transparency
Point to Point link protocols High level Data link control (HDLC) Frame format information supervisory unnumbered Elec. Eng. Dept. , IUST
Point to Point link protocols High level Data link control (HDLC) Frame format information supervisory unnumbered TYPE0: RECEIVE READY (Next) TYPE1: Negative Acknowledge (Next) TYPE2: RECEIVE NOT READY (before Next) stop the sender TYPE3: SLECTIVE REJECT (retransmission of Next) 32 frame types for control purpose or data in different protocols Elec. Eng. Dept. , IUST
Point to Point link protocols Data link layer in Internet Connecting user to internet (host to internet) Connecting different LANs by routers (router to router) Both of these connections are point to point Point to point protocol Elec. Eng. Dept. , IUST
Point to Point link protocols Point to point protocol (PPP) It is defined in RFC1661 standard and modified in RFC1662, RFC1663 Error correction support multiple protocols Allows IP address negotiated during connection time Permits authentication Elec. Eng. Dept. , IUST
Point to Point link protocols Main features of PPP Framing method defines start and end of frame without ambiguity A link control protocol (LCP) that allow bringing up the lines Test the line Negotiate options Bringing the lines down when not needed anymore A method to negotiate network layer options independent of network layer (NCP) Elec. Eng. Dept. , IUST
Point to Point link protocols PPP frame for unnumbered format It is byte oriented It use HDLC flag with byte stuffing It is mostly used as unnumbered Numbered frame is also defined in RFC1663 for wireless noisy channels LCP can negotiate to omit the address and control fields LCP,NCP,IP,IPX,APPLE Talk Negotiable with LCP (1500 Default) Elec. Eng. Dept. , IUST
Point to Point link protocols Simplified diagram for bringing line up and down Elec. Eng. Dept. , IUST
Point to Point link protocols LCP frame types Initiator Responder Elec. Eng. Dept. , IUST
Point to Point link protocols NCP It depends on the network layer protocols For each protocol list of negotiable options are defined For IP dynamic IP address assignment is important Elec. Eng. Dept. , IUST