DATA COMMUNICATION Lecture-39
Recap of Lecture 38 Flow Control Stop-and-Wait Sliding Window Error Control Stop-and-Wait ARQ
Overview of Lecture 39 Error Control Stop-and-Wait ARQ Sliding Window ARQ Go-back-n Selective Reject Data Link Protocols
Error Control
Stop-and-Wait ARQ: Damaged Frame
Stop-and-Wait ARQ: Lost Frame
Stop-and-Wait ARQ: Lost ACK
Go-Back-n ARQ: Damaged Frame
Go-Back-n ARQ: Lost Frame
Go-Back-n ARQ: Lost ACK
Selective-Reject ARQ: Damaged Frame
Data Link Protocols Data link protocol is a set of specifications used to implement the data link layer It contains rules for line discipline, flow control, and error handling
Data Link Protocols
Asynchronous Protocols Start and stop bits, variable-length gaps between characters Inherent slowness Not complex and inexpensive Used primarily in modems Being replaced by higher-speed synchronous mechanisms
Asynchronous Protocols
XMODEM File transfer protocol between PCs using telephone line Half-duplex stop-and-wait ARQ protocol Control frames from the receiver ACK: Acknowledgement NAK: Error or start of transmission CAN: Aborts the transmission
XMODEM
Summary Error Control Stop-and-Wait ARQ Sliding Window ARQ Go-back-n Selective Reject Data Link Protocols
Suggested Reading Section 10.3, 11.1, “Data Communications and Networking” 2nd Edition by Behrouz A. Forouzan