TAILIEUCHUNG - Lecture Digital communication systems - Lecture 21

The following will be discussed in this chapter: The press, the law, and the courts; protecting news sources; covering the courts; reporters’ access to information; defamation; invasion of privacy; copyright; obscenity and pornography; regulating broadcasting; regulating cable TV; the telecommunications act of 1996; regulating advertising. | 11 28 12 INTRODUCTION TO EECS n DIGITAL COMMUNICATION SBSTEMS Fall 2012 Lecture 21 Reliable Data Transport Redundancy via careful retransmission Sequence numbers acks Two protocols stop-and-wait sliding window Timeouts and round-trip time RTT estimation The Problem Given Best-effort network in which - Packets may be lost arbitrarily - Packets may be reordered arbitrarily - Packet delays are variable queueing - Packets may even be duplicated Sender S and receiver R want to communicate reliably - Application at R wants all data bytes in exactly the same order that S sent them - Each byte must be delivered exactly once These functions are provided by a reliable transport protocol - Application layered above transport protocol Fall 2012 Lecture 21 Slide 1 Fall 2012 Lecture 21 Slide 2 Proposed Plan Transmitter - Each packet includes a sequentially increasing sequence number - When transmitting save xmit time packet on un-ACKed list - When acknowledgement ACK is received from the destination for a particular sequence number remove the corresponding entry from un-ACKed list - Periodically check un-ACKed list for packets sent awhile ago Retransmit update xmit time in case we have to do it again awhile ago xmit time now timeout Receiver - Send ACK for each received packet reference sequence number - Deliver packet payload to application Stop-and-Wait Protocol Sender Receiver S R S R Timeout Retransmit Normal behavior no losses Data loss retransmission Duplicate packet reception Fall 2012 Lecture 21 Slide 3 Fall 2012 Wanted exactly once got at least once Lecture 21 Slide 4 1 11 28 12 Revised Plan Transmitter - Each packet includes a sequentially increasing sequence number - When transmitting save xmit time packet on un-ACKed list - When acknowledgement ACK is received from the destination for a particular sequence number remove the corresponding entry from un-ACKed list - Periodically check un-ACKed list for packets sent awhile ago Retransmit update

• Kĩ thuật Viễn thông
• Communication systems
• Digital communication systems
• Digital communication
• Multiuser communication
• Multicarrier system
• Adaptive equalization
• Filter channel
• communication systems research
• communication applications
• electronic media
• communication solutions
• systems management