Fairness 2 if we care about fairness give equal

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 200 230 20 11/4/13 Example of Adap7ve Timeout (2) 1000 Early 7meout 900 RTT (ms) 800 Timeout (SRTT + 4*Svar) 700 600 500 400 300 200 100 0 0 20 40 60 80 100 120 140 160 180 Seconds 200 231 Introduc7on to Computer Networks Conges7on Overview (§6.3, §6.5.10) Computer Science & Engineering 21 11/4/13 Topic •  Understanding conges7on, a “traffic jam” in the network –  Later we will learn how to control it What’s the hold up? Network 247 Nature of Conges7on •  Simplified view of per port output queues –  Typically FIFO (First In First Out), discard when full Router Router = Queued (FIFO) Queue Packets 249 22 11/4/13 Nature of Conges7on (2) •  Queues help by absorbing bursts when input > output rate •  But if input > output rate persistently, queue will overflow –  This is conges7on •  Conges7on is a func7on of the traffic pakerns – can occur even if every link have the same capacity 250 Effects of Conges7on •  What happens to performance as we increase the load? 251 23 11/4/13 Effects of Conges7on (2) •  What happens to performance as we increase the load? 252 Effects of Conges7on (3) •  As offered load rises, conges7on occurs as queues begin to fill: –  Delay and loss rise sharply with more load –  Throughput falls below load (due to loss) –  Goodput may fall below throughput (due to spurious retransmissions) •  None of the above is good! –  Want to operate network just before the onset of conges7on 253 24 11/4/13 Bandwidth Alloca7on •  Important task for network is to allocate its capacity to senders –  Good alloca7on is efficient and fair • ...
View Full Document

This document was uploaded on 04/04/2014.

Ask a homework question - tutors are online