ISA Services-Controlled load o Tightly approximates to best efforts under unloaded conditions o No upper bound on queuing delay High percentage of packets do not experience delay over minimum transit delay Propagation plus router processing with no queuing delay o Very high percentage delivered Almost no queuing loss e Adaptive real time applications a Receiver measures jitter and sets playback point Video can drop a frame or delay output slightly Voice can adjust silence periods 16
16 ISA Services –Controlled Load Tightly approximates to best efforts under unloaded conditions No upper bound on queuing delay ◼ High percentage of packets do not experience delay over minimum transit delay Propagation plus router processing with no queuing delay Very high percentage delivered ◼ Almost no queuing loss Adaptive real time applications ◼ Receiver measures jitter and sets playback point ◼ Video can drop a frame or delay output slightly ◼ Voice can adjust silence periods
6.2 Queuing Discipline o Traditionally first in first out(FIFO or first come first served (FCFS)at each router port e No special treatment to high priority packets(flows) o Small packets held up by large packets ahead of them in queue e Larger average delay for smaller packets Flows of larger packets get better service o Greedy TCP connection can crowd out altruistic connections If one connection does not back off, others may back off more
17 6.2 Queuing Discipline Traditionally first in first out (FIFO) or first come first served (FCFS) at each router port No special treatment to high priority packets (flows) Small packets held up by large packets ahead of them in queue ◼ Larger average delay for smaller packets ◼ Flows of larger packets get better service Greedy TCP connection can crowd out altruistic connections ◼ If one connection does not back off, others may back off more