There are many QoS's
We concern about QoS in computer networks
Some definitions:
the collective effect of service performances which determine the degree of satisfaction of a user of the service
the ability of a network to deliver time-bounded traffic types (e.g. real time video or voice) with predictable latencies
a way to specify an applications network performance requirements, and it is specified by performance parameters
What is QoS
What QoS means to us:
QoS is the guarantee of delivering network packets punctually and the guarantee of delivering an acceptable numbers of network packets in a compromised time interval, which would not annoy the receivers.
Why QoS
Statistic from Cisco shows that multimedia applications become more and more popular
Why QoS
Which one do you prefer
"C:\Program Files\Internet Explorer\IEXPLORE.EXE" G:\CUHK\lyu9903\工作中\rsvp_1c.gif
Normal
"C:\Program Files\Internet Explorer\IEXPLORE.EXE" G:\CUHK\lyu9903\工作中\rsvp_2c.gif
Long Delay
"C:\Program Files\Internet Explorer\IEXPLORE.EXE" G:\CUHK\lyu9903\工作中\rsvp_3c.gif
Lost Frame
How to Achieve QoS
Many ways
Bandwidth reservation + Packet scheduling
Bandwidth reservation
RSVP
Packet scheduling
CBQ
How to Achieve QoS
~ Bandwidth Reservation
RSVP is a protocol that allows channels or paths on the networks to be reserved for the transmission of video and other high-bandwidth messages.
How to Achieve QoS ~ RSVP
How to Achieve QoS
~ Packet Scheduling
There are many packet scheduling algorithms
Some examples:
FIFO - First In First Out
SFQ - Stochastic Fairness Queuing
WFQ - Weighted Fair Queuing
CBQ - Class Based Queuing
Focus on CBQ
How to Achieve QoS ~ CBQ
Hierarchical link-sharing structure

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