Feng Gang National Laboratory of Communication,UESTC Aug 2017 Ver 1.4 Unit 6 Packet Scheduling 2616009:Network Traffic Engineering 6:Packet Scheduling Page.1
2616009: Network Traffic Engineering Feng Gang National Laboratory of Communication, UESTC Aug 2017 Ver 1.4 6: Packet Scheduling Page.1 Unit 6 Packet Scheduling
Feng Gang National Laboratory of Communication,UESTC Aug 2017 Ver 1.4 Roadmap Why Scheduling? Problem Definition 。 Metrics and Requirements of Scheduling Discipline 。 Mechanisms to Create a Scheduling Discipline Scheduling Disciplines for Best Effort Connections 。 Scheduling Disciplines for Guaranteed-service Connections QoS Service curve model 2616009:Network Traffic Engineering 6:Packet Scheduling Page.2
2616009: Network Traffic Engineering Feng Gang National Laboratory of Communication, UESTC Aug 2017 Ver 1.4 6: Packet Scheduling Page.2 Roadmap • Why Scheduling? • Problem Definition • Metrics and Requirements of Scheduling Discipline • Mechanisms to Create a Scheduling Discipline • Scheduling Disciplines for Best Effort Connections • Scheduling Disciplines for Guaranteed-service Connections • QoS Service curve model
Feng Gang National Laboratory of Communication,UESTC Aug 2017 Ver 1.4 Why a Scheduling Discipline? Because applications need it - Sharing bandwidth Sharing bandwidth fairly Scheduling disciplines can allocate bandwidth,delay,loss>QoS 。 Best-effort (adaptive,non-real time),e.g.email,ftp Guaranteed service (non-adaptive,real time),e.g.interactive voice,video, stock quotes Meeting bandwidth guarantees(min and max) Meeting loss guarantees(multiple levels) Meeting delay guarantees(multiple levels) Reducing delay variation 2616009:Network Traffic Engineering 6:Packet Scheduling Page.3
2616009: Network Traffic Engineering Feng Gang National Laboratory of Communication, UESTC Aug 2017 Ver 1.4 6: Packet Scheduling Page.3 Why a Scheduling Discipline? • Because applications need it - Sharing bandwidth - Sharing bandwidth fairly - Scheduling disciplines can allocate bandwidth, delay, loss QoS • Best-effort (adaptive, non-real time), e.g. email, ftp • Guaranteed service (non-adaptive, real time), e.g. interactive voice, video, stock quotes - Meeting bandwidth guarantees (min and max) - Meeting loss guarantees (multiple levels) - Meeting delay guarantees (multiple levels) - Reducing delay variation
Feng Gang National Laboratory of Communication,UESTC Aug 2017 Ver 1.4 Why a Scheduling Discipline?(cont'd) QoS Guarantees require a number of mechanisms working together call admission control,traffic shaping,drop policies,buffer allocation,traffic scheduling,etc. These issues are related. - For example,zero-loss can be obtained by allocating PCR(but no multiplexing gain). Scheduling disciplines are the key to providing QoS guarantee for performance-critical applications 2616009:Network Traffic Engineering 6:Packet Scheduling Page.4
2616009: Network Traffic Engineering Feng Gang National Laboratory of Communication, UESTC Aug 2017 Ver 1.4 6: Packet Scheduling Page.4 Why a Scheduling Discipline?(cont’d) • QoS Guarantees require a number of mechanisms working together - call admission control, traffic shaping, drop policies, buffer allocation, traffic scheduling, etc. - These issues are related. - For example, zero-loss can be obtained by allocating PCR (but no multiplexing gain). • Scheduling disciplines are the key to providing QoS guarantee for performance-critical applications
Feng Gang National Laboratory of Communication,UESTC Aug 2017 Ver 1.4 Problem Definition Class 1 Class 2 Link Sever Class 3 Multiplexer.switch. router,... Scheduling Discipline handles the "contention"by deciding the order in which requests are serviced manages the service queue of requests awaiting service 2616009:Network Traffic Engineering 6:Packet Scheduling Page.5
2616009: Network Traffic Engineering Feng Gang National Laboratory of Communication, UESTC Aug 2017 Ver 1.4 6: Packet Scheduling Page.5 Problem Definition Sever Link Class 1 Class 2 Class 3 Multiplexer, switch, router,... Scheduling Discipline handles the “contention” by • deciding the order in which requests are serviced • manages the service queue of requests awaiting service