Feng Gang National Laboratory of Communication,UESTC Aug 2017 Ver 1.4 Traffic classes Networks should match offered service to source requirements (corresponds to utility functions) Example:telnet requires low bandwidth and low delay utility increases with decrease in delay network should provide a low-delay service or,telnet belongs to the low-delay traffic class Traffic classes encompass both user reguirements and network service offerings 2616009:Network Traffic Engineering 8:Traffic Management and Modeling Page.21
2616009: Network Traffic Engineering Feng Gang National Laboratory of Communication, UESTC Aug 2017 Ver 1.4 8: Traffic Management and Modeling Page.21 Traffic classes • Networks should match offered service to source requirements (corresponds to utility functions) • Example: telnet requires low bandwidth and low delay - utility increases with decrease in delay - network should provide a low-delay service - or, telnet belongs to the low-delay traffic class • Traffic classes encompass both user requirements and network service offerings
Feng Gang National Laboratory of Communication,UESTC Aug 2017 Ver 1.4 Traffic classes details A basic division:guaranteed service and best effort like flying with reservation or standby ·Guaranteed-service -utility is zero unless app gets a minimum level of service quality s bandwidth,delay,loss open-loop flow control with admission control e.g.telephony,remote sensing,interactive multiplayer games ·Best-effort send and pray closed-loop flow control e.g.email,net news 2616009:Network Traffic Engineering 8:Traffic Management and Modeling Page.22
2616009: Network Traffic Engineering Feng Gang National Laboratory of Communication, UESTC Aug 2017 Ver 1.4 8: Traffic Management and Modeling Page.22 Traffic classes - details • A basic division: guaranteed service and best effort - like flying with reservation or standby • Guaranteed-service - utility is zero unless app gets a minimum level of service quality § bandwidth, delay, loss - open-loop flow control with admission control - e.g. telephony, remote sensing, interactive multiplayer games • Best-effort - send and pray - closed-loop flow control - e.g. email, net news
Feng Gang National Laboratory of Communication,UESTC Aug 2017 Ver 1.4 GS vs.BE (cont.) ·Degree of synchrony time scale at which peer endpoints interact GS are typically synchronous or interactive s interact on the timescale of a round trip time s e.g.telephone conversation or telnet BE are typically asynchronous or non-interactive s interact on longer time scales s e.g.Email Sensitivity to time and delay GS apps are real-time s performance depends on wall clock BE apps are typically indifferent to real time s automatically scale back during overload 2616009:Network Traffic Engineering 8:Traffic Management and Modeling Page.23
2616009: Network Traffic Engineering Feng Gang National Laboratory of Communication, UESTC Aug 2017 Ver 1.4 8: Traffic Management and Modeling Page.23 GS vs. BE (cont.) • Degree of synchrony - time scale at which peer endpoints interact - GS are typically synchronous or interactive § interact on the timescale of a round trip time § e.g. telephone conversation or telnet - BE are typically asynchronous or non-interactive § interact on longer time scales § e.g. Email • Sensitivity to time and delay - GS apps are real-time § performance depends on wall clock - BE apps are typically indifferent to real time § automatically scale back during overload
Feng Gang National Laboratory of Communication,UESTC Aug 2017 Ver 1.4 Traffic subclasses (roadmap) ·ATM Forum ·IETF based on sensitivity to based on sensitivity to delay bandwidth -65 -G5 s intolerant s CBR,VBR s tolerant -BE BE s ABR,UBR s interactive burst s interactive bulk §asynchronous bulk 2616009:Network Traffic Engineering 8:Traffic Management and Modeling Page.24
2616009: Network Traffic Engineering Feng Gang National Laboratory of Communication, UESTC Aug 2017 Ver 1.4 8: Traffic Management and Modeling Page.24 Traffic subclasses (roadmap) • ATM Forum - based on sensitivity to bandwidth - GS § CBR, VBR - BE § ABR, UBR • IETF - based on sensitivity to delay - GS § intolerant § tolerant - BE § interactive burst § interactive bulk § asynchronous bulk
Feng Gang National Laboratory of Communication,UESTC Aug 2017 Ver 1.4 ATM Forum GS subclasses Constant Bit Rate(CBR) constant,cell-smooth traffic mean and peak rate are the same e.g.telephone call evenly sampled and uncompressed constant bandwidth,variable quality Variable Bit Rate (VBR) long term average with occasional bursts try to minimize delay can tolerate loss and higher delays than CBR e.g.compressed video or audio with constant quality,variable bandwidth 2616009:Network Traffic Engineering 8:Traffic Management and Modeling Page.25
2616009: Network Traffic Engineering Feng Gang National Laboratory of Communication, UESTC Aug 2017 Ver 1.4 8: Traffic Management and Modeling Page.25 ATM Forum GS subclasses • Constant Bit Rate (CBR) - constant, cell-smooth traffic - mean and peak rate are the same - e.g. telephone call evenly sampled and uncompressed - constant bandwidth, variable quality • Variable Bit Rate (VBR) - long term average with occasional bursts - try to minimize delay - can tolerate loss and higher delays than CBR - e.g. compressed video or audio with constant quality, variable bandwidth