Presentation on theme: "Aspects for Pre-emption resp. Time Aware Blocking Shaper (TABS)"— Presentation transcript:
1 Aspects for Pre-emption resp. Time Aware Blocking Shaper (TABS) September 2012IEEE AVB TG Meeting Santa CruzFranz-Josef Götz, Siemens AGAlbert Tretter, Siemens AG
2 TABS a Solution for Simple Networks TABS is a solution for networks with the following characteristic:Simple topologies (e.g. line)Simple communication relationspoint-to-pointSame link speed on all links of the networkRequires an engineered networkDrops Control Data frames received outside the time window Optimized latency for Control-Data-TrafficLine or Comb structures
3 Pre-emption a Solution for Meshed Networks Pre-emption in combination with BLSA (Burst Limiting Shaper Algorithm) isa solution for more complex networks with the following characteristics:(for BLSA see Franz Götz's presentation:Meshed networksMultiple Transmission Periods within one networkComplex communication relationspoint-to-pointpoint-to-multipointmultipoint-to-multipointDifferent link speeds within one network (e.g. 100MBit/s, 1GBit/s, … )Robust behavior in case of failuresuitable for safety critical applicationsSupports periodic and event-based CDT Low latency for Control-Data-TrafficRobust behavior in case of failure- suitable for safety critical applications-=======Fail operational behaviorEmergency operation featuresRobust for safety critical applications=============== Emergency operation features – (fail operational behavior)
4 Pre-emption versus Time Aware Blocking Shaper Pro Pre-emption:Easy to add to existing networksAdding devices or bridges that support pre-emption to a network containing devices or bridges that do not support pre-emption is possible and vica versaWorks well in networks with different link speedsNo need to configure the bridges for pre-emptionFlexibility, it is easy to change the network (e.g. add new stations, change the topology, …)No synchronization of the bridges (scheduler) requiredRobust against miss-configurationUsage of 100% of the available bandwidth is possible (see Norman Finn's presentationTransmission periods in the range from 31.25µs to 250µs are not possible without pre-emptionPro TABS:Provides the best latency performance (less jitter) for simple topologiesCompatible Erweiterung möglich
5 Some relevant Issues for the Bandwidth and Window Size Calculation for TABS Synchronization inaccuracy (1µs?)Sync tree is not identical with the data pathCable length (e.g. assumption 100m real 5m)Bridge forwarding delay for Control Data Frames must be knownForwarding mechanism (CT / S&F)Scheduling has to avoid overtake situatione.g. huge number of fan in and low number of fan outBridges with different link speeds on ingress and egress portse.g. 100MBit/s 1GBit/s and one window more switching resources are requirede.g. 100MBit/s 1GBit/s and multiple window
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