IEEE & Packet Transmission Pre-emption Solution and Problem Statement

Transcription

1 IEEE & Packet Transmission Pre-emption Solution and Problem Statement Yong roadcom July 2011 Plenary IEEE Pre-emption and Fragmentation Page 1

2 Pre-emption The Need The Problem Generic Solution for the Problem The IEEE 802.1/802.3 Functional Model Summary and Conclusions July 2011 Plenary IEEE Pre-emption and Fragmentation Page 2

3 Pre-emption Need 100 us over three bridge 100 Mb/s and above utomotive (from March 2011, 802.1) new-avb-kimnakamura-automotive-network-requirements-0311.pdf <5 us per hop, ~32 bridge 1000 Mb/s and above Industrial Ethernet (from January 2011, 802.1). 125 us over 32 hops desired. new-goetz-avb-ext-industrcom-0113-v01.pdf Refined objectives from system vendors expected. Problem Statement: Max Length Ethernet 100 Mb/s =~120 us greater than automotive requirements. Max Length Ethernet 1000 Mb/s =~12 us greater than industrial requirements. Head of Line blocked behind Max Length Frame exceeds the requirements above July 2011 Plenary IEEE Pre-emption and Fragmentation Page 3

4 The Problem (input to the ridge 1) 1 (output from ridge 1) Mb/s Worst Case End- Point End- Point ridge 1 1 ridge 2 ridge 3 Classic Head of Line problem. The worst case is urgent frame is scheduled behind best-effort maximum length frame. ut we desire urgent frame to get through (e.g Mb/s in 100 us). Except, now we want to do something about this to provide a solution to automotive and industrial network markets July 2011 Plenary IEEE Pre-emption and Fragmentation Page 4

5 Generic Preemption Solution (input to the ridge 1) 1 (output from ridge 1) 1 (desired output from ridge 1) (remaining) [Qualitative] Pre-Emption ehavior Suspend Transmit Resume There is no other solution to head of line blocking delay behind a max frame length packet. generic solution is to suspend the max frame length ( in this example) packet, transmit urgent frame, and resume previous. Note: Other completion options besides resumeprevious is retransmit entirely, or always fragment (regardless of existence of ) are not desirable) July 2011 Plenary IEEE Pre-emption and Fragmentation Page 5

6 Summary of Preemption Function Easy to explain easy to understand. Fairly straight forward to implement, pending selection of many [functionally] equivalent proposals. Observation Everyone knows what preemption means, but everyone has different ideas on how it may be implemented. Let s hold off on this. ut the MC Service interface (boundary between and 802.3) as defined (particularly.3 side) is not friendly to Pre-emption considerations. [Next Slide] Entire Frame is sent atomically to MC, as an example. No way to offer preempting frame to from July 2011 Plenary IEEE Pre-emption and Fragmentation Page 6

7 Existing and Service Interface ISS MC Service Interface T X MC Service Interface Entire Frame is sent atomically to MC No way to offer preempting frame to from May 2011 Interim IEEE Pre-emption and Fragmentation 7

8 IEEE Clause 4 or nnex 4 nnex 4 (Full-Duplex only) may be the best clause to consider for preemption function. Leave Claus 4 alone July 2011 Plenary IEEE Pre-emption and Fragmentation Page 8

9 Proposed & Service Interface Problem packet is sent from to in zero time transmits the frame. Generic Solution /802.3 MC Service Interface needs to be augmented to convey a second preempting frame. dditional information may be in form of preempt-indication, or second transmit-urgent-request or any other TD during standardization MC needs to handle preemption point and preemption framing. Depends on the latency objectives and fragmentation header formats. TD during standardization Services determine frames that are preemptable, preempting, and not preemptable. Effect of V shaper, transmit selection, congestion management (if relevant) TD during standardization July 2011 Plenary IEEE Pre-emption and Fragmentation Page 9

10 Thank you! One backup slide on model attached July Plenary IEEE Pre-emption and Fragmentation Page 10

11 Provider ackbone aggie Pants Model Suggested preemption Q-Rev work