Abstract
By 2015, the Institute of Electrical and Electronics Engineers (IEEE) time-sensitive networking (TSN) task group has released several TSN standards. Amongst them is 802.1Qbv, also known as a time-aware shaper, aiming to provide performance assurances of latency and delivery variation to enable applications in a TSN network. While there are several products and evaluation kits that employ 802.1Qbv in the market now, it is still not widely adopted yet due to the maturity of the standard. Hardware-enabled 802.1Qbv use hardware queues and timers to achieve accurate transmission of packets in the switch and bridge. This research aims to investigate the feasibility of using an existing end-station Ethernet controller, Intel I210, and its launch time control feature (commonly known as time-based packet scheduling) to shape traffic compatible to 802.1Qbv-enabled network bridges. A software solution is developed by implementing a software configurable gate-control list and employing open-source Linux RFC patches for per-packet transmit time specification. By configuring the kernel and mapping kernel-layer traffic classes to the hardware queues, packets can be transmitted out at precise times while attaching 802.1Q VLAN tags, required by bridges to identify packets. Through analysis, it is found that this solution will require an additional 30 μs transmit offset to be used effectively. That is 55% more time is needed to transmit a packet in a back-to-back connection and 17.6% on a 3-switch network to improve period peak jitter performance to just 8.9 μs compared to 1 ms on solutions that send packets out periodically using software sleep functions.
Highlights
Ethernet has been widely used for various consumer applications due to its cost, availability and throughput capabilities
Recent interest has increased in using Ethernet for industrial and automotive applications where existing communication channels such as CAN and FlexRay are not capable of providing the bandwidth needed for infotainment applications and camera-based Advanced Driver Assistance Systems (ADASs) such as, Lane Departure Warning and Traffic Sign Recognition (IEEE, March 18 2016) (Bello, 2014)
This paper aims to develop a functional prototype of a time-aware shaper using timebased packet scheduling with Intel I210 on a Linux platform; and to identify the transmit offset required to effectively implement time-based packet scheduling using a software gate-control list
Summary
Ethernet has been widely used for various consumer applications due to its cost, availability and throughput capabilities. Recent interest has increased in using Ethernet for industrial and automotive applications where existing communication channels such as CAN and FlexRay are not capable of providing the bandwidth needed for infotainment applications and camera-based Advanced Driver Assistance Systems (ADASs) such as, Lane Departure Warning and Traffic Sign Recognition (IEEE, March 18 2016) (Bello, 2014). 802.1Qbv aims to solve the problem of interfering frames in a time-sensitive network by introducing time-aware shapers (IEEE, March 18 2016) (Bello, 2014). The 802.1Qbv standard specifies how time-aware shapers are “smart shapers” that let frames out based on their size and the knowledge of expected times for time-sensitive frames. It is conventionally implemented at the hardware-level. One possible alternative is by using existing hardware to emulate the behavior of the standard by using time-based packet scheduling
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