Enhanced Transmission Selection
Network scheduler scheduling algorithm
Enhanced Transmission Selection (ETS) is a network scheduler scheduling algorithm that has been defined by the Data Center Bridging Task Group of the IEEE 802.1 Working Group. It is a hierarchical scheduler that combines static priority scheduling and a bandwidth sharing algorithms (such as Weighted round robin or Deficit round robin).
01Description
The Enhanced Transmission Selection algorithm is one scheduling algorithm supported by IEEE 802.1Q. In Enhanced Transmission Selection, they are two types or queues: Strict priority or Credit-based queues, and bandwidth-assigned queues. Each bandwidth-assigned queue has a bandwidth parameter, and the total for all bandwidth-assigned queue must be 100%.
If there is no frame ready for transmission, in the Strict priority and Credit-based queues, a frame from the bandwidth-assigned queue can be transmitted. A bandwidth-sharing algorithm is in charge of selecting the queue such that the bandwidth consumed by each queue approaches its percentage of the bandwidth leftover by the Strict priority and Credit-based queues. If a queue uses less than its percentage, the remainder of its percentage used by other queues.
The standard does not specify which bandwidth-sharing algorithm must be used since there are a number of variants of bandwidth sharing algorithm, but gives some constraints and references Weighted round robin. The Linux implementation of ETS does not consider Credit-based queues and uses Deficit round robin as bandwidth-sharing algorithm. ETS is also implemented in Microsoft Network Drivers
Sources and credits
This article is adapted from the Wikipedia article “Enhanced Transmission Selection”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- Example of Enhanced Transmission Selection Architecture.pdf by MarcBoyerONERA, CC BY-SA 4.0
Fathomly is not affiliated with or endorsed by the Wikimedia Foundation. Spotted a problem? Tell us.