Enhanced Transmission Selection

{{short description|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.

{{cite conference

| first = Antonio

| last = Scarfò

| title = The Evolution of Data Center Networking Technologies

| book-title = Proceedings of the First International Conference on Data Compression, Communications and Processing

| publisher = IEEE

| date = 21–24 June 2011

| location = Palinuro, Italy

| url = https://ieeexplore.ieee.org/document/6061124

| doi = 10.1109/CCP.2011.30

| url-access = subscription}} It is a hierarchical scheduler that combines static priority scheduling and a bandwidth sharing algorithms (such as Weighted round robin or Deficit round robin).

== Description ==

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%.{{Citation

| title = Media Access Control (MAC) Bridges and Virtual Bridged Local Area Networks — Amendment 18: Enhanced Transmission Selection for Bandwidth Sharing Between Traffic Classes

| publisher = IEEE

| date = September 2011

| doi = 10.1109/IEEESTD.2011.6034507

| isbn = 978-0-7381-6655-1}}

{{cite tech report

|first= Victor

|last= Lama

|title= Enhanced Transmission Selection - IEEE 802.1Qaz

|institution= CISCO

|date= 23 March 2011

|url= https://community.cisco.com/legacyfs/online/legacy/3/7/8/74873-Enhanced%20Transmission%20Selection%20v1.0.pdf}}

{{cite web

|url= https://docs.oracle.com/cd/E36784_01/html/E37516/gmfgz.html

|title= Managing Network Datalinks in Oracle® Solaris 11.2

|year= 2014

|publisher= ORACLE

|access-date= 5 October 2020}}

{{cite web

|url= https://www.gta.ufrj.br/ensino/eel879/trabalhos_vf_2014_2/matheus/ets.html

|author = Matheus Guedes de Andrade

|title= Enhancement Transmission Selection

|year= 2014

|publisher= Universidade Federal do Rio de Janeiro

|access-date= 5 October 2020}}

File:Example of Enhanced Transmission Selection Architecture.pdf

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 [https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/net/sched/sch_ets.c 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

{{cite web

|url= https://docs.microsoft.com/en-us/windows-hardware/drivers/network/enhanced-transmission-selection--ets--algorithm

|title= Enhanced Transmission Selection (ETS) Algorithm

|year= 2017

|publisher= Microsoft

|access-date= 5 October 2020}}