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Use forward and backward pass to determine project duration and critical path
Use forward and backward pass to determine project duration and critical path
Published: 2014/12/28
Channel: Engineer4Free
Using the Android Job Scheduler
Using the Android Job Scheduler
Published: 2014/06/25
Channel: Google Developers
The Scheduler Meets the Network
The Scheduler Meets the Network
Published: 2015/08/26
Channel: MesosCon
Airport Network Flight Scheduler Project
Airport Network Flight Scheduler Project
Published: 2015/08/15
Channel: Nevon Projects
What is NETWORK SCHEDULER? What does NETWORK SCHEDULER mean? NETWORK SCHEDULER meaning
What is NETWORK SCHEDULER? What does NETWORK SCHEDULER mean? NETWORK SCHEDULER meaning
Published: 2017/03/17
Channel: The Audiopedia
Project Scheduling
Project Scheduling
Published: 2014/12/02
Channel: Thayer School of Engineering at Dartmouth
Sched.net: A Network-Aware Kubernetes Scheduler [I] - Akash Gangil & Salvatore Orlando, VMware
Sched.net: A Network-Aware Kubernetes Scheduler [I] - Akash Gangil & Salvatore Orlando, VMware
Published: 2017/04/11
Channel: Cloud Native Computing Foundation - CNCF
Network scheduler
Network scheduler
Published: 2016/01/29
Channel: WikiAudio
HD Part 2A United Airlines NOC In-Flight Crew Scheduling Flight Attendants Network Operations Center
HD Part 2A United Airlines NOC In-Flight Crew Scheduling Flight Attendants Network Operations Center
Published: 2012/12/11
Channel: ✈ Jetsetter ✈
How Do Schedulers in Routers Work? Understanding RR, WRR, WFQ, and DRR Through Simple Examples
How Do Schedulers in Routers Work? Understanding RR, WRR, WFQ, and DRR Through Simple Examples
Published: 2016/03/10
Channel: MetanoiaInc
How Airlines Schedule Flights
How Airlines Schedule Flights
Published: 2017/08/01
Channel: Wendover Productions
Construction Scheduling I
Construction Scheduling I
Published: 2016/12/30
Channel: james Lee
Resource Based Scheduling
Resource Based Scheduling
Published: 2012/12/19
Channel: Project Management Tutorials
Airline Scheduling
Airline Scheduling
Published: 2017/04/20
Channel: AMSI Tubn
Buffer vs Hootsuite | Who Is The Best Social Media Manager?
Buffer vs Hootsuite | Who Is The Best Social Media Manager?
Published: 2015/01/02
Channel: Justin Bryant
How to set up your ISN Online Scheduler 2017
How to set up your ISN Online Scheduler 2017
Published: 2017/01/17
Channel: Inspection Support
Setting Up Royal Flush Network Scheduler
Setting Up Royal Flush Network Scheduler
Published: 2015/02/03
Channel: iyuri305
Network Request Scheduler Scale Testing Results
Network Request Scheduler Scale Testing Results
Published: 2012/04/24
Channel: RichReport
Link Scheduler for MTR Wireless Mesh Network
Link Scheduler for MTR Wireless Mesh Network
Published: 2015/10/15
Channel: Dinesh Lama
Airport Network Flight Scheduler Management System (Web Development)
Airport Network Flight Scheduler Management System (Web Development)
Published: 2017/08/02
Channel: Saad Mirza
Be the Best Pipeline Scheduler You Can Be | Stream Systems
Be the Best Pipeline Scheduler You Can Be | Stream Systems
Published: 2016/08/18
Channel: Stream Systems
Open source vehicle route planning & scheduling
Open source vehicle route planning & scheduling
Published: 2014/09/10
Channel: Open Door Logistics
Background work with JobScheduler (Android Development Patterns S3 Ep 12)
Background work with JobScheduler (Android Development Patterns S3 Ep 12)
Published: 2016/09/22
Channel: Android Developers
Disabling Qos Packet Scheduler(watch it on HD)
Disabling Qos Packet Scheduler(watch it on HD)
Published: 2010/10/26
Channel: dreamprojectify
Biosoftworld Medical Scheduler Network Setup
Biosoftworld Medical Scheduler Network Setup
Published: 2014/04/16
Channel: Biosoftworld
HTB Network Packet Scheduler implementation: experimenting with the new bucket size feature
HTB Network Packet Scheduler implementation: experimenting with the new bucket size feature
Published: 2017/04/26
Channel: MikroTik
Programmable Packet Scheduling at Line Rate
Programmable Packet Scheduling at Line Rate
Published: 2017/02/28
Channel: Anirudh Sivaraman
LTE Downlink Packet Scheduling VANET Vehicular Network Simulation Thesis
LTE Downlink Packet Scheduling VANET Vehicular Network Simulation Thesis
Published: 2017/01/03
Channel: Omnet++ Projects
How to: Automatically move files from one location to another using Task Scheduler
How to: Automatically move files from one location to another using Task Scheduler
Published: 2016/08/17
Channel: ravencraft
SMS scheduler, email scheduler, social network scheduler and task scheduler for Android
SMS scheduler, email scheduler, social network scheduler and task scheduler for Android
Published: 2017/04/03
Channel: Android Apps
Instant Payday Network - How To Use Hootsuite Scheduler To Post
Instant Payday Network - How To Use Hootsuite Scheduler To Post
Published: 2013/03/01
Channel: Carin Petty
Windows Task Scheduler Overview on Windows Server 2012
Windows Task Scheduler Overview on Windows Server 2012
Published: 2013/01/26
Channel: Sachin Samy
Automotive Workshop Scheduler Network Version
Automotive Workshop Scheduler Network Version
Published: 2013/02/05
Channel: green baby
Automotive Workshop Scheduler Network Version
Automotive Workshop Scheduler Network Version
Published: 2013/02/06
Channel: Gabriel Lee
Auto Bot Scheduler setting Naruto Online (naruto.oasgames.com) - GameBots Network
Auto Bot Scheduler setting Naruto Online (naruto.oasgames.com) - GameBots Network
Published: 2017/10/16
Channel: Game Bots
LTE Advanced Uplink Scheduling Network Simulator NS3 Projects
LTE Advanced Uplink Scheduling Network Simulator NS3 Projects
Published: 2016/10/19
Channel: PHD Projects
Weighted Differential Scheduler
Weighted Differential Scheduler
Published: 2012/08/27
Channel: RichReport
ROUND ROBIN SCHEDULING ALGORITHM
ROUND ROBIN SCHEDULING ALGORITHM
Published: 2013/03/10
Channel: Go GATE IIT
Create a scheduled task with Advanced Task Scheduler
Create a scheduled task with Advanced Task Scheduler
Published: 2013/02/20
Channel: SouthsoftwareTube
Event Viewer Task Scheduler İlişkisi -  Network Academy - Bülent Gür
Event Viewer Task Scheduler İlişkisi - Network Academy - Bülent Gür
Published: 2014/06/17
Channel: B Salih Sonverdi
Round Robin Algorithm Tutorial (CPU Scheduling)
Round Robin Algorithm Tutorial (CPU Scheduling)
Published: 2015/03/18
Channel: Gio Villanueva
Nova Scheduler- Optimizing, Configuring and Deploying NFV VNF
Nova Scheduler- Optimizing, Configuring and Deploying NFV VNF's on OpenStack
Published: 2017/05/10
Channel: OpenStack Foundation
Error 1068: Task Scheduler cannot start [Fixed]
Error 1068: Task Scheduler cannot start [Fixed]
Published: 2013/10/14
Channel: GameHDSet
Remotely Run Programs On Another Computer (NO SOFTWARE REQUIRED)
Remotely Run Programs On Another Computer (NO SOFTWARE REQUIRED)
Published: 2013/12/24
Channel: NovaComputing
Social Networking Minute Power Scheduler App
Social Networking Minute Power Scheduler App
Published: 2013/09/24
Channel: Andy Nathan
Droidcon NYC 2016 - JobScheduler is the Unavoidable Better Future
Droidcon NYC 2016 - JobScheduler is the Unavoidable Better Future
Published: 2016/11/23
Channel: touchlab
Process State Transition Diagram and various Schedulers
Process State Transition Diagram and various Schedulers
Published: 2014/11/20
Channel: Gate Lectures by Ravindrababu Ravula
GopherCon 2016: Kelsey Hightower - Building a custom Kubernetes scheduler
GopherCon 2016: Kelsey Hightower - Building a custom Kubernetes scheduler
Published: 2016/10/08
Channel: Gopher Academy
Final Year Projects 2015 | Dynamic Packet Scheduler Optimization in Wireless Relay Networks
Final Year Projects 2015 | Dynamic Packet Scheduler Optimization in Wireless Relay Networks
Published: 2015/05/23
Channel: ClickMyProject
First Come First Served - CPU Scheduling Algorithm
First Come First Served - CPU Scheduling Algorithm
Published: 2014/11/14
Channel: Mifta Sintaha
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WIKIPEDIA ARTICLE

From Wikipedia, the free encyclopedia
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Packets queuing in a FIFO (first in, first out) data structure.

A network scheduler, also called packet scheduler, queueing discipline, qdisc or queueing algorithm, is an arbiter on a node in packet switching communication network. It manages the sequence of network packets in the transmit and receive queues of the network interface controller. There are several network schedulers available for the different operating systems, that implement many of the existing network scheduling algorithms.

The network scheduler logic decides which network packet to forward next. The network scheduler is associated with a queuing system, storing the network packets temporarily until they are transmitted. Systems may have a single or multiple queues in which case each may hold the packets of one flow, classification, or priority.

In some cases it may not be possible to schedule all transmissions within the constraints of the system. In these cases the network scheduler is responsible for deciding which traffic to forward and what gets dropped.

Algorithms[edit]

In the course of time many network queueing disciplines have been developed. Each of these provides specific reordering or dropping of network packets inside various transmit or receive buffers.[1][2] Queuing disciplines are commonly used as attempts to compensate for various networking conditions, like reducing the latency for certain classes of network packets, and are generally used as part of quality of service (QoS) measures.[3][4][5]

Examples of algorithms suitable for managing network traffic include:

Several of the above have been implemented as Linux kernel modules[17] and are freely available.

Bufferbloat[edit]

Bufferbloat is a phenomenon in packet-switched networks generally, in which excess buffering of packets causes high latency and packet delay variation. Bufferbloat can be addressed by a network scheduler that strategically discards packets to avoid an unnecessarily high buffering backlog. Examples include CoDel and Random early detection.

Terminology[edit]

  • Active queue management (AQM) – the employment of an arbiter program
  • Network traffic control – an umbrella term for all measures aimed at the control of traffic
  • Traffic shaping – a form of AQM, where the available bandwidth is being limited to match certain use cases
  • Link sharing – this term is used when more individuals or customers share the same Internet connection
  • Traffic prioritizing – a form of AQM, that selectively prioritizes certain network packets (e.g. VoIP-packets)
  • TCP Turbo – by prioritizing ACK-packets on the upload, a slow-down of the download rate of a TCP connection is prevented
  • Bandwidth management – the management of the available bandwidth

Implementations[edit]

Linux kernel[edit]

The Linux kernel's packet scheduler is part of the network stack, together with netfilter, nftables, and Berkeley Packet Filter.

The Linux kernel packet scheduler is configured using the userspace CLI utility called tc (short for "traffic control"). As the default queuing discipline, the packet scheduler uses a FIFO implementation called pfifo_fast,[18] although systemd since its version 217 changes the default queuing discipline to fq_codel.[19] The packet scheduler is an integral part of the Linux kernel's network stack and manages the ring buffers of all NICs, by working on the layer 2 of the OSI model and handling Ethernet frames, for example. It manages the transmit and receive buffers of all NICs installed in a computer.

The user space programs ifconfig and ip enable system administrators to configure the buffer sizes txqueuelen and rxqueuelen for each device separately, with their units being number of Ethernet frames regardless of their size. The Linux kernel's network stack contains several other buffers, which are not managed by the network scheduler. The overall size of all buffers has been the point of critique by the Bufferbloat project, which provided a partial solution with CoDel that has been primarily tested in OpenWrt.

Another network scheduler is being developed as part of Netfilter and nftables.[clarification needed]

Berkeley Packet Filter filters can be attached to the packet scheduler's classifiers. The eBPF functionality brought by version 4.1 of the Linux kernel[20] extends the "classic" BPF programmable classifiers to eBPF, allowing user space to implement its own custom, safe, C-like classifiers. These can be compiled using the LLVM eBPF backend and loaded into a running kernel using the tc utility.[21][better source needed]

OpenBSD[edit]

Since OpenBSD version 5.5 ALTQ was totally replaced by HFSC scheduler.

BSD[edit]

ALTQ is the implementation of a network scheduler for BSDs.

See also[edit]

References[edit]

  1. ^ "Traffic Control HOWTO: Classless Queuing Disciplines (qdiscs)". tldp.org. Retrieved November 24, 2013. 
  2. ^ Saravanan Radhakrishnan (September 30, 1999). "QoS Support in Linux: Queuing Disciplines". qos.ittc.ku.edu. Retrieved March 18, 2014. 
  3. ^ "Traffic Control HOWTO: Components of Linux Traffic Control". tldp.org. Retrieved November 24, 2013. 
  4. ^ "Traffic Control HOWTO: Traditional Elements of Traffic Control". tldp.org. Retrieved November 24, 2013. 
  5. ^ "Queuing Disciplines: Order of Packet Transmission and Dropping" (PDF). tau.ac.il. October 25, 2006. Retrieved March 18, 2014. 
  6. ^ http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.108.4477&rep=rep1&type=pdf
  7. ^ "DRR Linux kernel network scheduler module". kernel.org. Retrieved 2013-09-07. 
  8. ^ "FavorQueue: a Parameterless Active Queue Management to Improve TCP Traffic Performance" (PDF). 
  9. ^ "Heavy-Hitter Filter qdisc". kernel.org. 
  10. ^ "HTB Linux kernel network scheduler module". kernel.org. Retrieved 2013-09-07. 
  11. ^ "QFQ Linux kernel network scheduler module". kernel.org. Retrieved 2013-09-07. 
  12. ^ "Fair Queue packet scheduler committed to Linux kernel 3.12". 
  13. ^ "Network emulator Linux kernel network scheduler module". kernel.org. Retrieved 2013-09-07. 
  14. ^ "Proportional Integral controller Enhanced (PIE)". kernel.org. 
  15. ^ "SFQ Linux kernel network scheduler module". kernel.org. Retrieved 2013-09-07. 
  16. ^ "TBF Linux kernel network scheduler module". kernel.org. Retrieved 2013-09-07. 
  17. ^ "The Linux kernel network scheduler". kernel.org. 2012-12-26. Retrieved 2013-09-07. 
  18. ^ "Linux Advanced Routing and Traffic Control HOWTO, Section 9.2.1. pfifo_fast". lartc.org. 2012-05-19. Retrieved 2014-09-19. 
  19. ^ "systemd System and Service Manager: NEWS file". freedesktop.org. 2015-05-22. Retrieved 2015-06-09. 
  20. ^ "Linux kernel 4.1, Section 11. Networking". kernelnewbies.org. 2015-06-21. 
  21. ^ "Linux kernel packet scheduler#classifiers". wiki.OpenWrt.org. 

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