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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
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
Using the Android Job Scheduler
Using the Android Job Scheduler
Published: 2014/06/25
Channel: Google Developers
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 ✈
Network scheduler
Network scheduler
Published: 2016/01/29
Channel: WikiAudio
Project Scheduling
Project Scheduling
Published: 2014/12/02
Channel: Thayer School of Engineering at Dartmouth
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
The Scheduler Meets the Network
The Scheduler Meets the Network
Published: 2015/08/26
Channel: MesosCon
Airline Scheduling (Toy Example in Maximum Flow)
Airline Scheduling (Toy Example in Maximum Flow)
Published: 2014/06/21
Channel: tudor pc
Windows Task Scheduler Overview on Windows Server 2012
Windows Task Scheduler Overview on Windows Server 2012
Published: 2013/01/26
Channel: Sachin Samy
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
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
Resource Based Scheduling
Resource Based Scheduling
Published: 2012/12/19
Channel: Project Management Tutorials
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
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
Construction Scheduling I
Construction Scheduling I
Published: 2016/12/30
Channel: james Lee
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: CNCF [Cloud Native Computing Foundation]
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
Airport Network Flight Scheduler Management System (Web Development)
Airport Network Flight Scheduler Management System (Web Development)
Published: 2017/08/02
Channel: Saad Mirza
Everything You Ever Wanted to Know About Resource Scheduling, But Were Afraid to Ask by Tim Hockin
Everything You Ever Wanted to Know About Resource Scheduling, But Were Afraid to Ask by Tim Hockin
Published: 2016/11/16
Channel: CNCF [Cloud Native Computing Foundation]
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
FIX Error 1068 - Task Scheduler Cannot Start
FIX Error 1068 - Task Scheduler Cannot Start
Published: 2016/12/30
Channel: MDTechVideos
Schedule a Meeting for Someone Else with Web Scheduler
Schedule a Meeting for Someone Else with Web Scheduler
Published: 2016/11/24
Channel: BlueJeans Training
Southwest Airlines: Inside Schedule Planning
Southwest Airlines: Inside Schedule Planning
Published: 2009/08/18
Channel: Southwest Airlines
Genetic Algorithms: Scheduling Optimization for Dummies
Genetic Algorithms: Scheduling Optimization for Dummies
Published: 2012/04/30
Channel: yumpopsickle
Link Scheduler for MTR Wireless Mesh Network
Link Scheduler for MTR Wireless Mesh Network
Published: 2015/10/15
Channel: Dinesh Lama
Biosoftworld Medical Scheduler Network Setup
Biosoftworld Medical Scheduler Network Setup
Published: 2014/04/16
Channel: Biosoftworld
Automotive Workshop Scheduler Network Version
Automotive Workshop Scheduler Network Version
Published: 2013/02/06
Channel: Gabriel Lee
ROUND ROBIN SCHEDULING ALGORITHM
ROUND ROBIN SCHEDULING ALGORITHM
Published: 2013/03/10
Channel: Go GATE IIT
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
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
Remotely Run Programs On Another Computer (NO SOFTWARE REQUIRED)
Remotely Run Programs On Another Computer (NO SOFTWARE REQUIRED)
Published: 2013/12/24
Channel: NovaComputing
Round Robin Algorithm Tutorial (CPU Scheduling)
Round Robin Algorithm Tutorial (CPU Scheduling)
Published: 2015/03/18
Channel: Gio Villanueva
Automotive Workshop Scheduler Network Version
Automotive Workshop Scheduler Network Version
Published: 2013/02/05
Channel: green baby
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
How To Speed Up Any Internet Connection On Windows 10 PC (really easy)
How To Speed Up Any Internet Connection On Windows 10 PC (really easy)
Published: 2016/03/19
Channel: Geeks Tutorial
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
Using the Canvas Scheduler: Canvas Q&A
Using the Canvas Scheduler: Canvas Q&A
Published: 2017/10/03
Channel: Online Network of Educators
Weighted Differential Scheduler
Weighted Differential Scheduler
Published: 2012/08/27
Channel: RichReport
Trustworthy Operations in Cellular Networks The Case of PF Scheduler
Trustworthy Operations in Cellular Networks The Case of PF Scheduler
Published: 2014/12/20
Channel: PROJECTS2014
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
Error 1068: Task Scheduler cannot start [Fixed]
Error 1068: Task Scheduler cannot start [Fixed]
Published: 2013/10/14
Channel: GameHDSet
Process State Transition Diagram and various Schedulers
Process State Transition Diagram and various Schedulers
Published: 2014/11/20
Channel: Gate Lectures by Ravindrababu Ravula
Social Networking Minute Power Scheduler App
Social Networking Minute Power Scheduler App
Published: 2013/09/24
Channel: Andy Nathan
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
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: 2015/06/12
Channel: myproject bazaar
Kron Task Scheduler lab in GNS3
Kron Task Scheduler lab in GNS3
Published: 2011/12/27
Channel: GNS3Vault
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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 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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