Link Sharing or CBQ Link sharing controls the distribution of bandwidth on “local” links Each class receives a guaranteed share during congestion Aggregate.

Slides:



Advertisements
Similar presentations
Fair Queueing. Design space Buffer management: –RED, Drop-Tail, etc. Scheduling: which flow to service at a given time –FIFO –Fair Queueing.
Advertisements

Transport Layer3-1 TCP AIMD multiplicative decrease: cut CongWin in half after loss event additive increase: increase CongWin by 1 MSS every RTT in the.
Abhay.K.Parekh and Robert G.Gallager Laboratory for Information and Decision Systems Massachusetts Institute of Technology IEEE INFOCOM 1992.
CS 268: Lecture 8 Router Support for Congestion Control Ion Stoica Computer Science Division Department of Electrical Engineering and Computer Sciences.
WebTP Meeting (10/18/1999) Link Sharing Principles Class Based Queueing (CBQ) S. Floyd and V. Jacobson - ToN 1995.
Differentiated Services. Service Differentiation in the Internet Different applications have varying bandwidth, delay, and reliability requirements How.
A Case for Relative Differentiated Services and the Proportional Differentiation Model Constantinos Dovrolis Parameswaran Ramanathan University of Wisconsin-Madison.
Worst-case Fair Weighted Fair Queueing (WF²Q) by Jon C.R. Bennett & Hui Zhang Presented by Vitali Greenberg.
Scheduling CS 215 W Keshav Chpt 9 Problem: given N packet streams contending for the same channel, how to schedule pkt transmissions?
CS 268: Lecture 15/16 (Packet Scheduling) Ion Stoica April 8/10, 2002.
Networking Issues in LAN Telephony Brian Yang
Generalized Processing Sharing (GPS) Is work conserving Is a fluid model Service Guarantee –GPS discipline can provide an end-to-end bounded- delay service.
ACN: IntServ and DiffServ1 Integrated Service (IntServ) versus Differentiated Service (Diffserv) Information taken from Kurose and Ross textbook “ Computer.
Katz, Stoica F04 EECS 122: Introduction to Computer Networks Packet Scheduling and QoS Computer Science Division Department of Electrical Engineering and.
Design Philosophy of Scheduler Design a very general and flexible scheduler at transport layer that can –work at different locations in the network –provide.
Computer Networking Lecture 17 – Queue Management As usual: Thanks to Srini Seshan and Dave Anderson.
A Strategy for Implementing Smart Market Pricing Scheme on Diff-Serv Murat Yuksel and Shivkumar Kalyanaraman Rensselaer Polytechnic Institute, Troy, NY.
Streaming Video Gabriel Nell UC Berkeley. Outline Scalable MPEG-4 video – Layered coding method – Integrated transport-decoder buffer model RAP streaming.
Promoting the Use of End-to-End Congestion Control & Random Early Detection of Network Congestion.
Packet Scheduling From Ion Stoica. 2 Packet Scheduling  Decide when and what packet to send on output link -Usually implemented at output interface 1.
CS640: Introduction to Computer Networks Aditya Akella Lecture 20 - Queuing and Basics of QoS.
Distributed Multimedia March 19, Distributed Multimedia What is Distributed Multimedia?  Large quantities of distributed data  Typically streamed.
Advance Computer Networking L-5 TCP & Routers Acknowledgments: Lecture slides are from the graduate level Computer Networks course thought by Srinivasan.
Congestion Control - Supplementary Slides are adapted on Jean Walrand’s Slides.
Fair Queueing. 2 First-Come-First Served (FIFO) Packets are transmitted in the order of their arrival Advantage: –Very simple to implement Disadvantage:
The Impact of Active Queue Management on Multimedia Congestion Control Wu-chi Feng Ohio State University.
CS640: Introduction to Computer Networks Aditya Akella Lecture 20 - Queuing and Basics of QoS.
Promoting the Use of End-to-End Congestion Control in the Internet Sally Floyd and Kevin Fall IEEE-ACAM Transactions on Networking, 馬儀蔓.
CprE 458/558: Real-Time Systems (G. Manimaran)1 CprE 458/558: Real-Time Systems Real-Time Networks – WAN Packet Scheduling.
Scheduling Determines which packet gets the resource. Enforces resource allocation to each flows. To be “Fair”, scheduling must: –Keep track of how many.
Explicit Allocation of Best-Effort Service Goal: Allocate different rates to different users during congestion Can charge different prices to different.
Random Early Detection (RED) Router notifies source before congestion happens - just drop the packet (TCP will timeout and adjust its window) - could make.
An End-to-End Service Architecture r Provide assured service, premium service, and best effort service (RFC 2638) Assured service: provide reliable service.
Queue Scheduling Disciplines
An End-to-End Service Architecture r Provide assured service, premium service, and best effort service (RFC 2638) Assured service: provide reliable service.
Providing QoS in IP Networks
Scheduling for QoS Management. Engineering Internet QoS2 Outline  What is Queue Management and Scheduling?  Goals of scheduling  Fairness (Conservation.
1 Lecture 15 Internet resource allocation and QoS Resource Reservation Protocol Integrated Services Differentiated Services.
Scheduling Mechanisms Applied to Packets in a Network Flow CSC /15/03 By Chris Hare, Ricky Johnson, and Fulviu Borcan.
04/02/08 1 Packet Scheduling IT610 Prof. A. Sahoo KReSIT.
Instructor Materials Chapter 6: Quality of Service
QoS & Queuing Theory CS352.
Topics discussed in this section:
Buffer Management in a Switch
HCF and EDCF Simulations
TCP Congestion Control
Measuring Service in Multi-Class Networks
Stratified Round Robin: A Low Complexity Packet Scheduler with Bandwidth Fairness and Bounded Delay Sriram Ramabhadran Joseph Pasquale Presented by Sailesh.
CPU Scheduling.
TCP, XCP and Fair Queueing
Quality of Service For Traffic Aggregates
Dusit Niyato, Student Member, IEEE Ekram Hossain, Senior Member, IEEE
Variations of Weighted Fair Queueing
Provision of Multimedia Services in based Networks
Hierarchical Scheduling Algorithms
Scheduling Algorithms in Broad-Band Wireless Networks
Fair Queueing.
Advance Computer Networking
ns-2 simulation of TCP + CBR traffic
Computer Science Division
Advance Computer Networking
Variations of Weighted Fair Queueing
Javad Ghaderi, Tianxiong Ji and R. Srikant
Packet Scheduling in Linux
15-744: Computer Networking
Introduction to Packet Scheduling
EECS 122: Introduction to Computer Networks Packet Scheduling and QoS
Hierarchical Scheduling Algorithms
Introduction to Packet Scheduling
کنترل جریان امیدرضا معروضی.
Presentation transcript:

Link Sharing or CBQ Link sharing controls the distribution of bandwidth on “local” links Each class receives a guaranteed share during congestion Aggregate “similar” connections in the same class Hierarchical link sharing A unified set of mechanisms to satisfy link sharing (organizational) and real-time (application) service requirements General scheduler + link-sharing scheduler General scheduler could be a priority-based scheduler During congestion, the link-sharing scheduler is invoked to rate-limit the “overlimit” class to its allocated bandwidth Explicitly prevents starvation of lower-priority traffic Distribution of “excess” bandwidth is a function of general scheduler Classes and bandwidth allocations could be static or dynamic

Goals and Formal Guidelines Main goal: each interior or leaf class should receive roughly its allocated bandwidth over appropriate time intervals, given sufficient demand Distribution of “excess” bandwidth should not be arbitrary, e.g. to higher priority classes in proportion to their allocations Within each class, congestion control for its queue can be done using TCP, admission control, RED, etc. Packets from a “regulated” class are scheduled by the link-sharing scheduler, from an “unregulated” class by the general scheduler Link-sharing scheduler rate-limits a regulated class, for example by decreasing its priority so that the general scheduler sends packets from that class less frequently The “estimator” estimates the bandwidth used by each class over a time interval

Formal Guidelines A leaf class is “unsatisfied” if it is “underlimit” and has a persistent backlog A non-leaf class is unsatisfied if it is underlimit and has some descendant class with a persistent backlog A class can continue unregulated if - the class is not overlimit, OR - the class has a not-overlimit ancestor al level i, and there are no unsatisfied classes at levels lower than i. Otherwise, the class will be regulated This check can be done by the general scheduler before transmitting a packet from that class, or less frequently

Approximations Avoid checking the “satisfied” status of other classes Ancestors-Only approximation: a class can continue unregulated if - the class is not overlimit, OR - the class has an underlimit ancestor A class can be regulated unnecessarily An overlimit class can continue unregulated until its parent is labeled not underlimit, even if a sibling class is unsatisfied Top-Level approximation: - the class has an underlimit ancestor whose level is at most Top-Level Top-Level indicates the highest level from which a class can borrow (infinity in Ancestors-Only, 1 means parent status not checked)

Simulations General scheduler uses strict priority For classes of same priority, the general scheduler uses a variant of weighted round robin with number of bytes served at each round proportional to bandwidth allocations The estimator updates the limit status for a class and its ancestor classes after a packet from that class is transmitted EWMA of inter-packet departure times (the reciprocal is the average rate) t = measured time since the departure of previous packet f = s/b, s is packet size and b the allocated rate diff = t - f is negative if class exceeds its allocated rate avg = (1-w) * avg + w * diff Limit avg to a maximum (positive value) so not to accumulate credits

Simulations (cont’d) Each class has a “time-to-send” field If a class has avg negative (i.e. overlimit), the estimator sets time-to-send to a time x seconds ahead of current time to bring avg to zero If time-to-send is zero, the class is at-limit or underlimit, and the general scheduler is allowed to send a packet from that class If time-to-send is greater than current time, then the class is overlimit. The general scheduler can only send a packet from that class if permitted by the link-sharing rules Each class is getting its allocated rate The excess is given to higher priority classes; divided in proportion of allocations among classes of same priority The approximations are good, with Ancestors-Only sometimes slightly imprecise

Comments Link sharing can protect non-real-time traffic E.g. when prediction of future traffic is incorrect and the predictive service class becomes oversubscribed Group compatible connections into classes (e.g. TCP connections, rate-adaptive video connections) and protect them from each other