October 15, 2002 MASCOTS 20021

WebTraff:A GUI for Web Proxy Cache

Workload Modeling and Analysis

Nayden Markatchev

Carey Williamson

Department of Computer Science

University of Calgary

October 15, 2002 MASCOTS 20022

Introduction

What is WebTraff?

- An extended and improved version of ProWGen (Proxy Workload Generator), including a GUI interface to a useful set of tools for Web traffic modeling and analysis

Purpose: To facilitate the easy generation and analysis of controllable and representative workloads for Web caching simulations

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Talk Overview

WebTraff General Information System Requirements, Data Formats,

Assumptions, Inputs, Outputs, Usage Simple Demo

Using WebTraff to generate and analyze a workload, plus Web proxy cache simulation

Questions and Discussion

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System Requirements

Software Requirements Unix based

environment running X windows

cc, gcc, g++, tcl 8.0 or newer, tk 8.0 or newer, wish, perl 5.0 or newer, gnuplot, gs

Hardware Requirements 64 MB or more RAM 100 MB hard disk

space (for storing long workload traces)

Future Work:Port to Windows(volunteers?)

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Example of the Web Workload Trace Format Used in WebTraff

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Overview of WebTraff

The WebTraff toolkit provides three main functions: Web workload trace generation Web workload trace analysis Web proxy cache simulation

Graphs displayed in PostScript format

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WebTraff GUI Interface

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Web Workload Generation

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Web Workload Generation

This portion of the tool provides a GUI to ProWGen [Busari/Williamson 2001]

ProWGen models four key characteristics of Web proxy workloads. Zipf-like document popularity distribution High degree of “one-time” referencing Heavy-tailed file and transfer size distributions Temporal locality property in references

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Web Workload Generation (cont’d) Name of trace file being generated Sliding widgets for:

Number of references (lines) in a workload file Number of distinct Web objects in workload Percentage of objects that are “one-timers” Slope of Zipf-like document popularity profile Slope of Pareto tail for document size distribution Degree of statistical correlation (if any) between

size and popularity for Web objects

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Web Workload Generation (cont’d)

The notion of “temporal locality” refers to temporal correlation in referencing behaviour (e.g., recent past good predictor of near future)

Four models for referencing behaviour: Independent Reference Model (IRM) Static LRU Stack Model (SLRU) Dynamic LRU Stack Model (DLRU) New LRU Stack Model (NLRU)

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Web Workload Generation (cont’d)

“Popularity Bias” parameter (hack!) This button was added to remedy a problem

in earlier version of ProWGen, which tended to choose one-timers early in the trace and popular documents late in the trace

Can now control this in workload generation Can visually check for stationarity of cache hit

ratio during simulations

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Web Workload Analysis

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Web Workload Analysis

Two main categories of analysis functions: Time series analysis (on the left) Web workload analysis (on the right)

Radio buttons, slide bars and text boxes available to control plotting characteristics

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Requests per Interval(time series plot)

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Bytes per Interval(time series plot)

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Popularity Distribution plot

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Document Size Distribution (zoomed)

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Log-Log Complementary Distribution (LLCD) plot (size)

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LRU Stack Depth Analysis(time series plot)

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LRU Stack Depth Analysis(marginal distribution)

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Web Proxy Cache Simulation

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Web Proxy Cache Simulation

Application-level caching simulation parameters Cache size Cache replacement policy

Five replacement policies currently available Random replacement (RAND) First-In-First-Out (FIFO) Least-Recently-Used (LRU) (default setting) Least-Frequently-Used (LFU) Greedy-Dual-Size (GDS)

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DHR Results from “Run Sizes”

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DHR Results from “Run Policies”

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BHR Results from “Run Policies”

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Assessing Cache “Steady State”

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For More Information…

WebTraff toolkit: http://www.cpsc.ucalgary.ca/~carey/software.htm

“ProWGen: A Synthetic Workload Generation Tool for the Simulation Evaluation of Web Proxy Caches” Busari/Williamson, Computer Networks, Vol 38, No 6, June 2002 http://www.cpsc.ucalgary.ca/~carey/publications.htm

Contact information: Email {carey,nayden}@cpsc.ucalgary.ca