DOCSLIB.ORG

Mobile Voip (Mvoip) Application

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Mobile Voip (Mvoip) Application POLYTECHNIC OF NAMIBIA SCHOOL OF INFORMATION TECHNOLOGY DEPARTMENT OF SOFTWARE ENGINEERING TITLE: Research and Development of a mobile voice over IP application which is hosted by open source software running on inexpensive backend servers Thesis presented in partial fulfilment of the requirements for the degree of Master of Information Technology at the Polytechnic of Namibia. Presented by: Veiko Muronga (9864431) Supervisor: Prof. Hippolyte Nsung-Nza Muyingi Second Supervisor: None. March 2013 DECLARATION I, Veiko Mpareke Muronga, hereby declare that the work contained in the mini–thesis, entitled: ”Research and Development of a mobile voice over IP application which is hosted by open source software running on inexpensive backend servers”, is my own original work and that I have not previously in its entirety or in part submitted it at any University or other higher education institution for the award of a degree. Signature:……………………….. Date:………………………….. RETENTION AND USE OF THESIS I, Veiko Mpareke Muronga, being a candidate for the degree of Master of Information Technology accepts the requirements of the Polytechnic relating to the retention and use of Master’s theses/ mini-theses deposited in the Library. In terms of these conditions, I agree that the original of my thesis/mini-thesis deposited in the Library will be accessible for purpose of study and research, in accordance with the normal conditions established by the Librarian for the care, loan or reproduction of theses/mini-theses. Signature:……………………….. Date:………………………….. 2 ABSTRACT Voice over IP has been driven by the convergence of voice and data on a single transport medium. This means cheaper service usage fees for the user if the offering is costed properly. But for a service provider there is still an increase in expenditure, solely related to spending on infrastructure such as call servers, phones and gateways. This study is aimed at analysing a different strategy of deploying VoIP, by starting at a lower base, meaning hosting the VoIP application on inexpensive hardware and open source Software. Secondly, the study looks at how to extend the service to mobile subscriber by introducing a mobile VoIP (mVoIP) application. The study’s main goal is to introduce telecommunication services at the lowest cost possible while considering reduced complexity, optimisation, manageability and flexibility. Barriers to deploying VoIP such as reliability and quality of service are also addressed by the study. The mVoIP infrastructure is made out of the following main components: Mobile VoIP app, Wireless Access Point and VoIP Server. Each main component’s functionality and characteristic are carefully explored in order to understand its contribution to the solution and the study as a whole. The research also looks at other projects where similar approaches were used to deploy inexpensive VoIP services. Factors leading to acceptance or rejection of the technology have served as guidance to the study. During the design, the research compares different open source VoIP server software’s functionalities and features in order to make a selection of the software to use for the projects pilot network deployment. A development platform for the mobile application is also selected based on characteristics such as: the range of devices it runs on, the market share of the platform and the learning curve of the platform. The development of the application follows the six steps from the Eri Mobile’s “Mobile Development Process”: Concept Sketching, Research/Strategies, Wire-Framing, User Interface Design, Development and Testing. The test scenarios for the research are all lab-based, but it is highlighted that implementing the solution on broadband, 3G and 4G networks can improve the service drastically in the areas of network coverage, Quality of Service and Mobility. 3 ACKNOWLEDGEMENT As anyone who has undertaken the task of writing knows that writing a thesis is a difficult and time consuming effort. Therefore my first acknowledgement must be to my wife Abigahil and son Mika who spend their nights alone, while I was writing this thesis. Secondly, I would like to thank my supervisor Prof. H.N. Muyingi for his valuable inputs and constant support and guidance during this whole journey. And to my parents (Mr. Mika Muronga and Mrs. Renate Muronga), I would like to give a big thank you for always being there for me in everything that I have tried. To the rest of my family and friends, thanks for your patience and support during my studies and I promise that soon we will get back on track to execute all our plans. Last but most importantly I would like to say thanks to the Mighty Father GOD for giving me the strength and endurance through my studies and beyond. 4 Table of Contents Declaration .......................................................................................................................................... 2 Retention and Use of Thesis ............................................................................................................... 2 Abstract ............................................................................................................................................... 3 Acknowledgement .............................................................................................................................. 4 List of Acronyms ................................................................................................................................ 9 List of Figures ................................................................................................................................... 13 List of Tables .................................................................................................................................... 15 1. INTRODUCTION .................................................................................................................... 16 1.1. Definition of the Problem ..................................................................................................... 16 1.2. Motivation ............................................................................................................................. 16 1.3. Scope ..................................................................................................................................... 18 1.4. Project Objectives – Deliverables ......................................................................................... 19 1.5. Definition of Terms ................................................................................................................... 20 1.5.1. Core Network Terminology .......................................................................................... 20 1.5.2. Transport Network Terms ............................................................................................. 21 1.5.3. Access Network Terms ................................................................................................. 21 1.5.4. Security Terms .............................................................................................................. 23 1.5.5. Protocols ....................................................................................................................... 24 1.5.6. Standards ....................................................................................................................... 25 1.5.7. Other Terms .................................................................................................................. 26 1.6. Hypothesis and Research Questions to be investigated ............................................................ 26 1.7. Thesis Structure .................................................................................................................... 27 1.8. Summary ............................................................................................................................... 28 2. LITERATURE REVIEW ......................................................................................................... 29 2.1. Introduction ........................................................................................................................... 29 2.2. Voice over IP ........................................................................................................................ 29 2.2.1. Requirements of a VoIP Network ................................................................................. 31 5 2.2.2. Protocols Related To VoIP ........................................................................................... 33 2.2.3. SIP Architectural Components ...................................................................................... 44 2.2.4. SIP Messages ................................................................................................................ 45 2.2.5. SIP Transactions ........................................................................................................... 48 2.2.6. Conclusion .................................................................................................................... 50 2.3. Adoption Factors of VoIP ..................................................................................................... 50 2.4. Mobile VoIP .......................................................................................................................... 52 2.5. IEEE 802.11 Architecture ....................................................................................................
Load more

Recommended publications
  • A Framework for Real-Time Communications
    Anton is a leading experts on Real Time Anton Venema Communications solutions, and the 1 Chief Technology Officer visionary lead architect behind IceLink, WebSync and LiveSwitch. iRTC Internet-Based Real Time Communications Introduction What’s the first thought that comes into your mind when you think about real-time communications? Is it a phone call you had a few minutes ago? A text message sent to your mobile? Maybe something more modern, like a tweet or video broadcast? All of these fall under the umbrella of what we like to call Internet-based real time communications, or iRTC for short. Real-time communications have been a part of our lives for a long time. From public telephone networks to radios all the way back to the telegraph, humanity has a history of seeking out new and better ways to use technology to improve communication. In the past decade, technology has arguably advanced more than the past century before it. Smartphones have stormed the market, mobile processors are advancing in line with Moore’s law, LTE rollouts are delivering unprecedented Internet speeds across the world, and WiFi hotspots are becoming ubiquitous. iRTC Includes Many Applications The availability of high-speed Internet services just about everywhere is causing a fundamental shift in the way people want to communicate and consume media. Cable networks are finding it more difficult to distinguish between their Internet and TV services, especially when companies like Netflix and HBO are able to publish their content directly to consumers over the Internet. Even live broadcasts, TV’s last stronghold, are being slowly replaced as platforms like YouTube allow content to be broadcast live to millions of users simultaneously over the Internet.
    [Show full text]
  • Installing and Configuring Openfire
    Technical Note PegaCHAT™ 7.1 Installing and Configuring OpenFire Copyright 2013 Pegasystems Inc., Cambridge, MA All rights reserved. This document describes products and services of Pegasystems Inc. It may contain trade secrets and proprietary information. The document and product are protected by copyright and distributed under licenses restricting their use, copying distribution, or transmittal in any form without prior written authorization of Pegasystems Inc. This document is current as of the date of publication only. Changes in the document may be made from time to time at the discretion of Pegasystems. This document remains the property of Pegasystems and must be returned to it upon request. This document does not imply any commitment to offer or deliver the products or services described. This document may include references to Pegasystems product features that have not been licensed by your company. If you have questions about whether a particular capability is included in your installation, please consult your Pegasystems service consultant. For Pegasystems trademarks and registered trademarks, all rights reserved. Other brand or product names are trademarks of their respective holders. Although Pegasystems Inc. strives for accuracy in its publications, any publication may contain inaccuracies or typographical errors. This document or Help System could contain technical inaccuracies or typographical errors. Changes are periodically added to the information herein. Pegasystems Inc. may make improvements and/or changes in the information described herein at any time. This document is the property of: Pegasystems Inc. One Rogers Street Cambridge, MA 02142 Phone: (617) 374-9600 Fax: (617) 374-9620 www.pega.com Document: Technical Note for Installing and Configuring Openfire Software Version: PegaCHAT™ 7.1 Updated: November 7, 2013 Tech Note – Installing and Configuring Openfire 2 Contents Overview .....
    [Show full text]
  • Voip): SIP and Related Protocols Fall 2013, Period 1 Lecture Notes of G
    IK2554 Practical Voice Over IP (VoIP): SIP and related protocols Fall 2013, Period 1 Lecture notes of G. Q. Maguire Jr. For use in conjunction with: Henry Sinnreich and Alan B. Johnston, Internet Communications Using SIP: Delivering VoIP and Multimedia KTH Information and Services with Session Initiation Protocol, 2nd Edition, Wiley, Communication Technology August 2006, ISBN: 0-471-77657-2. © 2004-2013 G.Q.Maguire Jr. All rights reserved. No part of this course may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without written permission of the author. Last modified: 2013.08.30:12:51 Maguire Cover.fm Total pages: 1 [email protected] 2013.08.30 Module 1: Introduction........................................................................... 35 Welcome to the course! .......................................................................... 36 Staff Associated with the Course............................................................ 37 Instructor (Kursansvarig) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 37 Goals, Scope and Method....................................................................... 38 Goals of the Course - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 38 Scope and Method - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    [Show full text]
  • FOSDEM 2017 Schedule
    FOSDEM 2017 - Saturday 2017-02-04 (1/9) Janson K.1.105 (La H.2215 (Ferrer) H.1301 (Cornil) H.1302 (Depage) H.1308 (Rolin) H.1309 (Van Rijn) H.2111 H.2213 H.2214 H.3227 H.3228 Fontaine)… 09:30 Welcome to FOSDEM 2017 09:45 10:00 Kubernetes on the road to GIFEE 10:15 10:30 Welcome to the Legal Python Winding Itself MySQL & Friends Opening Intro to Graph … Around Datacubes Devroom databases Free/open source Portability of containers software and drones Optimizing MySQL across diverse HPC 10:45 without SQL or touching resources with my.cnf Singularity Welcome! 11:00 Software Heritage The Veripeditus AR Let's talk about The State of OpenJDK MSS - Software for The birth of HPC Cuba Game Framework hardware: The POWER Make your Corporate planning research Applying profilers to of open. CLA easy to use, aircraft missions MySQL Using graph databases please! 11:15 in popular open source CMSs 11:30 Jockeying the Jigsaw The power of duck Instrumenting plugins Optimized and Mixed License FOSS typing and linear for Performance reproducible HPC Projects algrebra Schema Software deployment 11:45 Incremental Graph Queries with 12:00 CloudABI LoRaWAN for exploring Open J9 - The Next Free It's time for datetime Reproducible HPC openCypher the Internet of Things Java VM sysbench 1.0: teaching Software Installation on an old dog new tricks Cray Systems with EasyBuild 12:15 Making License 12:30 Compliance Easy: Step Diagnosing Issues in Webpush notifications Putting Your Jobs Under Twitter Streaming by Open Source Step. Java Apps using for Kinto Introducing gh-ost the Microscope using Graph with Gephi Thermostat and OGRT Byteman.
    [Show full text]
  • JIRA ID JIRA Name RN Content Enhancement/Fix/Known Issue UC-1443 Agent Should Be Able to Add a a Basic OUTBOUND CALL Gadget
    JIRA ID JIRA name RN Content Enhancement/Fix/Known Issue UC-1443 Agent should be able to add a a basic OUTBOUND The first iteration should consist of the outbound call gadget is a call controller. Enhancement CALL gadget Only the main section of the gadget is covered. The main section consists of the following: * A status icon * A text field for the phone number * A Call button The status icon displayed should either be the following: * Precall - if idle * Outgoing - if ringing * In session - if on call Limitations: * An outbound call is allowed ONLY when the agent is released and not processing any session. * Note that there is no wrapup / call disposition selection yet Additional Requirements: An agent that has connected to a destination using the outbound widget must have the capability of conferencing/transferring to other parties in the same way that they would do that for an inbound call that they are connected to. UC-1565 sipx-servtest The script sipx-servtest was removed in version 4.6. This script has been invaluable at sites where Enhancement remote monitoring and notification are needed. Recommend restoring this script to production code so it can be maintained. This was re-added with the re-add of sipXtools. UC-1638 Agent should be able to control an OUTBOUND Related to UC-1443 Enhancement CALL from the dashboard UC-1932 Agent should be able to do a transfer/conference Agents can perform the transfer and create conference actions when listening to a voice mail call Enhancement when calling back for a voicemail back through the new menu option in Reach named Transfer/Conference.
    [Show full text]
  • Getting Started with Openbts BUILD OPEN SOURCE MOBILE NETWORKS
    Compliments of Getting Michael Iedema Started with Foreword by Harvind Samra OpenBTS BUILD OPEN SOURCE MOBILE NETWORKS Getting Started with OpenBTS Michael Iedema Getting Started with OpenBTS by Michael Iedema Copyright © 2015 Range Networks. All rights reserved. Printed in the United States of America. Published by O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472. O’Reilly books may be purchased for educational, business, or sales promotional use. Online editions are also available for most titles (http://safaribooksonline.com). For more information, contact our corporate/ institutional sales department: 800-998-9938 or [email protected]. Editor: Brian MacDonald Indexer: WordCo Indexing Services Production Editor: Melanie Yarbrough Cover Designer: Karen Montgomery Copyeditor: Lindsy Gamble Interior Designer: David Futato Proofreader: Charles Roumeliotis Illustrator: Rebecca Demarest January 2015: First Edition Revision History for the First Edition: 2015-01-12: First release See http://oreilly.com/catalog/errata.csp?isbn=9781491910658 for release details. The O’Reilly logo is a registered trademark of O’Reilly Media, Inc. Getting Started with OpenBTS, the cover image of a Sun Conure, and related trade dress are trademarks of O’Reilly Media, Inc. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and O’Reilly Media, Inc. was aware of a trademark claim, the designations have been printed in caps or initial caps. While the publisher and the author have used good faith efforts to ensure that the information and instruc‐ tions contained in this work are accurate, the publisher and the author disclaim all responsibility for errors or omissions, including without limitation responsibility for damages resulting from the use of or reliance on this work.
    [Show full text]
  • LNS Is a Game Changer ������������������������������������������������7
    MOBILE : MOBILE MESSAGING EXCHANGE EXTENDING THE REACH OF TWO-WAY TEXT MESSAGING AND VOICE MOBILE : MOBILE MESSAGING EXCHANGE TABLE OF CONTENTS The background . 3 The problem . 3 The options . 4 A smarter, more powerful solution . 5 The opportunity . 6 Why Tata Communications’ mobile LNS is a game changer . 7 Creating a New World of Communication™ through innovation . 7 For more information, visit us at www.tatacommunications.com. © 2015 Tata Communications. All Rights Reserved. TATA COMMUNICATIONS and TATA are trademarks of Tata Sons Limited in certain countries. MOBILE : MOBILE MESSAGING EXCHANGE THE BACKGROUND There are two key conditions necessary for communications networks to function efficiently. First, as many end points as possible should be connected to the network. Second, multiple networks must be able to connect with each other. Global, inter-connected communications networks enable multiple individuals to inter-connect. Generally, their connections can be completed regardless of the originating or terminating network, its geography and the type of handset used at both ends of the link. The arrival of new communications methods enabled by over the top (OTT) service providers challenges this model. These services take a more ‘closed community’ approach that does not pro- vide for connectivity across the broader global communications environment. THE PROBLEM These OTT-enabled services have resulted in communication options that are more fragmented than they were ten years ago – with individuals often communicating within a closed community of similarly connected users. The fact that OTT apps for voice and messaging services are generally free to use is an attractive proposition. However, the service is only free if one user is sending a message or having a voice conversation with another user via the same application.
    [Show full text]
  • Webrtc About
    WebRTC About WebRTC provides Real-Time Communications directly from better web browsers and devices without requiring plug-ins such as Adobe Flash nor Silverlight. WebRTC always operates in secure mode.FreeSWITCH provides a WebRTC portal to its public conference bridge to demonstrate the possibilities for handling telephony via a web page; join us for our weekly conference calls. The process for configuring FreeSWITCH with WSS certificates is the same whether for use with classic WebRTC or the FreeSWITCH Verto endpoint. Installation The configuration for Secure Web Sockets is slightly different than for TLS over SIP. This guide covers WSS certificate setup. Debian 7 (Wheezy) Install Debian 7 (Wheezy) minimal. Building FreeSWITCH Building apt-get install git build-essential automake autoconf libtool wget python zlib1g-dev libjpeg-dev libncurses5- dev libssl-dev libpcre3-dev libcurl4-openssl-dev libldns-dev libedit-dev libspeexdsp-dev libspeexdsp-dev libsqlite3-dev apache2 cd /usr/src/ git clone https://freeswitch.org/stash/scm/fs/freeswitch.git cd freeswitch ./bootstrap.sh -j ./configure -C make make install cd-sounds-install cd-moh-install mkdir -p /usr/local/freeswitch/certs edit /usr/local/freeswitch/conf/sip_profiles/internal.xml # Set these params and save the file: <param name="tls-cert-dir" value="/usr/local/freeswitch/certs"/> <param name="wss-binding" value=":7443"/> If behind N.A.T. make sure to set the ext-sip-ip and ext-rtp-ip in vars.xml to the public IP address of your FreeSWITCH. If talking to clients both inside and outside the N.A.T. you must set the local-network-acl rfc1918.auto, and prefix the ext-sip-ip and ext-rtp-ip to autonat:X.X.
    [Show full text]
  • A Survey of Open Source Products for Building a SIP Communication Platform
    Hindawi Publishing Corporation Advances in Multimedia Volume 2011, Article ID 372591, 21 pages doi:10.1155/2011/372591 Research Article A Survey of Open Source Products for Building a SIP Communication Platform Pavel Segec and Tatiana Kovacikova Department of InfoCom Networks, University of Zilina, Univerzitna 8215/1, 010 26 Zilina, Slovakia Correspondence should be addressed to Tatiana Kovacikova, [email protected] Received 29 July 2011; Revised 31 October 2011; Accepted 15 November 2011 Academic Editor: T. Turletti Copyright © 2011 P. Segec and T. Kovacikova. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Session Initiation Protocol (SIP) is a multimedia signalling protocol that has evolved into a widely adopted communication standard. The integration of SIP into existing IP networks has fostered IP networks becoming a convergence platform for both real- time and non-real-time multimedia communications. This converged platform integrates data, voice, video, presence, messaging, and conference services into a single network that offers new communication experiences for users. The open source community has contributed to SIP adoption through the development of open source software for both SIP clients and servers. In this paper, we provide a survey on open SIP systems that can be built using publically available software. We identify SIP features for service deve- lopment and programming, services and applications of a SIP-converged platform, and the most important technologies support- ing SIP functionalities. We propose an advanced converged IP communication platform that uses SIP for service delivery.
    [Show full text]
  • Freeswitch 1.6 Cookbook
    www.itbook.store/books/9781785280917 FreeSWITCH 1.6 Cookbook Over 45 practical recipes to empower you with the latest FreeSWITCH 1.6 features Anthony Minessale II Michael S Collins Giovanni Maruzzelli BIRMINGHAM - MUMBAI www.itbook.store/books/9781785280917 FreeSWITCH 1.6 Cookbook Copyright © 2015 Packt Publishing All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews. Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the authors, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book. Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information. First published: February 2012 Second Edition: July 2015 Production reference: 1170715 Published by Packt Publishing Ltd. Livery Place 35 Livery Street Birmingham B3 2PB, UK. ISBN 978-1-78528-091-7 www.packtpub.com www.itbook.store/books/9781785280917 Credits Authors Copy Editors Anthony Minessale II Miss Yesha G Michael S Collins Vikrant
    [Show full text]
  • FCC 11-107.Pdf
    Federal Communications Commission FCC 11-107 Before the Federal Communications Commission Washington, D.C. 20554 In the Matter of ) ) Amending the Definition of Interconnected VoIP ) GN Docket No. 11-117 Service in Section 9.3 of the Commission’s Rules ) ) PS Docket No. 07-114 Wireless E911 Location Accuracy Requirements ) ) WC Docket No. 05-196 E911 Requirements for IP-Enabled Service ) Providers ) ) NOTICE OF PROPOSED RULEMAKING, THIRD REPORT AND ORDER, AND SECOND FURTHER NOTICE OF PROPOSED RULEMAKING Adopted: July 12, 2011 Released: July 13, 2011 Comment Date: [60 days after publication in the Federal Register] Reply Comment Date: [90 days after publication in the Federal Register] By the Commission: Chairman Genachowski and Commissioners Copps, McDowell, and Clyburn issuing separate statements. TABLE OF CONTENTS Heading Paragraph # I. INTRODUCTION.................................................................................................................................. 1 II. BACKGROUND.................................................................................................................................... 5 III. THIRD REPORT AND ORDER ......................................................................................................... 13 A. Unitary Location Accuracy Standard............................................................................................. 13 1. Outdoor Location Accuracy Testing ....................................................................................... 24 2. Legal Authority
    [Show full text]
  • Modeling and Analysis of Next Generation 9-1-1 Emergency Medical Dispatch Protocols
    MODELING AND ANALYSIS OF NEXT GENERATION 9-1-1 EMERGENCY MEDICAL DISPATCH PROTOCOLS Neeraj Kant Gupta, BE(EE), MBA, MS(CS) Dissertation Prepared for the Degree of DOCTOR OF PHILOSOPHY UNIVERSITY OF NORTH TEXAS August 2013 APPROVED: Ram Dantu, Major Professor Kathleen Swigger, Committe Member Paul Tarau, Committee Member Sam G Pitroda Committee Member Barrett Bryant, Chair of the Department of Computer Science and Engineering Costas Tsatsoulis, Dean of the College of Engineering Mark Wardell, Dean of the Toulouse Graduate School Gupta, Neeraj Kant. Modeling and Analysis of Next Generation 9-1-1 Emergency Medical Dispatch Protocols. Doctor of Philosophy (Computer Science), August 2013, 192 pp., 12 tables, 72 figures, bibliography, 196 titles. In this thesis I analyze and model the emergency medical dispatch protocols for Next Generation 9-1-1 (NG9-1-1) architecture. I have identified various technical aspects to improve the NG9-1-1 dispatch protocols. The specific contributions in this thesis include developing applications that use smartphone sensors. The CPR application uses the smartphone to help administer effective CPR even if the person is not trained. The application makes the CPR process closed loop, i.e., the person who administers the CPR as well as the 9-1-1 operator receive feedback and prompt from the application about the correctness of the CPR. The breathing application analyzes the quality of breathing of the affected person and automatically sends the information to the 9-1-1 operator. In order to improve the human computer interface at the caller and the operator end, I have analyzed Fitts law and extended it so that it can be used to improve the instructions given to a caller.
    [Show full text]