Verkkoke 1.1 User Manual
Contents
1. 4 1 Learning Management System 000 cece nen 4 2 Backing Up Verkkoke 0 00 cece eee eee eee 5 Compiling From Source Optional 10 Chapter 1 Introduction 1 1 Introduction Verkkoke 1 1 is an online teaching environment for telecommunications software and rout ing based on learning by doing philosophy It is designed for use in conjuction with a programming assignment The assignment introduces students to socket programming and simplified routing protocols Students write client programs which connect to the Verkkoke 1 1 server The server simulates a network of routers The student s client represents one router in the simulated network First the student s client authenticates with the server Upon successfull authentication the server sends routing protocol messages to the student s client The client then builds its routing table according to the received routing protocol messages Finally the client submits its routing table to the server Key features of Verkkoke 1 1 e Creates individual simulated networks with representative topologies for the students e Simulates two simplified routing protocols one distance vector protocol and one link state protocol Sends protocol messages to the client e Automatically checks the submitted routing tables e Gives feedback to students so that they can learn from their mistakes fix them and resubmit the corrected solutions e Compat2. descriptions of different parameters and other help Please remember that GCI must be run at least once and configuration saved to synchronize different configuration files in the system If you know or wish to know what you are doing you can edit configuration file phpinc config php by hand File is quite well documented so it should be relatively easy to change some settings through there if needed There is also a file phpinc resources php that contains resource links that are shown to students if their score is less than 100 Edit it if you wish to add or remove resources Chapter 3 Using Verkkoke as Student 5 3 Using Verkkoke as Student As mentioned in Chapter 1 Introduction page 1 Verkkoke 1 1 is designed for use in conjunction with a programming assignment To do the programming assignment the student takes the following steps 1 The student logs in to the Learning Management System LMS to read assignment instructions to commence the assignment and retrieve assignment results 2 Externally the student makes the client program then logs back into the LMS to start the assignment 3 The system generates a random topology for the student 4 The student has the client program contact the simulation server The simulation server sends routing messages to the client based on the topology generated for the student 5 The client builds its routing table based on the routing messages and sends that rou
3. form SUBMISSION OK feedback or SUBMISSION FAILED reason if the routing table message was invalid or there was some internal error Finally the server closes the TCP connection The reguirements for the submitted routing table are different for the DV protocol and the LS protocol The difference is that for the LS protocol if there are multiple shortest paths of egual cost with different next hops and thus different interface ids for a destination the routing table must contain an entry for each of these options This is called Egual Cost Multipath ECMP routing ECMP is reguired so that the student can demonstrate that the algorithm used in the client finds all the shortest paths In real world routing ECMP can be used for load balancing ECMP is supported by OSPF ECMP is not reguired with the DV protocol however The ECMP reguirement in the LS protocol also serves to balance the difficulty of implementing the two protocols since the DV protocol involves implementing stop and wait ARO whereas the LS protocol just uses TCP The submission server compares the submitted routing table with the routing table of the student s node in the simulation The simulation table contains all ECMP entries The feedback to the student consists of a score passed failed and the number of incorrect or missing routing table destinations The submission server sends this information to the student s client The result can later be accessed through the LMS
4. simply done by copying war file to webapps directory 4 This is Debian s default setting Chapter 2 Getting Started 4 2 1 3 4 Updating Configuration Files Usually configuration files should be updated using Graphical Configuration Interface GCI is located in web configGUI and should be accessible using web browser and working if web server is correctly configured To update configuration files simply log in to GCI and save configuration once CGI has explanations of different parameters Main Verkkoke configuration file is phpinc config php Simula tion Server and Topology Generator have their own configuration files server bin simulationserver properties and topology_generator conf respectively but they are just subsets of parameters in config php If files are edited manually they must be kept in sync to avoid problems 2 1 3 5 Starting Simulation Server Simulation Server is located in directory server bin along with run sh script to run it It should be ready to run after configuration files have been updated Server is able to follow changes made to configuration file and automatically adopts new settings 2 2 Configuring Verkkoke The post installation configuration of Verkkoke 1 1 should be done using web based Graph ical Configuration Interface GCI main script file is web configGUI index php which should be accessible if your web server is configured correctly GCI has
5. Distance Vector and LS which stands for Link State and they are loosely based on the real protocols RIP and OSPF respectively Chapter 3 Using Verkkoke as Student 7 The student s client sends its routing table to the server using a separate submission protocol which uses TCP The server then compares the submitted routing table with the routing table of the student s node in the simulation 3 1 The DV Protocol The DV protocol uses UDP so that the student gets experience with datagram sockets Because UDP does not guarantee reliable data transfer and because in order to build its routing table the client must receive all DV messages the DV protocol includes a basic reliability mechanism called stop and wait Automatic Repeat reQuest ARQ Stop and wait ARQ provides reliability by requiring that each packet sent is acknowledged The sender sends a packet and waits for an acknowledgement ACK packet before continuing Since packets also ACK packets can be lost or duplicated sequence numbers are used to determine which ACK acknowledges what In fact when a receiver acknowledges reception of a packet it attaches to the ACK the sequence number of the next packet it expects First the student s client sends the authentication message The server responds with the message AUTH OK s where s is a random integer sequence number from within the range 1 2 All messages sent by the server contain a sequence number and the client
6. L Boston University All rights re served Permission to use copy modify and distribute this software and its documentation for any purpose and without fee is hereby granted provided that the above copyright notice appear in all copies and that both the copyright notice and this permission notice appear in supporting documentation The QoS Networking Laboratory QNL of the Computer Science Department at Boston University makes no representations about the suitability of this software for any purpose It is provided as is without express or implied warranty Table of Contents 1 ANGPOCMCUION lt occ os 44604 a KEEN dey ss 2 Getting Started LLuuuuuuueuu 2 1 Installing Verkkoke oossoo nn 2 l l Proroguisttesiau c esce nennen Ha 2 1 2 Installation Steps 0 eee eee sense 2 1 3 Detailed Installation ssseseseeeeee eee 2 1 3 1 Configuring Web Server 0 eee eee eens 2 1 3 2 Deploying Topology Generator 2 22222000 2 1 3 3 Deploying SCORM Package 0 2 00 eee 2 1 3 4 Updating Configuration Files 00 2 1 3 5 Starting Simulation Server 00 eee ee eee 2 2 Configuring Verkkoke oossoo ene nee ki 3 Using Verkkoke as Student 3 1 The DV Protocol ende 3 2 The LS Protocol 1 1 0 u ech 3 3 Routing Table Submission so sossun nnen 4 Using Verkkoke as Teacher
7. Verkkoke 1 1 User Manual Copyright c 2007 Telecommunications Software and Multimedia Laboratory TML Helsinki University of Technology Permission is hereby granted free of charge to any person obtaining a copy of this soft ware and associated documentation files the Software to deal in the Software without restriction including without limitation the rights to use copy modify merge publish distribute sublicense and or sell copies of the Software and to permit persons to whom the Software is furnished to do so subject to the following conditions The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software THE SOFTWARE IS PROVIDED AS IS WITHOUT WARRANTY OF ANY KIND EXPRESS OR IMPLIED INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY FITNESS FOR A PARTICULAR PURPOSE AND NONIN FRINGEMENT IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM DAMAGES OR OTHER LIABILITY WHETHER IN AN ACTION OF CONTRACT TORT OR OTHERWISE ARISING FROM OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE Verkkoke 1 0 includes third party components i e J Sim 1 3 and Brite 2 1 binaries The inclusion of these components reguires inclusion of their respective copyright statements J Sim 1 3 Copyright c 1998 2004 Distributed Real time Computing Lab DRCL All rights reserved Redistribution a
8. d write permissions for whole verkkoke directory and subdirectories This should not be a problem Execute permission is needed for dot Topology Generator uses reflection so java lang reflect ReflectPermission suppressAccessChecks must be set Finally Topology Generator s URL must be updated to phpinc config php either by manually editing the file or by Graphical Configuration Interface GCI is located in web configGUI and should be accessible using web browser and working if web server is correctly configured Name of the parameter is topologyGeneratorURL Default value for URL is to assume that servlet engine is run on a local machine localhost at port 81804 2 1 3 3 Deploying SCORM Package Before SCORM package can be deployed to LMS it must be updated In scorm simassignment launch htm find parameter onLoad launchSim http host directory simassignment php Edit the URL according to your web server settings to match simassignment php in verkkoke web directory Then package contents of the scorm simassignment directory to a zip file This zip file is now ready to be deployed to your LMS n All of the mentioned programs are available via apt in Debian GNU Linux including Sun s Java Virtual Machine In Apache it is easy to use Alias and Directory commands to publish just about any directory in arbitrary URL within domain of course N 3 In Apache Tomcat this is usually
9. ibility with modern learning management systems through its adherence to the Sharable Content Object Reference Model SCORM specification e Graphical Configuration Interface GCI to easily setup and maintain Verkkoke e Modularity and extensibility which allows using the sophisticated network simulation engine for teaching other network protocols in addition to the routing protocols Chapter 2 Getting Started 2 2 Getting Started 2 1 Installing Verkkoke 2 1 1 Prereguisites The software depends on the following components e A SCORM compliant Learning Management System LMS e g Moodle e A php 5 0 enabled web server e g Apache e A Java servlet engine e g Tomcat e A Java runtime environment version 1 5 or later e The Graphviz graph visualization software The dot command of Graphviz is used This is included in many Linux distributions To install these components please refer to their own instructions 2 1 2 Installation Steps See Detailed Installation page 2 for more thorough instructions 1 Extract the contents of the package tar zxf verkkoke 1 1 tar gz 2 Copy the verkkoke root folder and its contents to the desired deployment location 3 4 Deploy the topologygenerator war file in the verkkoke folder to your servlet engine Configure your PHP enabled web server to publish files under web directory Refer to your servlet engine s documentation on how to depl
10. ile phpinc config php should be copied Chapter 5 Compiling From Source Optional 10 5 Compiling From Source Optional Verkkoke can be compiled using Apache Ant the build file is build xml For details refer to http ant apache org Change to the server directory and issue any of the following commands ant Compiles Verkkoke ant build the war Builds the topology generator WAR Web ARchive file ant javadoc Creates the Javadoc documentation Javadocs are not complete and therefore not very useful ant clean Removes the compiled classes
11. must respond to every message received with an acknowledgement of the form ACK s 1 Upon reception of the acknowledgement of the AUTH OK s message the server starts sending the routing data The routing data messages have the format x y z s where x is the network interface number y is the name of a router z is the distance to router y and s is the seguence number The seguence number is incremented by one for each new message The server resends by default with one second intervals if a message is not acknowledged If no ACK is received in 15 seconds the server gives up and stops resending the message These timeouts can be configured in a configuration file as discussed in Section Section 2 2 Configuring Verkkoke page 4 Each of these messages are sent in separate UDP packets In the DV protocol the distance between two adjacent routers is assumed to be always one As the client receives the routing messages it calculates its routing table using a distributed Bellman Ford algorithm 3 2 The LS Protocol The LS protocol uses TCP so that the students get experience with byte stream sockets The new line character separates different messages Since TCP provides a reliable byte stream no additional reliability mechanism is reguired Like with the DV protocol the student s client first sends an authentication message that identifies the student If authentication succeeds the server responds with the message AUTH OK Upon succes
12. nd use in source and binary forms with or without modification are per mitted provided that the following conditions are met 1 Redistributions of source code must retain the above copyright notice this list of con ditions and the following disclaimer 2 Redistributions in binary form must reproduce the above copyright notice this list of conditions and the following disclaimer in the documentation and or other materials provided with the distribution 3 Neither the name of DRCL nor the names of its contributors may be used to en dorse or promote products derived from this software without specific prior written permission THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIB UTORS AS IS AND ANY EXPRESS OR IMPLIED WARRANTIES INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT IN DIRECT INCIDENTAL SPECIAL EXEMPLARY OR CONSEOUENTIAL DAMAGES INCLUDING BUT NOT LIMITED TO PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES LOSS OF USE DATA OR PROFITS OR BUSINESS INTERRUPTION HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY WHETHER IN CON TRACT STRICT LIABILITY OR TORT INCLUDING NEGLIGENCE OR OTHER WISE ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE Brite 2 1 Copyright c 2002 Q0S Networking Laboratory ON
13. on the result page Chapter 4 Using Verkkoke as Teacher 9 4 Using Verkkoke as Teacher 4 1 Learning Management System A Learning Management System LMS is used with Verkkoke 1 1 for managing student as signment statuses and results submitting documents related to the assignment e g assign ment plans for reporting purposes and for other value adding functionality that a particular LMS may provide Since a university giving a networking course is likely to already have an LMS in use it is usually desired to use this existing system to manage course information such as students and their assignment scores Typically a teacher performs the following tasks with Verkkoke 1 1 e Add students to LMS e Accept assignment related documents submitted by students e g plans or final reports e Look at the assignment report with the grades for the different assignment parts for each student Since the programming assignment grades are automatically stored in the LMS the teacher does not need to learn how to use any new system All of the teacher s tasks are done through the LMS which the teacher is probably already familiar with 4 2 Backing Up Verkkoke Normally all result data is stored to the Learning Management System and there should be no reason to store any other data topologies etc If for some reason all data has to be backed up it is enough to copy directory data student data If one wishes to backup configuration f
14. ontents of the package tar zxf verkkoke 1 1 tar gz This should cre ate directory verkkoke with some subdirectories data log phpinc scorm server and web There should also be default_brite_conf default_student_data data and topology_generator conf files 2 1 3 1 Configuring Web Server Configure your web server to publish files in web directory including its subdirectories Note that scripts in web directory need access to some files in verkkoke directory or its subdirectories so web directory should not be copied or moved anywhere neither should verkkoke directory be accessible via HTTP Web server or more precisely the PHP engine must also be able to write files to data directory If Graphical Configuration Interface is used server must also be able to write Simulation Servers and Topology Generator s configuration files server bin simulationserver properties and topology_generator conf respectively Also note that the web server must be able to handle PHP 5 0 2 1 3 2 Deploying Topology Generator Deploy server topologygenerator war to your servlet engine Make sure that Topol ogy Generator servlet can read its configuration file topology_generator conf Read and write permissions are needed for topology and data files in data and web topologyPics directories It is probably easiest to grant read an
15. oy a WAR Web ARchive file Make sure that the topologygeneratorURL variable in config php matches the URL of the deployed servlet Deploy the SCORM package to your LMS See the README txt file in the scorm folder Configure file system permissions Web server must be able to read from and under verkkoke directory It must also be able to write to data student data directory and to files server bin simulationserver properties and topology_generator conf Topology Generator must be able to read topology_generator conf from verkkoke directory write to data student_data data brite and web topologyPics and to execute dot Simulation Server must be able to read its own files including simulationserver properties written by web server and to write its log files if logging is required to log directory Launch Graphical Configuration Interface by pointing your web browser to web configGUI index php Save settings once even if you do not need to change anything to update Simulation Server s and Topology Generator configuration files 2 1 3 Detailed Installation First make sure you have installed everything needed that is needed by Verkkoke A PHP 5 0 capable web server e g Apache a servlet engine e g Apache Tomcat a SCORM Chapter 2 Getting Started 3 supporting learning management system e g Moodle Java 5 0 or newer and Graphviz dot program Extract the c
16. r name is the name of the router which is sending its link information and neighbor name is the name of one of its neighbors e g INFORM 3 5 2 distance is the distance between the two routers To get link information from the server the client sends the message INFORM The server responds by sending INFORM router name neighbor name distance messages to the client After all these messages has been sent the server closes the TCP connection At this point the student s client will have enough information to build a link state database and calculate its routing table using Dijkstra s shortest path algorithm If the server receives an invalid protocol message from a client it responds by sending the message ERROR 3 3 Routing Table Submission The student s client sends its routing table to the server using a separate submission protocol which uses TCP The server then compares the submitted routing table with the routing table of the student s node in the simulation The submission protocol advances as follows First the client sends the authentication message The server responds with the message AUTH OK Then the client sends its routing table in this format x y z x y Z X y Z where x is the name of a destination router y is the distance to that destination and z is the number of the interface through which the destination is reached Each routing table row ends with a semicolon The server responds with a message of the
17. sful authentication the client sends a HELLO message to the server In a real routing protocol the HELLO message would be sent through all network interfaces and thus to all neighbors Since the simulation server represents the entire virtual network the client sends the HELLO message only to the simulation server The server responds with a message for each neighbor of the student s router in the simulated network The response message has the form HELLO name interface where name is the name of the neighbor that would have sent this response and interface is the number of the interface through which the message would have arrived e g HELLO 3 2 When responses for all neighbors have been sent the simulation server sends the message NOMORENEIGHBORS 0 Chapter 3 Using Verkkoke as Student 8 Next the client determines the distance to each of its neighbors by sending an ECHO message The server responds with a message for each neighbor of the form ECHOREPLY name distance where name is the name of the neighbor that would have sent this response and distance is the distance to that neighbor e g ECHOREPLY 3 2 Now the client has all relevant information about its neighbors To be able to build its routing table the client needs information about the rest of the network In the LS protocol routers communicate information about their links with INFORM messages These have the form INFORM router name neighbor name distance where route
18. ting table to the server The simulation server checks whether the routing table is correct and stores the result in the LMS The student goes back to step 1 to see the result If the routing table is not correct the student is allowed to submit again Chapter 3 Using Verkkoke as Student 6 Login to LMS Canaris Kirjaudu sis n Client EE kiudu sisaan PG Server K yt pakslus aan Ub your Ser ce Dre sends messages import java io F address J sublic class Example c a public static vc Client builds i Server URL hut ne outing table URLConnectic checks amp stores BufferedReac LMS Step 3 in the above process description can be reached in two different modes practice mode and submission mode When in practice mode the student can choose the size of the generated topology picture of the topology is shown when it has been generated The student has the option to generate a new topology if desired When in submission mode the system will always generate a new topology of certain teacher configurable number of nodes and the topology is not shown to the student The student s client builds its routing table based on routing messages sent by the server The format and content of these messages depend on the simulated routing pro tocol Verkkoke 1 1 simulates two routing protocols which are abstractions of real routing protocols The abstractions are called DV which stands for
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